[GHC] #7429: Unexplained performance boost with +RTS -h

[GHC]

#7429: Unexplained performance boost with +RTS -h
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  Reporter:  simonmar                 |          Owner:                  
      Type:  bug                      |         Status:  closed          
  Priority:  normal                   |      Milestone:  7.8.1           
 Component:  Compiler                 |        Version:  7.6.1           
Resolution:  wontfix                  |       Keywords:                  
        Os:  Unknown/Multiple         |   Architecture:  Unknown/Multiple
   Failure:  Runtime performance bug  |     Difficulty:  Unknown         
  Testcase:                           |      Blockedby:                  
  Blocking:                           |        Related:                  
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Comment(by simonmar):

 The laziness here is in the contents of the `STRef`, where you can't put a
 bang pattern.  Now the problem is that because you're creating a circular
 list, there must be at least ''one'' lazy element in it, because you're
 using laziness to create the circularity.  So you could probably add one
 bang pattern in `twoItemList`, but not two (I haven't tried this).

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7429#comment:11>
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