#2252: Extreme performance degradation on minor code change
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Reporter: simona | Owner:
Type: bug | Status: new
Priority: normal | Milestone:
Component: Compiler | Version: 6.8.2
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Testcase: | Architecture: x86_64 (amd64)
Os: Linux |
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Comment (by simonpj):
Crumbs! So switching on -O makes `GoodPerform` run slowly too!
Can you try with `-fno-state-hack`?
How fast do you ''expect'' this to run? For example, if you do just one
of the fixpoints 1000 times, is that fast? Is it supposed to be fast?
I'm trying to ask whether `GoodPerform` is going bizarrely fast or
`BadPerform` is going bizarrely slowly.
Well done cutting down `fixpoint`. It'd be a huge help if you could so so
some more, so that GLPK, gmp etc were not needed. If it runs too fast,
just do something expensive, like `min [i+j | i <- [1..n], j <- [1..n]]`.
Simon
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2252#comment:5>
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The Glasgow Haskell Compiler
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