The Linux alternative

30 July 2001

CAE has built power plant simulators on both the Unix and Windows NT operating systems. Project Darkstar, undertaken in early 2000, sought to expand their suite to offer a Linux-based simulator.

Unix-based simulators have proven to be extremely robust over the years. Windows NT offers efficiencies in the area of improved hardware costs and off-the-shelf software compatibility. Could Linux-based simulators provide the best of both worlds?

The base requirements of the project were threefold. Firstly, the Linux-based simulator would need to run CAE’s existing software applications including the ROSE simulation environment, the TIGERS graphics editor and the ISIS instructor station. Secondly, existing standards for real-time operability, flexibility and stability would need to be achieved. Finally, performance standards in both the simulation and computer arenas would have to be met.

For the purposes of gauging and testing its final product, the decision was made to convert an operating Unix-based simulator running both traditional line coding and ROSE systems. An existing CAE customer, Entergy’s Pilgrim station, whose simulator met these requirements, expressed an interest in helping to develop the product. Under the agreement, CAE would develop the platform while Pilgrim would port the modeling software and test the simulator.

Why Linux?

Linux is an open source operating system, which originated in 1991 as an initiative from Linus Torvalds. In conjunction with a worldwide team of developers, Mr Torvalds developed Linux – a free Unix-like operating system. At low cost, the open-source nature of Linux provides a highly reliable operating system, whereby millions of people around the world have access to the source code and can report problems, suggest enhancements and contribute to its development. Today, there are several distributions available, all of which share a common solid kernel. They also offer a familiar and easy to use look-and-feel environment to the very stable and powerful Linux operating system.

The central nervous system of Linux is the kernel – the operating system (OS) code that runs the whole computer. The kernel design is modular, so that the actual OS code is very small yet able to load whatever functionality it needs when it needs it, and is then able to free the memory afterwards.

Linux systems excel in many areas, ranging from end-user concerns such as stability, speed, and ease of use, to serious concerns such as development and networking. Linux has been gaining worldwide acceptance and many large corporations are already supporting Linux as the operating system of the future. Amongst these we find Oracle, IBM, Corel, Compaq, Silicon Graphics and many more. Linux is growing exponentially as programmers, enthusiasts, and end-users exchange thoughts, implement ideas, contribute code and cooperate to produce the Linux operating system.

Linux offers some advantages that lend themselves well for use in simulation. These include:

•Reliability. Being able to run a simulator on a personal computer with an extremely reliable operating system.

•Stability. Linux boxes have been known to run for months or even years at a time without crashing, freezing, or having to be rebooted.

•Speed. The operating system is very efficient at managing resources such as memory, CPU power, and disk space.

Software porting

Because Linux is a Unix-type operating system, the development work primarily consisted of porting existing software running under Unix, to the Linux environment.

The following software packages were ported:

•ISIS modular instructor station. Virtual control panels, pop-up control menus, windowing techniques and automation provide an intuitive user interface, allowing the instructor to control and monitor the simulator while concentrating on training.

•TIGERS integrated graphical environment for development of sophisticated real-time virtual panels and system schematic displays.

•CAELIB software development environment consists of the simulator executive (SIMex), dispatcher, run-time library, configuration management and performance monitoring tools.

•ROSE graphical modeling tool and real-time simulation environment for developing simulations of complex systems. It has extensive model libraries making it easy for the user to develop real-world simulations at low cost.

Pilgrim simulator porting

Once ready, the Linux-based simulator environment was validated using the existing Pilgrim simulator, having gone through a recent upgrade of the core and thermal-hydraulics models. Being conversant with the original simulator’s Unix operating system, Pilgrim staff also performed some porting work:

Application software

The application software consists of all the software modules actually performing the simulation, including the ANTHEM two-phase thermalhydraulic model and the COMET reactor kinetics model. The majority of these modules were written in Fortran.

Virtual panels & system schematic displays

Virtual panel displays are graphic representations of the actual reference plant control panels while system schematic displays are graphic representations of modeled systems. These displays were originally created in the Unix version of TIGERS.


Following the availability and integration of all software tools and models alike, the new Linux-based Pilgrim simulator was validated to ensure that the original simulator’s high fidelity performance was respected in the transition. Pilgrim is now the proud owner of a second true-to-life simulator – this time, in the Linux domain.

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