Re: [GHC] #11707: Don't desugar large lists with build

15 Mar 2016

      #11707: Don't desugar large lists with build
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        Reporter:  bgamari           |                Owner:
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  7.10.3
      Resolution:                    |             Keywords:
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Runtime           |  Unknown/Multiple
  performance bug                    |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bgamari):

 Replying to [comment:3 simonpj]:
...
Why do `integrate` and `rewrite` regress so much?
In the case of `integrate` we have,
 {{{#!hs
   let  d = (u-l)/8.0 in
      d * sum
       [ (f l)*0.5,
         f (l+d),
         f (l+(2.0*d)),
         f (l+(3.0*d)),
         f (l+(4.0*d)),
         f (u-(3.0*d)),
         f (u-(2.0*d)),
         f (u-d),
         (f u)*0.5]
 }}}
 which is precisely the sort of pattern I was concerned about.

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11707#comment:4
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