make nofib awesome
Nofib is the standard tool GHC developers use to benchmark changes to the compiler. Its overall design is OK but it's had no love and care for many years and has bittrotted such that it isn't useful in a lot of situations.
This task is about making nofib useful again.
The breakdown for this is something like:
- Think and maybe fix nofib framework design. It has 'ways' which I think correspond to compilation method but more in the sense of 'dynamic' vs 'static', seems it may not suite being able to use ways for 'fasm' vs 'fllvm'. There is also the concept of 'modes' which corresponds to different benchmark input. So 'normal' and 'slow' for getting different run-times. At moment no easy way to select which benchmark groups to run, so may want to change that. I guess we should just decide, what knobs do we want to be able to easily tweak, and see how well the current design allows that.
Note there is a shake build system attached that does a lot of this (done by Neil Mitchell!). An explanation of it can be found here: http://neilmitchell.blogspot.com/2013/02/a-nofib-build-system-using-shake.html
The design discussion of it is mostly lost as it was done on private email sorry.
- ~~Fixup the runtimes for benchmarks to be significant. This might be best done by changing the way we run benchmarks and collect results to make sure they are meaningful (cf. #15357 (closed))~~ done in #15999 (closed).
E.g., Lots of great discussion and links to papers on this thread
- ~~Above task is to fix normal but we may want to fixup slow as well and perhaps add a 'fast' mode where benchmarks run in around 1 second.~~ Done, we determined that 0.1-0.2/1-2/5-10 for fast/norm/slow are the brackets to aim for.
- Maybe add more benchmarks to the suite (text, bytestring, performance regressions from ghc testsuite, vector....)