[Scip] Scip 3.1.0 is much more slower than 3.0.2

[Marc Pfetsch]

Hi Vladimir,

it is likely that you experienced what is called performance 
variability: Small changes in the implementation of the (LP-)solver (or 
input) can lead to a completely different solution process. This cannot 
really be avoided.

More information can be found in answers to the following email to this 
list:

http://listserv.zib.de/pipermail/scip/2013-November/001734.html

If the newer version is consistently slower on a very large testset, 
however, the reason possibly is more structural.

Best

Marc


On 06.06.2014 16:34, Vladimir VV wrote:
> Dear SCIP team,
> I was surprised when found than last version of Scip works more slowly
> than previous 3.0.2 did.
> For example, the same MILP problem of the following dimensions (from
> scipampl log):
> "... 134 variables (114 bin, 0 int, 0 impl, 20 cont) and 1159 constraints"
> has been solved by SCIP 3.0.2 in ~170 sec.
> "Solving Time (sec) : 169.58
> Solving Nodes      : 210199
> Primal Bound       : +8.38888888888988e+00 (51 solutions)"
> and by SCIP 3.1.0 in ~900 sec.
> "Solving Time (sec) : 891.05
> Solving Nodes      : 3333047
> Primal Bound       : +8.38888888888929e+00 (41 solutions)
> Dual Bound         : +8.38888888888929e+00"
>
> Both solvers had run with the default parameters settings at the same host.
> But looking at solvers' outputs I see that 3.1.0 processes the search
> tree completely differently than 3.0.2 does.
>
> The same effect I see with many other problems... What is the reason of that?
>