几种读入方式效率比较
测试人：成都石室中学 邓皓宇 测试平台：Ubuntu 18.04 测试如下读入方式(所有代码均附在文末)：
- cin(cin.cpp)
- cin(关闭捆绑)(cin(close sync).cpp)
- cin(管捆绑 tie(0))(cin(close sync tie(0)))
- scanf (scanf.cpp)
数据生成器:gen.cpp 测试时间器：judge.cpp
测试1 整数读入
范围 10000000 个int类型读入，运行50次，比较运行时间求平均值。为了模拟最真实的情况，从程序加载时开始计时，程序结束运行时，结束计时 测试结果如下： |项目名|T1|T2|T3|T4|T5|T6|T7|T8|T9|T10|AVERAGE| |:–:|:–:|:–:|:–:|:–:|:–:|:–:|:–:|:–:|:–:|:–:|:–:| |cin|526 ms|516 ms|504 ms|530 ms|489 ms|494 ms|438 ms|602 ms|532 ms|515 ms|514.6 |cin_close_sync|428 ms|420 ms|392 ms|444 ms|395 ms|405 ms|428 ms|416 ms|476 ms|632 ms|443.6 |cin_close_sync_tie0|489 ms|584 ms|467 ms|413 ms|417 ms|397 ms|389 ms|418 ms|404 ms|594 ms|457.2 |scanf|10411 ms|9816 ms|9820 ms|10414 ms|9725 ms|10081 ms|9922 ms|9594 ms|10289 ms|9956 ms|10002.8
我不这道怎么回事，为什么会出现这种结果，但这是真实的测试结果，我只能选择尊重客观事实。。。事实就是dhy太弱了
代码： cin:
# include <iostream>
using namespace std;
const int MAXN = 10000000;
int a[MAXN+1];
int main(){
for(int i = 1;i<=MAXN;i++){
cin>>a[i];
}
return 0;
}
cin__close_sync:
# include <iostream>
using namespace std;
const int MAXN = 10000000;
int a[MAXN+1];
int main(){
ios::sync_with_stdio(false);
for(int i = 1;i<=MAXN;i++){
cin>>a[i];
}
return 0;
}
cin tie(0)
# include <iostream>
using namespace std;
const int MAXN = 10000000;
int a[MAXN+1];
int main(){
ios::sync_with_stdio(false);
cin.tie(0);
for(int i = 1;i<=MAXN;i++){
cin>>a[i];
}
return 0;
}
scanf
# include <cstdio>
const int MAXN = 10000000;
int a[MAXN+1];
int main(){
for(int i = 1;i<=MAXN;i++){
scanf("%d",&a[i]);
}
return 0;
}
judge:
# include <cstdlib>
# include <cstdio>
# include <ctime>
# include <fstream>
using namespace std;
int main(){
int T = 10;
ofstream out("res");
long long start,end;
system("./gen>in");
int tot = 0;
/*******cin*******/
printf("%s\n","Start new test");
out<<"|cin|";
for(int i = 1;i<=T;i++){
start = clock();
system("./cin<in");
end = clock();
out<<end-start<<" ms|";
tot+=end-start;
printf("%s%d\n","test item:",i);
}
out<<double(tot)/double(10)<<endl;
/*******cin close sync*******/
tot = 0;
printf("%s\n","Start new test");
out<<"|cin_close_sync|";
for(int i = 1;i<=T;i++){
start = clock();
system("./cin_close<in");
end = clock();
out<<end-start<<" ms|";
tot+=end-start;
printf("%s%d\n","test item:",i);
}
out<<double(tot)/double(10)<<endl;
/*******cin_tie0*******/
printf("%s\n","Start new test");
tot = 0;
out<<"|cin_close_sync_tie0|";
for(int i = 1;i<=T;i++){
start = clock();
system("./cin_close_sync_tie0<in");
end = clock();
out<<end-start<<" ms|";
tot+=end-start;
printf("%s%d\n","test item:",i);
}
out<<double(tot)/double(10)<<endl;
/*******scanf*******/
printf("%s\n","Start new test");
tot = 0;
out<<"|scanf|";
for(int i = 1;i<=T;i++){
start = clock();
system("./scanf<in");
end = clock();
out<<end-start<<" ms|";
tot+=end-start;
printf("%s%d\n","test item:",i);
}
out<<double(tot)/double(10)<<endl;
printf("Done");
return 0;
}
gen:
# include <cstdlib>
# include <cstdio>
const int MAXN = 10000000;
int main(){
srand(19260817);
for(int i = 1;i<=MAXN;i++)printf("%d",rand());
}
