lapack-3.3.1/BLAS/SRC/sdot.f

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      REAL FUNCTION SDOT(N,SX,INCX,SY,INCY)
*     .. Scalar Arguments ..
      INTEGER INCX,INCY,N
*     ..
*     .. Array Arguments ..
      REAL SX(*),SY(*)
*     ..
*
*  Purpose
*  =======
*
*     SDOT forms the dot product of two vectors.
*     uses unrolled loops for increments equal to one.
*
*  Further Details
*  ===============
*
*     jack dongarra, linpack, 3/11/78.
*     modified 12/3/93, array(1) declarations changed to array(*)
*
*  =====================================================================
*
*     .. Local Scalars ..
      REAL STEMP
      INTEGER I,IX,IY,M,MP1
*     ..
*     .. Intrinsic Functions ..
      INTRINSIC MOD
*     ..
      STEMP = 0.0e0
      SDOT = 0.0e0
      IF (N.LE.0) RETURN
      IF (INCX.EQ.1 .AND. INCY.EQ.1) THEN
*
*        code for both increments equal to 1
*
*
*        clean-up loop
*
         M = MOD(N,5)
         IF (M.NE.0) THEN
            DO I = 1,M
               STEMP = STEMP + SX(I)*SY(I)
            END DO
            IF (N.LT.5) THEN
               SDOT=STEMP
            RETURN
            END IF
         END IF
         MP1 = M + 1
         DO I = MP1,N,5
          STEMP = STEMP + SX(I)*SY(I) + SX(I+1)*SY(I+1) +
     $            SX(I+2)*SY(I+2) + SX(I+3)*SY(I+3) + SX(I+4)*SY(I+4)
         END DO
      ELSE
*
*        code for unequal increments or equal increments
*          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 I = 1,N
            STEMP = STEMP + SX(IX)*SY(IY)
            IX = IX + INCX
            IY = IY + INCY
         END DO
      END IF
      SDOT = STEMP
      RETURN
      END