[Patch] Optimize _BFSExecutor in regex

[Tim Shen]

On Mon, Oct 7, 2013 at 7:11 PM, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
> The version in your gist (which is *not* what your first patch did!)
> is faster for any size of _M_exists and any ratio of _M_states.size()
> / _M_exists.size():

Sorry for my original patch, I made a mistake! It's:
      while (!_BaseT::empty())
        _BaseT::pop_back();
but I truely meant:
      while (!this->_M_empty())
        this->_M_pop();
To make all trues reset.

In my machine the while loop is slower than assign() when the
_M_states.size() / _M_exists.size() is more than even 7/1000. so let's
keep the assign(), because the ratio in regex could probably be more
than 25%.


-- 
Tim Shen
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