1: static char help[] = "Reads a PETSc matrix and vector from a file; expands the matrix with the vector\n\n";

  3: /*
  4:   Include "petscmat.h" so that we can use matrices.
  5:   automatically includes:
  6:      petscsys.h       - base PETSc routines   petscvec.h    - vectors
  7:      petscmat.h    - matrices
  8:      petscis.h     - index sets            petscviewer.h - viewers
  9: */
 10: #include <petscmat.h>

 12: /*

 14:    Adds a new column and row to the vector (the last) containing the vector
 15: */
 16: PetscErrorCode PadMatrix(Mat A, Vec v, PetscScalar c, Mat *B)
 17: {
 18:   PetscInt           n, i, *cnt, *indices, nc;
 19:   const PetscInt    *aj;
 20:   const PetscScalar *vv, *aa;

 22:   PetscFunctionBegin;
 23:   PetscCall(MatGetSize(A, &n, NULL));
 24:   PetscCall(VecGetArrayRead(v, &vv));
 25:   PetscCall(PetscMalloc1(n, &indices));
 26:   for (i = 0; i < n; i++) indices[i] = i;

 28:   /* determine number of nonzeros per row in the new matrix */
 29:   PetscCall(PetscMalloc1(n + 1, &cnt));
 30:   for (i = 0; i < n; i++) {
 31:     PetscCall(MatGetRow(A, i, &nc, NULL, NULL));
 32:     cnt[i] = nc + (vv[i] != 0.0);
 33:     PetscCall(MatRestoreRow(A, i, &nc, NULL, NULL));
 34:   }
 35:   cnt[n] = 1;
 36:   for (i = 0; i < n; i++) cnt[n] += (vv[i] != 0.0);
 37:   PetscCall(MatCreateSeqAIJ(PETSC_COMM_SELF, n + 1, n + 1, 0, cnt, B));
 38:   PetscCall(MatSetOption(*B, MAT_IGNORE_ZERO_ENTRIES, PETSC_TRUE));

 40:   /* copy over the matrix entries from the matrix and then the vector */
 41:   for (i = 0; i < n; i++) {
 42:     PetscCall(MatGetRow(A, i, &nc, &aj, &aa));
 43:     PetscCall(MatSetValues(*B, 1, &i, nc, aj, aa, INSERT_VALUES));
 44:     PetscCall(MatRestoreRow(A, i, &nc, &aj, &aa));
 45:   }
 46:   PetscCall(MatSetValues(*B, 1, &n, n, indices, vv, INSERT_VALUES));
 47:   PetscCall(MatSetValues(*B, n, indices, 1, &n, vv, INSERT_VALUES));
 48:   PetscCall(MatSetValues(*B, 1, &n, 1, &n, &c, INSERT_VALUES));

 50:   PetscCall(MatAssemblyBegin(*B, MAT_FINAL_ASSEMBLY));
 51:   PetscCall(MatAssemblyEnd(*B, MAT_FINAL_ASSEMBLY));
 52:   PetscCall(VecRestoreArrayRead(v, &vv));
 53:   PetscCall(PetscFree(cnt));
 54:   PetscCall(PetscFree(indices));
 55:   PetscFunctionReturn(PETSC_SUCCESS);
 56: }

 58: int main(int argc, char **args)
 59: {
 60:   Mat         A, B;
 61:   PetscViewer fd;                       /* viewer */
 62:   char        file[PETSC_MAX_PATH_LEN]; /* input file name */
 63:   PetscBool   flg;
 64:   Vec         v;

 66:   PetscFunctionBeginUser;
 67:   PetscCall(PetscInitialize(&argc, &args, (char *)0, help));
 68:   /*
 69:      Determine files from which we read the two linear systems
 70:      (matrix and right-hand-side vector).
 71:   */
 72:   PetscCall(PetscOptionsGetString(NULL, NULL, "-f0", file, sizeof(file), &flg));
 73:   PetscCheck(flg, PETSC_COMM_WORLD, PETSC_ERR_USER, "Must indicate binary file with the -f0 option");

 75:   PetscCall(PetscViewerBinaryOpen(PETSC_COMM_WORLD, file, FILE_MODE_READ, &fd));

 77:   PetscCall(MatCreate(PETSC_COMM_WORLD, &A));
 78:   PetscCall(MatSetType(A, MATSEQAIJ));
 79:   PetscCall(MatLoad(A, fd));
 80:   PetscCall(VecCreate(PETSC_COMM_WORLD, &v));
 81:   PetscCall(VecLoad(v, fd));
 82:   PetscCall(MatView(A, PETSC_VIEWER_STDOUT_SELF));
 83:   PetscCall(PadMatrix(A, v, 3.0, &B));
 84:   PetscCall(MatView(B, PETSC_VIEWER_STDOUT_SELF));
 85:   PetscCall(MatDestroy(&B));
 86:   PetscCall(MatDestroy(&A));
 87:   PetscCall(VecDestroy(&v));
 88:   PetscCall(PetscViewerDestroy(&fd));

 90:   PetscCall(PetscFinalize());
 91:   return 0;
 92: }

 94: /*TEST

 96:    test:
 97:       args: -f0 ${wPETSC_DIR}/share/petsc/datafiles/matrices/ns-real-int32-float64
 98:       requires: double !complex !defined(PETSC_USE_64BIT_INDICES)

100: TEST*/