154 lines
3.8 KiB
Fortran
154 lines
3.8 KiB
Fortran
*> \brief \b CSROT
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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 CSROT( N, CX, INCX, CY, INCY, C, S )
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*
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* .. Scalar Arguments ..
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* INTEGER INCX, INCY, N
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* REAL C, S
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* ..
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* .. Array Arguments ..
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* COMPLEX CX( * ), CY( * )
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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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*> CSROT applies a plane rotation, where the cos and sin (c and s) are real
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*> and the vectors cx and cy are complex.
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*> jack dongarra, linpack, 3/11/78.
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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] N
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*> \verbatim
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*> N is INTEGER
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*> On entry, N specifies the order of the vectors cx and cy.
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*> N must be at least zero.
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*> \endverbatim
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*>
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*> \param[in,out] CX
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*> \verbatim
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*> CX is COMPLEX array, dimension at least
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*> ( 1 + ( N - 1 )*abs( INCX ) ).
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*> Before entry, the incremented array CX must contain the n
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*> element vector cx. On exit, CX is overwritten by the updated
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*> vector cx.
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*> \endverbatim
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*>
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*> \param[in] INCX
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*> \verbatim
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*> INCX is INTEGER
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*> On entry, INCX specifies the increment for the elements of
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*> CX. INCX must not be zero.
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*> \endverbatim
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*>
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*> \param[in,out] CY
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*> \verbatim
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*> CY is COMPLEX array, dimension at least
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*> ( 1 + ( N - 1 )*abs( INCY ) ).
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*> Before entry, the incremented array CY must contain the n
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*> element vector cy. On exit, CY is overwritten by the updated
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*> vector cy.
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*> \endverbatim
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*>
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*> \param[in] INCY
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*> \verbatim
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*> INCY is INTEGER
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*> On entry, INCY specifies the increment for the elements of
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*> CY. INCY must not be zero.
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*> \endverbatim
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*>
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*> \param[in] C
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*> \verbatim
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*> C is REAL
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*> On entry, C specifies the cosine, cos.
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*> \endverbatim
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*>
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*> \param[in] S
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*> \verbatim
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*> S is REAL
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*> On entry, S specifies the sine, sin.
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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 December 2016
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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 CSROT( N, CX, INCX, CY, INCY, C, S )
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*
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* -- Reference BLAS level1 routine (version 3.7.0) --
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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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* December 2016
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*
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* .. Scalar Arguments ..
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INTEGER INCX, INCY, N
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REAL C, S
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* ..
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* .. Array Arguments ..
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COMPLEX CX( * ), CY( * )
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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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INTEGER I, IX, IY
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COMPLEX CTEMP
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* ..
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* .. Executable Statements ..
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*
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IF( N.LE.0 )
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$ RETURN
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IF( INCX.EQ.1 .AND. INCY.EQ.1 ) THEN
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*
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* code for both increments equal to 1
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*
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DO I = 1, N
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CTEMP = C*CX( I ) + S*CY( I )
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CY( I ) = C*CY( I ) - S*CX( I )
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CX( I ) = CTEMP
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END DO
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ELSE
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*
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* code for unequal increments or equal increments not equal
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* to 1
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*
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IX = 1
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IY = 1
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IF( INCX.LT.0 )
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$ IX = ( -N+1 )*INCX + 1
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IF( INCY.LT.0 )
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$ IY = ( -N+1 )*INCY + 1
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DO I = 1, N
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CTEMP = C*CX( IX ) + S*CY( IY )
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CY( IY ) = C*CY( IY ) - S*CX( IX )
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CX( IX ) = CTEMP
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IX = IX + INCX
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IY = IY + INCY
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END DO
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END IF
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RETURN
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END
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