From: Marcin Raczkowski <swistak@...>
Date: 2007-06-01T19:52:44+09:00
Subject: Re: DRb and Thread safety

On Friday 01 June 2007 09:42, Erwin Abbott wrote:
> Marcin and Brian,
>
> Thank you for the help, I feel like I have a pretty good starting
> place now to figure the details out myself. I'm still not sure what
> the differences between all the data structures like Mutex, Condition
> Variable, Semaphore, Monitor, etc are... but I can work that out.

Mutex - is block that can't be run concurently
Semaphore - is like "stop" sign - execution will stop untill semaphore is 
lifted in another thread
Monitor - is class that throught specially made accessors allows only 
synchronous access to it's methods/variables (Queue class in standard lib is 
good example)
Condition Variable is something oposite to Semaphore


>
> On 5/31/07, Brian Candler <B.Candler@pobox.com> wrote:
> > This is where a good book comes in. There are some relevant articles on
> > wikipedia. Googling for "philosophers" and "spaghetti" may also be
> > helpful :-)
>
> Yes, very helpful. It also led me to:
> - Sleeping barber problem
> - Cigarette smokers problem
> - Dining cryptographers protocol
all these algorithms are very complicated in c - but in ruby are usually 
really easy - you only need to use thread safe classes (like Queue) or 
Monitor mixin 

for example in ruby solving Writers and Readers

require 'thread'

bookstore = Queue.new

writers = 4
readers = 5

writers.times do |w|
  Thread.new {
    5.times { |x|
      bookstore.put("new book "+x.to_s+" by "+w)
      sleep 1+rand(5)
   }
  }
end

readers.times do
  Thread.new {
    4.times {
      puts bookstore.pop
   }
  }
end



>
> The Concurrency category on Wikipedia should give me plenty to read,
> or at least know what to look for at the bookstore...
> http://en.wikipedia.org/wiki/Category:Concurrency
>

I'm not sure what's the most popular book about algorithmics in you country - 
but try spending some money or go to library ^^

> Thanks again,
>   Erwin





-- 
Marcin Raczkowski
---
Friends teach what you should know
Enemies Teach what you have to know