void on_this_start_cb(const std::function<void(Comm const&)>& cb) { on_this_start.connect(cb); }
CommPtr set_copy_data_callback(const std::function<void(kernel::activity::CommImpl*, void*, size_t)>& callback);
void on_this_start_cb(const std::function<void(Comm const&)>& cb) { on_this_start.connect(cb); }
CommPtr set_copy_data_callback(const std::function<void(kernel::activity::CommImpl*, void*, size_t)>& callback);