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

[Zhang, Junchao via petsc-dev]

Stafano recently modified the following code,

PetscErrorCode VecCreate_SeqCUDA(Vec V)
{
  PetscErrorCode ierr;

  PetscFunctionBegin;
  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;
  PetscFunctionReturn(0);
}

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
enum 
{PETSC_OFFLOAD_UNALLOCATED=0x0,PETSC_OFFLOAD_GPU=0x1,PETSC_OFFLOAD_CPU=0x2,PETSC_OFFLOAD_BOTH=0x3}
and then use if (V->valid_GPU_array & PETSC_OFFLOAD_GPU). What do you think?

--Junchao Zhang