epetra/example/BlockGmres/BlockFlexGmresEpetraExFile.cpp

This is an example of how to use the Belos::BlockGmresSolMgr solver manager with flexible Gmres.

This is an example of how to use the Belos::BlockGmresSolMgr solver manager with flexible Gmres.

// @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.  An ILU preconditioner
// is constructed using the Ifpack factory.
//
#include "BelosConfigDefs.hpp"
#include "BelosLinearProblem.hpp"
#include "BelosEpetraAdapter.hpp"
#include "BelosBlockGmresSolMgr.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_CommandLineProcessor.hpp"
#include "Teuchos_ParameterList.hpp"
#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
  Epetra_SerialComm Comm;
#endif
  //
  typedef double                            ST;
  typedef Teuchos::ScalarTraits<ST>        SCT;
  typedef SCT::magnitudeType                MT;
  typedef Epetra_MultiVector                MV;
  typedef Epetra_Operator                   OP;
  typedef Belos::MultiVecTraits<ST,MV>     MVT;
  typedef Belos::OperatorTraits<ST,MV,OP>  OPT;
 
  using Teuchos::ParameterList;
  using Teuchos::RCP;
  using Teuchos::rcp;
 
  bool success = false;
  bool verbose = false;
  try {
    bool proc_verbose = 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 maxrestarts = 15;      // maximum number of restarts allowed
    int maxiters = -1;         // maximum number of iterations allowed per linear system
    int maxsubspace = 25;      // maximum number of blocks the solver can use for the subspace
    std::string filename("orsirr1.hb");
    MT tol = 1.0e-5;           // relative residual tolerance
 
    // Specify whether to use RHS as initial guess. If false, use zero.
    bool useRHSAsInitialGuess = false;
 
    Teuchos::CommandLineProcessor cmdp(false,true);
    cmdp.setOption("verbose","quiet",&verbose,"Print messages and results.");
    cmdp.setOption("use-rhs","use-zero",&useRHSAsInitialGuess,"Use RHS as initial guess.");
    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 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.");
    if (cmdp.parse(argc,argv) != Teuchos::CommandLineProcessor::PARSE_SUCCESSFUL) {
      return EXIT_FAILURE;
    }
 
    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);
    }
 
    // If requested, use a copy of B as initial guess
    if (useRHSAsInitialGuess)
    {
      X->Update(1.0, *B, 0.0);
    }
 
    //
    // ************Construct preconditioner*************
    //
    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().
    RCP<Belos::EpetraPrecOp> belosPrec = rcp( new Belos::EpetraPrecOp( Prec ) );
 
    //
    // *****Create parameter list for the block GMRES solver manager*****
    //
    const int NumGlobalElements = B->GlobalLength();
    if (maxiters == -1)
      maxiters = NumGlobalElements/blocksize - 1; // maximum number of iterations to run
    //
    ParameterList belosList;
    belosList.set( "Flexible Gmres", true );               // Flexible Gmres will be used to solve this problem
    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
    if (numrhs > 1) {
      belosList.set( "Show Maximum Residual Norm Only", true );  // Show only the maximum residual norm
    }
    if (verbose) {
      belosList.set( "Verbosity", Belos::Errors + Belos::Warnings +
          Belos::TimingDetails + Belos::StatusTestDetails );
      if (frequency > 0)
        belosList.set( "Output Frequency", frequency );
    }
    else
      belosList.set( "Verbosity", Belos::Errors + Belos::Warnings );
    //
    // *******Construct a preconditioned linear problem********
    //
    RCP<Belos::LinearProblem<double,MV,OP> > problem
      = rcp( new Belos::LinearProblem<double,MV,OP>( A, X, B ) );
    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 EXIT_FAILURE;
    }
 
    // Create an iterative solver manager.
    RCP< Belos::SolverManager<double,MV,OP> > solver
      = rcp( new Belos::BlockGmresSolMgr<double,MV,OP>(problem, rcp(&belosList,false)));
 
    //
    // *******************************************************************
    // *************Start the block Gmres iteration*************************
    // *******************************************************************
    //
    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 << "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 = solver->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;
      }
    }
 
    success = ret==Belos::Converged && !badRes;
    if (success) {
      if (proc_verbose)
        std::cout << "End Result: TEST PASSED" << std::endl;
    } else {
      if (proc_verbose)
        std::cout << "End Result: TEST FAILED" << std::endl;
    }
  }
  TEUCHOS_STANDARD_CATCH_STATEMENTS(verbose, std::cerr, success);
 
#ifdef EPETRA_MPI
  MPI_Finalize();
#endif
 
  return ( success ? EXIT_SUCCESS : EXIT_FAILURE );
}