Annotation of rpl/lapack/lapack/zlaqr2.f, revision 1.17

1.11      bertrand    1: *> \brief \b ZLAQR2 performs the unitary similarity transformation of a Hessenberg matrix to detect and deflate fully converged eigenvalues from a trailing principal submatrix (aggressive early deflation).
1.8       bertrand    2: *
                      3: *  =========== DOCUMENTATION ===========
                      4: *
1.15      bertrand    5: * Online html documentation available at
                      6: *            http://www.netlib.org/lapack/explore-html/
1.8       bertrand    7: *
                      8: *> \htmlonly
1.15      bertrand    9: *> Download ZLAQR2 + dependencies
                     10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/zlaqr2.f">
                     11: *> [TGZ]</a>
                     12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/zlaqr2.f">
                     13: *> [ZIP]</a>
                     14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/zlaqr2.f">
1.8       bertrand   15: *> [TXT]</a>
1.15      bertrand   16: *> \endhtmlonly
1.8       bertrand   17: *
                     18: *  Definition:
                     19: *  ===========
                     20: *
                     21: *       SUBROUTINE ZLAQR2( WANTT, WANTZ, N, KTOP, KBOT, NW, H, LDH, ILOZ,
                     22: *                          IHIZ, Z, LDZ, NS, ND, SH, V, LDV, NH, T, LDT,
                     23: *                          NV, WV, LDWV, WORK, LWORK )
1.15      bertrand   24: *
1.8       bertrand   25: *       .. Scalar Arguments ..
                     26: *       INTEGER            IHIZ, ILOZ, KBOT, KTOP, LDH, LDT, LDV, LDWV,
                     27: *      $                   LDZ, LWORK, N, ND, NH, NS, NV, NW
                     28: *       LOGICAL            WANTT, WANTZ
                     29: *       ..
                     30: *       .. Array Arguments ..
                     31: *       COMPLEX*16         H( LDH, * ), SH( * ), T( LDT, * ), V( LDV, * ),
                     32: *      $                   WORK( * ), WV( LDWV, * ), Z( LDZ, * )
                     33: *       ..
1.15      bertrand   34: *
1.8       bertrand   35: *
                     36: *> \par Purpose:
                     37: *  =============
                     38: *>
                     39: *> \verbatim
                     40: *>
                     41: *>    ZLAQR2 is identical to ZLAQR3 except that it avoids
                     42: *>    recursion by calling ZLAHQR instead of ZLAQR4.
                     43: *>
                     44: *>    Aggressive early deflation:
                     45: *>
                     46: *>    ZLAQR2 accepts as input an upper Hessenberg matrix
                     47: *>    H and performs an unitary similarity transformation
                     48: *>    designed to detect and deflate fully converged eigenvalues from
                     49: *>    a trailing principal submatrix.  On output H has been over-
                     50: *>    written by a new Hessenberg matrix that is a perturbation of
                     51: *>    an unitary similarity transformation of H.  It is to be
                     52: *>    hoped that the final version of H has many zero subdiagonal
                     53: *>    entries.
                     54: *>
                     55: *> \endverbatim
                     56: *
                     57: *  Arguments:
                     58: *  ==========
                     59: *
                     60: *> \param[in] WANTT
                     61: *> \verbatim
                     62: *>          WANTT is LOGICAL
                     63: *>          If .TRUE., then the Hessenberg matrix H is fully updated
                     64: *>          so that the triangular Schur factor may be
                     65: *>          computed (in cooperation with the calling subroutine).
                     66: *>          If .FALSE., then only enough of H is updated to preserve
                     67: *>          the eigenvalues.
                     68: *> \endverbatim
                     69: *>
                     70: *> \param[in] WANTZ
                     71: *> \verbatim
                     72: *>          WANTZ is LOGICAL
                     73: *>          If .TRUE., then the unitary matrix Z is updated so
                     74: *>          so that the unitary Schur factor may be computed
                     75: *>          (in cooperation with the calling subroutine).
                     76: *>          If .FALSE., then Z is not referenced.
                     77: *> \endverbatim
                     78: *>
                     79: *> \param[in] N
                     80: *> \verbatim
                     81: *>          N is INTEGER
                     82: *>          The order of the matrix H and (if WANTZ is .TRUE.) the
                     83: *>          order of the unitary matrix Z.
                     84: *> \endverbatim
                     85: *>
                     86: *> \param[in] KTOP
                     87: *> \verbatim
                     88: *>          KTOP is INTEGER
                     89: *>          It is assumed that either KTOP = 1 or H(KTOP,KTOP-1)=0.
                     90: *>          KBOT and KTOP together determine an isolated block
                     91: *>          along the diagonal of the Hessenberg matrix.
                     92: *> \endverbatim
                     93: *>
                     94: *> \param[in] KBOT
                     95: *> \verbatim
                     96: *>          KBOT is INTEGER
                     97: *>          It is assumed without a check that either
                     98: *>          KBOT = N or H(KBOT+1,KBOT)=0.  KBOT and KTOP together
                     99: *>          determine an isolated block along the diagonal of the
                    100: *>          Hessenberg matrix.
                    101: *> \endverbatim
                    102: *>
                    103: *> \param[in] NW
                    104: *> \verbatim
                    105: *>          NW is INTEGER
                    106: *>          Deflation window size.  1 .LE. NW .LE. (KBOT-KTOP+1).
                    107: *> \endverbatim
                    108: *>
                    109: *> \param[in,out] H
                    110: *> \verbatim
                    111: *>          H is COMPLEX*16 array, dimension (LDH,N)
                    112: *>          On input the initial N-by-N section of H stores the
                    113: *>          Hessenberg matrix undergoing aggressive early deflation.
                    114: *>          On output H has been transformed by a unitary
                    115: *>          similarity transformation, perturbed, and the returned
                    116: *>          to Hessenberg form that (it is to be hoped) has some
                    117: *>          zero subdiagonal entries.
                    118: *> \endverbatim
                    119: *>
                    120: *> \param[in] LDH
                    121: *> \verbatim
1.17    ! bertrand  122: *>          LDH is INTEGER
1.8       bertrand  123: *>          Leading dimension of H just as declared in the calling
                    124: *>          subroutine.  N .LE. LDH
                    125: *> \endverbatim
                    126: *>
                    127: *> \param[in] ILOZ
                    128: *> \verbatim
                    129: *>          ILOZ is INTEGER
                    130: *> \endverbatim
                    131: *>
                    132: *> \param[in] IHIZ
                    133: *> \verbatim
                    134: *>          IHIZ is INTEGER
                    135: *>          Specify the rows of Z to which transformations must be
                    136: *>          applied if WANTZ is .TRUE.. 1 .LE. ILOZ .LE. IHIZ .LE. N.
                    137: *> \endverbatim
                    138: *>
                    139: *> \param[in,out] Z
                    140: *> \verbatim
                    141: *>          Z is COMPLEX*16 array, dimension (LDZ,N)
                    142: *>          IF WANTZ is .TRUE., then on output, the unitary
                    143: *>          similarity transformation mentioned above has been
1.15      bertrand  144: *>          accumulated into Z(ILOZ:IHIZ,ILOZ:IHIZ) from the right.
1.8       bertrand  145: *>          If WANTZ is .FALSE., then Z is unreferenced.
                    146: *> \endverbatim
                    147: *>
                    148: *> \param[in] LDZ
                    149: *> \verbatim
1.17    ! bertrand  150: *>          LDZ is INTEGER
1.8       bertrand  151: *>          The leading dimension of Z just as declared in the
                    152: *>          calling subroutine.  1 .LE. LDZ.
                    153: *> \endverbatim
                    154: *>
                    155: *> \param[out] NS
                    156: *> \verbatim
1.17    ! bertrand  157: *>          NS is INTEGER
1.8       bertrand  158: *>          The number of unconverged (ie approximate) eigenvalues
                    159: *>          returned in SR and SI that may be used as shifts by the
                    160: *>          calling subroutine.
                    161: *> \endverbatim
                    162: *>
                    163: *> \param[out] ND
                    164: *> \verbatim
1.17    ! bertrand  165: *>          ND is INTEGER
1.8       bertrand  166: *>          The number of converged eigenvalues uncovered by this
                    167: *>          subroutine.
                    168: *> \endverbatim
                    169: *>
                    170: *> \param[out] SH
                    171: *> \verbatim
1.17    ! bertrand  172: *>          SH is COMPLEX*16 array, dimension (KBOT)
1.8       bertrand  173: *>          On output, approximate eigenvalues that may
                    174: *>          be used for shifts are stored in SH(KBOT-ND-NS+1)
                    175: *>          through SR(KBOT-ND).  Converged eigenvalues are
                    176: *>          stored in SH(KBOT-ND+1) through SH(KBOT).
                    177: *> \endverbatim
                    178: *>
                    179: *> \param[out] V
                    180: *> \verbatim
                    181: *>          V is COMPLEX*16 array, dimension (LDV,NW)
                    182: *>          An NW-by-NW work array.
                    183: *> \endverbatim
                    184: *>
                    185: *> \param[in] LDV
                    186: *> \verbatim
1.17    ! bertrand  187: *>          LDV is INTEGER
1.8       bertrand  188: *>          The leading dimension of V just as declared in the
                    189: *>          calling subroutine.  NW .LE. LDV
                    190: *> \endverbatim
                    191: *>
                    192: *> \param[in] NH
                    193: *> \verbatim
1.17    ! bertrand  194: *>          NH is INTEGER
1.8       bertrand  195: *>          The number of columns of T.  NH.GE.NW.
                    196: *> \endverbatim
                    197: *>
                    198: *> \param[out] T
                    199: *> \verbatim
                    200: *>          T is COMPLEX*16 array, dimension (LDT,NW)
                    201: *> \endverbatim
                    202: *>
                    203: *> \param[in] LDT
                    204: *> \verbatim
1.17    ! bertrand  205: *>          LDT is INTEGER
1.8       bertrand  206: *>          The leading dimension of T just as declared in the
                    207: *>          calling subroutine.  NW .LE. LDT
                    208: *> \endverbatim
                    209: *>
                    210: *> \param[in] NV
                    211: *> \verbatim
1.17    ! bertrand  212: *>          NV is INTEGER
1.8       bertrand  213: *>          The number of rows of work array WV available for
                    214: *>          workspace.  NV.GE.NW.
                    215: *> \endverbatim
                    216: *>
                    217: *> \param[out] WV
                    218: *> \verbatim
                    219: *>          WV is COMPLEX*16 array, dimension (LDWV,NW)
                    220: *> \endverbatim
                    221: *>
                    222: *> \param[in] LDWV
                    223: *> \verbatim
1.17    ! bertrand  224: *>          LDWV is INTEGER
1.8       bertrand  225: *>          The leading dimension of W just as declared in the
                    226: *>          calling subroutine.  NW .LE. LDV
                    227: *> \endverbatim
                    228: *>
                    229: *> \param[out] WORK
                    230: *> \verbatim
1.17    ! bertrand  231: *>          WORK is COMPLEX*16 array, dimension (LWORK)
1.8       bertrand  232: *>          On exit, WORK(1) is set to an estimate of the optimal value
                    233: *>          of LWORK for the given values of N, NW, KTOP and KBOT.
                    234: *> \endverbatim
                    235: *>
                    236: *> \param[in] LWORK
                    237: *> \verbatim
1.17    ! bertrand  238: *>          LWORK is INTEGER
1.8       bertrand  239: *>          The dimension of the work array WORK.  LWORK = 2*NW
                    240: *>          suffices, but greater efficiency may result from larger
                    241: *>          values of LWORK.
                    242: *>
                    243: *>          If LWORK = -1, then a workspace query is assumed; ZLAQR2
                    244: *>          only estimates the optimal workspace size for the given
                    245: *>          values of N, NW, KTOP and KBOT.  The estimate is returned
                    246: *>          in WORK(1).  No error message related to LWORK is issued
                    247: *>          by XERBLA.  Neither H nor Z are accessed.
                    248: *> \endverbatim
                    249: *
                    250: *  Authors:
                    251: *  ========
                    252: *
1.15      bertrand  253: *> \author Univ. of Tennessee
                    254: *> \author Univ. of California Berkeley
                    255: *> \author Univ. of Colorado Denver
                    256: *> \author NAG Ltd.
1.8       bertrand  257: *
1.17    ! bertrand  258: *> \date June 2017
1.8       bertrand  259: *
                    260: *> \ingroup complex16OTHERauxiliary
                    261: *
                    262: *> \par Contributors:
                    263: *  ==================
                    264: *>
                    265: *>       Karen Braman and Ralph Byers, Department of Mathematics,
                    266: *>       University of Kansas, USA
                    267: *>
                    268: *  =====================================================================
1.1       bertrand  269:       SUBROUTINE ZLAQR2( WANTT, WANTZ, N, KTOP, KBOT, NW, H, LDH, ILOZ,
                    270:      $                   IHIZ, Z, LDZ, NS, ND, SH, V, LDV, NH, T, LDT,
                    271:      $                   NV, WV, LDWV, WORK, LWORK )
                    272: *
1.17    ! bertrand  273: *  -- LAPACK auxiliary routine (version 3.7.1) --
1.8       bertrand  274: *  -- LAPACK is a software package provided by Univ. of Tennessee,    --
                    275: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.17    ! bertrand  276: *     June 2017
1.1       bertrand  277: *
                    278: *     .. Scalar Arguments ..
                    279:       INTEGER            IHIZ, ILOZ, KBOT, KTOP, LDH, LDT, LDV, LDWV,
                    280:      $                   LDZ, LWORK, N, ND, NH, NS, NV, NW
                    281:       LOGICAL            WANTT, WANTZ
                    282: *     ..
                    283: *     .. Array Arguments ..
                    284:       COMPLEX*16         H( LDH, * ), SH( * ), T( LDT, * ), V( LDV, * ),
                    285:      $                   WORK( * ), WV( LDWV, * ), Z( LDZ, * )
                    286: *     ..
                    287: *
1.8       bertrand  288: *  ================================================================
1.1       bertrand  289: *
                    290: *     .. Parameters ..
                    291:       COMPLEX*16         ZERO, ONE
                    292:       PARAMETER          ( ZERO = ( 0.0d0, 0.0d0 ),
                    293:      $                   ONE = ( 1.0d0, 0.0d0 ) )
                    294:       DOUBLE PRECISION   RZERO, RONE
                    295:       PARAMETER          ( RZERO = 0.0d0, RONE = 1.0d0 )
                    296: *     ..
                    297: *     .. Local Scalars ..
                    298:       COMPLEX*16         BETA, CDUM, S, TAU
                    299:       DOUBLE PRECISION   FOO, SAFMAX, SAFMIN, SMLNUM, ULP
                    300:       INTEGER            I, IFST, ILST, INFO, INFQR, J, JW, KCOL, KLN,
                    301:      $                   KNT, KROW, KWTOP, LTOP, LWK1, LWK2, LWKOPT
                    302: *     ..
                    303: *     .. External Functions ..
                    304:       DOUBLE PRECISION   DLAMCH
                    305:       EXTERNAL           DLAMCH
                    306: *     ..
                    307: *     .. External Subroutines ..
                    308:       EXTERNAL           DLABAD, ZCOPY, ZGEHRD, ZGEMM, ZLACPY, ZLAHQR,
                    309:      $                   ZLARF, ZLARFG, ZLASET, ZTREXC, ZUNMHR
                    310: *     ..
                    311: *     .. Intrinsic Functions ..
                    312:       INTRINSIC          ABS, DBLE, DCMPLX, DCONJG, DIMAG, INT, MAX, MIN
                    313: *     ..
                    314: *     .. Statement Functions ..
                    315:       DOUBLE PRECISION   CABS1
                    316: *     ..
                    317: *     .. Statement Function definitions ..
                    318:       CABS1( CDUM ) = ABS( DBLE( CDUM ) ) + ABS( DIMAG( CDUM ) )
                    319: *     ..
                    320: *     .. Executable Statements ..
                    321: *
                    322: *     ==== Estimate optimal workspace. ====
                    323: *
                    324:       JW = MIN( NW, KBOT-KTOP+1 )
                    325:       IF( JW.LE.2 ) THEN
                    326:          LWKOPT = 1
                    327:       ELSE
                    328: *
                    329: *        ==== Workspace query call to ZGEHRD ====
                    330: *
                    331:          CALL ZGEHRD( JW, 1, JW-1, T, LDT, WORK, WORK, -1, INFO )
                    332:          LWK1 = INT( WORK( 1 ) )
                    333: *
                    334: *        ==== Workspace query call to ZUNMHR ====
                    335: *
                    336:          CALL ZUNMHR( 'R', 'N', JW, JW, 1, JW-1, T, LDT, WORK, V, LDV,
                    337:      $                WORK, -1, INFO )
                    338:          LWK2 = INT( WORK( 1 ) )
                    339: *
                    340: *        ==== Optimal workspace ====
                    341: *
                    342:          LWKOPT = JW + MAX( LWK1, LWK2 )
                    343:       END IF
                    344: *
                    345: *     ==== Quick return in case of workspace query. ====
                    346: *
                    347:       IF( LWORK.EQ.-1 ) THEN
                    348:          WORK( 1 ) = DCMPLX( LWKOPT, 0 )
                    349:          RETURN
                    350:       END IF
                    351: *
                    352: *     ==== Nothing to do ...
                    353: *     ... for an empty active block ... ====
                    354:       NS = 0
                    355:       ND = 0
                    356:       WORK( 1 ) = ONE
                    357:       IF( KTOP.GT.KBOT )
                    358:      $   RETURN
                    359: *     ... nor for an empty deflation window. ====
                    360:       IF( NW.LT.1 )
                    361:      $   RETURN
                    362: *
                    363: *     ==== Machine constants ====
                    364: *
                    365:       SAFMIN = DLAMCH( 'SAFE MINIMUM' )
                    366:       SAFMAX = RONE / SAFMIN
                    367:       CALL DLABAD( SAFMIN, SAFMAX )
                    368:       ULP = DLAMCH( 'PRECISION' )
                    369:       SMLNUM = SAFMIN*( DBLE( N ) / ULP )
                    370: *
                    371: *     ==== Setup deflation window ====
                    372: *
                    373:       JW = MIN( NW, KBOT-KTOP+1 )
                    374:       KWTOP = KBOT - JW + 1
                    375:       IF( KWTOP.EQ.KTOP ) THEN
                    376:          S = ZERO
                    377:       ELSE
                    378:          S = H( KWTOP, KWTOP-1 )
                    379:       END IF
                    380: *
                    381:       IF( KBOT.EQ.KWTOP ) THEN
                    382: *
                    383: *        ==== 1-by-1 deflation window: not much to do ====
                    384: *
                    385:          SH( KWTOP ) = H( KWTOP, KWTOP )
                    386:          NS = 1
                    387:          ND = 0
                    388:          IF( CABS1( S ).LE.MAX( SMLNUM, ULP*CABS1( H( KWTOP,
                    389:      $       KWTOP ) ) ) ) THEN
                    390:             NS = 0
                    391:             ND = 1
                    392:             IF( KWTOP.GT.KTOP )
                    393:      $         H( KWTOP, KWTOP-1 ) = ZERO
                    394:          END IF
                    395:          WORK( 1 ) = ONE
                    396:          RETURN
                    397:       END IF
                    398: *
                    399: *     ==== Convert to spike-triangular form.  (In case of a
                    400: *     .    rare QR failure, this routine continues to do
                    401: *     .    aggressive early deflation using that part of
                    402: *     .    the deflation window that converged using INFQR
                    403: *     .    here and there to keep track.) ====
                    404: *
                    405:       CALL ZLACPY( 'U', JW, JW, H( KWTOP, KWTOP ), LDH, T, LDT )
                    406:       CALL ZCOPY( JW-1, H( KWTOP+1, KWTOP ), LDH+1, T( 2, 1 ), LDT+1 )
                    407: *
                    408:       CALL ZLASET( 'A', JW, JW, ZERO, ONE, V, LDV )
                    409:       CALL ZLAHQR( .true., .true., JW, 1, JW, T, LDT, SH( KWTOP ), 1,
                    410:      $             JW, V, LDV, INFQR )
                    411: *
                    412: *     ==== Deflation detection loop ====
                    413: *
                    414:       NS = JW
                    415:       ILST = INFQR + 1
                    416:       DO 10 KNT = INFQR + 1, JW
                    417: *
                    418: *        ==== Small spike tip deflation test ====
                    419: *
                    420:          FOO = CABS1( T( NS, NS ) )
                    421:          IF( FOO.EQ.RZERO )
                    422:      $      FOO = CABS1( S )
                    423:          IF( CABS1( S )*CABS1( V( 1, NS ) ).LE.MAX( SMLNUM, ULP*FOO ) )
                    424:      $        THEN
                    425: *
                    426: *           ==== One more converged eigenvalue ====
                    427: *
                    428:             NS = NS - 1
                    429:          ELSE
                    430: *
                    431: *           ==== One undeflatable eigenvalue.  Move it up out of the
                    432: *           .    way.   (ZTREXC can not fail in this case.) ====
                    433: *
                    434:             IFST = NS
                    435:             CALL ZTREXC( 'V', JW, T, LDT, V, LDV, IFST, ILST, INFO )
                    436:             ILST = ILST + 1
                    437:          END IF
                    438:    10 CONTINUE
                    439: *
                    440: *        ==== Return to Hessenberg form ====
                    441: *
                    442:       IF( NS.EQ.0 )
                    443:      $   S = ZERO
                    444: *
                    445:       IF( NS.LT.JW ) THEN
                    446: *
                    447: *        ==== sorting the diagonal of T improves accuracy for
                    448: *        .    graded matrices.  ====
                    449: *
                    450:          DO 30 I = INFQR + 1, NS
                    451:             IFST = I
                    452:             DO 20 J = I + 1, NS
                    453:                IF( CABS1( T( J, J ) ).GT.CABS1( T( IFST, IFST ) ) )
                    454:      $            IFST = J
                    455:    20       CONTINUE
                    456:             ILST = I
                    457:             IF( IFST.NE.ILST )
                    458:      $         CALL ZTREXC( 'V', JW, T, LDT, V, LDV, IFST, ILST, INFO )
                    459:    30    CONTINUE
                    460:       END IF
                    461: *
                    462: *     ==== Restore shift/eigenvalue array from T ====
                    463: *
                    464:       DO 40 I = INFQR + 1, JW
                    465:          SH( KWTOP+I-1 ) = T( I, I )
                    466:    40 CONTINUE
                    467: *
                    468: *
                    469:       IF( NS.LT.JW .OR. S.EQ.ZERO ) THEN
                    470:          IF( NS.GT.1 .AND. S.NE.ZERO ) THEN
                    471: *
                    472: *           ==== Reflect spike back into lower triangle ====
                    473: *
                    474:             CALL ZCOPY( NS, V, LDV, WORK, 1 )
                    475:             DO 50 I = 1, NS
                    476:                WORK( I ) = DCONJG( WORK( I ) )
                    477:    50       CONTINUE
                    478:             BETA = WORK( 1 )
                    479:             CALL ZLARFG( NS, BETA, WORK( 2 ), 1, TAU )
                    480:             WORK( 1 ) = ONE
                    481: *
                    482:             CALL ZLASET( 'L', JW-2, JW-2, ZERO, ZERO, T( 3, 1 ), LDT )
                    483: *
                    484:             CALL ZLARF( 'L', NS, JW, WORK, 1, DCONJG( TAU ), T, LDT,
                    485:      $                  WORK( JW+1 ) )
                    486:             CALL ZLARF( 'R', NS, NS, WORK, 1, TAU, T, LDT,
                    487:      $                  WORK( JW+1 ) )
                    488:             CALL ZLARF( 'R', JW, NS, WORK, 1, TAU, V, LDV,
                    489:      $                  WORK( JW+1 ) )
                    490: *
                    491:             CALL ZGEHRD( JW, 1, NS, T, LDT, WORK, WORK( JW+1 ),
                    492:      $                   LWORK-JW, INFO )
                    493:          END IF
                    494: *
                    495: *        ==== Copy updated reduced window into place ====
                    496: *
                    497:          IF( KWTOP.GT.1 )
                    498:      $      H( KWTOP, KWTOP-1 ) = S*DCONJG( V( 1, 1 ) )
                    499:          CALL ZLACPY( 'U', JW, JW, T, LDT, H( KWTOP, KWTOP ), LDH )
                    500:          CALL ZCOPY( JW-1, T( 2, 1 ), LDT+1, H( KWTOP+1, KWTOP ),
                    501:      $               LDH+1 )
                    502: *
                    503: *        ==== Accumulate orthogonal matrix in order update
                    504: *        .    H and Z, if requested.  ====
                    505: *
                    506:          IF( NS.GT.1 .AND. S.NE.ZERO )
                    507:      $      CALL ZUNMHR( 'R', 'N', JW, NS, 1, NS, T, LDT, WORK, V, LDV,
                    508:      $                   WORK( JW+1 ), LWORK-JW, INFO )
                    509: *
                    510: *        ==== Update vertical slab in H ====
                    511: *
                    512:          IF( WANTT ) THEN
                    513:             LTOP = 1
                    514:          ELSE
                    515:             LTOP = KTOP
                    516:          END IF
                    517:          DO 60 KROW = LTOP, KWTOP - 1, NV
                    518:             KLN = MIN( NV, KWTOP-KROW )
                    519:             CALL ZGEMM( 'N', 'N', KLN, JW, JW, ONE, H( KROW, KWTOP ),
                    520:      $                  LDH, V, LDV, ZERO, WV, LDWV )
                    521:             CALL ZLACPY( 'A', KLN, JW, WV, LDWV, H( KROW, KWTOP ), LDH )
                    522:    60    CONTINUE
                    523: *
                    524: *        ==== Update horizontal slab in H ====
                    525: *
                    526:          IF( WANTT ) THEN
                    527:             DO 70 KCOL = KBOT + 1, N, NH
                    528:                KLN = MIN( NH, N-KCOL+1 )
                    529:                CALL ZGEMM( 'C', 'N', JW, KLN, JW, ONE, V, LDV,
                    530:      $                     H( KWTOP, KCOL ), LDH, ZERO, T, LDT )
                    531:                CALL ZLACPY( 'A', JW, KLN, T, LDT, H( KWTOP, KCOL ),
                    532:      $                      LDH )
                    533:    70       CONTINUE
                    534:          END IF
                    535: *
                    536: *        ==== Update vertical slab in Z ====
                    537: *
                    538:          IF( WANTZ ) THEN
                    539:             DO 80 KROW = ILOZ, IHIZ, NV
                    540:                KLN = MIN( NV, IHIZ-KROW+1 )
                    541:                CALL ZGEMM( 'N', 'N', KLN, JW, JW, ONE, Z( KROW, KWTOP ),
                    542:      $                     LDZ, V, LDV, ZERO, WV, LDWV )
                    543:                CALL ZLACPY( 'A', KLN, JW, WV, LDWV, Z( KROW, KWTOP ),
                    544:      $                      LDZ )
                    545:    80       CONTINUE
                    546:          END IF
                    547:       END IF
                    548: *
                    549: *     ==== Return the number of deflations ... ====
                    550: *
                    551:       ND = JW - NS
                    552: *
                    553: *     ==== ... and the number of shifts. (Subtracting
                    554: *     .    INFQR from the spike length takes care
                    555: *     .    of the case of a rare QR failure while
                    556: *     .    calculating eigenvalues of the deflation
                    557: *     .    window.)  ====
                    558: *
                    559:       NS = NS - INFQR
                    560: *
                    561: *      ==== Return optimal workspace. ====
                    562: *
                    563:       WORK( 1 ) = DCMPLX( LWKOPT, 0 )
                    564: *
                    565: *     ==== End of ZLAQR2 ====
                    566: *
                    567:       END

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