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Functionality of put!, take!, and Channels
3 posts by 1 author  



michael 	

Mar 8


I'm fairly new to parallel processing but I'm trying to use Channels in a way I think is consistent with the documentation but I may be misinterpreting it. I've explained in more detail in a StackOverflow post but essentially what I'm trying to do is have an integer variable that several processes can access and, if one returns an integer smaller than that variable, can update. The general approach is something like this:

x = Channel{Int64}(1)
put!(x,n)

@everywhere function f(item,chan)
    going = true
    count = 0
    while(going)
        going = false
        # perform some operations
        if (count < fetch(chan) && !conditions_met())
            # conditions_met checks the other termination conditions
            going = true
            count += 1
        end
    end

    count += 1

    if (count < fetch(chan))
        take!(chan)
        put!(chan,count)
    end

    return count
end

y = @parallel (min) for i in collection
    f(i,x)
end

Am I correct in my logic? Is this something I should be able to do?
 


michael 	

Mar 10


At the suggestion of @axsk I tried this again but using a SharedArray instead of a channel and it seems to be working now. I am curious as to why my approach didn't work, if anyone cares to explain.

(I'm on v0.4.3)
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michael 	

Mar 11


Going off of an answer on StackOverflow using RemoteRef instead of Channel works as well. The answerer points out the reason why the latter doesn't work.
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