592 lines
		
	
	
		
			19 KiB
		
	
	
	
		
			Fortran
		
	
	
	
			
		
		
	
	
			592 lines
		
	
	
		
			19 KiB
		
	
	
	
		
			Fortran
		
	
	
	
*> \brief <b> DGGEV3 computes the eigenvalues and, optionally, the left and/or right eigenvectors for GE matrices (blocked algorithm)</b>
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*
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*  =========== DOCUMENTATION ===========
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*
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* Online html documentation available at
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*            http://www.netlib.org/lapack/explore-html/
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*
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*> \htmlonly
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*> Download DGGEV3 + dependencies
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dggev3.f">
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*> [TGZ]</a>
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dggev3.f">
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*> [ZIP]</a>
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dggev3.f">
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*> [TXT]</a>
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*> \endhtmlonly
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*
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*  Definition:
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*  ===========
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*
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*       SUBROUTINE DGGEV3( JOBVL, JOBVR, N, A, LDA, B, LDB, ALPHAR,
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*      $                   ALPHAI, BETA, VL, LDVL, VR, LDVR, WORK, LWORK,
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*      $                   INFO )
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*
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*       .. Scalar Arguments ..
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*       CHARACTER          JOBVL, JOBVR
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*       INTEGER            INFO, LDA, LDB, LDVL, LDVR, LWORK, N
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*       ..
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*       .. Array Arguments ..
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*       DOUBLE PRECISION   A( LDA, * ), ALPHAI( * ), ALPHAR( * ),
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*      $                   B( LDB, * ), BETA( * ), VL( LDVL, * ),
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*      $                   VR( LDVR, * ), WORK( * )
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*       ..
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*
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*
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*> \par Purpose:
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*  =============
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*>
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*> \verbatim
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*>
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*> DGGEV3 computes for a pair of N-by-N real nonsymmetric matrices (A,B)
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*> the generalized eigenvalues, and optionally, the left and/or right
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*> generalized eigenvectors.
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*>
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*> A generalized eigenvalue for a pair of matrices (A,B) is a scalar
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*> lambda or a ratio alpha/beta = lambda, such that A - lambda*B is
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*> singular. It is usually represented as the pair (alpha,beta), as
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*> there is a reasonable interpretation for beta=0, and even for both
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*> being zero.
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*>
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*> The right eigenvector v(j) corresponding to the eigenvalue lambda(j)
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*> of (A,B) satisfies
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*>
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*>                  A * v(j) = lambda(j) * B * v(j).
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*>
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*> The left eigenvector u(j) corresponding to the eigenvalue lambda(j)
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*> of (A,B) satisfies
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*>
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*>                  u(j)**H * A  = lambda(j) * u(j)**H * B .
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*>
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*> where u(j)**H is the conjugate-transpose of u(j).
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*>
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*> \endverbatim
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*
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*  Arguments:
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*  ==========
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*
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*> \param[in] JOBVL
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*> \verbatim
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*>          JOBVL is CHARACTER*1
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*>          = 'N':  do not compute the left generalized eigenvectors;
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*>          = 'V':  compute the left generalized eigenvectors.
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*> \endverbatim
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*>
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*> \param[in] JOBVR
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*> \verbatim
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*>          JOBVR is CHARACTER*1
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*>          = 'N':  do not compute the right generalized eigenvectors;
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*>          = 'V':  compute the right generalized eigenvectors.
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*> \endverbatim
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*>
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*> \param[in] N
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*> \verbatim
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*>          N is INTEGER
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*>          The order of the matrices A, B, VL, and VR.  N >= 0.
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*> \endverbatim
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*>
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*> \param[in,out] A
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*> \verbatim
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*>          A is DOUBLE PRECISION array, dimension (LDA, N)
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*>          On entry, the matrix A in the pair (A,B).
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*>          On exit, A has been overwritten.
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*> \endverbatim
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*>
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*> \param[in] LDA
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*> \verbatim
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*>          LDA is INTEGER
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*>          The leading dimension of A.  LDA >= max(1,N).
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*> \endverbatim
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*>
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*> \param[in,out] B
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*> \verbatim
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*>          B is DOUBLE PRECISION array, dimension (LDB, N)
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*>          On entry, the matrix B in the pair (A,B).
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*>          On exit, B has been overwritten.
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*> \endverbatim
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*>
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*> \param[in] LDB
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*> \verbatim
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*>          LDB is INTEGER
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*>          The leading dimension of B.  LDB >= max(1,N).
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*> \endverbatim
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*>
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*> \param[out] ALPHAR
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*> \verbatim
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*>          ALPHAR is DOUBLE PRECISION array, dimension (N)
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*> \endverbatim
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*>
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*> \param[out] ALPHAI
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*> \verbatim
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*>          ALPHAI is DOUBLE PRECISION array, dimension (N)
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*> \endverbatim
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*>
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*> \param[out] BETA
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*> \verbatim
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*>          BETA is DOUBLE PRECISION array, dimension (N)
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*>          On exit, (ALPHAR(j) + ALPHAI(j)*i)/BETA(j), j=1,...,N, will
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*>          be the generalized eigenvalues.  If ALPHAI(j) is zero, then
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*>          the j-th eigenvalue is real; if positive, then the j-th and
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*>          (j+1)-st eigenvalues are a complex conjugate pair, with
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*>          ALPHAI(j+1) negative.
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*>
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*>          Note: the quotients ALPHAR(j)/BETA(j) and ALPHAI(j)/BETA(j)
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*>          may easily over- or underflow, and BETA(j) may even be zero.
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*>          Thus, the user should avoid naively computing the ratio
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*>          alpha/beta.  However, ALPHAR and ALPHAI will be always less
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*>          than and usually comparable with norm(A) in magnitude, and
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*>          BETA always less than and usually comparable with norm(B).
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*> \endverbatim
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*>
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*> \param[out] VL
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*> \verbatim
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*>          VL is DOUBLE PRECISION array, dimension (LDVL,N)
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*>          If JOBVL = 'V', the left eigenvectors u(j) are stored one
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*>          after another in the columns of VL, in the same order as
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*>          their eigenvalues. If the j-th eigenvalue is real, then
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*>          u(j) = VL(:,j), the j-th column of VL. If the j-th and
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*>          (j+1)-th eigenvalues form a complex conjugate pair, then
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*>          u(j) = VL(:,j)+i*VL(:,j+1) and u(j+1) = VL(:,j)-i*VL(:,j+1).
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*>          Each eigenvector is scaled so the largest component has
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*>          abs(real part)+abs(imag. part)=1.
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*>          Not referenced if JOBVL = 'N'.
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*> \endverbatim
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*>
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*> \param[in] LDVL
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*> \verbatim
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*>          LDVL is INTEGER
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*>          The leading dimension of the matrix VL. LDVL >= 1, and
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*>          if JOBVL = 'V', LDVL >= N.
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*> \endverbatim
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*>
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*> \param[out] VR
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*> \verbatim
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*>          VR is DOUBLE PRECISION array, dimension (LDVR,N)
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*>          If JOBVR = 'V', the right eigenvectors v(j) are stored one
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*>          after another in the columns of VR, in the same order as
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*>          their eigenvalues. If the j-th eigenvalue is real, then
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*>          v(j) = VR(:,j), the j-th column of VR. If the j-th and
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*>          (j+1)-th eigenvalues form a complex conjugate pair, then
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*>          v(j) = VR(:,j)+i*VR(:,j+1) and v(j+1) = VR(:,j)-i*VR(:,j+1).
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*>          Each eigenvector is scaled so the largest component has
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*>          abs(real part)+abs(imag. part)=1.
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*>          Not referenced if JOBVR = 'N'.
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*> \endverbatim
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*>
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*> \param[in] LDVR
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*> \verbatim
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*>          LDVR is INTEGER
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*>          The leading dimension of the matrix VR. LDVR >= 1, and
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*>          if JOBVR = 'V', LDVR >= N.
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*> \endverbatim
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*>
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*> \param[out] WORK
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*> \verbatim
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*>          WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK))
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*>          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
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*> \endverbatim
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*>
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*> \param[in] LWORK
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*> \verbatim
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*>          LWORK is INTEGER
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*>
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*>          If LWORK = -1, then a workspace query is assumed; the routine
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*>          only calculates the optimal size of the WORK array, returns
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*>          this value as the first entry of the WORK array, and no error
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*>          message related to LWORK is issued by XERBLA.
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*> \endverbatim
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*>
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*> \param[out] INFO
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*> \verbatim
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*>          INFO is INTEGER
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*>          = 0:  successful exit
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*>          < 0:  if INFO = -i, the i-th argument had an illegal value.
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*>          = 1,...,N:
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*>                The QZ iteration failed.  No eigenvectors have been
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*>                calculated, but ALPHAR(j), ALPHAI(j), and BETA(j)
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*>                should be correct for j=INFO+1,...,N.
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*>          > N:  =N+1: other than QZ iteration failed in DLAQZ0.
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*>                =N+2: error return from DTGEVC.
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*> \endverbatim
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*
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*  Authors:
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*  ========
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*
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*> \author Univ. of Tennessee
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*> \author Univ. of California Berkeley
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*> \author Univ. of Colorado Denver
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*> \author NAG Ltd.
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*
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*> \ingroup doubleGEeigen
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*
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*  =====================================================================
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      SUBROUTINE DGGEV3( JOBVL, JOBVR, N, A, LDA, B, LDB, ALPHAR,
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     $                   ALPHAI, BETA, VL, LDVL, VR, LDVR, WORK, LWORK,
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     $                   INFO )
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*
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*  -- LAPACK driver routine --
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*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
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*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
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*
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*     .. Scalar Arguments ..
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      CHARACTER          JOBVL, JOBVR
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      INTEGER            INFO, LDA, LDB, LDVL, LDVR, LWORK, N
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*     ..
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*     .. Array Arguments ..
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      DOUBLE PRECISION   A( LDA, * ), ALPHAI( * ), ALPHAR( * ),
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     $                   B( LDB, * ), BETA( * ), VL( LDVL, * ),
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     $                   VR( LDVR, * ), WORK( * )
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*     ..
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*
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*  =====================================================================
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*
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*     .. Parameters ..
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      DOUBLE PRECISION   ZERO, ONE
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      PARAMETER          ( ZERO = 0.0D+0, ONE = 1.0D+0 )
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*     ..
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*     .. Local Scalars ..
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      LOGICAL            ILASCL, ILBSCL, ILV, ILVL, ILVR, LQUERY
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      CHARACTER          CHTEMP
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      INTEGER            ICOLS, IERR, IHI, IJOBVL, IJOBVR, ILEFT, ILO,
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     $                   IN, IRIGHT, IROWS, ITAU, IWRK, JC, JR, LWKOPT
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      DOUBLE PRECISION   ANRM, ANRMTO, BIGNUM, BNRM, BNRMTO, EPS,
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     $                   SMLNUM, TEMP
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*     ..
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*     .. Local Arrays ..
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      LOGICAL            LDUMMA( 1 )
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*     ..
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*     .. External Subroutines ..
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      EXTERNAL           DGEQRF, DGGBAK, DGGBAL, DGGHD3, DLAQZ0, DLABAD,
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     $                   DLACPY, DLASCL, DLASET, DORGQR, DORMQR, DTGEVC,
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     $                   XERBLA
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*     ..
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*     .. External Functions ..
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      LOGICAL            LSAME
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      DOUBLE PRECISION   DLAMCH, DLANGE
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      EXTERNAL           LSAME, DLAMCH, DLANGE
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*     ..
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*     .. Intrinsic Functions ..
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      INTRINSIC          ABS, MAX, SQRT
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*     ..
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*     .. Executable Statements ..
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*
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*     Decode the input arguments
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*
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      IF( LSAME( JOBVL, 'N' ) ) THEN
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         IJOBVL = 1
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         ILVL = .FALSE.
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      ELSE IF( LSAME( JOBVL, 'V' ) ) THEN
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         IJOBVL = 2
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         ILVL = .TRUE.
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      ELSE
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         IJOBVL = -1
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         ILVL = .FALSE.
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      END IF
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*
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      IF( LSAME( JOBVR, 'N' ) ) THEN
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         IJOBVR = 1
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         ILVR = .FALSE.
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      ELSE IF( LSAME( JOBVR, 'V' ) ) THEN
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         IJOBVR = 2
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         ILVR = .TRUE.
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      ELSE
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         IJOBVR = -1
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         ILVR = .FALSE.
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      END IF
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      ILV = ILVL .OR. ILVR
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*
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*     Test the input arguments
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*
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      INFO = 0
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      LQUERY = ( LWORK.EQ.-1 )
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      IF( IJOBVL.LE.0 ) THEN
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         INFO = -1
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      ELSE IF( IJOBVR.LE.0 ) THEN
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         INFO = -2
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      ELSE IF( N.LT.0 ) THEN
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         INFO = -3
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      ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
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         INFO = -5
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      ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
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         INFO = -7
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      ELSE IF( LDVL.LT.1 .OR. ( ILVL .AND. LDVL.LT.N ) ) THEN
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         INFO = -12
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      ELSE IF( LDVR.LT.1 .OR. ( ILVR .AND. LDVR.LT.N ) ) THEN
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         INFO = -14
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      ELSE IF( LWORK.LT.MAX( 1, 8*N ) .AND. .NOT.LQUERY ) THEN
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         INFO = -16
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      END IF
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*
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*     Compute workspace
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*
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      IF( INFO.EQ.0 ) THEN
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         CALL DGEQRF( N, N, B, LDB, WORK, WORK, -1, IERR )
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         LWKOPT = MAX(1, 8*N, 3*N+INT( WORK( 1 ) ) )
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         CALL DORMQR( 'L', 'T', N, N, N, B, LDB, WORK, A, LDA, WORK, -1,
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     $                IERR )
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         LWKOPT = MAX( LWKOPT, 3*N+INT( WORK ( 1 ) ) )
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         IF( ILVL ) THEN
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            CALL DORGQR( N, N, N, VL, LDVL, WORK, WORK, -1, IERR )
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            LWKOPT = MAX( LWKOPT, 3*N+INT( WORK ( 1 ) ) )
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         END IF
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         IF( ILV ) THEN
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            CALL DGGHD3( JOBVL, JOBVR, N, 1, N, A, LDA, B, LDB, VL,
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     $                   LDVL, VR, LDVR, WORK, -1, IERR )
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            LWKOPT = MAX( LWKOPT, 3*N+INT( WORK ( 1 ) ) )
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            CALL DLAQZ0( 'S', JOBVL, JOBVR, N, 1, N, A, LDA, B, LDB,
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     $                   ALPHAR, ALPHAI, BETA, VL, LDVL, VR, LDVR,
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     $                   WORK, -1, 0, IERR )
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            LWKOPT = MAX( LWKOPT, 2*N+INT( WORK ( 1 ) ) )
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         ELSE
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            CALL DGGHD3( 'N', 'N', N, 1, N, A, LDA, B, LDB, VL, LDVL,
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     $                   VR, LDVR, WORK, -1, IERR )
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            LWKOPT = MAX( LWKOPT, 3*N+INT( WORK ( 1 ) ) )
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            CALL DLAQZ0( 'E', JOBVL, JOBVR, N, 1, N, A, LDA, B, LDB,
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     $                   ALPHAR, ALPHAI, BETA, VL, LDVL, VR, LDVR,
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     $                   WORK, -1, 0, IERR )
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            LWKOPT = MAX( LWKOPT, 2*N+INT( WORK ( 1 ) ) )
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         END IF
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         WORK( 1 ) = LWKOPT
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      END IF
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*
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      IF( INFO.NE.0 ) THEN
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         CALL XERBLA( 'DGGEV3 ', -INFO )
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         RETURN
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      ELSE IF( LQUERY ) THEN
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         RETURN
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      END IF
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*
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*     Quick return if possible
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*
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      IF( N.EQ.0 )
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     $   RETURN
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*
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*     Get machine constants
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*
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      EPS = DLAMCH( 'P' )
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      SMLNUM = DLAMCH( 'S' )
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      BIGNUM = ONE / SMLNUM
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      CALL DLABAD( SMLNUM, BIGNUM )
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      SMLNUM = SQRT( SMLNUM ) / EPS
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      BIGNUM = ONE / SMLNUM
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*
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*     Scale A if max element outside range [SMLNUM,BIGNUM]
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*
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      ANRM = DLANGE( 'M', N, N, A, LDA, WORK )
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      ILASCL = .FALSE.
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      IF( ANRM.GT.ZERO .AND. ANRM.LT.SMLNUM ) THEN
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         ANRMTO = SMLNUM
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         ILASCL = .TRUE.
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      ELSE IF( ANRM.GT.BIGNUM ) THEN
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         ANRMTO = BIGNUM
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         ILASCL = .TRUE.
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      END IF
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      IF( ILASCL )
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     $   CALL DLASCL( 'G', 0, 0, ANRM, ANRMTO, N, N, A, LDA, IERR )
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*
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*     Scale B if max element outside range [SMLNUM,BIGNUM]
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*
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      BNRM = DLANGE( 'M', N, N, B, LDB, WORK )
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      ILBSCL = .FALSE.
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      IF( BNRM.GT.ZERO .AND. BNRM.LT.SMLNUM ) THEN
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						|
         BNRMTO = SMLNUM
 | 
						|
         ILBSCL = .TRUE.
 | 
						|
      ELSE IF( BNRM.GT.BIGNUM ) THEN
 | 
						|
         BNRMTO = BIGNUM
 | 
						|
         ILBSCL = .TRUE.
 | 
						|
      END IF
 | 
						|
      IF( ILBSCL )
 | 
						|
     $   CALL DLASCL( 'G', 0, 0, BNRM, BNRMTO, N, N, B, LDB, IERR )
 | 
						|
*
 | 
						|
*     Permute the matrices A, B to isolate eigenvalues if possible
 | 
						|
*
 | 
						|
      ILEFT = 1
 | 
						|
      IRIGHT = N + 1
 | 
						|
      IWRK = IRIGHT + N
 | 
						|
      CALL DGGBAL( 'P', N, A, LDA, B, LDB, ILO, IHI, WORK( ILEFT ),
 | 
						|
     $             WORK( IRIGHT ), WORK( IWRK ), IERR )
 | 
						|
*
 | 
						|
*     Reduce B to triangular form (QR decomposition of B)
 | 
						|
*
 | 
						|
      IROWS = IHI + 1 - ILO
 | 
						|
      IF( ILV ) THEN
 | 
						|
         ICOLS = N + 1 - ILO
 | 
						|
      ELSE
 | 
						|
         ICOLS = IROWS
 | 
						|
      END IF
 | 
						|
      ITAU = IWRK
 | 
						|
      IWRK = ITAU + IROWS
 | 
						|
      CALL DGEQRF( IROWS, ICOLS, B( ILO, ILO ), LDB, WORK( ITAU ),
 | 
						|
     $             WORK( IWRK ), LWORK+1-IWRK, IERR )
 | 
						|
*
 | 
						|
*     Apply the orthogonal transformation to matrix A
 | 
						|
*
 | 
						|
      CALL DORMQR( 'L', 'T', IROWS, ICOLS, IROWS, B( ILO, ILO ), LDB,
 | 
						|
     $             WORK( ITAU ), A( ILO, ILO ), LDA, WORK( IWRK ),
 | 
						|
     $             LWORK+1-IWRK, IERR )
 | 
						|
*
 | 
						|
*     Initialize VL
 | 
						|
*
 | 
						|
      IF( ILVL ) THEN
 | 
						|
         CALL DLASET( 'Full', N, N, ZERO, ONE, VL, LDVL )
 | 
						|
         IF( IROWS.GT.1 ) THEN
 | 
						|
            CALL DLACPY( 'L', IROWS-1, IROWS-1, B( ILO+1, ILO ), LDB,
 | 
						|
     $                   VL( ILO+1, ILO ), LDVL )
 | 
						|
         END IF
 | 
						|
         CALL DORGQR( IROWS, IROWS, IROWS, VL( ILO, ILO ), LDVL,
 | 
						|
     $                WORK( ITAU ), WORK( IWRK ), LWORK+1-IWRK, IERR )
 | 
						|
      END IF
 | 
						|
*
 | 
						|
*     Initialize VR
 | 
						|
*
 | 
						|
      IF( ILVR )
 | 
						|
     $   CALL DLASET( 'Full', N, N, ZERO, ONE, VR, LDVR )
 | 
						|
*
 | 
						|
*     Reduce to generalized Hessenberg form
 | 
						|
*
 | 
						|
      IF( ILV ) THEN
 | 
						|
*
 | 
						|
*        Eigenvectors requested -- work on whole matrix.
 | 
						|
*
 | 
						|
         CALL DGGHD3( JOBVL, JOBVR, N, ILO, IHI, A, LDA, B, LDB, VL,
 | 
						|
     $                LDVL, VR, LDVR, WORK( IWRK ), LWORK+1-IWRK, IERR )
 | 
						|
      ELSE
 | 
						|
         CALL DGGHD3( 'N', 'N', IROWS, 1, IROWS, A( ILO, ILO ), LDA,
 | 
						|
     $                B( ILO, ILO ), LDB, VL, LDVL, VR, LDVR,
 | 
						|
     $                WORK( IWRK ), LWORK+1-IWRK, IERR )
 | 
						|
      END IF
 | 
						|
*
 | 
						|
*     Perform QZ algorithm (Compute eigenvalues, and optionally, the
 | 
						|
*     Schur forms and Schur vectors)
 | 
						|
*
 | 
						|
      IWRK = ITAU
 | 
						|
      IF( ILV ) THEN
 | 
						|
         CHTEMP = 'S'
 | 
						|
      ELSE
 | 
						|
         CHTEMP = 'E'
 | 
						|
      END IF
 | 
						|
      CALL DLAQZ0( CHTEMP, JOBVL, JOBVR, N, ILO, IHI, A, LDA, B, LDB,
 | 
						|
     $             ALPHAR, ALPHAI, BETA, VL, LDVL, VR, LDVR,
 | 
						|
     $             WORK( IWRK ), LWORK+1-IWRK, 0, IERR )
 | 
						|
      IF( IERR.NE.0 ) THEN
 | 
						|
         IF( IERR.GT.0 .AND. IERR.LE.N ) THEN
 | 
						|
            INFO = IERR
 | 
						|
         ELSE IF( IERR.GT.N .AND. IERR.LE.2*N ) THEN
 | 
						|
            INFO = IERR - N
 | 
						|
         ELSE
 | 
						|
            INFO = N + 1
 | 
						|
         END IF
 | 
						|
         GO TO 110
 | 
						|
      END IF
 | 
						|
*
 | 
						|
*     Compute Eigenvectors
 | 
						|
*
 | 
						|
      IF( ILV ) THEN
 | 
						|
         IF( ILVL ) THEN
 | 
						|
            IF( ILVR ) THEN
 | 
						|
               CHTEMP = 'B'
 | 
						|
            ELSE
 | 
						|
               CHTEMP = 'L'
 | 
						|
            END IF
 | 
						|
         ELSE
 | 
						|
            CHTEMP = 'R'
 | 
						|
         END IF
 | 
						|
         CALL DTGEVC( CHTEMP, 'B', LDUMMA, N, A, LDA, B, LDB, VL, LDVL,
 | 
						|
     $                VR, LDVR, N, IN, WORK( IWRK ), IERR )
 | 
						|
         IF( IERR.NE.0 ) THEN
 | 
						|
            INFO = N + 2
 | 
						|
            GO TO 110
 | 
						|
         END IF
 | 
						|
*
 | 
						|
*        Undo balancing on VL and VR and normalization
 | 
						|
*
 | 
						|
         IF( ILVL ) THEN
 | 
						|
            CALL DGGBAK( 'P', 'L', N, ILO, IHI, WORK( ILEFT ),
 | 
						|
     $                   WORK( IRIGHT ), N, VL, LDVL, IERR )
 | 
						|
            DO 50 JC = 1, N
 | 
						|
               IF( ALPHAI( JC ).LT.ZERO )
 | 
						|
     $            GO TO 50
 | 
						|
               TEMP = ZERO
 | 
						|
               IF( ALPHAI( JC ).EQ.ZERO ) THEN
 | 
						|
                  DO 10 JR = 1, N
 | 
						|
                     TEMP = MAX( TEMP, ABS( VL( JR, JC ) ) )
 | 
						|
   10             CONTINUE
 | 
						|
               ELSE
 | 
						|
                  DO 20 JR = 1, N
 | 
						|
                     TEMP = MAX( TEMP, ABS( VL( JR, JC ) )+
 | 
						|
     $                      ABS( VL( JR, JC+1 ) ) )
 | 
						|
   20             CONTINUE
 | 
						|
               END IF
 | 
						|
               IF( TEMP.LT.SMLNUM )
 | 
						|
     $            GO TO 50
 | 
						|
               TEMP = ONE / TEMP
 | 
						|
               IF( ALPHAI( JC ).EQ.ZERO ) THEN
 | 
						|
                  DO 30 JR = 1, N
 | 
						|
                     VL( JR, JC ) = VL( JR, JC )*TEMP
 | 
						|
   30             CONTINUE
 | 
						|
               ELSE
 | 
						|
                  DO 40 JR = 1, N
 | 
						|
                     VL( JR, JC ) = VL( JR, JC )*TEMP
 | 
						|
                     VL( JR, JC+1 ) = VL( JR, JC+1 )*TEMP
 | 
						|
   40             CONTINUE
 | 
						|
               END IF
 | 
						|
   50       CONTINUE
 | 
						|
         END IF
 | 
						|
         IF( ILVR ) THEN
 | 
						|
            CALL DGGBAK( 'P', 'R', N, ILO, IHI, WORK( ILEFT ),
 | 
						|
     $                   WORK( IRIGHT ), N, VR, LDVR, IERR )
 | 
						|
            DO 100 JC = 1, N
 | 
						|
               IF( ALPHAI( JC ).LT.ZERO )
 | 
						|
     $            GO TO 100
 | 
						|
               TEMP = ZERO
 | 
						|
               IF( ALPHAI( JC ).EQ.ZERO ) THEN
 | 
						|
                  DO 60 JR = 1, N
 | 
						|
                     TEMP = MAX( TEMP, ABS( VR( JR, JC ) ) )
 | 
						|
   60             CONTINUE
 | 
						|
               ELSE
 | 
						|
                  DO 70 JR = 1, N
 | 
						|
                     TEMP = MAX( TEMP, ABS( VR( JR, JC ) )+
 | 
						|
     $                      ABS( VR( JR, JC+1 ) ) )
 | 
						|
   70             CONTINUE
 | 
						|
               END IF
 | 
						|
               IF( TEMP.LT.SMLNUM )
 | 
						|
     $            GO TO 100
 | 
						|
               TEMP = ONE / TEMP
 | 
						|
               IF( ALPHAI( JC ).EQ.ZERO ) THEN
 | 
						|
                  DO 80 JR = 1, N
 | 
						|
                     VR( JR, JC ) = VR( JR, JC )*TEMP
 | 
						|
   80             CONTINUE
 | 
						|
               ELSE
 | 
						|
                  DO 90 JR = 1, N
 | 
						|
                     VR( JR, JC ) = VR( JR, JC )*TEMP
 | 
						|
                     VR( JR, JC+1 ) = VR( JR, JC+1 )*TEMP
 | 
						|
   90             CONTINUE
 | 
						|
               END IF
 | 
						|
  100       CONTINUE
 | 
						|
         END IF
 | 
						|
*
 | 
						|
*        End of eigenvector calculation
 | 
						|
*
 | 
						|
      END IF
 | 
						|
*
 | 
						|
*     Undo scaling if necessary
 | 
						|
*
 | 
						|
  110 CONTINUE
 | 
						|
*
 | 
						|
      IF( ILASCL ) THEN
 | 
						|
         CALL DLASCL( 'G', 0, 0, ANRMTO, ANRM, N, 1, ALPHAR, N, IERR )
 | 
						|
         CALL DLASCL( 'G', 0, 0, ANRMTO, ANRM, N, 1, ALPHAI, N, IERR )
 | 
						|
      END IF
 | 
						|
*
 | 
						|
      IF( ILBSCL ) THEN
 | 
						|
         CALL DLASCL( 'G', 0, 0, BNRMTO, BNRM, N, 1, BETA, N, IERR )
 | 
						|
      END IF
 | 
						|
*
 | 
						|
      WORK( 1 ) = LWKOPT
 | 
						|
      RETURN
 | 
						|
*
 | 
						|
*     End of DGGEV3
 | 
						|
*
 | 
						|
      END
 |