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#include <iostream>
#include <iomanip>
#include <fstream>
#include <vector>
#include <numeric>
#include <boost/scope_exit.hpp>
#include <amgcl/mpi/util.hpp>
#include <amgcl_mpi.h>
#include "domain_partition.hpp"
double STDCALL constant_deflation(int, ptrdiff_t, void*) {
return 1;
}
int main(int argc, char *argv[]) {
int provided;
MPI_Init_thread(&argc, &argv, MPI_THREAD_MULTIPLE, &provided);
BOOST_SCOPE_EXIT(void) {
MPI_Finalize();
} BOOST_SCOPE_EXIT_END
int rank, size;
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
MPI_Comm_size(MPI_COMM_WORLD, &size);
if (rank == 0)
std::cout << "World size: " << size << std::endl;
const ptrdiff_t n = argc > 1 ? atoi(argv[1]) : 1024;
const ptrdiff_t n2 = n * n;
// Partition
boost::array<ptrdiff_t, 2> lo = { {0, 0} };
boost::array<ptrdiff_t, 2> hi = { {n - 1, n - 1} };
domain_partition<2> part(lo, hi, size);
ptrdiff_t chunk = part.size( rank );
std::vector<ptrdiff_t> domain(size + 1);
MPI_Allgather(
&chunk, 1, amgcl::mpi::datatype<ptrdiff_t>(),
&domain[1], 1, amgcl::mpi::datatype<ptrdiff_t>(),
MPI_COMM_WORLD);
std::partial_sum(domain.begin(), domain.end(), domain.begin());
ptrdiff_t chunk_start = domain[rank];
ptrdiff_t chunk_end = domain[rank + 1];
std::vector<ptrdiff_t> renum(n2);
for(ptrdiff_t j = 0, idx = 0; j < n; ++j) {
for(ptrdiff_t i = 0; i < n; ++i, ++idx) {
boost::array<ptrdiff_t, 2> p = {{i, j}};
std::pair<int,ptrdiff_t> v = part.index(p);
renum[idx] = domain[v.first] + v.second;
}
}
// Assemble
std::vector<ptrdiff_t> ptr;
std::vector<ptrdiff_t> col;
std::vector<double> val;
std::vector<double> rhs;
ptr.reserve(chunk + 1);
col.reserve(chunk * 5);
val.reserve(chunk * 5);
rhs.reserve(chunk);
ptr.push_back(0);
const double hinv = (n - 1);
const double h2i = (n - 1) * (n - 1);
for(ptrdiff_t j = 0, idx = 0; j < n; ++j) {
for(ptrdiff_t i = 0; i < n; ++i, ++idx) {
if (renum[idx] < chunk_start || renum[idx] >= chunk_end) continue;
if (j > 0) {
col.push_back(renum[idx - n]);
val.push_back(-h2i);
}
if (i > 0) {
col.push_back(renum[idx - 1]);
val.push_back(-h2i - hinv);
}
col.push_back(renum[idx]);
val.push_back(4 * h2i + hinv);
if (i + 1 < n) {
col.push_back(renum[idx + 1]);
val.push_back(-h2i);
}
if (j + 1 < n) {
col.push_back(renum[idx + n]);
val.push_back(-h2i);
}
rhs.push_back(1);
ptr.push_back( col.size() );
}
}
// Setup
amgclHandle prm = amgcl_params_create();
amgcl_params_sets(prm, "local.coarsening.type", "smoothed_aggregation");
amgcl_params_sets(prm, "local.relax.type", "spai0");
amgcl_params_sets(prm, "isolver.type", "bicgstabl");
#ifdef AMGCL_HAVE_PASTIX
amgcl_params_sets(prm, "dsolver.type", "pastix");
#else
amgcl_params_sets(prm, "dsolver.type", "skyline_lu");
#endif
amgclHandle solver = amgcl_mpi_create(
MPI_COMM_WORLD,
chunk, ptr.data(), col.data(), val.data(),
1, constant_deflation, NULL, prm
);
// Solve
std::vector<double> x(chunk, 0);
conv_info cnv = amgcl_mpi_solve(solver, rhs.data(), x.data());
std::cout << "Iterations: " << cnv.iterations << std::endl
<< "Error: " << cnv.residual << std::endl;
// Clean up
amgcl_mpi_destroy(solver);
amgcl_params_destroy(prm);
if (n <= 4096) {
if (rank == 0) {
std::vector<double> X(n2);
std::copy(x.begin(), x.end(), X.begin());
for(int i = 1; i < size; ++i)
MPI_Recv(&X[domain[i]], domain[i+1] - domain[i], MPI_DOUBLE, i, 42, MPI_COMM_WORLD, MPI_STATUS_IGNORE);
std::ofstream f("out.dat", std::ios::binary);
int m = n2;
f.write((char*)&m, sizeof(int));
for(ptrdiff_t i = 0; i < n2; ++i)
f.write((char*)&X[renum[i]], sizeof(double));
} else {
MPI_Send(x.data(), chunk, MPI_DOUBLE, 0, 42, MPI_COMM_WORLD);
}
}
}
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