Experimenting with Your Simulation

In this months newsletter we are looking at how to carry out our experiments in SIMUL8, and how to maximize efficiency when we run simulations.

Run Your Simulations using Parallel Processing

Full Size Image

SIMUL8’s parallel processing feature dramatically reduces the time to get results from simulation trials. It allows you to spread the runs of your simulation model between two or more networked computers where you have installed SIMUL8. The PCs use only spare CPU cycles so the user of the PC does not notice that SIMUL8 is using the processor to help get results.

This feature is particularly useful for simulations that run for a long period of time, or when the number of replications in a trial is high. If you have 100 PCs available you can do a 100 run trial in 100 th of the normal time.

To set parallel processing up on your network, firstly go into the Preferences settings (File\Preferences). Click on the results tab and check the box that says “Let my PC help SIMUL8 on other PCs get fast results”. You need to do this on all of the networked machines that you want the runs to be shared over. You also need to specify a location on the network that all these PCs can access for use by SIMUL8 internally (for example \\myserver\sharedtemporaryfiles\SIMUL8parallel). This needs to be the same physical location for all of the PCs. (Note – this folder should exist, but you should not store your simulations or any other files in this folder. It is for SIMUL8 to use during the run only).

Any SIMUL8 installed on your network will remember this information and be ready to help out any other SIMUL8 even when it is closed.

To use the feature in a particular simulation trial, just check the “Use Parallel Processors” check box.

Once this is checked all trials (from here or from the quick trials buttons) will use any available spare processing power on PCs that have been set up on the LAN.

If you want to know how to do the File/Preferences set up automatically on all PCs contact support and we’ll give you the details.

If you want your simulation to be faster (with or without parallel) remember to look at our newsletter on Faster Simulation.

The parallel feature works with SIMUL8 Standard and Professional, but not with SIMUL8 Viewer.

And don’t worry about other people’s simulation models taking your processing power while you are trying to work – SIMUL8 will run in the background so you won’t even notice it is running!

Scenario Runner

The Scenario Runner is a powerful feature that allows you to run different scenarios with the same model one after the other. The Scenario Runner also manages Trials and collates all results together ready for export via a text file.

The Scenario Runner interface consists of a table to record the decision variables and values that you want to experiment with, and some control buttons for running the scenarios.

Decision Factors:

Decision Factors are the entities within your simulation that you wish to experiment with. For example, variable values, properties of SIMUL8 Objects, values of spreadsheet cells etc.

The Value field allows you to put in a selection of values that you want to test. For example, you might want to test having between 1 and 4 resources available. You would therefore type "1-4" in the value field next to the decision factor "Resource.Max Available". When you run the scenarios, SIMUL8 will run the simulation first with 1 resources, then with 2, then with 3 and so on. As well as values running in scales, you can also select specific values to test. For example, for Storage area Max Size, you might want to increment the values by 10 each time. So you would type the values 10,20,30,40,50 separated by commas into the value cell next to the decision factor Storage Area 1.Max Size.

You can add as many values as you like, and as many Decision Factors as you like. The real power of this feature comes when you run the scenarios. SIMUL8 will run every combination of decision factor value.

If, for example, you are testing the number of resources available from 1 to 10, and the number of work centers available from 1 to 10, SIMUL8 would run 100 times. If you wanted to run trials of 10 runs each, SIMUL8 would then run 1000 times.

Results Method:

In the results method section you can specify whether you want to run trials of single runs. If you select trials, SIMUL8 uses the number of runs in a trial as specified in Trials>Conduct Trials.

Results Export:

In the results export section you can specify a text file to export the results to. If you leave this field blank, SIMUL8 will create a text file called "scenario_results.txt" which will pop up at the end of the scenario run. You can then save this file in the usual way to a location on your computer.

The "include Decision Values in report" check box allows you to choose whether or not to display the values of the decision factors in the text file. This might be useful if you are looking at a wide range of values, or running a high number of replications.

Background Execution:

The background execution option allows the user to run SIMUL8 as a low priority, i.e. in the background. For example, you might want to go off and work in another application while the scenario runner is running, but sometimes other applications can seem slow when your computer is running a long simulation. This option makes SIMUL8 run as a low priority application, but does not have a huge impact on the time it takes to complete the runs.

The button "Generate Scenarios Sheet" opens up a spreadsheet containing all combinations of runs that SIMUL8 is going to make based on the entries in the Decision Factors table. This allows you to remove any runs that you are not interested in - for example particular combinations of values.

Clicking the button "Get Results from Scenarios Sheet" will run the scenarios listed in the Scenarios sheet and export the results to a text file once it has finished.

Clicking the button "Get Results for all Combinations" will run the scenarios according to the Decision Factors table rather than the Scenarios list - therefore if you decide you want all of the results after having removed scenarios from the Scenarios sheet then you still have access to them.

Free Downloads

Our website is always being updated with new support resources. Here are details on some of the downloads that were added this month.

A new service pack for SIMUL8 2006 Build 1222 has been released.
Download the Service Pack | Full Details of What's in the Service Pack

If you have any questions generated from, or comments about this newsletter then email Newsletter@SIMUL8.com