General Information about J-Sim

J-Sim is an object-oriented library for discrete-time process-oriented simulation. Its main application area is queueing network simulation, however, the range of its use can be very wide – almost any system where object states change discretely can be modelled using J-Sim. J-Sim is a Simula-like simulation environment written in Java. For the programmer, it provides the same possibilities as the Simula language does. Plus much more.

Little theory...

The basic building blocks of every J-Sim simulation are processes and queues. Processes are active, while queues and other elements of the simulation are passive. The simulation is executed in a step-by-step manner. During a step, just one process is given an chance to run.

J-Sim is built up upon some very well known principles inherited from the Simula language, such as:

• life of processes, described as a sequence of actions;
• simulation time, shared by all processes within a simulation world;
• process state manipulation routines (hold(), passivate(), ...), controlling simulation progress;
• queue facilities HEAD and LINK, used for easy manipulation with queues and elements contained within them.

In addition to the standard features that a Simula user might expect, some extra features are provided:

• simulation of Dijkstra semaphores – processes may get blocked and unblocked on them;
• simulation of message passing – blocking and non-blocking send and receive operations; symmetric, asymetric, and indirect communication supported;
• independent random number generators (exponential, Gaussian, boolean, and uniform distribution) that can be initialized by user-defined seed and therefore guarantee repeatability of experiments;
• console mode and two GUI modes (batch and interactive);

J-Sim is written in pure Java

J-Sim is written completely in Java and therefore 100% portable. All you need is a Java runtime environment running on your computer. J-Sim has been tested on Solaris 8, OS/2 Warp 4, eComStation 1.1, Windows NT 4, Windows XP, and Linux (Not all J-Sim versions on all operating systems). Please note that starting with J-Sim 0.6.0, you need Java 1.5 or newer. There are older versions available for Java 1.4 and even Java 1.1.

Released under an approved open source licence

Source texts of J-Sim are available as a standard part of the distribution. Starting with version 0.5.0, J-Sim is released under The Academic Free Licence v. 2.1, a licence certified by the Open Source Initiative (OSI). J-Sim can be therefore called an "OSI Certified Open Source Software".

Start now!

Start using J-Sim now! Go to the Download Page, choose one of the available formats of J-Sim distribution, and install it. Then, you can explore examples included in the distribution to get familiar with J-Sim. Or, you can read the documentation first.