[firedrake] Firedrake benchmarks

Hi firedrakers, I have set up a repository of Firedrake benchmarks [1] to assess performance for a varied set of applications and parameters. Implemented so far are: 1) matrix assembly for mass, laplace, helmholtz 2) stationary Poisson 3) advection-diffusion (split form) 4) Navier-Stokes (split form) 5) Cahn-Hilliard I have started compiling some preliminary results [2], which I plan to updated from time to time as I have new measurements. As of now there is assembly and advection-diffusion. Cheers, Florian [1]: https://github.com/firedrakeproject/firedrake-bench [2]: https://gist.github.com/kynan/116211fa75d66a66311e