"

======================================================================

|

| Copyright (C) 1988, 1989 Free Software Foundation, Inc.

| Written by Steve Byrne.

|

| This file is part of GNU Smalltalk.

|

| GNU Smalltalk is free software; you can redistribute it and/or modify it

| under the terms of the GNU General Public License as published by the Free

| Software Foundation; either version 1, or (at your option) any later version.

| 

| GNU Smalltalk is distributed in the hope that it will be useful, but WITHOUT

| ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

| FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more

| details.

| 

| You should have received a copy of the GNU General Public License along with

| GNU Smalltalk; see the file LICENSE.  If not, write to the Free Software

| Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  

|

======================================================================

see notice in (Random>>documentation)

"

"{ Package: 'stx:libbasic2' }"

"{ NameSpace: Smalltalk }"

Stream subclass:#Random

	instanceVariableNames:'seed increment multiplier modulus'

	classVariableNames:'SharedGenerator RandomSalt'

	poolDictionaries:''

	category:'Magnitude-Numbers-Random'

!

!Random class methodsFor:'documentation'!

copyright

"

======================================================================

|

| Copyright (C) 1988, 1989 Free Software Foundation, Inc.

| Written by Steve Byrne.

|

| This file is part of GNU Smalltalk.

|

| GNU Smalltalk is free software; you can redistribute it and/or modify it

| under the terms of the GNU General Public License as published by the Free

| Software Foundation; either version 1, or (at your option) any later version.

| 

| GNU Smalltalk is distributed in the hope that it will be useful, but WITHOUT

| ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

| FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more

| details.

| 

| You should have received a copy of the GNU General Public License along with

| GNU Smalltalk; see the file LICENSE.  If not, write to the Free Software

| Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.  

|

======================================================================

see notice in (Random>>documentation)

"

!

documentation

"

    WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING

    =======================================================================================

    DO NOT USE THIS GENERATOR FOR CRYPTOGRAPHY OR OTHER SECURITY RELATED WORK, 

    because linear congruential generators are predictable and can be broken easily!!

    Smalltalk/X includes a better generator named RandomGenerator, which uses the best

    available generator of the system (either OS-random, /dev/random or as a less dangerous

    fallback, an RC4-based random generator).

    Please use that one.

    =======================================================================================

    A simple random numbers - thanks to Steves GNU Smalltalk

    This implements a linear congruential maximum period random number generator

    which passes the spectral test for randomness for dimensions 2 3 4 5 6.

    Notice: although being included here,

            this file is NOT covered by the ST/X license, but by

            the FSF copyLeft (see copyright method).

            You can redistribute it under the terms stated there ...

            Also, the price you pay for ST/X does not include a charge for

            this file - it has to be considered as a separate piece of

            software, which can be copied and given away without any 

            restriction from my (CG) side.

    [author:]

        Steve Byrne

        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"

    ^ self basicNew initialize

!

random

    "return a new random generator.

     Defined here for compatibility with StreamCipher"

    ^ self new

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

!

seed:seedValue

    "return a new random generator with initial seed"

    ^self basicNew setSeed:seedValue

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

!

sharedGenerator

    "return a shared random generator."

    SharedGenerator isNil ifTrue:[

        SharedGenerator := self new.

    ].

    ^ SharedGenerator

!

standard

    "return the 'standard' generator"

    ^ self new

! !

!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 step.

    ^ seed / modulus asFloat

    "

     |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 step.