Newsgroups: comp.parallel.mpi
From: "Michael D. Beynon" <beynon@cs.umd.edu>
Subject: Re: LAM amd PThreads
Organization: Computer Science Department, University of Maryland
Date: Thu, 02 May 1996 17:38:30 -0400
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Message-ID: <31892B56.41C67EA6@cs.umd.edu>

Lothar Thum wrote:
> i'm testing how MPI can work with PThreads. Now i came to a problem
> with a (in my eyes) simple program. Process 0 starts several threads,
> each thread is sending an MPI_INT to one of the other ranks in
> MPI_COMM_WORLD. The other processes should receive this MPI_INT in a
> single thread.
> This program always hangs up, the other processes don't get all the
> messages - one or two do sometimes, the other not.
> I don't understand this, the standard says that
> << a blocking call blocks only the invoking thread, allowing the
> scheduling of another >>.

I am using LAM 6.0 MPI in a multi threaded application.  George's
response that LAM 6.0 is not thread safe is true, but can be worked
around using a single pthread mutex around every MPI call.

For now, this is the only way it is possible.

Mike.
===================================================================
Michael D. Beynon                    Department of Computer Science
A.V. Williams Bldg, University of Maryland, College Park, MD  20742
Email: beynon@cs.umd.edu        WWW: http://www.cs.umd.edu/~beynon/

