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Subject: Re: [OMPI devel] Threading
From: Kenneth Lloyd (kenneth.lloyd_at_[hidden])
Date: 2010-10-12 10:51:29

In certain hybrid, heterogeneous HPC configurations, mpirun often cannot or
should not be threaded through the OS under which OpenMPI runs. The primary
OS and MPI can configure management nodes and topologies (even other MPI
layers) that subsequently spawn various OSes and other lightweight kernels.
These share memory spaces and indirectly access the program stacks in
various devices.

In short, yes, there are environments where this would cause a problem.

Kenneth A. Lloyd
Watt Systems Technologies Inc.

-----Original Message-----
From: devel-bounces_at_[hidden] [mailto:devel-bounces_at_[hidden]] On
Behalf Of Barrett, Brian W
Sent: Tuesday, October 12, 2010 8:24 AM
To: Open MPI Developers
Subject: Re: [OMPI devel] Threading

On Oct 11, 2010, at 11:41 PM, Ralph Castain wrote:

> Does anyone know of a reason why mpirun can -not- be threaded, assuming
that all threads block and do not continuously chew cpu? Is there an
environment where this would cause a problem?

We don't have any machines at Sandia where I could see this being a problem.


  Brian W. Barrett
  Dept. 1423: Scalable System Software
  Sandia National Laboratories
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