Re: Random labeling options for CLPFD

From: <lausgans_at_gmail.com>
Date: Thu, 5 Nov 2015 20:10:34 +0300


> 5 нояб. 2015 г., в 16:04, Michael Hanus <mh_at_informatik.uni-kiel.de> написал(а):
>
> On 11/05/2015 07:11 AM, lausgans_at_gmail.com wrote:
>>
>>> 4 нояб. 2015 г., в 18:48, Michael Hanus <mh_at_informatik.uni-kiel.de> написал(а):
>>>
>>> Hi Alex,
>>>
>>> it is no problem to add this extension to the next release of PAKCS.
>>> There is the disadvantage that this does not work with SICStus Prolog,
>>> but at least you get a reasonable error message from the Prolog system.
>>>
>>> Best regards,
>>>
>>> Michael
>>
>> Could you please also add random_value(Seed) in a same way?
>
> Sure, I could do it, but since it is an undocumented feature,
> please could you explain the difference between random_value
> and random_variable (in order to put the right documentation
> comment into the library)?
>
> Best regards,
>
> Michael

Michael, I will try.

random_variable is the variable selection strategy: the random variable is selected next for instantiation (so stochastic not yet tried permutation per solution in contrast to controlled vars traversal in other strategies).
random_value is the value order option: the domain is explored for instantiation in random order (set random not yet tried value within domain to selected variable instead of incrementation with up/down orders).

They may be used separately for a single solution with either random permutation or random set of values requirements, or combined together for random distribution when multiple solutions are needed. The only current problem I know is that they both set the seed, so when used together, the option order matters: https://github.com/SWI-Prolog/swipl-devel/blob/master/library/clp/clpfd.pl#L1496 Not a case for time-dependent seed value though :-)

Alex

>
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Received on Tue Nov 10 2015 - 11:23:45 CET

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