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Annotation of rpl/lapack/blas/drot.f, revision 1.16

1.8       bertrand    1: *> \brief \b DROT
                      2: *
                      3: *  =========== DOCUMENTATION ===========
                      4: *
1.13      bertrand    5: * Online html documentation available at
                      6: *            http://www.netlib.org/lapack/explore-html/
1.8       bertrand    7: *
                      8: *  Definition:
                      9: *  ===========
                     10: *
                     11: *       SUBROUTINE DROT(N,DX,INCX,DY,INCY,C,S)
1.13      bertrand   12: *
1.8       bertrand   13: *       .. Scalar Arguments ..
                     14: *       DOUBLE PRECISION C,S
                     15: *       INTEGER INCX,INCY,N
                     16: *       ..
                     17: *       .. Array Arguments ..
                     18: *       DOUBLE PRECISION DX(*),DY(*)
                     19: *       ..
1.13      bertrand   20: *
1.8       bertrand   21: *
                     22: *> \par Purpose:
                     23: *  =============
                     24: *>
                     25: *> \verbatim
                     26: *>
                     27: *>    DROT applies a plane rotation.
                     28: *> \endverbatim
                     29: *
1.14      bertrand   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: *
1.8       bertrand   71: *  Authors:
                     72: *  ========
                     73: *
1.13      bertrand   74: *> \author Univ. of Tennessee
                     75: *> \author Univ. of California Berkeley
                     76: *> \author Univ. of Colorado Denver
                     77: *> \author NAG Ltd.
1.8       bertrand   78: *
                     79: *> \ingroup double_blas_level1
                     80: *
                     81: *> \par Further Details:
                     82: *  =====================
                     83: *>
                     84: *> \verbatim
                     85: *>
                     86: *>     jack dongarra, linpack, 3/11/78.
                     87: *>     modified 12/3/93, array(1) declarations changed to array(*)
                     88: *> \endverbatim
                     89: *>
                     90: *  =====================================================================
1.1       bertrand   91:       SUBROUTINE DROT(N,DX,INCX,DY,INCY,C,S)
1.8       bertrand   92: *
1.16    ! bertrand   93: *  -- Reference BLAS level1 routine --
1.8       bertrand   94: *  -- Reference BLAS is a software package provided by Univ. of Tennessee,    --
                     95: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
                     96: *
1.1       bertrand   97: *     .. Scalar Arguments ..
                     98:       DOUBLE PRECISION C,S
                     99:       INTEGER INCX,INCY,N
                    100: *     ..
                    101: *     .. Array Arguments ..
                    102:       DOUBLE PRECISION DX(*),DY(*)
                    103: *     ..
                    104: *
                    105: *  =====================================================================
                    106: *
                    107: *     .. Local Scalars ..
                    108:       DOUBLE PRECISION DTEMP
                    109:       INTEGER I,IX,IY
                    110: *     ..
                    111:       IF (N.LE.0) RETURN
1.7       bertrand  112:       IF (INCX.EQ.1 .AND. INCY.EQ.1) THEN
                    113: *
                    114: *       code for both increments equal to 1
                    115: *
                    116:          DO I = 1,N
                    117:             DTEMP = C*DX(I) + S*DY(I)
                    118:             DY(I) = C*DY(I) - S*DX(I)
                    119:             DX(I) = DTEMP
                    120:          END DO
                    121:       ELSE
1.1       bertrand  122: *
                    123: *       code for unequal increments or equal increments not equal
                    124: *         to 1
                    125: *
1.7       bertrand  126:          IX = 1
                    127:          IY = 1
                    128:          IF (INCX.LT.0) IX = (-N+1)*INCX + 1
                    129:          IF (INCY.LT.0) IY = (-N+1)*INCY + 1
                    130:          DO I = 1,N
                    131:             DTEMP = C*DX(IX) + S*DY(IY)
                    132:             DY(IY) = C*DY(IY) - S*DX(IX)
                    133:             DX(IX) = DTEMP
                    134:             IX = IX + INCX
                    135:             IY = IY + INCY
                    136:          END DO
                    137:       END IF
1.1       bertrand  138:       RETURN
1.16    ! bertrand  139: *
        !           140: *     End of DROT
        !           141: *
1.1       bertrand  142:       END