Hello, I’m starting now with CUDA and maybe this is a dumb question, still, I haven’t found a good answer for it. I know I can’t call system functions inside the Kernel, but is there a way to make a pseudo-random number inside a kernel, with something like this? srand(time(NULL)); rand(); thanks…

There are no random number generator intrinsics or CUDA library functions. If you need a random number generator inside kernels, you are going to have to use kernel code for it. The SDK contains at least one random number generator you might want to look at (Mersenne Twister).

You should also carefully consider the issues with random numbers in a massively parallel algorithm: If the code you typed in the first post had actually worked, it would be quite likely that large groups of threads would get the same initial seed, and therefore use an identical random number seq…

If your application does not require rigorous random numbers, you can do what I do. I create a device array to hold as many random numbers as I want to be in a table, NUMRANDS. I typically setup 16K or 64K elements. Then during program initialization, I create the random numbers by having the ho…

it should be something in this style. Sorry, but I can’t check it by compilation and execution right now. device unsigned long int next = 1; #define step_next (next = next * 1103515245 + 12345+ (unsigned long) sqrt( (threadIdx.x)(threadIdx.x)+(threadIdx.y)(threadIdx.y) ) ); device int k_rand(v…

So, you are proposing a congruential random number generator? That is indeed a way to generate random numbers, but in this case , the k_srand() function is not thread safe. If multiple kernel threads call this function, there will be collisions when they try to all read and write the ‘next’ varia…

Sure, Ken. You are right. Linear congruential PRG with some addition for generation unique number for each thread. And of course next variable should be private for thread or use atomic operations. I think first better for productivity then second. Probably next can be an array next[max_threads…

Dmitry, Yes, in most of my programming over the past many years, I have used linear congruential pseudo-random number generator functions any time I needed something better than rand(). For most casual random number generation, rand() is fine after scaled to a float. A few weeks ago I considered…

I use a varient of the Combined Tausworthe Generator, where I partially share states across a warp. This allows a fairly high quality RNG (better than LCG anyway) while still taking only 32 words of shared memory per block. If you’re worried about the occasional collision between different warps i…

Yes, indeed linear congruential PRNG good only for small data sets and have only one plus: it works fast. What speed you are expecting form PRNG ? And how about others expectation from PRNG for your application ? A some crazy words: may be memory collisions for next variable will be not so bad f…

random numbers inside the Kernel

Accelerated Computing CUDA CUDA Programming and Performance

zarnick January 8, 2010, 6:50pm 3

Hum, I was afraid of that.

It’s impossible to run them on a device function as well right?

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random numbers inside the Kernel

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