代码功能:循环拼接字符串,并替换子字符串

硬件环境:Intel Core2 Duo T7500@2.20Ghz CPU; 2 GB RAM; OS Debian GNU/Linux 2.6.32 i686

代码执行时长

代码运行时长

代码性能对比图
代码性能对比图

最慢: Java gcj (native executable)  
较慢: Java (openJDK); Java (Sun); Lua  
稍慢: tcl; Javascript (spidermonkey)  
较快: Python; Ruby; PHP; C++; Javascript V8; C; Perl5  
最快的是Perl,最慢的gcj,你能接受吗?

内存使用情况

内存使用情况

内存对比图:
内存对比图

测试源码:

C (source); Result: C gcc (Debian 4.4.4-1) 4.4.4

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>

int main(){

setbuf(stdout,NULL); //disable output buffering

char *str=malloc(8);
strcpy(str,"abcdefgh");

str=realloc(str,strlen(str)+8);
strcat(str,"efghefgh");     //sprintf(str,"%s%s",str,"efghefgh");

int imax=1024/strlen(str)*1024*4;

printf("%s","exec.tm.sec\tstr.length\n"); //fflush(stdout);

time_t starttime=time(NULL);
char *gstr=malloc(0);
int i=0;
char *pos;
int lngth;

char *pos_c=gstr;
int str_len=strlen(str);

    while(i++ < imax+1000){
        lngth=strlen(str)*i;
        gstr=realloc(gstr,lngth+str_len);
        strcat(gstr,str);    //sprintf(gstr,"%s%s",gstr,str);
        pos_c+=str_len;

        pos=gstr;
        while(pos=strstr(pos,"efgh")){
            memcpy(pos,"____",4);
        }

        if(lngth % (1024*256)==0){
            printf("%dsec\t\t%dkb\n",time(NULL)-starttime,lngth/1024); //fflush(stdout);
        }
    }
//printf("%s\n",gstr);

}

C++ (source) Result: C++ g++ (Debian 4.4.3-7) 4.4.3

#include <iostream>
#include <string>
#include <time.h>

using namespace std;

main ()
{
  string str = "abcdefgh";
    str += "efghefgh";
  int imax = 1024 /str.length() * 1024 *4;
  time_t currentTime = time(NULL);
  cout << "exec.tm.sec\tstr.length" << endl;

  string find= "efgh";
  string replace ="____";
  string gstr;
  int i=0;
  int length;
//  int end=0; //  size_t end=0;

  while(i++ < imax +1000){
    gstr += str;
    gstr = gstr;
    size_t start, sizeSearch=find.size(), end=0;

    while((start=gstr.find(find,end))!=string::npos){
        end=start+sizeSearch;
        gstr.replace(start,sizeSearch,replace);
    }
    length = str.length()*i;
    if((length%(1024 * 256))==0){
        cout << time(NULL) - currentTime << "sec\t\t" << length/1024 << "kb" <<  endl;
    }
  }
// cout << gstr << endl;

return 0;
}

Javascript (source); Results: Javascript (Spidermonkey – Mozilla) 1.8.0 pre-release 1 2007-10-03,
Javascript (V8 – Chrome)

#!/usr/local/bin/js

var str = "abcdefgh"+"efghefgh";
var imax = 1024 / str.length * 1024 * 4;

var time = new Date();
print("exec.tm.sec\tstr.length");

var gstr = "";
var i=0;
var lngth;

while (i++ < imax+1000) {
    gstr += str;
    gstr = gstr.replace(/efgh/g, "____");
        lngth=str.length*i;
        if ((lngth % (1024*256)) == 0) {
                var curdate=new Date();
                print(parseInt(((curdate.getTime()-time.getTime())/1000))+"sec\t\t"+lngth/1024+"kb");
        }
}

Java (source) Results: Java (OpenJDK) “1.6.0 18″,
Java (Sun) “1.6.0 16″,
Java (gcj) (Debian 4.4.3-1) 4.4.3

public class java_test {

    public static final void main(String[] args) throws Exception {
        String str = "abcdefgh"+"efghefgh";
        int imax = 1024 / str.length() * 1024 * 4;

        long time = System.currentTimeMillis();
        System.out.println("exec.tm.sec\tstr.length\tallocated memory:free memory:memory used");
        Runtime runtime = Runtime.getRuntime();
        System.out.println("0\t\t0\t\t"+runtime.totalMemory()/1024 +":"+ runtime.freeMemory()/1024+":"+(runtime.totalMemory()-runtime.freeMemory())/1024);

        String gstr = "";
        int i=0;
        int lngth;

        while (i++ < imax+1000) {
            gstr += str;
            gstr = gstr.replaceAll("efgh", "____");
            lngth=str.length()*i;
                if ((lngth % (1024*256)) == 0) {
                        System.out.println(((System.currentTimeMillis()-time)/1000)+"sec\t\t"+lngth/1024+"kb\t\t"+runtime.totalMemory()/1024+":"+runtime.freeMemory()/1024+":"+(runtime.totalMemory()-runtime.freeMemory())/1024);
                }
        }
    }
}

Perl5 (source); Result: This is perl, v5.10.1

#!/usr/bin/perl
$|=1;    #disable output buffering, this is necessary for proper output through pipe

my $str='abcdefgh'.'efghefgh';
my $imax=1024/length($str)*1024*4;               # 4mb

my $starttime=time();
print "exec.tm.sec\tstr.length\n";

my $gstr='';
my $i=0;

while($i++ < $imax+1000){   #adding 1000 iterations to delay exit. This will allow to capture memory usage on last step

        $gstr.=$str;
        $gstr=~s/efgh/____/g;
        my $lngth=length($str)*$i;   ##     my $lngth=length($gstr);        # Perhaps that would be a slower way
        print time()-$starttime,"sec\t\t",$lngth/1024,"kb\n" unless $lngth % (1024*256); #print out every 256kb
}

PHP (source); Result: PHP 5.3.1-5 with Suhosin-Patch (cgi-fcgi)

<?php


$str="abcdefgh"."efghefgh";
$imax=1024/strlen($str)*1024*4;      # 4mb

$starttime=time();
print("exec.tm.sec\tstr.length\n");

$gstr='';
$i=0;

while($i++ < $imax+1000){

        $gstr.=$str;
        $gstr=preg_replace('/efgh/','____',$gstr);
        $lngth=strlen($str)*$i;
        if($lngth % (1024*256)==0){
                print (time()-$starttime."sec\t\t".($lngth/1024)."kb\n");
        }
}

?>

Python3 (source); Result: Python 3.1.3

#!/usr/bin/python3 -u
import re
import time
import sys

str='abcdefgh'+'efghefgh'
imax=1024/len(str)*1024*4   # 4mb

starttime=time.time();
print "exec.tm.sec\tstr.length"
sys.stdout.flush()

gstr=''
i=0

while (i < imax+1000):
        i=i+1
        gstr+=str
        gstr=re.sub('efgh','____',gstr)
        lngth=len(str)*i
        if(lngth % (1024*256) == 0):
                print int(time.time()-starttime),"sec\t\t",(lngth/1024),"kb"
                sys.stdout.flush()

Ruby (source); Result: ruby 1.8.7

#!/usr/bin/ruby
$stdout.sync=true;

str='abcdefgh'+'efghefgh';
imax=1024/str.length*1024*4;       # 4mb

starttime=Time.new;
print("exec.tm.sec\tstr.length\n");

gstr='';
i=0;

while i < imax+1000
        i=i+1;
        gstr+=str;
        gstr=gstr.gsub(/efgh/, "____")

        lngth=str.length*i;
        if(lngth % (1024*256)==0)
                print(((Time.new-starttime).ceil).to_s+"sec\t\t",(lngth/1024).to_s,"kb\n");
        end
end

#puts gstr;

Lua (source); Result: Lua 5.1.4

#!/usr/bin/lua

io.stdout:setvbuf "no";             --  io.flush();

str='abcdefgh'..'efghefgh';
imax=1024/string.len(str)*1024*4;         -- 4mb

starttime=os.time();
print "exec.tm.sec\tstr.length";

gstr='';
i=0;

while i < imax+1000 do
        i=i+1;
        gstr=gstr..str;
        gstr=string.gsub(gstr,"efgh","____");
        lngth=string.len(str)*i;
        if(math.mod(lngth,1024*256)==0) then
                print(os.time()-starttime.."sec\t\t"..(lngth/1024).."kb");
        end
end

tcl (source); Result: tcl 8.4.19

#!/usr/bin/tclsh

set str "abcdefgh"
append str "efghefgh"

set imax [expr {1024/[string length $str]*1024*4}]

set starttime [clock clicks -milliseconds]
puts "exec.tm.sec\tstr.length";

set gstr ""
set i 0

while {$i<[expr {$imax+1000}]} {
        incr i
        append gstr $str;
        regsub -all {efgh} $gstr ____ gstr
        set lngth [expr {[string length $str]*$i}]
        if {[expr {$lngth % (1024*256)}] == 0} {
                puts "[expr int([expr [clock clicks -milliseconds] - $starttime] / 1000)]sec\t\t[expr {$lngth/1024}]kb"
        }
}

exit

结论

各语言随着版本升级,也在不断优化,想要用好每个语言的特性,需要摸透她的脾气,这个需要不断的加深了解。

选语言就像选恋人,情人眼里出西施,你中意的,就是最好的,所以对以上结果别太较真。

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