"
 COPYRIGHT (c) 2014 Claus Gittinger
              All Rights Reserved

 This software is furnished under a license and may be used
 only in accordance with the terms of that license and with the
 inclusion of the above copyright notice.   This software may not
 be provided or otherwise made available to, or used by, any
 other person.  No title to or ownership of the software is
 hereby transferred.
"
"{ Package: 'stx:libbasic2' }"

"{ NameSpace: Smalltalk }"

Object subclass:#RandomBlumBlumShub
	instanceVariableNames:'p q m seed'
	classVariableNames:''
	poolDictionaries:''
	category:'Magnitude-Numbers-Random'
!

!RandomBlumBlumShub class methodsFor:'documentation'!

copyright
"
 COPYRIGHT (c) 2014 Claus Gittinger
              All Rights Reserved

 This software is furnished under a license and may be used
 only in accordance with the terms of that license and with the
 inclusion of the above copyright notice.   This software may not
 be provided or otherwise made available to, or used by, any
 other person.  No title to or ownership of the software is
 hereby transferred.
"
!

documentation
"
    NO WARRANTY

    This generator uses the blum blub shub algorithm to generate random numbers.
    It is very slow, but considered to provide good random numbers.

    RandomBlumBlumShub new nextInteger

    [see also:]
        RandomGenerator - the default; uses the machine's /dev/random if available
        Random  - fast, but generates less quality random numbers
        RandomTT800 - another random generator
        RandomParkMiller - another random generator
        RandomMT19937 - another random generator
        RandomKISS - another random generator
        exept:libcrypt - a library containing more stuff based on hashes and cyphers

    [author:]
        Claus Gittinger.
"
! !

!RandomBlumBlumShub class methodsFor:'instance creation'!

new
    ^ self basicNew 
        initialize;
        seed:(Random randomSeed)
!

new:seed
    self isSupported ifFalse:[ self error:'this generator needs a cpu with rdgen instruction' ].
    ^ self basicNew 
        initialize;
        seed:seed
! !

!RandomBlumBlumShub methodsFor:'initialization'!

initialize
    "The two primes, p and q, should both be congruent to 3 (mod 4)"

    p := 615389388455725613122981570401989286707.
    q := 8936277569639798554773638405675965349567.
    m := p * q.

    "/ (p \\ 4) = 3 ifFalse:[ self halt: 'unsuitable p' ].
    "/ (q \\ 4) = 3 ifFalse:[ self halt: 'unsuitable p' ].

    "
     self new initialize
    "
!

seed:seedArg
    seed := seedArg.

    self assert:(seed < m).
    self assert:(seed gcd:m) = 1.
! !

!RandomBlumBlumShub methodsFor:'random numbers'!

nextBoolean
    "generates the next random boolean"

    seed := seed*seed \\ m.
    ^ seed bitTest:1
!

nextInteger
    "generates the next integer in 0..FFFFFFFF"

    |num|

    num := 0.
    32 timesRepeat:[
        seed := (seed * seed) \\ m.
        num := (num<<1) + (seed bitAnd:1).
    ].
    ^ num.

    "
     self new nextInteger.

     |r|
     r := self new
     100 timesRepeat:[ Transcript showCR:r nextInteger].
    "
! !

!RandomBlumBlumShub class methodsFor:'documentation'!

version
    ^ '$Header$'
!

version_CVS
    ^ '$Header$'
! !