diff options
Diffstat (limited to 'jni/ruby/lib/prime.rb')
-rw-r--r-- | jni/ruby/lib/prime.rb | 487 |
1 files changed, 487 insertions, 0 deletions
diff --git a/jni/ruby/lib/prime.rb b/jni/ruby/lib/prime.rb new file mode 100644 index 0000000..b2b55f1 --- /dev/null +++ b/jni/ruby/lib/prime.rb @@ -0,0 +1,487 @@ +# +# = prime.rb +# +# Prime numbers and factorization library. +# +# Copyright:: +# Copyright (c) 1998-2008 Keiju ISHITSUKA(SHL Japan Inc.) +# Copyright (c) 2008 Yuki Sonoda (Yugui) <yugui@yugui.jp> +# +# Documentation:: +# Yuki Sonoda +# + +require "singleton" +require "forwardable" + +class Integer + # Re-composes a prime factorization and returns the product. + # + # See Prime#int_from_prime_division for more details. + def Integer.from_prime_division(pd) + Prime.int_from_prime_division(pd) + end + + # Returns the factorization of +self+. + # + # See Prime#prime_division for more details. + def prime_division(generator = Prime::Generator23.new) + Prime.prime_division(self, generator) + end + + # Returns true if +self+ is a prime number, else returns false. + def prime? + Prime.prime?(self) + end + + # Iterates the given block over all prime numbers. + # + # See +Prime+#each for more details. + def Integer.each_prime(ubound, &block) # :yields: prime + Prime.each(ubound, &block) + end +end + +# +# The set of all prime numbers. +# +# == Example +# +# Prime.each(100) do |prime| +# p prime #=> 2, 3, 5, 7, 11, ...., 97 +# end +# +# Prime is Enumerable: +# +# Prime.first 5 # => [2, 3, 5, 7, 11] +# +# == Retrieving the instance +# +# +Prime+.new is obsolete. Now +Prime+ has the default instance and you can +# access it as +Prime+.instance. +# +# For convenience, each instance method of +Prime+.instance can be accessed +# as a class method of +Prime+. +# +# e.g. +# Prime.instance.prime?(2) #=> true +# Prime.prime?(2) #=> true +# +# == Generators +# +# A "generator" provides an implementation of enumerating pseudo-prime +# numbers and it remembers the position of enumeration and upper bound. +# Furthermore, it is an external iterator of prime enumeration which is +# compatible with an Enumerator. +# +# +Prime+::+PseudoPrimeGenerator+ is the base class for generators. +# There are few implementations of generator. +# +# [+Prime+::+EratosthenesGenerator+] +# Uses eratosthenes' sieve. +# [+Prime+::+TrialDivisionGenerator+] +# Uses the trial division method. +# [+Prime+::+Generator23+] +# Generates all positive integers which are not divisible by either 2 or 3. +# This sequence is very bad as a pseudo-prime sequence. But this +# is faster and uses much less memory than the other generators. So, +# it is suitable for factorizing an integer which is not large but +# has many prime factors. e.g. for Prime#prime? . + +class Prime + include Enumerable + @the_instance = Prime.new + + # obsolete. Use +Prime+::+instance+ or class methods of +Prime+. + def initialize + @generator = EratosthenesGenerator.new + extend OldCompatibility + warn "Prime::new is obsolete. use Prime::instance or class methods of Prime." + end + + class << self + extend Forwardable + include Enumerable + # Returns the default instance of Prime. + def instance; @the_instance end + + def method_added(method) # :nodoc: + (class<< self;self;end).def_delegator :instance, method + end + end + + # Iterates the given block over all prime numbers. + # + # == Parameters + # + # +ubound+:: + # Optional. An arbitrary positive number. + # The upper bound of enumeration. The method enumerates + # prime numbers infinitely if +ubound+ is nil. + # +generator+:: + # Optional. An implementation of pseudo-prime generator. + # + # == Return value + # + # An evaluated value of the given block at the last time. + # Or an enumerator which is compatible to an +Enumerator+ + # if no block given. + # + # == Description + # + # Calls +block+ once for each prime number, passing the prime as + # a parameter. + # + # +ubound+:: + # Upper bound of prime numbers. The iterator stops after it + # yields all prime numbers p <= +ubound+. + # + # == Note + # + # +Prime+.+new+ returns an object extended by +Prime+::+OldCompatibility+ + # in order to be compatible with Ruby 1.8, and +Prime+#each is overwritten + # by +Prime+::+OldCompatibility+#+each+. + # + # +Prime+.+new+ is now obsolete. Use +Prime+.+instance+.+each+ or simply + # +Prime+.+each+. + def each(ubound = nil, generator = EratosthenesGenerator.new, &block) + generator.upper_bound = ubound + generator.each(&block) + end + + + # Returns true if +value+ is a prime number, else returns false. + # + # == Parameters + # + # +value+:: an arbitrary integer to be checked. + # +generator+:: optional. A pseudo-prime generator. + def prime?(value, generator = Prime::Generator23.new) + return false if value < 2 + for num in generator + q,r = value.divmod num + return true if q < num + return false if r == 0 + end + end + + # Re-composes a prime factorization and returns the product. + # + # == Parameters + # +pd+:: Array of pairs of integers. The each internal + # pair consists of a prime number -- a prime factor -- + # and a natural number -- an exponent. + # + # == Example + # For <tt>[[p_1, e_1], [p_2, e_2], ...., [p_n, e_n]]</tt>, it returns: + # + # p_1**e_1 * p_2**e_2 * .... * p_n**e_n. + # + # Prime.int_from_prime_division([[2,2], [3,1]]) #=> 12 + def int_from_prime_division(pd) + pd.inject(1){|value, (prime, index)| + value * prime**index + } + end + + # Returns the factorization of +value+. + # + # == Parameters + # +value+:: An arbitrary integer. + # +generator+:: Optional. A pseudo-prime generator. + # +generator+.succ must return the next + # pseudo-prime number in the ascending + # order. It must generate all prime numbers, + # but may also generate non prime numbers too. + # + # === Exceptions + # +ZeroDivisionError+:: when +value+ is zero. + # + # == Example + # For an arbitrary integer: + # + # n = p_1**e_1 * p_2**e_2 * .... * p_n**e_n, + # + # prime_division(n) returns: + # + # [[p_1, e_1], [p_2, e_2], ...., [p_n, e_n]]. + # + # Prime.prime_division(12) #=> [[2,2], [3,1]] + # + def prime_division(value, generator = Prime::Generator23.new) + raise ZeroDivisionError if value == 0 + if value < 0 + value = -value + pv = [[-1, 1]] + else + pv = [] + end + for prime in generator + count = 0 + while (value1, mod = value.divmod(prime) + mod) == 0 + value = value1 + count += 1 + end + if count != 0 + pv.push [prime, count] + end + break if value1 <= prime + end + if value > 1 + pv.push [value, 1] + end + return pv + end + + # An abstract class for enumerating pseudo-prime numbers. + # + # Concrete subclasses should override succ, next, rewind. + class PseudoPrimeGenerator + include Enumerable + + def initialize(ubound = nil) + @ubound = ubound + end + + def upper_bound=(ubound) + @ubound = ubound + end + def upper_bound + @ubound + end + + # returns the next pseudo-prime number, and move the internal + # position forward. + # + # +PseudoPrimeGenerator+#succ raises +NotImplementedError+. + def succ + raise NotImplementedError, "need to define `succ'" + end + + # alias of +succ+. + def next + raise NotImplementedError, "need to define `next'" + end + + # Rewinds the internal position for enumeration. + # + # See +Enumerator+#rewind. + def rewind + raise NotImplementedError, "need to define `rewind'" + end + + # Iterates the given block for each prime number. + def each + return self.dup unless block_given? + if @ubound + last_value = nil + loop do + prime = succ + break last_value if prime > @ubound + last_value = yield prime + end + else + loop do + yield succ + end + end + end + + # see +Enumerator+#with_index. + alias with_index each_with_index + + # see +Enumerator+#with_object. + def with_object(obj) + return enum_for(:with_object) unless block_given? + each do |prime| + yield prime, obj + end + end + end + + # An implementation of +PseudoPrimeGenerator+. + # + # Uses +EratosthenesSieve+. + class EratosthenesGenerator < PseudoPrimeGenerator + def initialize + @last_prime_index = -1 + super + end + + def succ + @last_prime_index += 1 + EratosthenesSieve.instance.get_nth_prime(@last_prime_index) + end + def rewind + initialize + end + alias next succ + end + + # An implementation of +PseudoPrimeGenerator+ which uses + # a prime table generated by trial division. + class TrialDivisionGenerator<PseudoPrimeGenerator + def initialize + @index = -1 + super + end + + def succ + TrialDivision.instance[@index += 1] + end + def rewind + initialize + end + alias next succ + end + + # Generates all integers which are greater than 2 and + # are not divisible by either 2 or 3. + # + # This is a pseudo-prime generator, suitable on + # checking primality of an integer by brute force + # method. + class Generator23<PseudoPrimeGenerator + def initialize + @prime = 1 + @step = nil + super + end + + def succ + if (@step) + @prime += @step + @step = 6 - @step + else + case @prime + when 1; @prime = 2 + when 2; @prime = 3 + when 3; @prime = 5; @step = 2 + end + end + return @prime + end + alias next succ + def rewind + initialize + end + end + + # Internal use. An implementation of prime table by trial division method. + class TrialDivision + include Singleton + + def initialize # :nodoc: + # These are included as class variables to cache them for later uses. If memory + # usage is a problem, they can be put in Prime#initialize as instance variables. + + # There must be no primes between @primes[-1] and @next_to_check. + @primes = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101] + # @next_to_check % 6 must be 1. + @next_to_check = 103 # @primes[-1] - @primes[-1] % 6 + 7 + @ulticheck_index = 3 # @primes.index(@primes.reverse.find {|n| + # n < Math.sqrt(@@next_to_check) }) + @ulticheck_next_squared = 121 # @primes[@ulticheck_index + 1] ** 2 + end + + # Returns the cached prime numbers. + def cache + return @primes + end + alias primes cache + alias primes_so_far cache + + # Returns the +index+th prime number. + # + # +index+ is a 0-based index. + def [](index) + while index >= @primes.length + # Only check for prime factors up to the square root of the potential primes, + # but without the performance hit of an actual square root calculation. + if @next_to_check + 4 > @ulticheck_next_squared + @ulticheck_index += 1 + @ulticheck_next_squared = @primes.at(@ulticheck_index + 1) ** 2 + end + # Only check numbers congruent to one and five, modulo six. All others + + # are divisible by two or three. This also allows us to skip checking against + # two and three. + @primes.push @next_to_check if @primes[2..@ulticheck_index].find {|prime| @next_to_check % prime == 0 }.nil? + @next_to_check += 4 + @primes.push @next_to_check if @primes[2..@ulticheck_index].find {|prime| @next_to_check % prime == 0 }.nil? + @next_to_check += 2 + end + return @primes[index] + end + end + + # Internal use. An implementation of eratosthenes' sieve + class EratosthenesSieve + include Singleton + + def initialize + @primes = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101] + # @max_checked must be an even number + @max_checked = @primes.last + 1 + end + + def get_nth_prime(n) + compute_primes while @primes.size <= n + @primes[n] + end + + private + def compute_primes + # max_segment_size must be an even number + max_segment_size = 1e6.to_i + max_cached_prime = @primes.last + # do not double count primes if #compute_primes is interrupted + # by Timeout.timeout + @max_checked = max_cached_prime + 1 if max_cached_prime > @max_checked + + segment_min = @max_checked + segment_max = [segment_min + max_segment_size, max_cached_prime * 2].min + root = Integer(Math.sqrt(segment_max).floor) + + sieving_primes = @primes[1 .. -1].take_while { |prime| prime <= root } + offsets = Array.new(sieving_primes.size) do |i| + (-(segment_min + 1 + sieving_primes[i]) / 2) % sieving_primes[i] + end + + segment = ((segment_min + 1) .. segment_max).step(2).to_a + sieving_primes.each_with_index do |prime, index| + composite_index = offsets[index] + while composite_index < segment.size do + segment[composite_index] = nil + composite_index += prime + end + end + + segment.each do |prime| + @primes.push prime unless prime.nil? + end + @max_checked = segment_max + end + end + + # Provides a +Prime+ object with compatibility to Ruby 1.8 when instantiated via +Prime+.+new+. + module OldCompatibility + # Returns the next prime number and forwards internal pointer. + def succ + @generator.succ + end + alias next succ + + # Overwrites Prime#each. + # + # Iterates the given block over all prime numbers. Note that enumeration + # starts from the current position of internal pointer, not rewound. + def each + return @generator.dup unless block_given? + loop do + yield succ + end + end + end +end |