How can I save the matrix in PETSc and load it in matlab? I tried this but it does not work: PetscViewer view; PetscViewerCreate (PETSC_COMM_WORLD, &view); PetscViewerSetFormat (view, PETSC_VIEWER_ASCII_MATLAB); PetscViewerAsciiOpen(PETSC_COMM_WORLD, "matrix.mat", &view); MatView(A, view); PetscViewerDestroy(view); Billy.