[Cbc] memory leaks in time-constrained parallel cbc-based solver

[Pietro Belotti]

Thanks John. All of these cuts are ~100% dense and global as they form
the outer approximation of a convex quadratic constraint. However,
it's likely that not all of them are necessary throughout the run.
Also, it would be really nice to merge the changeset into stable/2.8.

Regards,
Pietro


On Fri, Nov 21, 2014 at 11:28 AM, John Forrest
<john.forrest at fastercoin.com> wrote:
> Pietro,
>
> On 08/11/14 11:56, Pietro Belotti wrote:
>
> 1) if a time or node limit is given, there are memory leaks at the end
> (see the two attachments valg-out2-200nodes.txt and
> valg-out2-10s.txt), but no leak happens when reaching optimalitiy (see
> valg-out2.txt); most of these seem to be cuts added through addCuts()
> at CbcNodeInfo.cpp:354. I have removed non-Cbc output from these
> files.
>
>
> Hopefully trunk improves memory leaks on limit.
>
> 2) The parallel version seems to use more memory than the single-CPU
> version at a given time. A back-to-back solve shows that the parallel
> version uses 2x the memory of the sequential one even when they are
> exploring the same number of nodes; memory occupation is the same
> until the BB starts.
>
> There will be more memory used - with N threads there will be N extra copies
> of solver and each solver will have some/most of cuts.  Are these cuts
> global? - it would be possible to do better in handling them (but some
> work).
>
> John
>
> It should be emphasized that this solver generates a large number of
> cuts, and for some instances after 500,000 nodes it is killed after
> using the 240GB memory limit. I could not replicate this with the
> console version of parallel cbc with time/node limit on a MILP, so I
> suspect I might be doing something wrong. Has anything like this
> happened in the past?
>
> Thanks,
> Pietro
>
>
>
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