native implementation of set.rb

[kares]

work towards having Set/SortedSet natively instead of set.rb

had these changes lying around for a long-time (mostly waiting to target 9.2)
primarily this has been motivated for premium Java Integration features :
Set implements java.util.Set and SortedSet implements java.util.SortedSet

but there's also a significant gain in performance.
set.rb is rather loosely written with some ugly-ness such as patching/features-detection on SortedSet.new

for maximum compatibility sets are backed by a Hash like before (and serializes the same as before), this is important for some older versions of Sprockets when under Rails switching between MRI and JRuby.

SortedSet uses Java's TreeSet implementation for ordering as it was available and performs better than the pieces in set.rb

some (naive) performance numbers, also showcasing Set is now at Java's HashSet speed :

Ruby Set#include? hit   0.530000   0.000000   0.530000 (  0.473302)
Ruby Set#include? miss  0.450000   0.000000   0.450000 (  0.452750)
HashSet#include? hit    0.390000   0.000000   0.390000 (  0.388358)
HashSet#include? miss   0.370000   0.000000   0.370000 (  0.364610)
     Set.new([1,2,3])    1.860000   0.010000   1.870000 (  1.847379)
SortedSet.new([1,2,3])   3.560000   0.010000   3.570000 (  3.538512)
     Set#inspect         4.180000   0.000000   4.180000 (  4.157021)
SortedSet#inspect        4.160000   0.010000   4.170000 (  4.145266)
     Set#flatten         1.510000   0.000000   1.510000 (  1.504799)
     Set#each {|e| e}    1.310000   0.000000   1.310000 (  1.306374)

JRuby 9.1.9

Ruby Set#include? hit   0.660000   0.000000   0.660000 (  0.657267)
Ruby Set#include? miss  0.810000   0.000000   0.810000 (  0.811419)
HashSet#include? hit    0.430000   0.000000   0.430000 (  0.421336)
HashSet#include? miss   0.370000   0.000000   0.370000 (  0.367006)
     Set.new([1,2,3])    8.600000   0.010000   8.610000 (  8.455883)
SortedSet.new([1,2,3])  15.920000   0.020000  15.940000 ( 15.828404)
     Set#inspect         6.710000   0.000000   6.710000 (  6.633052)
SortedSet#inspect        5.730000   0.010000   5.740000 (  5.663528)
     Set#flatten         8.960000   0.000000   8.960000 (  8.879096)
     Set#each {|e| e}    1.680000   0.000000   1.680000 (  1.663696)

MRI 2.3.3

Ruby Set#include? hit   0.960000   0.000000   0.960000 (  0.957069)
Ruby Set#include? miss  1.040000   0.000000   1.040000 (  1.043396)
     Set.new([1,2,3])   20.590000   0.010000  20.600000 ( 20.606219)
SortedSet.new([1,2,3])  30.410000   0.000000  30.410000 ( 30.411511)
     Set#inspect        10.890000   0.000000  10.890000 ( 10.889514)
SortedSet#inspect       11.010000   0.000000  11.010000 ( 11.007346)
     Set#flatten        20.050000   0.000000  20.050000 ( 20.054732)
     Set#each {|e| e}    2.680000   0.000000   2.680000 (  2.686750)

[kares]

also to be noted that due use of Sets in Rails this has a noticeable impact on a decently sized Rails app.
... e.g. I am seeing a 15% rake test on master compared to 9.1.9.0 (probably not all due this but some).

UPDATE: compared to 9.1.12 its still seems to be a consistent 5% improvement using this branch ...