From: Sidney Cadot (sidney_at_janis.pds.twi.tudelft.nl)
Date: 2000-03-09 22:12:53
Hi,
The random generator as available in lib/common/rand.s is quite awkward.
It enters a cycle at the 264th call of length 95.
This is in part due to a bug in the rand() function: the author (Ullrich
or Steve Judds, I don't know who is to blame ;-)) intended to do this:
signed rand(void)
{
unsigned STATE=0;
STATE = (STATE*5U)+13841U;
return (signed)(STATE&0x7FFFU);
}
but he forgot to do a CLC after adding (4*STATE) and (STATE).
The intended behaviour however may be even worse: the values as obtained
by that method alternate between even and odd. Flipping a coin using
such a rand()%2 would yield nice odds in the casino :-)
I will implement a better (high-period) random function soon. I would like
it to have a period > 2^16, however this would mean that the state would
have to be more than one word. In principle, that's no problem: the
srand() call could clear the high-order state bits.
Regards,
Sidney Cadot
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This archive was generated by hypermail 2.1.3 : 2001-12-14 22:05:35 CET