[petsc-dev] refactoring petsccusp.h needed

[Karl Rupp]

Hi,

@naming:
returning a PetscScalar * for a device handle is certainly a design 
flaw, because this does not extent to any other programming approach for 
GPUs. Better call it a 'handle' or something similar.

Best regards,
Karli


On 03/08/2013 04:19 PM, Barry Smith wrote:
>
> On Mar 8, 2013, at 4:07 PM, Paul Mullowney <paulm at txcorp.com> wrote:
>
>> Not quite. I want to expose a PetscScalar * rather than a CUSPARRAY *.
>
>     Well it cannot expose a PetscScalar since PetscScalar lives in CPU memory space, not GPU memory space.
>
>      Do you mean the raw pointer inside a CUSPARRAY array? It would be fine to have functions to return those whose prototypes go in petsccusp.h
>
>     Barry
>
>
>
>>>> 1) I would like a public method that exposes the GPU device pointers to the user. For example, we have VecGetArrayRead(). But, this gives a CPU pointer (which in turn causes a memcpy from CPU to GPU).  We need something that returns the GPU device pointer. This is useful for embedded PETSc solves in external apps that want to use the GPU.
>>>    Yup. Are these not just
>>> #undef __FUNCT__
>>> #define __FUNCT__ "VecCUSPGetArrayReadWrite"
>>> PETSC_STATIC_INLINE PetscErrorCode VecCUSPGetArrayReadWrite(Vec v, CUSPARRAY **a)
>>> {
>>>    PetscErrorCode ierr;
>>>
>>>    PetscFunctionBegin;
>>>    *a   = 0;
>>>    ierr = VecCUSPCopyToGPU(v);CHKERRQ(ierr);
>>>    *a   = ((Vec_CUSP*)v->spptr)->GPUarray;
>>>    PetscFunctionReturn(0);
>>> }
>>>
>>> and friends? Just make them not static inline and put the prototypes for them in petsccusp.h  The function call cost can be lived with.
>>>
>>> (You would make them not static inline because we don't want Vec_CUSP to be public.)
>>>
>>>
>>> Thanks
>>>
>>>      Barry
>>>
>>>     Barry
>>>
>>>> 2) As for other things. I have a patch for ICC that I'm nearly finished with. After that, I'm going to try to harden the other CUSP preconditioners so that they work with the CUSP and CUSPARSE classes.
>>>>
>>>> -Paul
>>>>>     Do you think you can make that change and anything else that needs doing before the release?
>>>>>
>>>>>     Thanks
>>>>>      Barry
>>>>>
>>
>