File:  [local] / rpl / lapack / lapack / zgeevx.f
Revision 1.2: download - view: text, annotated - select for diffs - revision graph
Wed Apr 21 13:45:28 2010 UTC (14 years ago) by bertrand
Branches: MAIN
CVS tags: rpl-4_0_17, rpl-4_0_16, rpl-4_0_15, HEAD
En route pour la 4.0.15 !

    1:       SUBROUTINE ZGEEVX( BALANC, JOBVL, JOBVR, SENSE, N, A, LDA, W, VL,
    2:      $                   LDVL, VR, LDVR, ILO, IHI, SCALE, ABNRM, RCONDE,
    3:      $                   RCONDV, WORK, LWORK, RWORK, INFO )
    4: *
    5: *  -- LAPACK driver routine (version 3.2) --
    6: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
    7: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
    8: *     November 2006
    9: *
   10: *     .. Scalar Arguments ..
   11:       CHARACTER          BALANC, JOBVL, JOBVR, SENSE
   12:       INTEGER            IHI, ILO, INFO, LDA, LDVL, LDVR, LWORK, N
   13:       DOUBLE PRECISION   ABNRM
   14: *     ..
   15: *     .. Array Arguments ..
   16:       DOUBLE PRECISION   RCONDE( * ), RCONDV( * ), RWORK( * ),
   17:      $                   SCALE( * )
   18:       COMPLEX*16         A( LDA, * ), VL( LDVL, * ), VR( LDVR, * ),
   19:      $                   W( * ), WORK( * )
   20: *     ..
   21: *
   22: *  Purpose
   23: *  =======
   24: *
   25: *  ZGEEVX computes for an N-by-N complex nonsymmetric matrix A, the
   26: *  eigenvalues and, optionally, the left and/or right eigenvectors.
   27: *
   28: *  Optionally also, it computes a balancing transformation to improve
   29: *  the conditioning of the eigenvalues and eigenvectors (ILO, IHI,
   30: *  SCALE, and ABNRM), reciprocal condition numbers for the eigenvalues
   31: *  (RCONDE), and reciprocal condition numbers for the right
   32: *  eigenvectors (RCONDV).
   33: *
   34: *  The right eigenvector v(j) of A satisfies
   35: *                   A * v(j) = lambda(j) * v(j)
   36: *  where lambda(j) is its eigenvalue.
   37: *  The left eigenvector u(j) of A satisfies
   38: *                u(j)**H * A = lambda(j) * u(j)**H
   39: *  where u(j)**H denotes the conjugate transpose of u(j).
   40: *
   41: *  The computed eigenvectors are normalized to have Euclidean norm
   42: *  equal to 1 and largest component real.
   43: *
   44: *  Balancing a matrix means permuting the rows and columns to make it
   45: *  more nearly upper triangular, and applying a diagonal similarity
   46: *  transformation D * A * D**(-1), where D is a diagonal matrix, to
   47: *  make its rows and columns closer in norm and the condition numbers
   48: *  of its eigenvalues and eigenvectors smaller.  The computed
   49: *  reciprocal condition numbers correspond to the balanced matrix.
   50: *  Permuting rows and columns will not change the condition numbers
   51: *  (in exact arithmetic) but diagonal scaling will.  For further
   52: *  explanation of balancing, see section 4.10.2 of the LAPACK
   53: *  Users' Guide.
   54: *
   55: *  Arguments
   56: *  =========
   57: *
   58: *  BALANC  (input) CHARACTER*1
   59: *          Indicates how the input matrix should be diagonally scaled
   60: *          and/or permuted to improve the conditioning of its
   61: *          eigenvalues.
   62: *          = 'N': Do not diagonally scale or permute;
   63: *          = 'P': Perform permutations to make the matrix more nearly
   64: *                 upper triangular. Do not diagonally scale;
   65: *          = 'S': Diagonally scale the matrix, ie. replace A by
   66: *                 D*A*D**(-1), where D is a diagonal matrix chosen
   67: *                 to make the rows and columns of A more equal in
   68: *                 norm. Do not permute;
   69: *          = 'B': Both diagonally scale and permute A.
   70: *
   71: *          Computed reciprocal condition numbers will be for the matrix
   72: *          after balancing and/or permuting. Permuting does not change
   73: *          condition numbers (in exact arithmetic), but balancing does.
   74: *
   75: *  JOBVL   (input) CHARACTER*1
   76: *          = 'N': left eigenvectors of A are not computed;
   77: *          = 'V': left eigenvectors of A are computed.
   78: *          If SENSE = 'E' or 'B', JOBVL must = 'V'.
   79: *
   80: *  JOBVR   (input) CHARACTER*1
   81: *          = 'N': right eigenvectors of A are not computed;
   82: *          = 'V': right eigenvectors of A are computed.
   83: *          If SENSE = 'E' or 'B', JOBVR must = 'V'.
   84: *
   85: *  SENSE   (input) CHARACTER*1
   86: *          Determines which reciprocal condition numbers are computed.
   87: *          = 'N': None are computed;
   88: *          = 'E': Computed for eigenvalues only;
   89: *          = 'V': Computed for right eigenvectors only;
   90: *          = 'B': Computed for eigenvalues and right eigenvectors.
   91: *
   92: *          If SENSE = 'E' or 'B', both left and right eigenvectors
   93: *          must also be computed (JOBVL = 'V' and JOBVR = 'V').
   94: *
   95: *  N       (input) INTEGER
   96: *          The order of the matrix A. N >= 0.
   97: *
   98: *  A       (input/output) COMPLEX*16 array, dimension (LDA,N)
   99: *          On entry, the N-by-N matrix A.
  100: *          On exit, A has been overwritten.  If JOBVL = 'V' or
  101: *          JOBVR = 'V', A contains the Schur form of the balanced
  102: *          version of the matrix A.
  103: *
  104: *  LDA     (input) INTEGER
  105: *          The leading dimension of the array A.  LDA >= max(1,N).
  106: *
  107: *  W       (output) COMPLEX*16 array, dimension (N)
  108: *          W contains the computed eigenvalues.
  109: *
  110: *  VL      (output) COMPLEX*16 array, dimension (LDVL,N)
  111: *          If JOBVL = 'V', the left eigenvectors u(j) are stored one
  112: *          after another in the columns of VL, in the same order
  113: *          as their eigenvalues.
  114: *          If JOBVL = 'N', VL is not referenced.
  115: *          u(j) = VL(:,j), the j-th column of VL.
  116: *
  117: *  LDVL    (input) INTEGER
  118: *          The leading dimension of the array VL.  LDVL >= 1; if
  119: *          JOBVL = 'V', LDVL >= N.
  120: *
  121: *  VR      (output) COMPLEX*16 array, dimension (LDVR,N)
  122: *          If JOBVR = 'V', the right eigenvectors v(j) are stored one
  123: *          after another in the columns of VR, in the same order
  124: *          as their eigenvalues.
  125: *          If JOBVR = 'N', VR is not referenced.
  126: *          v(j) = VR(:,j), the j-th column of VR.
  127: *
  128: *  LDVR    (input) INTEGER
  129: *          The leading dimension of the array VR.  LDVR >= 1; if
  130: *          JOBVR = 'V', LDVR >= N.
  131: *
  132: *  ILO     (output) INTEGER
  133: *  IHI     (output) INTEGER
  134: *          ILO and IHI are integer values determined when A was
  135: *          balanced.  The balanced A(i,j) = 0 if I > J and
  136: *          J = 1,...,ILO-1 or I = IHI+1,...,N.
  137: *
  138: *  SCALE   (output) DOUBLE PRECISION array, dimension (N)
  139: *          Details of the permutations and scaling factors applied
  140: *          when balancing A.  If P(j) is the index of the row and column
  141: *          interchanged with row and column j, and D(j) is the scaling
  142: *          factor applied to row and column j, then
  143: *          SCALE(J) = P(J),    for J = 1,...,ILO-1
  144: *                   = D(J),    for J = ILO,...,IHI
  145: *                   = P(J)     for J = IHI+1,...,N.
  146: *          The order in which the interchanges are made is N to IHI+1,
  147: *          then 1 to ILO-1.
  148: *
  149: *  ABNRM   (output) DOUBLE PRECISION
  150: *          The one-norm of the balanced matrix (the maximum
  151: *          of the sum of absolute values of elements of any column).
  152: *
  153: *  RCONDE  (output) DOUBLE PRECISION array, dimension (N)
  154: *          RCONDE(j) is the reciprocal condition number of the j-th
  155: *          eigenvalue.
  156: *
  157: *  RCONDV  (output) DOUBLE PRECISION array, dimension (N)
  158: *          RCONDV(j) is the reciprocal condition number of the j-th
  159: *          right eigenvector.
  160: *
  161: *  WORK    (workspace/output) COMPLEX*16 array, dimension (MAX(1,LWORK))
  162: *          On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
  163: *
  164: *  LWORK   (input) INTEGER
  165: *          The dimension of the array WORK.  If SENSE = 'N' or 'E',
  166: *          LWORK >= max(1,2*N), and if SENSE = 'V' or 'B',
  167: *          LWORK >= N*N+2*N.
  168: *          For good performance, LWORK must generally be larger.
  169: *
  170: *          If LWORK = -1, then a workspace query is assumed; the routine
  171: *          only calculates the optimal size of the WORK array, returns
  172: *          this value as the first entry of the WORK array, and no error
  173: *          message related to LWORK is issued by XERBLA.
  174: *
  175: *  RWORK   (workspace) DOUBLE PRECISION array, dimension (2*N)
  176: *
  177: *  INFO    (output) INTEGER
  178: *          = 0:  successful exit
  179: *          < 0:  if INFO = -i, the i-th argument had an illegal value.
  180: *          > 0:  if INFO = i, the QR algorithm failed to compute all the
  181: *                eigenvalues, and no eigenvectors or condition numbers
  182: *                have been computed; elements 1:ILO-1 and i+1:N of W
  183: *                contain eigenvalues which have converged.
  184: *
  185: *  =====================================================================
  186: *
  187: *     .. Parameters ..
  188:       DOUBLE PRECISION   ZERO, ONE
  189:       PARAMETER          ( ZERO = 0.0D0, ONE = 1.0D0 )
  190: *     ..
  191: *     .. Local Scalars ..
  192:       LOGICAL            LQUERY, SCALEA, WANTVL, WANTVR, WNTSNB, WNTSNE,
  193:      $                   WNTSNN, WNTSNV
  194:       CHARACTER          JOB, SIDE
  195:       INTEGER            HSWORK, I, ICOND, IERR, ITAU, IWRK, K, MAXWRK,
  196:      $                   MINWRK, NOUT
  197:       DOUBLE PRECISION   ANRM, BIGNUM, CSCALE, EPS, SCL, SMLNUM
  198:       COMPLEX*16         TMP
  199: *     ..
  200: *     .. Local Arrays ..
  201:       LOGICAL            SELECT( 1 )
  202:       DOUBLE PRECISION   DUM( 1 )
  203: *     ..
  204: *     .. External Subroutines ..
  205:       EXTERNAL           DLABAD, DLASCL, XERBLA, ZDSCAL, ZGEBAK, ZGEBAL,
  206:      $                   ZGEHRD, ZHSEQR, ZLACPY, ZLASCL, ZSCAL, ZTREVC,
  207:      $                   ZTRSNA, ZUNGHR
  208: *     ..
  209: *     .. External Functions ..
  210:       LOGICAL            LSAME
  211:       INTEGER            IDAMAX, ILAENV
  212:       DOUBLE PRECISION   DLAMCH, DZNRM2, ZLANGE
  213:       EXTERNAL           LSAME, IDAMAX, ILAENV, DLAMCH, DZNRM2, ZLANGE
  214: *     ..
  215: *     .. Intrinsic Functions ..
  216:       INTRINSIC          DBLE, DCMPLX, DCONJG, DIMAG, MAX, SQRT
  217: *     ..
  218: *     .. Executable Statements ..
  219: *
  220: *     Test the input arguments
  221: *
  222:       INFO = 0
  223:       LQUERY = ( LWORK.EQ.-1 )
  224:       WANTVL = LSAME( JOBVL, 'V' )
  225:       WANTVR = LSAME( JOBVR, 'V' )
  226:       WNTSNN = LSAME( SENSE, 'N' )
  227:       WNTSNE = LSAME( SENSE, 'E' )
  228:       WNTSNV = LSAME( SENSE, 'V' )
  229:       WNTSNB = LSAME( SENSE, 'B' )
  230:       IF( .NOT.( LSAME( BALANC, 'N' ) .OR. LSAME( BALANC, 'S' ) .OR.
  231:      $    LSAME( BALANC, 'P' ) .OR. LSAME( BALANC, 'B' ) ) ) THEN
  232:          INFO = -1
  233:       ELSE IF( ( .NOT.WANTVL ) .AND. ( .NOT.LSAME( JOBVL, 'N' ) ) ) THEN
  234:          INFO = -2
  235:       ELSE IF( ( .NOT.WANTVR ) .AND. ( .NOT.LSAME( JOBVR, 'N' ) ) ) THEN
  236:          INFO = -3
  237:       ELSE IF( .NOT.( WNTSNN .OR. WNTSNE .OR. WNTSNB .OR. WNTSNV ) .OR.
  238:      $         ( ( WNTSNE .OR. WNTSNB ) .AND. .NOT.( WANTVL .AND.
  239:      $         WANTVR ) ) ) THEN
  240:          INFO = -4
  241:       ELSE IF( N.LT.0 ) THEN
  242:          INFO = -5
  243:       ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
  244:          INFO = -7
  245:       ELSE IF( LDVL.LT.1 .OR. ( WANTVL .AND. LDVL.LT.N ) ) THEN
  246:          INFO = -10
  247:       ELSE IF( LDVR.LT.1 .OR. ( WANTVR .AND. LDVR.LT.N ) ) THEN
  248:          INFO = -12
  249:       END IF
  250: *
  251: *     Compute workspace
  252: *      (Note: Comments in the code beginning "Workspace:" describe the
  253: *       minimal amount of workspace needed at that point in the code,
  254: *       as well as the preferred amount for good performance.
  255: *       CWorkspace refers to complex workspace, and RWorkspace to real
  256: *       workspace. NB refers to the optimal block size for the
  257: *       immediately following subroutine, as returned by ILAENV.
  258: *       HSWORK refers to the workspace preferred by ZHSEQR, as
  259: *       calculated below. HSWORK is computed assuming ILO=1 and IHI=N,
  260: *       the worst case.)
  261: *
  262:       IF( INFO.EQ.0 ) THEN
  263:          IF( N.EQ.0 ) THEN
  264:             MINWRK = 1
  265:             MAXWRK = 1
  266:          ELSE
  267:             MAXWRK = N + N*ILAENV( 1, 'ZGEHRD', ' ', N, 1, N, 0 )
  268: *
  269:             IF( WANTVL ) THEN
  270:                CALL ZHSEQR( 'S', 'V', N, 1, N, A, LDA, W, VL, LDVL,
  271:      $                WORK, -1, INFO )
  272:             ELSE IF( WANTVR ) THEN
  273:                CALL ZHSEQR( 'S', 'V', N, 1, N, A, LDA, W, VR, LDVR,
  274:      $                WORK, -1, INFO )
  275:             ELSE
  276:                IF( WNTSNN ) THEN
  277:                   CALL ZHSEQR( 'E', 'N', N, 1, N, A, LDA, W, VR, LDVR,
  278:      $                WORK, -1, INFO )
  279:                ELSE
  280:                   CALL ZHSEQR( 'S', 'N', N, 1, N, A, LDA, W, VR, LDVR,
  281:      $                WORK, -1, INFO )
  282:                END IF
  283:             END IF
  284:             HSWORK = WORK( 1 )
  285: *
  286:             IF( ( .NOT.WANTVL ) .AND. ( .NOT.WANTVR ) ) THEN
  287:                MINWRK = 2*N
  288:                IF( .NOT.( WNTSNN .OR. WNTSNE ) )
  289:      $            MINWRK = MAX( MINWRK, N*N + 2*N )
  290:                MAXWRK = MAX( MAXWRK, HSWORK )
  291:                IF( .NOT.( WNTSNN .OR. WNTSNE ) )
  292:      $            MAXWRK = MAX( MAXWRK, N*N + 2*N )
  293:             ELSE
  294:                MINWRK = 2*N
  295:                IF( .NOT.( WNTSNN .OR. WNTSNE ) )
  296:      $            MINWRK = MAX( MINWRK, N*N + 2*N )
  297:                MAXWRK = MAX( MAXWRK, HSWORK )
  298:                MAXWRK = MAX( MAXWRK, N + ( N - 1 )*ILAENV( 1, 'ZUNGHR',
  299:      $                       ' ', N, 1, N, -1 ) )
  300:                IF( .NOT.( WNTSNN .OR. WNTSNE ) )
  301:      $            MAXWRK = MAX( MAXWRK, N*N + 2*N )
  302:                MAXWRK = MAX( MAXWRK, 2*N )
  303:             END IF
  304:             MAXWRK = MAX( MAXWRK, MINWRK )
  305:          END IF
  306:          WORK( 1 ) = MAXWRK
  307: *
  308:          IF( LWORK.LT.MINWRK .AND. .NOT.LQUERY ) THEN
  309:             INFO = -20
  310:          END IF
  311:       END IF
  312: *
  313:       IF( INFO.NE.0 ) THEN
  314:          CALL XERBLA( 'ZGEEVX', -INFO )
  315:          RETURN
  316:       ELSE IF( LQUERY ) THEN
  317:          RETURN
  318:       END IF
  319: *
  320: *     Quick return if possible
  321: *
  322:       IF( N.EQ.0 )
  323:      $   RETURN
  324: *
  325: *     Get machine constants
  326: *
  327:       EPS = DLAMCH( 'P' )
  328:       SMLNUM = DLAMCH( 'S' )
  329:       BIGNUM = ONE / SMLNUM
  330:       CALL DLABAD( SMLNUM, BIGNUM )
  331:       SMLNUM = SQRT( SMLNUM ) / EPS
  332:       BIGNUM = ONE / SMLNUM
  333: *
  334: *     Scale A if max element outside range [SMLNUM,BIGNUM]
  335: *
  336:       ICOND = 0
  337:       ANRM = ZLANGE( 'M', N, N, A, LDA, DUM )
  338:       SCALEA = .FALSE.
  339:       IF( ANRM.GT.ZERO .AND. ANRM.LT.SMLNUM ) THEN
  340:          SCALEA = .TRUE.
  341:          CSCALE = SMLNUM
  342:       ELSE IF( ANRM.GT.BIGNUM ) THEN
  343:          SCALEA = .TRUE.
  344:          CSCALE = BIGNUM
  345:       END IF
  346:       IF( SCALEA )
  347:      $   CALL ZLASCL( 'G', 0, 0, ANRM, CSCALE, N, N, A, LDA, IERR )
  348: *
  349: *     Balance the matrix and compute ABNRM
  350: *
  351:       CALL ZGEBAL( BALANC, N, A, LDA, ILO, IHI, SCALE, IERR )
  352:       ABNRM = ZLANGE( '1', N, N, A, LDA, DUM )
  353:       IF( SCALEA ) THEN
  354:          DUM( 1 ) = ABNRM
  355:          CALL DLASCL( 'G', 0, 0, CSCALE, ANRM, 1, 1, DUM, 1, IERR )
  356:          ABNRM = DUM( 1 )
  357:       END IF
  358: *
  359: *     Reduce to upper Hessenberg form
  360: *     (CWorkspace: need 2*N, prefer N+N*NB)
  361: *     (RWorkspace: none)
  362: *
  363:       ITAU = 1
  364:       IWRK = ITAU + N
  365:       CALL ZGEHRD( N, ILO, IHI, A, LDA, WORK( ITAU ), WORK( IWRK ),
  366:      $             LWORK-IWRK+1, IERR )
  367: *
  368:       IF( WANTVL ) THEN
  369: *
  370: *        Want left eigenvectors
  371: *        Copy Householder vectors to VL
  372: *
  373:          SIDE = 'L'
  374:          CALL ZLACPY( 'L', N, N, A, LDA, VL, LDVL )
  375: *
  376: *        Generate unitary matrix in VL
  377: *        (CWorkspace: need 2*N-1, prefer N+(N-1)*NB)
  378: *        (RWorkspace: none)
  379: *
  380:          CALL ZUNGHR( N, ILO, IHI, VL, LDVL, WORK( ITAU ), WORK( IWRK ),
  381:      $                LWORK-IWRK+1, IERR )
  382: *
  383: *        Perform QR iteration, accumulating Schur vectors in VL
  384: *        (CWorkspace: need 1, prefer HSWORK (see comments) )
  385: *        (RWorkspace: none)
  386: *
  387:          IWRK = ITAU
  388:          CALL ZHSEQR( 'S', 'V', N, ILO, IHI, A, LDA, W, VL, LDVL,
  389:      $                WORK( IWRK ), LWORK-IWRK+1, INFO )
  390: *
  391:          IF( WANTVR ) THEN
  392: *
  393: *           Want left and right eigenvectors
  394: *           Copy Schur vectors to VR
  395: *
  396:             SIDE = 'B'
  397:             CALL ZLACPY( 'F', N, N, VL, LDVL, VR, LDVR )
  398:          END IF
  399: *
  400:       ELSE IF( WANTVR ) THEN
  401: *
  402: *        Want right eigenvectors
  403: *        Copy Householder vectors to VR
  404: *
  405:          SIDE = 'R'
  406:          CALL ZLACPY( 'L', N, N, A, LDA, VR, LDVR )
  407: *
  408: *        Generate unitary matrix in VR
  409: *        (CWorkspace: need 2*N-1, prefer N+(N-1)*NB)
  410: *        (RWorkspace: none)
  411: *
  412:          CALL ZUNGHR( N, ILO, IHI, VR, LDVR, WORK( ITAU ), WORK( IWRK ),
  413:      $                LWORK-IWRK+1, IERR )
  414: *
  415: *        Perform QR iteration, accumulating Schur vectors in VR
  416: *        (CWorkspace: need 1, prefer HSWORK (see comments) )
  417: *        (RWorkspace: none)
  418: *
  419:          IWRK = ITAU
  420:          CALL ZHSEQR( 'S', 'V', N, ILO, IHI, A, LDA, W, VR, LDVR,
  421:      $                WORK( IWRK ), LWORK-IWRK+1, INFO )
  422: *
  423:       ELSE
  424: *
  425: *        Compute eigenvalues only
  426: *        If condition numbers desired, compute Schur form
  427: *
  428:          IF( WNTSNN ) THEN
  429:             JOB = 'E'
  430:          ELSE
  431:             JOB = 'S'
  432:          END IF
  433: *
  434: *        (CWorkspace: need 1, prefer HSWORK (see comments) )
  435: *        (RWorkspace: none)
  436: *
  437:          IWRK = ITAU
  438:          CALL ZHSEQR( JOB, 'N', N, ILO, IHI, A, LDA, W, VR, LDVR,
  439:      $                WORK( IWRK ), LWORK-IWRK+1, INFO )
  440:       END IF
  441: *
  442: *     If INFO > 0 from ZHSEQR, then quit
  443: *
  444:       IF( INFO.GT.0 )
  445:      $   GO TO 50
  446: *
  447:       IF( WANTVL .OR. WANTVR ) THEN
  448: *
  449: *        Compute left and/or right eigenvectors
  450: *        (CWorkspace: need 2*N)
  451: *        (RWorkspace: need N)
  452: *
  453:          CALL ZTREVC( SIDE, 'B', SELECT, N, A, LDA, VL, LDVL, VR, LDVR,
  454:      $                N, NOUT, WORK( IWRK ), RWORK, IERR )
  455:       END IF
  456: *
  457: *     Compute condition numbers if desired
  458: *     (CWorkspace: need N*N+2*N unless SENSE = 'E')
  459: *     (RWorkspace: need 2*N unless SENSE = 'E')
  460: *
  461:       IF( .NOT.WNTSNN ) THEN
  462:          CALL ZTRSNA( SENSE, 'A', SELECT, N, A, LDA, VL, LDVL, VR, LDVR,
  463:      $                RCONDE, RCONDV, N, NOUT, WORK( IWRK ), N, RWORK,
  464:      $                ICOND )
  465:       END IF
  466: *
  467:       IF( WANTVL ) THEN
  468: *
  469: *        Undo balancing of left eigenvectors
  470: *
  471:          CALL ZGEBAK( BALANC, 'L', N, ILO, IHI, SCALE, N, VL, LDVL,
  472:      $                IERR )
  473: *
  474: *        Normalize left eigenvectors and make largest component real
  475: *
  476:          DO 20 I = 1, N
  477:             SCL = ONE / DZNRM2( N, VL( 1, I ), 1 )
  478:             CALL ZDSCAL( N, SCL, VL( 1, I ), 1 )
  479:             DO 10 K = 1, N
  480:                RWORK( K ) = DBLE( VL( K, I ) )**2 +
  481:      $                      DIMAG( VL( K, I ) )**2
  482:    10       CONTINUE
  483:             K = IDAMAX( N, RWORK, 1 )
  484:             TMP = DCONJG( VL( K, I ) ) / SQRT( RWORK( K ) )
  485:             CALL ZSCAL( N, TMP, VL( 1, I ), 1 )
  486:             VL( K, I ) = DCMPLX( DBLE( VL( K, I ) ), ZERO )
  487:    20    CONTINUE
  488:       END IF
  489: *
  490:       IF( WANTVR ) THEN
  491: *
  492: *        Undo balancing of right eigenvectors
  493: *
  494:          CALL ZGEBAK( BALANC, 'R', N, ILO, IHI, SCALE, N, VR, LDVR,
  495:      $                IERR )
  496: *
  497: *        Normalize right eigenvectors and make largest component real
  498: *
  499:          DO 40 I = 1, N
  500:             SCL = ONE / DZNRM2( N, VR( 1, I ), 1 )
  501:             CALL ZDSCAL( N, SCL, VR( 1, I ), 1 )
  502:             DO 30 K = 1, N
  503:                RWORK( K ) = DBLE( VR( K, I ) )**2 +
  504:      $                      DIMAG( VR( K, I ) )**2
  505:    30       CONTINUE
  506:             K = IDAMAX( N, RWORK, 1 )
  507:             TMP = DCONJG( VR( K, I ) ) / SQRT( RWORK( K ) )
  508:             CALL ZSCAL( N, TMP, VR( 1, I ), 1 )
  509:             VR( K, I ) = DCMPLX( DBLE( VR( K, I ) ), ZERO )
  510:    40    CONTINUE
  511:       END IF
  512: *
  513: *     Undo scaling if necessary
  514: *
  515:    50 CONTINUE
  516:       IF( SCALEA ) THEN
  517:          CALL ZLASCL( 'G', 0, 0, CSCALE, ANRM, N-INFO, 1, W( INFO+1 ),
  518:      $                MAX( N-INFO, 1 ), IERR )
  519:          IF( INFO.EQ.0 ) THEN
  520:             IF( ( WNTSNV .OR. WNTSNB ) .AND. ICOND.EQ.0 )
  521:      $         CALL DLASCL( 'G', 0, 0, CSCALE, ANRM, N, 1, RCONDV, N,
  522:      $                      IERR )
  523:          ELSE
  524:             CALL ZLASCL( 'G', 0, 0, CSCALE, ANRM, ILO-1, 1, W, N, IERR )
  525:          END IF
  526:       END IF
  527: *
  528:       WORK( 1 ) = MAXWRK
  529:       RETURN
  530: *
  531: *     End of ZGEEVX
  532: *
  533:       END

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