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Date: Sat, 8 Nov 2008 16:20:44 -0800 (PST)
From: "Martin Sebor (JIRA)" <jira@apache.org>
To: issues@stdcxx.apache.org
Subject: [jira] Issue Comment Edited: (STDCXX-914) sstream ctors inefficient
 in reentrant modes
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    [ https://issues.apache.org/jira/browse/STDCXX-914?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12646015#action_12646015 ] 

sebor edited comment on STDCXX-914 at 11/8/08 4:18 PM:
--------------------------------------------------------------

Here are the top 10 functions from the {{[stdcxx-914-gprof-gcc-4.3.0-12S.txt|https://issues.apache.org/jira/secure/attachment/12393570/stdcxx-914-gprof-gcc-4.3.0-12S.txt]}} attachment (with template argument lists removed for better readability). Looks like the {{_C_is_managed()}} function could stand to be optimized...

{noformat}
Each sample counts as 0.01 seconds.
  %   cumulative   self              self     total           
 time   seconds   seconds    calls  ms/call  ms/call  name    
 32.40      2.99     2.99 30000000     0.00     0.00  __rw::__rw_locale::_C_is_managed(int) const
 13.98      4.28     1.29 50000000     0.00     0.00  __rw::__rw_locale::_C_manage(__rw::__rw_locale*, char const*)
  6.83      4.91     0.63 10000000     0.00     0.00  std::istream& std::operator>>(std::istream&, std::string&)
  4.98      5.37     0.46 10000001     0.00     0.00  std::string::operator=(std::string const&)
  4.98      5.83     0.46 10000000     0.00     0.00  std::ostream& __rw::__rw_insert(std::ostream&, long)
  4.66      6.26     0.43 10000000     0.00     0.00  std::num_put::_C_put(std::ostreambuf_iterator, std::ios_base&, char, int, void const*) const
  3.36      6.57     0.31 10000000     0.00     0.00  std::string lex_cast<std::string, long>(long const&)
  3.25      6.87     0.30 10000000     0.00     0.00  __rw::__rw_dtoa(char*, unsigned long, unsigned int)
  3.03      7.15     0.28                             main
  2.49      7.38     0.23 30000000     0.00     0.00  std::locale::~locale()
  ...
{noformat}

      was (Author: sebor):
    Here are the top 10 functions from the {{[stdcxx-914-gprof-gcc-4.3.0-12S.txt|https://issues.apache.org/jira/secure/attachment/12393570/stdcxx-914-gprof-gcc-4.3.0-12S.txt]}} attachment. Looks like the {{_C_is_managed()}} function could stand to be optimized...

{noformat}
Each sample counts as 0.01 seconds.
  %   cumulative   self              self     total           
 time   seconds   seconds    calls  ms/call  ms/call  name    
 32.40      2.99     2.99 30000000     0.00     0.00  __rw::__rw_locale::_C_is_managed(int) const
 13.98      4.28     1.29 50000000     0.00     0.00  __rw::__rw_locale::_C_manage(__rw::__rw_locale*, char const*)
  6.83      4.91     0.63 10000000     0.00     0.00  std::istream& std::operator>><char, std::char_traits<char>, std::allocator<char> >(std::istream&, std::string&)
  4.98      5.37     0.46 10000001     0.00     0.00  std::string::operator=(std::string const&)
  4.98      5.83     0.46 10000000     0.00     0.00  std::ostream& __rw::__rw_insert<char, std::char_traits<char>, long>(std::ostream&, long)
  4.66      6.26     0.43 10000000     0.00     0.00  std::num_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::_C_put(std::ostreambuf_iterator<char, std::char_traits<char> >, std::ios_base&, char, int, void const*) const
  3.36      6.57     0.31 10000000     0.00     0.00  std::string lex_cast<std::string, long>(long const&)
  3.25      6.87     0.30 10000000     0.00     0.00  __rw::__rw_dtoa(char*, unsigned long, unsigned int)
  3.03      7.15     0.28                             main
  2.49      7.38     0.23 30000000     0.00     0.00  std::locale::~locale()
  ...
{noformat}
  
> sstream ctors inefficient in reentrant modes
> --------------------------------------------
>
>                 Key: STDCXX-914
>                 URL: https://issues.apache.org/jira/browse/STDCXX-914
>             Project: C++ Standard Library
>          Issue Type: Improvement
>          Components: 27. Input/Output
>    Affects Versions: 4.1.2, 4.1.3, 4.1.4, 4.2.0, 4.2.1
>            Reporter: Martin Sebor
>            Priority: Critical
>             Fix For: 4.2.2
>
>         Attachments: stdcxx-914-gprof-gcc-4.1.2-12D.txt, stdcxx-914-gprof-gcc-4.3.0-12S.txt
>
>   Original Estimate: 12h
>          Time Spent: 2.5h
>  Remaining Estimate: 9.5h
>
> As discussed in this [thread|http://markmail.org/message/hqlsw5dq23gx7d4o] stream ctors in thread-safe builds are inefficient due to the initialization of the mutex data member in every stream, even in those that never use it. As soon as binary compatibility rules permit it we should remove the mutex and/or defer its initialization until it's needed. It might be possible to implement the deferred initialization as early as 4.2.2, or maybe 4.3. Complete removal will need to wait until 5.0.

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