Dear Mohammad,


it doesn't help me, or I did not understand your explanation.

If I do this:

  /* copy internal values (THIS WORKS, BUT COPIES NO BUFFER VALUES) */

  for(Int i=0; i<n; i++) {
    Int gi = mesh.nodes[i].global_number;
    VecGetValues(x, 1, &gi, &unk[i]);
  }

  /* copy ghost values (CREATES MANY WARNINGS */

  for(Int i=n; i<N; i++) {

    VecGetValues(x, 1, &i, &unk[i]);
  }

I get arnings are like this.

[0]PETSC ERROR: --------------------- Error Message ------------------------------------
[0]PETSC ERROR: Argument out of range!

[0]PETSC ERROR: Can only get local values, trying 3518!
[3]PETSC ERROR: --------------------- Error Message ------------------------------------
[3]PETSC ERROR: Argument out of range!
[3]PETSC ERROR: Can only get local values, trying 3511!
[3]PETSC ERROR: ------------------------------------------------------------------------

What am I doing wrong here?


    Cheers,


    Bojan

On 2/23/2012 11:23 PM, Mohammad Mirzadeh wrote:

just index x with the local numberings. if you have 'n' local nodes and 'g' ghost nodes in x, ghost nodes indecies run from 'n' to 'n+g-1'

On Feb 23, 2012 1:16 PM, "Bojan Niceno" <bojan.niceno@psi.ch> wrote:

Dear Jed,

thanks.

Now I have the following:

- Array unk, which should hold values inside the partition and in ghost cells.  It is big enough to hold both
- Vec x, created by command VecCreateGhost, with proper padding for ghost cells
- Successful call to linear solver in parallel.

But I need to copy ghost values from x to my array unk.

How can I do it?


    Kind regards,


    Bojan

On 2/23/2012 10:10 PM, Jed Brown wrote:

On Thu, Feb 23, 2012 at 15:05, Bojan Niceno <bojan.niceno@psi.ch> wrote:

No, I use global.

The local form is just a local vector. It doesn't even know that a global problem exists. You can't index into it using global indices. (In general, there is no efficient way to look up information in the local vector (includes ghost points) using global indices.)

 

  for(Int i=0; i<n; i++) {
    Int gi = mesh.nodes[i].global_number;
    VecGetValues(x, 1, &gi, &unk[i]);
  }

"n" is defined as the number of cells inside, i.e. without buffers.  "unk" is my external array.  If I try to access buffer values, I use:

  for(Int i=0; i<N; i++) {
    Int gi = mesh.nodes[i].global_number;
    VecGetValues(x, 1, &gi, &unk[i]);
  }

But then I end up with tons of warnings, presumably because I am going beyond "n".  Vector x was created with VecCreateGhost.

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