  function Feb21()

% In general no. But suppose A is symmetric and A = LDL' with
% diagonal D. If D1 is another diagonal matrix then the matrix
%
%                   A*D1 = L*(D*L'*D1)
%
% is structurally symmetric and A*D1 = L*U where  U = D*L'*D1) is upper
% triangular. In this case, L(i,j) and U(j,i) are either both zero or
% bothnonzero.
