RandomActivation scheduler not working after upgrade 2.1 -> 2.2.3 about mesa

[EwoutH]

Thanks for reaching out. I will test this tomorrow morning, if no one else has done it by then.

Furthermore if I not call super().init() in the model class, the first agent is not added to the scheduler.

Calling super().__init__() was always recommended, but now it’s required. It initializes Model.agents among other things. You’re using the Mesa Model class, so you should properly initialize it.

[EwoutH]

I've narrowed it down to the fact that the AgentSet's shuffle(inplace=True) doesn't shuffle the agents. Could be because the shuffle isn't working, or the in place updating isn't.

mesa/mesa/time.py

Lines 144 to 147 in 99b35fc

	def do_each(self, method, shuffle=False):
	if shuffle:
	self.agents.shuffle(inplace=True)
	self.agents.do(method)

[EwoutH]

It's the inplace updating that isn't working. Without it, it works correctly:

@quaquel you wrote this code and know more about the AgentSet implementation. Could assist in fixing the inplace updating?

[EwoutH]

@profConradi we just released Mesa 2.2.4 which should fix this issue. Could you confirm this is the case?

[profConradi]

Yes, the RandomActivation Scheduler of 2.2.4 works correctly! Thanks!

[EwoutH]

Great to hear, thanks a lot for reporting this issue!

For such a serious bug to slip thought the the review, test and release process is really unfortunate. I wrote some thoughts on it here: #1909 (comment)

[EwoutH]

@rht do you have time to investigate this?

[rht]

I'd need some help debugging all the problems caused by 2.1.x -> 2.2.x. Hands are full with elsewhere.

[EwoutH]

Unfortunately, I can reproduce this issue for both Mesa 2.2.0 and 2.2.3, while the correct behavior (shuffled agent steps) on Mesa 2.1.5. @projectmesa/maintainers this is a major issue and needs immediate care, we broke RandomActivation.

I will investigate further.

[profConradi]

Thanks for your work, Mesa is an amazing framework!

[quaquel]

I can try this afternoon. I don't see an obvious mistake in the code.

AgentSet.shuffle

        shuffled_agents = list(self)
        self.random.shuffle(shuffled_agents)

        return (
            AgentSet(shuffled_agents, self.model)
            if not inplace
            else self._update(shuffled_agents)
        )

random.shuffle is inplace. List(self) returns a list of hard refs to the agents.

AgentSet._update

    def _update(self, agents: Iterable[Agent]):
        """Update the AgentSet with a new set of agents.
        This is a private method primarily used internally by other methods like select, shuffle, and sort.
        """

        self._agents = weakref.WeakKeyDictionary({agent: None for agent in agents})
        return self

We create a new WeakKeyDictionary so it should shuffle.

Accidentally, This is the code I was playing with for #1993. So my to do;

• add a unittest that reproduces the error
• figure out why the error exists, because based on the code I don't
• test my fix from #1993

[EwoutH]

Thanks. I had already written an additional unittest for RandomActivation itself, we can test updates also against that (#2007).

[quaquel]

Found it. The problem is in the scheduler not in AgentSet.

do_each should be

    def do_each(self, method, shuffle=False):
        if shuffle:
            self._agents.shuffle(inplace=True)
        self._agents.do(method)

[quaquel]

I committed the fix to #2007.