From: "Y. NOBUOKA" <nobuoka@...>
Date: 2010-11-17T17:08:43+09:00
Subject: Re: Thread problem

I think that the reason of this problem is the simultaneous use of a
common resource. In your example, the common resource is the variable
*sum*. You need to use a Mutex object to avoid the simultaneous use of
that variable.
cf. Mutex class: http://ruby-doc.org/core/classes/Mutex.html

---
 require 'thread'
 threads = []

 sum = 0
 mutex = Mutex.new

 1.upto(1000) { |external|
   threads << Thread.new(external) { |local|
     sleep(rand(0.01))
     mutex.synchronize {
       sum = sum + local
     }
   }
 }

 threads.each() { |thread| thread.join() }

 puts sum
---

2010/11/17 Jaeyong Lee <crizin@gmail.com>:
> Hi all,
>
> I learning ruby thread and faced to thread problem.
> Here's my test code that sum 1 to 1000.
>
> --
> threads = []
>
> sum = 0
>
> 1.upto(1000) { |external|
>  threads << Thread.new(external) { |local|
>    sleep(rand(0.01))
>    sum = sum + local
>  }
> }
>
> threads.each() { |thread| thread.join() }
>
> puts sum
> --
>
> I expected '500500' but output is smaller than. (ex: 499864)
> Please let me know what problem is.
>

-- 
NOBUOKA Yuya