Run a simulation

Once the system is set up and data is loaded to the database, SimSyn simulations are initialized and run in four simple steps:

1. Connect one or multiple database tables by specifying respective database parameters.
2. Browse for a VENSIM model and load it to SimSyn.
3. Add data link(s) and define their use as ‘Time Series’ (TSL) or ‘Subscript’ (SDL). Time may optionally be defined for Time-dependent subscripting links (see 'Time (optional)' in Fig. 3).
4. Run the simulation.

Fig. 3. SimSyn Interface

In the example above (see Fig. 3) a model of teacher’s unemployment is loaded to SimSyn. The table column ‘num’ of database table named ‘num_students’ is linked as subscript to a VENSIM model variable named students_overall. In this way, 100 simulations (one for every row in column ‘num’) were run. Simulation outputs are written to the same database. The output table name is ‘sim_out’ per default.

The use of multiple data links is exemplified in Neuwirth (2017).

Re-run simulations

The output table ‘sim_out’ is overwritten by subsequent simulation runs. SimSyn prompts users to push the ‘Reset Button’ to clear outputs of a previous run. Alternatively the output table may be deleted manually in PostgreSQL using the following line in the SQL query window of pgAdmin III.

DROP TABLE sim_out;

In order to avoid overwriting, the export of ‘sim_out’ to file is recommended (see also Query outputs).