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    1: *> \brief \b ZDROT
    2: *
    3: *  =========== DOCUMENTATION ===========
    4: *
    5: * Online html documentation available at 
    6: *            http://www.netlib.org/lapack/explore-html/ 
    7: *
    8: *  Definition:
    9: *  ===========
   10: *
   11: *       SUBROUTINE ZDROT( N, CX, INCX, CY, INCY, C, S )
   12: * 
   13: *       .. Scalar Arguments ..
   14: *       INTEGER            INCX, INCY, N
   15: *       DOUBLE PRECISION   C, S
   16: *       ..
   17: *       .. Array Arguments ..
   18: *       COMPLEX*16         CX( * ), CY( * )
   19: *       ..
   20: *  
   21: *
   22: *> \par Purpose:
   23: *  =============
   24: *>
   25: *> \verbatim
   26: *>
   27: *> Applies a plane rotation, where the cos and sin (c and s) are real
   28: *> and the vectors cx and cy are complex.
   29: *> jack dongarra, linpack, 3/11/78.
   30: *> \endverbatim
   31: *
   32: *  Arguments:
   33: *  ==========
   34: *
   35: *> \param[in] N
   36: *> \verbatim
   37: *>          N is INTEGER
   38: *>           On entry, N specifies the order of the vectors cx and cy.
   39: *>           N must be at least zero.
   40: *> \endverbatim
   41: *>
   42: *> \param[in,out] CX
   43: *> \verbatim
   44: *>          CX is COMPLEX*16 array, dimension at least
   45: *>           ( 1 + ( N - 1 )*abs( INCX ) ).
   46: *>           Before entry, the incremented array CX must contain the n
   47: *>           element vector cx. On exit, CX is overwritten by the updated
   48: *>           vector cx.
   49: *> \endverbatim
   50: *>
   51: *> \param[in] INCX
   52: *> \verbatim
   53: *>          INCX is INTEGER
   54: *>           On entry, INCX specifies the increment for the elements of
   55: *>           CX. INCX must not be zero.
   56: *> \endverbatim
   57: *>
   58: *> \param[in,out] CY
   59: *> \verbatim
   60: *>          CY is COMPLEX*16 array, dimension at least
   61: *>           ( 1 + ( N - 1 )*abs( INCY ) ).
   62: *>           Before entry, the incremented array CY must contain the n
   63: *>           element vector cy. On exit, CY is overwritten by the updated
   64: *>           vector cy.
   65: *> \endverbatim
   66: *>
   67: *> \param[in] INCY
   68: *> \verbatim
   69: *>          INCY is INTEGER
   70: *>           On entry, INCY specifies the increment for the elements of
   71: *>           CY. INCY must not be zero.
   72: *> \endverbatim
   73: *>
   74: *> \param[in] C
   75: *> \verbatim
   76: *>          C is DOUBLE PRECISION
   77: *>           On entry, C specifies the cosine, cos.
   78: *> \endverbatim
   79: *>
   80: *> \param[in] S
   81: *> \verbatim
   82: *>          S is DOUBLE PRECISION
   83: *>           On entry, S specifies the sine, sin.
   84: *> \endverbatim
   85: *
   86: *  Authors:
   87: *  ========
   88: *
   89: *> \author Univ. of Tennessee 
   90: *> \author Univ. of California Berkeley 
   91: *> \author Univ. of Colorado Denver 
   92: *> \author NAG Ltd. 
   93: *
   94: *> \date November 2011
   95: *
   96: *> \ingroup complex16_blas_level1
   97: *
   98: *  =====================================================================
   99:       SUBROUTINE ZDROT( N, CX, INCX, CY, INCY, C, S )
  100: *
  101: *  -- Reference BLAS level1 routine (version 3.4.0) --
  102: *  -- Reference BLAS is a software package provided by Univ. of Tennessee,    --
  103: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
  104: *     November 2011
  105: *
  106: *     .. Scalar Arguments ..
  107:       INTEGER            INCX, INCY, N
  108:       DOUBLE PRECISION   C, S
  109: *     ..
  110: *     .. Array Arguments ..
  111:       COMPLEX*16         CX( * ), CY( * )
  112: *     ..
  113: *
  114: * =====================================================================
  115: *
  116: *     .. Local Scalars ..
  117:       INTEGER            I, IX, IY
  118:       COMPLEX*16         CTEMP
  119: *     ..
  120: *     .. Executable Statements ..
  121: *
  122:       IF( N.LE.0 )
  123:      $   RETURN
  124:       IF( INCX.EQ.1 .AND. INCY.EQ.1 ) THEN
  125: *
  126: *        code for both increments equal to 1
  127: *
  128:          DO I = 1, N
  129:             CTEMP = C*CX( I ) + S*CY( I )
  130:             CY( I ) = C*CY( I ) - S*CX( I )
  131:             CX( I ) = CTEMP
  132:          END DO
  133:       ELSE
  134: *
  135: *        code for unequal increments or equal increments not equal
  136: *          to 1
  137: *
  138:          IX = 1
  139:          IY = 1
  140:          IF( INCX.LT.0 )
  141:      $      IX = ( -N+1 )*INCX + 1
  142:          IF( INCY.LT.0 )
  143:      $      IY = ( -N+1 )*INCY + 1
  144:          DO I = 1, N
  145:             CTEMP = C*CX( IX ) + S*CY( IY )
  146:             CY( IY ) = C*CY( IY ) - S*CX( IX )
  147:             CX( IX ) = CTEMP
  148:             IX = IX + INCX
  149:             IY = IY + INCY
  150:          END DO
  151:       END IF
  152:       RETURN
  153:       END