[petsc-dev] SF broken in master !

[Tobin Isaac]

On Wed, Oct 15, 2014 at 12:04:47AM -0500, Jed Brown wrote:
> Barry Smith <bsmith at mcs.anl.gov> writes:
> 
> >   and yet it is not broke in next. I thought that was impossible!
> 
> This commit was bad:
> 
>   https://bitbucket.org/petsc/petsc/commits/60a1948e59517edd5702a5e277d78229b7015096
> 
> Toby pointed it out and fixed it in this commit, which went into 'next':
> 
>   https://bitbucket.org/petsc/petsc/commits/38e7336fef8d310d693744ab39306ec09879f8c2
> 
> Meanwhile, Matt didn't put this in his branch and went on to make other
> changes to SF, including a similar commit:
> 
>   https://bitbucket.org/petsc/petsc/commits/9837ea968140067d7f638ef40a3e6ee2b94657e5
> 
> Again, Toby pointed out the bug in this commit, which Matt had to
> resolve when merging to 'next' because it conflicted with Toby's correct
> version.  The tests certainly did not pass in Matt's branch, but they
> passed in 'next' because Toby's branch fixed the bug.
> 
> Ultimately, Matt merged to 'master' without merging Toby's bug fix.
> 
> I have now merged Toby's branch and 'master' works again.  Thanks, Toby.

The praise might be misplaced: their bad commit assumed that sf->nroots
is always as big as the index space of the leaves; my commit assumed
that sf->nleaves was always big enough.  For sparse leaves, neither
may be the case (see Michael's comment on the first commit above).  I
though Matt had a commit that was the "right" think to do...

  Toby

> 
> 
> Note that prior to this merge, the following was the only difference
> between 'master' and 'next':
> 
> diff --git c/src/vec/is/sf/interface/sf.c w/src/vec/is/sf/interface/sf.c
> index af2dc58..26a286a 100644
> --- c/src/vec/is/sf/interface/sf.c
> +++ w/src/vec/is/sf/interface/sf.c
> @@ -794,7 +794,7 @@ PetscErrorCode PetscSFGetMultiSF(PetscSF sf,PetscSF *multi)
>      ierr = PetscMalloc1(sf->nleaves,&remote);CHKERRQ(ierr);
>      for (i=0; i<sf->nleaves; i++) {
>        remote[i].rank  = sf->remote[i].rank;
> -      remote[i].index = outoffset[sf->mine ? sf->mine[i] : 1];
> +      remote[i].index = outoffset[sf->mine ? sf->mine[i] : i];
>      }
>      ierr = PetscSFDuplicate(sf,PETSCSF_DUPLICATE_RANKS,&sf->multi);CHKERRQ(ierr);
>      ierr = PetscSFSetGraph(sf->multi,inoffset[sf->nroots],sf->nleaves,NULL,PETSC_COPY_VALUES,remote,PETSC_OWN_POINTER);CHKERRQ(ierr);
> 
> 
> To avoid this in the future, I suggest
> 
>   1. Run tests on topic branches, especially those tests related to the
>   modification.  If you're tinkering with SF, the least you can do is
>   run the SF tests.
> 
>   2. Fix content bugs in the topic branch instead of sneaking it into a
>   merge commit that's oh so easy to forget.


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