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, NULL, 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*/