CentOS 4.6 x86_64 g++ 3.4.6 中vector的Grow策略
2011-03-26 10:26
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写了一个小程序,测试了一下vector是如何分配内存的:
Code: Select all
程序的输出是:
Vector size is: 0, capacity is: 0
Vector size is: 1, capacity is: 1
Vector size is: 2, capacity is: 2
Vector size is: 3, capacity is: 4
Vector size is: 4, capacity is: 4
Vector size is: 5, capacity is: 8
Vector size is: 6, capacity is: 8
Vector size is: 7, capacity is: 8
Vector size is: 8, capacity is: 8
Vector size is: 9, capacity is: 16
Vector size is: 10, capacity is: 16
Vector size is: 11, capacity is: 16
Vector size is: 12, capacity is: 16
Vector size is: 13, capacity is: 16
Vector size is: 14, capacity is: 16
Vector size is: 15, capacity is: 16
Vector size is: 16, capacity is: 16
Vector size is: 17, capacity is: 32
Vector size is: 18, capacity is: 32
Vector size is: 19, capacity is: 32
Vector size is: 20, capacity is: 32
Vector size is: 21, capacity is: 32
Vector size is: 22, capacity is: 32
Vector size is: 23, capacity is: 32
Vector size is: 24, capacity is: 32
Vector size is: 25, capacity is: 32
Vector size is: 26, capacity is: 32
Vector size is: 27, capacity is: 32
Vector size is: 28, capacity is: 32
Vector size is: 29, capacity is: 32
Vector size is: 30, capacity is: 32
Vector size is: 32, capacity is: 50
所以,可以看出,这个平台上,vector的内存分配策略是1, 2, 4, 8, 16, 32......
g++的版本信息是:
g++ (GCC) 3.4.6 20060404 (Red Hat 3.4.6-9)
Code: Select all
#include <iostream> #include <vector> #include <string> using namespace std; int main() { vector<string> vec1; cout << "Vector size is: " << vec1.size() << ", capacity is: " << vec1.capacity() << endl; for (int i=0; i<30; i++) { vec1.push_back("String 1"); cout << "Vector size is: " << vec1.size() << ", capacity is: " << vec1.capacity() << endl; } vec1.reserve(50); vec1.push_back("String 2"); vec1.push_back("String 3"); cout << "Vector size is: " << vec1.size() << ", capacity is: " << vec1.capacity() << endl; return 0; }
程序的输出是:
Vector size is: 0, capacity is: 0
Vector size is: 1, capacity is: 1
Vector size is: 2, capacity is: 2
Vector size is: 3, capacity is: 4
Vector size is: 4, capacity is: 4
Vector size is: 5, capacity is: 8
Vector size is: 6, capacity is: 8
Vector size is: 7, capacity is: 8
Vector size is: 8, capacity is: 8
Vector size is: 9, capacity is: 16
Vector size is: 10, capacity is: 16
Vector size is: 11, capacity is: 16
Vector size is: 12, capacity is: 16
Vector size is: 13, capacity is: 16
Vector size is: 14, capacity is: 16
Vector size is: 15, capacity is: 16
Vector size is: 16, capacity is: 16
Vector size is: 17, capacity is: 32
Vector size is: 18, capacity is: 32
Vector size is: 19, capacity is: 32
Vector size is: 20, capacity is: 32
Vector size is: 21, capacity is: 32
Vector size is: 22, capacity is: 32
Vector size is: 23, capacity is: 32
Vector size is: 24, capacity is: 32
Vector size is: 25, capacity is: 32
Vector size is: 26, capacity is: 32
Vector size is: 27, capacity is: 32
Vector size is: 28, capacity is: 32
Vector size is: 29, capacity is: 32
Vector size is: 30, capacity is: 32
Vector size is: 32, capacity is: 50
所以,可以看出,这个平台上,vector的内存分配策略是1, 2, 4, 8, 16, 32......
g++的版本信息是:
g++ (GCC) 3.4.6 20060404 (Red Hat 3.4.6-9)
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