d3/d37/pyeicg_8f_source.html

C*********************************************************************


C...PYEIGC

C...Finds eigenvalues of a general complex matrix

C

C     THIS SUBROUTINE CALLS THE RECOMMENDED SEQUENCE OF

C     SUBROUTINES FROM THE EIGENSYSTEM SUBROUTINE PACKAGE (EISPACK)

C     TO FIND THE EIGENVALUES AND EIGENVECTORS (IF DESIRED)

C     OF A COMPLEX GENERAL MATRIX.

C

C     ON INPUT

C

C        NM  MUST BE SET TO THE ROW DIMENSION OF THE TWO-DIMENSIONAL

C        ARRAY PARAMETERS AS DECLARED IN THE CALLING PROGRAM

C        DIMENSION STATEMENT.

C

C        N  IS THE ORDER OF THE MATRIX  A=(AR,AI).

C

C        AR  AND  AI  CONTAIN THE REAL AND IMAGINARY PARTS,

C        RESPECTIVELY, OF THE COMPLEX GENERAL MATRIX.

C

C        MATZ  IS AN INTEGER VARIABLE SET EQUAL TO ZERO IF

C        ONLY EIGENVALUES ARE DESIRED.  OTHERWISE IT IS SET TO

C        ANY NON-ZERO INTEGER FOR BOTH EIGENVALUES AND EIGENVECTORS.

C

C     ON OUTPUT

C

C        WR  AND  WI  CONTAIN THE REAL AND IMAGINARY PARTS,

C        RESPECTIVELY, OF THE EIGENVALUES.

C

C        ZR  AND  ZI  CONTAIN THE REAL AND IMAGINARY PARTS,

C        RESPECTIVELY, OF THE EIGENVECTORS IF MATZ IS NOT ZERO.

C

C        IERR  IS AN INTEGER OUTPUT VARIABLE SET EQUAL TO AN ERROR

C           COMPLETION CODE DESCRIBED IN THE DOCUMENTATION FOR COMQR

C           AND COMQR2.  THE NORMAL COMPLETION CODE IS ZERO.

C

C        FV1, FV2, AND  FV3  ARE TEMPORARY STORAGE ARRAYS.

C

C     QUESTIONS AND COMMENTS SHOULD BE DIRECTED TO BURTON S. GARBOW,

C     MATHEMATICS AND COMPUTER SCIENCE DIV, ARGONNE NATIONAL LABORATORY

C

C     THIS VERSION DATED AUGUST 1983.

C


      SUBROUTINE pyeicg(NM,N,AR,AI,WR,WI,MATZ,ZR,ZI,FV1,FV2,FV3,IERR)


      INTEGER n,nm,is1,is2,ierr,matz

      DOUBLE PRECISION ar(4,4),ai(4,4),wr(4),wi(4),zr(4,4),zi(4,4),

     x       fv1(4),fv2(4),fv3(4)

      IF (n .LE. nm) goto 100

      ierr = 10 * n

      goto 120

C

  100 CALL  pycbal(nm,n,ar,ai,is1,is2,fv1)

      CALL  pycrth(nm,n,is1,is2,ar,ai,fv2,fv3)

      IF (matz .NE. 0) goto 110

C     .......... FIND EIGENVALUES ONLY ..........

      CALL  pycmqr(nm,n,is1,is2,ar,ai,wr,wi,ierr)

      goto 120

C     .......... FIND BOTH EIGENVALUES AND EIGENVECTORS ..........

  110 CALL  pycmq2(nm,n,is1,is2,fv2,fv3,ar,ai,wr,wi,zr,zi,ierr)

      IF (ierr .NE. 0) goto 120

      CALL  pycba2(nm,n,is1,is2,fv1,n,zr,zi)

  120 RETURN

      END