[Haskell-cafe] Re: Experiments with defunctionalization, church-encoding and CPS

1 Nov 2009

      David Menendez wrote:
...
On Sun, Nov 1, 2009 at 7:12 AM, Heinrich Apfelmus
 wrote:
...
Even then, the results are mixed. The Church-encoding shines in GHCi as
it should, but loses its advantage when the code is being compiled. I
guess we have to look at the core if we want to know what exactly is
going on.
What optimization level did you compile with?
No optimization. From the bottom of the paste

  http://hpaste.org/fastcgi/hpaste.fcgi/view?id=10686#a11420

    Results:

    In ghci, the church encodings clearly win.

        *Main> force testTree
            ()
            (1.63 secs, 13948748 bytes)
        *Main> test findMaybe 0
            100000
            (1.70 secs, 15026356 bytes)
        *Main> test findChurch 0
            100000
            (0.72 secs, 15553668 bytes)
        *Main> test findChurch' 0
            100000
            (0.71 secs, 13456600 bytes)

    But when compiling, the algebraic data types wins.

    ghc --make Test.hs

        data Maybe
            mean: 90.08407 ms, lb 86.36974 ms, ub 94.13646 ms
        Church encoding
            mean: 152.0198 ms, lb 144.0916 ms, ub 161.0063 ms
        Church encoding optimised
            mean: 114.0715 ms, lb 107.3498 ms, ub 122.6881 ms

I am a bit surprised. Then again, I probably shouldn't be surprised that
the cost model is not like I imagine it to be.

Regards,
apfelmus

--
http://apfelmus.nfshost.com