Fastest Implementation of a Random Number Generator in Ruby?

Whats the fastest way to write a ruby random number generator? Are there academic formulas for this?

I'm doin开发者_运维问答g this, and for 10,000 random numbers it takes about ~4 seconds:

def generate_random_num(count = 1)
  count.times.map do |i|
    # make a setting!
    num = rand(99999)
    num = "0" * (5 - num.to_s.length) + num.to_s
    redo if codes.include?(num)
    codes << num
  end
end

I'm just trying to generate up to 99999 random numbers, all 5 digits. Any tips?

This gives you 10000 unique numbers (strings) with leading zeroes:

(1..10000).to_a.shuffle!.map{|n| n.to_s.rjust(5,'0')}

Benchmark (using Benchmark.measure):

user       system     total       real
0.020000   0.000000   0.020000 (  0.017471)

I would, however, just use:

(1..10000).to_a.shuffle!

Which is faster:

user       system     total       real
0.000000   0.000000   0.000000 (  0.001692)

And add the leading zeroes when you output each value. According to this post Ruby's shuffle use the Fisher-Yates algorithm Saeed mentions.

Update:

So to answer your question, you could generate 10000 unique random numbers in the range [0,99999] with the following code:

(0..99999).to_a.shuffle!.slice(0..9999).map{|n| n.to_s.rjust(5, '0')}

With a benchmark of:

user       system     total       real
0.020000   0.000000   0.020000 (  0.026122)