Re: [eclipse-clp-users] ECLiPSe - Real variables domain propagation problem

From: Wayne Mac Adams <waynemacadams_at_...6...>
Date: Mon, 27 Jul 2009 13:14:23 +0100
It might be a seperate issue but I am getting an unexpected result from the
following query also (again assuming ic loaded)

?- [A, B] :: 0.0 .. 0.5, C $= A + B, Cost $= -(C), minimize((locate([A, B,
C], 1.0), get_min(Cost, Min)), Min).
A = A{0.0 .. 0.5}
B = B{0.0 .. 0.5}
C = C{0.0 .. 0.5}
Cost = Cost{-0.5 .. -0.0}
Min = -0.5
There are 2 delayed goals.
Yes (0.00s cpu)

Surely the maximum for C is 1.0, and there should be a solution with Cost
-1.0?

Am I simply using minimize wrong, or is there another problem?

Wayne

On Mon, Jul 27, 2009 at 12:54 PM, Solly Brown <sollyb@...25...>wrote:

> Mark Wallace wrote:
>
>> Hi Wayne,
>> It's a bit late at night here, but I confess I'm puzzled by the following
>> (inspired by your query):
>> ?- [B, C] :: 0.0 .. 1.0, D $= C * (1.0 - B).
>> B = B{0.0 .. 1.0}
>> C = C{0.0 .. 1.0}
>> D = D{-1.0 .. 1.0}
>> It seems to me D ought to be constrained to be non-negative.
>>    Cheers
>>        Mark
>>
> Eclipse treats this situation as D $= C - C*B and the allowed bounds of
> these two terms are calculated independently before being combined. So the
> first term has bounds 0 < C < 1 and the second term has bounds 0 < C*B < 1.
> When the second term is subtracted from the first the lowest possible bound
> is 0 - 1 = -1, whilst the upper bound is 1 - 0 = 1.
>
> Cheers, Solly
>
>
>>> If i had
>>> ?- A :: 0.0 .. 0.5, [B, C] :: 0.0 .. 1.0, A $= eval(B + C).
>>> A = A{0.0 .. 0.5}
>>> B = B{0.0 .. 0.5}
>>> C = C{0.0 .. 0.5}
>>> There is 1 delayed goal.
>>> Yes (0.00s cpu)
>>>
>>
>>
>> --
>> Professor Mark Wallace
>> Room 6.43
>> Faculty of Information Technology
>> Building H
>> Monash University
>> Caulfield
>>
>> Tel: 34276
>> ------------------------------------------------------------------------
>>
>>
>> ------------------------------------------------------------------------------
>>  ------------------------------------------------------------------------
>>
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>>
>>
>
>
Received on Mon Jul 27 2009 - 12:15:12 CEST

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