Appreciate the clarification. Unfortunately, the answer is “no” for any of our current releases. We only use the “host” info argument to tell us which nodes to use – the info has no bearing on the eventual mapping of ranks to nodes. Repeated entries are simply ignored.

I was mainly asking for the version to check if you were working with our svn trunk. The upcoming 1.3 release does support mapping such as you describe. However, it currently only supports it for entries in a hostfile, not as specified via –host or in the host info argument.

Historically, we have maintained a direct correspondence between hostfile and –host operations – i.e., whatever you can do with a hostfile could also be done via –host. I’ll have to discuss with the developers whether or not to extend this to sequential mapping of ranks.

The short answer, therefore, is that we don’t support what you are requesting at this time, and may not support it in 1.3 (though you could get around that perhaps by putting the ordering in a file).


On 5/30/08 11:32 AM, "Bruno Coutinho" <> wrote:

I'm using open mpi 1.2.6 from the open mpi site, but I can switch to another version if necessary.

2008/5/30 Ralph H Castain <>:
I'm afraid I cannot answer that question without first knowing what version
of Open MPI you are using. Could you provide that info?


On 5/29/08 6:41 PM, "Bruno Coutinho" <> wrote:

> How mpi handles the host string passed in the info argument to
> mpi_comm_spawn() ?
> if I set host to:
> "host1,host2,host3,host2,host2,host1"
> then ranks 0 and 5 will run in host1, ranks 1,3,4 in host 2 and rank 3
> in host3?
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