Re: [ublas] mapped_matrix is exceedingly slow

From: Karl Meerbergen (karl.meerbergen_at_[hidden])
Date: 2008-01-19 03:48:21

This is a known problem. Use compressed_matrix instead.

Karl

James Sutherland wrote:
> All,
>
> I compiled an application using ublas with mapped_matrix<double>. I am 
> running an optimized build (with –DNDEBUG), and I am finding very poor 
> performance on mapped_matrix.
>
> Running gprof shows that more than 50% of the execution time is spent in
> std::_Rb_tree<unsigned long, std::pair<unsigned long const, double>, 
> std::_Select1st<std::pair<unsigned long const, double> >, 
> std::less<unsigned long>, std::allocator<std::pair<unsigned long 
> const, double> > >::lower_bound(unsigned long const&) const
>
> More than 30% of the execution time is spent in:
> boost::numeric::ublas::mapped_matrix::find1
>
> And 6% of the execution time is spent in mapped_matrix::find2
>
> This application runs a lot of matvec operations, so that should be 
> the bottleneck. I have just migrated from another linear algebra 
> package that runs the same problem orders of magnitude faster.
>
> I suppose that the obvious question is if there is a more efficient 
> way to do sparse matrix operations?
>
> Thanks for any advice,
>
> James
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