class FibonacciRng

The class of Fibonacci inspired random number generators.

Constants

ASCII_7_BIT: The printable seven bit ASCII characters.
BASE
BYTE
CHOP
DEPTHS
DOUBLE
INITS
TOP
VERSION
WORD

Attributes

depth[R]

The depth of the Fibonacci array.

init[R]

The init value used by this generator.

seed[R]

The seed value used by this generator.

Public Class Methods

new(arg_a=nil, arg_b=nil, arg_c=nil) click to toggle source

Initialize the PRN generator

# File lib/fibonacci_rng.rb, line 32
def initialize(arg_a=nil, arg_b=nil, arg_c=nil)
  #Extract the parameters.
  if arg_a.is_a?(Hash)
    seed   = arg_a[:seed]
    @depth = arg_a[:depth]
    @init  = arg_a[:init]
  else
    seed   = arg_a
    @depth = arg_b
    @init  = arg_c
  end

  #Set up the default parameters if needed.
  seed   ||= FibonacciRng.new_seed
  @depth ||= 8

  #Validate the depth.
  unless DEPTHS === @depth
    fail "Invalid depth value #{@depth}. Allowed values are #{DEPTHS}"
  end

  @init ||= 32 * @depth + 768

  #Validate the depth.
  unless INITS === @init
    fail "Invalid init value #{@init}. Allowed values are #{INITS}"
  end

  #Build the generator.
  srand(seed)
end

rand(max=0) click to toggle source

Get a random number from the class based generator. This exists only for compatibility purposes. It is far better to create instances of generators than to use a shared, global one.
Returns

The computed pseudo-random value.

# File lib/fibonacci_rng.rb, line 69
def self.rand(max=0)
  (@hidden ||= FibonacciRng.new).rand(max)
end

srand(seed=FibonacciRng.new_seed, depth=8) click to toggle source

Initialize the class based generator. This exists only for compatibility purposes. It is far better to create instances of generators than to use a shared, global one.
Returns

The old seed value.

# File lib/fibonacci_rng.rb, line 78
def self.srand(seed=FibonacciRng.new_seed, depth=8)
  old = (@hidden && @hidden.seed)
  @hidden = FibonacciRng.new(seed, depth)
  old
end

Private Class Methods

new_seed() click to toggle source

Create the default seed string.

# File lib/fibonacci_rng/seeder.rb, line 41
def self.new_seed
  @sync.synchronize {Time.now.to_s + @tickle.succ!}
end

Public Instance Methods

<<(data) click to toggle source

Append data to the generator

# File lib/fibonacci_rng/hasher.rb, line 19
def <<(data)
  (str = data.to_s).each_byte.each do |value|
    add_value(value)
  end

  do_spin if str.empty?
  validate
end

byte() click to toggle source

Get a pseudo random byte

# File lib/fibonacci_rng/generator.rb, line 33
def byte
  do_spin
  validate
  @buffer[0] & BYTE
end

bytes(length) click to toggle source

Get a string of random bytes

# File lib/fibonacci_rng/generator.rb, line 40
def bytes(length)
  result = ""
  length.times {result << byte.chr}
  result
end

dice(sides) click to toggle source

Roll a dice.

# File lib/fibonacci_rng/generator.rb, line 21
def dice(sides)
  limit = ((CHOP+1) / sides) * sides

  begin
    do_spin
  end until (value = @buffer[0]) < limit

  validate
  value % sides
end

double() click to toggle source

Get a better pseudo random float

# File lib/fibonacci_rng/generator.rb, line 61
def double
  do_spin
  part_one = raw_float * BASE
  do_spin
  validate
  (part_one + raw_float) / DOUBLE
end

float() click to toggle source

Get a pseudo random float

# File lib/fibonacci_rng/generator.rb, line 54
def float
  do_spin
  validate
  raw_float / BASE
end

hash_string() click to toggle source

Get the value of the rng state as a string.

# File lib/fibonacci_rng/hasher.rb, line 14
def hash_string
  hash_value.to_s(36)
end

hash_value() click to toggle source

Get the value of the rng state as a number.

# File lib/fibonacci_rng/hasher.rb, line 7
def hash_value
  result = 0
  @buffer[0...@depth].each {|value| result = (result << 29) + value }
  result
end

rand(max=0) click to toggle source

A (mostly) compatible access point for random numbers.
Endemic Code Smells

:reek:FeatureEnvy

# File lib/fibonacci_rng/generator.rb, line 9
def rand(max=0)
  if max.is_a?(Range)
    min = max.min
    dice(1 + max.max - min) + min
  elsif max.zero?
    float
  else
    dice(max.to_i)
  end
end

reseed(seed=FibonacciRng.new_seed)

Alias for: srand

spin(count=1) click to toggle source

Cycle through the PRNG count times.

# File lib/fibonacci_rng/spinner.rb, line 7
def spin(count=1)
  count.times do
    do_spin
  end
  
  validate
end

srand(seed=FibonacciRng.new_seed) click to toggle source

Set up a new seed value

# File lib/fibonacci_rng/seeder.rb, line 7
def srand(seed=FibonacciRng.new_seed)
  @seed = seed
  @buffer = Array.new(@depth+2, 0)
  seedsrc = (seed.to_s + fudge(seed) + 'Leonardo Pisano').each_byte.cycle
  indxsrc = (0...depth).cycle
  do_reseed(indxsrc, seedsrc)
end

Also aliased as: reseed

string(length, set=ASCII_7_BIT) click to toggle source

Create a random string
Endemic Code Smells.

:reek:FeatureEnvy

# File lib/fibonacci_rng/generator.rb, line 75
def string(length, set=ASCII_7_BIT)
  set_length = set.length
  result = ""
  length.times {result << set[dice(set_length)]}
  result
end

validate() click to toggle source

Validate the sanity of the generator.

# File lib/fibonacci_rng/validate.rb, line 10
def validate
  @buffer.each do |element| 
    return true unless element.zero?
  end
  
  fail InvalidFibonacciRngState
end

word() click to toggle source

Get a pseudo random word

# File lib/fibonacci_rng/generator.rb, line 47
def word
  do_spin
  validate
  @buffer[0] & WORD
end

Private Instance Methods

add_value(value) click to toggle source

Add a value to the generator.

# File lib/fibonacci_rng/hasher.rb, line 31
def add_value(value)
  index = @buffer[0] % @depth
  do_spin
  @buffer[index] += value
  do_spin
  validate
end

do_reseed(indxsrc, seedsrc) click to toggle source

Do the work of reseeding the PRNG

# File lib/fibonacci_rng/seeder.rb, line 46
def do_reseed(indxsrc, seedsrc)
  @init.times do
    @buffer[indxsrc.next] += seedsrc.next
    do_spin
  end
end

do_spin() click to toggle source

Cycle through the PRNG once.

# File lib/fibonacci_rng/spinner.rb, line 18
def do_spin
  @buffer[-2] = @buffer[0]
  @buffer[-1] = @buffer[1]

  (0...@depth).each do |idx|
    tmp = @buffer[idx+2]
    @buffer[idx] = (@buffer[idx+1] + ((tmp >> 1)|(tmp.odd? ? TOP : 0))) & CHOP
  end
end

fudge(seed) click to toggle source

A patch for the seeder class name bug.
Endemic Code Smells

:reek:UtilityFunction

# File lib/fibonacci_rng/seeder.rb, line 22
def fudge(seed)
  if seed.is_a?(Integer)
    if (-1073741824..1073741823) === seed
      "Fixnum"
    else
      "Bignum"
    end
  else
    seed.class.to_s
  end
end

raw_float() click to toggle source

Get a float value.

# File lib/fibonacci_rng/generator.rb, line 85
def raw_float
  @buffer[0].to_f
end