Newsgroups: comp.parallel.mpi
From: kowallik@ifh.de (Rainer Kowallik)
Subject: Shared memory driver for MPICH
Organization: DESY-IfH
Date: 1 Nov 1994 10:10:06 GMT
Message-ID: <39545u$9lk@dscomsa.desy.de>

We have written a SYS5 shared memory driver for MPICH (SEP 14) which
makes MPI applications portable to our SGI challenge and allows
one to debug parallel programs on a single processor machine.


The driver is available in our ftp archive:
ftp.ifh.de:/pub/unix/parallel/mpi/mpich/mpid/ch_shm.tar.Z

In the same directory you find a pvm3 driver. This driver was originally
written for an older Version of MPICH and may have some shortcomings.



Status:
This driver is not thoroughly tested, but it works for a set of example
applications and testing routines.
It is still possible, that a process deadlocks on a blocking receive.
This driver has been tested on an IBM RS6000 Workstation (one SP1 node)
under AIX 3.2 and an SGI challenge with 14 processors under IRIX 5.2.
It is possible to use this driver on a single processor machine and
simulate a multiprocessor machine. This feature is usefull for testing
applications on small workstations before going to the parallel computer.

To do:
Up to now only one process has access to the shared memory at a given
time. At least reading should be possible for several processes at the
same time.
The garbage collection routine may need some more attention.
Increasing the shared memory buffer on the fly does not work correctly.

BUGS:
Many.
At least you should be aware, that it may happen, that a shared memory
area is not released. Please make use of the UNIX command "ipcs"
to find out if this happend to you. Feel free to use the script
"ipc_clear" which comes with the distribution.
------------------------------------------------------------------------

Bug reports for this shared memory driver to

Rainer Kowallik

Email: kowallik@ifh.de


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