crotg()

subroutine crotg	(	complex	CA,
		complex	CB,
		real	C,
		complex	S
	)

CROTG

Purpose:

 CROTG determines a complex Givens rotation.

Parameters

[in]	CA	CA is COMPLEX
[in]	CB	CB is COMPLEX
[out]	C	C is REAL
[out]	S	S is COMPLEX

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date

November 2017

Definition at line 64 of file crotg.f.

*
*  -- Reference BLAS level1 routine (version 3.8.0) --
*  -- Reference BLAS is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*     November 2017
*
*     .. Scalar Arguments ..
      COMPLEX CA,CB,S
      REAL C
*     ..
*
*  =====================================================================
*
*     .. Local Scalars ..
      COMPLEX ALPHA
      REAL NORM,SCALE
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC cabs,conjg,sqrt
*     ..
      IF (cabs(ca).EQ.0.) THEN
         c = 0.
         s = (1.,0.)
         ca = cb
      ELSE
         scale = cabs(ca) + cabs(cb)
         norm = scale*sqrt((cabs(ca/scale))**2+ (cabs(cb/scale))**2)
         alpha = ca/cabs(ca)
         c = cabs(ca)/norm
         s = alpha*conjg(cb)/norm
         ca = alpha*norm
      END IF
      RETURN

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