random numbers

deveraux83 · 05-14-2005, 08:39 PM

Hey guys,

Just wanted to ask some questions about random number generators in C++, specifically those using the functions:
initstate(), setstate(), srandom() and random().

Can anyone explain what exactly does the char *state in both initstate and setstate do? I have tried altering the values of state when I call initstate but the the output remains the same. I thought, from the man pages, that state points to an array used by the random number generator and hence should effect it quite significantly.

Thanks for your time.

jim mcnamara · 05-16-2005, 11:15 AM

char *state is a state table. You will change things only AFTER you start calling random().

The state table is set to an initial value, and subsequent calls to random() reset it to new values.

I hope you don't plan to mess with the state table, it is not going to help anything. In fact it could do the reverse.

deveraux83 · 05-16-2005, 12:23 PM

That's what I did. I called random() AFTER I called initstate() with a char *state of my own. And it didn't generate a different number pattern than if I just left it at it's default value. (i.e. the sequence of numbers is exactly the same).

What I am hoping to do is make the random number generator more "configurable" since I need it for an encryption sequence I am creating. Do you know of any sites that might explain what the state table is since I didn't get any good hits on google.

Thanks for your reply.

jim mcnamara · 05-16-2005, 12:27 PM

No. I'm not clear. Mess with the state table AFTER random() has been called at least once.

deveraux83 · 05-17-2005, 02:26 AM

Oh ok. I get your point now. I will try that. Thanks!