ADAS Subroutine xxeign

      SUBROUTINE XXEIGN(A,IA,N,RR,RI,VR,VI,IV1,FV1,IERR)
C-----------------------------------------------------------------------
C
C ROUTINE: XXEIGN
C
C PURPOSE: FINDS THE EIGENVALUES AND EIGENVECTORS OF A GENERAL REAL
C          MATRIX.
C
C          REPLACES NAG ROUTINE F02AGF ALTHOUGH THERE ARE SEVERAL
C          DIFFERENCES - YOU SHOULD COMPARE THE DOCUMENTATION. THIS
C          IS A FRONT-END TO THE NETLIB LIBRARY PROGRAM RG.F WHICH
C          FOLLOWS TOGETHER WITH ALL ITS DEPENDENCIES.
C
C      *** N.B. THE EIGENVECTORS ARE NOT NORMALIZED TO UNIT LENGTH ***
C
C CALLING PROGRAM: GENERAL USE
C
C INPUT:
C
C     (R*8)   A(,)    CONTAINS THE REAL GENERAL MATRIX.
C
C     (I*4)   IA      THE ROW DIMENSION OF THE TWO-DIMENSIONAL
C                     ARRAY PARAMETERS AS DECLARED IN THE CALLING
C                     PROGRAM DIMENSION STATEMENT.
C
C     (I*4)   N       THE ORDER OF THE MATRIX  A.
C     (I*4)   IV1()   WORK ARRAY, DIMENSION = N.
C     (R*4)   FV1()   WORK ARRAY, DIMENSION = N.
C
C OUTPUT:
C
C     (R*8)   RR()    REAL PART OF THE EIGENVALUES
C     (R*8)   RI()    IMAGINARY PART OF EIGENVALUES
C                     COMPLEX CONJUGATE PAIRS OF EIGENVALUES APPEAR
C                     CONSECUTIVELY WITH THE EIGENVALUE HAVING THE
C                     POSITIVE IMAGINARY PART FIRST.
C
C     (R*8)   VR(,)   REAL PARTS OF THE EIGENVECTORS. FIRST DIMENSION
C                     = IA.
C                     THE REAL PART OF THE EIGENVECTOR CORRESPONDING TO
C                     THE I-TH EIGENVALUE IS IN VR(J,I), J=1...N
C     (R*8)   VI(,)   IMAGINARY PARTS OF THE EIGENVECTORS. FIRST
C                     DIMENSION = IA
C                     THE IMAGINARY PART OF THE EIGENVECTOR
C                     CORRESPONDING TO THE I-TH EIGENVALUE IS IN
C                     VR(J,I), J=1...N
C     (I*4)   IERR    AN ERROR CODE SET TO ZERO IF NO ERROR. SEE HRQ AND
C                     HRQ2 FOR A DESCRIPTION OF THIS VARIABLE
C
C ROUTINES:
C-----------------------------------------------------------------------
C     NAME     SOURCE   PURPOSE
C-----------------------------------------------------------------------
C     RG       NETLIB   CALCULATES THE EIGENVALUES AND EIGENVECTORS
C     DPMPAR   ADAS/NETLIB   RETURNS MACHINE DEPENDANT PARAMETERS
C-----------------------------------------------------------------------
C
C AUTHOR: WILLIAM OSBORN (TESSELLA SUPPORT SERVICES PLC.)
C
C DATE:   10/06/96
C 
C VERSION 1.1                             DATE: 10/06/96
C MODIFIED: WILLIAM OSBORN
C           - FIRST VERSION
C VERSION: 1.2				     DATE:27/06/96
C MODIFIED: WILLIAM OSBORN
C	    - REMOVED UNUSED VARIABLES
C
C VERSION: 1.3				     DATE:27/06/96
C MODIFIED: WILLIAM OSBORN
C	    - ADDED PDONE VARIABLE TO ELIMINATE THE NEED FOR ASSIGNMENT
C             TO A DO-LOOP COUNTER.
C
C VERSION: 1.4				     DATE:17/05/07
C MODIFIED: Allan Whiteford
C           - Updated comments as part of subroutine documentation
C             procedure.
C
C-----------------------------------------------------------------------
C
      INTEGER             IA,          IERR,        IV1(N),      N
      REAL*8              A(IA,N),     FV1(N),      RI(N),       RR(N)
      REAL*8              VI(IA,N),    VR(IA,N)
      DOUBLE PRECISION    A(NM,N),     FV1(N),      WI(N),       WR(N)
      DOUBLE PRECISION    Z(NM,N)
      INTEGER             IERR,        IV1(N),      MATZ,        N
      INTEGER             NM
      DOUBLE PRECISION    A(NM,N),     SCALE(N)
      INTEGER             IGH,         LOW,         N,           NM
      DOUBLE PRECISION    SCALE(N),    Z(NM,M)
      INTEGER             IGH,         LOW,         M,           N
      INTEGER             NM
      DOUBLE PRECISION    AI,          AR,          BI,          BR
      DOUBLE PRECISION    CI,          CR
      DOUBLE PRECISION    A(NM,N)
      INTEGER             IGH,         INT(IGH),    LOW,         N
      INTEGER             NM
      DOUBLE PRECISION    A(NM,IGH),   Z(NM,N)
      INTEGER             IGH,         INT(IGH),    LOW,         N
      INTEGER             NM
      DOUBLE PRECISION    H(NM,N),     WI(N),       WR(N)
      INTEGER             IERR,        IGH,         LOW,         N
      INTEGER             NM
      DOUBLE PRECISION    H(NM,N),     WI(N),       WR(N),       Z(NM,N)
      INTEGER             IERR,        IGH,         LOW,         N
      INTEGER             NM