Random Numbers

This is a discussion on Random Numbers within the C Programming forums, part of the General Programming Boards category; Hi, I have written a program that uses the random number generator function from the GNU scientific library. Every time ...

  1. #1
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    Random Numbers

    Hi,

    I have written a program that uses the random number generator function from the GNU scientific library.
    Every time I execute the program it generates the same random numbers. Is there anyway I can generate different random number every time I execute the program.

    Thanks
    Vibhuti

  2. #2
    C++ Witch laserlight's Avatar
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    You probably need to seed the random number generator with a different seed.
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  3. #3
    Captain Crash brewbuck's Avatar
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    To go even further, you could provide a way for the user to specify the seed, either as a command line argument, environment variable, or something else. That way, the user can reproduce a result if they want to.

    (It also makes debugging less impossible if you have a way to reproduce the seed)
    Code:
    //try
    //{
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);
    //}

  4. #4
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    Most random number generators work on a seed. In the normal C library random generator, that's srand(). I don't know what it's called in GSL, but google finds this:
    http://www.gnu.org/software/gsl/manu...alization.html

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    Please don't PM me for help - and no, I don't do help over instant messengers.

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    Thank you!! Changing the seed works

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    I have the same problem.
    But i do not understand how u change the seed

    can someone please give me more info on that
    im still very new to C. :-)

  7. #7
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by cursedninja
    But i do not understand how u change the seed
    According to the documentation that matsp linked to, it is by using the gsl_rng_set() function. Have you tried using it? (Or if you are talking about the C standard library's rand() function, it will be srand(), also mentioned by matsp.)
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    I did not understand much about the gsl_rng_set() function.

    i am using the standard library function.
    How do i change the seed for the srand?

    could u just show me what code i should use?

  9. #9
    C++ Witch laserlight's Avatar
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    Quote Originally Posted by cursedninja
    i am using the standard library function.
    How do i change the seed for the srand?
    Read this article on using rand().
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    Smile

    thank you very much.

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