一、vector
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void TestVector()
{
cout << "begin create vector" << endl;
int iSize = 10000000;
vector<int> test_vec;
for (int i = 0; i < iSize; i++)
{
test_vec.push_back(i);
}
cout << "create vector end" << endl;
Sleep(2*1000);
cout << "clear vector" << endl;
test_vec.clear();
cout << "clear vector end" << endl;
Sleep(1*1000);
cout << "after clear new data come if the size bigger" << endl;
for (int i = 0; i < iSize; i++)
{
test_vec.push_back(i);
}
cout << "new data push_back end" << endl;
Sleep(1*1000);
cout << "swap vector" << endl;
{
vector<int> tmp_vec;
test_vec.swap(tmp_vec);
}
cout << "swap vector end" << endl;
Sleep(1*1000);
}
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测试过程：
结论：
1. vector clear 之后，内存没有释放，但在下次分配时会复用该块内存。
2. vector swap 空数据之后，会释放内存。
二、map
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void TestMap()
{
cout << "begin create map" << endl;
int iSize = 1000000;
map<int, int> test_map;
for (int i = 0; i < iSize; i++)
{
test_map[i] = i;
}
cout << "create map end" << endl;
Sleep(2*1000);
cout << "clear map" << endl;
test_map.clear();
cout << "clear map end" << endl;
getchar();
cout << "swap map" << endl;
{
map<int, int> tmp_map;
test_map.swap(tmp_map);
}
cout << "swap map end" << endl;
getchar();
}
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测试过程：
结论：
1. map clear 之后，会释放内存。
2. map swap 空数据之后，会释放内存。
https://www.cnblogs.com/SZxiaochun/p/8432817.html
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