While doing some benchmarking to answer this question about the fastest way to concatenate arrays I was surprised that when I did the same benchmarks in with jRuby the tests were a lot slower.
Does this mean that the old adagio about jRuby being faster than MRI Ruby is gone ? Or is this about how arrays are treated in jRuby ?
Here the benchmark and the results in both MRI Ruby 2.3.0 and jRuby 9.1.2.0
Both run on a 64bit Windows 7 box, all 4 processors busy for 50-60%, memory in use ± 5.5GB. The jRuby had to be started with the parameter -J-Xmx1500M to provide enough heap space. I had to remove the test with push because of stack level too deep and also removed the slowest methods to not make the tests too long. Used Jave runtime: 1.7.0_21
require 'Benchmark'
N = 100
class Array
def concat_all
self.reduce([], :+)
end
end
# small arrays
a = (1..10).to_a
b = (11..20).to_a
c = (21..30).to_a
Benchmark.bm do |r|
r.report('plus ') { N.times { a + b + c }}
r.report('concat ') { N.times { [].concat(a).concat(b).concat(c) }}
r.report('splash ') { N.times {[*a, *b, *c]} }
r.report('concat_all ') { N.times { [a, b, c].concat_all }}
r.report('flat_map ') { N.times {[a, b, c].flat_map(&:itself)} }
end
#large arrays
a = (1..10_000_000).to_a
b = (10_000_001..20_000_000).to_a
c = (20_000_001..30_000_000).to_a
Benchmark.bm do |r|
r.report('plus ') { N.times { a + b + c }}
r.report('concat ') { N.times { [].concat(a).concat(b).concat(c) }}
r.report('splash ') { N.times {[*a, *b, *c]} }
r.report('concat_all ') { N.times { [a, b, c].concat_all }}
r.report('flat_map ') { N.times {[a, b, c].flat_map(&:itself)} }
end
This question is not about the different methods used, see the original question for that. In both situations MRI is 7 times faster ! Can someone exlain me why ? I'm also curious to how other implementations do, like RBX (Rubinius)
C:\Users\...>d:\jruby\bin\jruby -J-Xmx1500M concat3.rb
user system total real
plus 0.000000 0.000000 0.000000 ( 0.000946)
concat 0.000000 0.000000 0.000000 ( 0.001436)
splash 0.000000 0.000000 0.000000 ( 0.001456)
concat_all 0.000000 0.000000 0.000000 ( 0.002177)
flat_map 0.010000 0.000000 0.010000 ( 0.003179)
user system total real
plus 140.166000 0.000000 140.166000 (140.158687)
concat 143.475000 0.000000 143.475000 (143.473786)
splash 139.408000 0.000000 139.408000 (139.406671)
concat_all 144.475000 0.000000 144.475000 (144.474436)
flat_map143.519000 0.000000 143.519000 (143.517636)
C:\Users\...>ruby concat3.rb
user system total real
plus 0.000000 0.000000 0.000000 ( 0.000074)
concat 0.000000 0.000000 0.000000 ( 0.000065)
splash 0.000000 0.000000 0.000000 ( 0.000098)
concat_all 0.000000 0.000000 0.000000 ( 0.000141)
flat_map 0.000000 0.000000 0.000000 ( 0.000122)
user system total real
plus 15.226000 6.723000 21.949000 ( 21.958854)
concat 11.700000 9.142000 20.842000 ( 20.928087)
splash 21.247000 12.589000 33.836000 ( 33.933170)
concat_all 14.508000 8.315000 22.823000 ( 22.871641)
flat_map 11.170000 8.923000 20.093000 ( 20.170945)
-J-Xmx1500M. I didn't use that option at first, so Java's default max heap size was used (4096Mon my system) and it worked just fine. If I provide that option, thus lowering the value to1500M, I get painfully slow results. – Decorativeconcat_allis only executedNtimes, soNshould be … – Cringe