It's faster than Love's love.math.random and love.math.randomNormal, but slower than Lua's math.random.
It has a nice even distribution. The "Mash" function might also be useful as a general purpose hash function.
Code: Select all
-- A LuaJIT port of Johannes Baagøe's Alea
-- From http://baagoe.com/en/RandomMusings/javascript/
-- Johannes Baagøe <baagoe@baagoe.com>, 2010
-- Mirrored at:
-- https://github.com/nquinlan/better-random-numbers-for-javascript-mirror
local rshift, bor, floor = bit.rshift, bit.bor, math.floor
local function Mash ()
local n = 0xefc8249d
local function mash (data)
data = tostring(data)
for i = 1, data:len() do
n = n + data:byte(i)
local h = 0.02519603282416938 * n
n = rshift(floor(h), 0)
h = h - n
h = h * n
n = rshift(floor(h), 0)
h = h - n
n = n + h * 0x100000000 -- 2^32
end
return rshift(floor(n), 0) * 2.3283064365386963e-10 -- 2^-32
end
-- mash.version = 'Mash 0.9';
return mash
end
local function Alea (...)
return (function (args)
local s0 = 0
local s1 = 0
local s2 = 0
local c = 1
if #args == 0 then
args = { os.time() }
end
local mash = Mash()
s0 = mash(' ')
s1 = mash(' ')
s2 = mash(' ')
for i = 1, #args do
s0 = s0 - mash(args[i])
if s0 < 0 then
s0 = s0 + 1
end
s1 = s1 - mash(args[i])
if s1 < 0 then
s1 = s1 + 1
end
s2 = s2 - mash(args[i])
if s2 < 0 then
s2 = s2 + 1
end
end
mash = nil
local random = {}
local function _random ()
local t = 2091639 * s0 + c * 2.3283064365386963e-10 -- 2^-32
s0 = s1
s1 = s2
c = bor(floor(t), 0)
s2 = t - c
return s2
end
function random.uint32 ()
return random() * 0x100000000 -- 2^32
end
function random.fract53 ()
return random() +
bor(floor(random() * 0x200000), 0) * 1.1102230246251565e-16 -- 2^-53
end
random.version = 'Alea 0.9'
random.args = args
return setmetatable(random, { __call = _random })
end)({ ... })
end
return Alea
