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Re: "No more memory available" -- a recurring problem

On 8/2/06 at 5:24 AM, cbrummitt at (Charlie Brummitt) wrote:

>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."

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

<various things tried snipped>

The one thing I didn't notice on your list was minimizing the memory used to store old computations. Specifically, the default setting for $HistoryLength is often responsible for consuming a lot of memory. You might try changing this setting to a small number or 0.

You mentioned optimizing your code but you didn't indicate your experience level with Mathematica. Optimizing Mathematica code is often quite different than optimizing C or C++ code.

>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.

>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?

There are a variety of tools available to determine how much and what memory is being used by an application on Mac OS X. The GUI tool that comes with Mac OS X for this purpose is Activity Monitor. Look at the help file that comes with it for details of usage.

If you are comfortable with the command line, there is top. Type man top in a terminal window for more information.

Beyond this there are a number of third party freeware utilities for monitoring CPU and memory usage that can be found on the usual internet sites such as VersionTracker.

>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 access?

Determining memory usage is as described above. The memory allocated to an application is determined by the operating system dynamically. It is not something you can change.
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