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    1: *> \brief \b DROT
    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 DROT(N,DX,INCX,DY,INCY,C,S)
   12: *
   13: *       .. Scalar Arguments ..
   14: *       DOUBLE PRECISION C,S
   15: *       INTEGER INCX,INCY,N
   16: *       ..
   17: *       .. Array Arguments ..
   18: *       DOUBLE PRECISION DX(*),DY(*)
   19: *       ..
   20: *
   21: *
   22: *> \par Purpose:
   23: *  =============
   24: *>
   25: *> \verbatim
   26: *>
   27: *>    DROT applies a plane rotation.
   28: *> \endverbatim
   29: *
   30: *  Arguments:
   31: *  ==========
   32: *
   33: *> \param[in] N
   34: *> \verbatim
   35: *>          N is INTEGER
   36: *>         number of elements in input vector(s)
   37: *> \endverbatim
   38: *>
   39: *> \param[in,out] DX
   40: *> \verbatim
   41: *>          DX is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
   42: *> \endverbatim
   43: *>
   44: *> \param[in] INCX
   45: *> \verbatim
   46: *>          INCX is INTEGER
   47: *>         storage spacing between elements of DX
   48: *> \endverbatim
   49: *>
   50: *> \param[in,out] DY
   51: *> \verbatim
   52: *>          DY is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCY ) )
   53: *> \endverbatim
   54: *>
   55: *> \param[in] INCY
   56: *> \verbatim
   57: *>          INCY is INTEGER
   58: *>         storage spacing between elements of DY
   59: *> \endverbatim
   60: *>
   61: *> \param[in] C
   62: *> \verbatim
   63: *>          C is DOUBLE PRECISION
   64: *> \endverbatim
   65: *>
   66: *> \param[in] S
   67: *> \verbatim
   68: *>          S is DOUBLE PRECISION
   69: *> \endverbatim
   70: *
   71: *  Authors:
   72: *  ========
   73: *
   74: *> \author Univ. of Tennessee
   75: *> \author Univ. of California Berkeley
   76: *> \author Univ. of Colorado Denver
   77: *> \author NAG Ltd.
   78: *
   79: *> \date November 2017
   80: *
   81: *> \ingroup double_blas_level1
   82: *
   83: *> \par Further Details:
   84: *  =====================
   85: *>
   86: *> \verbatim
   87: *>
   88: *>     jack dongarra, linpack, 3/11/78.
   89: *>     modified 12/3/93, array(1) declarations changed to array(*)
   90: *> \endverbatim
   91: *>
   92: *  =====================================================================
   93:       SUBROUTINE DROT(N,DX,INCX,DY,INCY,C,S)
   94: *
   95: *  -- Reference BLAS level1 routine (version 3.8.0) --
   96: *  -- Reference BLAS is a software package provided by Univ. of Tennessee,    --
   97: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
   98: *     November 2017
   99: *
  100: *     .. Scalar Arguments ..
  101:       DOUBLE PRECISION C,S
  102:       INTEGER INCX,INCY,N
  103: *     ..
  104: *     .. Array Arguments ..
  105:       DOUBLE PRECISION DX(*),DY(*)
  106: *     ..
  107: *
  108: *  =====================================================================
  109: *
  110: *     .. Local Scalars ..
  111:       DOUBLE PRECISION DTEMP
  112:       INTEGER I,IX,IY
  113: *     ..
  114:       IF (N.LE.0) RETURN
  115:       IF (INCX.EQ.1 .AND. INCY.EQ.1) THEN
  116: *
  117: *       code for both increments equal to 1
  118: *
  119:          DO I = 1,N
  120:             DTEMP = C*DX(I) + S*DY(I)
  121:             DY(I) = C*DY(I) - S*DX(I)
  122:             DX(I) = DTEMP
  123:          END DO
  124:       ELSE
  125: *
  126: *       code for unequal increments or equal increments not equal
  127: *         to 1
  128: *
  129:          IX = 1
  130:          IY = 1
  131:          IF (INCX.LT.0) IX = (-N+1)*INCX + 1
  132:          IF (INCY.LT.0) IY = (-N+1)*INCY + 1
  133:          DO I = 1,N
  134:             DTEMP = C*DX(IX) + S*DY(IY)
  135:             DY(IY) = C*DY(IY) - S*DX(IX)
  136:             DX(IX) = DTEMP
  137:             IX = IX + INCX
  138:             IY = IY + INCY
  139:          END DO
  140:       END IF
  141:       RETURN
  142:       END