#10944: powModInteger slower than computing pow and mod separately -------------------------------------+------------------------------------- Reporter: iago | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Core | Version: 7.8.3 Libraries | Keywords: integer-gmp | Operating System: Linux Architecture: x86_64 | Type of failure: Runtime (amd64) | performance bug Test Case: | Blocked By: Blocking: | Related Tickets: Differential Rev(s): | -------------------------------------+------------------------------------- {{{#!hs module Foo where import GHC.Integer.GMP.Internals ( powModInteger ) test1, test2 :: Integer -> Integer -> Int -> Integer test1 a b c = (a ^ b) `mod` (2^c) test2 a b c = powModInteger a b (2^c) }}} I was expecting `test2` to perform better than `test1`, but I'm getting quite the opposite: the use of `powModInteger` seems to be several orders of magnitude slower. I have tested this with GHC 7.10.2 and integer-gmp 1.0.0.0 too, with similar results. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/10944 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler