cimba 0.3.0

Python bindings for Cimba, a multithreaded discrete-event-simulation C library

Cimba Python

Fast discrete event simulation for Python

Cimba Python is a Python interface to Cimba, a multithreaded discrete event simulation engine written in C and assembly.

It is designed for Python simulation models that need more speed than pure Python event scheduling can usually provide. In the included M/M/1 benchmark, Cimba Python runs about 27-33x faster than SimPy after its one-time Numba compile, while keeping model code in Python.

On an AMD Ryzen 7 9700X under WSL Ubuntu 24.04, averaged over 10 runs:

Benchmark	SimPy	Cimba Python	Cimba C
Single core, single trial	2.612 s	0.096 s	0.083 s
Multicore, 100 trials	36.807 s	1.131 s	0.970 s

The benchmark data and charts are in benchmark/AMD_Ryzen_7_9700X_WSL.ods.

Install

pip install cimba

or with uv:

uv add cimba

Python 3.13 or newer is required. The wheel embeds the Cimba C library, so you do not need to install Cimba separately.

What is it?

Cimba Python gives Python models access to Cimba's native simulation engine through the cimba.sim API: processes, event queues, buffers, queues, stores, priority queues, resources, resource pools, conditions, timers, events, random distributions, logging helpers, and experiment tables.

What does the code look like?

import cimba.sim as sim


class MM1(sim.Model):
    utilization: sim.Param
    avg_queue_length: sim.Output
    queue: sim.Queue


model = MM1("MM1")


@model.process
def arrival(env: MM1):
    while True:
        sim.hold(sim.exponential(1.0 / env.utilization))
        sim.put(env.queue, 1)


@model.process
def service(env: MM1):
    while True:
        sim.get(env.queue, 1)
        sim.hold(sim.exponential(1.0))


@model.collect
def collect_stats(env: MM1):
    env.avg_queue_length = sim.mean_level(env.queue)


exp = model.experiment(
    utilization=0.75,
    replications=100,
    duration=1000.0,
    warmup=100.0,
    seed=123,
)
exp.run()

print(exp["avg_queue_length"].mean())

More examples, tutorials, background notes, and the API reference are in the documentation.

Development

From a fresh clone:

git submodule update --init --recursive
uv sync
uv run pytest

License

Cimba Python is licensed under Apache-2.0. See LICENSE and NOTICE.

The bundled Cimba C library is also Apache-2.0 licensed. See subprojects/cimba/NOTICE for attribution.