Extract data from sparse matrix in a parfor loop

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d 2017-5-29

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https://ww2.mathworks.cn/matlabcentral/answers/342337-extract-data-from-sparse-matrix-in-a-parfor-loop

Hi, I need to find eigenvectors and eigenvalues for a lot of 100*100 tri-diagonal matrices. they defined as follow:

 A_kk       = a_n  ; %      main diagonal (a_n is some vector)
 A_kk_below = b_n*f; %below main diagonal (b_n is some vector, and f is a number which differ at each matrix)
 A_kk_above = c_n*f; %above main diagonal (c_n is some vector, and f is a number which differ at each matrix)

I'm looking for a fast way to do it so my strategy was to define a large large tridiagonal sparse matrix. Then inside a parfor loop to take part of the sparse matrix and calculate its eigenvectors/values

 N=100;
 Len_f=100;
 a_ln_t=zeros(N,N,Len_f);
 parfor i=1:Len_f
        A_f = full(A((i-1)*N+(1:N),(i-1)*N+(1:N))); % take part of the sparse matrix A
        [EigV,Eig]   = eig(A_f,'vector');           % find eigenvectors/values
        [Eig,iEig]   = sort(Eig);                   % sort eigenvalues
        EigV         = EigV(:,iEig);                % sort eigenvectors
        Eig_f(:,:,i) = EigV;                        % save results in variable
 end