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A more formal specification of the cost calculation is:
| Equation 1 |  |
|---|
Recall that negative costs are incentives. Accordingly, in this table, the greatest incentive is to retain any water in the bottom-most 10% of the capacity of the storage (for carry-over to the next time-step), followed by the water in the next 40% of the capacity of the storage. By interleaving base costs and increment values, releases from multiple storages can be controlled quite precisely to maintain a desired balance.
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Table 1. Storage breakpoints (data file format)
| Row | Column (comma-separated) | |
|---|---|---|
| 1 | 2 | |
| 1 | Carry over number | Active storage (%) |
| 2..n | n | point |
where:
n is an integer in the range 1..n representing the carry-over number.
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Table 2. Storage cost functions (example)
| Storage Carryover Arc | Storage 1 | Storage 2 | ||
|---|---|---|---|---|
| Base Cost | -11000 | Base Cost | -11001 | |
| Increment | 2 | Increment | 2 | |
| Storage % | Arc Cost | Storage % | Arc Cost | |
| 1 | 5.6 | -11000 | 7.4 | –11001 |
| 2 | 11.1 | -10998 | 14.8 | –10999 |
| 3 | 16.7 | –10996 | 22.2 | –10997 |
| 4 | 22.2 | –10994 | 29.6 | –10995 |
| 5 | 27.8 | –10992 | 37.0 | –10993 |
| 6 | 33.3 | –10990 | 44.4 | –10991 |
| 7 | 38.9 | –10988 | 51.9 | –10989 |
| 8 | 44.4 | –10986 | 59.3 | –10987 |
| 9 | 50.0 | –10984 | 66.7 | –10985 |
| 10 | 100.0 | –10982 | 100.0 | –10983 |
The result of the design intention is shown in Figure 3. Note that, in the absence of any inflows that replenish the storages, the X-axis can also be interpreted as expressing time.
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Table 3. Storage targets (data file format)
Row | Column (comma-separated) | |
|---|---|---|
| 1 | 2..13 | |
| 1 | Storage | month |
| 2..n | sname | cname |
Where
month is the first three characters of the month of the year (eg “Feb”)
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Table 4. Demand priorities (data file format)
| Row | Column (comma-separated) | ||
|---|---|---|---|
| 1 | 2 | 3 | |
| 1 | Demand | Priority | Computation Sequence |
| 2..n | sname | pri | seq |
where:
sname is the name of the supply point
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Table 5. Shortfall arc costs (example)
| Scenario | Supply point | Priority | Computation sequence | Shortfall arc | Satisfaction order | |
|---|---|---|---|---|---|---|
| Number | Cost | |||||
| A | 1 | 1 | 1 | 1 | 11000002 | 2 |
| 2 | 11000004 | 4 | ||||
| 3 | 11000006 | 6 | ||||
| 4 | 11000008 | 8 | ||||
| 2 | 1 | 2 | 1 | 11000001 | 1 | |
| 2 | 11000003 | 3 | ||||
| 3 | 11000005 | 5 | ||||
| 4 | 11000007 | 7 | ||||
| B | 1 | 1 | 2 | 1 | 11000001 | 1 |
| 2 | 11000003 | 3 | ||||
| 3 | 11000005 | 5 | ||||
| 4 | 11000007 | 7 | ||||
| 2 | 1 | 1 | 1 | 11000002 | 2 | |
| 2 | 11000004 | 4 | ||||
| 3 | 11000006 | 6 | ||||
| 4 | 11000008 | 8 | ||||
| C | 1 | 2 | 1 | 1 | 11000001 | 1 |
| 2 | 11000002 | 2 | ||||
| 3 | 11000003 | 3 | ||||
| 4 | 11000004 | 4 | ||||
| 2 | 1 | 1 | 1 | 11000005 | 5 | |
| 2 | 11000006 | 6 | ||||
| 3 | 11000007 | 7 | ||||
| 4 | 11000008 | 8 | ||||
NetLP ordering at nodes
In Source, networks are composed of arcs which have maximum capacities and costs associated with them. These costs can either be positive (disincentive) or negative (incentive). The optimum flow for each arc is determined by the netLP so that water will flow along the least cost pathway.
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| Info | ||
|---|---|---|
| ||
| Note: Ensure that the forecast supply is greater than the total order size. If this is not the case, the following error message will occur at the first node that this occurs at: Forecast supply greater than total order size in interpretation of network LP. Try checking inflow forecasts at inflow nodes, and that all confluence inputs are defined to be regulated. |
Inspecting an arc-node network (simple)
Troubleshooting It is possible to inspect textual representations of visualise the arc-node networks that are generated by Source for processing by the solver. The steps are:
- Select the active scenario in the Project Hierarchy (Project Explorer);
- Locate the Arc-Node Network entry in the Model Parameters list (also Project Explorer) and enable it for recording;
- Run the scenario; and
- In the Values column of the Recording Manager (Complex time series, summary), locate and open View Multiple Supply Path Setup. The window will be similar to Figure 6.
Figure 6 is a work in progress so most of the labels are inaccurate. The graph provides a measure of computational complexity (iterations to solve) at each time-step. Note that the peaks are clipped to the value of the Maximum Iterations parameter in this dialog.
Figure 6. Inspecting the generated arc-node model
Clicking any point in the time line causes a textual representation of the arc-node model for that time-step to be displayed in the upper part of the window. The text can be selected and placed on the clipboard for re-use.
Note that it is beyond the scope of this guide to explain the format of the arc-node model dump.
Inspecting an arc-node network (advanced)
It is also possible to visualise the arc-node networks that are generated by Source. However, you will first need to download and install a third-party software package called Graphviz. The home page for this application is:
Choose the current stable release in preference to any development snapshots. Consult your Windows system administrator if you need help installing Graphviz.
To enable debugging and visualisation support in Source:
- Choose Edit » Ordering Algorithm...;
- Enable Export iterations;
- If your model operates over a large number of time-steps, you may wish to restrict the date-range for which arc-node output is produced using the Start and End date controls in this dialog; and
- Click OK.
Next, run your model. Enabling Export iterations creates a folder on your Desktop with a name in the pattern:
MspNetworkOutput-yyyy-mm-dd
At the end of a run, this folder will contain three files per time-step:
- A visual representation (.DOT) of the arc-node network suitable for display in Graphviz;
- A textual representation of the arc-node network; and
- A textual representation of the test case for that time-step.
| Info | ||
|---|---|---|
| ||
| Note: You should avoid double-clicking files with a .DOT extension. You may find that files with a .DOT extension will launch Microsoft Word rather than Graphviz. |
To visualise an arc-node network for a given time-step:
- Use the Windows Start menu to launch Gvedit, which is part of Graphviz;
- Choose File » Open and select the .DOT file of interest. Gvedit will respond by opening a textual representation of the arc-node network as shown in the central window in Figure 7; and
- Click the Run button on the Gvedit toolbar (Figure 7).
Figure 7. Gvedit (opening an arc-node network)
Graphviz always generates a graphical representation of your arc-node network in two forms. One is displayed on your screen and the other is saved as a file. By default, the version saved as a file is in .GIF format but you can change this using the Output File Type pop-up menu in Figure 8. Note that Graphviz can also generate high-resolution vector-based representations such as .SVG.
By default, the file is saved in the same folder as the original .DOT file. You can change this by clicking the ellipsis button (...) to the right of the Output File Name field in Figure 8.
Figure 8. Graphviz settings dialog
Once the settings have been configured to your requirements, click OK. Figure 9 is an excerpt from an arc-node network diagram produced by Graphviz. The elements inside the blue rectangle correspond with a Splitter node in the original Source schematic.
Figure 9. NetLP arc-node network for Splitter node
by Source using third party software. For more information please see: Troubleshooting and Debugging