Core War

Core War

A game of Core War running under the pMARS simulator
Original author(s)	D. G. Jones & A. K. Dewdney
Initial release	1984
Type	Programming game

Core War is a 1984 programming game created by D. G. Jones and A. K. Dewdney in which two or more battle programs (called "warriors") compete for control of a virtual computer. These battle programs are written in an abstract assembly language called Redcode.

At the beginning of a game, each battle program is loaded into memory at a random location, after which each program executes one instruction in turn. The object of the game is to cause the processes of opposing programs to terminate (which happens if they execute an invalid instruction), leaving the victorious program in sole possession of the machine.

A number of versions of Redcode exist. The earliest version described by A. K. Dewdney differs in many respects from the later standards established by the International Core War Society, and could be considered a different, albeit related, language. The form of Redcode most commonly used today is based on a draft standard submitted to the ICWS in 1994 that was never formally accepted, as the ICWS had become effectively defunct around that time. Development of Redcode, however, has continued in an informal manner, chiefly via online forums such as the rec.games.corewarnewsgroup.

Warriors are commonly divided into a number of broad categories, although actual warriors may often combine the behavior of two or more of these. Three of the common strategies (replicator, scanner and bomber) are also known as paper, scissors and stone, since their performance against each other approximates that of their namesakes in the well-known playground game.

With an understanding of Core War strategies, a programmer can create a warrior to achieve certain goals. Revolutionary ideas come once in a while; most of the time, however, programmers base their programs on already published warriors. Using optimizers such as OptiMax or core-step optimizer tools, a more effective warrior can be created.

Warriors can also be generated by genetic algorithms or genetic programming. Programs that integrate this evolutionary technique are known as evolvers. Several evolvers were introduced by the Core War community and tend to focus on generating warriors for smaller core settings. The latest evolver with significant success was µGP which produced some of the most successful nano and tiny warriors. Nevertheless, evolutionary strategy still needs to prove its effectiveness on larger core settings.