#7436: Derived Foldable and Traversable instances become extremely inefficient
due
to eta-expansion
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Reporter: shachaf | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 7.6.1
Keywords: | Os: Unknown/Multiple
Architecture: Unknown/Multiple | Failure: Runtime performance bug
Difficulty: Unknown | Testcase:
Blockedby: | Blocking:
Related: |
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Comment(by simonpj):
I'm very surprised that the eta-expanded version has asymptotically worse
behaviour.
Could you generate an example with hand-written code (not generated by
`deriving`) that elicits this behaviour? I'm gueesing that'd be simple do
to, and it'd save wading through mountains of irrelevant Core. The
smaller and more standalone the test case, the better.
I'm vaguely wondering whether it might be a space issue; ie takes lots of
space for chains of partial applications etc. Maybe you can use `+RTS -s`
for each version and give us the output. Thanks!
Simon
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7436#comment:2>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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