max

max.rb

require 'benchmark'

a = (1..100000).map {rand(100000)}

Benchmark.bm(10) do |b|
  b.report("Max")    { a.max }
  b.report("Max by") { a.max_by {|a| a} }
end


                 user     system      total        real
Max          0.010000   0.000000   0.010000 (  0.011210)
Max by       0.020000   0.000000   0.020000 (  0.019909)

---
require 'benchmark'

a = (1..100000).map {rand(100000)}

Benchmark.bm(10) do |b|
  b.report("Max")    { a.max{|x,y| x <=> y} }
  b.report("Max by") { a.max_by {|a| a} }
end
                 user     system      total        real
Max          0.010000   0.000000   0.010000 (  0.017095)
Max by       0.010000   0.000000   0.010000 (  0.017910)

---
require 'benchmark'

a = (1..100000).map {rand(100000)}

Benchmark.bm(10) do |b|
  b.report("Max")    { a.max{|x,y| x*x <=> y*y} }
  b.report("Max by") { a.max_by {|a| a*a} }
end
                 user     system      total        real
Max          0.090000   0.000000   0.090000 (  0.084940)
Max by       0.050000   0.000000   0.050000 (  0.047784)

有意思..低估max了..