dolfin team mailing list archive

[Jed Brown <jed@xxxxxxxx>]

On Sat 2008-05-17 21:19, Murtazo Nazarov wrote:
> This is from 3D Navier-Stokes equation with linear elements. The first
> time assembly takes longer because it does initialization of the matrix,
> it calculates the sparsity pattern. But, then the sparsity pattern and
> A.init() is not done. Maybe I cannot gain so much, but as I posted in
> previous posts, I did exactly the same test with another package, with the
> same mesh, the same elements and the same equations, and that was at least
> 3 times faster than assembly we have in dolfin. So, instead of 7 seconds
> it is spent 7/3 seconds which I can gain 10 days from my simulation which
> takes now 14 days.

I don't understand.  Don't you solve a system with these matrices?  Your numbers
indicate that the solve takes negative time.

If you want to speed up the insertion of element matrices, I think the correct
way is to do clever caching so that, for instance, an entire row contribution
can be inserted at once.  Anders mentioned this earlier in this thread.  My
understanding is that computing the element matrices is supposed to be very fast
in Dolfin since it uses FFC-optimized code.  Can you profile and see exactly
where the time is being spent?  Is it in FFC-generated code or in insertion?

Jed

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