98 lines
1.9 KiB
Fortran
98 lines
1.9 KiB
Fortran
*> \brief \b CROTG
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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 CROTG(CA,CB,C,S)
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*
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* .. Scalar Arguments ..
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* COMPLEX CA,CB,S
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* REAL 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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*> CROTG determines a 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
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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
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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 REAL
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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
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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 complex_blas_level1
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*
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* =====================================================================
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SUBROUTINE CROTG(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 CA,CB,S
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REAL 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 ALPHA
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REAL NORM,SCALE
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC CABS,CONJG,SQRT
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* ..
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IF (CABS(CA).EQ.0.) THEN
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C = 0.
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S = (1.,0.)
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CA = CB
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ELSE
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SCALE = CABS(CA) + CABS(CB)
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NORM = SCALE*SQRT((CABS(CA/SCALE))**2+ (CABS(CB/SCALE))**2)
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ALPHA = CA/CABS(CA)
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C = CABS(CA)/NORM
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S = ALPHA*CONJG(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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