attr_accessor versus ivar-returning method on MacRuby, JRuby, MRI, and Rubinius

gistfile1.txt

system ~/projects/jruby $ macruby -rbenchmark -e "class A; def initialize; @a = 1; end; attr_accessor :a; end; 5.times { puts Benchmark.measure { a = A.new; i=0; while i<100_000_000; a.a; i+=1; end } }"
  5.690000   0.000000   5.690000 (  5.686256)
  5.660000   0.000000   5.660000 (  5.657916)
  5.670000   0.000000   5.670000 (  5.664147)
  5.690000   0.010000   5.700000 (  5.691450)
  5.690000   0.000000   5.690000 (  5.699265)

system ~/projects/jruby $ macruby -rbenchmark -e "class A; def initialize; @a = 1; end; def a; @a; end; end; 5.times { puts Benchmark.measure { a = A.new; i=0; while i<100_000_000; a.a; i+=1; end } }"
  5.680000   0.010000   5.690000 (  5.685863)
  5.690000   0.000000   5.690000 (  5.693407)
  5.670000   0.000000   5.670000 (  5.662142)
  5.670000   0.000000   5.670000 (  5.677396)
  5.670000   0.000000   5.670000 (  5.671487)

system ~/projects/jruby $ jruby -rbenchmark -e "class A; def initialize; @a = 1; end; attr_accessor :a; end; 5.times { puts Benchmark.measure { a = A.new; i=0; while i<100_000_000; a.a; i+=1; end } }"
  4.240000   0.070000   4.310000 (  3.982000)
  3.950000   0.010000   3.960000 (  3.844000)
  4.170000   0.020000   4.190000 (  4.056000)
  4.110000   0.020000   4.130000 (  4.054000)
  4.230000   0.010000   4.240000 (  4.161000)

system ~/projects/jruby $ jruby -rbenchmark -e "class A; def initialize; @a = 1; end; def a; @a; end; end; 5.times { puts Benchmark.measure { a = A.new; i=0; while i<100_000_000; a.a; i+=1; end } }"
  4.960000   0.090000   5.050000 (  4.602000)
  5.050000   0.020000   5.070000 (  4.972000)
  4.540000   0.020000   4.560000 (  4.439000)
  4.480000   0.020000   4.500000 (  4.393000)
  4.470000   0.020000   4.490000 (  4.404000)

system ~/projects/jruby $ jruby -Xcompile.invokedynamic=true -rbenchmark -e "class A; def initialize; @a = 1; end; attr_accessor :a; end; 5.times { puts Benchmark.measure { a = A.new; i=0; while i<100_000_000; a.a; i+=1; end } }"
  1.440000   0.060000   1.500000 (  1.226000)
  1.120000   0.010000   1.130000 (  1.086000)
  1.430000   0.010000   1.440000 (  1.348000)
  1.350000   0.010000   1.360000 (  1.326000)
  1.370000   0.000000   1.370000 (  1.338000)

system ~/projects/jruby $ jruby -Xcompile.invokedynamic=true -rbenchmark -e "class A; def initialize; @a = 1; end; def a; @a; end; end; 5.times { puts Benchmark.measure { a = A.new; i=0; while i<100_000_000; a.a; i+=1; end } }"
  1.580000   0.060000   1.640000 (  1.324000)
  1.230000   0.010000   1.240000 (  1.203000)
  1.460000   0.010000   1.470000 (  1.432000)
  1.470000   0.010000   1.480000 (  1.430000)
  1.460000   0.000000   1.460000 (  1.430000)

system ~/projects/jruby $ ruby-1.9.3 -rbenchmark -e "class A; def initialize; @a = 1; end; attr_accessor :a; end; 5.times { puts Benchmark.measure { a = A.new; i=0; while i<100_000_000; a.a; i+=1; end } }"
  8.490000   0.000000   8.490000 (  8.493755)
  8.490000   0.010000   8.500000 (  8.488008)
  8.510000   0.000000   8.510000 (  8.510421)
  8.510000   0.000000   8.510000 (  8.513919)
  8.940000   0.010000   8.950000 (  8.958641)

system ~/projects/jruby $ ruby-1.9.3 -rbenchmark -e "class A; def initialize; @a = 1; end; def a; @a; end; end; 5.times { puts Benchmark.measure { a = A.new; i=0; while i<100_000_000; a.a; i+=1; end } }"
 10.650000   0.000000  10.650000 ( 10.650636)
 10.720000   0.000000  10.720000 ( 10.727523)
 10.640000   0.010000  10.650000 ( 10.643023)
 10.630000   0.000000  10.630000 ( 10.632696)
 10.660000   0.000000  10.660000 ( 10.655910)

system ~/projects/jruby $ ../rubinius/bin/rbx -rbenchmark -e "class A; def initialize; @a = 1; end; attr_accessor :a; end; 5.times { puts Benchmark.measure { a = A.new; i=0; while i<100_000_000; a.a; i+=1; end } }"
  6.815830   0.004340   6.820170 (  6.820387)
  6.847853   0.003030   6.850883 (  6.837327)
  1.171625   0.000144   1.171769 (  1.171874)
  1.164679   0.000409   1.165088 (  1.165070)
  1.165900   0.001009   1.166909 (  1.166942)

system ~/projects/jruby $ ../rubinius/bin/rbx -rbenchmark -e "class A; def initialize; @a = 1; end; def a; @a; end; end; 5.times { puts Benchmark.measure { a = A.new; i=0; while i<100_000_000; a.a; i+=1; end } }"
  6.491848   0.002118   6.493966 (  6.471991)
  1.186767   0.000118   1.186885 (  1.186871)
  1.179810   0.000155   1.179965 (  1.180013)
  1.182180   0.000815   1.182995 (  1.183034)
  1.235873   0.000114   1.235987 (  1.236103)