Compilation optimisation performance example - HaRe

[Alan & Kim Zimmerman]

At the moment HaRe has -O0 set for the library.

Here are some timing differences on my machine with optimisation on and off

With normal optimisation, we get

        $ rm -fr dist-newstyle/
        $ cabal new-configure --enable-test
        $ time cabal new-build

        real    6m54.778s
        user    7m3.156s
        sys    0m4.504s

With -O0, the timing  for the same commands is

        real    0m36.427s
        user 0m41.448s
        sys 0m2.544s

So optimisation slows it down from 36 seconds to 7 minutes.

Alan
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