Hi
I have made a simple single server single queue model in Flexsim 2017 Enterprise licensed version. All the inputs have been correctly entered.
But I am getting the same output everytime I run the model. When I used to run models in earlier versions I used to get different output for every simulation run. However, now it is showing constant results.
Input used is:
Source: Exponential dist. 0,60
Queue: 20
Server: Lognormal distribution. 31,3.1,0.5
Run time - 18000
Kindly help.
This is by design. Your model should run the same way every time if you don't change anything. This makes it possible to debug your model when it's not doing what you want it to. This extends to the experimenter too. Each replication should run exactly the same each time you run the experimenter. This way you can choose a specific replication and run it in your model (using the same scenario variables and random stream numbers) when you need to debug or you want to see how a replication produced a certain result.
If you need more data you can increase the number of replications.
There is a way to stop the model repeating random streams (Statistics > Repeat Random Streams), but in general we don't recommend this as it makes it nearly impossible to debug models.
In Staistics Option, you can uncheck 'Repeat random streams' to get different answers.
Which is correct in simulation - getting same output for multiple runs or different output for multiple runs?
Kindly clarify.
@YEOLE SHIVRAJ NARAYAN, the "Repeat Random Streams" option is very useful when you are building your model. By getting reproducible output, it makes it easier to debug the model for yourself and for others. When you run multiple replications of the model in order to calculate statistics such as mean and standard deviation, you obviously want different results. When you use the Experimenter feature to do this, you will automatically get different random streams on every replication, but when you run the model manually, you need to disable the feature in the Statistics menu as @Visakh Sakulan showed.
So FlexSim uses a different random stream for each replication in than experiment. When you repeat an experiment with no changes in the model, will FlexSim use the same random number streams that it used in the first experiment?
@YEOLE SHIVRAJ NARAYAN, As far as I know there is nothing wrong in getting same answers, we run the model with different random number streams to test the model.
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