Re: TSP formulation

From: Mark Wallace <>
Date: Thu 02 Jan 2003 07:51:10 PM GMT
Message-ID: <>
Hi Jesper,

:- Cities =.. [cities|[X,Y,Z,X]]
Cities = cities(X,Y,Z,X)
which has four arguments.

Then if I write
:- MyCity is Cities[3]
MyCity becomes (unified with) Z.

dist(Term1,Term2,Dist) does three things:
* it evaluates the terms, extracting the underlying variable
  (thus Cities[3] evaluates to Z)
* it admits either order of the cities
  (because the data only records one of the two directions between each pair of cities)
* it turns the test
   (c(X,Y,D) ; c(Y,X,D))
  into a constraint through the annotation "infers ac".
  (This stops ECLiPSe from making a choice within the test: the test is only used 
  to narrow the domains of the variables)

Perhaps Milano and Focacci do the nearest thing to a comparison: See Proc. CP'99
(LNCS 1713), "Cost-Based Domain Filtering, pp189-203 (esp pp197-198)


Dr. Mark Wallace, IC-Parc,		Phone  +44 (0)20 7594 8434 
William Penney Laboratory, 		Fax    +44 (0)20 7594 8432
Imperial College, London SW7 2AZ, UK.	Email:
Received on Thu Jan 02 19:51:39 2003

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