Catching multiple SIGCHLD processes for Unix Style Shell in C
Determine pid of terminated process
What algorithm for a tic-tac-toe game can I use to determine the "best move" for the AI? GUI/Unity crashing in 16.04 LTS after updates 2018-01-04, compiz segfaults The latest updates (4/1/2018) make my laptop constantly crash the GUI/Unity:  (Intel Pentium su4100 processor)  syslog:  Jan  5 11:38:53 1810 kernel: [ 1850.327738] compiz[11911]: segfault at 0 ip 00007f6c7baf0c16 sp 00007ffd5ec71c60 error 4 in i965_dri.so[7f6c7b513000+82d000]   After login I end up with an empty desktop, just a wallpaper, GUI/Unity are in a crash loop:   No panel.  No dash.  Can't start a program. Launcher disappears. Sidebar disappears. System crash. Windows key not working. The key combination Alt+Tab not working.   Simply, the computer is not usable. Same for guest login. The only thing working: open up a terminal CTRL+ALT+T to examine log files.  I somehow forced  to let me log in and file the bug, but still lots of problems:   Dash not working Alt+Tab not working Sometimes windows all disappear for a few seconds     Any ideas for a solution or workaround?   UPDATE     If you have the same/ very similar problems, follow the link to my    report and mark there that you're affected too. Or file your own. Please leave a comment   if you wish, or upvote - this is a nasty problem - but an answer should   offer a fix or a workaround so users can use their computer again.    Without , Ubuntu can't fix issues. Is it possible to scale up an image to increase the the pixel density? Why do all Winforms programs require the [STAThread] attribute? Windows 10 won't let me set default apps for file extensions Where did the Q come from, before the Q Continuum? In the Star Trek Universe where did the Q come from? I mean before they were Q in the Q Continuum? In Star Trek Voyager you learn that the race is somewhat intolerant of individualism (in the episode of the Q Civil War) but Q also suggest they have always been Q. Is that statement true, have the Q always been the Q? or were they a race that evolved into omniscience? How do ${0##*/} and ${0%/*} work? I'm quite confused about the following regular expressions I found in a shell script:  ${0##*/} ${0%/*}   How do they work? Principled way of collapsing categorical variables with many levels? What techniques are available for collapsing (or pooling) many categories to a few, for the purpose of using them as an input (predictor) in a statistical model?    Consider a variable like  (discipline chosen by an undergraduate student). It is unordered and categorical, but it can potentially have dozens of distinct levels. Let's say I want to use major as a predictor in a regression model.  Using these levels as-is for modeling leads to all sorts of issues because there are just so many. A lot of statistical precision would be thrown away to use them, and the results are hard to interpret. We're rarely interested in specific majors -- we're much more likely to be interested in broad categories (subgroups) of majors. But it isn't always clear how to divide up the levels into such higher-level categories, or even how many higher-level categories to use.  For typical data I would be happy to use factor analysis, matrix factorization, or a discrete latent modeling technique. But majors are mutually exclusive categories, so I'm hesitant to exploit their covariance for anything.  Furthermore I don't care about the major categories on their own. I care about producing higher-level categories that are coherent with respect to my regression outcome. In the binary outcome case, that suggests to me something like linear discriminant analysis (LDA) to generate higher-level categories that maximize discriminative performance. But LDA is a limited technique and that feels like dirty data dredging to me. Moreover any continuous solution will be hard to interpret.  Meanwhile something based on covariances, like multiple correspondence analysis (MCA), seems suspect to me in this case because of the inherent dependence among mutually exclusive dummy variables -- they're better suited for studying multiple categorical variables, rather than multiple categories of the same variable.  edit: to be clear, this is about collapsing categories (not selecting them), and the categories are predictors or independent variables. In hindsight, this problem seems like an appropriate time to "regularize 'em all and let God sort 'em out". Glad to see this question is interesting to so many people! Is there a way to log all Microsoft SQL Server queries executed on a certain server, with their respective durations?  I'd like to be able to analyze all queries will a tool like what  does for PostgreSQL. While we're at it: do you know of any such tools? Jump between open windows on multiple monitors in Task View on Windows 10 with keyboard I'm using two monitors with Windows 10 and I have a few windows open on each monitor. When I open the Task View (Win + Tab) I can only navigate between the main monitor's windows with keyboard (using arrow keys or the Tab key). I see the other display's windows on that display but can't figure out how to cycle through those windows with my keyboard.  Is there a way I can give focus to secondary monitor's windows in the Task View using keyboard?  To put it another way, how do I select the first item on the right monitor in the following screenshot using keyboard? Was it just coincidence that Tahir Mahmood went on stage? How to install and use CDI on Tomcat? Help me identify this fantasy book about two near-omnipotent wizard run empires I have to find an easy ring which this ring is isomorphic with.  I can prove that $5 = (2+i)(2-i) \in (2+i)$ but this doesn't help me further.  My book says the answer is $\mathbb {Z_5} $ What is the true origin of the orcs? There are a bunch of theories about the true origin of the orcs. Tolkien tried out a few different origins for his Orcs throughout his life but died before he could fully revise The Silmarillion with his final view on their origins and nature.   There is a list of origins proposed by Tolkien():   Made of stone and slime through the sorcery of Morgoth; East Elves, where The Silmarillion contains a suggestion that Orcs are descended from East Elves captured by Melkor, their minds and bodies distorted and corrupted. Sentient beasts, another of Tolkien's theories proposes that Orcs may have begun as soulless animals of vaguely humanoid shapes, empowered by the will of the Dark Lord (Morgoth) and learning language only as parrots do. Fallen Maiar, there are hints in the History of Middle-earth series of books, (especially in Morgoth's Ring in the section "Myths Transformed"), that some Orc leaders, such as the First Age's Boldog, or the Great Goblin encountered by Bilbo and the Dwarves, may in fact have been fallen Maiar which had taken Orc form. Corrupted Men, while Tolkien at some point saw all Orcs as descended from the original corrupted and tortured Elves, later comments of his indicate, according to Christopher Tolkien in Morgoth's Ring "Myths Transformed" text X, that he began to feel uncomfortable with this theory. At about the same time he removed the references to the Thrall-Ñoldorin, he also began searching for a new origin for the Orcs. It seems Tolkien wanted to change the origin of the Orcs to make them corrupted and twisted Humans.  A mix of corrupted Elves and Men, A late idea of Tolkien seems to be that Orcs (or Orks, showing the late spelling change) had a mixed origin of Elves and Men. Some cross-bred with Men, Tolkien also suggested that Men were cross-bred with Orcs under Morgoth's lieutenant, Sauron (and possibly under Morgoth himself). The process was later repeated during the War of the Ring by Saruman. This possibly refers to the way the Uruk-hai and the Half-Orcs were created, in The Lord of the Rings.   Of all these theories, which is the most accepted, and which did Tolkien agree with the most? I always thought that orcs were made of East Elves, as explained in The Lord of The Rings, but the story goes beyond this, there are the stories in many other books that explain different things.  What can you tell me about this? Hypothetical party:  1st level human wizard (PC) 3x guard NPC 1x acolyte NPC    This is the player's first time, and it's a solo campaign. The first mini-adventure involves recovering the cargo of a supply caravan that didn't make it to her magic academy due to bandit hijacking (as a sort of graduate-test). The guards and healer are on contract from the school to assist her. The acolyte is essentially just to hang back and tend to wounds and probably won't engage in combat unless someone goes down or the PC is seriously wounded.  So, with that "party" makeup, how do I determine the XP budget for a "medium" or "hard" encounter since there's no clear CR->level mapping in 5e for those NPCs (who will certainly factor into any combat as meatshields and melee damage)? I was thinking about reverse-engineering them as crumby lvl2 fighters (given the 2 HD worth of HP they have), but they certainly aren't on par with a lvl2 fighter, given the lack of action surge, second wind, etc., so the encounters would end up being too hard compared to PCs or DMPCs.   Could they be lvl1-equivalents, essentially trading any abilities a PC would have for extra HP? How would this work at later levels with higher CR NPCs (veteran, priest, mage, etc.)? I'd rather not have to build a bunch of DMPCs as hirelings, because I want the NPCs to be a bit vanilla compared to the versatility of my player. I'm already introducing 1-2 DMPCs to the game for her to take control over as she gets a feel for the flow of the game (for now, she'll handle them out of combat, and I'll effectively show her how to utilize them until she's ready).     Just to be clear, I'm comfortable with the monster-generation rules for crafting NPCs as enemies to determine their CR, but I'm confused on how to use them in the adventuring party when budgeting encounter difficulty XP. It should be trivial, and it might even be in the help, but I can't figure out how to navigate it. How do I indent multiple lines quickly in vi? Editing Photoshop (PSD) files on Ubuntu? I was wondering that is it possible to edit PSD files on Ubuntu (like with Gimp). Actually, I need to edit layers. I haven't managed to do it. It would be nice if there is a chance! :) If Newton's third law is true, why can we sink in sand? Newton's third law of motion states that every action has an equal and opposite reaction. That is the reason we do not sink into the earth, because when our weight exerts a force on the earth it also exerts an equal and opposite force on us.  But when we stand on quicksand or on fluids we can sink in. How is this possible? Does it not exert an equal and opposite force on us? Or are Newton's laws different in the case of fluids and substances of low densities? Was Louis stalked days in advance too?