dolfin team mailing list archive

[Garth Wells <668862@xxxxxxxxxxxxxxxxxx>]

On 10/11/10 22:50, Johan Hake wrote:
>> I guess it is this line that takes time:
>>
>>     diagonal[I].insert(map_j[j]);
>
> diagonal is of course not a std::set but a dolfin::Set. Anyhow it is
> definately the call to std::find that takes time, in the dolfin::Set::find
> method.
>
> Not sure why it should take so much longer time searching a vector when a Real
> space is used.
>
> Using a std::set might probably speed up it for this case?
>

We use a home-made set because std::set is very slow (it's sorted). It 
may be worth trying boost::unordered_set.

Garth


> Johan
>

-- 
Sparsity pattern computation dead slow with 'real' spaces
https://bugs.launchpad.net/bugs/668862
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Status in DOLFIN: New

Bug description:
The computation of the sparsity pattern is dead slow when real spaces are used, i.e.,

    R = FunctionSpace(mesh, 'R', 0)

To see the problem, compare the neumann-poisson and poisson demos with fine meshes (256x256)