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MathGroup Archive 2001

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FindMinimum

  • To: mathgroup at smc.vnet.net
  • Subject: [mg31134] FindMinimum
  • From: Julie RIGAUD <Julie.Rigaud at edf.fr>
  • Date: Fri, 12 Oct 2001 03:36:53 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Hi !
I have a big problem by using "FindMinimum" to minimize a function which use a simulation software.
In fact, i want to minimize this kind of function :
g[x]= a - f[x]
"a"  is a real constant and is well known, but "f" is a sum of command like copy of file and script shell which allow to run my simulation software...
At the end, "f " return a real value which must be the best approximated value of  "a".
So, "f " can't be derivable and i use "FindMinimum" like this :
                FindMinimum[a-f[x],{x,xstart,xmin,xmax}]
Mathematica runs with "xstart" one time but after it stops and says :
"FindMinimum::fmgz:
   Encountered a vanishing gradient. The result returned may not be a minimum;
    it may be a maximum or a saddle point."
I suppose that it is probably due to the HoldAll attribute of FindMinimum but i don't
know how to solve this problem ...
Can somebody help me ...?
Thanks a lot !
Julie


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