Open MPI logo

Open MPI User's Mailing List Archives

  |   Home   |   Support   |   FAQ   |   all Open MPI User's mailing list

Subject: Re: [OMPI users] possible bug exercised by mpi4py
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2012-05-24 21:13:16


On May 24, 2012, at 11:57 AM, Lisandro Dalcin wrote:

> The standard says this:
>
> "Within each group, all processes provide the same recvcounts
> argument, and provide input vectors of sum_i^n recvcounts[i] elements
> stored in the send buffers, where n is the size of the group"
>
> So, I read " Within each group, ... where n is the size of the group"
> as being the LOCAL group size.

Actually, that seems like a direct contradiction with the prior sentence:

If comm is an intercommunicator, then the result of the reduction of the data provided by processes in one group (group A) is scattered among processes in the other group (group B), and vice versa.

It looks like the implementors of 2 implementations agree that recvcounts should be the size of the remote group. Sounds like this needs to be brought up in front of the Forum...

-- 
Jeff Squyres
jsquyres_at_[hidden]
For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/