What is causing this intermittent error in parfor?

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Chris
Chris 2025-12-8，21:59
编辑： Matt J 2025-12-9，13:04
The attached script produces an intermittent error:
Increasing n in untitled_script.m appears to increase the likelihood of the error occuring. Replacing parfor with for prevents the error from occuring. Setting n=1 prevents the error from occuring. Replacing "test(ii,1)=Test(input,ii);" with "Test(input,ii);" prevents the error from occuring.
Anyone understand what is going on here?
  1 个评论
Chris
Chris 2025-12-8，22:10
Replacing "test(ii,1)=Test(input,ii);" with "test{ii}=Test(input,ii);" also appears to prevent the error from occuring.

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采纳的回答

Matt J
Matt J 2025-12-9，0:56
编辑：Matt J 2025-12-9，1:04
If you add the indicated line, your class constructor will support no-argument calls, and the error will go away:
function obj = Test(inputArg1,ii)
arguments
inputArg1
ii = 2
end
if ~nargin, return; end %<---- Add this
display(num2str(ii))
obj = obj.method1(inputArg1);
end
This is necessary because the loop variable values ii in a parfor loop will not be visited in in sequential order, meaning that certain elements in the vector test will need to be populated temporarily with argument-free constructor calls.
  2 个评论
Matt J
Matt J 2025-12-9，1:01
编辑：Matt J 2025-12-9，1:05
Alternattively (and perhaps preferably), pre-allocate the test array,
input.test_field=1;
input.test_field2=1;
n=3;
test(1:n,1)=Test(input); %<--- pre-allocate
parfor ii=1:n
test(ii,1)=Test(input,ii);
end

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