Random Number Question

On Sat, 31 Jul 2004 13:40:55 +0200, "Pjotr Wedersteers" <x33159@westerterp.com>
wrote:

>> Modern CPUs have hardware random number generator built-in so it
>> seems a better idea to hit /dev/random when you need a truely random
>> number.
>
>True random generator in a computer ? Me thinks that's a bit of an
>impossibility, unless it takes in analog signals from somewhere.
>And the problem is the seeding of the (pseudo) randomizer plus the fact most
>randomizers don't cover the full range to 2^52.

Hardware RNG's, at least on Intel chips, use "thermal noise" to generate their
values, making them pretty reasonably random. They're certainly not
pseudo-random based off an algorithm, they're based on a randomly fluctuating
physical property.

--
Andy Hassall <andy@andyh.co.uk> / Space: disk usage analysis tool
http://www.andyh.co.uk / http://www.andyhsoftware.co.uk/space

Andy Hassall wrote:
> On Sat, 31 Jul 2004 13:40:55 +0200, "Pjotr Wedersteers"
> <x33159@westerterp.com> wrote:
>
>>> Modern CPUs have hardware random number generator built-in so it
>>> seems a better idea to hit /dev/random when you need a truely random
>>> number.
>>
>> True random generator in a computer ? Me thinks that's a bit of an
>> impossibility, unless it takes in analog signals from somewhere.
>> And the problem is the seeding of the (pseudo) randomizer plus the
>> fact most randomizers don't cover the full range to 2^52.
>
> Hardware RNG's, at least on Intel chips, use "thermal noise" to
> generate their values, making them pretty reasonably random. They're
> certainly not pseudo-random based off an algorithm, they're based on
> a randomly fluctuating physical property.

That's cool! (or hot). Indeed, if analog data is the randomizer source, true
randomness can be had. Any idea on the range of this randomizer ? Or links
to good in depth articles ? Thanks! Very happy with this, if I can use that
I can throw the soundcardnoise/input based randomizer out!
Pjotr

I can share with you the code i use for my random routine (isnt perfect but
works) ;)

here it goes.....


// FUNCTION TO TRY AND MAKE A BETTER RANDOM NUMBER
function make_seed() {
list($usec, $sec) = explode(' ', microtime());
return (float) $sec + ((float) $usec * 100000);
}

$solucao = 0
$options = 1
srand((double)microtime()*intval(rand(1,1000000))) ;
$respostas[1] = rand (1,52);
$solucao++;
while ($solucao <= $options)
{
srand(make_seed());
$pergunta = rand(1, 52);
if (!in_array($pergunta, $respostas))
{
$respostas[$solucao] = $pergunta;
$solucao++;
}
}

print_r ($respostas); // PRINTS THE ARRAY WITH UNIQUE CARDS ALREADY ADDED

************************************************** *
explanation:
************************************************** *
you say how many cards ($options) you want to add to the already picked
cards in the example 1


--
ZXSpectrum "Name The Game" - Can you guess the name of ZXSpectrum games,
just by looking at a ingame picture? Well you can find out if you can (or
not) at.... http:/ntg.docaj.net
--

Also, I didn't see this mentioned...

rather than doing rand(1,52) each time through the loop and subsequent
multiple attempts to "draw" a random number that hasn't already been
picked, why not do a "real world" approach and only pick a random num
from what is avail?

have a $current_deck array or $cards_left array..
after you "draw" a card: unset($current_deck[card_x]);

you can get a random card from this deck with
$rand_card = array_rand($current_deck);

complete psudo code:

while ( sizeof($current_deck) > 0 )
{
// this code is executed exactly 52 times
$rand_card = array_rand($current_deck);
unset($current_deck[$rand_card]);
}


"Paul C-T" <paulcharltonthomson@hotmail.com> wrote in message news:<4109b542$0$63371$ed2e19e4@ptn-nntp-reader04.plus.net>...
> Hi,
>
> Is there a way to repeat a set of code until a certain if statement is
> satisfied. If it is then to exit the loop and if not repeat the code?
>
> Say I want to write a card game application in PHP and I want to chose a
> card from the deck $card1 = rand(1,52); gets me my first card.
>
> I need to record which card has been dealt so I have a variable $dealt which
> starts out as a string of 52 zeros. I update the position of $card1 in the
> $dealt string to "1".
>
> So the 5 of Spades makes $dealt = "000010000000000 ..."
>
> I want to choose another card so I use $card2 = rand(1,52); and then need to
> check if it has already been dealt. If the position in $dealt is a 1 then I
> need to repeat the random number code until it is a 0 when I can update it
> to a 1 and move on ...
>
> Or is there a better way of doing this sort of thing ??
>
> Help, as always, appreciated.
>
> Paul.

Paul C-T wrote:
> Thanks for the advice ... seems like I need to do a bit more
> flowcharting of the problem ... and investigate some new PHP function.
>
> :-)
>
> Much obliged.
>
> Paul.

Yw. Some nice background on real-life issues for poker-sites (applies to any
similar gametype of course)
Quite a good explanation:
http://www.bugsysclub.com/club/about/integrity.htm