Behavior of parfeval when its input arguments get updated?

Hi all,

I'd like to make sure the new function parfeval (<http://www.mathworks.com/help/distcomp/parfeval.html>) meets my need before subscribing to Matlab 2013b. My question is as follows (see the example code below).

Suppose I have a variable x which is an argument to the function used in parfeval (in my example, it is @magic). As I am collecting results and updating x, will I (a) get the same results (the update of x doesn't affect parfeval), and (b) potentially get different results due to the update of x ? I'd really like to have (b) instead of (a).

    p = gcp();
    % To request multiple evaluations, use a loop.
    x = 0
    for idx = 1:10
      f(idx) = parfeval(p,@magic,1,x); % Square size determined by idx
    end

    % Collect the results as they become available.
    for idx = 1:10
      % fetchNext blocks until next results are available.
      [completedIdx,value] = fetchNext(f);
      fprintf('Got result with index: %d.\n', completedIdx);
      x = x + completedIdx; 
    end

Thanks,

Regards, Thang

Answer 1

[Edric Ellis]

The updates to 'x' will not be seen by the workers. When you call PARFEVAL, the input arguments and function are all packaged up together ready to be sent to a worker, and the value of 'x' is copied into that package. So, you'll get (a).