## Yeah, Top Ten!

As I announced in my previous article, I took part in a contest. And, what should I say, I’m one of the six best programmer - worldwide!

Ok, ok - the contest has just started, there aren’t any results yet, but they already announced only six bots are facing off. It’s a pity that there aren’t more people taking place in this game, but however, the lesser opponents the easier it is to conquer a place on the podium :-P

Good luck for everyone participating!

## FM-Contest: Tactics

As I announced in my last articles I’ve submitted a programmed bot for the contest organized by freiesMagazin. Here I present my bots tactics.

The submitted bots are grouped to teams. On one hand the BLUE team, or preys, they have to run and hide. On the other hand the RED team, or predators, their task is to catch a bot of the BLUE team. If anyone of the BLUE team got captured by a RED team member he changes the team from BLUE to RED. If there was no teamchange for a longer time, one of the BLUE team is forced to change. That are the simplified tasks, for more details visit their website. All in all if you are BLUE run and hide, otherwise hunt the BLUE’s.

The map is very simple organized, there are wall-fields and floor-fields. You are neither able to access wall-fields nor to see through such fields. Floor-fields are acessible, but toxic. So they decrease your health status. You can look in each of eight directions: NORTH, NORTH_WEST, WEST, SOUTH_WEST, SOUTH, SOUTH_EAST, EAST, NORTH_EAST. You’ll only see enemies that are standing in the direction you are looking to (180°) and don’t hide behind a wall. Positions of your team members are told by communicators, so you’ll know where your team is hanging around. In each round you’re able to walk exactly one field in one of eight directions, and you can choose where to look for the next turn.

That are the basics. How does my bot handle each situation? In general with every turn my bot tries to look in the opposite direction. To see at least every second round all see-able enemies (those that are not behind a wall).

Suppose to be a BLUE team member, my bot first checks whether it has seen a RED one within the last rounds. If there was an enemy the bot of course has to run! That is, my bot holds a so called distance map for every opponent. This map tells my bot how many turns each opponent needs to reach a single point on the map. These distance maps are created via an adaption of Dijkstra’s algorithm [Dij59]. So in principle the bot could search for a position on the map, that it reaches before any of the enemies can reach it. But there is a problem. Consider a room you’re hiding in, that has two doors, and an enemy is entering this room through one of these doors. Finding the best field concerning these distance maps means in too many times running in the opposite direction of the enemies door. Hence, you’ll reach a blind alley and drop a brick. So it might be more promising to first check the doors whether you are faster as your enemy or not and decide afterward where to go. Unfortunately there are no doors defined on the map, but I’ll explain in a next article how to parse the map.

If my bot is BLUE and no RED bot is in sight he calls one random room out of a multinomial distribution of rooms. Here each rooms gets a score resulting from its position. The score is bigger the shorter the distance to the room and the higher the distance from this room to the center of the map (try to remain on the sidelines). These scores are normalized, you can understand them as a multinomial distribution. So the bot is searching for a room that is near and in a corner of the map. Of course random, cause enemies might search for it in optimal rooms ;-) If that room is reached the bot will hang around there (as far away as possible from doors and at positions with minimal toxicity) until a teammate has change the team (this bot still knows where we are) or at least every 20 rounds to raise the entropy in the motion profile. While these room changes the bot is very vulnerable to loitering enemies, but nevertheless it might be a weaker victim if it stays in one and the same room all the time…

On the other side of life, when the bot is RED, there is no time for chilling out in a room far away from all happenings. It should be inside, not only near by. If it’s seeing a BLUE bot he’s of course following and tries to catch it. Here would be space to predict flee-possibilities of our victims to cut their way. But due to a lack of time this bot is simply following it’s victims. Nobody visible? Go hunting! The bot tries to find the prey that was last seen on it’s position where we’ve seen it. That’s the next place for advantages. I’m tracking motion profiles of any opponent, here one could use these information to predict a better position for the opponents (for example using neural networks or something like this)… If no enemy can be found my bot is canvassing all rooms of the map, trying to find anyone to catch. Within this exploration of the map it is always interested in going long ways through the map. The more rooms it’s visiting the higher the probability to find someone..

Each turn is limited to a maximum of five seconds to decide what to do. In my first attempt I tried to process these tactics by threading. The idea was to hold the main tool in a loop, testing whether 5 secs are over or the AI has finished searching for a next turn. So the AI could decide for different proceedings within this time, based on scores, and this algorithm would be something like anytime. That means anytime you’ll stop it there is a decision for a next step, the later you stop it the better the decision. Due to the simplicity of my AI I decided against this procedure. So the possible actions are processed without threads. But if you take a look at the code, you’ll find a lot of rudiments remaining, didn’t had the leisure to clean up…

# References

[Dij59]
Edsger W. Dijkstra A note on two problems in connexion with graphs Numerische Mathematik, 1(1):269–271–271, December 1959. http://www-m3.ma.tum.de/twiki/pub/MN0506/WebHome/dijkstra.pdf

## Created an AI for a contest

This year the journal freiesMagazin organized the third contest in a series. This time it’s about programming an AI for a predator-prey-like game. I just submitted my short solution.

As I said, it’s the third programming contest. The first one was about switching gems and in the second contest it was the goal to navigate a robot through a factory. I didn’t got the announce of the first one and missed the second one as a consequence of a lack of time. Hence it’s a premiere for me!

Citing their introduction:

Same procedure as every day: It is late in the evening and you're still sitting at your office desk and listening to some music. Suddenly a siren sounds through all rooms, the doors are closing automatically and you cannot open them anymore. A light green mist appears and some creepy shapes wander around the hall. Sometimes you really hate Mondays …

So, at the beginning of the game all programmed bots are in the same team. After some time one of them changes to the opposite team, trying to catch one of the other while the other ones are fleeing. Simple and clear. It’s running through sockets and the bot-programmers can win vouchers. More information can be found at their website.

On one hand I’m interested in socket programming since a while and on the other hand I’m of course interested in the voucher, so I decided to take part in the contest although there are enough other things to do for me. I agreed with myself to put about two days of work into it. In the end I worked about three days, but however, I could program about 365 more. If you take a look at the code it’s kept more or less simple and many functions aren’t in use. For example I track a motion profile of each opponent, but when I’m predator I don’t care about it. It would be more promising to predict a actual position of a prey (for example with neural networks or something like that) instead of searching without any profoundness. But this would go beyond my scope…

So lets see how many people are also joining this contest. The result will be published mid-January. At least I’m last, but that’s not wicked. I had a lot of fun and even learned something. That’s the main thing. It’s taking part that counts! ;-)

I attached my bot, it’s licensed under GPLv3. In some further articles I’ll explain some smart details of my code, I think some of them are quiet nice to know.

Download: Java: Repository @ GitHub (Please take a look at the man-page. Browse bugs and feature requests.)

## Vim plugin for R

Just found a very nice plugin for using R in Vim. It’s unbelievable comfortable!

There are at least two ways to install it. If your are working on a Debian based distro you can use the .deb package provided by the author Jakson Alves de Aquino itself. On this site you’ll also find some smart screen shots. Another way is the installation by hand (I did so). Download the package, in your download directory type something like this:

Yes, that’s it! To start an R session just open a R-file ( .R or .Rnw or .Rd ) with vim and type \\rf . To close the session type \\rq (not saving hist) or \rw (saving history). The handling needs to getting used to.. Here is a list of common commands from the documentation (might want to print them as a cheat sheet!?) :

But if you got used to, it’s very handy! At the start-up it opens a new R-console (just close it, doesn’t matter) and you can send single lines, a block or a whole file to R (see the documentation). Every thing I tried worked really fine!

A small example in action is presented in the image. In an earlier post I explained how to produce such a title consisting of R objects and Greek letters.

I’ve attached the documentation of this plugin, first and foremost for me for cheating, but of course you’re allowed to use it also ;-)

## Open Research Computation

I want to announce a new scientific journal: Open Research Computation.

I think it sounds quiet interesting, citing their aims & scope:

Open Research Computation publishes peer reviewed articles that describe the development, capacities, and uses of software designed for use by researchers in any field. Submissions relating to software for use in any area of research are welcome as are articles dealing with algorithms, useful code snippets, as well as large applications or web services, and libraries. Open Research Computation differs from other journals with a software focus in its requirement for the software source code to be made available under an Open Source Initiative compliant license, and in its assessment of the quality of documentation and testing of the software. In addition to articles describing software Open Research Computation also welcomes submissions that review or describe developments relating to software based tools for research. These include, but are not limited to, reviews or proposals for standards, discussion of best practice in research software development, educational and support resources and tools for researchers that develop or use software based tools.

Looking forward…

You may also be interested in a more detailed announce: Can a journal make a difference? Let’s find out.

## Similar to ...

one of my idols. At least twitter thinks so! I’m proud.

## Value of an R object in an expression

Just wanted to create an expression, existing of some mathematical annotation and a value of an R object. Wasn’t that intuitive!

Each single goal is easy to reach, for example to combine a value of an R object with text just use paste :

To have a plot title with an $\alpha_1$ you can use expression :

But to let the the title of a plot contain objects and Greek letters isn’t that easy. Those of you who think it’s just about combining paste and expression might try it on their own and come back head-ached after few minutes of unsuccessful testings.

The problem is, that expression interprets chars as expression and not as object identifier, of course, how should it know whether you mean the var alpha or the Greek letter!? The solution is called substitute ! With substitute you can replace objects inline, here is a small example:

You see, substitute got a list what to substitute and replaces the v in paste with the content of var . Run eval to evaluate to result:

Now it’s easy to create a more complex plot title:

Go out and produce imposing graphs! (-;

## Too much at once

Just installed a new Grml system, annoyingly from a bit too far outdated image so aptitude fails to handle everything at once…

Here is the error:

Aha, too many open files.. So I had to install everything piecewise in a disturbing manner..

Btw. updating iptables 1.4.6-2 -> 1.4.10-1 before xtables-addons-common 1.23-1 -> 1.26-2 is a bad idea and fails for some reasons. So try to do it the other way round.

## Crypto off

if you haven’t noticed yet: SSL is turned off…

Of course it isn’t really turned off, all content is still available through encrypted connections (all links are still working), but it’s disabled by default.

But why!? I got a lot of mails during the last weeks, telling me that there is a problem with my SSL cert. Yes, your browser is completely right, my cert isn’t valid because I’ve signed it by myself.. To get a trusted certificate that your browser recognizes to be valid is very expensive. For a cheap one I still have to pay about \$100, that’s neither worthy nor affordable for me and my private blog. But I’m always interested in ideally offering secure mechanisms, so I tried to provide SSL. Another reason for SSL was my auth stuff. Wordpress doesn’t provide both SSL and SSL-free access. In an installation you have to decide whether to use https://... or http://... for URL’s. So all links are either to SSL encrypted content or the next click is unencrypted. Don’t ask me why they don’t check whether SSL was turned on/off for the last query and decide afterwards on using SSL for all further links.. However, I didn’t want to authenticate myself unencrypted and so I enabled SSL by default.

To be congenial to my visitors I turned off SSL, until somebody sponsors a valid certificate. There are also many disgusting tools having problems with my website, so it might be the better way to deliver unencrypted contend. The information on my site isn’t that secret ;-)

As a consequences you aren’t able to register/login anymore. I scripted a little bit to find a secure way for authenticating myself, but you aren’t allowed to take this path :-P Nevertheless, comments are still open and doesn’t require any authentication.

If you can find any SSL zombies please inform me!

## ShortCut[siblings]: tail and its derivatives

Every text-tool-user should know about tail! You can print the last few lines of a file or watch it growing. But there are three improved derivatives, just get into it.

I think there is no need for further explanation of tail itself, so lets begin with the first derivative.

# colortail

colortail is based on tail with support for colors, so it helps to keep track of important content. Common options and parameters are resembled closely to them of tail, so it won’t be a big adjustment to new circumstances for tail fans. The content that it presents is of course the same as if it comes from tail, but colorized ;) With -k you can additional submit a configuration file that defines some regular expressions and its colors. On a Debian some examples can be found in /usr/share/doc/colortail/examples/ . In figure 1 you can see an example output of colortail on the syslog of a virtual machine.

# multitail

The second tool in this article is multitail. Like colortail it can colorize the output, but all is presented in a ncurses based user interface so it is able to create multiple windows on your console. If you open a file in multitail it’s automatically in a following mode ( -f in case of tail and colortail). If you are monitoring multiple log files your console is split horizontal or vertical or a mix of both. You can pause the output, search for regular expressions and a lot more. Enter F1 to get a small help window. Figure 2 presents a sample output. Its project page keeps much more information.

# logtail

logtail pursues a different goal. It’s not interested in prettifying the output, it remembers the content that was still displayed and just prints the differences to the last run. So it is an ideal tool for log analyzer, log messages doesn’t have to be parsed multiple times. logtail is written in perl, you can also monitor logfiles on different machines.

I hope I could give you some smart inspirations.