Ventana software support forum

Hi Tony
Thanks for the reply. Actually its a single *.txt file which is updated in each time step. It seems that I have to use external function but couldn't figure it out. Do you have any advice for me?

Thanks again

Hi Tony
Thanks for the quick response. However, Vensim manual dosent't have much information that I am asking for.
In every time step I will get a text file and need to read those in matrix format while simulation is going on . What do you think?

Hi
I have a text file, which contains around 40 parameter value for each timestep. My intension is to read those data at every timestep during the simulation period. If anyone can help me to findout, how to read those data in Vensim from the Matrix format.

Best
Khaled

Thanks bob for your kind reply. However, I followed your advice to run Vensim as administrator but I am still having the same trouble. Then I created a new VENSIM.DLL file and checked in my older PC which works fine, but it's not working in my new machine. So, there could be 2 issues as per my view:...

Thanks Bob
In the old mechine it works fine. However, I just followed all your instructions to resolve the issue with my new PC but still I am having the same problem. Any more idea or suggestion?

Yes, I am. I then copied this dll file to another location (thinking that it may not be able to access the root directory) and changed the path, but the same message is appearing! Any suggestion?

The message that I am getting, "? The external functions in I:\VENSIM.DLL -could not be loaded. Do you want to try loading again next time?"

I tried with clean & reform option but it's not working.

Hi, I just faced another problem regarding external function. Previously my external function was working fine. However, I just transfered all my files to my new PC (Windows7, 64 bit). I coppied the actual VENSIM.DLL file and then mentioned the path in 'startup', but I am not able to see my external...

Thanks a lot.

Thanks Bob.
Finally I am able to implement autocalibration. Could you please let me know, how can I make my "width" time dependent, so that I can have a nice fitting?

Hi I am trying to implement auto-calibration within Vensim. I have observed data in vensim environment. My intension is to make the calibration parameter (in this case calibration parameter is "width" and I am trying to match my "stock" with "observed”) time dependent. I loo...

Thanks a lot.

I am just wondering, does anybody know how to carryout matrix multiplication in Vensim, without writing the whole equation manually?

Yes, I am using Vensim5.10a DSS. I am having problem in writing anything within the vensim external function. It's not same as writing in C++, as I need to know the correct place to insert that code. If possible, can I please have a *.DLL file which can export data from Vensim to a text or xls file,...

Thanks tomfid,
If any body has already done it, then please let me have a chance to look at your external library.

Hi tomfid. Thanks for your response. All the parameters that are entering in to the optimization are mostly unit less. We are using some kind of conversion factor for each of them. Some variables are related to energy price of different sources, energy reserve, emission and etc. Yes, the solution I ...

HI Thanks for your advice. I think, I don't have any unit error. In response to you second point (reducing size), I would say that I am unable to reduce the number of variables. Regadring the bigger time step, I am in bit problem, as rest of the model needs small calculation time step to avoid insta...

I want to export, part of my model result (continuously) to a text/Excel file, in every step of my calculation, so that value can be used by another program. I know how to export data after the simulation, but I need to know how to do the same thing during the simulation period. Can anybody please h...

Hi Bob Thanks for your advice. Actually I tested that model with double precision in both 5.3a and 5.10a and I am getting better result in Vensim 5.10a. My question was what are the changes/up gradation you made in version 5.10a, so that it can perform better? However, even with version 5.10a, I can...

Hi, I just remember that in case of 'L', I used a multiplying factor 6, so that the model can be simulated at least for few time steps. If I remove this factor then the model is not able to run even a single timestep. Surprisingly, I was able to run the model for entire simulation period in Vensim 1...

This one is not using previous value as an initial guess for the next time step.

Hi Tomfid So far I know, matlab's ‘fsolve’ (non-linear equation solver) is something called a 'trust-region dogleg'. The algorithm approximates the function with a piecewise linear polygon. I should thank Bob, as he helped me helped me to use FIND ZERO function. Unfortunately, I couldn't get much in...

Sorry tomfid, I should say thanks to you , as you responded many of my quries. Unfortunately, I mentioned you as Bob in several times today. Sorry about that

Hi Bob Actually its a typing error (Vensimfloder ), while I was composing mail to you, but the model is fine. Thanks for this correction. I need to do simulation and optimization at the same time for my research work. Initiall I tried to do the optimization with the external facilities of Vensim but...

Thanks Bob for your quick response. Actually I created 'vensimfolder' to install both Vensim DSS and Model Reader. Is it OK?