This document presents SimJ, a framework for developing distributed simulators. SimJ aims to simplify the development of HLA-based discrete event simulators by providing components like entities, events, ports and links that abstract away the need to directly program with HLA. SimJ allows distributed simulators to be developed similarly to local simulators. An example application demonstrates how a local simulator can be distributed across multiple federates using SimJ. The framework is estimated to reduce the effort required for developing HLA simulators by 30-60% compared to programming directly with HLA.

1. Summer Computer Simulation
Conference 2006 (SCSC'06), July
31st - August 2nd, Calgary, CA 1
SimJ
A Framework to Develop Distributed Simulators
Andrea D’Ambrogio, Daniele Gianni and Giuseppe Iazeolla
Dept. of Computer Science
University of Roma “Tor Vergata”
Roma (Italy)
Presented by
Daniele Gianni
PhD Student
Dept. Of Computer Science
University of Roma “TorVergata” Roma (Italy)
Visiting Student
Georgia Institute of Technology
Parallel and Distributed Simulation Research Group

2. Summer Computer Simulation Conference 2006
(SCSC'06), July 31st - August 2nd, Calgary, CA 2
Presentation Overview
 Problems of using HLA
 Fewer problems by use of SimJ
• SimJ main goals
• SimJ main components
 SimJ Example
 SimJ Effort Saving

3. Summer Computer Simulation Conference 2006
(SCSC'06), July 31st - August 2nd, Calgary, CA 3
Problems of using HLA
 What HLA offers:
• A general framework to develop several kinds
of distributed simulators
• Distributed simulation oriented services
 What HLA does not support:
• Federate internal issues as:
 Events management,
 Federate logic – RTI synchronizations,
 Etc.
• Explicit simulation paradigms (Continuous
Simulation, Discrete Event Simulation (DES)
– PI, ES, AS –, etc.)

4. Summer Computer Simulation Conference 2006
(SCSC'06), July 31st - August 2nd, Calgary, CA 4
Steps in developing HLA simulators
 Development of an HLA distributed simulator
requires:
 HLA knowledge
 Decisions on design choices:
• Which federates to be developed? Which can be
reused?
• Which time management modality?
• Which data to be exchanged and with which?
• Which communication modalities to be used?

5. Summer Computer Simulation Conference 2006
(SCSC'06), July 31st - August 2nd, Calgary, CA 5
This paper problem
How to develop an HLA-based discrete event
distributed simulator
• Without
 knowledge of HLA
 need of decisions on HLA-related design choices
• As it were a local simulator

6. Summer Computer Simulation Conference 2006
(SCSC'06), July 31st - August 2nd, Calgary, CA 6
This paper solution
Introduce a technology to
 Elevate the HLA conceptual framework to the level
of the DES conceptual one
 Ease the development of HLA-based DES simulators
In other words:
 A technology to develop distributed HLA-based
simulators
• In a simple and quick way
• With a negligible extra effort compared to the one for the
local version

7. Summer Computer Simulation Conference 2006
(SCSC'06), July 31st - August 2nd, Calgary, CA 7
The SimJ technology
 SimJ includes
• A Java Library
• A DES framework
 An interface of DES services implemented both in a
local and distributed environment
 A set of components to be customized in the
necessary domain

8. Summer Computer Simulation Conference 2006
(SCSC'06), July 31st - August 2nd, Calgary, CA 8
SimJ Advantages
 HLA simulators can be developed without
explicit HLA knowledge by simple use of
standard DES services
 Distributed HLA-based simulators can be
developed as they were local ones
 Simple reuse of SimJ local simulators and
components to develop SimJ distributed
simulators

9. Summer Computer Simulation Conference 2006
(SCSC'06), July 31st - August 2nd, Calgary, CA 9
SimJ main components 1
 Entity: a logical process, i.e. a fundamental
building block in the PI paradigm.
• Can be
 Local
 Remote
 Event: the basic events in the PI paradigm (e.g.
start, notify, sleep, etc.)
 Port: used by Entities to send and receive Events
• Can be of
 input or output type
 local or remote type

10. Summer Computer Simulation Conference 2006
(SCSC'06), July 31st - August 2nd, Calgary, CA 10
SimJ main components 2
 Link: connects output Ports to input Ports
• Can be
 point-to-point
 multi-sender
 multi-recipient
 local or distributed
 Engine: facility for the simulator initialization and
execution
• Local and Distributed PI
 FederationManager (HLA federate) to direct the
execution of the whole federation

11. Summer Computer Simulation Conference 2006
(SCSC'06), July 31st - August 2nd, Calgary, CA 11
SimJ Entities
E1
ev1
ev3
ev2
ev4
E2
E3
Key
Entity
Input Port
Out Port
Link/Event ev

12. Summer Computer Simulation Conference 2006
(SCSC'06), July 31st - August 2nd, Calgary, CA 12
Simj Engines
Current hierarchy (additions and restylings will not affect
the other Simj components)
SimEngine
ES_SimEngine AS_SimEngine PI_SimEngine
PI_Local_SimEngine
PI_HLA_SimEngine

13. Summer Computer Simulation Conference 2006
(SCSC'06), July 31st - August 2nd, Calgary, CA 13
SimJ Applications
Use-1: Integration of already developed
simulators
• Integrating existing heterogeneous simulators from remote sites
• Integration includes reuse in case the existing simulators were
developed in SimJ
Use-2: Development of new distributed
simulators
• Build the whole simulator as it were a local one and then distribute it
to the remote sites

14. Summer Computer Simulation Conference 2006
(SCSC'06), July 31st - August 2nd, Calgary, CA 14
Use-2 Example (system)
Internet
LAN
Gateway
Client 2
Web Server 1
Web Server 8
Web Server 7
Web Server 6
Web Server 5
Web Server 4
Web Server 3
Web Server 2
Client 1

15. Summer Computer Simulation Conference 2006
(SCSC'06), July 31st - August 2nd, Calgary, CA 15
Use-2 Example (local simulator)
Client
1
Client
2
LAN
Internet
Key
SimJ Entity
Input port
Out port
Link
Web
Server
1
Web
Server
2
Web
Server
3
Web
Server
4
Web
Server
5
Web
Server
6
Web
Server
7
Web
Server
8
Gate-
way

16. Summer Computer Simulation Conference 2006
(SCSC'06), July 31st - August 2nd, Calgary, CA 16
Use-2 Example (distributed simulator)
Client
1
Client
2
LAN
Internet
Key
SimJ Entity
Input port
Out port
Link
Web
Server
1
Web
Server
2
Web
Server
3
Web
Server
4
Web
Server
5
Web
Server
6
Web
Server
7
Web
Server
8
Gate-
way
Federate1
Federate2
Federate3

17. Summer Computer Simulation Conference 2006
(SCSC'06), July 31st - August 2nd, Calgary, CA 17
Use-2 Example (Federate1)
Client
1
Client
2
LAN
Gate-
way
Internet
Key
SimJ Local Entity
SimJ RemoteEntityRef
Input port
Output port
Link
Remote Input port
DIS Link
Client
1
Client
2
LAN
Internet
Key
SimJ Entity
Input port
Out port
Link
Web
Server
1
Web
Server
2
Web
Server
3
Web
Server
4
Web
Server
5
Web
Server
6
Web
Server
7
Web
Server
8
Gate-
way
Federate1
Federate2
Federate3

18. Summer Computer Simulation Conference 2006
(SCSC'06), July 31st - August 2nd, Calgary, CA 18
Use-2 Example (Federate2)
Gate-
way
Internet
Web
Server
1
Web
Server
2
Web
Server
3
Web
Server
4
Web
Server
5
Web
Server
6
Web
Server
7
Web
Server
8
Key
SimJ Local Entity
SimJ RemoteEntityRef
Input port
Output port
Link
Remote Input Port
Remote Output Port
DIS Link
Client
1
Client
2
LAN
Internet
Key
SimJ Entity
Input port
Out port
Link
Web
Server
1
Web
Server
2
Web
Server
3
Web
Server
4
Web
Server
5
Web
Server
6
Web
Server
7
Web
Server
8
Gate-
way
Federate1
Federate2
Federate3

19. Summer Computer Simulation Conference 2006
(SCSC'06), July 31st - August 2nd, Calgary, CA 19
Use-2 Example (Federate3)
Internet
Web
Server
5
Web
Server
6
Web
Server
7
Web
Server
8
Key
SimJ Local Entity
SimJ Remote EntityRef
Input port
Output port
Link
Remote Input port
DIS Link
Client
1
Client
2
LAN
Internet
Key
Simj Entity
Input port
Out port
Link
Web
Server
1
Web
Server
2
Web
Server
3
Web
Server
4
Web
Server
5
Web
Server
6
Web
Server
7
Web
Server
8
Gate-
way
Federate1
Federate2
Federate3

20. Summer Computer Simulation Conference 2006
(SCSC'06), July 31st - August 2nd, Calgary, CA 20
SimJ Effort Savings
 SimJ developers can concentrate on the simulation
logic only
 This brings an effort savings (in MM) of
• Around 30% for average experienced developers
• Around 60% for beginners
Compared with a HLA simulator developed without SimJ
 Besides a fixed saving of about 1.2 MM per federate

21. Summer Computer Simulation Conference 2006
(SCSC'06), July 31st - August 2nd, Calgary, CA 21
Conclusions
 SimJ: A Java library that eases the development of
distributed discrete event simulators
 By SimJ the HLA conceptual framework is elevated
to the DES conceptual framework
 Development of distributed DES simulators as they
were local ones
 Significant savings in effort for HLA-based DES
simulators