[GHC] #14880: GHC panic: updateRole

[GHC]

#14880: GHC panic: updateRole
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        Reporter:  RyanGlScott       |                Owner:  goldfire
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  Compiler (Type    |              Version:  8.2.2
  checker)                           |
      Resolution:                    |             Keywords:  TypeInType
Operating System:  Unknown/Multiple  |         Architecture:
 Type of failure:  Compile-time      |  Unknown/Multiple
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:  #15076            |  Differential Rev(s):  Phab:D4769
       Wiki Page:                    |
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Comment (by tdammers):

 Replying to [comment:58 simonpj]:
 > > the "unions" approach: unions . map singleton
 >
 > That is essentially `foldr (union . singleton) empty`, which is really
 very close to `foldr insert empty`.
 >
 > What if you do a balanced tree of binary `union` operations?  I suppose
 something like
 > {{{
 > bigSet :: Int -> Int -> IntSet
 > bigSet m n
 >   | m==n = singleton n
 >   | otherwise = bigSet m mid `union` bigSet (mid+1) n
 >   where
 >     mid = (n+m)/2
 > }}}

 Did exactly that, benchmark code attached. Results:

 {{{
 ./intmapbench insert    1.32s user 0.05s system 99% cpu 1.370 total
 ./intmapbench union     1.01s user 0.01s system 99% cpu 1.029 total
 ./intmapbench balanced  0.24s user 0.01s system 98% cpu 0.260 total
 }}}

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/14880#comment:64>
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