Sample model “SAMPLE IF TRUE” not working

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Fred
Junior Member
Posts: 2
Joined: Sun Feb 28, 2021 4:27 pm
Vensim version: PLE

Sample model “SAMPLE IF TRUE” not working

Post by Fred »

Hi everyone,

I would like to run this sample model:
http://vensim.com/documentation/Models/ ... 20TRUE.mdl

However, I receive a warning after running the model:
“WARNING: ACTIVE INITIAL differences found. Use Options>Setting to control reporting. “
I tried to find the settings to control the reporting. Could anyone of you please help me finding it?

1.
This post was not helpful, because the toolbar/menu struture changed (my assumption).
viewtopic.php?t=5477

2.
I found something similar, the “active initial” settings here:
Model –> Settings: In the bottom section “Active Initial”
Sadly, changing “Relative” and “Absolute” does not change anything or reduce the number of warnings.

I know, that SAMPLE IF TRUE following the documentation is not meant to be available in PLE.
Maybe my inability to switch of the warning is connected to that?

Thanks a lot for your help. It’s highly appreciated!

Fred
tomfid
Administrator
Posts: 3252
Joined: Wed May 24, 2006 4:54 am

Re: Sample model “SAMPLE IF TRUE” not working

Post by tomfid »

The warning happens because there's a different draw from the random number generator in the initialization step and the first time step. That changes the random value of workforce used to initialize the sampling. In a more normal deterministic model, that wouldn't happen.
Fred
Junior Member
Posts: 2
Joined: Sun Feb 28, 2021 4:27 pm
Vensim version: PLE

Re: Sample model “SAMPLE IF TRUE” not working

Post by Fred »

Hello Tom,

I assumed that the error in the sample model and my model were the same. But they are not. Still you helped me discover the error in my model.
Even though my error is not connected to the function RANDOM UNIFORM(m,x,s) which is used in the sample model.

My model does not use the function RANDOM UNIFORM(m,x,s). But in my model within the function SAMPLE IF TRUE (condition, input, initial value), the inital value was not equal to the input value at the time step t=0. So the warning indicated that the model was not 100% consistent at that point in time. I simply adjusted the defintion of the initial value - now it works like a charm.

Thanks for your quick answer!

Fred
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