59 lines
1.5 KiB
FortranFixed
59 lines
1.5 KiB
FortranFixed
LOGICAL FUNCTION DLCTES( ZR, ZI, D )
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*
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* -- LAPACK test routine (version 3.1) --
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* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
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* November 2006
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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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* Purpose
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* =======
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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 succesfully sorts eigenvalues.
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*
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* Arguments
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* =========
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*
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* ZR (input) 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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*
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* ZI (input) 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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*
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* D (input) 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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*
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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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