boost::unordered_map 和 std::map 的效率，内存比较
// Test_Boost_Unordered.cpp : 定义控制台应用程序的入口点。//#include "stdafx.h"#include "boost/unordered_map.hpp"#include <iostream>#include <map>#include "time.h"using namespace std;int _tmain(int argc, _TCHAR* argv[]){{time_t first_time = time(0);boost::unordered_map<int, int> test_hash;for (int i = 0; i < 50000000; i++){test_hash.insert(std::pair<int, int>(i, i));}cout << test_hash.size() << endl;time_t second_time = time(0);for (int i = 0; i< 50000001; ++i){boost::unordered_map<int, int>::iterator iter = test_hash.find(i);if (iter == test_hash.end()){cout << "false" << endl;}}time_t third_time = time(0);cout << "second - first " << second_time - first_time << endl;cout << "third - second " << third_time - second_time << endl;}{time_t first_time = time(0);std::map<int, int> test_hash;for (int i = 0; i < 50000000; i++){test_hash.insert(std::pair<int, int>(i, i));}cout << test_hash.size() << endl;time_t second_time = time(0);for (int i = 0; i< 50000001; ++i){std::map<int, int>::iterator iter = test_hash.find(i);if (iter == test_hash.end()){cout << "false" << endl;}}time_t third_time = time(0);cout << "second - first " << second_time - first_time << endl;cout << "third - second " << third_time - second_time << endl;}return 0;}

执行结果:

50000000
false
second - first 12
third - second 3
50000000
false
second - first 52
third - second 15

运行环境:

windows -- vs -- Release -- win32

内存消耗: boost::unordered_map 消耗 1.2 G, std::map 1.5 G

结论: unordered_map 查找效率快五倍，插入更快，节省一定内存。如果没有必要排序的话，尽量使用 hash_map(unordered_map 就是 boost 里面的 hash_map 实现)。