Monte Carlo Simulation option unavailable in product system calculation properties window

Question

I'm trying to perform a Monte Carlo Simulation with a process built in the USLCI database, but the calculation window won't allow it as an option.
I added uncertainty to flows in the process by importing the Ciroth et al data quality system for flows. Then I use the pedigree matrix to create an uncertainty distribution.
When I create a product system and click on "Calculate," the option to perform a Monte Carlo is unavailable (grey text).
How do I get the calculation setup to allow MC simulations? Am I missing a step somewhere? I'm more familiar with ecoinvent where the functionality is built in, so maybe there's some edit I need to make to the USLCI database.
For reference on versions: openLCA 2.3.0, USLCI 1.2024-10.0

Comments

I'm also running into an issue with this and troubleshooting. At this moment, I suspect that there's a problem somewhere in the model graph (like an output flow connected to the input of the same process). As a starting point you might try building out the product system using only default providers.

I'm guessing openLCA is finding the issue with the product system though and disabling Monte Carlo. Any way for us to see what flows/processes might be causing the issue?

Answer 1

Hello mrmlca,

Unfortunately, the Monte Carlo simulation is not available when using libraries at the moment. We are currently working on it and hope to include it in upcoming releases.

Regards,

François

Comments

Thanks Francois! For anyone who runs into this issue and comes to this thread, you can consider using an older version of USLCI (2024 Q1 and earlier) since libraries were implemented in 2024 Q2.

Answer 2

Hi, can you post a screenshot? The MC simulation is agnostic to the database, in case there is no uncertainty there are no results, but the option is still offered. See here for our version of the LCA Commons database.

Thank you!

Comments

We've noticed this as well, and are troubleshooting with the user (https://github.com/FLCAC-admin/uslci-content/issues/20)

Do libraries impact whether Monte Carlo is available?

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I'm seeing that in my own test. The second I add a process from a library, the option gets greyed out.