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

[Michael Hennebry]

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
>
>
> 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?

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