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"{ Package: 'stx:libbasic2' }"
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Object subclass:#RandomBlumBlumShub
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instanceVariableNames:'p q m seed'
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classVariableNames:''
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poolDictionaries:''
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category:'Magnitude-Numbers'
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!
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!RandomBlumBlumShub class methodsFor:'documentation'!
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documentation
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"
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NO WARRANTY
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This generator uses the blum blub shub algorithm to generate random numbers.
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It is very slow, but considered to provide good random numbers.
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RandomBlumBlumShub new nextInteger
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[see also:]
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RandomGenerator - the default; uses the machine's /dev/random if available
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Random - fast, but generates less quality random numbers
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RandomTT800 - another random generator
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RandomParkMiller - another random generator
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RandomMT19937 - another random generator
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RandomKISS - another random generator
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exept:libcrypt - a library containing more stuff based on hashes and cyphers
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[author:]
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Claus Gittinger.
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"
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! !
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!RandomBlumBlumShub class methodsFor:'instance creation'!
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new
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^ self basicNew
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initialize;
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seed:(Random randomSeed)
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!
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new:seed
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self isSupported ifFalse:[ self error:'this generator needs a cpu with rdgen instruction' ].
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^ self basicNew
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initialize;
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seed:seed
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! !
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!RandomBlumBlumShub methodsFor:'initialization'!
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initialize
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"The two primes, p and q, should both be congruent to 3 (mod 4)"
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p := 615389388455725613122981570401989286707.
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q := 8936277569639798554773638405675965349567.
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m := p * q.
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"/ (p \\ 4) = 3 ifFalse:[ self halt: 'unsuitable p' ].
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"/ (q \\ 4) = 3 ifFalse:[ self halt: 'unsuitable p' ].
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"
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self new initialize
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"
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!
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seed:seedArg
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seed := seedArg.
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self assert:(seed < m).
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self assert:(seed gcd:m) = 1.
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! !
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!RandomBlumBlumShub methodsFor:'random numbers'!
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nextBoolean
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"generates the next random boolean"
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seed := seed*seed \\ m.
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^ seed bitTest:1
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!
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nextInteger
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"generates the next integer in 0..FFFFFFFF"
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|num|
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num := 0.
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32 timesRepeat:[
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seed := (seed * seed) \\ m.
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num := (num<<1) + (seed bitAnd:1).
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].
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^ num.
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"
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self new nextInteger.
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|r|
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r := self new
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100 timesRepeat:[ Transcript showCR:r nextInteger].
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"
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! !
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!RandomBlumBlumShub class methodsFor:'documentation'!
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version
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^ '$Header: /cvs/stx/stx/libbasic2/RandomBlumBlumShub.st,v 1.1 2014-10-02 16:24:30 cg Exp $'
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!
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version_CVS
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^ '$Header: /cvs/stx/stx/libbasic2/RandomBlumBlumShub.st,v 1.1 2014-10-02 16:24:30 cg Exp $'
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! !
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