[continued from previous message]

standard, dubbed ICWS'94, to be submitted to the ICWS for
evaluation. Unfortunately, the ICWS became inactive and the
proposal was never officially adopted. The draft proposal has
become widely accepted as the de facto Core War standard.

A major change is the addition of "instruction modifiers" that
allow instructions to modify A-field, B-field or both. Also new
are 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. The ICWS'94 draft is available at
http://www.koth.org/info/icws94.html.
____________________________________________________________

6. What is the ICWS?

The "International Core Wars Society" (ICWS) was established in
1985, the year after Core War first appeared in Scientific
American. The ICWS was responsible for the creation of two Core
War standards (ICWS'86 and ICWS'88) and the running of eight
annual Core War tournaments. The ICWS is no longer active.
____________________________________________________________

7. What is Core Warrior?

Following in the tradition of The Core War News Letter, Push Off,
and The 94 Warrior, Core Warrior was a newsletter covering
strategies and current standings in Core War. Started in October
1995, back issues of Core Warrior are available at
https://corewar.co.uk/cw. The final issue of Core Warrior was
published in May 2007. There is a Core Warrior index at
http://www.shadowmagic.org.uk/corewar/warrior.html which has a
summary of the contents of each issue. Many of the earlier issues
contain useful information for beginners.
____________________________________________________________

8. Where are the Core War archives?

Many documents such as the guidelines, the ICWS standards,
previous tournament Redcode entries and Core War systems are
available via ftp from ftp://ftp.koth.org/pub/corewar.

Past rec.games.corewar postings (including Redcode source
listings) are archived at https://corewar.co.uk/rgc.htm.
____________________________________________________________

9. Where can I find a Core War system?

CAUTION! There are many Core War systems available which are not
ICWS'94 (or ICWS'88) compatible. Generally, the older the program
- the less likely it will be ICWS compatible. The three most
popular systems which support ICWS'94 are pMARS, CoreWin and
ARES.

pMARS (with binaries for Windows) is available from:

* https://corewar.co.uk/pmars.htm
* http://www.koth.org/pmars
* https://sourceforge.net/projects/corewar
* https://corewar.co.uk/pihlaja/pmars-sdl

CoreWin is a full-featured, GUI-based Core War simulator for
Windows:

* https://corewar.co.uk/wendell

ARES is an IDE and Core War simulator for Windows with some
experimental features:

* https://harald.ist.org/sites/ares/

There are several notable MARS suitable for embedding or use in
an evolver. Joonas Pihlaja wrote exhaust which Martin Ankerl
later rewrote as exMARS:

* https://corewar.co.uk/pihlaja/exhaust
* https://corewar.co.uk/ankerl/exmars.htm

PyCorewar is simple Python library for debugging and benchmarking
Core War programs:

* https://corewar.co.uk/gutzeit/pycorewar

corewar.io is an online interactive Core War simulator and
debugger:

* https://www.corewar.io
____________________________________________________________

10. Where can I find warrior code?

To learn the game it is a good idea to study previously posted
warrior code. Damien "Planar" Doligez has a well organized
library of the warriors published before 2002 at
http://para.inria.fr/~doligez/corewar/

The most up-to-date collection of warrior code is available on
Christoph C. Birk's Koenigstuhl infinite hills at
https://users.obs.carnegiescience.edu/birk/COREWAR/koenigstuhl.html
____________________________________________________________

11. I do not have access to Usenet. How can I read the Core War
newsgroup?

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.

Google Groups provides a gateway to Usenet and rec.games.corewar
at https://groups.google.com/group/rec.games.corewar.
____________________________________________________________

12. Are there any Core War related WWW sites?

You bet. The following websites offer convenient access to
software, tutorials, past newsletters and warrior code:

* https://users.obs.carnegiescience.edu/birk/COREWAR
* http://para.inria.fr/~doligez/corewar
* http://www.koth.org
* https://corewar.co.uk
* http://newton.freehostia.com/net/corewar
* http://www.corewar.info
____________________________________________________________

13. 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 a Redcode
program (warrior) with special comments via plain text email. 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 a set number of battles against
each of the programs currently on the Hill. You normally receive
3 points for each win and 1 point for each tie. All scores are
updated to reflect your battles and the programs on the hill are
ranked from high to low. If you are in last place you are pushed
off the hill, otherwise 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. 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 December 1991 and discontinued after almost
three years of service.

Currently, KotHs offering a wide variety of hills are are running
at two sites: KOTH.org is maintained by Scott J. Ellentuch and
sal.discontinuity.info by Barkley Vowk. The way you submit warriors
to both KotHs is pretty much the same.

Entry Rules for King of the Hill Core War

* Write a Core War program. KotH is fully ICWS '94 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. Additionally, a ";name
<program name>" and ";author <your name>" are required. You
can also describe the algorithm you use if you have lines
beginning with ";strategy".
* Email this file as plain text to koth@koth.org or
koth@sal.discontinuity.info.
* Within a few minutes you should receive an email telling you
whether your program assembled correctly or not. If it did
assemble, sit back and wait; if not, make the change required
and re-submit.
* In 15 minutes or so you should get more mail telling you how
your program performed against the current top 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.

Sample Entry

;redcode
;name Imp
;author A. K. Dewdney
;strategy the simplest Redcode program able to relocate itself

imp mov imp, imp+1

end ; nothing after the end instruction will be assembled

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 switch to quiet mode. See the KotH information at
http://www.koth.org/koth.html or
https://sal.discontinuity.info/help.html for more details.

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 v1.0 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.

Popular Hills

----------------------------------------------------------------------------------------
Hill Core Max Max Min Instr
Hill Name Size Size Proc Cycles Len Dis Rounds Set
-------------------------- ------ ------- ------- -------- ----- ----- -------- --------
KOTH.org's '88 Standard 20 8000 8000 80000 100 100 250 ICWS '88
Hill (";redcode")

KOTH.org's '94 Standard 20 8000 8000 80000 100 100 250 Extended
Hill (";redcode-94") ICWS '94

KOTH.org's '94 No Pspace 20 8000 8000 80000 100 100 250 ICWS '94
Hill (";redcode-94nop")

KOTH.org's '94 Big 20 55440 10000 500000 200 200 250 Extended
Hill (";redcode-94x") ICWS '94

KOTH.org's '94 Multiwar 10 8000 8000 80000 100 100 500 Extended
Hill (";redcode-94m") ICWS '94

SAL's Beginner's 25 8000 8000 80000 100 100 6x250 Extended
Hill (";redcode-94b") ICWS '94

SAL's Tiny 25 800 800 8000 20 20 6x250 Extended
Hill (";redcode-tiny") ICWS '94

SAL's Nano 50 80 80 800 5 5 30x250 Extended
Hill (";redcode-nano") ICWS '94

SAL's Limited Process 25 8000 8 80000 200 200 6x250 Extended
Hill (";redcode-lp") ICWS '94
----------------------------------------------------------------------------------------

Note: Warriors on the beginner's hill are retired at age 50.
____________________________________________________________

14. Is it DAT 0, 0 or DAT #0, #0? How do I compare to core under ICWS'88
rules?

Core is initialized to DAT 0, 0. Under ICWS'88 rules this is an
illegal instruction and '88 standard assemblers will not assemble
it, only DAT #0, #0. This begs the question, how to compare
something to see if it is empty core under ICWS'88 rules? The
answer is, the instructions before your warrior's first
instruction and after your warrior's last instruction are most
likely DAT 0, 0. So you can use them, or any other unmodified
instructions, for comparison.

Note: under ICWS'94 rules DAT 0, 0 is a legal instruction and '94
standard assemblers will assemble DAT 0, 0.
____________________________________________________________

15. How does SLT (Skip if Less Than) work?

SLT skips the next instruction if the value of the A-operand is
less than value of the B-operand. SLT can sometimes cause
confusion 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. For example, -1 becomes
CORESIZE-1.

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.
____________________________________________________________

16. 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, <L2
L2 dat #0, #1

Under in-register evaluation, the L2 instruction is saved in a
buffer before the L2 memory location is decremented by evaluation
of the B-operand of L1. The saved DAT #0,#1 instruction is then
written to L2, leaving it unchanged.

Under in-memory evaluation, the L2 instruction is not buffered
and thus decremented by evaluation of the B-operand. After
execution of L1, L2 changes to DAT #0,#0.
____________________________________________________________

17. What is P-space?

P-space is a separate area of memory which only your program's
processes can access. The contents of each P-space cell are
preserved between rounds in a multi-round match. Unlike core
memory each P-space cell can only store one number, not a whole
instruction. Also the addressing in P-space is absolute, i.e.
P-space address 1 is always 1 regardless of where the instruction
is referenced from.

P-space can only be accessed by two special instructions, LDP and
STP. The syntax of these two instructions is a bit unusual. STP
has an ordinary number in core as its source which is put into
the P-space cell pointed to by the destination. The P-space cell
isn't determined by the destination address, but by its value,
i.e. the value that would be overwritten if this were a MOV. So
STP.AB #Q, #R would put the number Q into the P-space cell R mod
PSPACESIZE. Similarly,

stp.b 2, 3
dat 0, 0
dat 0, 9
dat 0, 7

would put the number 9 into the P-space cell 7. LDP works the
same way, except the source is a P-space cell and the destination
is a field in core.

The P-space cell 0 is a special cell. It is initialized to a
special value before each round. This value is:

* -1 (or CORESIZE-1) at the beginning of the first round
* 0 if the program died in the previous round
* The number of surviving programs if the program did not die
in the previous round

This means that for one-on-one matches, loss=0, win=1 and tie=2.

The default size of P-space is 1/16 of the core size. This size
is the value of the predefined variable PSPACESIZE. All cells in
P-space (except for cell 0) are initialized to 0.
____________________________________________________________

18. What does "Missing ;assert" in my message from KotH mean?

This means you have omitted an ";assert" line in your submission.
";assert" is used to specify which environments your code will
work under or was designed for. For example, if your warrior was
written for the '94 draft hill then you can put:

;assert CORESIZE==8000

in your code, meaning that an error will occur if you attempt to
compile the code for a different core size. If you don't want to
use the features of ";assert" and you want to get rid of the
annoying warning just put:

;assert 1

in your code, which means it will compile unconditionally.
____________________________________________________________

19. How should I format my code?

The way you format your code is really your own choice. If you
are new to the game then use the style you feel most comfortable
with. However, using a common format helps others to understand
your code quicker. Most players tend to use the following
conventions when writing code:

* use meaningful label names
* enclose EQUate expressions in parentheses, e.g. step equ
(2430+5)
* use lower case for label names and opcodes
* don't add opcode modifiers if you don't need to, e.g. add.ab
#1, #2 is the same as add #1, #2
* use whitespace after every comma
* use tabs to align the opcodes, the instruction field(s) and
any comments
* do not use $ (direct addressing mode) or : (suffix of some
labels)
____________________________________________________________

Credits

Additions, corrections, etc. to this document are solicited.
Thanks in particular to the following people who have contributed
major portions of this document:

* Mark Durham (wrote the original version of the FAQ)
* Paul Kline
* Randy Graham
* Stefan Strack
* Anton Marsden
* Barkley Vowk
* John Metcalf

Copyright © 1991–2022 the Core War FAQ Contributors. Content of
the FAQ is available under the GNU Free Documentation License,
version 1.3.

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