[gecode-users] Constraints on "wave" form

[Richard Portelli]

Sorry it's RIchard again,
you meant :


2014-06-12 11:50 GMT+02:00 Mikael Zayenz Lagerkvist <zayenz at gmail.com>:

> Richard Portelli skrev 12/06/14 10:32:
>
>  Hello Christian,
>> I would like to know if there is an easy way to implement a special
>> constraint.
>> I have an array with 10 numbers.
>> My constraint would be : if you plot the array values in function of the
>> index,  you should have a wave aspect /\.
>> For example with 10 numbers
>>
>> 1 3 5 9 11 7 6 5 4 2 0 (increasing then decreasing) There is no
>> importance at witch index there is the inflexion point.
>>
>> Would you have an idea how to implement that in a clean way?
>>
>>
> For reference, this is similar to the inflexion constraint (
> http://www.emn.fr/z-info/sdemasse/gccat/Cinflexion.html) with the number
> of inflexions set to 1 (assuming that valleys are also ok).
>
> The simplest way in my opinion to model this constraint would be the
> following.
>
>   Assume the sequence of numbers is called x and has n entries.
>   Define a new boolean array of variables y with n-1 values.
>   For each place i in y, add the constraint
>     y[i] = (x[i] < y[i])
>   (that is, reified ordering).
>   On the y variables, add the constraint regular(y, 1*0*)
>
> The ordering constraint and the regular expression can be modified to suit
> your particular needs.
>
> Cheers,
> Mikael
>
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