QPR Knowledge Base 2012.1

Enter the Simulation Properties to a Process Step and a Flow in the Model

Enter the Simulation Properties to a Process Step and a Flow in the Model

Previous topic Next topic  

Enter the Simulation Properties to a Process Step and a Flow in the Model

Previous topic Next topic  

Before a simulation can be run, the simulation properties of process steps, flows and stores need to be defined.

 

mouse_24 Exercise 87: Examine the simulation properties of a process step and a flow.

 

BTN_AR131. Open the Simulation Example Model. The simulation properties have already been defined in this model, but to see where they can be defined, we'll take a look at the simulation properties of the starting step and a flow.
BTN_AR132. Right-click the Make Order process step and select Simulation Properties... from the pop-up menu:

pic_popup_simulation_properties

BTN_AR133. Verify that the simulation data is as shown in the picture below:

dlg_simulation_properties_general

There are four options for defining the processing time: Constant, Triangular distribution, Normal distribution, and Custom series:

Constant processing time means that each activation of the process step lasts always for a specified period.

For Triangular Distribution, three values are given: minimum, mean, and maximum. Minimum value is the shortest possible processing time, mean is the most common processing time, and maximum value is the longest possible processing time. The actual processing time for each activation is then calculated according to this distribution:

 

pic_triangular_distribution

For Normal Distribution the mean value and the standard deviation are specified. Standard deviation specifies the width of the deviation, i.e. how much variation there will be between the actual values and the mean value:

pic_normal_distribution

Custom Series can be used to define special patterns for processing time. During the simulation, the processing times in the series are used in the given order and in cycles: when the end of series is encountered the series is started again from the first value.

 

Priority of the process step specifies its importance. The higher the priority the more important the process step is. A checkbox is provided to indicate whether this process step can be suspended while it is active in simulation and resumed later. A process step can suspend other active process steps, which have a lower priority and take the needed resources from them if the resources are not free. The activation of process steps with lower priority will be resumed later, when the needed resources are free again.

 

There has to be one process step or flow, which starts the simulation. This step or flow is usually the first process element of the process. This self-activating process step has its Start simulation checkbox checked. If the checkbox is unchecked, only entry rules and incoming flows can activate the process step. If the process step is self-activating the number of activations has to be defined. The number of activations defines the number of times the process step is activated during the simulation. In addition, the frequency of these activations has to be specified. The same distributions as for the processing time are available also for defining the interval between the activations.

 

BTN_AR134. Switch to the Entry Rules tab. Entry rules are conditions under which the process step will be activated:

dlg_simulation_properties_entry

Process step entry rules define all combinations of incoming flows, which are needed for the activation of a process step. If the entry rule is any incoming flow, any of the incoming flows will activate the process step. The second option is that all the flows have to be present before the process step is activated. Custom rules are combinations of incoming flows, which activate the process step.

 

BTN_AR135. Switch to the Exit Rules tab. The Exit Rules tab specifies how outgoing flows are sent after the activation of the process step:

dlg_simulation_properties_exit

The exit rules page contains two options: All outgoing flows and Custom rule. If the first option is selected, all outgoing flows are sent every time the activation of the process step is ended. Custom rules can be used to model more complex situations. A new rule is created selecting the sent flows from the Outgoing flows list and clicking the right arrow button.

 

BTN_AR136. Currently the probability of both activations are the same, 50%. However, recently the amount of phone orders has decreased, so select the Order by Phone rule and change its probability to 40:

pic_simulation_properties_phoneorderprob40

BTN_AR137. Similarly, change the the probability of the Order by EDI rule to 60.
BTN_AR138. Click OK to close the dialog.

For more information, see the Simulation topic and its subtopics in QPR Modeling Client - User's Guide.