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99 lines
2.3 KiB
99 lines
2.3 KiB
2 years ago
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*> \brief \b DLCTES
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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 DLCTES( ZR, ZI, D )
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*
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* .. Scalar Arguments ..
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* DOUBLE PRECISION D, ZI, ZR
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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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*> DLCTES returns .TRUE. if the eigenvalue (ZR/D) + sqrt(-1)*(ZI/D)
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*> is to be selected (specifically, in this subroutine, if the real
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*> part of the eigenvalue is negative), and otherwise it returns
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*> .FALSE..
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*>
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*> It is used by the test routine DDRGES to test whether the driver
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*> routine DGGES successfully sorts eigenvalues.
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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] ZR
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*> \verbatim
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*> ZR is DOUBLE PRECISION
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*> The numerator of the real part of a complex eigenvalue
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*> (ZR/D) + i*(ZI/D).
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*> \endverbatim
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*>
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*> \param[in] ZI
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*> \verbatim
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*> ZI is DOUBLE PRECISION
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*> The numerator of the imaginary part of a complex eigenvalue
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*> (ZR/D) + i*(ZI).
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*> \endverbatim
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*>
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*> \param[in] D
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*> \verbatim
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*> D is DOUBLE PRECISION
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*> The denominator part of a complex eigenvalue
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*> (ZR/D) + i*(ZI/D).
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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 double_eig
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*
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* =====================================================================
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LOGICAL FUNCTION DLCTES( ZR, ZI, D )
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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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DOUBLE PRECISION D, ZI, ZR
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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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DOUBLE PRECISION ZERO, ONE
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PARAMETER ( ZERO = 0.0D+0, ONE = 1.0D+0 )
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC SIGN
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* ..
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* .. Executable Statements ..
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*
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IF( D.EQ.ZERO ) THEN
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DLCTES = ( ZR.LT.ZERO )
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ELSE
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DLCTES = ( SIGN( ONE, ZR ).NE.SIGN( ONE, D ) )
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END IF
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*
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RETURN
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*
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* End of DLCTES
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*
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END
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