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;

 17:   PetscFunctionBeginUser;
 18:   PetscCall(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:   PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
 24:   PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));

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

 30:   PetscCall(VecCreate(PETSC_COMM_WORLD, &input));
 31:   PetscCall(VecSetSizes(input, PETSC_DECIDE, N0 * N1));
 32:   PetscCall(VecSetFromOptions(input));
 33:   PetscCall(VecSetRandom(input, rdm));
 34:   PetscCall(VecDuplicate(input, &output));
 35:   PetscCall(PetscObjectSetName((PetscObject)input, "Real space vector"));
 36:   PetscCall(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:   PetscCall(MatCreateFFT(PETSC_COMM_WORLD, DIM, dim, MATFFTW, &A));
 43:   PetscCall(MatCreateVecsFFTW(A, &x, &y, &z));

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

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

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

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

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

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

 73:   PetscCall(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*/