[Trilinos-Users] Memory leak inside Ifpack_IC::Compute()?

[Rony Speck]

Hi there

I'm doing my master thesis at the ETH in Zurich.

I'm using the Ifpack_IC preconditioner in a time-dependent setting. Within a time increment, 
multiple linear systems of equations are solved which all have the same matrix structure (only
the numerical values change). I therefore create an Ifpack_IC object at the beginning of the
increment and keep it throughout the whole increment and only call Ifpack_IC::Compute().
After the increment is done, I delete the object and create a new one for the next increment. 
I now noticed that a lot of memory is used this way. When I delete the preconditioner after 
each single system is solved (not keeping it for a whole increment), the memory usage is normal. 
So it seems, that multiple calls to Ifpack_IC::Compute() leeds to a memory leak. The code below 
shows the problem in a simpler setting. The code just creates a 2D Laplace problem with the help of
the matrix gallery. CG inside AztecOO is used together with the Ifpack_IC preconditioner. Compute() 
is called twice on the Ifpack_IC object to simulate my setting.

#include "AztecOO_config.h"
#ifdef HAVE_MPI
#include "mpi.h"
#include "Epetra_MpiComm.h"
#else
#include "Epetra_SerialComm.h"
#endif
#include "Epetra_Map.h"
#include "Epetra_Vector.h"
#include "Epetra_CrsMatrix.h"
#include "AztecOO.h"
#include "Trilinos_Util_CrsMatrixGallery.h"
#include "Ifpack_IC.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
	
	// Create matrix and vectors	
	int problemSize = 10000;
	Trilinos_Util::CrsMatrixGallery gallery("laplace_2d", comm);
	gallery.Set("problem_size", problemSize);
	gallery.Set("map_type", "linear");
	gallery.Set("exact_solution", "random");
	
	Epetra_CrsMatrix *A = gallery.GetMatrix();
	Epetra_Vector *b = (Epetra_Vector*) gallery.GetRHS();
	Epetra_Vector *x = (Epetra_Vector*) gallery.GetStartingSolution();
	
	// Create linear problem
	Epetra_LinearProblem problem(A, x, b);	
	
	// Create preconditioner		
	Ifpack_IC *M = new Ifpack_IC(A);
	Teuchos::ParameterList ifpackList;
	int k = 2;
	double alpha = 0.0;
	double rho = 1.0;
	double droptol = 0.0;
	ifpackList.set("fact: level-of-fill", k);
	ifpackList.set("fact: absolute threshold", alpha);
	ifpackList.set("fact: relative threshold", rho);
	ifpackList.set("fact: drop tolerance", droptol);
	M->SetParameters(ifpackList);
        M->Compute();
	M->Compute();				
	
	// Create solver object
	AztecOO solver(problem);
	solver.SetPrecOperator(M);
	Teuchos::ParameterList aztecList;
	aztecList.set("AZ_conv", AZ_rhs);
	aztecList.set("AZ_solver", AZ_cg);
	aztecList.set("AZ_output", AZ_all);
	solver.SetParameters(aztecList, true);
		
	// Solve		
	solver.Iterate(10000, 0.001);		
	
	// Free memory
	delete M;		
			
	#ifdef HAVE_MPI
		MPI_Finalize() ;
	#endif	
}

When running this code with valgrind --leak-check=full, it says that 360,004 bytes are definitely lost.
If Compute() is called only once, nothing is lost. According to valgrind, the source of the problem seems
to be Ifpack_AIJMatrix_alloc inside crout_ict.

Best regards
Rony Speck


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