[Haskell-cafe] Vector sort poor performance

[Felipe Lessa]

On 21-08-2014 11:22, Felipe Lessa wrote:
> I suggest that you add a few SPECIALIZE pragmas to vector-algorithms and
> check its performance again.

Scratch that, I remembered that one may just copy & paste :).

Here's the code and criterion results:
https://gist.github.com/meteficha/1acef6dc1e1ed81b63ae

This is the relevant part:

benchmarking --nothing--/10
time 151.5 ns (151.2 ns .. 151.8 ns)
1.000 R² (1.000 R² .. 1.000 R²)
mean 151.8 ns (151.6 ns .. 152.1 ns)
std dev 868.8 ps (732.4 ps .. 1.030 ns)

benchmarking --best--/10
time 157.4 ns (157.1 ns .. 157.7 ns)
1.000 R² (1.000 R² .. 1.000 R²)
mean 157.1 ns (156.6 ns .. 157.4 ns)
std dev 1.297 ns (786.7 ps .. 2.366 ns)

benchmarking Optimal/10
time 1.173 μs (1.168 μs .. 1.180 μs)
1.000 R² (1.000 R² .. 1.000 R²)
mean 1.194 μs (1.187 μs .. 1.204 μs)
std dev 27.45 ns (22.18 ns .. 36.34 ns)
variance introduced by outliers: 29% (moderately inflated)

benchmarking Optimal'/10
time 157.7 ns (157.5 ns .. 158.0 ns)
1.000 R² (1.000 R² .. 1.000 R²)
mean 157.8 ns (157.5 ns .. 158.2 ns)
std dev 1.178 ns (872.4 ps .. 1.965 ns)

Optimal', which is a copy of Optimal, takes almost the same as --best--,
which does no comparisons at all!

So vector-algorithms really needs either to force INLINE (leading to
code size bloat) or sprinkle SPECIALIZE pragmas everywhere.  I suggest
contacting the package's maintainer to see what their thoughts are on
this matter.

Cheers,

-- 
Felipe.

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