Sim# is a .NET port of SimPy, process-based discrete event simulation framework
C# Batchfile
Latest commit 037b46a Mar 23, 2016 @abeham Increased version number to 3.0.9
Updated copyright year and added missing license information to some source files
Failed to load latest commit information.
SimSharp.Benchmarks Increased version number to 3.0.9 Mar 23, 2016
SimSharp.Performance Increased version number to 3.0.9 Mar 23, 2016
LICENSE.txt initial commit Mar 31, 2014
TODO.txt Removed RandomDist and integrated random number sampling into the Env… Apr 11, 2014


Sim# (SimSharp)

A .NET port of SimPy, process-based discrete event simulation framework

Sim# is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE. Sim# is free software: you can redistribute it and/or modify it under the
terms of the  GNU General Public License (GPL) as published by the Free Software
Foundation, either version 3 of the license, or (at your option) any later version. 

Sim# aims to port the concepts used in SimPy [1] to the .NET world. It is
implemented in C# and builds on the .NET Framework 4.0. Sim# uses an efficient
event queue (adapted from [2]) that allows to compute models very fast. Simulating
10 years of the MachineShop sample [3] that uses preemptive resources requires
only 2.5s on a Core i7 2.6Ghz. This model generates more than 5 million events.

SimPy allows to model processes easily and with little boiler plate code. A
process is described as a method that yields events. When an event is yielded, the
process waits on it. Processes are themselves events and so it is convenient to
spawn sub-processes that can either be waited upon or that run next to each other.
There is no need to inherit from classes or understand a complex object oriented

To demonstrate how simple models can be expressed with little code, consider a
model of an m/m/1 queueing system as expressed in Sim#:

TimeSpan ARRIVAL_TIME = TimeSpan.FromSeconds(...);
TimeSpan PROCESSING_TIME = TimeSpan.FromSeconds(...);
TimeSpan SIMULATION_TIME = TimeSpan.FromHours(...);

IEnumerable<Event> MM1Q(Environment env) {
  var server = new Resource(env, capacity: 1);
  while (true) {
    yield return env.TimeoutExponential(ARRIVAL_TIME);
    env.Process(Item(env, server));

IEnumerable<Event> Item(Environment env, Resource server) {
  using (var s = server.Request()) {
    yield return s;
    yield return env.TimeoutExponential(PROCESSING_TIME);
    Console.WriteLine("Duration {0}", env.Now - s.Time);

void RunSimulation() {
  var env = new Environment(randomSeed: 42);

Sim# tries to be as easy to use as SimPy, but also remains true to the .NET
Framework. The most obvious difference between SimPy and Sim# is handling process
interruptions. In Sim# a process that can be interrupted needs to call

  if (Environment.ActiveProcess.HandleFault()) {...}
after each yield in which an interruption can occur and before continuing to
yield further events. This is due to a limitation of the .Net Framework: In
Python it is possible to put a try-except block around a yield statement, and an
exception can be injected into the iterator. In .Net this is not possible.

Also in Sim# it was decided to base the unit for current time and delays on
DateTime and TimeSpan in the simulation clock. There is however an API, called
D-API (short for double-API) that allows you to use doubles as in SimPy, e.g.
env.Now returns a DateTime, env.NowD returns a double, env.Timeout(delay) expects
a TimeSpan as delay, env.TimeoutD(delay) expects a double, etc.. It is possible
to initialize the Environment with a default timestep in case both APIs are used:

  var env = new Environment(defaultStep: TimeSpan.FromMinutes(1));
In that environment, calling env.TimeoutD(1) would be equal to calling the more
elaborate normal API env.Timeout(TimeSpan.FromMinutes(1)).