Ventana software support forum

Here's another version of the model that handles the Poisson arrivals/departures as discrete events. One thing to note is that in the original model, the TIME STEP (0.5) was too short given the service time (0.05) - if a queue or level is modeled explicitly, the time step needs to be shorter than th...

Actually you want the .vpm version that I posted here, http://models.metasd.com/2010/04/rental ... -dynamics/

You can run it with the free Vensim Model Reader, which handles things that PLE won't (arrays, advanced functions, ...)

Tom

You might take a look at the handling of the discrete arrivals in the carRental.mdl model in this thread:
http://www.ventanasystems.co.uk/forum/v ... php?t=4076

Tom

Not sure exactly what you mean by not showing your variables, but if your graphs are blank the cause may be that you haven't loaded a dataset (MENU>LOAD_RUN or SPECIAL>LOADRUN) or started a synthesim simulation. Can you describe your problem more fully, or post some code?

Tom

DELAY1 is indeed treated like a macro. Internally, it looks like:

DELAY1=LV/delay time
LV=INTEG(input-DELAY1,input*delay time)

If you switch to DELAY1i and supply an initial value that's outside the simultaneous loop, your structure should work as is.

Can you post the full message? (Do View>As Text then Model>Check Model).

Not entirely sure, but generally the #...# notation indicates a variable that's internal to a macro equation. A few of the built in functions are treated like macros, so it's possible that you're encountering one of those. You could try setting Tools>Options>Settings>Macro variables to "show&qu...

Interesting ... I agree that this would be convenient in some cases, especially where the conversion has a fixed definition, as from English to SI units (feet to meters, for example). Conversions involving time often imply a shift from stock (widget) to flow (widget/time) dimensions, in which case t...

Here are two examples. The first makes parameter changes directly with SETVAL, and the second loads changes in .cin files. If you have 30 models in separate files, you can load them with repeated calls to LOADMODEL. SPECIAL>LOADMODEL|? SIMULATE>DATA|base.vdf,alldata4.vdf,factproddata.vdf,f8xlsdata.v...

I don't know how it works in Powersim, but in general, I think that building unit conversions into equations is not a good practice. It's too easy to introduce inconsistencies or errors, where a unit conversion is used in multiple places. Also, implicit unit conversions often hide an actual uncertai...

Do you still have the original models folder? If not, you can restore it by reinstalling Vensim (I'm guessing that what you downloaded is one of the installer archives, which won't work by itself). When you reinstall, be sure that the option to reset the .ini settings is unchecked, if you want to sa...

Not sure exactly. Is everything in the same folder? The direct cause of the message is that Vensim is unable to open the model in your specified location.

Tom

If you're using an advanced version, you can do search & replace in text view or an external editor, though it may be cumbersome. The free editor Notepad++ has a nice feature (on the TextFX menu) for converting text case; I think it would work well if you want to make blanket changes to your mod...

OK, good luck. If you share more details on what you're trying to accomplish, you might get additional comments.

Tom

Three ways: - right-click on any variable or comment on the model diagram to bring up a settings dialog with font controls - select variables, then use the bottom toolbar buttons (with no variables selected, these change the sketch defaults) - use the Tools>Options... menu to change font defaults Tom

You can write an external function that returns an array. I don't have the documentation in front of me, but I think if you look at the example external function library you'll find an applicable example.

The call from Vensim would probably look like:

val : (v1-v27)
myResult[val] = MYFUNC( ... )

Venapps are in .vcd files, which are just plain text. You can edit them inside Vensim via File>Edit File ... which has the huge advantage of permitting you to switch to sketch view (View>As Sketch) to check/edit the placement of on-screen graphs, buttons, etc. Use the buttons and menu in the bottom ...

1) Check to be sure that you can't solve your problem with the FIND ZERO function. If you need to go the external function route, consider hooking up some external library to do most of the work. I once connected Vensim to LINDO (an LP solver) for a similar purpose. 2) External functions have to be ...

Can't the C example be brought into the latest MSVC? (I haven't tried, but suspect that it's straightforward). Incidentally, MIT's Climate Collaboratorium has posted java code for wrapping the multicontext .dll to serve a model. They're running entirely on Linux with the shared library version of th...

Start Vensim, and choose File>Open Model... Change the file type to "Vensim Application Definitions" Navigate to the sample models (normally in the directory where Vensim is installed), e.g. C:\Program Files\Vensim\models\sample Open Intro.vcd, which is a portal to a variety of sample mode...

One good way to start is to try the various venapp interfaces included in the sample models, find one you like, and start modifying it. It's generally easier to proceed incrementally from something that's working. Another possibility, if you're more comfortable with C, Java, Visual Basic, etc., is t...

Try working through the User's Guide, Chapters 3 & 6 (Hands On Example and Building a Model). These are available in the Help menu.

If you're stuck on something specific, ask a more detailed question?

Tom

Make sure you have a sensitivity graph instance in your toolset (if not, try mine, http://blog.metasd.com/2009/04/setting-up-vensim/ ). Then select the variable you're after (i.e. make it the workbench variable) and use the tool to get results. Sensitivity graphs, stats, and histograms only work on ...

The problem is that the DELAY functions initialize the internal state of the delay (which is basically a chain of a bunch of levels) to a constant rather than some presumed historical profile of the inflow. One solution would be to create an explicit chain of levels, which you could then initialize ...

Ahh, OK. Then your IF THEN ELSE should work. If not, it could be due to roundoff error: if Time isn't exactly equal to 3, the equation will fail, even though 3.0001 might be close enough from your perspective. As an alternative, you can do one of two things: IF THEN ELSE( time > AqTime-TIME STEP/2 :...