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Unit Triangular Matrices

Some LAPACK routines have an option to handle unit triangular matrices (that is, triangular matrices with diagonal elements = 1). This option is specified by an argument DIAG. If DIAG = 'U' (Unit triangular), the diagonal elements of the matrix need not be stored, and the corresponding array elements are not referenced by the LAPACK routines. The storage scheme for the rest of the matrix (whether conventional, packed or band) remains unchanged, as described in subsections 5.3.1, 5.3.2 and 5.3.3.

Susan Blackford