The 窶彜imulation view窶 is mainly used when you want to run a simulation on a model. This view is very similar to the 窶廸ode table view窶. The only difference is that in the 窶彜imulation view窶 you have access to some additional parameters used during the simulations. These are found at the upper region of the window.
Simulation sets
DynRisk lets you run simulations at any level of a model. You can in fact run simulations on arbitrary sets of nodes.
To create a simulation set, make sure that all the nodes you want to include in the set, are represented in a folder, either by their 窶彳go窶 node or by an alias. Since you may create as many aliases you like of a single ego node, you can define as many simulation sets you like as well. Simply create a folder for each set, and create aliases for each of the nodes in the sets inside their respective folders.
A simulation on a simulation set, can be divided into two different 窶徘hases窶:
窶「 Main simulation
窶「 Crit. simulation
However, a particular simulation may be set up such that only one of the phases actually occurs.
The main simulation phase occurs if the following is satisfied:
1) The 窶# Main simul. runs窶 field contains a positive integer.
2) At least one node has one or more of its 窶彜im.窶, 窶廚rit.窶 and 窶彜ens.窶 attributes turned 窶徙n窶.
The crit. simulation phase occurs if the following is satisfied:
1) The 窶# Crit. simul. runs窶 field contains a positive integer.
2) At least one node has one or more of its 窶廚rit.窶 and 窶彜ens.窶 attributes turned 窶徙n窶.
3) You have selected a 窶廨oal node窶 for the simulation set.
Although it is possible to run a simulation consisting only of the crit. simulation phase, this is not recommended. The reason for this, is that the crit. simulation phase ideally needs some statistics from the main simulation phase to achieve acceptable numerical precision.
It is perfectly OK to run simulations consisting of only the main simulation phase, though. In fact you will probably do this more often than you run complete two-phase sessions. To quickly exclude the crit. simulation phase, simply unselect the 窶廨oal node窶. This is done by clicking the 窶廨oal node窶 field while none of the nodes are selected. Similarly, to quickly include the crit. simulation phase again, simply reselect the 窶廨oal node窶.
During a simulation, the output values of those nodes in the simulation set which have their 窶彜im.窶 attribute switched 窶徙n窶, are stored in a result file. Furthermore, if you include the crit. simulation phase, DynRisk will estimate criticality and sensitivity for the nodes in the simulation set according to their 窶廚rit.窶 and 窶彜ens.窶 attributes. Thus, by choosing a particular simulation set, you focus your attention on this set, at least for the moment.
Note that if you switch off the 窶彜im.窶, 窶廚rit.窶 and 窶彜ens.窶 attributes of a node in a simulation set, this node is no longer a member of this simulation set, even though it is represented in the folder. It is sometimes useful to be able to temporarily leave out nodes of the simulation set this way without having to move the nodes out of the folder.
Note that if a node is selected as 窶廨oal node窶, its 窶彜im.窶 attribute is automatically switched 窶徙n窶, and locked in this position. Furthermore, the 窶廚rit.窶 and 窶彜ens.窶 attributes are automatically switched 窶徙ff窶, and locked as well. Note also that events can never be included in simulation sets.
In order to simulate the nodes in the simulation set, we need to calculate all direct and indirect predecessors to these nodes as well. When you run a simulation on a set of nodes, DynRisk starts out with the chosen simulation set, and then traces all the paths of edges from the nodes in the set, and backwards through the model. Each node encountered in this process either belongs to the simulation set itself, or is a direct or indirect predecessor of a node in the set. When all the edge paths are traced, DynRisk has a complete list of all nodes it needs to calculate during the simulations of the chosen simulation set.
If a simulation set contains all 窶彳nd窶 nodes in a model, the resulting list of traced nodes, may in fact contain every node in the model. In other cases, a simulation set can be calculated by including just a small subset of the entire node set. Anyway, DynRisk takes care of the model tracing for you, so you can rest assured that the simulations will be done using a minimal but yet sufficiently large set of nodes.
To understand the purpose of a simulation set, it is important to understand the difference between the simulation set and the set of traced nodes. The simulation set implicitly determines the usually much larger set of traced nodes. By selecting a simulation set, instead of specifying the set of traced nodes, we save a lot of work. Moreover, if we later restructure our model, the old simulation sets will still work just fine, while the set of traced nodes may change a lot. In fact if we delete a node from the model which used to belong to a simulation set, DynRisk will automatically remove it from this set for us.
The only time we may want to update the simulation set, is when we decide to include yet another node in the set, or when we want to exclude a node from the set. Such decisions are very easy to make just by examining the simulation set itself.