I updated my petsc-dev copy and it works now. Thanks, -Gautam. On Feb 20, 2012, at 6:16 PM, Matthew Knepley wrote: On Mon, Feb 20, 2012 at 4:25 PM, Bisht, Gautam <[email protected]<mailto:[email protected]>> wrote: Hi, I have a MPIAIJ matrix A as listed below: row 0: (36, 1) (37, 1) (42, 1) (43, 1) row 1: (37, 1) (38, 1) (43, 1) (44, 1) row 2: (38, 1) (39, 1) (44, 1) (45, 1) row 3: (39, 1) (40, 1) (45, 1) (46, 1) row 4: (40, 1) (41, 1) (46, 1) (47, 1) When I try to transpose the matrix, while running on 2 processors, the code crashes. Attached below is the F90 code. I would appreciate any help in figuring out why the code crashes. Runs fine for me: knepley:/PETSc3/petsc/petsc-dev$ /PETSc3/petsc/petsc-dev/arch-c-f90-debug/bin/mpiexec -n 2 /PETSc3/petsc/petsc-dev/arch-c-f90-debug/lib/mattrans-obj/mattrans -mat_view Matrix Object: 1 MPI processes type: mpiaij row 0: (36, 1) (37, 1) (42, 1) (43, 1) row 1: (37, 1) (38, 1) (43, 1) (44, 1) row 2: (38, 1) (39, 1) (44, 1) (45, 1) row 3: (39, 1) (40, 1) (45, 1) (46, 1) row 4: (40, 1) (41, 1) (46, 1) (47, 1) Matrix Object: 1 MPI processes type: mpiaij row 0: (36, 1) (37, 1) (42, 1) (43, 1) row 1: (37, 1) (38, 1) (43, 1) (44, 1) row 2: (38, 1) (39, 1) (44, 1) (45, 1) row 3: (39, 1) (40, 1) (45, 1) (46, 1) row 4: (40, 1) (41, 1) (46, 1) (47, 1) Matrix Object: 1 MPI processes type: mpiaij row 0: row 1: row 2: row 3: row 4: row 5: row 6: row 7: row 8: row 9: row 10: row 11: row 12: row 13: row 14: row 15: row 16: row 17: row 18: row 19: row 20: row 21: row 22: row 23: row 24: row 25: row 26: row 27: row 28: row 29: row 30: row 31: row 32: row 33: row 34: row 35: row 36: (0, 1) row 37: (0, 1) (1, 1) row 38: (1, 1) (2, 1) row 39: (2, 1) (3, 1) row 40: (3, 1) (4, 1) row 41: (4, 1) row 42: (0, 1) row 43: (0, 1) (1, 1) row 44: (1, 1) (2, 1) row 45: (2, 1) (3, 1) row 46: (3, 1) (4, 1) row 47: (4, 1) Matrix Object: 1 MPI processes type: mpiaij row 0: row 1: row 2: row 3: row 4: row 5: row 6: row 7: row 8: row 9: row 10: row 11: row 12: row 13: row 14: row 15: row 16: row 17: row 18: row 19: row 20: row 21: row 22: row 23: row 24: row 25: row 26: row 27: row 28: row 29: row 30: row 31: row 32: row 33: row 34: row 35: row 36: (0, 1) row 37: (0, 1) (1, 1) row 38: (1, 1) (2, 1) row 39: (2, 1) (3, 1) row 40: (3, 1) (4, 1) row 41: (4, 1) row 42: (0, 1) row 43: (0, 1) (1, 1) row 44: (1, 1) (2, 1) row 45: (2, 1) (3, 1) row 46: (3, 1) (4, 1) row 47: (4, 1) Matt Thanks, -Gautam. -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener