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From: | Meketon, Marc |
Subject: | Re: [Help-glpk] [Fwd: Constraints on 2 successive elements of a set] |
Date: | Tue, 20 Nov 2012 12:25:48 -0600 |
Would this work for you? set J; var x{i in J}; s.t. c{i in K : i < card(J)} x[i] >= x[i+1] -----Original Message----- -------- Forwarded Message -------- From: paterijk <address@hidden> To: address@hidden Subject: [Help-glpk] Constraints on 2 successive elements of a set Date: Tue, 20 Nov 2012 09:40:00 -0800 (PST) Hi, I'm trying to model a constraint using the GMPL modeling language.
To start, we have a set of n indices called J, and a variable vector x with n components. The constraint then should look like : x_i >= x_{i+1} for i=1..n-1 (obviously we do not want i+1 to go beyond the limits of J) What I do is the following, but I do not find it very elegant :
set J; set K; var x{i in J}; s.t. c{i in K} x[i] >= x[i+1] In the data section I then define : set J := 1 2 3; set K := 1 2; Does anybody know how to handle this without having to go through this set K which I have to adapt in the data section when the set J changes? K is just J minus the last element. Note that this also does not work when J (and K) contain
non numerical elements (because of the i+1 in the constraints). Thanks for any hint, Patrick -- View this message in context:
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