[Scip] VRP example

[Stefan Heinz]

Hi Tuomo,

I just tried to solve one of the instances of the VRP example with SCIP
and CLP (1.8.2 and 1.10.0) and discovered the same observation as you.

It looks like that there is a bug in the interface to CLP. I have a look
at it. Thanks, for pointing that out.

In case of using SoPlex or Cplex as LP-solver everything works as it should.

Therefore, I suggest that you switch to CPLEX (if you have a license) or
SoPlex (is also free for academics).

Best Stefan

PS: The changes in the makefile should not matter.

> Hi,
>
> is there a special reason why all VRP examples return "infeasible"?
>
>
> For debugging purposes (read: fun) I dumped the LP in main_vrp.cpp:436 and
> checked for the source of
> the infeasibility of eil7.vrp.
>
> The solution is given below. Variables *_s indicate additional slacks with
> high penalty. Apparently,
> plenty of those are needed.
>
>
> Best regards
> Tuomo
>
> PS. I used Clp instead of Soplex, and removed the superfluous entries for
> bz2, zlib and lapack in
> make.project in order to compile the thing. Shouldn't be the cause, right?
>
>
> solution status: optimal solution found
> objective value:                              6000068
> E3_2                                                2   (obj:10)
> E4_0                                                2   (obj:12)
> E5_1                                                2   (obj:10)
> E6_0                                                2   (obj:2)
> C1_s                                                1   (obj:1000000)
> C2_s                                                1   (obj:1000000)
> C3_s                                                1   (obj:1000000)
> C4_s                                                1   (obj:1000000)
> C5_s                                                1   (obj:1000000)
> C6_s                                                1   (obj:1000000)
>
> --
> __
> Dr. Tuomo Takkula
> Geschäftsbereich Systeme Logistik
> INFORM GmbH,     Pascalstraße 23,    52076 Aachen
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-- 
Stefan Heinz

Konrad-Zuse-Zentrum (ZIB)
Takustr. 7
D-14195 Berlin-Dahlem
Germany

Phone:	[++49] (30) 841 85 - 428
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www:     http://www.zib.de/heinz