Return to dsdot.f CVS log

Up to [local] / rpl / lapack / blas

Annotation of rpl/lapack/blas/dsdot.f, revision 1.10

1.6       bertrand    1: *> \brief \b DSDOT
                      2: *
                      3: *  =========== DOCUMENTATION ===========
                      4: *
                      5: * Online html documentation available at 
                      6: *            http://www.netlib.org/lapack/explore-html/ 
                      7: *
                      8: *  Definition:
                      9: *  ===========
                     10: *
                     11: *       DOUBLE PRECISION FUNCTION DSDOT(N,SX,INCX,SY,INCY)
                     12: * 
                     13: *       .. Scalar Arguments ..
                     14: *       INTEGER INCX,INCY,N
                     15: *       ..
                     16: *       .. Array Arguments ..
                     17: *       REAL SX(*),SY(*)
                     18: *       ..
                     19: *  
                     20: *    AUTHORS
                     21: *    =======
                     22: *    Lawson, C. L., (JPL), Hanson, R. J., (SNLA), 
                     23: *    Kincaid, D. R., (U. of Texas), Krogh, F. T., (JPL)
                     24: *  
                     25: *
                     26: *> \par Purpose:
                     27: *  =============
                     28: *>
                     29: *> \verbatim
                     30: *>
                     31: *> Compute the inner product of two vectors with extended
                     32: *> precision accumulation and result.
                     33: *>
                     34: *> Returns D.P. dot product accumulated in D.P., for S.P. SX and SY
                     35: *> DSDOT = sum for I = 0 to N-1 of  SX(LX+I*INCX) * SY(LY+I*INCY),
                     36: *> where LX = 1 if INCX .GE. 0, else LX = 1+(1-N)*INCX, and LY is
                     37: *> defined in a similar way using INCY.
                     38: *> \endverbatim
                     39: *
                     40: *  Arguments:
                     41: *  ==========
                     42: *
                     43: *> \param[in] N
                     44: *> \verbatim
                     45: *>          N is INTEGER
                     46: *>         number of elements in input vector(s)
                     47: *> \endverbatim
                     48: *>
                     49: *> \param[in] SX
                     50: *> \verbatim
                     51: *>          SX is REAL array, dimension(N)
                     52: *>         single precision vector with N elements
                     53: *> \endverbatim
                     54: *>
                     55: *> \param[in] INCX
                     56: *> \verbatim
                     57: *>          INCX is INTEGER
                     58: *>          storage spacing between elements of SX
                     59: *> \endverbatim
                     60: *>
                     61: *> \param[in] SY
                     62: *> \verbatim
                     63: *>          SY is REAL array, dimension(N)
                     64: *>         single precision vector with N elements
                     65: *> \endverbatim
                     66: *>
                     67: *> \param[in] INCY
                     68: *> \verbatim
                     69: *>          INCY is INTEGER
                     70: *>         storage spacing between elements of SY
                     71: *> \endverbatim
                     72: *>
                     73: *> \result DSDOT
                     74: *> \verbatim
                     75: *>          DSDOT is DOUBLE PRECISION
                     76: *>         DSDOT  double precision dot product (zero if N.LE.0)
                     77: *> \endverbatim
                     78: *
                     79: *  Authors:
                     80: *  ========
                     81: *
                     82: *> \author Univ. of Tennessee 
                     83: *> \author Univ. of California Berkeley 
                     84: *> \author Univ. of Colorado Denver 
                     85: *> \author NAG Ltd. 
                     86: *
                     87: *> \date November 2011
                     88: *
                     89: *> \ingroup double_blas_level1
                     90: *
                     91: *> \par Further Details:
                     92: *  =====================
                     93: *>
                     94: *> \verbatim
                     95: *> \endverbatim
                     96: *
                     97: *> \par References:
                     98: *  ================
                     99: *>
                    100: *> \verbatim
                    101: *>
                    102: *>      
                    103: *>  C. L. Lawson, R. J. Hanson, D. R. Kincaid and F. T.
                    104: *>  Krogh, Basic linear algebra subprograms for Fortran
                    105: *>  usage, Algorithm No. 539, Transactions on Mathematical
                    106: *>  Software 5, 3 (September 1979), pp. 308-323.
                    107: *>
                    108: *>  REVISION HISTORY  (YYMMDD)
                    109: *>
                    110: *>  791001  DATE WRITTEN
                    111: *>  890831  Modified array declarations.  (WRB)
                    112: *>  890831  REVISION DATE from Version 3.2
                    113: *>  891214  Prologue converted to Version 4.0 format.  (BAB)
                    114: *>  920310  Corrected definition of LX in DESCRIPTION.  (WRB)
                    115: *>  920501  Reformatted the REFERENCES section.  (WRB)
                    116: *>  070118  Reformat to LAPACK style (JL)
                    117: *> \endverbatim
                    118: *>
                    119: *  =====================================================================
1.1       bertrand  120:       DOUBLE PRECISION FUNCTION DSDOT(N,SX,INCX,SY,INCY)
1.6       bertrand  121: *
                    122: *  -- Reference BLAS level1 routine (version 3.4.0) --
                    123: *  -- Reference BLAS is a software package provided by Univ. of Tennessee,    --
                    124: *  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
                    125: *     November 2011
                    126: *
1.1       bertrand  127: *     .. Scalar Arguments ..
                    128:       INTEGER INCX,INCY,N
                    129: *     ..
                    130: *     .. Array Arguments ..
                    131:       REAL SX(*),SY(*)
                    132: *     ..
                    133: *
1.6       bertrand  134: *  Authors:
                    135: *  ========
1.1       bertrand  136: *  Lawson, C. L., (JPL), Hanson, R. J., (SNLA), 
                    137: *  Kincaid, D. R., (U. of Texas), Krogh, F. T., (JPL)
                    138: *
                    139: *  =====================================================================
                    140: *
                    141: *     .. Local Scalars ..
                    142:       INTEGER I,KX,KY,NS
                    143: *     ..
                    144: *     .. Intrinsic Functions ..
                    145:       INTRINSIC DBLE
                    146: *     ..
                    147:       DSDOT = 0.0D0
                    148:       IF (N.LE.0) RETURN
1.5       bertrand  149:       IF (INCX.EQ.INCY .AND. INCX.GT.0) THEN
1.1       bertrand  150: *
1.5       bertrand  151: *     Code for equal, positive, non-unit increments.
1.1       bertrand  152: *
1.5       bertrand  153:          NS = N*INCX
                    154:          DO I = 1,NS,INCX
                    155:             DSDOT = DSDOT + DBLE(SX(I))*DBLE(SY(I))
                    156:          END DO
                    157:       ELSE
1.1       bertrand  158: *
1.5       bertrand  159: *     Code for unequal or nonpositive increments.
1.1       bertrand  160: *
1.5       bertrand  161:          KX = 1
                    162:          KY = 1
                    163:          IF (INCX.LT.0) KX = 1 + (1-N)*INCX
                    164:          IF (INCY.LT.0) KY = 1 + (1-N)*INCY
                    165:          DO I = 1,N
                    166:             DSDOT = DSDOT + DBLE(SX(KX))*DBLE(SY(KY))
                    167:             KX = KX + INCX
                    168:             KY = KY + INCY
                    169:          END DO
                    170:       END IF
1.1       bertrand  171:       RETURN
                    172:       END