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158 lines
3.8 KiB
158 lines
3.8 KiB
2 years ago
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*> \brief \b ZLACRT performs a linear transformation of 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 ZLACRT + dependencies
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*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/zlacrt.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/zlacrt.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/zlacrt.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 ZLACRT( 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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* COMPLEX*16 C, S
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* ..
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* .. Array Arguments ..
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* COMPLEX*16 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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*> ZLACRT performs the operation
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*>
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*> ( c s )( x ) ==> ( x )
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*> ( -s c )( y ) ( y )
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*>
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*> where c and s are complex and the vectors x and y 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*16 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*16 array, dimension (N)
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*> On input, the vector y.
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*> On output, CY is overwritten with -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. INCY <> 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 COMPLEX*16
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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*16
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*> C and S define the matrix
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*> [ C S ].
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*> [ -S C ]
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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 complex16OTHERauxiliary
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*
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* =====================================================================
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SUBROUTINE ZLACRT( 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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COMPLEX*16 C, S
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* ..
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* .. Array Arguments ..
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COMPLEX*16 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*16 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 )
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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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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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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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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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30 CONTINUE
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RETURN
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END
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