Friday, February 05, 2016

Would your department refuse to host the recipient of a very competitive post-doctoral award?

Suppose that your department were given the chance to host the recipient of a very competitive post-doctoral award. That award would pay 95% of the salary of the post-doctoral researcher, who also leads a project funded in 2016 (worth 185,373.66€) and one funded in 2015 (worth 222,568.50€). I am fairly confident that your department would welcome that award- and grant-winning post-doctoral researcher with open arms.

This is not what has happened to Vincenzo Dimonte, an Italian set theorist who is presently a post-doctoral researcher at the Kurt Gödel Research Center for Mathematical Logic in Vienna. Dimonte was one of the three recipients in the field of mathematics  of a prestigious and competitive Rita Levi Montalcini award for 2016. In his application for the award, Vincenzo Dimonte gave a ranked list of five three mathematics department in Italy that were willing to host him, the top one being the Department of Mathematics at the Politecnico di Torino. I presume that he even enclosed a letter from someone at that department saying that they were willing to host him. The choice of Turin as top location in his list was natural since Turin hosts a group of top-class set theorists Andretta, Viale, Motto Ros and Camerlo (who is actually at the Politecnico).

However, when Vincenzo Dimonte won the grant, the department twice refused to host him! Of course, he'll go down his own list and I trust that one of the four other destinations he chose will actually welcome him. The fact remains that such decisions are hard to understand when viewed from a purely scientific perspective and may have a negative impact on the future career of someone who has been deemed to be worthy of a top award for young researchers in Italy.

Wednesday, February 03, 2016

Comments of the European research environment in logic and computation (contribution by Joost-Pieter Katoen and Wolfgang Thomas)

This is the last piece I received in response to my call for opinions on the report on logic activities in Europe that Yuri Gurevich wrote in 1992.

Joost-Pieter Katoen and Wolfgang Thomas discuss the sections of Yuri's report devoted to the European research environment (funding, research centres and other issues) related to logic in computation. You can read their contribution here. Thanks to Joost-Pieter and Wolfgang  for taking the time to write this piece and for allowing me to share it on this blog. Enjoy it!

Monday, February 01, 2016

Rūsiņš Mārtiņš Freivalds (1942-2016)

Andris Ambainis has kindly allowed me to post on this blog the obituary of Rūsiņš Freivalds he wrote for the February issue of the Bulletin of the EATCS. It is a fitting tribute to the importance of Rūsiņš's  lifetime work for TCS in general and for Latvian CS. 

Rūsiņš Mārtiņš Freivalds (1942-2016)


Rusins Freivalds, one of European pioneers of theoretical computer science, passed away on January 4, 2016 at the age of 73.
Freivalds was born on November 10, 1942 in Cesvaine, Latvia. He studied at the University of Latvia and, during his studies, he had an opportunity to spend two years in Novosibirsk, one of leading theoretical computer science research groups in the Soviet Union. There, he started working with Boris Trachtenbrot, one of leading Soviet computer scientists, who supervised his Ph.D. dissertation (defended in 1971 at Novosibirsk State University).
Freivalds is best known for his probabilistic algorithm for testing matrix multiplication, invented in 1977 (https://en.wikipedia.org/wiki/Freivalds'_algorithm). Freivalds' discovery was that, given the result of matrix multiplication, one could check its correctness substantially faster than the time for multiplying the matrices with the best algorithm that is known. Freivalds' algorithm was also one of the first probabilistic algorithms which were faster than deterministic algorithms.
Freivalds' algorithm became an inspiration for other researchers who started studying probabilistic algorithms. In particular, Turing Award winner Manuel Blum mentioned it as an important inspiration in his 1995 Turing Award lecture. Now, Freivalds' algorithm is a part of textbooks on probabilistic algorithms and is taught in many universities.
More generally, Freivalds was one of the first to study probabilistic algorithms and to compare the power of algorithms that use random coin flips with algorithms that do not use randomness. His focus was on finding situations in which one could prove that randomness increases the computational power. For example, Freivalds showed that there is a language that can be recognized by a probabilistic 2-way finite automaton but not by a deterministic 2-way finite automaton. He also showed similar results for 1-way automata with multiple heads, pushdown automata and other computational models. Freivalds’ research in this direction in 1970s and 1980s was among the first results of this type.
Freivalds was interested in many research topics and published over 200 research papers. Another major research interest of Freivalds was inductive inference - a mathematical theory which models the process of learning on an abstract level, using computability theory.
Starting from late 1990s, Freivalds worked on quantum computing and quantum automata. Together with Andris Ambains, he showed that quantum automata can use exponentially less space than probabilistic automata. Most recently, he invented ultrametric automata, a model of automata with p-adic transition probabilities, winning a Best Paper Award at Turing-100 conference in Manchester.
Freivalds supervised 19 Ph.D. dissertations and a number of M.Sc. and B.Sc. theses, including Andris Ambainis (known as a leading quantum computing expert) and Daina Taimina (known for her crocheted models of hyperbolic planes). He was very active in introducing undergraduate students to theoretical computer science and bringing them to research conferences, teaching them to enjoy both research and cultural events (for example, opera or popular science museums).
A number of those undergraduates went on to do their Ph.D., either with him, or other faculty members at the University of Latvia or different universities abroad (including Berkeley, Yale, University of Maryland and University of Waterloo).
Freivalds was an excellent teacher and popularizer of theoretical computer science in Latvia. He was an engaging lecturer who was keen on showing connections between different subfields of mathematics and theoretical computer science. In 2006, University of Latvia students voted him to be the "Teacher of the Year" for all of the natural sciences. Through his teaching and student supervision, he left a major influence on theoretical computer science in Latvia.
Freivalds was highly recognized both in Latvia and internationally. In 2003, he received the Grand Medal of the Latvian Academy of Science (the highest Latvian award for lifetime achievement in research). Freivalds was a member of Academia Europeae and gave a number of invited talks at highly recognized international conferences (such as ICALP - International Colloqium on Automata, Languages and Programming and MFCS - Mathematical Foundations of Computer Science).


Viewpoints on “Logic activities in Europe”, twenty years later

This is the third post related to the viewpoints I commissioned on the report on logic activities in Europe that Yuri Gurevich wrote in 1992.

In case you are interested, you can read my viewpoint contribution (pdf file) that will serve as a preface to the pieces by Thomas Henzinger, Joost-Pieter Katoen and Wolfgang Thomas, and Moshe Vardi. All the contributions will appear in the February 2016 issue of the Bulletin of the EATCS.

Friday, January 29, 2016

EATCS Award 2016 to Dexter Kozen (Cornell University, USA)

The EATCS bestows the EATCS Award 2016 to Dexter Kozen (Cornell University, USA) for fundamental contributions across the whole spectrum of theoretical computer science

The EATCS is proud to announce that the EATCS Award Committee consisting of Fedor Fomin, Kim G. Larsen (chair) and Jean-Eric Pin has selected Dexter Kozen (Cornell University, USA; http://www.cs.cornell.edu/~kozen/ as the recipient of the EATCS Award 2016.

Dexter Kozen is a theoretical computer scientist, perhaps the  theoretical computer scientist, who has excelled across the entire spectrum of our field and crashed through the so-called Volume A/Volume B barrier. Even within these tracks he has exhibited remarkable diversity and depth. This makes him an exceptional candidate for the EATCS Award and he continues the lineage of stellar scientists who have received the EATCS Career Award so far.

Dexter Kozen is known for his many contributions to theoretical computer science. These include, among many others, the most succinct and beautiful proof imaginable of completeness for PDL, a stunning treatment of the far more challenging mu-calculus and the elegant treatment of logics of programs in the setting of Kleene algebra. He has also made fundamental contributions to complexity theory. In fact, one of the first contributions of Dexter Kozen to the scientific community was the definition of the notion of alternating Turing machine, a deep contribution to complexity theory that made it possible to connect time and space complexity. The results were viewed as so significant that they almost immediately became part of the graduate curriculum in complexity theory. Dexter’s work on alternation appeared initially in his singly-authored FOCS’76 paper, independent of the Chandra-Stockmeyer paper that was published back-to-back with it in the same volume; the two later became the famous combined, very high-cited, triply-authored J.ACM version for which the authors won an IBM Outstanding Innovation Award in 1980.

Dexter Kozen’s work on modal logic and Kleene algebra has undoubtedly had a major impact in the area of programming logics and gathered a huge number of citations as it opened up this field.

Besides complexity theory and modal logic, Dexter Kozen also produced major results on algebra, such as the complexity of the theory of real closed algebraic theories, and on computer algebra, such as the Kozen-Landau theorem.

Dexter Kozen has also been a pioneer in probabilistic semantics. Long before it became fashionable, he worked on a measure-theoretic semantics  for probabilistic programs which remains the inspiration for the intense activity in topics like probabilistic programming languages, probabilistic process algebra and logics.

Dexter Kozen has had many collaborations. His connections to Amsterdam, Aarhus and Warsaw are probably the most well-known. He has spent several one year sabbaticals in Europe with successful collaborations. He is an inspiring person  and his presence in a department is of immeasurable value for young researchers. It is worth mentioning that Dexter Kozen’s support for the contacts with Eastern European colleagues has been admirable, at a time when this was rather difficult and complex to achieve.

David Harel's two-page  laudation that appears in the volume for Dexter's 60th birthday (available at http://www.wisdom.weizmann.ac.il/~harel/papers/Kozen.pdf) provides a wonderful introduction to Dexter Kozen as a scientist and as a colleague.

The  EATCS Award is given to acknowledge extensive and widely recognized contributions to theoretical computer science over a life-long scientific career. The list of the previous recipients of the EATCS Award is available at

http://eatcs.org/index.php/eatcs-award.

The EATCS Award carries a prize money of 1000 Euros and will be presented at ICALP 2016, which will take place in Rome (Italy) from the 12th till the 15th of July 2016.

Wednesday, January 27, 2016

Report on Dagstuhl Seminar 15511 on the Graph Isomorphism Problem (contribution by Anuj Dawar)

Anuj Dawar has kindly allowed me to post here his report on Dagstuhl Seminar 15511 on the Graph Isomorphism Problem, which will appear in the February 2016 issue of the Bulletin of the EATCS. IMHO, it is a real gem and conveys the excitement of the event wonderfully well. Enjoy it!

The February 2016 issue of the BEATCS will be brimming with interesting and though-provoking content, and will be open access as usual. I hope that you'll make a point of reading it, when it is published. Watch this space for further news on the issue.

Friday, January 22, 2016

Computer Science in Europe (contribution by Thomas A. Henzinger)

This is the second viewpoint piece I received in response to my call for opinions on the report on logic activities in Europe that Yuri Gurevich wrote in 1992. Thanks to Tom for taking the time to write this piece and for allowing me to share it on this blog. Enjoy it! 

Computer Science in Europe



It saddens me but it would be difficult to refute a claim that, in the past two decades, Europe has been falling further behind the United States in the dynamism of the information technology industry, the popularity of the computer science major, and the impact of frontier research in computing. The vast majority of Turing awards still goes to researchers who work in the United States. It is particularly disconcerting that the main strengths of European computer science appear largely unchanged from 1994: on the academic side, Europe's research leaders are still concentrated disproportionately in formal methods, and on the industrial side, Europe's technology leaders are still found primarily in the "old" economy, exemplified by the automotive industry.

To close the gap, Europe desperately needs new organizational structures in academia, a greater entrepreneurial spirit of society, an improved image for computer science as a career choice, especially among women, the mandatory acquisition of computational thinking and coding skills in secondary education, and more emphasis on principles of systems building which are critical to industry in university curricula of computer science. Israel offers a role model for closing the gap with the United States with regard to the first three points ---academic structures, entrepreneurial culture, and the public image of computer science--- and has been a leader in computer science education.

There are a few encouraging signs of European computer science changing. The European systems community has begun to organize itself through efforts such as the Eurosys conference and some countries are trying to remedy their deficiencies in systems research. Germany, for example, founded the Max Planck Institute for SoftwareSystems. Several European countries and institutions have started to copy key aspects of the American career model, such as tenure tracks that give faculty early independence and doctoral programs that give students a broad graduate education. Student mobility and structured doctoral education are strongly supported by the Marie Curie program of the European Union and by the funding agencies of some countries, to counteract the wide-spread habit of researchers advancing in the same lab from undergraduate to faculty level.

There have been some remarkable institutional changes. EPFL has demonstrated that changes in the organization and recruiting can lead to dramatic improvements in the scientific reputation and attractiveness of an institution. Even entirely new institutions have been founded, such as IST Austria, which naturally find it easier to implement new structures such as a tenure track and an institutional doctoral school.

The most significant development can be found, perhaps surprisingly, on the European level. I am referring to the creation of the EuropeanResearch Council, which supports frontier research based purely on scientific criteria. This program has no counterpart in the United States, but if it manages to remain scientifically independent and well-funded, I am confident that its impact will change the game. These are big if's, of course, and the ERC is constantly being threatened by national interests and sectorial lobbies that favor traditional programs which distribute the available funds to more different countries, sectors, and groups. Given that politicians love to pride themselves with the founding of "strategic" consortia, centers, and flagships, and industry likes to get every possible cut of public money, the initial success of the ERC has been all the more remarkable. Let's work together so that it will trump the less effective funding formats and lift the strength of computer science in Europe.

Monday, January 18, 2016

On the Two Sides of the Atlantic in Logic and Computation (contribution by Moshe Y. Vardi)

Prompted by a reference to it in a recent CACM editorial by Moshe Vardi, I belatedly read the very interesting piece on logic activities in Europe that Yuri Gurevich wrote in 1992. I was struck by the idea that it might be interesting to ask some selected colleagues to contribute (short) opinion pieces to the Bulletin of the EATCS reflecting on the points raised by Yuri in that article twenty years later. 
In order to whet your appetite, I post below Moshe's contribution. Thanks to Moshe for taking the time to write this piece and for allowing me to share it on this blog. Enjoy it! 


On the Two Sides of the Atlantic in Logic and Computation
Rice University

In his 1977 EWD Note 611, “On the fact that the Atlantic Ocean has twosides,” Edsger Dijkstra noted the different attitudes towards computing research in Northern America and Western Europe. Yuri Gurevich noted the same phenomenon in his 1992 report, "Logic Activities inEurope." In a 2015 Communications of the ACM editorial I revisited this issue and asked “Why Doesn't ACM Have a SIG for Theoretical ComputerScience?"
The key issue raised in that editorial was the split between Volume-A-type and Volume-B-type research in Theoretical Computer Science (TCS), referring to the 1990 Handbook of Theoretical Computer Science, with Jan van Leeuwen as editor. The handbook consisted of Volume A, focusing on algorithms and complexity, and Volume B, focusing on formal models and semantics. In other words, Volume A is the theory of algorithms, while Volume B is the theory of systems (hardware and software). North American TCS tends to be quite heavily focused on Volume A, while European TCS tends to encompass both Volume A and Volume B. The ACM Special Interest Group on Algorithms and Computation Theory (SIGACT) is, de facto, a special-interest group for Volume-A TCS.
I pointed out in my editorial that this division did not exist prior to the 1980s. In fact, the tables of contents of the proceedings of two North American premier TCS conferences—IEEE Symposium on Foundations of Computer Science (FOCS) and ACM Symposium on Theory of Computing (STOC)---from the 1970s reveal a surprisingly (from today's perspective) high level of Volume-B content. In the 1980s, the level of TCS activities in North America grew beyond the capacity of two annual single-track three-day conferences, which led to the launching of what was known then as "satellite conferences." Shedding the "satellite" topics allowed FOCS and STOC to specialize and develop a narrower focus on TCS. But this narrower focus in turn has influenced what is considered TCS in North America. In contrast, the European Association for Theoretical Computer Science (EATCS), expanded the scope of its flagship conference, the International Colloquium on Automata, Languages, and Programming (ICALP), by reorganizing the conference along several tracks. In 2015, ICALP consisted of three tracks: Track A: Algorithms, Complexity and Games; Track B: Logic, Semantics, Automata and Theory of Programming; and Track C: Foundations of Networked Computation: Models, Algorithms and Information Management. The reorganization along tracks allowed EATCS to broaden its scope, rather than narrow it like SIGACT.
But the reality is that if one zooms into Volume-B research, one finds again the Volume-A/Volume-B dichotomy, also reflected in the range of topics of the Symposium on Logic in Computer Science (LICS), the flagship conference of the ACM Special Interest Group on Logic and Computation (SIGLOG). Sub-volume A of Volume-B research is concerned with connections between logic, algorithms, and computational complexity. Descriptive-Complexity Theory, for example, aims at bridging computational complexity and logic by studying the expressive power needed to describe problems in given complexity classes. A celebrated result in this area is Fagin’s Theorem, which relates NP to Existential Second-Order Logic. Model Checking, as another example, studies the evaluation of logical formalisms, including various temporal logics, over finitely represented structures. Automata theory often provides tools to bridge between logic and algorithms. The Büchi-Elgot-Trakhtenbrot Theorem, for example, provides automata-theoretic tools for solving the satisfiability problem for Monadic Second-Order Logic on finite words.
Sub-volume B of Volume-B research, in contrast, is concerned with semantical and methodological foundations for programming and programming languages. Domain theory, for example, studies special kinds of partially ordered sets called domains. Domain theory is used to specify denotational semantics, especially for functional programming languages. Category theory, as another example, formalizes mathematical structure and its concepts in terms of a collection of objects and of arrows (also called morphisms). Category theory provides powerful modeling idioms and has deep connections to types in programming languages. Concurrency theory studies formalisms for modeling and analyzing concurrent systems. Proof Theory is of major interest in Sub-volume B of Volume B research, and a distinguished result is the Curry–Howard Correspondence, which provides a direct relationship between types in computer programs and formal proofs in certain logics.
The split between Sub-volumes A and B within Volume-B research can perhaps be traced to the standard division of mathematical Logic into several branches: computability theory, model theory, proof Theory, and set Theory. (See the 1989 Handbook of Mathematical Logic, with John Barwise as editor.) While set theory has no clear computer-science counterpart, Sub-volume A of Volume-B research can be traced to computability theory and model theory, while Sub-volume B of Volume-B research can be traced to proof theory. Indeed, a scientific discipline, as it grows and matures, inevitably grows branches, which gradually grow apart from each other. As scientists are forced to go deeper, it becomes gradually impossible for them to keep track of developments in more than a very small number of branches. In fact different branches develop their own specialized languages, impeding communication between branches.
It is often at the interfaces between branches, however, that the most exciting developments occur. Consider Artificial Intelligence, for example. Since the establishment of the field in the late 1950s, logic has played a key role as the fundamental formalism for describing reasoning. Ultimately, however, logical tools were not fully adequate to capture the common-sense reasoning that characterizes human reasoning. In the 21st Century, probabilistic and statistical approaches have become dominant, for example, in machine learning. Synthesizing the logical and probabilistic approaches is a new frontier, where I expect to see many exciting developments in the next few years.
Finally, while 25 years ago computing-research took place mostly in North America and Western Europe, computing research has since globalized. The Atlantic Ocean is no longer as dominant as it used to be. I look forward to the day when we will write about “The Two Sides of the Pacific/Indian Ocean in Logic and Computation.”