insert unknown command to execvp()

Question: hi
if i'm passing an unknown command to execvp i'm getting this error in the errno :
"no such file or directory"
when i should get this error:
"command not found"
how can i get the second error?
Answer: Because "command not found" does not correspond to a standard error code (see e.g. http://linux.die.net/man/3/errno).
Answer: There is no "command not found" error that can be returned from execvp. The closest is ENOENT, which means that the file specified (or its interpreter, or a required dynamic library) was not found.
If you want, your program could print out "command not found" rather than the text returned by strerror.

insert unknown command to execvp()


How to shim shed floor joists resting on sleepers

Question: I have a 12 x 14 shed with 16 inch on center floor joists resting on sleepers on the two ends and in the center to support the down. However some of the 2x6 floor joists on the end are shy of being flush with the butt joint fronts (maybe 1/8 to 1/4 of inch due to end of one being skinnier) when resting on the sleepers. Can I shim under the floor joists to lift them up and if so what is the best method for this?
Answer: With shed framing, 1/8" is rarely a concern. 1/4" is slightly more so, but still not much in this case. You could leave the joists resting down on the sleepers, install your floor sheathing, and build your walls with no ill effects. It's a very minor cosmetic issue if anything.
If you like, shim the rim up flush with the top of the joists. Just be sure that you aren't introducing humps in your floor, which would be a much more significant issue. Use a long level or other straightedge to check that out.
Correction: I see now that it's the rim that's low. Just float it. All the load of the walls and roof will be carried by the common joists. It's not a problem at all.
Comment: Added a pic above. I ended up going with your first suggestion. I removed the screws and drilled in the toenail so everything is resting directly on the sleepers and not floating. There is a tiny lip at that corner joint (thinking of maybe just planing it down slightly but sounds like I don't have too). Some other joists also didn't seem flush and I am guessing it's more imperfections so I bought these angle braces at Lowe's which were thick enough to get the joists flush by slipping under them then screwing joist in as usual but wedding down metal plate. Does that seem sufficient?
Comment: I'd say so, but I don't think there was a problem to begin with. :)


Job interview for a PhD

Question: I was recently invited to a job interview regarding a PhD. I was told to make a short presentation of a few ideas regarding the project topic. I also have received an overview over the project aims, preliminary work etc.. I must admit that I am quite clueless what to present. In this project a new simulation platform should be developed with the help of the methods already implemented by the two participating work groups in their own software. I thought about presenting some methodology, but this would largely consist of implementing methods that these both groups already published and nothing really new. Also I'm new to the simulation method that is used in this project. Do you think that it would be sufficient to list the methods that can be used for the several parts of the simulation and in which order I would plan to implement these?
Answer: What you say here is a lot of what you need to include, but what I'm missing is something about the end goal. What do you hope to learn in doing this research? How will it advance the field to know the answers, whether they are positive or negative? If you keep that goal in mind, the details of the attack can change and still make progress.
Focus a bit less on the actions and a bit more on the expected knowledge. Not that the actions are unimportant, of course.
Answer: I would approach any interview with the mindset of "how can I convince the interviewer that I am the right person for the job". To accomplish this I would focus on three things:

What is the job you are expected to do.
What can you do to get the job done.
What else have I done that qualifies me.

With that I would break down the expectations into a few key items. You could go by aims, or by concepts, or techniques, or whatever other ordering category you can identify. And then in each of these categories you can show how you will contribute. The 3rd part is there to show off some additional skills that are not necessarily related to the project you are interviewing for (like a past project you worked on). Here you can demonstrate how you are able to tackle a challenging problem, learn something new, or be thorough/meticulous in executing a project.

Job interview for a PhD


Can I use a 3-in-1 mix with an overseed machine?

Question: This lawncare product is a 3-in-1 solution containing seed, fertilizer, and soil improver.  Can I use an overseed machine with the fertilizer and soil improver mixed in or will that harm the machine since those additions are not shaped like a grass seed?
Comment: You need to talk to that machine owner...did you rent this machine?  Another great call for you to make is to a local grass seed spray company.  Far far better than trying to do this yourself...what the heck is 'soil improver' that they've mixed into the mix?  The only ONLY soil improver is decomposed organic matter.  That and an initial fruffing or double digging for the plant bed.  Sounds as if you are considering renting a machine?  Seed spray companies have already invented that wheel and the next best thing to laying sod is a seed spray company!
Comment: I don't have the machine yet but yes, I am renting.  I'm trying to decide between this and a de-thatcher. The overseed machine is less work. Spray like hydroseed? Probably overkill for my budget and the state of my lawn.  I'll confirm with the rental company that this product can be used, thanks.
Comment: Hydroseed is amazing inexpensive.  The cool thing is that they are lawn experts, grass seed growing experts in your area.  Just ask for an estimate  and ask questions with a grass expert walking beside you.  Far as I know that is still free.  It is guaranteed.  They come back just to fill in patches.  Dethatching is something I avoided.  Not healthy for the grass or for your back.  Prevention of thatch by aeration once per year, application of this thatch eating bacteria, bagging clippings...if thatch was bad I'd use a sod cutter and  new sod, start over.
Comment: There are really no patched in my lawn. It's just not thick enough.
Comment: Where is it that you live?  If you are talking about cool season grasses, the problems are; mowing too short, watering too often, too few balanced fertilizer applications...which is the best way to grow a crop of lawn weeds.  Proper installation, proper maintenance and that ensures a gorgeous healthy lawn.  Have you read some of our other questions and answers about lawn installation and care?  You have to send pictures of your lawn, the environment, what zone, what type of soil...your management practices to date.  Thatch usually means cool season grasses.  Grins, we can help more info & pics
Comment: @Merovingian Johnson How large is your lawn? Is there a reason you can't seed and fertilize with a hand spreader?
Answer: I am assuming you have cool season lawn grasses.  Thatch is not a problem with 365 days of warmth for decomposition.
Overseeding is not a regular, normal process for lawns...cool season lawns.  Without proper preparation, the correct seed mix, being able to water tiny areas within a huge body of lawn...seed needs a consistently just so moist soil or forget germination.  That means watering when ever that surface soil dries out, sometimes up to 7 times per day in hot weather and bright sun.
This weird specialized watering for your SPOTS lasts until you are able to do the virgin mow.  Then you use that grass, the newbie grass to tell you when to water again until all of that grass is on the same schedule, all with deep roots and NEVER having less than 3 inches of top growth.  Below that length, the grass gets stressed.  Genetically gifted I guess with huge root systems, those root systems need the top growth to FEED those roots or that grass plant is stressed and fragile.  Allows weeds to insert themselves.
I haven't used, probably will never use a 3 in 1 product for overseeding.  Just trying to tell you I've never seen the need for overseeding much less invest in overseeding.
I would most certainly ask for estimates from your local grass companies.  Free.  Might even make sense for your pocket book.  Remember, grass seed or sod companies have to be successful to continue business.  They would be very into teaching you how to grow this monster the lawn so they don't have to do a call back.
So sorry I am not answering your question.  I just am able to know there is more to this story and this problem that I could help fix, help you understand.  I do not think you should mess with this machine. Spraying grass seed, fertilizer, soil improvement stuff from a machine does not ensure a thicker grass.  I've never found overseeding to help at all.  If a lawn isn't thick and lush there is something going on that has to be addressed.  Overseeding is not a regular part of lawn maintenance. A thin lawn needs to be diagnosed first.  Overseeding is rarely a fix.
There is nothing one can spray on soil to improve it.
Adding fertilizer to newly germinating seed is contraindicated.
Comment: Yes, I have cool season grasses.  Unfortunately it's snowing now so I can't get a good picture of my lawn.  I got an evaluation from the a landscaper and a couple fertilization companies prior to deciding to do it myself.  They recommend overseeding.  My lawn is weedy and a bit thin.  They say that the overseeding will help to choke out the weeds, as well as thicken up my lawn.  Many people in my area dethatch or aerate and overseed in the fall.  I'm not concerned about the watering frequently until the new grass is established.
Comment: Mero, I am glad you have cool season grasses.  I am very much an expert with cool season grass crops/lawns.  Landscapers, fertilization companies have little knowledge about lawns.  Overseeding is not the answer.  If your grass crop is unhappy there are reasons why and overseeding will only make more unhappy grasses.  Dethatching is a major bandaid on a problem that should not happen if proper maintenance is in place.  What is the depth of your thatch?  Aeration is done anytime, preferably during warm weather so that the plugs disintegrate better.  Not in the fall.
Comment: If you could send some pictures we could help you to not waste money.  this overseeder might be helpful had you really ripped up your lawn, removed all non decomposed debris, top dressed with 1" of sifted top soil mixed with decomposed organic matter, grade, grade, grade and ROLL with a water filled roller before spraying.  Thatching should not be viewed as a regular practice. Nor should overseeding be considered an annual task. Until problems are corrected and a new seed bed in place, overseeding feeds the birds.  Mowing no less than 3", water deeply and do not water again until footprints.


How to handle constraints/undesirable outcomes in Reinforcement Learning

Question: What are the methods of handling constrains in RL? As I understand there are two types of environments: constrained (doesn't allow some actions and states) and unconstrained (allows any action and state).
1. Is adding penalty to reward the only way to handle undesirable outcomes if the environment is unconstrained?
2. How to handle situation when environment is constrained and agent takes unfeasible action (i.e. tries to insert more items into knapsack than it can actually hold)? Terminate episode early? Add penalty to reward? Anything else?
Answer:

Is adding penalty to reward the only way to handle undesirable outcomes if the environment is unconstrained?

Yes, pretty much this. The reward function is the feedback mechanism that the agent will use to learn what is marked as undesirable. To avoid catastrophic end results, then pre-training in simulation, and planning phases (also a form of simulation) before acting in the real environment may help, but these will refer to the reward function to discover and avoid any low reward outcome.

How to handle situation when environment is constrained and agent takes unfeasible action (i.e. tries to insert more items into knapsack than it can actually hold)?

That is not possible. When an environment is constrained, it means that the action cannot be taken.
If you mean that the agent might select an impossible action due to it being the highest predicted value, or as direct output of a policy function, then there are a few different approaches you can take:

Use information from the environment to filter the agent to only select from allowed actions. If possible this is simple and clean. It is how Alpha Go selects game moves, for example. This does require that the environment provides some way to enumerate or set bounds on the allowed actions.
Let the environment respond by not changing state and returning some small reward penalty for the time step when an impossible action is selected. This works in environments where it is not possible to tell in advance that an action was not possible, and there is no consequence other than lost time for attempting the impossible action*. This is usually less preferable to filtering the actions, because the agent must use resources to learn the disallowed actions in addition to the rest of the optimisation problem.
If you are thinking of ending an episode, perhaps with a penalty, then this has effectively turned your constrained environment into an unconstrained one where the agent can fail overall at the task. This might be OK in a training environment with safety features e.g. to stop a robot walking off a table, when in a production environment it may not have the same safety features. Efectively you would simulate just the catastrophic parts of the environment in your constrained training setup, so that the agent learns to avoid undesirable outcomes in an unconstrained environment.

* This is also quite a common scenario described in toy grid world problems, where the agent is allowed to bump into obstacles whilst solving a simple maze. However, those problems are to demonstrate learning algorithms, not necessarily best practice in designing an agent to solve a more complex problem.
Comment: If I understand correctly agent should be updated on the action he has taken. In servo motor case it is the whole signal. It doesn't matter that servo motor refused the whole signal. In real world environment may be constrained by physical laws and by undesirable outcomes (i.e. unmanned aircraft flying over a country which doesn't allow this). So in the first case agent is updated based on action he has taken - not the one which was realized by environment - while in the second  agent is penalized. Correct?
Comment: @TFbie: Yes. In your example case, you may need to adjust what you think of as the boundaries of the agent. The agent is *only* the decision-making component. The servo motor in your example is not part of the agent, even though it directly converts the agent's decision into movement. In the same way you might think of the "agent" of an animal being its nervous system, and not include its muscles or body.
Comment: Just need some clarification on 2. Autonomous aircraft wants to make a sharp turn of 45 degrees. Because of laws of physics it is possible to turn only 5 so the environment turns the aircraft by 5 and provides feedback via state that aircraft turned only by 5. Then the agent uses 5 (instead of 45) when updating his neural net (DDQN). Or should it use penalize reward? I see several messages: for a given state action 45 is not feasible while action 5 is. How to communicate this to value (DDQN), policy(DSPG), or both(A2C) networks?
Comment: @TFbie: The agent should be updated based on the output that was used. If you constrain *after* accepting the output (e.g. by servo motors refusing to use the whole signal), then that is a property of the environment, and there is no consequence to the agent. I would not even penalise in that scenario, just take the action as whatever the agent sends to the control box.


What is this plant with rosette leaf arrangement that grew beside my palm?

Question: What is the name of this plant with small leaves? Is it bad for my palm? Should I keep it or remove it? Or can I replant it into another pot?
Comment: As a side note, I think your palm is not a real palm but _Cycas revoluta_. Some call it a Sago palm, but it is not a real palm.
Comment: Leave it for now! Won't hurt your palm for a while.  Have you fertilized your palm lately?  At all?  Do you have a bird near this plant?  Is this indoors or out of doors?  Does the palm get moved sometimes?  What happened a month ago?  Is this soil potting soil or is it garden soil?  Fun little mystery.  Let's figure out what it is first, then if it is cool we'll help you to repot it or if not wanted how to rip  it out and put it in the compost bin.
Comment: Hi. Yes, I've used a fertilizer about a month ago. No, I don't have a bird. It's indoors. Yes, I leave it beside the kitchen window during the day and bring it to my room in the evening. I'm not sure what soil is this because I'm new to plants and bought it from flower shop about two months ago. Thank you for your advice. I'll leave it and see what will happen. :-)
Comment: Do the leaves smell on touching?
Comment: Wondering where the seed came from to be planted in your pot.  Plants do well together to a certain extent.  I rarely have just one plant in a pot.  As long as one is on top of the chemistry.  What kind of fertilizer?  A month ago?  Kind of sounds as if that was when a seed could have been added to your pot, huh?
Comment: @b.nota  Glad you brought that up...I agree.
Answer: I don't recognise it currently, but if there's any chance it's something you might want to keep, extract it carefully now, keeping the roots as intact as possible without damaging the roots of the palm, and pot it up separately. All the time its growing there, its stealing a tiny amount of  nutrients and water from the palm, but worse, the roots are getting larger and intertwining with the palm roots - if its something you want, you won't be able to extract it successfully later, and if its something you don't want, it'll be difficult to get all the roots out so it doesn't  grow again.
The likelihood is, it's something you don't want, but either way, it needs to come out of that pot now.


How to monitor a SAN server (via iSCSI)?

Question: What options do I have to monitor a SAN server that provides iSCSI storage to a network for availability and performance? (Windows options preferred)
Comment: That depends upon the system that your iSCSI server is running...
Comment: To clarify: I do not want to monitor the system itself (through SNMP et al.), I want to monitor the iSCSI "ports".
Answer: More information would help (the type of SAN server, specifically), but have you considered looking at SNMP traps with something like Nagios or Cacti?


Do you have to stop a programmable logic controller to update its logic?

Question: Must the operation of a PLC (programmable logic controller) be halted while its logic is being changed or can new logic be downloaded to it during runtime, without memory loss, giving a seamless transition from one operation cycle to other?
Answer: The function you are looking is called online change (e.g. Beckhoff Online Change), at least by some PLC Manufacturers. If you change a few blocks (in case of FBD) or a few contacts (in case of LAD) or a few lines of code (in case of IL or ST) you can do it online by most major PLC manufacturers. (Siemens, Beckhoff and the Codesys world has this functionality). Usually you can only change or add some blocks or owerwrite memory addresses. Adding new (large) program parts usually requires arestart. You can only use this functionality if you have the exact version of the PLC program which is running on the PLC.
The sequence is not exactly as you mentioned. You have to open the PLC Program in the IDE and go online (in monitoring mode) with the running PLC. Now you can change blocks and apply the changes. Diffrent PLCs from different manufacurers behave differently, but if you have to press "upload" (or dowload) to PLC button or similar in most cases it will loose data stored in volatile memory.
I would advise to always make a test first with that specific PLC and IDE (same version and firmware if possible) if memory is lost before attempting to change a live system (where critical data can be lost) this way!
Further example:
Siemens S7-200 Edit in Run Mode:
Comment: Work with GE RX3i PLCs; can confirm.
Answer: Definitely possible on +90% of modern PLC's (example, Allen-Bradley compactlogix permits but Allen-Bradley micrologix 1500 does not) with some limitations.  Normally just modifying existing logic is feasible, sometimes with a test mode, however modifying memory allocation or hardware configuration is locked until the plc is out of run state.
Normally online changes actually write the new module elsewhere in the controller memory and make the program jump over the old one.  Over time the program can become fragmented, which usually has a negligible impact but limits the amount of online changes that can be done in a controller without a 'clean up' or 'rebuild all', finally requiring a plc stop and full download.
Comment: "Normally online changes actually write the new module elsewhere in the controller memory and make the program jump over the old one." - thank you! That's exactly what I thought might happen but I couldn't find it written anywhere.
Comment: Do you have to do it (change the logic while running) using the programming software, or can it be done directly using commands to the PLC?
Comment: By 'Direct PLC commands', what do you mean, over RS-232 ASCII communication or something similar?  I would say there isn't a PLC out there with this feature.  YOu  'almost' always will need an IDE.
Comment: Maybe I should clarify; You do not always need to do an online change, you can always modify your code and do full downloads, but of course you'll always have to stop the PLC.  However, IDE's are almost always required for PLC programming.  There are only a few PLC's out there where there PLC project files are just ASCII text, however you'll still need an IDE to compile.


Auto-reverting only renderable PDF buffers

Question: I'm using pdf-view mode and the global auto-revert mode with LaTeX and
latexmk.  This works fine, except that, a couple of times during the
compilation, the PDF is in a useless state and the PDF window shows raw
data.  I was wondering whether it is possible to detect these useless,
unrenderable, states and dispense with the automatic reversion when they
obtain.  That is to say, whether it is possible to have PDF buffers
reverted only when the PDF is renderable.
Comment: What mode do you use for LaTeX? If you use AUCTeX, you can stop using auto-revert-mode in the PDF buffers, and let AUCTeX refresh the pdfview buffer when compilation is finished.
Comment: @Omar, I use AUCTeX and org babel.
Answer: A workaround is to do make file.pdf && \mv file.pdf view-file.pdf and keep view-file.pdf open (auto-reverting) in emacs. The mv operation is "instant" so you don't see any partial file.


Changing SRAM Apex brifters to flat bar - which is it possible to get hydraulic brake levers and trigger shifters to match?

Question: I've got a Tempest gravel bike from Planet X that came with drops and the Apex HRD groups. It works well but the whole drop handle bar positioning is a very literal pain -- I ended up with crucifying back pain while touring East Germany last summer.
I want to change to a Jones bar (like a riser bar but with greater choice of hand and body positions) yet can't find a simple way to transfer the brake and gear shifter. The only option seems to be to change the entire Apex drive train, which is very expensive.
Any advice?
Answer: The SRAM Apex line includes flat bar trigger shifters.
I don't think there are flat bar brake levers compatible with Apex hydraulic calipers, so you'd be looking at getting separate MTB levers and calipers. SRAM MTB and Road levers and calipers are not compatible with each other - see this answer.


How to hide the filename in drupal 7 files and add link to icon?

Question: I would like to know how to hide the filename in Drupal 7 files and add a link to an icon? The default style is awful I would like to change that.
I am looking for the simplest solution because I just know basic HTML and CSS.
Maybe I can use some module to do that? If somebody can explain me step by step how to do it will be great.
Answer: Ran across your question looking for the same answer... This is what I found. I'm at best a novice with Drupal, so I need easy solutions.
There is this module: https://www.drupal.org/project/file_field_icons
There are also some more options/notes here using CSS: How to change File field icons (without changing core)?
Comment: Thank you for your reply Alison, but I know how to change an icon, I would like to know where I can add code link to the icon and delete/hide the name of the file in CSS. My case is about the linking icon not changing icon. I hope that is clear now :-)


Need proper pace training for a 1.5 mile run on a treadmill

Question: What is the proper pace training for a 1.5 mile run on a treadmill? When I was training for the PAT for Correction Officer in the past, I remember there being a time/speed increase at small intervals. I would like to ultimately run it in 11-12 mins. Please note, that my beginning point will be from the standpoint of not running on a treadmill at all. I'm also looking for a weekly/monthly schedule to improve this distance.
Comment: I'd start with any of the Couch 2 5k programs, and then the Macmillan running site listed in an answer below is also an excellent resource.
Answer: I use this site to work out what pace I need to be running at to hit target times. You put in your current time for a certain distance, the target time you want to do for that distance then it tell you how fast you need to be running for specific distances to hit that target time. It also tells you what pace you should be running each type of run. Easy/tempo/speed work/long run etc.
For a short distance like 1.5 miles, I would recommend some short, sharp intervals (say, 5 or 6 reps of 0.25k hard, 0.25k/0.5k recovery) then some longer slow runs, say 3 to 5 miles. As the weeks progress then increase the speed and/or quantity of interval reps. On a treadmill you have the advantage of being able to pace and time your training very accurately. I wouldn't neglect the roads though. I find treadmill running very boring so if I were you I'd do my longer runs on the road. Each to their own though. Good luck
Answer: The 1.5 mile run is also used in the U.S. Navy PT testing. Any time lower than 13:30 is passing, so I think 11 - 12 minutes isn't a bad target (assuming the qualifying is comparable).
You can use this to calculate a good average treadmill pace for 12 minutes which is 8 min/mile which is a speed setting of 7.5.
Ideally you're able to hit 11:00, which would be a pace of 7:20 using the speed setting 8.2 to give you some breathing room in your examination.


Communcations and the MDV in "The Martian"

Question: In the book "The Martian", communication is lost with Earth after the Mars Ascent Vehicle leaves. It seems to me the Mars Descent Vehicle (MDV), which they landed in, would have had some kind of a communication system. I don't recall hearing anything about the MDV. Why couldn't the communications be used from the MDV, or why wasn't there any communications included?
Comment: Which ascent stage are we describing? The one where the supply rocket explodes? Watney's ascent into orbit to be picked up?
Comment: Decent, not ascent. Decent is the stage where they go from the Hermes to the surface of Mars.
Comment: Ah. OK, so you're saying that communications is lost with the MAV, but that the MDV that they landed in should have had communications.
Comment: I edited as if you were referring to the MAV and MDV. Please fix it if I incorrectly guessed.
Answer: To quote from the first chapter:

The MDV is basically a big can with some light thrusters and parachutes attached. Its sole purpose is to get six humans from Mars orbit to the surface without killing any of them.

The concept behind the MDV was just to get the crew to the surface. Once there, they would be able to use the MAV to perform communications with the Hermes. It's not outright stated in the book, but I suspect that it was trimmed down as far as possible to save weight and space since there was already a functional MAV on the surface (and the book notes that, if the MAV were not fully functional, they would have just gone home without landing) and probably because communication would be difficult on the descent due to interference of atmosphere, etc. The descent vehicle wasn't going to have to dock with an orbiting spaceship, and no one on Earth would be able to help them if something went wrong, so they eschewed communications.
Additionally, even if it had carried communications gear, it might not have survived. A relevant excerpt from the book:

The MDV is on its side and there's a breach in the hull. Looks like the storm ripped the cowling off the reserve chute (which we didn't have to use on landing). Once the chute was exposed, it dragged the MDV all over the place, smashing it against every rock in the area.

It's worth noting that, if you watched the movie, you'd be even more lost because they barely mentioned the MDV at all.
Comment: That's what I get for not re-reading the book before asking a question... Thanks!
Answer:
It seems to me the descent stage would have had some kind of a communication system.

Why?
While the astronauts are on the surface, they communicate using the MAV. Why put a second, redundant comm system in the MDV which remains on the surface after they leave?
Shipping material to Mars is astronomically expensive (so to speak). The cost is estimated at US$45,000 per kilogram.
The second comm system would be useful only if one or more astronauts were inadvertently left behind. Presumably, NASA deemed this to be too unlikely to justify the extra costs involved.
Comment: To me, I'd put a communication system on the MDV, because if it landed off course, they'd still have a way to talk with Earth. But maybe that's just me...
Comment: @PearsonArtPhoto - Especially important if they aren't quite sure where they are in relation to the MAV and the supplies that are waiting for them.
Answer: I think its probable that the MDV did have a communications system, but there is something that is being overlooked here - the MDV communications system does not have to be a high power one, as the only time it was on Mars and manned was when the Hermes was in orbit, meaning that it could use the Hermes communications system to talk to Earth and thus only needed a low power communications system, which saves weight and power.
Once it was down and safe, the crew could use the MAV communications system, which was required to be high power as it needed to be monitored from Earth prior to the mission start.
In short, there is no requirement for the MDV to act in an isolated capacity, so it uses the support systems that are built for it to use.
Comment: You would think they could build it such that it could talk with the satellites in Mars orbit, which there were obviously many, but...
Comment: @PearsonArtPhoto only if there is a need to communicate with those satellites, and I can't think of any - none of those mentioned in the book or  the film are communications satellites, so why would the MDV need to talk to them?
Comment: Not talk to them, talk using them. It's done by every landing on Mars in recent memory, including Pathfinder, Phoenix, Spirit/Opportunity, and even Curiosity, all of them can communicate using Mars orbiting satellites as relays.
Comment: @PearsonArtPhoto as I said in my previous comment - "none of those mentioned in the book or the film are communications satellites".  The probes, rovers and orbiters that you mention all use relay satellites specifically designed to act as such.  We have no evidence that any such satellites are in orbit in the book or film.  You cant just turn any old satellite into a comms relay, there are numerous hardware and software issues to resolve first.
Comment: True enough, but I suppose that's another question entirely. Hmmm...


Can anybody recommend some organic farms for volunteering on the Canary Islands?

Question: The coming two years I will combine studying (permaculture) and backpacking through Europe while volunteering on organic farms. Can anyone recommend some farms on La Palma, one of the Canary Islands?
Answer: A quick google search reveals a number of results for wwoof la palma. These include blog stories of people who have actually volunteered, as well as WWOOF farms in La Palma (here is a random result). For more information on the topic I would suggest you look on the WWOOF España website.


How to do a proper way to copy URL->bstrVal to a global variable?

Question: I have this function inside my program:
void CBar::NavigateComplete2(IDispatch *pDisp, VARIANT *URL)
  {

try {
    UpdateBar(UpdateNavigateComplete);
} catch (...) {
    ASSERT(0);
}
  }

I need to have the URL value from URL->bstrVal from this function and to copy it to a global variable so that my other function can easily refer to it.
What is the appropriate way to do this? since my current method destroys the stability of my program..it crash all the time.
Comment: You may want to explain you current architecture a little better. Using global variables only rarely is a good solution.
Answer: I'm not sure I understand the question or the motivation. If all you want to do is, as described in the question, copy the value of URL->bstrVal then the simplest way to to use a wrapper BSTR class for the global.
namespace { // keep global private to .cpp file
    CComBSTR globalURL;
}

void CBar::NavigateComplete2(IDispatch *pDisp, VARIANT *URL)
{
    if (URL != NULL && URL->vt == VT_BSTR)
        globalURL = URL->bstrVal;

Otherwise you should use a raw BSTR and copy it with SysAllocString (and don't forget to SysFreeString it when you're done with the global.
If you don't copy the string (and only copy the pointer) the VARIANT's owner will destroy it giving you a global with a dangling pointer.
Comment: Can i assign the 'global' to a std::wstring currentUrl  ? So that my 'currentUrl' will have the value from 'global'.
Comment: @karikari, yes since a `BSTR` is only a `wchar_t*` (with different semantics) you can copy it into a `std::wstring` since the `wstring` will copy the string and not just the pointer.
Answer: Use SysAllocString(URL->bstrVal) to create a copy off the BSTRVAL. you will have to free it when you're done with it using SysFreeString().
Though I have to agree with @Space_C0wb0y that using global varsity for this is error prone. Unless UpdateBar does something asynchronously, you should just pass URL->bstrVal as a parameter to it. And even if UpdateBar schedules asynchronous work, it should still encapsulate creating the BSTR copy and associating it with the asynchronous work, to avoid race between the background code and another NavigateComplete event both trying to access the global var. (Or you have to lock the access to it, which pretty much negates the asynchronous idea, unless you know how to optimize your locks really well)


Uniform convergence of a sequence of polynomials

Question: If a sequence of polynomials converge uniformly in $\mathbb{R}$ to $f$, is $f$ necessarily a polynomial?
Comment: Your question is subtle as the domain of convergence. A taylor series of $\sin(x)$, $\cos(x)$ and $e^x$, for exemple, converge  uniformly in compact intervals of $\mathbb{R}$ and pontise in all $\mathbb{R}$. That is, fixed in any compact interval $[a,b]$ in $\mathbb{R}$ the the series converges uniformly.
Answer:
Claim: If $\{P_n\}$ is a sequence of polynomials which converges to $0$ uniformly on an unbounded subset $S$ of the real line, then $P_n$ is constant for $n$ large enough.

Indeed, $\sup_{x\in S}|P_n(x)|<1$ for $n$ large enough, hence $P_n$ is bounded on $S$. Fix such a $n$.  Let $x_k\in S$, $|x_k|\to +\infty$. If $P_n$ is of degree $d$, then $1>|P_n(x_k)|\geqslant |c_nx_k^d|$, where $2c_n$ is the leading term. It enforces $d=0$.
Now, we apply the preceding result to $P_{n+1}-P_n$.
Answer: Yes.
Any two functions $f,g$ with $\sup|f(x)-g(x)|<\infty$ must grow at the same rate.
A degree $d$ polynomial $g$ grows at rate $O(|x|^d)$.
So if polynomials $g_1,g_2,\dots$ converge uniformly to $f$ then all of $f,g_1,g_2,\dots$ grow at rate $O(|x|^d)$ for some integer $d$, and thus $g_1,g_2,\dots$ must have degree $d$. By Lagrange interpolation, for each $j$ the $j$'th coefficient of $g_k$ converges as $k\to\infty$ to some $c_j$, and $f$ is the polynomial with these limits $c_j$ as coefficients.
Comment: MacQuillan, there is any reference book for it result?


Tone Clusters Explained?

Question: Can someone elaborate on tone-clusters and what exactly makes a set of notes be considered a tone-cluster? How  are they similar and how do they differ from chords? To the users that are thinking of going and pasting a link to Wikipedia or flagging my question because they feel like I haven't put forth any effort "researching" the topic please don't comment at all! I have been reading and watching videos for the past week but can fully grasp the topic.
Comment: You don't need to make the comment about Wikipedia links. Such answers will get downvoted by the forum. 2/3 of your question text can be removed.
Comment: Sorry, I can't resist - https://www.youtube.com/watch?v=-J9O5Yj3-I4 ;)
Answer: Your confusion is understandable; there is certainly a gray area between tone clusters and extended chords where a group of notes could be viewed as both.
Since you've been looking for definitions already, I'll try to supply one of my own. To me, a tone cluster is a collection of three or more pitches that includes at least two consecutive half-step intervals and never has more than a second between consecutive pitches.
Consecutive half steps are relatively rare in tonal music outside a completely chromatic context. As such, something with two or more consecutive half steps would immediately signify a tone cluster to me.
Furthermore, the appearance of three simultaneous, consecutive pitches separated by second (major or minor) is pretty rare in tonal music. Someone could theoretically claim that it's, say, a ninth chord in third inversion (you would thus have the seventh, root, ninth, and third all in a row), but I think that's really stretching the limits of functional tonality.
Answer: Tone clusters are chords depending how you define chords. A tone cluster is just a chord made up of mostly seconds. Whether a chord is a tone cluster, a chord by seconds (a chord made by stacking major or minor seconds), or an inverted ninth chord is all dependent on context and can arguably be more than one of those depending what's going on around it.
Tone clusters also do not need consecutive minor seconds. Some of the most useful clusters are the first five notes of any church mode. That being said tone clusters are usually divided into two categories: diatonic (meaning from the notes of major or minor scales or one of their modes) or chromatic (meaning all the notes).
According to Vincent Persichetti the top and bottom notes of clusters are the most important notes and form two melodies. Tone clusters also appear in uncontroversially tonal music. The first song of Kindertotenlieder by Mahler contains a three note cluster. After finishing a traditional tonal theory text I would highly recommend Vincent Persichetti's 20th Century Harmony Creative Aspects and Practices. Henry Cowell's book might also be helpful. Cowell and Charles Ives would have been among the first composers to use tone clusters.
Answer: Just to add a bit to @Richard's answer.
In common tonal harmony you often have intervals of harmonic seconds from things like inverted seventh chords or types of suspensions. For example V2/4 moving to I6, or a suspension like C F G resolving to C E G. But, notice how the seconds resolve to thirds. This provides tonal clarity so that the seconds sound like a dissonant, but harmonic interval.
You could look at seconds and clusters of seconds and ask if they are somehow resolving, being treated as dissonant chords. If they move freely, without resolving, then a cluster label starts to make more sense.
An example you might look into where the boundaries are blurred is D. Scarlatti. Ralph Kirkpatrick has a book about Scarlatti and devoted a section to what he calls harmonic superposition where elements like pedals, suspensions, and superimposed chords create cluster-like harmonies.
Answer: Tone cluster, note cluster, pitch cluster
To add further to answers... and not a conclusive answer...
... the term tone cluster occurs in phonology (seems to be about different vowel sounds in a multi-syllabic words. e.g. to—ma—to  has a tone cluster, ga—ga doesn't ). Maybe the term is borrowed from phonology.
It occurs notably in piano music and I'd imagine orchestral music followed.
Cluster is a collective noun: cluster of grapes, cluster of diamonds, a cluster of stars.
Note you'd expect to find more than three of these things above.
Cluster is like "around something", so I guess something already exists and other things "gather around it".
Tone cluster: does tone here mean:

A (whole or half)toneis aninterval or Atoneis anote?

I.e. are we thinking:

Aclusteroftone intervals?
or
Aclusterofnotes?

To be clear here the language is confusing. To be certain, do the collocations "pitch cluster" and "note cluster" exist in the same context?
A search for "pitch cluster", shows:
Scales, Modes, and Chord/Cluster Concepts for 20th-Century Techniques Exam
[from Western Michigan University].
It states:

[e.g. A quintal pitch cluster etc..]
Elaine Gould  in her Behind Bars consistently uses "note cluster" not "tone cluster" (and uses if freely between determinate and indeterminate pitch); so I would say that there is a school of thought that says that "note cluster" and "tone cluster" are synonymous, but I choose to disagree and consider that they have separate but related meanings.
I will be brave and give some definition of what I think the terms could mean:

Note cluster: has indeterminate pitch, can't say it's exactly c c# d d#, but give some range or location of the cluster.

Pitch cluster: has determinate pitch, can give exact note values e.g. c c# d d#.

Tone cluster:

Is it a general term that it includes the above two?
Or has the tone cluster become to mean a cluster of intervals that mainly include a tone or semi-tone (because of the tone = note vs tone = interval confusion)?

But there's no question that tone cluster does mean a group of notes between a semitone and tone, probably with at least a semitone in the group.

Tone Clusters Explained?


A computation problem of algebraic connectivity of a tree

Question: The algebraic connectivity of a graph G is the second-smallest eigenvalue of the Laplacian matrix of G.  This eigenvalue is greater than 0 if and only if G is a connected graph. This is a corollary to the fact that the number of times 0 appears as an eigenvalue in the Laplacian is the number of connected components in the graph. It is known that the algebraic connectivity of a n-vertex path P_n is 2(1-cos(\pi/n)). Now, my question is what is the algebraic connectivity of a tree which is formed by connecting an isolated vertex to the second vertex of a path P_{n-1} ? Or, can you find its approximate value ?
Answer: Firstly, your tree is just a Coxeter/Dynkin diagram of type $D$, so you may want to search MathSciNet with this in mind as your question might have been answered exactly at some point.
If you are happy enough with some bounds, it's easy to obtain $$\frac{4}{n(n-2)}\leq \lambda_2(P)\leq \frac{12(n+2)}{n(n^2-1)},$$ so that $\lambda_2(P)=\Theta\left(\frac{1}{n(n-1)}\right).$ (See Bojan Mohar's algebraic connectivity survey, Equations 6.10 and 7.1.) Perhaps a more in-depth reading of that paper would get you a better answer.
Comment: Thanks for your answer. Actually, it helps. Now, I wonder that can we enhance the lower bound to 10/n(n−2)≤λ_2.


Do transfering steam games to another computer reset that game's save data?

Question: I have a steam account and I want to transfer some games to my laptop. I was just wondering if I transfer the games to my laptop, would it reset the data?
Answer: If you have Steam Cloud synchronization enabled, any applicable games will back up their saves to the cloud so you can access them from whatever device you install the game on.
To make sure this option is turned on:

Open Steam
In the top right, click Steam, then click Settings.
Click Cloud on the left hand list.
Make sure Enable Steam Cloud synchronization for applications which support it is checked.

You should be good to go after this! Note that some games might not be compatible with Steam's cloud support, but most modern games should be.
Comment: It's worth asking permission to do this if you're playing on someone else's account, they may want their saves backed up.
Answer: Some games use the Steam cloud sync as Kaizerwolf wrote, some don't
In addition enabling Steam Cloud Sync, you could potentially copy over most of them yourself.
A lot of games store their saves under
<code>C:\Users\<Username>\Documents\My Games
</code>
If you copy this entire directory over (or individually for saves that you're missing), you'll be able to ensure most of your saves are moved across.
Comment: Game save location are entirely up to the developer.  I've seen enough in AppData also.
Comment: Very true, I had meant to add this as well!
Comment: @Nelson - True, but it comes down to semantics. 'Appdata' is meant for any configuration files etc that your program needs. 'Documents' is meant for any user-created files. Technically speaking, Saves are user-created files, but I can see how some devs would do otherwise (for example, games where you don't implicitly save, or the 'real' save is not meant to be edited or copied, especially online profiles and the such)
Comment: There is no guaranteed rule to find save files.  Just Google the specific game.


Derivative of $f(x)=\int^{x^2}_0 \frac{\sin(t)}{t}dt$

Question:
Let $f(x)=\int^{x^2}_0 \frac{\sin(t)}{t}dt$. Find $f'(x)$.

Is that integral undefined/nonexistant, or just impossible to integrate?
In this case does $f'(x)$ exist and can be solved normally?
Is it correct that $f'(x)=\frac{\sin(x^2)}{x^2}2x$?
Comment: Fundamental theorem of calculus.
Comment: $\int_0^{x^2} \frac{\sin(t)}{t}\,dt$ is integrable for all $x$.
Comment: for all x? Does that mean that t is never 0 for any x?
Answer: Notice that if we call $$g(u) = \int^{u}_0 \frac{sin(t)}{t}dt$$ then we know that $g'(u)=\frac{\sin u}{u}$
But $f(x)=g(x^2)$. Then you apply the chain rule to get your result.

Is that integral undefined/nonexistant

The integral is perfectly defined. It just cannot be expressed in closed form, in terms of elementary functions. But that does not matter at all.
Answer: By the fundamental theorem of calculus, if $F$ is an antiderivative of $f$, then
$$\int_{\ell(x)}^{u(x)}f(t)\text{ d}t = F(u(x)) - F(\ell(x))\text{.}$$
It follows that, after applying the chain rule,
$$\dfrac{\text{d}}{\text{d}x}\int_{\ell(x)}^{u(x)}f(t)\text{ d}t = F^{\prime}(u(x))u^{\prime}(x) - F^{\prime}(\ell(x))\ell^{\prime}(x)\text{.}$$
but since $F$ is an antiderivative of $f$, it follows that $F^{\prime} = f$, hence
$$\dfrac{\text{d}}{\text{d}x}\int_{\ell(x)}^{u(x)}f(t)\text{ d}t = f(u(x))u^{\prime}(x) - f(\ell(x))\ell^{\prime}(x)\text{.}$$
This rule obviously requires many conditions (notice, in this case, $f(\ell(x))$ is undefined), so we use a slight modification here: observe that if $F$ is an antiderivative of $\dfrac{\sin(x)}{x}$, $F(0)$ is obviously a constant; then,
$$\dfrac{\text{d}}{\text{d}x}\int_{0}^{x^2}\underbrace{\dfrac{\sin(t)}{t}}_{f(t)}\text{ d}t = \underbrace{\dfrac{\sin(x^2)}{x^2}}_{f(x^2)}\underbrace{(2x)}_{\text{deriv. of }x^2} - \dfrac{\text{d}}{\text{d}x}[F(0)] = \dfrac{2\sin(x^2)}{x}\text{.}$$
Answer: For a simpler and fundamental question, do you know what is $g'(x)$ when
$$
g(x)=\int^{x}_0 \frac{\sin(t)}{t}\ dt?
$$
In general, do you know what is $g'(x)$
$$
g(x)=\int_0^xh(t)\ dt?\tag{*}
$$
Once you know what is $g'(x)$ for (*), can you find by chain rule what is the derivative of $f(x)=g(x^2)$?
Answer: The answer provided by @Clarinetist is the most efficient way to solve this problem. Here is another way.
Using the series definition of the sine function we have
\begin{equation}
\sin(z) = \sum\limits_{n=1}^{\infty} \frac{(-1)^{n-1}}{(2n-1)!} x^{2n-1}
\end{equation}
and
\begin{align}
f(x) &= \int\limits_{0}^{x^{2}} \frac{\sin(z)}{z} \mathrm{d}z \\
&= \sum\limits_{n=1}^{\infty} \frac{(-1)^{n-1}}{(2n-1)!} \int\limits_{0}^{x^{2}} z^{2n-2} \mathrm{d}z
\end{align}
The integral on the right hand side above is
\begin{equation}
\int\limits_{0}^{x^{2}} z^{2n-2} \mathrm{d}z = \frac{1}{2n-1} (x^{2})^{2n-1}
\end{equation}
and now we have
\begin{equation}
f(x) = \sum\limits_{n=1}^{\infty} \frac{(-1)^{n-1}}{(2n-1)!(2n-1)} (x^{2})^{2n-1}
\end{equation}
Let
\begin{equation}
g(x) = (x^{2})^{2n-1}
\end{equation}
then
\begin{equation}
\frac{\mathrm{d}g}{\mathrm{d}x} = \frac{2}{x}(2n-1)(x^{2})^{2n-1}
\end{equation}
Now we have
\begin{align}
\frac{\mathrm{d}f}{\mathrm{d}x} &= \sum\limits_{n=1}^{\infty} \frac{(-1)^{n-1}}{(2n-1)!(2n-1)} \frac{\mathrm{d}g}{\mathrm{d}x} \\
&= \frac{2}{x} \sum\limits_{n=1}^{\infty} \frac{(-1)^{n-1}}{(2n-1)!} (x^{2})^{2n-1} \\
&= \frac{2}{x} \sin(x^{2})
\end{align}


My Samsung Monitor keeps powering off... How can I fix this?

Question: The PC is just fine, been runing okay for a few years. The monitor however, has issues. It is an odd issue that might be a sign of future broken monitor. For no apparent reason the monitor will just power off, so I have to manually turn it back on and it is fine. Is there something I can do to fix this besides the warranty? I already had it repair and I don't feel like shiping it again. I kind of want to just open it up, learn how to solder and well, you know the saying: If you want something done right then do it yourself.
Comment: I'm voting to close this question as off-topic because 1) the problem is 5 yrs old and has surely been overtaken by events, so there is no longer something to solve. 2) it cannot be solved based on the information available, and reasonable guesses have been unsuccessful and exhausted. 3) the evidence is that this is a unique problem specific to the OP's monitor. 4) hands-on repair has been unsuccessful so remote guesses at SU will not solve it.
Comment: None of these are acceptable answers, then again Samsung monitors aren't either.
Answer: Does it really power off or go to standby?

If it's standby then it could indicate a problem with the display signal, either from the computer or in the cable itself.
if it actually switches off entirely then it is most likely a problem with the monitor's power supply.

If it's a TFT with an external power supply, then you could try to replace the power supply (but be careful to get one with a matching output!).
If it's a CRT, or a TFT with internal power supply, then it needs to be repaired or replaced.

Given the cost of new TFT monitors, I'd consider replacing the monitor.
Comment: Power off compleletly... I should have made this clear in the original question....
Comment: @Zombies: It sounds like a malfunction of the power supply, especially if it happens more and more often over the course of some months. Otherwise it could be a malfunction in the on/off circuitry. In either case, I'd replace the monitor (use the warranty if possible).
Answer: The reasons I know, why monitors power off are:

Cable problems: The green color usually has the sync frequency and if that is not arriving well, it may let some part of the monitor think it is out of sync. Check if all cable parts are OK by plugging them out and in again.
Heat: It may be overheated and thus turns off. Especially the power supply section has such features. Reason could be dust (remove power cord and blow the dust out). If the place you use it has not enough air circulation (or sun shining on the monitor back), that could be the problem.
Dust: Overheat in one of the areas due to not enough air circulation. Removing the dust can help
Age Errors: Some Capacitors get bad over years and before finally dying the security feature is shutting it off. This would be a reason to be careful keeping it running
Answer: Your capacitors could be bad, try powering on the monitor and turn the brightness all the way down to the lowest. If it stays on longer than it did before shutting down automatically it is the capacitors that need to be replaced. Since you say you have no problem opening it up, check the capacitors (be careful with this as these can give you a nice/nasty jolt as they store electrical charge), and probably look on Google and Youtube to see examples of bad capacitors, and while you're at it there are great tutorials on there on how to solder and replace that sort of stuff.
Answer: I have the same problem. What I found is that, inside the monitor -in the circuit board -you'll be able to see some capacitors,
 Take a tester and place it over the metal part of the capacitors this will Tell you whether they're good or damaged
And next thing try it over one of the resistors having multiple color code if you observe it
You see that  the monitor ons when the light in the tester ons. This says it's a problem in the board
Comment: Since no one else is saying it... Do not do this. Unless you are an electronics professional with proper safeguards, do NOT open a CRT monitor. You will likely be zapped, in a big way, if you are not careful
Comment: And where does one buy this magic tester that you just place over components and it tells you whether they are damaged?


How can I use the component CD4538 or a 555 timer on Multisim?

Question: How can I use the component CD4538 or a 555 timer on Multisim for a delay of 1 second ? I want both of the nor gates to be 1  for roughly  1 second when the output of the op-amps is  either 01 or 10.
Answer: So The Op amps are acting as two comparators with the same reference voltage feeding into an RS flip flop and an RS flip flop is undefined when both V1 (the top op amp's (+) input) and v2 (the boittom op amp input's (+) input) are belopw the reference voltage and there is no change in the RS flip flop when they are both above the reference voltage so you are getting a functioning circuit only if the inputs of V2 and v1 are on either below or above the vref respectively or the opposite. Basically the circuit functions only when the op amp's output (1,0) or (0,1). SINCE TO OF THE nor INPUTS are tied and the RS flip flop can only output Output_1=0/Output_2=1 or Output_1=1/Output_2=0 then if you want one of the nor gates to be one for only one second and then revert to a state of zero then you would have the tied input to the NOR gates connected to your Astable 555 timers output that is actually inverted so that the nor gates are always receiving a high signal and the delay is caused by a low signal from the 555 timer.
You need to trigger the 55 timer and since The RS Flip Flop is undefined and unchanging unless it's inputs are different then I would have each op-amps output go to a unique 555 timer in monostablestable operation each (so two times) such that when one op amp outputs a high signal it then triggers the 555 timer to output a high signal and you choose the resistor between the Vcc pin and the Discharge pin (which is tied to the threshold pin and the capacitor to ground) and you choose the capacitor value so that the output is high only for one second. I would then tie both of the 555 timer outputs into your extra 4011s NAND gate and use is as an inverter so that it retains a high (1) signal until either 555 timer outputs a 1 which is inverted and then that allows one of the NOR gates to receive two low (0) inputs which is what you want.
Here is how the Mono-Stable 555 Timer is designs and it's delay time is calculated as T=1.1*R1*C1 and a 1 second delay could be made using various combinations of resistors and capacitors, but the capacitors should be un-polarized because connecting the power incorrectrly could not only destroy your 555 timer but will certainly explode your electrolytic capacitor:
Here is the Monostable easily explained in picture format from Electronics-Tutorials.com

From Electronics-Tutorials.com's excellent website Or think of an RS Flip-Flop like this where the enable pin is the delay from the 555 timer in Mono-stable mode. Since you have NAND gates you would need Inverters before the AND gates.

Here is my circuit with Mono-stable 555 Timers using 10 Mega-OHM resistors as R1 and .1uF Timing capacitors to get T=1.1*R1*C1=1-second


At times I am unable to see the name of the person I am tagging but then I just type his name. Is he/she actually getting tagged?

Question: I had this doubt from the start. When I try to tag some people in my comment , their name is suggested to me on the top left. But occasionally this is not the case, they dont get suggested. And in that situation I just type the first name , do they get notified if I do that ?
Answer: If you comment on a question the OP is always automatically notified and the OP's name is NOT added as a link in your comment.
The same applies if you add a comment to an answer and attempt to notify the answer's writer.
If you comment on a question or answer and cite a person who is involved in the conversation who is NOT the person who wrote the question or answer then the name should "autocomplete".
You can usually check if a notification has occurred by clicking on the cited name (or shift-click for new tab in Windows). This should take you to the profile of the person converned. If this works they have been notified.
Adding comments from others:
You can only 'ping' one person in a comment. (Memory says that this needs to be at the start of the comment).
It is not possible to 'ping' users who are not already active in the comment thread immediately associated with the post being commented on. [eg in commenting on an answer you cannot ping a person who has commented on the question (and vice versa)].
Comment: What about the situation where you try to '@' a user who has not yet been involved in the question? ( I think I already know the answer to this, but adding it would complete your answer).
Comment: Is it possible to tag a person not in conversation ? I though that was impossible. @brhans
Comment: No its not possible to ping persons who are not in that conversation.
Comment: ... and you can only ping one user in a comment.


Proving xor operation

Question: I wrote out Xor operation as $(\lnot x \land y) \lor (x \land \lnot y)$ but don't know how to simplify from here. I don't know if De Morgan's laws will just make things more complicated, and I don't know how to factor anything out when there are NOTS on everything.
Comment: There really isn't any way to "simplifiy" this expression. What do you want to accomplish?
Comment: How do I know when I am done simplifying?
Comment: Experience, like most other things. :) Keep practicing!
Comment: If you look up Karnaugh maps you'll see that, at least in terms of AND and OR operations, there are no adjacencies to be simplified. http://fourier.eng.hmc.edu/e85_old/homework/xor_xnor_4.gif
Answer: What would a simplification look like to you? There aren't much simpler ways to write the exclusive disjunction in terms of $\neg, \land, \lor$. You could write $\neg(x \leftrightarrow y)$, but it's not much cleaner, as usually $x \leftrightarrow y$ is just an abbreviation for $(x \to y) \land (y \to x)$.
(Personally, I find $(x \lor y) \land \neg (x \land y)$ the clearest -- that's how I would describe the exclusive disjunction in words.)
Answer: You can't simplify this expression with boolean algebra as xor is it's own logical connective often denoted with $\oplus$. Thus what you wrote down could be written $x\oplus y$

Proving xor operation


In Recommendation systems, Does we need to build each model for each product if we are using Logistic regression?

Question: I am reading this paper wide and deep learning recommedation system paper and haven't understood one thing.
To serve the latency, they actually first get the 100 best apps according to user query and rank them according to the probability score.
Does this mean that while buidling the model we have to build individual model for each app?
Are there any other Deep learning frameworks similar to this ?
Answer: I can only guess that since it is binary classifier based recommender model, it predicts whether a product is recommendable to a user or not with a probability score which can be set to a threshold.


mixpanel not working in 2011 samsung smart tv but working fine in 2013

Question: mixpanel is not working in 2011 smart TV I put Script tag in head that same code
working fine in 2013 TV
Is there any problem in 2011 to add Script tag in body??
Answer: Opps! finally found solution script tag copied from mixpanel has one url in it format is like ("//cdn.something.com") so that we need to replace with("http://cdn.something.com") adding http: will work coz in 2011 mappel engine TV not append it automatically but in 2012 onwards TV append it automatically
Answer: Samsung 2013 devices uses WebKit browser engine, Samsung 2011 uses Maple browser engine.
Check that Mixpanel does not use features unsupported in Maple browser.


Are there any unlockables which require classic mode?

Question: I got Fire Emblem Awakening and I'm considering playing on Casual mode because I don't want to restart a chapter each time a character dies, but I don't want to miss any unlockable either. Are there characters or gaiden maps which are only on Classic mode?
Answer: No, you will only miss out on one thing by playing on casual mode. If you beat the game while playing casual on the Lunatic difficulty, the NG+ for Lunatic will be casual only. This is different from beating it on classic mode which unlocks both. This is also different from the other two difficulties where beating it in casual unlocks both classic and casual NG+.
Other than that the games are identical except in casual mode permanents deaths are turned off and you can save in battle, you're allotted two slots for this. There are no extra boards/characters/etc. that can only be obtained by playing on classic.
Comment: This barely addresses the question at all.  We already have a question about character recruiting; this is about things *besides* characters.
Comment: @fbueckert He asked if he would miss anything by playing on casual. I answered the question. You don't miss anything, the game is identical except the loss of characters/save during battles.
Comment: It's hard to prove a negative.  Do you have a source or anything else you can link to?


x11 forwarding fails with some apps opening in remote display and some in local display

Question: I have mac with xquartz as a remote client for X11 on my latest ubuntu linux. I am able to connect with ssh and start applications like xclock remotely. With most of the apps like gnome-calculator the app opens in ubuntu local display instead of remote display as intended. SSH configuration should be fine and to my best understanding this has something to do with display parameter in x11 forwarding. Any help will be appreciated.
Answer: I had the same problem with ssh -X user@remote. Some applications are showing on local side (e.g. xclock), and some on the remote side (e.g. gedit). I believe this is a problem is with all GTK/Gnome applications. It only happened when a remote display was running (I was using NoMachine at the same time)
I found a workaround: unset XDG_RUNTIME_DIR environment variable.
ssh -X -C user@remote
unset XDG_RUNTIME_DIR
gnome-calculator

The same effect is by using su - $USER. The - is important here
ssh -X -C user@remote
su - $USER
gnome-calculator

Now application shows on local display always, even when a remote desktop is opened.
Comment: It isn't related to DISPLAY or XAUTHORITY, but somehow with XDG_RUNTIME_DIR
Comment: thanks, it works, for some extra oddity some apps like gedit and gnome-calculator, while gnome-terminal keeps showing on the other side. Luckily enough there are plenty of other non-gnome terminal options .
Comment: In my case, I had to unset `GDK_BACKEND` as well as `XDG_RUNTIME_DIR` - just doing `XDG_RUNTIME_DIR` resulted in `Gtk-WARNING **: 16:50:48.916: cannot open display: localhost:10.0`
Comment: This fixed my problem where some applications (like gedit or virt-manager) would not display a window, while some others like xterm or the clock or firefox worked fine. Any idea what causes this? Bundling it into a script like "killall application; unset XDG_RUNTIME_DIR; application;" works but would rather know the root cause and if there's a cleaner fix...
Answer: Apparently sudo app_name helped. For some reason without sudo the application starts as local instead of remote display. Apparently same user can't be logged in from console same time as remote X connection starts application or it will launch the application in console.
Comment: Fixed my issue where i could run all apps except gnome ones
Answer: I've read the three posts here, and I think there is a little misunderstanding of the -X option.
The intention of the -X option of the ssh client is to forward a remote display to a local one thus you can run remote resources and view them locally... for more information read man ssh.
When you are using sudo or su these commands just break the normal work of the X-forwarding, thus the GUI applications are running on the remote display. Something more when you are using sudo some-gui-app it breaks the ownership of the files in your $HOME directory, which could cause some issues - the fix is: sudo chown -R $USER:USER $HOME, and next time use sudo -i ... or sudo -H ....
In order to run a GUI application on the remote display from within ssh session, you need to export the values $DISPLAY and $XAUTHORIT (and in some cases some other variables) of the desktop session where you want to run the application - normally this is the active session, where the user is logged-in and the session is displayed on the physical screen.
Time ago, I've developed a bash script that is able to detect the active desktop session and export all its variables from within the current session (ssh|cron|tty|etc.). Initially I needed to solve similar task for crontab, this is the reason of the original name of the script cron-gui-launcher, but it has a wider field of usage. The script, all necessary explanations, and couple of example of usage are available within my GitHub's repository: https://github.com/pa4080/cron-gui-launcher.
Here is a video demonstration how the script works: Ubuntu: CRON GUI Launcher Demo - SSH.
Comment: I noticed that unsetting environment variable XDG_RUNTIME_DIR fixes the issue (a workaround?). Do you know why it works?
Comment: the interesting observation  is that IF an X app  instance is running on the remote machine your are ssh ing into is diverting the DISPLAY to that machine.
so even if you start it remotely with the DISPLAY set to X11 tunnel its not working out of the box.
the easy workaround is to stop the instance on the remote. but thats not always an option


PS3 membership accessing ps4 content

Question: If I have a PSmembership using a PS3....do I need a new membership for PS4?
Can I log in to the PSnetwork with my member info from PS3 and access PS4 content?
Comment: I'm assuming with "PS membership" you're talking about PS Plus?
Answer: Yes you can access use one account on a PS3 and PS4

One membership for PS4, PS3 and PS Vita

while the link talks about Playstation Plus, all it is is an upgrade of a regular Playstation Network account which can be accessed in the same way. i can vouch for that from personal experience as i own all 3 consoles and i only have a normal PSN Account (No PS+)
On the PS3/4/Vita you can also view trophies collected on the other consoles and since you can't view this data in the offline mode on the PS3 or Vita and you need a PSN account to use the online mode then it stand to reason the account can be shared between the consoles.
Ofcause there is one catch, when your PSN account is on a console, that console is considered "activated" to your PSN account and there are limits, quick summery

One (1) PS4™ as your 'Primary PS4' and one (1) other as a secondary PS4™
Two (2) PS3™
Two (2) portable PlayStation systems (PSP or PlayStation®Vita)

the link provided will also direct you to deactivating consoles. not sure what happens if you reach your limit and try and put your PSN account on another console since i don't own that many.
On a side note, you can have Multiple PSN accounts on one PS3/PS4, i have a AUS (Main), UK and US accounts on my PS3 and PS4, with the PS3 all content downloaded from any account will work on the system (have gotten UK and US DLC and played it on my profile with my AUs Account, works fine). with my PS4 i have yet to get into a situation where i needed DLC from the UK or US (and hopefully i never will)
As for content wise, it depends, some games when brought as PSN Voucher Codes to download a game for either system like Child of Light

Child of Light Deluxe Edition Includes:

A Digital, Cross-Buy, Version of the game for PS3 or PS4
An exclusive A2 Poster designed by Yoshitaka Amano.
A 24 page art book with unrevealed Ark work.
Two bonus digital content packs - Dark Aurora and Golem.
An Igniculus key ring
No disc in box
Will Require UK/EU PSN account to download game

however most games/DLC can't. to my understanding the PS4 still lacks backwards compatibility so you can't play PSOne/2/3 games you brought on the PS3 on the PS4 and you can not play PS4 games on a PS3 (unless they are like Child of Light). i think the Playstation Store/Transaction History doesn't even list content that can't be used on the system
i would assume Movies and Music can be accessed between systems since i can't see any limitation posed by the hardware (as with the case with games) but i get movies/music the normal way, physical copies i actually own and can do whatever i want with (rip, burn, convert, backup, etc. as many times as i want)

PS3 membership accessing ps4 content


Can this integral be evaluated/approximated?

Question: I've been trying to evaluate this integral without much success:
$$
\int_{-\infty}^{\infty}\mathrm{e}^{\mathrm{i}ax}\,\,
\frac{1 - \mathrm{e}^{-c\sinh^{\,2}\,\left(bx\right)}}{\sinh^{2}\left(bx\right)}\,\,\mathrm{d}x
$$
I've tried contour integration. There are no poles, but I can't find a suitable contour such that all contributions other than that from the real line disappear.
If anyone can help with evaluating/ approximating this in the regime where $c$ is large, that would be greatly appreciated.
Comment: then i would suggest that u also add the "asymtptotics" and or the "approximation" tag
Comment: Any reason to believe that there is a closed form?
Comment: Not really. But it's the definite integral that I'm after. Any help in obtaining an approximate answer would also be very useful.

this is what I can do: I can obtain a contour integral of $ \displaystyle \int_{-\infty}^\infty dz\, e^{iax} \frac{1- e^{-c\sinh^2 bz}}{\sinh^2 bz}$
Comment: ..with the rectangular contour :$ (-\infty, -i\pi/4)$ to $(\infty,-i\pi/4)$ to $(\infty, i\pi/4)$ to  $(-\infty, -i\pi/4)$ to $(-\infty, -i\pi/4)$. This is zero due to the absence of poles, and the contributions at $\pm \infty$ vanish. Also the integrals parallel to the real line are proportional.
So I get : $ \displaystyle \int dz\, e^{iax} \frac{1- e^{-c\sinh^2 bz}}{\sinh^2 bz} = 0$ along the lines z=$(-\infty, \pm i\pi/4)$ to $(\infty, \pm i\pi/4)$.

@tired: OK I will do that, thanks for the suggestion.
Comment: Furthermore u could scale away one parameter. that makes things easier :)
Answer: Let's begin by converting this to a simpler double integral:
$$\begin{align}b \int_{-\infty}^{\infty} dx \, e^{i a x/b} \int_0^c du \, e^{-u \sinh^2{x}} &= b \int_0^c du \int_{-\infty}^{\infty} dx \, e^{i a x/b} \, e^{-u \sinh^2{x}}\\ &=b \int_0^c du \, e^{u/2}\,\int_0^{\infty} dx \, \cos{\left (\frac{a x}{2 b} \right )} e^{-(u/2) \cosh{x}} \\ &= 2 b\int_0^{c/2} du \, e^{u} \, K_{i \frac{a}{2 b}} \left (u \right ) \end{align}$$
I turned to Mathematica for this integral, and it is a little ugly but could be worse as an exact representation of the integral:

$$-b \operatorname{Re}{\left [2^{i a/b} c^{1-i a/(2 b)} \Gamma \left (-1-i \frac{a}{2 b} \right ) \, _2F_2 \left (\begin{array} \\ \frac12+i \frac{a}{2 b} & 1+i \frac{a}{2 b}\\2+i \frac{a}{2 b}&1+i \frac{a}{b} \end{array} ; c\right ) \right ]} $$

I did a numerical verification of this using $a=2$, $b=1$, and plotted against $c \in [0,1]$ and got indistinguishable plots.
Of course, we can debate whether this is truly a useful closed form.  Within Mathematica, the answer is clear - it sure is.  Mathematica can compute the closed form in a small fraction of the time it took to compute a numerical approximation to the integral (and it had a hard time doing so).
Comment: The nice thing is that ur integral is welled suited for an asymptotic analysis , because the asymptotics of bessel functions are well known :) (+1)
Comment: Of course, it would be nice if the OP could specify what approximation (s)he wants.  Is $a$ large?  Is $c$?  Or are they small?  Or is it $b$ that is restricted?  Hard to do asymptotic/approximations when we have no idea about the domains of our inputs.
Comment: @NirmalyaKajuri: I am quite sure about that one.  Here's a ref: http://dlmf.nist.gov/10.32#i (#10.32.9).  For this, use the fact that $\cos{z} = \cosh{(i z)}$.  Besides, I checked the numerics before posting.
Comment: I was going to suggest something similar: Differentiating under the integral sign with respect to c.
Comment: Are you quite sure about the integration over x? because mathematica is not giving me anything on that one.
Sorry, I should have specified the domain for approximation. $c$ is large.
Comment: @RonGordon it seems that this reducible to a $_1F_1$ .


How do radical skeptics address the following knowledge "Something may be or may not be"?

Question: How do radical skeptics address the following knowledge "Something may be or may not be"? The proposition "Something may be or may not be" covers all possibilities and therefore is absolute knowledge. A = B or A != B. How do they address this proposition and do they think this is knowledge or their definition of what is knowledge differs from mine?
Comment: No, it is not knowledge at all. It is a tautology, i.e. a statement that does not exclude any truth-condition. See W's Tractatus, 4.46
Comment: I don't know about radical skeptics, but Buddhist thinkers long ago broke up that statement by arguing that a thing might *both* be *and not be, or that a thing might *neither* be *nor* not be. We might think about the peculiarities of quantum superposition in this regard, so it's not mere word-play...
Comment: I would like to watch the arguments of such a skeptic, something that it and its existence and non-existence don't exist. (Binary thinking is infused in us).
Answer: The most obvious remark is that if we have no knowledge as to whether some proposition is or is not the case, then we have no knowledge at all. Might-or-might-not is a state of ignorance not a state of knowledge.
Since you have not proffered your definition of "knowledge", how can the poor sceptic judge whether it is the same as theirs or not? They cannot even know what your question means. (But of course, once you do offer a definition, expect the radical sceptic to immediately shred it to ribbons).
Answer: Please bear in mind there's a difference between law of non-contradiction (LNC) and law of excluded middle (LEM). LNC essentially says any proposition and its negation cannot both be true at the same time, while LEM essentially says any proposition is either true or false and there's no middle case. And as we know both laws can be violated in non-classic logic such as paraconsistent logic and intuitionistic logic, respectively.
It seems your question can be paraphrased as "the proposition A=B is either true or false is knowledge or not". If we accept knowledge as justified true belief in most philosophy references, then your question is essentially that is the proposition LEM is qualified as JTB knowledge true? It's a tautology which is a justified true belief under most logics such as classic propositional or predicate logic, thus it's a knowledge. But for the more cautious intuitionists such as some constructive or intuitionistic mathematician like Brouwer, LEM as stated in usual form is not justified as referenced here:

In general, intuitionists allow the use of the law of excluded middle when it is confined to discourse over finite collections (sets), but not when it is used in discourse over infinite sets (e.g. the natural numbers). Thus intuitionists absolutely disallow the blanket assertion: "For all propositions P concerning infinite sets D: P or ~P" (Kleene 1952:48). For more about the conflict between the intuitionists (e.g. Brouwer) and the formalists (Hilbert) see Foundations of mathematics and Intuitionism.

So for intuitionists at least your question can be answered in the negative as the above paraphrased proposition is false. By the way, intuitionists care called radical constructivists, not radical skeptics though since they still agree with most other laws and inference rules with classic logicians.


How to get all SPL token mints of a wallet address?

Question: Using getTokenAccountsByOwner we can get all token accounts and using getTokenAccountBalanace we can use the token account to get it's balance. However I was wondering what would be the most efficient and fastest method to get all mints of tokens held by an account? What I want to do is to display all tokens held by a user but unsure how to do so.
Answer: You can do this using findDataByOwner via Metaplex js library.
Example:
const myNfts = await metaplex
    .nfts()
    .findAllByOwner({ owner: metaplex.identity().publicKey })
    .run();


Auction winner in one word

Question: Is there a one-word term for a person who won the auction? Top bidder comes to my mind, but it's actually two words.
Comment: Why do you need one word? Two seem to suit you just fine.
Answer: The generally adopted term for this is successful bidder as recognized in commercial and, probably also, legal contexts.
Strictly speaking, the highest bidder is considered as the tentative 'winner'. If his bid is technically cleared and no objections are raised, he would be the 'successful bidder'. He may or may not eventually buy -- if he completes the formalities and pays up, he would be the 'buyer'.
A single word may be possible but can be a problem being different from the well-understood phrase.
Comment: Ok, this is pretty descriptive. Also thank you for fetching the commonly used terms.
Comment: @ElijahSaounkine Nice to be of help. You could see the logic in using the set phrase, though your need was for a single word! Can you fit in the phrase?
Answer: Buyer? Only the top bidder can actually buy the auction lot.
Winner? There is only one winner (and you actually used the word won yourself).
Comment: I'm not with *buyer*, the successful bidder may or may not eventually buy. Not winner either -- that sounds inappropriate to me though not sure why.

Auction winner in one word


WSO2 WSF/PHP - WSDL w WS-Security Certificate Signing

Question: I am trying to connect to a WSDL that uses WS-Security Certificate Signing over HTTPS.
Only the outgoing messages are signed and it uses Binary Security Token (could not find this specific option in WSO2 but so I am unsure I am using the correct option in the code below).
I have looked at the code in the Samples of the WSO2 WSF/PHP and have joined together the WDSL client example and the Signing example.
Code:
<code>$my_cert = ws_get_cert_from_file("./keys/cert.pem");
$my_key = ws_get_key_from_file("./keys/key.pem");

$sec_array = array("sign"=>TRUE,
                   "algorithmSuite" => "Basic256Rsa15",
                   "securityTokenReference" => "EmbeddedToken");  //Is this correct for Binary Security Token?

$policy = new WSPolicy(array("security"=>$sec_array));

$sec_token = new WSSecurityToken(array("privateKey" => $my_key,
                                       "certificate" => $my_cert));

$client = new WSClient(array("wsdl"=>"https://.../Informationservice.WSDL",
                             "useWSA" => TRUE,
                             "policy" => $policy,
                             "securityToken" => $sec_token));

$proxy = $client->getProxy();

$return_val =  $proxy->StreetTypes();
</code>
Any help would be much appreciated as I haven't been able to find an examples of connecting to a service like this online anywhere.  Most services seem to sign with Username and Password rather than Certificates and when looking for WSDL and Certificate Signing I don't find anything at all.
Answer: You need to specify the CACert option for https to work with "to" endpoint set to the https endpoint. Also use the non wsdl mode as there are some known issues with wsdl mode.


PhoneGap not loading local files

Question: So I was having this issue where no matter what I did, built PhoneGap apps wouldn't load JavaScript files. At first it seemed as if jQuery Mobile would not work or was broken, shortly after that it looked like this was because of an issue with the actual jQuery file. After a lot of trial and error I found that if I would refer the script to the jQuery CDNs and not the local files, it would work; both jQuery and jQuery mobile. Hours of headache go by but I have the answer for the people who were lucky enough to make the same mistake as me.
Answer: The issue relates to the placement of the jQuery and jQuery Mobile files, or any js files for that matter. My mistake was placing the libraries in 'www/lib/jquery'. PhoneGap only compiles JavaScript files placed in the 'www/js' folder. Hopefully I helped someone out who was experiencing the same headache as me... If not, good luck on your further endeavors.
Answer: If i'm not wrong then you trying to place the "jquery.mobile.js" before the "jquery.js" in your HTML file.

Further, don't forget to place the following in you "index.html"

Comment: This is not the case. I imported jQuery first, as Im meant to, and the cordova.js file is also imported.

PhoneGap not loading local files


How do I implement a hit box system in a fighting game?

Question: In a fighting game, a move that you execute is basically just a series of hit boxes that are enabled and disabled at certain times. I want to know how do you create this hit box system.
I have no idea as to how to make a flexible system where I can enable and disable a hit box on any frame of a move and also add additional frame data. All I can think of is having a list that is the size of the amount of frames of the move, and add all of the enables, disables, and frame data as one list item. The problem with that is that a list item can only be one object, so I have to somehow make all my frame data and hit box enables & disables into one object. If I can have as many hit boxes in a move as I want then this list item object needs to have a list as well, which I don't think is a good way of doing it.
So, I just want to know a good way of implementing a hit box system in a fighting game.
Comment: You can make a list of list. Start with that, if it's fast enough you're done. You only have 2 players so the CPU load shouldn't be that large.
Comment: Paragraphs and a concrete example of what you're stuck on would be appreciated.
Comment: Guaranteed that a list of lists will be fast enough for any two person fighter on any platform more beefy than an embedded LCD game on a watch.
Answer: There's a couple of ways you could go about such a system, as with anything. I'll try to describe the core of one such system in a pretty general sense here:
An animation consists of AnimationFrames. An animation frame contains a bunch of data.
struct AnimationFrame
    {
    //The graphic for this frame
    Sprite * sprite;

    //Duration (for example, in milliseconds)
    unsigned int duration;

    Hitbox hitboxes[N];
    Hitbox hurtboxes[N];
    };

So each frame has a list of hitboxes and hurtboxes. Inside the game, they would look like something like this: http://ensabahnur.free.fr/BastonNew/hitboxesDisplay.php?sMode=f&iChar=2&sMoveType=fd_normals&sAction=w&iMove=6
What, then, is a hitbox or a hurtbox? Of course its a rectangle with four values (offsets from the character's world position), but it also holds additional data.
Every frame you will be polling whether each hitbox of each character's current animation's current frame collides with a hurtbox of another character. But what happens when the rects do collide is up to the hitbox. There's a couple of ways to imlement this. Say you have a generic hitbox struct:
struct Hitbox
    {
    int x, y, w, h;
    //...other data
    };

What is the other data in addition to the rectangle's dimensions?
It could be a function pointer (say, to a function that deals damage to the current opponent.)
It could also be an integer ID. Each Strike or Ability a character had would define what happened if a Hitbox of a given ID during a certain frame collided. Additionally, the AnimationFrames themselves could have an ID, a function pointer or similar event appointed to them.
Lastly, each animation is simply a list of AnimationFrames. Its up to other systems how these are updated or handled.
I hope that gives you at least some ideas.
Answer: What comes to my mind would be to have a list of each collision box per frame of the attack, then advance each hit box every frame and check if it collides with any enemy. If so, set the attack hit to true so the enemy doesn't get hit twice or more times for the same attack. If this doesn't make sense, here's an example of the code in Java:
public void updateEntity()
{
    if(isAttacking && !attacked)
    {
        if(attackFrame++ < attackBoxes.length)
        {
            for(int i = 0; i < entities.size(); i++)
            {
                if(entities.get(i).bounds.intersects(attackBoxes[i]))
                {
                    attacked = true;
                    entities.get(i).damage(...);
                }
            }
        }
        else
        {
            attacked = isAttacking = false;
            attackFrame = 0;
        }
    }
}

The attackFrame variable is also what you can use to render each animation frame for the attack. The attackBoxes variable can be an array to hold each collision box for each frame, which you will have to set on each attack.


AIC, BIC parsimony

Question: I've set up code to give me a graphical depiction of AIC vs BIC parsimony over various degrees of polynomial models.  On the rare occassion AIC does not match BIC trends, which parsimonious model would you select and why?
Comment: It depends on what you're trying to achieve
Answer: I would not make an automatic choice. Sometimes you want a more parsimonious model, sometimes you want a less parsimonious model. Sometimes you want a model that is less parsimonious than either AIC or BIC recommends.
In almost all cases you will want to look at several models and see which is the most useful to you, for your particular purposes, with your knowledge of the substantive area, with the amount of data you have.
Attempts to automate these decisions are ways of saying to your boss "Don't pay me so much, the computer does my thinking".
:-)
Comment: Well.... you have to make up your mind as to whether more or less parsimony is "better" for whatever your definition of "good" is. Personally, I think polynomial terms higher than 2 are hard to interpret and, if they are needed, I prefer splines. But AIC and BIC (and their variants) all have fierce partisans - if you search Google, you can find many papers. But the reason software offers both choices is that neither is that the decision on which is "better" isn't in yet.
Comment: Sorry, more context might be appropriate--I'm trying to select a polynomial degree for the "best" fit to run a predictive polynomial model.  I do need some criterion for best.  I thought that was the purpose for tools like AIC, BIC, and crossvalidation?
Answer: The AIC can select models that are over-parameterized, because the model-size penalty is pretty low. The BIC also increases the penalty as the sample size increases, which seems like a desirable feature. Personally, I would favor the BIC.
Answer: You should read the original journal articles.  AIC is and was intended to be an approximation as a ready or obvious solution was not available.  The paper behind the AIC is quite logical and well done, but the AIC was solved in a non-proof-like manner.  The BIC follows as a theorem from a proof.  It is not an approximation, it is the exact answer, subject to the assumptions.  It is proportionate to the posterior density subject to a cost function and any statistical assumptions regarding the models involved.  They should move together.

AIC, BIC parsimony


More than two windows split view

Question: Is there some sort of clever hack of achieving that, because I did not find anything. I have a 27" Mac and everything is still kind of huge.
Comment: Because other people with the same question will be directed here, I think it's reasonable for answers to include paid versions, so that you and others can make the decision about whether to pay people for their work that provides you with something that you value.
Comment: It's linked with a rather similar one, with similar answers. Nothing gets deleted, nothing is wasted, but it makes it easier to find answers for future visitors.
Comment: @nohillside so you're closing a good question because of (2 slightly) bad answers? Wouldn't it make more sense to ping a non-answer with a downvote, and link to the related question as a comment on those answers (so the knowledge doesn't go to waste), rather than close the question?
Comment: I'm going to ask on meta if anyone objects to merging this with the canonical question. It's fine being linked, but the answers fit a "what window managers exist" type question better IMO and this language will feed the canonical question with excellent use case and wording. +1 stevec it's a great question no will bring people to our canonical answer.
Comment: @nohillside although the related question doesn't specify free/native solutions. All 5 answers on the related question are paid: Moom, BetterSnapTool, Divvy, Magnet, BetterTouchTool (and Spectacle is no longer maintained). Hence this question specifically for free/open source software (or, preferably, a native way)
Comment: I'm aware of that. But you got four answers here, two of them are for paid tools so basically not answering your question. And all of them match both questions.
Answer: Rectangle
You can use Rectangle to achieve this for free.

Rectangle is a window management app based on Spectacle, written in Swift.

After downloading, installing, and granting the app accessibility permissions in System Preferences, you'll be able to enable the default keyboard shortcut scheme, which allows you to press ctrl + opt + U/I/K/J to snap a window to the top left/top right/bottom right/bottom left, respectively. By assigning four windows each to one of these four positions, you can create a four-way split screen view (and if you enable Dock and Menu Bar hiding, you might be able to get a bit more screen real estate, if needed).
Comment: This one worked quite well. I split the screen into 3 with minimal shortcuts. Amazing for a free app!
Comment: Tried this as well. It's super helpful.
Comment: Such a good recommendation, does what it says, great default shortcuts, and it's free.
Answer: No - you get two windows in the current implementation. One on the left and one on the right.
I suppose the notification center slide over could be considered a "third window" but you can't put an application window there - it's just a system tray of sorts.
I would look at a program like Divvy on the Mac App Store for customizing a workspace with multiple tiled windows. It's not split view, but it's far more flexible and able to make use of the 27 inch display space to quite a granular basis.
Answer: I can recommend:

Spectacle which is free, you can move and expand windows to
sides and corners with keyboard shortcuts
BetterTouchTool which is paid-for, and includes drag-to-edge to size windows to sides or corners, among many other features
Comment: I found a similar tool with a similar name, let me add as a comment for reference by future visitors, BetterSnapTool at https://apps.apple.com/us/app/bettersnaptool/id417375580?mt=12
Comment: BetterSnapTool is now paid for, but cheaper than BetterTouchTool. They're by the same developer, and BetterTouchTool includes the snapping functionality, but also a lot more with respect to defining custom keyboard shortcuts, mouse gestures, and more.
Comment: Should be marked as best answer!!
Answer: yabai
If you want a more powerful alternative to Rectangle, you could use the free and open-soure Yabai, which you can configure however you like.

yabai is a window management utility that is designed to work as an extension to the built-in window manager of macOS. yabai allows you to control your windows, spaces and displays freely using an intuitive command line interface and optionally set user-defined keyboard shortcuts using skhd and other third-party software.
Comment: It's worth noting that Yabai requires that "System Integrity Protection…be (partially) disabled" in order for "many advanced features" to function.
Comment: The basic tiling functions do not require SIP to be disabled
Answer: Hopefully something like this becomes a standard Mac feature.  I like the split screen feature, but sometimes I want/need more than two screens.  I found a pretty good solution on the Apps store that will let you have split screen, one window half/two in quarters, or 4 windows is quarters.   It is called Magnet.  Works great on OSx Sierra, and is much cheaper than Divvy.  Here's the link!
Answer: The app I am now using is Magnet. It is available on the Mac AppStore and performs beautifully. It has shortcuts, graphical buttons and you can drag the windows to the sides of the screen to snap them to halves or to corners to snap them to quarters.
Answer: BetterSnapTool
An app you might want to check is BetterSnapTool. It does what you want and is available from the Mac App Store. It sells for $2.99. I know you wanted a free app but I couldn't find one for the Mac.

BetterSnapTool allows you to easily manage your window positions and sizes by either dragging them to one of your screens corners or to the top, left or right side of your screen. This lets you easily maximize your windows or position them side by side. In addition, you can set keyboard shortcuts in order to move and resize your windows the way you want.
Answer: SizeUp
SizeUp is a window manager app like the others. It costs $12.99 at the time of writing, but offers unlimited free trial (it just reminds you every now and then to pay).

SizeUp allows you to quickly resize and position your windows with keyboard shortcuts or a handy menu bar icon.

It is not open source, though.
Answer: @Harry is actually providing a very good recommendation without being very specific about it.
Spectacle does (almost) exactly what you're looking for. It's not strictly speaking split view, but it allows you to split windows between the three third of the screen via simple shortcuts:

In addition, it's free and open-source.
Comment: Love the open source part of it more than free part :)
Thank you.
Answer: Me from the future here; I ended up settling for Magnet
It has nice logical shortcuts to snap windows to quarters, halves and thirds of the screen and supports dragging to the edges of the screen, like in Windows. Easily worth the 1.09€ for me.

Update 2019/2020:
Ended up switching to Divvy. It allows me to place windows anywhere on a customizable grid (kind of like a less aggressive tiling window manager). And I can define custom shortcuts. So I took Magnet's shortcuts and added a whole bunch of other ones, like centering, top left sixth, bottom quarter, etc.
It also allows to set a custom window separation, which I think looks pretty good.
Answer: Moom
This is my favorite... I have tried quite a few, and paid for them.
there is a quick menu on the window

you can split into blocks which are configurable

and can be triggered when switching displays

this is the help screen ....
Comment: Welcome to Ask Different :) Can you please [edit](https://apple.stackexchange.com/posts/360657/edit) the post to include a link to the app homepage/App Store link?
Comment: Here is a link: https://apps.apple.com/app/moom/id419330170
Answer: BetterSnapTool has worked well for me for years
Answer: Its not the same feautre as Windows, But little bit default Mac feature
Follow the steps

Four finger down. You will window desktop bar
Drag the application to besides desktop.(Make sure you are not dragging into desktop but creating new app pane besides, the mistake i was doing)
You can now drag one more application to the lonely single applcation in desktop bar.
Now they will split evenly in two
Comment: Welcome the SE.network and thanks for contributing. Unfortunately, your answer misses the mark. The question was about how to get more than two windows side by side.

More than two windows split view


Embedded board level functional test at factory

Question: My embedded project has a GSM and a GPS module. What is the best way to test the radios of these modules after the production of CCA like in a factory conditions.I was thinking of signal generators transmitting at the required frequencies. Is there a better way to solve this problem?
Comment: Many factories can assist in testing hardware after assembly, see what they have to say.
Answer: I don't know about your specific modules, but many devices that work through a bus have an acknowledge signal that the host can request.  Of course, that doesn't test the whole device, but if you get the high sign back it means the device is on the bus correctly and powered.