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69 lines
2.7 KiB
TeX
69 lines
2.7 KiB
TeX
\section{\module{whrandom} ---
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Pseudo-random number generator}
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\declaremodule{standard}{whrandom}
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\modulesynopsis{Floating point pseudo-random number generator.}
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This module implements a Wichmann-Hill pseudo-random number generator
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class that is also named \class{whrandom}. Instances of the
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\class{whrandom} class conform to the Random Number Generator
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interface described in section \ref{rng-objects}. They also offer the
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following method, specific to the Wichmann-Hill algorithm:
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\begin{methoddesc}[whrandom]{seed}{\optional{x, y, z}}
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Initializes the random number generator from the integers \var{x},
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\var{y} and \var{z}. When the module is first imported, the random
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number is initialized using values derived from the current time.
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If \var{x}, \var{y}, and \var{z} are either omitted or \code{0}, the
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seed will be computed from the current system time. If one or two
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of the parameters are \code{0}, but not all three, the zero values
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are replaced by ones. This causes some apparently different seeds
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to be equal, with the corresponding result on the pseudo-random
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series produced by the generator.
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\end{methoddesc}
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\begin{funcdesc}{choice}{seq}
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Chooses a random element from the non-empty sequence \var{seq} and returns it.
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\end{funcdesc}
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\begin{funcdesc}{randint}{a, b}
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Returns a random integer \var{N} such that \code{\var{a}<=\var{N}<=\var{b}}.
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\end{funcdesc}
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\begin{funcdesc}{random}{}
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Returns the next random floating point number in the range [0.0 ... 1.0).
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\end{funcdesc}
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\begin{funcdesc}{seed}{x, y, z}
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Initializes the random number generator from the integers \var{x},
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\var{y} and \var{z}. When the module is first imported, the random
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number is initialized using values derived from the current time.
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\end{funcdesc}
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\begin{funcdesc}{uniform}{a, b}
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Returns a random real number \var{N} such that \code{\var{a}<=\var{N}<\var{b}}.
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\end{funcdesc}
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When imported, the \module{whrandom} module also creates an instance of
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the \class{whrandom} class, and makes the methods of that instance
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available at the module level. Therefore one can write either
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\code{N = whrandom.random()} or:
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\begin{verbatim}
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generator = whrandom.whrandom()
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N = generator.random()
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\end{verbatim}
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Note that using separate instances of the generator leads to
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independent sequences of pseudo-random numbers.
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\begin{seealso}
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\seemodule{random}{Generators for various random distributions and
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documentation for the Random Number Generator
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interface.}
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\seetext{Wichmann, B. A. \& Hill, I. D., ``Algorithm AS 183:
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An efficient and portable pseudo-random number generator'',
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\citetitle{Applied Statistics} 31 (1982) 188-190.}
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\end{seealso}
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