160 lines
4.0 KiB
Fortran
160 lines
4.0 KiB
Fortran
*> \brief \b CROT applies a plane rotation with real cosine and complex sine to a pair of complex vectors.
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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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*> \htmlonly
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*> Download CROT + dependencies
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/crot.f">
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*> [TGZ]</a>
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/crot.f">
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*> [ZIP]</a>
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/crot.f">
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*> [TXT]</a>
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*> \endhtmlonly
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*
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* Definition:
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* ===========
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*
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* SUBROUTINE CROT( 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
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* COMPLEX 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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*> CROT applies a plane rotation, where the cos (C) is real and the
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*> sin (S) is complex, and the vectors CX and CY are complex.
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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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*> The number of elements in the vectors CX and CY.
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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 (N)
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*> On input, the vector X.
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*> On output, CX is overwritten with C*X + S*Y.
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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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*> The increment between successive values of CX. INCX <> 0.
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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 (N)
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*> On input, the vector Y.
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*> On output, CY is overwritten with -CONJG(S)*X + C*Y.
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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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*> The increment between successive values of CY. INCX <> 0.
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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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*> \endverbatim
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*>
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*> \param[in] S
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*> \verbatim
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*> S is COMPLEX
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*> C and S define a rotation
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*> [ C S ]
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*> [ -conjg(S) C ]
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*> where C*C + S*CONJG(S) = 1.0.
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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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*> \ingroup complexOTHERauxiliary
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*
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* =====================================================================
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SUBROUTINE CROT( N, CX, INCX, CY, INCY, C, S )
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*
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* -- LAPACK auxiliary routine --
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* -- LAPACK 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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*
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* .. Scalar Arguments ..
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INTEGER INCX, INCY, N
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REAL C
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COMPLEX 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 STEMP
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* ..
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* .. Intrinsic Functions ..
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INTRINSIC CONJG
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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 )
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$ GO TO 20
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*
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* Code for unequal increments or equal increments not equal 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 10 I = 1, N
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STEMP = C*CX( IX ) + S*CY( IY )
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CY( IY ) = C*CY( IY ) - CONJG( S )*CX( IX )
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CX( IX ) = STEMP
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IX = IX + INCX
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IY = IY + INCY
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10 CONTINUE
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RETURN
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*
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* Code for both increments equal to 1
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*
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20 CONTINUE
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DO 30 I = 1, N
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STEMP = C*CX( I ) + S*CY( I )
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CY( I ) = C*CY( I ) - CONJG( S )*CX( I )
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CX( I ) = STEMP
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30 CONTINUE
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RETURN
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END
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