Pareto-based Island Model presented at GECCO 2013

Yesterday I presented my work Migration Study on a Pareto-based Island Model for MOACOs, accepted as full-paper at the Genetic and Evolutionary Computation Conference 2013, held in Amsterdam.

The paper abstract is:

Pareto-based island model is a multi-colony distribution scheme recently presented for the resolution, by means of ant colony optimization algorithms, of bi-criteria problems. It yielded very promising results, but the model was implemented considering a unique Pareto-front-shaped unidirectional neighborhood migration topology, and a constant migration rate.
In the present work two additional neighborhood topology schemes, and four different migration rates have been tested, considering the algorithm which obtained the best results in average in the model presentation article: MOACS (Multi-Objective Ant Colony System).
Several experiments have been conducted, including statistical tests for better support the study.
High values for the migration rate and the use of a bidirectional neighborhood migration topology yields the best results.

It is the next step in the research previously published in Soft Computing Journal and commented here.

The presentation is this:

Enjoy it! :D

Parallel Ants at IWANN 2011

Some days ago we presented at the IWANN Conference our new work devoted to study the parallelization of Multi-Objective Ant Colony Optimization algorithms (MOACOs) following different schemes.

It was a very funny presentation (and very interesting, of course :D), because the slides included some CC memes. ;)

These are the slides:

The whole paper can be found here.

Enjoy them! ;)

Military Ants at NICSO 2010

Hi to all!
(the milliards of readers :D).

The last Wednesday (13 of May), we presented (again) our Multiobjective Ant Colony Optimization algorithm (yes, the famous CHAC :D) at NICSO 2010, which was held in Granada, in the same building where we work everyday…
… what a so far trip… :-| :D

The paper presents a study of the objective balancing parameter (named LAMBDA), used in this algorithm. ;)

Here you are the presentation:

Enjoy it! ;)

KohonAnts Slides (ALIFE XI)

Hello again to everyone!

These are the slides of the presentation of KohonAnts algorithm in ALIFE XI conference. ;)

It is an hybrid Ant Colony and Self-organizing Map algorithm for clustering and pattern classification.

A bit late, but I had some troubles with slideshare…

In any case…….Enjoy it. ;) :D

Here you can see an example of the evolution of the ants in the grid for the IRIS dataset:

Ants movement in the toroidal grid

Ants movement in the toroidal grid

Green class is quite similar to the other two classes, so it is difficult to get a fine cluster with it.

Thanks to Dave Oranchak. ;)

Pherographia in SIGEvolution

Our partner Carlos Fernandes has published an article on the latest number of SIG evolution, called A Camera Obscura for Ants. This article describes from the scientific point of view his Pherography method, that uses ant colony algorithms for creating curious and nice effects on photography. A bit like our Kohonants, but without the Kohonen part.

Kohonants: a gentle introduction

Next week, Carlos Fernandes will present in the ANTS 2008 conference our paper KANTS: Artificial Ant System for Classification (hope the typo is not in the proceedings, but I’m afraid it will be). The algorithm was already presented by Antonio in ALIFE XI, with the paper KohonAnts: a self-organizing ant algorithm for clustering and pattern classification (which is also available from arxiv). Antonio was questioned about what was good about this algorithm, and I guess this is as good a place as any other to tell about it.
The basic idea of Kohonants is to use stigmergy for clustering and classification. Usual ant clustering algorithm place data as objects in the grid ants move around, and then, via some natural inspiration and a great deal of heuristics, they manage to cluster them according to proximity.
Kohonants, on the other hand, makes each data item an ant (or several, if needed). Pheromones are also vectorial in nature, in the same dimension as data, and what ants do when they move about is first take into account what’s the pheromone levels they have around in their neighborhood, and second modify it making them closer to the vector they represent.
That is why they are called Kohonen’s Ants: Kohonen’s algorithm behaves in the same way. Takes a training data vector, compares it to all the vectors in a two-dimensional array, and whoever wins is made closer to the data vector. Ants in Kohonants take the place of data vector in Kohonen’s algorithm, and the two-dimensional vector array that is trained is substituted by the two-dimensional (vectorial) pheromone field in Kohonants.
Results so far have been quite good, but we’ll continue with it to see what are their limits, and how well it fares against other ant and non-ant clustering algorithms. Meanwhile, as we mentioned in our previous post, you can download full code from the GeNeura code repository

New paper on multiobjective ant colony optimization available

Springer alerts me about the availability of the paper hCHAC-4, an ACO Algorithm for Solving the Four-Criteria Military Path-finding Problem, which was published some time ago at the NICSO 2007 conference. Here’s the abstract:

Algorithms for decision support in the battlefield have to take into account separately all factors with an impact of success: speed, visibility, and consumption of material and human resources. It is usual to combine several objectives, since military commanders give more importance to some factors than others, but it is interesting to also explore and optimize all objectives at the same time, to have a wider range of possible solutions to choose from, and explore more efficiently the space of all possible paths. In this paper we introduce hCHAC-4, the four-objective version of the hCHAC bi-objective ant colony optimization algorithm, and compare results obtained with them and also with some other approaches (extreme and mono-objective ones). It is concluded that this new version of the algorithm is more robust, and covers more efficiently the Pareto front of all possible solutions, so it can be consider as a better tool for military decision support.

If SpringerLink is not available at your institution and you are interested in a copy, please drop us a line. This article is further ahead the research line than the previous article, which used two objectives that were an aggregate of several sub-objectives. Results are better in this case, and all sub-objectives can be pursued at the same time.

Introducing KohonAnts, a new stigmergic clustering and classification algorithm

We have submitted, and at the same time uploaded to ArXiV, a paper on this new algorithm the masterminds of GeNeura + Carlos Fernandes and Vitorino Ramos (who are practically now full-privileges GeNeura members). You can download it from ArXiV; the title is KohonAnts: A Self-Organizing Ant Algorithm for Clustering and Pattern Classification:

In this paper we introduce a new ant-based method that takes advantage of the cooperative self-organization of Ant Colony Systems to create a naturally inspired clustering and pattern recognition method. The approach considers each data item as an ant, which moves inside a grid changing the cells it goes through, in a fashion similar to Kohonen’s Self-Organizing Maps. The resulting algorithm is conceptually more simple, takes less free parameters than other ant-based clustering algorithms, and, after some parameter tuning, yields very good results on some benchmark problems.

We’ll be very soon doing the rounds with this algorithm with the usual conferences. It is new, it works surprisingly well, and, as usual, source code is available from your friendly Forja subversion repository (not updated, though).