parfor loop output and input are not matched in order

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I have a code segment here:
so I wish to use parfor to calculate a function called OFreduced. The OFreduced takes in 10 numbers each time as input.
I have stored all input variables in modified_geo as a matrix of 3*10, where each entire row is one input to the function. So in total I have 3 sets of input that are needed to be calculated in parfor.
The output from the function OFreduced is simply just a number, and I stored that in another array v, which should contain the 3 results from the input.
It should produce three different answers and stored in v, and I could perfectly run this in serial with no problem. However parfor gives me the same number for the three inputs (i.e. three numbers are indentical in v). It seems like I have not matched the input index to the output index, and the results are "overwriting".
Please advise how shall I modify this to "match" the outputs and the inputs in the correct order. Many thanks in advance!
% compute cost using simplified OF
modified_cost1 = zeros(3,1);
v = zeros(3,1);
% run OF with temporary variable
parfor j = 1:3
v(j) = OFreduced(modified_geo(j,:));
modified_cost1 = v(1,1:3);

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Accepted Answer

Rik on 23 Jan 2023
I suspect the source of the problem is the interaction with the file system.
You should consider generating a random file name (either with randi indexing from allowed characters, or with tempname). That way you ensure you don't overwrite the file that the other process is using.
I would suggest avoiding cd if at all possible. You can use tempdir if you need the temp folder location.

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