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I am receiving a relatively large number of errors when I run my Monte Carlo assessment, all or most of which have the following form (image below):

Examining the parameters mentioned in this log entry I see no issues (i.e. all the formulas are evaluating appropriately). A little more background, the Monte Carlo proceeds and I get a result. When I create a new product system for specific processes that call these parameters (within my larger product system), every simulation beyond the first one produces an identical result. 

A few questions:

  • Any general suggestions on errors of this form would be useful.
  • Can you recommend any specific resources for interpreting and resolving Errors catalogued in the console? For example, the error defines locations such as "line 1, column 40 at line 1". To what is this referring and can it be used to resolve errors?
  • Is there a script or other command that I can use to export a copy of all parameter values for for each simulation within a monte carlo run? I would like to see if certain parameters are not evaluating and maybe trace that back to a source.

My apologies if I am missing something simple. Thank you in advance for your help!

in openLCA by (190 points)

1 Answer

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by (115k points)

The screenshot is somewhat hard to read (you could also copy as text, e.g., that would be easier) but I think I see sth like "evaluation of expression NO2ground failed". These errors should be fixed. You can see all incorrect formulas (and other issues in the database) by running a database validation, and can then jump to the listed incorrect formulas directly.

Common mistakes are commas instead of dots for decimal separators, but also typos in parameter names, or missing parameters that are input somewhere. The parameters are a bit tricky since the formula field is just text, and parsed afterwards, which means that you can initially enter also incorrect formulas. You see this though in the process by switching from formula view to amount view, the amount view shows then 0:

(entering independent and dependent parameter)

(entering in the process amounts)

(formula is evaluated and an incorrect formula is flagged but you can proceed)

From the formula view to the values view

and vice versa. So with the incorrect formula:

I hope this helps!

Best wishes,


by (160 points)
Thank you, that's very helpful!
I also solved the issue now by making all of my parameters global. Seems like the program couldn't handle local parameters, even though they were fixed values without any uncertainty assigned to them.