[ruby-core:30219] [Bug #1560] multi core operations are slower on trunk (possible regression)

Issue #1560 has been updated by Yusuke Endoh.


Hi,

> I think it would be nice for this to be fixed before 1.9.2 is released.
> Any objections to reopening this or should I open a new ticket?

Sorry for late response, but I object.

We should not call Time.new in busy loop if performance is needed.
In this case, you want to use timeout.  It can run much faster
(about 15-20 times), even if you use 1.9.1:

  +------------+----------+---------+
  |            |   1.9.1  |   trunk |
  +------------+----------+---------+
  |original.rb |  3711882 |  3572907|
  |timeout.rb  | 59852485 | 76665074|
  +------------+----------+---------+


  # timeout.rb

  require 'thread'
  require 'timeout'
  threads = []
  counter = 0
  mutex = Mutex.new

  4.times do
    threads << Thread.new {
      x=0
      y=0
      time=Time.new

      begin
        Timeout.timeout(10) do
          while true do
            x=1.00/24000000000.001
            y+=1
          end
        end
      rescue Timeout::Error
      end
      mutex.synchronize { counter+=y.to_i }
    }
  end
  threads.each { |t| t.join }

  puts "Total number of insane floating point divisions in 10 seconds is "+counter.to_s

-- 
Yusuke Endoh <[e-mail]>
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