[petsc-dev] Should v->valid_GPU_array be a bitmask?

Zhang, Junchao jczhang at mcs.anl.gov
Tue Oct 1 22:24:27 CDT 2019

Stafano recently modified the following code,

PetscErrorCode VecCreate_SeqCUDA(Vec V)
  PetscErrorCode ierr;

  ierr = PetscLayoutSetUp(V->map);CHKERRQ(ierr);
  ierr = VecCUDAAllocateCheck(V);CHKERRQ(ierr);
  ierr = VecCreate_SeqCUDA_Private(V,((Vec_CUDA*)V->spptr)->GPUarray_allocated);CHKERRQ(ierr);
  ierr = VecCUDAAllocateCheckHost(V);CHKERRQ(ierr);
  ierr = VecSet(V,0.0);CHKERRQ(ierr);
  ierr = VecSet_Seq(V,0.0);CHKERRQ(ierr);
  V->valid_GPU_array = PETSC_OFFLOAD_BOTH;

That means if one creates an SEQCUDA vector V and then immediately tests if (V->valid_GPU_array == PETSC_OFFLOAD_GPU), the test will fail. That is counterintuitive.  I think we should have
and then use if (V->valid_GPU_array & PETSC_OFFLOAD_GPU). What do you think?

--Junchao Zhang
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