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 +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

Constant Summary

MAX_XOR_SHIFTABLE_INT = 
MAX_INT - 1

Class Method Summary (collapse)

Instance Method Summary (collapse)

Class Method Details

+ (Object) get

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



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# File 'lib/thread_safe/util/xor_shift_random.rb', line 19

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

+ (Object) xorshift(x)

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



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# File 'lib/thread_safe/util/xor_shift_random.rb', line 26

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

Instance Method Details

- (Object) get

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



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# File 'lib/thread_safe/util/xor_shift_random.rb', line 19

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

- (Object) xorshift(x)

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



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# File 'lib/thread_safe/util/xor_shift_random.rb', line 26

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