From: Robert Klemme <shortcutter@...>
Date: 2010-10-04T04:04:13+09:00
Subject: Re: Point me to help w/ multithreading in 1.9.2-p0

On 03.10.2010 20:30, Caleb Clausen wrote:
> On 10/3/10, Robert Klemme<shortcutter@googlemail.com>  wrote:
>> On 03.10.2010 02:38, Caleb Clausen wrote:

>>>> You can probably get away without the condition variable by just
>>>> acquiring the lock (lock.synchronize) in the main thread before you
>>>> create all threads and let all threads just synchronize with an empty
>>>> block.
>>>
>>> I can't see any holes in this scheme, so it's probably the best idea.
>>
>> Even then it could be that some threads execute code before the
>> synchronize and thus not start concurrently with other threads.
>
> But you made the synchronize statement at the very start of the thread
> body, so this would seem to not be a concern in this case.

The access to the cond var in the synchronize block was also the first 
statement in the thread body:

   Thread.new do
     lock.synchronize do
       until start
         cond.wait(lock)
       end
     end

     # work
     # return results
     [rand(10), rand(100)]
   end

So there is really not that much difference.  In practice this will 
usually not be a problem but from a more formal perspective it does not 
matter how many operations are performed before the synchronization - it 
still may be that a thread does not get CPU to get there.  That's why I 
said that for a test scenario I would only bother to have all threads 
started concurrently if there was a lot of ramp up work to do.

Kind regards

	robert

-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/