Thread: a very large interval of rundom numbers

  1. #16
    The superhaterodyne twomers's Avatar
    Join Date
    Dec 2005
    It's an integer (unless .RandInt means something different). Cast it or something, I guess.

    EDIT: Couldn't you do something like this (un-debugged):

    int Rand( unsigned int UpperValue )
    	unsigned int Bound = 0;
    	while ( Bound < UpperValue )
    		Bound *= rand();
    	return Bound%UpperValue;
    then divide that by the 14 million number?

    unless I'm completely missing the point again
    Last edited by twomers; 08-02-2006 at 01:38 PM.

  2. #17
    Registered User
    Join Date
    Jan 2005
    In that case I guess you do need something more complicated than a simple call to rand() and perhaps the MTRand, boost's random library, or some other more advanced random number generator can help you out.

  3. #18
    (?<!re)tired Mario F.'s Avatar
    Join Date
    May 2006
    RandInt() will produce unsigned longs in the range specified by the machine where it is run. Usually, for 32 bit machines this means 2^32, which is more than enough for your needs.

    Just as Daved suggested, The Boost library is another option.
    Originally Posted by brewbuck:
    Reimplementing a large system in another language to get a 25% performance boost is nonsense. It would be cheaper to just get a computer which is 25% faster.

  4. #19
    Registered User
    Join Date
    Aug 2006
    Thank you very much for all of replys, you have helped me very much. I think that now I generate very well my random numbers with the algorithm that I have pasted before and therefore I will continue my project of end of career, this is one example of the numbers:

    0.165794,0.0661423,0.923107,0.531084,0.34571,0.203 416,0.029796,0.230248,0.232488,0.3
    13662,0.290937,0.399191,0.268811,0.0109423,0.72024 4,0.971198,0.747598,0.391661,0.841
    39,0.503972,0.516979,0.889657,0.662066,0.386967,0. 165785,0.818416,0.44327,0.397976,0.
    912517,0.141096,0.225495,0.417585,0.681512,0.35767 8,0.728592,0.849111,0.944788,0.713
    195,0.768732,0.169899,0.330627,0.935429,0.0824016, 0.596916,0.708728,0.800829,0.50701
    4,0.562885,0.424306,0.492069,0.0279898,0.905467,0. 898149,0.470343,0.368699,0.582445,0.290043,0.57629 ,0.47501,0.898634,0.645065,0.504504,0.45487,0.8500 83,0.733836,0.215999,
    0.635212,0.869203,0.687654,0.901373,0.149824,0.814 778,0.396815,0.555215,0.4301,0.8225
    78,0.0158782,0.53381,0.283836,0.670007,0.273425,0. 834816,0.969183,0.94561,0.607918,0.
    319848,0.333663,0.350953,0.572609,0.393557,0.73656 9,0.548893,0.471629,0.249477,0.978
    695,0.905908,0.197679,0.795876,0.216934,0.0718069, 0.155776,0.0472373,0.442245,0.

  5. #20
    Registered User
    Join Date
    May 2002

    Look for L'Ecuyer or Marsaglia, both have written large period random numbers and C algorithms are available online.

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