We all love SD for the clarity it brings with small to medium scale models sometimes refered to as 'insight models'. If SD is to survive in business consulting - it seems to still remain a mostly academic endeavor - it should not flinch from detail rich problems due to memory limitations. For example one of the more recent issues of the SD review dealt with SD in the domain of transportation modeling which naturally introduces spatial complexity next to that defined in time. While Vensim already surpases the restrictions of say PowerSim Studio (6 subscripts and only 500.000 elements per variable, as far as I know) models in some areas can become very complex. What has started out as a way to make complexity tractable on computers in the 60s and 70s (aggregated stock and flow simulation) tends to become a liability nowadays when one builds bigger models using subscripts. I would like to propose a much more mundane improvement: Go with the time and make Vensim a 64bit application. directly reading numerical values from graphs, improvements with reality checks (JJ: they are indeed very worthy to keep) and so on. Many of the improvements that have been mentioned here are right on the spot and would make life with Vensim more enjoyable: e.g. This way only the specific constraint gets checked and one is sure that the run saved concerns that specific check. I avoid the problem by not using a test input and writing the same equation in the test input of each constraints. If one uses the same test input with different constraints and if one wants to test one specific RC, even if one highlights the sim active button, all the constraints concerned that have the same test inputs are checked at the same time. Second problem still with reality checks. But it is rather cumbersome even if one hides all the alias variables. If one changes the value of the constant, the variable constant_name_var is kept and all the values are show on a graph or table. I generally solve the problem by creating a new variable constant_name_var = constant_name. In synthesim if one save the run all the values taken by the constant are saved and shown. It would be better that in this case, all the values taken by the constant be shown as it is done with the synthesim if one overrides a constant with a specific non constant value. This is rather annoying if you want to know exactly the values taken by the constant. I have two other problems that I would like to adress if possible.įirst: if one forces a constant to a determined behavior in a test input of the reality checks by example: constant = RC decay(constant,decay time,rc start time) with decay time = 3 months and rc start time = 10 months for instance and if you run the check highlighting only the check you want to test to save the run, the value that takes the constant is not saved and generally you get only one value instead of a value for each period. The important thing for me is that the reality checks tools remain available in new future releases, as it seems surprisingly very seldom used. It is possible that in the future it may generate new unsatisfied needs about the software. With the new method which is based on reality checks, I am forced to use Vensim very differently, use new tools that I did not use precedently or use old tools differently. With the old diagram based methods, I think that Vensim is a very mature product and I had no technical problems. I have totally changed the way I build, use and analyse Vensim models very recently. The best solution would be to have available a table option right in the RC control panel or at least to have the numerical values of the graph available. It is possible to get the value but one must define a new RC with the right side of the constraint as a test input of the new RC which is very cumbersome. The only thing that one sees about that right side is on a graph. In particular when one chooses to test a specific RC with the sim active option, the results of the run is saved, but unfortunately not the value at the right side of the contraints. The RC control panel gives the possibility to view graphs but unfortunately it would be often useful to have the exact value of the graphs. I have too the same kind of problem using reality checks. Karan has a good idea about the graph showing the exact values.
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