Check if numbers are power of 2

po2.rb

# based on http://stackoverflow.com/questions/29718767/check-if-array-elements-are-power-of-two

require 'benchmark'

class Po2
  def self.via_to_s(n)
    (n.to_s(2) =~ /^10*$/) ? 0 : 1 # faster for more than about 100 numbers
  end

  def self.via_log(n)
    (Math.log2(2**n+1) % 1) == 0 # faster for less than about 100 numbers
  end
end

# data = [0,1,2,3,4,5,6,7,8,9,10]
# data = 10.times.to_a
# data = 100.times.to_a
data = 1000.times.to_a

data00001 = [0,1,2,3,4,5,6,7,8,9]
data00010 = [10,11,12,13,14,15,16,17,18,19]
data00100 = [100,101,102,103,104,105,106,107,108,109]
data01000 = [1000,1001,1002,1003,1004,1005,1006,1007,1008,1009]
data10000 = [10000,10001,10002,10003,10004,10005,10006,10007,10008,10009]

puts data.inspect
puts data.collect {|n| Po2.via_to_s(n)}.inspect
puts data.collect {|n| Po2.via_log(n)}.inspect

Benchmark.bm do |x|
  x.report('po2_to_s') { data.collect {|n| Po2.via_to_s(n)} }
  x.report('po2_log') { data.collect {|n| Po2.via_log(n)} }
end;nil

Benchmark.bm do |x|
  [data00001,data00010,data00100,data01000,data10000].each do |d|
    x.report("po2_to_s #{d}") { d.collect {|n| Po2.via_to_s(n)} }
    x.report("po2_log  #{d}") { d.collect {|n| Po2.via_log(n)} }
  end
end;nil