Server becomes too slow with high traffic http requests for tracking page loads of multiple sites
Can you help me with my capacity planning?
Spacial curvature and expanding space If we take the analogy that in an empty space the space is just a flat sheet then if there is a single planet or a star then the flat sheet will curve below the planet leaving a curvature shaped like a hemisphere below the object, my question is, Does this curvature change as space expands? Limits of trig functions My family PC has Windows Vista and lately it has became unusable, having strange errors and taking hours to do anything at all, so I'm installing Ubuntu 11.10 alongside it.  I went into GParted to resize the Vista partition but found that it had an exclamation point in a red circle next to it:   I tried to resize it but the Resize/Move button was grayed out.  I thought that this might have to do with the exclamation point so I looked at the information and found a load of errors:   What does the exclamation point mean?  How can I resize my partition?  UPDATE 1  I booted into Safe Mode with Command Prompt in Vista as suggested by eug and ranchkdsk c: /F /R (/F Fixed errors on the disk, /R Locates bad sectors and recovers readable information) and got:  Chkdsk cannot run because the volume is in use by another process.  Would you like to schedule this volume to be checked the next time the system restarts? (Y/)   When I reboot it doesn't run chkdsk, I'm selecting Safe Mode with Command Prompt again because I can't boot normally.  How can I stop it being used?  UPDATE 2  I tried doing what Luis suggested.  Here is the terminal output:  ubuntu@ubuntu:~$ sudo ntfsfix /dev/sda3 Mounting volume... OK Processing of $MFT and $MFTMirr completed successfully. NTFS volume version is 3.1. NTFS partition /dev/sda3 was processed successfully. ubuntu@ubuntu:~$ sudo apt-get install ntfsprogs Reading package lists... Done Building dependency tree        Reading state information... Done Note, selecting 'ntfs-3g' instead of 'ntfsprogs' ntfs-3g is already the newest version. 0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.   I still cannot resize the partition.  Ntfsfix doesn't look like it did anything and ntfsprogs is already installed.  I can access the hard drive and do backups with the Ubuntu Live CD which I'm using now.  Any other suggestions?  UPDATE 3  I attempted to use the ntfsresize command but I got an error:  ERROR: Volume is scheduled for check. Run chkdsk /f and please try again, or see option -f.   This is because I ran chkdsk in Vista Safe Mode with Command Prompt and it couldn't do it because it was in use but offered to do it at the next reboot.  I reboot and I get to the menu to the menu to choose whether to Start Windows Normally, Safe Mode, etc instead of checking the disk.  Is there any way I can unschedule?  EDIT  I just found out that I could use the -f option to force it.  It failed and told me to run chkdsk /f in Windows and then reboot twice.  But the chkdsk program is in the partition I am trying to check so it says it is in use. Nesting HTML- anchor tags Remove space around tikz How can I remove ALL space around TiKZ. So given MWE below, I want no space between fbox and the node box (so essentially I want to see 1 line). How to realize this?   Is this space in tikzpicture or in \fbox?   How to remove space between \fbox and node    MWE  \documentclass{article} \usepackage{tikz}  \begin{document} \fbox{%   \begin{tikzpicture}[node distance = 0.8cm and 0.2cm]%     \node[draw] (center) {CENTER}; %   \end{tikzpicture}% } \end{document} How did "When" become the customary answer to "say when"? When a waiter at a restaurant comes by with pepper or Parmesan cheese, he says, "say when" and starts putting it on your food.  Many people will say "OK" or "that's enough," but it seems that the customary answer is "when".  How did this become the customary answer?  Did everyone decide to make the exact same joke, until it became commonplace.  I thought it was funny when I was a kid, but even now as an adult, I still say it.  For evidence that this is indeed commonplace, see .  The answer "when" is used and is external to the joke of the strip. But even so, I'm curious as to just how commonplace this really is.  I see it a lot in the US.  Is it used elsewhere in the world?  (by the way, I'm new to asking questions on this site, and I have no idea what tags to put on this question) Entry to The US before 30-day grace period for student visa The F student visa allows me to enter the US up to 30 days before the program starts. For starting to set up things it is of my interest to arrive sooner than that. How hard is it to travel there beforehand with a tourist visa (waiver) and leave to, say Mexico, to then re enter on a proper date within the 30 days with the student visa? This seems easier than requesting for a status change inside the US from tourist to student.. What does the big intersection or union sign of a set mean? In some cases, we will have to consider the union or the intersection of several, even infinitely many sets, defined in the obvious way. For example, if for every positive integer $n$, we are given a set $S_n$, then   $$\bbox[border:1px solid red]{\bigcup_{n=1}^\infty S_n}=S_1\cup S_2\cup\cdots=\{x\mid x\in S_n\text{ for some }n\},$$   and   $$\bigcap_{n=1}^\infty S_n=S_1\cap S_2\cap\cdots=\{x\mid x\in S_n\text{ for all }n\}.$$   Two sets are said to be disjoint if their intersection is empty. More generally, several sets are said to be disjoint if no two of them have a common element. A collection of sets is said to be a partition of a set $S$ if the sets in the collection are disjoint and their union is $S$.   Normally what I know is that you can make a union or an intersection between only two sets. In this expression, there is a big union of sets. I'm asking about the meaning of this expression – what does it mean? What does the infinity sign do at the top?  Things are even more complicated with De Morgan's laws, which use the same expression:     Two particularly useful properties are given by De Morgan's laws which state that   $$\left(\bigcup_nS_n\right)^c=\bigcap_nS_n^c,\quad\quad\quad\quad\left(\bigcap_nS_n\right)^c=\bigcup_nS_n^c.$$   Anyone who can explain to me the expression or De Morgan's laws would be much appreciated. How are Star Wars blasters properly reloaded/charged/etc.? I've been looking into the inner workings of blaster weapons primarily using Wookieepedia. While most of it I understand, I still can't figure out how many rounds a gun would fire before needing the ammunition component replaced/reloaded. Is there any solid answer?  I'm someone who likes to design and draw his own weapons and such, but likes to keep to how the technology of an era is in mind. While Star Wars weapons don't really have magazines (and you don't really see them reloading during battle), other people's work still has magazines and treat ammunition consumption as though it's pretty much the same as our modern era.  I guess that I just find it hard to believe, with the technology of the Star Wars Universe, that characters would need to carry lots of ammunition (hence why clones/storm troopers/battle droids don't visually seem to carry very much).  Example: DC-15A     "The weapon's tibanna gas cartridge carried enough gas for up to 500 shots, depending on the power settings of the weapon, while the charge pack lasted about 50 shots"   Source:   I've read in several places that this can be seen in two different ways.  1. Which ever ran out first, had to be replaced before the weapon could fire again. 2. The weapon contained two different sources of ammunition (so I guess you could switch between the two) How to run a specific program as root without a password prompt? I need to run something as sudo without a password, so I used visudo and added this to my sudoers file:  MYUSERNAME ALL = NOPASSWD: /path/to/my/program   Then I tried it out:  $ sudo /path/to/my/program [sudo] password for MYUSERNAME:    Why does it ask for a password? How can I run/use commands as root with a non-root user, without asking for a password? Given $m$ rows with $n$ variables where $m &lt; n$, and given that there exists a combination of some of the rows that gives a zero vector. Is it promised when computing the reduced-row echelon form, with Gaussian elimination to find a zero vector?  Update: I clearly don't know, how to pick up the right words to ask my question. So let me give you the full context and please help me say it right, so the question will make sense. I am solving step 3 in the quadratic sieve algorithm, here is a  description of it.  Suppose the composite number N is being factored. Bound $B$ is chosen, and the factor base is identified (which is called $P$), the set of all primes less than or equal to $B$. Next, positive integers $z$ are sought such that $z_2$ mod $N$ is B-smooth. Therefore it can be written, for suitable exponents $a_i$, $${\displaystyle z^{2}{\text{ mod }}N=\prod _{p_{i}\in &gt; P}p_{i}^{a_{i}}}$$ When enough of these relations have been generated (it is generally sufficient that the number of relations be a few more than the size of P), the methods of linear algebra can be used (for example, Gaussian elimination) to multiply together these various relations in such a way that the exponents of the primes on the right-hand side are all even: $${\displaystyle {z_{1}^{2}z_{2}^{2}\cdots z_{k}^{2}\equiv \prod &gt; _{p_{i}\in P}p_{i}^{a_{i,1}+a_{i,2}+\cdots +a_{i,k}}\ {\pmod {N}}\quad ({\text{where }}a_{i,1}+a_{i,2}+\cdots +a_{i,k}\equiv 0{\pmod &gt; {2}})}}$$  Now, let's say I found $m$ relations and the number of primes in $P$ is $n$, such that $m&lt;n$. It is given that there exists a combination of some of the $m$ relations that their product is a square number. My question is: When I perform the Gaussian elimination over F2 to find a null space combination, is it promised that I will find one? I successfully implemented the algorithm and the matrix part of my implementation works. But what I see is that if I found a null space(a combination of making a null space) and latter I add more relations(still $m &lt; n$), I lose the null space solution and not able to solve the matrix again. Each time I add a new relation I start solving it from the beginning, I don't remember any previous state. So what I want to know, could it be that there is a limitation with the Gaussian elimination algorithm, that it does not promise to find the null space if $m &lt; n$? Writing letters of recommendation for more than one student to the same department Suppose multiple students have asked me for letters of recommendation to the same graduate department in the US. Am I expected to explicitly compare the students to one another? Am I supposed to do this in both letters (assuming they haven't been submitted yet)? Do I need to explicitly state a preference for one over the other, or can I just get away with listing relative strengths and weaknesses (for instance, "X is stronger academically, but Y has more research experience and is a stronger programmer")? Importing installed package from script raises "AttributeError: module has no attribute" or "ImportError: cannot import name" the output when I start firefox from Terminal Comparing areas in scanned historical land use maps using QGIS? I've been looking all over for a proper explanation of how to delete photos from the device (nexus 5) to reclaim some space, while being sure that the pictures are still in the Google+ backup. Unfortunatley i have not found one, other than "wild claims" it works somehow, while other say it does not. Plus deleting photos via the Pictures app actually warns you (now?) that it will delete the backed up copies too. Do i have to delete them in the Gallery app?  I did delete some photos recently, and i was quite sure they ware still backed up (still showed up on the Google+ website) but looking now i see they are in the trash in the device.  Is there really no way to be able to know for sure if the pictures are backed up savely while i can delete them from the device?  Alternatively i'm also open for alternative solutions to this problem, or i just go back to the "good old copy and paste when plugging the phone". I want to put a link to my SO profile on my homepage. I remember a codesnippet i saw somewhere that would basically display my Username and my reputation. Where was that? In "Winnie the Pooh", Why isn't the Hundred Acre Wood  plural? When I read some of these Winnie the Pooh stories to my kids at night, the place where the story takes place is the Hundred Acre Wood, not Hundred Acre Woods.  Why is that? When should N-Gons be used, and when shouldn't they? Why is my Canon 300D not switching on despite changing both batteries and the CF card?