I haven't had much time to do performance tzar work yet, but I did run nofib on the last few GHC releases to see the current trend. The benchmarks where run on my 64-bit Core i7-3770 @ 3.40GHz Linux machine. Here are the results:

7.0.4 to 7.4.2:

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Program Size Allocs Runtime Elapsed TotalMem

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Min -1.6% -57.3% -39.1% -36.4% -25.0%

Max +21.5% +121.5% +24.5% +25.4% +300.0%

Geometric Mean +8.5% -0.7% -7.1% -5.2% +2.0%

The big loser here in terms of runtime is "kahan", which I added to test tight loops involving unboxed arrays and floating point arithmetic. I believe there was a regression in fromIntegral RULES during this release, which meant that some conversions between fixed-width types went via Integer, causing unnecessary allocation.

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Program Size Allocs Runtime Elapsed TotalMem
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Min -5.1% -23.8% -11.8% -12.9% -50.0%
Max +5.3% +225.5% +7.2% +8.8% +200.0%
Geometric Mean -0.4% +2.1% +0.3% +0.2% +0.7%

The biggest loser here in terms of runtime is "integrate". I haven't looked into why yet.

7.6.1 to 7.6.2:

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Program Size Allocs Runtime Elapsed TotalMem

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Min -2.9% +0.0% -4.8% -4.4% -1.9%

Max +0.0% +1.0% +4.5% +6.4% +20.8%

Geometric Mean -1.7% +0.0% +0.1% +0.3% +0.2%

I have two takeaways:

* It's worthwhile running nofib before releases as it does find some programs that regressed.

* There are some other regressions out there (i.e. in code on Hackage) that aren't reflected here, suggesting that we need to add more programs to nofib.

Cheers,

Johan