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Subject: [OMPI devel] A Couple of Questions
From: Timothy Hayes (hayesti_at_[hidden])
Date: 2009-04-12 21:58:05

I was wondering if someone might be able to shed some light on a couple of
questions I have.

When you receive a fragment/base_descriptor in a BTL module, is the raw data
allowed to be fragmented when you invoke the callback function? By that I
mean, I'm using a circular buffer in each endpoint so sometimes data loops
back around. Currently I'm doing a two step copy: from my socket to the
circular buffer and then from the circular buffer to the fragment. This
actually effects my total throughput quite a bit, it would be much nicer to
just point to the buffer instead. When I tried using two base_segments to
point to the start and end of buffer I got some pretty strange errors. I'm
just wondering if someone could confirm or deny that you can or can't do
this, maybe those errors were down to human error instead.

My other question is about the BTL failover system. Would someone be able to
briefly explain how it works or maybe point me to some docs? I'm actually
expecting the file descriptors in my module to fail a certain point during
an Open MPI job and I'd like my BTL module to fail gracefully and allow the
TCP module to take over in its place. I'm not sure how to explicitly make
the the BTL module say to the rest of Open MPI "don't use my anymore"

Happy Easter