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• Printer Canon MP540 succesfully added finally but doesn't print? (Attached Debug log)

  - by NES

  i tried to setup my printer in Ubuntu 10.10. I had to use special guide to install because Canon used libcupsys2 in its packages and ubuntu expects libscupsys i followed this guide in reference to this advice. The first problem was this one (the ubuntu "add printer dialog asked for root credentials". The suggested workarout in Launchpad to create a root password worked. Now i added the printer. It's available for printing. Then i got an error message "cups insecure filter" which prevented me from printing. That could be solved by setting the need root rights in the /usr/lib/cups/filter/ directory. The error message disappeared after restarting cups service. Now it should work but it doesn't. The main problem is now, the printer seems to be proper setup but when i try to print a document, the printer icon appears for short time in gnomepanel. There's a printing job in Queue which got completed, but the printer doesn't print. I attached the Debuglog provided by printer error control, had to upload to another site, since it was to big in the question body here. Perhaps someone can identify the problem with it? Note: i know that it once worked fine with an older release of Ubuntu, but not sure which version this was.

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• Ubuntu boots in read-only filesystem after upgrade!

  - by akatzbreaker

  I got a serious problem here: I recently upgraded to the Latest Version of Ubuntu. Now, I boot to my Ubuntu Partition, and I get a Low-Graphics error! I boot to a Recovery-Mode to see what the Problem is. Then, I try to Fix any Damaged Packages, to run fsck but nothing solved the Problem. Then, from the Recovery Menu, I open a Root Shell. I try to create a File and I understand that the Filesystem is Read-Only. Then, I run: mount -o remount,rw / and it Worked for that Terminal Session! When I go back to recovery, I select to resume Boot Normally but I get the Same Error! a I also tried to Boot to my Root Shell again, remount as Read-Write and Start Gnome from there. It Worked! (But the user is ROOT, and is quite Dangerous!) However, I can't do all this proccess at every boot! Any Solution? (Note that when I try to create a new File in my Ubuntu Partition from another OS, I don't get any Errors!)

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• Asus A8V overcurrent

  - by user139710

  This is not as much as a question as it is a note to those out there that upgrade their motherboards with better processors and the like. Here's my story. Recently I upgraded my processor. System specifications: • Asus A8V Deluxe • 4GB RAM • ATI Radeon 3870 AGP graphics card (I believe that's it) Anyway, I decided to put a dual core Opteron 180 in this rig, but the problem was that I needed to update the BIOS to V-1017, and not knowing the consequences, I went up to the Asus site and got the newest, the latest and the greatest, 1018.002 thinking that it was the best for this board, however it wasn't. I used the Asus EXFlash, which makes life a lot easier, flashed the BIOS and all of a sudden I start getting this message: USB overcurrent protection, system shutting down in 15 seconds to protect your system. WELL SHIT... This is a new one on me... I read the blogs, all the posts on this thing, and did all that everyone else did to correct the problem, but nothing helped. So i decided to start from square one, went back to Asus and looked at the BIOS download... OMG... IT WAS A BETA. So, I downloaded the update that was suggested 1017< and installed it and wouldn't you know, it took care of the problem, no more USB overcurrent protection, no more crashing. I write this today to let you all know about this, just in case you have an issue such as this. Well there you all go. Fly safe and eat your vegetables.

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• Password not working for sudo ("Authentication failure")

  - by Souta

  Before I mention anything further, DO NOT give me a response saying that terminal won't show password input. I'm AWARE of that. I'm typing my user password in (not a capslock issue), and for some reason it still says 'Authentication Failure'. Is there some other password (one I'm not aware of) I'm supposed to be using other than my user password? I've had this ubuntu before, on another hard drive and I didn't have this problem. (And it was the same ubuntu, ubuntu 12.04 LTS) ai@AiNekoYokai:~$ groups ai adm cdrom sudo dip plugdev lpadmin sambashare ai@AiNekoYokai:~$ lsb_release -rd Description: Ubuntu 12.04 LTS Release: 12.04 ai@AiNekoYokai:~$ pkexec cat /etc/sudoers # # This file MUST be edited with the 'visudo' command as root. # # Please consider adding local content in /etc/sudoers.d/ instead of # directly modifying this file. # # See the man page for details on how to write a sudoers file. # Defaults env_reset Defaults secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin" # Host alias specification # User alias specification # Cmnd alias specification # User privilege specification root ALL=(ALL:ALL) ALL # Members of the admin group may gain root privileges %admin ALL=(ALL) ALL # Allow members of group sudo to execute any command %sudo ALL=(ALL:ALL) ALL # See sudoers(5) for more information on "#include" directives: #includedir /etc/sudoers.d I can log in with my password, but it's not accepted as valid for authentication <-- That is pretty much my issue. (Although, I haven't gone into recovery mode.) I've ran: ai@AiNekoYokai:~$ ls /etc/sudoers.d README And also reinstalled sudo with: pkexec apt-get update pkexec apt-get --purge --reinstall install sudo pkexec usermod -a -G admin $USER <- Says admin does not exist su $USER <- worked for me, however, my password still does not do much (in sense of not working for other things) I changed my password with pkexec passwd $USER. I was able to change it no problem. gksudo xclock was something I was able to get into, no problem. (Clock showed) ai@AiNekoYokai:~$ gksudo xclock

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• Limiting my heavy thinking to my job [closed]

  - by Robin Castlin

  This might be a weird problem which is only to a half relevant to actual programming, but hopefully there are people here that knows what I'm talking about. Basicly I'm proud of how I can deal with coding problems and fix them in short notice and many other aspects like building new systems and such. I'm fast on finding solutions and I often think about the impact my changes does to existing systems and so on, therefor preventing problem from arising at all and such. I am simply happy with how my mind operates when it comes to programming and I wouldn't want to change it at all. The problem, however is when I'm not programming. I find myself rather limited in social situations. I can't determine if it is through programming, but I sometimes think way to much about the consequences when it comes to being social. I know from own experience that most times you earn by not thinking about consequences, but it's hard for me not to. Often my friends tells me "I think too much" and even though I agree, I can't seem to change this behavior. My brain wants to think, and it likes to overthink simple stuff. Does anyone recognize the bad habit of not leaving advanced thinking at work, and in what way do you deal with it? If this isn't a suitable place to ask this question, I apologize and hope you may point me to the right site.

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• Can't login to Unity 3d after enabling Xinerama for a short moment

  - by Amir Adar

  Today I connected a second monitor to my computer. I set it up using nVidia's control panel, and all was working quite well, so I figured it won't be a problem to try Xinerama, just to see the difference between that and twinview. After enabling Xinerama and restarting the X session, I saw that I was logged into a Unity 2d session. I thought it was a problem with Xinerama, so I switched back to twinview, but it still logged me into Unity 2d. I tried disconnecting the second monitor, no luck: still Unity 2d. I tried changing GPU drivers and installing drivers from a separate ppa, and still I was logged into Unity 2d. Up until this point, I didn't have any problem logging into Unity 3d. It only happened after I tried using Xinerama. I should note that I was doing all this while updates were going on in the background, so it could be something related to that, though I can't imagine what (I tried booting with another kernel, but no luck). So what exactly happened? Did changing the mode to Xinerama triggered some other changes that I'm not aware of? Did these updates cause a certain malfunction in the driver? Is it something else?

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• Wifi won't connect to certain networks

  - by Dave M G

  As I write this, I'm in a coffee shop on my laptop, and I am trying to connect to the free wifi network they offer. Every time I select their network from the wifi applet drop down menu, it connects for a second and then disconnects. At the same time, I have my Android phone with me, and it connects to the coffee shop's network without problem. There are a couple of people around me also using the same network with no issues. I asked the staff to check and as far as they can tell there is no problem with their router or anything. I have tried rebooting, but it has not made a difference. I have double and triple checked that I am using the correct WEP password. As an added wrinkle, when I connect to another network, it seems to connect (although I can't use them because they are paid gateway services). So I'm able to ask this question now because I have tethered my laptop to my phone, but it's slow and a workaround, not a solution. All indications are that it's a problem with my computer against this one network. Why would that be and how can I fix it?

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• Never Bet Against the Impossible

  - by BuckWoody

  My uncle used to say “If a man tells you that his car squirts milk in his eye when you lift the hood, don’t bet against that. You’ll end up with milk in your eye.” My friend Allen White tells me this is taken from a play (and was said about playing cards), but I think the sentiment holds, even in database work. I mentioned the other day that you should allow the other person to talk and actively listen before you propose a solution. Well, I saw a consultant “bet against the impossible”  the other day – and it bit her. She explained to the person telling her the problem that the situation simply couldn’t exist that way, and he proceeded to show her that it did. She got silent, typed a few things, muttered a little, and then said “well, must be something else.” She just couldn’t admit she was wrong. So don’t go there. If someone explains a problem to you with their database, listen with purpose, and then explore the troubleshooting steps you know to find the problem. But keep your absolutes to yourself. In fact, I have a friend that has recently sent me one of those. He connects to a system with SQL Server Management Studio (SSMS) version 2008 (if I recall correctly) and it shows a certain version number of the target system in the connection tab. Then he connects to it using SSMS 2008 R2 and gets a different number. Now, as far as I know, we didn’t change the connection string information, and that’s provided by the target system, so this is impossible. But I won’t tell him that. Not until I look a little more. :) Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• How do I stop video tearing? (Nvidia prop driver, non-compositing window manager)

  - by Chan-Ho Suh

  I have that problem which seemingly afflicts many using the proprietary Nvidia driver: Video tearing: fine horizontal lines (usually near the top of my display) when there is a lot of panning or action in the video. (Note: switching back to the default nouveau driver is not an option, as its seemingly nonexistent power-management drains my battery several times faster) I've tried Totem, Parole, and VLC, and tearing occurs with all of them. The best result has been to use X11 output in VLC, but there is still tearing with relatively moderate action. Hardware: MacBook Air 3,2 -- which has an Nvidia GeForce 320M. There are two common fixes for tearing with Nvidia prop drivers: Turn off compositing, since Nvidia proprietary drivers don't usually play nice with compositing window managers on Linux (Compiz is an exception I'm aware of). But I use an extremely lightweight window manager (Awesome window manager) which is not even capable of compositing (or any cool effects). I also have this problem in Xfce, where I have compositing disabled. Enabling sync to VBlank. To enable this, I set the option in nvidia-settings and then autostart it as nvidia-settings -l with my other autostart programs. This seems to work, because when I run glxgears, I get: $ glxgears Running synchronized to the vertical refresh. The framerate should be approximately the same as the monitor refresh rate. 303 frames in 5.0 seconds = 60.500 FPS 300 frames in 5.0 seconds = 59.992 FPS And when I check the refresh rate using nvidia-settings: $ nvidia-settings -q RefreshRate Attribute 'RefreshRate' (wampum:0.0; display device: DFP-2): 60.00 Hz. All this suggests sync to VBlank is enabled. As I understand it, this is precisely designed to stop tearing, and a lot of people's problem is even getting something like glxgears to output the correct info. I don't understand why it's not working for me. xorg.conf: http://paste.ubuntu.com/992056/ Example of observed tearing::

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• How do I interpolate air drag with a variable time step?

  - by Valentin Krummenacher

  So I have a little game which works with small steps, however those steps vary in time, so for example I sometimes have 10 Steps/second and then I have 20 Steps/second. This changes automatically depending on how many steps the user's computer can take. To avoid inaccurate positioning of the game's player object I use y=v0*dt+g*dt^2/2 to determine my objects y-position, where dt is the time since the last step, v0 is the velocity of my object in the beginning of my step and g is the gravity. To calculate the velocity in the end of a step I use v=v0+g*dt what also gives me correct results, independent of whether I use 2 steps with a dt of for example 20ms or one step with a dt of 40ms. Now I would like to introduce air drag. For simplicity's sake I use a=k*v^2 where a is the air drag's acceleration (I am aware that it would usually result in a force, but since I assume 1kg for my object's mass the force is the same as the resulting acceleration), k is a constant (in this case I'm using 0.001) and v is the speed. Now in an infinitely small time interval a is k multiplied by the velocity in this small time interval powered by 2. The problem is that v in the next time interval would depend on the drag of the last which again depends on the v of the last interval and so on... In other words: If I use a=k*v^2 I get different results for my position/velocity when I use 2 steps of 20ms than when I use one step of 40ms. I used to have this problem for my position too, but adding +g*dt^2/2 to the formula for my position fixed the problem since it takes into account that the position depends on the velocity which changes slightly in every infinitely small time interval. Does something like that exist for air drag too? And no, I dont mean anything like Adding air drag to a golf ball trajectory equation or similar, for that kind of method only gives correct results when all my steps are the same. (I hope you can understand my intermediate english, it's not my main language so I would like to say sorry for all the silly mistakes I might have made in my question)

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• Derived template override return type of member function C++

  - by Ruud v A

  I am writing matrix classes. Take a look at this definition: template <typename T, unsigned int dimension_x, unsigned int dimension_y> class generic_matrix { ... generic_matrix<T, dimension_x - 1, dimension_y - 1> minor(unsigned int x, unsigned int y) const { ... } ... } template <typename T, unsigned int dimension> class generic_square_matrix : public generic_matrix<T, dimension, dimension> { ... generic_square_matrix(const generic_matrix<T, dimension, dimension>& other) { ... } ... void foo(); } The generic_square_matrix class provides additional functions like matrix multiplication. Doing this is no problem: generic_square_matrix<T, 4> m = generic_matrix<T, 4, 4>(); It is possible to assign any square matrix to M, even though the type is not generic_square_matrix, due to the constructor. This is possible because the data does not change across children, only the supported functions. This is also possible: generic_square_matrix<T, 4> m = generic_square_matrix<T, 5>().minor(1,1); Same conversion applies here. But now comes the problem: generic_square_matrix<T, 4>().minor(1,1).foo(); //problem, foo is not in generic_matrix<T, 3, 3> To solve this I would like generic_square_matrix::minor to return a generic_square_matrix instead of a generic_matrix. The only possible way to do this, I think is to use template specialisation. But since a specialisation is basically treated like a separate class, I have to redefine all functions. I cannot call the function of the non-specialised class as you would do with a derived class, so I have to copy the entire function. This is not a very nice generic-programming solution, and a lot of work. C++ almost has a solution for my problem: a virtual function of a derived class, can return a pointer or reference to a different class than the base class returns, if this class is derived from the class that the base class returns. generic_square_matrix is derived from generic_matrix, but the function does not return a pointer nor reference, so this doesn't apply here. Is there a solution to this problem (possibly involving an entirely other structure; my only requirements are that the dimensions are a template parameter and that square matrices can have additional functionality). Thanks in advance, Ruud

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• Should I encrypt data in database?

  - by Tio

  I have a client, for which I'm going to do an Web application about patient care, managing patients, consults, history, calendars, everything about that basically. The problem is that this is sensitive data, patient history and such. The client insists on encrypting the data at the database level, but I think this is going to deteriorate the performance of the web app. ( But maybe I shouldn't be worried about this ) I've read the laws about data protection on health issues ( Portugal ), but isn't very specific about this ( I just questioned them about this, I'm waiting for their response ). I've read the following link, but my question is different, should I encrypt the data in the database, or not. One problem that I foresee in encrypting data, is that I'm going to need a key, this could be the user password, but we all know how user passwords are ( 12345 etc etc ), and generating a key I would have to store it somewhere, this means that the programmer, dba, whatever could have access to it, any thoughts on this? Even adding an random salt to the user password isn't going to solve the problem since I can always access it, and therefore decrypt the data.

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• A Disk Read Error Occured. Press CTRL+ALT+DEL to restart

  - by darroosh

  I'm new to linux world. Just downloaded ubuntu and installed it alongside with windows 7 . In grub when I choose ubuntu, it opens with no problem, but when I try to open windows 7, this message appears: A Disk Read Error Occured. Press CTRL+ALT+DEL to restart. I googled for that problem which directed me to download a boot repair tool, when I choose : advanced options / retore MBR --> apply, then restart computer , It boot to win 7 without loading the grub menu. then I opened the live ubuntu from a USB, launched the "boot repair" again, choose : recommended repair , then restart, It returns to the first problem , grub menu appear, from which I can choose only ubuntu , but win 7 show this msg again : A Disk Read Error Occured. Press CTRL+ALT+DEL to restart. I repeated more and more with the same results ... What should I do? I created a boot info summary using the "boot repair tool" if this can help , it's in this URL.

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• OpenXML error “file is corrupt and cannot be opened.”

  - by nmgomes

  From time to time I ear some people saying their new web application supports data export to Excel format. So far so good … but they don’t tell the all story … in fact almost all the times what is happening is they are exporting data to a Comma-Separated file or simply exporting GridView rendered HTML to an xls file. Ok … it works but it’s not something I would be proud of. So … yesterday I decided to take a look at the Office Open XML File Formats Specification (Microsoft Office 2007+ format) based on well-known technologies: ZIP and XML. I start by installing Open XML SDK 2.0 for Microsoft Office and playing with some samples. Then I decided to try it on a more complex web application and the “file is corrupt and cannot be opened.” message start happening. Google show us that many people suffer from the same and it seems there are many reasons that can trigger this message. Some are related to the process itself, others with encodings or even styling. Well, none solved my problem and I had to dig … well not that much, I simply change the output file extension to zip and extract the zip content. Then I did the same to the output file from my first sample, compare both zip contents with SourceGear DiffMerge and found that my problem was Culture related. Yes, my complex application sets the Thread.CurrentThread.CurrentCulture  to a non-English culture. For sample purposes I was simply using the ToString method to convert numbers and dates to a string representation but forgot that XML is culture invariant and thus using a decimal separator other than “.” will result in a deserialization problem. I solve the “file is corrupt and cannot be opened.” by using Convert.ToString(object, CultureInfo.InvariantCulture) method instead of the ToString method. Hope this can help someone.

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• Google Chrome with strange behavior

  - by user72274

  I'm former Chromium-browser user, but after not upgrading the PPA for 2 months, I switched to Google Chrome browser yesterday. Everything is okay, except some strange behavior on some pages and crashing after loading "chrome://" configuration pages. The best known website with strange behavior is youtube, there is a picture what I see: When I open user menu in top right corner, it crashes that way and even after closing the menu, some parts of menu stay display. You may say it's Youtube problem, no, I have this problem at least on three other websites, here it is on Imgur: The problem isn't for the whole side, sometimes it happens from the middle of the screen. The interesting part is that it happens everytime in the same distance from the right border. When I check the DOM elements with the Developer tool, the overlay which shows element's position is rendered how it should be. What is more, if there is anchor after the crashed area, it works after clicking on it. Selecting text in crashed page is impossible. I hope there is enough information to give me an advice, thanks in advance. :) EDIT: Here is what the browser posted in "chrome://gpu-internals/": Graphics Feature Status Canvas: Software only, hardware acceleration unavailable Compositing: Hardware accelerated 3D CSS: Hardware accelerated CSS Animation: Software animated. WebGL: Hardware accelerated WebGL multisampling: Hardware accelerated Problems Detected Accelerated CSS animation has been disabled at the command line. Accelerated 2d canvas is unstable in Linux at the moment. Ubuntu 12.04 | Gnome-shell 3.4.1 | ATI Radeon 4550 | Screen resolution 1024*768 | Chrome version 20.0.1132.57 (Official Build 145807)

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• Programmatically triggering events in Javascript for IE using jQuery

  - by Dan Herbert

  When an Event is triggered by a user in IE, it is set to the window.event object. The only way to see what triggered the event is by accessing the window.event object (as far as I know) This causes a problem in ASP.NET validators if an event is triggered programmatically, like when triggering an event through jQuery. In this case, the window.event object stores the last user-triggered event. When the onchange event is fired programmatically for a text box that has an ASP.NET validator attached to it, the validation breaks because it is looking at the element that fired last event, which is not the element the validator is for. Does anyone know a way around this? It seems like a problem that is solvable, but from looking online, most people just find ways to ignore the problem instead of solving it. To explain what I'm doing specifically: I'm using a jQuery time picker plugin on a text box that also has 2 ASP.NET validators associated with it. When the time is changed, I'm using an update panel to post back to the server to do some things dynamically, so I need the onchange event to fire in order to trigger the postback for that text box. The jQuery time picker operates by creating a hidden unordered list that is made visible when the text box is clicked. When one of the list items is clicked, the "change" event is fired programmatically for the text box through jQuery's change() method. Because the trigger for the event was a list item, IE sees the list item as the source of the event, not the text box, like it should. I'm not too concerned with this ASP.NET validator working as soon as the text box is changed, I just need the "change" event to be processed so my postback event is called for the text box. The problem is that the validator throws an exception in IE which stops any event from being triggered. Firefox (and I assume other browsers) don't have this issue. Only IE due to the different event model. Has anyone encountered this and seen how to fix it? I've found this problem reported several other places, but they offer no solutions: jQuery's forum, with the jQuery UI Datepicker and an ASP.NET Validator ASP.NET forums, bug with ValidatorOnChange() function

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• When decomposing a large function, how can I avoid the complexity from the extra subfunctions?

  - by missingno

  Say I have a large function like the following: function do_lots_of_stuff(){ { //subpart 1 ... } ... { //subpart N ... } } a common pattern is to decompose it into subfunctions function do_lots_of_stuff(){ subpart_1(...) subpart_2(...) ... subpart_N(...) } I usually find that decomposition has two main advantages: The decomposed function becomes much smaller. This can help people read it without getting lost in the details. Parameters have to be explicitly passed to the underlying subfunctions, instead of being implicitly available by just being in scope. This can help readability and modularity in some situations. However, I also find that decomposition has some disadvantages: There are no guarantees that the subfunctions "belong" to do_lots_of_stuff so there is nothing stopping someone from accidentally calling them from a wrong place. A module's complexity grows quadratically with the number of functions we add to it. (There are more possible ways for things to call each other) Therefore: Are there useful convention or coding styles that help me balance the pros and cons of function decomposition or should I just use an editor with code folding and call it a day? EDIT: This problem also applies to functional code (although in a less pressing manner). For example, in a functional setting we would have the subparts be returning values that are combined in the end and the decomposition problem of having lots of subfunctions being able to use each other is still present. We can't always assume that the problem domain will be able to be modeled on just some small simple types with just a few highly orthogonal functions. There will always be complicated algorithms or long lists of business rules that we still want to correctly be able to deal with. function do_lots_of_stuff(){ p1 = subpart_1() p2 = subpart_2() pN = subpart_N() return assembleStuff(p1, p2, ..., pN) }

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• Fresh Ubuntu 12.10 install no desktop or wing bar

  - by Travis

  After a fresh installm of ubuntu 12.10 (complete erase) after logging in it appears i have no taskbar or much of anything, although i can still execute my terminal with CTRL+ALT+T. i looked around a little, seems i'm not the only person who has had this problem. I found here: http://ubuntuforums.org/showthread.php?p=12303179#post12303179 From there, i found myself here: https://bugs.launchpad.net/ubuntu/+source/nvidia-graphics-drivers-updates/+bug/1068341 I followed precisely the instructions provided which were: this problem is solved this way Switch to a terminal (Ctrl-Alt-F1). Login as your username. Install linux source (sudo apt-get install linux-source) and headers (sudo apt-get install linux-headers-3.5.0-17-generic). Uninstall nvidia driver - this depends on which version you installed (sudo apt-get remove nvidia-current or sudo apt-get remove nvidia-current-updates or sudo apt-get remove nvidia-experimental-304). Reinstall nvidia driver (sudo apt-get install nvidia-current-updates). If it successfully installs, restart the computer (sudo shutdown -r now). Source Desktop does not show when I installed nvidia drivers! I have rebooted, and i am still having the exact same problem. so i back at square one. can someone help me please? this is my room mates computer and i told him i was "fixing" it and now i feel like i've ruined it. Any help is greatly appreciated. Thank you for your time.

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• Is typeid of type name always evaluated at compile time in c++ ?

  - by cyril42e

  I wanted to check that typeid is evaluated at compile time when used with a type name (ie typeid(int), typeid(std::string)...). To do so, I repeated in a loop the comparison of two typeid calls, and compiled it with optimizations enabled, in order to see if the compiler simplified the loop (by looking at the execution time which is 1us when it simplifies instead of 160ms when it does not). And I get strange results, because sometimes the compiler simplifies the code, and sometimes it does not. I use g++ (I tried different 4.x versions), and here is the program: #include <iostream> #include <typeinfo> #include <time.h> class DisplayData {}; class RobotDisplay: public DisplayData {}; class SensorDisplay: public DisplayData {}; class RobotQt {}; class SensorQt {}; timespec tp1, tp2; const int n = 1000000000; int main() { int avg = 0; clock_gettime(CLOCK_REALTIME, &tp1); for(int i = 0; i < n; ++i) { // if (typeid(RobotQt) == typeid(RobotDisplay)) // (1) compile time // if (typeid(SensorQt) == typeid(SensorDisplay)) // (2) compile time if (typeid(RobotQt) == typeid(RobotDisplay) || typeid(SensorQt) == typeid(SensorDisplay)) // (3) not compile time ???!!! avg++; else avg--; } clock_gettime(CLOCK_REALTIME, &tp2); std::cout << "time (" << avg << "): " << (tp2.tv_sec-tp1.tv_sec)*1000000000+(tp2.tv_nsec-tp1.tv_nsec) << " ns" << std::endl; } The conditions in which this problem appear are not clear, but: - if there is no inheritance involved, no problem (always compile time) - if I do only one comparison, no problem - the problem only appears only with a disjunction of comparisons if all the terms are false So is there something I didn't get with how typeid works (is it always supposed to be evaluated at compilation time when used with type names?) or may this be a gcc bug in evaluation or optimization? About the context, I tracked down the problem to this very simplified example, but my goal is to use typeid with template types (as partial function template specialization is not possible). Thanks for your help!

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• Choppy USB mice on just one of USB ports

  - by user20532

  I've got Lenovo b560 laptop with latest, properly updated Kubuntu on it (11.04 natty, kernel 2.6.38-8-generic). It has three USB2.0 ports onboard. I usually plug a mouse into one of them (I've got 3 different mice - in office, at home and for when on the go). Sometimes, usually after laptop awakening from sleep, the mouse still works but cursor movements are choppy, as if the processor was extremely loaded (it's usually not). I found that if I re-plug the mouse cord into the other USB port, it works just fine. If I plug it back to problematic port, it is still choppy and remains choppy until next boot. Of course I want my mice to always work fine. Problem is: I cannot reproduce this behavior for sure, it happens sporadically but regularly. I use different USB ports (problem has ever happened on each of them since), I use different mice (each has failed me this way at least once), I cannot generally find what exactly is going wrong and why plugging to different port fixes the mouse instantly. So I'd like to hear at least clues where to look at, what to try to identify my problem. A bit of update: while beginning this post, I had the issue once again. I have just replugged the mouse back to problematic port and it is not recognized at all. On the other port it works smoothly.

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• Can't connect nonlocally after 12.10 upgrade

  - by user101815

  I've just upgraded one of my systems from 12.04 to 12.10. Now I can't connect on that system beyond my local network. Connections within the local network seem to work fine, and I can make nonlocal connections from other machines (like the one I'm asking this question from). I suspect that some routing information has been messed up, but I don't know where to look for it. It's not a nameserver problem -- pinging outside sites by their IP addresses doesn't work either. I have another laptop next to this one, also running Kubuntu 12.10. On the one that can't connect, arp produces no output. On the other one, it produces 192.168.0.1 ether 00:23:69:fa:ce:ae C wlan0 On the working machine, the output of netstat starts with some tcp entries. On the nonworking one, those entries are absent. I asked this question on the Ubuntu forum but haven't gotten any answers there. One further complication: since the troublesome machine has no outside connection, it's extremely difficult to download anything to it. For what it's worth, "ping 8.8.8.8" produces "connect: Network is unreachable". Update: after a lot of fiddling, I have my external world back. I don't know what the key action was, but the first indication of progress was that "ping 8.8.8.8" worked. At that point I still didn't have a working nameserver, so external URLs didn't work. But I did this (based on an online post, of course): sudo dpkg-reconfigure resolvconf and answered Yes to all prompts. That did the trick!! Apparently my problem was unique, or close to it, since I couldn't find any online references to it: local net working, remote net not working, including explicit IP addresses. So I suppose that if no one else has this problem, no one cares about the solution!!

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• Collision Detection Problems

  - by MrPlosion

  So I'm making a 2D tile based game but I can't quite get the collisions working properly. I've taken the code from the Platformer Sample and implemented it into my game as seen below. One problem I'm having is when I'm on the ground for some strange reason I can't move to the left. Now I'm pretty sure this problem is from the HandleCollisions() method because when I stop running it I can smoothly move around with no problems. Another problem I'm having is when I'm close to a tile the character jitters very strangely. I will try to post a video if necessary. Here is the HandleCollisions() method: Thanks. void HandleCollisions() { Rectangle bounds = BoundingRectangle; int topTile = (int)Math.Floor((float)bounds.Top / World.PixelTileSize); int bottomTile = (int)Math.Ceiling((float)bounds.Bottom / World.PixelTileSize) - 1; int leftTile = (int)Math.Floor((float)bounds.Left / World.PixelTileSize); int rightTile = (int)Math.Ceiling((float)bounds.Right / World.PixelTileSize) - 1; isOnGround = false; for(int x = leftTile; x <= rightTile; x++) { for(int y = topTile; y <= bottomTile; y++) { if(world.Map[y, x].Collidable == true) { Rectangle tileBounds = new Rectangle(x * World.PixelTileSize, y * World.PixelTileSize, World.PixelTileSize, World.PixelTileSize); Vector2 depth = RectangleExtensions.GetIntersectionDepth(bounds, tileBounds); if(depth != Vector2.Zero) { if(Math.Abs(depth.Y) < Math.Abs(depth.X)) { isOnGround = true; position = new Vector2(position.X, position.Y + depth.Y); } else { position = new Vector2(position.X + depth.X, position.Y); } bounds = BoundingRectangle; } } } }

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• 2 Computers, same network, different outgoing speeds when uploading to internet?

  - by user117339

  I have 2 work machines in my office, a PowerMac G5 and a MacBook Air. Both behind an IPCop firewall. The PowerMac is connected through a gigabit switch, the MacBook Air is connected through a Netgear 802.11g access point that is then plugged into the gigabit switch. There is also a FreeNAS box, both machines are able to read and write files to it at close to their pipe speeds. The main problem is when I am trying to upload files to the internet at large. The G5 is only hitting 0.1 - 0.25 Mbps. The Macbook is able to hit 2-3 Mbps. The setup (G5 / IPCop / Network) has been the same for 5 years. The issues with the internet speed started about 3 months ago. I hadn't tested on the Macbook at this point. I had complained to the ISP, they said their modem needed a firmware update, did that nothing changed. Reset IPCop, turned off squid, etc. No changes. The ISP switched the office over to a better plan with a theoretical 6 Mbps up, still no change. At this point I tried testing the Macbook, and lo and behold there's the speed. But why? I have tried changing out everything, cables, switches, using another ethernet port on the G5, wiping the system, using DHCP, using manual IPs, changing DNS servers, etc. Nothing works. I figured that if there was something horribly wrong with the network, then internally I would find a similar issue, but that is perfect. iperf, ping, etc show no dropped packets and near saturation of the internal network. I'm at a loss as to what the heck is going on. Any ideas would be appreciated! Below are some screenshots of speedtest.net: G5: Macbook Air:

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• PHP Based session variable not retaining value. Works on localhost, but not on server.

  - by Foo

  I've been trying to debug this problem for many hours, but to no avail. I've been using PHP for many years, and got back into it after long hiatus, so I'm still a bit rusty. Anyways, my $_SESSION vars are not retaining their value for some reason that I can't figure out. The site worked on localhost perfectly, but uploading it to the server seemed to break it. First thing I checked was the PHP.ini server settings. Everything seems fine. In fact, my login system is session based and it works perfectly. So now that I know $_SESSIONS are working properly and retaining their value for my login, I'm presuming the server is setup and the problem is in my script. Here's a stripped version of the code that's causing a problem. $type, $order and $style are not being retained after they are set via a GET variable. The user clicks a link, which sets a variable via GET, and this variable is retained for the remainder of their session. Is there some problem with my logic that I'm not seeing? <?php require_once('includes/top.php'); //first line includes a call to session_start(); require_once('includes/db.php'); $type = filter_input(INPUT_GET, 't', FILTER_VALIDATE_INT); $order = filter_input(INPUT_GET, 'o', FILTER_VALIDATE_INT); $style = filter_input(INPUT_GET, 's', FILTER_VALIDATE_INT); /* According to documentation, filter_input returns a NULL when variables are undefined. So, if t, o, or s are not set via URL, $type, $order and $style will be NULL. */ print_r($_SESSION); /* All other sessions, such as the login session, etc. are displayed here. After the sessions are set below, they are displayed up here to... simply with no value. This leads me to believe the problem is with the code below, perhaps? */ // If $type is not null (meaning it WAS set via the get method above) // or it's false because the validation failed for some reason, // then set the session to the $type. I removed the false check for simplicity. // This code is being successfully executed, and the data is being stored... if(!is_null($type)) { $_SESSION['type'] = $type; } if(!is_null($order)) { $_SESSION['order'] = $order; } if(!is_null($style)) { $_SESSION['style'] = $style; } $smarty->display($template); ?> If anyone can point me in the right direction, I'd greatly appreciate it. Thanks.

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• How do I find actors in an area on a poly-precise basis?

  - by Almo

  Ok, I've been asking various questions and getting some good answers, but I think I need to rethink my method, so I'll describe the problem. I have a player who has a big blue box in front of him. This box shows which KActors will be pushed when he pulls the trigger: Currently, the blue box spawns a descendant of Actor which checks collision to see which KActors are touching it: foreach Owner.TouchingActors(class'DynamicSMActor', DynamicActorItt) { // do stuff } The problem is, if you check for touching between Actors and KActors, it looks like it does a plain axis-aligned bounding-box collision. The power will push the box on the lower right, when it's clear it's not touching the blue box. How should I do this properly? I just need a way to find out which KActors are touching that area, on a poly-by-poly level. These collisions are only done with rectangular boxes and simple sphere collision; we are aware of the potential for performance issues with complex objects and poly-collision. I've tried making the collision checker a KActor, but it doesn't report any TouchingActors. This issue is causing us trouble in a lot of other places as well. So solving this problem is a core issue in our game.

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