Autobahn

A tool for inferring strictness annotations in Haskell programs using a genetic algorithm.

Build and Run

Autobahn uses stack to build and run. It currently builds with stack lts-14.6.

Build with

> stack build
> stack install

WARNING: Autobahn will overwrite the original source of any project you point it at. You should copy or clone your project into a fresh / temporary directory before running Autobahn on it.

Once you have done this, run the executable with e.g. (assuming $HOME/.local/bin is in your PATH):

> cd test/hello
> Autobahn

Autobahn takes either a configuration file, named config.atb in the present working directory, or asks the user for inputs on the command line to craft a configuration in the event that config.atb is not found.

Limitations

Currently,

• Autobahn requires the program builds with cabal (unless the program is nofib).
• You must specify ghc-options: -rtsopts "-with-rtsopts=-T" in the executable section of your project.cabal file.
• The name of the project and the basename of main-is must be the same
• Any files that Autobahn profiles must already have the BangPatterns extension enabled in the LANGUAGE section at the top of each file.

See test/hello for a minimal example, as taken and modified from http://www.haskell.org/hello/. We are working on making Autobahn more flexible in terms of the cabal configurations Autobahn will accept.

Config File Specification

The specification of a configuration file for a run of Autobahn is as follows

• projectDirectory : The path to the source files.
• budgetTime : The number of hours Autobahn can spend optimizing the program. While in hours, decimal numbers can be used. Autobahn uses this to determine
  • number of generations (rounds) to evolve the program
  • number of chromosomes (programs) to create per generation
  • number of chromosomes to archive (save) from a generation
• coverage : The files Autobahn will add strictness annotations to.
• targetMetric : The metric Autobahn will optimize the program for. The current choices are
  • "peakAlloc" : Autobahn will minimize the bytes allocated by the program
  • "runtime" : The runtime of the program
  • ""gc" : The time a program spends in garbage collection
• inputArg : The input the program needs to run
• absenceImpact: The amount of decrease in performance in the absence of a bang required to preserve it
• hotSpotThresh: The amount of percentage cost of a cost center for it to be considered a hot spot
• profile metric: Metric to parse GHC profile with (MEM for memory allocations or RT for runtime)

Example Config File

When Pat and Chris want to run their program bintree through Autobahn, they create the file below called config.atb.

projectDirectory = "/home/pat/haskell-projects/bintree"
budgetTime = 0.1h
coverage = "Main.hs"
executable = "Main.hs"
targetMetric = "peakAlloc"
inputArg = "5 7 8 0.05 0.06 RT"

Output

Autobahn will display statistics about each generation on the command line as it goes.

The final Autobahn 1.0 output appears in the project directory under two directories

• autobahn-survivor : Holds the edited sources of the best scoring program
• autobahn-results : Holds an HTML file detailing the specific configuration Autobahn used as well as the results of all the programs in the final round that did not time out or end in error

Results for Autobahn 2.0 are presented in:

• minresults : File which records performance of Autobahn 1.0 vs. Autobahn 2.0
• original files : Overwritten with Autobahn 2.0 results

Running Autobahn 2.0

• It is necessary to enable profiling in your project:
  • For cabal projects:
  • For nofib benchmark:
    • Uncomment benchmarking and build project code specific to nofib benchmarks in Profiling.hs
  • In opts.mk, add the -pa flag to SRC_RUNTEST_OPTS
  • In boilerplate.mk, add -prof -fprof-auto flags to NoFibHcOpts
  • Remember to clean and remake the harness after the changes and separately make nofib-analyse again