MB03QX

Eigenvalues of an upper quasi-triangular matrix

Purpose

  To compute the eigenvalues of an upper quasi-triangular matrix.

      SUBROUTINE MB03QX( N, T, LDT, WR, WI, INFO )
C     .. Scalar Arguments ..
      INTEGER          INFO, LDT, N
C     .. Array Arguments ..
      DOUBLE PRECISION T(LDT, *), WI(*), WR(*)

Input/Output Parameters

  N       (input) INTEGER
          The order of the matrix T.  N >= 0.

  T       (input) DOUBLE PRECISION array, dimension(LDT,N)
          The upper quasi-triangular matrix T.

  LDT     INTEGER
          The leading dimension of the array T.  LDT >= max(1,N).

  WR, WI  (output) DOUBLE PRECISION arrays, dimension (N)
          The real and imaginary parts, respectively, of the
          eigenvalues of T. The eigenvalues are stored in the same
          order as on the diagonal of T. If T(i:i+1,i:i+1) is a
          2-by-2 diagonal block with complex conjugated eigenvalues
          then WI(i) > 0 and WI(i+1) = -WI(i).

  INFO    INTEGER
          = 0:  successful exit;
          < 0:  if INFO = -i, the i-th argument had an illegal
                value.

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Program Text

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