[Bug libstdc++/66414] New: Regression: string::find ten times slower than strstr

[Bug libstdc++/66414] New: Regression: string::find ten times slower than strstr

[neleai at seznam dot cz]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66414

            Bug ID: 66414
           Summary: Regression: string::find ten times slower than strstr
           Product: gcc
           Version: 4.9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: neleai at seznam dot cz
  Target Milestone: ---

Hi, as I seen bug with string::== being slower than using strcmp I decided to
check other functions for regressions. Here string::find doesn't simply call
optimized strstr and as result its ten times slower in following benchmark on
my sandy bridge.


#include <cstring>
#include <cstdlib>
#include <string>
using namespace std;

int
main()
{
  int i;
  char s[10000];
  for (i = 0; i < 10000; i++)
    s[i] = ((unsigned) rand() % 128) + 1;
  s[9999] = 0;
  int sum = 0;
  std::string foo = s;
  std::string bar;
  char *needle = strdup("needle");

  for (i = 0; i < 100000; i++)
    {
      needle[0] = ((unsigned) rand() % 128) + 1;
#ifdef STRSTR
      sum += (long) strstr(s, needle);
#else
      sum += foo.find(needle);
#endif
    }
  return sum;
}

[Bug libstdc++/66414] string::find ten times slower than strstr

[hiraditya at msn dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66414

AK <hiraditya at msn dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |hiraditya at msn dot com

--- Comment #8 from AK <hiraditya at msn dot com> ---
Should we consider this fixed?

[Bug libstdc++/66414] string::find ten times slower than strstr

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66414

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to AK from comment #8)
> Should we consider this fixed?

I think we can still do better, by using GNU memmem when it's available:

https://gcc.gnu.org/pipermail/gcc-patches/2017-January/466460.html
https://gcc.gnu.org/pipermail/gcc-patches/2017-January/466469.html
https://gcc.gnu.org/pipermail/gcc-patches/2017-January/466471.html

For now we should also use the new code in basic_string_view::find which is
currently much slower.

[Bug libstdc++/66414] string::find ten times slower than strstr

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66414

--- Comment #10 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jonathan Wakely <redi@gcc.gnu.org>:

https://gcc.gnu.org/g:a199da782fc165fd45f42a15cc9020994efd455d

commit r11-6931-ga199da782fc165fd45f42a15cc9020994efd455d
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Wed Jan 27 13:21:52 2021 +0000

    libstdc++: Optimize std::string_view::find [PR 66414]

    This reuses the code from std::string::find, which was improved by
    r244225, but string_view was not changed to match.

    libstdc++-v3/ChangeLog:

            PR libstdc++/66414
            * include/bits/string_view.tcc
            (basic_string_view::find(const CharT*, size_type, size_type)):
            Optimize.

[Bug libstdc++/66414] string::find ten times slower than strstr

[scc at teamt5 dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66414

Chih-Hsuan Yang <scc at teamt5 dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |scc at teamt5 dot org

--- Comment #11 from Chih-Hsuan Yang <scc at teamt5 dot org> ---
Hi all, 

I hope this message finds you well.

I wanted to inquire about the current status of our project. It has come to my
attention that our program is facing performance issues when using gcc 13.2.
Considering this situation, I am willing to take on the responsibility of
addressing this issue by taking ownership of the related ticket.

Could you please provide an update on the progress here?

Thank you for your attention to this matter.

[Bug libstdc++/66414] string::find ten times slower than strstr

[scc at teamt5 dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66414

--- Comment #12 from Chih-Hsuan Yang <scc at teamt5 dot org> ---
Hi all,


I hope this message finds you well.

I wanted to inquire about the current status of our project. It has come to my
attention that our program is facing performance issues when using gcc 13.2.
Considering this situation, I am willing to take on the responsibility of
addressing this issue by taking ownership of the related ticket.

Could you please provide an update on the progress here?

Thank you for your attention to this matter.

[Bug libstdc++/66414] string::find ten times slower than strstr

[scc at teamt5 dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66414

--- Comment #13 from Chih-Hsuan Yang <scc at teamt5 dot org> ---
Hi all,


I hope this message finds you well.

I wanted to inquire about the current status of our project. It has come to my
attention that our program is facing performance issues when using gcc 13.2.
Considering this situation, I am willing to take on the responsibility of
addressing this issue by taking ownership of the related ticket.

Could you please provide an update on the progress here?

Thank you for your attention to this matter.

[Bug libstdc++/66414] string::find ten times slower than strstr

[scc at teamt5 dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66414

--- Comment #14 from Chih-Hsuan Yang <scc at teamt5 dot org> ---
(In reply to Chih-Hsuan Yang from comment #11)
> Hi all, 
> 
> I hope this message finds you well.
> 
> I wanted to inquire about the current status of our project. It has come to
> my attention that our program is facing performance issues when using gcc
> 13.2. Considering this situation, I am willing to take on the responsibility
> of addressing this issue by taking ownership of the related ticket.
> 
> Could you please provide an update on the progress here?
> 
> Thank you for your attention to this matter.

sorry, it's my fault, it seems being solved.

[Bug libstdc++/66414] string::find ten times slower than strstr

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66414

--- Comment #15 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Chih-Hsuan Yang from comment #11)
> Could you please provide an update on the progress here?


All progress is already recorded above.

[Bug libstdc++/66414] string::find ten times slower than strstr

[scc at teamt5 dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66414

--- Comment #16 from Chih-Hsuan Yang <scc at teamt5 dot org> ---
(In reply to Jonathan Wakely from comment #15)
> (In reply to Chih-Hsuan Yang from comment #11)
> > Could you please provide an update on the progress here?
> 
> 
> All progress is already recorded above.

Would you like to change this ticket's status to close? And marking this issue
is solved since gcc 10.1, libstdc++6.0.28

[Bug libstdc++/66414] string::find ten times slower than strstr

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66414

--- Comment #17 from Jonathan Wakely <redi at gcc dot gnu.org> ---
See comment 9