Test of voxel map using hash table (`unordered_map`)

hash_test.cpp

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#include <iostream>
#include <unordered_map>
#define HASH_P 116101
#define MAX_N 10000000000
using namespace std;

int main()
{
    int64_t a = 10;
    int64_t b = 20;
    int64_t c = 33;
    
    cout << std::hash<int64_t>()(a) << ", ";
    cout << std::hash<int64_t>()(b) << ", ";
    cout << std::hash<int64_t>()(c) << endl;
    
    cout << (std::hash<int64_t>()(a) << 1) << ", ";
    cout << (std::hash<int64_t>()(b) << 1) << ", ";
    cout << (std::hash<int64_t>()(c) << 1) << endl;
    
    cout << ( std::hash<int64_t>()(a) ^ (std::hash<int64_t>()(a) << 1) ) << ", ";
    cout << ( std::hash<int64_t>()(b) ^ (std::hash<int64_t>()(b) << 1) ) << ", ";
    cout << ( std::hash<int64_t>()(c) ^ (std::hash<int64_t>()(c) << 1) ) << endl;
    
    cout << ( ( std::hash<int64_t>()(a) ^ (std::hash<int64_t>()(a) << 1) ) >> 1) << ", ";
    cout << ( ( std::hash<int64_t>()(b) ^ (std::hash<int64_t>()(b) << 1) ) >> 1) << ", ";
    cout << ( ( std::hash<int64_t>()(c) ^ (std::hash<int64_t>()(c) << 1) ) >> 1) << endl;
    
    unordered_map<int64_t, int64_t> m;
    int num_already_in = 0;
    int num_new = 0;
    int64_t count = 0;
    for (int64_t sx = -10; sx < 10; ++ sx) {
        for (int64_t sy = -10; sy < 10; ++ sy) {
            for (int64_t sz = -10; sz < 10; ++ sz) {
                // From livox_camera_calib
                // size_t key_of_m = ((hash<int64_t>()(sx) ^ (hash<int64_t>()(sy) << 1)) >> 1) ^ (hash<int64_t>()(sz) << 1);
                // From voxel map. [NOTE] Below one is better!!!!1
                int64_t key_of_m = ((((sz) * HASH_P) % MAX_N + (sy)) * HASH_P) % MAX_N + (sx);
                // cout << key_of_m  << ", ";
                if (m.find(key_of_m) == m.end()) {
                    m[key_of_m] = count;
                    ++num_new;
                } else { 
                    cout <<" It's alread in! "<< endl; 
                    cout << sx << ", " << sy << ", " << sz <<endl;
                    ++num_already_in;
                }
                ++count;
            }
        }    
    }
    cout << endl;
    cout << num_already_in << " vs " << num_new << endl; 
    
    return 0;
}

We have to use ((((sz) * HASH_P) % MAX_N + (sy)) * HASH_P) % MAX_N + (sx)!!!!