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

1.8       bertrand    1: *> \brief \b DAXPY
                      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 DAXPY(N,DA,DX,INCX,DY,INCY)
1.13      bertrand   12: *
1.8       bertrand   13: *       .. Scalar Arguments ..
                     14: *       DOUBLE PRECISION DA
                     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: *>    DAXPY constant times a vector plus a vector.
                     28: *>    uses unrolled loops for increments equal to one.
                     29: *> \endverbatim
                     30: *
1.14      bertrand   31: *  Arguments:
                     32: *  ==========
                     33: *
                     34: *> \param[in] N
                     35: *> \verbatim
                     36: *>          N is INTEGER
                     37: *>         number of elements in input vector(s)
                     38: *> \endverbatim
                     39: *>
                     40: *> \param[in] DA
                     41: *> \verbatim
                     42: *>          DA is DOUBLE PRECISION
                     43: *>           On entry, DA specifies the scalar alpha.
                     44: *> \endverbatim
                     45: *>
                     46: *> \param[in] DX
                     47: *> \verbatim
                     48: *>          DX is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCX ) )
                     49: *> \endverbatim
                     50: *>
                     51: *> \param[in] INCX
                     52: *> \verbatim
                     53: *>          INCX is INTEGER
                     54: *>         storage spacing between elements of DX
                     55: *> \endverbatim
                     56: *>
                     57: *> \param[in,out] DY
                     58: *> \verbatim
                     59: *>          DY is DOUBLE PRECISION array, dimension ( 1 + ( N - 1 )*abs( INCY ) )
                     60: *> \endverbatim
                     61: *>
                     62: *> \param[in] INCY
                     63: *> \verbatim
                     64: *>          INCY is INTEGER
                     65: *>         storage spacing between elements of DY
                     66: *> \endverbatim
                     67: *
1.8       bertrand   68: *  Authors:
                     69: *  ========
                     70: *
1.13      bertrand   71: *> \author Univ. of Tennessee
                     72: *> \author Univ. of California Berkeley
                     73: *> \author Univ. of Colorado Denver
                     74: *> \author NAG Ltd.
1.8       bertrand   75: *
                     76: *> \ingroup double_blas_level1
                     77: *
                     78: *> \par Further Details:
                     79: *  =====================
                     80: *>
                     81: *> \verbatim
                     82: *>
                     83: *>     jack dongarra, linpack, 3/11/78.
                     84: *>     modified 12/3/93, array(1) declarations changed to array(*)
                     85: *> \endverbatim
                     86: *>
                     87: *  =====================================================================
1.1       bertrand   88:       SUBROUTINE DAXPY(N,DA,DX,INCX,DY,INCY)
1.8       bertrand   89: *
1.16    ! bertrand   90: *  -- Reference BLAS level1 routine --
1.8       bertrand   91: *  -- Reference BLAS is a software package provided by Univ. of Tennessee,    --
                     92: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
                     93: *
1.1       bertrand   94: *     .. Scalar Arguments ..
                     95:       DOUBLE PRECISION DA
                     96:       INTEGER INCX,INCY,N
                     97: *     ..
                     98: *     .. Array Arguments ..
                     99:       DOUBLE PRECISION DX(*),DY(*)
                    100: *     ..
                    101: *
                    102: *  =====================================================================
                    103: *
                    104: *     .. Local Scalars ..
                    105:       INTEGER I,IX,IY,M,MP1
                    106: *     ..
                    107: *     .. Intrinsic Functions ..
                    108:       INTRINSIC MOD
                    109: *     ..
                    110:       IF (N.LE.0) RETURN
                    111:       IF (DA.EQ.0.0d0) 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: *
                    117: *        clean-up loop
                    118: *
                    119:          M = MOD(N,4)
                    120:          IF (M.NE.0) THEN
                    121:             DO I = 1,M
                    122:                DY(I) = DY(I) + DA*DX(I)
                    123:             END DO
                    124:          END IF
                    125:          IF (N.LT.4) RETURN
                    126:          MP1 = M + 1
                    127:          DO I = MP1,N,4
                    128:             DY(I) = DY(I) + DA*DX(I)
                    129:             DY(I+1) = DY(I+1) + DA*DX(I+1)
                    130:             DY(I+2) = DY(I+2) + DA*DX(I+2)
                    131:             DY(I+3) = DY(I+3) + DA*DX(I+3)
                    132:          END DO
                    133:       ELSE
1.1       bertrand  134: *
                    135: *        code for unequal increments or equal increments
                    136: *          not equal to 1
                    137: *
1.7       bertrand  138:          IX = 1
                    139:          IY = 1
                    140:          IF (INCX.LT.0) IX = (-N+1)*INCX + 1
                    141:          IF (INCY.LT.0) IY = (-N+1)*INCY + 1
                    142:          DO I = 1,N
1.1       bertrand  143:           DY(IY) = DY(IY) + DA*DX(IX)
                    144:           IX = IX + INCX
                    145:           IY = IY + INCY
1.7       bertrand  146:          END DO
                    147:       END IF
1.1       bertrand  148:       RETURN
1.16    ! bertrand  149: *
        !           150: *     End of DAXPY
        !           151: *
1.1       bertrand  152:       END