Ventana software support forum

Ventity also does data.

It starts with PLE+, though if you want to do much with the data (e.g., calibration optimization) you really want Pro or DSS.
https://vensim.com/comparison-chart-for ... gurations/

For visual comparison, I think there is one option: the Reference Mode tool. However, if you want your data to drive the model behavior, the lookup is it.

We'll look into it. In the meantime, if you have any detail about the circumstances, you can shoot us an email at vensim at vensim.com - if they arrive roughly concurrently, we'll know what's what.

Ah ... try this ...

However, this is an area of active development, using the shortest independent loop set methodology originated by Kampmann and developed by a number of others in the SD literature.

Also, when the input becomes nonzero, should there be an immediate pulse, or should the pulses be restricted to a particular time (for example, always in month 6 of the year)?

Is the input going to go from 0 to nonzero in a single step, or vary on/off over time?

I'm not sure there are any Modelica experts around here, but it can't hurt to ask. It's hard to give general advice though because tools are so different. For example, I suspect that little to none of the Vensim advice here https://metasd.com/2011/01/optimizing-vensim-models/ would be relevant. The ...

I think what you have is correct. Since there are 2 distinct processes, it might be cleaner to have 2 stocks, but this works.

Part of the challenge here is that the standard description of the LV model is nicely physical, but challenging to parameterize. For example: pred births = params*predator*prey in typical SD practice might be written as pred births = predator*fractional birth rate fractional birth rate = reference b...

Nice to see a model with balanced units. Generally to debug a problem like this, there are two things that are very helpful: - Use synthesim overrides to freeze one or more of the stocks at a constant value; then you can more easily see how other things respond - Use the table tool to walk through t...

Sounds like an installer issue. Manually move the dll to \program files\ ?

This should work fine. Any chance the stock of cow, or birth rate, is 0 at time 6, when the first pulse should occur?

You may be right, and it may depend whether zoom is set to "fit" or a definite value. I'll check.

The helper threads actually do increment the seed. However, this only affects selection of the starting points, because the Powell algorithm is deterministic. There's one exception: XPAR occasionally tests crossover directions, which convey information from one thread to another, and the crossover s...

The third argument is the inflow that prevailed over the duration of the delay prior to INITIAL TIME. I think the behavior you're seeing is correct. In your middle case, STEP(reference shipping rate,0) will return 1 at initial time, so the delay contains 20 days*1 unit/day of stuff. Your 'total arri...

I think we need more information.

GET XLS CONSTANTS is not for time varying variables. For that you need GET XLS DATA.

There are sample models for the GET functions in the help system (normally these install to c:\users\public\vensim on Windows).

I agree that this would be useful. Another issue is that the target is sometimes hidden, which means you get a blank selection box. At present I suspect this would interfere with the scroll/zoom settings for views. I find that I'm often searching for a variable that appears on several views, and I w...

I'll have to think back about what changed for VECTOR ELM MAP; I think we had to change something for correct equation sequencing, but it was way back.

What we probably should have for situations like this is a set of linear program-based functions. In addition to the situation you describe, I can think of several others that could be handled by an LP: - multiple suppliers and demanders of a commodity product, but with a [supplier,demander] matrix ...

I think MARKET MATCH may have issues. Probably the best way to do this at present is with FIND ZERO. I think I have an example.

Computational cost will depend on size of the dimensions, but if it's only 5ish, it shouldn't be problematic.

There are two seeds: - One for the algorithm, set in the voc file - One for the simulation, set in NOISE SEED or some other user variable, used in the RANDOM functions I'm guessing that you want to vary the second one? One possibility would be to use GET TIME VALUE to randomize. https://www.vensim.c...

This is similar to creating a prior on a parameter value. 1. Create a variable something like: ab constraint = INITIAL( excess a penalty*MAX(0,a-b)^2 ) whether this should be positive or negative, and the scale, depends on whether you are maximizing or minimizing the rest of your payoff. 2. Add this...

1. XPAR does ignore restart max at present. XPAR basically gets you one optimum as quickly as possible. If you want to explore multiple optima, RPAR is more efficient. 2. For RPAR I tend to leave RESTART_MAX unset (0) and just let it run until I'm tired of waiting. The performance of the search will...