74 lines
2.0 KiB
FortranFixed
74 lines
2.0 KiB
FortranFixed
LOGICAL FUNCTION ZSLECT( Z )
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*
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* -- LAPACK test routine (version 3.1.1) --
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* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
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* February 2007
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*
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* .. Scalar Arguments ..
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COMPLEX*16 Z
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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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* ZSLECT 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 ZCHK41 to test if ZGEES succesfully sorts eigenvalues,
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* and by ZCHK43 to test if ZGEESX succesfully 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 ZSLECT 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, ZSLECT returns SELVAL(SELOPT) and adds 1
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* to SELOPT, cycling back to 1 at SELMAX.
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*
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* Arguments
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* =========
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*
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* Z (input) COMPLEX*16
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* The eigenvalue Z.
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*
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* =====================================================================
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*
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* .. Parameters ..
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DOUBLE PRECISION ZERO
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PARAMETER ( ZERO = 0.0D0 )
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* ..
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* .. Local Scalars ..
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INTEGER I
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DOUBLE PRECISION 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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DOUBLE PRECISION 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, DBLE, DCMPLX
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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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ZSLECT = ( DBLE( Z ).LT.ZERO )
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ELSE
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RMIN = ABS( Z-DCMPLX( SELWR( 1 ), SELWI( 1 ) ) )
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ZSLECT = SELVAL( 1 )
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DO 10 I = 2, SELDIM
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X = ABS( Z-DCMPLX( SELWR( I ), SELWI( I ) ) )
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IF( X.LE.RMIN ) THEN
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RMIN = X
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ZSLECT = 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 ZSLECT
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*
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END
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