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LOGICAL FUNCTION DLCTES( ZR, ZI, D )
* * -- LAPACK test routine (version 3.1) -- * Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. * November 2006 * * .. Scalar Arguments .. DOUBLE PRECISION D, ZI, ZR * .. * * Purpose * ======= * * DLCTES returns .TRUE. if the eigenvalue (ZR/D) + sqrt(-1)*(ZI/D) * is to be selected (specifically, in this subroutine, if the real * part of the eigenvalue is negative), and otherwise it returns * .FALSE.. * * It is used by the test routine DDRGES to test whether the driver * routine DGGES succesfully sorts eigenvalues. * * Arguments * ========= * * ZR (input) DOUBLE PRECISION * The numerator of the real part of a complex eigenvalue * (ZR/D) + i*(ZI/D). * * ZI (input) DOUBLE PRECISION * The numerator of the imaginary part of a complex eigenvalue * (ZR/D) + i*(ZI). * * D (input) DOUBLE PRECISION * The denominator part of a complex eigenvalue * (ZR/D) + i*(ZI/D). * * ===================================================================== * * .. Parameters .. DOUBLE PRECISION ZERO, ONE PARAMETER ( ZERO = 0.0D+0, ONE = 1.0D+0 ) * .. * .. Intrinsic Functions .. INTRINSIC SIGN * .. * .. Executable Statements .. * IF( D.EQ.ZERO ) THEN DLCTES = ( ZR.LT.ZERO ) ELSE DLCTES = ( SIGN( ONE, ZR ).NE.SIGN( ONE, D ) ) END IF * RETURN * * End of DLCTES * END |