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: PetscInt main(PetscInt argc,char **args)
  5: {
  7:   PetscMPIInt    rank,size;
  8:   PetscInt       N0=2048,N1=2048,N2=3,N3=5,N4=5,N=N0*N1;
  9:   PetscRandom    rdm;
 10:   PetscReal      enorm;
 11:   Vec            x,y,z,input,output;
 12:   Mat            A;
 13:   PetscInt       DIM, dim[5],vsize;
 14:   PetscReal      fac;
 15:   PetscScalar    one=1,two=2,three=3;

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

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

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

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

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

 50:   InputTransformFFT(A,input,x);

 52:   MatMult(A,x,y);
 53:   VecAssemblyBegin(y);
 54:   VecAssemblyEnd(y);
 55:   VecView(y,PETSC_VIEWER_STDOUT_WORLD);

 57:   MatMultTranspose(A,y,z);

 59:   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:   PetscPrintf(PETSC_COMM_SELF,"  Error norm of |x - z| %e\n",enorm);
 75: /*      } */

 77:   VecDestroy(&output);
 78:   VecDestroy(&input);
 79:   VecDestroy(&x);
 80:   VecDestroy(&y);
 81:   VecDestroy(&z);
 82:   MatDestroy(&A);
 83:   PetscRandomDestroy(&rdm);
 84:   PetscFinalize();
 85:   return ierr;

 87: }