Module: ThreadSafe::Util::XorShiftRandom

Extended by:

XorShiftRandom

Included in:

XorShiftRandom

Defined in:

lib/thread_safe/util/xor_shift_random.rb

Overview

A xorshift random number (positive Fixnums) 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

Constant Summary

MAX_XOR_SHIFTABLE_INT =

MAX_INT - 1

Instance Method Summary

• #get ⇒ Object

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

• #xorshift(x) ⇒ Object

  using the “yˆ=y>>a; yˆ=y<<b; yˆ=y>>c;” transform with the (a,b,c) tuple with values (1,1,54) to minimise Bignum overflows.

Instance Method Details

#get ⇒ Object

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

# File 'lib/thread_safe/util/xor_shift_random.rb', line 17

def get
  Kernel.rand(MAX_XOR_SHIFTABLE_INT) + 1 # 0 can't be xorshifted
end

#xorshift(x) ⇒ Object

using the “yˆ=y>>a; yˆ=y<<b; yˆ=y>>c;” transform with the (a,b,c) tuple with values (1,1,54) to minimise Bignum overflows

# File 'lib/thread_safe/util/xor_shift_random.rb', line 24

def xorshift(x)
  x ^= x >> 3
  x ^= (x << 1) & MAX_INT # cut-off Bignum overflow
  x ^= x >> 14
end