## MA02OD

### Compute the number of zero rows (and zero columns) of a real (skew-)Hamiltonian matrix

[Specification] [Arguments] [Method] [References] [Comments] [Example]

Purpose

      To compute the number of zero rows (and zero columns) of a real
      (skew-)Hamiltonian matrix,

            (  A    D   )
        H = (           ).
            (  E  +/-A' )

Specification

          INTEGER FUNCTION MA02OD( SKEW, M, A, LDA, DE, LDDE )
    C     .. Scalar Arguments ..
          CHARACTER          SKEW
          INTEGER            LDA, LDDE, M
    C     .. Array Arguments ..
          DOUBLE PRECISION   A( LDA, * ), DE( LDDE, * )

Function Value

      MA02OD  INTEGER
              The number of zero rows.

Arguments

Mode Parameters

      SKEW    CHARACTER*1
              Specifies whether the matrix is Hamiltonian or skew-
              Hamiltonian as follows:
              = 'H':  The matrix is Hamiltonian;
              = 'S':  The matrix is skew-Hamiltonian.

Input/Output Parameters

      M       (input) INTEGER
              The order of the matrices A, D, and E.  M >= 0.

      A       (input) DOUBLE PRECISION array, dimension (LDA,M)
              The leading M-by-M part of this array must contain the
              matrix A.

      LDA     INTEGER
              The leading dimension of the array A.  LDA >= max(1,M).

      DE      (input) DOUBLE PRECISION array, dimension (LDDE,M+1)
              The leading M-by-M lower triangular part of this array
              must contain the lower triangular part of the (skew-)
              symmetric matrix E, and the M-by-M upper triangular
              part of the submatrix in the columns 2 to M+1 of this
              array must contain the upper triangular part of the
              (skew-)symmetric matrix D. If S is skew-Hamiltonian, the
              parts containing the diagonal and the first superdiagonal
              of this array, which should be zero, are not referenced.

      LDDE    INTEGER
              The leading dimension of the array DE.  LDDE >= MAX(1,M).

Further Comments

      None

Example

Program Text

      None

Program Data

      None

Program Results

      None

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