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MathGroup Archive 2002

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excessive RAM use with Mathematica

  • To: mathgroup at smc.vnet.net
  • Subject: [mg32617] excessive RAM use with Mathematica
  • From: Michael Peter Bakich <mike.bakich at cox-internet.com>
  • Date: Thu, 31 Jan 2002 01:46:00 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Hi,

I am simplifying certain expressions in Mathematica and find that Linux
(RedHat 7.1) uses a lot of RAM.  I have read on a user site for Linux
that everything is put in RAM and STAYS there as long as the process
(such as Mathematica) is active.  Not only does it stay there but it
accumulates!  I think I can find a way to limit the amount of RAM  use
in RedHat Linux 7.1 with a setting but that means older processes that
are not updated will be taken out of RAM.  And there is this as evidence
of the above:  When I start my RedHat Linux 7.1 session I am up to
almost 90 Megs RAM.  If I just let it sit there and I do absolutely
nothing, the RAM usage will increase!  With nothing running, that is,
with nothing activated beyond boot up with the GUI you get and with no
input from me, I have seen it go over 200 Megs as I watched.  Large
jumps in RAM use seem to be accompanied by disk activity.  Now, my
Mathematica calculations require a lot of RAM.  I am not interested yet
in finding a way to make my calculation "leaner and meaner" so to
speak.  For instance, how would you simplify the command "FullSimplify[
]" when you want FullSimplify and not just Simplify.  I have found that
applying this command at various points along the way helps but the
heart of the issue is not this.  If I can limit how long something
remains in RAM in Linux, does that have the potential to destroy a large
calculation in Mathematica?  If this is true, is there a setting in
Mathematica that will cause it to "give back" RAM space when the
information stored there is no longer vital to the calculation?  This
last thing; when all the 500 Megs of RAM are used and well over 500 Megs
of swap space are used, I can stop the process, shut Mathematica down
completely and RAM and swap space use only drops to about 300 Megs
each.  In other words useage does not drop to anywhere near pre
Mathematica session useage and, in fact, to get back all the RAM I can I
have to do a COMPLETE shut down (not just log out and log back in to my
session)-so, no, it is not all Mathematica but I am looking anywhere for
a fix.

Mike Bakich



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