How to get a “random” number in OpenCL

Question

I\'m looking to get a random number in OpenCL. It doesn\'t have to be real random or even that random. Just something simple and quick.

I see there is a ton of rea

Answer 1

This is my version of OpenCL float pseudorandom noise, using trigonometric function

//noise values in range if 0.0 to 1.0
static float noise3D(float x, float y, float z) {
    float ptr = 0.0f;
    return fract(sin(x*112.9898f + y*179.233f + z*237.212f) * 43758.5453f, &ptr);
}

__kernel void fillRandom(float seed, __global float* buffer, int length) {
    int gi = get_global_id(0);
    float fgi = float(gi)/length;
    buffer[gi] = noise3D(fgi, 0.0f, seed);
}

You can generate 1D or 2D noize by passing to noise3D normalized index coordinates as a first parameters, and the random seed (generated on CPU for example) as a last parameter.

Here are some noise pictures generated with this kernel and different seeds:

Answer 2

the following is the algorithm used by the java.util.Random class according to the doc:

(seed * 0x5DEECE66DL + 0xBL) & ((1L << 48) - 1)

See the documentation for its various implementations. Passing the worker's id in for the seed and looping a few time should produce decent randomness

or another metod would be to have some random operations occur that are fairly ceratain to overflow:

 long rand= yid*xid*as_float(xid-yid*xid);
 rand*=rand<<32^rand<<16|rand;
 rand*=rand+as_double(rand);

with xid=get_global_id(0); and yid= get_global_id(1);

Answer 3

It seems OpenCL does not provide such functionality. However, some people have done some research on that and provide BSD licensed code for producing good random numbers on GPU.

Answer 4

GPU don't have good sources of randomness, but this can be easily overcome by seeding a kernel with a random seed from the host. After that, you just need an algorithm that can work with a massive number of concurrent threads.

This link describes a Mersenne Twister implementation using OpenCL: Parallel Mersenne Twister. You can also find an implementation in the NVIDIA SDK.

Answer 5

you cant generate random numbers in kernel , the best option is to generate the random number in host (CPU) and than transfer that to the GPU through buffers and use it in the kernel.

Answer 6

I had the same problem. www.thesalmons.org/john/random123/papers/random123sc11.pdf

You can find the documentation here. http://www.thesalmons.org/john/random123/releases/latest/docs/index.html

You can download the library here: http://www.deshawresearch.com/resources_random123.html