99 lines
2.1 KiB
Fortran
99 lines
2.1 KiB
Fortran
*> \brief \b ZROTG
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*
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* =========== DOCUMENTATION ===========
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*
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* Online html documentation available at
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* http://www.netlib.org/lapack/explore-html/
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*
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* Definition:
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* ===========
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*
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* SUBROUTINE ZROTG(CA,CB,C,S)
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*
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* .. Scalar Arguments ..
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* COMPLEX*16 CA,CB,S
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* DOUBLE PRECISION C
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* ..
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*
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*
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*> \par Purpose:
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* =============
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*>
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*> \verbatim
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*>
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*> ZROTG determines a double complex Givens rotation.
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*> \endverbatim
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*
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* Arguments:
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* ==========
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*
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*> \param[in] CA
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*> \verbatim
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*> CA is COMPLEX*16
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*> \endverbatim
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*>
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*> \param[in] CB
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*> \verbatim
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*> CB is COMPLEX*16
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*> \endverbatim
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*>
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*> \param[out] C
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*> \verbatim
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*> C is DOUBLE PRECISION
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*> \endverbatim
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*>
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*> \param[out] S
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*> \verbatim
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*> S is COMPLEX*16
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*> \endverbatim
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*
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* Authors:
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* ========
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*
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*> \author Univ. of Tennessee
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*> \author Univ. of California Berkeley
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*> \author Univ. of Colorado Denver
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*> \author NAG Ltd.
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*
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*> \date November 2017
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*
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*> \ingroup complex16_blas_level1
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*
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* =====================================================================
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SUBROUTINE ZROTG(CA,CB,C,S)
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*
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* -- Reference BLAS level1 routine (version 3.8.0) --
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* -- Reference BLAS is a software package provided by Univ. of Tennessee, --
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* -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
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* November 2017
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*
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* .. Scalar Arguments ..
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COMPLEX*16 CA,CB,S
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DOUBLE PRECISION C
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* ..
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*
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* =====================================================================
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*
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* .. Local Scalars ..
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COMPLEX*16 ALPHA
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DOUBLE PRECISION NORM,SCALE
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC CDABS,DCMPLX,DCONJG,DSQRT
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* ..
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IF (CDABS(CA).EQ.0.0d0) THEN
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C = 0.0d0
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S = (1.0d0,0.0d0)
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CA = CB
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ELSE
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SCALE = CDABS(CA) + CDABS(CB)
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NORM = SCALE*DSQRT((CDABS(CA/DCMPLX(SCALE,0.0d0)))**2+
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$ (CDABS(CB/DCMPLX(SCALE,0.0d0)))**2)
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ALPHA = CA/CDABS(CA)
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C = CDABS(CA)/NORM
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S = ALPHA*DCONJG(CB)/NORM
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CA = ALPHA*NORM
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END IF
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RETURN
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END
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