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MathGroup Archive 2004

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NMinimize inconsistencies

  • To: mathgroup at smc.vnet.net
  • Subject: [mg51293] NMinimize inconsistencies
  • From: skirmantas.janusonis at yale.edu (Skirmantas)
  • Date: Tue, 12 Oct 2004 01:58:07 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

I'm puzzled by some inconsistencies of NMinimize.
Namely,
NMinimize[{ Log[( C + P*m - b*P*m)/( C + P*m - a*P*m)]/(a - b), 105 <
C < 315&&2000 < P < 4000&&0 < a < 1 &&0 < b < 1 &&a < b &&0 < m < 5},
{{C, 105, 315}, {P, 2000,4000}, {a, 0, 1}, {b, 0, 1}, {m, 0, 5}},
Method -> "NelderMead"]
converges to 0 on a computer running Mathematica 5.0.0. and complains
about 1/0 infinities on a computer running Mathematica 5.0.1. In
Mathematica 5.0.1., changing a<b to a>b still leads to 1/0 infinities
(why?) but then changing a>b to a!=b converges to a solution that is,
amazingly, a>b. Why does NMinimize keep running into 1/0 infinities if
I demand that a>b but not if a!=b? Are there any differences in the
NMinimize implementation in Mathematica 5.0.0. and Mathematica 5.0.1.?
Any help would be appreciated.
Skirmantas


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