A Navaei wrote: > 2009/3/23 Kent Andre <[email protected]>: >> The code that FFC produces is about as fast as light. It has been >> documented in a number of papers. > > Is there any data available comparing the FFC performance to the hardware > peak? >
FFC does not operate in isolation, so it is not possible to make a comparison to max flops of a CPU. Furthermore, in a typical simulation with code generated by FFC, other parts of the solution process dominate (such as insertion as mentioned by Kent) and the linear solve, so whether or not FFC generated code is optimal in terms of peak flops of a machine is not relevant to runtime performance. >> I don't think you should try to beat FFC with generic meta-programming. >> Or you could do it but, but don't have to high expectations... >> >> Insertion into the matrix is currently the bottleneck. But FFC does >> not have anything to do with this. > > While FFC doesn't have anything to do with this, dolfin does. In the > case of the MTL4 backend wrapper, it is implemented badly by ignoring > the meta-programming potentials. This is not a constructive comment. Patches are welcome. For instance, sparse matrix insertion > is done by forming a sparsity pattern outside of MTL4 and then > assigning the pointers to MTL4 API, while loop unrolling could have > been used here. > If you look at the code, the FFC backend does not use the sparsity pattern. The MTL4 inserter does have some options which we have not yet been taken advantage of, so again patches are welcome. Garth > > -Ali > >> Kent >> >> >> On ma., 2009-03-23 at 10:11 +0000, A Navaei wrote: >>> The success of MTL4 based on generic meta-programming, arises the >>> question about re-visiting the efficiency of code-generation >>> approaches, including FFC. Given that FEM can particularly benefit >>> from major meta-programming characteristics, namely static >>> polymorphism and loop unrolling, MTL4 demonstrates that the >>> code-generation part can be much more efficiently replaced by inlining >>> performed at compile-time. >>> >>> Without having a concrete meta-programming implementation, it may be >>> impossible to predict how much performance one would gain compared to >>> FFC. However, MTL4 has been reported to be many times faster than >>> code-generation means such as ATLAS. >>> >>> Based on this, are there any specific benefits in FFC code-generation >>> which may not be covered by meta-programming? >>> >>> >>> -Ali >>> _______________________________________________ >>> DOLFIN-dev mailing list >>> [email protected] >>> http://www.fenics.org/mailman/listinfo/dolfin-dev >> > _______________________________________________ > DOLFIN-dev mailing list > [email protected] > http://www.fenics.org/mailman/listinfo/dolfin-dev _______________________________________________ DOLFIN-dev mailing list [email protected] http://www.fenics.org/mailman/listinfo/dolfin-dev
