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Re: [Help-glpk] [Fwd: Either...or logic]

From: Michael Hennebry
Subject: Re: [Help-glpk] [Fwd: Either...or logic]
Date: Wed, 19 Jun 2013 10:22:41 -0500 (CDT)
User-agent: Alpine 1.00 (DEB 882 2007-12-20)

On Wed, 19 Jun 2013, Andrew Makhorin wrote:

-------- Forwarded Message --------
From: Alan Zinober <address@hidden>
To: address@hidden
Subject: Either...or logic
Date: Wed, 19 Jun 2013 09:54:28 +0100


set S;   #  eg S = {1,3,4,6,8}

N = card(S);

var x{i in S} binary;   # x = 1 if the item i is active   ;     x = 0 if
no items are included

I have a logical constraint having the form:

sum{i in S} x[i] = N


   sum{i in S} x[i] = 0

In words either all the items x[i] are included or none are.

This will be repeated many times in my model. What is the optimal manner of 
implementing this in the model?

i in S, j in S : x[i] = x[j]

I'm sure I've mangled the syntax.

Michael   address@hidden
"On Monday, I'm gonna have to tell my kindergarten class,
whom I teach not to run with scissors,
that my fiance ran me through with a broadsword."  --  Lily

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