Actual source code: ex158.c
1: static char help[] = "Illustrate how to use mpi FFTW and PETSc-FFTW interface \n\n";
3: /*
4: Usage:
5: mpiexec -n <np> ./ex158 -use_FFTW_interface NO
6: mpiexec -n <np> ./ex158 -use_FFTW_interface YES
7: */
9: #include <petscmat.h>
10: #include <fftw3-mpi.h>
14: PetscInt main(PetscInt argc,char **args)
15: {
16: PetscErrorCode ierr;
17: PetscMPIInt rank,size;
18: PetscInt N0=50,N1=20,N=N0*N1;
19: PetscRandom rdm;
20: PetscScalar a;
21: PetscReal enorm;
22: Vec x,y,z;
23: PetscBool view=PETSC_FALSE,use_interface=PETSC_TRUE;
25: PetscInitialize(&argc,&args,(char *)0,help);
26: #if defined(PETSC_USE_COMPLEX)
27: SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_SUP, "This example requires real numbers. Your current scalar type is complex");
28: #endif
30: PetscOptionsBegin(PETSC_COMM_WORLD, PETSC_NULL, "FFTW Options", "ex158");
31: PetscOptionsBool("-use_FFTW_interface", "Use PETSc-FFTW interface", "ex158",use_interface, &use_interface, PETSC_NULL);
32: PetscOptionsEnd();
34: MPI_Comm_size(PETSC_COMM_WORLD, &size);
35: MPI_Comm_rank(PETSC_COMM_WORLD, &rank);
37: PetscRandomCreate(PETSC_COMM_WORLD, &rdm);
38: PetscRandomSetFromOptions(rdm);
40: if (!use_interface){
41: /* Use mpi FFTW without PETSc-FFTW interface, 2D case only */
42: /*---------------------------------------------------------*/
43: fftw_plan fplan,bplan;
44: fftw_complex *data_in,*data_out,*data_out2;
45: ptrdiff_t alloc_local,local_n0,local_0_start;
47: if (!rank) printf("Use FFTW without PETSc-FFTW interface\n");
48: fftw_mpi_init();
49: N = N0*N1;
50: alloc_local = fftw_mpi_local_size_2d(N0,N1,PETSC_COMM_WORLD,&local_n0,&local_0_start);
52: data_in = (fftw_complex*)fftw_malloc(sizeof(fftw_complex)*alloc_local);
53: data_out = (fftw_complex*)fftw_malloc(sizeof(fftw_complex)*alloc_local);
54: data_out2 = (fftw_complex*)fftw_malloc(sizeof(fftw_complex)*alloc_local);
55: VecCreateMPIWithArray(PETSC_COMM_WORLD,(PetscInt)local_n0*N1,(PetscInt)N,(const PetscScalar*)data_in,&x);
56: PetscObjectSetName((PetscObject) x, "Real Space vector");
57: VecCreateMPIWithArray(PETSC_COMM_WORLD,(PetscInt)local_n0*N1,(PetscInt)N,(const PetscScalar*)data_out,&y);
58: PetscObjectSetName((PetscObject) y, "Frequency space vector");
59: VecCreateMPIWithArray(PETSC_COMM_WORLD,(PetscInt)local_n0*N1,(PetscInt)N,(const PetscScalar*)data_out2,&z);
60: PetscObjectSetName((PetscObject) z, "Reconstructed vector");
62: fplan = fftw_mpi_plan_dft_2d(N0,N1,data_in,data_out,PETSC_COMM_WORLD,FFTW_FORWARD,FFTW_ESTIMATE);
63: bplan = fftw_mpi_plan_dft_2d(N0,N1,data_out,data_out2,PETSC_COMM_WORLD,FFTW_BACKWARD,FFTW_ESTIMATE);
65: VecSetRandom(x, rdm);
66: if (view){VecView(x,PETSC_VIEWER_STDOUT_WORLD);}
68: fftw_execute(fplan);
69: if (view){VecView(y,PETSC_VIEWER_STDOUT_WORLD);}
71: fftw_execute(bplan);
73: /* Compare x and z. FFTW computes an unnormalized DFT, thus z = N*x */
74: a = 1.0/(PetscReal)N;
75: VecScale(z,a);
76: if (view){VecView(z, PETSC_VIEWER_STDOUT_WORLD);}
77: VecAXPY(z,-1.0,x);
78: VecNorm(z,NORM_1,&enorm);
79: if (enorm > 1.e-11){
80: PetscPrintf(PETSC_COMM_SELF," Error norm of |x - z| %A\n",enorm);
81: }
83: /* Free spaces */
84: fftw_destroy_plan(fplan);
85: fftw_destroy_plan(bplan);
86: fftw_free(data_in); VecDestroy(&x);
87: fftw_free(data_out); VecDestroy(&y);
88: fftw_free(data_out2);VecDestroy(&z);
90: } else {
91: /* Use PETSc-FFTW interface */
92: /*-------------------------------------------*/
93: PetscInt i,*dim,k,DIM;
94: Mat A;
95: Vec input,output;
97: N=30;
98: for (i=2; i<5; i++){
99: DIM = i;
100: PetscMalloc(i*sizeof(PetscInt),&dim);
101: for(k=0;k<i;k++){
102: dim[k]=30;
103: }
104: N *= dim[i-1];
105:
106: /* Create FFTW object */
107: if (!rank) printf("Use PETSc-FFTW interface...%d-DIM:%d \n",DIM,N);
108: MatCreateFFT(PETSC_COMM_WORLD,DIM,dim,MATFFTW,&A);
110: /* Create FFTW vectors that are compatible with parallel layout of A */
111: MatGetVecsFFTW(A,&x,&y,&z);
112: PetscObjectSetName((PetscObject) x, "Real space vector");
113: PetscObjectSetName((PetscObject) y, "Frequency space vector");
114: PetscObjectSetName((PetscObject) z, "Reconstructed vector");
116: /* Create and set PETSc vector */
117: VecCreate(PETSC_COMM_WORLD,&input);
118: VecSetSizes(input,PETSC_DECIDE,N);
119: VecSetFromOptions(input);
120: VecSetRandom(input,rdm);
121: VecDuplicate(input,&output);
122: if (view){VecView(input,PETSC_VIEWER_STDOUT_WORLD);}
124: /* Vector input is copied to another vector x using VecScatterPetscToFFTW. This is because the user data
125: can have any parallel layout. But FFTW requires special parallel layout of the data. Hence the original
126: data which is in the vector "input" here, needs to be copied to a vector x, which has the correct parallel
127: layout for FFTW. Also, during parallel real transform, this pads extra zeros automatically
128: at the end of last dimension. This padding is required by FFTW to perform parallel real D.F.T. */
129: VecScatterPetscToFFTW(A,input,x);
130:
131: /* Apply FFTW_FORWARD and FFTW_BACKWARD */
132: MatMult(A,x,y);
133: if (view){VecView(y,PETSC_VIEWER_STDOUT_WORLD);}
134: MatMultTranspose(A,y,z);
136: /* Output from Backward DFT needs to be modified to obtain user readable data the routine VecScatterFFTWToPetsc
137: performs the job. In some sense this is the reverse operation of VecScatterPetscToFFTW. This routine gets rid of
138: the extra spaces that were artificially padded to perform real parallel transform. */
139: VecScatterFFTWToPetsc(A,z,output);
141: /* Compare x and z. FFTW computes an unnormalized DFT, thus z = N*x */
142: a = 1.0/(PetscReal)N;
143: VecScale(output,a);
144: if (view){VecView(output,PETSC_VIEWER_STDOUT_WORLD);}
145: VecAXPY(output,-1.0,input);
146: VecNorm(output,NORM_1,&enorm);
147: if (enorm > 1.e-09 && !rank){
148: PetscPrintf(PETSC_COMM_SELF," Error norm of |x - z| %e\n",enorm);
149: }
151: /* Free spaces */
152: PetscFree(dim);
153: VecDestroy(&input);
154: VecDestroy(&output);
155: VecDestroy(&x);
156: VecDestroy(&y);
157: VecDestroy(&z);
158: MatDestroy(&A);
159: }
160: }
161: PetscRandomDestroy(&rdm);
162: PetscFinalize();
163: return 0;
164: }