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"No more memory available" -- a recurring problem

I keep getting the following error message while running a search of many PDE's:

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

This message is becoming so common that it is crippling my research
project, which is to find the simplest PDE with one quadratic
nonlinearity that is chaotic.

I have Googled and searched the Mathgroup archives for help, and I
employed the following fixes:

1) Share[] -- does not help because my code rarely has common elements
that Share[] could consolidate.

2) I used Module[] and made as many variables local as possible. I
eliminated extra variables and functions in addition to adding Clear[]
in several places in the code to clear variables that are no longer

3) I streamlined and optimized the code in general, and I made the
routines as simple and least data-intensive as possible.

4) I never have any other applications open when running Mathematica.
(Unfortunately, closing other applications is the only suggestion that
Mathematica provides in the "out of memory" error message.)

5) I should note that I run the latest version of Mathematica (

1) I upgraded from a 12" PowerBook to a 15" MacBook Pro. This computer
has an 2.16 GHz Intel Core Duo processor.

2) I upgraded the RAM on this new computer from 1 GB to 2 GB.

3) I now have much more free hard drive space (20 GB) in case
Mathematica needs to use virtual memory. In addition, this hard drive
is 7200 rpm versus the standard 5400 rpm.

I have been using functions like MemoryInUse[] and On[MemoryConserve]
to monitor the use of memory. I almost always find that I am only
using a few megabytes at a time (usually 5-10 MB, sometimes as high as
100 or once 1000 after a large computation). However, despite finding
that I usually use only a few megabytes during my computations, I
often get the above "out of memory" error message, and I can never
figure out why and how much memory was needed in that particular

Some questions:
1) How can I tell whether Mathematica is using virtual memory or not?
It seems to me that it is not. I have 20 GB of hard drive space free
and it never seems to use it. Why should I ever run out of memory if I
have 20 GB free in case it needs more memory than my RAM provides?

2) Is there a way to determine how much of my 2 GB of RAM are
allocated to Mathematica? Can I increase how much RAM Mathematica can

Thanks in advance for any help you may be able to provide! I greatly
appreciate it. If you need more information on my code or the
computations I am doing, I would be happy to provide it.


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