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epetra/example/RCG/RCGEpetraExFile.cpp

This is an example of how to use the Belos::RCGSolMgr solver manager in Epetra.

// @HEADER
// *****************************************************************************
// Belos: Block Linear Solvers Package
//
// Copyright 2004-2016 NTESS and the Belos contributors.
// SPDX-License-Identifier: BSD-3-Clause
// *****************************************************************************
// @HEADER
//
// This driver reads a problem from a Harwell-Boeing (HB) file.
// The right-hand-side from the HB file is used instead of random vectors.
// The initial guesses are all set to zero.
//
// NOTE: No preconditioner is used in this case.
//
#include "BelosEpetraAdapter.hpp"
#include "BelosEpetraUtils.h"
#include "Trilinos_Util.h"
#include "Epetra_CrsMatrix.h"
#include "Epetra_Map.h"
#include "Teuchos_StandardCatchMacros.hpp"
int main(int argc, char *argv[]) {
//
#ifdef EPETRA_MPI
// Initialize MPI
MPI_Init(&argc,&argv);
#endif
bool verbose = true;
bool success = true;
try {
//
using Teuchos::RCP;
using Teuchos::rcp;
//
// Get test parameters from command-line processor
//
bool proc_verbose = false;
int frequency = -1; // frequency of status test output.
std::string filename("bcsstk14.hb"); // default input filename
double tol = 1.0e-6; // relative residual tolerance
int numBlocks = 100; // maximum number of blocks the solver can use for the Krylov subspace
int recycleBlocks = 10; // maximum number of blocks the solver can use for the recycle space
int numrhs = 2; // number of right-hand sides to solve for
int maxiters = 4000; // maximum number of iterations allowed per linear system
cmdp.setOption("verbose","quiet",&verbose,"Print messages and results.");
cmdp.setOption("frequency",&frequency,"Solvers frequency for printing residuals (#iters).");
cmdp.setOption("filename",&filename,"Filename for test matrix.");
cmdp.setOption("tol",&tol,"Relative residual tolerance used by the RCG solver.");
cmdp.setOption("max-subspace",&numBlocks,"Maximum number of vectors in search space (not including recycle space).");
cmdp.setOption("recycle",&recycleBlocks,"Number of vectors in recycle space.");
cmdp.setOption("num-rhs",&numrhs,"Number of right-hand sides to be solved for.");
cmdp.setOption("max-iters",&maxiters,"Maximum number of iterations per linear system (-1 = adapted to problem/block size).");
return -1;
}
if (!verbose)
frequency = -1; // reset frequency if test is not verbose
//
// Get the problem
//
int MyPID;
RCP<Epetra_CrsMatrix> A;
RCP<Epetra_MultiVector> B, X;
int return_val =Belos::Util::createEpetraProblem(filename,NULL,&A,&B,&X,&MyPID);
if(return_val != 0) return return_val;
proc_verbose = ( verbose && (MyPID==0) );
//
// Solve using Belos
//
typedef double ST;
typedef Epetra_Operator OP;
typedef Epetra_MultiVector MV;
//
// *****Construct initial guess and right-hand sides *****
//
if (numrhs != 1) {
X = rcp( new Epetra_MultiVector( A->Map(), numrhs ) );
MVT::MvInit( *X, 1.0 );
B = rcp( new Epetra_MultiVector( A->Map(), numrhs ) );
OPT::Apply( *A, *X, *B );
MVT::MvInit( *X, 0.0 );
}
else { // initialize exact solution to be vector of ones
MVT::MvInit( *X, 1.0 );
OPT::Apply( *A, *X, *B );
MVT::MvInit( *X, 0.0 );
}
//
// ********Other information used by block solver***********
// *****************(can be user specified)******************
//
const int NumGlobalElements = B->GlobalLength();
if (maxiters == -1)
maxiters = NumGlobalElements - 1; // maximum number of iterations to run
//
ParameterList belosList;
belosList.set( "Maximum Iterations", maxiters ); // Maximum number of iterations allowed
belosList.set( "Num Blocks", numBlocks); // Maximum number of blocks in Krylov space
belosList.set( "Num Recycled Blocks", recycleBlocks ); // Number of vectors in recycle space
belosList.set( "Convergence Tolerance", tol ); // Relative convergence tolerance requested
if (verbose) {
belosList.set( "Verbosity", Belos::Errors + Belos::Warnings +
if (frequency > 0)
belosList.set( "Output Frequency", frequency );
}
else
belosList.set( "Verbosity", Belos::Errors + Belos::Warnings );
//
// 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;
}
//
// Create an iterative solver manager.
//
RCP< Belos::SolverManager<double,MV,OP> > newSolver
= rcp( new Belos::RCGSolMgr<double,MV,OP>(rcp(&problem,false), rcp(&belosList,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 << "Max number of RCG iterations: " << maxiters << std::endl;
std::cout << "Max number of vectors in Krylov space: " << numBlocks << std::endl;
std::cout << "Number of vectors in recycle space: " << recycleBlocks << std::endl;
std::cout << "Relative residual tolerance: " << tol << std::endl;
std::cout << std::endl;
}
//
// Perform solve
//
Belos::ReturnType ret = newSolver->solve();
//
// Compute actual residuals.
//
bool badRes = false;
std::vector<double> actual_resids( numrhs );
std::vector<double> rhs_norm( numrhs );
Epetra_MultiVector resid(A->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 << std::endl << "ERROR: Belos did not converge!" << std::endl;
}
else {
success = true;
if (proc_verbose)
std::cout << std::endl << "SUCCESS: Belos converged!" << 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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