[cfe-dev] openmp 4.5 and cuda streams

[Finkel, Hal J. via cfe-dev]

[+Ye, Johannes]

I recall that we've also observed this behavior. Ye, Johannes, we had a 
work-around and a patch, correct?

  -Hal

On 10/30/19 12:28 PM, Alessandro Gabbana via cfe-dev wrote:
> Dear All,
>
> I'm using clang 9.0.0 to compile a code which offloads sections of a 
> code on a GPU using the openmp target construct.
> I also use the nowait clause to overlap the execution of certain 
> kernels and/or host<->device memory transfers.
> However, using the nvidia profiler I've noticed that when I compile 
> the code with clang only one cuda stream is active,
> and therefore the execution gets serialized. On the other hand, when 
> compiling with XLC I see that kernels are executed
> on different streams. I could not understand if this is the expected 
> behavior (e.g. the nowait clause is currently not supported),
> or if I'm missing something. I'm using a NVIDIA Tesla P100 GPU and 
> compiling with the following options:
>
> -target x86_64-pc-linux-gnu -fopenmp 
> -fopenmp-targets=nvptx64-nvidia-cuda 
> -Xopenmp-target=nvptx64-nvidia-cuda -march=sm_60
>
> best wishes
>
> Alessandro
>
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-- 
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory