Filters optimization
Following the explanations given at http://cpp-next.com/archive/2009/08/want-speed-pass-by-value/
It seems that we should write the filters in a different way:
std::vector vecM; for(all filters) vecM = filter(vecM); done
and filter's prototype being std::vector filter( std::vector input) that returns input after modifying it. The compiler would skip several vector copies that we currently have...