[Freeciv-Dev] Re: random shuffling (was: Two patches)

[Jeff Mallatt <jjm@xxxxxxxxxxxx>]

At 2000/07/25 11:56 , Reinier Post wrote:
>On Tue, Jul 25, 2000 at 11:25:24PM +1000, David Pfitzner wrote:
>> > At 2000/06/28 16:28 , Kero van Gelder wrote:
>> > >First patchs improves the shuffle_players() to perfect randomness (it
>> > >was close, but n! is not a perfect divisor of n^n), save the
>> > >randomness of my_rand().
>
>[...]
>  
>>    for(i=0; i<game.nplayers; i++) {
>> -    pos = myrand(game.nplayers);
>> +    /* for each run: shuffled[ <i ] is already shuffled [Kero] */
>> +    pos = game.nplayers - myrand(game.nplayers) - 1;
>>      tmpplr = shuffled[i]; 
>>      shuffled[i] = shuffled[pos];
>>      shuffled[pos] = tmpplr;
>> 
>> I believe Kero has the right idea, and the current code is wrong,
>> but Kero's implementation is off.
>
>Yes, if myrand(x) uniformly produces an integer between 0 and x-1 inclusive,
>this patch has no effect.

This is all I meant.

jjm