...
Insight is eWater’s multiple-objective optimisation decision support framework. This framework allows for more efficient evaluation of planning options than the traditional manual trial and error approach that is often used. In other words, the main aim of Insight is to optimise decision rules for all multiple objectives. The framework allows optimisation across single or multiple scenarios. The optimisation tool enables a more thorough examination of potential planning scenarios and the resulting trade-offs between desired outcomes.
...
- What the key drivers are likely to be (relevance);
- Which parameter in the model represents the decision variable;
- The number of decision variables, and the consequence of multiple decision variables;
- Are they discrete or continuous (“real” numbers)?; and
- What are realistic ranges? Are there any constraints on the likely acceptable range for the decision variables?
...
Objectives
Mathematically known as objective functions, these can contain multiple parts, such as measure of cost, a measure of environmental impact and a measure of social costs. Examples of objective functions might include: minimising the operating cost of the system, minimising environmental impacts, or minimising time spent in water restrictions, or minimising time spent in water restrictions. In Insight objective funcitons must be expressed as minimisation problems. Maximisation problems can be optimised by expressing the objective function as a negative.
When choosing objectives, it is important to consider:
...
- A Source scenario containing decision variables and objectives expressed as Source functions;
- Access to the Source command line tool;
- An Insight settings file (containing the Source project location, objectives and decision variables);
- The number of generations; and
- The population size of each generation.
The decision variables and objectives must be defined in the Source project as global expressionsfunctions. Insight can then run the Source model thousands of times, setting different values for the decision variable expressions and evaluating the corresponding objectives for every individual run.
This means that in order for a Source parameter to be included in an optimisation problem, that parameter needs to be defined using the Function manager in Source.
...
- File » Load Settings - Load settings that were previously configured and saved (optional);
- File » Save Settings - Saves the current run settings;
- File » Load results - Loads the results of a previously saved optimisation run (optional);
- File » Save results - Save the results of the current optimisation run; and
- File » Exit - Quits Insight.
...
| Info |
|---|
Note: Prior to using Insight, ensure that you have created and saved a Source project containing all Source projects contain only one scenario only. |
Setting up an optimisation run/Creating a settings file
- Open Insight and click Browse (as shown in Figure 1) to choose the directory containing the project(s). Projects can also be in subdirectories below the directory pointed to;
- Click Load to populate the left panel with all the objective available functions that were created defined in the loaded projects;
- For each of the panels on the right, use the appropriate button to add or remove objectives functions or decision variables from the main objectives function list to the individual panel. For example, click Add objective » to add an objective function to the Objectives panel. Moreover, to move a discrete decision variable back to the main list of objective functions, click « Remove discrete decision variable.
- In the Objectives panel, the Multi-project Aggregation Method drop-down menu allows you to choose how you want to aggregate the individual time-step results. The Aggregate over full timeseries checkbox allows you to choose how to setup the objectives. If enabled, the objective needs to be set up so that all values of the global expression are used (via the selected statistical function) to give the objective value. If not, the last value of the global expression gives the objective value. You can also remove an objective from the Objectives panel by choosing it from the list and clicking . This will move the objective back to the main objectives list.
- Choose the number of generations and the population size of each generation. These parameters define how many simulation runs are performed by the optimiser. The required values will depend on the complexity of the optimisation project. If the number of runs is too small, the optimiser will not be given sufficient time to search for the multi-objective optimal set of results.
- Specify whether to run the optimisation on your local machine (enable the Run Source optimisation locally radio button), or across server endpoints (using the Run Source optimisation on endpoints radio button). Server endpoints allow you to run the optimisation across several machines simultaneously. Load the endpoints settings file by clicking Load Endpoints and point Insight to the appropriate file. If running Source optimisation on a local machine, set the number of cores to use with the Local server limit scroll button. The number of cores to use depends on the machine you will are using.
- Save your settings using File » Save Settings. This creates a settings file, which can be used later.
...