CODEWITHSUNDEEP
openacc
Jacob
Jacob

Reputation: 3801

OpenACC boundary issue

I am doing a very simple vector addition kernel in OpenACC. And I am wondering whether this is an issue with the compiler I am using (accULL with OpenCL), as I am having issue it seems copying data back to the host from the device. All the results are correct BUT result[0]. E.g. the following code:

  for (i=0; i<VEC_SIZE; i++) {
    a[i] = i;
    b[i] = VEC_SIZE-i;
    result[i]=0;
  }
  #pragma acc kernels copyin(a,b) copy(result)
  for (i=0; i<VEC_SIZE; i++) {
    result[i] = a[i]+b[i];
  }

  // verify result
  for (i=0; i<VEC_SIZE; i++) {
    if ( (a[i] + b[i]) != result[i]) {
      fprintf(stderr, "Incorrect results id %d val: %d \n", i, result[i]);
    }
  }

Returns the following:

Incorrect results id 0 val: 0

Which means all results but the one at index 0 is correct, it seems like the result for index zero is not copied over from the device.

Is this a compiler/runtime bug or did I miss something in regards of my coding?

Upvotes: 0

Views: 79

Answers (1)

Shouyu Chen
Shouyu Chen

Reputation: 655

Yes, I also think that is a bug of your compiler, because your code looks right, you can have a try PGI complier, I am using it now, and it belongs to NVIDIA now. Besides, you can change your code "copy(result)" to "copyout(result)" to decrease memory I/O time, because the initial value of result is useless for device.

Upvotes: 0

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