Annotation of rpl/lapack/lapack/zgges.f, revision 1.8
1.8 ! bertrand 1: *> \brief <b> ZGGES computes the eigenvalues, the Schur form, and, optionally, the matrix of Schur vectors 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 ZGGES + dependencies
! 10: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/zgges.f">
! 11: *> [TGZ]</a>
! 12: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/zgges.f">
! 13: *> [ZIP]</a>
! 14: *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/zgges.f">
! 15: *> [TXT]</a>
! 16: *> \endhtmlonly
! 17: *
! 18: * Definition:
! 19: * ===========
! 20: *
! 21: * SUBROUTINE ZGGES( JOBVSL, JOBVSR, SORT, SELCTG, N, A, LDA, B, LDB,
! 22: * SDIM, ALPHA, BETA, VSL, LDVSL, VSR, LDVSR, WORK,
! 23: * LWORK, RWORK, BWORK, INFO )
! 24: *
! 25: * .. Scalar Arguments ..
! 26: * CHARACTER JOBVSL, JOBVSR, SORT
! 27: * INTEGER INFO, LDA, LDB, LDVSL, LDVSR, LWORK, N, SDIM
! 28: * ..
! 29: * .. Array Arguments ..
! 30: * LOGICAL BWORK( * )
! 31: * DOUBLE PRECISION RWORK( * )
! 32: * COMPLEX*16 A( LDA, * ), ALPHA( * ), B( LDB, * ),
! 33: * $ BETA( * ), VSL( LDVSL, * ), VSR( LDVSR, * ),
! 34: * $ WORK( * )
! 35: * ..
! 36: * .. Function Arguments ..
! 37: * LOGICAL SELCTG
! 38: * EXTERNAL SELCTG
! 39: * ..
! 40: *
! 41: *
! 42: *> \par Purpose:
! 43: * =============
! 44: *>
! 45: *> \verbatim
! 46: *>
! 47: *> ZGGES computes for a pair of N-by-N complex nonsymmetric matrices
! 48: *> (A,B), the generalized eigenvalues, the generalized complex Schur
! 49: *> form (S, T), and optionally left and/or right Schur vectors (VSL
! 50: *> and VSR). This gives the generalized Schur factorization
! 51: *>
! 52: *> (A,B) = ( (VSL)*S*(VSR)**H, (VSL)*T*(VSR)**H )
! 53: *>
! 54: *> where (VSR)**H is the conjugate-transpose of VSR.
! 55: *>
! 56: *> Optionally, it also orders the eigenvalues so that a selected cluster
! 57: *> of eigenvalues appears in the leading diagonal blocks of the upper
! 58: *> triangular matrix S and the upper triangular matrix T. The leading
! 59: *> columns of VSL and VSR then form an unitary basis for the
! 60: *> corresponding left and right eigenspaces (deflating subspaces).
! 61: *>
! 62: *> (If only the generalized eigenvalues are needed, use the driver
! 63: *> ZGGEV instead, which is faster.)
! 64: *>
! 65: *> A generalized eigenvalue for a pair of matrices (A,B) is a scalar w
! 66: *> or a ratio alpha/beta = w, such that A - w*B is singular. It is
! 67: *> usually represented as the pair (alpha,beta), as there is a
! 68: *> reasonable interpretation for beta=0, and even for both being zero.
! 69: *>
! 70: *> A pair of matrices (S,T) is in generalized complex Schur form if S
! 71: *> and T are upper triangular and, in addition, the diagonal elements
! 72: *> of T are non-negative real numbers.
! 73: *> \endverbatim
! 74: *
! 75: * Arguments:
! 76: * ==========
! 77: *
! 78: *> \param[in] JOBVSL
! 79: *> \verbatim
! 80: *> JOBVSL is CHARACTER*1
! 81: *> = 'N': do not compute the left Schur vectors;
! 82: *> = 'V': compute the left Schur vectors.
! 83: *> \endverbatim
! 84: *>
! 85: *> \param[in] JOBVSR
! 86: *> \verbatim
! 87: *> JOBVSR is CHARACTER*1
! 88: *> = 'N': do not compute the right Schur vectors;
! 89: *> = 'V': compute the right Schur vectors.
! 90: *> \endverbatim
! 91: *>
! 92: *> \param[in] SORT
! 93: *> \verbatim
! 94: *> SORT is CHARACTER*1
! 95: *> Specifies whether or not to order the eigenvalues on the
! 96: *> diagonal of the generalized Schur form.
! 97: *> = 'N': Eigenvalues are not ordered;
! 98: *> = 'S': Eigenvalues are ordered (see SELCTG).
! 99: *> \endverbatim
! 100: *>
! 101: *> \param[in] SELCTG
! 102: *> \verbatim
! 103: *> SELCTG is procedure) LOGICAL FUNCTION of two COMPLEX*16 arguments
! 104: *> SELCTG must be declared EXTERNAL in the calling subroutine.
! 105: *> If SORT = 'N', SELCTG is not referenced.
! 106: *> If SORT = 'S', SELCTG is used to select eigenvalues to sort
! 107: *> to the top left of the Schur form.
! 108: *> An eigenvalue ALPHA(j)/BETA(j) is selected if
! 109: *> SELCTG(ALPHA(j),BETA(j)) is true.
! 110: *>
! 111: *> Note that a selected complex eigenvalue may no longer satisfy
! 112: *> SELCTG(ALPHA(j),BETA(j)) = .TRUE. after ordering, since
! 113: *> ordering may change the value of complex eigenvalues
! 114: *> (especially if the eigenvalue is ill-conditioned), in this
! 115: *> case INFO is set to N+2 (See INFO below).
! 116: *> \endverbatim
! 117: *>
! 118: *> \param[in] N
! 119: *> \verbatim
! 120: *> N is INTEGER
! 121: *> The order of the matrices A, B, VSL, and VSR. N >= 0.
! 122: *> \endverbatim
! 123: *>
! 124: *> \param[in,out] A
! 125: *> \verbatim
! 126: *> A is COMPLEX*16 array, dimension (LDA, N)
! 127: *> On entry, the first of the pair of matrices.
! 128: *> On exit, A has been overwritten by its generalized Schur
! 129: *> form S.
! 130: *> \endverbatim
! 131: *>
! 132: *> \param[in] LDA
! 133: *> \verbatim
! 134: *> LDA is INTEGER
! 135: *> The leading dimension of A. LDA >= max(1,N).
! 136: *> \endverbatim
! 137: *>
! 138: *> \param[in,out] B
! 139: *> \verbatim
! 140: *> B is COMPLEX*16 array, dimension (LDB, N)
! 141: *> On entry, the second of the pair of matrices.
! 142: *> On exit, B has been overwritten by its generalized Schur
! 143: *> form T.
! 144: *> \endverbatim
! 145: *>
! 146: *> \param[in] LDB
! 147: *> \verbatim
! 148: *> LDB is INTEGER
! 149: *> The leading dimension of B. LDB >= max(1,N).
! 150: *> \endverbatim
! 151: *>
! 152: *> \param[out] SDIM
! 153: *> \verbatim
! 154: *> SDIM is INTEGER
! 155: *> If SORT = 'N', SDIM = 0.
! 156: *> If SORT = 'S', SDIM = number of eigenvalues (after sorting)
! 157: *> for which SELCTG is true.
! 158: *> \endverbatim
! 159: *>
! 160: *> \param[out] ALPHA
! 161: *> \verbatim
! 162: *> ALPHA is COMPLEX*16 array, dimension (N)
! 163: *> \endverbatim
! 164: *>
! 165: *> \param[out] BETA
! 166: *> \verbatim
! 167: *> BETA is COMPLEX*16 array, dimension (N)
! 168: *> On exit, ALPHA(j)/BETA(j), j=1,...,N, will be the
! 169: *> generalized eigenvalues. ALPHA(j), j=1,...,N and BETA(j),
! 170: *> j=1,...,N are the diagonals of the complex Schur form (A,B)
! 171: *> output by ZGGES. The BETA(j) will be non-negative real.
! 172: *>
! 173: *> Note: the quotients ALPHA(j)/BETA(j) may easily over- or
! 174: *> underflow, and BETA(j) may even be zero. Thus, the user
! 175: *> should avoid naively computing the ratio alpha/beta.
! 176: *> However, ALPHA will be always less than and usually
! 177: *> comparable with norm(A) in magnitude, and BETA always less
! 178: *> than and usually comparable with norm(B).
! 179: *> \endverbatim
! 180: *>
! 181: *> \param[out] VSL
! 182: *> \verbatim
! 183: *> VSL is COMPLEX*16 array, dimension (LDVSL,N)
! 184: *> If JOBVSL = 'V', VSL will contain the left Schur vectors.
! 185: *> Not referenced if JOBVSL = 'N'.
! 186: *> \endverbatim
! 187: *>
! 188: *> \param[in] LDVSL
! 189: *> \verbatim
! 190: *> LDVSL is INTEGER
! 191: *> The leading dimension of the matrix VSL. LDVSL >= 1, and
! 192: *> if JOBVSL = 'V', LDVSL >= N.
! 193: *> \endverbatim
! 194: *>
! 195: *> \param[out] VSR
! 196: *> \verbatim
! 197: *> VSR is COMPLEX*16 array, dimension (LDVSR,N)
! 198: *> If JOBVSR = 'V', VSR will contain the right Schur vectors.
! 199: *> Not referenced if JOBVSR = 'N'.
! 200: *> \endverbatim
! 201: *>
! 202: *> \param[in] LDVSR
! 203: *> \verbatim
! 204: *> LDVSR is INTEGER
! 205: *> The leading dimension of the matrix VSR. LDVSR >= 1, and
! 206: *> if JOBVSR = 'V', LDVSR >= N.
! 207: *> \endverbatim
! 208: *>
! 209: *> \param[out] WORK
! 210: *> \verbatim
! 211: *> WORK is COMPLEX*16 array, dimension (MAX(1,LWORK))
! 212: *> On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
! 213: *> \endverbatim
! 214: *>
! 215: *> \param[in] LWORK
! 216: *> \verbatim
! 217: *> LWORK is INTEGER
! 218: *> The dimension of the array WORK. LWORK >= max(1,2*N).
! 219: *> For good performance, LWORK must generally be larger.
! 220: *>
! 221: *> If LWORK = -1, then a workspace query is assumed; the routine
! 222: *> only calculates the optimal size of the WORK array, returns
! 223: *> this value as the first entry of the WORK array, and no error
! 224: *> message related to LWORK is issued by XERBLA.
! 225: *> \endverbatim
! 226: *>
! 227: *> \param[out] RWORK
! 228: *> \verbatim
! 229: *> RWORK is DOUBLE PRECISION array, dimension (8*N)
! 230: *> \endverbatim
! 231: *>
! 232: *> \param[out] BWORK
! 233: *> \verbatim
! 234: *> BWORK is LOGICAL array, dimension (N)
! 235: *> Not referenced if SORT = 'N'.
! 236: *> \endverbatim
! 237: *>
! 238: *> \param[out] INFO
! 239: *> \verbatim
! 240: *> INFO is INTEGER
! 241: *> = 0: successful exit
! 242: *> < 0: if INFO = -i, the i-th argument had an illegal value.
! 243: *> =1,...,N:
! 244: *> The QZ iteration failed. (A,B) are not in Schur
! 245: *> form, but ALPHA(j) and BETA(j) should be correct for
! 246: *> j=INFO+1,...,N.
! 247: *> > N: =N+1: other than QZ iteration failed in ZHGEQZ
! 248: *> =N+2: after reordering, roundoff changed values of
! 249: *> some complex eigenvalues so that leading
! 250: *> eigenvalues in the Generalized Schur form no
! 251: *> longer satisfy SELCTG=.TRUE. This could also
! 252: *> be caused due to scaling.
! 253: *> =N+3: reordering falied in ZTGSEN.
! 254: *> \endverbatim
! 255: *
! 256: * Authors:
! 257: * ========
! 258: *
! 259: *> \author Univ. of Tennessee
! 260: *> \author Univ. of California Berkeley
! 261: *> \author Univ. of Colorado Denver
! 262: *> \author NAG Ltd.
! 263: *
! 264: *> \date November 2011
! 265: *
! 266: *> \ingroup complex16GEeigen
! 267: *
! 268: * =====================================================================
1.1 bertrand 269: SUBROUTINE ZGGES( JOBVSL, JOBVSR, SORT, SELCTG, N, A, LDA, B, LDB,
270: $ SDIM, ALPHA, BETA, VSL, LDVSL, VSR, LDVSR, WORK,
271: $ LWORK, RWORK, BWORK, INFO )
272: *
1.8 ! bertrand 273: * -- LAPACK driver routine (version 3.4.0) --
1.1 bertrand 274: * -- LAPACK is a software package provided by Univ. of Tennessee, --
275: * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
1.8 ! bertrand 276: * November 2011
1.1 bertrand 277: *
278: * .. Scalar Arguments ..
279: CHARACTER JOBVSL, JOBVSR, SORT
280: INTEGER INFO, LDA, LDB, LDVSL, LDVSR, LWORK, N, SDIM
281: * ..
282: * .. Array Arguments ..
283: LOGICAL BWORK( * )
284: DOUBLE PRECISION RWORK( * )
285: COMPLEX*16 A( LDA, * ), ALPHA( * ), B( LDB, * ),
286: $ BETA( * ), VSL( LDVSL, * ), VSR( LDVSR, * ),
287: $ WORK( * )
288: * ..
289: * .. Function Arguments ..
290: LOGICAL SELCTG
291: EXTERNAL SELCTG
292: * ..
293: *
294: * =====================================================================
295: *
296: * .. Parameters ..
297: DOUBLE PRECISION ZERO, ONE
298: PARAMETER ( ZERO = 0.0D0, ONE = 1.0D0 )
299: COMPLEX*16 CZERO, CONE
300: PARAMETER ( CZERO = ( 0.0D0, 0.0D0 ),
301: $ CONE = ( 1.0D0, 0.0D0 ) )
302: * ..
303: * .. Local Scalars ..
304: LOGICAL CURSL, ILASCL, ILBSCL, ILVSL, ILVSR, LASTSL,
305: $ LQUERY, WANTST
306: INTEGER I, ICOLS, IERR, IHI, IJOBVL, IJOBVR, ILEFT,
307: $ ILO, IRIGHT, IROWS, IRWRK, ITAU, IWRK, LWKMIN,
308: $ LWKOPT
309: DOUBLE PRECISION ANRM, ANRMTO, BIGNUM, BNRM, BNRMTO, EPS, PVSL,
310: $ PVSR, SMLNUM
311: * ..
312: * .. Local Arrays ..
313: INTEGER IDUM( 1 )
314: DOUBLE PRECISION DIF( 2 )
315: * ..
316: * .. External Subroutines ..
317: EXTERNAL DLABAD, XERBLA, ZGEQRF, ZGGBAK, ZGGBAL, ZGGHRD,
318: $ ZHGEQZ, ZLACPY, ZLASCL, ZLASET, ZTGSEN, ZUNGQR,
319: $ ZUNMQR
320: * ..
321: * .. External Functions ..
322: LOGICAL LSAME
323: INTEGER ILAENV
324: DOUBLE PRECISION DLAMCH, ZLANGE
325: EXTERNAL LSAME, ILAENV, DLAMCH, ZLANGE
326: * ..
327: * .. Intrinsic Functions ..
328: INTRINSIC MAX, SQRT
329: * ..
330: * .. Executable Statements ..
331: *
332: * Decode the input arguments
333: *
334: IF( LSAME( JOBVSL, 'N' ) ) THEN
335: IJOBVL = 1
336: ILVSL = .FALSE.
337: ELSE IF( LSAME( JOBVSL, 'V' ) ) THEN
338: IJOBVL = 2
339: ILVSL = .TRUE.
340: ELSE
341: IJOBVL = -1
342: ILVSL = .FALSE.
343: END IF
344: *
345: IF( LSAME( JOBVSR, 'N' ) ) THEN
346: IJOBVR = 1
347: ILVSR = .FALSE.
348: ELSE IF( LSAME( JOBVSR, 'V' ) ) THEN
349: IJOBVR = 2
350: ILVSR = .TRUE.
351: ELSE
352: IJOBVR = -1
353: ILVSR = .FALSE.
354: END IF
355: *
356: WANTST = LSAME( SORT, 'S' )
357: *
358: * Test the input arguments
359: *
360: INFO = 0
361: LQUERY = ( LWORK.EQ.-1 )
362: IF( IJOBVL.LE.0 ) THEN
363: INFO = -1
364: ELSE IF( IJOBVR.LE.0 ) THEN
365: INFO = -2
366: ELSE IF( ( .NOT.WANTST ) .AND. ( .NOT.LSAME( SORT, 'N' ) ) ) THEN
367: INFO = -3
368: ELSE IF( N.LT.0 ) THEN
369: INFO = -5
370: ELSE IF( LDA.LT.MAX( 1, N ) ) THEN
371: INFO = -7
372: ELSE IF( LDB.LT.MAX( 1, N ) ) THEN
373: INFO = -9
374: ELSE IF( LDVSL.LT.1 .OR. ( ILVSL .AND. LDVSL.LT.N ) ) THEN
375: INFO = -14
376: ELSE IF( LDVSR.LT.1 .OR. ( ILVSR .AND. LDVSR.LT.N ) ) THEN
377: INFO = -16
378: END IF
379: *
380: * Compute workspace
381: * (Note: Comments in the code beginning "Workspace:" describe the
382: * minimal amount of workspace needed at that point in the code,
383: * as well as the preferred amount for good performance.
384: * NB refers to the optimal block size for the immediately
385: * following subroutine, as returned by ILAENV.)
386: *
387: IF( INFO.EQ.0 ) THEN
388: LWKMIN = MAX( 1, 2*N )
389: LWKOPT = MAX( 1, N + N*ILAENV( 1, 'ZGEQRF', ' ', N, 1, N, 0 ) )
390: LWKOPT = MAX( LWKOPT, N +
391: $ N*ILAENV( 1, 'ZUNMQR', ' ', N, 1, N, -1 ) )
392: IF( ILVSL ) THEN
393: LWKOPT = MAX( LWKOPT, N +
394: $ N*ILAENV( 1, 'ZUNGQR', ' ', N, 1, N, -1 ) )
395: END IF
396: WORK( 1 ) = LWKOPT
397: *
398: IF( LWORK.LT.LWKMIN .AND. .NOT.LQUERY )
399: $ INFO = -18
400: END IF
401: *
402: IF( INFO.NE.0 ) THEN
403: CALL XERBLA( 'ZGGES ', -INFO )
404: RETURN
405: ELSE IF( LQUERY ) THEN
406: RETURN
407: END IF
408: *
409: * Quick return if possible
410: *
411: IF( N.EQ.0 ) THEN
412: SDIM = 0
413: RETURN
414: END IF
415: *
416: * Get machine constants
417: *
418: EPS = DLAMCH( 'P' )
419: SMLNUM = DLAMCH( 'S' )
420: BIGNUM = ONE / SMLNUM
421: CALL DLABAD( SMLNUM, BIGNUM )
422: SMLNUM = SQRT( SMLNUM ) / EPS
423: BIGNUM = ONE / SMLNUM
424: *
425: * Scale A if max element outside range [SMLNUM,BIGNUM]
426: *
427: ANRM = ZLANGE( 'M', N, N, A, LDA, RWORK )
428: ILASCL = .FALSE.
429: IF( ANRM.GT.ZERO .AND. ANRM.LT.SMLNUM ) THEN
430: ANRMTO = SMLNUM
431: ILASCL = .TRUE.
432: ELSE IF( ANRM.GT.BIGNUM ) THEN
433: ANRMTO = BIGNUM
434: ILASCL = .TRUE.
435: END IF
436: *
437: IF( ILASCL )
438: $ CALL ZLASCL( 'G', 0, 0, ANRM, ANRMTO, N, N, A, LDA, IERR )
439: *
440: * Scale B if max element outside range [SMLNUM,BIGNUM]
441: *
442: BNRM = ZLANGE( 'M', N, N, B, LDB, RWORK )
443: ILBSCL = .FALSE.
444: IF( BNRM.GT.ZERO .AND. BNRM.LT.SMLNUM ) THEN
445: BNRMTO = SMLNUM
446: ILBSCL = .TRUE.
447: ELSE IF( BNRM.GT.BIGNUM ) THEN
448: BNRMTO = BIGNUM
449: ILBSCL = .TRUE.
450: END IF
451: *
452: IF( ILBSCL )
453: $ CALL ZLASCL( 'G', 0, 0, BNRM, BNRMTO, N, N, B, LDB, IERR )
454: *
455: * Permute the matrix to make it more nearly triangular
456: * (Real Workspace: need 6*N)
457: *
458: ILEFT = 1
459: IRIGHT = N + 1
460: IRWRK = IRIGHT + N
461: CALL ZGGBAL( 'P', N, A, LDA, B, LDB, ILO, IHI, RWORK( ILEFT ),
462: $ RWORK( IRIGHT ), RWORK( IRWRK ), IERR )
463: *
464: * Reduce B to triangular form (QR decomposition of B)
465: * (Complex Workspace: need N, prefer N*NB)
466: *
467: IROWS = IHI + 1 - ILO
468: ICOLS = N + 1 - ILO
469: ITAU = 1
470: IWRK = ITAU + IROWS
471: CALL ZGEQRF( IROWS, ICOLS, B( ILO, ILO ), LDB, WORK( ITAU ),
472: $ WORK( IWRK ), LWORK+1-IWRK, IERR )
473: *
474: * Apply the orthogonal transformation to matrix A
475: * (Complex Workspace: need N, prefer N*NB)
476: *
477: CALL ZUNMQR( 'L', 'C', IROWS, ICOLS, IROWS, B( ILO, ILO ), LDB,
478: $ WORK( ITAU ), A( ILO, ILO ), LDA, WORK( IWRK ),
479: $ LWORK+1-IWRK, IERR )
480: *
481: * Initialize VSL
482: * (Complex Workspace: need N, prefer N*NB)
483: *
484: IF( ILVSL ) THEN
485: CALL ZLASET( 'Full', N, N, CZERO, CONE, VSL, LDVSL )
486: IF( IROWS.GT.1 ) THEN
487: CALL ZLACPY( 'L', IROWS-1, IROWS-1, B( ILO+1, ILO ), LDB,
488: $ VSL( ILO+1, ILO ), LDVSL )
489: END IF
490: CALL ZUNGQR( IROWS, IROWS, IROWS, VSL( ILO, ILO ), LDVSL,
491: $ WORK( ITAU ), WORK( IWRK ), LWORK+1-IWRK, IERR )
492: END IF
493: *
494: * Initialize VSR
495: *
496: IF( ILVSR )
497: $ CALL ZLASET( 'Full', N, N, CZERO, CONE, VSR, LDVSR )
498: *
499: * Reduce to generalized Hessenberg form
500: * (Workspace: none needed)
501: *
502: CALL ZGGHRD( JOBVSL, JOBVSR, N, ILO, IHI, A, LDA, B, LDB, VSL,
503: $ LDVSL, VSR, LDVSR, IERR )
504: *
505: SDIM = 0
506: *
507: * Perform QZ algorithm, computing Schur vectors if desired
508: * (Complex Workspace: need N)
509: * (Real Workspace: need N)
510: *
511: IWRK = ITAU
512: CALL ZHGEQZ( 'S', JOBVSL, JOBVSR, N, ILO, IHI, A, LDA, B, LDB,
513: $ ALPHA, BETA, VSL, LDVSL, VSR, LDVSR, WORK( IWRK ),
514: $ LWORK+1-IWRK, RWORK( IRWRK ), IERR )
515: IF( IERR.NE.0 ) THEN
516: IF( IERR.GT.0 .AND. IERR.LE.N ) THEN
517: INFO = IERR
518: ELSE IF( IERR.GT.N .AND. IERR.LE.2*N ) THEN
519: INFO = IERR - N
520: ELSE
521: INFO = N + 1
522: END IF
523: GO TO 30
524: END IF
525: *
526: * Sort eigenvalues ALPHA/BETA if desired
527: * (Workspace: none needed)
528: *
529: IF( WANTST ) THEN
530: *
531: * Undo scaling on eigenvalues before selecting
532: *
533: IF( ILASCL )
534: $ CALL ZLASCL( 'G', 0, 0, ANRM, ANRMTO, N, 1, ALPHA, N, IERR )
535: IF( ILBSCL )
536: $ CALL ZLASCL( 'G', 0, 0, BNRM, BNRMTO, N, 1, BETA, N, IERR )
537: *
538: * Select eigenvalues
539: *
540: DO 10 I = 1, N
541: BWORK( I ) = SELCTG( ALPHA( I ), BETA( I ) )
542: 10 CONTINUE
543: *
544: CALL ZTGSEN( 0, ILVSL, ILVSR, BWORK, N, A, LDA, B, LDB, ALPHA,
545: $ BETA, VSL, LDVSL, VSR, LDVSR, SDIM, PVSL, PVSR,
546: $ DIF, WORK( IWRK ), LWORK-IWRK+1, IDUM, 1, IERR )
547: IF( IERR.EQ.1 )
548: $ INFO = N + 3
549: *
550: END IF
551: *
552: * Apply back-permutation to VSL and VSR
553: * (Workspace: none needed)
554: *
555: IF( ILVSL )
556: $ CALL ZGGBAK( 'P', 'L', N, ILO, IHI, RWORK( ILEFT ),
557: $ RWORK( IRIGHT ), N, VSL, LDVSL, IERR )
558: IF( ILVSR )
559: $ CALL ZGGBAK( 'P', 'R', N, ILO, IHI, RWORK( ILEFT ),
560: $ RWORK( IRIGHT ), N, VSR, LDVSR, IERR )
561: *
562: * Undo scaling
563: *
564: IF( ILASCL ) THEN
565: CALL ZLASCL( 'U', 0, 0, ANRMTO, ANRM, N, N, A, LDA, IERR )
566: CALL ZLASCL( 'G', 0, 0, ANRMTO, ANRM, N, 1, ALPHA, N, IERR )
567: END IF
568: *
569: IF( ILBSCL ) THEN
570: CALL ZLASCL( 'U', 0, 0, BNRMTO, BNRM, N, N, B, LDB, IERR )
571: CALL ZLASCL( 'G', 0, 0, BNRMTO, BNRM, N, 1, BETA, N, IERR )
572: END IF
573: *
574: IF( WANTST ) THEN
575: *
576: * Check if reordering is correct
577: *
578: LASTSL = .TRUE.
579: SDIM = 0
580: DO 20 I = 1, N
581: CURSL = SELCTG( ALPHA( I ), BETA( I ) )
582: IF( CURSL )
583: $ SDIM = SDIM + 1
584: IF( CURSL .AND. .NOT.LASTSL )
585: $ INFO = N + 2
586: LASTSL = CURSL
587: 20 CONTINUE
588: *
589: END IF
590: *
591: 30 CONTINUE
592: *
593: WORK( 1 ) = LWKOPT
594: *
595: RETURN
596: *
597: * End of ZGGES
598: *
599: END
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