numeric-linalg

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*> \brief \b CSLECT
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at
*            http://www.netlib.org/lapack/explore-html/
*
*  Definition:
*  ===========
*
*       LOGICAL          FUNCTION CSLECT( Z )
*
*       .. Scalar Arguments ..
*       COMPLEX            Z
*       ..
*
*
*> \par Purpose:
*  =============
*>
*> \verbatim
*>
*> CSLECT returns .TRUE. if the eigenvalue Z is to be selected,
*> otherwise it returns .FALSE.
*> It is used by CCHK41 to test if CGEES successfully sorts eigenvalues,
*> and by CCHK43 to test if CGEESX successfully sorts eigenvalues.
*>
*> The common block /SSLCT/ controls how eigenvalues are selected.
*> If SELOPT = 0, then CSLECT return .TRUE. when real(Z) is less than
*> zero, and .FALSE. otherwise.
*> If SELOPT is at least 1, CSLECT returns SELVAL(SELOPT) and adds 1
*> to SELOPT, cycling back to 1 at SELMAX.
*> \endverbatim
*
*  Arguments:
*  ==========
*
*> \param[in] Z
*> \verbatim
*>          Z is COMPLEX
*>          The eigenvalue Z.
*> \endverbatim
*
*  Authors:
*  ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \ingroup complex_eig
*
*  =====================================================================
      LOGICAL          FUNCTION CSLECT( Z )
*
*  -- LAPACK test routine --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
*     .. Scalar Arguments ..
      COMPLEX            Z
*     ..
*
*  =====================================================================
*
*     .. Parameters ..
      REAL               ZERO
      PARAMETER          ( ZERO = 0.0E0 )
*     ..
*     .. Local Scalars ..
      INTEGER            I
      REAL               RMIN, X
*     ..
*     .. Scalars in Common ..
      INTEGER            SELDIM, SELOPT
*     ..
*     .. Arrays in Common ..
      LOGICAL            SELVAL( 20 )
      REAL               SELWI( 20 ), SELWR( 20 )
*     ..
*     .. Common blocks ..
      COMMON             / SSLCT / SELOPT, SELDIM, SELVAL, SELWR, SELWI
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC          ABS, CMPLX, REAL
*     ..
*     .. Executable Statements ..
*
      IF( SELOPT.EQ.0 ) THEN
         CSLECT = ( REAL( Z ).LT.ZERO )
      ELSE
         RMIN = ABS( Z-CMPLX( SELWR( 1 ), SELWI( 1 ) ) )
         CSLECT = SELVAL( 1 )
         DO 10 I = 2, SELDIM
            X = ABS( Z-CMPLX( SELWR( I ), SELWI( I ) ) )
            IF( X.LE.RMIN ) THEN
               RMIN = X
               CSLECT = SELVAL( I )
            END IF
   10    CONTINUE
      END IF
      RETURN
*
*     End of CSLECT
*
      END