Random Numbers in a Range Using Generic Programming


	Random Numbers in a Range Using Generic Programming

prostoalex

3-23-2008 2:39 AM

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Consider the generation of random numbers in an interval, say the generation of an integer in {0,1,...,m-1} where the probability of each integer is 1/m. Usually, you have a source of randomness that provides random bits in chunks of architecture word size—something like the wrapper around the mtrand library (bedaux.net/mtrand); see Listing One.</P></blockquote><div style="height: 2px; font-size: 2px; background: #dcdcdc; border-bottom: solid 1px #f5f5f5; margin: 2px 4px;"></div><blockquote style="text-align: left; padding: 0px 8px; margin: 4px 0px 8px 0px; background: transparent; border: none;" cite="http://www.ddj.com/article/printableArticle.jhtml?articleID=206904716&dept_url=/cpp/"><P>
Mtrand implements the Mersenne Twister random-number generator (<A href="http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html">www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html</A>), which is a high-quality source of randomness. By "high quality," I mean that you don't need to consider low-order bits of words produced by the generator to be of inferior quality than high-order bits. In principle, you can take the value returned by <I>next()</I> <I>modulo</I> <I>m</I> to produce an integer in the range [<I>0,m-1</I>].  </P></blockquote></div><div style="margin: 0px 6px 6px 4px;"><table style="font-size: 11px;border-spacing: 0px;padding: 0px;" cellpadding="0" cellspacing="0" width="100%"><tr><td style="background:transparent;border-width:0px;padding:0px;">&nbsp;</td><td align="right" style="background:transparent;border-width:0px;padding:0px;width:107px" width="107"><a href="http://clipmarks.com/share/4B8A33CB-406A-42CE-807E-A854DDC9372F/blog/" title="blog or email this clip"><img src="http://content8.clipmarks.com/images/c2b-foot.png" border="0" alt="blog it" width="107" height="17" style="border-width:0px;padding:0px;margin:0px;" /></a></td></tr></table></div></div>

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