[GHC] #9304: Floating point woes; Different behavior on 32- vs 64-bit x86

[GHC]

#9304: Floating point woes; Different behavior on 32- vs 64-bit x86
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        Reporter:  lerkok            |            Owner:
            Type:  bug               |           Status:  new
        Priority:  normal            |        Milestone:
       Component:  Compiler          |          Version:  7.8.3
      Resolution:                    |         Keywords:  floating point
Operating System:  Unknown/Multiple  |     Architecture:  Unknown/Multiple
 Type of failure:  None/Unknown      |       Difficulty:  Unknown
       Test Case:                    |       Blocked By:  9276
        Blocking:                    |  Related Tickets:
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Comment (by simonpj):

 Is this really a bug at all? As Reid says, there are no guarantees about
 the precision of `Double`.  A difference in the least significant bit of a
 `Double` on 64 bit vs 32 bit seems a remarkably small divergence to me.

 However I don't understand Reid's comment that "the optimiser is constant-
 folding the multiplication".  Which optimiser?  The user-guide link just
 says that some calculations are done in 80-bit without going back to
 64-bit at each intermediate.

 Simon

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/9304#comment:26>
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