sse_vector_dot_test.cpp

#include <xmmintrin.h>
#include <chrono>
#include <iostream>
using namespace std;
using namespace chrono;
 
#ifdef _MSC_VER
__declspec(align(16)) struct vector4
#else
struct alignas(16) vector4
#endif
{
    float v[4];
};
 
template<int N>
struct dot_unroller;

template<>
struct dot_unroller<1>
{
    static float eval(float const* v1, float const* v2)
    {
        return *v1 * *v2;
    }
};
 
template<int N>
struct dot_unroller
{
    static float eval(float const* v1, float const* v2)
    {
        return dot_unroller<1>::eval(v1, v2) + dot_unroller<N - 1>::eval(v1 + 1, v2 + 1);
    }
};
 
float dot_std(vector4 const& v1, vector4 const& v2)
{
    return dot_unroller<4>::eval(v1.v, v2.v);
}
 
float dot_unroll(vector4 const& v1, vector4 const& v2)
{
    return v1.v[0] * v2.v[0] +
        v1.v[1] * v2.v[1] +
        v1.v[2] * v2.v[2] +
        v1.v[3] * v2.v[3];
}
 
float dot_sse(vector4 const& v1, vector4 const& v2)
{
#ifdef _MSC_VER
    __declspec(align(16)) float r[4];
#else
    alignas(16) float r[4];
#endif
    __m128 a, b;
    a = _mm_load_ps(v1.v);
    b = _mm_load_ps(v2.v);
    _mm_store_ps(r, _mm_mul_ps(a, b));
    return r[0] + r[1] + r[2] + r[3];
}
 
struct timer
{
    char const* name;
    high_resolution_clock::time_point start;
    timer(char const* p)
        : name{ p }
        , start{ high_resolution_clock::now() }
    {
    }
 
    ~timer()
    {
        auto duration = high_resolution_clock::now() - start;
        cout << name << ": " << duration_cast<nanoseconds>(duration).count() << endl;
    }
};
 
template<typename F>
void time_it(char const* name, F f, int count)
{
    float res;
    {
        timer t{ name };
        vector4 a = { 1, 2, 3, 4 };
        for (int i = 0; i < count; ++i)
        {
            res = f(a, a);
        }
    }

    cout << res << endl;
}
 
int main()
{
    int const count = 1000000;
    for (int i = 0; i < 3; ++i)
    {
        time_it("dot_std", dot_std, count);
        time_it("dot_unroll", dot_unroll, count);
        time_it("dot_sse", dot_sse, count);
    }
}