Core War

Coding Games

With an understanding ofCore Warstrategies, 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.

Dewdney, A.K.(January 1987).A program called MICE nibbles its way to victory at the first Core War tournament.

A vampire tries to make its opponents processes jump into a piece of its own code called a pit. Vampires can be based on either bombers or scanners. A major weakness of vampires is that they can be easily attacked indirectly, since they must by necessity scatter pointers to their code all over the core. Their attacks are also slow, as it takes an extra round for the processes to reach the pit.

Dewdney, A.K.(March 1985).A Core War bestiary of viruses, worms and other threats to computer memories.

Imps are named after the first ever published warrior,

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Doligez, Damien; Durham, Mark (8 November 1995).Annotated Draft of the Proposed 1994 Core War Standard

A bomber blindly copies a bomb at regular intervals in the core, hoping to hit the enemy. The bomb is often a

instruction. A process dies when it executes a

pMARS-SDLon corewar.co.uk by Joonas Pihlaja (7 May 2003)

download numbers corewareonsourceforge(access 2017-03-22)

instruction, although other instructions, or even multi-instruction bombs, may be used. A bomber can be small and fast, and they gain an extra edge over scanning opponents since the bombs also serve as convenient distractions. Bombers are often combined with imp spirals to gain extra resiliency against replicators.

) is of finite size, but onlyrelative addressingis used, that is, address

Jones, D. G.;Dewdney, A.K.(March 1984).Core War Guidelines

instructions. Scanners are also generally more complex, and therefore larger and more fragile, than other types of warriors.

Metcalf, John (April 2004).Anatomy of the Scanner, A Basic Introduction

Constant instruction length and time

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 from real assembly.

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is a very simple scanner that only scans the core until it finds the first target, and then permanently switches to an attack strategy, usually a core clear.

Video games with available source code

A replicator makes repeated copies of itself and executes them in parallel, eventually filling the entire core with copies of its code. Replicators are hard to kill, but often have difficulty killing their opponents. Replicators therefore tend to score a lot of ties, particularly against other replicators.

is a special type of very rapid replicator, named after

Metcalf, John.A Brief History of Corewar

) consists of imps spaced at equal intervals around the core and executing alternately. The imps at each arm of the ring/spiral copy their instruction to the next arm, where it is immediately executed again. Rings and spirals are even harder to kill than simple imps, and they even have a (small) chance of killing warriors not protected against them. The number of arms in an imp ring or spiral must berelatively primewith the size of the core.

Core Warwas inspired by aself-replicatingprogram calledCreeperand a subsequent program called Reaper that destroyed copies of Creeper.[12]Creeper was created by Bob Thomas atBBN.[13]Dewdney was not aware of the origin of Creeper and Reaper and refers to them as a rumor originating fromDarwinand the worm experiments ofShochand Hupp. The 1984Scientific Americanarticle onCore War[12]nevertheless cites the gameDarwin, played byVictor A. VyssotskyRobert Morris, andDouglas McIlroyatBell Labsin 1961. The word Core in the name comes frommagnetic-core memory, an obsoleterandom-access memorytechnology.

Warriors can also be generated bygenetic algorithmsorgenetic programming. Programs that integrate this evolutionary technique are known asevolvers. Several evolvers were introduced by theCore Warcommunity and tend to focus on generating warriors for smaller core settings. The latest evolver with significant success wasGP[10]which produced some of the most successful nano and tiny warriors. Nevertheless, evolutionary strategy still needs to prove its effectiveness on larger core settings.[11]

by Roy van Rijn is an example of a oneshot.

The memory is addressed in units of one instruction. The memory space (or

instruction or performs a division by zero. A program is considered dead when it has no more processes left.

The first description of the Redcode language was published in March 1984, inCore War Guidelinesby D. G. Jones andA. K. Dewdney.[1]The game was introduced to the public in May 1984, in an article written by Dewdney inScientific American. Dewdney revisitedCore Warin his Computer Recreations column in March 1985,[14]and again in January 1987.[15]

by Juha Pohjalainen. Most modern replicators are of this type. Silk replicators use parallel execution to copy their entire code with one instruction, and begin execution of the copy before it is finished.

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is a 1984programming gamecreated by D. G. Jones andA. K. Dewdneyin which two or more battle programs (called warriors) compete for control of avirtual computer. These battle programs are written in an abstractassembly languagecalled

for each program containing a variable number of instruction pointers which the simulator cycles through. Each program starts with only one process, but new processes may be added to the queue using the

This page was last edited on 24 May 2018, at 21:56.

Dewdney, A. K.(May 1984).In the game called Core War hostile programs engage in a battle of bits.

A number of versions of Redcode exist. The earliest version described byA. K. Dewdney[1]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[2]newsgroup.

A core clear sequentially overwrites every instruction in the core, sometimes even including itself. Core clears are not very common as stand-alone warriors, but are often used as an end-game strategy by bombers and scanners.

Vowk, Barkley; Wait, Alexander; Schmidt, Christian.An Evolutionary Approach Generates Human Competitive Corewar Programs

Pohjalainen, Jippo.Silk Warrior 1.3

(3): 172180.doi10.1145/358453.358455.

Instead of a singleinstruction pointera Redcode simulator has a

to the instruction after it, and so on. The maximum address value is set to equal one less than the number of memory locations, and will wrap around if necessary. As a result, there is a one-to-one correspondence between addresses and memory locations, but it is impossible for a Redcode program to determine any absolute address. A process that encounters no invalid or jump instructions will continue executing successive instructions endlessly, eventually returning to the instruction where it started.

Redcode is theprogramming languageused inCore War. It is executed by avirtual machineknown as aMemory Array Redcode Simulator, orMARS. The design of Redcode is loosely based on actualof the early 1980s, but contains several features not usually found in actual computer systems.

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 common implementation pMars was downloaded 30,000 times between 2000 and 2017 fromSourceforge.[21]

Pohjalainen, Jippo (April 1995).Replicators? – Phoenix & TimeScape source

Redcode and the MARS architecture provide no input or output functions. The simulator is a closed system, with the only input being the initial values of the memory and the process queues, and the only output being the outcome of the battle, i.e., which programs had surviving processes. Of course, the simulator may still allow external inspection and modification of the memory while the simulation is running.

byA. K. Dewdney, a trivial one-instruction mobile warrior that continually copies its sole instruction just ahead of itsinstruction pointer. Imps are hard to kill but next to useless for offense. Their use lies in the fact that they can easily be spawned in large numbers, and may survive even if the rest of the warrior is killed.

Each Redcode instruction occupies exactly one memory slot and takes exactly one cycle to execute. The rate at which a process executes instructions, however, depends on the number of other processes in the queue, as processing time is shared equally.

Wangsaw, tro to Art in 88: Paper – Stone – Scissors Trilogy

always refers to the currently executing instruction, address

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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,scannerandbomber) are also known aspaper, scissors and stone, since their performance against each other approximates that of their namesakes in the well-known playground game.[3]

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 ICWS-94 standard has 16 instructions. However, Redcode supports a number of differentaddressing modesand (from ICWS-94) 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.

A scanner is designed to beat replicators. A scanner does not attack blindly, but tries to locate its enemy before launching a targeted attack. This makes it more effective against hard-to-kill opponents like replicators, but also leaves it vulnerable to decoys. A scanner usually bombs memory with

A quickscanner attempts to catch its opponent early by using a very fast unrolled scanning loop. Quickscanning is an early-game strategy, and always requires some other strategy as a backup. Adding a quickscanning component to a warrior can improve its score against long warriors such as other quickscanners. However, the unrolled scan can only target a limited number of locations, and is unlikely to catch a small opponent.

Shoch, J.; Hupp, J. (March 1982). The Worm Programs – Early Experience with a Distributed Computation.

Development of implementations of the game continued over the years by several authors. There are multiple versions of the game available,[18]portedfor several platforms. For instancepMARSwhich isopen source softwarewithsource codeonSourceforge,[19]or theSDLbasedSDL pMARSfor Windows.[20]

Core War – the war of the programmers

by Paulsson is an example of a vampire.

The International Core Wars Society (ICWS) was founded in 1985, one year after Dewdneys 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.[16]Nonetheless, the 1994 draft was commonly adopted and extended, and forms the basis of thede factostandard for Redcode today. The ICWS was directed by Mark Clarkson (19851987), William R. Buckley (19871992), and Jon Newman (1992); currently the ICWS is defunct.[17]

Annotated Draft of the Proposed 1994 Core War Standard

instructions. This causes the enemy to create a huge number of processes which do nothing but create more processes, slowing down useful processes. When the enemy becomes so slow that it is unable to do anything useful, the memory is bombed with

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