Hi, especially David and Dan, I wanted to announce this only when I had time to polish more corners, but since you are busy hacking on list fusion, experimenting with foldrW etc., maybe it’s better to release early (and you might enjoy polishing the corners yourself). Together with John Wiegly at ICFP, I started to create a list performance laboratory. You can find it at: https://github.com/nomeata/list-fusion-lab The idea is simple: Have a number of modules (in ListImpls/) that provide the same list functions (see ListImpls/exports). Then there is a test suite (Benchmarks.hs) and a driver (driver.hs). The latter takes, as arguments, a number of ghc binaries and a number of modules from ListImpls, compiles a small helper (ListTestsTemplate.hs) with all combinations (using CPP to select the right module), runs the benchmarks and aggregates the results. Note that the tests are not run in the same process as the runner, which reduces the number of libraries that the tested compiler needs to have installed. It is half finished in a few ways: * The reporting is unfinished. We used criterion’s default, but it is not quite what we want to see. * It still requires the tested compiler to have criterion installed, which is tricky for GHC-HEAD. I’d like to have two modules providing a function "(Int -> ()) -> IO Double", one with criterion and one with some ad-hoc measurement, and a way for the driver to choose. This way you can get rough measurements without criterion. * I’d like to also measure allocations. Again, that’d be nicer with a way of running the benchmarks without criterion. * There are clearly not enough benchmarks. The plan for this is that when evaluating a different implementation of a list function, or possibly a completely different fusion implementation (foldrW, stream fusion), we can simply add it here and have something reliable to base our decisions on, instead of waiting for one of the experienced wizards to come along and cast a verdict. Enjoy, and send pull requests! Greetings, Joachim -- Joachim “nomeata” Breitner mail@joachim-breitner.de • http://www.joachim-breitner.de/ Jabber: nomeata@joachim-breitner.de • GPG-Key: 0xF0FBF51F Debian Developer: nomeata@debian.org