Is this combination of parfor and global variables prone to errors?

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Mitsu
Mitsu on 26 Oct 2021
Commented: Mitsu on 26 Oct 2021
In the main script mainScript.m, a parfor loop goes through N cases.
In each case of the parfor loop, the function principalFunction() is called.
%mainScript.m
parfor i = 1:N
someInputData = inputData(i,:);
results(i,1) = principalFunction(someInputData);
end
No global variables are declared or used anywhere in this file.
However, principalFunction() is a function that will declare global variables, and share them across function1, ..., functionN that will be called within principalFunction(). These functions will use the global variables along with any local variables passed.
%principalFunction.m
function result = principalFunction(someInputData)
global globalVariable1 globalVariable 2
% Call some functions where local variables are passed, and which will use
% global variables as well
localVariable1 = function1(someInputData);
localVariable2 = function2(someInputData,localVariable1);
localVariable3 = function3(someInputData);
result = functionN(localVariable1,localVariable2,localVariable3);
end
Most functions are part of a third-party library, and rewritting them to avoid using global variables is not an option.
I have tried a number of cases in parallel and in series for N < 30, and it seems to yield the same results.
However, I would still like to know for sure that there is nothing I am overlooking in this approach. Is there?

Accepted Answer

Walter Roberson
Walter Roberson on 26 Oct 2021
That should work, as long as the principal function sets the global variables on every call, or at least tests whether they already exist non-empty and if not then assigns to them.
  1 Comment
Mitsu
Mitsu on 26 Oct 2021
Yes, they are initialized in the principal function before they are used anywhere else. Thank you.

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