[cfe-dev] OpenMP offloaded target region executed in both host and target-device

Alexey Bataev via cfe-dev cfe-dev at lists.llvm.org
Mon Apr 9 07:41:51 PDT 2018

Seems to me, your program crashes on GPU and then tries to execute the
same code on cpu, though this behavior seems wrong to me.

The problem is in your code. When you try to map A, B and E array,
you're ding it it the wrong way. Instead of mapping the arrays you just
map pointers to these arrays and do not allocate the memory for them on
the GPU.

Best regards,
Alexey Bataev

09.04.2018 8:21, Piyumi Lakshani via cfe-dev пишет:
> Hi,
> I'm working on a project which requires OpenMP offloading to Nvidia
> GPUs using Clang. 
> System specification
> OS - Ubuntu 16.04 LTS
> Clang -version 4.00
> Processor - Intel(R) Core(TM) i7 -4700MQ CPU
> Cuda -version - 9.0
> Nvidia GPU - GeForce 740M (sm_capability - 35)
> But the problem is I when I execute a sample program to test OpenMP
> offloading to Nvidia GPUs, part of the target region tends to run in
> GPU and then same target region starts executing in the host.
> Please find the sample program  attached herewith, This a small C
> program written to multiply 2 matrices. 
> The reason to claim that target region is being executed in both host
> and target-device is due to the abnormal output received from the
> print function residing in the target region. (My processor has 4
> cores capable of handling 2 hardware level threads per core.).
> Please find the image of the command line output attached herewith.
> the program was compiled with -
>      clang -fopenmp -fopenmp-targets=nvptx64-nvidia-cuda
> I can not figure out whether runtime believes that the GPU execution
> is not completing successfully?. So the target region is being
> executed in the host again. 
> Thank you!
> -- 
> *Piyumi Rameshka*

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