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