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From "Travis Vitek (JIRA)" <j...@apache.org>
Subject [jira] Commented: (STDCXX-493) std::string::append() slow
Date Tue, 11 Sep 2007 20:20:32 GMT

    [ https://issues.apache.org/jira/browse/STDCXX-493?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12526590
] 

Travis Vitek commented on STDCXX-493:
-------------------------------------

All I did was merge the patch with the current version of the affected file. This was necessary
so that I could test the patch. If you want the original patch, it can be found via the link
you posted above.

Since you've mentioned it, how would one go about _adding_ themselves to the ChangeLog? I've
only seen entries with one author and it might be useful to know what the expected format
is for the future.

> std::string::append() slow
> --------------------------
>
>                 Key: STDCXX-493
>                 URL: https://issues.apache.org/jira/browse/STDCXX-493
>             Project: C++ Standard Library
>          Issue Type: Bug
>          Components: 21. Strings
>    Affects Versions: 4.1.3
>         Environment: gcc 4.1.2 on Linux/x86_64
>            Reporter: Mark Brown
>            Assignee: Travis Vitek
>             Fix For: 4.2
>
>         Attachments: stdcxx-493.patch
>
>
> This is a similar problem to STDCXX-492: all overloads of string::append() are slower
than the same overloads in gcc:
> $ let n=0; while [ $n -lt 3 ]; do time LD_LIBRARY_PATH=../lib ./append-stdcxx-4.1.3 500000000
$n; let n=`expr $n + 1`; done
> real    0m11.221s
> user    0m9.941s
> sys     0m1.104s
> real    0m13.065s
> user    0m11.661s
> sys     0m1.236s
> real    0m7.837s
> user    0m6.660s
> sys     0m1.160s
> $ let n=0; while [ $n -lt 3 ]; do time ./append-gcc-4.1.2 500000000 $n; let n=`expr $n
+ 1`; done
> real    0m4.865s
> user    0m4.172s
> sys     0m0.692s
> real    0m7.617s
> user    0m6.920s
> sys     0m0.696s
> real    0m5.787s
> user    0m5.068s
> sys     0m0.720s
> The program I used to do the comaprison is below:
> #include <cassert>
> #include <cstdlib>
> #include <string>
> int main (int argc, char *argv[])
> {
>     const int N = argc < 2 ? 1 : std::atoi (argv [1]);
>     const int op = argc < 3 ? 0 : std::atoi (argv [2]);
>     std::string str;
>     const std::string x ("X");
>     if (op == 0) {
>         for (int i = 0; i < N; ++i)
>             str.append (1, 'x');
>     } else if (op == 1) {
>         for (int i = 0; i < N; ++i)
>             str.append ("x");
>     } else {
>         for (int i = 0; i < N; ++i)
>             str.append (x);
>     }
>     assert (str.size () == std::size_t (N));
> }

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