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    1:       SUBROUTINE DAXPY(N,DA,DX,INCX,DY,INCY)
    2: *     .. Scalar Arguments ..
    3:       DOUBLE PRECISION DA
    4:       INTEGER INCX,INCY,N
    5: *     ..
    6: *     .. Array Arguments ..
    7:       DOUBLE PRECISION DX(*),DY(*)
    8: *     ..
    9: *
   10: *  Purpose
   11: *  =======
   12: *
   13: *     DAXPY constant times a vector plus a vector.
   14: *     uses unrolled loops for increments equal to one.
   15: *
   16: *  Further Details
   17: *  ===============
   18: *
   19: *     jack dongarra, linpack, 3/11/78.
   20: *     modified 12/3/93, array(1) declarations changed to array(*)
   21: *
   22: *  =====================================================================
   23: *
   24: *     .. Local Scalars ..
   25:       INTEGER I,IX,IY,M,MP1
   26: *     ..
   27: *     .. Intrinsic Functions ..
   28:       INTRINSIC MOD
   29: *     ..
   30:       IF (N.LE.0) RETURN
   31:       IF (DA.EQ.0.0d0) RETURN
   32:       IF (INCX.EQ.1 .AND. INCY.EQ.1) GO TO 20
   33: *
   34: *        code for unequal increments or equal increments
   35: *          not equal to 1
   36: *
   37:       IX = 1
   38:       IY = 1
   39:       IF (INCX.LT.0) IX = (-N+1)*INCX + 1
   40:       IF (INCY.LT.0) IY = (-N+1)*INCY + 1
   41:       DO 10 I = 1,N
   42:           DY(IY) = DY(IY) + DA*DX(IX)
   43:           IX = IX + INCX
   44:           IY = IY + INCY
   45:    10 CONTINUE
   46:       RETURN
   47: *
   48: *        code for both increments equal to 1
   49: *
   50: *
   51: *        clean-up loop
   52: *
   53:    20 M = MOD(N,4)
   54:       IF (M.EQ.0) GO TO 40
   55:       DO 30 I = 1,M
   56:           DY(I) = DY(I) + DA*DX(I)
   57:    30 CONTINUE
   58:       IF (N.LT.4) RETURN
   59:    40 MP1 = M + 1
   60:       DO 50 I = MP1,N,4
   61:           DY(I) = DY(I) + DA*DX(I)
   62:           DY(I+1) = DY(I+1) + DA*DX(I+1)
   63:           DY(I+2) = DY(I+2) + DA*DX(I+2)
   64:           DY(I+3) = DY(I+3) + DA*DX(I+3)
   65:    50 CONTINUE
   66:       RETURN
   67:       END