[Cbc] Suboptimal solution as optimal?

[Rhavar]

I just realized, an easy way to prove the solver is finding a suboptimal solution is by forcing it's hand and adding an additional constraint:

force: i22 = 1

and you will see it returns a better solution that it didn't see before

-Ryan

> -------- Original Message --------
> Subject: Suboptimal solution as optimal?
> Local Time: December 27, 2017 12:37 PM
> UTC Time: December 27, 2017 6:37 PM
> From: rhavar at protonmail.com
> To: cbc at list.coin-or.org <cbc at list.coin-or.org>
>
> I have a problem:
> https://gist.github.com/RHavar/dfb9de631363ecb9e1c326fff5ebd09b
>
> (lp file and solution file attached)
>
> In the solution it says: "Optimal - objective value"  but I think I have found a superior solution by hand:
>
>  o6 = 1
> i22 = 1
>
> Which gives a better objective (70 instead of 825)
>
> --
>
> So I guess my question is, does "Optimal - objective value"  mean that it's guaranteed to be the optimal solution? Or am I doing something wrong? Or is there a bug in cbc?
>
> -Ryan
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