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paign10
Journeyman III

Kernel Workspaces

I was developing a kernel for a while on my machine (R9 270X, Catalyst 14.12) and everything run smoothly. But then I got to execute it on another machine (HD 6520G), just to get the following error: clEnqueueNDRangeKernel (CL_INVALID_WORK_GROUP_SIZE).

These were the workspaces I was using: global (52, 4096), local (16, 16). So, the problem was that global[0] was not a multiple of local[0].

The question now is, why was I able to run the kernel on my machine? Is this a feature, or a bug?

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3 Replies
nou
Exemplar

Re: Kernel Workspaces

OpenCL 2.0 relaxed limitation where global work group size must be multiple of local workgroup group size. AFAIK R9 270X does support 2.0 but 6520 does not.

paign10
Journeyman III

Re: Kernel Workspaces

Sadly no, R9 270X doesn't support OpenCL 2.0.

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dipak
Staff
Staff

Re: Kernel Workspaces

Thanks for reporting this. It seems that "not divisible work-groups" are running fine on GCN cards but not on pre GCN i.e. VLIW/TeraScale cards. As I checked on the following cards, my observation was as below:

HD 6520G --> failed

HD 6850 ---> failed

HD 7870  ----> worked

R9 290X ---> worked

So, though the relaxation is an OpenCL 2.0 feature, however, it seems that the feature is working fine on any GCN cards. I'll check with concerned team and file a report, if needed.

Regards,

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