This web mail archive is frozen.
This page is part of a frozen web archive of this mailing list.
You can still navigate around this archive, but know that no new mails
have been added to it since July of 2016.
Click here to be taken to the new web archives of this list; it includes all the mails that are in this frozen archive plus all new mails that have been sent to the list since it was migrated to the new archives.
On Thu, 2008-03-20 at 10:27 -0700, Dave Grote wrote:
After reading the previous discussion on AllReduce and AlltoAll, I
thought I would ask my question. I have a case where I have data
unevenly distributed among the processes (unevenly means that the
processes have differing amounts of data) that I need to globally
redistribute, resulting in a different uneven distribution. Writing the
code to do the redistribution using AlltoAll is straightforward.
The problem though is that there are often special cases where each
process only needs to exchange data with it neighbors. So the question
is that when two processors don't have data to exchange, is the OpenMPI
AlltoAll is written in such a way so that they don't do any
communication? Will the AlltoAll be as efficient (or at least nearly as
efficient) as direct send/recv among neighbors?
AlltoAll takes a single size of message and communictes that amount of
data from everybody to everybody. You might want to look at AlltoAllw
and AlltoAllv, neither of which I have any experience of however.
users mailing list