what is the best way to generate random numbers

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Keep the holy day sacred.......halllllllukan

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"The very idea of freedom presupposes some objective moral law which overarches rulers and ruled alike." -- C. S. Lewis (1898 - 1963), "The Poison of Subjectivism" (from Christian Reflections; p. 108)

Switch Mayhem now available! Get it here
Codename: Roler - hoping to get more done over the holidays . . .

randomize();
<variable> = random(#);

But it'll cost you

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The Stank pwns you!

[This message has been edited by CapnStank (edited January 30, 2005).]

thanks cobra...I know what you mean by seed, but how do i do it

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Keep the holy day sacred.......halllllllukan

srand( (unsigned) time(0) );

int number = rand();

int number = rand() % 100 + 1;

Good luck and God bless!

two question, why would i want it to generate a random age? would I do that so the program could run itself?

and how do i make it sort?

have a good day in Christ

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Keep the holy day sacred.......halllllllukan

[This message has been edited by en972 (edited February 01, 2005).]

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Vita sine Ieso est mors.
Life without Jesus is death.
Enter The Circle

Well you wouldn't have to add a random number to your age program. You should play around with it a bit so you understand how it works though.
Your other question is a bit more complicated. There are algorithms that can sort numbers. Search for bubble sort or quick sort and you should find a good sorting algorithm.

@mellonamin

If you want to create more than one random number, all you have to do is create more variables.
Here is an example:

void main() { // Create our integer variables int randnum1, randnum2; // This number is completely random randnum1 = rand(); // This number ranges from 1-50 randnum2 = rand()%50+1; // Print out numbers cout << "First Number: " << randnum1 << endl; cout << "Second Number: " << randnum2 << endl; // Just used to hold everything on the screen cin >> randnum1; }

[This message has been edited by HeardTheWord (edited February 01, 2005).]

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Vita sine Ieso est mors.
Life without Jesus is death.
Enter The Circle

I am not sure why the C header files do not work. I was able to get separate random numbers this way.

[This message has been edited by HeardTheWord (edited February 01, 2005).]

[This message has been edited by mellonamin (edited February 02, 2005).]

Unless your computer comes with a radioactive decay of Cesium to
generate your random numbers, the "rand()" function only generates
pseudo-numbers. The "rand()" function only appears random, achieving a
relatively flat distribution curve over a generation of billions of
numbers (seed), the sequence will be exactly the same. A true random
number generator will never repeat like this. A true random number
generator will always provide a good distribution curve (neither skewed
or "near flat").

Here is an example of why you would not want to use "rand()" and why you
should always create your own random number generator;
Lets say that you have a AI character that taunts. If you use the "rand()"
implementation, you will get a "true" character behavior. On the other hand
if you use an implementation other than the "rand()", you get an entirely
different pattern in AI behavior. This means that your character will
display "unpredictable" behavior. This is because your random number
generator is drawing from a good or "true" (better) distribution of
numbers. By using the "rand()" function you would not be drawing from a
good set of random numbers. (Have you ever noticed how characters in a
single player game react?) Drawing from a good distribution of numbers
is what you want to do when developing AI characters.

In short what game developers do is create a set of random numbers and a
set of objects (i.e. AI characters) then map each set of random numbers to
each object thus producing each and ever AI object a unique set of
behaviors.

Food for thought.

Welcome to the board!

The problem you describe is true - however, it is easily avoided by seeding the generator with something that will be different each time, such as the current time (as in the example given above by HeardTheWord), the number of milliseconds the computer has been on, a hash of all the keystrokes and mouse movements since the program started, etc.

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Brian

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"The very idea of freedom presupposes some objective moral law which overarches rulers and ruled alike." -- C. S. Lewis (1898 - 1963), "The Poison of Subjectivism" (from Christian Reflections; p. 108)

Switch Mayhem now available! Get it here
Codename: Roler - hoping to get more done over the holidays . . .

um, lemme see... in java, the
random() command will give you a random double number between 0 and 1. then, u just modify it to get whatever range you want.

so...
int rand = (int) (random() * 10 + 1);

should get you a random integer between 1 and 10. want twenty, change the 10 into twenty? want between 10 and 20? change the 1 into a 10. stuff like that.

no need to seed here, cuz it seeds from the clock. pretty cool if you ask me...

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Soterion Studios

I am certainly not arguing that people should not use the “rand()”
function. My first post was an “FYI” not to be meant to argue the finer
points on a language, but rather to enlighten on the mathematical points
of the “rand()” function.

Given the following code;

int rand = (int) (random() * 10 + 1);

If a person is happy about the results not being pooled from a fair
distribution of numbers then use it. However, you would not want to do
this with, again, in large scale gamming engines. CobraA1 is hit the nail
on the head. If you don’t care about the finer points of randomness,
then just use “rand()”. The implentation of code for some random number
generator, i.e. "rand()" is based on it mathematics not the code itself.
The code in its self is pointless, its only the math behind the code
that matters the most. When I first learned that I could use "rand()" or
some other variation of it, the first thing I asked myself is "how do
they generate those numbers?", "How is the code REALLY implemented,(how
did they write the "rand()" function)?" When I learned that the "rand()"
finction pools from numbers on the physical architecture, I knew right
away there were problems. So ArchAngel hit on a good topic from
mathematics.

What will be really shock to most people is that there is no way of
pooling a TRULY random number! Think about it, there are infinite set of
numbers right? How do you give an equal amount of chance of pooling one
number from an set of infinite numbers? It is impossible!

random based on atmospheric noise.. BETTER
http://www.random.org

random based on radioactive decay... BEST
http://www.fourmilab.ch/hotbits/

I realize and understand those limitations of rand(). However, the even bigger picture is "how much does it matter?" You said about rand(), "However, you would not want to do this with, again, in large scale gamming engines."

Really, why not? I cannot think of any examples in a gaming engine where it would matter. (I'm not arguing, just wondering. )

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Brian

When developing large scale physics engines, i.e. games, developers
generally like to stay away from using built in functions. (This not
only applies to functions like “rand()”, but also to “new” and “delete”
as well.) Of course this means they need to develop there own
functions like "rand()". Developers want to be able to develop
software that is more “mathematically sound”. They want to make
functions that provide “best opportunity” of getting some random
number and the “rand()” function does not provide the “best” fit
for physics engines. So by providing there own random number
generator, they can get “better” or “truer” random numbers.
It all boils down to statistics.

The “rand()” function polls numbers from a pool of relative flat
distribution curve, there just no arguing that, it’s the way it was
designed. Now then, if we can write some code that will improve that
distribution curve ,we can use it in our physics engine (i.e. game )
and get better results, for example better random interaction with
objects.

For your readers learning how to use the “rand()” function; use it and
don’t worry about the mathematical theory behind random numbers.

Jim

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Karl /GODCENTRIC
Visionary Media
the creative submitted to the divine.
Husband of my amazing wife Aleshia
Klumsy@xtra.co.nz

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I dont like siggys. They are to hard to think up :(

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Keep the holy day sacred.......halllllllukan