dolfin team mailing list archive

["Garth N. Wells" <gnw20@xxxxxxxxx>]

Johan Hake wrote:
> On Monday 01 June 2009 16:53:55 Garth N. Wells wrote:
> > Anders Logg wrote:
> > > On Mon, Jun 01, 2009 at 04:06:40PM +0200, DOLFIN wrote:
> > > > One or more new changesets pushed to the primary dolfin repository.
> > > > A short summary of the last three changesets is included below.
> > > >
> > > > changeset:   6245:30c1540b12097130e3ed48ed572819471c884a7b
> > > > tag:         tip
> > > > user:        "Garth N. Wells <gnw20@xxxxxxxxx>"
> > > > date:        Mon Jun 01 15:06:26 2009 +0100
> > > > files:       dolfin/la/EpetraSparsityPattern.cpp
> > > > dolfin/la/EpetraSparsityPattern.h dolfin/la/GenericSparsityPattern.h
> > > > dolfin/la/SparsityPattern.cpp dolfin/la/SparsityPattern.h
> > > > dolfin/la/uBLASMatrix.h description:
> > > > Use std::set in SparsityPattern.
> > > >
> > > > Some performance issues seem to have been resolved with std::set.
> > > >
> > > > std::tr1::unsorted_set is faster, but requires some effort to sort.
> > > > Sorting is only relevant to the uBLAS backend at this point.
> > > Building the sparsity pattern seems to be slightly faster, but
> > > deleting it takes significantly longer. The relative slowdown for that
> > > step is a factor 15-20.
> > >
> > > I was wondering why we used std::vector instead of std::set, but this
> > > might be the reason: It takes a *long* time to delete std::set. We
> > > should look for something else.
> > I recall set insertion also being dead slow, which is why I used
> > std::vector with a homemade insert. Despite having programmed it, it
> > took me a bit to understand what the code I wrote does which I why I
> > tried set again.
> >
> > We should try std::tr1::unsorted_set. It's faster for insertion but I
> > don't know about the delete. We can cook something up to do the sort for
> > uBLAS.
>
> Isn't the performance issue on destruction the common problem of deleting a 
> lot of small objects? This would probably not be any difference with 
> unsorted_set?

We don't see this with std::vector<std::vector<uint> >. unsorted_set 
does have the same problem with slow destruction, but this is 
compensated for by faster insertion.

> Would it be worth trying a pooled memory management? Something like:
>
> #include <boost/pool/pool_alloc.hpp>
> typedef std::set<int, unsigned int, boost::fast_pool_allocator<unsigned int> > 
> setuint;

Yes, this is an option.

Garth

> Johan
>
> > Garth
> >
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