Actual source code: ex142.c
petsc-3.6.4 2016-04-12
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>
13: int main(int argc,char **args)
14: {
15: typedef enum {RANDOM, CONSTANT, TANH, NUM_FUNCS} FuncType;
16: const char *funcNames[NUM_FUNCS] = {"random", "constant", "tanh"};
17: PetscMPIInt size;
18: int n = 10,N,Ny,ndim=4,i,dim[4],DIM;
19: Vec x,y,z;
20: PetscScalar s;
21: PetscRandom rdm;
22: PetscReal enorm;
23: PetscInt func = RANDOM;
24: FuncType function = RANDOM;
25: PetscBool view = PETSC_FALSE;
26: PetscErrorCode ierr;
27: PetscScalar *x_array,*y_array,*z_array;
28: fftw_plan fplan,bplan;
30: PetscInitialize(&argc,&args,(char*)0,help);
31: #if defined(PETSC_USE_COMPLEX)
32: SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_SUP, "This example requires real numbers");
33: #endif
35: MPI_Comm_size(PETSC_COMM_WORLD, &size);
36: if (size != 1) SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_SUP, "This is a uniprocessor example only!");
37: PetscOptionsBegin(PETSC_COMM_WORLD, NULL, "FFTW Options", "ex142");
38: PetscOptionsEList("-function", "Function type", "ex142", funcNames, NUM_FUNCS, funcNames[function], &func, NULL);
39: PetscOptionsBool("-vec_view draw", "View the functions", "ex142", view, &view, NULL);
40: function = (FuncType) func;
41: PetscOptionsEnd();
43: for (DIM = 0; DIM < ndim; DIM++) {
44: dim[DIM] = n; /* size of real space vector in DIM-dimension */
45: }
46: PetscRandomCreate(PETSC_COMM_SELF, &rdm);
47: PetscRandomSetFromOptions(rdm);
49: for (DIM = 1; DIM < 5; DIM++) {
50: /* create vectors of length N=dim[0]*dim[1]* ...*dim[DIM-1] */
51: /*----------------------------------------------------------*/
52: N = Ny = 1;
53: for (i = 0; i < DIM-1; i++) {
54: N *= dim[i];
55: }
56: Ny = N; Ny *= 2*(dim[DIM-1]/2 + 1); /* add padding elements to output vector y */
57: N *= dim[DIM-1];
60: PetscPrintf(PETSC_COMM_SELF, "\n %d-D: FFTW on vector of size %d \n",DIM,N);
61: VecCreateSeq(PETSC_COMM_SELF,N,&x);
62: PetscObjectSetName((PetscObject) x, "Real space vector");
64: VecCreateSeq(PETSC_COMM_SELF,Ny,&y);
65: PetscObjectSetName((PetscObject) y, "Frequency space vector");
67: VecDuplicate(x,&z);
68: PetscObjectSetName((PetscObject) z, "Reconstructed vector");
70: /* Set fftw plan */
71: /*----------------------------------*/
72: VecGetArray(x,&x_array);
73: VecGetArray(y,&y_array);
74: VecGetArray(z,&z_array);
76: unsigned int flags = FFTW_ESTIMATE; /*or FFTW_MEASURE */
77: /* The data in the in/out arrays is overwritten during FFTW_MEASURE planning, so such planning
78: should be done before the input is initialized by the user. */
79: PetscPrintf(PETSC_COMM_SELF,"DIM: %d, N %d, Ny %d\n",DIM,N,Ny);
81: switch (DIM) {
82: case 1:
83: fplan = fftw_plan_dft_r2c_1d(dim[0], (double*)x_array, (fftw_complex*)y_array, flags);
84: bplan = fftw_plan_dft_c2r_1d(dim[0], (fftw_complex*)y_array, (double*)z_array, flags);
85: break;
86: case 2:
87: fplan = fftw_plan_dft_r2c_2d(dim[0],dim[1],(double*)x_array, (fftw_complex*)y_array,flags);
88: bplan = fftw_plan_dft_c2r_2d(dim[0],dim[1],(fftw_complex*)y_array,(double*)z_array,flags);
89: break;
90: case 3:
91: fplan = fftw_plan_dft_r2c_3d(dim[0],dim[1],dim[2],(double*)x_array, (fftw_complex*)y_array,flags);
92: bplan = fftw_plan_dft_c2r_3d(dim[0],dim[1],dim[2],(fftw_complex*)y_array,(double*)z_array,flags);
93: break;
94: default:
95: fplan = fftw_plan_dft_r2c(DIM,(int*)dim,(double*)x_array, (fftw_complex*)y_array,flags);
96: bplan = fftw_plan_dft_c2r(DIM,(int*)dim,(fftw_complex*)y_array,(double*)z_array,flags);
97: break;
98: }
100: VecRestoreArray(x,&x_array);
101: VecRestoreArray(y,&y_array);
102: VecRestoreArray(z,&z_array);
104: /* Initialize Real space vector x:
105: The data in the in/out arrays is overwritten during FFTW_MEASURE planning, so planning
106: should be done before the input is initialized by the user.
107: --------------------------------------------------------*/
108: if (function == RANDOM) {
109: VecSetRandom(x, rdm);
110: } else if (function == CONSTANT) {
111: VecSet(x, 1.0);
112: } else if (function == TANH) {
113: VecGetArray(x, &x_array);
114: for (i = 0; i < N; ++i) {
115: x_array[i] = tanh((i - N/2.0)*(10.0/N));
116: }
117: VecRestoreArray(x, &x_array);
118: }
119: if (view) {
120: VecView(x, PETSC_VIEWER_STDOUT_WORLD);
121: }
123: /* FFT - also test repeated transformation */
124: /*-------------------------------------------*/
125: VecGetArray(x,&x_array);
126: VecGetArray(y,&y_array);
127: VecGetArray(z,&z_array);
128: for (i=0; i<4; i++) {
129: /* FFTW_FORWARD */
130: fftw_execute(fplan);
131:
132: /* FFTW_BACKWARD: destroys its input array 'y_array' even for out-of-place transforms! */
133: fftw_execute(bplan);
134: }
135: VecRestoreArray(x,&x_array);
136: VecRestoreArray(y,&y_array);
137: VecRestoreArray(z,&z_array);
139: /* Compare x and z. FFTW computes an unnormalized DFT, thus z = N*x */
140: /*------------------------------------------------------------------*/
141: s = 1.0/(PetscReal)N;
142: VecScale(z,s);
143: if (view) {VecView(x, PETSC_VIEWER_DRAW_WORLD);}
144: if (view) {VecView(z, PETSC_VIEWER_DRAW_WORLD);}
145: VecAXPY(z,-1.0,x);
146: VecNorm(z,NORM_1,&enorm);
147: if (enorm > 1.e-11) {
148: PetscPrintf(PETSC_COMM_SELF," Error norm of |x - z| %g\n",(double)enorm);
149: }
151: /* free spaces */
152: fftw_destroy_plan(fplan);
153: fftw_destroy_plan(bplan);
154: VecDestroy(&x);
155: VecDestroy(&y);
156: VecDestroy(&z);
157: }
158: PetscRandomDestroy(&rdm);
159: PetscFinalize();
160: return 0;
161: }