source: downloads/boost_1_34_1/libs/xpressive/perf/time_boost.cpp @ 69

/*
 *
 * Copyright (c) 2002
 * John Maddock
 *
 * Use, modification and distribution are subject to the
 * Boost Software License, Version 1.0. (See accompanying file
 * LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 *
 */

#include "./regex_comparison.hpp"
#include <boost/timer.hpp>
#include <boost/regex.hpp>

namespace b{

double time_match(const std::string& re, const std::string& text)
{
    boost::regex e(re, boost::regex_constants::ECMAScript | boost::regex_constants::optimize);
    boost::smatch what;
    boost::timer tim;
    int iter = 1;
    int counter, repeats;
    double result = 0;
    double run;
    do
    {
        tim.restart();
        for(counter = 0; counter < iter; ++counter)
        {
            boost::regex_match(text, what, e);
        }
        result = tim.elapsed();
        iter *= 2;
    }while(result < 0.5);
    iter /= 2;

    // repeat test and report least value for consistency:
    for(repeats = 0; repeats < REPEAT_COUNT; ++repeats)
    {
        tim.restart();
        for(counter = 0; counter < iter; ++counter)
        {
            boost::regex_match(text, what, e);
        }
        run = tim.elapsed();
        result = (std::min)(run, result);
    }
    return result / iter;
}

//bool dummy_grep_proc(const boost::smatch&)
//{ return true; }

struct noop
{
    void operator()( boost::smatch const & ) const
    {
    }
};

double time_find_all(const std::string& re, const std::string& text)
{
    boost::regex e(re, boost::regex_constants::ECMAScript | boost::regex_constants::optimize);
    boost::smatch what;
    boost::timer tim;
    int iter = 1;
    int counter, repeats;
    double result = 0;
    double run;
    do
    {
        tim.restart();
        for(counter = 0; counter < iter; ++counter)
        {
            boost::sregex_iterator begin( text.begin(), text.end(), e ), end;
            std::for_each( begin, end, noop() );
            //boost::regex_grep(&dummy_grep_proc, text, e);
        }
        result = tim.elapsed();
        iter *= 2;
    }while(result < 0.5);
    iter /= 2;

    if(result >10)
        return result / iter;

    // repeat test and report least value for consistency:
    for(repeats = 0; repeats < REPEAT_COUNT; ++repeats)
    {
        tim.restart();
        for(counter = 0; counter < iter; ++counter)
        {
            boost::sregex_iterator begin( text.begin(), text.end(), e ), end;
            std::for_each( begin, end, noop() );
            //boost::regex_grep(&dummy_grep_proc, text, e);
        }
        run = tim.elapsed();
        result = (std::min)(run, result);
    }
    return result / iter;
}

}