NMI Watchdog: BUG: soft lockup Have had Ubuntu 16.04 on my new machine for about 4-5 months now (ever since I bought it).  Today when shutting down, it generated a message which said:  NMI Watchdog: BUG: soft lockup - CPU#0 stuck for 22s! [swapper/0:0]   Can someone please help me get to the bottom of this?  My laptop is still in warranty, and if there is any hardware issue, maybe I can get it replaced right now. Not too worried about software bugs, but of course would like to have this rectified in any case.  Please let me know about any additional information which might be needed.
NMI watchdog: BUG: soft lockup - CPU#2 stuck for 23s! [plymouthd:305] I get this error message   NMI watchdog: BUG: soft lockup - CPU#2 stuck for 23s! [plymouthd:305]    on the startup of my system (even with live-cd).  My PC is a dell inspiron 7559 with intel graphic and nvidia.  UPDATE - this issue also happens when attempting to install ubuntu 18.10 using LiveUSB
Does a non-abelian semigroup without identity exist? Demonstrate that if $f$ is surjective then $X = f(f^{-1}(X))$ I haven't been able to do this exercise:     Let $f: A \rightarrow B$ be any function. $f^{-1}(X)$ is the inverse   image of $X$. Demonstrate that if $f$ is surjective then $X = f(f^{-1}(X))$ where $X \subseteq B$.   Since $X \subseteq B$, all the elements in $X$ belong to the codomain of $f$.  Since $f$ is surjective, it means that all elements in the codomain $B$ have some preimage in $A$. Given that $X \subseteq B$, all elements in $X$ must also have a preimage in $A$.  Have $\triangle = f^{-1}(X)$, $\triangle$ is now a set containing the preimages of the elements in $X$. Because of this, $\triangle \subseteq A$.  If we evaluate $f(\triangle)$, we...... nope, I don't know what I'm doing now.    What do you think? When do you use the "this" keyword? I was curious about how other people use the this keyword. I tend to use it in constructors, but I may also use it throughout the class in other methods. Some examples:  In a constructor:  public Light(Vector v) {     this.dir = new Vector(v); }   Elsewhere  public void SomeMethod() {     Vector vec = new Vector();     double d = (vec * vec) - (this.radius * this.radius); } Apt sources.list problem , packages not found? I am trying to install WICD but getting following errors on my ubuntu 10.04 box  sudo apt-get install wicd   Err http://archive.ubuntu.schoolnet.lk/ubuntu/ lucid/universe python-wicd 1.7.0+ds1-2   Could not connect to archive.ubuntu.schoolnet.lk:80 (103.29.60.18). - connect (111: Connection refused) Err http://archive.ubuntu.schoolnet.lk/ubuntu/ lucid/main python-iniparse 0.3.1-1   Unable to connect to archive.ubuntu.schoolnet.lk:http: Err http://archive.ubuntu.schoolnet.lk/ubuntu/ lucid/universe wicd-daemon 1.7.0+ds1-2   Unable to connect to archive.ubuntu.schoolnet.lk:http: Err http://archive.ubuntu.schoolnet.lk/ubuntu/ lucid/universe wicd-gtk 1.7.0+ds1-2   Unable to connect to archive.ubuntu.schoolnet.lk:http: Err http://archive.ubuntu.schoolnet.lk/ubuntu/ lucid/universe wicd 1.7.0+ds1-2   Unable to connect to archive.ubuntu.schoolnet.lk:http: Failed to fetch http://archive.ubuntu.schoolnet.lk/ubuntu/pool/universe/w/wicd/python-wicd_1.7.0+ds1-2_all.deb  Could not connect to archive.ubuntu.schoolnet.lk:80 (103.29.60.18). - connect (111: Connection refused) Failed to fetch http://archive.ubuntu.schoolnet.lk/ubuntu/pool/main/p/python-iniparse/python-iniparse_0.3.1-1_all.deb  Unable to connect to archive.ubuntu.schoolnet.lk:http: Failed to fetch http://archive.ubuntu.schoolnet.lk/ubuntu/pool/universe/w/wicd/wicd-daemon_1.7.0+ds1-2_all.deb  Unable to connect to archive.ubuntu.schoolnet.lk:http: Failed to fetch http://archive.ubuntu.schoolnet.lk/ubuntu/pool/universe/w/wicd/wicd-gtk_1.7.0+ds1-2_all.deb  Unable to connect to archive.ubuntu.schoolnet.lk:http: Failed to fetch http://archive.ubuntu.schoolnet.lk/ubuntu/pool/universe/w/wicd/wicd_1.7.0+ds1-2_all.deb  Unable to connect to archive.ubuntu.schoolnet.lk:http: E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing? Level 10 vim adventures beers on the wall complete solution I saw this question  but it doesn't have a full solution. What is the full solution to the 99 bottles of beer on the wall for Vim adventures?  Context: for the sake of being a good SO member I will give more details but a full solution will answer my question. It seems from reading the other post that my register is incorrect for some reason. I can't get the &lt;NL&gt;. I think that's the issue since pasting won't work... I just found out about the Mesh Display : Length feature in the "N" panel (thanks to ) that allows one to measure the length of a face or vertice.  But my first encounter with this tool gives me complex feelings of love and hate, see how, as I was trying to measure the aspect ratio of this TV screen, I am getting WIDTH = 20.33 and HEIGHT = 37.57.  These values seem awfully wrong, since my betrusted eyes tell me the height should be shorter than the width.    I have tried measuring the single vertices as well, to identical results. Is $(x^2+y^2+z^2) \ \sin \frac{1}{\sqrt{x^2+y^2+z^2}}$ Differentiable in $(0,0,0)$? I started by Time Series Analysis by Hamilton, but I am lost hopelessly. This book is really too theoretical for me to learn by myself.   Does anybody have a recommendation for a textbook on time series analysis that's suitable for self-study? I see that the code in many packages and examples contains percent signs % at the end of (many) lines. What are they used for? Do they affect the parsing of those lines? Hypernym for “import” and “export”? What word could describe an operation of either importing or exporting?  X is to import and export as migration is to immigration and emigration.  Porting isn't the word I'm looking for, I don't think, but that's what I'm getting at. Cheers! Can I combine extension tubes and macro filters at once to give better macros? basic geometry angle problem Two straight lines, AB and AD, lie in the same vertical plane. AB makes an angle of 25 degrees with the horizontal, and AD makes 32 degrees with the vertical. What is the angle between AB and AD?  The answer is 33 degrees or 93 degrees.   I cannot visualize what this question is asking. It says both AD and AD lie on the same vertical plane, then immediately says AD makes 32 degrees with the vertical. Isn't this a contradiction? What are "electron holes" in semiconductors? I'm tutoring senior high school students. So far I've explained them the concepts of atomic structure (Bohr's model &amp; Quantum mechanical model) very clearly. Now the next topic to be taught is semiconductors.  I myself am not conviced with the concept of electron holes. If there is no electron then there is no electron. How can it be a hole. We define a hole when there is some thing every where except at a place. But inside an atom how can we define a HOLE.  Kindly explain it with the help of Bohr's model. What was the need of introducing such abstract concept in semi conductors? pgfplots: lines and markers in different colors With pgfplots, I am creating a simple coordinate plot with error bars like this:    \documentclass[crop,10pt]{standalone} \usepackage[english]{babel} \usepackage{pgfplots}      \begin{document}%         \setlength{\linewidth}{246pt}%              \begin{tikzpicture}             \begin{axis}[             width=\linewidth,             ytick pos = left,             xtick pos = left,             clip=false,             axis on top,             tick align = outside,             yticklabel style={%             /pgf/number format/fixed,             /pgf/number format/precision=1,             /pgf/number format/fixed zerofill         },             ytick scale label code/.code={},             xlabel={X},             ylabel={Y},     ]             \addplot[mark=*]             plot[             error bars/.cd,             y dir=both,             y fixed=0.0001     ]             coordinates{(1,0.0005) (1.1,0.0013) (5,0.0015)};             \end{axis}             \end{tikzpicture}     \end{document}   In the original plot I have a lot more points. I would now like the line and the markers (including the error bars) to have different colors to better distinguish the line from the error bars. Is that somehow possible? The only way I found so far is to plot the data just as a line in one color and then plot it again just as markers in another color. This works, but I guess there must be some better solution to this. Thanks for the support, John Renaming hundreds of files at once for proper sorting Converting a number with comma as decimal point to float Find a recurrence relation for the number of $n$-digit binary sequences with no pair of consecutive $1$s Find a recurrence relation for the number of $n$-digit binary sequences with no pair of consecutive $1$s.  I know my base case:$$a_1 = 2$$ for either $1$ or $0$. Normally to construct the recurrent relation I would say fill in $n-1$ spaces then add a $1$ or $0$, which is simply:$$a_n = 2\cdot a_{n-1}$$However, I don't believe this is right, because this doesn't take into account that there can't be any consecutive $1$s.  Even when I use the base case of $2$ digits:$$a_2 = 3$$for either $01$, $10$, or $00$, I still get the recurrence relation of:$$a_n = 3\cdot a_{n-2}$$which also does not account for $01$ and $10$ occurring consecutively.   So how would I express this? Why can't I move a window to the top left corner with wmctrl in Unity? I've been playing around with wmctrl to take more control of my windows. I've encountered a weird behaviour where Unity reserves double the space. See this screen shot:    I opened the terminal and moved the window using the top command. It should be at the top left corner (X=0 Y=0). But for some reason there is some margin between the terminal and the Unity bars.  If I understand the man pages correctly it might have something to do with the WA: 65,24.  Can anybody help me to fix this? Has anyone managed to get the Citrix receiver client (icaclient) working in Ubuntu? I know that I can append &amp; to a command to run the process in the background.   I'm SSH'ing into an Ubuntu 12.04 box and running a python program with $python program.py &amp; -- but when I go to close the terminal window I get a message saying that closing the terminal will kill the running process.   Why is this? I am using the ampersand to run the process in the background. How can I get it to run regardless of if I am SSH'ed in?