Random Number Generator

This is a discussion on Random Number Generator within the C++ Programming forums, part of the General Programming Boards category; True provided the implmentation your using has a linear-congruential generator (which in hindsight, it probably is, so you're right about ...

  1. #16
    Toaster Zach L.'s Avatar
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    True provided the implmentation your using has a linear-congruential generator (which in hindsight, it probably is, so you're right about that). Not necessarily true for other types of PRNGs, though.

    The following usually works well for the 1...n range:

    1 + (int)(n * rand() / (RAND_MAX + 1.0));
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  2. #17
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    Originally posted by Cat
    Zach, Stoustrup says exactly the opposite in The C++ Programming Language, 22.7. He recommends another method:
    int( (double(rand()) / RAND_MAX) * n)

    for numbers from 0 to n-1. Note this does have a miniscule but nonzero chance (0.00000005% for 31 bits of randomness) of returning n itself, so a serious application would have to take this into account.
    It doesn't look like another method to me. It looks like the same method. I am obviously missing something.

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