1: static char help[]="This program illustrates the use of PETSc-fftw interface for real DFT\n";
  2:  #include <petscmat.h>
  3: #include <fftw3-mpi.h>

  5: extern PetscErrorCode InputTransformFFT(Mat,Vec,Vec);
  6: extern PetscErrorCode OutputTransformFFT(Mat,Vec,Vec);
  7: PetscInt main(PetscInt argc,char **args)
  8: {
 10:   PetscMPIInt    rank,size;
 11:   PetscInt       N0=3,N1=3,N2=3,N3=3,N4=3,N=N0*N1*N2*N3;
 12:   PetscRandom    rdm;
 13:   PetscReal      enorm;
 14:   Vec            x,y,z,input,output;
 15:   Mat            A;
 16:   PetscInt       DIM, dim[5],vsize;
 17:   PetscReal      fac;
 18:   PetscScalar    one=1;

 20:   PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
 21: #if defined(PETSC_USE_COMPLEX)
 22:   SETERRQ(PETSC_COMM_WORLD,PETSC_ERR_SUP, "This example requires real numbers");
 23: #endif

 25:   MPI_Comm_size(PETSC_COMM_WORLD, &size);
 26:   MPI_Comm_rank(PETSC_COMM_WORLD, &rank);

 28:   PetscRandomCreate(PETSC_COMM_WORLD, &rdm);
 29:   PetscRandomSetFromOptions(rdm);
 30:   VecCreate(PETSC_COMM_WORLD,&input);
 31:   VecSetSizes(input,PETSC_DECIDE,N);
 32:   VecSetFromOptions(input);
 33:   VecSetRandom(input,rdm);
 34:   VecAssemblyBegin(input);
 35:   VecAssemblyEnd(input);
 36: /*  VecView(input,PETSC_VIEWER_STDOUT_WORLD); */
 37:   VecDuplicate(input,&output);

 39:   DIM    = 4;
 40:   dim[0] = N0; dim[1] = N1; dim[2] = N2; dim[3] = N3; dim[4] = N4;

 42:   MatCreateFFT(PETSC_COMM_WORLD,DIM,dim,MATFFTW,&A);
 43:   MatCreateVecs(A,&x,&y);
 44:   MatCreateVecs(A,&z,NULL);
 45:   VecGetSize(x,&vsize);
 46:   printf("The vector size from the main routine is %d\n",vsize);

 48:   InputTransformFFT(A,input,x);

 50:   MatMult(A,x,y);
 51:   VecAssemblyBegin(y);
 52:   VecAssemblyEnd(y);
 53:   VecView(y,PETSC_VIEWER_STDOUT_WORLD);
 54:   MatMultTranspose(A,y,z);
 55:   VecGetSize(z,&vsize);
 56:   printf("The vector size of zfrom the main routine is %d\n",vsize);

 58:   OutputTransformFFT(A,z,output);

 60:   fac  = 1.0/(PetscReal)N;
 61:   VecScale(output,fac);

 63:   VecAssemblyBegin(input);
 64:   VecAssemblyEnd(input);
 65:   VecAssemblyBegin(output);
 66:   VecAssemblyEnd(output);

 68:   VecView(input,PETSC_VIEWER_STDOUT_WORLD);
 69:   VecView(output,PETSC_VIEWER_STDOUT_WORLD);

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




 82: /* MatCreateVecs(A,&z,NULL); */
 83: /*  printf("Vector size from ex148 %d\n",vsize); */
 84: /*  PetscObjectSetName((PetscObject) x, "Real space vector"); */
 85: /*      PetscObjectSetName((PetscObject) y, "Frequency space vector"); */
 86: /*      PetscObjectSetName((PetscObject) z, "Reconstructed vector"); */

 88:   VecDestroy(&output);
 89:   VecDestroy(&input);
 90:   VecDestroy(&x);
 91:   VecDestroy(&y);
 92:   VecDestroy(&z);
 93:   MatDestroy(&A);
 94:   PetscRandomDestroy(&rdm);
 95:   PetscFinalize();
 96:   return ierr;
 97: }