#8313: Poor performance of higher-order functions with unboxing
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Reporter: dolio | Owner:
Type: task | Status: new
Priority: low | Milestone: _|_
Component: Compiler | Version: 7.6.3
Resolution: | Keywords: slow unboxed
Operating System: Unknown/Multiple | higher order
Type of failure: Runtime | Architecture: Unknown/Multiple
performance bug | Difficulty: Easy (less than 1
Test Case: | hour)
Blocking: | Blocked By: 6084
| Related Tickets:
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Comment (by nomeata):
Checking if this is really fixed, but here, `manual` is still slower than
`auto`, so it does not seem to be fixed (although it might have been even
slower before). Also, `manual` allocates much more – is that the symptom
of this problem, or is it something else?
I had slightly change the test due to
[f6e2398adb63f5c35544333268df9c8837fd2581/base] to
{{{#!haskell
{-# LANGUAGE BangPatterns #-}
{-# LANGUAGE LambdaCase #-}
{-# LANGUAGE MagicHash #-}
import GHC.Exts
import System.Environment
rel# :: Int# -> Int# -> Int# -> Int#
rel# i# j# k# = (i# +# j# +# k#) ># 100000000#
rel :: Int -> Int -> Int -> Bool
rel (I# i#) (I# j#) (I# k#) = tagToEnum# (rel# i# j# k#)
manual :: (Int# -> Int# -> Int# -> Int#) -> (Int, Int, Int)
manual r# = go 0# 0# 0#
where
go i# j# k# | tagToEnum# (r# i# j# k#) = (I# i#, I# j#, I# k#)
| otherwise = go j# k# (i# +# 1#)
{-# NOINLINE manual #-}
auto :: (Int -> Int -> Int -> Bool) -> (Int, Int, Int)
auto r = go 0 0 0
where
go !i !j !k | r i j k = (i, j, k)
| otherwise = go j k (i+1)
{-# NOINLINE auto #-}
main = getArgs >>= \case
"manual" : _ -> print $ manual rel# -- This case is significantly
slower.
"auto" : _ -> print $ auto rel -- Why?
}}}
and I get these numbers:
{{{
$ ./T8313 manual +RTS -t
(33333333,33333334,33333334)
<