[gecode-users] sequence constraint: variable occurring multiply

Kish Shen kisshen at cisco.com
Thu Aug 19 02:03:12 CEST 2010


Hi,

I have another question about the sequence constraint: exception 
ArumentSame is thrown if a variable occurs more than once. Should this 
exception be thrown? I can see that it does not make sense for a 
variable to occur in a subsequence of q variables, but if the 'distance' 
between the same variable > q, i.e. it cannot occur multiply in the same 
subsequence, should this be allowed? Can the implemented algorithm deal 
with this?

There are useful cases for variables to occur multiply, the simplest is 
a cycle, e.g. say for the following variables

x1,x2,x3,x4,x5

and a cycle would be

x1,x2,x3,x4,x5,x1,x2,....

such cycle could be used for a schedule that repeats.

Cheers,

Kish
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