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Subject: Re: [OMPI users] hostfiles
From: Ralph Castain (rhc_at_[hidden])
Date: 2010-02-04 18:51:44


That is correct and has always been the behavior. If you want OMPI to
respect host order, you have to use the sequential mapper instead of the
default round-robin mapper.

On Thu, Feb 4, 2010 at 4:37 PM, Eugene Loh <Eugene.Loh_at_[hidden]> wrote:

> I'd check the man page, but since I just rewrote it I don't think that's
> going to help!
>
> I have two nodes, A and B, and I run "mpirun -hostfile myhostfile
> -tag-output hostname" with five different hostfiles. Here is what I get:
>
> B slots=2
> B slots=2
> A slots=2
> A slots=2
> B B B B A A A A
>
> B slots=2
> A slots=2
> B slots=2
> A slots=2
> B B B B A A A A
>
> A slots=2
> B slots=2
> A slots=2
> B slots=2
> A A A A B B B B
>
> B slots=2
> A slots=2
> A slots=2
> B slots=2
> A A A A B B B B
>
> A slots=1
> B slots=1
> A slots=1
> B slots=1
> A slots=1
> B slots=1
> A slots=1
> B slots=1
> A A A A B B B B
>
> This is with openmpi-1.7a1r22109. After each hostfile, I list the nodes I
> get in MPI rank order. So, it appears the hostfile cannot be used to
> control in what order processes are mapped to nodes. It can only be used to
> specify the total number of slots per node. Slots are filled up one node at
> a time. I assume we don't want to make any claims about the node order?
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