a compiled program is slower than byte code

[Kazu Yamamoto ( 山本和彦 )]

Hello Simon,

> $ ghc-nightly2 ./kazu.hs -O2 -fforce-recomp; time ./kazu
> [1 of 1] Compiling Main             ( kazu.hs, kazu.o )
> Linking kazu ...
> 4.17s real   4.16s user   0.01s system   99% ./kazu

OK. I ran it on 32bit Linux.

6.12.3  runghc   -- 2.22s user 0.40s system 96% cpu 2.724 total
        ghc      -- 1.96s user 0.14s system 97% cpu 2.151 total
        ghc -O   -- 2.18s user 0.10s system 97% cpu 2.333 total
        ghc -O2  -- 2.27s user 0.07s system 97% cpu 2.393 total

ghc-7.0 runghc   -- 3.43s user 0.35s system 97% cpu 3.861 total
        ghc      -- 5.11s user 0.07s system 97% cpu 5.299 total
        ghc -O   -- 5.38s user 0.03s system 97% cpu 5.534 total
        ghc -O2  -- 5.54s user 0.10s system 97% cpu 5.783 total

ghc-7.0 is slower than 6.12.3. And if the code is compiled with
ghc-7.0, it is slower than runghc.

> HEAD is more than twice as fast on this program.  Fusion not working,
> perhaps?

Here is the results of "ghc -O -ddump-simpl-stats":

ghc-7.0:

19 RuleFired
    6 ++
    2 <=#
    1 fold/build
    5 foldr/app
    1 foldr/augment
    1 foldr/single
    1 map
    1 unpack
    1 unpack-list

6.12.3:

25 RuleFired
    6 ++
    2 <=#
    3 fold/build
    6 foldr/app
    1 foldr/augment
    1 map
    2 repeat
    2 take
    1 unpack
    1 unpack-list

They are exactly the same on Linux and Mac.

--Kazu