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Subject: [OMPI users] coll_ml_priority in openmpi-1.7.5
From: tmishima_at_[hidden]
Date: 2014-03-20 20:56:35


Hi Ralph, congratulations on releasing new openmpi-1.7.5.

By the way, opnempi-1.7.5rc3 has been slowing down our application
with smaller size of testing data, where the time consuming part
of our application is so called sparse solver. It's negligible
with medium or large size data - more practical one, so I have
been defering this problem.

However, this slowdown disappears in the final version of
openmpi-1.7.5. After some investigations, I found coll_ml caused
this slowdown. The final version seems to set coll_ml_priority as zero
again.

Could you explain briefly about the advantage of coll_ml? In what kind
of situation it's effective and so on ...

In addition, I'm not sure why coll_my is activated in openmpi-1.7.5rc3,
although its priority is lower than tuned as described in the message
of changeset 30790:
  We are initially setting the priority lower than
  tuned until this has had some time to soak in the trunk.

Tetsuya