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epetra/example/BlockGmres/BlockGmresPolyEpetraExFile.cpp

This is an example of how to use the Belos::GmresPolySolMgr with 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 file, which can be in Harwell-Boeing (*.hb),
// Matrix Market (*.mtx), or triplet format (*.triU, *.triS). The right-hand side
// from the problem, if it exists, will be used instead of multiple
// random right-hand-sides. The initial guesses are all set to zero.
//
// NOTE: No preconditioner is used in this example.
//
#include "BelosEpetraAdapter.hpp"
#include "EpetraExt_readEpetraLinearSystem.h"
#include "Epetra_Map.h"
#ifdef EPETRA_MPI
#include "Epetra_MpiComm.h"
#else
#include "Epetra_SerialComm.h"
#endif
#include "Epetra_CrsMatrix.h"
#include "Ifpack.h"
#include "Teuchos_StandardCatchMacros.hpp"
int main(int argc, char *argv[]) {
//
int MyPID = 0;
#ifdef EPETRA_MPI
// Initialize MPI
MPI_Init(&argc,&argv);
Epetra_MpiComm Comm(MPI_COMM_WORLD);
MyPID = Comm.MyPID();
#else
#endif
//
typedef double ST;
typedef SCT::magnitudeType MT;
typedef Epetra_MultiVector MV;
typedef Epetra_Operator OP;
using Teuchos::RCP;
using Teuchos::rcp;
bool verbose = false;
bool success = true;
try {
bool proc_verbose = false;
bool debug = false;
bool userandomrhs = true;
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 maxdegree = 25; // maximum degree of polynomial
int maxsubspace = 50; // maximum number of blocks the solver can use for the subspace
int maxrestarts = 15; // number of restarts allowed
std::string outersolver("Block Gmres");
std::string polytype("Arnoldi");
std::string filename("orsirr1.hb");
std::string precond("right");
MT tol = 1.0e-5; // relative residual tolerance
MT polytol = tol/10; // relative residual tolerance for polynomial construction
cmdp.setOption("verbose","quiet",&verbose,"Print messages and results.");
cmdp.setOption("debug","nondebug",&debug,"Print debugging information from solver.");
cmdp.setOption("use-random-rhs","use-rhs",&userandomrhs,"Use linear system RHS or random RHS to generate polynomial.");
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("outersolver",&outersolver,"Name of outer solver to be used with GMRES poly");
cmdp.setOption("poly-type",&polytype,"Name of the polynomial to be generated.");
cmdp.setOption("precond",&precond,"Preconditioning type (none, left, right).");
cmdp.setOption("tol",&tol,"Relative residual tolerance used by GMRES solver.");
cmdp.setOption("poly-tol",&polytol,"Relative residual tolerance used to construct the GMRES polynomial.");
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-degree",&maxdegree,"Maximum degree of the GMRES polynomial.");
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.");
return -1;
}
if (!verbose)
frequency = -1; // reset frequency if test is not verbose
//
// Get the problem
//
RCP<Epetra_Map> Map;
RCP<Epetra_CrsMatrix> A;
RCP<Epetra_MultiVector> B, X;
RCP<Epetra_Vector> vecB, vecX;
EpetraExt::readEpetraLinearSystem(filename, Comm, &A, &Map, &vecX, &vecB);
A->OptimizeStorage();
proc_verbose = verbose && (MyPID==0); /* Only print on the zero processor */
// Check to see if the number of right-hand sides is the same as requested.
if (numrhs>1) {
X = rcp( new Epetra_MultiVector( *Map, numrhs ) );
B = rcp( new Epetra_MultiVector( *Map, numrhs ) );
X->Random();
OPT::Apply( *A, *X, *B );
X->PutScalar( 0.0 );
}
else {
X = Teuchos::rcp_implicit_cast<Epetra_MultiVector>(vecX);
B = Teuchos::rcp_implicit_cast<Epetra_MultiVector>(vecB);
}
//
// ************Construct preconditioner*************
//
RCP<Belos::EpetraPrecOp> belosPrec;
if (precond != "none") {
ParameterList ifpackList;
// allocates an IFPACK factory. No data is associated
// to this object (only method Create()).
Ifpack Factory;
// create the preconditioner. For valid PrecType values,
// please check the documentation
std::string PrecType = "ILU"; // incomplete LU
int OverlapLevel = 1; // must be >= 0. If Comm.NumProc() == 1,
// it is ignored.
RCP<Ifpack_Preconditioner> Prec = Teuchos::rcp( Factory.Create(PrecType, &*A, OverlapLevel) );
assert(Prec != Teuchos::null);
// specify parameters for ILU
ifpackList.set("fact: level-of-fill", 1);
// the combine mode is on the following:
// "Add", "Zero", "Insert", "InsertAdd", "Average", "AbsMax"
// Their meaning is as defined in file Epetra_CombineMode.h
ifpackList.set("schwarz: combine mode", "Add");
// sets the parameters
IFPACK_CHK_ERR(Prec->SetParameters(ifpackList));
// initialize the preconditioner. At this point the matrix must
// have been FillComplete()'d, but actual values are ignored.
IFPACK_CHK_ERR(Prec->Initialize());
// Builds the preconditioners, by looking for the values of
// the matrix.
IFPACK_CHK_ERR(Prec->Compute());
// Create the Belos preconditioned operator from the Ifpack preconditioner.
// NOTE: This is necessary because Belos expects an operator to apply the
// preconditioner with Apply() NOT ApplyInverse().
belosPrec = rcp( new Belos::EpetraPrecOp( Prec ) );
}
//
// ********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 );
ParameterList polyList;
polyList.set( "Polynomial Type", polytype ); // Type of polynomial to be generated
polyList.set( "Maximum Degree", maxdegree ); // Maximum degree of the GMRES polynomial
polyList.set( "Polynomial Tolerance", polytol ); // Polynomial convergence tolerance requested
polyList.set( "Verbosity", verbosity ); // Verbosity for polynomial construction
polyList.set( "Random RHS", userandomrhs ); // Use RHS from linear system or random vector
if ( outersolver != "" ) {
polyList.set( "Outer Solver", outersolver );
polyList.set( "Outer Solver Params", belosList );
}
//
// Construct an unpreconditioned linear problem instance.
//
problem.setInitResVec( B );
if (precond == "left") {
problem.setLeftPrec( belosPrec );
}
if (precond == "right") {
problem.setRightPrec( belosPrec );
}
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 block Gmres iteration*************************
// *******************************************************************
//
// Create an iterative solver manager.
RCP< Belos::SolverManager<double,MV,OP> > newSolver
= rcp( new Belos::GmresPolySolMgr<double,MV,OP>(rcp(&problem,false), rcp(&polyList,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 restart cycle: " << maxiters << 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(*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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