[Trilinos-Users] exited on signal 11 (Segmentation fault) of example code

[Kar, Debashis *]

Hi Chen,

Probably it ran out of memory - 5000 squared is a pretty large chunk of memory to assign at one go. Maybe using a dynamic memory allocation instead would be advisable.

Best regards
Debashis

-----Original Message-----
From: trilinos-users-bounces at software.sandia.gov [mailto:trilinos-users-bounces at software.sandia.gov] On Behalf Of chenliang wang
Sent: Saturday, August 04, 2012 3:27 AM
To: trilinos-users at software.sandia.gov
Subject: [Trilinos-Users] exited on signal 11 (Segmentation fault) of example code

Hi,
I copy the example code from "Solve a linear system _Ax=b_ using Ifpack and AztecOO" ,change the nx to 5000. I run it on single node or multiple nodes and got the error signal "exited on signal 11 (Segmentation fault)". I reduced nx to 4000, it complained the method was broken down.
I reduced nx to 2000 or even more smaller , it worked perfectly .

Chen-Liang Wang

***********************************************************************************************************************************************************************************************************************************************************************
//the example code:
#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_LinearProblem.h"
#include "Galeri_Maps.h"
#include "Galeri_CrsMatrices.h"
#include "Teuchos_ParameterList.hpp"
#include "Teuchos_RCP.hpp"
#include "AztecOO.h"
#include "Ifpack.h"
#include "Ifpack_AdditiveSchwarz.h"

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

#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 = 5000;// 5000: Segmentation fault, 4000: broken down 2000:
worked perfectly
GaleriList.set("n", nx * nx);
GaleriList.set("nx", nx);
GaleriList.set("ny", nx);
Teuchos::RCP<Epetra_Map> Map = Teuchos::rcp( Galeri::CreateMap("Linear", Comm, GaleriList) ); Teuchos::RCP<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 = "ILU"; // incomplete LU int OverlapLevel = 1; // must be >= 0. If Comm.NumProc() == 1, // it is ignored.

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

// specify parameters for ILU
List.set("fact: drop tolerance", 1e-9);
List.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
List.set("schwarz: combine mode", "Add"); // 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.
IFPACK_CHK_ERR(Prec->Initialize());

// Builds the preconditioners, by looking for the values of // the matrix.
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
Solver.Iterate(1550,1e-8);

std::cout << *Prec;

#ifdef HAVE_MPI
MPI_Finalize() ;
#endif

return(EXIT_SUCCESS);
}


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