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zgeev examples
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Man Page Details
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ZGEEV computes the eigenvalues and, optionally, the left and/or right
eigenvectors for GE matrices

 Online html documentation available at 
            http://www.netlib.org/lapack/explore-html/ 

 Definition:
 ===========

       SUBROUTINE ZGEEV( JOBVL, JOBVR, N, A, LDA, W, VL, LDVL, VR, LDVR,
                         WORK, LWORK, RWORK, INFO )
 
       .. Scalar Arguments ..
       CHARACTER          JOBVL, JOBVR
       INTEGER            INFO, LDA, LDVL, LDVR, LWORK, N
       ..
       .. Array Arguments ..
       DOUBLE PRECISION   RWORK( * )
       COMPLEX*16         A( LDA, * ), VL( LDVL, * ), VR( LDVR, * ),
      $                   W( * ), WORK( * )
       ..
  

 Purpose:
 =============

  ZGEEV computes for an N-by-N complex nonsymmetric matrix A, the
  eigenvalues and, optionally, the left and/or right eigenvectors.

  The right eigenvector v(j) of A satisfies
                    A * v(j) = lambda(j) * v(j)
   where lambda(j) is its eigenvalue.
  The left eigenvector u(j) of A satisfies
               u(j)**H * A = lambda(j) * u(j)**H
   where u(j)**H denotes the conjugate transpose of u(j).

 The computed eigenvectors are normalized to have Euclidean norm
 equal to 1 and largest component real.

 Arguments:
 ==========

  [in] JOBVL

          JOBVL is CHARACTER*1
          = 'N': left eigenvectors of A are not computed;
          = 'V': left eigenvectors of are computed.

  [in] JOBVR

          JOBVR is CHARACTER*1
          = 'N': right eigenvectors of A are not computed;
          = 'V': right eigenvectors of A are computed.

  [in] N

          N is INTEGER
          The order of the matrix A. N >= 0.

  [in,out] A

          A is COMPLEX*16 array, dimension (LDA,N)
          On entry, the N-by-N matrix A.
          On exit, A has been overwritten.

  [in] LDA

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

  [out] W

          W is COMPLEX*16 array, dimension (N)
          W contains the computed eigenvalues.

  [out] VL

          VL is COMPLEX*16 array, dimension (LDVL,N)
          If JOBVL = 'V', the left eigenvectors u(j) are stored one
          after another in the columns of VL, in the same order
          as their eigenvalues.
          If JOBVL = 'N', VL is not referenced.
          u(j) = VL(:,j), the j-th column of VL.

  [in] LDVL

          LDVL is INTEGER
          The leading dimension of the array VL.  LDVL >= 1; if
          JOBVL = 'V', LDVL >= N.

  [out] VR

          VR is COMPLEX*16 array, dimension (LDVR,N)
          If JOBVR = 'V', the right eigenvectors v(j) are stored one
          after another in the columns of VR, in the same order
          as their eigenvalues.
          If JOBVR = 'N', VR is not referenced.
          v(j) = VR(:,j), the j-th column of VR.

  [in] LDVR

          LDVR is INTEGER
          The leading dimension of the array VR.  LDVR >= 1; if
          JOBVR = 'V', LDVR >= N.

  [out] WORK

          WORK is COMPLEX*16 array, dimension (MAX(1,LWORK))
          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.

  [in] LWORK

          LWORK is INTEGER
          The dimension of the array WORK.  LWORK >= max(1,2*N).
          For good performance, LWORK must generally be larger.

          If LWORK = -1, then a workspace query is assumed; the routine
          only calculates the optimal size of the WORK array, returns
          this value as the first entry of the WORK array, and no error
          message related to LWORK is issued by XERBLA.

  [out] RWORK

          RWORK is DOUBLE PRECISION array, dimension (2*N)

  [out] INFO

          INFO is INTEGER
          = 0:  successful exit
          < 0:  if INFO = -i, the i-th argument had an illegal value.
          > 0:  if INFO = i, the QR algorithm failed to compute all the
                eigenvalues, and no eigenvectors have been computed;
                elements and i+1:N of W contain eigenvalues which have
                converged.


 Authors:
 ========

   Univ. of Tennessee 
   Univ. of California Berkeley 
   Univ. of Colorado Denver 
   NAG Ltd. 

 November 2011

