[Bug c++/53292] New: multi-threaded (OpenMP) is slower than single-threaded

[fh_p at hotmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53292

             Bug #: 53292
           Summary: multi-threaded (OpenMP) is slower than single-threaded
    Classification: Unclassified
           Product: gcc
           Version: 4.6.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: fh_p@hotmail.com


Created attachment 27352
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=27352
cpp file to compile

Hello,

The problem is : multi-threaded (OpenMP) is slower than single-threaded

Test has been ran several times successively.
ChunkSize imposed to avoid false sharing.
Test ran on Ubuntu 12.04 64 bits / 4Gb RAM / CPU i3 (dual core hyper-threaded :
2 physical cores + 2 logical cores) / gcc version : 4.6.2.

Is the problem related to CPU ? i3 hyper-threaded would not be "handled
correctly" by g++ or Ubuntu ?

Can somebody help or give me clue ?

Thanks,

FH

PS : I am not used to post bug, if this bug has not been posted in the right
place feel free to tell me where to post it