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  • How to check if a Webcam is broken?

    - by user84812
    I just bought an Acer Aspire 3830TG, it comes with an integrated 1.3M HD Webcam. Before buying it i tried with a bootable Lubuntu usb stick, everything worked well except for the webcam, which i thought I had to tweak. The thing is that it seems the camera should work with no problems in ubuntu. The driver is detected, I try dmesg | grep uvcvideo and the output is [ 12.226174] uvcvideo: Found UVC 1.00 device 1.3M HD WebCam (058f:b002) [ 12.245553] usbcore: registered new interface driver uvcvideo I've also tried using different software (guvcview is black when camera output is MJPG and turns to funny colors when YU12 or YV12, cheese is always black, camorama is always with funny colors...). I should have checked that it was working properly with the default os (windows) but now it's too late for that. I even booted with a official Ubuntu Quantal distro from the usb pen, and the results are the same. so, my question is: is there any way to check that the camera is righmt or broken? So, if it's broken, at least i can go to the shop, show them that it's really broken and get an external webcam for free, or st like that. cheers. UPDATE 1 Thanks, jrp. I run sudo lsinput, and the output info about my video is the following: /dev/input/event6 bustype : BUS_USB vendor : 0x58f product : 0xb002 version : 2 name : "1.3M HD WebCam" phys : "usb-0000:00:1a.0-1.3/button" bits ev : EV_SYN EV_KEY /dev/input/event7 bustype : BUS_HOST vendor : 0x0 product : 0x6 version : 0 name : "Video Bus" phys : "LNXVIDEO/video/input0" bits ev : EV_SYN EV_KEY With this info, i'm not pretty sure about running the luvcview command. If I run luvcview -d /dev/video0 -L, the output is the following: SDL information: Video driver: x11 A window manager is available Device information: Device path: /dev/video0 { pixelformat = 'YUYV', description = 'YUV 4:2:2 (YUYV)' } { discrete: width = 640, height = 480 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 160, height = 120 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 176, height = 144 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 320, height = 240 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 352, height = 288 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 1280, height = 720 } Time interval between frame: 1/7, 1/5, { discrete: width = 1280, height = 800 } Time interval between frame: 1/7, 1/5, { discrete: width = 1280, height = 960 } Time interval between frame: 1/7, 1/5, { discrete: width = 1280, height = 1024 } Time interval between frame: 1/7, 1/5, { pixelformat = 'MJPG', description = 'MJPEG' } { discrete: width = 640, height = 480 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 160, height = 120 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 176, height = 144 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 320, height = 240 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 352, height = 288 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 1280, height = 720 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 1280, height = 800 } Time interval between frame: 1/15, 1/10, 1/5, { discrete: width = 1280, height = 960 } Time interval between frame: 1/15, 1/10, 1/5, { discrete: width = 1280, height = 1024 } Time interval between frame: 1/15, 1/10, 1/5, { pixelformat = 'RGB3', description = 'RGB3' } { discrete: width = 640, height = 480 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 160, height = 120 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 176, height = 144 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 320, height = 240 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 352, height = 288 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 1280, height = 720 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 1280, height = 800 } Time interval between frame: 1/15, 1/10, 1/5, { discrete: width = 1280, height = 960 } Time interval between frame: 1/15, 1/10, 1/5, { discrete: width = 1280, height = 1024 } Time interval between frame: 1/15, 1/10, 1/5, { pixelformat = 'BGR3', description = 'BGR3' } { discrete: width = 640, height = 480 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 160, height = 120 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 176, height = 144 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 320, height = 240 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 352, height = 288 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 1280, height = 720 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 1280, height = 800 } Time interval between frame: 1/15, 1/10, 1/5, { discrete: width = 1280, height = 960 } Time interval between frame: 1/15, 1/10, 1/5, { discrete: width = 1280, height = 1024 } Time interval between frame: 1/15, 1/10, 1/5, { pixelformat = 'YU12', description = 'YU12' } { discrete: width = 640, height = 480 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 160, height = 120 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 176, height = 144 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 320, height = 240 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 352, height = 288 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 1280, height = 720 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 1280, height = 800 } Time interval between frame: 1/15, 1/10, 1/5, { discrete: width = 1280, height = 960 } Time interval between frame: 1/15, 1/10, 1/5, { discrete: width = 1280, height = 1024 } Time interval between frame: 1/15, 1/10, 1/5, { pixelformat = 'YV12', description = 'YV12' } { discrete: width = 640, height = 480 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 160, height = 120 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 176, height = 144 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 320, height = 240 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 352, height = 288 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 1280, height = 720 } Time interval between frame: 1/30, 1/25, 1/20, 1/15, 1/10, 1/5, { discrete: width = 1280, height = 800 } Time interval between frame: 1/15, 1/10, 1/5, { discrete: width = 1280, height = 960 } Time interval between frame: 1/15, 1/10, 1/5, { discrete: width = 1280, height = 1024 } Time interval between frame: 1/15, 1/10, 1/5, if i run luvcview by itself, the image is funny (blue and red colors, mainly, with myself in negative state). tx

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  • using isight camera in macbookpro(8,2) on ubuntu 12.04 virtualbox VM

    - by Kurt Spindler
    I'm having a lot of trouble using the built-in isight camera on my macbookpro8,2 (early 2011) from an ubuntu 12.04 virtual machine, run inside VirtualBox. The following is the log I get when I try to run guvcview ubuntu@ubuntu:~$ guvcview guvcview 1.5.3 ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.surround71 ALSA lib setup.c:565:(add_elem) Cannot obtain info for CTL elem (MIXER,'IEC958 Playback Default',0,0,0): No such file or directory ALSA lib setup.c:565:(add_elem) Cannot obtain info for CTL elem (MIXER,'IEC958 Playback Default',0,0,0): No such file or directory ALSA lib setup.c:565:(add_elem) Cannot obtain info for CTL elem (MIXER,'IEC958 Playback Default',0,0,0): No such file or directory ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.hdmi ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.hdmi ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.modem ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.modem ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.phoneline ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.phoneline ALSA lib audio/pcm_bluetooth.c:1614:(audioservice_expect) BT_GET_CAPABILITIES failed : Input/output error(5) ALSA lib audio/pcm_bluetooth.c:1614:(audioservice_expect) BT_GET_CAPABILITIES failed : Input/output error(5) ALSA lib audio/pcm_bluetooth.c:1614:(audioservice_expect) BT_GET_CAPABILITIES failed : Input/output error(5) ALSA lib audio/pcm_bluetooth.c:1614:(audioservice_expect) BT_GET_CAPABILITIES failed : Input/output error(5) ALSA lib pcm_dmix.c:957:(snd_pcm_dmix_open) The dmix plugin supports only playback stream Cannot connect to server socket err = No such file or directory Cannot connect to server socket jack server is not running or cannot be started video device: /dev/video0 Init. FaceTime HD Camera (Built-in) (location: usb-0000:00:0b.0-1) { pixelformat = 'YUYV', description = 'YUV 4:2:2 (YUYV)' } { discrete: width = 160, height = 120 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 176, height = 144 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 320, height = 240 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 352, height = 288 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 640, height = 480 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 1280, height = 720 } Time interval between frame: 1/10, { pixelformat = 'MJPG', description = 'MJPEG' } { discrete: width = 960, height = 540 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 1024, height = 576 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 1280, height = 720 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { pixelformat = 'RGB3', description = 'RGB3' } { discrete: width = 160, height = 120 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 176, height = 144 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 320, height = 240 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 352, height = 288 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 640, height = 480 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 1280, height = 720 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 960, height = 540 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 1024, height = 576 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { pixelformat = 'BGR3', description = 'BGR3' } { discrete: width = 160, height = 120 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 176, height = 144 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 320, height = 240 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 352, height = 288 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 640, height = 480 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 1280, height = 720 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 960, height = 540 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 1024, height = 576 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { pixelformat = 'YU12', description = 'YU12' } { discrete: width = 160, height = 120 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 176, height = 144 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 320, height = 240 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 352, height = 288 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 640, height = 480 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 1280, height = 720 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 960, height = 540 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 1024, height = 576 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { pixelformat = 'YV12', description = 'YV12' } { discrete: width = 160, height = 120 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 176, height = 144 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 320, height = 240 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 352, height = 288 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 640, height = 480 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 1280, height = 720 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 960, height = 540 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, { discrete: width = 1024, height = 576 } Time interval between frame: 100/2997, 1/25, 1/24, 1/15, vid:05ac pid:8509 driver:uvcvideo checking format: 1196444237 VIDIOC_G_COMP:: Invalid argument compression control not supported fps is set to 1/25 drawing controls no codec detected for H264 no codec detected for MP3 - (lavc) Checking video mode 960x540@32bpp : OK Could not grab image (select timeout): Resource temporarily unavailable Could not grab image (select timeout): Resource temporarily unavailable Could not grab image (select timeout): Resource temporarily unavailable Could not grab image (select timeout): Resource temporarily unavailable Could not grab image (select timeout): Resource temporarily unavailable Could not grab image (select timeout): Resource temporarily unavailable Could not grab image (select timeout): Resource temporarily unavailable Could not grab image (select timeout): Resource temporarily unavailable Could not grab image (select timeout): Resource temporarily unavailable write /home/ubuntu/.guvcviewrc OK free controls cleaned allocations - 100% Closing portaudio ...OK Closing GTK... OK ubuntu@ubuntu:~$ Any help would be greatly appreciated. Only clue I have is that I initially was having problems, tried using the old method of fixing isights (involving installing isight-firmware-tools) before realizing that I just hadn't turned on the VM setting to allow the VM to access the webcam. :) Anyway, I wonder if installing that messed something up. However, I think this is a red herring because I've: shut down and turned back on the Mac, restarted the VM, tried a different VM (for which I never installed isight-firmware-tools, and created an entirely new ubuntu vm. All instances have had this problem. Similarly, other viewers, such as cheese, avplay, avconv have had all various kinds of errors.

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  • Disable of discrete/native graphics on MacBook Retina when using apps like VMware, VLC, etc

    - by badkitteh
    I got a MacBook Pro Retina a few months ago and I'm really happy with it. However, since I do a lot of work in different environments/OSes, I make heavy use of VMware to have them with me when I'm on the road. The MBPr has a great battery life - as long as integrated graphics are being used. Unfortunately as soon as I launch VMware, the MacBook switches to discrete graphics and battery life is effectively halved. I noticed that after installing gfxCardStatus, and now I'm wondering if there is a way to force the integrated graphics being used all of the time, so I can enjoy maximum battery life. Thanks.

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  • Discrete and Continuous Classifier on Sparse Data

    - by Chris S
    I'm trying to classify an example, which contains discrete and continuous features. Also, the example represents sparse data, so even though the system may have been trained on 100 features, the example may only have 12. What would be the best classifier algorithm to use to accomplish this? I've been looking at Bayes, Maxent, Decision Tree, and KNN, but I'm not sure any fit the bill exactly. The biggest sticking point I've found is that most implementations don't support sparse data sets and both discrete and continuous features. Can anyone recommend an algorithm and implementation (preferably in Python) that fits these criteria? Libraries I've looked at so far include: Orange (Mostly academic. Implementations not terribly efficient or practical.) NLTK (Also academic, although has a good Maxent implementation, but doesn't handle continuous features.) Weka (Still researching this. Seems to support a broad range of algorithms, but has poor documentation, so it's unclear what each implementation supports.)

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  • On a dual-GPU laptop, is using the discrete GPU ever more power efficient?

    - by Mahmoud Al-Qudsi
    Given a laptop with a dual integrated/discrete GPU configuration, is it ever more power efficient to use the discrete GPU instead of the integrated? Obviously when writing an email or working on a spreadsheet, the integrated GPU will always use less power. But let's say you're doing something graphics-medium but not graphics-intensive/heavy - is there a point where it actually makes sense to fire up the discrete GPU, not for performance but for power-saving reasons? Off the top of my head, I can think of a scenario where the external GPU supports hardware decoding of a particular video codec - I'd imagine there is a "price point" where using the GPU saves more energy than decoding that fully in software would. But I think most GPUs, integrated or discrete, pretty much decode just the plain-Jane h264. But maybe there is something more complicated, perhaps if you're doing something like desktop/windowing animations or a flash animation on a website (not an embedded flash video) - maybe the discrete GPU will use enough less power to make up for switching to it? I guess this question can be summed up as to whether or not you can say beyond doubt that if you don't care for performance on a laptop with two GPUs, always use the integrated GPU for maximum battery life.

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  • Hybrid Graphics on Ubuntu 12.04 switching to discrete

    - by cfstras
    I have a Sony Vaio VPCCB-27FX with hybrid graphics. Using vgaswitcheroo enables me to switch my discrete card off to save power. Now when i want to switch to the discrete card for performance, my system freezes. I already tried logging out and killing x with service lightdm stop, but still, it freezes as soon as I echo DIS > switch. typing blindly, echo IGD > switch returns me to my console where it reads [ 179.555171] i915: switched off, but it seems the discrete card never gets switched on... running echo DDIS > switch gives me the following: [540....] [drm:atop_op_jump] *ERROR* atombios stuck in loop for more than 5secs aborting [540....] [drm:atom_execute_table_locked] *ERROR* atombios stuck executing CEE2 (len 62, WS 0, PS 0) @ 0xCEFE [540....] [drm:atom_execute_table_locked] *ERROR* atombios stuck executing BBF6 (len 1036, WS 4, PS 0) @ 0xBCF3 [540....] [drm:atom_execute_table_locked] *ERROR* atombios stuck executing BB8C (len 76, WS 0, PS 0) @ 0xBB94 [541....] [drm:r600_RING_TEST] *ERROR* radeon: ring test failed (scratch(0x8504)=0xFFFFFFFF) [541....] [drm:evergreen_resume] *ERROR* evergreen startup failed on resume after that, the atombios part repeats a few times. also, the terminal locks up again and sysrq+REISUB is my only rescue. Has anybody an idea how I can switch to my discrete card without the system locking up? #uname -srvmpio Linux 3.2.0-24-generic #39-Ubuntu SMP Mon May 21 16:52:17 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux #lsb_release -r Description: Ubuntu 12.04 LTS

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  • Discrete mathematics problem - Probability theory and counting

    - by Mohammad
    Hello All, I'm taking a discrete mathematics course, and I encountered a question and I need your help. I don't know if this is the right place for that though :) It says: Each user on a computer system has a password, which is six to eight characters long, where each character is an uppercase letter or a digit. Each password must contain at least one digit. How many possible passwords are there? The book solves this by adding the probabilities of having six,seven and eight characters long password. However, when he solves for probability of six characters he does this P6 = 36^6 - 26^6 and does P7 = 36^7 - 26^7 and P8 = 36^8 - 26^8 and then add them all I understand the solution, but my question is why doesn't calculating, P6 = 10*36^5 and the same for P7 and P8, work? 10 for the digit and 36 for the alphanumeric? Also, if anyone could give me another solution, other than the one in the book. Thank you very much :)

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  • How to disable discrete GPU using NVIDIA drivers?

    - by penzoiders
    I have a DELL studio XPS 13 (aka 1340) as of 12.04 most things run smoothly out of the box, but I have some power draining and warmness issues (if not to be called terrible heat issues) The system came with a NVIDIA GeForce 9500M (which has Hybrid SLI) and it shows up in "lspci" as these 2 cards 02:00.0 VGA compatible controller: NVIDIA Corporation G98 [GeForce 9200M GS] (rev a1) 03:00.0 VGA compatible controller: NVIDIA Corporation C79 [GeForce 9400M G] (rev b1) I had to install nvidia-current over noveau driver 'cause noveau does freeze the system after suspension. By installing nvidia-current and running nvidia-xconfig the resume process after suspension is fixed. By the way both with nvidia-current and noveau the system drains a lot of battery and heats up a lot. I suppose this is because the discrete GPU is always on. I don't really need 3D graphics on this system, if not the minimal to run unity and compiz for window management. So my question is: How do I disable, using nvidia-current, the discrete GPU 9200M and use only the integrated one 9400M? notes: In BIOS I have no option to disable discrete GPU This I think is not applicable because of the suspension-freeze issue (with noveau): https://help.ubuntu.com/community/HybridGraphics I've found this but I don't know which --sli option I should choose to fit my needs: http://manpages.ubuntu.com/manpages/hardy/man1/nvidia-xconfig.1.html My system has not optimus or cuda, but anyone can tell me if bumblebee can work for me?

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  • Deriving arrays in mathematics

    - by Gio Borje
    So I found some similarities between arrays and set notation while learning about sets and sequences in precalc e.g. set notation: {a | cond } = { a1, a2, a3, a4, ..., an} given that n is the domain (or index) of the array, a subset of Natural numbers (or unsigned integer). Most programming languages would provide similar methods to arrays that are applied to sets e.g. upperbounds & lowerbounds; possibly suprema and infima too. Where did arrays come from?

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  • Pohlig–Hellman algorithm for computing discrete logarithms

    - by drelihan
    Hi Folks, I'm working on coding the Pohlig-Hellman Algorithm but I am having problem understand the steps in the algorithm based on the definition of the algorithm. Going by the Wiki of the algorithm: http://en.wikipedia.org/wiki/Pohlig%E2%80%93Hellman_algorithm I know the first part 1) is to calculate the prime factor of p-1 - which is fine. Howeever, I am not sure what I need to do in steps 2) and 3). Can someone help with explaining this in plain english (i) - or pseudocode. I want to code the solution myself obviously but I cannot make any more progress unless i understand the algorithm. Note: I have done a lot of searching for this and I read S. Pohlig and M. Hellman (1978). "An Improved Algorithm for Computing Logarithms over GF(p) and its Cryptographic Significance but its still not really making sense to me. Thanks in advance

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  • Coordinate geometry operations in images/discrete space

    - by avd
    I have images which have line segments, rays etc. I am representing these line segments using Bresenham algorithm (means whatever coordinates I get using this algorithm between two points). Now I want to do operations such as finding intersection point between two line segments, finding the projection of one vector onto other etc... The problem is I am not working in continuous space. The line segments are being approximated using Bresenham algorithm. So I want suggestions on what are the best and most efficient ways to do this? A link to C++ library or implementation would also be good enough. Please suggest some books which deal with such problems.

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  • What does mathematics have to do with programming?

    - by Rory
    I just started a diploma in software development. Right now we're starting out with basic Java and such (so right from the bottom you might say) - which is fine, I have no programming experience apart from knowing how to do "Hello World" in Java. I keep hearing that mathematics is pertinent to coding, but how is it so? What general examples would show how mathematics and programming go together, or are reliant on one another? I apologize of my question is vague, I'm barely starting to get a rough idea of the kind of world I'm stepping into as a code monkey student...

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  • Disable discrete AMD GPU

    - by Smajl
    My notebook has two graphic cards and it suffers from severe overheating after installing Ubuntu (no problem with Windows 7 on the same machine). I figured out that the problem may be in the graphic card and I would like to disable the discrete one. I followed some tutorials on this topic (for example http://planetoss.com/articles/how-to-disable-the-discrete-amd-graphics-card-in-linux/). But the problem is, that after executing the commands, nothing really happens and both GPU are still running. Here is what I have done: smajl@smajl-mini:~$ sudo chown smajl /sys/kernel/debug/vgaswitcheroo/switchsmajl@smajl-mini:~$ echo IGD > /sys/kernel/debug/vgaswitcheroo/switch smajl@smajl-mini:~$ sudo cat /sys/kernel/debug/vgaswitcheroo/switch 0:IGD:+:DynPwr:0000:01:05.0 1:DIS-Audio: :Pwr:0000:02:00.1 2:DIS: :DynPwr:0000:02:00.0 smajl@smajl-mini:~$ echo OFF > /sys/kernel/debug/vgaswitcheroo/switch smajl@smajl-mini:~$ sudo cat /sys/kernel/debug/vgaswitcheroo/switch 0:IGD:+:DynPwr:0000:01:05.0 1:DIS-Audio: :Pwr:0000:02:00.1 2:DIS: :DynPwr:0000:02:00.0 What am I missing here? Also, more on the overheating topic: 1) Installed TLP 2) updated system 3) set power setting mode to "power save" ...and nothing helps Tried same thing with Linux Mint without success. Is there anything else to try if I manage to disable the second GPU and the problem preserves? Otherwise I would have to get back to win in order not to melt my laptop.. :-/

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  • Discrete Math and Computing Course

    - by ShrimpCrackers
    I was recently admitted into a Computing and Software Systems program (basically software engineering) and one of the first courses I'll be taking is called Mathematical Principles of Computing. The course description: "Integrating mathematical principles with detailed instruction in computer programming. Explores mathematical reasoning and discrete structures through object-oriented programming. Includes algorithm analysis, basic abstract data types, and data structures." I'm not a fan of math, but I've been doing well in all my math classes mostly A's and B's ever since I started two years ago, and I've been doing math every quarter - never took a quarter without math - so I've been doing it all in sequence without gaps. However, I'm worried about this class. I've read briefly on what discrete math is and from what my advisor told me, its connection with computer science is that it has alot to do with proving algorithms. One thing that my instructors briefly touched on and never went into detail was proving algorithms, and when I tried, I just wasn't very good at mathematical induction. It's one of the things that I ignored every time it showed up in a homework problem (usually in Calculus III which I'm finishing up right now). Questions: 1. What can I expect from this class? 2. How can I prepare myself for this class? 3. Other tips? Thank you.

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  • Mathematics for Computer Science

    - by jiewmeng
    I am going into university next year. I think maths would be one of the more important aspects of computer science? I recently saw the MIT Intro to Algorithms video on YouTube and the maths required is quite hardcore. I wonder what parts of maths do i need, probability, calculus, trigo etc. Will the book Concrete Mathematics - it claims to be foundation for computer science - on Amazon cover most of whats required?

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  • JavaOne 2012: Lessons from Mathematics

    - by darcy
    I was pleased to get notification recently that my bof proposal for Lessons from Mathematics was accepted for JavaOne 2012. This is a bit of a departure from the project-centric JavaOne talks I usually give, but whisps of this kind of material have appeared before. I'm looking forward to presenting material from linear algebra, stochastics, and numerical optimization that have influence my thinking about technical problems in the JDK and elsewhere.

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  • Moving camera, or camera with discrete "screens"?

    - by Jacob Millward
    I'm making a game with a friend, but having trouble deciding on a camera style. The basic idea for the game, is having a randomly generated 2-dimensional world, with settlements in it. These settlements would have access to different resources, and it would be the job of the player to create bridges and ladders and links between these villages so they can trade. The player would advance personally by getting better gear, fighting monsters and looking for materials in the world, in order to craft and trade them at the settlements. My friend wants to use an old-style camera, where the world is split into a discrete number of screens that the player moves between. Similar to early Zelda dungeons, or Knytt Stories. This is opposite to me, as I want a standard camera that follows the player around as I feel the split-screen style camera limits the game. Can anyone argue the case either way? We've hit a massive roadblock here and can't seem to get past it.

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  • Switching between Discrete and Integrated GPUs

    - by void-pointer
    Hello everyone, I develop CUDA applications on my Alienware M17x portable back-breaker, which has two discrete GTX 285M GPUs and one integrated GeForce 9400M GPU. I can currently switch between them using NVIDIA's software, but I would like the ability to do so within my applications for purposes of benchmarking and general convenience. Apparently this requires the "NDA version" of NVIDIA's Driver API, which I know not how to obtain. Would using this API be the only way to accomplish what I seek, and if so, how would I obtain it? A solution using Windows APIs would also be acceptable, though less preferable to one which would leverage a cross-platform API. I have created a similar thread concerning the matter on NVIDIA's forum, which is down at the time of this writing. Thanks for reading my question; it is much appreciated!

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  • F# in ASP.NET, mathematics and testing

    - by DigiMortal
    Starting from Visual Studio 2010 F# is full member of .NET Framework languages family. It is functional language with syntax specific to functional languages but I think it is time for us also notice and study functional languages. In this posting I will show you some examples about cool things other people have done using F#. F# and ASP.NET As I am ASP/ASP.NET MVP I am – of course – interested in how people use different languages and technologies with ASP.NET. C# MVP Tomáš Petrícek writes about developing ASP.NET MVC applications using F#. He also shows how to use LINQ To SQL in F# (using F# PowerPack) and provides sample solution and Visual Studio 2010 template for F# MVC web applications. You may also find interesting how you can create controllers in F#. Excellent work, Tomáš! Vladimir Matveev has interesting example about how to use F# and ApplicationHost class to process ASP.NET requests ouside of IIS. This is simple and very straight-forward example and I strongly suggest you to take a look at it. Very cool example is project Strom in Codeplex. Storm is web services testing tool that is fully written on F#. Take a look at this site because Codeplex offers also source code besides binaries. Math Functional languages are strong in fields like mathematics and physics. When I wrote my C# example about BigInteger class I found out that recursive version of Fibonacci algorithm in C# is not performing well. In same time I made same experiment on F# and in F# there were no performance problems with recursive version. You can find F# version of Fibonacci algorithm from Bob Palmer’s blog posting Fibonacci numbers in F#. Although golden spiral is useful for solving many problems I looked for some practical code example and found one. Kean Walmsley published in his Through the Interface blog very interesting posting Creating Fibonacci spirals in AutoCAD using F#. There are also other cool examples you may be interested in. Using numerical components by Extreme Optimization  it is possible to make some numerical integration (quadrature method) using F# (also C# example is available). fsharp.it introduces factorials calculation on F#. Robert Pickering has made very good work on programming The Game of Life in Silverlight and F# – I definitely suggest you to try out this example as it is very illustrative too. Who wants something more complex may take a look at Newton basin fractal example in F# by Jonathan Birge. Testing After some searching and surfing I found out that there is almost everything available for F# to write tests and test your F# code. FsCheck - FsCheck is a port of Haskell's QuickCheck. Important parts of the manual for using FsCheck is almost literally "adapted" from the QuickCheck manual and paper. Any errors and omissions are entirely my responsibility. FsTest - This project is designed to Language Oriented Programming constructs around unit testing and behavior testing in F#. The goal of this project is to create a Domain Specific Language for testing F# code in a way that makes sense for functional programming. FsUnit - FsUnit makes unit-testing with F# more enjoyable. It adds a special syntax to your favorite .NET testing framework. xUnit.NET - xUnit.net is a developer testing framework, built to support Test Driven Development, with a design goal of extreme simplicity and alignment with framework features. It is compatible with .NET Framework 2.0 and later, and offers several runners: console, GUI, MSBuild, and Visual Studio integration via TestDriven.net, CodeRush Test Runner and Resharper. It also offers test project integration for ASP.NET MVC. Getting started Well, as a first thing you need Visual Studio 2010. Then take a look at these resources: F# samples @ MSDN Microsoft F# Developer Center @ MSDN F# Language Reference @ MSDN F# blog F# forums Real World Functional Programming: With Examples in F# and C# (Amazon) Happy F#-ing! :)

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  • count of distinct acyclic paths from A[a,b] to A[c,d]?

    - by Sorush Rabiee
    I'm writing a sokoban solver for fun and practice, it uses a simple algorithm (something like BFS with a bit of difference). now i want to estimate its running time ( O and omega). but need to know how to calculate count of acyclic paths from a vertex to another in a network. actually I want an expression that calculates count of valid paths, between two vertices of a m*n matrix of vertices. a valid path: visits each vertex 0 or one times. have no circuits for example this is a valid path: but this is not: What is needed is a method to find count of all acyclic paths between the two vertices a and b. comments on solving methods and tricks are welcomed.

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  • count of paths from A[a,b] to A[c,d] without duplicating?

    - by Sorush Rabiee
    I write a sokoban solver for fun and practice, it uses a simple algorithm (something like BFS). now i want to estimate its running time ( O and omega). but i need to know how to calculate count of paths from a vertex to another in a network. each path from a to b is a sequence of edges with no circuit. for example this is a correct path: http://www.imgplace.com/viewimg143/4789/501k.png but this is not: http://www.imgplace.com/viewimg143/6140/202.png

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  • Counting problem: possible sudoko tables?

    - by Sorush Rabiee
    Hi, I'm working on a sudoko solver. my method is using a game tree and explore possible permutations for each set of digits by DFS Algorithm. in order to analyzing problem, i want to know what is the count of possible valid and invalid sudoko tables? - a 9*9 table that have 9 one, 9 two, ... , 9 nine. (this isn't exact duplicate by this question) my solution is: 1- First select 9 cells for 1s: (*) 2- and like (1) for other digits (each time, 9 cells will be deleted from remaining available cells): C(81-9,9) , C(81-9*2,9) .... = 3- finally multiply the result by 9! (permutation of 123456789 in (*)) this is not equal to accepted answer of this question but problems are equivalent. what did i do wrong?

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  • Extreme Optimization Numerical Libraries for .NET – Part 1 of n

    - by JoshReuben
    While many of my colleagues are fascinated in constructing the ultimate ViewModel or ServiceBus, I feel that this kind of plumbing code is re-invented far too many times – at some point in the near future, it will be out of the box standard infra. How many times have you been to a customer site and built a different variation of the same kind of code frameworks? How many times can you abstract Prism or reliable and discoverable WCF communication? As the bar is raised for whats bundled with the framework and more tasks become declarative, automated and configurable, Information Systems will expose a higher level of abstraction, forcing software engineers to focus on more advanced computer science and algorithmic tasks. I've spent the better half of the past decade building skills in .NET and expanding my mathematical horizons by working through the Schaums guides. In this series I am going to examine how these skillsets come together in the implementation provided by ExtremeOptimization. Download the trial version here: http://www.extremeoptimization.com/downloads.aspx Overview The library implements a set of algorithms for: linear algebra, complex numbers, numerical integration and differentiation, solving equations, optimization, random numbers, regression, ANOVA, statistical distributions, hypothesis tests. EONumLib combines three libraries in one - organized in a consistent namespace hierarchy. Mathematics Library - Extreme.Mathematics namespace Vector and Matrix Library - Extreme.Mathematics.LinearAlgebra namespace Statistics Library - Extreme.Statistics namespace System Requirements -.NET framework 4.0  Mathematics Library The classes are organized into the following namespace hierarchy: Extreme.Mathematics – common data types, exception types, and delegates. Extreme.Mathematics.Calculus - numerical integration and differentiation of functions. Extreme.Mathematics.Curves - points, lines and curves, including polynomials and Chebyshev approximations. curve fitting and interpolation. Extreme.Mathematics.Generic - generic arithmetic & linear algebra. Extreme.Mathematics.EquationSolvers - root finding algorithms. Extreme.Mathematics.LinearAlgebra - vectors , matrices , matrix decompositions, solvers for simultaneous linear equations and least squares. Extreme.Mathematics.Optimization – multi-d function optimization + linear programming. Extreme.Mathematics.SignalProcessing - one and two-dimensional discrete Fourier transforms. Extreme.Mathematics.SpecialFunctions

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