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MathGroup Archive 2007

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Maximum memory accessible by Mathematica 6.0 in Windows XP

  • To: mathgroup at smc.vnet.net
  • Subject: [mg77544] Maximum memory accessible by Mathematica 6.0 in Windows XP
  • From: "L. Dwynn Lafleur" <lafleur at louisiana.edu>
  • Date: Tue, 12 Jun 2007 01:28:10 -0400 (EDT)

Computing Platform:
Dell PC with Intel Dual Core CPU @ 2.66 GHz
4 GB RAM installed
Windows XP SP2 (Media Center Edition)

-------------------------------------------

As I understand it (see, e.g.,
http://msdn2.microsoft.com/en-us/library/aa366778.aspx), a single
application in Windows XP can use to 2 GB of memory (RAM + virtual).
However, I have not been able get Mathematica 6.0 to use 2 GB, although
I have been able to do so with other programs, e.g., Python.  With only
background processes and Windows Task Manager (WTM) running, I load
Python 2.5.1 through its interactive IDLE shell. After entering the
command "nn=range(129000000)", the Python shell remains loaded and
functional, and the Process tab in WTM shows the pythonw.exe process
using 2,053,644 KB of memory.

OTOH, again with only background processes and WTM running, suppose I
open Mathematica 6.0 instead of Python.  If I execute the line

nn = Range[312000000]; MaxMemoryUsed[]/(1024.0*1024.0)

the output is "1195.67"; i.e.,  Mathematica reports about 1.2 GB of
memory being used, and the kernel is still loaded and functional.  At
that point WTM shows the following memory usages:

MathKernel.exe process ... 1,238,728 KB
Mathematica.exe process ..    24,712 KB,
Total Commit Charge ...... 1,528,652 KB (WTM > Performance tab)

(Why a Mathematica list of 312 million integers should require far less
memory than a Python list of 129 million integers is beside the point
here; I am only interested in the total memory accessed by the two
programs.)

If the Range argument in the above Mathematica command were larger by
a fraction of a percent, I would expect only a small increase in the
reported memory usage.  Specifically, MathKernel.exe should still use
well under 2 GB and still be in  functional state. However, when I quit
the Mathematica kernel, then execute

nn = Range[313000000];MaxMemoryUsed[]/(1024.0*1024.0)

only this message appears:

-------------------------
No more memory available.
Mathematica kernel has shut down.
Try quitting other applications and then retry.
------------------------

(WTM verifies that MathKernel.exe is indeed no longer running and that
Mathematica.exe is using 25,448 KB of memory.)

Am I misunderstanding what is going on?  Shouldn't I be able to get
Mathematica to use more than about 1.2 GB of memory in Windows XP?  Is
Mathematica self-limiting the amount of memory it requests from Windows?

-- 
======================================
L. Dwynn Lafleur
Professor of Physics
University of Louisiana at Lafayette
lafleur at louisiana.edu
======================================


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