boost::unordered_map <std::string, s4u::Mailbox *> *s4u::Mailbox::mailboxes = new boost::unordered_map<std::string, s4u::Mailbox*> ();
boost::unordered_map <std::string, s4u::Mailbox *> *s4u::Mailbox::mailboxes = new boost::unordered_map<std::string, s4u::Mailbox*> ();