dolfin team mailing list archive

[Johan Hake <hake@xxxxxxxxx>]

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?

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;

Johan

> Garth
>
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