Difference between revisions of "Running Your Model"

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(Clock Settings)
(Run Buttons)
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==Run Buttons==
 
==Run Buttons==
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Once you have built a model in Nova, you can run it by clicking '''Capture''' → '''Load''' → '''Exec.''' Let’s break it down and see what each of these buttons does.
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;Capture: This button “captures” the structure from the components of the model you’ve built and turns it into a NovaScript program.
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;Load: Clicking '''Load''' loads the information captured from the model and prepares it to run.
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;Exec: Clicking '''Exec''' executes the run command on the model. You will be unable to select '''Exec''' until you have first selected '''Capture''' and '''Load.'''
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;Init: You can also run the model by clicking '''Capture''' → '''Load''' → '''Init.''' '''Init''' initializes the simulation run. After you’ve selected '''Init,''' you can either select '''Run''' to run the model at the selected speed, or click '''Step''' to run the model one time-step at a time.
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When you are in timeline mode, you can use the '''Back''' button to go back exactly one time step.
  
 
==Timeline==
 
==Timeline==

Revision as of 21:21, 10 January 2015

This section describes how you run a model built with Nova's visual interface.

Clock Settings

Once you have built a model but before you can run it as a simulation, you must first set the clock parameters. The clock settings consist of the following 4 parameters:

  • Start The time (in model time) when the simulation starts (this is usually 0).
  • End The time (in model time) when the simulation ends.
  • Dt The unit of increment (in model time) for updates.
  • Integration Method The mathematical algorithm used to update Stocks and Variables.

Nova currently uses an abstract unit of time ("model time") that serves as the equivalent of some model-dependent real time unit (seconds, minutes, hours, days, years).

Dt, the increment, or "delta t", value, is the amount of time that elapses between State updates. For discrete models this is usually 1 (see below), but can be any value (0.1, 0.01, 0.05, 2, 20).

Nova supports 3 different integration methods

Euler
Current state values are used in computations to determine the next state. Used for all discrete models.
RK2, RK4
These Runge-Kutta algorithms treat Stocks and Variables as continuous functions and reduce the error by subdividing the update interval. Simulations run slower but with more accuracy. RK4 is the preferred option of the two.
Discrete
This is not actually an integration method; rather it sets Dt to 1 and uses the Euler method. The result is a sequence of State values rather than an attempt to approximate a continuous function.

Run Buttons

Once you have built a model in Nova, you can run it by clicking CaptureLoadExec. Let’s break it down and see what each of these buttons does.

Capture
This button “captures” the structure from the components of the model you’ve built and turns it into a NovaScript program.
Load
Clicking Load loads the information captured from the model and prepares it to run.
Exec
Clicking Exec executes the run command on the model. You will be unable to select Exec until you have first selected Capture and Load.
Init
You can also run the model by clicking CaptureLoadInit. Init initializes the simulation run. After you’ve selected Init, you can either select Run to run the model at the selected speed, or click Step to run the model one time-step at a time.

When you are in timeline mode, you can use the Back button to go back exactly one time step.

Timeline

Automode

IMode