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tpetra/example/BlockCG/BlockCGTpetraExFile.cpp

This is an example of how to use the Belos::BlockCGSolMgr solver manager in Tpetra.

// @HEADER
// *****************************************************************************
// Belos: Block Linear Solvers Package
//
// Copyright 2004-2016 NTESS and the Belos contributors.
// SPDX-License-Identifier: BSD-3-Clause
// *****************************************************************************
// @HEADER
//
// Update of belos/epetra/example/BlockCG/BlockCGEpetraExFile.cpp
//
// This driver reads a problem from a Harwell-Boeing (HB) file.
// The right-hand-side corresponds to a randomly generated solution.
// The initial guesses are all set to zero.
//
// NOTE: No preconditioner is used in this example.
//
// Tpetra
#include <Tpetra_Map.hpp>
#include <Tpetra_Core.hpp>
#include <Tpetra_Vector.hpp>
#include <Tpetra_CrsMatrix.hpp>
// I/O for Harwell-Boeing files
#define HIDE_TPETRA_INOUT_IMPLEMENTATIONS
#include <Tpetra_MatrixIO.hpp>
// Teuchos
#include <Teuchos_RCP.hpp>
#include <Teuchos_Comm.hpp>
#include <Teuchos_CommHelpers.hpp>
#include <Teuchos_DefaultComm.hpp>
#include "Teuchos_StandardCatchMacros.hpp"
// Belos
#include "BelosTpetraAdapter.hpp"
template <typename ScalarType>
int run(int argc, char *argv[]) {
using ST = typename Tpetra::Vector<ScalarType>::scalar_type;
using LO = typename Tpetra::Vector<>::local_ordinal_type;
using GO = typename Tpetra::Vector<>::global_ordinal_type;
using NT = typename Tpetra::Vector<>::node_type;
using SCT = typename Teuchos::ScalarTraits<ST>;
using MT = typename SCT::magnitudeType;
using MV = typename Tpetra::MultiVector<ST,LO,GO,NT>;
using OP = typename Tpetra::Operator<ST,LO,GO,NT>;
using tmap_t = Tpetra::Map<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;
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
std::string filename("bcsstk14.hb");
MT tol = 1.0e-5; // relative residual tolerance
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. Acceptable file extensions: *.hb,*.mtx,*.triU,*.triS");
cmdp.setOption("tol",&tol,"Relative residual tolerance used by CG solver.");
cmdp.setOption("num-rhs",&numrhs,"Number of right-hand sides to be solved for.");
cmdp.setOption("block-size",&blockSize,"Block size used by CG.");
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
procVerbose = verbose && (MyPID==0); /* Only print on the zero processor */
// Get the problem
RCP<tcrsmatrix_t> A;
Tpetra::Utils::readHBMatrix(filename,Comm,A);
RCP<const tmap_t> Map = A->getDomainMap();
// Create initial vectors
RCP<MV> B, X;
X = rcp( new MV(Map,numrhs) );
MVT::MvRandom( *X );
B = rcp( new MV(Map,numrhs) );
OPT::Apply( *A, *X, *B );
MVT::MvInit( *X, 0.0 );
// ********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( "Block Size", blockSize ); // BlockSize to be used by iterative solver
belosList.set( "Maximum Iterations", maxIters ); // Maximum number of iterations allowed
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.
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;
}
// Create an iterative solver manager.
RCP< Belos::BlockCGSolMgr<ST,MV,OP> > newSolver
= rcp( new Belos::BlockCGSolMgr<ST,MV,OP>(rcp(&problem,false), rcp(&belosList,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 << "Max number of iterations allowed: " << maxIters << std::endl;
std::cout << "Block size used by solver: " << blockSize << 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 << std::endl << "ERROR: Belos did not converge!" << std::endl;
} else {
success = true;
if (procVerbose)
std::cout << std::endl << "SUCCESS: Belos converged!" << 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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