Actual source code: ex142.c
1: static char help[] = "Test sequential r2c/c2r FFTW without PETSc interface \n\n";
3: /*
4: Compiling the code:
5: This code uses the real numbers version of PETSc
6: */
8: #include <petscmat.h>
9: #include <fftw3.h>
11: int main(int argc, char **args)
12: {
13: typedef enum {
14: RANDOM,
15: CONSTANT,
16: TANH,
17: NUM_FUNCS
18: } FuncType;
19: const char *funcNames[NUM_FUNCS] = {"random", "constant", "tanh"};
20: PetscMPIInt size;
21: int n = 10, N, Ny, ndim = 4, i, dim[4], DIM;
22: Vec x, y, z;
23: PetscScalar s;
24: PetscRandom rdm;
25: PetscReal enorm;
26: PetscInt func = RANDOM;
27: FuncType function = RANDOM;
28: PetscBool view = PETSC_FALSE;
29: PetscScalar *x_array, *y_array, *z_array;
30: fftw_plan fplan, bplan;
32: PetscFunctionBeginUser;
33: PetscCall(PetscInitialize(&argc, &args, NULL, help));
34: #if defined(PETSC_USE_COMPLEX)
35: SETERRQ(PETSC_COMM_WORLD, PETSC_ERR_SUP, "This example requires real numbers");
36: #endif
38: PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
39: PetscCheck(size == 1, PETSC_COMM_WORLD, PETSC_ERR_WRONG_MPI_SIZE, "This is a uniprocessor example only!");
40: PetscOptionsBegin(PETSC_COMM_WORLD, NULL, "FFTW Options", "ex142");
41: PetscCall(PetscOptionsEList("-function", "Function type", "ex142", funcNames, NUM_FUNCS, funcNames[function], &func, NULL));
42: PetscCall(PetscOptionsBool("-vec_view draw", "View the functions", "ex142", view, &view, NULL));
43: function = (FuncType)func;
44: PetscOptionsEnd();
46: for (DIM = 0; DIM < ndim; DIM++) { dim[DIM] = n; /* size of real space vector in DIM-dimension */ }
47: PetscCall(PetscRandomCreate(PETSC_COMM_SELF, &rdm));
48: PetscCall(PetscRandomSetFromOptions(rdm));
50: for (DIM = 1; DIM < 5; DIM++) {
51: /* create vectors of length N=dim[0]*dim[1]* ...*dim[DIM-1] */
52: /*----------------------------------------------------------*/
53: N = Ny = 1;
54: for (i = 0; i < DIM - 1; i++) N *= dim[i];
55: Ny = N;
56: Ny *= 2 * (dim[DIM - 1] / 2 + 1); /* add padding elements to output vector y */
57: N *= dim[DIM - 1];
59: PetscCall(PetscPrintf(PETSC_COMM_SELF, "\n %d-D: FFTW on vector of size %d \n", DIM, N));
60: PetscCall(VecCreateSeq(PETSC_COMM_SELF, N, &x));
61: PetscCall(PetscObjectSetName((PetscObject)x, "Real space vector"));
63: PetscCall(VecCreateSeq(PETSC_COMM_SELF, Ny, &y));
64: PetscCall(PetscObjectSetName((PetscObject)y, "Frequency space vector"));
66: PetscCall(VecDuplicate(x, &z));
67: PetscCall(PetscObjectSetName((PetscObject)z, "Reconstructed vector"));
69: /* Set fftw plan */
70: /*----------------------------------*/
71: PetscCall(VecGetArray(x, &x_array));
72: PetscCall(VecGetArray(y, &y_array));
73: PetscCall(VecGetArray(z, &z_array));
75: unsigned int flags = FFTW_ESTIMATE; /*or FFTW_MEASURE */
76: /* The data in the in/out arrays is overwritten during FFTW_MEASURE planning, so such planning
77: should be done before the input is initialized by the user. */
78: PetscCall(PetscPrintf(PETSC_COMM_SELF, "DIM: %d, N %d, Ny %d\n", DIM, N, Ny));
80: switch (DIM) {
81: case 1:
82: fplan = fftw_plan_dft_r2c_1d(dim[0], (double *)x_array, (fftw_complex *)y_array, flags);
83: bplan = fftw_plan_dft_c2r_1d(dim[0], (fftw_complex *)y_array, (double *)z_array, flags);
84: break;
85: case 2:
86: fplan = fftw_plan_dft_r2c_2d(dim[0], dim[1], (double *)x_array, (fftw_complex *)y_array, flags);
87: bplan = fftw_plan_dft_c2r_2d(dim[0], dim[1], (fftw_complex *)y_array, (double *)z_array, flags);
88: break;
89: case 3:
90: fplan = fftw_plan_dft_r2c_3d(dim[0], dim[1], dim[2], (double *)x_array, (fftw_complex *)y_array, flags);
91: bplan = fftw_plan_dft_c2r_3d(dim[0], dim[1], dim[2], (fftw_complex *)y_array, (double *)z_array, flags);
92: break;
93: default:
94: fplan = fftw_plan_dft_r2c(DIM, (int *)dim, (double *)x_array, (fftw_complex *)y_array, flags);
95: bplan = fftw_plan_dft_c2r(DIM, (int *)dim, (fftw_complex *)y_array, (double *)z_array, flags);
96: break;
97: }
99: PetscCall(VecRestoreArray(x, &x_array));
100: PetscCall(VecRestoreArray(y, &y_array));
101: PetscCall(VecRestoreArray(z, &z_array));
103: /* Initialize Real space vector x:
104: The data in the in/out arrays is overwritten during FFTW_MEASURE planning, so planning
105: should be done before the input is initialized by the user.
106: --------------------------------------------------------*/
107: if (function == RANDOM) {
108: PetscCall(VecSetRandom(x, rdm));
109: } else if (function == CONSTANT) {
110: PetscCall(VecSet(x, 1.0));
111: } else if (function == TANH) {
112: PetscCall(VecGetArray(x, &x_array));
113: for (i = 0; i < N; ++i) x_array[i] = tanh((i - N / 2.0) * (10.0 / N));
114: PetscCall(VecRestoreArray(x, &x_array));
115: }
116: if (view) PetscCall(VecView(x, PETSC_VIEWER_STDOUT_WORLD));
118: /* FFT - also test repeated transformation */
119: /*-------------------------------------------*/
120: PetscCall(VecGetArray(x, &x_array));
121: PetscCall(VecGetArray(y, &y_array));
122: PetscCall(VecGetArray(z, &z_array));
123: for (i = 0; i < 4; i++) {
124: /* FFTW_FORWARD */
125: fftw_execute(fplan);
127: /* FFTW_BACKWARD: destroys its input array 'y_array' even for out-of-place transforms! */
128: fftw_execute(bplan);
129: }
130: PetscCall(VecRestoreArray(x, &x_array));
131: PetscCall(VecRestoreArray(y, &y_array));
132: PetscCall(VecRestoreArray(z, &z_array));
134: /* Compare x and z. FFTW computes an unnormalized DFT, thus z = N*x */
135: /*------------------------------------------------------------------*/
136: s = 1.0 / (PetscReal)N;
137: PetscCall(VecScale(z, s));
138: if (view) PetscCall(VecView(x, PETSC_VIEWER_DRAW_WORLD));
139: if (view) PetscCall(VecView(z, PETSC_VIEWER_DRAW_WORLD));
140: PetscCall(VecAXPY(z, -1.0, x));
141: PetscCall(VecNorm(z, NORM_1, &enorm));
142: if (enorm > 1.e-11) PetscCall(PetscPrintf(PETSC_COMM_SELF, " Error norm of |x - z| %g\n", (double)enorm));
144: /* free spaces */
145: fftw_destroy_plan(fplan);
146: fftw_destroy_plan(bplan);
147: PetscCall(VecDestroy(&x));
148: PetscCall(VecDestroy(&y));
149: PetscCall(VecDestroy(&z));
150: }
151: PetscCall(PetscRandomDestroy(&rdm));
152: PetscCall(PetscFinalize());
153: return 0;
154: }
156: /*TEST
158: build:
159: requires: fftw !complex
161: test:
162: output_file: output/ex142.out
164: TEST*/