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antwerp sprouts

The
game of sprouts is a two-person game invented by John Conway and Michael Paterson in 1967 (for some
historical comments visit the encyclopedia). You just need pen and paper to
play it. Here are the rules : Two players, Left and Right, alternate
moves until no more moves are possible. In the normal game, the last
person to move is the winner. In misere play, the last person to move is
the loser. The starting position is some number of small circles called
“spots”. A move consists of drawing a new spot g and then drawing two
lines, in the loose sense, each terminating at one end at spot g and at
the other end at some other spot. (The two lines can go to different
spots or the same spot, subject to the following conditions.) The lines
drawn cannot touch or cross any line or spot along the way. Also, no
more than three lines can terminate at any spot. A spot with three lines
attached is said to be “dead”, since it cannot facilitate any further
action.

You can play sprouts online using this Java applet.
There is also an ongoing discussion about sprouts on the geometry math forum. Probably the most complete
information can be found at the world game
of sprouts association
. The analysis of the game involves some nice
topology (the Euler number) and as the options for Left and Right are
the same at each position it is an impartial game and the outcome
depends on counting arguments. There is also a (joke) variation on the
game called Brussels sprouts (although some people seem to miss the point
entirely).

Some years ago I invented some variations
on sprouts making it into a partizan game (that is, at a given
position, Left and Right have different legal moves). Here are the rules
:

Cold Antwerp Sprouts : We start with n White
dots. Left is allowed to connect two White dots or a White and bLue dot
or two bLue dots and must draw an additional Red dot on the connecting
line. Right is allowed to connect two White dots, a Red and a White dot
or two Red dots and must draw an additional bLue dot on the connecting
line.

Hot Antwerp Sprouts : We start with n
White dots. Left is allowed to connect two White dots or a White and
bLue dot or two bLue dots and must draw an additional bLue dot on the
connecting line. Right is allowed to connect two White dots, a Red and a
White dot or two Red dots and must draw an additional Red dot on the
connecting line.

Although the rules look pretty
similar, the analysis of these two games in entirely different. On
february 11th I’ll give a talk on this as an example in
Combinatorial Game Theory. I will show that Cold Antwerp Sprouts
is very similar to the game of COL, whereas Hot Antwerp Sprouts resembles SNORT.

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homemade .mac

The
other members of my family don’t understand what I am trying to do the
last couple of days with all those ethernet-cables, airport-stations,
computer-books and the like. ‘Improving our network’ doesn’t make
much of an impression. To them, our network is fine as it is : from
every computer one has access to the internet and to the only
house-printer and that is what they want. To them, my
computer-phase is just an occupational therapy while recovering
from the flu. Probably they are right but I am obstinate in
experimenting to prove them wrong. Not that there is much hope,
searching the web for possible fun uses of home-networks does not give
that many interesting pages. A noteworthy exception is a series of four
articles by Alan Graham for the macdevcenter
on the homemade dot-mac with OS X-project.

In
the first article Homemade Dot-Mac with OS X he explains how to
set-up a house-network (I will give a detailed account of our
home-network shortly) and firing up your Apache webserver. One nice
feature I learned from this is to connect a computer by ethernet to the
router and via an Airport card to the network (you can force this by
specifying the order of active network ports in the
SystemPreferences/Network/Show Network port configuration-pane :
first Built-in Ethernet and second Airport). This way you
get a faster connection to the internet while still connecting to the
other computers on the network. In the second part he explains how to
get yourself a free domain name even if you have (as we do) a dynamic
IP-address via a service like DynDNS. Indeed it is quite easy to set this up but
so far I failed to reach my new DNS-server from outside the network,
probably because of bad port-mapping of my old isb2lan-router.
This afternoon I just lost two hours trying to fix this (so far :
failed) as I didn’t even know how to talk to my router as I lost the
manual which is no longer online. A few Google-searches further I
learned that i just had to type http://192.168.0.1 to get at the set-up pages
(there is even a hidden page) but you shouldnt try these links
unless you are connected to one of these routers. Maybe I will need
another look at this review.

In the second
article, Homemade Dot-Mac with OS X, Part 2 he discusses in
length setting up a firewall with BrickHouse (shareware costing $25) compared to the
built-in firewall-pane in SystemPreferences/Sharing convincing me
to stay with the built-in option. Further he explains what tools one can
use to set up a homepage (stressing the iPhoto-option).Finally, and this
is the most interesting part (though a bit obscure), he hints at the
possibility of setting up your own iDisk facility either using
FTP (insecure) or WebDAV.

The third article in the
series is Homemade Dot Mac: Home Web Radio in which he
claims that one can turn the standard OS X-Apache server into an iTunes
streaming server. He uses for this purpose the QuickTime Streaming Sever which you can get for
free from the Apple site but which I think works only when you have an
X-server. It seems that all nice features require an X-server so
maybe I should consider buying one…

The (so far)
final article is Six Great Tips for Homemade Dot Mac Servers is
really interesting and I will come back to most op these possibilities
when (if) I get them to work. The for me most promising options are :
the central file server (which he synchronizes using the
shareware-product ExecutiveSync ($15 for an academic license) but
I’m experimenting also a bit with the freeware Lacie-program Silverkeeper which seems to be doing roughly the
same things. The iTunes central-hack is next on my ToDo-list as
is (at a later stage) the WebDav and the Rendezvous-idea. So it seems
I’ll prolong my occupational therapy a while…

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combinatorial game software


As I am going to give a talk on Combinatorial Game Theory early
next month I have to update my rusty knowledge of canonical forms of
two-person game positions, their temperature theory and the like. As
most of the concepts in this field are recursive they are hard to work
out by humans but easy for computers. So it is nice to have a good
program to use. I remember that David Wolfe wrote a couple of years ago the Gamesman Toolkit but it seems he has taken it off
his website. Still, you can get it from the Software released by Michael Ernst page. So,
download the games.tar.gz-file and uncompress it on your Desktop.
Then do the following

cd Desktop/games sudo make sudo cp
games /usr/bin/ /usr/bin/games

to get it up and
running (for documentation of how to use it see the Gamesman
Toolkit-paper above. But, it seems that as of July 2003 there is a much
better alternative around : the Combinatorial Game Suite of Aaron Siegel. It is an open source Java-program so it
runs on many platforms (including Mac OSX). Here is the way to get it
going : first download it and you will get a
cgsuite-0.4-folder on your desktop. Then type

cd
Desktop/cgsuite-0.4 java -jar cgsuite.jar

and after a few
questions (including whether you want to be on the mailing list of the
project) the program starts up. It is very well documented with an
on-line manual which I have to read over the coming
days…

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SSL on Mac OSX

A
longer term project is to get the web-server www.matrix.ua.ac.be integrated in our home-network
as an external WebDAV-server (similar to the .Mac-service
offered by Apple). But as this server runs all information about the
master-class on non-comutative geometry connecting to it via HTTP to use
WebDAV is too great of a security risk as all username/password
combinations will be send without encryption. Hence the natural question
whether this server can be set up to run SSL (Secure Sockets
Layer) such that one can connect via HTTPS and all exchanged information
will be encrypted. As the server is an Apache it comes down to get
mod-ssl running. A Google on mod_ssl OS X gives the
ADC-document Using mod-ssl on Mac OS X which seems to be just
what I want. This page is very well documented giving detailed
instructions of using the openssl command. However, the
end-result is rather weak : it only makes the localhost running
HTTPS, that is, one can connect to your own computer safely… which is
pretty ridiculous (other computers in the same network cannot even
connect safely).

So, back to the Google-list on which
one link raises my interest Configuring mod-ssl on Mac OS X which looks like
the previous link but has one essential difference : the page is written
by Marc Liyanage. If you ever tried to get PHP and/or MySQL
running under OS X you will have noticed that his pages are by far the
most reliable on the subject, hence maybe he has also something
interesting to say on mod-ssl. However, the bottom line of the
document is not very promising :

You
should now be able to access the content with https://127.0.0.1 from
the same machine.

which is again the
localhost. So perhaps it is just impossible to run mod-ssl
without having an X-server. Anyway, let us try out his procedure.
Begin by issuing the following commands in the Terminal

sudo -s cd /etc/httpd mkdir ssl chmod 700 ssl cd
ssl gzip -c --best /var/log/system.log > random.dat openssl rand
-rand file:random.dat 0

Next, we need a server certificate. If you
want to do it properly you need a certificate from a certification
authority
such as Thawte but this costs at least $200 a year which I
am not willing to pay. The alternative is to use a self-signed
certificate
which will force the browser to display an error-message
but if the user dismisses it all traffic exchanged with the server will
still be encrypted which is just what I want. So, type the command

openssl req -keyout privkey-2001.pem -newkey rsa:1024
 -nodes -x509 -days 365 -out cert-2001.pem

(all on one line).
You will be asked a couple of questions (the only important one is the
Common Name (eg, YOUR name). Here you should take care to enter
the host name of your web server exactly as it will be used later in the
common name field. In my test-case, if I want to get my server
used by other computers in the network this name will be
imaclieven.local. (note the trailing .). Now issue the following
commands

chmod 600 privkey-2001.pem chown root
privkey-2001.pem apxs -e -a -n ssl /usr/libexec/httpd/libssl.so

which will activate the SSL-module (if at a later state you want
to de-activate it you have to change -a by -A in the last command).
Finally, we have to change the /etc/httpd/httpd.conf file so
first save a backup-version and then add the following lines at the end
of the file :

(IfModule mod-ssl.c)     Listen 80    
Listen 443     SSLCertificateFile /etc/httpd/ssl/cert-2001.pem    
SSLCertificateKeyFile /etc/httpd/ssl/privkey-2001.pem    
SSLRandomSeed startup builtin     SSLRandomSeed connect builtin   
 (VirtualHost -default- :443)         SSLEngine on    
(/VirtualHost) (/IfModule)

Observe that round brackets ()
should be replaced by <>. Finally, we do

apachectl
stop apachectl start

and we are done! Going to another computer
in the network and typing in Safari https://imaclieven.local./
will result in an error message


Just click Continue and you will have a secure connection
to the server. Thanks Marc Liyanage!

(Added january
11th) Whereas the above allows one to make a HTTPS connection it is not
enough for my intended purposes. In order to get a secure connection to
a WebDAV server, this server must have the mod-auth-digest module
running which seems to be impossible for the standard Apache server of
10.3. You need an X-server to have this facility. So I think I have to
scale down my ambitions a bit.

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one week blogging

So far I
found it rather easy to post one or more messages a day as I was
installing a lot of software or trying to get things working and was
merely logging my progress for future reference. These notes are useful
to me but probably not to the rest of the world. Another thing I noticed
is that I’m using this blog sometimes as a replacement for my
Bookmarks, merely listing interesting web-pages without too much
personal comments. I will continue to post both install-logs and
bookmark-logs but in addition I want to write (say weekly) a lengthier
post on a specific topic with more background, more details (such as
screenshots) and more personal comments. We will see how this works out
in the coming weeks…

Another thing that slightly
worried me is that people visiting my homepage and clicking on to my
blog may expect entirely different things there. But this cant be
helped, I’m sitting on an OSX-cloud at the moment but no doubt this
will change quickly. Beginning of february I have to give a talk on
Combinatorial Game Theory and soon afterwards the
Non-commutative Geometry Master Class starts in which I’m giving
a couple of courses, so mathematics will become more dominant in this
blog from next month on…

On a
blog-tech matter : I found a quite good editor pMpost
which is meant to write pMachine-blogs offline and upload them by one
click. It also synchronizes categories etc. on login. Further, it has a
spelling-checker but the thing I really like about it is that you can
save texts as a draft and continue at a later time (sadly, it remember
the date/hour when you start your post so when you finally submit it it
will be posted at the starting- rather than the posting-day. Still,
there is nothing that copy/paste cannot solve. I hope to use this
facility when (read if) I’m going for a more in-depth post. Another
matter that I will address to as quickly as possible (probably over the
weekend) is teh layout of this site. The main annoying thing is that the
text doesnt resize when you increase/decrease window width. So I will
address this matter first and probably leave a personal layout and
color-scheme to later. Fortunately, I did find a good site containg a
lot of CSS templates for pMachine weblogs. Another site I’ll have to
investigate over the weekend is pMtemplates. But don’t expect too much from the
layout-side, I still have other projects to worry about : SSL, WebDAV,
streaming iTunes, getting on Ethernet-DVD player to work and so
on.

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