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Thread: Kernel doesn't work on Intel CPU,but works fine on GeForce and SOMETIMES at Intel HD

  1. #1
    Junior Member
    Join Date
    Aug 2014
    Posts
    5

    Unhappy Kernel doesn't work on Intel CPU,but works fine on GeForce and SOMETIMES at Intel HD

    Hello!

    I have a strange trouble with my kernel...

    I use laptop Lenovo U430p with Intel Haswell i5 processor with integrated Nvidia GeForce GT 730M (Nvidia Optimus).

    Kernel works on NVidia all the time.
    Kernel DOES NOT work on Intel CPU all the time.
    Kernel DOES NOT works on Intel GPU SOMETIMES (very rarely).

    Looks like a bug in a synchronization.

    Visual Studio 2012 solution with tests can be downloaded at https://www.dropbox.com/s/xwfwoq7v7ywd13x/MyNN.zip
    Screenshot 1 screenshot0.jpg
    Screenshot 2 screenshot1.jpg

    Can anyone reproduce this bug?
    Is there bug in my code instead of the bug in Intel OpenCL implementation?
    Any ideas about how to enlight this bug?

    I have COMPLETELY no ideas how to investigate this issue...

    Thanks!

    ps. addition - I use C# with OpenCL.Net.
    pps. I use actual version of Intel OpenCL SDK.
    Attached Images Attached Images
    Last edited by lsoft2K; 08-01-2014 at 04:11 AM.

  2. #2
    Newbie
    Join Date
    Aug 2014
    Posts
    1
    I am having the same problem. I noticed that if the barriers are taken off, the kernel is compiled and executed, but it doesn´t gave the correct answer.

  3. #3
    Junior Member
    Join Date
    Aug 2014
    Posts
    5
    I've found something interesting...

    1) switch read-write mem

    __global float * gdata

    to read-only mode.

    2) introduce a new write-only mem:

    __global float * tdata,

    3) write results to tdata instead of gdata:

    if(get_local_id(0) == 0)
    {
    tdata[get_group_id(0)] = ldata[0];
    }

    Then the kernel works fine at all three platforms (intel cpu, intel gpu, NVidia geforce gt 730m). Unfortunately, it's not an answer too ))

    Fixed solution can be found here: https://www.dropbox.com/s/6dl0duixk4...NN%20fixed.zip

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