IFPACK Development
Ex_AmesosPrec
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//       Ifpack: Object-Oriented Algebraic Preconditioner Package
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#include "Ifpack_ConfigDefs.h"

#ifdef HAVE_MPI
#include "Epetra_MpiComm.h"
#else
#include "Epetra_SerialComm.h"
#endif
#include "Epetra_CrsMatrix.h"
#include "Epetra_MultiVector.h"
#include "Epetra_Map.h"
#include "Epetra_BlockMap.h"
#include "Epetra_LinearProblem.h"
#include "Galeri_Maps.h"
#include "Galeri_CrsMatrices.h"
#include "Teuchos_ParameterList.hpp"
#include "Teuchos_RefCountPtr.hpp"
#include "AztecOO.h"
#include "Ifpack.h"

int main(int argc, char *argv[])
{

// initialize MPI and Epetra communicator
#ifdef HAVE_MPI
MPI_Init(&argc,&argv);
Epetra_MpiComm Comm( MPI_COMM_WORLD );
#else
Epetra_SerialComm Comm;
#endif

Teuchos::ParameterList GaleriList;

// The problem is defined on a 2D grid, global size is nx * nx.
int nx = 30;
GaleriList.set("nx", nx);
GaleriList.set("ny", nx * Comm.NumProc());
GaleriList.set("mx", 1);
GaleriList.set("my", Comm.NumProc());
Teuchos::RefCountPtr<Epetra_Map> Map = Teuchos::rcp( Galeri::CreateMap("Cartesian2D", Comm, GaleriList) );
Teuchos::RefCountPtr<Epetra_RowMatrix> A = Teuchos::rcp( Galeri::CreateCrsMatrix("Laplace2D", &*Map, GaleriList) );

// =============================================================== //
// B E G I N N I N G   O F   I F P A C K   C O N S T R U C T I O N //
// =============================================================== //

Teuchos::ParameterList List;

// 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
string PrecType = "Amesos";
int OverlapLevel = 2; // must be >= 0. If Comm.NumProc() == 1,
// it is ignored.

Teuchos::RefCountPtr<Ifpack_Preconditioner> Prec = Teuchos::rcp( Factory.Create(PrecType, &*A, OverlapLevel) );
assert(Prec != Teuchos::null);

// specify the Amesos solver to be used.
// If the selected solver is not available,
// IFPACK will try to use Amesos' KLU (which is usually always
// compiled). Amesos' serial solvers are:
// "Amesos_Klu", "Amesos_Umfpack", "Amesos_Superlu"
List.set("amesos: solver type", "Amesos_Klu");

// sets the parameters
IFPACK_CHK_ERR(Prec->SetParameters(List));

// initialize the preconditioner. At this point the matrix must
// have been FillComplete()'d, but actual values are ignored.
// At this call, Amesos will perform the symbolic factorization.
IFPACK_CHK_ERR(Prec->Initialize());

// Builds the preconditioners, by looking for the values of
// the matrix. At this call, Amesos will perform the
// numeric factorization.
IFPACK_CHK_ERR(Prec->Compute());

// =================================================== //
// E N D   O F   I F P A C K   C O N S T R U C T I O N //
// =================================================== //

// At this point, we need some additional objects
// to define and solve the linear system.

// defines LHS and RHS
Epetra_Vector LHS(A->OperatorDomainMap());
Epetra_Vector RHS(A->OperatorDomainMap());

// solution is constant
LHS.PutScalar(1.0);
// now build corresponding RHS
A->Apply(LHS,RHS);

// now randomize the solution
RHS.Random();

// need an Epetra_LinearProblem to define AztecOO solver
Epetra_LinearProblem Problem(&*A,&LHS,&RHS);

// now we can allocate the AztecOO solver
AztecOO Solver(Problem);

// specify solver
Solver.SetAztecOption(AZ_solver,AZ_gmres);
Solver.SetAztecOption(AZ_output,32);

// HERE WE SET THE IFPACK PRECONDITIONER
Solver.SetPrecOperator(&*Prec);

// .. and here we solve
// NOTE: with one process, the solver must converge in
// one iteration.
Solver.Iterate(1550,1e-8);

#ifdef HAVE_MPI
MPI_Finalize() ;
#endif

return(EXIT_SUCCESS);
}