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Altera_Forum's avatar
Altera_Forum
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8 years ago

Work-groups' number

Hi everyone,

I would like to say how I can set the number of work groups. I know the attribute "reqd_work_group_size(X,Y,Z)" allows to establish the number of W-I inside a work group (W-G's dimension) in three dimensions but it is not clear to me how to decide the number of these W-G. Could you help me? Thanks for your help

4 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    8 years ago

    The local size (number of work-items per work-group) and global size (total number of work-items) are both set in the host code and passed as arguments to clEnqueueNDRangeKernel(). The number of work-groups per dimension is equal to global size per dimension divided by local size per dimension. If you are using reqd_work_group_size() in the kernel, the local size you pass to clEnqueueNDRangeKernel() in the host code MUST match the numbers you pass to reqd_work_group_size() or else the kernel launch will fail.

  • Altera_Forum's avatar
    Altera_Forum
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    8 years ago

    Ok thanks. Then the numbers in the attribute "reqd_work_group_size" represent the local size (in three dimensions) not the global size, is it correct? Thanks.

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    8 years ago

    --- Quote Start ---

    Ok thanks. Then the numbers in the attribute "reqd_work_group_size" represent the local size (in three dimensions) not the global size, is it correct? Thanks.

    --- Quote End ---

    Yes, it represents the local size (also called work-group size).