[Scip] system vs. user time

[berthold@zib.de]

Hi James.

A quick, wild guess: If the enumeration in your sub-SCIP tree is very fast
(e.g. because you do not solve LPs there), it might be that measuring the
time already takes most of it. I experienced this once with a highly
symmetric MIP.
In this case, you might want to try to disable time measuring in SCIP
completely, by setting the Boolean parameter timing/enabled to FALSE. The
remedy of this is obvious: you cannot easily stop your sub-SCIP by setting
a time limit but you need to set another limit, e.g. number of nodes or an
external limit from the Unix shell.

Cheers,
Timo


> I've just used SCIP to solve a large problem. I used UNIX time to time
> it, which gave me this result:
>
> 64.85user 66315.90system 19:24:06elapsed 33%CPU (0avgtext+0avgdata
> 1968896maxresident)k
>
> It's notable that virtually all the time is spent on system calls. It
> may well be that nothing is "wrong" but I would be interested to know
> (1) if such behaviour is common and (2) if there is anything worth
> trying to reduce the time spent there.
>
> I'm using a subscip to find good cutting planes - most of the time is
> spent doing this. The subscip has only binary variables and "and"
> constraints and uses depth-first search. My guess is that much time is
> spent allocating memory for the tree, but I haven't investigated this
> properly yet.
>
> James
>
> --
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