*> \brief \b SDOT * * =========== DOCUMENTATION =========== * * Online html documentation available at * http://www.netlib.org/lapack/explore-html/ * * Definition: * =========== * * REAL FUNCTION SDOT(N,SX,INCX,SY,INCY) * * .. Scalar Arguments .. * INTEGER INCX,INCY,N * .. * .. Array Arguments .. * REAL SX(*),SY(*) * .. * * *> \par Purpose: * ============= *> *> \verbatim *> *> SDOT forms the dot product of two vectors. *> uses unrolled loops for increments equal to one. *> \endverbatim * * Arguments: * ========== * *> \param[in] N *> \verbatim *> N is INTEGER *> number of elements in input vector(s) *> \endverbatim *> *> \param[in] SX *> \verbatim *> SX is REAL array, dimension ( 1 + ( N - 1 )*abs( INCX ) ) *> \endverbatim *> *> \param[in] INCX *> \verbatim *> INCX is INTEGER *> storage spacing between elements of SX *> \endverbatim *> *> \param[in] SY *> \verbatim *> SY is REAL array, dimension ( 1 + ( N - 1 )*abs( INCY ) ) *> \endverbatim *> *> \param[in] INCY *> \verbatim *> INCY is INTEGER *> storage spacing between elements of SY *> \endverbatim * * Authors: * ======== * *> \author Univ. of Tennessee *> \author Univ. of California Berkeley *> \author Univ. of Colorado Denver *> \author NAG Ltd. * *> \ingroup single_blas_level1 * *> \par Further Details: * ===================== *> *> \verbatim *> *> jack dongarra, linpack, 3/11/78. *> modified 12/3/93, array(1) declarations changed to array(*) *> \endverbatim *> * ===================================================================== REAL FUNCTION SDOT(N,SX,INCX,SY,INCY) * * -- Reference BLAS level1 routine -- * -- Reference BLAS is a software package provided by Univ. of Tennessee, -- * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- * * .. Scalar Arguments .. INTEGER INCX,INCY,N * .. * .. Array Arguments .. REAL SX(*),SY(*) * .. * * ===================================================================== * * .. 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 of SDOT * END