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Re: How to reduce memory usage of the MathKernel.exe?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg93036] Re: How to reduce memory usage of the MathKernel.exe?
  • From: Bill Rowe <readnews at sbcglobal.net>
  • Date: Fri, 24 Oct 2008 02:31:23 -0400 (EDT)

On 10/22/08 at 5:38 AM, jan.baetens at ugent.be (Janneke Baetens) wrote:

>Currently, I'm using Mathematica 6.0 on a Windows XP machine which
>has 2 Gb of RAM to perform massive numerical computations. It all
>works great but sometimes the Kernel needs to shut because it's out
>of memory. I can follow this memory depletion in the Windows task
>manager.

>First, I thought this would be caused be wanting to store too much
>variables consisting of millions of elements. Because of that I
>tried to clear the memory after each individual computation by using
>the command ClearSystemCache, though this doesn't seem to affect the
>memory needed by the MathKernel. Even if I used that command and
>clear all variables the kernel keeps on needing   the same amount of
>memory as I can see in the Windows Task Manager.

If you look at the documentation for ClearSystemCache you will
find it is not intended to minimize memory usage. Specifically,
it clears internal caches of data. I doubt it removes those
caches or frees memory for other usage. Most likely, Mathematica
sets up cache sizes as one of the start up actions.

To free memory associated with a given variable, use Clear or
Remove. But not while Remove[expr] will delete that expression
it may not completely free all of the memory associated with it.
That is because it likely is referenced as part of the session
history. To minimize memory usage it is essential to do

$HistoryLength = 0

By default, this is set to infinity which tracks all
computations made, making it possible to re-do any when needed.

Other things to look at are Share and tutorial/MemoryManagement.

If none of the above is sufficient, then likely you will need to
re-work you computation so as to do only part of it at a time.


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