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| 1 | +""" |
| 2 | +Copyright (c) 2025 Philippe Schmouker, schmouk (at) gmail.com |
| 3 | +
|
| 4 | +Permission is hereby granted, free of charge, to any person obtaining a copy |
| 5 | +of this software and associated documentation files (the "Software"), to deal |
| 6 | +in the Software without restriction, including without limitation the rights |
| 7 | +to use, copy, modify, merge, publish, distribute, sublicense, and/or sell |
| 8 | +copies of the Software, and to permit persons to whom the Software is |
| 9 | +furnished to do so, subject to the following conditions: |
| 10 | +
|
| 11 | +The above copyright notice and this permission notice shall be included in all |
| 12 | +copies or substantial portions of the Software. |
| 13 | +
|
| 14 | +THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| 15 | +IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| 16 | +FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| 17 | +AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| 18 | +LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, |
| 19 | +OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE |
| 20 | +SOFTWARE. |
| 21 | +""" |
| 22 | + |
| 23 | +#============================================================================= |
| 24 | +from .baserandom import BaseRandom |
| 25 | +from .annotation_types import SeedStateType, StatesListAndExt |
| 26 | + |
| 27 | + |
| 28 | +#============================================================================= |
| 29 | +class BaseCWG( BaseRandom ): |
| 30 | + """Definition of the base class for all Collatz-Weyl pseudo-random Generators. |
| 31 | + |
| 32 | + This module is part of library PyRandLib. |
| 33 | +
|
| 34 | + Copyright (c) 2025 Philippe Schmouker |
| 35 | +
|
| 36 | + CWG models are chaotic generators that are combined with Weyl sequences to |
| 37 | + eliminate the risk of short cycles. They have a large period, a uniform |
| 38 | + distribution, and the ability to generate multiple independent streams by |
| 39 | + changing their internal parameters (Weyl increment). CWGs owe their |
| 40 | + exceptional quality to the arithmetical dynamics of noninvertible, |
| 41 | + generalized, Collatz mappings based on the wellknown Collatz conjecture. |
| 42 | + There is no jump function, but each odd number of the Weyl increment |
| 43 | + initiates a new unique period, which enables quick initialization of |
| 44 | + independent streams (this text is extracted from [8], see README.md). |
| 45 | +
|
| 46 | + The internal implementation of the CWG algorithm varies according to its |
| 47 | + implemented version. See implementation classes to get their formal |
| 48 | + description. |
| 49 | + |
| 50 | + See Cwg64 for a minimum 2^70 (i.e. about 1.18e+21) period CW-Generator |
| 51 | + with low computation time, medium period, 64- bits output values and very |
| 52 | + good randomness characteristics. |
| 53 | + See Cwg128_64 for a minimum 2^71 (i.e. about 2.36e+21) period CW-Generator |
| 54 | + with very low computation time, medium period, 64-bits output values and |
| 55 | + very good randomness characteristics. |
| 56 | + See Cwg128 for a minimum 2^135 (i.e. about 4.36e+40) period CW-generator |
| 57 | + with very low computation time, medium period, 64- bits output values and |
| 58 | + very good randomness characteristics. |
| 59 | +
|
| 60 | + Furthermore this class is callable: |
| 61 | + rand = BaseCWG() # Caution: this is just used as illustrative. This base class cannot be instantiated |
| 62 | + print( rand() ) # prints a pseudo-random value within [0.0, 1.0) |
| 63 | + print( rand(a) ) # prints a pseudo-random value within [0, a) or [0.0, a) depending on the type of a |
| 64 | + print( rand(a, n) ) # prints a list of n pseudo-random values each within [0, a) |
| 65 | +
|
| 66 | + Reminder: |
| 67 | + We give you here below a copy of the table of tests for the CWGs that have |
| 68 | + been implemented in PyRandLib, as presented in paper [8] - see file README.md. |
| 69 | +
|
| 70 | + | PyRandLib class | [8] generator name | Memory Usage | Period | time-32bits | time-64 bits | SmallCrush fails | Crush fails | BigCrush fails | |
| 71 | + | --------------- | ------------------ | ------------- | -------- | ----------- | ------------ | ---------------- | ----------- | -------------- | |
| 72 | + | Cwg64 | CWG64 | 8 x 4-bytes | >= 2^70 | n.a. | n.a. | 0 | 0 | 0 | |
| 73 | + | Cwg128_64 | CWG128_64 | 10 x 4-bytes | >= 2^71 | n.a. | n.a. | 0 | 0 | 0 |_ |
| 74 | + | Cwg128 | CWG128 | 16 x 4-bytes | >= 2^135 | n.a. | n.a. | 0 | 0 | 0 | |
| 75 | +
|
| 76 | + * _small crush_ is a small set of simple tests that quickly tests some of |
| 77 | + the expected characteristics for a pretty good PRNG; |
| 78 | + * _crush_ is a bigger set of tests that test more deeply expected random |
| 79 | + characteristics; |
| 80 | + * _big crush_ is the ultimate set of difficult tests that any GOOD PRNG |
| 81 | + should definitively pass. |
| 82 | + """ |
| 83 | + |
| 84 | + #------------------------------------------------------------------------- |
| 85 | + def __init__(self, _seedState: SeedStateType = None) -> None: |
| 86 | + """Constructor. |
| 87 | + |
| 88 | + Should _seedState be None then the local time is used as a seed (with |
| 89 | + its shuffled value). |
| 90 | + Notice: method setstate() is not implemented in base class BaseRandom. |
| 91 | + So, it must be implemented in classes inheriting BaseLCG and it must |
| 92 | + initialize attribute self._state. |
| 93 | + """ |
| 94 | + super().__init__( _seedState ) # this internally calls 'setstate()' which |
| 95 | + # MUST be implemented in inheriting classes |
| 96 | + |
| 97 | + |
| 98 | + #------------------------------------------------------------------------- |
| 99 | + def getstate(self) -> StatesListAndExt: |
| 100 | + """Returns an object capturing the current internal state of the generator. |
| 101 | + |
| 102 | + This object can be passed to setstate() to restore the state. |
| 103 | + For CWG, this state is defined by a list of control values |
| 104 | + (a, weyl and s - or a list of 4 coeffs) and an internal state |
| 105 | + value, which are used in methods 'next() and 'setstate() of |
| 106 | + every inheriting class. |
| 107 | +
|
| 108 | + All inheriting classes MUST IMPLEMENT this method. |
| 109 | + """ |
| 110 | + return (self._a, self._weyl, self._s, self._state) |
| 111 | + |
| 112 | + |
| 113 | +#===== end of module basecwg.py ======================================== |
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