What are the recommended books for an introductory study of elliptic curves?

Question: I am currently doing a self study on algebraic geometry but my ultimate goal is to study more on elliptic curves. Which are the most recommended textbooks I can use to study? I need something not so technical for a junior graduate student but at the same time I would wish to get a book with authority on elliptic curves. Thanks
Comment: If you want to get into the number theoretic investigations, for a gentle introduction start with Cassels, "Lectures on elliptic curves". You can supplement that later with Knapp's "Elliptic Curves". After you have had a look at both, you can start reading Silverman's book.
Answer: Silverman and Tate to start, then Silverman, and finally Silverman again. These are basically canonical references for the subject.
Comment: BTW, if you end up looking for a nice easy introduction to the relationship between modular forms and elliptic curves, then Knapp is pretty good: http://books.google.com/books?id=-e_qVoKF8H8C
Comment: As someone who's never really done more than glance at a few early sections of Hartshorne, I am personally glad for that approach. I think that elliptic curves and toric varieties are two of the best topics for motiviating AG and that an approach that takes this into account is good for AG. Indeed, this is the only thing that has caused me (and probably others like me with an applied bent) to even contemplate learning about schemes.
Comment: You may also find McKean and Moll ( http://books.google.com/books?id=ovGVquPwo7oC ) has a nice flavor. But this should be considered as a complementary reference. McKean's books typically have somewhat unusual but extremely tasteful takes on subjects, and this is such a case.
Comment: And you might like the book of Cassels too.
Comment: I sometimes feel that the elementary approach of Silverman obscures the arguments. If he had assumed that readers know more algebraic geometry and group cohomology, the result could have been made more readable. Of course this is a compromise to enlarge the user base. But it would be nice to have a kind of more highbrow Silverman.
Comment: And if you want to generalize it eventually, Silverman and Hindry: http://books.google.com/books?id=5rcU1ksin0gC&lpg=PP1&dq=silverman%20hindry&pg=PP1#v=onepage&q=&f=false
Comment: If you want a historical perspective, I recommend following up Silverman and Tate with the notes by Stevenhagen: http://websites.math.leidenuniv.nl/algebra/
Comment: There is also Husemöller, Dale
Elliptic curves.
Graduate Texts in Mathematics, 111. Springer-Verlag, New York, 2004. xxii+487 pp. ISBN: 0-387-95490-2
Answer: The other book suggestions are all so far excellent; the only caveat with them is that they all get into the number theoretic aspects very soon. I am taking the guess that you are more geometrically minded since you are starting with algebraic geometry rather than with number theory.
Also I am taking the guess that you are reading algebraic geometry from the standard book of Hartshorne. I assume you are reading the first chapter.
My advice to you would be to first understand affine and projective varieties as given in chap I of Hartshorne, and then move straight ahead to chapter IV on algebraic curves. You would have to take a few things like the Riemann-Roch theorem (rather, Serre duality theorem) for granted and you would have to replace any occurrence of "scheme" with variety, and there may be a few gaps. I suggest that you ignore these and read it. This will give you a very solid and rather modern introduction into the subject algebraic curves, and to elliptic curves in particular.
Afterwards you can go back to chaps. II and III and read the theory of schemes and the machinery of sheaf cohomology, if you wish to further pursue algebraic geometry.
Answer: I highly recommend Elliptic Curves by Alain Robert. It is very clearly written, has few prerequisites, yet brings the reader straight into the connection between the complex analytic side of algebraic curves and the algebro-geometric side. It eventually discusses $p$-adic curves and their relation to $p$-adic analytic functions, as well as using these to prove the main theorem of complex multiplication (that $j(\tau)$ is an algebraic integer).
Answer: Elliptic curves lie at the intersection of several areas of mathematics which have been approached in different ways. So the problem in learning the subject is deciding which approach to adopt.
Lawrence Washington's book is very approachable and doable, written by a serious mathematician with the novice in mind, and it is realistic to expect that it can be worked out.
Knapp's notes are very readable, and after the outlines of the subject are familiar furnish enrichment and orientation-they are compulsively readable-and can mislead one into thinking that his notes can be easily mastered!
Silverman's two volumes are the definitive treatment of the arithmetic aspects of the subject for the average researcher. As to the quibbles about scheme theory being omitted in his treatment, one has to ask oneself what one is learning the subject for.  As Silverman remarks, it is easy to write down a particular elliptic curve and pursue interesting arithmetic research questions without using scheme theory.
One could view Mordell's finite generation theorem as either being "elementary" or "interesting". Both points of view have a measure of truth in them. This is a foundational theorem in the subject, and its proof requires no more than high school mathematics! This is of course a testament to the fact that elliptic curves are amazing objects. Not sure Andrew Wiles used scheme theory in his proof of FLT. He may well have relied on deep results obtained using scheme theory, but that does not make his proof less valid.
Another example is Mazur's theorem on the torsion subgroup for elliptic curves over Q. The result is very useful, even if we do not understand its proof, it is easy to apply.  Very few of us have the time to learn algebraic geometry in its rigorous modern formulation. Silverman remarks on this matter in his introduction. One has to view the study of this subject as a prerequisite to engaging in research which really is the point of any serious study.
I have been lucky enough to write and publish papers on the subject with very limited knowledge. Elliptic curves are deep mathematical objects especially when viewed from an arithmetic perspective, but interesting problems can be pursued with modest equipment. So unless one wants to be an algebraic geometer, it is possible to pursue arithmetic questions as topics for research without knowing about schemes.
I have found myself referring to Silverman's books and to Knapp's notes when the "chips were down" and I was tackling research problems. My problems may have been superficial, but the results were published - so there must be a community that finds them interesting. Maybe I am slow, but I am leary of advice that gives a sequence of books to be read for learning something. I suspect most of us will read very few books thoroughly - and skimming a mathematics book doesn't seem like a useful pursuit to me.
As Goethe (?) said, "Art is long. Life is short. Decisions are difficult, and opportunities are fleeting."  My two cents for whatever it is worth.
Comment: Upvote because Lawrence Washington gave a presentation on EC's to my REU appx 5 years ago.
Answer: If you are also interested in exercises on elliptic curves with solutions I recommend
the book "Computational Commutative Algebra and Algebraic Geometry: Course and exercises with detailed solutions" by Yengui, see https://www.amazon.com/dp/1096374447?ref_=pe_3052080_397514860
Answer: The books by Silverman can't be beat and I won't simply repeat what's been said below.
Adding to the books already mentioned, Lawrence Washington's recent text is supposed to be excellent, but I haven't seen it yet.
Miles Reid also wrote a beautiful set of lecture notes that was used at Cambridge for many years-they may or may not still be available online for download.
And of course no introduction to algebraic geometry through elliptic curves would be complete without mentioning the classic introduction to algebraic curves by William Fulton, which is available online free for download by googling it.


Is the Nth ports on 127.0.0.1 and 127.0.0.2 same ?

Question: I want to create ssh tunnels between 2 clients and 1 server. Can I use the same port numbers for both but binding one of them to 127.0.0.1:N and the other to 127.0.0.2:N ? Are these ports same or can I use them separately ?
Comment: Did any answer help you? if so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you could post and accept your own answer.
Answer:
Can I use the same port numbers for both but binding one of them to
  127.0.0.1:N and the other to 127.0.0.2:N ?

Yes, you can use the same port number on two different 127.X.X.X addresses.

Are these ports same or can I use them separately ?

You can use them separately.
See illustration below.
lab@ubu10:~$ nc -l 127.0.0.1 2000 &
[1] 1035
lab@ubu10:~$ nc -l 127.0.0.2 2000 &
[2] 1036
lab@ubu10:~$ netstat -l -n
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State
tcp        0      0 127.0.0.2:2000          0.0.0.0:*               LISTEN
tcp        0      0 127.0.0.1:2000          0.0.0.0:*               LISTEN

Answer: It's not clear in your question whether you are tunnelling between both clients via the server, or tunnelling from each client to the server.
In either case on the client side, you can bind locally to the same IP/port on both sides e.g.:
ssh -f firstname.lastname@example.com -L 2000:server.com:22 -N

This will map 127.0.0.1:2000 on each client to the tunnel which terminates on the server.
On the server side, you will simply see the public IP address of each client, which will have (possibly) unique source IPs bound to unique source ports.
Answer: if you bind to port+ip you can use them separately.
Comment: Can you explain how can I do that ? I tried "ssh -N -R [127.0.0.2]:2222:host:port user@host" but it didn't work.
Comment: openssh should have -L [bind_address:]port:host:hostport
Comment: @StefanoSasso are you actually trying to use 127.0.0.0/8 addresses? That won't work since those are the loopback addresses that will immediately loop the traffic back inside the sender. A loopback address is only useful internal to a host. For multiple hosts, you need to use a different address range.
Comment: @BünyaminSarıgül Perhaps you need 2 tunnels: tunnel1: ssh -R 127.0.0.1:3000:127.0.0.1:2000 user@remotehost --> will forward 127.0.0.1:3000(at remotehost) to 127.0.0.1:2000
tunnel2: ssh -R 127.0.0.2:3000:127.0.0.2:2000 user@remotehost --> will forward 127.0.0.2:3000(at remotehost) to 127.0.0.2:2000


How to export a csv file based on a SQL query programatically

Question: I am not a SQL expert, so this may be a really obvious thing to those of you who are experts.  Anyway, I have created an application that has to generate a csv file based on a SQL Query.  In reading the internet tips on how to export a CSV file from SQL they all refer you to using Management Studio, right-click on the query results and use the Save-AS technique.  That will not practical for my purposes as the CSV file has to generated at the push of a button within my application.  I was hoping (and expected) to be able to do it with a pass through query or stored procedure, but I'm not seeing that SQL 2008 supports this.  Any help would be very much appreciated!
Comment: What language is your application written in?
Answer: The answer will vary depending on the language that your application is written in but to use C# as an example.  A common way is to populate a dataset from the sql query and then burn through the dataset using loops to generate the csv.
Here is an example of that approach from the interweb.
http://www.diaryofaninja.com/blog/2009/12/16/c-convert-dataset-to-csv
Here is another example using VB
http://www.vbnettutorial.net/?Id=119&Desc=Export-CSV-from-Dataset
The complexity of the data may require that you get fancy... (for example does your data have double quotes, coma's, binary data???


Personal mobile device monitoring by employer legal or not?

Question: So here is my case. I work at a company where I recently came to know that they were monitoring my personal mobile whenever I was connected to the company Wifi. No consent was taken nor was there any transparency about this. I was not told that even personal mobiles are monitored. Besides I want to know that can I sue my employer for this? Please suggest me regarding the applicable laws in India and how strong my case is because their monitoring has resulted in some personal issues which are now affecting me so I want to take them to court and sue them.
Comment: They might have monitored their WiFi...
Comment: To elaborate: to know if a personal device tried to connect to the WiFi, they don't need to monitor your device, they can check any connection attempts and, if they grant them, they are in all their right to monitor any traffic through their network.
Comment: @Trish Yes I asked them if any WiFi is available coz there are connectivity issues. So yes WiFi is available for everyone to connect to but is it legal to try to access your personal contacts and other things on your mobile? In the company's do and don't letter it is mentioned that they will monitor the work devices provided by them which I'm completely okay with and many companies do that but nothing is mentioned about monitoring mobile phone if it is connected to company WiFi. Also at the time of providing WiFi connectivity they didn't tell me that your mobile will be monitored.
Answer: Having a WiFi "availeable" does not mean it is "unmonitored". In fact, you should expect it to be monitored in all cases where you don't own the router!
The company is fully in their right to monitor the WiFi and might even be required to do so to shield themselves from liability from what you do. The Network architecture is basically like this: Your phone requests the company router to call a website, the router requests the website, then it sends the website to your phone. It's rather easy for the company to just maintain a log of which IP requested what site when, just like the servers you request data from are obligated to record under some cases who acces them when. But that is not monitoring your device it is monitoring the traffic you create. Which is different. The company might need to maintain these logs who of the company requested content in case that the accessed content was illegal or in case you compromised the company secrets.
And they told you about it: the router you use to access the network is a work device, so monitoring of it shall be expected.
Accessing your device?!
you alleged they access your device through the WiFi. But do you have proof they did this? Because they have the right to monitor the traffic you create that goes through their WiFi, which is not them accessing your device. If you send an unencrypted E-Mail, then it might show up in their logs, together with the text and contact address. That however is not them pinging your device, breaking the security that keeps the contacts n it from being read from outside and then using those.
Conclusion
I don't believe they illegally accessed your device in the first place. They might have monitored all the stuff you did on the internet, and that fully legally as they monitor the router that they own and that is a work issued device which they told you they monitor.
Comment: Even if you own the router, the traffic between the router and the rest of the internet could be monitored by the owner of the equipment to which the router is connected.
Comment: @phoog by the ISP, yes
Comment: It is not about any website which they monitored. Its more about that they tried to get access to my WhatsApp account and try to find my contacts in the list. Is that also legal?
Comment: @RolenKoh that is an entirely different premise and a different question. please ask it as such. You did express "I connected to a WiFi, can they use that to monitor me?" and I said "They are allowed to monitor any traffic through their network."
Answer: Regarding Indian law, the Personal Data Protection Act, 2019 (text of unknown authority) was introduced in Lok Sabha, but was tabled on 11 Dec 2019. That might have added GDPR-like protection, but it's presently just an idea and not a law. However, there is an existing law, the IT Act, 2000, which makes unauthorized access of a computer penalizable (§43). Now the question is whether they accessed your computer without your permission. A computer is

any electronic, magnetic, optical or other high-speed data processing
  device or system which performs logical, arithmetic,and memory
  functions by manipulations of electronic, magnetic or optical
  impulses, and includes all input, output, processing, storage,
  computer software or communication  facilities  which  are  connected
  or related  to  the  computer  in  a  computer  system  or computer
  network

so probably it is a computer. What's not clear is whether you violated the law by accessing their wireless network. I assume you accessed it with permission: I am not sure that you are aware of the exchange of permissions that took place "behind the scenes" whereby you could access the network. Mobile device OS's often respond to network-access protocols with "yeah, whatever, just give me access", without forcing you to read the TOS and explicitly click an "Okay, I understand and agree" button. So it is possible that you "agreed" without knowing that you agreed.
Somewhere there is a document that constitutes the conditions under which you can use the network. It may be difficult to find that document (it may not be in a single place, e.g. might reference other documents). It is possible that you unknowingly "agreed" to let them harvest your contacts. You would need to discuss this with a lawyer, being more explicit about what company this is, what they accessed, and the lawyer could more authoritatively tell you whether they violated any clause of the agreement, or whether any clause on the agreement allowing them to do what they did is illegal given Indian case law.
Comment: Well thanks for your reply which looks more relevant to my jurisdiction. My case is not about just personal contacts list access but about defamation/slander against me.


Would an illusion + archery build work? Do I need magicka for it?

Question: I want to make a build with full archery, full illusion, full light armor, partial sneak and non combat perks. Would a build like this work? I'm thinking I could use stealth+archery and illusion+dagger. How should I develop my magicka (if at all?). I know that there is a way to enchant 0% magic cost equipment, but that's probably late-game, and I'm not going to be a full-blown mage anyway so I think I would want to go for other more useful enchants.
Comment: @Annan It's not a useless school, Bethesda just did a terrible job of explaining how it works/what influences it. Take a look at [uesp.net/wiki/Skyrim:Illusion](http://www.uesp.net/wiki/Skyrim:Illusion). With the proper perks, the actual level caps are in a useful range. It would be nice if they had a chance of success influenced by level (or stats...) instead of a flat cap, but that would be some crazy advanced programming. We're talking "Gateway to the Savage Frontier" sort of stuff now.
Comment: I've always found illusion one of the most useless schools of magic. The best spell is invisibility which is great for assassinations or sneaking. The Calm/Fear/Frenzy-like spells are all limited to under level 25. Though if you like messing with AI it'd be rewarding.
Comment: possible duplicate of [choosing attributes when leveling](http://gaming.stackexchange.com/questions/38788/choosing-attributes-when-leveling)
Comment: @Fambida You could add a mod if you're on PC. Thanks for the heads up about the perks, I haven't really looked at them before. Dual cast Mayhem on boss, cast invisibility, eat popcorn... Makes me want to get out my illusion spells.
Comment: @David B Hmm I haven't really considered that. Isn't that the case for any build though? Wouldn't a pure warrior type character need magic at some point in the game? Also, how much magicka do you think is suitable for such a build.
Answer: This plan is great for taking out bandits, bears and trolls.  However it's not so great versus undead (while leveling) and dragons (always moving, or in melee range).

I can't really determine how much (base) magicka you'll need because there's a ton of unknowns.
Let me make some presumptions:  You wear armor and not a robe in the chest slot.  You don't want to use magicka potions.  You don't have spell cost reduction or magicka increasing enchantments.
Calm is the bread-and-butter illusion spell while leveling.  Considering perk and skill discounts, it will cost 40-60 magicka to cast.  If there are 4 baddies, you'll want to cast it at least 3 times, but 4 times is better.  If all baddies are calmed, you are out of combat and get out of combat mana regen rates (better than wearing a robe).  In general, if you can calm everyone, during that 30 seconds you'll get back enough magicka to do it again (assuming no misses).
Invisibility is the crowning spell of the illusion school at 75 skill.  Considering perk and skill discounts, it will cost 120-150 magicka.  I don't have practical experience in using it to break combat (hope to soon), but if it does you'll get back that magicka before needing to cast it again.
Harmony is the most expensive spell of the illusion school.  It costs ~310 magicka considering perk and skill discounts.
Comment: Invisibility broke my Oblivion game-experience for me, I intend on staying away from it in Skyrim as long as I can.


iMessage different on iPad then phone

Question: Just recently my iPad iMessage is not the same as my phone, I have no clue why it changed, if someone can help me get them to be the same, I would truly appreciate it.  I notice that from my iPad, it uses my Apple ID, and I do not want that. I went to settings and clicked on send and receive but it only shows 3 different email addresses no phone number. If I sign out, I am inable to send messages without signing in to Apple ID. Extremely frustrated thanks in advance for any help Bob
Comment: Is your iPad Wi-Fi only?
Answer: iPads can send and receive iMessages through your phone number because your iPhone associates its number to your iCloud account. According to Apple's troubleshooting steps and support forums, the first thing to try is to repeat the association process in case that's somehow come undone:

Toggle iMessage off (Settings -> Messages) on both your iPad and iPhone.
Wait a few minutes. Some guides say restart your iPhone, which can't hurt.
On your iPhone, toggle iMessage on. If you see blue text below the toggle that says "Use your Apple ID for iMessage", tap it to sign in.
Once your iPhone has activated iMessage and lists both your phone number and email addresses in (Settings -> Messages -> Send & Receive), toggle iMessage on in your iPad's Settings. Your phone number should now be one of the "Send & Receive" options on your iPad.

Note that receiving and sending non-iMessage SMS texts on your iPad is set up separately.

iMessage different on iPad then phone


ALT+CMD+SPACE Suddenly works differently

Question: It used to be that ALT+CMD+SPACE opened up new finder window. And without making any update to my mac, it started opening up finder in search mode.
What could have changed? How to turn it back?
Comment: Have you gone to system preferences/keyboard/shortcuts to check how these are set?
Answer: As far as I recall ⌘n has always been the Finder shortcut for New Window assuming that Finder is the active app, ⌘⇧n opens the Finder with search focused globally. See the 'Shortcuts' tab of Keyboard.prefPane:

I assume that ⌘⇧n as a new plain Finder window was being provided by some other means; Some configuration in that Shortcuts tab (perhaps under services), or a third party app that does a simple "bind these keys to this action", and for some reason that app failed to start, or crashed if you didn't even reboot your Mac.
Comment: If I have Chrome open cmd+shift+N opens new Chrome window. It used to be that Option+CMD+Space open new finder window from any context, now it opens search for me as you show in your screen shot.


mod_vhost_alias question

Question: Is it possible that mod_vhost_alias can read several directories (For example, each users) to find the sites? Like in a hosting setup where different users can create the directories in their home directory?
Answer: vhost_alias maps a domain received into a path on the filesystem.  It doesn't read the existing filesystem prior to serving the request to see if the files exist.
However, you can do something like have a stable directory listing of files, and use symlinks or bind mounts in the user directories to point to the actual web directories.
/var/www/domain.com
/var/www/domainb.com
and then
/home/user/domain.com is a symlink or bind mount to /var/www/domain.com
/home/userb/domainb.com is a symlink/bind mount to /var/www/domainb.com
Remember that mod_vhost_alias runs everything as the user running the apache service.  In a shared environment, make sure you know the ramifications for running apache like this.
Comment: Alright, sweet. Any quick ways to automatically make all those symbolic links?
Comment: When the domain is created, create the domain and the user's symlink.  If you are doing it the opposite direction where a user creates a domain directory, uploads content, your script would need to move that to the proper location and leave a symlink in place.  Some FTP software won't properly traverse symlinks which is why I suggested the bind mount.  With a bind mount, you need to update your /etc/fstab so that the mount comes back if the machine is rebooted.

mod_vhost_alias question


gImageReader Clipboard doesn't work on Windows

Question: I'm using gImageReader to do some OCR on Windows 7, and though I can copy from within the application itself, I can't copy to the external Windows 7 clipboard.  I believe the program is gtk based, and that maybe a setting within gtk needs to be changed to enable this functionality; I seem to remember having this issue before, with another gtk for Windows application , but I don't remember what I did to make this happen.
Answer: It appears to be a gtk related problem. Updating gtk to current version should help, but I haven't tried that yet.


How do I dismount my horse?

Question: In Skyrim VR, I'm stuck because I don't know how to dismount my horse. In normal Skyrim, I can press a key to dismount, but my HTC Vive does not have a keyboard.
Answer: According to this reddit post:

look down, point at the horse and press the move button
Answer: Just doing a long press on the right trackpad will do it.  No need to look down at the horse.

How do I dismount my horse?


Convert fixtures into Factory Girl in Rails

Question: I'd like to migrate my fixtures to "Factory Girl" in Rails.
Is there any easy way to convert all yml files in a factories.rb file?
Answer: I am assuming what you are looking to do is find a script which will look through your models and generate the factories for them.  I tried this once (with something other than factory_girl) and found it full of bad data.
I would suggest that you slowly transition to using factories.  As you write new tests or update old ones, create the necessary factories.  As time goes by, if you have the time and energy you can then choose an individual test case and replace all the fixtured data calls with the proper factory calls and remove the specific fixture requirement at the top of the test case.
Answer: I've just released a gem called fix_to_chix a few days ago to address the exact same issue.
It probably needs a lot of enhancements, but it might help you: http://github.com/caike/fix_to_chix (you need to copy and paste it on your browser since SO seems to put some chars in the url)
Comment: link to github project 404s
Comment: @MikeBuckbee I found this: https://github.com/yortz/fix_to_chix
Answer: What exactly would you expect the resulting factories to be? The whole idea of Factories is that you don't have to maintain a long list of test data. Instead, the data is created on the fly, close to your tests, where it should be.


Cycles imported whiskey glass not transparant

Question: I've just imported a whiskey glass from a file on Blendswap. When rendering it it just works fine, and looks like glass. When I import it to another scene, it's black untransparant glass? It's been a while since I've been "Blender-ing" so my Cycles experience isn't enough to know where the problem lies... Anyone with a lot of Cycles experience wanna take a look at it?
Answer: Just increase the number of total bounces in the scene (the other values are subdivisions of this main values).
Comment: Thanks, I figured it had something to do with cycles settings. But just don't know enough about it... I'm still a Internal Render-user :/
Comment: Try also to abilitate the caustics: more noise but more accuracy in glass reflections and refractions, and please mark the answer as accepted!


What principle of morality can be applied in the case on Hiroshima and Nagasaki World War Bombing?

Question: I am confused as to which principle of morality is applicable to World War II bombings. I am choosing between the lesser of two evils principles and the double effect. I think it can be justified through the Lesser of two evils principle; whether to bomb Japan, that can have only Japanese casualties or to invade Japan, that can have American and Japanese casualties, so it is better to bomb it although they are both evil. I also think that the Principle of double effect can also justify this, as to bomb Japan (evil) for them to surrender in order to stop the war (good). What principle of morality best justifies and applicable to the said event?
Comment: I may be wrong but I think you are assuming that the bombing can be justified and the question is : how ? It would have been better in my view not to start from this assumption but to ask whether on moral grounds the bombing can be justified. Some will argue  that it can be; others that it was absolutely unjustifiable. Excuse me if I have misinterpreted your question.
Comment: I have read  and , and I based those assumptions from them. I am asking if the two principles can justify the bombings or which of the two can justify.
Comment: For additional perspective on the premise that the bombings were militarily necessary, see my response to user34559's answer and that link: https://www.thenation.com/article/why-the-us-really-bombed-hiroshima/
Answer: I agree that it was ethical based on the lesser of 2 evils principle, and without the need to invoke the "saving of American lives" part.
Assume the nuclear option claimed ~700,000 souls, and destroyed the great culture of 2 cities.
In Hiroshima, "300,000: Total death toll to date, including those who have died from radiation-related cancers."
The non-nuclear option would have killed many more, and destroyed much more culture.  A single firebombing raid of Tokyo killed 100,000.
The double effect doesn't seem appropriate at all in this context.
However, thinking about it more, the nuclear option served to wake humanity up, increasing the fear of war in most, save the most deranged despots.
I hope the voices of those who survived Hiroshima & Nagasaki never fade.
A quick google search revealed these cold stats:
http://www.sandiegouniontribune.com/sdut-by-the-numbers-the-atomic-bombing-of-hiroshima-2016may27-story.html
On a lighter note, I highly recommend the new Mr. Rogers movie, which inspired me to visit this Philosophy Stack Exchange for the first time.
One of my favorite lines:
 from the Vietnam War era, when King Friday XIII, described as "one of the few remaining benevolent despots," establishes a border guard
https://www.newyorker.com/culture/cultural-comment/how-mr-rogers-made-fantasy-familiar
Comment: Some--such as Eisenhower, Nimitz, and other generals and admirals of that time-- have argued that the atomic bombing of Japan was unnecessary, because Japan was already defeated, particularly with the Soviet Union about to take on Japan as well. Here's one summary of this: https://www.thenation.com/article/why-the-us-really-bombed-hiroshima/


What to put in a binary data file's header

Question: I have a simulation that reads large binary data files that we create (10s to 100s of GB).  We use binary for speed reasons.  These files are system dependent, converted from text files on each system that we run, so I'm not concerned about portability.  The files currently are many instances of a POD struct, written with fwrite.
I need to change the struct, so I want to add a header that has a file version number in it, which will be incremented anytime the struct changes.  Since I'm doing this, I want to add some other information as well.  I'm thinking of the size of the struct, byte order, and maybe the svn version number of the code that created the binary file.  Is there anything else that would be useful to add?
Answer: In my experience, second-guessing the data you'll need is invariably wasted time. What's important is to structure your metadata in a way that is extensible. For XML files, that's straightforward, but binary files require a bit more thought.
I tend to store metadata in a structure at the END of the file, not the beginning. This has two advantages:

Truncated/unterminated files are
easily detected.
Metadata footers can often be
appended to existing files without
impacting their reading code.

The simplest metadata footer I use looks something like this:
<code>struct MetadataFooter{
  char[40] creatorVersion;
  char[40] creatorApplication;
  .. or whatever
}

struct FileFooter
{
  int64 metadataFooterSize;  // = sizeof(MetadataFooter)
  char[10] magicString;   // a unique identifier for the format: maybe "MYFILEFMT"
};
</code>
After the raw data, the metadata footer and THEN the file footer are written.
When reading the file, seek to the end - sizeof(FileFooter). Read the footer, and verify the magicString. Then, seek back according to metadataFooterSize and read the metadata. Depending on the footer size contained in the file, you can use default values for missing fields.
As KeithB points out, you could even use this technique to store the metadata as an XML string, giving the advantages of both totally extensible metadata, with the compactness and speed of binary data.
Comment: This is an interesting approach I hadn't though about.  You could even make the MetadataFooter an XML string, and get all of the benefits of a binary data file, and still have an easily extensible scheme for storing metadata.
Comment: @KeithB : Ah! That's a technique I hadn't considered. I like that ;-)
Answer: For large binaries I'd look seriously at HDF5 (Google for it).  Even if it's not something you want to adopt it might point you in some useful directions in designing your own formats.
Comment: I've heard about HDF5, but never had time to look into it.  It seems to be the standard for scientific computing. Its probably overkill for what we need, since our data is just multiple copies of one struct.  For something more complex, I would consider it.
Comment: I've used it for simple stuff and it's very useful. (Though i do wish they had a simpler Java binding.) They give you standard tools + MATLAB can parse it.
Answer: For large binaries, in addition to the version number I tend to put a record count and CRC, the reason being that large binaries are much more prone to get truncated and/or corrupted over time or during transfer than smaller ones.  I found recently to my horror that Windows does not handle this well at all, as I used explorer to copy about 2TB across a couple of hundred files to an attached NAS device, and found 2-3 files on each copy were damaged (not completely copied).
Comment: A record count is a good idea as another check.  The data isn't moved much, so a CRC might be overkill.  On the other hand, it would be easy to calculate when the file is written, and need not be checked every time the file is read.  We could have a stand alone utility for that.
Comment: My technique (see below) of storing metadata at the file END is a quick catch for this problem.
Comment: I tend to store metadata at the start rather than at the end because in my experience the end of the file is more liable to be lost.  If this is the case, the oppurtunities for partially recovering corrupt data are improved with the metadata at the start.
Comment: Additionally, placing metadata at the end of the file is likely to make appending to a file either slower or more complex.
Answer: An identifier for the type of the file would be useful if you will have other structures written to binary files later on.
Maybe this could be a short string so you can see by a look into the file (via hex editor) what it contains.
Answer: If they're that large, I'd reserve a healthy chunk (64K?) of space at the beginning of the file and put the metadata there in XML format followed by an end-of-file character (Ctrl-Z for DOS/Windows, ctrl-D for unix?). That way you can examine and parse the metadata easily with the wide range of toolsets out there for XML.
Otherwise I go with what other people have already said: timestamp for file creation, identifier for which machine it's created on, basically anything else that you can think of for diagnostic purposes. And ideally you would include the definition of the structure format itself. If you are changing the structure often, it's a big pain to maintain the proper version of code around to read various formats of old datafiles.
One big advantage of HDF5 as @highpercomp has mentioned, is that you just don't need to worry about changes in the structure format, as long as you have some convention of what the names and datatypes are. The structure names and datatypes are all stored in the file itself, so you can blow your C code to smithereens and it doesn't matter, you can still retrieve data from an HDF5 file. It lets you worry less about the format of data and more on the structure of data, i.e. I don't care about the sequence of bytes, that's HDF5's problem, but I do care about field names and the like.
Another reason I like HDF5 is you can choose to use compression, which takes a very small amount of time and can give you huge wins in storage space if the data is slowly-changing or mostly the same except for a few errant blips of interestingness.
Answer: @rstevens said 'an identifier for the type of file'...sound advice.  Conventionally, that's called a magic number and, in a file, isn't a term of abuse (unlike in code, where it is a term of abuse).  Basically, it is some number - typically at least 4 bytes, and I usually ensure that at least one of those bytes is not ASCII - that you can use to validate that the file is of the type you expect with a low probability of being confused.  You can also write a rule in /etc/magic (or local equivalent) to report that files containing your magic number are your special file type.
You should include a file format version number.  However, I would recommend not using the SVN number of the code.  Your code may change when the file format does not.
Comment: I was going to include both file format version and SVN version of the file creator, so that if we later find a bug in certain versions of the creator, it is easy to figure out which data files are affected.
Comment: OK - that works too (in fact, it is quite a good idea).  But the key point is that there is a version number for the file format which is separate from the version number of the code that wrote the file in the given format.
Answer: In addition to whatever information you need for schema versioning, add details that may be of value if you are troubleshooting an issue.   For example:

timestamps of when the file was created and update (if applicable).
the version string from the build (ideally you have a version string that is auto-incremented on every 'official' build ... this is different to the file schema version).
the name of the system creating the file, and maybe other statistics that are relevant to your app

We find this is very useful (a) in getting information we would otherwise have to ask the customer to provide and (b) getting correct information -- it is amazing how many customers report they are running a different version of the software to what the data claims!
Answer: You might consider putting a file offset in a fixed position in the header, which tells you where the actual data begins in the file.  This would let you change the size of the header when needed.
In a couple of cases, I put the value 0x12345678 into the header so I could detect if the file format, matched the endianism of the machine that was processing it.
Answer: As my experience with telecom equipment configuration and firmware upgrades shows you only really need several predefined bytes at the begin (this is important) which starts from version (fixed part of header). Rest of header is optional, by indicating proper version you can always show how to process it. Important thing here is you'd better place 'variable' part of header at the end of file. If you plan operations on header without modifying file content itself. Also this simplify 'append' operations which should recalculate variable header part.
Nice to have features for fixed size header (at the begin):

Common 'length' field (including header).
Something like CRC32 (including header).

OK, for variable part XML or some pretty extensible format in header is good idea but is it really needed? I had lot of experience with ASN encoding... in most cases its usage was overshot.
Well, maybe you will have additional understanding when you look at things like TPKT format which is described in RFC 2126 (chapter 4.3).
Answer: If you are putting a version number in the header you can change that version anytime you need to change the POD struct or add new fields to the header.
So don't add stuff to the header now because it might be interesting. You are just creating code that you have to maintain but that has little real value.
Answer: For large files, you might want to add data definitions, so your file format becomes self-describing.
Comment: This is a good idea in general.  In our specific case, a database is the "official" version of the data.  The binary files are only used to feed data into the simulation.
Answer: My variation combines Roddy and Jason S's approaches.
In summary - put formatted text metadata at the end of the file with a way to determine its length stored elsewhere.
1) Put an length field at the beginning of your file so you know the length of the metadata at the end rather than assuming a fixed length. That way, to get the metadata you just read that fixed-length initial field and then get the metadata blob from the end of file.
2) Use XML or YAML or JSON for the metadata. This is especially useful/safe if the metadata is appended at the end because nobody reading the file is going to automatically think it's all XML just because it starts with XML.
The only disadvantage in this approach is when your metadata grows, you have to update both the head of the file and the tail but it's likely other parts will have been updated anyway. If it's just updating trivia like a last-accessed date then the metadata length won't change so it only needs an update in-place.


Kiddush before or after a yahrtziet

Question: I know that there is a custom to get an Aliyah and give kiddush the Shabbat preceding a yaharzeit. Does this apply to the first yarhzeit as well, when the person is still in availus-assuming the deceased is a parent?
Answer: Nitei Gavriel Aveilus2:69:1 says that one should Daven Musaf the Shabbos before the Yarzheit even if he is still in the year.
On page 528 - 69:5 he brings from the Levush, Magen Avaraham 282:18, Minhagim Vermaiza 35, Shaarei Efraim 2:67, Kitzur Shulchan Aruch 78:11 that one should get an Aliya the Shabbos before the Yarzheit. There is no mention that it should not be done in the first year.
Don't know in regards to a Kiddush. Many people only give a Kiddush on Shabbos if the actual Yahrzheit is on Shabbos. If not they give tikkun on the day of the week it falls on.
Answer: The German minhag is to only get an aliyah if the day of the yartzheit falls on a Torah reading day, not to get one the Shabbos prior. Some have the custom to get one on the Shabbos prior if the yarzheit falls on a day when the Torah is not read. IE if the yarzheit is on Tuesday (that is also not a Rosh Chodesh etc) then one would get an aliyah on Shabbos, but if the yartzheit is on Monday then one wouldn't get an aliyah on Shabbos. Some try to get the aliyah both times, on prior Shabbos AND the actual day of the yartzheit if it falls on a Torah reading day.
Comment: I don't see how this answers the question
Comment: being the first yartzheit would for sure not impact getting an aliyah or not. It might possibly impact making a kiddush. My mother's first yarzheit fell on a Shabbos and I made a kiddush and got an aliyah but I did not lead davening since aveilus was not yet over since that goes by one year from the burial, not one year from death, and typically one does not lead davening on Shabbos if they are in aveilus.

Kiddush before or after a yahrtziet


Custom Post Limit for homepage only without plugin?

Question: I have a wordpress site where my most recent post is displayed on the home page larger than my other posts. Starting at post number 2, the posts are displayed in  a grid. I have pagination for 6 posts per page except for the first page, I need seven posts because of the fact that the most recent post is the largest and takes up two grid spaces. I am able to accomplish this with the plugin Custom Post Limits but I want to know if there is a way to do it without relying on a plugin. I have tried pre_get_posts, but don't know how to specify 7 posts on page 1 and 6 posts on every page after that.
I've tried something along these lines, but it doesn't work. Please help!
function custom_posts_per_page($query) {
    if ($query->is_home() && $query->is_main_query()) {
       $query->set('posts_per_page', '7');
       return;
    }

    if (!$query->is_home() && !$query->is_main_query()) {
       $query->set('posts_per_page', '6');
       return;
    }
}

add_action('pre_get_posts', 'custom_posts_per_page');

Answer: You should take another approach. On home page, you have to make 2 queries:
one for latest post with parameters post_per_page=1 to display the latest post;
and second query with parameters post_per_page=6&offset=1 to display other posts (except latest) with pagination: 6 posts per page.


Training like a bull

Question:
What are the benefits of training like a real bull, by moving HEAVY things on the daily?
Not full body every day, just heavy carries to overload the legs and traps.
Like yoke carries alternated with barbell/bag  incline caries,weighted climbing and dragging/pushing my car(1800kg)
Comment: You mean like a strong man? And everyday the whole body? How advanced are you in lifting/strength based sport?
Comment: Overload means building the muscle not by using it with a lot of reps but making it sore by slightly tearing it under high stress?
Comment: my actual yoke is at 176 kilograms , 2,2 times my bodyweight
Answer: (Partial answer as proof/studies referenced missing)
Benefits of regular heavy training

Your body will take on musclemass fast if regeneration is timed right.
Your body will adapt after a while, see strongmen

Downsides

Not suitable and unnecessary for beginners. That much stimulus is not needed but increases risk of injury and bad form
Bulls are heavy, their work must be seen compared to their mass and body type. You might lift wrong or too much
Bulls are ideally moving all day and their physical work is not just an hour in the gym but usually a way bigger amount of their time.
Heavy weights put a lot of stress on your joints even with proper form. This can result in health problems after a long time.
Being natural: Tearing or extreme soreness in muscles will result in them needing multiple days to recover. Doing so everyday with the same muscles will result in overtraining.
Using highly anabolic drugs: You would likely not be overtraining but as joints etc are lagging behind musclegrowth you would risk injury with heavy weights

Training like a bull


Running Schedule Apex immediately in Test class

Question:
How do we write a test class for a schedule batch to run / schedule the schedule batch immediately (without using con expression).
For example: Schedule batch is as below.
<code> global class scheduleexample implements Schedulable {
 global void execute(SchedulableContext sc) {
    batchclass batch = new batchclass();
    database.executebatch(batch);
   }
 }
</code>
When a schedule class is associated with a batch class, is it necessary to write two separate test classes for batch and schedule class or can I just write a test class for schedule class and cover the code for the batch class as well ?
Answer: This is one of those situations you'll want to look at the Test.startTest(); and Test.stopTest(); directives.
Generally you will wrap your asynchornous calls in your test class within these blocks. For example:
<code>Account a = new Account(Name = 'Testing Account');
Test.startTest();
    System.schedule('Schedule Name', CRON_EXP, new ScheduleableClass());
Test.stopTest();
</code>
Note: Indenting here isn't technically right, but I see many people do this, so... why not...
What happens, is that the test will stop at the Test.stopTest() call until all asynchronous calls have finished from within that block.
Since your schedule class is calling a batch job, then you will find that you have created a asynchronous task that the test will stop and wait for to finish before proceeding. i.e. it will test both your Schedule and Batch class.
Is this the best practise way of writing the test? Depends who you talk to. I like to test my schedule method separately from the batch execution purely to make my life debugging a little bit easier. If your schedule class changes, and you have multiple batch methods, then you will have to edit each test, where if you test it separately, you only have to edit it in one place
Comment: Thanks for the explanation. It definitely makes sense and also gave an insight. Keep sharing the knowledge.


What is the difference between a physical theory and mathematical theory?

Question: Is there same approach in physical theories like primitive notions,axioms and theorems as in maths ? If it is then is it an only method or approach to study different fields of knowledge?
Comment: Related: https://physics.stackexchange.com/q/44196/2451 , https://physics.stackexchange.com/q/87239/2451 and links therein.
Answer:
What is the difference between a physical theory and mathematical theory

A mathematical theory is self contained. It starts with axioms, develops theorems and a statement can be proven correct or false   with mathematical tools.
A physical theory is a subset of  a mathematical theory, the subset is picked by additional "axioms" which are called laws or postulates, and are a distillate of physical measurements. A physical theory can only be falsified by disagreement with measurements/data; it cannot be proven to be correct.
Example is the theory of quantum mechanics which depends on a number of postulates. These, from the mathematical theory of differential equations, choose that subset  which describes experiments at the quantum mechanical level, and , very important, are predictive.
Answer: In mathematical physics, theories while perhaps highly abstract (e.g. formulating a gauge theory entirely in fibre bundle language) usually are laid out in a manner different to mathematics.
However, that said, there are axiomatic formulations of various theories in physics. For example, in quantum field theory, one can assume the Wightman axioms:

There exists a physical Hilbert space $\mathscr H$ in which a unitary representation of the Poincaré spinor group acts, and there exists a state $|0\rangle$ invariant under translations.
The spectrum of the energy-momentum operator $P$ is concentrated in $V^+$, that is, the upper part of the light cone.
The quantum fields are operator-valued generalised functions over the Schwarz space with some domain $D$ (which contains $|0\rangle$), which is dense in $\mathscr H$.
$U(a,\Lambda)\phi_i(x)U(a,\Lambda)^{-1} = V_{ij}(\Lambda^{-1})\phi_j(\Lambda x+ a)$ where $U$ is a representation of the Poincaré spinor group and $V$ is a matrix representation of $SL(2,\mathbb C).$
Any two field components either commute or anti-commute under space-like separations and the set of combinations of the form $\phi_{i_1}(f_1) \dots \phi_{i_n}(f_n) |0\rangle$ is dense in $\mathscr H$.

One can take this approach to quantum field theory; for example it has been done for massive $\phi^3$ theory as well as the Thirring model to name a few. However, this approach is not necessarily forced on us as it is in mathematics.
If your intent is to compute scattering cross-sections for example to hand over to an experimentalist, you will be quite content doing things in the manner of say, Peskin and Schroeder's quantum field theory. However, if you'd like to prove a general statement within a theory, you may resort to an axiomatic approach so it is clear what is assumed.
This was done in the case of the famous no-go theorem by Coleman and Mandula in All Possible Symmetries of the S-matrix and in fact the axioms were an important part of the paper, because it was clear from them that the theorem did not restrict super-symmetry.
Answer:
Is there same approach in physical theories like primitive notions, axioms and theorems as in maths?

No, it is not. In mathematics all is derived from axioms.

An axiom or postulate is a statement that is taken to be true, to serve as a premise or starting point for further reasoning and arguments. ...used in deduction to build a mathematical theory. Axiom from Wikipedia

The point is that the deduction process

... is the process of reasoning from one or more statements (premises) to reach a logically certain conclusion. Deductive reasoning from Wikipedia

Comprehensively in mathematics all postulates (axioms) have to be proofed and until there is no inconsistency the theory will be accepted. Even the change of some fundamental properties is possible.
So the Euclidean axiomatic system was only as long right as long a non-Euclidean geometry starts dealing with non-flat surfaces. The clue is that non-flat surfaces are the "normal" surfaces (our earth is a sphere) and flat surfaces are only an approximation of non-flat surfaces for "small" distances.
What about physics?

The approach is a little bit more vague. Mostly we observe chaotic processes and derive from statistics some laws. Going in detail it was observed that all happens on the atomic and subatomic level. For example heat transfer could be described by radiation or more in detail by photon emission and photon absorption.
Instead of axioms or postulates physics mostly uses observations. Until such observations could be repeated in the range of some accuracy there is no need in change of the derived law. But the history of science shows that physical laws are changing time to time.
Indeed there are some theories that are deduced from phenomena and physical properties. Einsteins General relativity theory is such a thing. Plancks law about the Black body radiation, announcing the quantization of radiation, is such an astonishing thing. Or if you need an example for contradicting theories, take Newtons Particle theory of light against Huygens Wave theory of light.

If it is then is it an only method or approach to study different fields of knowledge?

So no, axioms are not the mostly used approach in physics. Mostly observations are used. But an axiomatic Ansatz is possible.
Answer:
Is there same approach in physical theories like primitive notions, axioms and theorems as in maths ?

Yes; necessarily, since these (along with "definitions") are constitutents of a theory in general.

What is the difference between a physical theory and mathematical theory?

Physical theories explicitly and specificly involve "empirical determinations"

as primitive, self-evident notion (the gathering of "observational data"; such as, especially, "determinations of space-time coincidences of material points", and therefore also the distinction and recognition of "identity" of any such "material point" or "participant"), or
by way of definitions, as "physical quantities" whose values are to be determined (measured), trial by trial, by applying the defined measurement operator to the available observational data.

In contrast, mathematical theories would refer to (Boolean, or numerical) values abstractly, or as primitive notions; perhaps going as far as considering simulations of empirically determined values.
But gathering actual observational data, and evaluating it to obtain results of actual measurement, is a methodology left to empirical science, carried out by experimentalists.
p.s.
Note the distinction between theories and models, especially pertaining to physics:
Any theory, i.e. any framework of primitive or self-evident notions, of axioms and definitions, and of their logical consequences or theorems is manifestly either consistent, or inconsistent (and therefore invalid) by itself; without involving any reference to actually gathered observational data, or to actually (through application of the defined measurement operator to actually gathered observational data) measured values.
In other words: a theory could not be considered falsified (and consequently be discarded) due to any empirical results; neither due to those specific results which would have been obtained through application of this very theory in the first place (and which arguably ought to be discarded, too, if the very theory were being discarded, based on which these results had been obtained), nor due to results obtained by applying any other theories (and measurement operators of their definition, to observational data of their framing).
What can be empirically tested, and possibly be found false, are instead (physical) models, i.e. collections of specific values of the defined physical quantities, summarizing all values which had been obtained already (from preceding trials) as well as specific expectations/predictions which values (or at least: range of values) might be found in subsequent trials (incl. subsequent evaluation of observational data that had been already "in stock").
Again: the completely ordinary case that some particular value of a defined physical quantity has been obtained by evaluating the observational data of "the latest" trial, and that therefore plenty of models have been found falsified (namely all those which had predicted some different value, in this trial), while some other models ("standard models") still remain corroborated, has no consequence at all on the validity, comprehensibility, applicability of the very theory which provided the definition (as measurement operator) of the physical quantity under consideration. A theory prescribes the range of values of a quantity; a model specific values, trial by trial.
However: given observational data may generally be evaluated in several different "ways" (i.e. by applying differently defined measurement operators; possibly even varying the prescription of what constitutes "one trial worth" of observational data). Especially if the available observational data is not suitable for obtaining values of some particular quantity (i.e. if the trials under consideration were not "eigenstates" of the corresponding measurement operator), then it may be possible and even advisable to seek or define some suitable other quantities (and given the need or opportunity, entire theories for this purpose), in order to extract some values from the available data after all.


HP Pavilion 15 with AMD dual graphics - Ubuntu live environment not starting

Question: I've had this laptop for about a day now and have decided to try Ubuntu on it and determine if I want to install it. I created a USB, it booted (Secure Boot was on, I tried with Secure Boot off to no effect), and then the problem occurred.
The screen turned off for a second, turned back on to a black screen, shut off again and turned back on with a dialogue box telling me that the system had to use low-graphics mode.  I clicked OK, selected low-graphics mode from the menu and clicked OK. The screen switched to the boot messages and did not go any further than this. Ctrl+Alt+DEL started rebooting the laptop though.
I tried booting again, but this time I edited the boot options in GRUB to add nomodeset. This time, the laptop only booted to a black screen. Ctrl+Alt+F2 took me to a prompt, I tried startx from there, but X didn't start, complaining that it wanted kernel mode setting back.
I can not seem to find any option to disable one graphics chip or the other in the UEFI setup menus.

Laptop : HP Pavilion 15-E004AU.
The CPU : AMD A6-4400M APU with Radeon(tm) HD Graphics
The graphics chip : AMD Radeon HD 7520G + 8670M Dual Graphics.
The Ubuntu version : 13.10, 64 bit.

Thanks.
EDIT: I tried 12.04.3 LTS, it managed to bring the desktop up. There are severe graphics glitches after about two minutes though.
Comment: would you try xubuntu? http://xubuntu.org/
Comment: This just produced an error screen that started with ` ==== START =====
divide error: 0000 [#1] SMP `.
Answer: I had similiar issue with Ubuntu 13.10 on HP Pavilion 17-e050sm laptop:
Microprocessor AMD Quad-Core A4-5000M APU with Radeon HD 8330 Graphics (1.5 GHz, 2 MB cache)
Chipset AMD A76M FCH
Memory 4 GB DDR3
Video Graphics AMD Radeon HD 8330 Graphics (up to 1.98 GB)
and solved it by passing nomodereset kernel option (press F6) before booting live session.
Hope it helps you,
Regards!
Answer: The one solution that solved this for me was trying Ubuntu 14.04's Beta 1 image, written to a USB. It booted from this image to the live environment without any issues whatsoever, and installation worked perfectly. After reboot, it booted from the HDD, then rebooted itself twice. After that, I was able to log in and use Ubuntu.
Answer: I could solving for ubuntu 14.04 in hp pavillion by installing fglrx
HP Pavillion is is AMD/Intel Hybrid system, so switch to shell mode and install fglrx and fglrx-pxpress:
sudo apt-get install fglrx fglrx-pxpress


Is it okay to set reduce_limit = false config in couchdb configuration?

Question: I am working on a map/reduce review and I always have reduce_overflow_error each time I run the view, if I set reduce_limit = false in couchdb configuration, it is working, I want to know if there is negative effect if I change this config setting? thank you
Answer: The setting reduce_limit=true enforces CouchDB to control the size of reduced output on each step of reduction. If stringified JSON output of a reduction step has more than 200 chars and it's twice or more longer than input, CouchDB's query server throws an error. Both numbers, 2x and 200 chars, are hard-coded.
Since a reduce function runs inside SpiderMonkey instance(s) with only 64Mb RAM available, the limitation set by default looks somehow reasonable. Theoretically, reduce must fold, not blow up the data given.
However, in real life it's quite hard to fly under the limitation in all cases. You can not control number of chunks for a (re)reduction step. It means you can run into situation, when your output for a particular chunk is more than twice longer in chars, although other chunks reduced are much shorter. In this case even one uncomfortable chunk breaks entire reduction if reduce_limit is set.
So unsetting reduce_limit might be helpful, if your reducer can sometimes output more data, than it received.
Common case – unrolling arrays into objects. Imagine you receive list of arrays like [[1,2,3...70], [5,6,7...], ...] as input rows. You want to aggregate your list in a manner {key0:(sum of 0th elts), key1:(sum of 1st elts)...}.
If CouchDB decides to send you a chunk with 1 or 2 rows, you have an error. Reason is simple – object keys are also accounted calculating result length.
Possible (but very hard to achieve) negative effect is SpiderMonkey instance constantly restarting/falling on RAM overquota, when trying to process a reduction step or entire reduction. Restarting SM is CPU and RAM intensive and costs hundreds milliseconds in general.


IMAP proxy setup to allow use of IMAP IDLE?

Question: First-time poster, long-time lurker/reader. Sorry for the obscenely-verbose question...I intended to keep it more concise. Also, sorry about the links not being "actual" links -- I don't have the required rep to post more than 2 in a question.
I work for a company which runs its own IMAP mail server, using VPOP3 Enterprise[1] v6.10 on Windows Server (sorry, not sure what version). Our sysadmin (mostly) likes the mail server we use, it's a paid license, and he makes the final decision. My only real complaint about the server is the lack of (or broken) IMAP IDLE support. I hate the lack of IDLE support, and I asked the Sysadmin about it. He says he previously enabled IDLE support in VPOP3, but there's apparently some strangeness with Outlook & IDLE (or maybe just VPOP3's implementation?) that prevented him from keeping it enabled [probably 1/2 the company, if not more, uses Outlook for their mail client]. I found very little documentation[2] on VPOP3's support for IMAP IDLE[3].
Many of us work "in the field," and it's nice to be able to get email while you're out of the office...so many of us use our smartphones to do so. Unfortunately, we have to set our devices to "poll" the server, which necessitates finding a balance between frequency of polling & battery life. I've been spoiled by "push" mail with Gmail & my University mail account (formerly running on their own IMAP servers before switching to Google Apps), so I'm really hoping to work around this issue.
With the background out of the way -- what I want to do is to set up another server on our LAN to "proxy" mail from the VPOP3 server, and allow clients to connect to it.
Ideally, I'd like the solution to:

automatically sync all changes from the proxy back to VPOP3 (e.g. mark messages as read, delete, move to folders, etc)
not require my intervention if others in the company want to use this proxy

I don't want to manually configure usernames & passwords to connect to the VPOP3 server. The preferred solution wouldn't cache/fetch any mail for the user until they log in to the proxy for the first time. Once they've logged in, cache their credentials (encrypted, hopefully!) & poll VPOP3 for email every minute(?) or so. That way, I won't waste resources for users who won't use it [which will probably be many].

allow clients to maintain an IDLE connection for "push" email support
require as little disk space as possible (i.e. avoid storing the mail itself on my proxy IMAP server)

I'd love it if most of the mail content itself (body, attachments) could remain on the VPOP3 server & the proxy just downloaded the messages on-the-fly. Or perhaps cache the last X days/MB/messages for users that have logged in (to avoid pounding the main mail server with requests). I'm fine with keeping headers/metadata on the proxy; I just don't want to store duplicate all of the messages & attachments on the proxy server.

Just a little more info about our servers:

VPOP3 server accepts unencrypted, SSL/TLS, or STARTTLS connections. Encryption would be nice, but I understand that can be tricky. Since both mail servers will be on our corporate LAN, I'm OK with an unencrypted option for grabbing mail.
VPOP3 IMAP capabilities: * CAPABILITY IMAP4rev1 AUTH=CRAM-MD5 NAMESPACE ACL STARTTLS LIST-EXTENDED CHILDREN SPECIAL-USE CREATE-SPECIAL-USE METADATA (this is what I get when connecting unencrypted; not sure if it's different over SSL/TLS)
the box I'd like to use for the proxy server is running FreeBSD 10.1-STABLE
I'll probably use Dovecot for the MDA, and either Sendmail or Postfix for the MTA. I'm willing to use other software instead, as long as it's well-supported on FreeBSD.
SMTP for outgoing mail will still go directly to our VPOP3 server

Options I've looked at (but not necessarily dismissed):

This question[4] discusses something similar, but it's hard to tell whether it's what I want because of the lack of question detail. I looked at imapc on dovecot as mentioned in the only answer to that question, and it looks like it might work for my application (especially after reading this mailing list post[5]), but I haven't found whether I can configure it as I've described above.
This question[6] is somewhat similar, but there are no answers.
Other potential options I've seen include OfflineIMAP[7], imapsync[8], fetchmail[9], and getmail[10]...but I haven't found out whether any of these will actually perform the way I want them to. OfflineIMAP seems more like a message-cache; imapsync seems to be pay-for w/ no trial available; fetchmail seems to be an IMAP-to-SMTP gateway (and I don't think that's what I'm after); getmail seems to be configured on a per-user basis.
Note that I'm not opposed to any of the five options I mentioned in the last two bullet points...I just haven't found a way to configure any of them for my numbered "requirements" above.

[1] www.pscs.co.uk/products/vpop3/enterprise.php
[2] www.pscs.co.uk/manual/index.html?services_imap_advanced.html
[3] wiki.pscs.co.uk/reference:imap4_advanced?s[]=idle
[4] serverfault.com/questions/458015/imap-proxy-with-message-cache
[5] dovecot.org/pipermail/dovecot/2013-June/090884.html
[6] serverfault.com/questions/500591/fetch-all-mail-from-an-imap-server-with-postfix-to-distribute-on-local-imap-serv
[7] offlineimap.org
[8] imapsync.lamiral.info
[9] www.fetchmail.info
[10] pyropus.ca/software/getmail/
Comment: Shouldn't the sysadmin be solving this problem?
Comment: Probably, but it doesn't seem to bother him as much, and he's currently unwilling to switch away from VPOP3 Enterprise for our mail server. And to be clear, I'm part of the team that manages the network...but I've only been with the company for ~18 months (the sysadmin has been with the company for ~15 years), so I don't have as much "pull".
Answer: main.c:      * If this token is IDLE, discard it.
main.c:     if ( ! strncasecmp( CP, "IDLE", strlen( "IDLE" ) ) )

if `IMAP proxy' is http://squirrelmail.org/download.php#imap_proxy then
IDLE capability is discarded.
maybe It's hard to make its function implement.
Comment: Nope, I don't have an IMAP proxy set up currently. That's what I'm asking about :-). Our mail server doesn't support IMAP IDLE.


How can I trigger the welcome email to users who didn't activate the account?

Question: It seems we set up a number of  users and pushed them a welcome email but didn't note the expiration date on the link.
The link expired for may users before they were able to set the initial password.
Now when the user tries to use the password reset function or I try to trigger the password reset from within the user, the password reset email is not being sent.
The log files show this email is sent but have confirmed with over 20 users that they are not getting it.
The only way i can think of to trigger the welcome email is to disable the user and then enable a new one but as these are partner users, I must then update their username to a unique value which is problematic.
Any suggestions to trigger this welcome email again to these users?  Thanks.
Comment: Have they checked their Spam folders? Did you check your local mail server to see if they were quarantined?
Answer: You should check your deliverability settings is not set to "no access"


Project Euler #4 - Largest Palindrome Product in Java

Question: I am seeing that this is actually not in accord with the difficulty level said there. Firstly I cannot list all possible improvements it could have.
/*
 * A palindromic number reads the same both ways. The largest palindrome
 * made from the product of two 2-digit numbers is 9009 = 91 × 99. Find the
 * largest palindrome made from the product of two 3-digit numbers.
 */
public static int get4() {
    int max = 1;
    for (int i = 100; i < 999; i++) {
        for (int j = i; j < 999; j++) {
            int n = i * j;
            int len = (int) Math.floor(Math.log10(n));
            boolean ispalindrome = true;
            for (int k = 0; k < 3; k++) {// 100^2=10^4,999^2=998001. 5-6
                                            // digits middle atmax 3
                int digitatk = (int) ((n % Math.pow(10, k + 1) - n
                        % Math.pow(10, k)) / Math.pow(10, k));
                // eg. digit at 3 of 12345 =
                // (12345%10^4-12345%10^3)/10^3=(2345-345)/10^3=2000/10^3=2
                int l = len - k;
                int digitatl = (int) ((n % Math.pow(10, l + 1) - n
                        % Math.pow(10, l)) / Math.pow(10, l));
                if (digitatl != digitatk) {
                    ispalindrome = false;
                }
            }
            if (ispalindrome && n > max) {
                max = n;
            }
        }
    }
    return max;
}

Output:

Answer is 906609
Time taken 2.82342934 seconds

Current problems (not exhaustive):

Time
\${\mathcal O}(n^2)\$ where \$n=999\$ for looping only.
Length-checking method
Checking palindrome
Digit-finding method
Answer: Algorithm
Your time and complexity problems are probably the more serious ones. Your code starts small (at 100), and then works up to 1000. This is not the most efficient way of brute-forcing the problem. A better solution would be to start at 999 and work back to 100, but limit it when the result becomes impossible.... let me explain:
    int max = Integer.MIN_VALUE;
    for (int i = 999; i > 100 && i * 999 > max; i--) {
        for (int j = 999; j > i; j--) {
            ....

start high (999 x 999)
Work backwards from there where the second number is larger than the first
track your maximum
terminate the loops if the current i (or smaller) values will never beat the maximum.

Using the above logic, you will eliminate a huge number of loops.
Length check & Finding digit
The Log function is a good check for the length of the value, it's fine. On the other hand, it may not be necessary at all... same applies to the "finding digit"
Palindrome
I like the following method for identifying palindromic numbers:
private static final int reverse(int value) {
    int result = 0;
    while (value != 0) {
        result *= 10;
        result += value % 10;
        value /= 10;
    }
    return result;
}

Using that function, your palindrome check simply becomes:
boolean ispalindrome = n == reverse(n);

Comment: please elaborate your point 4 above.
Answer: There are several improvements that can be made to answer this question. You could start your loop from the largest possible number which is 999 and come down to 100. Once a palindrome is found, you can break. This should increase your speed.
for(int i = 999; i >= 0; i--){
        for(int j = 999; j >=i; j-- ){
            if(isPalindrome(j*i)){
                if(j*i > max)
                max= j*i;
                break;
            }
        }
    }

For your isPalindrome function, you can test different ways to find if a number is a palindrome. You could convert the number to a string and do a string palindrome test.
public static boolean isPal(String s){
  if(s.length() == 0 || s.length() == 1){
      return true;
  }
  if(s.charAt(0) == s.charAt(s.length() -1))
      return isPal(s.substring(1,s.length()-1));
  return false;
}

Basically, if the length is 0 or 1 return true. Then keep checking first and last index recursively. Another way could be basically reversing the number and checking if they are equal.
Comment: nope this won't work as the first thing I get may not be the largest [yes it's true.]
Answer: You don't want to find all pairs with a palindromic product, only the largest one. So you don't need to check pairs (i, j) where i*j is less than the largest palindrome that you found so far. But you can take even better advantage of this by checking large products first. And since the order of i and j doesn't matter, you can assume that i >= j.
int largest_i = 0;
int largest_j = 0;
int largest = 0;

for (int i = 999; i >= 100 && i*i >= largest; --i)
{
    int min_j = largest / i;
    for (int  j = i; i >= min_j; --j)
    {
        if (ispalindrome (i * j))
        {
             largest = i*j;
             largest_i = i;
             largest_j = j;
             break;
        }
    }
}

You could also make a bet that there is most likely a palindrome >= 800,000 and let largest = 800,000 initially. So you would multiply 999 only with numbers from 999 to 801, for example. This would likely be faster again; if it fails to find any palindrome you have to do the full solution.
You could first look for palindromes >= 900,000 then for palindromes >= 800,000 etc. This has the advantage that you know which is the smallest digit, which makes the test faster. And smallest digit = 9 means i and j must both be odd. Last digit = 8 means j must be even if i is odd. Not that important for 3x3 digits, but assume you are asked to check for the largest palindrome from 8 digit numbers...


What is this tracking circle called as?

Question: I don't know what the circle in the image below used for changing directions and movements of a character is called. Can anyone provide me anything related to it? I want to include it in my game.
Answer: It's a virtual joystick.
Whether or not you should use one as a controller is debatable, as discussed here.

You can't see/feel where the joystick is pointing when you are using    it.
You can't feel where the 'edge' of the joystick is - meaning, you    can't know when you are reaching the maximum in any direction
You don't always know when you're pressing the joystick. You can    accidentally miss pressing it and not know, because you can't feel
  the joystick under your finger.
Comment: Thanks  your answer was very useful. I got what i needed! I'll sure research more before using it.

What is this tracking circle called as?


Deploying Interbase ToGo on Mac OS X

Question: Here are the conditions for the experiment:

Interbase ToGo is licensed
Interbase folder including the license folder is in the same folder
as my multi-platform application called myPgm.app developed
    by Delphi XE2 as HD-FMX application.

When right-click over myPgm.app and from the drop-down menu choose Show Package Contents I am getting the following listing:
Contents
<code>Info.plist
Mac
    myPgm
    myPgm.rsm
    libcgunwind.1.0.dylib
    libibtogo.dylib
Resources
    Icon.icns
</code>
After quite bit experiments with trying to run Interbase based application on Mac OS X I made the following observations:

If DatabaseName property of the Interbase component doesn't have any value, myPgm.app shows message: "Database name is missing"
If I fill up that property with any value either wrong or right I am getting message: "product INTERBASE in not licensed".

Following the logic that when the server is not embedded DatabaseName has to start with localhost: or actual address of the server I am suspecting Embarcadero planned the developer to put some "magic" word at the beginning of the actual .ib or .gbd file.
I am looking to find solution how to connect myPgm.app with myIBDb.ib, which is in the same folder as myPgm.app.
It is so pity Embarcadero sells these ToGo licenses (I purchased one for $60) and there are no guidelines about specifying the path and the name of the database on Mac OS X. Contrary on Win system there is no problem what so ever.
Answer: I guess I have to provide the answer myself. It came after back and forth exchange of messages with support personnel at Embarcadero. As you can sense from my question I got the feelings that it is a path issue from the beginning. In the spirit of FireMonkey I was playing "monkey" by plugging interbase folder everywhere but the last place that it never occur to me putting it was the bottom of hierarchy of package contents, namely inside MacOS folder. By being a Mac application I thought it will follow the guidelines from Apple about the root path for an application bundle – the level of .app file – but no. See the snapshot for the contents of the package. (sorry I don't have privileges to post images)
Now thankfully to Embarcadero one can develop with confidence desktop database driven applications thus creating alternative to the only desktop player – FileMaker. Keep in mind that there is no MS Access database for Mac OS.

Deploying Interbase ToGo on Mac OS X


What's the standard "roadmap" to learning quantum physics?

Question: I'm really interested in quantum physics and would like to learn more. However, I don't know where to start and in what order I should learn things. So, ideally I'm looking for some sort of roadmap of what to learn. What physics topics do I need to know to start learning about quantum mechanics? (In addition to the mathematical topics mentioned at What is the math knowledge necessary for starting Quantum Mechanics?)
My current knowledge is mostly popular science stuff, like tv shows on Discovery Science and National Geographic Channel. So I have a basic understanding of some basic principals. There's also a recent lecture from Brian Cox that I have watched which gave a bit more in-depth information.
Comment: Hi Simon - the problem with this question is that it's way too open-ended. But I'll close it as a duplicate of an earlier question we have about learning physics so that you have somewhere to look for resources. I'm not sure whether that earlier question should even be open, but that will have to be decided separately.
Comment: I was hoping there would have been some sort of generally accepted roadmap in the sense of 'first you need to learn x to be able to understand y, after which you can learn z.' But apparently there isn't such a thing? The other question has some interesting resources though :)
Comment: Oh, OK, I see what you're asking now. Physics education generally does follow a standard progression (in part) and it should be fine to ask about that. Hopefully you won't mind if I try to clarify that that's what you're looking for, though. If any of the edits I'm about to make are inaccurate, feel free to improve them.
Comment: I threw in a link to another question that includes mathematical prerequisites to learning QM.
Comment: @DavidZaslavsky Thank you very much for reopening the question.
Answer: I would suggest that you don't do any preliminary reading, and just learn QM directly. There is not much to it, the requisite background is very primitive linear algebra, and Dirac's book "The Principles of Quantum Mechanics" and Feynman's "Lectures on Physics Vol III" can be read with Wikipedia help without any prerequisites.
The classical mechanics you need to know is not very sophisticated either--- you just need to know Newton's laws, and how they come from a Lagrangian or Hamiltonian, which is covered in standard sources. You don't need so much deep stuff, although knowing Poisson brackets is handy for seeing the vestigial quantumness in the classical mechanics structure.
I would suggest reading the following Wikipedia pages for a historical perspective, which helps a lot with historical literature:

Old quantum theory
Adiabatic invariant
Correspondence principle
Matrix mechanics

This is wrongly left out of most books, and this is a shame. There is no unified presentation of the historical material except on Wikipedia, and this is why these pages are up there. Once you get the historical stuff (it's not a lot), Dirac gives a conceptually self-contained introduction to the mathematics, the notation, and the physics, while Feynman is path-integral friendly, so you can go on to read Feynman and Hibbs, or Mandelstam and Yourgrau without any delay.
It is usually a waste of time to try to go through prerequisites, as these are usually boring and most of the material doesn't end up getting used. For QM, you need to come in knowing what a matrix is, and what an eigenvalue is, which is probably best learned from Dirac.
Comment: Thank you for taking the time to post this answer and I hope, if you live in America, that you have a Happy Thanksgiving.  If not, just have a nice day.
Answer: I think the usual way as they take it at a university is pretty much the time efficient way to go. The math and$\ $  *at least*$\ $ Classical Mechanics will be necessary.
Nobel Laureate Gerard 't Hooft at one put together a selection of introductions in a roadmap style
$$\text{click}$$
The navigation system on that site doesn't work for me anymore. But the important part, the links on the right hand side, work.
Comment: Very interesting indeed :) Looks like a good roadmap.
Answer: I'm sorry to tell you that anything you learn on TV about quantum mechanics is useless. Not many people in the world understand quantum mechanics and many of those who claim to, are either naive or liers. I don't understand quantum mechanics, but I could calculate your things, even explain a model of the hydrogen atom. Quantum mechanics is not "just" understanding, it's about BREAKING all your concepts, it will destroy every notion you have up to this moment. With this said, I recommend you this college-like path:

Algebra and analysis: vectorial spaces, integrals, differential equations are BASIC, so go deep into them, specially vectorial spaces so you can "upgrade" to tensors from there.
While learning the basics of algebra and analysis you should learn about Newtonian mechanics and maxwell electromagnetics (in that order).
Once you have done it, learn everything about Newtonian mechanics again using the Lagrange and hamilton formulation. At that moment you will be able to mix maxwell electromagnetics and Newtonian physics.
If you really want to go deep you should make some digging in the special relativity, but that is somehow optional... (not if you want real understanding).
Now start with old quantum mechanics books, not very similar to modern physics, but absolutely necessary if you want to understand WHY did we go the way we went.
At this point you actually know something about QM and you are ready to learn the Dirac principles and finally destroy every concept about the reality you had before starting this path.

This could be a 2-4 year project, but it is possible. I would recommend you go to lessons (in my country you can go without paying, but they won't give you the certificate). Good luck.
Note: after ALL THAT, you will get a lot of profit by reading the EPR paradox, Bohr & Heisenberg opinion about quantum mechanics, and of course the Bell article about entangled particles. Don't get mixed up by von Neumann's principles, in my humble opinion, I think he was way too mathematician to understand the deep of Bohr and Heisenberg thinking. And by the way, if you ever don't understand something, you are doing it right.
Answer: Most of the other answers are discussing the mathematical "prerequisites," but let's try to describe a standard roadmap. Most (American) universities (that I have experience with!) have a sequence for physics and brave engineering undergraduates that begins with three courses in sequence, the only math you need generally being a firm grounding in high school calculus:

Newtonian mechanics
Electricity and magnetism (not quite at the level of Maxwell's equations)
Modern Physics (Includes special relativity and the basics of QM)

At that level, basically after a year of very relaxed training, you'll know enough about quantum mechanics to be dismissive of QM claims that pop up on the Discovery channel! If you want to be an expert, then certainly much more work is required, but I'm a firm believer that you can learn a lot about a topic without knowing everything...
This leads nicely into mathematical "prerequisites," and I use scare quotes because I think it is easy for a beginner to get overwhelmed by the idea that they basically need a degree in mathematics before they can understand physics. Every single one of the topics that Jose Moreira mentioned in his answer will help you understand QM more deeply (and be remiss not to recommend Strang's book for linear algebra!) but you'll learn the bits you need as you go. One of the best quantum mechanics books for undergrads -- totally accessible for someone who has completed the three courses above -- with self-contained introductions to the mathematical tools and a refreshingly "shut up and calculate" approach is D.J.Griffiths' Introduction to Quantum Mechanics.
Answer: I don't think there is a standard roadmap because it depends very much on what you're trying to achieve. I first learned QM when doing a Chemistry degree, and that was heavily focussed on the Schrodinger equation and time-independent solutions. My friends doing Physics took a more abstract and mathematical approach.
From your question, I'd guess you're looking for something like a traditional popular science book but more rigorous. The trouble is that QM doesn't lend itself to this approach. It isn't like general relativity, where you can imagine rubber sheets and get a reasonable idea of what is going on. There isn't any simple mental image of QM you can work with. The only good way to learn it is to get stuck into mathematics.
You might want to have a look at Susskind's lectures for non-physicists. See http://www.youtube.com/watch?v=2h1E3YJMKfA for the first lecture and search YouTube for the others. I thought they were rather slow-moving and only had the patience to watch a couple of lectures, but they seemed to me to give a reasonably simple but rigorous introduction to QM.
Comment: The rubber sheet doesn't work for GR, and for QM, there are some nice visualizations, like Pauling's orbital pictures.
Answer: Like Rennie said there is no standard roadmap for learning quantum mechanics. Even though there is no standard way of learning QM I'll show you one of the possible ways of doing so. I'll assume you have the basic high school math tools:
You will need a basic calculus course, one good book for that is Calculus, Stewart a general and simple but a good approach. Take a look at the MIT calculus courses (I and multivariable calculus);
Then you will need at least one general linear algebra book: Linear algebra from Hoffman would be my choice but Kunze is also very good.
Then you should have a notion on probabilities and statistics. For that, I would suggest  John E.Freund Statistics the first course as an introduction and then you should pick up one more heavy probabilities and statistics book you like. the one I mentioned won't be enough in my opinion.
You will need to know a book about differential equations "elements of ordinary differential equations and boundary value problems" will do just fine even though it is a bit introductory a more complex book after that one would be good.
Then to finish your mathematical preparation you will need to know Fourier analysis for that I suggest for a basic approach a book not exactly about Fourier analysis but a book that has a very good approach (in my opinion) Signals and Systems, Oppenheimer.
If you study and Understand all the topics above you will be able to learn QM with no problem. A good with a somehow historical introduction to QM is Modern Physics from Krane but this one is just a transposition from classical to QM not really a QM book. As a QM book quantum mechanics, Claude Cohen-Tannoudji is a good book.
There are two things I must say:
1st a knowledge of the mathematical tools isn't enough you will need to know Newtonian Mechanics and Electromagnetism along with an introduction to relativity AT LEAST.
2nd if you do want to learn QM be aware that it will shape the way you see the world for it will show you how little we know about it. It will show you how complex the laws governing our universe are.
Good luck.
Answer: For  theoretical  purposes  I would also  recommend  you  the  following :

Principles  of  Quantum  Mechanics  by  P.M. Dirac.
Mathematical  Foundations  of  Quantum  Mechanics  by  J. Von  Neumman.
An  Introduction  to  Quantum  Theory  by  Keith  Hannabus.

Now  because  of  your  interest ( according  to  your  profile )  on  computer  science,  you  may  want  to  read  something  about  quantum  computing. For  example  "An  Introduction  to  quantum  computing"  by Phillip Kaye, Raymond Laflamme  and  Michele Mosca.Or  the  following  arxiv.org  material :
http://arxiv.org/abs/quant-ph/9809016
http://arxiv.org/abs/0708.0261
Good  luck, I  am  also  trying  to  learn  Quantum Physics ! :)
Answer: If you want to do research in theoretical physics, you have to be very strong in math (abstract math).  Otherwise, if your goal is to understand what's going on in quantum physics, field theory etc, then you will not need any math beyond Boas' mathematical methods.
Answer: It is possible to learn Quantum Mechanics before taking Classical Mechanics.  That is what I did.  But you do have to know what a vector space, basis, change of basis, linear transformation, and matrix are.  Then read Dirac.  You can learn the Hamiltonian point of view from Dirac.  So I would say that the prerequisites are: Irving Adler, The New Mathematics, and Isaac Asimov, The Realm of Algebra.
Comment: So, "The New Mathematics", "The Realm of Algebra" and "Principles of Quantum Mechanics"?


IE11 F12 Developer Tools on Windows 7 functionality missing/not working?

Question: I was using IE10 on Windows 7 but it is such a buggy piece of you-know-what (hanging, crashing, etc.) that I gave up and installed IE11. It has not hung or crashed since installing. But I hate the F12 developer tools! Okay, not completely - there are some very cool new features. What I don't like is that they seem to have dropped several features that I really liked! Unless I'm just missing something... I've searched and searched on Google and Microsoft but all of the help I've found only describes the new features. Here is what I'm missing: Color picker, Ruler, and most of all, the Clear browser cache for this domain. They allege to have a Clear browser cache function, but it doesn't work! So when I make changes to my website, in particular changing graphics, the only way I can see the change is to delete all my temporary files from IE. Then I lose all of my cookies e.g. for automatically logging in to Stack Overflow! IE version 11.0.9600.16428 on Windows 7 Ultimate 64-bit.
Answer: For the issue of serving cached files try toggling on "Always refresh from server" on the network tool (3rd option from the left). This should get you the latest changes from your server.
Answer: The color picker is still available, go to the DOM Explorer tab and there is an eye dropper on the tool bar at the top towards the left. That activates the color picker.


Comparing two different Power Point presentations side by side

Question: I am trying to run two MS Office Power Point  2007 presentations side by side on two monitors on the same system . So they can be compared. But power Point will not allow two instances at the same time. Does anyone know of a trick without installing two copies of Power point on the same machine ?
Answer: Alex has the right idea, but let me help more:
After Arrange All, you can extend PowerPoint to be the width of both monitors, then manipulate each PPT's window to fit into that screen's window, giving you side by side.
Answer: Here's what you're looking for:

On the View tab of the ribbon, in the Window section, click on the Arrange All button.