代码

#define idx(i, j) ((i) * n + (j))

#define fA(p) *(c + p) += x * *(b + p)
#define fB(p) fA(p + 0), fA(p + 1)
#define fC(p) fB(p + 0), fB(p + 2)
#define fD(p) fC(p + 0), fC(p + 4)
#define fE(p) fD(p + 0), fD(p + 8)

void matrix_multiply(int n, const double *A, const double *B, double *C) {
    for (int i = 0; i < n; i++) for (int k = 0; k < n; k++) {
        double x = A[idx(i, k)], *c = C + i * n; const double *b = B + k * n;
        for (int j = 0; j < n; j += 16) fE(j);
    }
}

评测结果