The quoting is horrible.
Is there any other reason you did not send to the list?
On Fri, 8 Jan 2016, esma mehiaoui wrote:
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>
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> Le Jeudi 7 janvier 2016 19h14, Michael Hennebry <
address@hidden> a écrit :
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> On Thu, 7 Jan 2016, esma mehiaoui wrote:
>
>> Is it true that the _expression_ of the logical constraint (a and b) with the following constraints { x <=a ; x <= b ; a+b <= x+1} is less time consuming then its _expression_ with the only constraint 0 <= a + b – 2x <= 1 ?
>
> It took me a while to suspect the by "logical constraint"
> you meant that a, b and x were binary variables.
>>> YES, I MEANT BINARY VARIABLES. SORRY
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> Quite probably, it is true.
> The linear relaxation of the former is tighter than that of the latter.
> Assuming the linear relaxation includes 0<=a,b,x<=1,
> The first set of constraints defines the convex hull.
> Tighter is not possible with linear constraints.
> The second set of constraints allows a=1=b, x=0.5 ,
> but the first does not.
>>> THANK YOU FOR YOUR EXPLANATION
>
>> Another question, in my program i have a constraint that computes the value of the variable V as the sum of variables V1, V2 and V3 (V=V1+V2+V3 ). My problem is that the value of V is integer and it sould be real. For instance, V= 23 rather than 23.3. Do you have any suggestion for the origin of the problem ?
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> Perhaps you have a flag that says all variables are integer.
>>> NO, THIS IS NOT THE CASE BUT I NOTICED SOMETHING.>> WHEN MY SUM SHOULD BE EQUAL TO 200021.3, IT IS EQUAL TO 200021. >> AND WHEN I REDUCED THE VALUES OF V1,V2 AND V3, MY SUM IS CORRECT IT IS FOR INSTANCE 20021.3.
>>> Best regards
>>> Esma
>
> --
> Michael
address@hidden> "Sorry but your password must contain an uppercase letter, a number,
> a haiku, a gang sign, a heiroglyph, and the blood of a virgin."
> -- someeecards
>
>
--
Michael
address@hidden"Sorry but your password must contain an uppercase letter, a number,
a haiku, a gang sign, a heiroglyph, and the blood of a virgin."
-- someeecards