Xtank.FAQ
Kurt J. Lidl
FAQ for the rec.games.xtank.{play|programmer} newsgroups:
FAQ for the Xtank game, also!
There are three major sections in this revision of the
rec.games.xtank.{play|programmer} FAQ. Please make sure
that you check this FAQ before posting to the newsgroups.
Thanks.
If you have comments or corrections to this posting, please
mail them to xtank-...@eng.umd.edu. Thanks.
Section G -- General information topics
Section P -- Playing information topics
Section I -- Installation, compiling, & porting information
General Topics:
====================
G.01) What type of postings should be posted in rec.games.xtank.play?
G.02) What type of postings should be posted in rec.games.xtank.programmer?
G.03) What is Xtank all about?
G.04) What is the latest Xtank release?
G.05) Where can I get the Xtank release from?
G.06) How do I use "ftpmail" to get Xtank?
G.07) How do I make a patch file for Xtank?
G.08) Is there a place that I can get binaries from?
Playing Topics:
====================
P.01) Why can't I place HARMs on the vehicles I design?
Installation, compiling and porting Topics:
==============================
I.01) What software tools do I need to make a version of Xtank?
I.02) Will Xtank work on my unix system ?
I.03) What are some of the common problems with Xtank installs?
I.04) What does "Alarm Clock" mean, when I run Xtank?
I.05) What should I do if Xtank doesn't compile/work on my unix system ?
I.06) How should I go about porting Xtank to a new (unsupported) system?
=========================== ANSWERS to the FAQ ============================
G.01) What type of postings should be posted in rec.games.xtank.play?
This newsgroup is intended to be used for (but not limited to)
discussion of:
- exchange of ideas and strategy for human players
- game play between humans and robots
- discussion of combinations for robot competitions
- feature rants for a given program
- wish lists for future robots
- feedback to game designers about robot features and strategies
that are effective against their robots, from a human perspective
G.02) What type of postings should be posted in rec.games.xtank.programmer?
This newsgroup is intended to be used for (but not limited to)
discussion of:
- Modifications to the code of the Xtank program proper
- Modifications to robot programs that are contained in the
standard distribution
- Programmers of xtank robot programs should use this group
to solicit feedback from other programmers
- Bug reports and fixes for robots and the core distribution
- Reports of installation problems, but not general inquiries!
See the section on installations in this FAQ before posting!
This newsgroup is *NOT* intended for answering requests like:
- Does Xtank run on a <foo>? Where <foo> is a specific machine
type. Get the package, or finish reading this FAQ. The authors
and maintainers will *NOT* respond to these questions, and if
anyone else that gets USENET news does, you've been very lucky.
See the section on installations in this FAQ before posting!
In general, if you haven't read through the code of the main game
modules, or the robot you have a question about, this probably isn't
the correct place to post your question.
G.03) What is Xtank all about?
Briefly put, Xtank is a multi-player vehicular-based (normally
combat-oriented) game played in mazes of various sizes and types.
Humans control a vehicle (usually a tank) equipped with a variety of
armor and weaponry. Your objective depends on the type of game you
play. There are five different game scenarios for Xtank:
A) Combat -- Attempt to kill all the tanks not on your team.
(This is the default game for Xtank.) Players get a quantity of
points for killing opponents, and lose points for killing friends.
The amount of points received depends on the relative values of
your vehicle and the vehicle that you destroy.
B) War -- Win by taking over territory. You take over territory by
traveling over it in your vehicle.
C) Ultimate -- Sort of a cross between ultimate frisbee and
hockey. Score by catching the disc in the opponents' goal.
D) Capture -- A variant of ``Capture the Flag.'' Win by collecting
all the discs into your goal.
E) Race -- Win by being the first vehicle to get to a goal.
One of the more unique features about xtank is that it is a
multi-threaded game. This allows players to load a robot program
file (either written in "C" or a "C" linkable language) into the
running Xtank image and start playing with that program. Thus, each
player can have a robot program that can control (or share control) of
a vehicle for the duration of a game. On some systems, robot programs
can be dynamically loaded into a running game (works on DECstations,
Suns, maybe others).
The games are played in an maze (think of it as a type of gladiator
arena), which a play can design.
The vehicles described above are also player designed. The design of
playable vehicles is an art unto itself, so you will most likely have
to try a good many vehicles before you get one that is worth keeping.
G.04) What is the latest Xtank release?
The latest release of Xtank is the 1.3f release.
G.05) Where can I get the Xtank release from?
Please make sure that you get the latest version of Xtank if you are
installing it for the first time. We are continually fixing bugs in
the Xtank releases, as well as implementing new features, and merging in
changes from the various contributors to Xtank.
Here are the hosts that are known to have the latest release
of Xtank available for anonymous FTP:
Host mojo.eng.umd.edu (129.2.90.15)
Location: /pub/xtank
FILE -rw-r--r-- some_large_number Sep 13 xtank1.3f.tar.Z
Host azathoth.sura.net (128.167.254.184)
Location: /pub/xtank
FILE -rw-r--r-- some_large_number Sep 17 xtank1.3f.tar.Z
If you don't have anonymous FTP access, please *DON'T* mail or post
asking people to mail you a copy. The release is just too damn big
to do that often. Instead, see the section on "ftpmail".
G.06) How do I use "ftpmail" to get Xtank?
Mail the following message to "ftp...@decwrl.dec.com", with
just about anything as the "Subject:" line (it is ignored).
connect azathoth.sura.net
binary
chdir /pub/xtank
get xtank1.3f.tar.Z
If this doesn't work (like the version number has changed) you can
get more info about the ftpmail program by by mailing ftp...@decwrl.dec.com,
with the word "help" in the body (the Subject: line is ignored).
Please remember that the ftpmail service is their to help everyone, so
please don't abuse the privilege! Thanks.
G.07) How do I make a patch file for Xtank?
Basically, for each changed file, you do the following:
diff -c5 oldfile newfile
Please do *not* send "unidiff" differences, as I don't like dealing
with them, and we don't have a patch installed that is capable of
handling them, at least yet. This message will be updated to reflect
any changes in the status of our patch program...
========================
G.08) Is there a place that I can get binaries from?
The answer to this is, "It depends." In general, just grabbing a
binary is not the best idea. You should really get the source code
to the release and compile it yourself. You will probably learn
something, and it doesn't take too long to do it.
That said, on to the topic at hand. On occasions, binaries of Xtank
have been made available through AFS. Unfortunately, I left the
Unversity of Maryland, and no longer have any account that will allow
me to make available binaries via AFS. The good news is that I
have compiled up versions of the 1.2f game for sun3, sun4, decstation
and vax platforms, so you can ftp those versions.
They are only available through the host azathoth.sura.net,
in the directory /pub/xtank/pre-compiled. Please get the README
file there if you plan on using these binaries.
========================
P.01) Why can't I place HARMs on the vehicles I design?
HARMs can only be installed on the side mounts of a vehicle body.
Try placing them there, and you should have a good experience.
Additionally, they are fired differently than the other weapons
in Xtank -- you click on the target in the Radar mapper to
aim these puppies. Good luck.
========================
I.01) What software tools do I need to make a version of Xtank?
Well the short and sweet of it is: --> Imake <---
If you don't have this, you will need to get this. Imake is
available via FTP from export.lcs.mit.edu. Thanks to the foresight
of the members of the MIT staff and the X Consortium, you can grab
just the source to imake, and its configuration files. They are in
the directory /pub/R5untarred/mit/config. You will need to get all
the files there, and edit the "site.def" file to reflect where the X
Window Systems has actually been located on your machine, for your
particular X Window installation.
You don't need "flex" to re-build xtank, but you do need to read the
instructions! We include "pre-flexed" grammars for your compiling
pleasure. However, if you plan on changing either the vehicle save
format, or the vehicle structures such that you will need to save
more info, you will need to have a relatively recent version of flex
installed on your system. I'm not too sure how recent, but version
2.3 of flex is good enough for us.
flex is available via FTP from prep.ai.mit.edu
I.02) Will Xtank work on my system ?
Xtank is, shall we say, a large and complex body of code, some of which
works in a rather arcane way. It's not terribly portable, but we are
working on porting it to systems that have a fairly high-level way
of doing light-weight processes/threads. This is invariably where the
hard part of porting Xtank comes in.
Offhand, I know that Xtank runs on the following systems:
Sun hardware, Sun 3 (SunOS 3.5 or higher) or Sun 4 (SunOS 4.0 or
higher). DECstations, running either Ultrix 3.1, 4.1 or 4.2.
386/486 systems running 386BSD, with X11R5.
These are the only a few platforms we have access to test releases on
before we ship the code. (Generally, we test Xtank on Sun4 systems
and DECstations, and not the Sun3 systems. Althougth lately, we
have also been regression testing the releases on a VAX 3100 and
a DECstation 5000/25. Finally, we have it running on our 386BSD
systems. If you would like to have us test on more systems, get
us accounts on them, accessable through telnet. We can't promise
that we can test on everything, but it helps to have an account there.)
We have finished the port of Xtank to a SVR4 machine, using the
SVR4 low-level threading available via makecontext()/swapcontext().
Outside of adding the stub things needed in the Imakefile(s), Xtank
should work on those systems.
Someday, we may even support MACH threads. We may even support POSIX
threads, if they ever straighten out *that* mess.)
In the past, Xtank has compiled and run on the following machines. This
may or may not work on the latest release. We can't test it, but we
do actively apply fixes that people send us that are supposed to fix things.
NeXT machines
HP9000, series 300, running both 4.3BSD and HP-UX
HP9000, series 800 and series 700
IBM RS6000
IBM PC/RT
VAXes running Ultrix
Silicon Graphics
Motorola SysV boxes
Encore Multimaxes (Sys 5 universe)
Sequents (i386 based)
Not all features are working on all platforms. If your platform doesn't
have a particular feature, port it and send us a patch file!
I.03) What are some of the common problems with Xtank installs?
Many people have improperly installed X11 on their systems such that
system include files get included explicitly before the program
specific include file directories. It used to be that there was
very little chance that Xtank would compile properly on your system.
We've cleaned up the include files to the point that it ought to
work properly for your machines. If you have problems, let us know
the solutions.
Sometimes, people on non-BSD derived systems have configured their
X11 system to link with system libraries in the wrong place on
the compile line. This is also a no-go issue for Xtank. If you
have this problem, you should try to find a local guru to help
you.
I.04) What does "Alarm Clock" mean, when I run Xtank?
If you run Xtank, and setup a game, and then try to run it,
and Xtank dies after one frame of animation, you probably have
lied to Xtank about your system. This error typically shows up
in compiled copies of Xtank that were compiled with "-DSYSV", when
they should have been compiled with "-DSVR4". System V systems
prior to SVR4 handle signals differently, and this is a typical
indication of the resulting incompatibilities...
If you are working on a Unix machine that supports both SYSV, and BSD
(eg SunOS), this probably means that you have compiled something with
the SYSV version of the C compiler, rather then the BSD C compiler.
I.05) What should I do if Xtank doesn't compile/work on my unix system ?
First, make sure that you are trying to install the latest version
of Xtank. If you are not, then get the latest version, and try again.
Second, you should investigate exactly what is wrong with the
system. If you can't fix it yourself, then you should carefully
gather all the information in the README file and post that to
the network, in the rec.games.xtank.programmer. *WARNING* Failing to
submit a full description of the machine, and the error message is
liable to generate a flame in response to your posting. *WARNING*
For your convience, here is the list of questions to be filled out:
(taken from the README file)
* What your setup is:
- Hardware platform (eg Sun SPARCstation 1+)
- OS version (eg SunOS 4.1.2)
- Windowing System (eg OpenWin 3, or MIT X11R5, DecWindows, etc)
- Compiler used (eg gcc 1.37, vendor supplied cc, etc)
- any non-default Imakefile.Config -D flags
- what version of Xtank that you are trying to run
Please be as specific as possible. All the maintainers of Xtank
would much rather have too much information than too little.
Finally, you should include the line in the compile that caused the
install to die.
If xtank compiles OK, but does not run, and the release of Xtank that
you have is 1.3e or later, run "xtank.arch -V" and include that
output in your submitted bug report. (Where "xtank.arch" is the
generated executable for your architecture.) This is *very*
important.
If you have Makefile problems, try investigating the debugging flags
that you system supports, if any. Some systems support a "-d" or
"-D" flag, even though it is not documented. You've got nothing to
lose if you try it, even if your "make" manpage doesn't mention it.
I.06) How should I go about porting Xtank to a new (unsupported) system?
Many Unix systems out there have most of the support needed to run
Xtank, in at least some form or another.
Outside of needed to have reasonable X11 support, Xtank needs to have
access to good floating point routines. Additionally, there are two
sticky issues in porting Xtank -- both of which don't affect the
"core" game program. The two issues are the need for doing a
light-weight threading (how the robot programs are run) and the
ability to load in object files on the fly...
Having a light-weight threading package make Xtank a lot more fun,
because it is not just human players then, but also machine players.
Having the dynamic loading code working makes it much easier to write
and debug new robot programs. Obviously, it doesn't make sense to
work on dynamic loading if you don't have the threading working.
There are currently three ways of doing the light-weight threading --
use the SunOS LWP package, use the SVR4 style threading package,
or use the longjmp() hack. This are listed in roughly the order they
are preferred. Obviously, the LWP solution only works if you have
SunOS, or something like a Solbourne running their SunOS derived OS.
The SVR4 solution should work on any system that is SVR4 derived and
has a full SVR4 implementation. At least a few vendors have released
SVR4 ports that have broken threading. If your vendor has done this,
complain bitterly, and loudly.
If neither of the above systems work for you, investigate any
packages or light-weight threading packages that you might have
available to you. For example, on MACH derived systems, you should
have a good threading interface. The same can be said for Sprite (I
think). If you have a system available to you, try to use it, the
chances are that you won't have to do it again...
Finally, if neither of the above solutions are available to you, you
should investigate the longjmp() hack. This is not for the faint of
heart, however. It involves adding more knowledge to Xtank about
very, very, *very*, system specific things, like the format of a
saved longjmp() buffer, and whether or not your system's longjmp()
call can jump both up and down your system's stack (not all can, on
all platforms). If you longjmp() can't jump up and down your stack,
you will need to implement your own longjmp() call, that can. You
will need to do this in assembly (we *did* warn you...). There are
sample assembly pieces written for the IBM RS6000, DEC VAX machines,
and MIPS R[23]000 cpu's.
Assuming that you have a working longjmp() routine, you will need to
teach Xtank about the structure of your longjmp save buffers.
Examine the code the "thread.h" file, and see how it is done on other
platforms. Then write one that is tailored to your hardware... We
won't be able to help you out with this, because we don't have a
platform of whatever you are porting to help out on. If you want to
donate a particular hardware platform that runs Unix to us, we'll try
awfully hard to port Xtank to that platform. If you have gotten this
far, you should maybe check with your platform vendor to see if they
have done a port of Xtank themselves. A great number of people have
ported Xtank to various systems, but then never released those
changes back to us. Ask them, it can't hurt.
Assuming that you get the threading done and working reliably, you
should then attempt to get dynamic program loading working on your
platform. This is the other area that could use some work for
Xtank. We will be adding dynamic loading support via a dlopen()
interface, so people with SVR4-ish systems should be able to use
that. Otherwise, the current system will have to modified, or a new
system developed. The "current" system relies on the ability of "ld"
to generate a file that is supposed to be started at a particular
address. The object file is created on the fly (if needed) and then
opened by Xtank and the symbol table extracted from the file and
examined.
This is all roughly explained in the comments to the "unix.c" file --
you should check there for all the gory details. Typically, this
would be easiest to port if your system uses the "a.out" format for
storing object files. If your system uses "COFF", you should closely
examine the DECstation code in the "unix.c" file, as it uses a COFF
like file header.
The above really just covers some of the difficult parts in porting
Xtank. If you have suggestions or additions to the above text,
please send them to me, via the address listed at the beginning of
this FAQ.
--
/* Kurt J. Lidl (li...@pix.com) | Unix is the answer, but only if you */
/* UUCP: uunet!mimsy!pixcom!lidl | phrase the question very carefully. */