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MathGroup Archive 2004

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Re: NMinimize inconsistencies

  • To: mathgroup at smc.vnet.net
  • Subject: [mg51306] Re: [mg51293] NMinimize inconsistencies
  • From: "Janos D. Pinter" <jdpinter at hfx.eastlink.ca>
  • Date: Thu, 14 Oct 2004 06:35:29 -0400 (EDT)
  • References: <200410120558.BAA19272@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Skirmantas,

as a general rule, you have to specify closed sets for defining the 
feasible region in any continuous optimization problem (think of minimizing 
x on 0<x<1).

Regards,
Janos Pinter




At 02:58 AM 10/12/2004, Skirmantas wrote:
>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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