Using Solver Diagnostics for Run-time Issues and Performance
A model that performs all relevant processing, but then fails to integrate, is said to have a run-time issue. The following are typical run-time error messages observed in models:
cannot evaluate the solution past the initial point, problem may be initially singular or improperly set up
cannot evaluate the solution further right of T, probably a singularity
cannot evaluate the solution further right of T, accuracy goal cannot be achieved with specified 'minstep'
cannot evaluate the solution further right of T, too many step failures, tolerances may be too loose for problem
index-1 and derivative evaluation failure
In the preceding error messages, T is the time value at which the failure occurred.
Use the Solver Diagnostics option to find more information on the source of the problem.
Error messages appear in the diagnostic pane as you run your model. These messages identify the variables that are causing the run-time failure (see the following diagram).
Clicking the message in the diagnostic pane highlights the problem component or components. A second click on the message removes the highlight. When Solver Diagnostics is not selected the simulation fails with the error message cannot evaluate the solution further right of T, probably a singularity.
In addition to adding source detail to error messages, Solver Diagnostics also provides information on the integration performance for variable step methods, specifying which variables had the greatest contribution to the allowable error up to the point of failure, and also provides information on the most recent event (that is, configuration change) just prior to the failure. This information is provided in the console window in collapsible subsections inside the Integrating System section.
The preceding example is for the same model as the diagnostic pane example, and in this case there were no appreciable errors or events up to the point where the failure occurred.
Finally, Solver Diagnostics can be used to assess and improve the performance of a working model, as summary information on error control (for variable step solvers) and events over the entire integration is provided. The following example is from a double-wishbone suspension model integrated over 10 seconds, with only one event at t=1/10sec.
Note that in the error control summary, the dominant error is caused in the computation of the second derivative of the theta value of the DWS.R1 component. The value of 32.77% means that on average, over the course of the calculation, that value was at 32.77% of the requested error tolerance. This information could then be used to change or improve the computation of this value to provide improved performance of the integration.
To use Solver Diagnostics for detailed errors and performance:
In the Main Toolbar, ensure Solver Diagnostics ( ) is selected. Alternatively, in the Simulation Settings tab( ), in the Advanced Simulation section, select Solver Diagnostics.
Click Run Simulation ( ) in the main toolbar. If you are using a snapshot this icon changes to . Alternatively, from the File menu, select Simulate.
Click Diagnostic Information ( ) at the bottom of the MapleSim window to display the diagnostic console.
In the diagnostic pane, do the any of the following:
Expand the Simulation palette to see error messages related to the variables, equations, and components.
Click the Simulation palette to highlight the problem components in the Model Workspace.
Click the Message Console ( ) at the bottom of the MapleSim window to display the console.
Expand the Integrating System section to find the Integration Error Control Summary and Integration Event Summary subsections.
Open those subsections to view the information.
See Also
Advanced Simulation Settings
Debugging Console in Chapter 2 of the MapleSim User's Guide
Pruning a Model
Using Diagnostics
Using Solver Diagnostics for Inconsistent Systems
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