On Friday 01 February 2013, 13:06:09, Daniel Fischer wrote:
>
> zipWith' would [I haven't tested, but I'm rather confident] make a
> difference if you benchmarked
>
> bench "name" (whnf (fibs !!) 100000)
>
> etc.
Well, it took a little bit of persuasion to let GHC not cache the list(s), but
with
fibs :: Int -> Integer
fibs k = igo i !! k
where
i | k < 1000000 = 1
| otherwise = 2
igo :: Integer -> [Integer]
igo i = let go = 0 : i : zipWith (+) go (tail go) in go
etc., benchmarking
main :: IO ()
main = defaultMain $ [
bench "fibs " (whnf fibs 20000)
, bench "fibsP" (whnf fibsP 20000)
, bench "fibs'" (whnf fibs' 20000)
]
shows a clear difference:
benchmarking fibs
mean: 14.50178 ms, lb 14.27410 ms, ub 14.78909 ms, ci 0.950
benchmarking fibsP
mean: 13.69060 ms, lb 13.59516 ms, ub 13.81583 ms, ci 0.950
benchmarking fibs'
mean: 3.155886 ms, lb 3.137776 ms, ub 3.177367 ms, ci 0.950
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