[5312] in Hotline Meeting
Memory-intensive problems and Athena
daemon@ATHENA.MIT.EDU (cc@ATHENA.MIT.EDU)
Wed Jun 5 13:30:22 1991
From: cc@ATHENA.MIT.EDU
To: op@ATHENA.MIT.EDU
Cc: hotline@ATHENA.MIT.EDU
Date: Wed, 05 Jun 91 13:29:56 EDT
can someone please help out this individual.
thanks,
Connie
------- Forwarded Message
Received: by E40-PO.MIT.EDU (5.45/4.7) id AA15022; Wed, 5 Jun 91 13:25:38 EDT
Received: from GIS.MIT.EDU by ATHENA.MIT.EDU with SMTP
id AA08448; Wed, 5 Jun 91 13:25:33 EDT
From: tgrayson@ATHENA.MIT.EDU
Received: by gis.MIT.EDU (5.61/4.7) id AA13068; Wed, 5 Jun 91 13:24:58 -0400
Message-Id: <9106051724.AA13068@gis.MIT.EDU>
To: cc@ATHENA.MIT.EDU
Cc: tgrayson@ATHENA.MIT.EDU
Subject: Memory-intensive programs and Athena
Date: Wed, 05 Jun 91 13:24:57 EDT
One of our PhD candidates is working on a demanding linear programming
problem that we hope to use our new Athena workstation to solve. The
model uses a Fortran program that calls the XMP linear programming
package. Because he is using this package, he has little choice but to
allocate variables as it demands for his problem. In his case, it means
that he creates many arrays that require 70 MB of virtual memory.
As a test, I tried to run his program on a DECStation 3100 configured
for Athena and see that it would at least load normally. (Since the
simulation can take 9 hours to run, I was only trying to see if it
would start.) After increasing the stacksize to the maximum (85988K),
a scaled down version of the program that only requires
20 MB of memory, the program did, in fact, load successfully. On the
full-fledged 70 MB version, it failed immediately with a segmentation
violation. The machine I tried this on (pelli) is configured with
82 MB of swap space, half of which is in use for other applications.
Therefore, it seems likely that insufficient swap space is preventing
the program from working. Nevertheless, I would have expected a more
informative error message, such as "insufficient memory" or "out of
swap space" rather than a "segmentation violation." I created a version
of the program that only writes a message to the screen, then stops
immediately. The write statement is never executed.
Since one of the major reasons for our purchasing this workstation is
to allow this student to complete his research, I would like to assure
myself that his application will, in fact, run on it. Questions to
be answered are:
1) Can an Athena workstation be configured with sufficient swap
space to provide the amount of virtual memory we require?
2) If the answer to 1) is yes, do you have a machine on which
we might attempt a test of the student's program? I can make
the code available.
I will gladly provide whatever additional technical information
about the application that you require.
Thanks for your assistance,
Tom Grayson
------- End of Forwarded Message
