opm-simulators/opm/simulators/linalg/bda/cuda/cuWellContributions.cu
2024-05-24 14:09:12 +02:00

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/*
Copyright 2020 Equinor ASA
This file is part of the Open Porous Media project (OPM).
OPM is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
OPM is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with OPM. If not, see <http://www.gnu.org/licenses/>.
*/
#include <config.h> // CMake
#include <opm/simulators/linalg/bda/cuda/cuWellContributions.hpp>
#include <opm/common/ErrorMacros.hpp>
#include <opm/common/OpmLog/OpmLog.hpp>
#include <opm/simulators/linalg/bda/MultisegmentWellContribution.hpp>
#include <opm/simulators/linalg/bda/cuda/cuda_header.hpp>
#include <cuda_runtime.h>
namespace Opm
{
// apply WellContributions using y -= C^T * (D^-1 * (B * x))
template<class Scalar>
__global__ void apply_well_contributions(const Scalar* __restrict__ Cnnzs,
const Scalar* __restrict__ Dnnzs,
const Scalar* __restrict__ Bnnzs,
const int* __restrict__ Ccols,
const int* __restrict__ Bcols,
const Scalar* __restrict__ x,
Scalar* __restrict__ y,
const int dim,
const int dim_wells,
const unsigned int * __restrict__ val_pointers)
{
const int idx_b = blockIdx.x;
const int idx_t = threadIdx.x;
const unsigned int val_size = val_pointers[idx_b + 1] - val_pointers[idx_b];
const int vals_per_block = dim * dim_wells; // 12
const int num_active_threads = (32 / vals_per_block) * vals_per_block; // 24
const int num_blocks_per_warp = 32 / vals_per_block; // 2
const int lane = idx_t % 32;
const int c = lane % dim; // col in block
const int r = (lane / dim) % dim_wells; // row in block
extern __shared__ unsigned char smem[];
Scalar* __restrict__ z1 = reinterpret_cast<Scalar*>(smem);
Scalar* __restrict__ z2 = z1 + dim_wells;
if (idx_t < dim_wells) {
z1[idx_t] = 0.0;
}
__syncthreads();
// z1 = B * x
if (idx_t < num_active_threads) {
// multiply all blocks with x
Scalar temp = 0.0;
int b = idx_t / vals_per_block + val_pointers[idx_b]; // block id, val_size indicates number of blocks
while (b < val_size + val_pointers[idx_b]) {
int colIdx = Bcols[b];
temp += Bnnzs[b * dim * dim_wells + r * dim + c] * x[colIdx * dim + c];
b += num_blocks_per_warp;
}
// merge all blocks into 1 dim*dim_wells block
// since 3*4 blocks has give 2 parallel blocks, do not use a loop
// 0x00ffffff contains 24 ones, representing the two blocks that are added
// block 1: block 2:
// 0 1 2 12 13 14
// 3 4 5 15 16 17
// 6 7 8 18 19 20
// 9 10 11 21 22 23
// thread i will hold the sum of thread i and i + vals_per_block
temp += __shfl_down_sync(0x00ffffff, temp, dim * dim_wells);
// merge all (dim) columns of 1 block, results in a single 1*dim_wells vector, which is used to multiply with invD
if (idx_t < vals_per_block) {
// should be a loop as well, now only works for dim == 3
if (c == 0 || c == 2) {temp += __shfl_down_sync(0x00000B6D, temp, 2);} // add col 2 to col 0
if (c == 0 || c == 1) {temp += __shfl_down_sync(0x000006DB, temp, 1);} // add col 1 to col 0
}
// write 1*dim_wells vector to gmem, could be replaced with shfl broadcast to remove z1 altogether
if (c == 0 && idx_t < vals_per_block) {
z1[r] = temp;
}
}
__syncthreads();
// z2 = D^-1 * B * x = D^-1 * z1
if (idx_t < dim_wells) {
Scalar temp = 0.0;
for (int c = 0; c < dim_wells; ++c) {
temp += Dnnzs[idx_b * dim_wells * dim_wells + idx_t * dim_wells + c] * z1[c];
}
z2[idx_t] = temp;
}
__syncthreads();
// y -= C^T * D^-1 * B * x
// use dim * val_size threads, each block is assigned 'dim' threads
if (idx_t < dim * val_size) {
Scalar temp = 0.0;
int b = idx_t / dim + val_pointers[idx_b];
int cc = idx_t % dim;
int colIdx = Ccols[b];
for (unsigned int c = 0; c < dim_wells; ++c) {
temp += Cnnzs[b * dim * dim_wells + c * dim + cc] * z2[c];
}
y[colIdx * dim + cc] -= temp;
}
}
template<class Scalar>
WellContributionsCuda<Scalar>::~WellContributionsCuda()
{
// delete data for StandardWell
if (this->num_std_wells > 0) {
cudaFree(d_Cnnzs);
cudaFree(d_Dnnzs);
cudaFree(d_Bnnzs);
cudaFree(d_Ccols);
cudaFree(d_Bcols);
cudaFree(d_val_pointers);
}
if (this->num_ms_wells > 0 && h_x) {
cudaFreeHost(h_x);
cudaFreeHost(h_y);
h_x = h_y = nullptr; // Mark as free for constructor
}
}
template<class Scalar>
void WellContributionsCuda<Scalar>::APIalloc()
{
cudaMalloc((void**)&d_Cnnzs,
sizeof(Scalar) * this->num_blocks * this->dim * this->dim_wells);
cudaMalloc((void**)&d_Dnnzs,
sizeof(Scalar) * this->num_std_wells * this->dim_wells * this->dim_wells);
cudaMalloc((void**)&d_Bnnzs,
sizeof(Scalar) * this->num_blocks * this->dim * this->dim_wells);
cudaMalloc((void**)&d_Ccols, sizeof(int) * this->num_blocks);
cudaMalloc((void**)&d_Bcols, sizeof(int) * this->num_blocks);
cudaMalloc((void**)&this->d_val_pointers, sizeof(unsigned int) * (this->num_std_wells + 1));
cudaCheckLastError("apply_gpu malloc failed");
}
// Apply the WellContributions, similar to StandardWell::apply()
// y -= (C^T *(D^-1*( B*x)))
template<class Scalar>
void WellContributionsCuda<Scalar>::apply(Scalar* d_x, Scalar* d_y)
{
// apply MultisegmentWells
// make sure the stream is empty if timing measurements are done
cudaStreamSynchronize(stream);
if (this->num_ms_wells > 0) {
// allocate pinned memory on host if not yet done
if (h_x == nullptr) {
cudaMallocHost(&h_x, sizeof(Scalar) * this->N);
cudaMallocHost(&h_y, sizeof(Scalar) * this->N);
}
// copy vectors x and y from GPU to CPU
cudaMemcpyAsync(h_x, d_x, sizeof(Scalar) * this->N,
cudaMemcpyDeviceToHost, stream);
cudaMemcpyAsync(h_y, d_y, sizeof(Scalar) * this->N,
cudaMemcpyDeviceToHost, stream);
cudaStreamSynchronize(stream);
// actually apply MultisegmentWells
for (auto& well : this->multisegments) {
well->apply(h_x, h_y);
}
// copy vector y from CPU to GPU
cudaMemcpyAsync(d_y, h_y, sizeof(Scalar) * this->N,
cudaMemcpyHostToDevice, stream);
cudaStreamSynchronize(stream);
}
// apply StandardWells
if (this->num_std_wells > 0) {
int smem_size = 2 * sizeof(Scalar) * this->dim_wells;
apply_well_contributions <<< this->num_std_wells, 32, smem_size, stream>>>(d_Cnnzs,
d_Dnnzs,
d_Bnnzs,
d_Ccols,
d_Bcols,
d_x,
d_y,
this->dim,
this->dim_wells,
this->d_val_pointers);
}
}
template<class Scalar>
void WellContributionsCuda<Scalar>::APIaddMatrix(MatrixType type, int* colIndices,
Scalar* values, unsigned int val_size)
{
switch (type) {
case MatrixType::C:
cudaMemcpy(d_Cnnzs + this->num_blocks_so_far * this->dim * this->dim_wells,
values, sizeof(Scalar) * val_size * this->dim * this->dim_wells,
cudaMemcpyHostToDevice);
cudaMemcpy(d_Ccols + this->num_blocks_so_far, colIndices,
sizeof(int) * val_size, cudaMemcpyHostToDevice);
break;
case MatrixType::D:
cudaMemcpy(d_Dnnzs + this->num_std_wells_so_far * this->dim_wells * this->dim_wells,
values, sizeof(Scalar) * this->dim_wells * this->dim_wells,
cudaMemcpyHostToDevice);
break;
case MatrixType::B:
cudaMemcpy(d_Bnnzs + this->num_blocks_so_far * this->dim * this->dim_wells,
values, sizeof(Scalar) * val_size * this->dim * this->dim_wells,
cudaMemcpyHostToDevice);
cudaMemcpy(d_Bcols + this->num_blocks_so_far, colIndices,
sizeof(int) * val_size, cudaMemcpyHostToDevice);
this->val_pointers[this->num_std_wells_so_far] = this->num_blocks_so_far;
if (this->num_std_wells_so_far == this->num_std_wells - 1) {
this->val_pointers[this->num_std_wells] = this->num_blocks;
cudaMemcpy(d_val_pointers, this->val_pointers.data(),
sizeof(unsigned int) * (this->num_std_wells + 1),
cudaMemcpyHostToDevice);
}
break;
default:
OPM_THROW(std::logic_error, "Error unsupported matrix ID for WellContributions::addMatrix()");
}
cudaCheckLastError("WellContributions::addMatrix() failed");
}
template<class Scalar>
void WellContributionsCuda<Scalar>::setCudaStream(cudaStream_t stream_)
{
this->stream = stream_;
for (auto& well : this->multisegments) {
well->setCudaStream(stream_);
}
}
template class WellContributionsCuda<double>;
} //namespace Opm