Rand() not bieng very random

This is a discussion on Rand() not bieng very random within the C++ Programming forums, part of the General Programming Boards category; Sorry it's me again. Anyway, the title pretty much explains it all. My program chooses five random numbers ranging from ...

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    Rand() not bieng very random

    Sorry it's me again.

    Anyway, the title pretty much explains it all. My program chooses five random numbers ranging from 1-5, (inclusive,) but it always chooses the same numbers in the same order. Is this normal? I ask simply because I wish to know the nature of rand(). I just can't see how any proccess a system performs can be random, as it has pre-set commands to determine these numbers. Can anyone explain the concept of random number generating? If you can please do as I am really lost.

    Thanks for any replies.
    Necrofear

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    The superhaterodyne twomers's Avatar
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    Have you seeded rand() Generate random numbers?

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    No I hadn't. I wasn't sure how to generate a random seed, but I've just read the example you gave me, (Cheers for the link BTW,) and I'm going to try to use time as a seed like they did.

    Thanks for the reply.
    Necrofear

    P.S. I like your avatar. House is an amazing show! Thanks again

  4. #4
    Woof, woof! zacs7's Avatar
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    [/offtopic]

    Quote Originally Posted by twomers View Post
    Have you seeded rand() Generate random numbers?
    Fran ? :P

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    The superhaterodyne twomers's Avatar
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    You talking about my sig, zacs7? I think it was Bernard, not Fran who said it.

    Here's more reading about rand().

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    Woof, woof! zacs7's Avatar
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    Yeah I know , just Fran was in there somewhere , Ep with her shrinking walls methinks.

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    Cheers for the rand() info.
    I got the seed changing every execution now.

    Thanks for the help!
    Necrofear
    Last edited by Necrofear; 05-12-2007 at 09:26 AM.

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    Woof, woof! zacs7's Avatar
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    If you want to get different random numbers each time you run your program, you will also need to use the srand() function as well, as this will seed the generator. The srand() function is called only once during a programs execution.
    ....

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    Quote Originally Posted by zacs7 View Post
    ....
    ???

    If you mean what I think you mean by: ... , then I mean that every time the program is executed, it uses a different seed. Not that it changes seed halfway through. It use to always start at the same place.

    If you don't mean what I think you mean however then I'm confused.

  10. #10
    Woof, woof! zacs7's Avatar
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    Bah, sorry I thought you ment every loop execution (iteration)

  11. #11
    Registered User learning's Avatar
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    fyi they will only be pseudo random numbers not real randoms
    at night uv comes alive

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