输出流效率测试

这个问题Effective STL中有提过。今天编程时由于涉及到输出的效率，加上闲着没事，所以做了这测试。

测试对象：

1.cout<<

2.ostream_iterator

3.ostreambuf_iterator

4.printf

5.cout.put

6.rdbuf()->sputn

测试平台：

1.6GHz处理器

测试代码：

#include <iostream>#include <iterator>#include <cstdio>#include <ctime>#include <iomanip>using namespace std;int main(){   /*以10000个'a'作为输出目标*/   char a[10000] = {'a'};   for (char& x : a)   {      x = 'a';   }   clock_t start1, end1, start2, end2, start3, end3, start4, end4, start5, end5, start6, end6;   /*测试ostream_iterator*/   start1 = clock();   copy(a, a + 10000, ostream_iterator<char>(cout));   end1 = clock();   /*测试ostreambuf_iterator*/   start2 = clock();   copy(a, a + 10000, ostreambuf_iterator<char>(cout));   end2 = clock();   /*测试cout<<*/   start3 = clock();   for (char x: a)   cout << x;   end3 = clock();   /*测试printf*/   start4 = clock();   for (char x: a)   printf("%c", x);   end4 = clock();   /*测试cout.put*/   start5 = clock();   for (char x: a)   cout.put(x);   end5 = clock();   /*测试rdbuf()->sputn*/   start6 = clock();   cout.rdbuf()->sputn(a, 10000);   end6 = clock();   cout << endl;   cout << setw(25) << "ostream_iterator: " << static_cast<double>(end1 - start1) / CLOCKS_PER_SEC << " seconds"<< endl;   cout << setw(25) << "ostreambuf_iterator: " << static_cast<double>(end2 - start2) / CLOCKS_PER_SEC << " seconds"<< endl;   cout << setw(25) <<  "cout<<: " << static_cast<double>(end3 - start3) / CLOCKS_PER_SEC << " seconds"<< endl;   cout << setw(25) <<  "printf: " << static_cast<double>(end4 - start4) / CLOCKS_PER_SEC << " seconds"<< endl;   cout << setw(25) <<  "cout.put: " << static_cast<double>(end5 - start5) / CLOCKS_PER_SEC << " seconds"<< endl;   cout << setw(25) <<  "rdbuf()->sputn: " << static_cast<double>(end6 - start6) / CLOCKS_PER_SEC << " seconds"<< endl;    return 0;}

测试结果：

1.用MinGW编译

ostream_iterator:5.806 secondsostreambuf_iterator:0.142 secondscout<<:5.812 secondsprintf:5.673 secondscout.put:5.752 secondsrdbuf()->sputn:0.118 seconds

2.用Borland C++编译

ostream_iterator:5.569 secondsostreambuf_iterator:0.203 secondscout<<:4.789 secondsprintf:4.493 secondscout.put:4.555 secondsrdbuf()->sputn:0.141 seconds

3.用VS2012编译

ostream_iterator:4.809 secondsostreambuf_iterator:4.659secondscout<<:4.956 secondsprintf:5.848 secondscout.put:6.976 secondsrdbuf()->sputn:6.793 seconds

果然，用ostreambuf_iterator和rdbuf()->sputn来进行输出的确快很多，但不同的STL实现速度提升会不同，如VS2012就提升不明显了（例外？）。