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Excessive Mathematica memory use, revisited.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg46858] Excessive Mathematica memory use, revisited.
  • From: "Virgilio, Vincent" <Vincent.Virgilio at itt.com>
  • Date: Fri, 12 Mar 2004 02:02:43 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Hello,

First, thanks to Jens-Peer Kuska for responding to this issue back in
September,

http://forums.wolfram.com/mathgroup/archive/2003/Sep/msg00125.html.

I am now working with a much more powerful machine: P4 2.6 GHz, 2GB RAM,
Windows XP, Mathematica 5.0.0.

My goal is still to manipulate very large images. Currently I am trying
to use Experimental`BinaryImport to import an ~ 500MB image into
Mathematica. Each sample is an unsigned 16-bit integer.

I start the Windows Task Manager, display the process list, and sort by
memory usage.

Then, after issuing the following commands to a cold kernel, I watch the
Mathematica kernel rise to the top of the above list, consume chunks of
memory in steps of maybe 20MB, and exhaust physical memory.


<<ImageProcessing`

$MessagePrePrint=Short;

$HistoryLength=0;

<<Utilities`MemoryConserve`

Off[MemoryConserve::start];Off[MemoryConserve::end]

<<Experimental`

image=ToPackedArray[BinaryImport["500MBimage",{"UnsignedInteger16"...}]]
;


There is memory exhaustion with or without ToPackedArray[].

I could understand this behaviour if Mathematica is storing each sample
in a node of some sort of tree. Then the data volume would be multiplied
by some factor determined by the tree node size. If this is the case, is
there a way to avoid this, during import, with packed arrays?

Is there anything obviously wrong or inefficient in the above code? I've
tried to incorporte Jens' suggestions. One of his was to use Hold[]
wherever possible; I can't see where it would be productive to do that
here.

Note, I see similar behaviour on a smaller scale with much smaller
images (14MB, per earlier mail). Which is not a problem since the memory
ceiling has gone up considerably.

Perhaps 2GB is simply inadequate for this task, since I don't expect
Mathematica to use a data tile cache. Other products do, but then they
target a much more specific application domain.

Regards and thanks,

Vince Virgilio

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