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 PetscErrorCode ierr; 9 PetscMPIInt rank,size; 10 PetscInt N0=50,N1=50,N=N0*N1; 11 PetscRandom rdm; 12 PetscReal enorm; 13 Vec x,y,z,input,output; 14 Mat A; 15 PetscInt DIM,dim[2]; 16 PetscReal fac; 17 18 ierr = PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr; 19 #if defined(PETSC_USE_COMPLEX) 20 SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_SUP, "This example requires real numbers"); 21 #endif 22 23 CHKERRMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size)); 24 CHKERRMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank)); 25 26 /* Create and set PETSc vectors 'input' and 'output' */ 27 CHKERRQ(PetscRandomCreate(PETSC_COMM_WORLD, &rdm)); 28 CHKERRQ(PetscRandomSetFromOptions(rdm)); 29 30 CHKERRQ(VecCreate(PETSC_COMM_WORLD,&input)); 31 CHKERRQ(VecSetSizes(input,PETSC_DECIDE,N0*N1)); 32 CHKERRQ(VecSetFromOptions(input)); 33 CHKERRQ(VecSetRandom(input,rdm)); 34 CHKERRQ(VecDuplicate(input,&output)); 35 CHKERRQ(PetscObjectSetName((PetscObject)input, "Real space vector")); 36 CHKERRQ(PetscObjectSetName((PetscObject)output, "Reconstructed vector")); 37 38 /* Get FFTW vectors 'x', 'y' and 'z' */ 39 DIM = 2; 40 dim[0] = N0; dim[1] = N1; 41 CHKERRQ(MatCreateFFT(PETSC_COMM_WORLD,DIM,dim,MATFFTW,&A)); 42 CHKERRQ(MatCreateVecsFFTW(A,&x,&y,&z)); 43 44 /* Scatter PETSc vector 'input' to FFTW vector 'x' */ 45 CHKERRQ(VecScatterPetscToFFTW(A,input,x)); 46 47 /* Apply forward FFT */ 48 CHKERRQ(MatMult(A,x,y)); 49 50 /* Apply backward FFT */ 51 CHKERRQ(MatMultTranspose(A,y,z)); 52 53 /* Scatter FFTW vector 'z' to PETSc vector 'output' */ 54 CHKERRQ(VecScatterFFTWToPetsc(A,z,output)); 55 56 /* Check accuracy */ 57 fac = 1.0/(PetscReal)N; 58 CHKERRQ(VecScale(output,fac)); 59 CHKERRQ(VecAXPY(output,-1.0,input)); 60 CHKERRQ(VecNorm(output,NORM_1,&enorm)); 61 if (enorm > 1.e-11 && rank == 0) { 62 CHKERRQ(PetscPrintf(PETSC_COMM_SELF," Error norm of |x - z| %e\n",enorm)); 63 } 64 65 /* Free spaces */ 66 CHKERRQ(PetscRandomDestroy(&rdm)); 67 CHKERRQ(VecDestroy(&input)); 68 CHKERRQ(VecDestroy(&output)); 69 CHKERRQ(VecDestroy(&x)); 70 CHKERRQ(VecDestroy(&y)); 71 CHKERRQ(VecDestroy(&z)); 72 CHKERRQ(MatDestroy(&A)); 73 74 ierr = PetscFinalize(); 75 return ierr; 76 } 77 78 /*TEST 79 80 build: 81 requires: fftw !complex 82 83 test: 84 output_file: output/ex148.out 85 86 test: 87 suffix: 2 88 nsize: 3 89 output_file: output/ex148.out 90 91 TEST*/ 92