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## 11.8 `math.mt-random` - Mersenne Twister Random number generator

Module: math.mt-random
Provides a pseudo random number generator (RNG) based on "Mersenne Twister" algorithm developed by Makoto Matsumoto and Takuji Nishimura. It is fast, and has huge period of 2^19937-1. See MT, for details about the algorithm.

Class: <mersenne-twister>
A class to encapsulate the state of Mersenne Twister RNG. Each instance of this class has its own state, and can be used as an independent source of random bits if initialized by individual seed.

The random seed value can be given at the instantiation time by `:seed` initialization argument, or by using `mt-random-set-seed!` described below.

 ```(define m (make :seed (sys-time))) (mt-random-real m) => 0.10284287848537865 (mt-random-real m) => 0.463227748348805 (mt-random-real m) => 0.8628500643709712 ... ```

Function: mt-random-set-seed! mt seed
Sets random seed value seed to the Mersenne Twister RNG mt. Seed can be an arbitrary positive exact integer, or arbitrary length of u32vector (See section 10.4 `srfi-4` - Homogeneous vectors). If it is an integer, the lower 32bits are used for initialization. If it is a u32vector, up to 624 elements are used for initialization.

Function: mt-random-get-state mt
Function: mt-random-set-state! mt state
Retrieves and reinstalls the state of Mersenne Twister RNG mt. The state is represented by a u32vector of 625 elements. The state can be stored elsewhere, and then restored to an instance of `<mersenne-twister>` to continue to generate the pseudo random sequence.

Function: mt-random-real mt
Function: mt-random-real0 mt
Returns a random real number between 0.0 and 1.0. 1.0 is not included in the range. `Mt-random-real` doesn't include 0.0 either, while `mt-random-real0` does. Excluding 0.0 is from the draft SRFI-27.

Function: mt-random-integer mt range
Returns a random exact positive integer between 0 and range-1. Range can be any positive exact integer.

Function: mt-random-fill-u32vector! mt u32vector
Function: mt-random-fill-f32vector! mt f32vector
Function: mt-random-fill-f64vector! mt f64vector
Fills the given uniform vector by the random numbers. For `mt-random-fill-u32vector!`, the elements are filled by exact positive integers between 0 and 2^32-1. For `mt-random-fill-f32vector!` and `mt-random-fill-f64vector!`, it is filled by an inexact real number between 0.0 and 1.0, exclusive.

If you need a bunch of random numbers at once, these are much faster than getting one by one.

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This document was generated by Ken Dickey on November, 28 2002 using texi2html