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epetra/example/SolverFactory/SolverFactoryEpetraGaleriEx.cpp

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

// @HEADER
// *****************************************************************************
// Belos: Block Linear Solvers Package
//
// Copyright 2004-2016 NTESS and the Belos contributors.
// SPDX-License-Identifier: BSD-3-Clause
// *****************************************************************************
// @HEADER
#include "BelosEpetraAdapter.hpp"
#include "Epetra_CrsMatrix.h"
#include "Epetra_MultiVector.h"
// The Trilinos package Galeri has many example problems.
#include "Galeri_Maps.h"
#include "Galeri_CrsMatrices.h"
#include <Teuchos_oblackholestream.hpp>
#include <Teuchos_StandardCatchMacros.hpp>
// Include selected communicator class required by Epetra objects
#ifdef EPETRA_MPI
# include "Epetra_MpiComm.h"
#else
# include "Epetra_SerialComm.h"
#endif // EPETRA_MPI
// ****************************************************************************
// BEGIN MAIN ROUTINE
// ****************************************************************************
int
main (int argc, char *argv[])
{
int MyPID = 0;
// 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 Epetra_CrsMatrix) is an example
// of an operator; an Ifpack preconditioner is another example.
//
// Here, Scalar is double, MV is Epetra_MultiVector, and OP is
// Epetra_Operator.
typedef double ST;
typedef SCT::magnitudeType MT;
typedef Epetra_MultiVector MV;
typedef Epetra_Operator OP;
using Teuchos::RCP;
using Teuchos::rcp;
#ifdef EPETRA_MPI
MPI_Init (&argc, &argv);
Epetra_MpiComm Comm (MPI_COMM_WORLD);
#else
#endif // EPETRA_MPI
bool verbose = false;
bool success = true;
try {
bool proc_verbose = 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 solver.");
cmdp.setOption("num-rhs",&numrhs,"Number of right-hand sides to be solved for.");
cmdp.setOption("block-size",&blocksize,"Block size used by solver.");
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 solver.");
cmdp.setOption("nx",&nx,"Number of discretization points in each direction of 2D Laplacian.");
return -1;
}
if (!verbose)
frequency = -1; // reset frequency if test is not verbose
//
// 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);
RCP<Epetra_Map> Map = rcp (Galeri::CreateMap ("Linear", Comm, GaleriList));
RCP<Epetra_RowMatrix> A =
rcp (Galeri::CreateCrsMatrix ("Laplace2D", &*Map, GaleriList));
proc_verbose = verbose && (MyPID==0); /* Only print on the zero processor */
// 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));
Xexact->Random ();
A->Apply( *Xexact, *B );
//
// ********Other information used by block solver***********
// *****************(can be user specified)******************
//
const int NumGlobalElements = B->GlobalLength();
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.
//
bool set = problem.setProblem();
if (set == false) {
if (proc_verbose)
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 (proc_verbose) {
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 (proc_verbose)
std::cout << "Number of iterations performed for this solve: " << numIters << std::endl;
//
// Compute actual residuals.
//
bool badRes = false;
std::vector<double> actual_resids( numrhs );
std::vector<double> rhs_norm( numrhs );
Epetra_MultiVector resid(*Map, numrhs);
OPT::Apply( *A, *X, resid );
MVT::MvAddMv( -1.0, resid, 1.0, *B, resid );
MVT::MvNorm( resid, actual_resids );
MVT::MvNorm( *B, rhs_norm );
if (proc_verbose) {
std::cout<< "---------- Actual Residuals (normalized) ----------"<<std::endl<<std::endl;
for ( int i=0; i<numrhs; i++) {
double actRes = actual_resids[i]/rhs_norm[i];
std::cout<<"Problem "<<i<<" : \t"<< actRes <<std::endl;
if (actRes > tol) badRes = true;
}
}
if (ret!=Belos::Converged || badRes) {
success = false;
if (proc_verbose)
std::cout << "End Result: TEST FAILED" << std::endl;
} else {
if (proc_verbose)
std::cout << "End Result: TEST PASSED" << std::endl;
}
}
TEUCHOS_STANDARD_CATCH_STATEMENTS(verbose, std::cerr, success);
#ifdef EPETRA_MPI
MPI_Finalize();
#endif
return success ? EXIT_SUCCESS : EXIT_FAILURE;
}

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