1: static char help[] = "This program illustrates the use of PETSc-fftw interface for parallel real DFT\n";
  2: #include <petscmat.h>
  3: #include <fftw3-mpi.h>
  4: int main(int argc, char **args)
  5: {
  6:   PetscMPIInt rank, size;
  7:   PetscInt    N0 = 2048, N1 = 2048, N2 = 3, N3 = 5, N4 = 5, N = N0 * N1;
  8:   PetscRandom rdm;
  9:   PetscReal   enorm;
 10:   Vec         x, y, z, input, output;
 11:   Mat         A;
 12:   PetscInt    DIM, dim[5], vsize;
 13:   PetscReal   fac;
 14:   PetscScalar one = 1, two = 2, three = 3;

 16:   PetscFunctionBeginUser;
 17:   PetscCall(PetscInitialize(&argc, &args, NULL, help));
 18:   PetscCheck(!PetscDefined(USE_COMPLEX), PETSC_COMM_WORLD, PETSC_ERR_SUP, "This example requires real numbers");
 19:   PetscCallMPI(MPI_Comm_size(PETSC_COMM_WORLD, &size));
 20:   PetscCallMPI(MPI_Comm_rank(PETSC_COMM_WORLD, &rank));

 22:   PetscCall(PetscRandomCreate(PETSC_COMM_WORLD, &rdm));
 23:   PetscCall(PetscRandomSetFromOptions(rdm));
 24:   PetscCall(VecCreate(PETSC_COMM_WORLD, &input));
 25:   PetscCall(VecSetSizes(input, PETSC_DECIDE, N));
 26:   PetscCall(VecSetFromOptions(input));
 27:   /*  PetscCall(VecSet(input,one)); */
 28:   /*  PetscCall(VecSetValue(input,1,two,INSERT_VALUES)); */
 29:   /*  PetscCall(VecSetValue(input,2,three,INSERT_VALUES)); */
 30:   /*  PetscCall(VecSetValue(input,3,three,INSERT_VALUES)); */
 31:   PetscCall(VecSetRandom(input, rdm));
 32:   /*  PetscCall(VecSetRandom(input,rdm)); */
 33:   /*  PetscCall(VecSetRandom(input,rdm)); */
 34:   PetscCall(VecDuplicate(input, &output));

 36:   DIM    = 2;
 37:   dim[0] = N0;
 38:   dim[1] = N1;
 39:   dim[2] = N2;
 40:   dim[3] = N3;
 41:   dim[4] = N4;
 42:   PetscCall(MatCreateFFT(PETSC_COMM_WORLD, DIM, dim, MATFFTW, &A));
 43:   PetscCall(MatCreateVecsFFTW(A, &x, &y, &z));
 44:   /*  PetscCall(MatCreateVecs(A,&x,&y)); */
 45:   /*  PetscCall(MatCreateVecs(A,&z,NULL)); */

 47:   PetscCall(VecGetSize(x, &vsize));
 48:   printf("The vector size  of input from the main routine is %d\n", vsize);

 50:   PetscCall(VecGetSize(z, &vsize));
 51:   printf("The vector size of output from the main routine is %d\n", vsize);

 53:   PetscCall(InputTransformFFT(A, input, x));

 55:   PetscCall(MatMult(A, x, y));
 56:   PetscCall(VecAssemblyBegin(y));
 57:   PetscCall(VecAssemblyEnd(y));
 58:   PetscCall(VecView(y, PETSC_VIEWER_STDOUT_WORLD));

 60:   PetscCall(MatMultTranspose(A, y, z));

 62:   PetscCall(OutputTransformFFT(A, z, output));
 63:   fac = 1.0 / (PetscReal)N;
 64:   PetscCall(VecScale(output, fac));

 66:   PetscCall(VecAssemblyBegin(input));
 67:   PetscCall(VecAssemblyEnd(input));
 68:   PetscCall(VecAssemblyBegin(output));
 69:   PetscCall(VecAssemblyEnd(output));

 71:   /*  PetscCall(VecView(input,PETSC_VIEWER_STDOUT_WORLD)); */
 72:   /*  PetscCall(VecView(output,PETSC_VIEWER_STDOUT_WORLD)); */

 74:   PetscCall(VecAXPY(output, -1.0, input));
 75:   PetscCall(VecNorm(output, NORM_1, &enorm));
 76:   /*  if (enorm > 1.e-14) { */
 77:   PetscCall(PetscPrintf(PETSC_COMM_SELF, "  Error norm of |x - z| %e\n", enorm));
 78:   /*      } */

 80:   PetscCall(VecDestroy(&output));
 81:   PetscCall(VecDestroy(&input));
 82:   PetscCall(VecDestroy(&x));
 83:   PetscCall(VecDestroy(&y));
 84:   PetscCall(VecDestroy(&z));
 85:   PetscCall(MatDestroy(&A));
 86:   PetscCall(PetscRandomDestroy(&rdm));
 87:   PetscCall(PetscFinalize());
 88:   return 0;
 89: }