Unable to converge simultaneous loop

[roul]

Hello,

After running the simulation there are errors: Unable to converge simultaneous loop at time; and the floating point overflow error. Despite looking through the forum for a solution, I could not find one. Could you please explain how to solve the simultaneous loop time problem? And why does my "evaporation" variable report division by zero/overflow? Meanwhile, how do I execute the command "Partial Model Simulation"? Many thanks.

My Operating system: MacOS M1; Software Version: Vensim@ Professional Version 10.1.2 (Apple Silicon).

[Administrator]

You'll need to upload your model for us to be able to help.

It's rare that you even need to use this function, my guess is you have some sort of formulation problem.

[roul]

Hello, here is my model sample, many thanks.

[Administrator]

Have you been through any of the Vensim tutorials? I would start with the PLE tutorial at the following page,
http://www.public.asu.edu/~kirkwood/sysdyn/SDRes.htm

This will get you to the point where you can build a basic model. Once you've done this, I'd start again.

[roul]

Have you been through any of the Vensim tutorials? I would start with the PLE tutorial at the following page,
http://www.public.asu.edu/~kirkwood/sysdyn/SDRes.htm

This will get you to the point where you can build a basic model. Once you've done this, I'd start again.

Thank you for your response. I've studied the parts on "Business Process Analysis Workshops: System Dynamics Models" and "System Dynamics Methods: A Quick Introduction." I can use this information to develop and run a basic model using a few simple calculations. But what I'd like to ask is still why the sample model (it’s a part of my full model) I provided doesn't work. How should this situation be handled (unable to converge simultaneous loop at time and correct floating point error)?

[Administrator]

You've got some very basic errors in model formulation which is why I suggested going through the tutorial.

"Total surface water" should be a stock/level which increases via "Natural rainfall" and decreases via "evaporation". "Evaporation rate" is 36.9 (but this is dimensionless, so what is 36.9, it should be measured in litres/day or some other meaningful unit. "Natural rainfall" is also dimensionless (it's not in reality).

This model should not use the SIMULTANEOUS function at all. I don't think I've ever used it in a model.

I strongly suggest that you do a basic tutorial before you try doing something like this. These are very basic errors.