[GHC] #6082: Program compiled with 7.4.1 runs many times slower than compiled with 7.2.2

[GHC]

#6082: Program compiled with 7.4.1 runs many times slower than compiled with 7.2.2
-------------------------------------+--------------------------------------
 Reporter:  gchrupala                |          Owner:                  
     Type:  bug                      |         Status:  new             
 Priority:  normal                   |      Component:  Compiler        
  Version:  7.4.1                    |       Keywords:                  
       Os:  Unknown/Multiple         |   Architecture:  Unknown/Multiple
  Failure:  Runtime performance bug  |       Testcase:                  
Blockedby:                           |       Blocking:                  
  Related:                           |  
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 The morfette program (http://hackage.haskell.org/package/morfette), when
 compiled with 7.4.1 runs extremely slow: approx. 20x times slower than
 when compiled with 7.2.1.

 To reproduce, install morfette using both compilers, and run it on the
 attached `sample' file.

 {{{
 morfette train sample output --iter-pos=10 --iter-lemma=3
 }}}

 I attach the output of the profiler for both compilers. It would seem the
 performance bug is related to code from the modules
 GramLab.Perceptron.Multiclass and GramLab.Perceptron.Vector

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/6082>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler