Float value for random seed yields predicatable results

[wesleywerner]

Problem Statement

When the math.randomseed(n) function is called with float values < 1 then subsequent calls to math.random() yields the same amount.

The work-around is to seed the RNG using integers and not float values derived from math.random(). This ticket is a reminder of this fact, and also to document the steps to test, for anybody encountering this in the future.

Test Case

local seed_bag = {}

function love.draw ()
    love.graphics.print("click to generate random numbers, watch the web console.")
end

function love.mousepressed(x, y, button, istouch)
    if #seed_bag == 0 then
        print("filling bag with seeds.")
        for i = 0, 10 do
            table.insert(seed_bag, math.random())
        end
    end
    next_seed = table.remove(seed_bag)
    print("set random seed of " .. next_seed)
    math.randomseed(next_seed)
    random_amount = math.random(100, 500)
    print("random amount between 100 and 500 for this seed equals " .. random_amount)
end

The above code outputs the following when run in Löve on the Desktop:

filling bag with seeds.
set random seed of 0.11446190140255
random amount between 100 and 500 for this seed equals 319
set random seed of 0.56859228170254
random amount between 100 and 500 for this seed equals 389
set random seed of 0.42668680786097
random amount between 100 and 500 for this seed equals 479
set random seed of 0.73573903003308
random amount between 100 and 500 for this seed equals 378
set random seed of 0.33933341140343
random amount between 100 and 500 for this seed equals 150
etc cetera

The same code running via Löve .js:

filling bag with seeds.
set random seed of 0.421925941213
random amount between 100 and 500 for this seed equals 482
set random seed of 0.6700635201624
random amount between 100 and 500 for this seed equals 482
set random seed of 0.31313096560218
random amount between 100 and 500 for this seed equals 482
set random seed of 0.60369106969037
random amount between 100 and 500 for this seed equals 482
ad infinitum ...

This behaviour does not happen when the seed value is an integer value > 0.