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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, ZX, INCX, ZY, INCY, C, S )
   12: *
   13: *       .. Scalar Arguments ..
   14: *       INTEGER            INCX, INCY, N
   15: *       DOUBLE PRECISION   C, S
   16: *       ..
   17: *       .. Array Arguments ..
   18: *       COMPLEX*16         ZX( * ), ZY( * )
   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] ZX
   43: *> \verbatim
   44: *>          ZX is COMPLEX*16 array, dimension at least
   45: *>           ( 1 + ( N - 1 )*abs( INCX ) ).
   46: *>           Before entry, the incremented array ZX must contain the n
   47: *>           element vector cx. On exit, ZX 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: *>           ZX. INCX must not be zero.
   56: *> \endverbatim
   57: *>
   58: *> \param[in,out] ZY
   59: *> \verbatim
   60: *>          ZY is COMPLEX*16 array, dimension at least
   61: *>           ( 1 + ( N - 1 )*abs( INCY ) ).
   62: *>           Before entry, the incremented array ZY must contain the n
   63: *>           element vector cy. On exit, ZY 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: *>           ZY. 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: *> \ingroup complex16_blas_level1
   95: *
   96: *  =====================================================================
   97:       SUBROUTINE ZDROT( N, ZX, INCX, ZY, INCY, C, S )
   98: *
   99: *  -- Reference BLAS level1 routine --
  100: *  -- Reference BLAS is a software package provided by Univ. of Tennessee,    --
  101: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
  102: *
  103: *     .. Scalar Arguments ..
  104:       INTEGER            INCX, INCY, N
  105:       DOUBLE PRECISION   C, S
  106: *     ..
  107: *     .. Array Arguments ..
  108:       COMPLEX*16         ZX( * ), ZY( * )
  109: *     ..
  110: *
  111: * =====================================================================
  112: *
  113: *     .. Local Scalars ..
  114:       INTEGER            I, IX, IY
  115:       COMPLEX*16         CTEMP
  116: *     ..
  117: *     .. Executable Statements ..
  118: *
  119:       IF( N.LE.0 )
  120:      $   RETURN
  121:       IF( INCX.EQ.1 .AND. INCY.EQ.1 ) THEN
  122: *
  123: *        code for both increments equal to 1
  124: *
  125:          DO I = 1, N
  126:             CTEMP = C*ZX( I ) + S*ZY( I )
  127:             ZY( I ) = C*ZY( I ) - S*ZX( I )
  128:             ZX( I ) = CTEMP
  129:          END DO
  130:       ELSE
  131: *
  132: *        code for unequal increments or equal increments not equal
  133: *          to 1
  134: *
  135:          IX = 1
  136:          IY = 1
  137:          IF( INCX.LT.0 )
  138:      $      IX = ( -N+1 )*INCX + 1
  139:          IF( INCY.LT.0 )
  140:      $      IY = ( -N+1 )*INCY + 1
  141:          DO I = 1, N
  142:             CTEMP = C*ZX( IX ) + S*ZY( IY )
  143:             ZY( IY ) = C*ZY( IY ) - S*ZX( IX )
  144:             ZX( IX ) = CTEMP
  145:             IX = IX + INCX
  146:             IY = IY + INCY
  147:          END DO
  148:       END IF
  149:       RETURN
  150: *
  151: *     End of ZDROT
  152: *
  153:       END