Page 741 - ExtendSim User Guide
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Debugging Tools 715
Measuring performance to debug models
• Plotter blocks, from the Plotter library, conveniently display graphs and tables of data over time. Plotters are useful not only for showing results but for identifying trends and anoma- lies. You can choose what you want plotted and how you want it displayed, and you can use as many plotters in a model as you want. See “Plotters” on page 681 for more information.
• Animationshowstheflowofitemsinamodel,levelsofvalues,etc.ExtendSimblockshave built-in customizable animation; you can also add custom animation using the Animate tabs in block dialogs or by using blocks from the Animation 2D-3D library. Animation is espe- cially useful for verifying a model since it can show if portions of the model are operating as expected. Since animation can slow model performance considerably, it is common that you would use animation in the early stages of model-building or for presentations. See “Anima- tion features for debugging” on page 724 for more information.
• Therearenumerousblocksthatcanbeusedfordebuggingmodelsandverifyingresults.For instance, the Notify block (Value library) can stop the simulation and notify you when its input goes above or below a specified level. The Information block (Item library) provides information about the output of the block it is connected to (the interval between arrival times, how many items are currently present at the output, and so forth).
• Sensitivityanalysisallowsyoutovaryaparameterincrementally,randomly,orinanadhoc manner to determine how sensitive model results are to changes in one variable. See “Sensi- tivity analysis” on page 646 for more information.
• Runningsimulationsmultipletimes,suchasforMonteCarlosimulations,givesrangesof values indicating the possible outcomes for the model. See “Running a model multiple times” on page 600 for more information.
• The Run > Generate Report command, discussed in “Model reporting” on page 725, instructs ExtendSim to generate a text file of the final model results. You can report on all the blocks in a model, or use menu commands to specify which blocks are included in the report. Reports are especially useful for outputting to other applications, such as statistics packages, for further analysis.
• TheStatisticsblock(Valuelibrary)reportsandstatisticallyevaluatesresults.Forexample,it can display information about every queue-type block in the model and calculates the confi- dence intervals based on the results. As discussed in “Clear Statistics” on page 644, the Clear Statistics block resets statistical accumulators at random intervals or in response to a system event; this is used to eliminate statistical bias during the warm-up period.
• TheUtilitieslibrarycontainstwoblocksthatareusefulfordebuggingdiscreteeventmodels. The Record Message block, when connected between two value connectors, shows all of the messages, the values transferred, and whether the message came in the input or output con- nector. The Item Messages block records the message communication between two item connectors. See “Messaging in discrete event models” on page 319 for a detailed discussion of the item-based messaging system.
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