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 <[email protected]>: > 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. > > 1. How is sigma different than speedDev? > 2. 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! > > _______________________________________________ > sumo-user mailing list > [email protected] > To unsubscribe from this list, visit > https://www.eclipse.org/mailman/listinfo/sumo-user >
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