[mvapich-discuss] Issue with mpi_alltoall on 64 nodes or more

[Sayantan Sur]

Hello Rick,

* On Apr,1 Rick Warner<rick at microway.com> wrote :
> Hello all,
>  We are experiencing a problem on a medium sized infiniband cluster (89 
> nodes).  mpi_alltoall on 64 or more nodes takes an excessively long time.  On 
> 63 nodes, it completes in a fraction of a second.  On 64, it takes about 20 
> seconds.

Thanks for your report to the group. Could you please try to use the
Alltoall program like this:

$ mpirun_rsh -np 64 -hostfile mf DISABLE_RDMA_ALLTOALL=1 ./a.out

If you could report the result of this back, it will help us in
narrowing down the problem.

Thanks,
Sayantan.

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http://www.cse.ohio-state.edu/~surs