Annotation of rpl/lapack/lapack/dgeev.f, revision 1.9

1.9     ! bertrand    1: *> \brief <b> DGEEV computes the eigenvalues and, optionally, the left and/or right eigenvectors for GE matrices</b>
        !             2: *
        !             3: *  =========== DOCUMENTATION ===========
        !             4: *
        !             5: * Online html documentation available at 
        !             6: *            http://www.netlib.org/lapack/explore-html/ 
        !             7: *
        !             8: *> \htmlonly
        !             9: *> Download DGEEV + dependencies 
        !            10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/dgeev.f"> 
        !            11: *> [TGZ]</a> 
        !            12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/dgeev.f"> 
        !            13: *> [ZIP]</a> 
        !            14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/dgeev.f"> 
        !            15: *> [TXT]</a>
        !            16: *> \endhtmlonly 
        !            17: *
        !            18: *  Definition:
        !            19: *  ===========
        !            20: *
        !            21: *       SUBROUTINE DGEEV( JOBVL, JOBVR, N, A, LDA, WR, WI, VL, LDVL, VR,
        !            22: *                         LDVR, WORK, LWORK, INFO )
        !            23: * 
        !            24: *       .. Scalar Arguments ..
        !            25: *       CHARACTER          JOBVL, JOBVR
        !            26: *       INTEGER            INFO, LDA, LDVL, LDVR, LWORK, N
        !            27: *       ..
        !            28: *       .. Array Arguments ..
        !            29: *       DOUBLE PRECISION   A( LDA, * ), VL( LDVL, * ), VR( LDVR, * ),
        !            30: *      $                   WI( * ), WORK( * ), WR( * )
        !            31: *       ..
        !            32: *  
        !            33: *
        !            34: *> \par Purpose:
        !            35: *  =============
        !            36: *>
        !            37: *> \verbatim
        !            38: *>
        !            39: *> DGEEV computes for an N-by-N real nonsymmetric matrix A, the
        !            40: *> eigenvalues and, optionally, the left and/or right eigenvectors.
        !            41: *>
        !            42: *> The right eigenvector v(j) of A satisfies
        !            43: *>                  A * v(j) = lambda(j) * v(j)
        !            44: *> where lambda(j) is its eigenvalue.
        !            45: *> The left eigenvector u(j) of A satisfies
        !            46: *>               u(j)**T * A = lambda(j) * u(j)**T
        !            47: *> where u(j)**T denotes the transpose of u(j).
        !            48: *>
        !            49: *> The computed eigenvectors are normalized to have Euclidean norm
        !            50: *> equal to 1 and largest component real.
        !            51: *> \endverbatim
        !            52: *
        !            53: *  Arguments:
        !            54: *  ==========
        !            55: *
        !            56: *> \param[in] JOBVL
        !            57: *> \verbatim
        !            58: *>          JOBVL is CHARACTER*1
        !            59: *>          = 'N': left eigenvectors of A are not computed;
        !            60: *>          = 'V': left eigenvectors of A are computed.
        !            61: *> \endverbatim
        !            62: *>
        !            63: *> \param[in] JOBVR
        !            64: *> \verbatim
        !            65: *>          JOBVR is CHARACTER*1
        !            66: *>          = 'N': right eigenvectors of A are not computed;
        !            67: *>          = 'V': right eigenvectors of A are computed.
        !            68: *> \endverbatim
        !            69: *>
        !            70: *> \param[in] N
        !            71: *> \verbatim
        !            72: *>          N is INTEGER
        !            73: *>          The order of the matrix A. N >= 0.
        !            74: *> \endverbatim
        !            75: *>
        !            76: *> \param[in,out] A
        !            77: *> \verbatim
        !            78: *>          A is DOUBLE PRECISION array, dimension (LDA,N)
        !            79: *>          On entry, the N-by-N matrix A.
        !            80: *>          On exit, A has been overwritten.
        !            81: *> \endverbatim
        !            82: *>
        !            83: *> \param[in] LDA
        !            84: *> \verbatim
        !            85: *>          LDA is INTEGER
        !            86: *>          The leading dimension of the array A.  LDA >= max(1,N).
        !            87: *> \endverbatim
        !            88: *>
        !            89: *> \param[out] WR
        !            90: *> \verbatim
        !            91: *>          WR is DOUBLE PRECISION array, dimension (N)
        !            92: *> \endverbatim
        !            93: *>
        !            94: *> \param[out] WI
        !            95: *> \verbatim
        !            96: *>          WI is DOUBLE PRECISION array, dimension (N)
        !            97: *>          WR and WI contain the real and imaginary parts,
        !            98: *>          respectively, of the computed eigenvalues.  Complex
        !            99: *>          conjugate pairs of eigenvalues appear consecutively
        !           100: *>          with the eigenvalue having the positive imaginary part
        !           101: *>          first.
        !           102: *> \endverbatim
        !           103: *>
        !           104: *> \param[out] VL
        !           105: *> \verbatim
        !           106: *>          VL is DOUBLE PRECISION array, dimension (LDVL,N)
        !           107: *>          If JOBVL = 'V', the left eigenvectors u(j) are stored one
        !           108: *>          after another in the columns of VL, in the same order
        !           109: *>          as their eigenvalues.
        !           110: *>          If JOBVL = 'N', VL is not referenced.
        !           111: *>          If the j-th eigenvalue is real, then u(j) = VL(:,j),
        !           112: *>          the j-th column of VL.
        !           113: *>          If the j-th and (j+1)-st eigenvalues form a complex
        !           114: *>          conjugate pair, then u(j) = VL(:,j) + i*VL(:,j+1) and
        !           115: *>          u(j+1) = VL(:,j) - i*VL(:,j+1).
        !           116: *> \endverbatim
        !           117: *>
        !           118: *> \param[in] LDVL
        !           119: *> \verbatim
        !           120: *>          LDVL is INTEGER
        !           121: *>          The leading dimension of the array VL.  LDVL >= 1; if
        !           122: *>          JOBVL = 'V', LDVL >= N.
        !           123: *> \endverbatim
        !           124: *>
        !           125: *> \param[out] VR
        !           126: *> \verbatim
        !           127: *>          VR is DOUBLE PRECISION array, dimension (LDVR,N)
        !           128: *>          If JOBVR = 'V', the right eigenvectors v(j) are stored one
        !           129: *>          after another in the columns of VR, in the same order
        !           130: *>          as their eigenvalues.
        !           131: *>          If JOBVR = 'N', VR is not referenced.
        !           132: *>          If the j-th eigenvalue is real, then v(j) = VR(:,j),
        !           133: *>          the j-th column of VR.
        !           134: *>          If the j-th and (j+1)-st eigenvalues form a complex
        !           135: *>          conjugate pair, then v(j) = VR(:,j) + i*VR(:,j+1) and
        !           136: *>          v(j+1) = VR(:,j) - i*VR(:,j+1).
        !           137: *> \endverbatim
        !           138: *>
        !           139: *> \param[in] LDVR
        !           140: *> \verbatim
        !           141: *>          LDVR is INTEGER
        !           142: *>          The leading dimension of the array VR.  LDVR >= 1; if
        !           143: *>          JOBVR = 'V', LDVR >= N.
        !           144: *> \endverbatim
        !           145: *>
        !           146: *> \param[out] WORK
        !           147: *> \verbatim
        !           148: *>          WORK is DOUBLE PRECISION array, dimension (MAX(1,LWORK))
        !           149: *>          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
        !           150: *> \endverbatim
        !           151: *>
        !           152: *> \param[in] LWORK
        !           153: *> \verbatim
        !           154: *>          LWORK is INTEGER
        !           155: *>          The dimension of the array WORK.  LWORK >= max(1,3*N), and
        !           156: *>          if JOBVL = 'V' or JOBVR = 'V', LWORK >= 4*N.  For good
        !           157: *>          performance, LWORK must generally be larger.
        !           158: *>
        !           159: *>          If LWORK = -1, then a workspace query is assumed; the routine
        !           160: *>          only calculates the optimal size of the WORK array, returns
        !           161: *>          this value as the first entry of the WORK array, and no error
        !           162: *>          message related to LWORK is issued by XERBLA.
        !           163: *> \endverbatim
        !           164: *>
        !           165: *> \param[out] INFO
        !           166: *> \verbatim
        !           167: *>          INFO is INTEGER
        !           168: *>          = 0:  successful exit
        !           169: *>          < 0:  if INFO = -i, the i-th argument had an illegal value.
        !           170: *>          > 0:  if INFO = i, the QR algorithm failed to compute all the
        !           171: *>                eigenvalues, and no eigenvectors have been computed;
        !           172: *>                elements i+1:N of WR and WI contain eigenvalues which
        !           173: *>                have converged.
        !           174: *> \endverbatim
        !           175: *
        !           176: *  Authors:
        !           177: *  ========
        !           178: *
        !           179: *> \author Univ. of Tennessee 
        !           180: *> \author Univ. of California Berkeley 
        !           181: *> \author Univ. of Colorado Denver 
        !           182: *> \author NAG Ltd. 
        !           183: *
        !           184: *> \date November 2011
        !           185: *
        !           186: *> \ingroup doubleGEeigen
        !           187: *
        !           188: *  =====================================================================
1.1       bertrand  189:       SUBROUTINE DGEEV( JOBVL, JOBVR, N, A, LDA, WR, WI, VL, LDVL, VR,
                    190:      $                  LDVR, WORK, LWORK, INFO )
                    191: *
1.9     ! bertrand  192: *  -- LAPACK driver routine (version 3.4.0) --
1.1       bertrand  193: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
                    194: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.9     ! bertrand  195: *     November 2011
1.1       bertrand  196: *
                    197: *     .. Scalar Arguments ..
                    198:       CHARACTER          JOBVL, JOBVR
                    199:       INTEGER            INFO, LDA, LDVL, LDVR, LWORK, N
                    200: *     ..
                    201: *     .. Array Arguments ..
                    202:       DOUBLE PRECISION   A( LDA, * ), VL( LDVL, * ), VR( LDVR, * ),
                    203:      $                   WI( * ), WORK( * ), WR( * )
                    204: *     ..
                    205: *
                    206: *  =====================================================================
                    207: *
                    208: *     .. Parameters ..
                    209:       DOUBLE PRECISION   ZERO, ONE
                    210:       PARAMETER          ( ZERO = 0.0D0, ONE = 1.0D0 )
                    211: *     ..
                    212: *     .. Local Scalars ..
                    213:       LOGICAL            LQUERY, SCALEA, WANTVL, WANTVR
                    214:       CHARACTER          SIDE
                    215:       INTEGER            HSWORK, I, IBAL, IERR, IHI, ILO, ITAU, IWRK, K,
                    216:      $                   MAXWRK, MINWRK, NOUT
                    217:       DOUBLE PRECISION   ANRM, BIGNUM, CS, CSCALE, EPS, R, SCL, SMLNUM,
                    218:      $                   SN
                    219: *     ..
                    220: *     .. Local Arrays ..
                    221:       LOGICAL            SELECT( 1 )
                    222:       DOUBLE PRECISION   DUM( 1 )
                    223: *     ..
                    224: *     .. External Subroutines ..
                    225:       EXTERNAL           DGEBAK, DGEBAL, DGEHRD, DHSEQR, DLABAD, DLACPY,
                    226:      $                   DLARTG, DLASCL, DORGHR, DROT, DSCAL, DTREVC,
                    227:      $                   XERBLA
                    228: *     ..
                    229: *     .. External Functions ..
                    230:       LOGICAL            LSAME
                    231:       INTEGER            IDAMAX, ILAENV
                    232:       DOUBLE PRECISION   DLAMCH, DLANGE, DLAPY2, DNRM2
                    233:       EXTERNAL           LSAME, IDAMAX, ILAENV, DLAMCH, DLANGE, DLAPY2,
                    234:      $                   DNRM2
                    235: *     ..
                    236: *     .. Intrinsic Functions ..
                    237:       INTRINSIC          MAX, SQRT
                    238: *     ..
                    239: *     .. Executable Statements ..
                    240: *
                    241: *     Test the input arguments
                    242: *
                    243:       INFO = 0
                    244:       LQUERY = ( LWORK.EQ.-1 )
                    245:       WANTVL = LSAME( JOBVL, 'V' )
                    246:       WANTVR = LSAME( JOBVR, 'V' )
                    247:       IF( ( .NOT.WANTVL ) .AND. ( .NOT.LSAME( JOBVL, 'N' ) ) ) THEN
                    248:          INFO = -1
                    249:       ELSE IF( ( .NOT.WANTVR ) .AND. ( .NOT.LSAME( JOBVR, 'N' ) ) ) THEN
                    250:          INFO = -2
                    251:       ELSE IF( N.LT.0 ) THEN
                    252:          INFO = -3
                    253:       ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
                    254:          INFO = -5
                    255:       ELSE IF( LDVL.LT.1 .OR. ( WANTVL .AND. LDVL.LT.N ) ) THEN
                    256:          INFO = -9
                    257:       ELSE IF( LDVR.LT.1 .OR. ( WANTVR .AND. LDVR.LT.N ) ) THEN
                    258:          INFO = -11
                    259:       END IF
                    260: *
                    261: *     Compute workspace
                    262: *      (Note: Comments in the code beginning "Workspace:" describe the
                    263: *       minimal amount of workspace needed at that point in the code,
                    264: *       as well as the preferred amount for good performance.
                    265: *       NB refers to the optimal block size for the immediately
                    266: *       following subroutine, as returned by ILAENV.
                    267: *       HSWORK refers to the workspace preferred by DHSEQR, as
                    268: *       calculated below. HSWORK is computed assuming ILO=1 and IHI=N,
                    269: *       the worst case.)
                    270: *
                    271:       IF( INFO.EQ.0 ) THEN
                    272:          IF( N.EQ.0 ) THEN
                    273:             MINWRK = 1
                    274:             MAXWRK = 1
                    275:          ELSE
                    276:             MAXWRK = 2*N + N*ILAENV( 1, 'DGEHRD', ' ', N, 1, N, 0 )
                    277:             IF( WANTVL ) THEN
                    278:                MINWRK = 4*N
                    279:                MAXWRK = MAX( MAXWRK, 2*N + ( N - 1 )*ILAENV( 1,
                    280:      $                       'DORGHR', ' ', N, 1, N, -1 ) )
                    281:                CALL DHSEQR( 'S', 'V', N, 1, N, A, LDA, WR, WI, VL, LDVL,
                    282:      $                WORK, -1, INFO )
                    283:                HSWORK = WORK( 1 )
                    284:                MAXWRK = MAX( MAXWRK, N + 1, N + HSWORK )
                    285:                MAXWRK = MAX( MAXWRK, 4*N )
                    286:             ELSE IF( WANTVR ) THEN
                    287:                MINWRK = 4*N
                    288:                MAXWRK = MAX( MAXWRK, 2*N + ( N - 1 )*ILAENV( 1,
                    289:      $                       'DORGHR', ' ', N, 1, N, -1 ) )
                    290:                CALL DHSEQR( 'S', 'V', N, 1, N, A, LDA, WR, WI, VR, LDVR,
                    291:      $                WORK, -1, INFO )
                    292:                HSWORK = WORK( 1 )
                    293:                MAXWRK = MAX( MAXWRK, N + 1, N + HSWORK )
                    294:                MAXWRK = MAX( MAXWRK, 4*N )
                    295:             ELSE 
                    296:                MINWRK = 3*N
                    297:                CALL DHSEQR( 'E', 'N', N, 1, N, A, LDA, WR, WI, VR, LDVR,
                    298:      $                WORK, -1, INFO )
                    299:                HSWORK = WORK( 1 )
                    300:                MAXWRK = MAX( MAXWRK, N + 1, N + HSWORK )
                    301:             END IF
                    302:             MAXWRK = MAX( MAXWRK, MINWRK )
                    303:          END IF
                    304:          WORK( 1 ) = MAXWRK
                    305: *
                    306:          IF( LWORK.LT.MINWRK .AND. .NOT.LQUERY ) THEN
                    307:             INFO = -13
                    308:          END IF
                    309:       END IF
                    310: *
                    311:       IF( INFO.NE.0 ) THEN
                    312:          CALL XERBLA( 'DGEEV ', -INFO )
                    313:          RETURN
                    314:       ELSE IF( LQUERY ) THEN
                    315:          RETURN
                    316:       END IF
                    317: *
                    318: *     Quick return if possible
                    319: *
                    320:       IF( N.EQ.0 )
                    321:      $   RETURN
                    322: *
                    323: *     Get machine constants
                    324: *
                    325:       EPS = DLAMCH( 'P' )
                    326:       SMLNUM = DLAMCH( 'S' )
                    327:       BIGNUM = ONE / SMLNUM
                    328:       CALL DLABAD( SMLNUM, BIGNUM )
                    329:       SMLNUM = SQRT( SMLNUM ) / EPS
                    330:       BIGNUM = ONE / SMLNUM
                    331: *
                    332: *     Scale A if max element outside range [SMLNUM,BIGNUM]
                    333: *
                    334:       ANRM = DLANGE( 'M', N, N, A, LDA, DUM )
                    335:       SCALEA = .FALSE.
                    336:       IF( ANRM.GT.ZERO .AND. ANRM.LT.SMLNUM ) THEN
                    337:          SCALEA = .TRUE.
                    338:          CSCALE = SMLNUM
                    339:       ELSE IF( ANRM.GT.BIGNUM ) THEN
                    340:          SCALEA = .TRUE.
                    341:          CSCALE = BIGNUM
                    342:       END IF
                    343:       IF( SCALEA )
                    344:      $   CALL DLASCL( 'G', 0, 0, ANRM, CSCALE, N, N, A, LDA, IERR )
                    345: *
                    346: *     Balance the matrix
                    347: *     (Workspace: need N)
                    348: *
                    349:       IBAL = 1
                    350:       CALL DGEBAL( 'B', N, A, LDA, ILO, IHI, WORK( IBAL ), IERR )
                    351: *
                    352: *     Reduce to upper Hessenberg form
                    353: *     (Workspace: need 3*N, prefer 2*N+N*NB)
                    354: *
                    355:       ITAU = IBAL + N
                    356:       IWRK = ITAU + N
                    357:       CALL DGEHRD( N, ILO, IHI, A, LDA, WORK( ITAU ), WORK( IWRK ),
                    358:      $             LWORK-IWRK+1, IERR )
                    359: *
                    360:       IF( WANTVL ) THEN
                    361: *
                    362: *        Want left eigenvectors
                    363: *        Copy Householder vectors to VL
                    364: *
                    365:          SIDE = 'L'
                    366:          CALL DLACPY( 'L', N, N, A, LDA, VL, LDVL )
                    367: *
                    368: *        Generate orthogonal matrix in VL
                    369: *        (Workspace: need 3*N-1, prefer 2*N+(N-1)*NB)
                    370: *
                    371:          CALL DORGHR( N, ILO, IHI, VL, LDVL, WORK( ITAU ), WORK( IWRK ),
                    372:      $                LWORK-IWRK+1, IERR )
                    373: *
                    374: *        Perform QR iteration, accumulating Schur vectors in VL
                    375: *        (Workspace: need N+1, prefer N+HSWORK (see comments) )
                    376: *
                    377:          IWRK = ITAU
                    378:          CALL DHSEQR( 'S', 'V', N, ILO, IHI, A, LDA, WR, WI, VL, LDVL,
                    379:      $                WORK( IWRK ), LWORK-IWRK+1, INFO )
                    380: *
                    381:          IF( WANTVR ) THEN
                    382: *
                    383: *           Want left and right eigenvectors
                    384: *           Copy Schur vectors to VR
                    385: *
                    386:             SIDE = 'B'
                    387:             CALL DLACPY( 'F', N, N, VL, LDVL, VR, LDVR )
                    388:          END IF
                    389: *
                    390:       ELSE IF( WANTVR ) THEN
                    391: *
                    392: *        Want right eigenvectors
                    393: *        Copy Householder vectors to VR
                    394: *
                    395:          SIDE = 'R'
                    396:          CALL DLACPY( 'L', N, N, A, LDA, VR, LDVR )
                    397: *
                    398: *        Generate orthogonal matrix in VR
                    399: *        (Workspace: need 3*N-1, prefer 2*N+(N-1)*NB)
                    400: *
                    401:          CALL DORGHR( N, ILO, IHI, VR, LDVR, WORK( ITAU ), WORK( IWRK ),
                    402:      $                LWORK-IWRK+1, IERR )
                    403: *
                    404: *        Perform QR iteration, accumulating Schur vectors in VR
                    405: *        (Workspace: need N+1, prefer N+HSWORK (see comments) )
                    406: *
                    407:          IWRK = ITAU
                    408:          CALL DHSEQR( 'S', 'V', N, ILO, IHI, A, LDA, WR, WI, VR, LDVR,
                    409:      $                WORK( IWRK ), LWORK-IWRK+1, INFO )
                    410: *
                    411:       ELSE
                    412: *
                    413: *        Compute eigenvalues only
                    414: *        (Workspace: need N+1, prefer N+HSWORK (see comments) )
                    415: *
                    416:          IWRK = ITAU
                    417:          CALL DHSEQR( 'E', 'N', N, ILO, IHI, A, LDA, WR, WI, VR, LDVR,
                    418:      $                WORK( IWRK ), LWORK-IWRK+1, INFO )
                    419:       END IF
                    420: *
                    421: *     If INFO > 0 from DHSEQR, then quit
                    422: *
                    423:       IF( INFO.GT.0 )
                    424:      $   GO TO 50
                    425: *
                    426:       IF( WANTVL .OR. WANTVR ) THEN
                    427: *
                    428: *        Compute left and/or right eigenvectors
                    429: *        (Workspace: need 4*N)
                    430: *
                    431:          CALL DTREVC( SIDE, 'B', SELECT, N, A, LDA, VL, LDVL, VR, LDVR,
                    432:      $                N, NOUT, WORK( IWRK ), IERR )
                    433:       END IF
                    434: *
                    435:       IF( WANTVL ) THEN
                    436: *
                    437: *        Undo balancing of left eigenvectors
                    438: *        (Workspace: need N)
                    439: *
                    440:          CALL DGEBAK( 'B', 'L', N, ILO, IHI, WORK( IBAL ), N, VL, LDVL,
                    441:      $                IERR )
                    442: *
                    443: *        Normalize left eigenvectors and make largest component real
                    444: *
                    445:          DO 20 I = 1, N
                    446:             IF( WI( I ).EQ.ZERO ) THEN
                    447:                SCL = ONE / DNRM2( N, VL( 1, I ), 1 )
                    448:                CALL DSCAL( N, SCL, VL( 1, I ), 1 )
                    449:             ELSE IF( WI( I ).GT.ZERO ) THEN
                    450:                SCL = ONE / DLAPY2( DNRM2( N, VL( 1, I ), 1 ),
                    451:      $               DNRM2( N, VL( 1, I+1 ), 1 ) )
                    452:                CALL DSCAL( N, SCL, VL( 1, I ), 1 )
                    453:                CALL DSCAL( N, SCL, VL( 1, I+1 ), 1 )
                    454:                DO 10 K = 1, N
                    455:                   WORK( IWRK+K-1 ) = VL( K, I )**2 + VL( K, I+1 )**2
                    456:    10          CONTINUE
                    457:                K = IDAMAX( N, WORK( IWRK ), 1 )
                    458:                CALL DLARTG( VL( K, I ), VL( K, I+1 ), CS, SN, R )
                    459:                CALL DROT( N, VL( 1, I ), 1, VL( 1, I+1 ), 1, CS, SN )
                    460:                VL( K, I+1 ) = ZERO
                    461:             END IF
                    462:    20    CONTINUE
                    463:       END IF
                    464: *
                    465:       IF( WANTVR ) THEN
                    466: *
                    467: *        Undo balancing of right eigenvectors
                    468: *        (Workspace: need N)
                    469: *
                    470:          CALL DGEBAK( 'B', 'R', N, ILO, IHI, WORK( IBAL ), N, VR, LDVR,
                    471:      $                IERR )
                    472: *
                    473: *        Normalize right eigenvectors and make largest component real
                    474: *
                    475:          DO 40 I = 1, N
                    476:             IF( WI( I ).EQ.ZERO ) THEN
                    477:                SCL = ONE / DNRM2( N, VR( 1, I ), 1 )
                    478:                CALL DSCAL( N, SCL, VR( 1, I ), 1 )
                    479:             ELSE IF( WI( I ).GT.ZERO ) THEN
                    480:                SCL = ONE / DLAPY2( DNRM2( N, VR( 1, I ), 1 ),
                    481:      $               DNRM2( N, VR( 1, I+1 ), 1 ) )
                    482:                CALL DSCAL( N, SCL, VR( 1, I ), 1 )
                    483:                CALL DSCAL( N, SCL, VR( 1, I+1 ), 1 )
                    484:                DO 30 K = 1, N
                    485:                   WORK( IWRK+K-1 ) = VR( K, I )**2 + VR( K, I+1 )**2
                    486:    30          CONTINUE
                    487:                K = IDAMAX( N, WORK( IWRK ), 1 )
                    488:                CALL DLARTG( VR( K, I ), VR( K, I+1 ), CS, SN, R )
                    489:                CALL DROT( N, VR( 1, I ), 1, VR( 1, I+1 ), 1, CS, SN )
                    490:                VR( K, I+1 ) = ZERO
                    491:             END IF
                    492:    40    CONTINUE
                    493:       END IF
                    494: *
                    495: *     Undo scaling if necessary
                    496: *
                    497:    50 CONTINUE
                    498:       IF( SCALEA ) THEN
                    499:          CALL DLASCL( 'G', 0, 0, CSCALE, ANRM, N-INFO, 1, WR( INFO+1 ),
                    500:      $                MAX( N-INFO, 1 ), IERR )
                    501:          CALL DLASCL( 'G', 0, 0, CSCALE, ANRM, N-INFO, 1, WI( INFO+1 ),
                    502:      $                MAX( N-INFO, 1 ), IERR )
                    503:          IF( INFO.GT.0 ) THEN
                    504:             CALL DLASCL( 'G', 0, 0, CSCALE, ANRM, ILO-1, 1, WR, N,
                    505:      $                   IERR )
                    506:             CALL DLASCL( 'G', 0, 0, CSCALE, ANRM, ILO-1, 1, WI, N,
                    507:      $                   IERR )
                    508:          END IF
                    509:       END IF
                    510: *
                    511:       WORK( 1 ) = MAXWRK
                    512:       RETURN
                    513: *
                    514: *     End of DGEEV
                    515: *
                    516:       END

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