[SCIP] Long runtimes of VRP solver

[Gerald Gamrath]

Dear Shen,

don't worry, nothing went wrong, this is similar to the behavior I observed.

Note that the VRP example is just a very basic example for how a pricer 
can be implemented. It does not focus on providing good performance 
since this would complicate the code. If you want to implement a 
branch-and-price code, I would always recommend to look at the 
binpacking example or the coloring application. These two provide a 
better overview of what is normally needed for branch-and-price code, 
including problem data and a dedicated branching rule.

Best regards,
Gerald

On 30.01.19 11:51, Shen Li wrote:
> Dear SCIP mailing list
>
> I just compiled the VRP example of the SCIP package, and I obtained 
> the following output for eil22.vrp (part of the SCIP/VRP data files):
>
> (…)
>  time | node  | left  |LP iter|LP it/n| mem |mdpt |frac |vars |cons 
> |cols |rows |cuts |confs|strbr|  dualbound   | primalbound  |  gap
> (…)
>   428s|   300 |    15 |554079 |1689.8 | 256M|  20 |  29 |  37k| 273 |  
> 13k| 273 |   2 |   0 | 421 | 3.687105e+02 | 3.750000e+02 |   1.71%
>
> SCIP Status        : problem is solved [optimal solution found]
> Solving Time (sec) : 476.24
> Solving Nodes      : 359
> Primal Bound       : +3.75000000000000e+02 (23 solutions)
> Dual Bound         : +3.75000000000000e+02
> Gap                : 0.00 %
> SCIP Status        : problem is solved [optimal solution found]
> Total Time         :     476.24
>   solving          :     476.24
>   presolving       :       0.00 (included in solving)
>   reading          :       0.00
>   copying          :       0.06 (3 #copies) (minimal 0.02, maximal 
> 0.03, average 0.02)
> (…)
>
> I found it surprising that it took 428 seconds to solve this instance, 
> which is typically solved within fractions of a second. Is this is 
> similar to the behaviour you have observed? If not, any pointers to 
> where I may have gone wrong would be greatly appreciated!
>
> Many thanks
>
> Shen
>
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