faq 156237825

Simulation with large scale population file

by Yueshuai He on 2018-01-18 17:20:44

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Dear professor,

I'm trying to run a simulation on subway system of New York City. I used the road network with 5 boroughs of NYC and a population file with 2 million agents. It took me 3 days for one iteration. I'm wondering is this situation normal? I attached my config file. Thank you!

Best,

Yueshuai

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Comments: 3

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Re: Simulation with large scale population file

by harisbal on 2018-01-19 17:23:52

Hi He,

I suppose the developers will need your computer's specs to give you an answer although 2 million agents is indeed a big number.

Can I add a relevant question on top of yours? I would like to ask whether it makes sense that the " [PlanRouter] handled plan # xxxx " phase takes the most time for each iteration (I have around 400,000 agents with innovation switched on). The handling of plans seems to take longer event that the mobsim itself, is that normal?

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Re: Simulation with large scale population file

by Kai Nagel on 2018-01-20 02:36:19

With public transit, it is indeed the public transit router that takes much/most of the time. Re the original question: In the zeroth iteration, all pt plans need to be routed. In subsequent iterations, it is only (depending on your settings) about 10% of pt plans so it should be accordingly faster.

Also, if you take 0.plans.xml.gz from ITERS/it.0, you can use this as initial plans file for subsequent runs, and since there the pt will already be routed, the zeroth iteration will be much faster.

Having said this, I would still recommend to debug all this with a 1 percent sample of your population. 1pct is not enough for credible pt results, but it is enough to debug functionality. People tell me that they get plausible pt results with 25pct samples; that would still buy you a factor of 4 of computing speed.

A faster pt router should be technically possible; see the raptor and the connection scan methods in the recent literature. There are several attempts under way to come up with a faster pt router for matsim. So far, none of these has made it far enough to become at least beta status.

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Re: Simulation with large scale population file

by Yueshuai He on 2018-02-08 21:28:58

Thank you for your answers! I tried with 0.plans.xml.gz and it became much faster.