Thank you so much for your answer Jakob!
To answer your question (Just
for clarity: are you comparing simulation runs with different values of --seed?):
Yes,
that's exactly what I was trying to do.
With
your suggestion, I was able to see the randomness that I was looking for!
Thanks!
1) sigma (for the default carFollowModel) controls random slow-downs. Vehicles drive slower than their preferred/optimum speed in any given situation. This leads to a "ragged" look of the speed curve even in free flow conditions. In contrast, speedDev
controls the deviation of preferred speed. This set a fixed random speedFactor value for each vehicle so in the absense of sigma each vehicle would drive with a constant speed in free flow but each vehicle would do this at a different speed.
2) departure time is only affected directly if option --random-depart-offset is set. You may see some effects from sigma and speedDev due to departDelay-interactions at high density though. Vehilce type drawing should be affected though.
Just for clarity: are you comparing simulation runs with different values of --seed?
Am Mi., 3. März 2021 um 20:10 Uhr schrieb Bae, Jong In <
[hidden email]>:
Hello,
I've been working on using random seed and had some questions. I'm having trouble seeing the difference between before and after I assigned a random seed value.
I attached a screenshot of my sumocfg file just in case my syntax is incorrect.
- How is sigma different than speedDev?
- According to this link (https://sumo.dlr.de/docs/Simulation/Randomness.html#random_number_generation_rng),
I should be seeing randomness in loading vehicles.
To my understanding, I should expect to see randomness in the following two areas: (1) the entry time when vehicles enter the scenario should be different and (2) the sequence in vehicle type in vTypeDistribution should be different.
However, I am not seeing any difference in the vehicles' entry time or the sequence in vehicle type in vTypeDistribution. But I am seeing randomness in speed (tested with only one vehicle also). So I think the random seed is in effect. I'm just not sure why
I am not seeing randomness in the two areas mentioned above.
Thank you so much for the help!
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