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*> \brief \b ZROTG
*
* =========== DOCUMENTATION ===========
*
* Online html documentation available at
* http://www.netlib.org/lapack/explore-html/
*
* Definition:
* ===========
*
* SUBROUTINE ZROTG(CA,CB,C,S)
*
* .. Scalar Arguments ..
* COMPLEX*16 CA,CB,S
* DOUBLE PRECISION C
* ..
*
*
*> \par Purpose:
* =============
*>
*> \verbatim
*>
*> ZROTG determines a double complex Givens rotation.
*> \endverbatim
*
* Authors:
* ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \date November 2011
*
*> \ingroup complex16_blas_level1
*
* =====================================================================
SUBROUTINE ZROTG(CA,CB,C,S)
*
* -- Reference BLAS level1 routine (version 3.4.0) --
* -- Reference BLAS is a software package provided by Univ. of Tennessee, --
* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
* November 2011
*
* .. Scalar Arguments ..
COMPLEX*16 CA,CB,S
DOUBLE PRECISION C
* ..
*
* =====================================================================
*
* .. Local Scalars ..
COMPLEX*16 ALPHA
DOUBLE PRECISION NORM,SCALE
* ..
* .. Intrinsic Functions ..
INTRINSIC CDABS,DCMPLX,DCONJG,DSQRT
* ..
IF (CDABS(CA).EQ.0.0d0) THEN
C = 0.0d0
S = (1.0d0,0.0d0)
CA = CB
ELSE
SCALE = CDABS(CA) + CDABS(CB)
NORM = SCALE*DSQRT((CDABS(CA/DCMPLX(SCALE,0.0d0)))**2+
$ (CDABS(CB/DCMPLX(SCALE,0.0d0)))**2)
ALPHA = CA/CDABS(CA)
C = CDABS(CA)/NORM
S = ALPHA*DCONJG(CB)/NORM
CA = ALPHA*NORM
END IF
RETURN
END
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