Hi Federico,
I understand that you are encountering a warning message while using "parfor" in your code.
The warning message is due to the dependency of different parallel pool workers on the same variables, which are accessed by multiple workers at the same time. It is recommended to copy these common variables into local variables in the loop and use local variables for accessing data while running the parallel for loop.
The following code demonstrates this:
% I assumed that variable B_mat and C_mat are already defined.
N_RIPETIZIONI=2;
K=201;
parfor n=1:N_RIPETIZIONI*K
matB = B_mat;
matC = C_mat;
[r,k]=ind2sub([N_RIPETIZIONI,K],n);
B=matB{r};
C=matC{r};
end