LAPACK  3.8.0
LAPACK: Linear Algebra PACKage

◆ cggevx()

subroutine cggevx ( character  BALANC,
character  JOBVL,
character  JOBVR,
character  SENSE,
integer  N,
complex, dimension( lda, * )  A,
integer  LDA,
complex, dimension( ldb, * )  B,
integer  LDB,
complex, dimension( * )  ALPHA,
complex, dimension( * )  BETA,
complex, dimension( ldvl, * )  VL,
integer  LDVL,
complex, dimension( ldvr, * )  VR,
integer  LDVR,
integer  ILO,
integer  IHI,
real, dimension( * )  LSCALE,
real, dimension( * )  RSCALE,
real  ABNRM,
real  BBNRM,
real, dimension( * )  RCONDE,
real, dimension( * )  RCONDV,
complex, dimension( * )  WORK,
integer  LWORK,
real, dimension( * )  RWORK,
integer, dimension( * )  IWORK,
logical, dimension( * )  BWORK,
integer  INFO 
)

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

Download CGGEVX + dependencies [TGZ] [ZIP] [TXT]

Purpose:
 CGGEVX computes for a pair of N-by-N complex nonsymmetric matrices
 (A,B) the generalized eigenvalues, and optionally, the left and/or
 right generalized eigenvectors.

 Optionally, it also computes a balancing transformation to improve
 the conditioning of the eigenvalues and eigenvectors (ILO, IHI,
 LSCALE, RSCALE, ABNRM, and BBNRM), reciprocal condition numbers for
 the eigenvalues (RCONDE), and reciprocal condition numbers for the
 right eigenvectors (RCONDV).

 A generalized eigenvalue for a pair of matrices (A,B) is a scalar
 lambda or a ratio alpha/beta = lambda, such that A - lambda*B is
 singular. It is usually represented as the pair (alpha,beta), as
 there is a reasonable interpretation for beta=0, and even for both
 being zero.

 The right eigenvector v(j) corresponding to the eigenvalue lambda(j)
 of (A,B) satisfies
                  A * v(j) = lambda(j) * B * v(j) .
 The left eigenvector u(j) corresponding to the eigenvalue lambda(j)
 of (A,B) satisfies
                  u(j)**H * A  = lambda(j) * u(j)**H * B.
 where u(j)**H is the conjugate-transpose of u(j).
Parameters
[in]BALANC
          BALANC is CHARACTER*1
          Specifies the balance option to be performed:
          = 'N':  do not diagonally scale or permute;
          = 'P':  permute only;
          = 'S':  scale only;
          = 'B':  both permute and scale.
          Computed reciprocal condition numbers will be for the
          matrices after permuting and/or balancing. Permuting does
          not change condition numbers (in exact arithmetic), but
          balancing does.
[in]JOBVL
          JOBVL is CHARACTER*1
          = 'N':  do not compute the left generalized eigenvectors;
          = 'V':  compute the left generalized eigenvectors.
[in]JOBVR
          JOBVR is CHARACTER*1
          = 'N':  do not compute the right generalized eigenvectors;
          = 'V':  compute the right generalized eigenvectors.
[in]SENSE
          SENSE is CHARACTER*1
          Determines which reciprocal condition numbers are computed.
          = 'N': none are computed;
          = 'E': computed for eigenvalues only;
          = 'V': computed for eigenvectors only;
          = 'B': computed for eigenvalues and eigenvectors.
[in]N
          N is INTEGER
          The order of the matrices A, B, VL, and VR.  N >= 0.
[in,out]A
          A is COMPLEX array, dimension (LDA, N)
          On entry, the matrix A in the pair (A,B).
          On exit, A has been overwritten. If JOBVL='V' or JOBVR='V'
          or both, then A contains the first part of the complex Schur
          form of the "balanced" versions of the input A and B.
[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 in the pair (A,B).
          On exit, B has been overwritten. If JOBVL='V' or JOBVR='V'
          or both, then B contains the second part of the complex
          Schur form of the "balanced" versions of the input A and B.
[in]LDB
          LDB is INTEGER
          The leading dimension of B.  LDB >= max(1,N).
[out]ALPHA
          ALPHA is COMPLEX array, dimension (N)
[out]BETA
          BETA is COMPLEX array, dimension (N)
          On exit, ALPHA(j)/BETA(j), j=1,...,N, will be the generalized
          eigenvalues.

          Note: the quotient ALPHA(j)/BETA(j) ) may easily over- or
          underflow, and BETA(j) may even be zero.  Thus, the user
          should avoid naively computing the ratio ALPHA/BETA.
          However, ALPHA will be always less than and usually
          comparable with norm(A) in magnitude, and BETA always less
          than and usually comparable with norm(B).
[out]VL
          VL is COMPLEX array, dimension (LDVL,N)
          If JOBVL = 'V', the left generalized eigenvectors u(j) are
          stored one after another in the columns of VL, in the same
          order as their eigenvalues.
          Each eigenvector will be scaled so the largest component
          will have abs(real part) + abs(imag. part) = 1.
          Not referenced if JOBVL = 'N'.
[in]LDVL
          LDVL is INTEGER
          The leading dimension of the matrix VL. LDVL >= 1, and
          if JOBVL = 'V', LDVL >= N.
[out]VR
          VR is COMPLEX array, dimension (LDVR,N)
          If JOBVR = 'V', the right generalized eigenvectors v(j) are
          stored one after another in the columns of VR, in the same
          order as their eigenvalues.
          Each eigenvector will be scaled so the largest component
          will have abs(real part) + abs(imag. part) = 1.
          Not referenced if JOBVR = 'N'.
[in]LDVR
          LDVR is INTEGER
          The leading dimension of the matrix VR. LDVR >= 1, and
          if JOBVR = 'V', LDVR >= N.
[out]ILO
          ILO is INTEGER
[out]IHI
          IHI is INTEGER
          ILO and IHI are integer values such that on exit
          A(i,j) = 0 and B(i,j) = 0 if i > j and
          j = 1,...,ILO-1 or i = IHI+1,...,N.
          If BALANC = 'N' or 'S', ILO = 1 and IHI = N.
[out]LSCALE
          LSCALE is REAL array, dimension (N)
          Details of the permutations and scaling factors applied
          to the left side of A and B.  If PL(j) is the index of the
          row interchanged with row j, and DL(j) is the scaling
          factor applied to row j, then
            LSCALE(j) = PL(j)  for j = 1,...,ILO-1
                      = DL(j)  for j = ILO,...,IHI
                      = PL(j)  for j = IHI+1,...,N.
          The order in which the interchanges are made is N to IHI+1,
          then 1 to ILO-1.
[out]RSCALE
          RSCALE is REAL array, dimension (N)
          Details of the permutations and scaling factors applied
          to the right side of A and B.  If PR(j) is the index of the
          column interchanged with column j, and DR(j) is the scaling
          factor applied to column j, then
            RSCALE(j) = PR(j)  for j = 1,...,ILO-1
                      = DR(j)  for j = ILO,...,IHI
                      = PR(j)  for j = IHI+1,...,N
          The order in which the interchanges are made is N to IHI+1,
          then 1 to ILO-1.
[out]ABNRM
          ABNRM is REAL
          The one-norm of the balanced matrix A.
[out]BBNRM
          BBNRM is REAL
          The one-norm of the balanced matrix B.
[out]RCONDE
          RCONDE is REAL array, dimension (N)
          If SENSE = 'E' or 'B', the reciprocal condition numbers of
          the eigenvalues, stored in consecutive elements of the array.
          If SENSE = 'N' or 'V', RCONDE is not referenced.
[out]RCONDV
          RCONDV is REAL array, dimension (N)
          If SENSE = 'V' or 'B', the estimated reciprocal condition
          numbers of the eigenvectors, stored in consecutive elements
          of the array. If the eigenvalues cannot be reordered to
          compute RCONDV(j), RCONDV(j) is set to 0; this can only occur
          when the true value would be very small anyway.
          If SENSE = 'N' or 'E', RCONDV is not referenced.
[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).
          If SENSE = 'E', LWORK >= max(1,4*N).
          If SENSE = 'V' or 'B', LWORK >= max(1,2*N*N+2*N).

          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 (lrwork)
          lrwork must be at least max(1,6*N) if BALANC = 'S' or 'B',
          and at least max(1,2*N) otherwise.
          Real workspace.
[out]IWORK
          IWORK is INTEGER array, dimension (N+2)
          If SENSE = 'E', IWORK is not referenced.
[out]BWORK
          BWORK is LOGICAL array, dimension (N)
          If SENSE = 'N', BWORK is not referenced.
[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.  No eigenvectors have been
                calculated, but ALPHA(j) and BETA(j) should be correct
                for j=INFO+1,...,N.
          > N:  =N+1: other than QZ iteration failed in CHGEQZ.
                =N+2: error return from CTGEVC.
Author
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date
April 2012
Further Details:
  Balancing a matrix pair (A,B) includes, first, permuting rows and
  columns to isolate eigenvalues, second, applying diagonal similarity
  transformation to the rows and columns to make the rows and columns
  as close in norm as possible. The computed reciprocal condition
  numbers correspond to the balanced matrix. Permuting rows and columns
  will not change the condition numbers (in exact arithmetic) but
  diagonal scaling will.  For further explanation of balancing, see
  section 4.11.1.2 of LAPACK Users' Guide.

  An approximate error bound on the chordal distance between the i-th
  computed generalized eigenvalue w and the corresponding exact
  eigenvalue lambda is

       chord(w, lambda) <= EPS * norm(ABNRM, BBNRM) / RCONDE(I)

  An approximate error bound for the angle between the i-th computed
  eigenvector VL(i) or VR(i) is given by

       EPS * norm(ABNRM, BBNRM) / DIF(i).

  For further explanation of the reciprocal condition numbers RCONDE
  and RCONDV, see section 4.11 of LAPACK User's Guide.

Definition at line 376 of file cggevx.f.

376 *
377 * -- LAPACK driver routine (version 3.7.0) --
378 * -- LAPACK is a software package provided by Univ. of Tennessee, --
379 * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
380 * April 2012
381 *
382 * .. Scalar Arguments ..
383  CHARACTER balanc, jobvl, jobvr, sense
384  INTEGER ihi, ilo, info, lda, ldb, ldvl, ldvr, lwork, n
385  REAL abnrm, bbnrm
386 * ..
387 * .. Array Arguments ..
388  LOGICAL bwork( * )
389  INTEGER iwork( * )
390  REAL lscale( * ), rconde( * ), rcondv( * ),
391  $ rscale( * ), rwork( * )
392  COMPLEX a( lda, * ), alpha( * ), b( ldb, * ),
393  $ beta( * ), vl( ldvl, * ), vr( ldvr, * ),
394  $ work( * )
395 * ..
396 *
397 * =====================================================================
398 *
399 * .. Parameters ..
400  REAL zero, one
401  parameter( zero = 0.0e+0, one = 1.0e+0 )
402  COMPLEX czero, cone
403  parameter( czero = ( 0.0e+0, 0.0e+0 ),
404  $ cone = ( 1.0e+0, 0.0e+0 ) )
405 * ..
406 * .. Local Scalars ..
407  LOGICAL ilascl, ilbscl, ilv, ilvl, ilvr, lquery, noscl,
408  $ wantsb, wantse, wantsn, wantsv
409  CHARACTER chtemp
410  INTEGER i, icols, ierr, ijobvl, ijobvr, in, irows,
411  $ itau, iwrk, iwrk1, j, jc, jr, m, maxwrk, minwrk
412  REAL anrm, anrmto, bignum, bnrm, bnrmto, eps,
413  $ smlnum, temp
414  COMPLEX x
415 * ..
416 * .. Local Arrays ..
417  LOGICAL ldumma( 1 )
418 * ..
419 * .. External Subroutines ..
420  EXTERNAL cgeqrf, cggbak, cggbal, cgghrd, chgeqz, clacpy,
422  $ slabad, slascl, xerbla
423 * ..
424 * .. External Functions ..
425  LOGICAL lsame
426  INTEGER ilaenv
427  REAL clange, slamch
428  EXTERNAL lsame, ilaenv, clange, slamch
429 * ..
430 * .. Intrinsic Functions ..
431  INTRINSIC abs, aimag, max, REAL, sqrt
432 * ..
433 * .. Statement Functions ..
434  REAL abs1
435 * ..
436 * .. Statement Function definitions ..
437  abs1( x ) = abs( REAL( X ) ) + abs( aimag( x ) )
438 * ..
439 * .. Executable Statements ..
440 *
441 * Decode the input arguments
442 *
443  IF( lsame( jobvl, 'N' ) ) THEN
444  ijobvl = 1
445  ilvl = .false.
446  ELSE IF( lsame( jobvl, 'V' ) ) THEN
447  ijobvl = 2
448  ilvl = .true.
449  ELSE
450  ijobvl = -1
451  ilvl = .false.
452  END IF
453 *
454  IF( lsame( jobvr, 'N' ) ) THEN
455  ijobvr = 1
456  ilvr = .false.
457  ELSE IF( lsame( jobvr, 'V' ) ) THEN
458  ijobvr = 2
459  ilvr = .true.
460  ELSE
461  ijobvr = -1
462  ilvr = .false.
463  END IF
464  ilv = ilvl .OR. ilvr
465 *
466  noscl = lsame( balanc, 'N' ) .OR. lsame( balanc, 'P' )
467  wantsn = lsame( sense, 'N' )
468  wantse = lsame( sense, 'E' )
469  wantsv = lsame( sense, 'V' )
470  wantsb = lsame( sense, 'B' )
471 *
472 * Test the input arguments
473 *
474  info = 0
475  lquery = ( lwork.EQ.-1 )
476  IF( .NOT.( noscl .OR. lsame( balanc,'S' ) .OR.
477  $ lsame( balanc, 'B' ) ) ) THEN
478  info = -1
479  ELSE IF( ijobvl.LE.0 ) THEN
480  info = -2
481  ELSE IF( ijobvr.LE.0 ) THEN
482  info = -3
483  ELSE IF( .NOT.( wantsn .OR. wantse .OR. wantsb .OR. wantsv ) )
484  $ THEN
485  info = -4
486  ELSE IF( n.LT.0 ) THEN
487  info = -5
488  ELSE IF( lda.LT.max( 1, n ) ) THEN
489  info = -7
490  ELSE IF( ldb.LT.max( 1, n ) ) THEN
491  info = -9
492  ELSE IF( ldvl.LT.1 .OR. ( ilvl .AND. ldvl.LT.n ) ) THEN
493  info = -13
494  ELSE IF( ldvr.LT.1 .OR. ( ilvr .AND. ldvr.LT.n ) ) THEN
495  info = -15
496  END IF
497 *
498 * Compute workspace
499 * (Note: Comments in the code beginning "Workspace:" describe the
500 * minimal amount of workspace needed at that point in the code,
501 * as well as the preferred amount for good performance.
502 * NB refers to the optimal block size for the immediately
503 * following subroutine, as returned by ILAENV. The workspace is
504 * computed assuming ILO = 1 and IHI = N, the worst case.)
505 *
506  IF( info.EQ.0 ) THEN
507  IF( n.EQ.0 ) THEN
508  minwrk = 1
509  maxwrk = 1
510  ELSE
511  minwrk = 2*n
512  IF( wantse ) THEN
513  minwrk = 4*n
514  ELSE IF( wantsv .OR. wantsb ) THEN
515  minwrk = 2*n*( n + 1)
516  END IF
517  maxwrk = minwrk
518  maxwrk = max( maxwrk,
519  $ n + n*ilaenv( 1, 'CGEQRF', ' ', n, 1, n, 0 ) )
520  maxwrk = max( maxwrk,
521  $ n + n*ilaenv( 1, 'CUNMQR', ' ', n, 1, n, 0 ) )
522  IF( ilvl ) THEN
523  maxwrk = max( maxwrk, n +
524  $ n*ilaenv( 1, 'CUNGQR', ' ', n, 1, n, 0 ) )
525  END IF
526  END IF
527  work( 1 ) = maxwrk
528 *
529  IF( lwork.LT.minwrk .AND. .NOT.lquery ) THEN
530  info = -25
531  END IF
532  END IF
533 *
534  IF( info.NE.0 ) THEN
535  CALL xerbla( 'CGGEVX', -info )
536  RETURN
537  ELSE IF( lquery ) THEN
538  RETURN
539  END IF
540 *
541 * Quick return if possible
542 *
543  IF( n.EQ.0 )
544  $ RETURN
545 *
546 * Get machine constants
547 *
548  eps = slamch( 'P' )
549  smlnum = slamch( 'S' )
550  bignum = one / smlnum
551  CALL slabad( smlnum, bignum )
552  smlnum = sqrt( smlnum ) / eps
553  bignum = one / smlnum
554 *
555 * Scale A if max element outside range [SMLNUM,BIGNUM]
556 *
557  anrm = clange( 'M', n, n, a, lda, rwork )
558  ilascl = .false.
559  IF( anrm.GT.zero .AND. anrm.LT.smlnum ) THEN
560  anrmto = smlnum
561  ilascl = .true.
562  ELSE IF( anrm.GT.bignum ) THEN
563  anrmto = bignum
564  ilascl = .true.
565  END IF
566  IF( ilascl )
567  $ CALL clascl( 'G', 0, 0, anrm, anrmto, n, n, a, lda, ierr )
568 *
569 * Scale B if max element outside range [SMLNUM,BIGNUM]
570 *
571  bnrm = clange( 'M', n, n, b, ldb, rwork )
572  ilbscl = .false.
573  IF( bnrm.GT.zero .AND. bnrm.LT.smlnum ) THEN
574  bnrmto = smlnum
575  ilbscl = .true.
576  ELSE IF( bnrm.GT.bignum ) THEN
577  bnrmto = bignum
578  ilbscl = .true.
579  END IF
580  IF( ilbscl )
581  $ CALL clascl( 'G', 0, 0, bnrm, bnrmto, n, n, b, ldb, ierr )
582 *
583 * Permute and/or balance the matrix pair (A,B)
584 * (Real Workspace: need 6*N if BALANC = 'S' or 'B', 1 otherwise)
585 *
586  CALL cggbal( balanc, n, a, lda, b, ldb, ilo, ihi, lscale, rscale,
587  $ rwork, ierr )
588 *
589 * Compute ABNRM and BBNRM
590 *
591  abnrm = clange( '1', n, n, a, lda, rwork( 1 ) )
592  IF( ilascl ) THEN
593  rwork( 1 ) = abnrm
594  CALL slascl( 'G', 0, 0, anrmto, anrm, 1, 1, rwork( 1 ), 1,
595  $ ierr )
596  abnrm = rwork( 1 )
597  END IF
598 *
599  bbnrm = clange( '1', n, n, b, ldb, rwork( 1 ) )
600  IF( ilbscl ) THEN
601  rwork( 1 ) = bbnrm
602  CALL slascl( 'G', 0, 0, bnrmto, bnrm, 1, 1, rwork( 1 ), 1,
603  $ ierr )
604  bbnrm = rwork( 1 )
605  END IF
606 *
607 * Reduce B to triangular form (QR decomposition of B)
608 * (Complex Workspace: need N, prefer N*NB )
609 *
610  irows = ihi + 1 - ilo
611  IF( ilv .OR. .NOT.wantsn ) THEN
612  icols = n + 1 - ilo
613  ELSE
614  icols = irows
615  END IF
616  itau = 1
617  iwrk = itau + irows
618  CALL cgeqrf( irows, icols, b( ilo, ilo ), ldb, work( itau ),
619  $ work( iwrk ), lwork+1-iwrk, ierr )
620 *
621 * Apply the unitary transformation to A
622 * (Complex Workspace: need N, prefer N*NB)
623 *
624  CALL cunmqr( 'L', 'C', irows, icols, irows, b( ilo, ilo ), ldb,
625  $ work( itau ), a( ilo, ilo ), lda, work( iwrk ),
626  $ lwork+1-iwrk, ierr )
627 *
628 * Initialize VL and/or VR
629 * (Workspace: need N, prefer N*NB)
630 *
631  IF( ilvl ) THEN
632  CALL claset( 'Full', n, n, czero, cone, vl, ldvl )
633  IF( irows.GT.1 ) THEN
634  CALL clacpy( 'L', irows-1, irows-1, b( ilo+1, ilo ), ldb,
635  $ vl( ilo+1, ilo ), ldvl )
636  END IF
637  CALL cungqr( irows, irows, irows, vl( ilo, ilo ), ldvl,
638  $ work( itau ), work( iwrk ), lwork+1-iwrk, ierr )
639  END IF
640 *
641  IF( ilvr )
642  $ CALL claset( 'Full', n, n, czero, cone, vr, ldvr )
643 *
644 * Reduce to generalized Hessenberg form
645 * (Workspace: none needed)
646 *
647  IF( ilv .OR. .NOT.wantsn ) THEN
648 *
649 * Eigenvectors requested -- work on whole matrix.
650 *
651  CALL cgghrd( jobvl, jobvr, n, ilo, ihi, a, lda, b, ldb, vl,
652  $ ldvl, vr, ldvr, ierr )
653  ELSE
654  CALL cgghrd( 'N', 'N', irows, 1, irows, a( ilo, ilo ), lda,
655  $ b( ilo, ilo ), ldb, vl, ldvl, vr, ldvr, ierr )
656  END IF
657 *
658 * Perform QZ algorithm (Compute eigenvalues, and optionally, the
659 * Schur forms and Schur vectors)
660 * (Complex Workspace: need N)
661 * (Real Workspace: need N)
662 *
663  iwrk = itau
664  IF( ilv .OR. .NOT.wantsn ) THEN
665  chtemp = 'S'
666  ELSE
667  chtemp = 'E'
668  END IF
669 *
670  CALL chgeqz( chtemp, jobvl, jobvr, n, ilo, ihi, a, lda, b, ldb,
671  $ alpha, beta, vl, ldvl, vr, ldvr, work( iwrk ),
672  $ lwork+1-iwrk, rwork, ierr )
673  IF( ierr.NE.0 ) THEN
674  IF( ierr.GT.0 .AND. ierr.LE.n ) THEN
675  info = ierr
676  ELSE IF( ierr.GT.n .AND. ierr.LE.2*n ) THEN
677  info = ierr - n
678  ELSE
679  info = n + 1
680  END IF
681  GO TO 90
682  END IF
683 *
684 * Compute Eigenvectors and estimate condition numbers if desired
685 * CTGEVC: (Complex Workspace: need 2*N )
686 * (Real Workspace: need 2*N )
687 * CTGSNA: (Complex Workspace: need 2*N*N if SENSE='V' or 'B')
688 * (Integer Workspace: need N+2 )
689 *
690  IF( ilv .OR. .NOT.wantsn ) THEN
691  IF( ilv ) THEN
692  IF( ilvl ) THEN
693  IF( ilvr ) THEN
694  chtemp = 'B'
695  ELSE
696  chtemp = 'L'
697  END IF
698  ELSE
699  chtemp = 'R'
700  END IF
701 *
702  CALL ctgevc( chtemp, 'B', ldumma, n, a, lda, b, ldb, vl,
703  $ ldvl, vr, ldvr, n, in, work( iwrk ), rwork,
704  $ ierr )
705  IF( ierr.NE.0 ) THEN
706  info = n + 2
707  GO TO 90
708  END IF
709  END IF
710 *
711  IF( .NOT.wantsn ) THEN
712 *
713 * compute eigenvectors (STGEVC) and estimate condition
714 * numbers (STGSNA). Note that the definition of the condition
715 * number is not invariant under transformation (u,v) to
716 * (Q*u, Z*v), where (u,v) are eigenvectors of the generalized
717 * Schur form (S,T), Q and Z are orthogonal matrices. In order
718 * to avoid using extra 2*N*N workspace, we have to
719 * re-calculate eigenvectors and estimate the condition numbers
720 * one at a time.
721 *
722  DO 20 i = 1, n
723 *
724  DO 10 j = 1, n
725  bwork( j ) = .false.
726  10 CONTINUE
727  bwork( i ) = .true.
728 *
729  iwrk = n + 1
730  iwrk1 = iwrk + n
731 *
732  IF( wantse .OR. wantsb ) THEN
733  CALL ctgevc( 'B', 'S', bwork, n, a, lda, b, ldb,
734  $ work( 1 ), n, work( iwrk ), n, 1, m,
735  $ work( iwrk1 ), rwork, ierr )
736  IF( ierr.NE.0 ) THEN
737  info = n + 2
738  GO TO 90
739  END IF
740  END IF
741 *
742  CALL ctgsna( sense, 'S', bwork, n, a, lda, b, ldb,
743  $ work( 1 ), n, work( iwrk ), n, rconde( i ),
744  $ rcondv( i ), 1, m, work( iwrk1 ),
745  $ lwork-iwrk1+1, iwork, ierr )
746 *
747  20 CONTINUE
748  END IF
749  END IF
750 *
751 * Undo balancing on VL and VR and normalization
752 * (Workspace: none needed)
753 *
754  IF( ilvl ) THEN
755  CALL cggbak( balanc, 'L', n, ilo, ihi, lscale, rscale, n, vl,
756  $ ldvl, ierr )
757 *
758  DO 50 jc = 1, n
759  temp = zero
760  DO 30 jr = 1, n
761  temp = max( temp, abs1( vl( jr, jc ) ) )
762  30 CONTINUE
763  IF( temp.LT.smlnum )
764  $ GO TO 50
765  temp = one / temp
766  DO 40 jr = 1, n
767  vl( jr, jc ) = vl( jr, jc )*temp
768  40 CONTINUE
769  50 CONTINUE
770  END IF
771 *
772  IF( ilvr ) THEN
773  CALL cggbak( balanc, 'R', n, ilo, ihi, lscale, rscale, n, vr,
774  $ ldvr, ierr )
775  DO 80 jc = 1, n
776  temp = zero
777  DO 60 jr = 1, n
778  temp = max( temp, abs1( vr( jr, jc ) ) )
779  60 CONTINUE
780  IF( temp.LT.smlnum )
781  $ GO TO 80
782  temp = one / temp
783  DO 70 jr = 1, n
784  vr( jr, jc ) = vr( jr, jc )*temp
785  70 CONTINUE
786  80 CONTINUE
787  END IF
788 *
789 * Undo scaling if necessary
790 *
791  90 CONTINUE
792 *
793  IF( ilascl )
794  $ CALL clascl( 'G', 0, 0, anrmto, anrm, n, 1, alpha, n, ierr )
795 *
796  IF( ilbscl )
797  $ CALL clascl( 'G', 0, 0, bnrmto, bnrm, n, 1, beta, n, ierr )
798 *
799  work( 1 ) = maxwrk
800  RETURN
801 *
802 * End of CGGEVX
803 *
subroutine ctgsna(JOB, HOWMNY, SELECT, N, A, LDA, B, LDB, VL, LDVL, VR, LDVR, S, DIF, MM, M, WORK, LWORK, IWORK, INFO)
CTGSNA
Definition: ctgsna.f:313
subroutine ctgevc(SIDE, HOWMNY, SELECT, N, S, LDS, P, LDP, VL, LDVL, VR, LDVR, MM, M, WORK, RWORK, INFO)
CTGEVC
Definition: ctgevc.f:221
subroutine cggbal(JOB, N, A, LDA, B, LDB, ILO, IHI, LSCALE, RSCALE, WORK, INFO)
CGGBAL
Definition: cggbal.f:179
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 cungqr(M, N, K, A, LDA, TAU, WORK, LWORK, INFO)
CUNGQR
Definition: cungqr.f:130
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:145
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
integer function ilaenv(ISPEC, NAME, OPTS, N1, N2, N3, N4)
ILAENV
Definition: tstiee.f:83
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:117
subroutine xerbla(SRNAME, INFO)
XERBLA
Definition: xerbla.f:62
subroutine cgeqrf(M, N, A, LDA, TAU, WORK, LWORK, INFO)
CGEQRF
Definition: cgeqrf.f:138
subroutine slascl(TYPE, KL, KU, CFROM, CTO, M, N, A, LDA, INFO)
SLASCL multiplies a general rectangular matrix by a real scalar defined as cto/cfrom.
Definition: slascl.f:145
logical function lsame(CA, CB)
LSAME
Definition: lsame.f:55
real function slamch(CMACH)
SLAMCH
Definition: slamch.f:69
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 slabad(SMALL, LARGE)
SLABAD
Definition: slabad.f:76
subroutine cgghrd(COMPQ, COMPZ, N, ILO, IHI, A, LDA, B, LDB, Q, LDQ, Z, LDZ, INFO)
CGGHRD
Definition: cgghrd.f:206
subroutine cggbak(JOB, SIDE, N, ILO, IHI, LSCALE, RSCALE, M, V, LDV, INFO)
CGGBAK
Definition: cggbak.f:150
subroutine cunmqr(SIDE, TRANS, M, N, K, A, LDA, TAU, C, LDC, WORK, LWORK, INFO)
CUNMQR
Definition: cunmqr.f:170
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