[petsc-users] DMDACoor3d and VecView

[Roc Wang]

> From: jedbrown at mcs.anl.gov
> To: pengxwang at hotmail.com; petsc-users at mcs.anl.gov
> Subject: Re: [petsc-users] DMDACoor3d and VecView
> Date: Thu, 23 May 2013 10:10:19 -0500
> 
> Roc Wang <pengxwang at hotmail.com> writes:
> 
> > The coordinates of nodes are needed to plot the 3-D distributions of
> > the solution. The matrix and the vector are managed with DMDA, so the
> > array for the coordinates can be obtained by
> > DMDAGetCoordinateDA(da,&cda) and DMDAVecGetArray(cda,gc,&coors).
> > Here, coors is defined as DMDACoor3d ***coors.  Since the function
> > VecVeiw can only output one vector, Vec sol, to a binary file , the
> > array of coordinates must be output to another file and thus must be
> > read separately. 
> 
> Not true, just read them in the same order you wrote them.

Does this mean I can save the vectors in the same binary file? If yes, whether the following procedure is correct?
/* writing vectors in solver program */
   DM             cda;
   Vec            gc;
   ierr = DMDAGetCoordinateDA(da,&cda);CHKERRQ(ierr); 
   ierr = DMDAGetCoordinates(cda, &gc);CHKERRQ(ierr);


  ierr = PetscViewerBinaryOpen(PETSC_COMM_WORLD,"vector.bin",FILE_MODE_WRITE,&viewer);CHKERRQ(ierr);
  ierr = VecView(sol,viewer);CHKERRQ(ierr);  //write solution vector
  ierr = VecView(gc,viewer);CHKERRQ(ierr);   //write coordinate vector
  ierr = PetscViewerDestroy(&viewer);CHKERRQ(ierr);  

/* reading vectors in a stand-along program */
  ierr = VecCreate(PETSC_COMM_WORLD,&sol);CHKERRQ(ierr);
  ierr = VecCreate(PETSC_COMM_WORLD,&gc);CHKERRQ(ierr);
  
  ierr = PetscViewerBinaryOpen(PETSC_COMM_WORLD,"vector.bin",FILE_MODE_READ,&viewer);CHKERRQ(ierr);
  ierr = VecLoad(sol,viewer);CHKERRQ(ierr); //read solution vector
  ierr = VecLoad(gc,viewer);CHKERRQ(ierr);  //read coordinate vector
  ierr = PetscViewerDestroy(&viewer);CHKERRQ(ierr);  

> 
> > The problem is that the array of coordinates is local array and the
> > number of processes in the post-processing program must be same as
> > that in the solver. 
> 
> DMGetCoordinates() returns a global Vec.  Store that, not the local Vec.
> 
> From the names, you must have an older version of PETSc.  Please upgrade
> to petsc-3.4.
 		 	   		  
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