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From "Mark Brown (JIRA)" <j...@apache.org>
Subject [jira] Commented: (STDCXX-231) std::getline from <string> header is rather slow
Date Tue, 23 Oct 2007 17:37:50 GMT

    [ https://issues.apache.org/jira/browse/STDCXX-231?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12537089
] 

Mark Brown commented on STDCXX-231:
-----------------------------------

I just benchmarked getline() from stdcxx 4.1.3 against the same function in gcc 4.1 (the program
is below), and out of curiosity against the wc utility on Linux. stdcxx is more than twice
slower than gcc, and nearly ten times slower than wc.The timings for a 32MB text file are:

$ ls -l input.txt && time LD_LIBRARY_PATH=../lib ./getline 1 input.txt &&
time ./a.out 1 input.txt && time wc -l input.txt && cat getline.cpp
-rw-rw-r-- 1 mbrown mbrown 32942720 Oct 23 11:30 input.txt
892370

real    0m0.433s
user    0m0.400s
sys     0m0.036s
892370

real    0m0.149s
user    0m0.124s
sys     0m0.024s
892370 input.txt

real    0m0.053s
user    0m0.048s
sys     0m0.004s
#include <stdio.h>
#include <stdlib.h>
#include <fstream>
#include <string>

int main (int argc, char *argv[])
{
    unsigned long loops;
    const char* file;

    loops = 1 < argc ? strtoul (argv [1], 0, 0) : 1;
    file =  2 < argc ? argv [2] : __FILE__;

    unsigned long line_count = 0;
    std::string line;

    for (unsigned long i = 0; i != loops; ++i) {
        std::ifstream in (file);
        if (!in.is_open ())
            return 1;

        while (std::getline (in, line))
            ++line_count;
    }

    printf ("%lu\n", line_count);
}


> std::getline from <string> header is rather slow
> ------------------------------------------------
>
>                 Key: STDCXX-231
>                 URL: https://issues.apache.org/jira/browse/STDCXX-231
>             Project: C++ Standard Library
>          Issue Type: Improvement
>          Components: 21. Strings
>            Reporter: Martin Sebor
>
> Moved from the Rogue Wave bug tracking database:
> ****Created By: leroy @ Jan 25, 2001 03:20:01 PM****
> Environment
>   Compiler : SUNPRO 4.2
>   OS : Solaris 2.5.1
>   SCL : 1.3.0 (Summer-1999)
>   Tools : 7.1.0 (Summer-1999) --> Use only for RWBench
> Command line option :
>   for debug : 
>   CC -xildoff +w +p -g -o Test_dbg.exe test.cc -DRWDEBUG=1 -I/opt/RogueWave/Summer-1999/workspaces/SOLARIS251/SUNPRO42/11s
-I/opt/RogueWave/Summer-1999/workspaces/SOLARIS251/SUNPRO42/11s/include -I. -L/opt/RogueWave/Summer-1999/workspaces/SOLARIS251/SUNPRO42/11s/lib
-Bstatic -ltls11s -lstd11s -Bdynamic
>   for release :
> CC -xildoff +w +p -fast -o Test_release.exe test.cc -I/opt/RogueWave/Summer-1999/workspaces/SOLARIS251/SUNPRO42/8s
-I/opt/RogueWave/Summer-1999/workspaces/SOLARIS251/SUNPRO42/8s/include -I. -L/opt/RogueWave/Summer-1999/workspaces/SOLARIS251/SUNPRO42/8s/lib
-Bstatic -ltls8s -lstd8s -Bdynamic
>  (Uploaded file: 997149-test.cc)                                                    
                                                                                         
                                                                                         
                                                                                         
                                                                
> **** Entered By: Web @ Thursday, January 25, 2001 2:41:42 AM **** 
> Location of uploaded file: 
> http://thoth.bco.roguewave.com/uploads/997149-test.cc
> View all uploaded files for this incident: 
> http://webdev.roguewave.com/admin/tsvw/index.cfm?IncidentID=997149                  
                                                                                         
                                                                                         
                                                                                         
                                                                                         
                                                                                         
                                                                                         
                                                                                         
                                                                                         
                                                                                         
                                                                                         
                                                                                         
                                                                         
> **** Entered By: Web @ Thursday, January 25, 2001 2:44:56 AM **** 
> #web
> Please find my test case at the end of the note
> Environment
>   Compiler : SUNPRO 4.2
>   OS : Solaris 2.5.1
>   SCL : 1.3.0 (Summer-1999)
>   Tools : 7.1.0 (Summer-1999) --> Use only for RWBench
> Command line option :
>   for debug : 
>   CC -xildoff +w +p -g -o Test_dbg.exe test.cc -DRWDEBUG=1 -I/opt/RogueWave/Summer-1999/workspaces/SOLARIS251/SUNPRO42/11s
-I/opt/RogueWave/Summer-1999/workspaces/SOLARIS251/SUNPRO42/11s/include -I. -L/opt/RogueWave/Summer-1999/workspaces/SOLARIS251/SUNPRO42/11s/lib
-Bstatic -ltls11s -lstd11s -Bdynamic
>   for release :
> CC -xildoff +w +p -fast -o Test_release.exe test.cc -I/opt/RogueWave/Summer-1999/workspaces/SOLARIS251/SUNPRO42/8s
-I/opt/RogueWave/Summer-1999/workspaces/SOLARIS251/SUNPRO42/8s/include -I. -L/opt/RogueWave/Summer-1999/workspaces/SOLARIS251/SUNPRO42/8s/lib
-Bstatic -ltls8s -lstd8s -Bdynamic
> #Code
> #include <string>
> #include <fstream.h>
> #include <iostream.h>
> #include <rw/bench.h>
>  
>  
> class std_string_getline : public RWBench
> {
>   public:
>    std_string_getline() {;}
>  
>    void doLoop(unsigned long n);
>    void idleLoop(unsigned long n);
>    void what(ostream& os) const { os << "Standard String Getline : " <<
endl;}
> };
>  
> class classic_getline : public RWBench
> {
>   public:
>     classic_getline() {;}
>  
>     void doLoop(unsigned long n);
>     void idleLoop(unsigned long n);
>     void what(ostream& os) const { os << "Classic Getline : " << endl;}
> };
>  
> int
> main(int argc, char** argv)
> {
>  
>   std_string_getline test_std_string;
>   test_std_string.parse(argc, argv);
>   test_std_string.go();
>   test_std_string.report(cout);
>  
>   classic_getline test_classic_getline;
>   test_classic_getline.parse(argc, argv);
>   test_classic_getline.go();
>   test_classic_getline.report(cout);
> }
>  
> void
> std_string_getline::doLoop(unsigned long n)
> {
>   while (n--)
>   {
>     ifstream toRead(__FILE__);
>     string line;
>     line.reserve(512);
>  
>     while (!(toRead.eof()))
>     {
>       getline(toRead, line, '\n');
>     }
>   }
> }
>  
> void
> std_string_getline::idleLoop(unsigned long n)
> {
>   while (n--)
>   {
>     ifstream toRead(__FILE__);
>     string line;
>     line.reserve(512);
>   }
> }
>  
> void
> classic_getline::doLoop(unsigned long n)
> {
>   while (n--)
>   {
>     ifstream toRead(__FILE__);
>     char cLine[512];
>     string line;
>     line.reserve(512);
>  
>     while (!(toRead.eof()))
>     {
>       toRead.getline(cLine, 512);
>       line = cLine;
>     }
>   }
> }
>  
> void
> classic_getline::idleLoop(unsigned long n)
> {
>   while (n--)
>   {
>     ifstream toRead(__FILE__);
>     char cLine[512];
>     string line;
>     line.reserve(512);
>   }
> }
> #EndCode                
> There appears to be something to this.  I ran the program and here is the output:
> Sun C++ 
> Standard String Getline : 
> Iterations:                 1
> Inner loop operations:      1000
> Total operations:           1000
> Elapsed (user) time:        18.18
> Operations per second:      55.0055
> Sun C++ 
> Classic Getline : 
> Iterations:                 5
> Inner loop operations:      1000
> Total operations:           5000
> Elapsed (user) time:        4.67
> Kilo-operations per second: 1.07066

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