[Boost-users] large data sets and BOOST_FOREACH / boost:bind don't mix ?

5 Feb 2010


      In my application I have very large data sets, I was using BOOST_FOREACH
and boost bind. But I was surprised that performance wise they were the
worst ?
Take the following test:

class Fred {
public:
    Fred(int i = 0) : i_(i) {}
    void inc() { i_++;}
private:
    int i_;
};

BOOST_AUTO_TEST_CASE( test_loop )
{
    size_t vecSize = 200000000;
    std::vector<Fred> vec; vec.reserve(vecSize);
    for (size_t i = 0; i < vecSize ; i++) { vec.push_back(Fred(i));}

     boost::timer timer;
    BOOST_FOREACH(Fred& fred, vec) { fred.inc(); }
     cout << "Time: BOOST_FOREACH(Fred& fred, vec) { fred.inc(); } " <<
timer.elapsed() << "\n";

     timer.restart();
     std::for_each(vec.begin(),vec.end(),boost::bind(&Fred::inc,_1) );
     cout << "Time:
std::for_each(vec.begin(),vec.end(),boost::bind(&Fred::inc,_1) ); " <<
timer.elapsed() << "\n";

     timer.restart();
     std::vector<Fred>::iterator theEnd = vec.end();
     for (std::vector<Fred>::iterator  i = vec.begin(); i < theEnd ; i++) {
(*i).inc(); }
     cout << "Time: for (std::vector<Fred>::iterator  i = vec.begin(); i <
theEnd ; i++) { (*i).inc(); } " << timer.elapsed() << "\n";

     timer.restart();
     std::for_each(vec.begin(),vec.end(),std::mem_fun_ref(&Fred::inc) );
     cout << "Time:
std::for_each(vec.begin();vec.end(),std::mem_fun_ref(&Fred::inc)) " <<
timer.elapsed() << "\n";

     timer.restart();
     size_t theSize = vec.size();
    for (size_t i = 0; i < theSize ; i++) { vec[i].inc(); }
     cout << "Time: for (size_t i = 0; i < theSize ; i++) { vec[i].inc(); }
" << timer.elapsed() << "\n";
}

I get following times when run on suse linux with gcc 4.2.1/ boost 1.39

Time: BOOST_FOREACH(Fred& fred, vec) { fred.inc();
}                                               10.65
Time: std::for_each(vec.begin(),vec.end(),boost::bind(&Fred::inc,_1) );
                   9.76
Time: for (std::vector<Fred>::iterator  i = vec.begin(); i < theEnd ; i++) {
(*i).inc(); }  4.48
Time:
std::for_each(vec.begin();vec.end(),std::mem_fun_ref(&Fred::inc))
4.08
Time: for (size_t i = 0; i < theSize ; i++) { vec[i].inc();
}                                                      1.6

It appears that BOOST_FOREACH and use of boost::bind in performance critical
application should be avoided ?
-- 
  Best regards,
Ta,
   Avi

[Boost-users] large data sets and BOOST_FOREACH / boost:bind don't mix ?

Avi Bahra