Category Archives: Current Events

Best Paper award at SAT 2020

I am happy to report that my paper titled Abstract Cores in Implicit Hitting set MaxSat solving. Has been awarded a best paper award at the 2020 SAT conference. The paper reports on work that was started during my visit to Toronto in 2019. We propose a technique that seeks to address the inherent drawback in the so called implicit hitting set approach to MaxSAT solving, one of the most successful approaches to solving MaxSAT instances corresponding to real world applications. Abstract cores seek to reduce the number of cores that the algorithm needs to extract before terminating without increasing the complexity of the core extraction steps too much. The instantiation of this idea in the MaxHS solver was one of the best performing approaches in the 2020 MaxSAT Evaluation.

I would like to thank the conference organizers for the recognition and for putting together an event that, considering the current circumstances, was probably the best possible way of organizing SAT 2020. I would also like to thank my co-authors, especially Prof. Fahiem Bacchus for his efforts in the implementation and getting the experimental results.

New paper accepted

I am happy to inform you that my paper “Abstract Cores in Implicit Hitting Set MaxSat Solving” has been accepted to the SAT 2020 conference.

The paper proposes an improvement to the so called Implicit Hitting Set-based approach to exact MaxSAT solving. The paper summarises the work we did with professor Fahiem Bacchus and MSc, Alex Poole during my visit to Toronto last year. I am exited by the paper. Thanks to both of my co-authors!

I will add the paper to these pages once the camera ready version has been submitted.

 

New presentation

I gave a talk at the Logic Seminar of the department of Mathematics and Statistics today. I talked about the algorithmic benefits of using propositional logic when solving optimisation and decision problems. As a concrete example, I used the Bounded Treewidth Bayesian Network Structure Learning Problem that we worked on a few years ago. Please find my slides: here.

Thank you to the logic group for having me, it was both interesting and fun.

Excellent performance in the MaxSAT Evaluation

The MaxSAT Evaluation is an annual event meant to evaluate the state of the art in MaxSAT solving technology. The evaluation has two tracks: the complete track, where the goal is to find the provably optimal solution as fast as possible and the incomplete track where the goal is to find a solution which is as good as possible within a limited time.

This year we submitted a solver called Loandra to the incomplete track of the competition. Loandra implements core boosted linear search, an idea described in this paper that I worked on during my visit to Melbourne last fall. The results of the Evaluations were presented yesterday at the SAT conference, I’ve only seen a summary but I am happy to say that Loandra performed very well, achieving the highest score on the unweighted 300s track and the second to highest on the weighted 300s track. Overall a very nice result, I am very pleased.

I’d like to thank the organizers of the MaxSAT evaluation as well as my co-authors, Emir Demirovic and Peter Stuckey! I am currently on a holiday, but once I get back I will put up Loandra on github as well. It will also eventually be made available here.

EDIT: Loandra is now available at: https://github.com/jezberg/loandra and on the software pages.

 

The conferment ceremony of the Faculty of Philosophy

About a month ago I participated in the conferment ceremony of the Faculty of Philosophy, a formal, and very traditional three day celebration during which I was granted the rights to wear the symbols of my academic degree, a doctoral hat and a doctoral sword.
The three days were filled with dinners and other festivities, culminating in a formal ball and a night procession through the center of Helsinki. I’d like to thank all of the organizers of the event!  I had a great time. The ceremony will probably be up there amongst the most unique experiences of my life, I mean when I am I ever going to be a part of a que consisting of 200+ masters and doctors dancing through the streets of Helsinki again.

All of the pictures here were taken by the talented people at Bonafide Creatives. Check them out at: https://www.bonafideweddings.fi/.

 

My thesis won an award

My PhD thesis: Solving Optimization Problems via Maximum Satisfiability : Encodings and Re-Encodings (available from e-thesis) was awarded one of four doctoral dissertation awards for 2018 of The University of Helsinki. I am grateful and honoured by this recognition. Thank you to everyone who played a role in my nomination and congratulations to my three other fellow recipients.

More information can be found in the University’s own news story.

My thesis won an award

I was honoured to receive an e-mail on Friday informing me that my PhD-thesis: Solving Optimization Problems via Maximum Satisfiablity: Encodings and Re-Encodings has been recognized with an outstanding doctoral dissertation award by the Doctoral School of Natural Sciences at the University of Helsinki. I thank the school for this honour and everyone involved in nominating my thesis.

 

Research visits during Spring 2019

I will be travelling to Toronto in the spring of 2019 for a 3-month research visit to the University of Toronto, hosted by Prof. Fahiem Bacchus. Prof. Bacchus is a very well known researcher, both in my and many other fields. I am looking forward to working with him and learning from him. I will be leaving Helsinki on the 29.1 and coming back on 27.4. My sincerest thanks go to both Fahiem for agreeing to host me and The Helsinki Institute of Information Technology for financially supporting the trip.

Research visits in the autumn of 2018

I will be visiting the University of Melbourne during the autumn of 2018. More precisely, I was invited by Dr. Emir Demirović to come to Melbourne for three months to work with him and Prof. Peter Stuckey

I am looking forward to working with both of them, hopefully I can expand my knowledge about constraint optimization paradigms beyond MaxSAT while also being able to contribute to their line of work.

I defended my thesis

On Friday 25.5. at 12 o’clock noon I defended my PhD-thesis. My opponent was Associate Professor Inês Lynce and the Custos was my advisor, Associate Professor Matti Järvisalo. You can find the slides of my Lectio Praecursoria (a.k.a. my thesis for dummies) here and the whole thesis here. My sincerest thanks go to both Inês and Matti.

Many people have asked me how I think the defence went. My honest answer is, I do not know. The reason for this is a lack of points of reference. I have only ever been to two defences before mine. Comparing my own defence to either of those is difficult as I was not familiar with the respective fields of study. Maybe this is true for other PhD-students in general. Can anyone properly judge their own defence?

The PhD defence also marks the starting point of this blog. The main purpose of these pages is to be my online CV. However, I will also write blog posts of varying degrees of formality and seriousness from time to time. So thanks for stopping by, hope to see you again!

I leave you with some pictures from the occasion. Thanks to Christina for taking them.