61     PetscCall(PetscPrintf(PETSC_COMM_SELF, "\n Read matrix in ascii format ...\n"));  in main()
62     PetscCall(PetscFOpen(PETSC_COMM_SELF, Ain, "r", &Afile));  in main()
71 …PetscCheck(fscanf(Afile, "%d %d %d", &m, &n, &nz) == 3, PETSC_COMM_SELF, PETSC_ERR_FILE_UNEXPECTED…  in main()
73     PetscCall(PetscPrintf(PETSC_COMM_SELF, "m: %d, n: %d, nz: %d \n", m, n, nz));  in main()
74 …PetscCheck(m == n, PETSC_COMM_SELF, PETSC_ERR_ARG_SIZ, "Number of rows, cols must be same for this…  in main()
75     PetscCall(MatCreate(PETSC_COMM_SELF, &A));  in main()
82 …PetscCheck(fscanf(Afile, "%d %d %le", &row, &col, (double *)&val) == 3, PETSC_COMM_SELF, PETSC_ERR…  in main()
94     PetscCall(VecCreate(PETSC_COMM_SELF, &b));  in main()
97     PetscCall(PetscPrintf(PETSC_COMM_SELF, "\n Read rhs in ascii format ...\n"));  in main()
98     PetscCall(PetscFOpen(PETSC_COMM_SELF, rhs, "r", &bfile));  in main()
100 …PetscCheck(fscanf(bfile, "%d %le", &dummy, (double *)&val) == 2, PETSC_COMM_SELF, PETSC_ERR_FILE_U…  in main()
110     PetscCall(VecCreate(PETSC_COMM_SELF, &u));  in main()
113     PetscCall(PetscPrintf(PETSC_COMM_SELF, "\n Read exact solution in ascii format ...\n"));  in main()
114     PetscCall(PetscFOpen(PETSC_COMM_SELF, solu, "r", &ufile));  in main()
116 …PetscCheck(fscanf(ufile, "%d  %le", &dummy, (double *)&val) == 2, PETSC_COMM_SELF, PETSC_ERR_FILE_…  in main()
125   PetscCall(PetscPrintf(PETSC_COMM_SELF, "\n Write matrix in binary to 'matrix.dat' ...\n"));  in main()
126   PetscCall(PetscViewerBinaryOpen(PETSC_COMM_SELF, "matrix.dat", FILE_MODE_WRITE, &view));  in main()
130     PetscCall(PetscPrintf(PETSC_COMM_SELF, "\n Write rhs in binary to 'matrix.dat' ...\n"));  in main()
134 …PetscCall(PetscPrintf(PETSC_COMM_SELF, "\n Write exact solution in binary to 'matrix.dat' ...\n"));  in main()
144 …PetscCall(PetscPrintf(PETSC_COMM_SELF, "\n Accuracy of the reading data: | b - A*u |_2 : %g \n", r…  in main()