# Starting the Simulation

## Goals of this lesson

• More detailed insight into the starting procedure of the simulation

• Knowledge of the concept of stochastic seed

## How-to

• Prior to starting the simulation, the basic settings have to be considered.

• Click on the free space in the drawing board

 Ensure that the Property Set Simulation is selected.
• Now the Properties window shows general simulation properties.

• Let’s have a look at the Must-Have Properties first.

### Two different views

There are two possibilities to access the general simulation properties, but both are only available if you made sure that the Property Set Simulation is selected.

1. Click on the free space in the drawing board (See the first picture).

2. Click the Simulation tab at the top of IYOPRO (See the second picture).

Figure 1. General Simulation Properties
Figure 2. Another View of the General Simulation Properties

### Explanation

Both views contain the same information and options, although the simulation buttons (Diagram and Project) are only available in the latter view.

Anyways, in both views you can set a Start Date and the simulation’s duration or stop time (click the button beneath the Distribution caption. You should go on and prolong the duration, and then check how the report’s statistics have changed. Choosing the "right" simulation duration is crucial to the informative value of the report. Of course this "right" duration is depending on your purposes. Generally: The more the simulation’s duration is increased the more the report’s significance increases. But it obviously does not make sense to increase the simulation’s duration, if the circumstances in the reality will not allow it.

### Stochastic Seed

We use the concept of stochastic seeds for the simulation being able to reproduce the results of experiments. The stochastic seed is a basic value for all stochastic distributed values in the simulation from where the random numbers are generated. Running the same experiment twice without changing any parameters will result in two identical results. By changing the stochastic seed between two simulation runs (and by keeping all other parameters unchanged), the results will be different. You can set the Stochastic Seed as an integer in the Must-Have Properties. You should just try it and then compare the reports. It is indispensable to run multiple simulations on a model, each with different general seeds.

### Local Stochastic Seed

Additional Information: You can assign an individual stochastic seed for every stochastic distribution. The individual seed is independent of the general seed. For example, giving the distribution of the second activity of Model 1a an individual seed will result in the same values taken from the distribution in every simulation, even though the general seed could have changed.

Please have a look at the section General Simulation Properties for more information on the other properties.

To start the simulation in IYOPRO you will either have to click the (green) button or the button in the simulation tab of the IYOPRO tab bar.