Proposal: Faster toRational and fromRational
daniel.is.fischer at web.de
Thu Oct 21 15:35:30 EDT 2010
Proposal: include faster implementations for
1. toRational :: Float -> Rational
2. toRational :: Double -> Rational
3. fromRational :: Rational -> Float
4. fromRational :: Rational -> Double
The semantics of these functions shall remain the same as it is now, only
their speed will be affected.
For fromRational, a fast integer logarithm is essential. Without access to
the internal representation of Integer, it would be significantly slower,
so this proposal includes the addition of modules defining the needed
integer logarithm functions to the packages integer-gmp and integer-simple.
Since Int is not available in the integer-* packages, those functions would
return Int# values. I suggest adding wrappers integerLog2 :: Integer -> Int
and integerLogBase :: Integer -> Integer -> Int to some module in base
because those functions are far more generally useful. Currently
integerLogBase is available from GHC.Float, so we might stick them there,
although it's not very intuitive. Suggestions welcome.
Discussion period: one week, until 29th October 2010 (I'd like to see it in
there's a bundle containing the proposed new implementations, QuickCheck
tests and benchmarks.
I get a pretty impressive speedup.
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