Re: [Boost-users] [msm] Why does it take so many bytes to represent a state machine?

Subject: Re: [Boost-users] [msm] Why does it take so many bytes to represent a state machine?
From: Christophe Henry (christophe.j.henry_at_[hidden])
Date: 2012-11-13 16:31:39

>Thanks for the quick response and thanks for making this handy library.

>

>I turned off message queueing (typedef int no_message_queue) and I'm down to 20 bytes, much better, though still 
>with some unaccounted bytes. I'm looking for a better way.
>

>I don't use any attributes, except for event attributes, or submachines. I also don't care about event/state history. 

Event attributes have no memory cost on your state machine. History costs the same as the id (an int per region).

>This means the only state-related info is the state ID. What about just reading and storing the state ID, and using the stored ID 
>to restore the state next time I need to process an event? I know how to get state ID (current_state()), but how do I set state from ID?

You cannot set the state, MSM handles the lifecycle of its states.

>

>Josh

MSM just stores the id of the current state(s) in order to call on_entry/on_exit or for bookkeeping. MSM does not recreate the active states after each transition but insteads keeps them alive for performance reasons. This also allows you to store data in states (you need this quite often).
I don't know how many bytes still are needed for your text archive, you should ask this to Robert Ramey.

Christophe