[Bug libstdc++/42712] New: search_n/iterator.cc times out in parallel-mode

[Bug libstdc++/42712] New: search_n/iterator.cc times out in parallel-mode

[paolo dot carlini at oracle dot com]

I'm consistently seeing this time out when regtesting make check-parallel. Is
it unavoidable withing the current infrastructure? Besides slowing down the
testing itself (not a very big issue, momentarily, I will commit an hack for
this), seems a quite puzzling behavior to me: if parallel-mode runs orders of
magnitude slower than serial-mode, shouldn't in principle at minimum fall back
to the latter?


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           Summary: search_n/iterator.cc times out in parallel-mode
           Product: gcc
           Version: 4.5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: paolo dot carlini at oracle dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42712

[Bug libstdc++/42712] search_n/iterator.cc times out in parallel-mode

[singler at kit dot edu]

------- Comment #1 from singler at kit dot edu  2010-01-12 17:43 -------
Maybe rather an endless loop.


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singler at kit dot edu changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |singler at kit dot edu
                   |dot org                     |
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2010-01-12 17:43:17
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42712

[Bug libstdc++/42712] search_n/iterator.cc times out in parallel-mode

[paolo dot carlini at oracle dot com]

------- Comment #2 from paolo dot carlini at oracle dot com  2010-01-12 18:00 -------
My impression is that for some reason it's just slow, very slow: with
TEST_DEPTH=10 it completes in a decent amount of time...


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42712

[Bug libstdc++/42712] search_n/iterator.cc times out in parallel-mode

[singler at kit dot edu]

------- Comment #3 from singler at kit dot edu  2010-01-18 09:08 -------
Paolo, you were right, it was just the fallback switch missing for this case. 
And since this specific test issues many thousands of calls with very small
input, the overhead was very noticeable.  Patch upcoming...


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42712

[Bug libstdc++/42712] search_n/iterator.cc times out in parallel-mode

[paolo dot carlini at oracle dot com]

------- Comment #4 from paolo dot carlini at oracle dot com  2010-01-18 11:21 -------
Excellent. If possible, I would suggest removing my temporary hack from the
testcase together with the parallel-mode patch.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42712

[Bug libstdc++/42712] search_n/iterator.cc times out in parallel-mode

[singler at gcc dot gnu dot org]

------- Comment #5 from singler at gcc dot gnu dot org  2010-01-19 11:18 -------
Subject: Bug 42712

Author: singler
Date: Tue Jan 19 11:18:03 2010
New Revision: 156036

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=156036
Log:
2010-01-19  Johannes Singler  <singler@kit.edu>

        PR libstdc++/42712
        * include/parallel/settings.h (_Settings): Add search_minimal_n.
        * include/parallel/algo.h (__search_switch):
        Add serial fallback for too small inputs.
        (__search_n_switch): Likewise.  Call serial fallback on higher level
        to gain special treatment for __count 0 or 1.
        * testsuite/25_algorithms/search_n/iterator.cc:
        Reenable full test depth for parallel mode.


Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/include/parallel/algo.h
    trunk/libstdc++-v3/include/parallel/settings.h
    trunk/libstdc++-v3/testsuite/25_algorithms/search_n/iterator.cc


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42712

[Bug libstdc++/42712] search_n/iterator.cc times out in parallel-mode

[paolo dot carlini at oracle dot com]

------- Comment #6 from paolo dot carlini at oracle dot com  2010-01-19 12:08 -------
Confirmed fixed, thanks!


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paolo dot carlini at oracle dot com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42712