Hi, I am not a mathematician myself, but I predict that unless you make extensive tests over a very long period of time you will never find any corelations!
On Mon, 2006-03-06 at 13:39 +0100, Jonas Maebe wrote: > On 6 mrt 2006, at 13:37, Antal wrote: > > >> The Mersenne Twister Free Pascal uses is one of the best PRNGs known > >> today, it just has to be used the right way. But calling it from > >> several threads and "randomly" overwriting its state array is > >> definitely not the right way to use it. > > I'm disappointed, because I compiled the following program (on linux): > > rnd.pp > > begin > > Randomize; > > writeln(random(394)); > > end. > > > > and I ran it for 11 times, and the results are rather strange: > > 310. > > 198 > > 344 > > 322* > > 322* > > 317- > > 317- > > 192 > > 336. > > 382. > > 339. > > (upon noting the dups I had to re-run again twice, getting:) > > 120 > > 297. > > There is nothing strange about this. Randomize initialises randseed > based on the system clock value expressed in seconds. So if you run > it twice in the same second, you will get the same number. > > > so, I've got two times a repetition, though I only re-ran the program. > > (noted with * and - ) > > Then I made a new series of random generating: > > > > 297. > > 120 > > 310. > > 382. > > 336. > > 192 > > 317 > > 322 > > 344 > > 198 > > 339. > > > > I only have two problems with these random numbers: > > Firstly, I can notice a repetition of some "random" numbers (noted > > with ".") > > Then also 70% of them are 3xx > > I learnt about random numbers, that they do not behave by this way. > > You are not generating a series of random numbers based on the > Mersenne Twister here, because you only generate one random number > per program run. If you take all these values "together" as > supposedly belonging to a "series of random numbers", then the result > is that you are using a different "random" generator, where the next > "random" number is generated based on the next clock/time value as > opposed to the previously generated random number. > > To test it properly, you should change your test program into this: > > var > i: longint; > begin > Randomize; > for i := 1 to 20 do > writeln(random(394)); > end. > > And then you have to compare the random numbers generated in one such > a program run, not between different runs. > > > Jonas > _______________________________________________ > fpc-pascal maillist - fpc-pascal@lists.freepascal.org > http://lists.freepascal.org/mailman/listinfo/fpc-pascal _______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
