zrotg()

subroutine zrotg	(	complex*16	CA,
		complex*16	CB,
		double precision	C,
		complex*16	S
	)

ZROTG

Purpose:

    ZROTG determines a double complex Givens rotation.

Parameters

[in,out]	CA	CA is COMPLEX*16
[in]	CB	CB is COMPLEX*16
[out]	C	C is DOUBLE PRECISION
[out]	S	S is COMPLEX*16

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line 61 of file zrotg.f.

*
*  -- Reference BLAS level1 routine --
*  -- Reference BLAS is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
*     .. 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

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