string vs integer palindrome benchmarks

palindrome.rb

require 'benchmark'

def int_pal?(num)
  n = num
  reverse = 0
  while (num > 0)
    dig = num % 10
    reverse = reverse * 10 + dig
    num = num / 10
  end
  return n == reverse
end

def string_pal?(num)
  s = num.to_s
  s == s.reverse
end

Benchmark.bmbm do |bm|
  bm.report("Integer palindrome method"){ (1...10000000).each{|x| int_pal?(x)} }
  bm.report("String palindrome method"){ (1...10000000).each{|x| string_pal?(x)} }
end

=begin
Rehearsal -------------------------------------------------------------
Integer palindrome method   7.700000   0.000000   7.700000 (  7.705190)
String palindrome method    4.890000   0.010000   4.900000 (  4.907374)
--------------------------------------------------- total: 12.600000sec

                                user     system      total        real
Integer palindrome method   7.770000   0.000000   7.770000 (  7.773088)
String palindrome method    4.720000   0.010000   4.730000 (  4.726223)
=end

curious, I tried to rewrite int_pal? like this

def int_pal?(num)
  size = (Math.log10 num).floor
  (0..(size/2.0).ceil).each do |n|
    pow1, pow2 = 10**n, 10**(size-n)
    if num / pow1 % 10 != num / pow2 % 10
      return false
    end
  end
  return true
end

expecting it to get faster (at least with huge numbers...) but even benchmarking between 10000000...20000000 didn't show an improvement

this is slightly faster than my previous snippet, but it's still slower than your original int_pal?

def int_pal?(num)
  size = (Math.log10 num).floor
  pow1, pow2 = 1, 10**size
  (size/2.0).ceil.times do
    if num / pow1 % 10 != num / pow2 % 10
      return false
    end
    pow1 *= 10
    pow2 /= 10
  end
  return true
end