1 static char help[] = "Test sequential r2c/c2r FFTW without PETSc interface \n\n"; 2 3 /* 4 Compiling the code: 5 This code uses the real numbers version of PETSc 6 */ 7 8 #include <petscmat.h> 9 #include <fftw3.h> 10 11 int main(int argc,char **args) 12 { 13 typedef enum {RANDOM, CONSTANT, TANH, NUM_FUNCS} FuncType; 14 const char *funcNames[NUM_FUNCS] = {"random", "constant", "tanh"}; 15 PetscMPIInt size; 16 int n = 10,N,Ny,ndim=4,i,dim[4],DIM; 17 Vec x,y,z; 18 PetscScalar s; 19 PetscRandom rdm; 20 PetscReal enorm; 21 PetscInt func = RANDOM; 22 FuncType function = RANDOM; 23 PetscBool view = PETSC_FALSE; 24 PetscErrorCode ierr; 25 PetscScalar *x_array,*y_array,*z_array; 26 fftw_plan fplan,bplan; 27 28 PetscCall(PetscInitialize(&argc,&args,(char*)0,help)); 29 #if defined(PETSC_USE_COMPLEX) 30 SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_SUP, "This example requires real numbers"); 31 #endif 32 33 PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size)); 34 PetscCheck(size == 1,PETSC_COMM_WORLD,PETSC_ERR_WRONG_MPI_SIZE, "This is a uniprocessor example only!"); 35 ierr = PetscOptionsBegin(PETSC_COMM_WORLD, NULL, "FFTW Options", "ex142");PetscCall(ierr); 36 PetscCall(PetscOptionsEList("-function", "Function type", "ex142", funcNames, NUM_FUNCS, funcNames[function], &func, NULL)); 37 PetscCall(PetscOptionsBool("-vec_view draw", "View the functions", "ex142", view, &view, NULL)); 38 function = (FuncType) func; 39 ierr = PetscOptionsEnd();PetscCall(ierr); 40 41 for (DIM = 0; DIM < ndim; DIM++) { 42 dim[DIM] = n; /* size of real space vector in DIM-dimension */ 43 } 44 PetscCall(PetscRandomCreate(PETSC_COMM_SELF, &rdm)); 45 PetscCall(PetscRandomSetFromOptions(rdm)); 46 47 for (DIM = 1; DIM < 5; DIM++) { 48 /* create vectors of length N=dim[0]*dim[1]* ...*dim[DIM-1] */ 49 /*----------------------------------------------------------*/ 50 N = Ny = 1; 51 for (i = 0; i < DIM-1; i++) { 52 N *= dim[i]; 53 } 54 Ny = N; Ny *= 2*(dim[DIM-1]/2 + 1); /* add padding elements to output vector y */ 55 N *= dim[DIM-1]; 56 57 PetscCall(PetscPrintf(PETSC_COMM_SELF, "\n %d-D: FFTW on vector of size %d \n",DIM,N)); 58 PetscCall(VecCreateSeq(PETSC_COMM_SELF,N,&x)); 59 PetscCall(PetscObjectSetName((PetscObject) x, "Real space vector")); 60 61 PetscCall(VecCreateSeq(PETSC_COMM_SELF,Ny,&y)); 62 PetscCall(PetscObjectSetName((PetscObject) y, "Frequency space vector")); 63 64 PetscCall(VecDuplicate(x,&z)); 65 PetscCall(PetscObjectSetName((PetscObject) z, "Reconstructed vector")); 66 67 /* Set fftw plan */ 68 /*----------------------------------*/ 69 PetscCall(VecGetArray(x,&x_array)); 70 PetscCall(VecGetArray(y,&y_array)); 71 PetscCall(VecGetArray(z,&z_array)); 72 73 unsigned int flags = FFTW_ESTIMATE; /*or FFTW_MEASURE */ 74 /* The data in the in/out arrays is overwritten during FFTW_MEASURE planning, so such planning 75 should be done before the input is initialized by the user. */ 76 PetscCall(PetscPrintf(PETSC_COMM_SELF,"DIM: %d, N %d, Ny %d\n",DIM,N,Ny)); 77 78 switch (DIM) { 79 case 1: 80 fplan = fftw_plan_dft_r2c_1d(dim[0], (double*)x_array, (fftw_complex*)y_array, flags); 81 bplan = fftw_plan_dft_c2r_1d(dim[0], (fftw_complex*)y_array, (double*)z_array, flags); 82 break; 83 case 2: 84 fplan = fftw_plan_dft_r2c_2d(dim[0],dim[1],(double*)x_array, (fftw_complex*)y_array,flags); 85 bplan = fftw_plan_dft_c2r_2d(dim[0],dim[1],(fftw_complex*)y_array,(double*)z_array,flags); 86 break; 87 case 3: 88 fplan = fftw_plan_dft_r2c_3d(dim[0],dim[1],dim[2],(double*)x_array, (fftw_complex*)y_array,flags); 89 bplan = fftw_plan_dft_c2r_3d(dim[0],dim[1],dim[2],(fftw_complex*)y_array,(double*)z_array,flags); 90 break; 91 default: 92 fplan = fftw_plan_dft_r2c(DIM,(int*)dim,(double*)x_array, (fftw_complex*)y_array,flags); 93 bplan = fftw_plan_dft_c2r(DIM,(int*)dim,(fftw_complex*)y_array,(double*)z_array,flags); 94 break; 95 } 96 97 PetscCall(VecRestoreArray(x,&x_array)); 98 PetscCall(VecRestoreArray(y,&y_array)); 99 PetscCall(VecRestoreArray(z,&z_array)); 100 101 /* Initialize Real space vector x: 102 The data in the in/out arrays is overwritten during FFTW_MEASURE planning, so planning 103 should be done before the input is initialized by the user. 104 --------------------------------------------------------*/ 105 if (function == RANDOM) { 106 PetscCall(VecSetRandom(x, rdm)); 107 } else if (function == CONSTANT) { 108 PetscCall(VecSet(x, 1.0)); 109 } else if (function == TANH) { 110 PetscCall(VecGetArray(x, &x_array)); 111 for (i = 0; i < N; ++i) { 112 x_array[i] = tanh((i - N/2.0)*(10.0/N)); 113 } 114 PetscCall(VecRestoreArray(x, &x_array)); 115 } 116 if (view) { 117 PetscCall(VecView(x, PETSC_VIEWER_STDOUT_WORLD)); 118 } 119 120 /* FFT - also test repeated transformation */ 121 /*-------------------------------------------*/ 122 PetscCall(VecGetArray(x,&x_array)); 123 PetscCall(VecGetArray(y,&y_array)); 124 PetscCall(VecGetArray(z,&z_array)); 125 for (i=0; i<4; i++) { 126 /* FFTW_FORWARD */ 127 fftw_execute(fplan); 128 129 /* FFTW_BACKWARD: destroys its input array 'y_array' even for out-of-place transforms! */ 130 fftw_execute(bplan); 131 } 132 PetscCall(VecRestoreArray(x,&x_array)); 133 PetscCall(VecRestoreArray(y,&y_array)); 134 PetscCall(VecRestoreArray(z,&z_array)); 135 136 /* Compare x and z. FFTW computes an unnormalized DFT, thus z = N*x */ 137 /*------------------------------------------------------------------*/ 138 s = 1.0/(PetscReal)N; 139 PetscCall(VecScale(z,s)); 140 if (view) PetscCall(VecView(x, PETSC_VIEWER_DRAW_WORLD)); 141 if (view) PetscCall(VecView(z, PETSC_VIEWER_DRAW_WORLD)); 142 PetscCall(VecAXPY(z,-1.0,x)); 143 PetscCall(VecNorm(z,NORM_1,&enorm)); 144 if (enorm > 1.e-11) { 145 PetscCall(PetscPrintf(PETSC_COMM_SELF," Error norm of |x - z| %g\n",(double)enorm)); 146 } 147 148 /* free spaces */ 149 fftw_destroy_plan(fplan); 150 fftw_destroy_plan(bplan); 151 PetscCall(VecDestroy(&x)); 152 PetscCall(VecDestroy(&y)); 153 PetscCall(VecDestroy(&z)); 154 } 155 PetscCall(PetscRandomDestroy(&rdm)); 156 PetscCall(PetscFinalize()); 157 return 0; 158 } 159 160 /*TEST 161 162 build: 163 requires: fftw !complex 164 165 test: 166 output_file: output/ex142.out 167 168 TEST*/ 169