Local variables and threads


#1

Is there a way to ensure that a particular variable really is local to a
thread block? I have a problem with a threaded program that would be
explained if one of the local variable was actually global. I’ve
checked everything I can think of…

I miss my and local from perl which allowed me to explicitly control the
scope of variables.

Russell.


#2

Russell F. wrote:

Is there a way to ensure that a particular variable really is local to a
thread block? I have a problem with a threaded program that would be
explained if one of the local variable was actually global. I’ve
checked everything I can think of…

I miss my and local from perl which allowed me to explicitly control the
scope of variables.

Only variables prefixed with $ are global ($var and so on).
It is, however, certainly possible to have shared locals
if you have something like

some_var

t1 = Thread.new { … }
t2 = Thread.new { … }

Any variables that you define inside the thread block will
be local to that thread, though.

Russell.

E


#3

Russell F. wrote:

Is there a way to ensure that a particular variable really is local
to a thread block? I have a problem with a threaded program that
would be explained if one of the local variable was actually global.
I’ve checked everything I can think of…

I miss my and local from perl which allowed me to explicitly control
the scope of variables.

A typical problem with threads can be nicely illustrated with this:

09:21:51 [~]: ruby -e 'th=[]

for i in 0 … 5
th << Thread.new do
sleep(rand(5))
puts i
end
end
th.each {|t| t.join}

2
5
5
5
5
5
09:22:21 [~]:

Problem here is that all threads share the local var ‘i’. Solution:

09:22:21 [~]: ruby -e 'th=[]

for i in 0 … 5
th << Thread.new(i) do |x|
sleep(rand(5))
puts x
end
end
th.each {|t| t.join}’
0
1
5
4
2
3

I.e. provide value(s) as arguments to Thread.new and receive them as
block
parameter(s) with different name(s).

HTH

Kind regards

robert