[GHC] #8766: length [Integer] is twice as slow but length [Int] is 10 times faster

[GHC]

#8766: length [Integer] is twice as slow but length [Int] is 10 times faster
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        Reporter:  George                   |            Owner:
            Type:  bug                      |           Status:  new
        Priority:  normal                   |        Milestone:
       Component:  Compiler                 |          Version:  7.8.1-rc1
      Resolution:                           |         Keywords:
Operating System:  Unknown/Multiple         |     Architecture:
 Type of failure:  Runtime performance bug  |  Unknown/Multiple
       Test Case:                           |       Difficulty:  Unknown
        Blocking:                           |       Blocked By:
                                            |  Related Tickets:
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Comment (by George):

 Right, the important point of the ticket is the regression for [Integer]
 but implicit in mentioning the order of magnitude improvement for [Int] is
 the question of why [Integer] is, even after this bug is fixed, an order
 of magnitude slower than [Int] and would it be possible to make the time
 for [Integer] much closer to [Int]. After all length only traverses the
 spine of the list so why the big difference? This is probably obvious to
 many but not to me and I'd like to know why.

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/8766#comment:5>
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