module Concurrent::ThreadSafe::Util::XorShiftRandom

A xorshift random number (positive +Fixnum+s) generator, provides reasonably cheap way to generate thread local random numbers without contending for the global Kernel.rand.

Usage:

x = XorShiftRandom.get # uses Kernel.rand to generate an initial seed
while true
  if (x = XorShiftRandom.xorshift).odd? # thread-localy generate a next random number
    do_something_at_random
  end
end

Constants

MAX_XOR_SHIFTABLE_INT

Public Instance Methods

get() click to toggle source

Generates an initial non-zero positive Fixnum via Kernel.rand.

# File lib/concurrent-ruby/concurrent/thread_safe/util/xor_shift_random.rb, line 27
def get
  Kernel.rand(MAX_XOR_SHIFTABLE_INT) + 1 # 0 can't be xorshifted
end
xorshift(x) click to toggle source

using the “yˆ=y>>a; yˆ=y<<b; yˆ=y>>c;” transform with the (a,b,c) tuple with values (3,1,14) to minimise Bignum overflows

# File lib/concurrent-ruby/concurrent/thread_safe/util/xor_shift_random.rb, line 34
def xorshift(x)
  x ^= x >> 3
  x ^= (x << 1) & MAX_INT # cut-off Bignum overflow
  x ^= x >> 14
end