2: /*
  3:      Tools to help solve the coarse grid problem redundantly.
  4:   Provides two scatter contexts that (1) map from the usual global vector
  5:   to all processors the entire vector in NATURAL numbering and (2)
  6:   from the entire vector on each processor in natural numbering extracts
  7:   out this processors piece in GLOBAL numbering
  8: */

 10:  #include <petsc/private/dmdaimpl.h>

 12: /*@
 13:    DMDAGlobalToNaturalAllCreate - Creates a scatter context that maps from the
 14:      global vector the entire vector to each processor in natural numbering

 16:    Collective on da

 18:    Input Parameter:
 19: .  da - the distributed array context

 21:    Output Parameter:
 22: .  scatter - the scatter context

 24:    Level: advanced

 26: .seealso: DMDAGlobalToNaturalEnd(), DMLocalToGlobalBegin(), DMDACreate2d(),
 27:           DMGlobalToLocalBegin(), DMGlobalToLocalEnd(), DMDACreateNaturalVector()
 28: @*/
 29: PetscErrorCode  DMDAGlobalToNaturalAllCreate(DM da,VecScatter *scatter)
 30: {
 32:   PetscInt       N;
 33:   IS             from,to;
 34:   Vec            tmplocal,global;
 35:   AO             ao;
 36:   DM_DA          *dd = (DM_DA*)da->data;

 41:   DMDAGetAO(da,&ao);

 43:   /* create the scatter context */
 44:   VecCreateMPIWithArray(PetscObjectComm((PetscObject)da),dd->w,dd->Nlocal,PETSC_DETERMINE,0,&global);
 45:   VecGetSize(global,&N);
 46:   ISCreateStride(PetscObjectComm((PetscObject)da),N,0,1,&to);
 47:   AOPetscToApplicationIS(ao,to);
 48:   ISCreateStride(PetscObjectComm((PetscObject)da),N,0,1,&from);
 49:   VecCreateSeqWithArray(PETSC_COMM_SELF,dd->w,N,0,&tmplocal);
 50:   VecScatterCreate(global,from,tmplocal,to,scatter);
 51:   VecDestroy(&tmplocal);
 52:   VecDestroy(&global);
 53:   ISDestroy(&from);
 54:   ISDestroy(&to);
 55:   return(0);
 56: }

 58: /*@
 59:    DMDANaturalAllToGlobalCreate - Creates a scatter context that maps from a copy
 60:      of the entire vector on each processor to its local part in the global vector.

 62:    Collective on da

 64:    Input Parameter:
 65: .  da - the distributed array context

 67:    Output Parameter:
 68: .  scatter - the scatter context

 70:    Level: advanced

 72: .seealso: DMDAGlobalToNaturalEnd(), DMLocalToGlobalBegin(), DMDACreate2d(),
 73:           DMGlobalToLocalBegin(), DMGlobalToLocalEnd(), DMDACreateNaturalVector()
 74: @*/
 75: PetscErrorCode  DMDANaturalAllToGlobalCreate(DM da,VecScatter *scatter)
 76: {
 78:   DM_DA          *dd = (DM_DA*)da->data;
 79:   PetscInt       M,m = dd->Nlocal,start;
 80:   IS             from,to;
 81:   Vec            tmplocal,global;
 82:   AO             ao;

 87:   DMDAGetAO(da,&ao);

 89:   /* create the scatter context */
 90:   MPIU_Allreduce(&m,&M,1,MPIU_INT,MPI_SUM,PetscObjectComm((PetscObject)da));
 91:   VecCreateMPIWithArray(PetscObjectComm((PetscObject)da),dd->w,m,PETSC_DETERMINE,0,&global);
 92:   VecGetOwnershipRange(global,&start,NULL);
 93:   ISCreateStride(PetscObjectComm((PetscObject)da),m,start,1,&from);
 94:   AOPetscToApplicationIS(ao,from);
 95:   ISCreateStride(PetscObjectComm((PetscObject)da),m,start,1,&to);
 96:   VecCreateSeqWithArray(PETSC_COMM_SELF,dd->w,M,0,&tmplocal);
 97:   VecScatterCreate(tmplocal,from,global,to,scatter);
 98:   VecDestroy(&tmplocal);
 99:   VecDestroy(&global);
100:   ISDestroy(&from);
101:   ISDestroy(&to);
102:   return(0);
103: }