Optimal value for make -j
How to determine the maximum number to pass to make -j option?
What is the meaning of the "expansion of space"? When we say that "the space between galaxies is expanding," what do we really mean? For instance, if I think of space as being a Cartesian grid, then when space expands should I think of it as adding more grid-points or as making the distance between the grid-points larger? Or is this a flawed picture of space-time even when far from significant mass densities?  It seems to me that it must be the case that we are "adding more grid-points" because otherwise we would not observe the expansion since anything that occupied that part of the grid (e.g. light, my hand, etc.) would also expand by a corresponding amount (otherwise, after a sufficient amount of expansion, we would be able to observe sub-atomic scale processes as being macroscopic in scale). But if it is the case that we are adding more grid-points, then the "expansion" of space seems like a misnomer: shouldn't it be called the "creation" of space?  That being said, either case (adding grid-points or stretching distances) could conceivably be the same process depending on the nature of space-time (i.e. if it were discrete but dense - like the Rationals - rather than either strictly discrete (Integers) or strictly continuous (Reals)... I hope that analogy makes sense).   So what is really going on in intergalactic space? What is the meaning of its expansion? Does it correspond to creating more space, stretching the space that's already there, or something more subtle? sed : Ignore line starting whitespace for match I want to replace the default listening port of httpd to 9090. I can edit the line in httpd.conf file using below  sed -i "/^Listen/c\Listen 9090" /etc/httpd/conf/httpd.conf   But the line   Listen 80   may have white space before it.  How do I ignore this white space to match this line? If I fall off a cliff - say, 1000 feet - can I wait (readied action?) until I am near enough to the ground (my understanding is you fall 500 ft/round) then  safely to the ground? Or, does the momentum from the fall carry over through the teleport and I still splatter across the rocks? Currency formatting in Python I am looking to format a number like 188518982.18 to £188,518,982.18 using Python.  How can I do this? Is there an equivalent in mathematical language to the modulo (or mod) function in computing? Managing Metered Connections on OSX Why is looping over find's output bad practice? Show an exponential function has a valid density. Given:  Let $X$ be exponential with parameter $\lambda$, that is   $$ f_X(x) = \begin{cases} \lambda e^{-\lambda x} &amp; \text{if }x&gt; 0, \\ 0 &amp;\text{for }x\leq 0. \end{cases} $$  where $\lambda&gt;0$ is called the rate of the distribution.  Question:  Show that this is a valid probability density function (pdf).  Attempt:  Need to show that  $$ f(x) = \int^{\infty}_{-\infty} \lambda e^{-\lambda x}\,  dx=1\\\\ $$ Thus, \begin{eqnarray*} f(x)&amp;=&amp;\int^0_{-\infty} \lambda e^{-\lambda x} \, dx+\int^\infty_0 \lambda e^{-\lambda x} \,  dx\\[8pt] &amp;=&amp;0+\int^\infty_0 \lambda e^{-\lambda x} \, dx \\[8pt] &amp;=&amp;\lambda\int^\infty_0 e^{-\lambda x} \, dx \\[8pt] &amp;=&amp;1 \end{eqnarray*}  The problem is that my professor just told me that I skip a step right before I derive $1$. Any insight?  EDIT:  Given the great feedback, here is the answer:  \begin{eqnarray*} f(x)&amp;=&amp;\int^{\infty}_{-\infty} \lambda e^{-\lambda x} dx=1\\\\ f(x)&amp;=&amp;\int^{\infty}_{-\infty} f_X(x)dx\\ &amp;=&amp;\int^{0}_{-\infty} 0\,\,\, dx+\int^{\infty}_{0} \lambda e^{-\lambda x} dx\\ &amp;=&amp;0+\int^{\infty}_{0} \lambda e^{-\lambda x} dx\\ &amp;=&amp;\int^{\infty}_{0} \lambda e^{-\lambda x} dx\\ &amp;=&amp;\int^{\infty}_{0} e^{-\lambda x} \Big(\lambda \,\,\,dx\Big)\\ &amp;=&amp;\int^\infty_0e^{-u} du\\ &amp;=&amp;-e^{-u}\Big|^{\infty}_0\\ &amp;=&amp;1-\lim _{x \to \infty} e^{-u}\\ &amp;=&amp;1\\ \end{eqnarray*} I can't play Pokemon GO! What's wrong? Pokemon GO isn't working at all for me right now. I'm in one of the following circumstances and can't do anything:   My game is displaying a "Try Again" message I'm stuck on the Loading Screen When I sign in I get a message that the servers are experiencing problems. I see the map but nothing is loaded, and my team color is wrong The "loading" Pokeball just ends up spinning and I can't catch or interact with things When I try to catch a Pokemon, the Pokeball just sits on my screen doing nothing Gym opponents will drop to 1 HP and won't take any more damage or attack When I open a pokestop, the pokestop image and the name of the pokestop does not load.   What's causing this? Is there a way to fix it? When I type uname -a, it gives the following output.  Linux mars 2.6.9-67.0.15.ELsmp #1 SMP Tue Apr 22 13:50:33 EDT 2008 i686 i686 i386 GNU/Linux   How can I know from this that the given OS is 32 or 64 bit?  This is useful when writing configure scripts, for example: what architecture am I building for? As a disclaimer, I must admit this may benefit me (I haven't checked), but probably not as significantly as most others. This issue is also something that has prevented me from answering questions by users with 1 rep in the past, especially if they are poorly fashioned. The Problem New users with a programming question find SO from various methods, such as google. They ask a question with haste, hoping for a quick answer -- which they usually receive. Many of these users have no interest in Stack Overflow itself, but are simply interested in getting the solution they require. As a result of this, they'll check the site regularly for the first day or two until a sufficient answer has been posted. Once they get what they need, they bail; without the required rep or understanding that they should up-vote and select a response as the answer. The Result A great many questions on SO are abandoned by users with no intention of ever coming back. The answer they require has been provided, but for one or more reasons they have neglected their duty of contributing back by way of awarding reputation. The Reach (Since Jeff loves Datum) Some queries on the data dump examine the reach of this 'problem'. The query I used is based on extensions of the following base query; SELECT p1.Id, p1.Score, p1.OwnerUserId, p2.OwnerUserId, p2.Score FROM posts p1  INNER JOIN posts p2 ON (p1.Id=p2.ParentId) LEFT JOIN users ON (p1.OwnerUserId=users.Id) WHERE p2.Score &gt;= 2  AND p2.Score = ( SELECT MAX(p3.Score) FROM posts p3 WHERE p3.ParentId=p1.Id ) AND users.Reputation &lt; 15 AND p1.PostTypeId = 1 AND p1.AcceptedAnswerId = 0  Result: 3,288 Questions by users with under 15 rep which have answers with 2+ up votes that have no accepted answer. Adding: AND (users.LastAccessDate-p1.LastActivityDate) &lt; 604800 // 1 week AND p1.CreationDate &lt; 1249084800 // 1249084800 is 1 week before latest dump data  to the where clause further reveals that 877 questions that have answers with 2+ up votes have no accepted answer, and the owner of the question has not returned since the week the question was asked. Modifying there where clause, and removing the left join: AND p1.OwnerUserId = 0    Reveals a staggering 3,675 questions with answers of 2+ votes by deleted users.  These are questions that were probably answered but the users who did the work can never be recognized. Building off the previous and using an even more restrictive WHERE clause WHERE p2.Score &gt;=5  Still 1,178 posts that can never have an accepted answer. How many posts are there with over 5 up votes that don't provide the correct answer? Modifying the where clause for Reputation to AND users.Reputation = 1  Still reveals 388 questions by users with 1 rep have been abandoned. Solution Similar to how bounty questions work, if a user has abandons the site (not active since x time after the question was asked) with a question that has answers with 2+ up votes, force the answer with the most up votes to be the selected answer. This will reduce the amount of questions that are unanswered, and also give users more of an incentive to answer questions by new users without extra hesitation.  Update Added more statistics for deleted users.  Please feel free to add/remove rules to make this a truly practical feature. Using only the delta definition of a limit, how can we prove that the sequence $\{a_n\}$, where $a_n = \sin n$, as $n$ tends to infinity does not have a limit?  Thanks! What's the starting wealth for higher levels? The PHB only gives starting wealth for Level 1 PCs. Based on my experience in other games, specifically Pathfinder, I would expect to get more at higher levels. Where can I find an appropriate table or calculation? VirtualBox 5.0.40 crashes the whole host since update to kernel 4.13.0-26-generic I received the updates through normal Software Updater, 10-Jan-2018. After this VirtualBox would not start any VM, complaining about dkms and asking to make modprobe vboxdrv. Following the advice I reinstalled virtualbox-dkms with:  sudo apt-get --reinstall install virtualbox-dkms   After this and a reboot I tried to start a VM which freezed the whole machine and a hard reboot was necessary.  Is there a way to make VirtualBox work with the latest kernels?  EDIT:  As suggested by N0rbert, the command:  apt-cache policy `dpkg -S VirtualBox | head -n1 | sed -e 's/://g' | awk '{print $1}'`  gives:   virtualbox-qt:   Installed: 5.0.40-dfsg-0ubuntu1.16.04.2   Candidate: 5.0.40-dfsg-0ubuntu1.16.04.2   Version table:  *** 5.0.40-dfsg-0ubuntu1.16.04.2 500         500 http://fr.archive.ubuntu.com/ubuntu xenial-updates/multiverse amd64 Packages         100 /var/lib/dpkg/status      5.0.18-dfsg-2build1 500         500 http://fr.archive.ubuntu.com/ubuntu xenial/multiverse amd64 Packages   EDIT (on 29-Mar-2018): Issue is resolved for me, with the Ubuntu Ubdate from today. I have seen that it had some virtualbox-updates, therefore I tried to boot with the most recent kernel again. Then I had to run  sudo apt-get --reinstall install virtualbox-dkms  And after this my virtual machines in VirtualBox started working without crashing the whole computer. Finally! With biblatex, the author can be replaced by a dash (or “idem”) in the bibliography. Is it possible to have this replacement also if there are multiple authors, and the first of these multiple authors is the same as the author of the book listed before? (It is somewhat difficult to describe, see the attached example instead, where “Buchautor, Hans-Wilhelm” should be replaced in book3 as well.)   I assume that it should be possible by customising \DeclareNameFormat, but I don’t know how.  Minimal example:  \documentclass{scrartcl} \usepackage[T1]{fontenc} \usepackage[latin1]{inputenc} \usepackage[english]{babel} \usepackage{csquotes} \usepackage{filecontents} \begin{filecontents}{\jobname.bib} @BOOK{book1,   author = {Buchautor, Hans-Wilhelm},   title = {Irgendein Buch},   location = {Buch am Wald},   date = {2000} } @BOOK{book2,   author = {Buchautor, Hans-Wilhelm},   title = {Ein anderes Buch},   location = {Berlin},   date = {2001} } @BOOK{book3,   author = {Buchautor, Hans-Wilhelm and Zweitautor, Zoran},   title = {Noch ein Buch},   location = {London and New York},   date = {2010} } \end{filecontents}  \usepackage[ style=authortitle, backend=bibtex8 ]{biblatex} \bibliography{\jobname}  \renewcommand*{\bibnamedash}{%   \bibstring[\mkbibbold]{idem\thefield{gender}}}  \begin{document} \nocite{*}  \printbibliography \end{document}   Edit 15/02/2011 17:14   I should have added that there was a feature request for biber which pointed back to biblatex. See .  Edit 21/06/2011 9:26  Is this somehow possible now with biblatex 1.4/1.5? I played a bit with uniquename/uniquelist, but I could not get it to work. What are the practical applications of the Taylor Series? I started learning about the  in my calculus class, and although I understand the material well enough, I'm not really sure what actual applications there are for the series.  Question: What are the practical applications of the Taylor Series? Whether it's in a mathematical context, or in real world examples. Can "THAT" be omitted here? So we can say   "Do you think (that) he'll come?"   (in other words, we can omit THAT in conversation)  But what about with a sentence like   "Did he deny （that） he went to Thailand?"   Can "that" also be omitted like in the sentence above? How to open recovered files in word? My computer restarted while I was asleep because of system updates (need to turn that off), and when I opened up Word the first time after it restarted, it gave me a pane on the left hand side that showed me all the documents I had opened.  I chose one of the documents but I want to open them all, how can I bring that pane back?    Update:  I forgot to mention I'm on Word 2007.  I've found that if you go to      C:\Users*YOURUSER*\AppData\Roaming\Microsoft\Word   you can see the autorecovery files.  Mine are still in there, but I don't want to touch them, I'd rather bring back that pane and do it right just in case they disappear as soon as I double click haha... How can we show that the following sequence converges? $(a_n)$ is a bounded sequence with the following condition  $a_{n+1}\geq a_n-\frac{1}{2^n}$   The sequence converges, but how do we show it? Show that there exists a unique $v_0 \in H^1(0,1)$ such that $u(0)=\int_0^1(u'v_0'+uv_0), \forall u \in H^1(0,1)$