Re: Problem -- perhaps memory -- with Table[ FindMinimum[] ]
- To: mathgroup at smc.vnet.net
- Subject: [mg17451] Re: [mg17308] Problem -- perhaps memory -- with Table[ FindMinimum[] ]
- From: "Mark E. Harder" <harderm at ucs.orst.edu>
- Date: Sun, 9 May 1999 04:43:54 -0400
- Sender: owner-wri-mathgroup at wolfram.com
David,
The sort of behaviour you describe is what I encounter when either I'm
asking for too much memory, or I have created an infinite loop of some sort.
Are you sure that Table[] is not defining some symbol in terms of itself
somehow? Try using Do[] to run the loop instead of Table[]; does that help?
Maybe that will help you diagnose the problem.
Mark
-----Original Message-----
From: David Keith <dkeith at sarif.com>
To: mathgroup at smc.vnet.net
Subject: [mg17451] [mg17308] Problem -- perhaps memory -- with Table[ FindMinimum[] ]
>I am trying to optimize a rather complicated function of 4 variables using
>FindMinimum[]. (I won't try to show it here.) Since the function is not
>differentiable, I am using the {x,{x1,x2}} formulation for starting values.
>
>When run as FindMinimum[ f[a,b,c,d], {a,{a1,a2}}, . . . ] I have no
>problem. It yields a minimum in about 5 minutes. However, in order to look
>for a best -- perhaps global -- minimum, I want to evaluate this within
>Table[] like this:
>
> Table[
> FindMinimum[ f[a,b,c,d], {a,{a1,1.1 a1}}, . . . ] ,
> {a1, a1i, a1f, astep}, . . . . .
> ]
>
>The idea, of course, is to construct a table of solutions based on an array
>of starting values and examine them afterwards.
>
>The problem is that, although the index values I'm using for Table[]
require
>only 2^4 = 16 evaluations, which should complete within 2 hours, after
about
>10 minutes the hard disk begins to work furiously, which I usually
associate
>with virtual memory.
>
>Am I missing something here. The FindMinimum[] works fine by itself. When
it
>finishes the first one, Table[] needs so save a few hundred characters and
>move on to the next.
>
>Why the problem?
>
>I'm running 3.0.1 on a PII/400 NT4/SP3 with 128MBytes. I have overwritten
>mathkernel.exe with the out-of-memory patch.
>
>Thanks.
>
>
>
>