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)
general rule is (as mentioned in the comments) that JRuby/JVM needs warmup.
usually bmbm is good fit, although TIMES=1000 should be increased (at least for the small array cases), also 1.5G might be not enough for optimal performance of JRuby (noticed a considerable change in numbers going from -Xmx2g to -Xmx3g). here's the results :
ruby 2.3.1p112 (2016-04-26 revision 54768) [x86_64-linux]
$ ruby concat3.rb
Rehearsal -----------------------------------------------
plus 0.000000 0.000000 0.000000 ( 0.000076)
concat 0.000000 0.000000 0.000000 ( 0.000070)
splash 0.000000 0.000000 0.000000 ( 0.000099)
concat_all 0.000000 0.000000 0.000000 ( 0.000136)
flat_map 0.000000 0.000000 0.000000 ( 0.000138)
-------------------------------------- total: 0.000000sec
user system total real
plus 0.000000 0.000000 0.000000 ( 0.000051)
concat 0.000000 0.000000 0.000000 ( 0.000059)
splash 0.000000 0.000000 0.000000 ( 0.000083)
concat_all 0.000000 0.000000 0.000000 ( 0.000120)
flat_map 0.000000 0.000000 0.000000 ( 0.000173)
Rehearsal -----------------------------------------------
plus 43.040000 3.320000 46.360000 ( 46.351004)
concat 15.080000 3.870000 18.950000 ( 19.228059)
splash 49.680000 4.820000 54.500000 ( 54.587707)
concat_all 51.840000 5.260000 57.100000 ( 57.114867)
flat_map 17.380000 5.340000 22.720000 ( 22.716987)
------------------------------------ total: 199.630000sec
user system total real
plus 42.880000 3.600000 46.480000 ( 46.506013)
concat 17.230000 5.290000 22.520000 ( 22.890809)
splash 60.300000 7.480000 67.780000 ( 67.878534)
concat_all 54.910000 6.480000 61.390000 ( 61.404383)
flat_map 17.310000 5.570000 22.880000 ( 23.223789)
...
jruby 9.1.6.0 (2.3.1) 2016-11-09 0150a76 Java HotSpot(TM) 64-Bit Server VM 25.112-b15 on 1.8.0_112-b15 +jit [linux-x86_64]
$ jruby -J-Xmx3g concat3.rb
Rehearsal -----------------------------------------------
plus 0.010000 0.000000 0.010000 ( 0.001445)
concat 0.000000 0.000000 0.000000 ( 0.002534)
splash 0.000000 0.000000 0.000000 ( 0.001791)
concat_all 0.000000 0.000000 0.000000 ( 0.002513)
flat_map 0.010000 0.000000 0.010000 ( 0.007088)
-------------------------------------- total: 0.020000sec
user system total real
plus 0.010000 0.000000 0.010000 ( 0.002700)
concat 0.000000 0.000000 0.000000 ( 0.001085)
splash 0.000000 0.000000 0.000000 ( 0.001569)
concat_all 0.000000 0.000000 0.000000 ( 0.003052)
flat_map 0.000000 0.000000 0.000000 ( 0.002252)
Rehearsal -----------------------------------------------
plus 32.410000 0.670000 33.080000 ( 17.385688)
concat 18.610000 0.060000 18.670000 ( 11.206419)
splash 57.770000 0.330000 58.100000 ( 25.366032)
concat_all 19.100000 0.030000 19.130000 ( 13.747319)
flat_map 16.160000 0.040000 16.200000 ( 10.534130)
------------------------------------ total: 145.180000sec
user system total real
plus 16.060000 0.040000 16.100000 ( 11.737483)
concat 15.950000 0.030000 15.980000 ( 10.480468)
splash 47.870000 0.130000 48.000000 ( 22.668069)
concat_all 19.150000 0.030000 19.180000 ( 13.934314)
flat_map 16.850000 0.020000 16.870000 ( 10.862716)
... so it seems like the opposite - MRI 2.3 gets 2-5x slower than JRuby 9.1
cat concat3.rb
require 'benchmark'
N = (ENV['TIMES'] || 100).to_i
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.bmbm 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.bmbm 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