On Sun, Oct 10, 2010 at 7:02 PM, Daniel Fischer
Greetings,
I have put together a package to test possible implementations of the RealFrac methods for Double and Float (base-2 IEEE754) and uploaded a .tar.gz bundle to http://hackage.haskell.org/trac/ghc/ticket/2271 .
On the one hand, pure Haskell implementations, on the other hand implementations calling out to rint[f], trunc[f], floor[f] and ceil[f] from math.h.
Both ways go via Integer by default, with a specialised faster implementation for Int (and narrower types, but those RULES haven't yet been written) enabled by a rewrite rule.
Overall, the pure Haskell implementations don't fare badly on my computer. All give a speedup compared to the current implementation, for most conversions, pure Haskell is on par with or faster than the C-call (although that would probably change if the C functions were made primops).
The FFI calls are significantly faster for properFraction :: Double -> (Integer, Double) and for round (except round :: Integral a => Float -> a when compiled via C, then native and FFI are on par).
Sample results for the speedups against the current implementation (note: for truncate :: x -> Int, the Prelude value is fst . properFraction, not the rewritten float2Int or double2Int) are included in the tarball.
I would appreciate feedback from your tests/benchmarks on other platforms, especially 64-bit platforms (mine is x86 linux, 32 bit).
To run the QuickCheck tests, you need QuickCheck-2.*, to run the benchmarks, criterion.
More instructions in the README.
Thanks, Daniel
I got a lot of errors (or warnings?) during compilation. Is it something I should worry about? I'm using GHC 6.12.1 on 64-bit Linux. Antoine +++++ $sh build.sh [1 of 1] Compiling Main ( getSummary.hs, getSummary.o ) Linking getSummary ... building with the NCG [1 of 1] Compiling RFDouble ( RFDouble.hs, RFDouble.o ) RFDouble.hs:88:31: Not in scope: `negateInt64#' RFDouble.hs:89:33: Not in scope: `negateInt64#' RFDouble.hs:92:37: Not in scope: `minusInt64#' RFDouble.hs:111:31: Not in scope: `negateInt64#' RFDouble.hs:112:33: Not in scope: `negateInt64#' RFDouble.hs:146:40: Not in scope: `minusInt64#' [1 of 1] Compiling RFFloat ( RFFloat.hs, RFFloat.o ) [1 of 2] Compiling RFDouble ( RFDouble.hs, RFDouble.o ) RFDouble.hs:88:31: Not in scope: `negateInt64#' RFDouble.hs:89:33: Not in scope: `negateInt64#' RFDouble.hs:92:37: Not in scope: `minusInt64#' RFDouble.hs:111:31: Not in scope: `negateInt64#' RFDouble.hs:112:33: Not in scope: `negateInt64#' RFDouble.hs:146:40: Not in scope: `minusInt64#' [2 of 2] Compiling Main ( benchFloat.hs, benchFloat.o ) Linking benchFloat ... building via C [1 of 1] Compiling RFDouble ( RFDouble.hs, RFDouble.o ) RFDouble.hs:88:31: Not in scope: `negateInt64#' RFDouble.hs:89:33: Not in scope: `negateInt64#' RFDouble.hs:92:37: Not in scope: `minusInt64#' RFDouble.hs:111:31: Not in scope: `negateInt64#' RFDouble.hs:112:33: Not in scope: `negateInt64#' RFDouble.hs:146:40: Not in scope: `minusInt64#' [1 of 1] Compiling RFFloat ( RFFloat.hs, RFFloat.o ) [1 of 2] Compiling RFDouble ( RFDouble.hs, RFDouble.o ) RFDouble.hs:88:31: Not in scope: `negateInt64#' RFDouble.hs:89:33: Not in scope: `negateInt64#' RFDouble.hs:92:37: Not in scope: `minusInt64#' RFDouble.hs:111:31: Not in scope: `negateInt64#' RFDouble.hs:112:33: Not in scope: `negateInt64#' RFDouble.hs:146:40: Not in scope: `minusInt64#' Linking cbenchFloat ... [1 of 2] Compiling RFDouble ( RFDouble.hs, RFDouble.o ) RFDouble.hs:88:31: Not in scope: `negateInt64#' RFDouble.hs:89:33: Not in scope: `negateInt64#' RFDouble.hs:92:37: Not in scope: `minusInt64#' RFDouble.hs:111:31: Not in scope: `negateInt64#' RFDouble.hs:112:33: Not in scope: `negateInt64#' RFDouble.hs:146:40: Not in scope: `minusInt64#' +++++