|Developer(s)||D. G. Jones & A. K. Dewdney|
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 goal 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.
The earliest published version of Redcode defined only eight instructions. The ICWS-86 standard increased the number to 10 while the ICWS-88 standard increased it to 11. The currently used 1994 draft standard has 16 instructions. However, Redcode supports a number of different addressing modes and (starting from the 1994 draft standard) instruction modifiers which increase the actual number of operations possible to 7168. The Redcode standard leaves the underlying instruction representation undefined and provides no means for programs to access it. Arithmetic operations may be done on the two address fields contained in each instruction, but the only operations supported on the instruction codes themselves are copying and comparing for equality.
SPLinstruction. A process dies when it executes a DAT instruction or performs a division by zero. A program is considered dead when it has no more processes left.
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
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.
Core War was inspired by a self-replicating program called Creeper and a subsequent program called Reaper that destroyed copies of Creeper. Creeper was created by Bob Thomas at BBN. Dewdney was not aware of the origin of Creeper and Reaper and refers to them as a rumor originating from Darwin and the worm experiments of Shoch and Hupp. The 1984 Scientific American article on Core War nevertheless cites the game Darwin, played by Victor A. Vyssotsky, Robert Morris, and Douglas McIlroy at Bell Labs in 1961. The word "Core" in the name comes from magnetic-core memory, an obsolete random-access memory technology.
The first description of the Redcode language was published in March 1984, in Core War Guidelines by D. G. Jones and A. K. Dewdney. The game was introduced to the public in May 1984, in an article written by Dewdney in Scientific American. Dewdney revisited Core War in his "Computer Recreations" column in March 1985, and again in January 1987.
The International Core Wars Society (ICWS) was founded in 1985, one year after Dewdney's original article. The ICWS published new standards for the Redcode language in 1986 and 1988, and proposed an update in 1994 that was never formally set as the new standard. Nonetheless, the 1994 draft was commonly adopted and extended, and forms the basis of the de facto standard for Redcode today. The ICWS was directed by Mark Clarkson (1985–1987), William R. Buckley (1987–1992), and Jon Newman (1992–); currently the ICWS is defunct.
Redcode is the programming language used in Core War. It is executed by a virtual machine known as a Memory Array Redcode Simulator, or MARS. The design of Redcode is loosely based on actual CISC assembly languages of the early 1980s, but contains several features[vague] not usually found in actual computer systems.
Both Redcode and the MARS environment are designed to provide a simple and abstract platform without the complexity of actual computers and processors. Although Redcode is meant to resemble an ordinary CISC assembly language, it differs in many ways[which?] from "real" assembly.
Development of implementations of the game continued over the years by several authors. There are multiple versions of the game available,ported for several platforms. For instance pMARS which is open source software with source code on Sourceforge, or the SDL based SDL pMARS for Windows. Recently a fully web based simulator has been created https://www.corewar.io/ removing the need to download any platform specific tooling.
The common implementation pMars was downloaded over 35,000 times between 2000 and 2021 from Sourceforge.
Edited: 2021-06-18 18:18:03