retroforth/example/rng.retro

## xoroshiro128**

XOR/rotate/shift/rotate PNRG (See http://xoshiro.di.unimi.it/)


~~~
{{
  'JUMP d:create #2271477771 , #4114797267 , #1872770499 , #2012404571 ,
  'k var 't var 's0 var 's1 var 's2 var 's3 var
  :reseed (n-)  dup !s1 dup !s2 dup !s3 dup !k !t  ;
  :rotl   (x-)  !k [ @k n:negate shift ] [ #32 @k - shift ] bi or ;
  :res**  (-n)  @s0 #5 * #7 rotl #9 * ;
  :next   (-)
    @s1 dup #-9 shift push @s3 @s0 @s2
      \pudupoxo
      \pupu....
      \pudupoxo
      \swposwpo
      \dupuxopu
      \pudupoxo
      \popopoxo
    !s2 !s1 !s0 #11 rotl !s3 ;

  :xor-er (nananana-nananana)
      \dupufexo \pu......
      \dupufexo \pu......
      \dupufexo \pu......
      \dupufexo \pu......
      \popopopo \popopopo ;
  :jump? (nm-) [ JUMP + fetch ] dip #1 swap n:negate shift and ;
  :inner (n-n)
    #32 [ dup I jump? [ [ xor-er ] dip ] if next ] indexed-times ;
    
---reveal---
  :random:xoroshiro128** (-n)
    next res** ;
    
  :random:xoroshiro128**:jump (-)
    #0 &s3 #0 &s2 #0 &s1 #0 &s0
    #4 [ I inner drop ] indexed-times
    \stststst ;
    
  :random:xoroshiro128**:set-seed (n-)
    reseed #100 [ next ] times ;

  :random:xoroshiro128**:test-seed (nnnn-)
    !s0 !s1 !s2 !s3 ;
}}   
~~~

## Mersenne Twister

This is adapted from Samuel A. Falvo II's implementation. The
original commentary follows:

    As taken from ttp://en.wikipedia.org/wiki/Mersenne_twister 

    I am aware of Wil Baden's sources, but I had difficulty 
    getting it to compile under SwiftForth out of the box. 

    This module exposes the following API: 

    seeded ( uSeed -- ) 
      Seeds the random number generator with the provided 32-bit,
      unsigned value. 

    probability ( -- u ) 
      Returns a random value that falls in the range [0, 
      $FFFFFFFF]. 

    All other definitions are safe to shadow/redefine elsewhere. 

    Copyright (c) 2010, Samuel A. Falvo II 
    All rights reserved. 

    Redistribution and use in source and binary forms, with or 
    without modification, are permitted provided that the following 
    conditions are met: 
 
    * Redistributions of source code must retain the above copyright 
      notice, this list of conditions and the following disclaimer. 
 
    * Redistributions in binary form must reproduce the above 
      copyright notice, this list of conditions and the following 
      disclaimer in the documentation and/or other materials 
      provided with the distribution. 

    * Neither the name of Samuel A. Falvo II, Falvo Technical 
      Solutions, nor the names of its contributors may be used to 
      endorse or promote products derived from this software 
      without specific prior written permission. 
 
    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 
    CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, 
    INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF 
    MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
    DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR 
    CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, 
    SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT 
    LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF 
    USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 
    AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 
    LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING 
    IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF 
    THE POSSIBILITY OF SUCH DAMAGE. 

In adapting this, some concessions were made since RETRO only
has signed 32-bit values.

    random:mersenne:set-seed (n-) 
      Seeds the random number generator with the provided 32-bit,
      unsigned value. 

    random:mersenne (-n) 
      Returns a random value that falls in the range [0, 
      n:MAX]. 

~~~
{{
  'States d:create  #625 allot
  'Index  var

  :reset (n-)
    &States over n:dec + dup fetch #30 shift swap fetch
    xor #1812433253 * over + n:MAX and swap &States + store ;

  :randomized (-)
    #1 [ dup reset n:inc dup #624 gt? ] until drop ;

  :y (n-y)
    dup n:inc #624 mod &States + fetch n:MAX and
    swap &States + fetch #-31 shift + ;

  :altered (n-) 
    dup y dup #1 and #1073741823 *
    [ #2 / over #397 + #624 mod &States + fetch xor ] dip
  xor swap &States + store ;

  :scrambled (-)
    #0 [ dup altered n:inc dup #624 gt? ] until drop ;
---reveal---
  :random:mersenne:set-seed (n-) 
    !States  #0 !Index  randomized ;

  :random:mersenne (-n)
    @Index n:zero? &scrambled if @Index &States + fetch
    dup #11 shift xor dup #-7 shift #1073741823 and xor dup #-15 shift
    #2011365376 and xor dup #18 shift xor @Index n:inc #624 mod !Index ;
}}
~~~