@Niklas
You can use the `foldM` form the FoldL package to achieve equal results as
the fastest loops in your current benchmark. foldM will allow you to deal
with your loops at a high level of abstraction though. See the following
post, by Gabriel Gonzalez, for an example:
http://www.haskellforall.com/2013/08/foldl-100-composable-streaming-and.html
I have added the bench mark to my fork of your repo, and made a pull
request:
https://github.com/Davorak/loop
It looks like the only reason that `foldM` does not preform well with
`Word32` is because of the naive implementation of `enumFromTo` for Word32
as explained in my other email in more detail.
Here is the Criterion report:
http://htmlpreview.github.io/?https://github.com/Davorak/loop/blob/master/re...
On Tue, Apr 29, 2014 at 11:31 AM, Niklas Hambüchen
This is just a short notice that using
foldl' (+) 0 [0..100000::Int]
is over 10 times slower than using
flip execState 0 $ forLoop (0 :: Int) (< n) (+1) $ \i -> do x <- get put $! x + i
with `loopFor` as on https://github.com/nh2/loop.
Even using an IORef is twice as fast as the pure foldl' (but still 5 times slower than strict State).
The benchmark is at
http://htmlpreview.github.io/?https://github.com/nh2/loop/blob/master/result... .
(All benchmarks are linked from https://github.com/nh2/loop.)
You can see there that the problem is gone when using Vector.foldl', but only for Int - for Word32 it persists.
It seems that manual looping is beneficial even when dealing with prime examples of pure code that GHC ought to optimize well.
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