Hi,
Is there a way to know how many child processes that have been forked by
its parent process? The forked process may exit when it finishes, so if
parent process needs to know the status, it has to check it regularly.
I'm guess this number could be used to control the total numbers
processes to avert too many resources exhausted. Once the number is
reduced, new child could be forked.
Thanks.
--
Posted via http://www.ruby-forum.com/.
As far as I know you'd have to set up a counter within the parent and
increment / decrement it within the threads.
However, before moving into multiple threads you should do a bit of
benchmarking to ensure that it's the best way to proceed. You'll often
find that multithreading isn't your best option as the performance
bottleneck may be something that threads won't help with.
--
Posted via http://www.ruby-forum.com/.
Is there a way to know how many child processes that have been forked by
its parent process?
Yes, just record the PID in a Set or Array.
The forked process may exit when it finishes, so if
parent process needs to know the status, it has to check it regularly.
That's not how you typically do it. Typically you will fork child
processes and then wait for them to terminate once you are doing with
your work in the main process. If you want to limit the total number
of processes created you could store work items in a queue, start n
processes initially and then wait for one process to terminate. As
long as there is work in the queue fork a new process.
I'm guess this number could be used to control the total numbers
processes to avert too many resources exhausted. Once the number is
reduced, new child could be forked.
You just need to wait for termination (see above).
Example:
#!/usr/bin/ruby
$-w = true
require 'set'
N = 4
# work items are sleep seconds
queue = 20.times.map { 2 + rand(5) }
processes = Set.new
until queue.empty?
if processes.size >= N
pid = Process.wait
processes.delete pid
end
sl = queue.shift
pid = fork do
printf "PID %5d: Start\n", $$
sleep sl
printf "PID %5d: Stop\n", $$
end
processes.add pid
end
puts "Waiting for remaining processes..."
Process.waitall
puts "Done"
On Mon, Mar 18, 2013 at 10:12 AM, Ken Paul <lists@ruby-forum.com> wrote:
--
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/
I think it's the -w command line argument for Ruby, it means show
warnings.
--
Posted via http://www.ruby-forum.com/.
Robert Klemme wrote in post #1102059:
Thanks for the detailed explanation with a great example.
#!/usr/bin/ruby
$-w = true
What does this special variable means "$-w"?
--
Posted via http://www.ruby-forum.com/\.
Exactly.
$ ruby -e 'p $-w'
false
$ ruby -w -e 'p $-w'
true
Kind regards
robert
On Mon, Mar 18, 2013 at 3:39 PM, Joel Pearson <lists@ruby-forum.com> wrote:
I think it's the -w command line argument for Ruby, it means show
warnings.
--
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/