[ruby-core:106286] [Ruby master Feature#5378] Prime.each is slow

Issue #5378 has been updated by hsbt (Hiroshi SHIBATA).

Status changed from Assigned to Closed

prime.rb was extracted to https://github.com/ruby/prime as the bundled gems.

If you still have the motivation of this proposal, can you file this to the new canonical repository? Thanks.

----------------------------------------
Feature #5378: Prime.each is slow
https://bugs.ruby-lang.org/issues/5378#change-94911

* Author: mconigliaro (Mike Conigliaro)
* Status: Closed
* Priority: Normal
* Assignee: yugui (Yuki Sonoda)
----------------------------------------
See discussion here: https://gist.github.com/1246868


require 'benchmark'
require 'prime'

def primes_up_to(n)
  s = [nil, nil] + (2..n).to_a
  (2..(n ** 0.5).to_i).reject { |i| s[i].nil? }.each do |i|
    (i ** 2).step(n, i) { |j| s[j] = nil }
  end
  s.compact
end

Benchmark.bm(12) do |x|
  x.report('primes_up_to') { primes_up_to(2000000).inject(0) { |memo,obj| memo + obj } }
  x.report('Prime.each') { Prime.each(2000000).inject(0) { |memo,obj| memo + obj } }
end


$ ruby -v
ruby 1.9.2p290 (2011-07-09 revision 32553) [x86_64-darwin10.8.0]
$ ruby lol.rb 
                  user     system      total        real
primes_up_to  1.470000   0.020000   1.490000 (  1.491340)
Prime.each    7.820000   0.010000   7.830000 (  7.820969)

---Files--------------------------------
prime.patch (4.06 KB)


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