--- In [email protected], Thomas Hruska <[EMAIL PROTECTED]> wrote: > > onecrazeemom wrote: > > I finally completed the dice roll program. Now, what do > > I do to make the rolls more random? They seem to come up > > with doubles quite often. > > I used srand( time(0)) to get my random numbers. > > I used the modulus(I > > think that is what it is called) > > > > dieOne = 1 + rand() %6; > > dieTwo = 1 + rand() %6; > > > > srand( time(0) ); > > > > Just curious what gives you a true random number when the lines of > > code are run so close together. Here are a couple of rolls: > > > > 1. 3, 1 > > 2. 6, 1 > > 3. 6, 2 > > 4. 5, 5 > > 5. 1, 1 > > 6. 3, 4 > > 7. 4, 6 > > > > I guess they are more random than I thought, but the first > > two times I ran the program it came up with doubles. > > > > Thanks in advance, > > Stephanie > > Probably what you are "experiencing" is the side effect of > using the modulus of a random number with a number not > evenly divisible by the maximum range of the random number > generator. > > True random number generators are MUCH harder to create (all > the implementations of rand() that I've seen are simple > congruential pseudorandom generators). You get into heavy > math and/or cryptography VERY quickly if you start rolling > your own. <snip>
Stephanie, if you have access to a well-sorted public library, get your hands on volume 2 of Donald Knuth's "The Art Of Computer Programming"; really heavy stuff to work through, but he explained the basics of pseudo-number generation so well that this writing is still valid (it's been written in the early 1970's). And he explains how you can test your own pseudo-random number generators for their quality without much effort, only some time to have your check program run it. Pretty easy to implement. And very well explained (though the math background is too heavy for me). Regards, Nico
