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>    /*I   "petscdmda.h"   I*/

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

 18:    Collective on DMDA

 20:    Input Parameter:
 21: .  da - the distributed array context

 23:    Output Parameter:
 24: .  scatter - the scatter context

 26:    Level: advanced

 28: .keywords: distributed array, global to local, begin, coarse problem

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

 45:   DMDAGetAO(da,&ao);

 47:   /* create the scatter context */
 48:   VecCreateMPIWithArray(PetscObjectComm((PetscObject)da),dd->w,dd->Nlocal,PETSC_DETERMINE,0,&global);
 49:   VecGetSize(global,&N);
 50:   ISCreateStride(PetscObjectComm((PetscObject)da),N,0,1,&to);
 51:   AOPetscToApplicationIS(ao,to);
 52:   ISCreateStride(PetscObjectComm((PetscObject)da),N,0,1,&from);
 53:   VecCreateSeqWithArray(PETSC_COMM_SELF,dd->w,N,0,&tmplocal);
 54:   VecScatterCreate(global,from,tmplocal,to,scatter);
 55:   VecDestroy(&tmplocal);
 56:   VecDestroy(&global);
 57:   ISDestroy(&from);
 58:   ISDestroy(&to);
 59:   return(0);
 60: }

 64: /*@
 65:    DMDANaturalAllToGlobalCreate - Creates a scatter context that maps from a copy
 66:      of the entire vector on each processor to its local part in the global vector.

 68:    Collective on DMDA

 70:    Input Parameter:
 71: .  da - the distributed array context

 73:    Output Parameter:
 74: .  scatter - the scatter context

 76:    Level: advanced

 78: .keywords: distributed array, global to local, begin, coarse problem

 80: .seealso: DMDAGlobalToNaturalEnd(), DMLocalToGlobalBegin(), DMDACreate2d(),
 81:           DMGlobalToLocalBegin(), DMGlobalToLocalEnd(), DMDACreateNaturalVector()
 82: @*/
 83: PetscErrorCode  DMDANaturalAllToGlobalCreate(DM da,VecScatter *scatter)
 84: {
 86:   DM_DA          *dd = (DM_DA*)da->data;
 87:   PetscInt       M,m = dd->Nlocal,start;
 88:   IS             from,to;
 89:   Vec            tmplocal,global;
 90:   AO             ao;

 95:   DMDAGetAO(da,&ao);

 97:   /* create the scatter context */
 98:   MPI_Allreduce(&m,&M,1,MPIU_INT,MPI_SUM,PetscObjectComm((PetscObject)da));
 99:   VecCreateMPIWithArray(PetscObjectComm((PetscObject)da),dd->w,m,PETSC_DETERMINE,0,&global);
100:   VecGetOwnershipRange(global,&start,NULL);
101:   ISCreateStride(PetscObjectComm((PetscObject)da),m,start,1,&from);
102:   AOPetscToApplicationIS(ao,from);
103:   ISCreateStride(PetscObjectComm((PetscObject)da),m,start,1,&to);
104:   VecCreateSeqWithArray(PETSC_COMM_SELF,dd->w,M,0,&tmplocal);
105:   VecScatterCreate(tmplocal,from,global,to,scatter);
106:   VecDestroy(&tmplocal);
107:   VecDestroy(&global);
108:   ISDestroy(&from);
109:   ISDestroy(&to);
110:   return(0);
111: }