[sumo-user] Using random seed

classic Classic list List threaded Threaded
3 messages Options
Reply | Threaded
Open this post in threaded view
|

[sumo-user] Using random seed

Bae, Jong In
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
[hidden email]
To unsubscribe from this list, visit https://www.eclipse.org/mailman/listinfo/sumo-user

sumocfg.PNG (25K) Download Attachment
Reply | Threaded
Open this post in threaded view
|

Re: [sumo-user] Using random seed

Jakob Erdmann
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.
  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
[hidden email]
To unsubscribe from this list, visit https://www.eclipse.org/mailman/listinfo/sumo-user

_______________________________________________
sumo-user mailing list
[hidden email]
To unsubscribe from this list, visit https://www.eclipse.org/mailman/listinfo/sumo-user
Reply | Threaded
Open this post in threaded view
|

Re: [sumo-user] Using random seed

Bae, Jong In
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!

From: sumo-user <[hidden email]> on behalf of Jakob Erdmann <[hidden email]>
Sent: Thursday, March 4, 2021 2:05 AM
To: Sumo project User discussions <[hidden email]>
Subject: Re: [sumo-user] Using random seed
 
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.
  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
[hidden email]
To unsubscribe from this list, visit https://www.eclipse.org/mailman/listinfo/sumo-user

_______________________________________________
sumo-user mailing list
[hidden email]
To unsubscribe from this list, visit https://www.eclipse.org/mailman/listinfo/sumo-user