[petsc-dev] MatPinToCPU
Smith, Barry F.
bsmith at mcs.anl.gov
Sat Jul 27 12:00:21 CDT 2019
> On Jul 27, 2019, at 11:53 AM, Mark Adams <mfadams at lbl.gov> wrote:
>
>
> On Sat, Jul 27, 2019 at 11:39 AM Smith, Barry F. <bsmith at mcs.anl.gov> wrote:
>
> Good catch. Thanks. Maybe the SeqCUDA has the same problem?
>
> THis is done (I may have done it).
>
> Now it seems to me that when you call VecPinToCPU you are setting up and don't have data, so this copy does not seem necessary. Maybe remove the copy here:
>
> PetscErrorCode VecPinToCPU_MPICUDA(Vec V,PetscBool pin)
> {
> PetscErrorCode ierr;
>
> PetscFunctionBegin;
> V->pinnedtocpu = pin;
> if (pin) {
> ierr = VecCUDACopyFromGPU(V);CHKERRQ(ierr); ????
The copy from GPU should actually only do anything if the GPU already has data and PETSC_OFFLOAD_GPU. If the GPU does not have data
the copy doesn't do anything. When one calls VecPinToCPU() one doesn't know where the data is so the call must be made, but it may do nothing
Note that VecCUDACopyFromGPU() calls VecCUDAAllocateCheckHost() not VecCUDAAllocateCheck() so the GPU will not allocate space,
VecCUDAAllocateCheck() is called from VecCUDACopyToGPU().
Yes, perhaps the naming could be more consistent:
1) in one place it is Host in an other place it is nothing
2) some places it is Host, Device, some places GPU,CPU
Perhaps Karl can make these all consistent and simpler in his refactorization
Barry
>
> or
>
> Not allocate the GPU if it is pinned by added in a check here:
>
> PetscErrorCode VecCUDAAllocateCheck(Vec v)
> {
> PetscErrorCode ierr;
> cudaError_t err;
> cudaStream_t stream;
> Vec_CUDA *veccuda;
>
> PetscFunctionBegin;
> if (!v->spptr) {
> ierr = PetscMalloc(sizeof(Vec_CUDA),&v->spptr);CHKERRQ(ierr);
> veccuda = (Vec_CUDA*)v->spptr;
> if (v->valid_GPU_array != PETSC_OFFLOAD_CPU) {
> err = cudaMalloc((void**)&veccuda->GPUarray_allocated,sizeof(PetscScalar)*((PetscBLASInt)v->map->n));CHKERRCUDA(err);
> veccuda->GPUarray = veccuda->GPUarray_allocated;
> err = cudaStreamCreate(&stream);CHKERRCUDA(err);
> veccuda->stream = stream;
> veccuda->hostDataRegisteredAsPageLocked = PETSC_FALSE;
> if (v->valid_GPU_array == PETSC_OFFLOAD_UNALLOCATED) {
> if (v->data && ((Vec_Seq*)v->data)->array) {
> v->valid_GPU_array = PETSC_OFFLOAD_CPU;
> } else {
> v->valid_GPU_array = PETSC_OFFLOAD_GPU;
> }
> }
> }
> }
> PetscFunctionReturn(0);
> }
>
>
>
>
>
> > On Jul 27, 2019, at 10:40 AM, Mark Adams <mfadams at lbl.gov> wrote:
> >
> > Yea, I just figured out the problem. VecDuplicate_MPICUDA did not call PinToCPU or even copy pinnedtocpu. It just copied ops, so I added and am testing:
> >
> > ierr = VecCreate_MPICUDA_Private(*v,PETSC_TRUE,w->nghost,0);CHKERRQ(ierr);
> > vw = (Vec_MPI*)(*v)->data;
> > ierr = PetscMemcpy((*v)->ops,win->ops,sizeof(struct _VecOps));CHKERRQ(ierr);
> > ierr = VecPinToCPU(*v,win->pinnedtocpu);CHKERRQ(ierr);
> >
> > Thanks,
> >
> > On Sat, Jul 27, 2019 at 11:33 AM Smith, Barry F. <bsmith at mcs.anl.gov> wrote:
> >
> > I don't understand the context. Once a vector is pinned to the CPU the flag should be PETSC_OFFLOAD_CPU permanently until the pin to cpu is turned off. Do you have a pinned vector that has the value PETSC_OFFLOAD_GPU? For example here it is set to PETSC_OFFLOAD_CPU
> >
> > PetscErrorCode VecPinToCPU_MPICUDA(Vec V,PetscBool pin)
> > {
> > ....
> > if (pin) {
> > ierr = VecCUDACopyFromGPU(V);CHKERRQ(ierr);
> > V->valid_GPU_array = PETSC_OFFLOAD_CPU; /* since the CPU code will likely change values in the vector */
> >
> >
> > Is there any way to reproduce the problem?
> >
> > Barry
> >
> >
> >
> >
> > > On Jul 27, 2019, at 10:28 AM, Mark Adams <mfadams at lbl.gov> wrote:
> > >
> > > I'm not sure what to do here. The problem is that pinned-to-cpu vectors are calling VecCUDACopyFromGPU here.
> > >
> > > Should I set x->valid_GPU_array to something else, like PETSC_OFFLOAD_CPU, in PinToCPU so this block of code i s not executed?
> > >
> > > PetscErrorCode VecGetArray(Vec x,PetscScalar **a)
> > > {
> > > PetscErrorCode ierr;
> > > #if defined(PETSC_HAVE_VIENNACL)
> > > PetscBool is_viennacltype = PETSC_FALSE;
> > > #endif
> > >
> > > PetscFunctionBegin;
> > > PetscValidHeaderSpecific(x,VEC_CLASSID,1);
> > > ierr = VecSetErrorIfLocked(x,1);CHKERRQ(ierr);
> > > if (x->petscnative) {
> > > #if defined(PETSC_HAVE_VIENNACL) || defined(PETSC_HAVE_CUDA)
> > > if (x->valid_GPU_array == PETSC_OFFLOAD_GPU) {
> > > #if defined(PETSC_HAVE_VIENNACL)
> > > ierr = PetscObjectTypeCompareAny((PetscObject)x,&is_viennacltype,VECSEQVIENNACL,VECMPIVIENNACL,VECVIENNACL,"");CHKERRQ(ierr);
> > > if (is_viennacltype) {
> > > ierr = VecViennaCLCopyFromGPU(x);CHKERRQ(ierr);
> > > } else
> > > #endif
> > > {
> > > #if defined(PETSC_HAVE_CUDA)
> > > ierr = VecCUDACopyFromGPU(x);CHKERRQ(ierr);
> > > #endif
> > > }
> > > } else if (x->valid_GPU_array == PETSC_OFFLOAD_UNALLOCATED) {
> > > #if defined(PETSC_HAVE_VIENNACL)
> > > ierr = PetscObjectTypeCompareAny((PetscObject)x,&is_viennacltype,VECSEQVIENNACL,VECMPIVIENNACL,VECVIENNACL,"");CHKERRQ(ierr);
> > > if (is_viennacltype) {
> > > ierr = VecViennaCLAllocateCheckHost(x);CHKERRQ(ierr);
> > > } else
> > > #endif
> > > {
> > > #if defined(PETSC_HAVE_CUDA)
> > > ierr = VecCUDAAllocateCheckHost(x);CHKERRQ(ierr);
> > > #endif
> > > }
> > > }
> > > #endif
> > > *a = *((PetscScalar**)x->data);
> > > } else {
> > >
> > >
> > > On Tue, Jul 23, 2019 at 9:18 PM Smith, Barry F. <bsmith at mcs.anl.gov> wrote:
> > >
> > > Yes, it needs to be able to switch back and forth between the CPU and GPU methods so you need to move into it the setting of the methods that is currently directly in the create method. See how MatConvert_SeqAIJ_SeqAIJViennaCL() calls ierr = MatPinToCPU_SeqAIJViennaCL(A,PETSC_FALSE);CHKERRQ(ierr); to set the methods for the GPU initially.
> > >
> > > Barry
> > >
> > >
> > > > On Jul 23, 2019, at 7:32 PM, Mark Adams <mfadams at lbl.gov> wrote:
> > > >
> > > >
> > > > What are the symptoms of it not working? Does it appear to be still copying the matrices to the GPU? then running the functions on the GPU?
> > > >
> > > >
> > > > The object is dispatching the CUDA mat-vec etc.
> > > >
> > > > I suspect the pinning is incompletely done for CUDA (and MPIOpenCL) matrices.
> > > >
> > > >
> > > > Yes, git grep MatPinToCPU shows stuff for ViennaCL but not CUDA.
> > > >
> > > > I guess I can add something like this below. Do we need to set the device methods? They are already set when this method is set, right?
> > > >
> > > > We need the equivalent of
> > > >
> > > > static PetscErrorCode MatPinToCPU_SeqAIJViennaCL(Mat A,PetscBool flg)
> > > > {
> > > > PetscFunctionBegin;
> > > > A->pinnedtocpu = flg;
> > > > if (flg) {
> > > > A->ops->mult = MatMult_SeqAIJ;
> > > > A->ops->multadd = MatMultAdd_SeqAIJ;
> > > > A->ops->assemblyend = MatAssemblyEnd_SeqAIJ;
> > > > A->ops->duplicate = MatDuplicate_SeqAIJ;
> > > > } else {
> > > > A->ops->mult = MatMult_SeqAIJViennaCL;
> > > > A->ops->multadd = MatMultAdd_SeqAIJViennaCL;
> > > > A->ops->assemblyend = MatAssemblyEnd_SeqAIJViennaCL;
> > > > A->ops->destroy = MatDestroy_SeqAIJViennaCL;
> > > > A->ops->duplicate = MatDuplicate_SeqAIJViennaCL;
> > > > }
> > > > PetscFunctionReturn(0);
> > > > }
> > > >
> > > > for MPIViennaCL and MPISeqAIJ Cusparse but it doesn't look like it has been written yet.
> > > >
> > > >
> > > > >
> > > > > It does not seem to work. It does not look like CUDA has an MatCreateVecs. Should I add one and copy this flag over?
> > > >
> > > > We do need this function. But I don't see how it relates to pinning. When the matrix is pinned to the CPU we want it to create CPU vectors which I assume it does.
> > > >
> > > >
> > > > >
> > > > > Mark
> > > >
> > >
> >
>
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