Re: [GHC] #13615: Nondeterminism in ‘pure’ function w/ parallel evaluation & memo combinators
GHC
ghc-devs at haskell.org
Thu Apr 27 00:23:10 UTC 2017
#13615: Nondeterminism in ‘pure’ function w/ parallel evaluation & memo combinators
-------------------------------------+-------------------------------------
Reporter: pacak | Owner: (none)
Type: bug | Status: new
Priority: highest | Milestone: 8.2.1
Component: Compiler | Version: 8.2.1-rc2
Resolution: | Keywords:
Operating System: Unknown/Multiple | Architecture:
Type of failure: Incorrect result | Unknown/Multiple
at runtime | Test Case:
Blocked By: | Blocking:
Related Tickets: | Differential Rev(s):
Wiki Page: |
-------------------------------------+-------------------------------------
Comment (by pacak):
I've confirmed that ghc has an interesting sense of equality:
{{{
regroup :: (NFData a, Show a, Hashable a, Eq a, Ord a) => [(a, Int)] ->
[(a, Int)]
regroup xs =
let xs' = HM.toList $ HM.fromListWith (+) xs
s' = sum (map snd xs')
s = sum (map snd xs)
in if s' /= s
then if show s' == show s
then error "WAT????"
else error $ "Those are expected to be equal" ++ show
(s', s)
else xs'
}}}
{{{
gamebooksolver-solvebook02: Those are expected to be equal(141,121)
CallStack (from HasCallStack):
error, called at src/Main.hs:50:26 in main:Main
gamebooksolver-solvebook02: Those are expected to be equal(384,300)
CallStack (from HasCallStack):
error, called at src/Main.hs:50:26 in main:Main
gamebooksolver-solvebook02: Those are expected to be equal(1045,1045)
CallStack (from HasCallStack):
error, called at src/Main.hs:50:26 in main:Main
gamebooksolver-solvebook02: WAT????
CallStack (from HasCallStack):
error, called at src/Main.hs:49:26 in main:Main
gamebooksolver-solvebook02: WAT????
CallStack (from HasCallStack):
error, called at src/Main.hs:49:26 in main:Main
gamebooksolver-solvebook02: WAT????
CallStack (from HasCallStack):
error, called at src/Main.hs:49:26 in main:Main
}}}
Actually it's even worse, note third error.
--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13615#comment:16>
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