If you installed the sample models, you will have a utility named stel2ven.exe that converts Stella and ithink format files to Vensim format.
Vensim does not support the same graphical representations used in Stella and you must therefore save your Stella model as equations. These equations can then be transferred as a text file to the computer using Vensim. You will need a file transfer or disk copying utility to do this. Once this is done the utility stel2ven can be applied, giving the input name and desired output name as in
stel2ven software.stl software.vmf
On the Macintosh you can double click on Stel2Ven and then select the file you want to convert. Once you have done this you will be prompted for more input. Type the name of the output file and any options you want to use.
Vensim will add default run control parameters (INITIAL_TIME, TIME_STEP, FINAL_TIME, and SAVEPER) to the converted model but you may need to modify these. You can use the Sketch tool to reintroduce graphical information and modify structure graphically.
For Stella models the comments and units fields will be left blank. For ithink models saved with comments, the comments will be read into the Vensim comment field. This process will fail if the comment contains equation-like material (especially an = sign), so some additional hand correction may be necessary.
The units field of the Vensim model will be left blank.
Note that ithink equations are not definitive representations of model structure. Because of this the translation of these models may not be accurate. If you are using ovens, conveyers, uniflows, levels forced positive or any other non equation structural elements you will need to review the translation very carefully.
The translation program does provide two switches that attempt to modify level equations to conform to some forms commonly used in ithink models.
-u forces all rates to be positive (uniflows).
-p keeps all Levels positive no matter what.
Use these switches with care. It is preferable to perform a direct translation and make adjustments as necessary.
The file stella.mac contains macro definitions for functions used in Stella that are not directly supported in Vensim.
NOTEVensim checks for and reports problems such as divide by zero, logarithms of negative numbers, and overflows. If these conditions exist in your model they will need to be corrected before you can fully utilize the translated model.
