简单程序Perl C++的效率比较

来源：互联网发布：ping服务器的某个端口编辑：程序博客网时间：2024/05/18 01:30

之前要处理一个25W行的文件,用shell,慢的简直不能忍,即使优化了把那种通过管道启动新程序的脚本,如echo 'aaa' |grep xxx这种去掉,也用了7分钟,

于是乎,我又拿起了2年前用的perl重写一份,耗时0.6秒 !!!

real   0m0.647s
user   0m0.560s
sys   0m0.032s

本着我是c++爱好者的兴趣,我用c++重写了一份,发现还是0.5-0.6秒,怎么c++也没比perl快多少嘛

改编译参数,加了个-O3,发现速度没多少变化

real   0m0.560s
user   0m0.236s
sys        0m0.276s

我想,肯定是我写的有问题

看到sys 用了0.27,比perl的0.03多很多,我就猜测可能是io方面没有写好

后来,我发现我写的程序有诸如cout<< "xxx"<<endl;获取此处有问题

于是乎我改成了cout<<"xxx\n";

效率马上提高了

real   0m0.205s
user   0m0.160s
sys   0m0.024s

以上

my $PREV_TIME="";my $SUM=0;my $INIT=1;my $line;my $TIME;my $TPS;my $MSG;while(<>){  # Remove the line break  chomp;   $line=$_;  # Skip blank line  if (!$line){next;}   $TIME=substr($line,0,8);  $TPS=substr($line,10,99);  # Handle TPS Log is Enabled/Disabled  $MSG=substr($TPS,0,10);  if ( $MSG eq "TPS Log is" )  {print "$line\n";next;  }   $TPS=substr($TPS,0,rindex($TPS, "TPS")-1);  if ($INIT==1)  {$PREV_TIME=$TIME;$INIT=0;  }  if ($PREV_TIME eq $TIME)  {$SUM=$SUM+$TPS;  }else  {print "$PREV_TIME  $SUM TPS\n";$SUM=$TPS;  }  $PREV_TIME=$TIME;}print "$PREV_TIME  $SUM TPS\n";

string PREV_TIME;int SUM = 0;int INIT = 1;string line;string TIME;string TPS;fstream ifs;string MSG;int tps_number = 0;ifs.open("/var/tmp/sorted.tmp");while (!std::getline(ifs, line).eof()){if (line == "")continue;TIME = line.substr(0, 8);TPS = line.substr(10, 99);MSG = TPS.substr(0, 10);if (MSG == "TPS Log is"){cout << line << endl;continue;}int index = TPS.rfind("TPS");tps_number = atoi(TPS.substr(0, index - 1).c_str());if (INIT == 1){PREV_TIME = TIME;INIT = 0;}if (PREV_TIME == TIME){SUM = SUM + tps_number;}else{cout << PREV_TIME << "  " << SUM << " " << "TPS\n";SUM = tps_number;}PREV_TIME = TIME;}cout << PREV_TIME << "  " << SUM << " " << "TPS\n";