monte carlo, slow for small n + datasets?

[lugasraka]

Hello, I'm trying to test the uncertainty feature by running a simple MC, but the ab freezes if I set up n = 100 or even 1000 for 1 dataset from Ecoinvent (landfill disposal). Is it normal and that's why the n = 10 by default? How do I circumvent this to run an MC with large iterations?

[dgdekoning]

It is somewhat normal yes, the calculation setup (X functional units * Y impact categories) is completely recalculated for each Z iteration.

A possible way to circumvent this issue if you're only after the calculation results would be to use the underlying brightway framework to run the calculations. This will likely lead to a slight speed improvement at the cost of requiring some additional work to set up all the calculations.

[lugasraka]

Hello @dgdekoning alright! If I have created a calculation set up in AB, would it be automatically created also in BW2?

[dgdekoning]

Yes! Things such as calculation setups, databases, methods and parameters that are persistent in the AB (i.e. still exist after closing and reopening the AB) are managed by brightway.

Please see this for additional explanation and documentation of brightway2 functionality.

[bsteubing]

Hello @lugasraka it is indeed expected (although still much faster than in other LCA software). I will close this issue, but thanks for your question.

[lugasraka]

Hello @bsteubing yes thanks for the clarification! I also look forward to the wikipage if there's one coming up 👍