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Posted to issues@stdcxx.apache.org by "Travis Vitek (JIRA)" <ji...@apache.org> on 2008/01/30 02:05:37 UTC
[jira] Commented: (STDCXX-231) std::getline from header is
rather slow
[ https://issues.apache.org/jira/browse/STDCXX-231?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12563770#action_12563770 ]
Travis Vitek commented on STDCXX-231:
-------------------------------------
All of the above testcases are testing both the time taken by getline() and the time to create and setup a file stream. The following testcase tests just the time it takes to do the getline, everything else should be constant.
{noformat}
#include <iostream>
#include <fstream>
#include <string>
int main ()
{
size_t loops = 1000;
const char* file = __FILE__;
std::ifstream ifs (file);
if (!ifs.is_open ())
return 1;
size_t lines = 0;
std::string line;
for (size_t i = 0; i < loops; ++i)
{
while (std::getline (ifs, line, '\n'))
++lines;
ifs.clear ();
ifs.seekg (0);
}
std::cout << lines << std::endl;
return 0;
}
{noformat}
> 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
> Affects Versions: 4.1.2, 4.1.3, 4.1.4, 4.2.0
> Reporter: Martin Sebor
> Assignee: Travis Vitek
> Fix For: 4.2.1
>
>
> 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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