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 "BelosConfigDefs.hpp"
#include "BelosLinearProblem.hpp"
#include "BelosEpetraAdapter.hpp"
#include "BelosGmresPolySolMgr.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 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

    Teuchos::CommandLineProcessor cmdp(false,true);
    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.");
    if (cmdp.parse(argc,argv) != Teuchos::CommandLineProcessor::PARSE_SUCCESSFUL) {
      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) {
      verbosity += Belos::FinalSummary + Belos::TimingDetails + Belos::StatusTestDetails;
      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.
    //
    Belos::LinearProblem<double,MV,OP> problem( A, X, B );
    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;
}