[Cbc] Constraints order

[John Forrest]

Yves,

Error not where I thought it was.  Small changes i.e. order or compiler 
or anything made a subtle difference and a constraint was generated

x995 + x1018 + x1700 >= 1.0000001001

and the optimal solution had x995==0,x1018==1 and x1700==0 - but it was 
within tolerances (just)

One of the cut generators then thought 0.0000001001 is greater than 
primal tolerance of 1.0e-7 and created a bad cut.

I have modified code to be a bit more relaxed.

John Forrest

On 18/12/13 10:11, Yves Touchard wrote:
> Attached is a archive file (test.gz) containing an lp constraint file 
> (test.lp -> /tar xzf test.gz/)
>
> Executing cbc (#2.8.0)  on the test.lp file (/cbc test.lp/) provides 
> the following result
> /Result - Problem proven infeasible//
> //No feasible solution found
>
> /If the two first constraints of the LP file (lines 1258/1259) are 
> swapped, the same command provides a different result:
> /Result - Optimal solution found/
>
> So, what's wrong with this constraints fle? Is there any specific 
> order to declare constraints?
> Or is this a bug? And, if so, is there any workaround?
>
> Thanks in advance for any help.
>
> Regards,
>
> Yves
>
>
>
>
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