sdot.f
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| text/x-fortran
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FortranFixedLexer
| r1601 | *> \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. | ||||
| * | ||||
| *> \date November 2017 | ||||
| * | ||||
| *> \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 (version 3.8.0) -- | ||||
| * -- Reference BLAS is a software package provided by Univ. of Tennessee, -- | ||||
| * -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- | ||||
| * November 2017 | ||||
| * | ||||
| * .. 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 | ||||
