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MathGroup Archive 2006

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memory issues

  • To: mathgroup at smc.vnet.net
  • Subject: [mg68751] memory issues
  • From: "Christoph Lhotka" <lhotka at astro.univie.ac.at>
  • Date: Fri, 18 Aug 2006 03:11:53 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Hi!

Running Mathematica 5.2 on 64Bit (AMD) with 2GB of RAM Memory OS: WindowsXP 64
Pro. I get the message: No more memory available. Mathematica Kernel has shut
down...

How do I find out:

1) How much memory can Mathematica store in the RAM?
2) How much memory can Mathematica store on the Hard disk (swap file)?
3) At which memory limit does Mathematica begin writting to the had disk?
3) Can I influence these limit 3) using the OS or in Mathematica?
4) How do I find out at which point in the calculation the kernel stops?
5) Why does my dual core processor does not work higher than with 50%

Doing some tests on my own I got the following riddle:

In[]:=ByteCount[1]
Out[]:=16

In[]:=2000000000/16
Out[]:=125000000

In[]:=DAT=Table[i,{i,1,125000000}];

In[]:=ByteCount[DAT]
Out[]:=500000056

In[]:=MaxMemoryUsed[]
Out[]:= 502133312

Why is a list of 125 000 000 different integers (a 16 Byte) only 500 000 000
Bytes long? How should I estimate the memory limits in my algorithms, when
designing them on this basis?

Thank you in advance

Christoph


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