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"; 3 4 #include <petscmat.h> 5 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; 16 17 PetscCall(PetscInitialize(&argc,&args,(char*)0,help)); 18 #if defined(PETSC_USE_COMPLEX) 19 SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_SUP, "This example requires real numbers"); 20 #endif 21 22 PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size)); 23 PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank)); 24 25 /* Create and set PETSc vectors 'input' and 'output' */ 26 PetscCall(PetscRandomCreate(PETSC_COMM_WORLD, &rdm)); 27 PetscCall(PetscRandomSetFromOptions(rdm)); 28 29 PetscCall(VecCreate(PETSC_COMM_WORLD,&input)); 30 PetscCall(VecSetSizes(input,PETSC_DECIDE,N0*N1)); 31 PetscCall(VecSetFromOptions(input)); 32 PetscCall(VecSetRandom(input,rdm)); 33 PetscCall(VecDuplicate(input,&output)); 34 PetscCall(PetscObjectSetName((PetscObject)input, "Real space vector")); 35 PetscCall(PetscObjectSetName((PetscObject)output, "Reconstructed vector")); 36 37 /* Get FFTW vectors 'x', 'y' and 'z' */ 38 DIM = 2; 39 dim[0] = N0; dim[1] = N1; 40 PetscCall(MatCreateFFT(PETSC_COMM_WORLD,DIM,dim,MATFFTW,&A)); 41 PetscCall(MatCreateVecsFFTW(A,&x,&y,&z)); 42 43 /* Scatter PETSc vector 'input' to FFTW vector 'x' */ 44 PetscCall(VecScatterPetscToFFTW(A,input,x)); 45 46 /* Apply forward FFT */ 47 PetscCall(MatMult(A,x,y)); 48 49 /* Apply backward FFT */ 50 PetscCall(MatMultTranspose(A,y,z)); 51 52 /* Scatter FFTW vector 'z' to PETSc vector 'output' */ 53 PetscCall(VecScatterFFTWToPetsc(A,z,output)); 54 55 /* Check accuracy */ 56 fac = 1.0/(PetscReal)N; 57 PetscCall(VecScale(output,fac)); 58 PetscCall(VecAXPY(output,-1.0,input)); 59 PetscCall(VecNorm(output,NORM_1,&enorm)); 60 if (enorm > 1.e-11 && rank == 0) { 61 PetscCall(PetscPrintf(PETSC_COMM_SELF," Error norm of |x - z| %e\n",enorm)); 62 } 63 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)); 72 73 PetscCall(PetscFinalize()); 74 return 0; 75 } 76 77 /*TEST 78 79 build: 80 requires: fftw !complex 81 82 test: 83 output_file: output/ex148.out 84 85 test: 86 suffix: 2 87 nsize: 3 88 output_file: output/ex148.out 89 90 TEST*/ 91