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* lib/prime.rb (Prime::EratosthenesGenerator,

Browse source 
Prime::EratosthenesSieve): New implementation by
  robertjlooby <robertjlooby AT gmail.com>.

* test/test_prime.rb: updated with new method name

commit 4b6090ea852d63b26e02796c69b41caa0fa95077
Merge: ceda881 c8f7809
Author: Yuki Sonoda (Yugui) <yugui@yugui.jp>
Date:   Mon Jul 15 12:50:04 2013 +0900

    Merge commit 'c8f780987fbdfbae428977487e1cf793c4c36d3f'

    Conflicts:
    	lib/prime.rb

commit c8f780987f
Author: robertjlooby <robertjlooby@gmail.com>
Date:   Thu Jun 27 23:04:45 2013 -0500

    updated test/test_prime.rb with new method name

commit 996517bdbb
Author: robertjlooby <robertjlooby@gmail.com>
Date:   Thu Jun 27 22:59:39 2013 -0500

    new implementation of Prime::EratosthenesGenerator and Prime::EratosthenesSieve

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41982 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
This commit is contained in:
yugui 2013-07-15 04:21:34 +00:00
parent ceda881601
commit def83bff91
3 changed files with 44 additions and 55 deletions
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8
ChangeLog
View file

@ -1,3 +1,11 @@
Mon Jul 15 13:07:27 2013 Yuki Yugui Sonoda <yugui@yugui.jp>
* lib/prime.rb (Prime::EratosthenesGenerator,
Prime::EratosthenesSieve): New implementation by
robertjlooby <robertjlooby AT gmail.com>.
* test/test_prime.rb: updated with new method name
Mon Jul 15 11:32:46 2013 Zachary Scott <e@zzak.io>
* numeric.c (rb_cNumeric): [DOC] Added comment for Numeric to fix doc

89
lib/prime.rb
View file

@ -306,12 +306,13 @@ class Prime
# Uses +EratosthenesSieve+.
class EratosthenesGenerator < PseudoPrimeGenerator
def initialize
@last_prime = nil
@last_prime_index = -1
super
end
def succ
@last_prime = @last_prime ? EratosthenesSieve.instance.next_to(@last_prime) : 2
@last_prime_index += 1
EratosthenesSieve.instance.get_nth_prime(@last_prime_index)
end
def rewind
initialize
@ -422,68 +423,48 @@ class Prime
class EratosthenesSieve
include Singleton
BITS_PER_ENTRY = 16 # each entry is a set of 16-bits in a Fixnum
NUMS_PER_ENTRY = BITS_PER_ENTRY * 2 # twiced because even numbers are omitted
ENTRIES_PER_TABLE = 8
NUMS_PER_TABLE = NUMS_PER_ENTRY * ENTRIES_PER_TABLE
FILLED_ENTRY = (1 << NUMS_PER_ENTRY) - 1
def initialize # :nodoc:
# bitmap for odd prime numbers less than 256.
# For an arbitrary odd number n, @tables[i][j][k] is
# * 1 if n is prime,
# * 0 if n is composite,
# where i,j,k = indices(n)
@tables = [[0xcb6e, 0x64b4, 0x129a, 0x816d, 0x4c32, 0x864a, 0x820d, 0x2196].freeze]
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
# returns the least odd prime number which is greater than +n+.
def next_to(n)
n = (n-1).div(2)*2+3 # the next odd number to given n
table_index, integer_index, bit_index = indices(n)
loop do
extend_table until @tables.length > table_index
for j in integer_index...ENTRIES_PER_TABLE
if !@tables[table_index][j].zero?
for k in bit_index...BITS_PER_ENTRY
return NUMS_PER_TABLE*table_index + NUMS_PER_ENTRY*j + 2*k+1 if !@tables[table_index][j][k].zero?
end
end
bit_index = 0
end
table_index += 1; integer_index = 0
end
def get_nth_prime(n)
compute_primes while @primes.size <= n
@primes[n]
end
private
# for an odd number +n+, returns (i, j, k) such that @tables[i][j][k] represents primality of the number
def indices(n)
# binary digits of n: |0|1|2|3|4|5|6|7|8|9|10|11|....
# indices: |-| k | j | i
# because of NUMS_PER_ENTRY, NUMS_PER_TABLE
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
k = (n & 0b00011111) >> 1
j = (n & 0b11100000) >> 5
i = n >> 8
return i, j, k
end
segment_min = @max_checked
segment_max = [segment_min + max_segment_size, max_cached_prime * 2].min
root = Integer(Math.sqrt(segment_max).floor)
def extend_table
lbound = NUMS_PER_TABLE * @tables.length
ubound = lbound + NUMS_PER_TABLE
new_table = [FILLED_ENTRY] * ENTRIES_PER_TABLE # which represents primality in lbound...ubound
(3..Integer(Math.sqrt(ubound))).step(2) do |p|
i, j, k = indices(p)
next if @tables[i][j][k].zero?
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
start = (lbound.div(p)+1)*p # least multiple of p which is >= lbound
start += p if start.even?
(start...ubound).step(2*p) do |n|
_, j, k = indices(n)
new_table[j] &= FILLED_ENTRY^(1<<k)
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
@tables << new_table.freeze
segment.each do |prime|
@primes.push prime unless prime.nil?
end
@max_checked = segment_max
end
end

2
test/test_prime.rb
View file

@ -154,7 +154,7 @@ class TestPrime < Test::Unit::TestCase
# simulates that Timeout.timeout interrupts Prime::EratosthenesSieve#extend_table
def sieve.Integer(n)
n = super(n)
sleep 10 if /extend_table/ =~ caller.first
sleep 10 if /compute_primes/ =~ caller.first
return n
end