[gecode-users] question about counting constraint

[Guido Tack]

Oh, and thanks of course :-)

Guido

Guido Tack wrote:

> Hi Alberto,
> 
> that was a bug in the global count posting functions.  The values array (and thus the corresponding array of occurrence variables) had to be sorted.  I fixed this in the trunk to accept unsorted arrays, and it will be part of the upcoming 3.2.2 release.
> 
> Cheers,
> 	Guido
> 
> Alberto Delgado wrote:
> 
>> Hi all,
>> 
>> Let's say i have an IntVarArray vars,  an integer value b and an
>> IntVar car.  According to the documentation,  if i post the
>> constraint: count(*this,vars,b,IRT_EQ,car),  the variable car will
>> represent the number of occurrences of b in vars.
>> 
>> Now,  instead of b being an integer value let's assume it's an IntArgs
>> with all the elements of the domain of variables from vars, and that
>> car is now an IntVarArray that will represent the number of
>> occurrences of all values from b in vars.  I wanted to constrain the
>> occurrences of each value from b in vars according to car,  so i
>> implemented a for loop and posted a count constraint for each value in
>> b and variable in car:  count(*this,vars,b[i],IRT_EQ,car[i]).
>> 
>> Then I realized that it is possible to use just one count constraint:
>> count(*this,vars,car,b),  that should be equivalent to posting a count
>> constraint for each value in b.
>> 
>> Attached to this email there is an example that reflects what i
>> described above. When i run the example with line 64 uncommented and
>> line 67 commented,  this is using a loop to post a count constraint
>> for each value in b,  the solver finds a solution without failing at
>> all. If i comment line 64 and uncomment line 67,  posting just one
>> count constraint,  the solver fails right away.
>> 
>> Did i get wrong the definition of count(*this,vars,car,b) and it is
>> not equivalent to post a constraint for each value in b?
>> 
>> Thanks in advance,
>> 
>> Alberto
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> 
> 
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