Actual source code: ex184.c

  1: static char help[] = "Example of inverting a block diagonal matrix.\n"
  2:                      "\n";

  4: #include <petscmat.h>

  6: int main(int argc, char **args)
  7: {
  8:   Mat          A, A_inv;
  9:   PetscMPIInt  rank, size;
 10:   PetscInt     M, m, bs, rstart, rend, j, x, y;
 11:   PetscInt    *dnnz;
 12:   PetscScalar *v;
 13:   Vec          X, Y;
 14:   PetscReal    norm;

 17:   PetscInitialize(&argc, &args, (char *)0, help);
 18:   MPI_Comm_size(PETSC_COMM_WORLD, &size);
 19:   MPI_Comm_rank(PETSC_COMM_WORLD, &rank);

 21:   PetscOptionsBegin(PETSC_COMM_WORLD, NULL, "ex184", "Mat");
 22:   M = 8;
 23:   PetscOptionsGetInt(NULL, NULL, "-mat_size", &M, NULL);
 24:   bs = 3;
 25:   PetscOptionsGetInt(NULL, NULL, "-mat_block_size", &bs, NULL);
 26:   PetscOptionsEnd();

 28:   MatCreate(PETSC_COMM_WORLD, &A);
 29:   MatSetFromOptions(A);
 30:   MatSetSizes(A, PETSC_DECIDE, PETSC_DECIDE, M * bs, M * bs);
 31:   MatSetBlockSize(A, bs);
 32:   MatSetUp(A);
 33:   MatGetLocalSize(A, &m, NULL);
 34:   PetscMalloc1(m / bs, &dnnz);
 35:   for (j = 0; j < m / bs; j++) dnnz[j] = 1;
 36:   MatXAIJSetPreallocation(A, bs, dnnz, NULL, NULL, NULL);
 37:   PetscFree(dnnz);

 39:   PetscMalloc1(bs * bs, &v);
 40:   MatGetOwnershipRange(A, &rstart, &rend);
 41:   for (j = rstart / bs; j < rend / bs; j++) {
 42:     for (x = 0; x < bs; x++) {
 43:       for (y = 0; y < bs; y++) {
 44:         if (x == y) {
 45:           v[y + bs * x] = 2 * bs;
 46:         } else {
 47:           v[y + bs * x] = -1 * (x < y) - 2 * (x > y);
 48:         }
 49:       }
 50:     }
 51:     MatSetValuesBlocked(A, 1, &j, 1, &j, v, INSERT_VALUES);
 52:   }
 53:   PetscFree(v);
 54:   MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY);
 55:   MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY);

 57:   /* check that A  = inv(inv(A)) */
 58:   MatCreate(PETSC_COMM_WORLD, &A_inv);
 59:   MatSetFromOptions(A_inv);
 60:   MatInvertBlockDiagonalMat(A, A_inv);

 62:   /* Test A_inv * A on a random vector */
 63:   MatCreateVecs(A, &X, &Y);
 64:   VecSetRandom(X, NULL);
 65:   MatMult(A, X, Y);
 66:   VecScale(X, -1);
 67:   MatMultAdd(A_inv, Y, X, X);
 68:   VecNorm(X, NORM_MAX, &norm);
 69:   if (norm > PETSC_SMALL) {
 70:     PetscPrintf(PETSC_COMM_WORLD, "Norm of error exceeds tolerance.\nInverse of block diagonal A\n");
 71:     MatView(A_inv, PETSC_VIEWER_STDOUT_WORLD);
 72:   }

 74:   MatDestroy(&A);
 75:   MatDestroy(&A_inv);
 76:   VecDestroy(&X);
 77:   VecDestroy(&Y);

 79:   PetscFinalize();
 80:   return 0;
 81: }

 83: /*TEST
 84:   test:
 85:     suffix: seqaij
 86:     args: -mat_type seqaij -mat_size 12 -mat_block_size 3
 87:     nsize: 1
 88:   test:
 89:     suffix: seqbaij
 90:     args: -mat_type seqbaij -mat_size 12 -mat_block_size 3
 91:     nsize: 1
 92:   test:
 93:     suffix: mpiaij
 94:     args: -mat_type mpiaij -mat_size 12 -mat_block_size 3
 95:     nsize: 2
 96:   test:
 97:     suffix: mpibaij
 98:     args: -mat_type mpibaij -mat_size 12 -mat_block_size 3
 99:     nsize: 2
100: TEST*/