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Optimization : Setting Up and Running an Optimization Model : Create a Post-optimization Ruleset
Create a Post-optimization Ruleset
RiverWare will automatically generate a Post-optimization Ruleset if there is no ruleset loaded when switching from the Optimization controller to the Rulebased Simulation controller upon completing a run with the Optimization controller. The automatically generated ruleset contains rules to set each reservoir Outflow slot to the Outflow value from the Optimization solution.
Reservoir.Outflow[] = OptValue(Reservoir.Outflow, @”t”)
See Automatically Generated Ruleset for details about the automatically generated ruleset.
In many cases it is necessary to customize the Post-optimization Ruleset to do more than simply set reservoir Outflows to the Optimization values. Some common uses for a custom ruleset might be:
• A need to set Turbine Release and Spill independently based on their Optimization values rather than just total Outflow.
• If other water uses, such as diversions, need to be specified in the RBS based on the Optimization solution.
• To refine the Optimization solution further in the Post-optimization RBS, possibly to make small adjustments to the flows once outputs have been calculated with the approximation errors removed.
• To add post-processing calculations to the Post-optimization rules.
A useful approach for creating a custom Post-optimization Ruleset is to begin with the automatically generated set. Then revise the rules as needed using the basic structure of the automatically generated set.
While the Post-optimization Ruleset is a special case of a ruleset used specifically in the context of an Optimization run, from a technically perspective, it is the same as any RBS Ruleset. As such it can contain any components that might be in a standard RBS Ruleset. For example, there is nothing to technically prevent the Post-optimization Ruleset from completely overwriting the Optimization solution. It is the use of the OptValue function when setting the slot in the ruleset that ties to the Post-optimization Rulebased Simulation to the Optimization solution. The Post-optimization Ruleset can make use of as much or as little of the Optimization solution as desired as long as it adheres to all standard requirements for a RBS Ruleset.
That being said, the standard approach is to have rules set flows based on the Optimization solution and let RiverWare calculate all remaining values in Simulation. When using this standard approach, it is strongly recommend to write the rules such that they maintain the overall mass balance from the Optimization solution. This is because the feasibility of the Optimization solution is dependent on the mass balance used in the Optimization solution. In addition the satisfaction of policies such as Pool Elevation constraints in the Optimization solution is dependent on the mass balance.
As an example, Post-optimization Rules that adjust the solution by making shifts between Spill and Turbine Release but use the same total Outflow as the Optimization solution would maintain the mass balance from the Optimization solution. Whereas rules that modified the total Outflow from the Optimization solution would alter the mass balance. In the later case, it would be possible to have a run where the Storage exceeded the limits in the Elevation Volume Table in the Post-optimization Rulebased Simulation, causing the run to abort, even though it was within the required limits in the Optimization solution (or less severely violate elevation constraint limits in the Post-optimization Rulebased Simulation when they were satisfied in the Optimization solution). Of course it is possible to include logic in the rules to check for these issues, but the more this type of logic is included in the ruleset, the more the solution will tend to deviate from the Optimization solution and become more of a Rulebased Simulation solution. Depending on the intended use of the model, this may or may not be acceptable.
Once a custom Post-optimization Ruleset has been created, it can be saved as a separate file just like a standard RBS Ruleset by selecting File, then Save RBS Ruleset As from the Ruleset Editor dialog and/or it can be saved in the model file. Once a Ruleset has been saved with the model file, then the next time the model is opened, the Ruleset will automatically be opened and loaded. To save the Ruleset with the model file it must first be loaded. Then on the Run Control dialog select View, then Rulebased Simulation Run Parameters. In the resulting dialog, check the box for Save Loaded RPL Set with Model. Close the dialog, and save the model with the Ruleset now included.
Revised: 08/02/2021