This site is updated infrequently. For up-to-date information, please visit the new OCaml website at ocaml.org.

Random number generator
• Micha³_C
[ Home ] [ Index: by date | by threads ]
[ Search: ]

[ Message by date: previous | next ] [ Message in thread: previous | next ] [ Thread: previous | next ]
 Date: 2008-09-30 (13:17) From: Micha³_C Subject: Random number generator
```Hello!

Do You maybe have any idea how good is the standard RNG from random.ml
module? I know that it's quite fast but what about the quality of
generated numbers?

I've tried implementing various random number generators for the whole
yesterday but I couldn't bypass ocaml's int limitations. Almost
everything bases on unsigned integers (0..2^32-1) so despiting the
fact my range is half of that (using Int32) I'm having troubles when
integer overflows...

I would like to implement combined MWC (multiple with carry) algorithm
based on 2 x 16bit mwc's. I'ts very easy (at last in c/c++ where i can
use unsigned ints), fast and according to what I've read it's
generating very nice random numbers.

It goes like this:

z = w= some seeds (big numbers)

z  = 36969 * (z & 65535) + (z >> 16)
w = 18000 * (w & 65535) + (w >> 16)
return ( (z << 16) + (w & 65535) )		// combining two 16 bit numbers to
one 32 bit

but i cant think of anything by myself, i mean i could use some "abs"
or something but i doubt it wouldn't ruin the whole algorithm.

P.S.
some time ago I promised that I will keep you informed how my ray-
tracer will do, here it is:
http://neos1.blogspot.com

```