[GHC] #10108: Dramatic slowdown with -O2 bytestream and list streams combined.

22 Feb 2015


      #10108: Dramatic slowdown with -O2 bytestream and list streams combined.
-------------------------------------+-------------------------------------
              Reporter:  Truman      |             Owner:
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:  7.10.2
             Component:  Compiler    |           Version:  7.8.4
              Keywords:              |  Operating System:  Linux
          Architecture:              |   Type of failure:  Runtime
  Unknown/Multiple                   |  performance bug
             Test Case:              |        Blocked By:
  break_in.hs                        |   Related Tickets:
              Blocking:              |
Differential Revisions:              |
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 In a small testcase intended to filter log files from stdin, I
 found that using bytestreams and list streams in combination worked
 fine when compiled without optimization, but runtime performance slowed
 down by a factor of about 3600 when I compiled with -O2.  Changing the
 import of Data.List.Stream to Data.List gets rid of the problem.

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Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10108
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