LAPACK  3.6.0
LAPACK: Linear Algebra PACKage
cggesx.f
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1 *> \brief <b> CGGESX 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 CGGESX + dependencies
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11 *> [TGZ]</a>
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13 *> [ZIP]</a>
14 *> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/cggesx.f">
15 *> [TXT]</a>
16 *> \endhtmlonly
17 *
18 * Definition:
19 * ===========
20 *
21 * SUBROUTINE CGGESX( JOBVSL, JOBVSR, SORT, SELCTG, SENSE, N, A, LDA,
22 * B, LDB, SDIM, ALPHA, BETA, VSL, LDVSL, VSR,
23 * LDVSR, RCONDE, RCONDV, WORK, LWORK, RWORK,
24 * IWORK, LIWORK, BWORK, INFO )
25 *
26 * .. Scalar Arguments ..
27 * CHARACTER JOBVSL, JOBVSR, SENSE, SORT
28 * INTEGER INFO, LDA, LDB, LDVSL, LDVSR, LIWORK, LWORK, N,
29 * $ SDIM
30 * ..
31 * .. Array Arguments ..
32 * LOGICAL BWORK( * )
33 * INTEGER IWORK( * )
34 * REAL RCONDE( 2 ), RCONDV( 2 ), RWORK( * )
35 * COMPLEX A( LDA, * ), ALPHA( * ), B( LDB, * ),
36 * $ BETA( * ), VSL( LDVSL, * ), VSR( LDVSR, * ),
37 * $ WORK( * )
38 * ..
39 * .. Function Arguments ..
40 * LOGICAL SELCTG
41 * EXTERNAL SELCTG
42 * ..
43 *
44 *
45 *> \par Purpose:
46 * =============
47 *>
48 *> \verbatim
49 *>
50 *> CGGESX computes for a pair of N-by-N complex nonsymmetric matrices
51 *> (A,B), the generalized eigenvalues, the complex Schur form (S,T),
52 *> and, optionally, the left and/or right matrices of Schur vectors (VSL
53 *> and VSR). This gives the generalized Schur factorization
54 *>
55 *> (A,B) = ( (VSL) S (VSR)**H, (VSL) T (VSR)**H )
56 *>
57 *> where (VSR)**H is the conjugate-transpose of VSR.
58 *>
59 *> Optionally, it also orders the eigenvalues so that a selected cluster
60 *> of eigenvalues appears in the leading diagonal blocks of the upper
61 *> triangular matrix S and the upper triangular matrix T; computes
62 *> a reciprocal condition number for the average of the selected
63 *> eigenvalues (RCONDE); and computes a reciprocal condition number for
64 *> the right and left deflating subspaces corresponding to the selected
65 *> eigenvalues (RCONDV). The leading columns of VSL and VSR then form
66 *> an orthonormal basis for the corresponding left and right eigenspaces
67 *> (deflating subspaces).
68 *>
69 *> A generalized eigenvalue for a pair of matrices (A,B) is a scalar w
70 *> or a ratio alpha/beta = w, such that A - w*B is singular. It is
71 *> usually represented as the pair (alpha,beta), as there is a
72 *> reasonable interpretation for beta=0 or for both being zero.
73 *>
74 *> A pair of matrices (S,T) is in generalized complex Schur form if T is
75 *> upper triangular with non-negative diagonal and S is upper
76 *> triangular.
77 *> \endverbatim
78 *
79 * Arguments:
80 * ==========
81 *
82 *> \param[in] JOBVSL
83 *> \verbatim
84 *> JOBVSL is CHARACTER*1
85 *> = 'N': do not compute the left Schur vectors;
86 *> = 'V': compute the left Schur vectors.
87 *> \endverbatim
88 *>
89 *> \param[in] JOBVSR
90 *> \verbatim
91 *> JOBVSR is CHARACTER*1
92 *> = 'N': do not compute the right Schur vectors;
93 *> = 'V': compute the right Schur vectors.
94 *> \endverbatim
95 *>
96 *> \param[in] SORT
97 *> \verbatim
98 *> SORT is CHARACTER*1
99 *> Specifies whether or not to order the eigenvalues on the
100 *> diagonal of the generalized Schur form.
101 *> = 'N': Eigenvalues are not ordered;
102 *> = 'S': Eigenvalues are ordered (see SELCTG).
103 *> \endverbatim
104 *>
105 *> \param[in] SELCTG
106 *> \verbatim
107 *> SELCTG is procedure) LOGICAL FUNCTION of two COMPLEX arguments
108 *> SELCTG must be declared EXTERNAL in the calling subroutine.
109 *> If SORT = 'N', SELCTG is not referenced.
110 *> If SORT = 'S', SELCTG is used to select eigenvalues to sort
111 *> to the top left of the Schur form.
112 *> Note that a selected complex eigenvalue may no longer satisfy
113 *> SELCTG(ALPHA(j),BETA(j)) = .TRUE. after ordering, since
114 *> ordering may change the value of complex eigenvalues
115 *> (especially if the eigenvalue is ill-conditioned), in this
116 *> case INFO is set to N+3 see INFO below).
117 *> \endverbatim
118 *>
119 *> \param[in] SENSE
120 *> \verbatim
121 *> SENSE is CHARACTER*1
122 *> Determines which reciprocal condition numbers are computed.
123 *> = 'N' : None are computed;
124 *> = 'E' : Computed for average of selected eigenvalues only;
125 *> = 'V' : Computed for selected deflating subspaces only;
126 *> = 'B' : Computed for both.
127 *> If SENSE = 'E', 'V', or 'B', SORT must equal 'S'.
128 *> \endverbatim
129 *>
130 *> \param[in] N
131 *> \verbatim
132 *> N is INTEGER
133 *> The order of the matrices A, B, VSL, and VSR. N >= 0.
134 *> \endverbatim
135 *>
136 *> \param[in,out] A
137 *> \verbatim
138 *> A is COMPLEX array, dimension (LDA, N)
139 *> On entry, the first of the pair of matrices.
140 *> On exit, A has been overwritten by its generalized Schur
141 *> form S.
142 *> \endverbatim
143 *>
144 *> \param[in] LDA
145 *> \verbatim
146 *> LDA is INTEGER
147 *> The leading dimension of A. LDA >= max(1,N).
148 *> \endverbatim
149 *>
150 *> \param[in,out] B
151 *> \verbatim
152 *> B is COMPLEX array, dimension (LDB, N)
153 *> On entry, the second of the pair of matrices.
154 *> On exit, B has been overwritten by its generalized Schur
155 *> form T.
156 *> \endverbatim
157 *>
158 *> \param[in] LDB
159 *> \verbatim
160 *> LDB is INTEGER
161 *> The leading dimension of B. LDB >= max(1,N).
162 *> \endverbatim
163 *>
164 *> \param[out] SDIM
165 *> \verbatim
166 *> SDIM is INTEGER
167 *> If SORT = 'N', SDIM = 0.
168 *> If SORT = 'S', SDIM = number of eigenvalues (after sorting)
169 *> for which SELCTG is true.
170 *> \endverbatim
171 *>
172 *> \param[out] ALPHA
173 *> \verbatim
174 *> ALPHA is COMPLEX array, dimension (N)
175 *> \endverbatim
176 *>
177 *> \param[out] BETA
178 *> \verbatim
179 *> BETA is COMPLEX array, dimension (N)
180 *> On exit, ALPHA(j)/BETA(j), j=1,...,N, will be the
181 *> generalized eigenvalues. ALPHA(j) and BETA(j),j=1,...,N are
182 *> the diagonals of the complex Schur form (S,T). BETA(j) will
183 *> be non-negative real.
184 *>
185 *> Note: the quotients ALPHA(j)/BETA(j) may easily over- or
186 *> underflow, and BETA(j) may even be zero. Thus, the user
187 *> should avoid naively computing the ratio alpha/beta.
188 *> However, ALPHA will be always less than and usually
189 *> comparable with norm(A) in magnitude, and BETA always less
190 *> than and usually comparable with norm(B).
191 *> \endverbatim
192 *>
193 *> \param[out] VSL
194 *> \verbatim
195 *> VSL is COMPLEX array, dimension (LDVSL,N)
196 *> If JOBVSL = 'V', VSL will contain the left Schur vectors.
197 *> Not referenced if JOBVSL = 'N'.
198 *> \endverbatim
199 *>
200 *> \param[in] LDVSL
201 *> \verbatim
202 *> LDVSL is INTEGER
203 *> The leading dimension of the matrix VSL. LDVSL >=1, and
204 *> if JOBVSL = 'V', LDVSL >= N.
205 *> \endverbatim
206 *>
207 *> \param[out] VSR
208 *> \verbatim
209 *> VSR is COMPLEX array, dimension (LDVSR,N)
210 *> If JOBVSR = 'V', VSR will contain the right Schur vectors.
211 *> Not referenced if JOBVSR = 'N'.
212 *> \endverbatim
213 *>
214 *> \param[in] LDVSR
215 *> \verbatim
216 *> LDVSR is INTEGER
217 *> The leading dimension of the matrix VSR. LDVSR >= 1, and
218 *> if JOBVSR = 'V', LDVSR >= N.
219 *> \endverbatim
220 *>
221 *> \param[out] RCONDE
222 *> \verbatim
223 *> RCONDE is REAL array, dimension ( 2 )
224 *> If SENSE = 'E' or 'B', RCONDE(1) and RCONDE(2) contain the
225 *> reciprocal condition numbers for the average of the selected
226 *> eigenvalues.
227 *> Not referenced if SENSE = 'N' or 'V'.
228 *> \endverbatim
229 *>
230 *> \param[out] RCONDV
231 *> \verbatim
232 *> RCONDV is REAL array, dimension ( 2 )
233 *> If SENSE = 'V' or 'B', RCONDV(1) and RCONDV(2) contain the
234 *> reciprocal condition number for the selected deflating
235 *> subspaces.
236 *> Not referenced if SENSE = 'N' or 'E'.
237 *> \endverbatim
238 *>
239 *> \param[out] WORK
240 *> \verbatim
241 *> WORK is COMPLEX array, dimension (MAX(1,LWORK))
242 *> On exit, if INFO = 0, WORK(1) returns the optimal LWORK.
243 *> \endverbatim
244 *>
245 *> \param[in] LWORK
246 *> \verbatim
247 *> LWORK is INTEGER
248 *> The dimension of the array WORK.
249 *> If N = 0, LWORK >= 1, else if SENSE = 'E', 'V', or 'B',
250 *> LWORK >= MAX(1,2*N,2*SDIM*(N-SDIM)), else
251 *> LWORK >= MAX(1,2*N). Note that 2*SDIM*(N-SDIM) <= N*N/2.
252 *> Note also that an error is only returned if
253 *> LWORK < MAX(1,2*N), but if SENSE = 'E' or 'V' or 'B' this may
254 *> not be large enough.
255 *>
256 *> If LWORK = -1, then a workspace query is assumed; the routine
257 *> only calculates the bound on the optimal size of the WORK
258 *> array and the minimum size of the IWORK array, returns these
259 *> values as the first entries of the WORK and IWORK arrays, and
260 *> no error message related to LWORK or LIWORK is issued by
261 *> XERBLA.
262 *> \endverbatim
263 *>
264 *> \param[out] RWORK
265 *> \verbatim
266 *> RWORK is REAL array, dimension ( 8*N )
267 *> Real workspace.
268 *> \endverbatim
269 *>
270 *> \param[out] IWORK
271 *> \verbatim
272 *> IWORK is INTEGER array, dimension (MAX(1,LIWORK))
273 *> On exit, if INFO = 0, IWORK(1) returns the minimum LIWORK.
274 *> \endverbatim
275 *>
276 *> \param[in] LIWORK
277 *> \verbatim
278 *> LIWORK is INTEGER
279 *> The dimension of the array WORK.
280 *> If SENSE = 'N' or N = 0, LIWORK >= 1, otherwise
281 *> LIWORK >= N+2.
282 *>
283 *> If LIWORK = -1, then a workspace query is assumed; the
284 *> routine only calculates the bound on the optimal size of the
285 *> WORK array and the minimum size of the IWORK array, returns
286 *> these values as the first entries of the WORK and IWORK
287 *> arrays, and no error message related to LWORK or LIWORK is
288 *> issued by XERBLA.
289 *> \endverbatim
290 *>
291 *> \param[out] BWORK
292 *> \verbatim
293 *> BWORK is LOGICAL array, dimension (N)
294 *> Not referenced if SORT = 'N'.
295 *> \endverbatim
296 *>
297 *> \param[out] INFO
298 *> \verbatim
299 *> INFO is INTEGER
300 *> = 0: successful exit
301 *> < 0: if INFO = -i, the i-th argument had an illegal value.
302 *> = 1,...,N:
303 *> The QZ iteration failed. (A,B) are not in Schur
304 *> form, but ALPHA(j) and BETA(j) should be correct for
305 *> j=INFO+1,...,N.
306 *> > N: =N+1: other than QZ iteration failed in CHGEQZ
307 *> =N+2: after reordering, roundoff changed values of
308 *> some complex eigenvalues so that leading
309 *> eigenvalues in the Generalized Schur form no
310 *> longer satisfy SELCTG=.TRUE. This could also
311 *> be caused due to scaling.
312 *> =N+3: reordering failed in CTGSEN.
313 *> \endverbatim
314 *
315 * Authors:
316 * ========
317 *
318 *> \author Univ. of Tennessee
319 *> \author Univ. of California Berkeley
320 *> \author Univ. of Colorado Denver
321 *> \author NAG Ltd.
322 *
323 *> \date November 2011
324 *
325 *> \ingroup complexGEeigen
326 *
327 * =====================================================================
328  SUBROUTINE cggesx( JOBVSL, JOBVSR, SORT, SELCTG, SENSE, N, A, LDA,
329  $ b, ldb, sdim, alpha, beta, vsl, ldvsl, vsr,
330  $ ldvsr, rconde, rcondv, work, lwork, rwork,
331  $ iwork, liwork, bwork, info )
332 *
333 * -- LAPACK driver routine (version 3.4.0) --
334 * -- LAPACK is a software package provided by Univ. of Tennessee, --
335 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
336 * November 2011
337 *
338 * .. Scalar Arguments ..
339  CHARACTER JOBVSL, JOBVSR, SENSE, SORT
340  INTEGER INFO, LDA, LDB, LDVSL, LDVSR, LIWORK, LWORK, N,
341  $ sdim
342 * ..
343 * .. Array Arguments ..
344  LOGICAL BWORK( * )
345  INTEGER IWORK( * )
346  REAL RCONDE( 2 ), RCONDV( 2 ), RWORK( * )
347  COMPLEX A( lda, * ), ALPHA( * ), B( ldb, * ),
348  $ beta( * ), vsl( ldvsl, * ), vsr( ldvsr, * ),
349  $ work( * )
350 * ..
351 * .. Function Arguments ..
352  LOGICAL SELCTG
353  EXTERNAL selctg
354 * ..
355 *
356 * =====================================================================
357 *
358 * .. Parameters ..
359  REAL ZERO, ONE
360  parameter( zero = 0.0e+0, one = 1.0e+0 )
361  COMPLEX CZERO, CONE
362  parameter( czero = ( 0.0e+0, 0.0e+0 ),
363  $ cone = ( 1.0e+0, 0.0e+0 ) )
364 * ..
365 * .. Local Scalars ..
366  LOGICAL CURSL, ILASCL, ILBSCL, ILVSL, ILVSR, LASTSL,
367  $ lquery, wantsb, wantse, wantsn, wantst, wantsv
368  INTEGER I, ICOLS, IERR, IHI, IJOB, IJOBVL, IJOBVR,
369  $ ileft, ilo, iright, irows, irwrk, itau, iwrk,
370  $ liwmin, lwrk, maxwrk, minwrk
371  REAL ANRM, ANRMTO, BIGNUM, BNRM, BNRMTO, EPS, PL,
372  $ pr, smlnum
373 * ..
374 * .. Local Arrays ..
375  REAL DIF( 2 )
376 * ..
377 * .. External Subroutines ..
378  EXTERNAL cgeqrf, cggbak, cggbal, cgghrd, chgeqz, clacpy,
380  $ xerbla
381 * ..
382 * .. External Functions ..
383  LOGICAL LSAME
384  INTEGER ILAENV
385  REAL CLANGE, SLAMCH
386  EXTERNAL lsame, ilaenv, clange, slamch
387 * ..
388 * .. Intrinsic Functions ..
389  INTRINSIC max, sqrt
390 * ..
391 * .. Executable Statements ..
392 *
393 * Decode the input arguments
394 *
395  IF( lsame( jobvsl, 'N' ) ) THEN
396  ijobvl = 1
397  ilvsl = .false.
398  ELSE IF( lsame( jobvsl, 'V' ) ) THEN
399  ijobvl = 2
400  ilvsl = .true.
401  ELSE
402  ijobvl = -1
403  ilvsl = .false.
404  END IF
405 *
406  IF( lsame( jobvsr, 'N' ) ) THEN
407  ijobvr = 1
408  ilvsr = .false.
409  ELSE IF( lsame( jobvsr, 'V' ) ) THEN
410  ijobvr = 2
411  ilvsr = .true.
412  ELSE
413  ijobvr = -1
414  ilvsr = .false.
415  END IF
416 *
417  wantst = lsame( sort, 'S' )
418  wantsn = lsame( sense, 'N' )
419  wantse = lsame( sense, 'E' )
420  wantsv = lsame( sense, 'V' )
421  wantsb = lsame( sense, 'B' )
422  lquery = ( lwork.EQ.-1 .OR. liwork.EQ.-1 )
423  IF( wantsn ) THEN
424  ijob = 0
425  ELSE IF( wantse ) THEN
426  ijob = 1
427  ELSE IF( wantsv ) THEN
428  ijob = 2
429  ELSE IF( wantsb ) THEN
430  ijob = 4
431  END IF
432 *
433 * Test the input arguments
434 *
435  info = 0
436  IF( ijobvl.LE.0 ) THEN
437  info = -1
438  ELSE IF( ijobvr.LE.0 ) THEN
439  info = -2
440  ELSE IF( ( .NOT.wantst ) .AND. ( .NOT.lsame( sort, 'N' ) ) ) THEN
441  info = -3
442  ELSE IF( .NOT.( wantsn .OR. wantse .OR. wantsv .OR. wantsb ) .OR.
443  $ ( .NOT.wantst .AND. .NOT.wantsn ) ) THEN
444  info = -5
445  ELSE IF( n.LT.0 ) THEN
446  info = -6
447  ELSE IF( lda.LT.max( 1, n ) ) THEN
448  info = -8
449  ELSE IF( ldb.LT.max( 1, n ) ) THEN
450  info = -10
451  ELSE IF( ldvsl.LT.1 .OR. ( ilvsl .AND. ldvsl.LT.n ) ) THEN
452  info = -15
453  ELSE IF( ldvsr.LT.1 .OR. ( ilvsr .AND. ldvsr.LT.n ) ) THEN
454  info = -17
455  END IF
456 *
457 * Compute workspace
458 * (Note: Comments in the code beginning "Workspace:" describe the
459 * minimal amount of workspace needed at that point in the code,
460 * as well as the preferred amount for good performance.
461 * NB refers to the optimal block size for the immediately
462 * following subroutine, as returned by ILAENV.)
463 *
464  IF( info.EQ.0 ) THEN
465  IF( n.GT.0) THEN
466  minwrk = 2*n
467  maxwrk = n*(1 + ilaenv( 1, 'CGEQRF', ' ', n, 1, n, 0 ) )
468  maxwrk = max( maxwrk, n*( 1 +
469  $ ilaenv( 1, 'CUNMQR', ' ', n, 1, n, -1 ) ) )
470  IF( ilvsl ) THEN
471  maxwrk = max( maxwrk, n*( 1 +
472  $ ilaenv( 1, 'CUNGQR', ' ', n, 1, n, -1 ) ) )
473  END IF
474  lwrk = maxwrk
475  IF( ijob.GE.1 )
476  $ lwrk = max( lwrk, n*n/2 )
477  ELSE
478  minwrk = 1
479  maxwrk = 1
480  lwrk = 1
481  END IF
482  work( 1 ) = lwrk
483  IF( wantsn .OR. n.EQ.0 ) THEN
484  liwmin = 1
485  ELSE
486  liwmin = n + 2
487  END IF
488  iwork( 1 ) = liwmin
489 *
490  IF( lwork.LT.minwrk .AND. .NOT.lquery ) THEN
491  info = -21
492  ELSE IF( liwork.LT.liwmin .AND. .NOT.lquery) THEN
493  info = -24
494  END IF
495  END IF
496 *
497  IF( info.NE.0 ) THEN
498  CALL xerbla( 'CGGESX', -info )
499  RETURN
500  ELSE IF (lquery) THEN
501  RETURN
502  END IF
503 *
504 * Quick return if possible
505 *
506  IF( n.EQ.0 ) THEN
507  sdim = 0
508  RETURN
509  END IF
510 *
511 * Get machine constants
512 *
513  eps = slamch( 'P' )
514  smlnum = slamch( 'S' )
515  bignum = one / smlnum
516  CALL slabad( smlnum, bignum )
517  smlnum = sqrt( smlnum ) / eps
518  bignum = one / smlnum
519 *
520 * Scale A if max element outside range [SMLNUM,BIGNUM]
521 *
522  anrm = clange( 'M', n, n, a, lda, rwork )
523  ilascl = .false.
524  IF( anrm.GT.zero .AND. anrm.LT.smlnum ) THEN
525  anrmto = smlnum
526  ilascl = .true.
527  ELSE IF( anrm.GT.bignum ) THEN
528  anrmto = bignum
529  ilascl = .true.
530  END IF
531  IF( ilascl )
532  $ CALL clascl( 'G', 0, 0, anrm, anrmto, n, n, a, lda, ierr )
533 *
534 * Scale B if max element outside range [SMLNUM,BIGNUM]
535 *
536  bnrm = clange( 'M', n, n, b, ldb, rwork )
537  ilbscl = .false.
538  IF( bnrm.GT.zero .AND. bnrm.LT.smlnum ) THEN
539  bnrmto = smlnum
540  ilbscl = .true.
541  ELSE IF( bnrm.GT.bignum ) THEN
542  bnrmto = bignum
543  ilbscl = .true.
544  END IF
545  IF( ilbscl )
546  $ CALL clascl( 'G', 0, 0, bnrm, bnrmto, n, n, b, ldb, ierr )
547 *
548 * Permute the matrix to make it more nearly triangular
549 * (Real Workspace: need 6*N)
550 *
551  ileft = 1
552  iright = n + 1
553  irwrk = iright + n
554  CALL cggbal( 'P', n, a, lda, b, ldb, ilo, ihi, rwork( ileft ),
555  $ rwork( iright ), rwork( irwrk ), ierr )
556 *
557 * Reduce B to triangular form (QR decomposition of B)
558 * (Complex Workspace: need N, prefer N*NB)
559 *
560  irows = ihi + 1 - ilo
561  icols = n + 1 - ilo
562  itau = 1
563  iwrk = itau + irows
564  CALL cgeqrf( irows, icols, b( ilo, ilo ), ldb, work( itau ),
565  $ work( iwrk ), lwork+1-iwrk, ierr )
566 *
567 * Apply the unitary transformation to matrix A
568 * (Complex Workspace: need N, prefer N*NB)
569 *
570  CALL cunmqr( 'L', 'C', irows, icols, irows, b( ilo, ilo ), ldb,
571  $ work( itau ), a( ilo, ilo ), lda, work( iwrk ),
572  $ lwork+1-iwrk, ierr )
573 *
574 * Initialize VSL
575 * (Complex Workspace: need N, prefer N*NB)
576 *
577  IF( ilvsl ) THEN
578  CALL claset( 'Full', n, n, czero, cone, vsl, ldvsl )
579  IF( irows.GT.1 ) THEN
580  CALL clacpy( 'L', irows-1, irows-1, b( ilo+1, ilo ), ldb,
581  $ vsl( ilo+1, ilo ), ldvsl )
582  END IF
583  CALL cungqr( irows, irows, irows, vsl( ilo, ilo ), ldvsl,
584  $ work( itau ), work( iwrk ), lwork+1-iwrk, ierr )
585  END IF
586 *
587 * Initialize VSR
588 *
589  IF( ilvsr )
590  $ CALL claset( 'Full', n, n, czero, cone, vsr, ldvsr )
591 *
592 * Reduce to generalized Hessenberg form
593 * (Workspace: none needed)
594 *
595  CALL cgghrd( jobvsl, jobvsr, n, ilo, ihi, a, lda, b, ldb, vsl,
596  $ ldvsl, vsr, ldvsr, ierr )
597 *
598  sdim = 0
599 *
600 * Perform QZ algorithm, computing Schur vectors if desired
601 * (Complex Workspace: need N)
602 * (Real Workspace: need N)
603 *
604  iwrk = itau
605  CALL chgeqz( 'S', jobvsl, jobvsr, n, ilo, ihi, a, lda, b, ldb,
606  $ alpha, beta, vsl, ldvsl, vsr, ldvsr, work( iwrk ),
607  $ lwork+1-iwrk, rwork( irwrk ), ierr )
608  IF( ierr.NE.0 ) THEN
609  IF( ierr.GT.0 .AND. ierr.LE.n ) THEN
610  info = ierr
611  ELSE IF( ierr.GT.n .AND. ierr.LE.2*n ) THEN
612  info = ierr - n
613  ELSE
614  info = n + 1
615  END IF
616  GO TO 40
617  END IF
618 *
619 * Sort eigenvalues ALPHA/BETA and compute the reciprocal of
620 * condition number(s)
621 *
622  IF( wantst ) THEN
623 *
624 * Undo scaling on eigenvalues before SELCTGing
625 *
626  IF( ilascl )
627  $ CALL clascl( 'G', 0, 0, anrmto, anrm, n, 1, alpha, n, ierr )
628  IF( ilbscl )
629  $ CALL clascl( 'G', 0, 0, bnrmto, bnrm, n, 1, beta, n, ierr )
630 *
631 * Select eigenvalues
632 *
633  DO 10 i = 1, n
634  bwork( i ) = selctg( alpha( i ), beta( i ) )
635  10 CONTINUE
636 *
637 * Reorder eigenvalues, transform Generalized Schur vectors, and
638 * compute reciprocal condition numbers
639 * (Complex Workspace: If IJOB >= 1, need MAX(1, 2*SDIM*(N-SDIM))
640 * otherwise, need 1 )
641 *
642  CALL ctgsen( ijob, ilvsl, ilvsr, bwork, n, a, lda, b, ldb,
643  $ alpha, beta, vsl, ldvsl, vsr, ldvsr, sdim, pl, pr,
644  $ dif, work( iwrk ), lwork-iwrk+1, iwork, liwork,
645  $ ierr )
646 *
647  IF( ijob.GE.1 )
648  $ maxwrk = max( maxwrk, 2*sdim*( n-sdim ) )
649  IF( ierr.EQ.-21 ) THEN
650 *
651 * not enough complex workspace
652 *
653  info = -21
654  ELSE
655  IF( ijob.EQ.1 .OR. ijob.EQ.4 ) THEN
656  rconde( 1 ) = pl
657  rconde( 2 ) = pr
658  END IF
659  IF( ijob.EQ.2 .OR. ijob.EQ.4 ) THEN
660  rcondv( 1 ) = dif( 1 )
661  rcondv( 2 ) = dif( 2 )
662  END IF
663  IF( ierr.EQ.1 )
664  $ info = n + 3
665  END IF
666 *
667  END IF
668 *
669 * Apply permutation to VSL and VSR
670 * (Workspace: none needed)
671 *
672  IF( ilvsl )
673  $ CALL cggbak( 'P', 'L', n, ilo, ihi, rwork( ileft ),
674  $ rwork( iright ), n, vsl, ldvsl, ierr )
675 *
676  IF( ilvsr )
677  $ CALL cggbak( 'P', 'R', n, ilo, ihi, rwork( ileft ),
678  $ rwork( iright ), n, vsr, ldvsr, ierr )
679 *
680 * Undo scaling
681 *
682  IF( ilascl ) THEN
683  CALL clascl( 'U', 0, 0, anrmto, anrm, n, n, a, lda, ierr )
684  CALL clascl( 'G', 0, 0, anrmto, anrm, n, 1, alpha, n, ierr )
685  END IF
686 *
687  IF( ilbscl ) THEN
688  CALL clascl( 'U', 0, 0, bnrmto, bnrm, n, n, b, ldb, ierr )
689  CALL clascl( 'G', 0, 0, bnrmto, bnrm, n, 1, beta, n, ierr )
690  END IF
691 *
692  IF( wantst ) THEN
693 *
694 * Check if reordering is correct
695 *
696  lastsl = .true.
697  sdim = 0
698  DO 30 i = 1, n
699  cursl = selctg( alpha( i ), beta( i ) )
700  IF( cursl )
701  $ sdim = sdim + 1
702  IF( cursl .AND. .NOT.lastsl )
703  $ info = n + 2
704  lastsl = cursl
705  30 CONTINUE
706 *
707  END IF
708 *
709  40 CONTINUE
710 *
711  work( 1 ) = maxwrk
712  iwork( 1 ) = liwmin
713 *
714  RETURN
715 *
716 * End of CGGESX
717 *
718  END
subroutine claset(UPLO, M, N, ALPHA, BETA, A, LDA)
CLASET initializes the off-diagonal elements and the diagonal elements of a matrix to given values...
Definition: claset.f:108
subroutine cgeqrf(M, N, A, LDA, TAU, WORK, LWORK, INFO)
CGEQRF
Definition: cgeqrf.f:138
subroutine xerbla(SRNAME, INFO)
XERBLA
Definition: xerbla.f:62
subroutine slabad(SMALL, LARGE)
SLABAD
Definition: slabad.f:76
subroutine cggesx(JOBVSL, JOBVSR, SORT, SELCTG, SENSE, N, A, LDA, B, LDB, SDIM, ALPHA, BETA, VSL, LDVSL, VSR, LDVSR, RCONDE, RCONDV, WORK, LWORK, RWORK, IWORK, LIWORK, BWORK, INFO)
CGGESX computes the eigenvalues, the Schur form, and, optionally, the matrix of Schur vectors for GE...
Definition: cggesx.f:332
subroutine cunmqr(SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC, WORK, LWORK, INFO)
CUNMQR
Definition: cunmqr.f:170
subroutine cggbal(JOB, N, A, LDA, B, LDB, ILO, IHI, LSCALE, RSCALE, WORK, INFO)
CGGBAL
Definition: cggbal.f:179
subroutine clacpy(UPLO, M, N, A, LDA, B, LDB)
CLACPY copies all or part of one two-dimensional array to another.
Definition: clacpy.f:105
subroutine cggbak(JOB, SIDE, N, ILO, IHI, LSCALE, RSCALE, M, V, LDV, INFO)
CGGBAK
Definition: cggbak.f:150
subroutine cgghrd(COMPQ, COMPZ, N, ILO, IHI, A, LDA, B, LDB, Q, LDQ, Z, LDZ, INFO)
CGGHRD
Definition: cgghrd.f:206
subroutine clascl(TYPE, KL, KU, CFROM, CTO, M, N, A, LDA, INFO)
CLASCL multiplies a general rectangular matrix by a real scalar defined as cto/cfrom.
Definition: clascl.f:141
subroutine ctgsen(IJOB, WANTQ, WANTZ, SELECT, N, A, LDA, B, LDB, ALPHA, BETA, Q, LDQ, Z, LDZ, M, PL, PR, DIF, WORK, LWORK, IWORK, LIWORK, INFO)
CTGSEN
Definition: ctgsen.f:435
subroutine chgeqz(JOB, COMPQ, COMPZ, N, ILO, IHI, H, LDH, T, LDT, ALPHA, BETA, Q, LDQ, Z, LDZ, WORK, LWORK, RWORK, INFO)
CHGEQZ
Definition: chgeqz.f:286
subroutine cungqr(M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
CUNGQR
Definition: cungqr.f:130