[petsc-dev] Backend independent VecGetArray for GPUs

[Karl Rupp]

On 10/17/2014 06:40 PM, Jed Brown wrote:
> Karl Rupp <rupp at iue.tuwien.ac.at> writes:
>> If this should be provided, then the right names were
>>    VecCUDAGetArray()
>>    VecOpenCLGetArray()
>> The former returns an object of type PetscScalar* and the latter an
>> object of type cl_mem. Because one is stuck with two incompatible
>> pointer types here, I'd suggest not to provide a single interface at the
>> expense of giving up type safety.
>
> Agreed.
>
> Does cl_mem have a "null"?

Yes, cl_mem is a typedef for an opaque pointer to a struct. If you pass 
a cl_mem of 'NULL' to a kernel, the kernel is launched with a 'NULL' 
pointer for the respective argument.


>> Also, even if one gives up type safety, one would immediately have to
>> switch-case into a backend-specific implementation again, so there's
>> little value in a common interface.
>
> It's useful to have a non-error path for calling.

Can you sketch a use case for this?

Best regards,
Karli