Re: [Libvisual-devel] Re: Release planning, quality release upcoming week.

[Burkhard P. <pl...@ip...>]

>> You can use these two functions adapted from LiVES:
>>
>> static uint32_t fastrand_val;
>>
>> inline uint32_t fastrand(void)
>> {
>>  return (fastrand_val=fastrand_val*1073741789+32749);
>> }

This one seems better:

#define a 1664525L
#define c 1013904223L

return (fastrand_val= a * fastrand_val + c);

a is suggested by Knuth
c is suggested by H.W. Lewis and is a prime close to 2^32 * (sqrt(5) - 2)

> #include <sys/time.h>
> struct timeval tv;
> 
> gettimeofday(&tv,NULL);
> fastsrand(tv.tv_usec);

Ok, maybe /dev/urandom is better, because with tv_usec, you'll never get seed
values greater than 999999.

But assuming a libvisual program is started at random
times within a second, even with tv_usec the propability for the
same sequence in 2 subsequent program runs is 10^(-6).
I guess that should be enough.

-- 
_____________________________
Dr.-Ing. Burkhard Plaum
Institut fuer Plasmaforschung
Pfaffenwaldring 31
70569 Stuttgart
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Fax.:            -3102