"{ Encoding: utf8 }"

"

 COPYRIGHT (c) 1989 by 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 }"

Stream subclass:#Random

	instanceVariableNames:'seed'

	classVariableNames:'RandomSalt SharedGenerator'

	poolDictionaries:''

	category:'Magnitude-Numbers-Random'

!

!Random class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 1989 by 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

"

    A facade to the actual RandomGenerator.

    In previous versions, Random was a very bad fallback random generator,

    with an included warning, to not use it.

    Now this old generator was renamed to RandomGNUSmalltalk,

    and the default generator used is the one provided by the much

    better RandomGenerator class.

        Random new next:10   

    [author:]

        Claus Gittinger

    [see also:]

        http://www0.cs.ucl.ac.uk/staff/d.jones/GoodPracticeRNG.pdf

        RandomTT800      - a new random generator

        RandomParkMiller - another new random generator

"

!

examples

"

                                                                        [exBegin]

    |rnd|

    rnd := Random new.

    10 timesRepeat:[

        Transcript showCR:(rnd next)

    ]

                                                                        [exEnd]

    rolling a dice:

                                                                        [exBegin]

    |rnd|

    rnd := Random new.

    10 timesRepeat:[

        Transcript showCR:(rnd nextIntegerBetween:1 and:6)

    ]

                                                                        [exEnd]

"

! !

!Random class methodsFor:'instance creation'!

new

    "return a new random generator.

     Here, this instance creation message is forwarded to the standardGenerator"

    self == Random ifFalse:[^ super new].

    ^ self standard

    "

     Random new

    "

!

random

    "return a new random generator.

     Defined here for compatibility with StreamCipher"

    ^ self standard

    "Created: / 12.11.1999 / 17:52:08 / stefan"

!

seed:seedValue

    "return a new random generator with initial seed.

     Here, this instance creation message is forwarded to the standardGenerator"

    ^ self standardGeneratorClass basicNew setSeed:seedValue

    "Created: / 26-05-2007 / 21:27:18 / cg"

!

sharedGenerator

    "return a shared random generator."

    SharedGenerator isNil ifTrue:[

        SharedGenerator := self standard.

    ].

    ^ SharedGenerator

!

standard

    "return the 'standard' generator"

    ^ self standardGeneratorClass new

!

standardGeneratorClass

    "return the class used for the 'standard' generator"

    ^ RandomGenerator

! !

!Random class methodsFor:'random numbers'!

next

    "return the next random number in the range 0..1

     This method behaves like the corresponding instance method,

     but allows generation of random numbers without

     a need for an instance of Random to be kept around.

     This uses a common, shared generator."

    ^ self sharedGenerator next.

    "

     Transcript showCR:(Random next).

     Transcript showCR:(Random next).

     Transcript showCR:(Random next).

     Transcript showCR:(Random next).

    "

!

nextBetween:start and:stop

    "return a random number between start and stop.

     This method behaves like the corresponding instance method,

     but allows generation of random numbers without

     a need for an instance of Random to be kept around.

     This uses a common, shared generator."

    ^ self sharedGenerator nextBetween:start and:stop

    "

     Transcript showCR:(Random nextBetween:1 and:100).

     Transcript showCR:(Random nextBetween:1 and:100).

     Transcript showCR:(Random nextBetween:1 and:100).

     Transcript showCR:(Random nextBetween:1 and:100).

    "

    "Modified: 21.8.1997 / 18:08:56 / cg"

    "Created: 21.8.1997 / 18:09:36 / cg"

!

nextBoolean

    "return a boolean random.

     This method behaves like the corresponding instance method,

     but allows generation of random numbers without

     a need for an instance of Random to be kept around.

     This uses a common, shared generator."

    ^ self sharedGenerator nextBoolean.

    "

     Transcript showCR:(Random nextBoolean).

     Transcript showCR:(Random nextBoolean).

     Transcript showCR:(Random nextBoolean).

     Transcript showCR:(Random nextBoolean).

    "

    "Created: 21.8.1997 / 18:08:23 / cg"

!

nextInteger

    "return an integral random number.

     This method behaves like the corresponding instance method,

     but allows generation of random numbers without

     a need for an instance of Random to be kept around.

     This uses a common, shared generator."

    ^ self sharedGenerator nextInteger.

    "

     Transcript showCR:(Random nextInteger).

     Transcript showCR:(Random nextInteger).

     Transcript showCR:(Random nextInteger).

     Transcript showCR:(Random nextInteger).

    "

    "Created: 21.8.1997 / 18:08:23 / cg"

!

nextIntegerBetween:start and:stop

    "return an integral random number between start and stop.

     This method behaves like the corresponding instance method,

     but allows generation of random numbers without

     a need for an instance of Random to be kept around.

     This uses a common, shared generator."

    ^ self sharedGenerator nextIntegerBetween:start and:stop

    "

     Transcript showCR:(Random nextIntegerBetween:1 and:10).

     Transcript showCR:(Random nextIntegerBetween:1 and:10).

     Transcript showCR:(Random nextIntegerBetween:1 and:10).

     Transcript showCR:(Random nextIntegerBetween:1 and:10).

    "

    "Created: 21.8.1997 / 18:07:00 / cg"

    "Modified: 21.8.1997 / 18:08:56 / cg"

!

nextLettersOrDigits:count

    "get the next count printable letters or digits [0-9A-Za-z]."

    ^ self sharedGenerator nextLettersOrDigits:count

    "

     Transcript showCR:(Random nextLettersOrDigits:10).

     Transcript showCR:(Random nextLettersOrDigits:10).

     Transcript showCR:(Random nextLettersOrDigits:10).

     Transcript showCR:(Random nextLettersOrDigits:10).

    "

    "Created: 21.8.1997 / 18:07:00 / cg"

    "Modified: 21.8.1997 / 18:08:56 / cg"

! !

!Random class methodsFor:'seeding'!

randomSeed

    "return a number useful for seeding.

     This takes the current processor's time, plus the processor's process id,

     plus some value depending on the memory allocation state,

     plus a random salt, and shuffles those bits around.

     The entropy returned should be reasonable enough for a good seed of a good rnd

     generator. However, keep in mind, that it only has a limited number of entropy bits

     (in the order of 32). 

     But it should be much better than what is commonly used in older

     programs (current time) or even a constant."

    |hash|

    RandomSalt isNil ifTrue:[

        RandomSalt := 1.

    ] ifFalse:[

        RandomSalt := RandomSalt + 1.

    ].

    hash := MD5Stream new.

    hash 

        nextPut:RandomSalt;

        nextPut:Time microsecondClockValue; 

        nextPut:OperatingSystem getProcessId; 

        nextPut:(ObjectMemory addressOf:Object new); 

        nextPut:ObjectMemory oldSpaceUsed; 

        nextPut:ObjectMemory newSpaceUsed; 

        nextPut:OperatingSystem getCPUCycleCount. 

    "/ any other cheap sources of entropy?

    "/ I think there is no problem in that MD5 is not a secure hash algo here 

    "/ - the idea is to shuffle the bits around a bit

    "/ (because the numbers above usually have many high bits in common)

    "/ and then condense the bits into a smaller number.

    "/ Any comment from a crypto guy here - I am willing to change this to some other hash, if that makes a problem

    "/ Seeding rnd generators should take some bits from the returned number (i.e. their max. seed size)

    ^ LargeInteger digitBytes:hash hashValue.

    "

     10 timesRepeat:[Transcript showCR:self randomSeed].

     10 timesRepeat:[Transcript showCR:(self randomSeed bitAnd:16rFFFF)].

     self randomSeed bitAnd:16rFFFFFFFF

    "

! !

!Random class methodsFor:'testing'!

bucketTest: randy

    "A quick-and-dirty bucket test. Prints nbuckets values on the Transcript.

     Each should be 'near' the value of ntries. Any run with any value 'far' from ntries

     indicates something is very wrong. Each run generates different values.

     For a slightly better test, try values of nbuckets of 200-1000 or more; 

     go get coffee.

     This is a poor test; see Knuth.   

     Some 'OK' runs:

           1000 1023 998 969 997 1018 1030 1019 1054 985 1003

           1011 987 982 980 982 974 968 1044 976

           1029 1011 1025 1016 997 1019 991 954 968 999 991

           978 1035 995 988 1038 1009 988 993 976

    "

    | nbuckets buckets ntrys slot |

    nbuckets := 20.

    buckets := Array new: nbuckets withAll:0.

    ntrys :=  1000.

    ntrys*nbuckets timesRepeat: [

            slot := (randy next * nbuckets) floor + 1.

            buckets at: slot put: (buckets at: slot) + 1 ].

    Transcript cr.

    1 to: nbuckets do: [ :nb |

            Transcript show: (buckets at: nb) printString, ' ' ]

    "Execute this:  

         self bucketTest: self new

         self bucketTest: RandomGenerator new

    "

!

chiSquareTest   

    " Chi-Squared Test - from R.Sedgewick's 1st ed. of 'Algorithms', 

            o N = number of samples

            o r  = range of random numners is [0,r)      -- condition: N >= 10r.

            o Random number generator 'passes' if chisquare value is very close to r

            o Repeat test several times, since it may be *wrong* 1 out of 10 trials."

    | aGenerator frequencies n range t |

    aGenerator := self new.  "Seeded differently each time (if seeded at all)"

    range := 100.   

    n := 10000.

    frequencies := Array new:range withAll:0.

    1 to: n do: [:i |

        t := ((aGenerator next) * range) truncated + 1.

        frequencies at:t put: ((frequencies at:t) + 1).

    ].

    t := frequencies inject:0 into: [:nextValue :eachFreq |

            nextValue + eachFreq squared

        ].

    ^ ((range * t  / n) - n) asFloat.

    "

     self chiSquareTest 

     RandomGenerator chiSquareTest

    "

   "

    |fail|

    fail := 0.

    10 timesRepeat:[

        |testResult|

        testResult := RandomGenerator chiSquareTest.

        (100 - testResult) abs > 20 ifTrue:[Transcript showCR:testResult. fail := fail + 1].

    ].

    fail > 1 ifTrue:[self error:'test failed'].

    "

    "

      Sedgewick claims each chisquare number should be 100 +- 20. 

      The closer to 100, the better.

    "

! !

!Random methodsFor:'Compatibility-Squeak'!

nextInt:upperBound

    "Answer a random integer in the interval [1, anInteger]."

    (upperBound < 1) ifTrue:[self error:'invalid upper bound'].

    ^ self nextIntegerBetween:1 and:upperBound

    "

     Random new nextInt:10

    "

!

nextIntFrom:lowerBound to:upperBound

    "return a random integer in the given range"

    ^ self nextIntegerBetween:lowerBound and:upperBound

    "

     Random new nextIntFrom:5 to:10

    "

!

seed: anInteger

    self setSeed: anInteger.

    "Created: / 20-07-2013 / 01:52:03 / Jan Vrany <jan.vrany@fit.cvut.cz>"

! !

!Random methodsFor:'accessing-reading'!

next

    "return the next random number in the range ]0..1["

    self subclassResponsibility.

    "

     |r|

     r := Random new.

     Transcript showCR:r next.

     Transcript showCR:r next.

     Transcript showCR:r next.

     Transcript showCR:r next.

    "

    "Modified: 1.4.1997 / 22:44:46 / cg"

!

nextBetween:start and:stop

    "return a random number in the range ]start..stop[.

     claus: the original GNU version has a bug in returning values

     from the interval [start .. stop+1]"

    |rnd|

    rnd := self next.

    rnd := rnd * (stop - start) asFloat.

    rnd := rnd + start asFloat.

    ^ rnd

    "|r|

     r := Random new.

     Transcript showCR:(r nextBetween:1 and:10).

     Transcript showCR:(r nextBetween:1 and:10).

     Transcript showCR:(r nextBetween:1 and:10).

     Transcript showCR:(r nextBetween:1 and:10).

    "

    "Modified: / 21.8.1998 / 14:45:27 / cg"

!

nextBoolean

    "return true or false by random"

    ^ self next bitAnd:16r10.

    "

    |r|

     r := Random new.

     Transcript showCR:r nextBoolean.

     Transcript showCR:r nextBoolean.

     Transcript showCR:r nextBoolean.

     Transcript showCR:r nextBoolean.

    "

    "

     |r bag|

     r := Random new.

     bag := Bag new.

     1000000 timesRepeat:[

         bag add:(r nextBoolean).

     ].

     Transcript showCR:bag contents

    "

    "Modified: / 22-10-2008 / 15:17:57 / cg"

!

nextByte

    "return the next integral random number byte in the range 0 .. 16rFF"

    ^ self next bitAnd:16rFF

    "

     |r|