ExpressJS + MongoDB: Better to make one API call with 10,000 objects, or 10,000 individual API calls?
How do you do load testing and capacity planning for web sites?
Undefined control sequence BibTex This is one of the BibTex entries giving the problem:  @ARTICLE{2015ApJ...808L..36B,    author = {{Bonnivard}, V. and {Combet}, C. and {Maurin}, D. and {Geringer-Sameth}, A. and      {Koushiappas}, S.~M. and {Walker}, M.~G. and {Mateo}, M. and      {Olszewski}, E.~W. and {Bailey}, III, J.~I.},     title = "{Dark Matter Annihilation and Decay Profiles for the Reticulum II Dwarf Spheroidal Galaxy}",   journal = {\apjl}, archivePrefix = "arXiv",    eprint = {1504.03309},  primaryClass = "astro-ph.HE",  keywords = {dark matter, galaxies: dwarf, galaxies: individual: Reticulum II, gamma rays: galaxies, methods: statistical, stars: kinematics and dynamics},      year = 2015,     month = aug,    volume = 808,       eid = {L36},     pages = {L36},       doi = {10.1088/2041-8205/808/2/L36},    adsurl = {http://adsabs.harvard.edu/abs/2015ApJ...808L..36B},   adsnote = {Provided by the SAO/NASA Astrophysics Data System} }   and corresponding bbl file giving the error at compilation is  \bibitem{2009ApJ...697.1071A} {\sc W.~B. {Atwood}, A.~A. {Abdo}, M.~{Ackermann}, W.~{Althouse},   B.~{Anderson}, M.~{Axelsson}, L.~{Baldini}, J.~{Ballet}, D.~L. {Band},   G.~{Barbiellini}, and et~al.} \newblock {\bf {The Large Area Telescope on the Fermi Gamma-Ray Space Telescope   Mission}}. \newblock {\em \apj}, {\bf 697}:1071--1102, June 2009.   My guess is that Kile doesn't like references of the form 2015ApJ...808L..36B since these are the only ones giving the error.    Can somebody hint me to the problem in this? Thank you very much To EAV or not to EAV? Adjusting space between array rows and columns \documentclass[english]{article} \usepackage[T1]{fontenc} \usepackage[latin9]{inputenc} \usepackage{babel} \begin{document} % ... \[ \begin{array}{ccccc} x(1) &amp; = &amp; \frac{x(0)}{1} &amp; = &amp; x(0)\\ x(2) &amp; = &amp; \frac{x(1)}{2} &amp; = &amp; \frac{x(0)}{2}\\ x(3) &amp; = &amp; \frac{x(2)}{3} &amp; = &amp; \frac{x(0)}{2.3}\\ x(4) &amp; = &amp; \frac{x(3)}{4} &amp; = &amp; \frac{x(0)}{4!}\\  &amp;  &amp;  &amp;  &amp; \vdots\\ x(n) &amp; = &amp; \frac{x(n-1)}{n} &amp; = &amp; \frac{x(0)}{n!} \end{array} \] % ... \end{document}   Because of the fractions in the array cells, array elements are vertically too close to each other, they are literally touching to each other. Also the horizontal spacing is too much as you see in the image (screen shot from the output PDF file).  How do I make these cell-spacings look better? Why is the comma splice an error? It's always drilled into us that we shouldn't use comma splices. They're bad, to be avoided and poor form.  But why? What makes the comma a faulty choice in something like this:     I never liked school, it was boring and repetitive most of the time.   It could be replaced with a semicolon, dash, period or colon and be "correct." Yet to a fair amount of people, the comma seems fine. If it weren't, it wouldn't be found so often in online forums, text messages, emails and so on.  What makes the comma between two sentences an error? What is the difference between "What are you?" and "Who are you?"? I am often asked "Who are you?" and "What are you?", but I don't know the difference between these two questions.  Please explain it to me. A standard document (e.g. scrreprt) uses roman font family for text and Sansserif font family for titles etc. It is the other way round in beamer. How can I switch the two font families? Or why do beamer define the font families in this way?  For the background: I think this is my problem when using formulas, because they use the Sansserif font instead of the roman version. Formulas using the euler package look really poor.  P.S.: I compile with LuaLaTeX using TeXlive 2013. How can I disable the button of my CD/DVD drive? Up until Fedora 14 I was successfully using  to enable/disable the CD/DVD eject button on my laptop (Thinkpad T410). Sadly it has stopped working now.  I've consulted the methods discussed in these 2 questions:       None of which have worked for me. So I turn back to cdctl to see if we can't fix what's broken with it, since it's worked for so long.  Debugging the issue  So starting with cdctl switches I notice that most things seem to work just fine.  Examples  These things work.  ejects the drive  $ cdctl -e   list capabilities  $ cdctl -k Tray close             : 1 Tray open              : 1 Can disable eject      : 1 Selectable spin speed  : 1 Is a jukebox           : 0 Is multisession capable: 1 Can read the MCN (UPC) : 1 Can report media change: 1 Can play audio discs   : 1 Can do a hard reset    : 1 Can report drive status: 1   According to that list cdctl even thinks that it can enable/disable the eject button.   Can disable eject      : 1    So I continue on with debugging the issue.  Debugging cdctl  So I figure lets do an strace on cdctl to see if it can shed some light on what's going on.  $ strace cdctl -o1 ... brk(0)                                  = 0x1371000 open("/dev/cdrom", O_RDONLY|O_NONBLOCK) = -1 ENOENT (No such file or directory) open("/dev/cd", O_RDONLY|O_NONBLOCK)    = -1 ENOENT (No such file or directory) open("/dev/scd0", O_RDONLY|O_NONBLOCK)  = -1 ENOENT (No such file or directory) open("/dev/sr0", O_RDONLY|O_NONBLOCK)   = 3 ioctl(3, CDROM_LOCKDOOR, 0x1)           = 0 close(3)                                = 0 exit_group(0)                           = ? +++ exited with 0 +++   Curiously it seems like cdctl thinks it's disabling the button.   $ strace cdctl -o1 ioctl(3, CDROM_LOCKDOOR, 0x1)           = 0  $ strace cdctl -o0 ioctl(3, CDROM_LOCKDOOR, 0)             = 0   NOTE: If I understand this right, the return of a 0 means it was successful.  One thing that caught my eye here was the list of devices that cdctl is attempting to interact with. So I thought "what if I try these devices with eject"?  eject command  One of the other commands I used to use years ago was the eject command to interact with the CD/DVD device. I noticed that this command also now has a similar named switch:  $ eject --help  -i, --manualeject &lt;on|off&gt;  toggle manual eject protection on/off   Example  $ eject -i 1 /dev/sr0 eject: CD-Drive may NOT be ejected with device button  $ eject -i 0 /dev/sr0 eject: CD-Drive may be ejected with device button   So eject too thinks that it's disabling the button, yet it isn't either. Using strace here I see the same system calls:  $ strace eject -i 1 /dev/sr0 |&amp; grep ioctl ioctl(3, CDROM_LOCKDOOR, 0x1)           = 0  $ strace eject -i 0 /dev/sr0 |&amp; grep ioctl ioctl(3, CDROM_LOCKDOOR, 0)             = 0   So now I'm wondering if UDEV or something else is potentially blocking or taking ownership of device?  Thoughts? The following code  number=1 if [[ $number =~ [0-9] ]] then   echo matched fi   works. If I try to use quotes in the regex, however, it stops:  number=1 if [[ $number =~ "[0-9]" ]] then   echo matched fi   I tried "\[0-9\]", too. What am I missing?  Funnily enough,  suggests this should work.  Bash version 3.2.39. Black screen after suspend-after moving to the nvidia official drivers (not priority) Why does Worf want O'Brien to go to Minsk? I've just watched the last 20 minutes of an episode of Deep Space 9, and towards the end Worf is very insistent that O'Brien and his wife move to Minsk. Is there any in or out of universe reason for this? I wanted to apply texture on some house following an tutorial, I'm sure I did all what was needed but still don't see the texture.  Here's a screenshot: How to monitor process/program execution in windows? We are trying to develop a small application that can monitor the programs/processes that are executing in a windows machine.  If the program/process is not supposed to run, it should be blocked. It works similar to an antivirus.  This is the basic idea.  I want to know the ways to hook into the OS to get notified about every single program/process trying to run in the machine. What does 'Ign' , `Get` or 'Hit' mean when running an apt-get update? How to mount a remote (over SSH) directory to be available like a local directory (incl. in shell, not just in Gnome)? One problem I have found when learning calculus is that there are many different ways to denote the derivative. If $y=f(x)=x^2$, then we could write \begin{align} f'(x)&amp;=2x \\ y'&amp;=2x \\ \frac{df}{dx}(x)&amp;=2x \\ \frac{df(x)}{dx}&amp;=2x \\ \frac{d}{dx}f(x)&amp;=2x \\ \frac{dy}{dx}&amp;=2x \end{align} And this is just Lagrange and Leibniz's notations alone. What I find troubling is that they all seem to be suggesting subtly different things about what the derivative actually is. Is it a function, a limit of a quotient, or both? In the interests of keeping my post brief, I'll focus my attention on $f'(x)=2x$ and $\frac{dy}{dx}=2x$, as these seem to be the most common notations.  $$ f'(x)=2x $$  It does make sense to think of the derivative as the gradient function: $$ f'\colon x\mapsto\lim_{\Delta x \to 0}\frac{f(x+\Delta x)-f(x)}{\Delta x} $$ In this case the limit expression is equal to $2x$, and so we can write $$ f' \colon x \mapsto 2x $$ However, this notation seems a little counter-intuitive when we consider what it means to differentiate a function with respect to a variable other than $x$. If I ask what is the derivative of $f(x)$ with respect to $\frac{x}{2}$, does this question make sense? Is it simply $f'(\frac{x}{2})$? Or do we have to express $x^2$ in terms of $\frac{x}{2}$? And how can we can express this derivative using Lagrange's notation?  $$ \frac{dy}{dx}=2x $$  There are many things which are nice about Leibniz's notation, including the fact that it is explicit which variable you are differentiating with respect to. However, in this case, it is unclear whether we are talking about a function, or something else entirely. There are other issues. Some people say they dislike the Leibniz formulation of the chain rule $$ \frac{dy}{dx}=\frac{dy}{du}\frac{du}{dx} $$ saying that they find it to be inaccurate. I don't really understand why this is the case. Could someone please elaborate? Non-standard signature of main() compiles successfully On the , there is this line:      $p(\mathrm{height}|\mathrm{male}) = 1.5789$ (A probability distribution over 1 is OK. It is the area under the bell curve that is equal to 1.)    How can a value $&gt;1$ be OK? I thought all probability values were expressed in the range $0 \leq p \leq 1$. Furthermore, given that it is possible to have such a value, how is that value obtained in the example shown on the page? Are you allowed to stack Divine Smite and Eldritch Smite on the same attack? Why is it called the Millennium Falcon? Problem with TP-Link TL-WN823N Recently I installed Ubuntu 16.04 but cant get the usb wifi adapter to work properly , can anyone help me?  When wifi adpater is plugged , the lsusb output:  Bus 001 Device 003: ID 2357:0109 Bus 001 Device 002: ID 0e0f:000b VMware, Inc.  Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub  Bus 002 Device 004: ID 0e0f:0008 VMware, Inc.  Bus 002 Device 003: ID 0e0f:0002 VMware, Inc. Virtual USB Hub Bus 002 Device 002: ID 0e0f:0003 VMware, Inc. Virtual Mouse Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub   When wifi adapter is unplugged , the lsusb output:  Bus 001 Device 002: ID 0e0f:000b VMware, Inc.  Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 002 Device 004: ID 0e0f:0008 VMware, Inc.  Bus 002 Device 003: ID 0e0f:0002 VMware, Inc. Virtual USB Hub Bus 002 Device 002: ID 0e0f:0003 VMware, Inc. Virtual Mouse Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub