ndmitchell / ndmitchell/hlint

HLint slow on larger files

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#983 13 comments 0 reactions 0 assignees View on GitHub

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scope
Dominant language
Haskell
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Description

% wc cabal-install/Distribution/Client/Setup.hs   
  2709  12689 112567 cabal-install/Distribution/Client/Setup.hs

With hlint-3.1:

% time hlint cabal-install/Distribution/Client/Setup.hs
hlint cabal-install/Distribution/Client/Setup.hs  3,64s user 0,09s system 99% cpu 3,741 total

Where hlint-2.0.15:

hlint cabal-install/Distribution/Client/Setup.hs  1,19s user 0,06s system 98% cpu 1,261 total

i.e. I see 3x regression in performance.

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First steps

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  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reproducing the reported benchmark with hlint on cabal-install/Distribution/Client/Setup.hs, comparing hlint-3.1 with hlint-2.0.15 as shown. Trace the performance difference and verify that the current version no longer takes roughly three times as long on this larger Haskell file.

Written by the indexing model from the issue text.

Assessment

Tech stack
haskell
Domain
performance, tooling
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
30/100

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