fiat team mailing list archive

[Robert C. Kirby <kirby@xxxxxxxxxxxx>]

On May 12, 2005, at 9:36 AM, Anders Logg wrote:

> On Thu, May 12, 2005 at 09:06:40AM -0500, Robert C.Kirby wrote:
>
> > Perhaps it would be good to make it consistent between the two, just 
> > in
> > case we need it.
>
> ok. Tell me if and when you have pushed this into FIAT and I can check
> that I get correct results for the dof map.

I am working at home, and I seem to go need to beat bombadil -- I can't 
ssh into it from here.
Perhaps searching for higher order linear dependencies has sent it to 
an early grave :)

> I agree. In addition to FFC being able to generate potentially faster
> run-time code with such a structure, it would be faster compile
> time. When I did this manually before (checking for functions that are
> zero), the speedup was a factor 2 or 3 but then the evaluation of
> integrals was much slower so the speedup might not be that good.

I'm thinking of something much more on compile time.  First, you might 
be able to zero out entire blocks, not just particular functions 
(vector Laplacian).  Second, you will only look at scalar functions on 
each block as you know only one component of the vectors will be 
nonzero.  Third, if you break the problem into p different blocks, 
these are trivially parallel.  You could use Python MPI bindings (e.g. 
pyMPI by Pat Miller.  Matt also has some bindings that I think are 
wretched to install) to farm out the tensor computations for each block 
to different processors.  You could run this on fledermaus/ficus at UC 
if you want.  For 3D elasticity, remember there are nine blocks to 
compute.  If all the blocks were equal cost to compute (in fact the 
diagonal is worse for elasticity), you could get a speedup of nine for 
this (really it will be more like three or four since the diagonals 
dominate).

Rob

> /Anders
>
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