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tpetra/example/SolverFactory/SolverFactoryTpetraGaleriEx.cpp

This is an example of how to use the Belos::SolverFactory with Tpetra.

// @HEADER
// *****************************************************************************
// Belos: Block Linear Solvers Package
//
// Copyright 2004-2016 NTESS and the Belos contributors.
// SPDX-License-Identifier: BSD-3-Clause
// *****************************************************************************
// @HEADER
// Tpetra
#include <Tpetra_Core.hpp>
#include <Tpetra_CrsMatrix.hpp>
#include <Tpetra_MultiVector.hpp>
// Galeri
#include <Galeri_XpetraMaps.hpp>
#include <Galeri_XpetraMatrixTypes.hpp>
#include <Galeri_XpetraProblemFactory.hpp>
// Teuchos
#include <Teuchos_RCP.hpp>
#include <Teuchos_Comm.hpp>
#include <Teuchos_CommHelpers.hpp>
#include <Teuchos_DefaultComm.hpp>
#include <Teuchos_oblackholestream.hpp>
#include "Teuchos_StandardCatchMacros.hpp"
// Belos
#include "BelosTpetraAdapter.hpp"
// ****************************************************************************
// BEGIN RUN ROUTINE
// ****************************************************************************
template <typename ScalarType>
int run(int argc, char *argv[]) {
// Belos solvers have the following template parameters:
//
// - Scalar: The type of dot product results.
// - MV: The type of (multi)vectors.
// - OP: The type of operators (functions from multivector to
// multivector). A matrix (like Tpetra::CrsMatrix) is an example
// of an operator; an Ifpack2 preconditioner is another example.
//
// Here, ST is set by the main function, MV is Tpetra::MultiVector, and OP is
// Tpetra::Operator.
using ST = typename Tpetra::MultiVector<ScalarType>::scalar_type;
using LO = typename Tpetra::MultiVector<>::local_ordinal_type;
using GO = typename Tpetra::MultiVector<>::global_ordinal_type;
using NT = typename Tpetra::MultiVector<>::node_type;
using OP = typename Tpetra::Operator<ST,LO,GO,NT>;
using MV = typename Tpetra::MultiVector<ST,LO,GO,NT>;
using tmap_t = Tpetra::Map<LO,GO,NT>;
using tvector_t = Tpetra::Vector<ST,LO,GO,NT>;
using trowmatrix_t = Tpetra::RowMatrix<ST,LO,GO,NT>;
using tcrsmatrix_t = Tpetra::CrsMatrix<ST,LO,GO,NT>;
using MVT = typename Belos::MultiVecTraits<ST,MV>;
using OPT = typename Belos::OperatorTraits<ST,MV,OP>;
using Teuchos::RCP;
using Teuchos::rcp;
Teuchos::GlobalMPISession mpiSession (&argc, &argv, &std::cout);
const auto comm = Tpetra::getDefaultComm();
const int myPID = comm->getRank();
bool verbose = false;
bool success = true;
try {
bool procVerbose = false;
bool debug = false;
int frequency = -1; // frequency of status test output
int blockSize = 1; // blockSize
int numrhs = 1; // number of right-hand sides to solve for
int maxIters = -1; // maximum number of iterations allowed per linear system
int maxSubspace = 50; // maximum number of blocks the solver can use for the subspace
int maxRestarts = 15; // number of restarts allowed
int nx = 10; // number of discretization points in each direction
MT tol = 1.0e-5; // relative residual tolerance
cmdp.setOption("verbose","quiet",&verbose,"Print messages and results.");
cmdp.setOption("debug","nondebug",&debug,"Print debugging information from solver.");
cmdp.setOption("frequency",&frequency,"Solvers frequency for printing residuals (#iters).");
cmdp.setOption("tol",&tol,"Relative residual tolerance used by GMRES solver.");
cmdp.setOption("num-rhs",&numrhs,"Number of right-hand sides to be solved for.");
cmdp.setOption("block-size",&blockSize,"Block size used by GMRES.");
cmdp.setOption("max-iters",&maxIters,"Maximum number of iterations per linear system (-1 = adapted to problem/block size).");
cmdp.setOption("max-subspace",&maxSubspace,"Maximum number of blocks the solver can use for the subspace.");
cmdp.setOption("max-restarts",&maxRestarts,"Maximum number of restarts allowed for GMRES solver.");
cmdp.setOption("nx",&nx,"Number of discretization points in each direction of 3D Laplacian.");
return -1;
}
if (!verbose)
frequency = -1; // reset frequency if test is not verbose
procVerbose = ( verbose && (myPID==0) ); // Only print on the zero processor
if (procVerbose) {
std::cout << Belos::Belos_Version() << std::endl << std::endl;
}
// Set up the test problem.
//
// We use Trilinos' Galeri package to construct a test problem.
// Here, we use a discretization of the 2-D Laplacian operator.
// The global mesh size is nx * nx.
GaleriList.set ("n", nx * nx );
GaleriList.set ("nx", nx);
GaleriList.set ("ny", nx);
auto Map = RCP{Galeri::Xpetra::CreateMap<ST,GO,tmap_t>("Cartesian2D", comm, GaleriList)};
auto GaleriProblem = Galeri::Xpetra::BuildProblem<ST,LO,GO,tmap_t,tcrsmatrix_t,MV>("Laplace2D", Map, GaleriList);
// Create matrix from problem
auto A = GaleriProblem->BuildMatrix();
// Create RHS using random solution vector
RCP<MV> B = rcp (new MV (Map, numrhs));
RCP<MV> X = rcp (new MV (Map, numrhs));
RCP<MV> Xexact = rcp (new MV (Map, numrhs));
MVT::MvRandom(*Xexact);
OPT::Apply(*A, *Xexact, *B );
// ********Other information used by block solver***********
// *****************(can be user specified)******************
const int numGlobalElements = B->getGlobalLength();
if (maxIters == -1)
maxIters = numGlobalElements/blockSize - 1; // maximum number of iterations to run
ParameterList belosList;
belosList.set( "Num Blocks", maxSubspace); // Maximum number of blocks in Krylov factorization
belosList.set( "Block Size", blockSize ); // BlockSize to be used by iterative solver
belosList.set( "Maximum Iterations", maxIters ); // Maximum number of iterations allowed
belosList.set( "Maximum Restarts", maxRestarts ); // Maximum number of restarts allowed
belosList.set( "Convergence Tolerance", tol ); // Relative convergence tolerance requested
int verbosity = Belos::Errors + Belos::Warnings;
if (verbose) {
if (frequency > 0)
belosList.set( "Output Frequency", frequency );
}
if (debug) {
verbosity += Belos::Debug;
}
belosList.set( "Verbosity", verbosity );
// Construct an unpreconditioned linear problem instance.
Belos::LinearProblem<ST,MV,OP> problem( A, X, B );
bool set = problem.setProblem();
if (set == false) {
if (procVerbose)
std::cout << std::endl << "ERROR: Belos::LinearProblem failed to set up correctly!" << std::endl;
return -1;
}
//
// *******************************************************************
// ****************Start the solver iteration*************************
// *******************************************************************
//
// Create a solver factory
// Create an iterative solver manager
std::string solverName = "Block GMRES";
RCP< Belos::SolverManager<double,MV,OP> > newSolver = factory.create (solverName, rcp(&belosList,false));
// Set the problem on the solver manager
newSolver->setProblem( rcp(&problem,false) );
// **********Print out information about problem*******************
if (procVerbose) {
std::cout << std::endl << std::endl;
std::cout << "Dimension of matrix: " << numGlobalElements << std::endl;
std::cout << "Number of right-hand sides: " << numrhs << std::endl;
std::cout << "Block size used by solver: " << blockSize << std::endl;
std::cout << "Max number of restarts allowed: " << maxRestarts << std::endl;
std::cout << "Max number of Gmres iterations per linear system: " << maxIters << std::endl;
std::cout << "Relative residual tolerance: " << tol << std::endl;
std::cout << std::endl;
}
// Perform solve
Belos::ReturnType ret = newSolver->solve();
// Get the number of iterations for this solve.
int numIters = newSolver->getNumIters();
if (procVerbose)
std::cout << "Number of iterations performed for this solve: " << numIters << std::endl;
// Compute actual residuals.
bool badRes = false;
std::vector<ST> actualResids( numrhs );
std::vector<ST> rhsNorm( numrhs );
MV resid(Map, numrhs);
OPT::Apply( *A, *X, resid );
MVT::MvAddMv( -1.0, resid, 1.0, *B, resid );
MVT::MvNorm( resid, actualResids );
MVT::MvNorm( *B, rhsNorm );
if (procVerbose) {
std::cout<< "---------- Actual Residuals (normalized) ----------"<<std::endl<<std::endl;
for ( int i=0; i<numrhs; i++) {
ST actRes = actualResids[i]/rhsNorm[i];
std::cout<<"Problem "<<i<<" : \t"<< actRes <<std::endl;
if (actRes > tol) badRes = true;
}
}
if (ret!=Belos::Converged || badRes) {
success = false;
if (procVerbose)
std::cout << "End Result: TEST FAILED" << std::endl;
} else {
if (procVerbose)
std::cout << "End Result: TEST PASSED" << std::endl;
}
}
TEUCHOS_STANDARD_CATCH_STATEMENTS(verbose, std::cerr, success);
return success ? EXIT_SUCCESS : EXIT_FAILURE;
}
int main(int argc, char *argv[]) {
// run with different ST
return run<double>(argc,argv);
// run<float>(argc,argv); // FAILS
}

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