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MathGroup Archive 2005

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Memory use by NMaximize (and NMinimize)

  • To: mathgroup at smc.vnet.net
  • Subject: [mg61455] Memory use by NMaximize (and NMinimize)
  • From: "Carl Bergstrom" <ctbergstrom at gmail.com>
  • Date: Wed, 19 Oct 2005 02:17:07 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Hello everyone,

This is probably a very naive question, but could anyone help me
understand the following behavior?

In general, mathematica functions are very good about "returning" any
memory that is used during their execution.

For example, adding togeter a list of 1000000 integers uses only a
small amount of memory, as illustrated below.

-----------------------

In[6]:=
MemoryInUse[]

Out[6]=
2494728

In[7]:=
test=Apply[Plus,Range[0,1000000]]

Out[7]=
500000500000

In[8]:=
ByteCount[test]

Out[8]=
32

In[9]:=
MemoryInUse[]

Out[9]=
2496680

--------------

However, NMaximize does not behave in this way. It seems to eat up lots
of memory, as illustrated below:

--------------------------

In[1]:=
MemoryInUse[]

Out[1]=
2122936

In[2]:=
test=NMaximize[{Sin[x],x<Pi,x>0},{x}]

Out[2]=
{1.,{x\[Rule]1.5708}}

In[3]:=
ByteCount[test]

Out[3]=
120

In[4]:=
MemoryInUse[]

Out[4]=
2896152

-------------------------

Any ideas why this is happening and --- more importantly --- how to
resolve the problem?
I'm running out of memory when doing a large number of NMaximize
operations.

Thanks in advance,
Carl






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