Simplest 2-site VQE Ansatz to generate all states?

Question: For 1-site I was able to use an Rx gate followed by an Ry gate to generate every possible state. For two-sites, I initially tried to apply this to each qubit but realized this doesn't work because it does not entangle the qubits.
I have seen many examples of ansatz but they all seem to be optimized to particular hamiltonians and some don't generate every state. Is there a very simple 2-site ansatz I can use to generate all states?
Answer: Actually, we do not need to consider a generic two-qubit unitary since we start from the fiducial state $|00\rangle$, and therefore all that matters is the first column of the $4 \times 4$ matrix representation of the circuit that we apply onto the fiducial state. As @MicheleAmoretti correctly pointed out, an arbitrary SU(4) matrix can be parameterized with 15 free parameters. An arbitrary two-qubit state, in turn, takes only 6 free parameters (cf., e.g., @AdamZalcman's answer to this earlier question). The same reduction of the number of free parameters was already alluded to in the question itself: Two rotation gates suffice to prepare an arbitrary single-qubit state, but it takes 3 free parameters to encode an arbitrary SU(2) matrix.
As for the actual parameterized quantum circuit that realizes such a generic two-qubit state, we can consider a symmetric bipartition to reshape the 4-dimensional vector into a $2 \times 2$ matrix and then perform its singular value decomposition. This allows to derive a quantum circuit with a single CNOT and six rotation gates, as explained in Section VII of this paper.
Comment: Thank you for the detailed response!
Answer: The minimal circuit for a generic 2-qubit unitary $U$ is described in the following paper:
https://arxiv.org/pdf/quant-ph/0308033.pdf
(see Fig. 2). This amounts to 3 CNOT gates, 3 rotation gates, and 4 arbitrary single qubit gates which become 12 single rotation gates using ZYZ decomposition.
Comment: Thank you for the resource. When you say 4 arbitrary single qubit gates can be used, does this mean the Rx, Ry or Rz gates can be used in these positions?
Comment: Arbitrary means, in general, a combination of Rx, Ry and Rz (e.g., ZYZ).


1996 ford courier 2.6 petrol duel cab

Question: My clutch started sticking to the floor and then it went completely I've replaced the slave cylinder and bleed the clutch but it still seems to stick it got a little better after the bleed but after 5-10 mins it's back on the floor again
Comment: Did you check the line for leaks? Did you test the clutch master cylinder?
Comment: When you say "sticking", does it feel like something is jammed, or does the pedal just feel soft and easy to press down?
Comment: I push the peddle and it sucks it's self back to the floor
Answer: Frequently with clutches it's very hard to bleed the air out.  You can sit with a partner in the cabin of the vehicle and do this forever and never get all the air out.
I recommend you get a hand vacuum pump to bleed brakes and hydraulic clutches.
This is what they look like.

You attach a clear tube to the bleed nipple of the clutch master cylinder and put the catch container in line with that and the hand pump.
You don't need a partner to assist when you do this.  As well, you can see air coming out of the clear tubing so you get rewarded as your hand get's tired.  Be sure to keep fluid going into the fill for the clutch, if you go empty, you start to pull air in and your at square one.
If your in the states you can goto Harbor Freight and get these for under $20 US.  They are will worth every penny.
If you find you still have an issue after pulling out all of the air at least you know what it isn't and can rule that out before you start procuring more parts.  I see this as essential to success when bleeding brakes and clutches.
Best of luck, cheers!
Answer: Since you say that the pedal is sucked to the floor, the only thing that could be causing this is a fault in the brake booster (servo).  The booster uses vacuum from the engine to assist pressure from your foot when pressing the brake.  If there is a fault in the valve mechanism inside the booster, then the vacuum from the engine will keep assisting until the pedal hits the floor as you describe.  Presumably this only happens when the engine is running.  If you turn the engine off, does the pedal rise again?

1996 ford courier 2.6 petrol duel cab


How to disable Prelude Emacs and use system-wide Emacs

Question: I have installed Prelude Emacs by using wget --no-check-certificate https://github.com/bbatsov/prelude/raw/master/utils/installer.sh -O - | sh. I am using Debian and  new to Emacs. Now whenever I run emacs in terminal, it opens Prelude Emacs. I wonder it is possible to two versions of Emacs; one for system emacs (installed by apt-get install emacs ) and the other installed by the above command. I don't want to uninstall Prelude Emacs. But just having two different emacs. (This question could be asked for a different version emacs such as spacemacs which uses .emacs.d directory). So it will overwrite my configuration files inside ~/.emacs.d/ as Prelude did it for my system-wide Emacs.
Answer: If you want to test different setups in Emacs try using Chemacs 2 is an Emacs profile switcher, it makes it easy to run multiple Emacs configurations side by side.
Move the configuration that you want to keep as your default to ~/.emacs.default/init.el
Comment: Ive upvoted. And I use chemacs. But changeover is not entirely trivial. All paths like `~/.emacs.d/...` need to be changed to use `expand-file-name`
Answer: I'm not familiar with Prelude Emacs but you can launch emacs without any configuration file using emacs -q or with a special init file emacs -q -l ~/.emacs.d/special-init.el.
Maybe you want to create an alias e.g. alias RawEmacs = 'emacs -q'.
Comment: If I use new `init.el` file rather than defined one, this will load new packages from Melpa or will it borrow packages from `.emacs.d\elpa` directory?


Importing dates from excel or access to SQL Developer?

Question: I have a field of dates in an Excel that I am trying to import into SQL developer, but I either get an error message regarding the formatting or the date values come in their raw form from excel. Does anybody know how to import dates from Excel or Access into SQL Developer? Thanks.
Answer: Excel stores date in a different way.
You can change format in sql developer Tools >Preferences >Database->NLS
I think you can change the format to "DD-MON-RR HH.MI.SS" depending on your requirement.
http://www.jasonsdevelopercorner.com/?p=209


Library for drag and drop to specific areas

Question: What library can I use to implement the following kind of functionality
on Linux:
http://www.flickr.com/photos/65774455@N08/5983551492/in/photostream/
http://www.flickr.com/photos/65774455@N08/5983551494/in/photostream/
My goal is a locally installed app so stuff like JQuery is out of the question.
Preferred languages are C, Perl. But it doesn't have to be strictly confined to those 2 languages.
Any hints to which part of the library I should look at will be deeply appreciated.
Thanks!
Answer: In case your question is still up to date:
You could take a look at QT, which is a very good gui framework (KDE is built on top of QT) http://qt.nokia.com/. It really has tons of features and stuff, and you can of course build GUIs that support drag & drop. The framework is in C++ though.
The GTK framework (base of the gnome desktop environment) has C as well as C++ libs (http://www.gtk.org/).
Of course there are other gui libraries and frameworks for linux (http://en.wikipedia.org/wiki/List_of_widget_toolkits), I for one, would always choose QT over any other framework, because the API and documentation is really great.


Android: get past mobile data stats

Question: I'm trying to obtain the data stats in Android (also WiFi) of a past period.
I know there is the TrafficStats class, but it seems to make available just the infos about the current connection.
I'd like to obtain something about: "Get the data received in the last month".
Any suggestion?
Answer: There is nothing available for this in the Android SDK, unless you collect the data yourself via TrafficStats.

Android: get past mobile data stats


Cannot boot live USB with Ubuntu on a specific PC, on others the USB works fine?

Question: What I do:
I prepare Ubuntu live USB and boot with it. I select the USB pen drive. The PC tries to boot from it.
What happens
I receive an error message: boot error.
What is expected:
A normal boot procedure.
Some other information:
1) No matter how I prepare the USB, I get the same result. The USB works just fine on some other PC.
2) The PC will boot from USB made to boot MS-DOS.
3) The PC is dual-boot, Win7 and Ubuntu(installed from CD)
4) The BIOS is Phoenix-Award(version of bios dated 2008), the motherboard is comparatively new.
Comment: can you post the complete error message please
Comment: That is all:  "Verifying DMI Pool Data ....... Update Success"  "  "Boot Error". These are all messages I got - no Ubuntu menu, noting. Tried installing mbr and formatting the drive to zip drive format. Not quite sure I succeeded with the last two.
Comment: I tried bypassing BIOS  (I suspect) limitations with plop LiveCD, but still boot fails...
Comment: I have a computer that refuses to boot off a certain flash drive, even though I can boot with other flash drives, or even use the same flash drive to boot off other computers. I would suggest trying a different flash drive if you have one available, if not you can get a cheap SanDisk (which I have had really good luck with) or you can try booting a LiveCD, perhaps it isn't the flash drive at all. Also, what kind of flash drive is it?
Comment: Which **Ubuntu** version(s)?  on the PC (dual boot), and on USB (Live CD) attempting boot ..
Comment: Have you tired to manually pick the boot-device (using BIOS), rather than auto-select (boot order)?
Answer: This worked for me. i think the BIOS is to blame. Award-Phoenix 6.00PG.
1) I create DOS bootable USB. Simply dd the iso found here This will be called DOS-USB
After doing this, the DOS-USB is seen as harddrive by the bios, not as usb
2) Download grub4dos and extract grub.exe from the zip and copy it in the root of the DOS-USB.
GRUB4DOS download
3)Create file menu.lst(or copy the one from the zip) and add this:
<code>title Boot MultiBOOT LinuxUSB
find --set-root /boot/bootme.tag
kernel /boot/grub/core.img
savedefault
boot
</code>
(this entry assumes there is a file called bootme.tag in boot of your second, booting USB.You should create this one yourself. It is added as id file, since I assume most of you have Ubuntu installed, so searching for GRUB file will find two drives)
4) Create your booting USB(you need 2 USB for this solution) I call it Linux-USB. I use this tool but any GRUB2-based tool should work. MultisystemUSB though fails. I have not tried Unetbootin and Ubuntu Live USB
5) Create an Non-empty(some text will do) file, call it bootme.tag and copy it to /boot of your Linux-USB.
Reboot with both USBs plugged, select to booth from DOS-USB. When you see c:, enter grub.exe, and select Boot MultiBOOT LinuxUSB entry. This should find and boot the Linux-USB.
Answer: change usb drive from zip to hd and set it to first boot device.
Comment: I think this worked, though I fixed it a while ago. I will accept the answer, even though I am not quite sure if this fixed the issue, this is a valid answer similar problems. I learnt a few thinks for these 2 years
Answer: With Award BIOS 6.00PG I had the same problem, but it is entirely BIOS related. The way to do it is:

insert USB with live system
start machine and enter BIOS (del key)
select "Advanced Boot Parameters", in which the USB key should now be listed
move USB key to top of boot order
save and exit
let machine reboot -- it will use the USB key to boot that one time.


How do we use 죠 at the end of question ?

Question: I know it's short of 지요 but how do you use it in questions and what else do you use at the end of the questions if not this ?
Comment: use it same as you would 지요, like 예요/이에요
Answer: You would use 지요/죠 at the end of a question where you want to "check" with someone. As in, not a regular question, but you know the answer and you want to check if someone agrees with you.
For example:
Delicious?

맛있어요?

vs
Delicious isn't it?  (You aren't really asking, since you already think it's tasty, you are kind of just expecting them to agree with you).

맛있죠?
Answer: You can use something like below.

우리는 한국어 공부를 하지요.
  우리는 한국어 공부를 하죠.

or
In questions

하겠지요?
  => 하겠죠?


periodic continous function $f$

Question: I have a function $f: \mathbb{R} \longrightarrow \mathbb{R}$ that is continous with $f(x)=f(x+2)$ for all real numbers $x \in \mathbb{R}$. So, I have to show that an $a \in \mathbb{R}$ exists that $f(a)=f(a+1)$. I tried to proof this by using the periodicity of $f(x)$ and so I took a look on:
$f_1: [0,2] \longrightarrow \mathbb{R}$ I concluded that this $f_1$ has also uniform continouity. Then I took the definition of uniform continouity $\forall \epsilon > 0\exists \delta> 0 \forall x\in\mathbb{R}, y\in\mathbb{R}: |x-y|<\delta \Rightarrow |f_1(x)-f_1(y)|<\epsilon$ Unfortunately, I don't know what to do next and I am also not sure whether the solutions, that I have done, are right. Can someone help me with that, please?
Answer: Let $g(x)=f(x+1)-f(x)$. Let's notice that $g(0)=f(1)-f(0)$ and that $g(1)=f(2)-f(1)=f(0)-f(1)=-(f(1)-f(0))$. Therefore, $g(0), g(1)$ have opposite signs (one negative and one positive. there's a case where they're both $0$, and then we've proven what we want). Therefore according to the intermediate value theorem, the function $g$ must take all values between $g(1), g(0)$ in $(0,1)$  in particular, $0$, and therefore exists $x_0\in (0,1)$ such that $g(x_0)=0$ meaning $f(x_0)=f(x_0+1)$
Comment: My apologies for submitting an answer which duplicates yours. Your answer was not showing when I submitted mine.
Answer: Define $$ g(x) = f(x+1) - f(x)  $$
If it is ever zero you are done.
If $g$ is always positive, what happens? Always negative?
Comment: My apologies for submitting an answer similar to yours. Your answer was not yet showing when I submitted mine.
Comment: @JohnWaylandBales It happens, nothing to worry about.
Answer: Let $f(a),f(b)$ respectively be the maximum and minimum of $f$ on $[0,2]$. Since the image of $f$ in $[0,2]$ is the same as its image on $\mathbb{R}$, these are also its global extremum on $\mathbb{R}$.
Hence, $f(a) \geq f(a+1)$ and $f(b) \leq f(b+1)$ and the result follows from the IVT. Note if the above inequalities are equalities, we're already done.
Answer: Define $g(x)=f(x+1)-f(x)$ for all $x\in\mathbb{R}$. Then $g(x+1)=-g(x)$ for all $x\in\mathbb{R}$. If $g$ is identically $0$ then the wanted conclusion about $f$ follows. If $g$ is not identically $0$ then for some $x_0$ it is the case that $g(x_0)\ne0$. Since $g$ is continuous and $g(x_0)$ and $g(x_0+1)$ have opposite sign, there must exist an $a\in[x_0,x_0+1]$ for which $g(a)=0$. Thus $f(a+1)-f(a)=0$ and we are done.

periodic continous function $f$


Undecidable countable structure built on decidable relation?

Question: My question is, is there a relation $R$ on the integers that's decidable (i.e. the function
${\mathbb Z}^2 \to \lbrace \text{true},\text{false} \rbrace, \  (i,j) \mapsto i R j$ is computable) , but such that the structure ${\mathfrak A}=(\mathbb{Z},R)$ is undecidable, in the sense that the "truth value" function of a formula $\phi$ of ${\mathfrak A}$ is not computable? (a formula $\phi$ of ${\mathfrak A}$
is a meaningful sequence of quantifiers $\forall,\exists$, of logical connectives $\Rightarrow, \vee, \wedge$, of any number of variables $x_1, \ldots x_n$, and the $R$ symbol, of course).
Comment: as soon as you have unbounded quantification you are very likely to go above decidable structures.
Answer: Yes, the point is that $(V_\omega,\in)$ is bi-interpretable with $({\mathbb N},+,\times,0,1,<)$, which has undecidable theory. (Although this bi-interpretability is a stronger claim than what you are asking or what I sketch below.)
Fix a recursive bijection between ${\mathbb N}$ and ${\mathbb Z}$, so it is enough to define such an $R$ on ${\mathbb N}$. Set $iRj$ iff there is a 1 in the $i$-th place (from right to left) in the binary representation of $j$. Then $({\mathbb N},R)$ is isomorphic to $(V_{\omega},\in)$ where as usual $V_\omega=\bigcup_n V_n$, with $V_0=\emptyset$ and $V_{n+1}={\mathcal P}(V_n)$ for all $n$.
Clearly $R$ is decidable. On the other hand, any statement about $({\mathbb N},+,\times,0,1,<)$ can be translated as a statement about $(V_\omega,\in)$, as $\omega$ and the arithmetic operations on $\omega$ are definable in terms of $\in$.
I assume you know why $({\mathbb N},+,\times,0,1,<)$ has undecidable theory. To drive the point home, you may take as $\phi$ the translation of the statement "PA is consistent".
Comment: Very nice! I did not expect the $R$ relation to be that simple.
Answer: Yes, take for example $iRj$ for "Turing machine number $i$ halts in less than $j$ steps when started on an empty tape". Then $\phi(x) = \exists y. xRy$ is undecidable.
Comment: $\exists y. x R y$ has a free variable, so its truth value is not defined.
Comment: It is a unary predicate, with a well defined truth value for every $x$. It makes little sense to speak of whether any _single_ truth value is computable or not -- it always is, either by the program that simply outputs the constant "true" or by the program that simply outputs the constant "false". (We may not _know_ which of these programs is the right one, but one of them will certainly be).
Comment: That was my point, constants are not part of the language, so you can't form formulas $\exists y. \bar x R y$ for $x \in \mathbb Z$.
Comment: $x$ is not a constant, is is a _parameter_. The undecidable problem is, given $x$ as an input, to decide whether $x$ satisfies the predicate. How would you state _any_ nontrivial decision problem without having a free variable?
Comment: Easy, given a closed formula, determine whether it's true or not (there are countably many closed formulas). This is what OP asks, imho.
Comment: Okay, that's a reasonable interpretation of the question.


Completeness and Compactness of Cartesian Product of Metric Spaces

Question: Suppose $\{(X_i,d_i)\}_{i\in \mathbb{N}}$ is a collection of metric spaces with the cartesian product defined by $A=\prod_{i=1}^{\infty}X_i$. Let the metric on $A$ be given by $d(x,y)=\sum_{i=1}^{\infty}\frac{1}{2^i}\frac{d_i(x_i,y_i)}{d_i(x_1,y_i)+1}$. How would one go about proving that $(A,d)$ is complete iff each $(X_i,d_i)$ is complete and $(A,d)$ is compact iff each $(X_i,d_i)$ is compact?
Answer: The proof of this is rather long, but straightforward. To show this space is complete, take a Cauchy sequence. Show that it projects to a Cauchy sequence in each coordinate. Since each factor space is complete, you have a natural candidate $x$ for convergence. You can find an $N$ large enough that the $i$th coordinate of the $n$th term of the Cauchy sequence is within $\epsilon/2$ of the $i$th coordinate of $x$ whenever $i$ and $n$ are less than $N$, and so that $\sum_{i=N}^\infty 2^{-i}<\epsilon/2$. Then apply a standard $\epsilon/2$ argument by breaking the series at $i=N$. Compactness is proved via sequential compactness with essentially the same argument. Start with an arbitrary sequence. It has subsequences which converge in each coordinate. Carefully build a subsequence which converges in every coordinate by first taking a subsequence that converges in the first coordinate, then taking a subsubsequence which converges in the first two coordinates, and so on. By the above argument, this entire subsequence converges.
To prove the converse of each part, you have one $X_i$ that is not complete(compact), so there exists a bad Cauchy sequence which (sequence such that every subsequence) doesn't converge. Choose a sequence in the product space which matches your bad sequence in the $i$th coordinate, and is constant in the other coordinates. This sequence will behave poorly in the product space too.
Comment: I'm struggling to show that  a Cauchy sequence in A projects to a Cauchy sequence in each coordinate. If we suppose $x=x_n$ is a Cauchy sequence, then for all $\epsilon > 0$ we have there exists $N$ s.t. for all $k,m > N$ that $\sum_{i=1}^{\infty}\frac{1}{2^i}\frac{d_i(x_{k_i},y_{m_i})}{d_i(x_{k_i},y_{m_i})+1} < \epsilon$. Then it follows that each $\frac{1}{2^i}\frac{d_i(x_{k_i},y_{m_i})}{d_i(x_{k_i},y_{m_i})+1} < \epsilon$. Then we can rearrange to show that $d_i(x_{k_i},x_{m_i}) < \frac{\epsilon}{\epsilon^{-i}-\epsilon} = \delta$.But how does this show that either $x_k$ or $x_m$ is Cauchy??
Comment: You can get $\sum_{i=1}^\infty\frac{1}{2^i}\frac{d(x_i,y_i)}{1+d(x_i,y_i)}<\epsilon 2^{-k}$, so $d_k(x_k,y_k)<\frac{2^k}{2^k}\frac{d(x_k,y_k)}{1+d(x_k,y_k)}\leq 2^k\sum_{i=1}^\infty\frac{1}{2^i}\frac{d(x_i,y_i)}{1+d(x_i,y_i)}<\epsilon.$
Comment: But $x_k$ is an element of $x$ and $y_k$ is an element of $y$. This does not show that $x$ or $y$ is cauchy in $X_k$...?
Comment: I just used $x$ and $y$ as example symbols replace the letters with the ones you need to get the job done.


Why is $H_0(X)\cong \tilde{H}_0(X)\oplus \mathbb{Z}$?

Question: Here is how hatcher proves this. Let $(C_•(X),\partial_•)$ be the reduced singular chain complex where $X$ is a nonempty topological space. Since $\partial_0:C_0(X)\rightarrow \mathbb{Z}$ is an epimorphism, we have $C_0(X)/\ker(\partial_0)\cong \mathbb{Z}$. Since $im(\partial_1)\leq \ker(\partial_0)\leq C_0(X)$, by the third isomorphism theorem, we have $H_0(X)/\tilde{H}_0(X)\cong C_0(X)/\ker(\partial_0)\cong \mathbb{Z}$. Hatcher wrote that this implies that $H_0(X)\cong \tilde{H}_0(X)\oplus\mathbb{Z}$, but I do not understand why. How do I show this? Thank you in advance.
Comment: @Enigma, but why does it split?
Comment: The short exact sequence $$0\rightarrow\tilde{H}_0(X)\rightarrow{H}_0(X)\rightarrow H_0(X)/\tilde{H}_0(X)\rightarrow0$$ splits, where the maps are the canonical inclusion and projection maps.
Answer: We have the exact sequence
$$0 \to \widetilde{H_0}(X) \to H_0(X) \stackrel{r_*}{\to} H_0(P)\to 0,$$
where $P$ is a one-point space and $r:X \to P$ is the unique map from $X$ to $P$.
Any map $i: P \to X$ induces a splitting, since $Id_*=(r \circ i)_*=r_*\circ i_*$, from which follows that
$$H_0(X) \cong \widetilde{H_0}(X) \oplus H_0(P) .$$
Note that the argument holds for any homology theory satisfying Eilenberg-Steenrod axioms ($H_0(P)$ does not need to be free, for example) , since the splitting is given by functoriality of homology.
Comment: Nicely formulated.
Answer: There is a map $\mathbb{Z}\rightarrow H_0(X)$ inverse to $\partial$. Namely take sny point (or vertex) $v$ in X and define $n\mapsto n[v]$. The image of this map is isomorphic to $\mathbb{Z}$ and with the reduced group forms a direct sum.


Can time drift even after using NTP?

Question: We have NTP installed on our servers to keep time on them in sync. Can time of the servers still drift? If yes, how can we detect that? Can we force server to reset after certain max drift?
Comment: If you're running NTP as a daemon, the drift should be minimal unless your reference time sources are themselves not stable (which makes them a poor choice for a reference time source).  If you run NTP once at server startup (not in daemon mode), then you'd suffer from drift over time — fixable by running NTP again.  (I've not checked whether the NTP daemons can be run as a 'single shot' process — but you probably don't run it that way by accident.)  Have you checked the batteries on the real-time clocks on the machines where you have a drift problem?  (Batteries probably aren't a problem.)
Answer: This is a very tricky question to answer without knowing a lot more about your time domain setup.
If your time setup is correctly configured then no. All your servers will keep within an acceptable distance of true time. But that presumes you have both your own stratum 0 / 1 time receiver and at least 5 external reference sources of a low stratum.
If your time setup is 'closed' wherein you only take time from say your own S0/1 reference source then depending on that source yes your servers can drift from UTC but would all remain in sync. This would only really be true if you where using a pure PPS type source that dose not actually provide a timestamp.
If your time setup is 'bad' with say only 1 or 2 external reference servers at a high stratum then if the reference sources become wrong either by accident or through other interference then your servers could be off by a big factor. If all your servers used the same upstream source then as above they should all be in sync with each other but could be out against UTC. If all your servers used a different source then they could all be out of sync in comparison with each other & UTC.
To answer the last part of your question next; No I wouldn't force any server to do anything (like jumping the time/date) I'd make sure my ntp setup was working correctly so that it always ran with a valid drift file and kept the host in check how it was intended (Over a running period of time)
As to monitoring ntp this can be a tricky one. If you wanted to automate it then you can find scripts on the net which will allow the collection of ntp stats into mrtg that will allow you to plot drift, offset, disposition etc. I have successfully implemented this for a number of hosts and it appears to work quite well. It will give you graphs & alerts if you exceed limits you define. Otherwise you have things like ntpstats and other log files you can trawl through, but I suspect that's what you are trying to avoid.
Please feel free to update your question if you need a better or more specific answer. Hopefully this helps.
You could try this link for ideas on monitoring via a script and MRTG there is also a number of plugins for Icinga/Nagios here which might be of help. My scripts are based on the examples in the 1st link - but they allow +ive and -ive plots in my RRD files. To do that you need to generate the RRD first then run rrdtool tune <name_of_rrd>.rrd -i ds1:U -a ds1:U
But I also notice in the source file for ntp-4.2.6p5 I find the following dir /ntpsnmpd/ which has an interesting README which says you can access some values via an SNMP agentx. Have a look - I've not seen that till now & never tested it.
Comment: Thanks for the detailed answer! Can you provide some ntp stats collection script examples?

Can time drift even after using NTP?


Fast gmail client program

Question: This is a seemingly simple problem. I want to access my gmail mail account using some other client than googles web interface. Sounds easy right? Gmail supports IMAP so any email client should work.
Except none of all I've tried (Thunderbird, gnus, Wanderlust, ...) can handle the huge amount of mails I got. Workarounds such as deleting or archiving mails to keep the mailboxes small doesn't count as a solution. Gmail doesn't require me to do that so I shouldn't have to do that with another client either.
For example, I got a mailbox of python-list with ~900k mail which Gmail's web interface opens in less than 3 seconds. All other clients I've tried just chugs on it for minutes. Someone must have had the same problem as me and solved it somehow?
Edit: I'd like to state that there is an answer to the question, and the answer is that there is no such program. The gmail web client and android app uses a completely different interface than IMAP which is much better suited for handling large amounts of mails. It may also be undocumented and proprietary extensions to IMAP, but the effect is the same: no client other than GMail's own can work as fast as it does.
So there annoying question closers; the question had an objective valid answer.
Answer: Have You tried eM Client? It's pretty fast. Free version include 2 mail account.
Run on Windows.

Fast gmail client program


Show only one label for multiple points with same value in QGIS

Question: I have a point shapefile which has for a few occasions multiple points with the same ID. Doesn't look nice with the normal label-display.
Is it possible in QGIS to only display one label then? I couldn't find a check/uncheck option... Perhaps it would be possible to retrieve labels via a SQL-query, with a »GROUP BY id«?
Answer: I assume that you have multiple features with the same ID and not real multipoint.
If needed there is also a solution with real multipoint, let me know.
You can add an integer field to your shapefile that you populate with 1 if you want to display the label for this features and 0 for others.
Then in the renderer of the label use data-defined property for show or not labels.

EDIT :
Answer by @Kazuhito gave me an idea to go further.
You can also add two fields (x_lbl and y_lbl for example) and use them to get a total control on the placement of your label by using data-defined properties for label placement. Fill these fields with the coordinates where you need your label, you can then modify easily the place from the QGIS Interface. Look for this buttons:
Comment: I'm wondering if you have found any solution to labeling multipoint features because I'm stuck with this problem for real multipoint geometries now...
Answer: If a virtual layer is an option,
SELECT id, st_pointonsurface(st_union(geometry))
FROM your_layer
GROUP BY id

will place a point at around the center of each group.
I like the answer by @YoLecomte , which gives us more control to select where to put the label.
Answer: Another option is to use "Collect Geometries" under the Vector->Geometry Tools menu.
Then choose the field to group them by.
This will create multipart geometries with one table record and only one label will be generated for grouped features.


Xcode 6.0.1 Command /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swiftc failed with exit code 1

Question: I am getting this error on archive:

Command /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/swiftc failed with exit code 1

How to solve it?
Please see the screenshot.
Comment: Same here. Anyone have a resolution yet?!?!?
Comment: I don't have solution for this. Somehow the code got executed. Somewhere in the code I have written some thing that was creating problem. Actually, I was handling the Dictionary it had some issues. But, I don't know why xcode was not at all showing any error on those line. Finally, I commented the code and code was executed.
Comment: Check this answer -  http://stackoverflow.com/questions/25889723/swift-failed-with-exit-code-1-while-compiling-in-xcode-possibly-related-to-bri/27271734#27271734
Answer: This problem occurs when the Swift optimization level is not set to None for Release. Set the value to None and the issue goes away.

Open up your project and click on the projects root directory.
Click the build settings tab.
Search for Swift Compiler - Code Generation and under Optimization Level make sure Release is set to None.

EDIT
After upgrading to Xcode 6.1 these instructions caused other issues when archiving (building for debug/device worked fine). Setting the optimization to Fastest allowed me to archive again. There are apparent issues with Swift compiling still (archiving specifically).
Can't archive working 6.0.1 Swift project in Xcode 6.1 / Segmentation fault: 11
EDIT
I was not able to fund the Build Settings tab, until I read this answer.
how to find the build settings tab
Comment: Didn't work for me with Xcode 6.3.2.  @庄景鹏's answer worked for me.
Comment: Is It a good idea to leave realise build without optimisation?:-)
Comment: But, will this create any issues while archiving?
Comment: None, I have submitted an app successfully using this. It appears there is an issue with the optimization messing up something in swift code. My assumption is the bridging header.
Comment: assertionFailure will not turn into noop if you follow these instructions.
Comment: Didn't worked for me, instead @Johns answer led me into the right direction: My project had troubles finding a missing file.
Answer: This occurred for me when I had two of the exact same files, and also when I was missing I file I didn't know I had deleted. I clicked on the error message, and just above the error, it shows you what file you have more than 1 of or are missing.
Comment: For me it was a file that had been deleted from the project but was still referenced on the other computer. Your suggestion about git commits helped a ton!
Comment: This led me into the right direction. Thank you John!
Comment: For me the issue was that I had deleted a file from project without removing the reference. I had removed the file from terminal but the non existent file was still being referenced in the project.
Comment: How did you add the file again?
Answer: You can click the Product in the navigation and choose the "Clean" button; it will clean all compile error in your project. Then, you can debug for the latest error.
Answer: Deleted files reference keep in Build Phase and that's why it gives this error. Remove reference from there as well.
Project> Target > Build Phase
Under this section you will find your deleted files in red colour. Remove these files error will resolve.
Answer: I am not sure if it has one solution.
I recommend you to check the differences between your last git commit, and comment on/off the changes.
In my case, my code was
let anArray = ResultDict["ResultSet"] as [[NSDictionary : AnyObject]]
for aDict : NSDictionary in anArray {
    let anObject = ObjectType(ObjectDict: aDict)
    objectList.addObject(aDict)
}

no warning on the line, i got the same exit 1 compile error
then i changed it to the below it has compiled.
let anArray = ResultDict["ResultSet"] as [[NSDictionary : AnyObject]]
    for aDict in anArray {
        let anObject = ObjectType(ObjectDict: aDict)
        objectList.addObject(aDict)
    }

Answer: I don't know if this is really an answer, but...
I had the same issue. App worked when building/running, but archiving failed with "...swiftc failed with exit code 1", with no other helpful message at all. Luckily, when I tried to build my app with Nomad's ipa build, I got:
The following build commands failed:
    CompileSwift normal arm64 /path/to/erroneous/TableViewController.swift

So I started commenting out sections of that file and tracked the problem down to a tuple assignment.
// MARK: - Table Data

private var tableData: [(sectionName: String, item:ListItem)] = []

private func refreshTableData() {

    // let labor = ("Labor", laborListItem)                 // DOESN'T ARCHIVE
    let labor = (sectionName: "Labor", item: laborListItem) // ARCHIVES

    tableData = [labor]

    tableView.reloadData()
}

So apparently the compiler wanted the elements in thast tuple named (as defined by the type of tableData).. but only for archiving? The Dumb thing is, I use this same pattern in other view controllers, and the compiler seems to be fine with those.
For the record my Code Generation -> Optimization Level was set to None for debug and release.
Hope this helps someone! It took hours to figure this out.
Answer: It happened to me when I didn't put the parenthesis at the end of a call of a function:
let var = self.getNextPrimeNumber

solved it by:
let var = self.getNextPrimeNumber()

Comment: I also got this with XCode 7.3.1 and Swift 2.2.  Thanks for the suggestion
Comment: I got this in XCode 8, Swift 3 by calling viewcontroller without its parenthesis on UIViewControllerContextTransitioning.
Answer: In my case, it was caused by duplicate files, using the same name, in my project directory. As soon as I removed them, the error was gone.
Answer: This happened to me when I used static inline function from swift file
The function looks like this
static inline void openURLInSafari(NSString * _Nonnull urlString) {
[[UIApplication sharedApplication]openURL:[NSURL URLWithString:urlString]];}

Answer: this error comes from missing files so the compiler couldn't find the files and keep alerting.
Follow these steps to rebuild your app:

Look up for the red and invisible files within workspace
Remove their reference
Re-add files
Re-compile
Answer: I just had the same thing occur. I hunted down the cause to one file that caused the error even when empty. Examining the file, I discovered it had the wrong character set. When I set it to UTF-8, the error vanished. I think that it was decoding it with the wrong character set.
From this I surmise that the error simply indicates that something has happened that the compiler was unprepared for. Sorry that isn't very helpful to most people, but it may help to check your characters sets.
Answer: This error occurred for me after I noticed that a few of my .swift files were inexplicably in the wrong directory -- one level above my Xcode project directory.  When I noticed this, I moved them into the main project directory and cleaned the project, thinking everything would be fine.  However, upon building the project I got the above-mentioned "failed with exit code 1" error.  Just above the error message it listed the files I had just moved, indicating that it couldn't find them in the directory where they used to be. In addition to the error message, the files I moved were now showing up as red in the file navigation pane.
For each of the files in question what I did to resolve this was:
- Select the file from the list of files in the Xcode file navigation pane,
- Click on the little page icon in the rightmost pane of Xcode, which opens a file attributes pane,
- Click on the little folder icon underneath where it says "Location" in the file attributes pane,
- Choose the new location for the file,
- RESTART Xcode for the above changes to really do anything.
Answer: one more case that can lead to this error which just took me hours to track down: a failable initializer that always returns nil.
i had an initializer that looked like this:
init?(object: MyObject) {
    if object.importantProperty {
        // initialize
    }
    return nil
}

when what i meant was:
init?(object: MyObject) {
    if object.importantProperty {
        // initialize
    }
    else {
        return nil
    }
}

fixing the initializer made the error go away.
Answer: If using Core Data:
I had a Core Data entity for which I created the NSManagedObject subclasses (with Xcode's help). In addition, the entity was configured to generate code automatically (see screenshot), so basically 2 classes existed during runtime. Just switch the option to Manual/None and it won't generate it.
Answer: I experienced this error after performing a git merge. I solved new Xcode warnings and the project can be compiled.
Xcode 7.2.1 is used in my case.
Answer: In my way the error was due to UIDevice.currentDevice() in ((UIDevice.currentDevice().systemVersion as NSString).floatValue >= 8.0)
After commenting this all starts work fine.
XCode 7.2
Answer: in my case , at your project target Build Setttings, in Other Swift Flags,jsut delete the String "-serialize-debuggin-options"
enter image description here
Answer: In my case, the error was the result of missing files that were generated by Xcode. I tried the regular clean Opt+Shift+K and it didn't clean up all the errors. I found a post on the Apple Developer site that recomended going to the Product Menu in Xcode, holding down the opt key, and selecting Clean Build Folder. This appears to be a more comprehensive build as it pops up a modal dialog for you to confirm.
Answer: I had a resolution very similar to RyanM, where with an excess of hubris I tried to assign a variable to the default value of an inner function:
Fails to compile (though does not crash SourceKit):
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    func itemCell(_ indexPath: IndexPath = indexPath) -> UITableViewCell {//...}

Succeeds:
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    func itemCell(_ indexPath: IndexPath) -> UITableViewCell {//...}

Answer: One possible reason that this can happen is perhaps because you have deleted a file but not removed references to it. This will mess up the pbxproj file. I would check to see if that is the case.
Comment: Your answer seems more like a comment to me.
Answer: check "Development Pods" Folder all listed Frameworks path.
Answer: In my case swift development snapshot was selected instead of xcode 9.2. here are the steps and image.

keep xcode on screen and click on xcode top menu bar.
Than go to toolchains option and check on xcode 9.2. thats it.

Happy Coding!!!
Answer: So, I had the above and narrowed it down to a TFS issue with locking the file but only when I pasted or did any other edits besides small copies or manual typing. I noticed the original file would compile, but my edits wouldn't, even though they were syntactic OK. Also related is unable to save document: xcode The document "..." could not be saved
The fix for both was:

Duplicate working version.
Paste fully-merged new code into duplicate.
Copy and paste old file over new one. (I personally just renamed the old one to something else, then pasted duplicate and renamed it, too. Guessing both work since I pasted directly earlier for reverts during tests to see).

Voila. Lazy way to bypass merge-locking issue. Apparently full file-pastes are just fine, while edits aren't. Shared since the other answers don't seem to be as lazy as this. ;)
Note: I am suspecting a non-UTF-8 character made its way somewhere, but pastes worked in older versions so I don't know where, or if relevant.
Answer: Just go to the "project setting" and click on the "build phaces" after that you will find targets in that u have to delete the test file like my project name "WER"  so its showing like this WER&TEST so just delete that and clean ur project and run .........


Subdivided means alt. lmb not connecting edges

Question: I just subdivided the short perpendicular edges along the bottom floor of this object and now when I alt. lmb the edge along the long bottom edges (next to the red line along the sides) it only connects up to the next subdivision instead of the entire edge line. Is there a way to re- merge all the vertices along the bottom edges so I can connect the entire edge using alt. lmb? I've tried merge by distance with alternative variables to no avail. Any help most welcome!
Cheers, Dan
Comment: It should be possible to alt+click the face loop in face selection mode to select the loop of faces. Or you can use Ctrl+left clicking on different vertices to quickly select the nearest path between them
Answer: Unfortunately, with that topology, the edge loop selection will always be limited to sections between "quad-poles" (as far as I know). However, there's a good chance you can eliminate some of the tedium of selecting all the edges manually by using "Select Similar". Try with different constraints, if necessary. If there are varying sections of your edge loop (such as varying lengths, like the inner curve being shorter than the outer curve, for example), you may want to select multiple sections of different sizes (yes, this can be done), before you choose the Select Similar, to make sure you get them all.


Is there any way to wrap a cardano native asset to eth?

Question: I am looking for wrapping some native cardano tokens to the etherium network is there any way to achieve the same? Any help or urls will be very helpfull.
Answer: It can be done with Milkomeda C1 sidechain and Nomad bridge. See the Ethereum to Cardano walkthrough here: https://medium.com/@wingriderscom/how-to-transfer-erc20-assets-to-cardano-ba9c7b9b5a5
Comment: there is only limitted number of tokens are available if i want to wrap a token which is not in at thease list what i have to do for example a nft.
Comment: I am accepting the answer how ever there is no way to wrap many tokens out there nfts also a problem now.


How to start a BDD in test

Question: I want to develop a small feature in my rails app.How to start with it.Whether i need to go by cucumber features or by rspec itself
Answer: This is a matter of individual preference in most cases.  My personal approach is that if I am dealing with a customer requirement then Cucumber is an effective approach as it is generally more readable/understandable.  If I am developing for myself then rspec by itself is faster to get up an running and easier for me to control the build/test/refactor process.

How to start a BDD in test


Nagios (Return code of 255 is out of bounds)

Question: I am getting the error (Return code of 255 is out of bounds) on the http://localhost/nagios
But when I run the command from the shell, it runs fine
Comment: What command are you running? Is there anything useful in the nagios logs?
Comment: What version of Nagios are you running?
Comment: A quick Google found that the error 255 is Nagios not checking the fclose() when writing to a log file: http://markmail.org/message/3d5aabwfpzwgx4gl#query:nagios%20error%20255+page:1+mid:sgz5bq2s4jr6e65f+state:results
Comment: I am running Nagios Version 3.2.0

thanks
Answer: If you're using NRPE and receiving a 'NRPE: Unable to read output' error it is because the NRPE daemon is not returning text data.  The Nagios core depends on NRPE daemons to return a string that summarizes the results of the checks.  For instance, for a check result that is returning a healthy status, it may look like the former whereas an unhealthy status would be displayed the the latter.
OK - load average: 1.56, 1.37, 1.29
CRITICAL - load average: 16.59, 19.41, 21.96

If NRPE were to return something like this:
FOO: bar

You're going to get a 'NRPE: Unable to read output' error because FOO is not one of Nagios's known result states.  Run the remote NRPE command by running something like this (depending on your directories and checks):
libexec/check_nrpe -n -H localhost -c check_load

That should return OK, WARNING, CRITICAL, or UNKNOWN.  Anything else will cause that error.
Comment: You should probably run the check_nrpe command on the Nagios server and specify the external host running the service in question.
Answer: A Nagios check should return 0, 1, 2 or 3:

0: OK
1: Warning
2: Critical
3: Unknown

An exit status of 255 is perfectly valid when you run the command manually, so bash won't complain. You can check the exit status of the command in the variable $? after the command has run with:
echo $?

Comment: when echo $? I got zero.
But as I have mentioned I am seeing NRPE: Unable to read output  on the nagios webpage

Regards
Answer: For posterity, I'll add something for anyone who runs into this.
Two things you need to check:
Check that the server doing the checks has permission to access the client it is testing
In this case, localhost is the server (& the client). Nevertheless, NRPE on the client needs to explicitly grant permission to the server going to check it. If your NRPE is wrapped by the xinetd service, you need to add the nagios server to the only_from directive on the client conf file(/etc/xinetd.d/nrpe)
only_from       = 127.0.0.1 NagiosServerHostName

NagiosServerHostName needs to be in /etc/hosts. Alternatively, put the NagiosServerIP
Check that the firewall isn't blocking your checks. NRPE by default runs on port 5666; ensure that that port is allowed
Answer: You mention that you are calling the check command via nrpe. If you are using a check command which returns multi-line output you must use a recent version of nrpe that also supports multi-line output otherwise the check_nrpe script will not be able to parse the output.
Answer: i had this error, it turned out the plugin writes to a location where it has no rights to write so i just chmod 777 that location and it worked
Comment: `chmod 777` is in 99.9% of cases *not* a sane solution.
Answer: My guess would be that your check_nrpe command is not properly set up in the Nagios configuration file. If you open the Commands.cfg file in /usr/local/nagios/etc/objects/ and double check that the command setup you have there is exactly the same as the setup you are using in your bash script. The command I have setup is:
define command{
command_name    check_nrpe
command_line    $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
}

And my service definition:
define service{
use         generic-service
host_name       ********
service_description HTTP Requests
contact_groups  localadmin
check_command       check_nrpe!check_vbs_sample
}

Also I find it easier to use a simple script, for exampe a batch script that just returns OK to test its working first.
Answer: As several posters have said, if Nagios doesn't receive the response it expects from the script, it will generate this error.
There are lots of ways in which a script can generate an error. To find out what the error is, update your command definition so that Standard Error from the script is written to a log file:
command_line $USER1$/check_nrpe -H $ARG1$ -c $ARG2$ 2> /tmp/error.log

Answer: I just had the same error and it had to do with the firewall being on in the remote client.
Answer: Hope this helps, in my case the issue was an ssh issue. To resolve the return code error I remoted into the remote servers as the nagios user from the server where nagios is being used (master node if you will). Allowing an entry into the known_hosts file from the master nagios server.


Linux headers in Raspbian Jessie

Question: I have problem to install linux-headers in Raspbian on my RPi2. My kernel version is 4.1.17-v7+. I can't find the linux-headers package with apt-get.
Comment: You can find the answer here in this similar question: http://raspberrypi.stackexchange.com/questions/43619/linux-headers-generic-package-not-found/43903#43903
Answer: You can try sudo apt-get install raspberrypi-kernel-headers if you're running raspbian.
As suggested here
https://www.raspberrypi.org/forums/viewtopic.php?f=91&t=154749
Answer: Try:
sudo apt-get update
sudo apt-cache search linux-headers

It will list you the related packages.
Answer: At the moment there is no linux-headers for the 4.1.17 kernel version.
There are only headers for the 4.1.19 version for the 4.x branch. You can simply upgrade your kernel to the 4.1.19 version (now the newest stable branch showing 4.1.20):
sudo rpi-update f406502f5628d32e6ca5dadac34ff7ca59f8e27f

After install reboot your device and check typing uname -r if there is a 4.1.19-v7+ version. If it's OK, install linux-headers:
sudo apt-get install linux-headers-4.1.19-v7+

Comment: I updated my kernel to 4.1.20-v7+ by rpi-update but Raspbian's repo doesn't have any headers for 4.x kernel ;( Any solution how to install it?
Comment: You tried my rpi-update with this git hash ? It should update to 4.1.19 version. If this not you can try use other hash like:
**7e4f4cb0bf8c8f7469727d5b710818c3e6eea289** . It points to 4.1.19 kernel version
Comment: It won't help to solve that problem because raspian doesn't have headers newer than 3.18 in repo. I solved it by other way. I used "rpi-source" script which downloading and installing source for kernel. Thanks for your attepmts to help me ;)

Linux headers in Raspbian Jessie


Tetragrammaton in Non-Jewish Books

Question: If there was a New Testament in Hebrew and it contained the Tetragrammaton in it, how would you get rid of it? Obviously it cannot be buried next to Sifrei Torah or other Holy works.
Comment: `Obviously it cannot be buried next to Sifrei Torah or other Holy works.` Source? Remember that many seemingly obvious things are much more complex, in reality
Comment: Either burn it or cut out the tetragrammaton and burn the rest
Comment: @sabbahillel - G-d's Name in the form of the Tetragrammaton appears many times in a Hebrew NT so one would be sitting there for hours!
Comment: @mevaqesh - I mean the NT, not just Hashem's Name from it. Obviously if you cut out all the shemos and burned the rest you could bury it next to Sifrei Torah
Comment: @EzraHoerster I repeat my first comment.
Answer: See Gemara Gittin 45b:

R`Nahman said: We have it on tradition that a scroll of the Law which has been written by a Min should be burnt

meaning with all the shemot.
This is stated in SA YD 281, 1:

ספר תורה שכתבו אפיקורוס -- ישרף.

This concerns good contents written by bad person,  so bad contents need to be even less "kadoch". No need to bury it.
Comment: My prior comments were deleted. To repeat the main points, this does not explain why the Torah scroll of a "min" is to be destroyed and it is therefore very difficult to know whether or not this ruling applies to the case at hand. Additionally, the OP never said that the book in question was written by a "min", making this answer even poorer.

Tetragrammaton in Non-Jewish Books


Bluetooth not working on HP 15-BS1XX, how can I check which driver I need?

Question: I am using HP-Laptop-15-bs1xx. My Bluetooth is not working. How can I check whether the right Bluetooth driver is installed, and if necessary how can I install it?
Comment: Please edit the question to include results from terminal for `lspci -nnk | grep -iA3 net; lsusb; dmesg | egrep -i 'blue|firm'; rfkill list`
Answer: The lshw tool is among the best tools to check the hardware that can be seen under Linux on a specific system. It's highly recommended to use it with high privileges.
I'd suggest you to start with sudo lshw -businfo to get a first taste.
Then you can dive deeper with just sudo lshw (be warned: the output can be quite long to be read).
Then you can use a number of other tools like lsusb for USB related hardware, lspci for information about PCI-attached hardware and lsscsi for storage devices using the SCSI layer (almost all of them do). Man pages are available to tune the amount of details you want to get.
If you can dual-boot with another OS that can successfully use that hardware, please go on and take note about that hardware by inspecting the hardware details with that OS.
In any case, if your device isn't listed at all, that is likely meaning that it isn't supported by Linux or, at least, by the Ubuntu kernel you are using. Maybe an upgrade can help.


App settings & static data

Question: I need to store a few simple settings that describe the timing and behavior of an integration between Salesforce and a third party web app. In my former life, these things might have been stored in a config file or a few simple tables.  The two main pieces of data are the sync frequency between the apps (hourly, daily, weekly, monthly) and a list of objects to be synced.  I've searched around here and other places and came across some ideas for a singleton pattern with a custom object and also saw some references to environment variables global variables.  Is there a best practice for storing this kind of static data in Salesforce?  Thanks in advance for any suggestions!
Answer: There is a specialised form of custom object called a custom setting for this purpose.
These come in two flavors:

Hierarchy Custom Settings: these are singletons by design
List Custom Settings: these allow named instances

An advantage of using these instead of normal custom objects is that they are cached by the platform and if you use their normal API they do not count against governor limits. The hierarchy custom settings are also automatically made available in formula fields. And there is basic user interface provided by default to manage (set values for) the settings under Setup -> Develop -> Custom Settings. And you can write your own Apex/Visualforce to manage the settings.
The "hierarchical" part of the hierarchical custom settings refers to the ability to define an org-wide setting and then to also define profile or user specific overrides which can sometimes be useful.
Comment: @user886851 The values can be changed by a System Administrator through the default UI (that's usually how we use them). And if you need less privileged users to change them you can write a bit of Apex/Visualforce and choose which profile users have access rights to that. So I think you picked it up a bit wrong.
Comment: If I had to do it over again, I'd leverage org-wide hierarchical custom settings, for the simple reason that they are accessible in formula fields AND validation rules whereas list custom settings are not available in these use cases. Sadly, you can't write VR on custom settings themselves so if you need to validate values for legitimacy as opposed to trusting the sysad to always be 'right' - you'll need a VF page/controller
Comment: Thanks, this looks interesting. In reading over the custom settings from your link, it looks like once a setting has been saved, it can't be changed.  That seems a bit limiting as I do need the admin to be able to change the choices made for sync frequency and/or objects sync'd.  Did I read that right?
Comment: Great, thanks for your additional input.  Very helpful!
Answer: Custom settings will do what you want, but there's a simpler alternative.  Custom labels are easier to use if the limitations don't affect you.  You are allowed 5000 custom labels per org.  Each can be 1000 characters long.  They are text values and are read-only.  They can't be updated programmatically.
You access a custom label in Apex like this:
Program = Label.Current_Program;  // Program is type String

In visualforce, the reference is as follows
<apex:outputLabel value="{!$Label.Current_Program}"/>

Comment: Thanks, I appreciate your response.  This could be very handy.
Comment: vote it up if you like it.  There's no harm in voting for both answers.  ;-)

App settings & static data


Question about making a book like the contacts book on the iPad

Question: For any of you out there who have had a chance to download the iPhone 3.2 sdk and play around with the simulator knows that one of the apps built in is a contacts book. When you open this app up it looks like a book, and has a nice user friendly way to edit and view contacts. So if I wanted to make an app that uses a similar format, meaning I'd want it to be a book, that would allow for editing and viewing of different items. How would I do that? Is there a book template I just don't know about? :) I'm guessing that the book is just a nice photoshopped image that they are just laying the respective uiviews over the image but I may be wrong...any insights as to how I'd be able to implement a book as described would be greatly appreciated!! Thanks
Comment: There is an undocumented class `UIBookViewController` for this. :p
Comment: Not to mention the iPhone screen is too small for this type of workflow.
Answer: I recently built an app that had a "contacts" functionality.  I personally didn't want a book, so instead using photoshop, created a clipboard image for my background.  The background they are using that looks like a book, is just that, a background image.  they have other views and functionality built into the view controllers to make it slide around for editing.


How to download files in ftp using phpstorm

Question: I recently started connecting to my server using PHPStrom, and I can send files(upload) to the server just fine, but after having searched and searched, I can not find a way to download files from server. Is this feature not possible in PHPStorm?
Comment: Have you set up a mapping between your local and remote folders?
Comment: @OliverSalzburg I don't know what that means, but I am able to upload files to my server without any problems
Answer: To seamlessly up- and download files to and from your server, you're going to want to set up a deployment configuration with a mapping between a local and a remote folder. Here is how.

Open the deployment configuration window by selecting Tools → Deployment → Configuration... from the menu.

If you haven't already created a deployment connection, create one one. I have already created one here and switched the Mappings tab.

The Deployment path on server is the location on the server (relative to the Root path set up for the connection) where your project files are located.
In the Remote Host panel, you'll now be able to download files to your project folder.

Additionally, you can also download the server version of a file, by using the options available under the Deployment submenu in the context menu in the Project panel.
Comment: Super answer. Although, I am only able to download the file then change it and then upload it back again. But, in I can't seem to edit it directly or directly modify it. It would be nice if you could shed some lights on that one.
Comment: @ANW: You can't really directly edit a file on the remote host. You can set PHPStorm up to automatically sync a file to the remote host when you save though. In Settings, under Deployment -> Options, check the setting **Upload changed files automatically to the default server**. You can set it to automatically upload on Ctrl+S. But be sure to mark a server as the default server in your deployment settings. There's a **Mark as default** button above the deployment configuration list.
Comment: Where is Remote Host panel?
Comment: @JulianMoreno Sorry, I don't use WebStorm anymore and can't look it up for you.


Connecting To Oracle Database (on VMware Linux RedHat 5.4) with VS2010

Question: I got win7 home basic and on my VMware i got linux red hat 5.4. I created oracle database on that linux.
I'm asking that : can i connect the that oracle database with VS2010 from my win7 side ?
Is that possible ??
Answer: Oracle inside virtualized machine can accept connections. Make sure that networking setting on vm is allowed and that Linux firewall accepts requests for Oracle database (ports are open). I assume that you started database and listener and that you set and use correctly Oracle client side (ODBC,OCI,...)


Energy Consumed by my code in Ubuntu

Question: I'm working in Ubuntu with some kind of functions and I would like to know how energy they consume but I haven't found a good tool for this, or at least make it run.
I have tried with:

Intel Energy Checker. But I can't make it run, I have some erros in the productivy_link.h and I haven't touch this file, only download it.

PowerTOP This tool works but with this you can only see  the discharge rate of your battery and this is not very 'exact' due to some processes of the OS can be executed automatically.

Could someone help me? Thanks in advance.
Answer: Did you checkd pwrkap? You can install it with (and the gui too):
sudo apt-get install pwrkap pwrkap-gui

You can also check this link: powerstat: Power Consumption Calculator for Ubuntu Linux

Energy Consumed by my code in Ubuntu


Can I dual wield two-handed weapons?

Question: I've been looking into this for a while now. I have a level 4 Dragonborn Paladin with the Dual Wielder Feat. I currently have two warhammers, but I'd like to use two mauls for the extra dice. After all, 4d6 is better than 2d8. If this isn't something that would work, that's fine, but it'd really be nice.
Comment: How many hands you got on your paladin? :-)
Answer: No, you can't use a two-handed weapon with one hand.

Two-Handed.
  This weapon requires two hands when
  you attack with it.

Even if you could, two-weapon fighting is defined as

When you take the Attack action and attack with a light
  melee weapon that you're holding in one hand, you can
  use a bonus action to attack with a different light melee
  weapon that you're holding in the other hand.

And the Dual Wielder feat says that you can

use Two-Weapon Fighting, even when the one handed melee weapons you are using aren't light.

So even if you were somehow (maybe magically) capable of wielding two-handed weapons in one hand, you still wouldn't be able to use Two-Weapon Fighting with them, because even with the Dual Wielder feat you are still required to use one-handed weapons.
Comment: OTOH, if you were somehow able to "wield two-handed weapons as if they were one-handed", rather than merely "wielding two-handed weapons in one hand", then you'd be on track to combine the abilities. Which is why the precise wording can matter a great deal.
Comment: The wording might be improved to "but you cannot attack with 2-handed weapons wielded in one hand".
Answer: From the equipment list in the PHB on page 149, a Maul is a two-handed weapon. The rule for two-handed weapons is on PHB 147:

Two-handed. This weapon requires two hands to use.

Since you must use both of your hands in order to wield the maul, you wouldn't be able to wield a second weapon.
You can wield the warhammers because they are versatile, and you just opt to always use the one-handed damage while dual-wielding them.
Answer: As others have said, rules-as-written says no, per the definition of a two-handed weapon. "For the extra dice" is exactly why you can't do it; heavy-damage-dealing weapons quickly become overpowered if you can simply pick up two of them.
That being said, D&D is a creative and largely improv-based game, so assuming you're not playing in the Adventurer's League or anywhere official, talk to your DM! It's easy to re-skin weapons, so you can have "mauls" (for the aesthetic, basically) that have the stats of warhammers. You may even be able to work out a compromise with your DM that will allow your character to acquire a maul with the stats of a +1 Warhammer (or +2 or whatever they'll allow). A good DM might allow this, or even more damage, as part of a tradeoff - as your DM I would say, "Sure, you can dual-wield mauls, but they're heavy and unwieldy, so your attacks will have disadvantage (or maybe your attack rolls will gain -1 for every round of damage, to simulate your character getting more and more tired)."
So, to answer your question, "Can I dual wield two-handed weapons in D&D 5E" is really: "You can do absolutely anything that your particular game's framework--be it the DM, AL regulations, or RAW--will allow. It just so happens that AL and RAW say no."
Answer: There's nothing directly in the rules that would let you. However, D&D rules are bendable. I had a barbarian player who wanted to dual wield great-swords mostly for the aesthetic. Frankly I liked the idea but I didn't want him to be OP, so we worked out a compromise, he had to attain a strength above 20 and the damage die would reduce to d10s when dual wielding. This made it fair and it also made him feel badass. Point is this is a fantasy game and rules can sometimes be ignored as long as the result doesn't break the game. Work with your DM and find a compromise.

Can I dual wield two-handed weapons?


Why is a Kaon strange?

Question: I've read that because Kaons are produced by the strong interaction and decay by the weak interaction that this makes them strange. However protons and neutrons decay by the weak interaction as well i.e B+ or B- decay. So why aren't protons and neutrons also strange?
Comment: They are strange because they have an s-quark, protons and neutrons don't.
Comment: Ok, that makes sense but I've read that strangeness is a property allocated to them to explain their behaviour, i.e taking longer than expected to decay. I don't understand the significance of them decaying by weak interaction, when non strange particles do as well.
Answer: Here is the historical origin of the term strangeness,

Very early in the study of high-energy physics the only source of high energy particles was in cosmic rays (the first accelerators were not yet in existence). People exposed emulsions or set up bubble chambers to record the passage of particles raining down on the surface of the earth from the atmosphere. Most of these particles were identified as electrons and protons. Others came to be identified as anti-protons and pions. At that time we did not have the quark theory to describe these particles (see this link  for more on quarks), we simply had a list of particles and their masses and charges.
In the late 40s and early 50s people noticed particles that left very unusual tracks in their emulsions. We now call these particles 'kaons' and 'lambda hyperons,' but at the time they were simple 'strange particles.' They decayed into charged particles, so the tracks they left had kinks in them or formed a 'v.' They were generally heavier than the pions and protons that people were familiar with.
We now know that protons and pions are made up of up and down quarks, while these 'strange particles' have at least one of a new type of quark that is much like the down quark, only heavier. But in the early 50s we didn't have the quark theory. However, in the early 50s Murray Gell-Mann suggested that these new particles had a conserved quantum number which he called 'strangeness.' This was originally just a bookkeeping device that helped explain the decay patterns of the new particles into the old familiar particles. There was no underlying physical meaning to 'strangeness.' Later, when the quark theory was introduced, this new property was associated with a new particle, the unimaginatively-named 'strange' quark.
Comment: Just put the link as a comment.
Comment: @RobJeffries  that is what I had done at the beginning, but then I thought to give search engines some field on history of strangeness. It took me some time to find this write up, which I had lived through starting in 1965 (my thesis was from data of  K-proton at 8.25 GeV/c in the   CERN two meter bubble chamber), and comments have a way of disappearing and I do  not think are scanned by search engines.

Why is a Kaon strange?


Sitecore Clean Up Agent not running

Question: Is there a way to determine when the Sitecore cache Clean Up Agent runs?  Also, can somoene provide instructions on how to enable the Sitecore Clean Up Agent.  Sitecore does not provide instructions.
Thanks in advance,
Comment: are you referring this task: Sitecore.Tasks.CleanupAgent ?
Answer:
Is there a way to determine when the Sitecore cache Clean Up Agent runs?

You can know if the batch has ran by checking if the entries Scheduling.CleanupAgent started. FileCleaner count: and Scheduling.CleanupAgent done are in the logs.
Note that you need to make sure that you have the logging level as INFO
You may also have the entry Exception in Scheduling.CleanupAgent. Folder: if there are any errors.

Also, can somoene provide instructions on how to enable the Sitecore Clean Up

First, check the showconfig.aspx page (http://[domain]/sitecore/admin/showconfig.aspx) and search for agent type="Sitecore.Tasks.CleanupAgent".
Check the interval if it is not set to 00:00:00. 00:00:00 means the agent is disabled.
To configure it, change the interval. Default is every 6 hours.

As @Jay S mentioned in his answer, you can have more information about different errors at Sitecore Knowlegde Base
Comment: Thanks Hishaam.  Here is the clean up agent interval:
As no errors are reported in the log, does this mean it's running?  The deletion of files is not occurring so I trusted it wasn't running.  I have an item to delete JSON files every 1 day.
Comment: If you have logging level as INFO, do you see the entries `Scheduling.CleanupAgent started`?
Answer: You may wish to look for errors in the logs to see if there are any issues when the agent is running. The most typical issue would be permissions to remove the file on the system. Default should be 6 hours interval, if you have not disabled the agent. This KB article has details:
https://kb.sitecore.net/articles/113648
Comment: thanks for the input.  i checked the logs.  no errors are being thrown.  I'm thinking the pattern *.json is not acceptable in Sitecore and only *.* pattern can be used.

Sitecore Clean Up Agent not running


Difference between assembly code and disassembly listing

Question: Is the disassembly listing generated by a disassembler exactly the same as the assembly code listing that is optionally generated by a compiler during the compilation of C code?
Comment: Your question is unclear. What do you mean by "the assembly code generated by a compiler's assembler"? First off, I don't think any modern compiler still generates assembler at all, at least not by default. And secondly, the assembler doesn't generate assembly code, it *reads* assembly code and generates object code.
Comment: I assume the OP refers to the optional assembly-language listing file which a compiler can output.
Comment: is your disassembler operating on raw machine code from an executable?  or is it disassembling an object code file (that is input to the linker) that comes from compiling or assembling source code?  for the former, all labels and symbols are lost and the disassembler has to make them up.  for the latter, it is possible that the object files have all of the original symbols.  but in either case, all of the comments and formatting style is gone.
Comment: @JörgWMittag Let me put the question in a different way - what is the difference between assembly code (such as those in .s, .asm, etc) and assembly listing (.lst)?
Comment: @gautham: ["Listing" is an old word for "printout", from back in the early days of computing, when there were no screens, and the only way to display code was to print it out ("list it") on paper.](https://wikipedia.org/wiki/Listing_(computer)) Ever since the invention of the computer screen, it means essentially the same thing as "code".
Answer: No I'd expect that the compiler's assembly output can include symbolic names, of functions and of variables, even struct member names. The disassembly would only contain numbers.
In other words, both the compiler and the disassembler can output opcode instruction names, but the disassembler merely outputs numbers instead of symbols when it refers to memory addresses. Or if it's disassembling a DLL, the disassembler might output the public symbols exported from the DLL; but (unlike the compiler) not the symbolic names of internal variables and subroutines.
Apart from that, it's the same machine code. There's also a linker, which happens after the compiler (the linker's processing will be evident in the numeric addresses shown by the disassembler).
Answer: It depends upon the compiler, and usually it might not be the same (e.g. because the compiler generates many local labels that get lost).
If you use GCC to compile your foo.c source code (technically, a translation unit) I suggest to use
gcc -Wall -O -fverbose-asm -S foo.c

which produces the assembler code foo.s that you can look into with some editor. Thanks to -fverbose-asm that assembler file also contain useful generated comments (to help you understand what is going on).


How a new wallet knows balances locked in P2SH transactions?

Question: If my old wallet created and submitted a P2SH TX to the blockchain, and I migrate to a completely different wallet, how can the new wallet detect that that UTXO belongs to me? Since the script is hashed, it can be anything and contain unpredictable information, like other PKHs in multisig transactions
Answer: In short, it knows because it knows. Whatever information was used to make the original wallet construct the addresses (whether that consists of a seed, a set of keys, a master key, a descriptor, a mnemonic phrase, ...) must be imported into the new wallet too.
The P2SH redeemscript is not created randomly: there is a procedure to generate it from keys the wallet has, and those keys may themselves also be generated from such information. What that information is depends on the standards or schemes involved, so it's hard to be very specific here.
Deterministic wallets have been standard since 2013 or so, and pretty much all wallets have some means of deterministically constructing keys from some fixed immutable piece of data. For single key policies (simple wallets) a wallet also needs information to turn those keys into scripts/addresses. Common ways include P2PKH (address contains a hash of the public key), P2WPKH (similar, but uses segwit for spending), or P2SH-P2WPKH (where the address is a P2SH address containing the hash of a segwit program that contains the hash of the public key). The wallet needs to know which (possibly more than one of these) is used to convert the keys into scripts, and that implies also a way for computing the redeemscripts involved. Sometimes this choice is implicit in the standard being followed; sometimes it needs to be imported/chosen specifically.
For multisignature or other policies it is more complicated, as wallets also need to know how the other participants generate their keys, but this information is always needed - both in the first and the second wallet.
Comment: Thanks for answering, Pieter! I guess I was under the impression that all you need to access your funds is your mnemonic and then you can scan over deterministic paths and trivial spending scripts. But apparently, this is not the case if your funds are in multisig or other nontrivial script placed into P2SH UTXO. Need to be careful not create such "exotic" transactions in your wallet, to avoid loosing funds in case the wallet is lost. Or at least export and backup that extra information somehow, but is there a compatibility standard for that, so that wallets can be inter-operable?
Comment: There are multiple approaches. Don't expect wallets to be interoperable, especially not when doing more complicated things than just single signatures.
Answer: P2SH addresses can either be P2SH-P2WPKH addresses (wrapped segwit) or they can be multisig or something else. If your wallet is using P2SH-P2WPKH addresses, the wallet should be able to recognize your address upon initialization. Otherwise, you will probably have to manually import that address.
Regardless, the amount of btc held in that address is on the blockchain, so your node or wallet will know that amount of bitcoin held in that address once you have imported (if necessary) the address.


Automatic Failover in Availability Group

Question: I have 2 nodes in my SQL server fail over cluster. I use SQL Server 2012 Availability Groups for HA purpose.
The problem is that when one my server goes down the automatic fail over does not happen!
How can I enable automatic fail over?
Answer: If you want to enable automatic failover, you will need to ensure that you have an "automatic failover set", to include two replicas (in your case, that'd be your two nodes) both set with synchronous commit, as well as automatic failover.
When you setup the Availability Group, this can be accomplished through the GUI, but if you had this scripted out, it would appear in the CREATE AVAILABILITY GROUP command.  If you take a look at the syntax and possible parameters of CREATE AVAILABILITY GROUP, you would simply see the opportunity to set AVAILABILITY_MODE = SYNCHRONOUS_COMMIT as well as set FAILOVER_MODE = AUTOMATIC.  This is essentially the steps to setup automatic failover.
Likewise, if this is already setup you can modify these replica settings with ALTER AVAILABILITY GROUP ... MODIFY REPLICA ON ... and specify the same above parameters.
Before continuing on, though, with the above modifications it is definitely going to be worth verifying what you already have in place.  A quick query that will tell you what your commit mode and failover mode is for your current configuration is below:
select
    ar.replica_server_name,
    availability_group_name = ag.name,
    ar.availability_mode_desc,
    ar.failover_mode_desc
from sys.availability_replicas ar
inner join sys.availability_groups ag
on ar.group_id = ag.group_id
order by availability_group_name, replica_server_name;

Feel free to edit your question and put the output of the above query for review.
EDIT:  In order to address your comment, it is worth pointing out that to have automatic failover you must be utilizing synchronous commit.
Comment: Does Synchronous mode has more latency than Asynchronous mode for automatic failover?
Comment: There is no automatic failover for asynchronous commit.
Answer: Did setup below ?
cluster clusterName group "Your Availability Group" /properties FailoverThreshold=100

This parameter is making your cluster ready to automatic failover 100 times in some period of time. This period of time you can setup via FailoverPeriod property. More about cluster groups common properties setup you can read here msdn.microsoft.com/en-us/library/aa369680%28v=vs.85%29.aspx


SSL Setup in Marketing Cloud for Emails Mandatory?

Question: The unsubscribe and profile center links (standard marketing cloud ones, no customization) at the bottom of my emails are currently showing up as unsecured when clicked. Setting up SSL with marketing cloud is being quoted at 4-6 weeks which seems very excessive. Is there any way to expedite this or get a workaround where I can have those links link to a secure trusted landing page so they work.
Answer: As already mentioned in your other question.. It's not mandatory but it's the only way to go if you've purchased SAP.
When you place the order, you should get two SSL certificates in total, for:

Securing microsite, landing page, or CloudPage URLs which would typically use your existing Sender Authenticated domain (e.g. pages.SAPdomain.com, cloud.SAPdomain.com, or pub.SAPdomain.com). With this option we can also secure view. and click. URLs for links within your SFMC content.

Securing portfolio content URLs, which use your existing Sender Authenticated domain (e.g. image.SAPdomain.com).

The second one has become even more important lately with Chrome Blocking Mixed Content.
There is no other way around it and it's not possible to speed it up - even if you get the SSL yourself, you will end up waiting ~4 weeks to have it activated in your account.
Docu: https://help.salesforce.com/articleView?id=000339842&type=1&mode=1
Comment: new release makes SSL setup self service, so the 4 weeks thing might get faster. https://help.salesforce.com/articleView?id=mc_rn_october_2020_setup_selfserve_ssl.htm&type=5
Comment: Thanks for the detailed response, much appreciated. One more question, is this something that SFMC always handles exclusively even if you're hosting the DNS files internally but using their shared IP for sends? I would assume yes but want to be sure.
Comment: This is super cool @JonasLamberty, thanks for sharing! :-)
Comment: Thanks @JonasLamberty for the article!


Acid boric preparation

Question: Is there a simple reaction to yield boric acid ($\ce{H3BO3}$) from boron trifluoride ($\ce{BF3}$)?
Comment: "Quick questions" without elaboration effort are not very welcome, and may be closed.
Answer: Yes, hydrolysis of boron trifluoride.
$$\ce{4 BF3 + 3 H2O → 3 HBF4 + B(OH)3}$$
The reaction commences with the formation of the aquo adduct, $\ce{H2O−BF3}$, which then loses $\ce{HF}$ leading to formation of the products.
The heavier trihalides do not undergo analogous reactions, possibly due to the low stability of the tetrahedral ions $\ce{BCl4-}$ and $\ce{BBr4-}$.
Comment: I can imagine a less weird way to prepare  boric acid. :-)
Answer: Wikipedia gives several methods to get boric acid.  The first one uses a relatively common natural source of boron.  Curiously compared with the other answer, boron trifluoride is excluded among the halides.

Boric acid may be prepared by reacting borax (sodium tetraborate decahydrate) with a mineral acid, such as hydrochloric acid:

$\ce{Na2B4O7·10H2O + 2 HCl → 4 B(OH)3 [or H3BO3] + 2 NaCl + 5 H2O}$

It is also formed as a by product of hydrolysis of boron trihalides and diborane:[1]

$\ce{B2H6 + 6 H2O → 2 B(OH)3 + 6 H2}$
$\ce{BX3 + 3 H2O → B(OH)3 + 3 HX (X = Cl, Br, I)}$
Upon further review, boron trifluoride can be used to give boric acid as well, as shown in the other answer, but at reduced yield as most of the boron forms $\ce{HBF4}$ instead.  Using a heavier halogen favors all the boron going to boric acid.
Cited reference:
1.
Housecroft, C. E.; Sharpe, A. G. (2008). "Chapter 13: The Group 13 Elements". Inorganic Chemistry (3rd ed.). Pearson. p. 340. ISBN 978-0-13-175553-6.

Acid boric preparation


Is there a Giambelli identity with dual representations?

Question: For natural numbers $a,b$ with $b\leq n-1$, let $V_{ (a|b)}$ be the irreducible representation of $GL_n$ with highest weight vector $(a+1, 1^b, 0^{n-b-1})$ where the exponentiation denotes repetition.
The Giambelli identity states that if $a_1 > \dots > a_r$ and $b_1 > \dots > b_r$ are natural numbers with $b_1 \leq n-1$ then the determinant in the representation ring of the matrix $M$ with entries $M_{ij} = V_{ (a_i |b_j)} $ is an irreducible representation of $GL_n$ with highest weight vector $$( a_1 + 1,\dots, a_r +r, r^{b_r}, (r-1)^{b_{r-1} -b_r-1}, \dots, 1^{ b_1 - b_{2}-1} , 0 ^{n-1-b_1}).$$
Technically, the Giambelli identity is an identity in the ring of symmetric functions in infinitely many variables. We deduce this using the fact that the representation ring of $GL_n$ is the quotient ring of symmetric functions in $n$ variables, where each Schur function is sent to an irreducible representation or zero depending on the number of parts.

Let $a_1 > \dots a_r, b_1> \dots > b_{2r}, c_1> \dots c_r$ be natural numbers with $b_1 \leq n-1$.
Let $M$ be the matrix whose entries are $M_{ij} = V_{(a_i|b_j)}$ if $1 \leq i \leq r$ and $M_{ij} = V_{( c_{2r-i} | n-1-b_j )}^\vee$ if $ r+1 \leq i \leq 2r$.
Is $\det M$ an irreducible representation? Is it the one with highest weight vector $$(a_1+1,\dots, a+r+r, r^{b_{2r} }, (r-1)^{b_{2r-1}-b_{2r} -1},\dots, (-r+1)^{ b_1-b_2 -1},  (-r)^{n-1-b_{1}}, -c_r-r, \dots, -c_1-1)?$$
If not, does some similar formula hold for the class of this irreducible representation in the representation ring?

The motivation is that this would help generalize my work in arXiv:1810.01303 on the CFKRS conjecture for integral moments, from the moments conjectures to the ratios conjecture.
It doesn't seem possible to deduce this from any nice identity purely in the ring of symmetric functions, so the same approach might not work here.
Answer: Yes, your prediction is correct. The determinant identity in this case is theorem 3.5 in Division and the Giambelli Identity, by Wu and Yang (also published at Linear Algebra Appl. 406 (2005), 301-309).


Ease of Continental road wire bead tire mounting and dismounting

Question: Are the Continental road wire bead tires any better at mounting and unmounting then they used to be? Or  are they still a big pain in the ass. My buddy has some hard shell gators that are cheap.
Comment: I'm voting to close this question because it's impossible to answer.  Conti make a great many wire bead tyres each with its own manufacturing tolerance.  They will then be fitted to a huge array of different rims each with their own differing widths and tolerances
Comment: For me a huge revelation was that the rim has less diameter in the middle of the rim bed.  If you can't get the last bit of tire onto the rim, move the opposite side to the middle of the rim bed.
Answer: In my experience, Continental-brand tyres are neither difficult nor easy to fit when new.  They certainly require leverage tools like tyre levers or similar, but they're much easier than a Schwalbe Marathon.
I've fitted both GP4000 and Gatorshell tyres in the last year or so.
Personally I prefer kevlar bead tyres now over wire bead for weight, ease of fitting, and easier postage.
Comment: @AndrewHenle fair enough - a lot depends on the wheel rim's well too (ie its cross-section profile)- some combinations are hard.
Comment: *They certainly require leverage tools*  I'm usually able to get GP4Ks on without levers.  Sometimes new ones are tighter and I'll use levers. IME, it's been the same on DT Swiss RR415s, RR585s, R460s, Kinlin XR300s, a bunch of Neuvation wheels, several Mavic wheels, one offset rear rim I can't remember who made, and more than a few OEM wheels.  And I'm pretty sure GP4Ks have kevlar beads - they're certainly foldable. (Yes, GP4Ks are my go-to tire, err, tyre. My favorite *racing* front tire was the old Michelin PR3 - fragile and short-lived but the grip would pull paint off the wall.)
Answer: Schürmann Yak25 rim and Continental Contact Cruiser 27.5x2.40"E-25 SafetySys tire makes a pair that is very easy to mount, I can even put it on without tools. This answer may not be universal but no, not always just pain in the ass as you write.


What is the difference between Half Life: Source and the new Black Mesa?

Question: With the recent release of Black Mesa everyone seems to be very excited, but what are the main differences between Black Mesa and Half Life: Source?
Answer: Black Mesa is a fan made total conversion mod of HL2, recreating the original Half Life. A team of volunteer artists, coders and level designers have painstakingly recreated the beloved HL single player experience, adding vast amounts of new details such as more scenery objects, more detailed landscapes, and richer textures. They even recorded new dialog to freshen that up too.
Half Life: Source was a port by Valve of HL to the Source engine. There was no new content added and the textures werent updated, so the only differences were better lighting, shading, and physics. It looked a bit better, but played the same, and was really only ported as an experiment to test Source's modding capabilities.
In short, HL:S was a better way to experience HL if you'd never played it by the time HL2 arrived. BM is a chance at reliving all the magic again, but in a very new and handcrafted way.
Comment: *HL: Source* was such a disappointment, especially since they already *had* high-res textures in one the pre-Source special editions that I bought. *Black Mesa* is exactly what I've been wanted to play for years!
Comment: Can mods running on/made for Source really be called "total conversion mods"?
Comment: That's how they're branding it themselves on the official site. I'm not sure though if they mean it's based on the Source SDK as at the HL2 release, or if the starting point was HL2's actual code.
Comment: One thing that's struck me in playing it is that some of the reinterpreted map areas are vastly bigger than they were in the original game. The rocket silo and adjoining fan chambers seem much bigger this time around.
Comment: I really thought the ambient sounds in the beginning of Black Mesa were some of the best in any game I've ever played.  Really felt like the place was coming down around my ears.
Comment: Is Black Mesa _only_ a remake of the original _Half-Life_ game, or are there "revamped" versions of _Half-Life: Blue Shift (2001)_ and _Half-Life: Opposing Force (1999)_?
Answer:
It's free, you only need to have any Source game installed on Steam.
It is a remake, featuring new content and better graphics.
Comment: Quick update from 2015, Black Mesa is no longer free (at least not the most up to date version, the "legacy" version is still downloadable from their site). The game is now available as an "early access" game on Steam that is still being worked on: http://store.steampowered.com/app/362890/
Comment: I think part of his question is what is the "new content" that you mention?
Comment: Upvote for no. 1. It's an important distinction to make. Black Mesa is free, Half-Life Source is not.


Cleaning clothes before Passover?

Question: Does one have to clean all their dirty clothes before Pesach (on the principle of being careful to washout all the chametz from their house)? What is the general Halakha for your clothing collections (including your clean clothes) as it relates to removing Chametz before Passover?
Comment: #DustIsNotChometz
Comment: Oh my! Are we thinking about Pesach already? It's only 5 months away, I guess!
Answer: According to Shulchan Aruch Harav, you should check your pockets, especially if you sometimes put chametz in them:

Every person should be careful to check and shake out his gloves and
clothes-pockets, and those of [his] children, because at times chametz
is [placed] in them... All the above [applies with regard] to one who
is wont at times to [place] chametz in his gloves and
clothes-pockets... Nevertheless, may blessings be bestowed upon one
who is stringent [and searches these places (regardless)].

This article says that freshly laundered clothes don't have to be checked, as any chametz in them would have been destroyed.
Clothes worn on Erev Pesach should be checked or washed after you're done eating chametz.

Cleaning clothes before Passover?


In the Binitarian view, who or what is the Holy Spirit?

Question: In the Binitarian view, who or what is the Holy Spirit?
Is it the spirit of the Father, or the Son, or both, or is it a separate entity?
Answer: Most binitarians think that the Holy Spirit is, in some sense, God's power. A number of faith statements from binitarian denominations say something to this effect; for instance, here's what the Living Church of God has to say on the matter:

The Holy Spirit is God's out-flowing power (Luke 1:35). It is the
means by which He created and brought into existence the very universe
(Psalm 104:30). It is the power by which He works in the minds of
human beings made in His image (Genesis 6:3). It is the power by which
the lame miraculously walked, the blind saw, the deaf heard, and the
dead were raised during the earthly ministry of Jesus Christ (Luke
5:15–17).

Similarly, the United Church of God (Canada) says this:

The traditional Christian view of the Holy Spirit presents it not only
as the power of God, but also a third person with the Father and Son
in a Trinity. But when the Bible is taken at face value it's clear
that it's never presented as a separate person. It's always presented
as an attribute or power of God.

So, in short, binitarians (or at least, the major binitarian denominations) teach that the Holy Spirit is the power of God, rather than a separate person. I should clarify that I myself am not a binitarian; I merely hope to be informative.
Comment: You might also mention that most Bible translators, influenced by the Trinity Doctrine, personify "the holy spirit" by capitalizing it as "the Holy Spirit", even though the original Greek used only one case for everything. There are also instances where holy spirit is referred to using masculine pronouns (e.g. he, his) even though the Greek could have been translated as "it" and "its". E.g. John 16:7 ¶ Feel free to incorporate this information into your answer (so I don't have to write one).
Comment: +1 I'm full on studying binitarianism now, i see one group say the holy spirit sometimes means the fathers spirit, sometimes the son's. but that they share a united spirit.  i hope to add that as an answer once i've read more, unless someone beats me to it
Comment: @scm, [*Is God a Trinity?* | United Church of God](https://www.ucg.org/bible-study-tools/booklets/is-god-a-trinity) is a 90 page booklet on the topic.
Answer: According to at least one Binitarian group, the Father is sometimes called the Holy Spirit, and the Son is sometimes called the Holy Spirit, and that the Father and the Son have one single divine Spirit. The Holy Spirit is not a separate person.
The reference is their 22 Theses of Binitarianism
Thesis 14

We affirm that the Father and the Son
are one in spirit.
We affirm that together they share one
and the same divine spirit.
We affirm that the Father, the Holy
One, is occasionally called the Holy
Spirit. The Son, the Lord Jesus may
also be called the Spirit.
We affirm that most references to the
divine spirit are focused on the Father
who is spirit, with some focused on
the Son, who is also the spirit of life.
We also affirm that their one spirit is
holy and is to be reverenced.
We deny that the Father and the Son have two
separate divine spirits.
We deny that the spirit of the Father is
someone other than the Father Himself, or
that the spirit of the Son is someone other than
the Son himself.

We deny that the spirit of God is someone
other than the Father, or the Son of God, or
that the spirit of the Lord is someone other
than God or the Lord.
We also deny that words like "the spirit of
God," require a relationship of God with
someone else who shares His one divine
essential spirit.

And they reference the following scriptures for this position:
Mat. 10:20; John 4:24, 14:20; 17:20 – 23; Acts 2:32 – 36; Gal. 4:4 – 6; Rom. 8:9 – 11; 1 Cor. 12:11 - 13, 15:45; Eph. 4:4; 1 John 4:13