[petsc-users] DMLocalToGlobal PETScSF is BROKEN

[Jed Brown]

Barry Smith <bsmith at mcs.anl.gov> writes:
>     Ok, well the damn code is so convoluted it is hard to see that it
>     is even trying to do things right for multiple independent calls.

How would you change this to make it less convoluted?

static PetscErrorCode PetscSFReduceEnd_Basic(PetscSF sf,MPI_Datatype unit,const void *leafdata,void *rootdata,MPI_Op op)
{
  void             (*UnpackOp)(PetscInt,const PetscInt*,void*,const void*);
  PetscErrorCode   ierr;
  PetscSFBasicPack link;
  PetscInt         i,nrootranks;
  const PetscInt   *rootoffset,*rootloc;

  PetscFunctionBegin;
  ierr = PetscSFBasicGetPackInUse(sf,unit,rootdata,PETSC_OWN_POINTER,&link);CHKERRQ(ierr);
  /* This implementation could be changed to unpack as receives arrive, at the cost of non-determinism */
  ierr = PetscSFBasicPackWaitall(sf,link);CHKERRQ(ierr);
  ierr = PetscSFBasicGetRootInfo(sf,&nrootranks,NULL,&rootoffset,&rootloc);CHKERRQ(ierr);
  ierr = PetscSFBasicPackGetUnpackOp(sf,link,op,&UnpackOp);CHKERRQ(ierr);
  for (i=0; i<nrootranks; i++) {
    PetscMPIInt n          = rootoffset[i+1] - rootoffset[i];
    const void  *packstart = link->root+rootoffset[i]*link->unitbytes;

    (*UnpackOp)(n,rootloc+rootoffset[i],rootdata,packstart);
  }
  ierr = PetscSFBasicReclaimPack(sf,&link);CHKERRQ(ierr);
  PetscFunctionReturn(0);
}


>     You’ll have to pry out of Dhamendar his test case that fails.

That would be useful.
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