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Re: [Help-glpk] Non linear constraint


From: Michael Hennebry
Subject: Re: [Help-glpk] Non linear constraint
Date: Mon, 9 Nov 2015 17:32:37 -0600 (CST)
User-agent: Alpine 1.00 (DEB 882 2007-12-20)

Other constraints might be obtained from formulas for
minimizing the difference between a product of variables
and a linear combination of same.

min PROD x[j] - SUM c[k]*x[k]
    j in 1..n   k in 1..n

set the derivative with respect to x[L] to 0:

       PROD x[j] - c[L] = 0    for L in 1..n
    j in 1..n - {L}

       PROD x[j]     =  c[L]    for L in 1..n
    j in 1..n - {L}

multiplying n equations:

      PROD x[j]**(n-1)  = PROD c[j]
      j in 1..n           j in 1..n

      PROD x[j]   = PROD c[j]**(1/(n-1)
      j in 1..n     k in 1..n

dividing:

      x[L] = c[L]**-1 * PROD c[j]**(1/(n-1))
                        j in 1..n

Note that I have assumed c> 0 and x> 0 .

--
Michael   address@hidden
"Sorry but your password must contain an uppercase letter, a number,
a haiku, a gang sign, a heiroglyph, and the blood of a virgin."
                                                             --  someeecards



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