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Subject: [OMPI devel] Change in hostfile behavior
From: Ralph Castain (rhc_at_[hidden])
Date: 2008-07-28 11:43:58

Per an earlier telecon, I have modified the hostfile behavior slightly
to allow hostfiles to subdivide allocations.

Briefly: given an allocation, we allow users to specify --hostfile on
a per-app_context basis. In this mode, the hostfile info is used to
filter the nodes that will be used for that app_context. However, the
prior implementation only filtered the nodes themselves - i.e., it was
a binary filter that allowed you to include or exclude an entire node.

The change now allows you to include a specified #slots for a given
node as opposed to -all- slots from that node. You are limited to the
#slots included in the original allocation. I just realized that I
hadn't output a warning if you attempt to violate this condition -
will do so shortly. Rather than just abort if this happens, I set the
allocation to that of the original - please let me know if you would
prefer it to abort.

If you have interest in this behavior, please check it out and let me
know if this meets needs.