String#split is much, much faster without any arguments

string_split_benchmark.rb

require 'benchmark/ips'
number = "7316717653133062491922511967442657474235534919493496983520312774506326239578318016984801869478851843858615607891129494954595017379583319528532088055111254069874715852386305071569329096329522744304355766896648950445244523161731856403098711121722383113622298934233803081353362766142828064444866452387493035890729629049156044077239071381051585930796086670172427121883998797908792274921901699720888093776657273330010533678812202354218097512545405947522435258490771167055601360483958644670632441572215539753697817977846174064955149290862569321978468622482839722413756570560574902614079729686524145351004748216637048440319989000889524345065854122758866688116427171479924442928230863465674813919123162824586178664583591245665294765456828489128831426076900422421902267105562632111110937054421750694165896040807198403850962455444362981230987879927244284909188845801561660979191338754992005240636899125607176060588611646710940507754100225698315520005593572972571636269561882670428252483600823257530420752963450"

Benchmark.ips do |bm|
  bm.report('String#split with empty String') do
    number.split('').map!(&:to_i).each_cons(13).max_by { |factors| factors.inject(:*) }
  end

  bm.report('String#split with empty Regexp') do
    number.split(//).map!(&:to_i).each_cons(13).max_by { |factors| factors.inject(:*) }
  end

  bm.report('String#split without arg') do
    number.split.map!(&:to_i).each_cons(13).max_by { |factors| factors.inject(:*) }
  end
end

# Calculating -------------------------------------
# String#split with empty String 46.000  i/100ms
# String#split with empty Regexp 47.000  i/100ms
# String#split without arg        5.518k i/100ms
# -------------------------------------------------
# String#split with empty String 469.465  (± 1.5%) i/s -      2.392k
# String#split with empty Regexp 469.254  (± 1.3%) i/s -      2.350k
# String#split without arg        58.901k (± 1.1%) i/s -    297.972k