Ventana software support forum

Yes, that is my question. How to open two instances of Vensim at the same time?

That's useful, Thanks Tony. Is it also possible to open two or more models at the same time so that I can run them simultaneously?

Hi,

I could open two or more Vensim models in Windows 7, but cannot do that in Windows 8. Any suggestion!?

Thanks,

Junaid

Just a clarification: Runga Kutta 4 Auto is showing almost the same results that Euler is showing with time-step = 9e-6 and 5e-6.

For the Euler method, it is normally said that the shorter the time-step, the more accurate the simulation. In my model, I need a very short time-step (= 9e-6); otherwise, the stocks go negative. By chance, I realised that a variable "[O2] LP" was going slightly negative (= -3e-11; see Fig...

Thanks, Tom! Now it makes sense. I think the manual is too wordy and unclear. Someone needs to put such codes on the payoff computation page (http://www.vensim.com/documentation/ind ... ?23570.htm) in the manual.

Cheers,

Junaid

Hi, Your explanation of weights makes a lot of sense; thank you! I'm here concerned with calibration payoffs and am still confused about them. (I know what a payoff element is, and I need to specify that. But what is the payoff from which the squared weighted difference between the model and the mea...

Hi, From the manual, I can't figure out how assigning weights and payoff elements work. Here is what the manual says: "At each TIME STEP the data for variables to be compared is checked to see if a value is available. If it is available, the difference between the data and the model variable is...

Thank you, Tony, for your informative reply. Click "Windows->Pop Output forward". This will bring all your output forward. I tried that, and it does what I want. Still, I think it'd be much easier to see a 'pin' button or sign right above the graph. It can also read vertical data. I didn't...

No, the data set was not listed there. Listing the file with a new name there has solved the problem; thank you!

Vensim DSS 6.1c 1) I terribly miss the iThink/Stella feature to be able to easily change the scales of graphs and see the Y-axis value just by a single mouse-click. I also miss pinning the graphs onto the screen. Why doesn't the lock button lock (pin) the graph? It just disappears as soon as you cli...

Vensim DSS 6.1c Hi, I once imported data from an Excel file and changed the default name of the generated file from sheet1.vdf to Data_Set.vdf. Now whenever I import Excel data for the same model, of course, the process generates a vdf file with another name. But as I run the model, it gives this er...

I contacted HP chat support as I am using HP EliteBook. The technician asked me to perform the following procedure which solved the problem: Step 1: Click Start, click Run, type msconfig, and then click OK. The System Configuration Utility dialog box is displayed. Step 2: Configure selective startup...

Hi Tom,

Please find the model attached. I am trying to simulate it on another machine as well. I will let you know if it works alright there.

Thanks,

Junaid

Hi Tom,

I am having problems here with every set of parameters I have run so far. Can you please have a look at the document attached? I pasted a couple of print-screens in that.

Thanks,

Junaid

I just compared two runs, one with the "Net O2 Sampling Loss" equation like this: ( O2 in Headspace * Dilution - O2 Sampling Injection ) / Sampling Duration * SUM ( PULSE (Sampling at Time[Sampling Times Subscript!], Sampling Duration ) ) and the other modifying the equation to eliminate t...

Please simulate the attached model and have a look at the graphs it generates. You’d find broken curves in the graphs, and if you try to maximize a graph, even the previously visible curves would start disappearing. I think a bigger time step is causing this problem, but changing it to a higher valu...

This was very helpful, indeed. I've managed to get what I wanted. Thank you very much, Tom!

Thank you for looking into this issue, Tom. Yes, I am after a time series of pulses, but an irregular one. I previously thought to use the pulse function in the way you have suggested, i.e., adding up a number of pulses. However, I have around 40 pulses, which means that I would need 40 different va...

I looked into the help example and I tried to follow how you used it, but I am still unable to understand how this function works. subsc : (sub1-sub3) // What does this line mean? Is "subsc" another variable? What is "sub1-sub3" representing? Sampling at Time[subsc] = TABBED ARRA...

Hi, I have copied and pasted values from an Excel sheet but still this function does not work. I am using it exactly like this in Vensim Professional: TABBED ARRAY( 24 26 27 ) I am using these 24, 26, and 27 values as the time parameter for PULSE function, i.e., 200 * PULSE (Tabbed_Array, 5). I am a...

Thanks for this; I will try that one. I am interested to get the time value when O2 consumption reaches half of its maximum rate for the very first time.

No, the data is not being imported from Excel, instead the variable "O2 Consumption Rate" is calculated by the model.

Hi, I am having the following problem and would highly appreciate if someone may come up with some solution: I want to get the value of time when a variable is exactly half of its maximum value. For getting half of the maximum value, I guess I would use: GET DATA MAX (O2 Consumption Rate, INITIAL TI...