# Multisystem: Containers

### Introduction

In Octopus there is the possibility to group several systems into containers, which are implemented in the multisystem_basic_t class.

Containers can have different purposes and applications. In the simplest case, containers are simply a collection of other systems, and do not have their own interactions with anything else. In this case, containers do not introduce any different physics (or approximations), but simply help in the book-keeping of the problem.

Another use case might be to group systems into a container, and then only interact with the whole container, instead of the individual systems. This, however, is an approximation, and furthermore (at least, at the moment) has some limitations due to the implementation.

### Implementation

Most of the functionality is implemented at the level of the abstract class multisystem_t:

Definition of multisystem_t

The specific multisystem_basic_t class only adds the finalizer:

Definition of multisystem_basic_t