Jed,
You added these two lines. Any idea why they are needed?
Thanks
Barry
3e08d2bebf99 src/dm/impls/da/dadist.c (Barry Smith 2012-09-18 14)
PetscFunctionBegin;
c688c0463f6c src/dm/impls/da/dadist.c (Matthew Knepley 2012-11-11 15)
ierr = VecGetDM(g, &da);CHKERRQ(ierr);
2dcb2ebcaafe src/dm/impls/da/dadist.c (Barry Smith 2010-10-31 16)
ierr = DMCreateGlobalVector(da,gg);CHKERRQ(ierr);
077aedaf8cb5 src/dm/impls/da/dadist.c (Jed Brown 2013-02-11 17)
ierr = VecGetLayout(g,&map);CHKERRQ(ierr);
077aedaf8cb5 src/dm/impls/da/dadist.c (Jed Brown 2013-02-11 18)
ierr = VecSetLayout(*gg,map);CHKERRQ(ierr);
2dcb2ebcaafe src/dm/impls/da/dadist.c (Barry Smith 2010-10-31 19)
PetscFunctionReturn(0)
If we were a bit more clever we could probably avoid all communication in
VecDuplicate() but is it worth bothering unless we know it is problematic
> On Jun 19, 2018, at 4:30 PM, Junchao Zhang <[email protected]> wrote:
>
> I met an expensive VecDuplicate. See the attached call stack.
> VecDuplicate_MPI_DA indirectly calls MPI_Allreduce/Allgather to build the
> vector's layout, but it then immediately destroys it with VecGetLayout &
> VecSetLayout. Is it wrong?
> src/dm/impls/da/dadist.c
> PetscErrorCode VecDuplicate_MPI_DA(Vec g,Vec *gg)
> {
> PetscErrorCode ierr;
> DM da;
> PetscLayout map;
>
> PetscFunctionBegin;
> ierr = VecGetDM(g, &da);CHKERRQ(ierr);
> ierr = DMCreateGlobalVector(da,gg);CHKERRQ(ierr);
> ierr = VecGetLayout(g,&map);CHKERRQ(ierr);
> ierr = VecSetLayout(*gg,map);CHKERRQ(ierr);
> PetscFunctionReturn(0);
> }
>
> --Junchao Zhang
> <VecDup.png>
