%% tridiagLDL.m%% Compute the LDL^T decomposition without a ymmetric% tridiagonal matrix A. The subdiagonal, the diagonal,% and the superdiagonal of A are stored as follows%%            d(1)   e(1)%            e(1)   d(2)   e(2)%                   e(2)   d(3)   e(3)      %     %                        :      :      :%%                           e(n-2)   d(n-1)   e(n-1)%                                    e(n-1)   d(n)   %%%%%% function [d, e, iflag] = tridiagLDL( d, e )%% input:%        d:     diagonal%%        e:     superdiagonal%% output:%        e:     subdiagonal of L%%        d:     diagonal od D%%        iflag: error flag%               iflag = 0  LU decomposition could be computed%               iflag = 1  dimension of c or e do not match dimension of d%               iflag > 1  zero pivot element detected in row iflag+1%function [d, e, iflag] = tridiagLDL( d, e );iflag = 0;% get size of A and check dimensionsn  = size(d(:),1);if ( n-1 > size(e(:),1) )   iflag = 1;   returnendfor i = 1:n-1   if( d(i) == 0 )        iflag = i+1;       return   end    tmp    = e(i);   e(i)   = e(i) / d(i);   d(i+1) = d(i+1) - tmp * e(i);end