CODEWITHSUNDEEP
randomrandom-seed
DragonGamer
DragonGamer

Reputation: 900

Random value from two seeds

Have a twodimensional grid and need a reproducible, random value for every integer coordinate on this grid. This value should be as unique as possible. In a grid of, let's say 1000 x 1000 it shouldn't occur twice.

To put it more mathematical: I'd need a function f(x, y) which gives an unique number no matter what x and y are as long as they are each in the range [0, 1000]

f(x, y) has to be reproducible and not have side-effects.

Probably there is some trivial solution but everything that comes to my mind, like multiplying x and y, adding some salt, etc. does not lead anywhere because the resulting number can easily occur multiple times. One working solution I got is to use a randomizer and simply compute ALL values in the grid, but that is too computationally heavy (to do every time a value is needed) or requires too much memory in my case (I want to avoid pre-computing all the values).

Any suggestions? Huge thanks in advance.

Upvotes: 1

Views: 85

Answers (1)

Energya
Energya

Reputation: 2673

I would use the zero-padded concatenation of your x and y as a seed for a built-in random generator. I'm actually using something like this in some of my current experiments.

I.e. x = 13, y = 42 would become int('0013' + '0042') = 130042 to use as random seed. Then you can use the random generator of your choice to get the kind (float, int, etc) and range of values you need:

Example in Python 3.6+:

import numpy as np
from itertools import product

X = np.zeros((1000, 1000))
for x, y in product(range(1000), range(1000)):
    np.random.seed(int(f'{x:04}{y:04}'))
    X[x, y] = np.random.random()

Each value in the grid is randomly generated, but independently reproducible.

Upvotes: 1

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