random function

[M. Braun]

Hello,

first I have to say, my english isn't very well so just try to understand it
;-).

I've got a little problem with the PHP function rand().
I want to create a little programm which simulate a "roulette" game (you
know this stupid game you can play in a casino :) ).
But it is impossible to simulate such a game with a simple rand() function.
Of course I initilize the random generator with the program start, with
srand().
But fact is, that, in a roulette game, the probability for each game is the
same (for example: 1/37 for a simple number like '4' or '28').
So I tried to put 37 items in an array called numbers[] and start the random
generator with numbers from 0 to 36 and echoed the item to the screen.
But if I put this system into e loop and try to simulate about 1000 games I
evidently get e "Laplace" experiment.
But this is the fault. Statistic fails in a roulette game, I think. Do it?
I think the ball has no "brain" so the probability is the same for each
game. In fact it is possible that I get one number 50 times. But with the
random generator, which is obviously too good, it won't work. What can I do?
Thanks for help

Martin

[Chung Leong]

Re: random function

I don't know enough about the pseudo-random algorithm to say for sure, that
the result from one call doesn't somehow influence the result from the next.
In theory, the results are independent (pseudo-independent, I should say).
Run this little snippet and you'll see that rand() is perfectly capable of
returning the same number consecutively:

for($i = 0; $i = 100; $i++) {
$n = rand(1, 4);
echo "$n<br>";
}

And by the way, use mt_rand() instead. It's supposed to be better.

Uzytkownik "M. Braun" <braun@uni-koblenz.de> napisal w wiadomosci
news:bv0lo4$5us $1@news.uni-koblenz.de...[color=blue]
> Hello,
>
> first I have to say, my english isn't very well so just try to understand[/color]
it[color=blue]
> ;-).
>
> I've got a little problem with the PHP function rand().
> I want to create a little programm which simulate a "roulette" game (you
> know this stupid game you can play in a casino :) ).
> But it is impossible to simulate such a game with a simple rand()[/color]
function.[color=blue]
> Of course I initilize the random generator with the program start, with
> srand().
> But fact is, that, in a roulette game, the probability for each game is[/color]
the[color=blue]
> same (for example: 1/37 for a simple number like '4' or '28').
> So I tried to put 37 items in an array called numbers[] and start the[/color]
random[color=blue]
> generator with numbers from 0 to 36 and echoed the item to the screen.
> But if I put this system into e loop and try to simulate about 1000 games[/color]
I[color=blue]
> evidently get e "Laplace" experiment.
> But this is the fault. Statistic fails in a roulette game, I think. Do it?
> I think the ball has no "brain" so the probability is the same for each
> game. In fact it is possible that I get one number 50 times. But with the
> random generator, which is obviously too good, it won't work. What can I[/color]
do?[color=blue]
> Thanks for help
>
> Martin
>
>[/color]

[DvDmanDT]

Re: random function

srand(time()%37 ); // change 37 to some other number depending on what
chances you want...

--
// DvDmanDT
MSN: dvdmandt¤hotmai l.com
Mail: dvdmandt¤telia. com
"Chung Leong" <chernyshevsky@ hotmail.com> skrev i meddelandet
news:jbadnWd6QZ IdmYndRVn-uQ@comcast.com. ..[color=blue]
> I don't know enough about the pseudo-random algorithm to say for sure,[/color]
that[color=blue]
> the result from one call doesn't somehow influence the result from the[/color]
next.[color=blue]
> In theory, the results are independent (pseudo-independent, I should say).
> Run this little snippet and you'll see that rand() is perfectly capable of
> returning the same number consecutively:
>
> for($i = 0; $i = 100; $i++) {
> $n = rand(1, 4);
> echo "$n<br>";
> }
>
> And by the way, use mt_rand() instead. It's supposed to be better.
>
> Uzytkownik "M. Braun" <braun@uni-koblenz.de> napisal w wiadomosci
> news:bv0lo4$5us $1@news.uni-koblenz.de...[color=green]
> > Hello,
> >
> > first I have to say, my english isn't very well so just try to[/color][/color]
understand[color=blue]
> it[color=green]
> > ;-).
> >
> > I've got a little problem with the PHP function rand().
> > I want to create a little programm which simulate a "roulette" game (you
> > know this stupid game you can play in a casino :) ).
> > But it is impossible to simulate such a game with a simple rand()[/color]
> function.[color=green]
> > Of course I initilize the random generator with the program start, with
> > srand().
> > But fact is, that, in a roulette game, the probability for each game is[/color]
> the[color=green]
> > same (for example: 1/37 for a simple number like '4' or '28').
> > So I tried to put 37 items in an array called numbers[] and start the[/color]
> random[color=green]
> > generator with numbers from 0 to 36 and echoed the item to the screen.
> > But if I put this system into e loop and try to simulate about 1000[/color][/color]
games[color=blue]
> I[color=green]
> > evidently get e "Laplace" experiment.
> > But this is the fault. Statistic fails in a roulette game, I think. Do[/color][/color]
it?[color=blue][color=green]
> > I think the ball has no "brain" so the probability is the same for each
> > game. In fact it is possible that I get one number 50 times. But with[/color][/color]
the[color=blue][color=green]
> > random generator, which is obviously too good, it won't work. What can I[/color]
> do?[color=green]
> > Thanks for help
> >
> > Martin
> >
> >[/color]
>
>[/color]