From Troubleshoot Variables in parfor-Loops Documentation
If you run into variable classification problems, consider these approaches before you resort to the more difficult method of converting the body of a parfor-loop into a function.
If you use a nested for-loop to index into a sliced array, you cannot use that array elsewhere in the parfor-loop.
The code on the top does not work because A is sliced and indexed inside the nested for-loop.
The code on the bottom works because v is assigned to A outside the nested loop. You can compute an entire row, and then perform a single assignment into the sliced output.
Invalid
A = zeros(4, 10);
parfor i = 1:4
for j = 1:10
A(i, j) = i + j;
end
disp(A(i, 1))
end
Valid
A = zeros(4, 10);
parfor i = 1:4
v = zeros(1, 10);
for j = 1:10
v(j) = i + j;
end
disp(v(1))
A(i, :) = v;
end
