Running a Monte Carlo simulation in Tamara | Vose Software

Running a Monte Carlo simulation in Tamara

To run a Monte Carlo simulation of your project schedule, navigate to the Simulation Settings tab:

Enter the number of Monte Carlo samples that Tamara will run. 10,000 is a typical number, and is the default.

Check the Use Manual Seed box if you want the simulation to use a particular seed value, and enter the seed value to be used. It is generally good practice to do this, as it means that one can exactly reproduce the same simulation values for the same model by using the same seed value. The seed value can be any integer between 1 and 2,147,483,647. It is best to use an easily remembered number like 1, 10, 100, etc. By default, Use Manual Seed is checked, and a Seed Value of 1 is provided. The seed value used will be shown in any generated report.

Check the Calculate Costs box if you want simulations of costs. If unchecked, Tamara will only simulate the time component of the schedule which will be faster.

If costs are included, select how you wish costs to be presented in the results graphs and tables. Tamara assumes all entered costs are in units of the applicable currency (not, for example, in thousands of dollars).

In the Application Settings dialog, select the number of CPUs to use. Tamara will run on multiple CPUs. Most computers have 4 or 8 CPUs. The speed that Tamara runs its simulation is in proportion to the number of CPUs selected.  By default, Tamara detects the number of CPUs available on your computer and uses them all to maximize the speed of simulation. If you have a very large model (many thousand tasks), Tamara may take a minute or two to run the simulation, so if you need to use your computer in the meantime, reduce the CPUs used by one or two.

Now run the simulation. To do so, simply click on the Results tab. This will automatically initiate a Monte Carlo simulation. The results will appear almost instantly unless you have a very large schedule. Small models of 100-200 tasks, which are often adequate to get a good understanding of the schedule uncertainty, will take less than a second to complete 10,000 samples and graph the results. The progress bar at the bottom left of the Tamara screen shows how much of the simulation run has been completed, though for small schedules this will just be a flicker.

Tamara is many times faster than any other schedule risk analysis tool, and it is sometimes difficult for an observer to believe that it has actually run a simulation. You can illustrate this by looking at the extreme tail of the results histogram, then change the seed value, and click the results tab again. The tail will be a slightly different shape, showing that a new simulation has been run.