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

**From**: |
Andrew Makhorin |

**Subject**: |
[Help-glpk] [Fwd: Either...or logic] |

**Date**: |
Wed, 19 Jun 2013 15:27:08 +0400 |

-------- Forwarded Message --------
From: Alan Zinober <address@hidden>
To: address@hidden
Subject: Either...or logic
Date: Wed, 19 Jun 2013 09:54:28 +0100
Suppose
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:
either
sum{i in S} x[i] = N
or
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?
Alan
--
Sent from my MacBook Pro

**[Help-glpk] [Fwd: Either...or logic]**,
*Andrew Makhorin* **<=**