Actual source code: ex148.c

  1: static char help[] = "This program illustrates the use of PETSc-fftw interface for real 2D DFT.\n\
  2:                     See ~petsc/src/mat/tests/ex158.c for general cases. \n\n";

  4: #include <petscmat.h>

  6: int main(int argc, char **args)
  7: {
  8:   PetscMPIInt rank, size;
  9:   PetscInt    N0 = 50, N1 = 50, N = N0 * N1;
 10:   PetscRandom rdm;
 11:   PetscReal   enorm;
 12:   Vec         x, y, z, input, output;
 13:   Mat         A;
 14:   PetscInt    DIM, dim[2];
 15:   PetscReal   fac;

 18:   PetscInitialize(&argc, &args, (char *)0, help);
 19: #if defined(PETSC_USE_COMPLEX)
 20:   SETERRQ(PETSC_COMM_WORLD, PETSC_ERR_SUP, "This example requires real numbers");
 21: #endif

 23:   MPI_Comm_size(PETSC_COMM_WORLD, &size);
 24:   MPI_Comm_rank(PETSC_COMM_WORLD, &rank);

 26:   /* Create and set PETSc vectors 'input' and 'output' */
 27:   PetscRandomCreate(PETSC_COMM_WORLD, &rdm);
 28:   PetscRandomSetFromOptions(rdm);

 30:   VecCreate(PETSC_COMM_WORLD, &input);
 31:   VecSetSizes(input, PETSC_DECIDE, N0 * N1);
 32:   VecSetFromOptions(input);
 33:   VecSetRandom(input, rdm);
 34:   VecDuplicate(input, &output);
 35:   PetscObjectSetName((PetscObject)input, "Real space vector");
 36:   PetscObjectSetName((PetscObject)output, "Reconstructed vector");

 38:   /* Get FFTW vectors 'x', 'y' and 'z' */
 39:   DIM    = 2;
 40:   dim[0] = N0;
 41:   dim[1] = N1;
 42:   MatCreateFFT(PETSC_COMM_WORLD, DIM, dim, MATFFTW, &A);
 43:   MatCreateVecsFFTW(A, &x, &y, &z);

 45:   /* Scatter PETSc vector 'input' to FFTW vector 'x' */
 46:   VecScatterPetscToFFTW(A, input, x);

 48:   /* Apply forward FFT */
 49:   MatMult(A, x, y);

 51:   /* Apply backward FFT */
 52:   MatMultTranspose(A, y, z);

 54:   /* Scatter FFTW vector 'z' to PETSc vector 'output' */
 55:   VecScatterFFTWToPetsc(A, z, output);

 57:   /* Check accuracy */
 58:   fac = 1.0 / (PetscReal)N;
 59:   VecScale(output, fac);
 60:   VecAXPY(output, -1.0, input);
 61:   VecNorm(output, NORM_1, &enorm);
 62:   if (enorm > 1.e-11 && rank == 0) PetscPrintf(PETSC_COMM_SELF, "  Error norm of |x - z| %e\n", enorm);

 64:   /* Free spaces */
 65:   PetscRandomDestroy(&rdm);
 66:   VecDestroy(&input);
 67:   VecDestroy(&output);
 68:   VecDestroy(&x);
 69:   VecDestroy(&y);
 70:   VecDestroy(&z);
 71:   MatDestroy(&A);

 73:   PetscFinalize();
 74:   return 0;
 75: }

 77: /*TEST

 79:    build:
 80:       requires: fftw !complex

 82:    test:
 83:       output_file: output/ex148.out

 85:    test:
 86:       suffix: 2
 87:       nsize: 3
 88:       output_file: output/ex148.out

 90: TEST*/