## MB03QX

### Eigenvalues of an upper quasi-triangular matrix

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

Purpose

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

Specification

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

Arguments

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).

Error Indicator

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

Further Comments

      None

Example

Program Text

      None

Program Data

      None

Program Results

      None

Return to Supporting Routines index