JezK
Edit File: xor_shift_random.rb
module ThreadSafe module Util # 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 module XorShiftRandom extend self MAX_XOR_SHIFTABLE_INT = MAX_INT - 1 # Generates an initial non-zero positive +Fixnum+ via +Kernel.rand+. def get Kernel.rand(MAX_XOR_SHIFTABLE_INT) + 1 # 0 can't be xorshifted end # xorshift based on: http://www.jstatsoft.org/v08/i14/paper if 0.size == 4 # 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 def xorshift(x) x ^= x >> 3 x ^= (x << 1) & MAX_INT # cut-off Bignum overflow x ^= x >> 14 end else # 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 def xorshift(x) x ^= x >> 1 x ^= (x << 1) & MAX_INT # cut-off Bignum overflow x ^= x >> 54 end end end end end