 LAPACK  3.10.0 LAPACK: Linear Algebra PACKage

## ◆ cgegs()

 subroutine cgegs ( character JOBVSL, character JOBVSR, integer N, complex, dimension( lda, * ) A, integer LDA, complex, dimension( ldb, * ) B, integer LDB, complex, dimension( * ) ALPHA, complex, dimension( * ) BETA, complex, dimension( ldvsl, * ) VSL, integer LDVSL, complex, dimension( ldvsr, * ) VSR, integer LDVSR, complex, dimension( * ) WORK, integer LWORK, real, dimension( * ) RWORK, integer INFO )

CGEEVX computes the eigenvalues and, optionally, the left and/or right eigenvectors for GE matrices

Purpose:
``` This routine is deprecated and has been replaced by routine CGGES.

CGEGS computes the eigenvalues, Schur form, and, optionally, the
left and or/right Schur vectors of a complex matrix pair (A,B).
Given two square matrices A and B, the generalized Schur
factorization has the form

A = Q*S*Z**H,  B = Q*T*Z**H

where Q and Z are unitary matrices and S and T are upper triangular.
The columns of Q are the left Schur vectors
and the columns of Z are the right Schur vectors.

If only the eigenvalues of (A,B) are needed, the driver routine
CGEGV should be used instead.  See CGEGV for a description of the
eigenvalues of the generalized nonsymmetric eigenvalue problem
(GNEP).```
Parameters
 [in] JOBVSL ``` JOBVSL is CHARACTER*1 = 'N': do not compute the left Schur vectors; = 'V': compute the left Schur vectors (returned in VSL).``` [in] JOBVSR ``` JOBVSR is CHARACTER*1 = 'N': do not compute the right Schur vectors; = 'V': compute the right Schur vectors (returned in VSR).``` [in] N ``` N is INTEGER The order of the matrices A, B, VSL, and VSR. N >= 0.``` [in,out] A ``` A is COMPLEX array, dimension (LDA, N) On entry, the matrix A. On exit, the upper triangular matrix S from the generalized Schur factorization.``` [in] LDA ``` LDA is INTEGER The leading dimension of A. LDA >= max(1,N).``` [in,out] B ``` B is COMPLEX array, dimension (LDB, N) On entry, the matrix B. On exit, the upper triangular matrix T from the generalized Schur factorization.``` [in] LDB ``` LDB is INTEGER The leading dimension of B. LDB >= max(1,N).``` [out] ALPHA ``` ALPHA is COMPLEX array, dimension (N) The complex scalars alpha that define the eigenvalues of GNEP. ALPHA(j) = S(j,j), the diagonal element of the Schur form of A.``` [out] BETA ``` BETA is COMPLEX array, dimension (N) The non-negative real scalars beta that define the eigenvalues of GNEP. BETA(j) = T(j,j), the diagonal element of the triangular factor T. Together, the quantities alpha = ALPHA(j) and beta = BETA(j) represent the j-th eigenvalue of the matrix pair (A,B), in one of the forms lambda = alpha/beta or mu = beta/alpha. Since either lambda or mu may overflow, they should not, in general, be computed.``` [out] VSL ``` VSL is COMPLEX array, dimension (LDVSL,N) If JOBVSL = 'V', the matrix of left Schur vectors Q. Not referenced if JOBVSL = 'N'.``` [in] LDVSL ``` LDVSL is INTEGER The leading dimension of the matrix VSL. LDVSL >= 1, and if JOBVSL = 'V', LDVSL >= N.``` [out] VSR ``` VSR is COMPLEX array, dimension (LDVSR,N) If JOBVSR = 'V', the matrix of right Schur vectors Z. Not referenced if JOBVSR = 'N'.``` [in] LDVSR ``` LDVSR is INTEGER The leading dimension of the matrix VSR. LDVSR >= 1, and if JOBVSR = 'V', LDVSR >= N.``` [out] WORK ``` WORK is COMPLEX array, dimension (MAX(1,LWORK)) On exit, if INFO = 0, WORK(1) returns the optimal LWORK.``` [in] LWORK ``` LWORK is INTEGER The dimension of the array WORK. LWORK >= max(1,2*N). For good performance, LWORK must generally be larger. To compute the optimal value of LWORK, call ILAENV to get blocksizes (for CGEQRF, CUNMQR, and CUNGQR.) Then compute: NB -- MAX of the blocksizes for CGEQRF, CUNMQR, and CUNGQR; the optimal LWORK is N*(NB+1). If LWORK = -1, then a workspace query is assumed; the routine only calculates the optimal size of the WORK array, returns this value as the first entry of the WORK array, and no error message related to LWORK is issued by XERBLA.``` [out] RWORK ` RWORK is REAL array, dimension (3*N)` [out] INFO ``` INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value. =1,...,N: The QZ iteration failed. (A,B) are not in Schur form, but ALPHA(j) and BETA(j) should be correct for j=INFO+1,...,N. > N: errors that usually indicate LAPACK problems: =N+1: error return from CGGBAL =N+2: error return from CGEQRF =N+3: error return from CUNMQR =N+4: error return from CUNGQR =N+5: error return from CGGHRD =N+6: error return from CHGEQZ (other than failed iteration) =N+7: error return from CGGBAK (computing VSL) =N+8: error return from CGGBAK (computing VSR) =N+9: error return from CLASCL (various places)```

Definition at line 222 of file cgegs.f.

225 *
226 * -- LAPACK driver routine --
227 * -- LAPACK is a software package provided by Univ. of Tennessee, --
228 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
229 *
230 * .. Scalar Arguments ..
231  CHARACTER JOBVSL, JOBVSR
232  INTEGER INFO, LDA, LDB, LDVSL, LDVSR, LWORK, N
233 * ..
234 * .. Array Arguments ..
235  REAL RWORK( * )
236  COMPLEX A( LDA, * ), ALPHA( * ), B( LDB, * ),
237  \$ BETA( * ), VSL( LDVSL, * ), VSR( LDVSR, * ),
238  \$ WORK( * )
239 * ..
240 *
241 * =====================================================================
242 *
243 * .. Parameters ..
244  REAL ZERO, ONE
245  parameter( zero = 0.0e0, one = 1.0e0 )
246  COMPLEX CZERO, CONE
247  parameter( czero = ( 0.0e0, 0.0e0 ),
248  \$ cone = ( 1.0e0, 0.0e0 ) )
249 * ..
250 * .. Local Scalars ..
251  LOGICAL ILASCL, ILBSCL, ILVSL, ILVSR, LQUERY
252  INTEGER ICOLS, IHI, IINFO, IJOBVL, IJOBVR, ILEFT,
253  \$ ILO, IRIGHT, IROWS, IRWORK, ITAU, IWORK,
254  \$ LOPT, LWKMIN, LWKOPT, NB, NB1, NB2, NB3
255  REAL ANRM, ANRMTO, BIGNUM, BNRM, BNRMTO, EPS,
256  \$ SAFMIN, SMLNUM
257 * ..
258 * .. External Subroutines ..
259  EXTERNAL cgeqrf, cggbak, cggbal, cgghrd, chgeqz, clacpy,
261 * ..
262 * .. External Functions ..
263  LOGICAL LSAME
264  INTEGER ILAENV
265  REAL CLANGE, SLAMCH
266  EXTERNAL ilaenv, lsame, clange, slamch
267 * ..
268 * .. Intrinsic Functions ..
269  INTRINSIC int, max
270 * ..
271 * .. Executable Statements ..
272 *
273 * Decode the input arguments
274 *
275  IF( lsame( jobvsl, 'N' ) ) THEN
276  ijobvl = 1
277  ilvsl = .false.
278  ELSE IF( lsame( jobvsl, 'V' ) ) THEN
279  ijobvl = 2
280  ilvsl = .true.
281  ELSE
282  ijobvl = -1
283  ilvsl = .false.
284  END IF
285 *
286  IF( lsame( jobvsr, 'N' ) ) THEN
287  ijobvr = 1
288  ilvsr = .false.
289  ELSE IF( lsame( jobvsr, 'V' ) ) THEN
290  ijobvr = 2
291  ilvsr = .true.
292  ELSE
293  ijobvr = -1
294  ilvsr = .false.
295  END IF
296 *
297 * Test the input arguments
298 *
299  lwkmin = max( 2*n, 1 )
300  lwkopt = lwkmin
301  work( 1 ) = lwkopt
302  lquery = ( lwork.EQ.-1 )
303  info = 0
304  IF( ijobvl.LE.0 ) THEN
305  info = -1
306  ELSE IF( ijobvr.LE.0 ) THEN
307  info = -2
308  ELSE IF( n.LT.0 ) THEN
309  info = -3
310  ELSE IF( lda.LT.max( 1, n ) ) THEN
311  info = -5
312  ELSE IF( ldb.LT.max( 1, n ) ) THEN
313  info = -7
314  ELSE IF( ldvsl.LT.1 .OR. ( ilvsl .AND. ldvsl.LT.n ) ) THEN
315  info = -11
316  ELSE IF( ldvsr.LT.1 .OR. ( ilvsr .AND. ldvsr.LT.n ) ) THEN
317  info = -13
318  ELSE IF( lwork.LT.lwkmin .AND. .NOT.lquery ) THEN
319  info = -15
320  END IF
321 *
322  IF( info.EQ.0 ) THEN
323  nb1 = ilaenv( 1, 'CGEQRF', ' ', n, n, -1, -1 )
324  nb2 = ilaenv( 1, 'CUNMQR', ' ', n, n, n, -1 )
325  nb3 = ilaenv( 1, 'CUNGQR', ' ', n, n, n, -1 )
326  nb = max( nb1, nb2, nb3 )
327  lopt = n*(nb+1)
328  work( 1 ) = lopt
329  END IF
330 *
331  IF( info.NE.0 ) THEN
332  CALL xerbla( 'CGEGS ', -info )
333  RETURN
334  ELSE IF( lquery ) THEN
335  RETURN
336  END IF
337 *
338 * Quick return if possible
339 *
340  IF( n.EQ.0 )
341  \$ RETURN
342 *
343 * Get machine constants
344 *
345  eps = slamch( 'E' )*slamch( 'B' )
346  safmin = slamch( 'S' )
347  smlnum = n*safmin / eps
348  bignum = one / smlnum
349 *
350 * Scale A if max element outside range [SMLNUM,BIGNUM]
351 *
352  anrm = clange( 'M', n, n, a, lda, rwork )
353  ilascl = .false.
354  IF( anrm.GT.zero .AND. anrm.LT.smlnum ) THEN
355  anrmto = smlnum
356  ilascl = .true.
357  ELSE IF( anrm.GT.bignum ) THEN
358  anrmto = bignum
359  ilascl = .true.
360  END IF
361 *
362  IF( ilascl ) THEN
363  CALL clascl( 'G', -1, -1, anrm, anrmto, n, n, a, lda, iinfo )
364  IF( iinfo.NE.0 ) THEN
365  info = n + 9
366  RETURN
367  END IF
368  END IF
369 *
370 * Scale B if max element outside range [SMLNUM,BIGNUM]
371 *
372  bnrm = clange( 'M', n, n, b, ldb, rwork )
373  ilbscl = .false.
374  IF( bnrm.GT.zero .AND. bnrm.LT.smlnum ) THEN
375  bnrmto = smlnum
376  ilbscl = .true.
377  ELSE IF( bnrm.GT.bignum ) THEN
378  bnrmto = bignum
379  ilbscl = .true.
380  END IF
381 *
382  IF( ilbscl ) THEN
383  CALL clascl( 'G', -1, -1, bnrm, bnrmto, n, n, b, ldb, iinfo )
384  IF( iinfo.NE.0 ) THEN
385  info = n + 9
386  RETURN
387  END IF
388  END IF
389 *
390 * Permute the matrix to make it more nearly triangular
391 *
392  ileft = 1
393  iright = n + 1
394  irwork = iright + n
395  iwork = 1
396  CALL cggbal( 'P', n, a, lda, b, ldb, ilo, ihi, rwork( ileft ),
397  \$ rwork( iright ), rwork( irwork ), iinfo )
398  IF( iinfo.NE.0 ) THEN
399  info = n + 1
400  GO TO 10
401  END IF
402 *
403 * Reduce B to triangular form, and initialize VSL and/or VSR
404 *
405  irows = ihi + 1 - ilo
406  icols = n + 1 - ilo
407  itau = iwork
408  iwork = itau + irows
409  CALL cgeqrf( irows, icols, b( ilo, ilo ), ldb, work( itau ),
410  \$ work( iwork ), lwork+1-iwork, iinfo )
411  IF( iinfo.GE.0 )
412  \$ lwkopt = max( lwkopt, int( work( iwork ) )+iwork-1 )
413  IF( iinfo.NE.0 ) THEN
414  info = n + 2
415  GO TO 10
416  END IF
417 *
418  CALL cunmqr( 'L', 'C', irows, icols, irows, b( ilo, ilo ), ldb,
419  \$ work( itau ), a( ilo, ilo ), lda, work( iwork ),
420  \$ lwork+1-iwork, iinfo )
421  IF( iinfo.GE.0 )
422  \$ lwkopt = max( lwkopt, int( work( iwork ) )+iwork-1 )
423  IF( iinfo.NE.0 ) THEN
424  info = n + 3
425  GO TO 10
426  END IF
427 *
428  IF( ilvsl ) THEN
429  CALL claset( 'Full', n, n, czero, cone, vsl, ldvsl )
430  CALL clacpy( 'L', irows-1, irows-1, b( ilo+1, ilo ), ldb,
431  \$ vsl( ilo+1, ilo ), ldvsl )
432  CALL cungqr( irows, irows, irows, vsl( ilo, ilo ), ldvsl,
433  \$ work( itau ), work( iwork ), lwork+1-iwork,
434  \$ iinfo )
435  IF( iinfo.GE.0 )
436  \$ lwkopt = max( lwkopt, int( work( iwork ) )+iwork-1 )
437  IF( iinfo.NE.0 ) THEN
438  info = n + 4
439  GO TO 10
440  END IF
441  END IF
442 *
443  IF( ilvsr )
444  \$ CALL claset( 'Full', n, n, czero, cone, vsr, ldvsr )
445 *
446 * Reduce to generalized Hessenberg form
447 *
448  CALL cgghrd( jobvsl, jobvsr, n, ilo, ihi, a, lda, b, ldb, vsl,
449  \$ ldvsl, vsr, ldvsr, iinfo )
450  IF( iinfo.NE.0 ) THEN
451  info = n + 5
452  GO TO 10
453  END IF
454 *
455 * Perform QZ algorithm, computing Schur vectors if desired
456 *
457  iwork = itau
458  CALL chgeqz( 'S', jobvsl, jobvsr, n, ilo, ihi, a, lda, b, ldb,
459  \$ alpha, beta, vsl, ldvsl, vsr, ldvsr, work( iwork ),
460  \$ lwork+1-iwork, rwork( irwork ), iinfo )
461  IF( iinfo.GE.0 )
462  \$ lwkopt = max( lwkopt, int( work( iwork ) )+iwork-1 )
463  IF( iinfo.NE.0 ) THEN
464  IF( iinfo.GT.0 .AND. iinfo.LE.n ) THEN
465  info = iinfo
466  ELSE IF( iinfo.GT.n .AND. iinfo.LE.2*n ) THEN
467  info = iinfo - n
468  ELSE
469  info = n + 6
470  END IF
471  GO TO 10
472  END IF
473 *
474 * Apply permutation to VSL and VSR
475 *
476  IF( ilvsl ) THEN
477  CALL cggbak( 'P', 'L', n, ilo, ihi, rwork( ileft ),
478  \$ rwork( iright ), n, vsl, ldvsl, iinfo )
479  IF( iinfo.NE.0 ) THEN
480  info = n + 7
481  GO TO 10
482  END IF
483  END IF
484  IF( ilvsr ) THEN
485  CALL cggbak( 'P', 'R', n, ilo, ihi, rwork( ileft ),
486  \$ rwork( iright ), n, vsr, ldvsr, iinfo )
487  IF( iinfo.NE.0 ) THEN
488  info = n + 8
489  GO TO 10
490  END IF
491  END IF
492 *
493 * Undo scaling
494 *
495  IF( ilascl ) THEN
496  CALL clascl( 'U', -1, -1, anrmto, anrm, n, n, a, lda, iinfo )
497  IF( iinfo.NE.0 ) THEN
498  info = n + 9
499  RETURN
500  END IF
501  CALL clascl( 'G', -1, -1, anrmto, anrm, n, 1, alpha, n, iinfo )
502  IF( iinfo.NE.0 ) THEN
503  info = n + 9
504  RETURN
505  END IF
506  END IF
507 *
508  IF( ilbscl ) THEN
509  CALL clascl( 'U', -1, -1, bnrmto, bnrm, n, n, b, ldb, iinfo )
510  IF( iinfo.NE.0 ) THEN
511  info = n + 9
512  RETURN
513  END IF
514  CALL clascl( 'G', -1, -1, bnrmto, bnrm, n, 1, beta, n, iinfo )
515  IF( iinfo.NE.0 ) THEN
516  info = n + 9
517  RETURN
518  END IF
519  END IF
520 *
521  10 CONTINUE
522  work( 1 ) = lwkopt
523 *
524  RETURN
525 *
526 * End of CGEGS
527 *
integer function ilaenv(ISPEC, NAME, OPTS, N1, N2, N3, N4)
ILAENV
Definition: ilaenv.f:162
subroutine xerbla(SRNAME, INFO)
XERBLA
Definition: xerbla.f:60
logical function lsame(CA, CB)
LSAME
Definition: lsame.f:53
subroutine cggbal(JOB, N, A, LDA, B, LDB, ILO, IHI, LSCALE, RSCALE, WORK, INFO)
CGGBAL
Definition: cggbal.f:177
subroutine cggbak(JOB, SIDE, N, ILO, IHI, LSCALE, RSCALE, M, V, LDV, INFO)
CGGBAK
Definition: cggbak.f:148
real function clange(NORM, M, N, A, LDA, WORK)
CLANGE returns the value of the 1-norm, Frobenius norm, infinity-norm, or the largest absolute value ...
Definition: clange.f:115
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:284
subroutine cgeqrf(M, N, A, LDA, TAU, WORK, LWORK, INFO)
CGEQRF
Definition: cgeqrf.f:145
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:106
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:143
subroutine clacpy(UPLO, M, N, A, LDA, B, LDB)
CLACPY copies all or part of one two-dimensional array to another.
Definition: clacpy.f:103
subroutine cunmqr(SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC, WORK, LWORK, INFO)
CUNMQR
Definition: cunmqr.f:168
subroutine cgghrd(COMPQ, COMPZ, N, ILO, IHI, A, LDA, B, LDB, Q, LDQ, Z, LDZ, INFO)
CGGHRD
Definition: cgghrd.f:204
subroutine cungqr(M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
CUNGQR
Definition: cungqr.f:128
real function slamch(CMACH)
SLAMCH
Definition: slamch.f:68
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