dot_prod_10.c

dsp6713开发板的许多例程.对入门特别有用

int dot_prod(const short *restrict a, const short *restrict b,
             short *restrict c, int len)
{
    int i;
    int      sum = 0;                  /* 32-bit accumulation         */
    unsigned a3_a2, a1_a0;             /* Packed 16-bit values        */
    unsigned b3_b2, b1_b0;             /* Packed 16-bit values        */

    for (i = 0; i < len; i += 4)
    {
        a3_a2 = _hi(*(const double *) &a[i]);
        a1_a0 = _lo(*(const double *) &a[i]);

        b3_b2 = _hi(*(const double *) &b[i]);
        b1_b0 = _lo(*(const double *) &b[i]);

        /* Perform dot-products on pairs of elements, totalling the 
           results in the accumulator. */
        sum += _dotp2(a3_a2, b3_b2);
        sum += _dotp2(a1_a0, b1_b0);
    }

    return sum;
}