Date: Wed, 17 Feb 1999 11:31:19 -0800 From: Josef Grosch <jgrosch@mooseriver.com> To: cjclark@home.com Cc: patseal@hyperhost.net, freebsd-questions@FreeBSD.ORG Subject: Re: Random Numbers Message-ID: <19990217113119.A8120@mooseriver.com> In-Reply-To: <199902171508.KAA04420@cc942873-a.ewndsr1.nj.home.com>; from Crist J. Clark on Wed, Feb 17, 1999 at 10:08:41AM -0500 References: <19990216220931.B5145@mooseriver.com> <199902171508.KAA04420@cc942873-a.ewndsr1.nj.home.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Wed, Feb 17, 1999 at 10:08:41AM -0500, Crist J. Clark wrote:
> Josef Grosch wrote,
> > On Tue, Feb 16, 1999 at 09:36:40PM -0500, Patrick Seal wrote:
> > You should seed the random number generator first. Try the following;
Yes, you are correct.
>
> And it is my understanding you are best off only seeding it once. My
> minor changes to the code are not led by a '>.'
>
> > int randn()
> > {
> > int rc = 0;
> > long value = 0L;
> static unsigned long seed = 0L;
> >
> if ( ! seed ) {
> > pid_t pid = getpid();
> > time_t now = 0;
> >
> >
> > struct timeval tp;
> > struct timezone tzp;
> >
> > gettimeofday(&tp, &tzp);
> > now = tp.tv_sec; /* unnecessary but nice during debugging */
> > seed = (unsigned long)(now / pid);
> > srandom(seed);
> }
>
> > value = random();
> >
> > rc = (value % 10);
> >
> > return (rc);
> > }
This is much better than my ugly little hack.
>
> There is a _tiny_ chance the seed might be exactly '0' after the
> first pass, in which case the seed will be recalculated next
> use. However, this reduces to the previous algorithm which redid the
> seed each time.
>
> Also, if you want to make the code work like the original poster,
> where the range of the random number is specified, change the
> declaration of the function to take an arg,
>
> int randn(int range)
>
> And then instead of the last three lines,
>
> return (random() % range);
>
> The return value is 0 to (range - 1).
The above hack was ment more of a demo of what needs to be done. There are
a number of places in the code that could be improved.
Thanks
Josef
--
Josef Grosch | Another day closer to a | FreeBSD 3.0
jgrosch@MooseRiver.com | Micro$oft free world | UNIX for the masses
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-questions" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?19990217113119.A8120>