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gams:model_permutations [2007/08/10 11:04]
127.0.0.1 external edit
gams:model_permutations [2020/05/20 12:02] (current)
Frederik Fiand
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 ====== Modeling permutations ====== ====== Modeling permutations ======
  
 +Q: //How can I model a vector of integer variables x(i) that can assume values 1,​2,​...,​card(i),​ and each x(i)  should be different, i.e. ''​x(i) <> x(j) for all i <> j''​ ?//
  
-How can I model in GAMS the following restriction?​ A vector of integer variables x(i) can assume values 1,​2,​...,​card(i),​ and each x(i)  should be different, i.e.  +This looks like we need the help of a permutation matrix ​''​P=p(i,​j)''​,
- +
-     x(i) <> x(j) for all i <> j +
- +
-This looks like we need the help of a permutation matrix P=pij,+
 where there is exactly one 1 in each row and column, and the other where there is exactly one 1 in each row and column, and the other
 elements are zero. The identity matrix is a trivial example of a elements are zero. The identity matrix is a trivial example of a
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