From: 7stud -- <dolgun@...>
Date: 2007-09-28T16:09:27+09:00
Subject: Re: what is mean by thread scheduler in Ruby?

Vellingiri Arul wrote:
>      what is mean by thread scheduler in Ruby?with example?
> 
> 
> Please Any one help me?
> 
> by
> Vellingiri

Threads don't execute at the same time despite what the literature might 
say.  If you have two threads, for instance your main program and one 
thread, then one thread executes for a short time, and then execution 
switches to the other thread for a short time, and then execution 
switches back.  The switching back and forth happens so fast that it 
gives the appearance that the threads are executing at the same time. 
The thread scheduler determines which thread gets execution time and how 
much.

You should note that if both of your threads contain code that has no 
dead time or pauses in it, your program will take the same amount of 
time to execute without threads as it does with threads.  It's only when 
code has some pauses in it, like if your program has to wait for a 
requested web page to be returned, that threads can reduce the time your 
program takes to execute.  During the pauses, the thread scheduler will 
switch execution to another thread where there is code ready to execute.

You can manually manipulate the thread scheduler using methods like 
wait(), join(), stop(), and pass(). All those methods cause the thread 
scheduler to alter its normal behavior.

puts "Inside main program."
sleep(2) #execution halts here - no thread yet
puts

t = Thread.new do
  puts <<ENDx
Inside thread, but Thread.pass tells thread scheduler to go
elsewhere and look for code that is ready to execute.
ENDx
  Thread.pass  #Tells thread scheduler to go elsewhere
               #and look for code to execute.

  puts
  puts "Inside thread."
  puts
  sleep(12) #Because execution halts here, the thread scheduler
            #will look elsewhere for code to execute.
  puts "Inside thread: thread finished."
end

puts
puts  <<ENDy
Back inside main program. Halting main program. Send
execution back to thread and give it all the execution
time it needs until it finshes.
ENDy
t.join()

puts
puts "Inside main, thread finally finished, exiting..."

-- 
Posted via http://www.ruby-forum.com/.