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 PetscMPIInt rank, size; 8 PetscInt N0 = 50, N1 = 50, N = N0 * N1; 9 PetscRandom rdm; 10 PetscReal enorm; 11 Vec x, y, z, input, output; 12 Mat A; 13 PetscInt DIM, dim[2]; 14 PetscReal fac; 15 16 PetscFunctionBeginUser; 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; 40 dim[1] = N1; 41 PetscCall(MatCreateFFT(PETSC_COMM_WORLD, DIM, dim, MATFFTW, &A)); 42 PetscCall(MatCreateVecsFFTW(A, &x, &y, &z)); 43 44 /* Scatter PETSc vector 'input' to FFTW vector 'x' */ 45 PetscCall(VecScatterPetscToFFTW(A, input, x)); 46 47 /* Apply forward FFT */ 48 PetscCall(MatMult(A, x, y)); 49 50 /* Apply backward FFT */ 51 PetscCall(MatMultTranspose(A, y, z)); 52 53 /* Scatter FFTW vector 'z' to PETSc vector 'output' */ 54 PetscCall(VecScatterFFTWToPetsc(A, z, output)); 55 56 /* Check accuracy */ 57 fac = 1.0 / (PetscReal)N; 58 PetscCall(VecScale(output, fac)); 59 PetscCall(VecAXPY(output, -1.0, input)); 60 PetscCall(VecNorm(output, NORM_1, &enorm)); 61 if (enorm > 1.e-11 && rank == 0) { PetscCall(PetscPrintf(PETSC_COMM_SELF, " Error norm of |x - z| %e\n", enorm)); } 62 63 /* Free spaces */ 64 PetscCall(PetscRandomDestroy(&rdm)); 65 PetscCall(VecDestroy(&input)); 66 PetscCall(VecDestroy(&output)); 67 PetscCall(VecDestroy(&x)); 68 PetscCall(VecDestroy(&y)); 69 PetscCall(VecDestroy(&z)); 70 PetscCall(MatDestroy(&A)); 71 72 PetscCall(PetscFinalize()); 73 return 0; 74 } 75 76 /*TEST 77 78 build: 79 requires: fftw !complex 80 81 test: 82 output_file: output/ex148.out 83 84 test: 85 suffix: 2 86 nsize: 3 87 output_file: output/ex148.out 88 89 TEST*/ 90