Performance Improvements for Large-Scale Traffic Simulation in MATSim - Computational Approaches for Urban Environments - page 216

agents. The hardware used for this experiment is a Sun Fire X4600 M2, with 16
cores (8 dual core CPUs) and 128 GB of memory. Due to the large number of
simulations, not all runs could be repeated multiple times. To give a sense of the
variability of the JDEQSim results for a similar JDEQSim run over 50 iterations,
the standard deviation for the computation time amounted to 13 % of its mean value
(for micro-simulation and event handling).

9.4.1.2 Runtime: Micro-simulation and Event Handling

In the first experiment, the runtime of the three micro-simulations is compared using
nine configurations, where also the number of threads used is varied (see Fig. 9.4 ).
Configurations include runs with and without parallel event handling (abbreviated
as PEH in Fig. 9.4 ). Furthermore, runs with and without the EventWriterTXT event
handler are conducted (abbreviated as EWT in Fig. 9.4 ).
Both JDEQSim and JQueueSim runs with a single thread use the default event
handling, while runs with more than one thread use parallel event handling. For
example, the JDEQSim run with two threads uses one thread for the micro-
simulation and one for parallel event handling. In the DEQSim runs, first the
micro-simulation is run using the indicated number of threads, thereafter the events
are written to a file and read in by the nonparallel version of the event handler for
further processing.
The number of threads usable in the different configurations cannot be chosen
arbitrarily: The number of threads “ n ” which can be used by DEQSim is constrained
to n D 2 i ,where i 0. This is due to the network partitioning algorithm used. For
JDEQSim, the maximum number of usable threads in the presented scenario is
five without EWT and six with EWT. In these cases one thread is used for the

JQueueSim: without PEH, with
EWT
JQueueSim: without PEH,
without EWT
JQueueSim: with PEH and EWT

4:00

3:30

3:00

2:30

2:00

JQueueSim: with PEH, without
EWT
JDEQSim: without PEH, with
EWT
JDEQSim: without PEH,
without EWT
JDEQSim: with PEH and EWT

1:30

1:00

0:30

0:00

0 2 4 6 8

Number of CPUs

Fig. 9.4 The computation time for the three micro-simulations as a function of number of threads