atl_sdsrefdot.c

来自「基于Blas CLapck的.用过的人知道是干啥的」· C语言 代码 · 共 146 行

/* ---------------------------------------------------------------------
 *
 * -- Automatically Tuned Linear Algebra Software (ATLAS)
 *    (C) Copyright 2000 All Rights Reserved
 *
 * -- ATLAS routine -- Version 3.2 -- December 25, 2000
 *
 * Author         : Antoine P. Petitet
 * Originally developed at the University of Tennessee,
 * Innovative Computing Laboratory, Knoxville TN, 37996-1301, USA.
 *
 * ---------------------------------------------------------------------
 *
 * -- Copyright notice and Licensing terms:
 *
 *  Redistribution  and  use in  source and binary forms, with or without
 *  modification, are  permitted provided  that the following  conditions
 *  are met:
 *
 * 1. Redistributions  of  source  code  must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce  the above copyright
 *    notice,  this list of conditions, and the  following disclaimer in
 *    the documentation and/or other materials provided with the distri-
 *    bution.
 * 3. The name of the University,  the ATLAS group,  or the names of its
 *    contributors  may not be used to endorse or promote products deri-
 *    ved from this software without specific written permission.
 *
 * -- Disclaimer:
 *
 * THIS  SOFTWARE  IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES,  INCLUDING,  BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE UNIVERSITY
 * OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,  INDIRECT, INCIDENTAL, SPE-
 * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
 * TO,  PROCUREMENT  OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEO-
 * RY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT  (IN-
 * CLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * ---------------------------------------------------------------------
 */
/*
 * Include files
 */
#include "atlas_refmisc.h"
#include "atlas_reflevel1.h"

float ATL_sdsrefdot
(
   const int                  N,
   const float                B,
   const float                * X,
   const int                  INCX,
   const float                * Y,
   const int                  INCY
)
{
/*
 * Purpose
 * =======
 *
 * ATL_sdsrefdot returns the dot product b + x^T * y of two n-vectors x
 * and  y.  The  result  is internally  computed  using double precision
 * arithmetic and casted to a single precision scalar  just before being
 * returned.
 *
 * Arguments
 * =========
 *
 * N       (input)                       const int
 *         On entry, N specifies the length of the vector x. N  must  be
 *         at least zero. Unchanged on exit.
 *
 * B       (input)                       const double
 *         On entry, B specifies the scalar b. Unchanged on exit.
 *
 * X       (input)                       const double *
 *         On entry,  X  points to the  first entry to be accessed of an
 *         incremented array of size equal to or greater than
 *            ( 1 + ( n - 1 ) * abs( INCX ) ) * sizeof(   double  ),
 *         that contains the vector x. Unchanged on exit.
 *
 * INCX    (input)                       const int
 *         On entry, INCX specifies the increment for the elements of X.
 *         INCX must not be zero. Unchanged on exit.
 *
 * Y       (input)                       const double *
 *         On entry,  Y  points to the  first entry to be accessed of an
 *         incremented array of size equal to or greater than
 *            ( 1 + ( n - 1 ) * abs( INCY ) ) * sizeof(   double  ),
 *         that contains the vector y. Unchanged on exit.
 *
 * INCY    (input)                       const int
 *         On entry, INCY specifies the increment for the elements of Y.
 *         INCY must not be zero. Unchanged on exit.
 *
 * ---------------------------------------------------------------------
 */
/*
 * .. Local Variables ..
 */
   register double            dot = (double)(B), x0, x1, x2, x3, y0, y1, y2, y3;
   float                      * StX;
   register int               i;
   int                        nu;
   const int                  incX2 = 2 * INCX, incY2 = 2 * INCY,
                              incX3 = 3 * INCX, incY3 = 3 * INCY,
                              incX4 = 4 * INCX, incY4 = 4 * INCY;
/* ..
 * .. Executable Statements ..
 *
 */
   if( N > 0 )
   {
      if( ( nu = ( N >> 2 ) << 2 ) != 0 )
      {
         StX = (float *)X + nu * INCX;

         do
         {
            x0 = (double)(*X);       y0 = (double)(*Y);
            x1 = (double)(X[INCX ]); y1 = (double)(Y[INCY ]);
            x2 = (double)(X[incX2]); y2 = (double)(Y[incY2]);
            x3 = (double)(X[incX3]); y3 = (double)(Y[incY3]);
            dot += x0 * y0; dot += x1 * y1; dot += x2 * y2; dot += x3 * y3;
            X  += incX4; Y  += incY4;
         } while( X != StX );
      }

      for( i = N - nu; i != 0; i-- )
      {
         x0  = (double)(*X); y0  = (double)(*Y); dot += x0 * y0;
         X  += INCX;
         Y  += INCY;
      }
   }
   return( (float)(dot) );
/*
 * End of ATL_sdsrefdot
 */
}