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##

Real Diagonal Elements of Complex Matrices

Complex Hermitian matrices
have diagonal matrices that are by definition
purely real. In addition, some complex triangular matrices computed by
LAPACK routines are defined by the algorithm to have real diagonal elements
-- in Cholesky or *QR* factorization, for example.

If such matrices are supplied as input to LAPACK routines,
the imaginary parts of the diagonal elements are not referenced,
but are assumed to be zero. If such matrices are returned as output by LAPACK
routines, the computed imaginary parts are explicitly set to zero.

*Susan Blackford*

*1999-10-01*