Army simulations gain speed with move to Linux

Army simulations gain speed with move to Linux

The Army's Simulation, Training and Instrumentation Command has found a home for its advanced simulation software, moving it to Linux following the obsolescence of its VAX systems.

The Orlando, Fla., command uses the Corps Battle Simulation system to train military commanders. But after investing years of work and millions of dollars into the system, it faced a dilemma when the VAX operating system expired.

Rather than scrap what users regarded as a highly effective tool, STRICOM decided to port the war-gaming applications to PCs running the Linux OS. By moving to an open-source operating system, the command greatly reduced costs and gained performance in mapping out and executing battle scenarios.

'With PCs becoming technologically advanced and relatively cheap, it was decided that the new CBS platform should be as standard as possible,' said Dave Zedo, STRICOM's project manager for Corps Battle Simulation. 'The Linux operating system was chosen because of its flexibility and open architecture.'

Desktop PCs are faster

The command originally developed CBS to run on Digital Equipment Corp. VAX 7800 series minicomputers, each costing about $100,000. When DEC abandoned the VAX line, STRICOM initially attempted to maintain its simulation system by using after-market vendors and buying used or refurbished equipment. But the costs ran into millions of dollars a year, Zedo said.

The aging hardware also limited the system's usefulness. The VAX machines had reached their upper limits in speed and scenario complexity. Zedo said they couldn't cope well with coalition or multifaction warfare scenarios. By the mid-1990s, desktop PCs had eclipsed the computing power of the VAX. These limitations led the Army to schedule CBS for replacement.

But developing a new simulation program would take a year, so Army brass gave the system a stay of execution. Instead of scrapping the simulation program and building a new one, STRICOM decided to port CBS to a more robust platform as it developed a new system.

'Operationally, the Army needed to ensure that the CBS system would remain the highly functional training tool it has come to depend on,' Zedo said. 'The open architecture of Linux meant that CBS costs could be contained, while offering the flexibility and reliability demanded by such a complex program.'

STRICOM officials asked NASA's Jet Propulsion Laboratory in Pasadena, Calif., which has experience in developing and testing the revisions made to CBS each year, to port this year's version to Red Hat Linux 7.1 from Red Hat Inc. of Durham, N.C.

The simulation is written in Simscript II.5 from CACI International Inc. of Arlington, Va. The language acts as a C preprocessor, letting programmers compile C code on various platforms without portability concerns.

Simscript also has a checkpoint-modify-restart feature. When a bug is found, a programmer can pause the program, modify the code and continue the exercise without having to return to the beginning. This function is crucial because a single simulation can run for days or weeks, Zedo said.

Once it completed the changeover, STRICOM tested CBS on a PC with a 1.2-GHz Athlon processor from Advanced Micro Devices Inc. of Sunnyvale, Calif. Despite running the largest simulation ever, the PC performed three to four times faster than the most powerful VAX without sacrificing model fidelity.

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