[Haskell-cafe] Re: Desired behaviour of rounding etc.
daniel.is.fischer at web.de
Fri Oct 8 09:29:01 EDT 2010
On Friday 08 October 2010 14:08:01, Daniel Fischer wrote:
> On a related note, in my benchmarks,
> truncFloatGen :: Integral a => Float -> a
> truncFloatGen = fromInteger . truncFloatInteger
> truncFloatInteger :: Float -> Integer
> truncFloatInteger x =
> case decodeFloat x of
> (m,e) | e == 0 -> m
> | e < 0 ->
> let s = -e
> in if m < 0
> then - ((-m) `shiftR` s)
> else m `shiftR` s
> | otherwise -> m `shiftL` e
> is more than twice as fast as GHC.Float.float2Int, the corresponding for
> Double almost twice as fast as double2Int.
> Can anybody confirm that the above is faster than float2Int on other
That one is more or less solved. For values inside the Int range,
float2Int/double2Int are, as expected, much faster.
Only for values outside the Int range the picture changes, and I
benchmarked over a much larger range.
Still odd that float2Int/double2Int degrade so badly outside the range.
More information about the Haskell-Cafe