The NoFib Benchmark Suite

The NoFib benchmark suite is a collection of (mostly old) Haskell programs that we use for benchmarking GHC.

Getting nofib

The NoFib suite is kept in a separate darcs repository (see Repositories), and it should be checked out at the top level of a GHC source tree, i.e. at the same level as compiler and libraries. From your GHC tree, run:

./sync-all --nofib get

It will be pulled into the a "nofib" subdirectory.

Benchmarking

To run the tests:

  $ cd nofib
  $ make clean
  $ make boot
  $ make 2>&1 | tee nofib-log

will put the results in the file nofib-log.

To compare the results of multiple runs, use the program nofib/nofib-analyse/nofib-analyse. Something like this:

  $ nofib-analyse nofib-log-6.4.2 nofib-log-6.6

to generate a comparison of the runs in captured in nofib-log-6.4.2 and nofib-log-6.6. When making comparisons, be careful to ensure that the things that changed between the builds are only the things that you wanted to change. There are lots of variables: machine, GHC version, GCC version, C libraries, static vs. dynamic GMP library, build options, run options, and probably lots more. To be on the safe side, make both runs on the same unloaded machine.

To get measurements for simulated instruction counts, memory reads/writes, and "cache misses", you'll need to get hold of Cachegrind, which is part of  Valgrind. You can run nofib under valgrind like this:

  $ make SRC_RUNTEST_OPTS=-cachegrind

Complete recipe

cd nofib
make clean && make boot && make -k >& log1
make clean && make boot && make -k EXTRA_HC_OPTS=-fenable-cool-optimisation >& log2
nofib-analyse/nofib-analyse log1 log2

The output of the nofib-analyse tool is quite readable, with two provisios:

• Missing values in the output typically mean that the benchmark crashed and may indicate a problem with your optimisation
• If a difference between the two modes is displayed as an absolute quantity instead of a percentage, it means that the difference was below the threshold at which the analyser considers it significant

If the comparison identifies any particularly bad benchmark results, you can run them individually by changing into their directory and running something like:

EXTRA_HC_OPTS="-fenable-cool-optimisation -ddump-simpl" make

You can add whatever dumping flags you need to see the output and understand what is going wrong.

Tweaking things

To tweak things, add settings to your mk/build.mk (see Commentary/SourceTree).

• Each benchmark is run in each "way" in NoFibWays. By default NoFibWays is initialised to GhcLibWays, but you can override that in mk/build.mk. Typically, to just use the vanilla way, set NoFibWays to empty:

  NoFibWays =
  

• By default nofib uses the stage-2 compiler from your build tree. To tell nofib to use a different compiler, set WithNofibHc. For example:

  WithNofibHc = /home/simonpj/builds/HEAD/inplace/bin/ghc-stage1
  

• Many nofib programs have up to three test data sets. The mode variable tells the system which to use, thus:

  make -k mode=slow
  make -k mode=norm
  make -k mode=fast
  

See mk/opts.mk. The default is mode=norm.