distributed array

[Matt Funk]

Thanks for the response (and sorry for the late 'thanks'),

i can see how this is supposed to work. However, my question is then with the 
creation of the distributed array objects. I take it from your code that you 
create a DA for each patch (?). M and N then would be the dimension of my 2D 
patch. My question is what i would be specifying for n and m. I am a little 
confused in general what m and n are. It says they denote the process 
partition in each direction and that m*n must be equal the total number of 
processes in the communicator.
Sorry, i am almost sure this is something simple. 

thanks
mat

On Thursday 13 July 2006 23:13, Berend van Wachem wrote:
>  > Hi,
>  >
>  > i was wondering if it is possible (or advisable) to use a distributed
>
> array
>
>  > for when my domain is not necessarily rectangular but my subdomains are
>  > rectangular?
>  >
>  > thanks
>  > mat
>
> Hi Matt,
>
> This is exactly what I do; I work with a multi-block CFD problem, where
> the total geometry consists of a number of structured (not neccesarily
> rectangular) blocks. Each block has its own DA.
>
> How I solved it, with help from the petsc team, is by making functions
> which translate vectors from the complete domain (called block global in
> my code) to each block (called block local in my code). The matrix
> computation is done at the blockglobal level, and I can manipulate the
> vectors at the block local level. Just to give an example, I attatch the
> code at the end of this email. If you want more help/information please
> let me know.
>
> Good luck,
>
> Berend.
>
>
> #undef __FUNCT__
> #define __FUNCT__ "VecBlockGlobalToBlockLocalBegin"
> int VecBlockGlobalToBlockLocalBegin(Vec **B, Vec **A, char* name, struct
> CFDMesh *Mesh)
> {
>     int ierr, i;
>     double *tmpPTR=NULL;
>
>     PetscFunctionBegin;
>
>     AddToListofLocalVectors(&Mesh->BLCC,Mesh->NMyBlocks,A,tmpPTR,name);
>
>     for (i=0; i<Mesh->NMyBlocks; i++)
>     {
>        ierr=DAGetLocalVector(Mesh->CFDBlocks[i].da, &((*A)[i]));
> CHKERRQ(ierr);
>
> ierr=DAGlobalToLocalBegin(Mesh->CFDBlocks[i].da,(*B)[i],INSERT_VALUES,(*A)[
>i]); CHKERRQ(ierr);
>
> ierr=DAGlobalToLocalEnd(Mesh->CFDBlocks[i].da,(*B)[i],INSERT_VALUES,(*A)[i]
>); CHKERRQ(ierr);
>
>     }
>
>     PetscFunctionReturn(0);
> }
>
> #undef __FUNCT__
> #define __FUNCT__ "VecBlockGlobalToBlockLocalEnd"
> int VecBlockGlobalToBlockLocalEnd(Vec **B, Vec **A, struct CFDMesh
> *Mesh,int CopyData)
> {
>     int i,ierr;
>
>     PetscFunctionBegin;
>
>     for (i=0; i<Mesh->NMyBlocks; i++)
>     {
>       if (CopyData==MF_COPY_DATA)
>       {
>
> ierr=DALocalToGlobal(Mesh->CFDBlocks[i].da,(*A)[i],INSERT_VALUES,(*B)[i]);
> CHKERRQ(ierr);
>       }
>       ierr=DARestoreLocalVector(Mesh->CFDBlocks[i].da,&((*A)[i]));
> CHKERRQ(ierr);
>     }
>     DeleteFromListOfLocalVectors(&Mesh->BLCC,*A);
>
>     PetscFunctionReturn(0);
>
> }