[petsc-users] PCSETUP_FAILED due to FACTOR_NUMERIC_ZEROPIVOT

[lixin chu]

Hello,
trying my first PETSc program, some matrices ok, but this one showing error:
Linear solve did not converge due to DIVERGED_PCSETUP_FAILED iterations 0               PCSETUP_FAILED due to FACTOR_NUMERIC_ZEROPIVOT
Not sure what I can try (I tried PC and GMRES, both no good) ?

/* * Matrix A *   1  0  0  1  1  1 *   0  1  1  1  0  1 *   1  0  0  0  1  1 *   0  0 -1  0  1  1 *   1  1  0  1  1  1 *   0  1  1  1  0  0 * * Expected inverse result *  0  0  0  -1  1  -1 * -1  0  0   0  1   0 *  0  0  1   0 -1   1 *  1  0 -1   0  0   0 *  0 -1  1   1 -1   2 *  0  1  0   0  0  -1 * */
Here is my code:
 Vec            x,b;          Mat            A;             KSP           solver;           PC             pc;                 
 PetscMPIInt    size;
 int mpi_rank; bool is_mpi_root = FALSE;
 /*  *  initialize PETSc and MPI  */ PetscInitialize ( &argc, &argv, (char*)0, USAGE);

 int col_index [6][6] = { {0, 1, 2, 3, 4, 5}, {0, 1, 2, 3, 4, 5}, {0, 1, 2, 3, 4, 5}, {0, 1, 2, 3, 4, 5}, {0, 1, 2, 3, 4, 5}, {0, 1, 2, 3, 4, 5} };
 double v [6][6] = { {1., 0.,  0., 1., 1., 1.}, {0., 1.,  1., 1., 0., 1.}, {1., 0.,  0., 0., 1., 1.}, {0., 0., -1., 0., 1., 1.}, {1., 1.,  0., 1., 1., 1.}, {0., 1.,  1., 1., 0., 0.} };
 int nz_rows [] = {6, 6, 6, 6, 6, 6};
 int N = 6;
 int row, col; double value = 1.;
 int m, n;
 int b_start, b_end;
 // create x VecCreate ( PETSC_COMM_WORLD, &x ); VecSetSizes ( x, PETSC_DECIDE, N ); VecSetType ( x, VECMPI );

 // create b VecCreate ( PETSC_COMM_WORLD, &b ); VecSetSizes ( b, PETSC_DECIDE, N ); VecSetType ( b, VECMPI );

 // create A
 MatCreate ( PETSC_COMM_WORLD, &A ); MatSetSizes ( A, PETSC_DECIDE, PETSC_DECIDE, N, N );
 MatSetUp ( A );
 for ( row = 0; row < N; row++ ) {
 MatSetValues ( A, 1, &row, nz_rows[row], col_index[row], v[row], INSERT_VALUES ); } MatAssemblyBegin ( A, MAT_FINAL_ASSEMBLY ) ;
 MatAssemblyEnd ( A, MAT_FINAL_ASSEMBLY ) ;
 MatView ( A, PETSC_VIEWER_STDOUT_WORLD );

 /*  * setting up KSP  */ KSPCreate ( PETSC_COMM_WORLD, &solver ); KSPSetOperators ( solver, A, A ); // KSPSetType ( solver, KSPCG ); KSPSetType ( solver, KSPGMRES );
 for ( col = 0; col < N; col++ ) {
 // set b in root process VecGetOwnershipRange ( b , &b_start , &b_end ) ;
 // clear all values VecSet ( b, 0 ); // set 1 in the correct process. // each process owns a block of b : [b_start, b_end) // index starts from 0
 if ( col >= b_start && col < b_end ) VecSetValues ( b, 1, &col, &value, INSERT_VALUES );
 // distribute b VecAssemblyBegin ( b ) ; VecAssemblyEnd ( b ) ;
 // must be called from all processes //VecView ( b, PETSC_VIEWER_STDOUT_WORLD );
 KSPSolve ( solver, b, x );
 VecView ( x, PETSC_VIEWER_STDOUT_WORLD ); }
 /*  * destroy KSP  */ VecDestroy ( &b ); VecDestroy ( &x ); MatDestroy ( &A ); KSPDestroy(&solver);
 /*  * finalize PETSc  */ PetscFinalize();
 return 0;
I am running this with one MPI process, and the output seems to indicate that the A matrix is set correctly:
Mat Object: 1 MPI processes  type: seqaijrow 0: (0, 1.)  (1, 0.)  (2, 0.)  (3, 1.)  (4, 1.)  (5, 1.) row 1: (0, 0.)  (1, 1.)  (2, 1.)  (3, 1.)  (4, 0.)  (5, 1.) row 2: (0, 1.)  (1, 0.)  (2, 0.)  (3, 0.)  (4, 1.)  (5, 1.) row 3: (0, 0.)  (1, 0.)  (2, -1.)  (3, 0.)  (4, 1.)  (5, 1.) row 4: (0, 1.)  (1, 1.)  (2, 0.)  (3, 1.)  (4, 1.)  (5, 1.) row 5: (0, 0.)  (1, 1.)  (2, 1.)  (3, 1.)  (4, 0.)  (5, 0.) 

Thanks for any help ! rgds
LX
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