xref: /petsc/src/mat/tutorials/ex2.c (revision 48a46eb9bd028bec07ec0f396b1a3abb43f14558)

static char help[] = "testing SeqDense matrices with an LDA (leading dimension of the user-allocated array) larger than M.\n";
/*
 * Example code testing SeqDense matrices with an LDA (leading dimension
 * of the user-allocated array) larger than M.
 * This example tests the functionality of MatSetValues(), MatMult(),
 * and MatMultTranspose().
 */

#include <petscmat.h>

int main(int argc, char **argv) {
  Mat          A, A11, A12, A21, A22;
  Vec          X, X1, X2, Y, Z, Z1, Z2;
  PetscScalar *a, *b, *x, *y, *z, v, one = 1;
  PetscReal    nrm;
  PetscInt     size = 8, size1 = 6, size2 = 2, i, j;
  PetscRandom  rnd;

  PetscFunctionBeginUser;
  PetscCall(PetscInitialize(&argc, &argv, 0, help));
  PetscCall(PetscRandomCreate(PETSC_COMM_SELF, &rnd));

  /*
   * Create matrix and three vectors: these are all normal
   */
  PetscCall(PetscMalloc1(size * size, &a));
  PetscCall(PetscMalloc1(size * size, &b));
  for (i = 0; i < size; i++) {
    for (j = 0; j < size; j++) {
      PetscCall(PetscRandomGetValue(rnd, &a[i + j * size]));
      b[i + j * size] = a[i + j * size];
    }
  }
  PetscCall(MatCreate(PETSC_COMM_SELF, &A));
  PetscCall(MatSetSizes(A, size, size, size, size));
  PetscCall(MatSetType(A, MATSEQDENSE));
  PetscCall(MatSeqDenseSetPreallocation(A, a));
  PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));

  PetscCall(PetscMalloc1(size, &x));
  for (i = 0; i < size; i++) { x[i] = one; }
  PetscCall(VecCreateSeqWithArray(PETSC_COMM_SELF, 1, size, x, &X));
  PetscCall(VecAssemblyBegin(X));
  PetscCall(VecAssemblyEnd(X));

  PetscCall(PetscMalloc1(size, &y));
  PetscCall(VecCreateSeqWithArray(PETSC_COMM_SELF, 1, size, y, &Y));
  PetscCall(VecAssemblyBegin(Y));
  PetscCall(VecAssemblyEnd(Y));

  PetscCall(PetscMalloc1(size, &z));
  PetscCall(VecCreateSeqWithArray(PETSC_COMM_SELF, 1, size, z, &Z));
  PetscCall(VecAssemblyBegin(Z));
  PetscCall(VecAssemblyEnd(Z));

  /*
   * Now create submatrices and subvectors
   */
  PetscCall(MatCreate(PETSC_COMM_SELF, &A11));
  PetscCall(MatSetSizes(A11, size1, size1, size1, size1));
  PetscCall(MatSetType(A11, MATSEQDENSE));
  PetscCall(MatSeqDenseSetPreallocation(A11, b));
  PetscCall(MatDenseSetLDA(A11, size));
  PetscCall(MatAssemblyBegin(A11, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(A11, MAT_FINAL_ASSEMBLY));

  PetscCall(MatCreate(PETSC_COMM_SELF, &A12));
  PetscCall(MatSetSizes(A12, size1, size2, size1, size2));
  PetscCall(MatSetType(A12, MATSEQDENSE));
  PetscCall(MatSeqDenseSetPreallocation(A12, b + size1 * size));
  PetscCall(MatDenseSetLDA(A12, size));
  PetscCall(MatAssemblyBegin(A12, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(A12, MAT_FINAL_ASSEMBLY));

  PetscCall(MatCreate(PETSC_COMM_SELF, &A21));
  PetscCall(MatSetSizes(A21, size2, size1, size2, size1));
  PetscCall(MatSetType(A21, MATSEQDENSE));
  PetscCall(MatSeqDenseSetPreallocation(A21, b + size1));
  PetscCall(MatDenseSetLDA(A21, size));
  PetscCall(MatAssemblyBegin(A21, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(A21, MAT_FINAL_ASSEMBLY));

  PetscCall(MatCreate(PETSC_COMM_SELF, &A22));
  PetscCall(MatSetSizes(A22, size2, size2, size2, size2));
  PetscCall(MatSetType(A22, MATSEQDENSE));
  PetscCall(MatSeqDenseSetPreallocation(A22, b + size1 * size + size1));
  PetscCall(MatDenseSetLDA(A22, size));
  PetscCall(MatAssemblyBegin(A22, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(A22, MAT_FINAL_ASSEMBLY));

  PetscCall(VecCreateSeqWithArray(PETSC_COMM_SELF, 1, size1, x, &X1));
  PetscCall(VecCreateSeqWithArray(PETSC_COMM_SELF, 1, size2, x + size1, &X2));
  PetscCall(VecCreateSeqWithArray(PETSC_COMM_SELF, 1, size1, z, &Z1));
  PetscCall(VecCreateSeqWithArray(PETSC_COMM_SELF, 1, size2, z + size1, &Z2));

  /*
   * Now multiple matrix times input in two ways;
   * compare the results
   */
  PetscCall(MatMult(A, X, Y));
  PetscCall(MatMult(A11, X1, Z1));
  PetscCall(MatMultAdd(A12, X2, Z1, Z1));
  PetscCall(MatMult(A22, X2, Z2));
  PetscCall(MatMultAdd(A21, X1, Z2, Z2));
  PetscCall(VecAXPY(Z, -1.0, Y));
  PetscCall(VecNorm(Z, NORM_2, &nrm));
  if (nrm > 100.0 * PETSC_MACHINE_EPSILON) PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Test1; error norm=%g\n", (double)nrm));

  /*
   * Next test: change both matrices
   */
  PetscCall(PetscRandomGetValue(rnd, &v));
  i = 1;
  j = size - 2;
  PetscCall(MatSetValues(A, 1, &i, 1, &j, &v, INSERT_VALUES));
  j -= size1;
  PetscCall(MatSetValues(A12, 1, &i, 1, &j, &v, INSERT_VALUES));
  PetscCall(PetscRandomGetValue(rnd, &v));
  i = j = size1 + 1;
  PetscCall(MatSetValues(A, 1, &i, 1, &j, &v, INSERT_VALUES));
  i = j = 1;
  PetscCall(MatSetValues(A22, 1, &i, 1, &j, &v, INSERT_VALUES));
  PetscCall(MatAssemblyBegin(A, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(A, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyBegin(A12, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(A12, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyBegin(A22, MAT_FINAL_ASSEMBLY));
  PetscCall(MatAssemblyEnd(A22, MAT_FINAL_ASSEMBLY));

  PetscCall(MatMult(A, X, Y));
  PetscCall(MatMult(A11, X1, Z1));
  PetscCall(MatMultAdd(A12, X2, Z1, Z1));
  PetscCall(MatMult(A22, X2, Z2));
  PetscCall(MatMultAdd(A21, X1, Z2, Z2));
  PetscCall(VecAXPY(Z, -1.0, Y));
  PetscCall(VecNorm(Z, NORM_2, &nrm));
  if (nrm > 100.0 * PETSC_MACHINE_EPSILON) PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Test2; error norm=%g\n", (double)nrm));

  /*
   * Transpose product
   */
  PetscCall(MatMultTranspose(A, X, Y));
  PetscCall(MatMultTranspose(A11, X1, Z1));
  PetscCall(MatMultTransposeAdd(A21, X2, Z1, Z1));
  PetscCall(MatMultTranspose(A22, X2, Z2));
  PetscCall(MatMultTransposeAdd(A12, X1, Z2, Z2));
  PetscCall(VecAXPY(Z, -1.0, Y));
  PetscCall(VecNorm(Z, NORM_2, &nrm));
  if (nrm > 100.0 * PETSC_MACHINE_EPSILON) PetscCall(PetscPrintf(PETSC_COMM_WORLD, "Test3; error norm=%g\n", (double)nrm));
  PetscCall(PetscFree(a));
  PetscCall(PetscFree(b));
  PetscCall(PetscFree(x));
  PetscCall(PetscFree(y));
  PetscCall(PetscFree(z));
  PetscCall(MatDestroy(&A));
  PetscCall(MatDestroy(&A11));
  PetscCall(MatDestroy(&A12));
  PetscCall(MatDestroy(&A21));
  PetscCall(MatDestroy(&A22));

  PetscCall(VecDestroy(&X));
  PetscCall(VecDestroy(&Y));
  PetscCall(VecDestroy(&Z));

  PetscCall(VecDestroy(&X1));
  PetscCall(VecDestroy(&X2));
  PetscCall(VecDestroy(&Z1));
  PetscCall(VecDestroy(&Z2));
  PetscCall(PetscRandomDestroy(&rnd));
  PetscCall(PetscFinalize());
  return 0;
}

/*TEST

   test:

TEST*/