[GHC] #9345: Data.List.inits is extremely slow

[GHC]

#9345: Data.List.inits is extremely slow
-------------------------------------+-------------------------------------
              Reporter:  dfeuer      |            Owner:
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:  7.8.4
             Component:              |          Version:  7.8.3
  libraries/base                     |         Keywords:
            Resolution:              |     Architecture:  Unknown/Multiple
      Operating System:              |       Difficulty:  Easy (less than 1
  Unknown/Multiple                   |  hour)
       Type of failure:  Runtime     |       Blocked By:
  performance bug                    |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
-------------------------------------+-------------------------------------

Comment (by dfeuer):

 Replying to [comment:11 nomeata]:
 > I forgot to attach the report mentioned in comment:6, doing that now.

 I was finally able to figure out how to read that file, and ''wow''. Those
 are some impressive results. If we can verify that the fusion on the left
 is safe, `initsQ2` is clearly the way to go. If we can't, it looks like we
 probably want to use the same thing, but without the `build`.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9345#comment:12>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler