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Archive-name: games/corewar-faq
Last-Modified: September 4, 1999
Version: 4.2
URL: http://homepages.paradise.net.nz/~anton/cw/corewar-faq.html
Copyright: (c) 1999 Anton Marsden
Maintainer: Anton Marsden
Posting-Frequency: once every 2 weeks
Core War Frequently Asked Questions
(rec.games.corewar FAQ)
These are the Frequently Asked Questions (and answers) from the Usenet
newsgroup rec.games.corewar. A plain text version of this document is posted
every two weeks. The latest hypertext version is available at
http://homepages.paradise.net.nz/~anton/cw/corewar-faq.html and the latest
plain text version is available at
http://homepages.paradise.net.nz/~anton/cw/corewar-faq.txt.
This document is currently being maintained by Anton Marsden
(anton@paradise.net.nz).
Last modified: Sat Sep 4 00:22:22 NZST 1999
------------------------------------------------------------------------
To Do
* Add the new No-PSpace '94 hill location
* Add online location of Dewdney's articles
* Make question 17 easier to understand. Add a state diagram?
* Add info about infinite hills, related games (C-Robots, Tierra?, ...)
* New question: How do I know if my warrior is any good? Refer to
beginners' benchmarks, etc.
* Add a Who's Who list?
* Would very much like someone to compile a collection of the
"revolutionary" warriors so that beginners can see how the game has
developed over the years. Mail me if interested.
------------------------------------------------------------------------
What's New
* Changed primary location of FAQ (again!)
* Changed Philip Kendall's home page address.
* Updated list server information
* Changed primary location of FAQ
* Vector-launching code was fixed thanks to Ting Hsu.
* Changed the location of Ryan Coleman's paper (LaunchPad -> Launchpad)
* Changed pauillac.inria.fr to para.inria.fr
------------------------------------------------------------------------
Table of Contents
1. What is Core War
2. Is it "Core War" or "Core Wars"?
3. Where can I find more information about Core War?
4. Core War has changed since Dewdney's articles. Where do I get a copy of
the current instruction set?
5. What is ICWS'94? Which simulators support ICWS'94?
6. What is the ICWS?
7. What is Core Warrior?
8. Where are the Core War archives?
9. Where can I find a Core War system for ...?
10. Where can I find warrior code?
11. I do not have FTP. How do I get all this great stuff?
12. I do not have access to Usenet. How do I post and receive news?
13. Are there any Core War related WWW sites?
14. What is KotH? How do I enter?
15. Is it DAT 0, 0 or DAT #0, #0? How do I compare to core?
16. How does SLT (Skip if Less Than) work?
17. What is the difference between in-register and in-memory evaluation?
18. What is P-space?
19. What does "Missing ;assert .." in my message from KotH mean?
20. How should I format my code?
21. Are there any other Core War related resources I should know about?
22. What does (expression or term of your choice) mean?
23. Other questions?
------------------------------------------------------------------------
1. What is Core War?
Core War is a game played by two or more programs (and vicariously by their
authors) written in an assembly language called Redcode and run in a virtual
computer called MARS (for Memory Array Redcode Simulator). The object of the
game is to cause all processes of the opposing program to terminate, leaving
your program in sole posession of the machine.
There are Core War systems available for most computer platforms. Redcode
has been standardised by the ICWS, and is therefore transportable between
all standard Core War systems.
The system in which the programs run is quite simple. The core (the memory
of the simulated computer) is a continuous array of instructions, empty
except for the competing programs. The core wraps around, so that after the
last instruction comes the first one again.
There are no absolute addresses in Core War. That is, the address 0 doesn't
mean the first instruction in the memory, but the instruction that contains
the address 0. The next instruction is 1, and the previous one obviously -1.
However, all numbers are treated as positive, and are in the range 0 to
CORESIZE-1 where CORESIZE is the amount of memory locations in the core -
this means that -1 would be treated as CORESIZE-1 in any arithmetic
operations, eg. 3218 + 7856 = (3218 + 7856) mod CORESIZE. Many people get
confused by this, and it is particularly important when using the SLT
instruction. Note that the source code of a program can still contain
negative numbers, but if you start using instructions like DIV #-2, #5 it is
important to know what effect they will have when executed.
The basic unit of memory in Core War is one instruction. Each Redcode
instruction contains three parts:
* the opcode
* the source address (a.k.a. the A-field)
* the destination address (a.k.a. the B-field)
The execution of the programs is equally simple. The MARS executes one
instruction at a time, and then proceeds to the next one in the memory,
unless the instruction explicitly tells it to jump to another address. If
there is more than one program running, (as is usual) the programs execute
alternately, one instruction at a time. The execution of each instruction
takes the same time, one cycle, whether it is MOV, DIV or even DAT (which
kills the process).
Each program may have several processes running. These processes are stored
in a task queue. When it is the program's turn to execute an instruction it
dequeues a process and executes the corresponding instruction. Processes
that are not killed during the execution of the instruction are put back
into the task queue. Processes created by a SPL instruction are added to the
task queue after the creating process is put back into the task queue.
[ToC]
------------------------------------------------------------------------
2. Is it "Core War" or "Core Wars"?
Both terms are used. Early references were to Core War. Later references
seem to use Core Wars. I prefer "Core War" to refer to the game in general,
"core wars" to refer to more than one specific battle.
[ToC]
------------------------------------------------------------------------
3. Where can I find more information about Core War?
Core War was first described in the Core War Guidelines of March, 1984 by D.
G. Jones and A. K. Dewdney of the Department of Computer Science at The
University of Western Ontario (Canada). Dewdney wrote several "Computer
Recreations" articles in Scientific American which discussed Core War,
starting with the May 1984 article. Those articles are contained in two
anthologies:
Library of
Author Title Published ISBN Congress
Call Number
The Armchair
Dewdney, Universe: An New York: W. QA76.6 .D517
A. K. Exploration of H. Freeman ©0-7167-1939-8 1988
Computer Worlds 1988
The Magic 0-7167-2125-2
Dewdney, Machine: A New York: W.(Hardcover), QA76.6
A. K. Handbook of H. Freeman ©0-7167-2144-9 .D5173 1990
Computer Sorcery 1990 (Paperback)
A.K. Dewdney's articles are still the most readable introduction to Core
War, even though the Redcode dialect described in there is no longer
current. For those who are interested, Dewdney has a home page at
http://www.csd.uwo.ca/faculty/akd/.
[ToC]
------------------------------------------------------------------------
4. Core War has changed since Dewdney's articles. Where do I get a copy of
the current instruction set?
A draft of the official standard (ICWS'88) is available as
ftp://www.koth.org/corewar/documents/standards/redcode-icws-88.Z. This
document is formatted awkwardly and contains ambiguous statements. For a
more approachable intro to Redcode, take a look at Mark Durham's tutorials,
ftp://www.koth.org/corewar/documents/tutorial.1.Z and
ftp://www.koth.org/corewar/documents/tutorial.2.Z.
Steven Morrell has prepared a more practically oriented Redcode tutorial
that discusses different warrior classes with lots of example code. This and
various other tutorials can be found at http://www.koth.org/papers.html.
Even though ICWS'88 is still the "official" standard, you will find that
most people are playing by ICWS'94 draft rules and extensions.
[ToC]
------------------------------------------------------------------------
5. What is ICWS'94? Which simulators support ICWS'94?
There is an ongoing discussion about future enhancements to the Redcode
language. A proposed new standard, dubbed ICWS'94, is currently being
evaluated. A major change is the addition of "instruction modifiers" that
allow instructions to modify A-field, B-field or both. Also new is a new
addressing modes and unrestricted opcode and addressing mode combination
("no illegal instructions"). ICWS'94 is backwards compatible; i.e. ICWS'88
warriors will run correctly on an ICWS'94 system. Take a look at the ICWS'94
draft at ftp://www.koth.org/corewar/documents/icws94.0202.Z for more
information. There is a HTML version of this document available at
http://www.koth.org/info/icws94.html. You can try out the new standard by
submitting warriors to the '94 hills of the KotH servers. Two corewar
systems currently support ICWS'94, pMARS (many platforms) and Redcoder
(Mac), both available at ftp://www.koth.org/corewar. Note that Redcoder only
supports a subset of ICWS'94.
[ToC]
------------------------------------------------------------------------
6. What is the ICWS?
About one year after Core War first appeared in Scientific American, the
"International Core War Society" (ICWS) was established. Since that time,
the ICWS has been responsible for the creation and maintenance of Core War
standards and the running of Core War tournaments. There have been six
annual tournaments and two standards (ICWS'86 and ICWS'88). The ICWS is no
longer active.
[ToC]
------------------------------------------------------------------------
7. What is Core Warrior?
Following in the tradition of the Core War News Letter, Push Off, and The 94
Warrior, Core Warrior is a newsletter about strategies and current standings
in Core War. Started in October 1995, back issues of Core Warrior (and the
other newsletters) are available at http://para.inria.fr/~doligez/corewar/.
There is also a Core Warrior index page at
http://www.kendalls.demon.co.uk/pak21/corewar/warrior.html which has a
summary of the contents of each issue of Core Warrior. Many of the earlier
issues contain useful information for beginners.
[ToC]
------------------------------------------------------------------------
8. Where are the Core War archives?
Many documents such as the guidelines and the ICWS standards along with
previous tournament Redcode entries and complete Core War systems are
available via anonymous ftp from ftp://ftp.csua.berkeley.edu/pub/corewar.
Also, most of past rec.games.corewar postings (including Redcode source
listings) are archived there. Jon Blow (blojo@csua.berkeley.edu) is the
archive administrator. When uploading to /pub/corewar/incoming, ask Jon to
move your upload to the appropriate directory and announce it on the net.
This site is mirrored at:
* http://www.koth.org/corewar/
* ftp://www.koth.org/corewar/
* ftp://ftp.inria.fr/INRIA/Projects/para/doligez/cw/mirror
The plain text version of this FAQ is automatically archived by news.answers
(but this version is probably out-of-date).
[ToC]
------------------------------------------------------------------------
9. Where can I find a Core War system for . . . ?
Core War systems are available via anonymous FTP from www.koth.org in the
corewar/systems directory. Currently, there are UNIX, IBM PC-compatible,
Macintosh, and Amiga Core War systems available there. It is a good idea to
check ftp://www.koth.org/corewar/incoming for program updates first.
CAUTION! There are many, many Core War systems available which are NOT
ICWS'88 (or even ICWS'86) compatible available at various archive sites
other than www.koth.org. Generally, the older the program - the less likely
it will be ICWS compatible.
If you are looking for an ICWS'94 simulator, get pMARS, which is available
for many platforms and can be downloaded from:
* ftp://ftp.csua.berkeley.edu/pub/corewar (original site)
* ftp://www.koth.org/corewar (koth.org mirror)
* ftp://ftp.inria.fr/INRIA/Projects/para/doligez/cw/mirror (Planar
mirror)
* http://www.nc5.infi.net/~wtnewton/corewar/ (Terry Newton)
* ftp://members.aol.com/ofechner/corewar (Fechter)
Notes:
* If you have trouble running pMARS with a graphical display under Win95
then check out http://www.koth.org/pmars.html which should have a
pointer to the latest compilation of pMARS for this environment.
* RPMs for the Alpha, PowerPC, Sparc and i386 can be found at
ftp://ftp.inria.fr/INRIA/Projects/para/doligez/cw/pmars-rpm/
Reviews of Core War systems would be greatly appreciated in the newsgroup
and in the newsletter.
Below is a not necessarily complete or up-to-date list of what's available
at www.koth.org:
MADgic41.lzh corewar for the Amiga, v4.1
MAD4041.lzh older version?
MAD50B.lha corewar for the Amiga, beta version 5.0
Redcoder-21.hqx corewar for the Mac, supports ICWS'88 and '94
(without extensions)
core-11.hqx corewar for the Mac
core-wars-simulator.hqx same as core-11.hqx?
corewar_unix_x11.tar.Z corewar for UNIX/X-windows, ICWS'86 but not ICWS'88
compatible
koth31.tar.Z corewar for UNIX/X-windows. This program ran the
former KotH server at intel.com
koth.shar.Z older version
kothpc.zip port of older version of KotH to the PC
deluxe20c.tar.Z corewar for UNIX (broken X-windows or curses) and
PC
mars.tar.Z corewar for UNIX, likely not ICWS'88 compatible
icons.zip corewar icons for MS-Windows
macrored.zip a redcode macro-preprocessor (PC)
c88v49.zip PC corewar, textmode display
mars88.zip PC corewar, graphics mode display
corwp302.zip PC corewar, textmode display, slowish
mercury2.zip PC corewar written in assembly, fast!
mtourn11.zip tournament scheduler for mercury (req. 4DOS)
pmars08s.zip portable system, ICWS'88 and '94, runs on UNIX, PC,
Mac, Amiga. C source archive
pmars08s.tar.Z same as above
pmars08.zip PC executables with graphics display, req 386+
macpmars02.sit.hqx pMARS executable for Mac (port of version 0.2)
buggy, no display
MacpMARS1.99a.cpt.hqx port of v0.8 for the Mac, with display and debugger
MacpMARS1.0s.cpt.hqx C source (MPW, ThinkC) for Mac frontend
pvms08.zip pMARS v0.8 for VMS build files/help (req.
pmars08s.zip)
ApMARS03.lha pMARS executable for Amiga (port of version 0.3.1)
wincor11.zip MS-Windows system, shareware ($15)
[ToC]
------------------------------------------------------------------------
10. Where can I find warrior code?
To learn the game, it is a good idea to study previously posted warrior
code. The FTP archives have code in the ftp://www.koth.org/corewar/redcode
directory. A clearly organized on-line warrior collection is available at
the Core War web sites (see below).
[ToC]
------------------------------------------------------------------------
11. I do not have FTP. How do I get all this great stuff?
There is an FTP email server at bitftp@pucc.princeton.edu. This address may
no longer exist. I haven't tested it yet. Send email with a subject and body
text of "help" (without the quotes) for more information on its usage. Note
that many FTP email gateways are shutting down due to abuse. To get a
current list of FTP email servers, look at the Accessing the Internet by
E-mail FAQ posted to news.answers. If you don't have access to Usenet, you
can retrieve this FAQ one of the following ways:
* Send mail to mail-server@rtfm.mit.edu with the body containing "send
usenet/news.answers/internet-services/access-via-email".
* Send mail to mailbase@mailbase.ac.uk with the body containing "send
lis-iis e-access-inet.txt".
[ToC]
------------------------------------------------------------------------
12. I do not have access to Usenet. How do I post and receive news?
To receive rec.games.corewar articles by email, join the COREWAR-L list run
on the Koth.Org list processor. To join, send the message
SUB COREWAR-L FirstName LastName
to listproc@koth.org. You can send mail to corewar-l@koth.org to post even
if you are not a member of the list. Responsible for the listserver is Scott
J. Ellentuch (ttsg@ttsg.com).
Servers that allow you to post (but not receive) articles are available.
Refer to the Accessing the Internet by E-Mail FAQ for more information.
[ToC]
------------------------------------------------------------------------
13. Are there any Core War related WWW sites?
You bet. Each of the two KotH sites sport a world-wide web server.
Stormking's Core War page is http://www.koth.org; pizza's is
http://www.ecst.csuchico.edu/~pizza/koth . Damien Doligez (a.k.a. Planar)
has a web page that features convenient access to regular newsletters (Push
Off, The '94 Warrior, Core Warrior) and a well organized library of
warriors: http://para.inria.fr/~doligez/corewar/. Convenient for U.S. users,
this site is also mirrored at koth.org.
[ToC]
------------------------------------------------------------------------
14. What is KotH? How do I enter?
King Of The Hill (KotH) is an ongoing Core War tournament available to
anyone with email. You enter by submitting via email a Redcode program
(warrior) with special comment lines. You will receive a reply indicating
how well your program did against the current top programs "on the hill".
There are two styles of KotH tournaments, "classical" and "multi-warrior".
The "classical" KotH is a one-on-one tournament, that is your warrior will
play 100 battles against each of the 20 other programs currently on the
Hill. You receive 3 points for each win and 1 point for each tie. (The
existing programs do not replay each other, but their previous battles are
recalled.) All scores are updated to reflect your battles and all 21
programs are ranked from high to low. If you are number 21 you are pushed
off the Hill, if you are higher than 21 someone else is pushed off.
In "multi-warrior" KotH, all warriors on the hill fight each other at the
same time. Score calculation is a bit more complex than for the one-on-one
tournament. Briefly, points are awarded based on how many warriors survive
until the end of a round. A warrior that survives by itself gets more points
than a warrior that survives together with other warriors. Points are
calculated from the formula (W*W-1)/S, where W is the total number of
warriors and S the number of surviving warriors. The pMARS documentation has
more information on multi-warrior scoring.
The idea for an email-based Core War server came from David Lee. The
original KotH was developed and run by William Shubert at Intel starting in
1991, and discontinued after almost three years of service. Currently, KotHs
based on Bill's UNIX scripts but offering a wider variety of hills are are
running at two sites: koth@koth.org is maintained by Scott J. Ellentuch
(tuc@ttsg.com) and pizza@ecst.csuchico.edu by Thomas H. Davies
(sd@ecst.csuchico.edu). Up until May '95, the two sites provided overlapping
services, i.e. the some of the hill types were offered by both "pizza" and
"stormking". To conserve resources, the different hill types are now divided
up among the sites. The way you submit warriors to both KotHs is pretty much
the same. Therefore, the entry rules described below apply to both "pizza"
and "stormking" unless otherwise noted.
Entry Rules for King of the Hill Corewar
* Write a corewar program. KotH is fully ICWS '88 compatible, EXCEPT that
a comma (",") is required between two arguments.
* Put a line starting with ";redcode" (or ";redcode-94", etc., see below)
at the top of your program. This MUST be the first line. Anything
before it will be lost. If you wish to receive mail on every new
entrant, use ";redcode verbose". Otherwise you will only receive mail
if a challenger makes it onto the hill. Use ";redcode quiet" if you
wish to receive mail only when you get shoved off the hill.
Additionally, adding ";name " and ";author "
will be helpful in the performance reports. Do NOT have a line
beginning with ";address" in your code; this will confuse the mail
daemon and you won't get mail back. Using ";name" is mandatory on the
Pizza hills.
In addition, it would be nice if you have lines beginning with
";strategy" that describe the algorithm you use.
There are currently seven separate hills you can select by starting
your program with ;redcode-94, ;redcode-b, ;redcode-lp, ;redcode-x,
;redcode, ;redcode-94x or ;redcode-94m. The former four run at "pizza",
the latter three at "stormking". More information on these hills is
listed below.
* Mail this file to koth@koth.org or pizza@ecst.csuchico.edu. "Pizza"
requires a subject of "koth" (use the -s flag on most mailers).
* Within a few minutes you should get mail back telling you whether your
program assembled correctly or not. If it did assemble correctly, sit
back and wait; if not, make the change required and re-submit.
* In an hour or so you should get more mail telling you how your program
performed against the current top 20 (or 10) programs. If no news
arrives during that time, don't worry; entries are put in a queue and
run through the tournament one at a time. A backlog may develop. Be
patient.
If your program makes it onto the hill, you will get mail every time a new
program makes it onto the hill. If this is too much mail, you can use
";redcode[-??] quiet" when you first mail in your program; then you will
only get mail when you make it on the top 25 list or when you are knocked
off. Using ";redcode[-??] verbose" will give you even more mail; here you
get mail every time a new challenger arrives, even if they don't make it
onto the top 25 list.
Often programmers want to try out slight variations in their programs. If
you already have a program named "foo V1.0" on the hill, adding the line
";kill foo" to a new program will automatically bump foo 1.0 off the hill.
Just ";kill" will remove all of your programs when you submit the new one.
The server kills programs by assigning an impossibly low score; it may
therefore take another successful challenge before a killed program is
actually removed from the hill.
Sample Entry
;redcode
;name Dwarf
;author A. K. Dewdney
;strategy Throw DAT bombs around memory, hitting every 4th memory cell.
;strategy This program was presented in the first Corewar article.
bomb DAT #0
dwarf ADD #4, bomb
MOV bomb, @bomb
JMP dwarf
END dwarf ; Programs start at the first line unless
; an "END start" pseudo-op appears to indicate
; the first logical instruction. Also, nothing
; after the END instruction will be assembled.
Duration Max.
Hill Name Hill Core Max. Before Entry Min. Rounds Instr.
Size Size Processes Distance Fought Set
Tie Length
Pizza's ICWS '94
Draft Hill Extended
(Accessed with 25 8000 8000 80000 100 100 200 ICWS '94
";redcode-94") Draft
Pizza's Beginner's Extended
Hill (Accessed 25 8000 8000 80000 100 100 200 ICWS '94
with ";redcode-b") Draft
Pizza's
Experimental Extended
(Small) Hill 25 800 800 8000 20 20 200 ICWS '94
(Accessed with Draft
";redcode-x")
Pizza's Limited
Process (LP) Hill Extended
(Accessed with 25 8000 8 80000 200 200 200 ICWS '94
";redcode-lp") Draft
Stormking's ICWS
'88 Standard Hill
(Accessed with 20 8000 8000 80000 100 100 250 ICWS '88
";redcode")
Stormking's ICWS
'94 No Pspace Hill
(Accessed with 20 8000 8000 80000 100 100 250 ICWS '94
";redcode-94nop")
Stormking's ICWS
'94 Experimental Extended
(Big) Hill 20 55440 55440 500000 200 200 250 ICWS '94
(Accessed with Draft
";redcode-94x")
Stormking's ICWS
'94 Multi-Warrior Extended
Hill (Accessed 10 8000 8000 80000 100 100 200 ICWS '94
with Draft
";redcode-94m")
Note: Warriors on the beginner's hill are retired at age 100.
If you just want to get a status report without actually challenging the
hills, send email with ";status" as the message body (and don't forget
"Subject: koth" for "pizza"). If you send mail to "pizza" with "Subject:
koth help" you will receive instructions that may be more up to date than
those contained in this document.
At "stormking", a message body with ";help" will return brief instructions.
If you submit code containing a ";test" line, your warrior will be assembled
but not actually pitted against the warriors on the hill.
At "pizza", you can use ";redcode[-??] test" to do a test challenge of the
Hill without affecting the status of the Hill. These challenges can be used
to see how well your warrior does against the current Hill warriors.
All hills run portable MARS (pMARS) version 0.8, a platform-independent Core
War system available at www.koth.org.
The '94 and '94x hills allow five experimental opcodes and three
experimental addressing modes currently not covered in the ICWS'94 draft
document:
* LDP - Load P-Space
* STP - Store P-Space
* SEQ - Skip if EQual (synonym for CMP)
* SNE - Skip if Not Equal
* NOP - (No OPeration)
* * - indirect using A-field as pointer
* { - predecrement indirect using A-field
* } - postincrement indirect using A-field
[ToC]
------------------------------------------------------------------------
15. Is it DAT 0, 0 or DAT #0, #0? How do I compare to core?
Core is initialized to DAT 0, 0. This is an illegal instruction (in source
code) under ICWS'88 rules and strictly compliant assemblers (such as KotH or
pmars -8) will not let you have a DAT 0, 0 instruction in your source code -
only DAT #0, #0. So this begs the question, how to compare something to see
if it is empty core. The answer is, most likely the instruction before your
first instruction and the instruction after your last instruction are both
DAT 0, 0. You can use them, or any other likely unmodified instructions, for
comparison. Note that under ICWS'94, DAT 0, 0 is a legal instruction.
[ToC]
------------------------------------------------------------------------
16. How does SLT (Skip if Less Than) work?
SLT gives some people trouble because of the way modular arithmetic works.
It is important to note that all negative numbers are converted to positive
numbers before a battles begins. Example: -1 becomes M-1 where M is the
memory size (core size).
Once you realize that all numbers are treated as positive, it is clear what
is meant by "less than". It should also be clear that no number is less than
zero.
[ToC]
------------------------------------------------------------------------
17. What is the difference between in-register and in-memory evaluation?
These terms refer to the way instruction operands are evaluated. The '88
Redcode standard ICWS'88 is unclear about whether a simulator should
"buffer" the result of A-operand evaluation before the B-operand is
evaluated. Simulators that do buffer are said to use in-register evaluation,
those that don't, in-memory evaluation. ICWS'94 clears this confusion by
mandating in-register evaluation. Instructions that execute differently
under these two forms of evaluation are MOV, ADD, SUB, MUL, DIV and MOD
where the effective address of the A-operand is modified by evaluation of
the B-operand. This is best illustrated by an example:
L1 mov L2,
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