text:       SUBROUTINE DAXPY(N,DA,DX,INCX,DY,INCY)
  
  C     CONSTANT TIMES A VECTOR PLUS A VECTOR.
  C     USES UNROLLED LOOPS FOR INCREMENTS EQUAL TO ONE.
  C     JACK DONGARRA, LINPACK, 3/11/78.
  
        DOUBLE PRECISION DX(*),DY(*),DA
        INTEGER I,INCX,INCY,IX,IY,M,MP1,N
  
        IF(N.LE.0)RETURN
        IF(DA.EQ.0.0D0)RETURN
        IF(INCX.EQ.1.AND.INCY.EQ.1)GO TO 20
  
  C        CODE FOR UNEQUAL INCREMENTS OR EQUAL INCREMENTS
  C        NOT EQUAL TO 1
  
        IX = 1
        IY = 1
        IF(INCX.LT.0)IX = (-N+1)*INCX + 1
        IF(INCY.LT.0)IY = (-N+1)*INCY + 1
        DO 10 I = 1,N
          DY(IY) = DY(IY) + DA*DX(IX)
          IX = IX + INCX
          IY = IY + INCY
     10 CONTINUE
        RETURN
  
  C        CODE FOR BOTH INCREMENTS EQUAL TO 1
  
  C        CLEAN-UP LOOP
  
     20 M = MOD(N,4)
        IF( M .EQ. 0 ) GO TO 40
        DO 30 I = 1,M
          DY(I) = DY(I) + DA*DX(I)
     30 CONTINUE
        IF( N .LT. 4 ) RETURN
     40 MP1 = M + 1
        DO 50 I = MP1,N,4
          DY(I) = DY(I) + DA*DX(I)
          DY(I + 1) = DY(I + 1) + DA*DX(I + 1)
          DY(I + 2) = DY(I + 2) + DA*DX(I + 2)
          DY(I + 3) = DY(I + 3) + DA*DX(I + 3)
     50 CONTINUE
        RETURN
        END
        