[Scip] system vs. user time

[michael.winkler@zib.de]

Hi James,

I wanted to add that if the reason is really time measurement that you
could also try to change it from cpu to wall clock time by changing the
parameter set/timing/clocktype to 2. But maybe it's another reason,
because your numbers look very strange. Was there no endless loop? Do you
have a SCIP statistic on your run where you can see where the time was
spent?
If you don't know already, if you have valgrind you could determine
exactly were the time is spend by first compiling your programm with the
"-g" option and run it by
"valgrind -v --tool=callgrind your_executable_with_options_and_parameters".
This will create an file "callgrind.out.PID" (PID process id) and you can
look at all your lines of code where exactly the time is spent by open the
output file with "kcachegrind".

Best, Michael

> 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
>>
>> --
>> James Cussens	         ---- NEW CONTACT DETAILS ----
>> Dept of Computer Science &
>> York Centre for Complex Systems Analysis             jc at cs.york.ac.uk
>> Room 326, The Hub, Deramore Lane              Tel  +44 (0)1904 325371
>> University of York                            Fax  +44 (0)1904 500159
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