17 Feb 2005
CS 3243 - Constraint Satisfaction
41
All Different
nSuppose
Dx = {2,3} = Dy, Dz = {1,2,3}
nAll the
constraints x¹y, y¹z, z¹x are all arc consistent
ne.g.
x=2 supports the value z = 3
nThe single
ternary constraint AllDifferent(x,y,z) is not!
nWe
must set z = 1
nA special
purpose algorithm exists for All-Different to establish GAC in efficient time
nSpecial
purpose propagation algorithms are vital