C + + stitching string efficiency comparison (+ =, append, StringStream, sprintf)

Turn from: http://www.cnblogs.com/james6176/p/3222671.htmlc++ stitching string Efficiency comparison (+ =, append, StringStream, sprintf)

Recently wrote the program with a large number of splicing strings, in order to improve the efficiency of splicing, compared to + =, append, StringStream, sprintf four kinds of splicing string method.

Test method

The comparison method is to write 4 functions, respectively, with + =, append, StringStream, sprintf the way to stitch the string, stitching method is s1= "ABCEDFG", s2= "HIJKLMN", s3= "Opqrst" three strings are stitched together, The total loop is 60 times. The 4 functions are then called sequentially in the main function and timed with a timestamp. In order to make the time difference more obvious, we can take the time of cyclic n (n can be 100 or 1000000) times. The code is as follows:

1 #include <iostream>2 #include <String>3 #include <sys/time.h>4 #include <sstream>5 #include <stdio.h>6UsingNamespaceStd7#define OUT_IN_REPEATE_NUM 100008#define IN_REPEATE_NUM 60910String s1="Abcedfg";11String s2="Hijklmn";12String s3="Opqrst";13void Plustest (string&Ret14{15Forint i=0; i<in_repeate_num; i++)16{+ ret + =S1;RET + =S2;RET + =S3;20}21st}22void Appendtest (string&Ret23{24Forint i=0; i<in_repeate_num; i++)25{26Ret.append (S1);27Ret.append (S2);28Ret.append (S3);29}30}31void Sprintftest (string&Ret32{33Const size_t Length=26*In_repeate_num;34CharTmp[length];35char* CP =tmpsize_t strlength=s1.length () +s2.length () +S3.length ();37Forint i=0; i<in_repeate_num; i++)38{sprintf (CP,"%s%s%s", S1.c_str (), S2.c_str (), S3.c_str ());cp+=Strlength;41}RET =tmp43}4445void Sstest (string&Ret46{47StringStream SS;48Forint i=0; i<in_repeate_num; i++)49{ss<<S1;Wuyi ss<<S2;ss<<S3;53}The RET =Ss.str ();55}56IntMain () {57StringSS, plus, append, sprintf;58structTimeval stime, ETime;59Gettimeofday (&Stime, NULL);61Forint i=0; i<out_in_repeate_num; i++)62{sprintf="";64Sprintftest (sprintf);65}Gettimeofday (&ETime, NULL);67Long sprintftime = (etime.tv_sec-stime.tv_sec) *1000000+ (ETIME.TV_USEC-STIME.TV_USEC);//Exetime units are microseconds68Gettimeofday (&Stime, NULL);70Forint i=0; i<out_in_repeate_num; i++)71{Append="";73Appendtest (append);74} Gettimeofday (& ETime, NULL); Long appendtime = (etime.tv_sec-stime.tv_sec) *1000000+ (ETIME.TV_USEC-STIME.TV_USEC); Exetime Unit is microsecond gettimeofday (&stime, NULL); for (int i=0; i<out_in_repeate_num; i++), {Bayi ss= "", "the sstest (ss); (Gettimeofday, NULL); Sstime = (etime.tv_sec-stime.tv_sec) *1000000+ (ETIME.TV_USEC-STIME.TV_USEC); Exetime Unit is microsecond gettimeofday (&stime, NULL); (int i=0; i<out_in_repeate_num; i++), Plustest (Gettimeofday, NULL); plus= &etime (plus); 94 Long Plustime = (etime.tv_sec-stime.tv_sec) *1000000+ (ETIME.TV_USEC-STIME.TV_USEC); Exetime Unit is microsecond cout<< "Plustime is:" <<PlusTime<<endl; cout<< "Appendtime is:" <<AppendTime<<endl; 98 cout<< "Sstime is:" <<SsTime<<endl; cout<< "Sprintftime is:" <<sprintftime<<endl;100 if (ss==sprintf && Append==plus & & Ss==plus) 101 {102 cout<< "They is same" <<endl;103 }104 else105 {106 cout<< "different!" <<endl;107 cout<< "Sprintf:" <<sprintf<<endl;108 cout<< "ss:" <<ss<<endl; 109 cout<< "Plus:" <<plus<<endl;110 cout<< "Append:" <<append<<endl;111}112 113}

Test Results:

In the Linux environment, compile the above code with g++, and the result is as follows (the time unit is μm):

Outer loop 1000000 times	Outer loop 100000 times	Outer Loop 10000 times	Outer Loop of three times	Outer Loop of three times
Plustime is:3405450 Appendtime is:4020078 Sstime is:7835499 Sprintftime is:14875433 They is same	Plustime is:337229 Appendtime is:401719 Sstime is:788242 Sprintftime is:1517999 They is same	Plustime is:32177 Appendtime is:40265 Sstime is:78928 Sprintftime is:150839 They is same	Plustime is:3402 Appendtime is:4074 Sstime is:7984 Sprintftime is:15425 They is same	Plustime is:369 Appendtime is:429 Sstime is:921 Sprintftime is:1591 They is same

Conclusion:

Based on the above results, if you are using a Linux system and are g++ (GCC) compilers, the efficiency of a large number of stitching strings is from high to low: + =, append (), StringStream, sprintf ().

-Rookie Jim Original, if there is a mistake, please correct me!

C + + stitching string efficiency comparison (+ =, append, StringStream, sprintf)