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