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authorSiddhesh Wani2015-05-25 14:46:31 +0530
committerSiddhesh Wani2015-05-25 14:46:31 +0530
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Original Version
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+ SUBROUTINE DGGEV( JOBVL, JOBVR, N, A, LDA, B, LDB, ALPHAR, ALPHAI,
+ $ BETA, VL, LDVL, VR, LDVR, WORK, LWORK, INFO )
+*
+* -- LAPACK driver routine (version 3.1) --
+* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
+* November 2006
+*
+* .. Scalar Arguments ..
+ CHARACTER JOBVL, JOBVR
+ INTEGER INFO, LDA, LDB, LDVL, LDVR, LWORK, N
+* ..
+* .. Array Arguments ..
+ DOUBLE PRECISION A( LDA, * ), ALPHAI( * ), ALPHAR( * ),
+ $ B( LDB, * ), BETA( * ), VL( LDVL, * ),
+ $ VR( LDVR, * ), WORK( * )
+* ..
+*
+* Purpose
+* =======
+*
+* DGGEV computes for a pair of N-by-N real nonsymmetric matrices (A,B)
+* the generalized eigenvalues, and optionally, the left and/or right
+* generalized eigenvectors.
+*
+* A generalized eigenvalue for a pair of matrices (A,B) is a scalar
+* lambda or a ratio alpha/beta = lambda, such that A - lambda*B is
+* singular. It is usually represented as the pair (alpha,beta), as
+* there is a reasonable interpretation for beta=0, and even for both
+* being zero.
+*
+* The right eigenvector v(j) corresponding to the eigenvalue lambda(j)
+* of (A,B) satisfies
+*
+* A * v(j) = lambda(j) * B * v(j).
+*
+* The left eigenvector u(j) corresponding to the eigenvalue lambda(j)
+* of (A,B) satisfies
+*
+* u(j)**H * A = lambda(j) * u(j)**H * B .
+*
+* where u(j)**H is the conjugate-transpose of u(j).
+*
+*
+* Arguments
+* =========
+*
+* JOBVL (input) CHARACTER*1
+* = 'N': do not compute the left generalized eigenvectors;
+* = 'V': compute the left generalized eigenvectors.
+*
+* JOBVR (input) CHARACTER*1
+* = 'N': do not compute the right generalized eigenvectors;
+* = 'V': compute the right generalized eigenvectors.
+*
+* N (input) INTEGER
+* The order of the matrices A, B, VL, and VR. N >= 0.
+*
+* A (input/output) DOUBLE PRECISION array, dimension (LDA, N)
+* On entry, the matrix A in the pair (A,B).
+* On exit, A has been overwritten.
+*
+* LDA (input) INTEGER
+* The leading dimension of A. LDA >= max(1,N).
+*
+* B (input/output) DOUBLE PRECISION array, dimension (LDB, N)
+* On entry, the matrix B in the pair (A,B).
+* On exit, B has been overwritten.
+*
+* LDB (input) INTEGER
+* The leading dimension of B. LDB >= max(1,N).
+*
+* ALPHAR (output) DOUBLE PRECISION array, dimension (N)
+* ALPHAI (output) DOUBLE PRECISION array, dimension (N)
+* BETA (output) DOUBLE PRECISION array, dimension (N)
+* On exit, (ALPHAR(j) + ALPHAI(j)*i)/BETA(j), j=1,...,N, will
+* be the generalized eigenvalues. If ALPHAI(j) is zero, then
+* the j-th eigenvalue is real; if positive, then the j-th and
+* (j+1)-st eigenvalues are a complex conjugate pair, with
+* ALPHAI(j+1) negative.
+*
+* Note: the quotients ALPHAR(j)/BETA(j) and ALPHAI(j)/BETA(j)
+* may easily over- or underflow, and BETA(j) may even be zero.
+* Thus, the user should avoid naively computing the ratio
+* alpha/beta. However, ALPHAR and ALPHAI will be always less
+* than and usually comparable with norm(A) in magnitude, and
+* BETA always less than and usually comparable with norm(B).
+*
+* VL (output) DOUBLE PRECISION 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 the j-th eigenvalue is real, then
+* u(j) = VL(:,j), the j-th column of VL. If the j-th and
+* (j+1)-th eigenvalues form a complex conjugate pair, then
+* u(j) = VL(:,j)+i*VL(:,j+1) and u(j+1) = VL(:,j)-i*VL(:,j+1).
+* Each eigenvector is scaled so the largest component has
+* abs(real part)+abs(imag. part)=1.
+* Not referenced if JOBVL = 'N'.
+*
+* LDVL (input) INTEGER
+* The leading dimension of the matrix VL. LDVL >= 1, and
+* if JOBVL = 'V', LDVL >= N.
+*
+* VR (output) DOUBLE PRECISION 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 the j-th eigenvalue is real, then
+* v(j) = VR(:,j), the j-th column of VR. If the j-th and
+* (j+1)-th eigenvalues form a complex conjugate pair, then
+* v(j) = VR(:,j)+i*VR(:,j+1) and v(j+1) = VR(:,j)-i*VR(:,j+1).
+* Each eigenvector is scaled so the largest component has
+* abs(real part)+abs(imag. part)=1.
+* Not referenced if JOBVR = 'N'.
+*
+* LDVR (input) INTEGER
+* The leading dimension of the matrix VR. LDVR >= 1, and
+* if JOBVR = 'V', LDVR >= N.
+*
+* WORK (workspace/output) DOUBLE PRECISION array, dimension (MAX(1,LWORK))
+* On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
+*
+* LWORK (input) INTEGER
+* The dimension of the array WORK. LWORK >= max(1,8*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.
+*
+* INFO (output) INTEGER
+* = 0: successful exit
+* < 0: if INFO = -i, the i-th argument had an illegal value.
+* = 1,...,N:
+* The QZ iteration failed. No eigenvectors have been
+* calculated, but ALPHAR(j), ALPHAI(j), and BETA(j)
+* should be correct for j=INFO+1,...,N.
+* > N: =N+1: other than QZ iteration failed in DHGEQZ.
+* =N+2: error return from DTGEVC.
+*
+* =====================================================================
+*
+* .. Parameters ..
+ DOUBLE PRECISION ZERO, ONE
+ PARAMETER ( ZERO = 0.0D+0, ONE = 1.0D+0 )
+* ..
+* .. Local Scalars ..
+ LOGICAL ILASCL, ILBSCL, ILV, ILVL, ILVR, LQUERY
+ CHARACTER CHTEMP
+ INTEGER ICOLS, IERR, IHI, IJOBVL, IJOBVR, ILEFT, ILO,
+ $ IN, IRIGHT, IROWS, ITAU, IWRK, JC, JR, MAXWRK,
+ $ MINWRK
+ DOUBLE PRECISION ANRM, ANRMTO, BIGNUM, BNRM, BNRMTO, EPS,
+ $ SMLNUM, TEMP
+* ..
+* .. Local Arrays ..
+ LOGICAL LDUMMA( 1 )
+* ..
+* .. External Subroutines ..
+ EXTERNAL DGEQRF, DGGBAK, DGGBAL, DGGHRD, DHGEQZ, DLABAD,
+ $ DLACPY,DLASCL, DLASET, DORGQR, DORMQR, DTGEVC,
+ $ XERBLA
+* ..
+* .. External Functions ..
+ LOGICAL LSAME
+ INTEGER ILAENV
+ DOUBLE PRECISION DLAMCH, DLANGE
+ EXTERNAL LSAME, ILAENV, DLAMCH, DLANGE
+* ..
+* .. Intrinsic Functions ..
+ INTRINSIC ABS, MAX, SQRT
+* ..
+* .. Executable Statements ..
+*
+* Decode the input arguments
+*
+ IF( LSAME( JOBVL, 'N' ) ) THEN
+ IJOBVL = 1
+ ILVL = .FALSE.
+ ELSE IF( LSAME( JOBVL, 'V' ) ) THEN
+ IJOBVL = 2
+ ILVL = .TRUE.
+ ELSE
+ IJOBVL = -1
+ ILVL = .FALSE.
+ END IF
+*
+ IF( LSAME( JOBVR, 'N' ) ) THEN
+ IJOBVR = 1
+ ILVR = .FALSE.
+ ELSE IF( LSAME( JOBVR, 'V' ) ) THEN
+ IJOBVR = 2
+ ILVR = .TRUE.
+ ELSE
+ IJOBVR = -1
+ ILVR = .FALSE.
+ END IF
+ ILV = ILVL .OR. ILVR
+*
+* Test the input arguments
+*
+ INFO = 0
+ LQUERY = ( LWORK.EQ.-1 )
+ IF( IJOBVL.LE.0 ) THEN
+ INFO = -1
+ ELSE IF( IJOBVR.LE.0 ) THEN
+ INFO = -2
+ ELSE IF( N.LT.0 ) THEN
+ INFO = -3
+ ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
+ INFO = -5
+ ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
+ INFO = -7
+ ELSE IF( LDVL.LT.1 .OR. ( ILVL .AND. LDVL.LT.N ) ) THEN
+ INFO = -12
+ ELSE IF( LDVR.LT.1 .OR. ( ILVR .AND. LDVR.LT.N ) ) THEN
+ INFO = -14
+ END IF
+*
+* Compute workspace
+* (Note: Comments in the code beginning "Workspace:" describe the
+* minimal amount of workspace needed at that point in the code,
+* as well as the preferred amount for good performance.
+* NB refers to the optimal block size for the immediately
+* following subroutine, as returned by ILAENV. The workspace is
+* computed assuming ILO = 1 and IHI = N, the worst case.)
+*
+ IF( INFO.EQ.0 ) THEN
+ MINWRK = MAX( 1, 8*N )
+ MAXWRK = MAX( 1, N*( 7 +
+ $ ILAENV( 1, 'DGEQRF', ' ', N, 1, N, 0 ) ) )
+ MAXWRK = MAX( MAXWRK, N*( 7 +
+ $ ILAENV( 1, 'DORMQR', ' ', N, 1, N, 0 ) ) )
+ IF( ILVL ) THEN
+ MAXWRK = MAX( MAXWRK, N*( 7 +
+ $ ILAENV( 1, 'DORGQR', ' ', N, 1, N, -1 ) ) )
+ END IF
+ WORK( 1 ) = MAXWRK
+*
+ IF( LWORK.LT.MINWRK .AND. .NOT.LQUERY )
+ $ INFO = -16
+ END IF
+*
+ IF( INFO.NE.0 ) THEN
+ CALL XERBLA( 'DGGEV ', -INFO )
+ RETURN
+ ELSE IF( LQUERY ) THEN
+ RETURN
+ END IF
+*
+* Quick return if possible
+*
+ IF( N.EQ.0 )
+ $ RETURN
+*
+* Get machine constants
+*
+ EPS = DLAMCH( 'P' )
+ SMLNUM = DLAMCH( 'S' )
+ BIGNUM = ONE / SMLNUM
+ CALL DLABAD( SMLNUM, BIGNUM )
+ SMLNUM = SQRT( SMLNUM ) / EPS
+ BIGNUM = ONE / SMLNUM
+*
+* Scale A if max element outside range [SMLNUM,BIGNUM]
+*
+ ANRM = DLANGE( 'M', N, N, A, LDA, WORK )
+ ILASCL = .FALSE.
+ IF( ANRM.GT.ZERO .AND. ANRM.LT.SMLNUM ) THEN
+ ANRMTO = SMLNUM
+ ILASCL = .TRUE.
+ ELSE IF( ANRM.GT.BIGNUM ) THEN
+ ANRMTO = BIGNUM
+ ILASCL = .TRUE.
+ END IF
+ IF( ILASCL )
+ $ CALL DLASCL( 'G', 0, 0, ANRM, ANRMTO, N, N, A, LDA, IERR )
+*
+* Scale B if max element outside range [SMLNUM,BIGNUM]
+*
+ BNRM = DLANGE( 'M', N, N, B, LDB, WORK )
+ ILBSCL = .FALSE.
+ IF( BNRM.GT.ZERO .AND. BNRM.LT.SMLNUM ) THEN
+ 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
+* (Workspace: need 6*N)
+*
+ 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)
+* (Workspace: need N, prefer N*NB)
+*
+ 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
+* (Workspace: need N, prefer N*NB)
+*
+ 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
+* (Workspace: need N, prefer N*NB)
+*
+ 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
+* (Workspace: none needed)
+*
+ IF( ILV ) THEN
+*
+* Eigenvectors requested -- work on whole matrix.
+*
+ CALL DGGHRD( JOBVL, JOBVR, N, ILO, IHI, A, LDA, B, LDB, VL,
+ $ LDVL, VR, LDVR, IERR )
+ ELSE
+ CALL DGGHRD( 'N', 'N', IROWS, 1, IROWS, A( ILO, ILO ), LDA,
+ $ B( ILO, ILO ), LDB, VL, LDVL, VR, LDVR, IERR )
+ END IF
+*
+* Perform QZ algorithm (Compute eigenvalues, and optionally, the
+* Schur forms and Schur vectors)
+* (Workspace: need N)
+*
+ IWRK = ITAU
+ IF( ILV ) THEN
+ CHTEMP = 'S'
+ ELSE
+ CHTEMP = 'E'
+ END IF
+ CALL DHGEQZ( CHTEMP, JOBVL, JOBVR, N, ILO, IHI, A, LDA, B, LDB,
+ $ ALPHAR, ALPHAI, BETA, VL, LDVL, VR, LDVR,
+ $ WORK( IWRK ), LWORK+1-IWRK, 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
+* (Workspace: need 6*N)
+*
+ 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
+* (Workspace: none needed)
+*
+ 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
+*
+ 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
+*
+ 110 CONTINUE
+*
+ WORK( 1 ) = MAXWRK
+*
+ RETURN
+*
+* End of DGGEV
+*
+ END