pyjevsim 1.3.1

A DEVS(Discrete Event System Specification) Modeling & Simulation environment with journaling functionality

pyjevsim

Introduction

pyjevsim is a DEVS(discrete event system specification) environment that provides journaling functionality. It provides the ability to snapshot and restore models or simulation engines. It's compatible with Python versions 3.10+.

For more information, see the documentation. : pyjevsim

Installing

You can install pyjevsim via

git clone https://github.com/eventsim/pyjevsim

Dependencies

The only dependency required by pyjevsim is dill ~= 0.3.6 for model serialization and restoration.
dill is an essential library for serializing models and simulation states and can be installed via.

pip install dill

Optional Dependencies

pytest is an optional dependency required for running test cases and example executions. You can install pyjevsim via

pip install pytest

Additionally, you can install all necessary libraries, including optional dependencies, by running the following command:

pip install -r requirements.txt

Working with pyjevsim

Once you have installed the library, you can begin working with it.

Quick Start

The docs describe how to configure a simulation via pyjevsim's BehaviorModel and SysExecutor. Check out the documentation to configure your simulation.

Example

There is a banksim example that uses pyjevsim's DEVS functionality and journaling features. documentation

Execution Modes

SysExecutor supports three execution modes via ExecutionType:

Mode	Description
V_TIME	Virtual time — simulation runs as fast as possible
R_TIME	Real time — simulation paces itself to wall-clock time
HLA_TIME	HLA/RTI-controlled time — time advancement is driven externally

from pyjevsim.system_executor import SysExecutor
from pyjevsim.definition import ExecutionType

se = SysExecutor(1, ex_mode=ExecutionType.V_TIME)

Multi-threading Support

SysExecutor provides thread-safe APIs for multi-threaded simulation environments where external threads inject events while the simulation runs.

Pause / Resume

Pause the simulation to allow external threads to accumulate events, then resume.

se.pause_sim()    # Pauses the simulation loop
# External threads can safely call insert_external_event() while paused
se.resume_sim()   # Resumes the simulation loop

External Event Injection

Insert events from external threads into the simulation. Thread-safe via internal synchronization.

se.insert_external_event("port_name", message, scheduled_time=0)

Output Event Callback

Register a callback to be notified when output events are generated, avoiding polling.

se.set_output_event_callback(lambda: print("output ready"))
events = se.handle_external_output_event()

HLA/RTI Integration (HLA_TIME Mode)

For HLA/RTI-controlled simulations, use HLA_TIME mode with step() and get_next_event_time().

se = SysExecutor(1, ex_mode=ExecutionType.HLA_TIME)
se.register_entity(model)
se.init_sim()

# RTI-driven loop
while not se.is_terminated():
    next_time = se.get_next_event_time()
    # ... request time advance from RTI, wait for grant ...
    granted_time = ...  # time granted by RTI
    output_events = se.step(granted_time)
    # ... publish output_events to RTI ...

step(granted_time)

Executes one simulation step up to the granted time. Returns output events generated during the step.

get_next_event_time()

Returns the earliest scheduled event time (internal or external). Used to determine the Time Advance Request value for the RTI.

Graceful Termination

se.terminate_simulation()  # Sets SIMULATION_TERMINATED state
se.is_terminated()         # Returns True if terminated

Signal handlers (SIGTERM, SIGINT) automatically invoke terminate_simulation() on all registered SysExecutor instances.

License

Author: Changbeom Choi (@cbchoi)
Copyright (c) 2014-2020 Handong Global University
Copyright (c) 2021-2024 Hanbat National University
License: MIT. The full license text is available at:

• https://github.com/eventsim/pyjevsim/blob/main/LICENSE