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## Re: [Help-glpk] Help: How to build MIP model

 From: Jeffrey Kantor Subject: Re: [Help-glpk] Help: How to build MIP model Date: Fri, 4 Jan 2013 09:11:30 -0500

Hi Lucas,

This version of the problem also has issues. Subtracting the second equality constraint from the first leaves

x2 = c4(i)-c5

so without going further, this problem wouldn't have a feasible solution unless all c4(i) are equal.  Since x2 is binary, even then you'd need either c4(i) = c5 or c4(i) = c5 + 1. This is a strange problem, and likely a very frustrating choice for your first stab at writing a problem specific solver.

Jeff

On Fri, Jan 4, 2013 at 9:01 AM, lucacoopers wrote:

First, thanks to all. Jeff you're right. I misspelled my problem. The problem
is:

minimize { sum[from i=1 to 96] of {c1*x1(i)+c2*x2+c3*x3(i)} }
with this constraints:
x1(i)+x2+x3(i)=c4(i)
x1(i)+x3(i)=c5
x1(i)>=5
0<=x3(i)<=100
0<=x2<=1 binary

where x1, x3 and c4 are vectors of 96 elements. c1,c2,c3,c5 are
numbers.

Sorry for the mistake. I wish someone would write the problem in a form
similar to that described above. I need to learn how to write a minimization
problem with glpk with the language c.

thanks again to all:-)
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