Why is the first random number always the same on some platforms in lua?

Question

Consider the following lua code snippet :

local time = os.time()
for _= 1, 10 do
    time = time + 1
    print(\'Seeding with \' .. time)
    math.randomseed         


        

Answer 1

Lua's random used to use C's rand(3) and srand(3) functions (see here). UPDATE: newer Lua versions use random(3) where available.

Both the C90 standard and POSIX suggest an cross-platform implementation of rand and srand that isn't the best. It especially lacks randomness in the lower bits.

Some platforms like Linux moved off of the standard recommendation to a better implementation (e.g. random(3)).

OS/X remains true to the classic rand implementation, and Lua inherits it.