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LOGICAL FUNCTION DSLECT( ZR, ZI )
*
* -- LAPACK test routine (version 3.0) --
* Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,
* Courant Institute, Argonne National Lab, and Rice University
* February 29, 1992
*
* .. Scalar Arguments ..
DOUBLE PRECISION ZI, ZR
* ..
*
* Purpose
* =======
*
* DSLECT returns .TRUE. if the eigenvalue ZR+sqrt(-1)*ZI is to be
* selected, and otherwise it returns .FALSE.
* It is used by DCHK41 to test if DGEES succesfully sorts eigenvalues,
* and by DCHK43 to test if DGEESX succesfully sorts eigenvalues.
*
* The common block /SSLCT/ controls how eigenvalues are selected.
* If SELOPT = 0, then DSLECT return .TRUE. when ZR is less than zero,
* and .FALSE. otherwise.
* If SELOPT is at least 1, DSLECT returns SELVAL(SELOPT) and adds 1
* to SELOPT, cycling back to 1 at SELMAX.
*
* Arguments
* =========
*
* ZR (input) DOUBLE PRECISION
* The real part of a complex eigenvalue ZR + i*ZI.
*
* ZI (input) DOUBLE PRECISION
* The imaginary part of a complex eigenvalue ZR + i*ZI.
*
* =====================================================================
*
* .. Arrays in Common ..
LOGICAL SELVAL( 20 )
DOUBLE PRECISION SELWI( 20 ), SELWR( 20 )
* ..
* .. Scalars in Common ..
INTEGER SELDIM, SELOPT
* ..
* .. Common blocks ..
COMMON / SSLCT / SELOPT, SELDIM, SELVAL, SELWR, SELWI
* ..
* .. Local Scalars ..
INTEGER I
DOUBLE PRECISION RMIN, X
* ..
* .. Parameters ..
DOUBLE PRECISION ZERO
PARAMETER ( ZERO = 0.0D0 )
* ..
* .. External Functions ..
DOUBLE PRECISION DLAPY2
EXTERNAL DLAPY2
* ..
* .. Executable Statements ..
*
IF( SELOPT.EQ.0 ) THEN
DSLECT = ( ZR.LT.ZERO )
ELSE
RMIN = ZERO
DO 10 I = 1, SELDIM
X = DLAPY2( ZR-SELWR( I ), ZI-SELWI( I ) )
IF( X.LE.RMIN ) THEN
RMIN = X
DSLECT = SELVAL( I )
END IF
10 CONTINUE
END IF
RETURN
*
* End of DSLECT
*
END
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