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