i just wanted to know how many servers Stack Overflow runs on, with 240,000 users on the site, im thinking they have 1,000 of servers? but i wondered if you guys knew
What tools and technologies are used to build the Stack Exchange Network?  See also:
How do I sort a list of dictionaries by a value of the dictionary? Why is XOR preferred over XNOR? The XOR operator seems to be a frequently used building block inside many cryptographic primitives.  As far as I can see, its most desirable properties seem be that for the XOR of two bits $a\oplus b=c$:   The information is preserved.  Either $a$ or $b$ can be recovered from $c$ and the other bit. The information is hidden.  An adversary can not learn anything about $a$ or $b$ from $c$ alone.   Neither AND nor OR has these properties but XNOR does.  It seems like any cryptographic application using XOR could be constructed equivalently with XNOR, without incurring any loss in security.  One possible reason to prefer XOR might be that XOR is equivalent to addition modulo 2, whereas XNOR would be addition plus 1 modulo 2, but this seems to be entirely mathematical, and I'm not sure if it actually results in any additional hardware complexity in practice.  Is the choice of XOR then an arbitrary one, made for historical reasons, or is there any tangible underlying motivation for using it over XNOR? Java: Sorting user-input array upon return I want to model the transfer function of a resistor mathematically, and am after some resources / tips on if it's possible to do so.  For example, if I put 1V into a 1 Ohm resistor, I want to know how long and how (shape) it will take to reach a steady state temperature, given 25 deg C ambient.  I.e.   $$ \frac{T(s)}{V(s)} = ??? $$  Where T(s) is the laplace transform of temperature T(t), measured in say Kelvin.  I understand there are a lot of factors which will affect this model (material, size, shape, ambient (?)), but I'm not sure where to even start. A  shows the heat rise at a certain load, but not really how it gets there. I can't find a time-domain function for the temperature rise either. pgfplots and using axis cs to add points I am trying to mark two inflection points using a foreach loop in a pgfplot, but it isn't working.  \documentclass[tikz]{standalone} \usepackage{pgfplots} \pgfplotsset{compat = 1.10}  \begin{document} \begin{tikzpicture}   \pgfmathsetmacro{\infx}{1/sqrt(2)}   \pgfmathsetmacro{\infy}{exp(-.5)}   \begin{axis}[     xmin = -3,     xmax = 3,     ymin = -0.1,     ymax = 1.05,     domain = -4:4     ]     \addplot[blue, samples = 500, smooth] gnuplot {exp(-x^2)};      \foreach \x/\y in {\infx/\infy, -\infx/\infy}{       \draw[red] (axis cs: \x, \y) circle[radius = .025];     }   \end{axis} \end{tikzpicture} \end{document}   I am being told:  Undefined control sequence.^M &lt;argument&gt; axis cs: \x ^M                        , \y ^M l.34   \end{axis}^M Compact operators on an infinite dimensional Banach space cannot be surjective I am reading a book about functional analysis and have a question:      Let $X$ be a infinite-dimensional Banach-space and $A:X \rightarrow X$ a compact operator. How can one show that $A$ can not be surjective? I have tried using glm::rotate and such. glm::translate works fine, but rotate doesn't work (if I rotate before/after a translation).  Here is my current setup:  glm::vec4 Off = glm::vec4(0, 0, 0, 1); glm::vec4 result = Util::createTransform(offset) * Off;  for (int i = 0; i &lt; Tvertex.size(); i++) {     Tvertex[i] += glm::vec3(result.x, result.y, result.z);     Tcolors[i] = currentColor; }   And here is my Util::createTransform:  glm::mat4 Util::createTransform(glm::vec3 pos) {     glm::mat4 trans = glm::mat4(1.0);     trans = glm::translate(trans, pos);     return trans; }  glm::mat4 Util::createTransform(glm::vec3 pos, glm::vec3 rot) {     glm::mat4 trans = glm::mat4(1.0);     trans = glm::rotate(trans, glm::radians(rot.x), glm::vec3(1, 0, 0));     trans = glm::rotate(trans, glm::radians(rot.y), glm::vec3(0, 1, 0));     trans = glm::rotate(trans, glm::radians(rot.z), glm::vec3(0, 0, 1));     trans = glm::translate(trans, pos);     return trans; } I want to find an example of a homomorphism $f:G\to H$ such that $A$ is a normal subgroup of $G,$ but $f(A)$ is not so in $H.$  I know that if $f$ was onto $f(A )$ must be normal , but otherwise i want to find an example! The main effect will be non-significant if the interaction is significant? Can I run Android apps on Ubuntu? Is it possible to run Android apps on Ubuntu? And I don't mean inside an emulator, but natively, as you would with any other application installed using the Ubuntu Software Center. Table and figure side-by-side with independent captions Looking to put a table and a figure side by side so that the table and figure have their own captions. A crude sketch    ------------              -----------------     TABLE    | a |  b |                     FIGURE   | c |  d |  ------------              Table 2: Caption           -----------------                            Figure 7: Caption   The closest I've gotten is:  \begin{table}% \centering \parbox{0.4\textwidth}{ \begin{footnotesize} \begin{tabular}{| l | r |} \hline some &amp; table\\ \end{tabular} \end{footnotesize} \caption{Table} \label{tab:table} } \qquad \begin{minipage}[c]{0.53\textwidth}% \centering     \includegraphics[width=1\textwidth]{awesome} \caption{Figure} \label{fig:figure} \end{minipage} \end{table}   But that gives two Table X: Caption captions. I didn't find anything in subfig.  Help? How do you make the camera in blender cycles render everything so it looks like pixels? I want everything in my scene to look pixelly like this image I found: How to learn physics effectively and efficiently Proving a trig identity: $\frac{\sin(A + B)}{\sin(A - B)}=\frac{\tan A + \tan B}{\tan A - \tan B}$ The square root of a prime number is irrational If $p$ is a prime number, then $\sqrt{p}$ is irrational.  I know that this question has been asked but I just want to make sure that my method is clear. My method is as follows:  Let us assume that the square root of the prime number $p$ is rational. Hence we can write $\sqrt{p} = \frac{a}{b}$. (In their lowest form.) Then $p = \frac{a^2}{b^2}$, and so $p b^2 = a^2$. Hence $p$ divides $a^2$, so $p$ divides $a$. Substitute $a$ by $pk$. Find out that $p$ divides $b$. Hence this is a contradiction as they should be relatively prime, i.e., gcd$(a,b)=1$. When exactly does tmpwatch clear out files I place in /tmp? JProgressBar in new thread JDialog What happens when a caster targets an object that looks like a creature with a spell that targets only creatures? chown as non-root user Definite article, repetition in lists Which would be correct?        The fridge, the shelves, the walls, the floor, and John himself, were all covered in foam.   The fridge, shelves, walls, floor, and John himself, were all covered in foam.      The the can be applied to all the nouns, so is there a need to repeat it?