LÖVE

Taehl wrote:What's wrong with that is, it produces the screenshot above.

function math.drand(seed, min, max) 
    math.randomseed(seed)
    math.random(min, max)
end

Taehl wrote:it requires that I can make a deterministic chain of pseudorandom numbers for any given coordinate.

Taehl wrote:If it's supposed to give me NANs, why do I get numbers like 131072, 16777216, and 134217728 passing through my modulo operation?

Robin wrote:The main problem is that you seed every time. Of course the results don't look very random then.

At the beginning of your code, call math.randomseed(os.time()). When you need a random number, call math.random(min, max)

vrld wrote:

Taehl wrote:What's wrong with that is, it produces the screenshot above.

I was actually referring not to your implementation, but this:

Code: Select all

function math.drand(seed, min, max) 
    math.randomseed(seed)
    math.random(min, max)
end

It meets your requirement:

Taehl wrote:it requires that I can make a deterministic chain of pseudorandom numbers for any given coordinate.

The seed could be something like y * with + x.

vrld wrote:

Taehl wrote:If it's supposed to give me NANs, why do I get numbers like 131072, 16777216, and 134217728 passing through my modulo operation?

Your implementation with math.sinh is not well suited for pseudo random numbers. Look at this plot of sinh(x):

You can see that the values of sinh(x) get really big really fast. It's already about 10000 for x = 10 and you are using numbers up to 999. Wolframalpha says this number is bigger 10^433 (a 1 with 433 zeros!)

Lua uses doubles as number type (at least on a PC/Mac). But a double cannot handle numbers that big. In fact, the bigger the number gets, some strange things happen. Adding a small number to a big number does not change the value; the small number gets "eaten". Some big (as well as some really small) numbers cannot be represented properly.
A combination of these and other effects could lead to your result.

vrld wrote:If you absolutely do not want to use math.random() in combination with math.randomseed() to get predictable numbers, you could use the Middle-square method. The quality (= time to get to the same number with which you started is small) of this method is worse than what math.random() uses, but as you reseed for every cell anyway, it should not be a problem (it will be slower than the provided random though).

Taehl wrote:

Robin wrote:The main problem is that you seed every time. Of course the results don't look very random then.

At the beginning of your code, call math.randomseed(os.time()). When you need a random number, call math.random(min, max)

That's no good - a given coordinate must always return the same list of pseudorandom numbers. If I put os.time in the mix, the list will always be different.

Taehl wrote:I know, but that's exactly the method I was using when I made that screenshot.

Taehl wrote:Is there any way to implement that that doesn't require making it a string, messing with it, and making it a number again (i.e., is slow)?

local seed = 58008
function msrand(digits)
    local r = seed * seed
    local pad = math.floor( (#tostring(r) - digits) / 2 )
    if pad > 0 then
        r = math.floor(r / math.pow(10, pad)) % math.pow(10, pad)
    end

    if r == 0 or r == 1 then
        seed = 5138008
    else
        seed = r
    end
    return r
end

Taehl wrote:

Robin wrote:The main problem is that you seed every time. Of course the results don't look very random then.

At the beginning of your code, call math.randomseed(os.time()). When you need a random number, call math.random(min, max)

That's no good - a given coordinate must always return the same list of pseudorandom numbers. If I put os.time in the mix, the list will always be different.

-- at the beginning of your code
math.randomseed(314159265)