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➜ Electronics
➜ Microprocessors
➜ Lightweight pseudo-random number generator for Arduino
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Lightweight pseudo-random number generator for Arduino
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| Posted by
| Nick Gammon
Australia (23,158 posts) Bio
Forum Administrator |
| Date
| Thu 02 Oct 2014 05:21 AM (UTC) Amended on Thu 02 Oct 2014 05:42 AM (UTC) by Nick Gammon
|
| Message
| This PRNG is supposed to improve upon the built-in rand() function which comes with the Arduino standard library, and is also faster.
/* Implementation of a 32-bit KISS generator which uses no multiply instructions */
// Initial seed
static unsigned long x = 123456789,
y = 234567891,
z = 345678912,
w = 456789123,
c = 0;
unsigned long JKISS32 ()
{
long t;
y ^= y << 5;
y ^= y >> 7;
y ^= y << 22;
t = z + w + c;
z = w;
c = t < 0;
w = t & 2147483647;
x += 1411392427;
return x + y + w;
} // end of JKISS32
Author of the generator: George Marsaglia
Wikipedia article on George Marsaglia.
Example seeder:
void Seed_JKISS32 (const unsigned long newseed)
{
if (newseed != 0)
{
x = 123456789;
y = newseed;
z = 345678912;
w = 456789123;
c = 0;
}
} // end of Seed_JKISS32
Of course, a better seeder would change the other numbers as well. Avoid seeding with y = 0.
For more info see this PDF: http://www.cs.ucl.ac.uk/staff/d.jones/GoodPracticeRNG.pdf
If you are using this on a "proper" PC (rather than an Arduino) replace "long" by "int" (assuming your int is 32-bits). |
- Nick Gammon
www.gammon.com.au, www.mushclient.com | | Top |
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