Inquiry: Is the Non-Decreasing Behavior of inventory_input in SCML Simulation Design Intentional?

[Sota-Sakaguchi]

Dear @yasserfarouk

My name is Sota Sakaguchi, joining SCML(std) 2025.
Hi, thank you so much for maintaining this project — I really appreciate all your work.

I’m currently trying to better understand how inventory_input is updated in the simulation, and I came across a part of the code in world.py (line 1871) that made me a bit confused.

It seems that the line:
remaining_in = max(0, self._input_quantity[aid] - producible) self._inventory_input[aid] += remaining_in

only adds any unused portion of input_quantity to inventory_input, but never subtracts from it. So if an agent consumes from its inventory in order to produce (i.e., input_quantity < producible), this consumption isn’t reflected in the inventory — it never decreases.

As a result, inventory_input appears to always either increase or remain the same over time, which might explain why the input inventory graph keeps increasing even when production occurs.

I might be misunderstanding the logic here — if so, I’m really sorry for the confusion. But I just wanted to ask if this is the intended behavior, or whether the consumption from inventory should also be accounted for in this part.

Thanks again for your time and for reading this!

Best Regards,
Sota Sakaguchi
Nagoya Institute of Technology University

[yasserfarouk]

Dear Sakaguchi-sanThank you for raising this issue. We will go back and check the logic and return to you with the explanation (most likely the inventory is controlled by two factors). Please wait a little.Best regardsyasserSent from my iPhoneOn May 23, 2025, at 0:49, Sota-Sakaguchi ***@***.***> wrote: Dear @yasserfarouk My name is Sota Sakaguchi, joining SCML(std) 2025. Hi, thank you so much for maintaining this project — I really appreciate all your work. I’m currently trying to better understand how inventory_input is updated in the simulation, and I came across a part of the code in world.py (line 1871) that made me a bit confused. It seems that the line: remaining_in = max(0, self._input_quantity[aid] - producible) self._inventory_input[aid] += remaining_in only adds any unused portion of input_quantity to inventory_input, but never subtracts from it. So if an agent consumes from its inventory in order to produce (i.e., input_quantity < producible), this consumption isn’t reflected in the inventory — it never decreases. As a result, inventory_input appears to always either increase or remain the same over time, which might explain why the input inventory graph keeps increasing even when production occurs. I might be misunderstanding the logic here — if so, I’m really sorry for the confusion. But I just wanted to ask if this is the intended behavior, or whether the consumption from inventory should also be accounted for in this part. Thanks again for your time and for reading this! Best Regards, Sota Sakaguchi Nagoya Institute of Technology University —Reply to this email directly, view it on GitHub, or unsubscribe.You are receiving this because you were mentioned.Message ID: ***@***.***>

[yasserfarouk]

We checked the logic. It is intentional but the names may be confusing.
self._input_quantity is where we stores the accomulated amount of the input product bought. This is changed by adding the quantity bought at every step:

self._input_quantity[contract.annotation["buyer"]] += bought

self._inventory_input is the accomulated amount of the input product that was not converted to an output product.

This is why _inventory_input is always increasing. It is because it is the accomulated amount. The name should have been something like _accomulated_input_inventory.

Does this make sense?

[Sota-Sakaguchi]

Thank you very much for your detailed response.
I now understand that inventory_input accumulates the unused input quantity at each step.

That said, what I currently need is not this accumulated value,
but the real-time inventory level at a given point in time.

Is there a way to obtain such inventory information?
Or would I need to manage and compute it on the agent side myself?

[yasserfarouk]

The agent should compute this itself. I think if you just keep track of the previous value of _input_quantity/_output_quantity and subtract it from the new value, you would get the current inventory.

[Sota-Sakaguchi]

I understood everything I want to know.
Thank you for answering.