Hi all,

We discussed the neighborhood reductions at the last Forum and the straw
vote if we should include them in the next revision was:

- yes: 18
- no: 0
- abstain: 3

I addressed all the issues in the draft that were brought up at the
Forum. The new draft is now at http://www.unixer.de/sec/topol.pdf . Look
for ticket "XXX".

The other interfaces for MPI_Ineighbor_reduce do not contain the "I" (page 40, line 25 and 30); MPI_Ineighbor_reducev

does not have the "v" (page 41, line 26 and 31).

One open question remains: would a single send buffer for
neighbor_reduce suffice or do we need one buffer per destination
process? The second case could always be done with neighbor_reducev
(with small additional costs). This questions is more to the potential
users (Jed etc.).

My understanding of Neighbor_reducev is that I send different sizes to each neighbor, but receive the same size from every neighbor (reducing into exactly one buffer). That isn't really a useful operation in domain decomposed methods. The useful operation is that I reduce different sized received buffers into different (but sometimes overlapping) parts of my local buffer.

The single send buffer (with different datatype arguments) imposes no restriction and is natural.