Re: [ProgSoc] Randomisation

[Matt Beauregard <marauder@nospam.lavinia.marauder.tm>]

On Tue, Feb 02, 1999 at 08:08:19AM +1100, Peter Meric wrote:
> On Tue, 2 Feb 1999, Matt Beauregard wrote:
> 
> > >         srand(time(NULL));
> > 
> > If there's a possibility that the program will be run twice in the same
> > second you might want to combine time() with, say, getpid() to mix
> > things up a bit.
> 
> This merely initialises the RNG. Probably no need to do it twice in any
> given second.

You're missing the point: if the program is run twice in the same second, using time() to set the seed will result in the seed being the same both times. By bitwise-combining time() with getpid() you lessen the likelihood of getting the same stream of numbers in two consecutive runs of the program, which is a very real danger for networked or short-run programs. You're not seeding it twice, just seeding it better.

-- 
screen so pure and blue
this computer is at peace
control alt delete

matthew beauregard
viper communications
systems programmer
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