pinecone/core-2020-05-10-deduplication huggingface dataset:
A New Lower Bound on the Maximum Number of Satisfied Clauses in Max-SAT
  and its Algorithmic Applications

A pair of unit clauses is called conflicting if it is of the form $(x)$,
$(\bar{x})$. A CNF formula is unit-conflict free (UCF) if it contains no pair
of conflicting unit clauses. Lieberherr and Specker (J. ACM 28, 1981) showed
that for each UCF CNF formula with $m$ clauses we can simultaneously satisfy at
least $\pp m$ clauses, where $\pp =(\sqrt{5}-1)/2$. We improve the
Lieberherr-Specker bound by showing that for each UCF CNF formula $F$ with $m$
clauses we can find, in polynomial time, a subformula $F'$ with $m'$ clauses
such that we can simultaneously satisfy at least $\pp m+(1-\pp)m'+(2-3\pp)n"/2$
clauses (in $F$), where $n"$ is the number of variables in $F$ which are not in
$F'$.
  We consider two parameterized versions of MAX-SAT, where the parameter is the
number of satisfied clauses above the bounds $m/2$ and $m(\sqrt{5}-1)/2$. The
former bound is tight for general formulas, and the later is tight for UCF
formulas. Mahajan and Raman (J. Algorithms 31, 1999) showed that every instance
of the first parameterized problem can be transformed, in polynomial time, into
an equivalent one with at most $6k+3$ variables and $10k$ clauses. We improve
this to $4k$ variables and $(2\sqrt{5}+4)k$ clauses. Mahajan and Raman
conjectured that the second parameterized problem is fixed-parameter tractable
(FPT). We show that the problem is indeed FPT by describing a polynomial-time
algorithm that transforms any problem instance into an equivalent one with at
most $(7+3\sqrt{5})k$ variables. Our results are obtained using our improvement
of the Lieberherr-Specker bound above
Parameterizing by the Number of Numbers

The usefulness of parameterized algorithmics has often depended on what
Niedermeier has called, "the art of problem parameterization". In this paper we
introduce and explore a novel but general form of parameterization: the number
of numbers. Several classic numerical problems, such as Subset Sum, Partition,
3-Partition, Numerical 3-Dimensional Matching, and Numerical Matching with
Target Sums, have multisets of integers as input. We initiate the study of
parameterizing these problems by the number of distinct integers in the input.
We rely on an FPT result for ILPF to show that all the above-mentioned problems
are fixed-parameter tractable when parameterized in this way. In various
applied settings, problem inputs often consist in part of multisets of integers
or multisets of weighted objects (such as edges in a graph, or jobs to be
scheduled). Such number-of-numbers parameterized problems often reduce to
subproblems about transition systems of various kinds, parameterized by the
size of the system description. We consider several core problems of this kind
relevant to number-of-numbers parameterization. Our main hardness result
considers the problem: given a non-deterministic Mealy machine M (a finite
state automaton outputting a letter on each transition), an input word x, and a
census requirement c for the output word specifying how many times each letter
of the output alphabet should be written, decide whether there exists a
computation of M reading x that outputs a word y that meets the requirement c.
We show that this problem is hard for W[1]. If the question is whether there
exists an input word x such that a computation of M on x outputs a word that
meets c, the problem becomes fixed-parameter tractable
Are there any good digraph width measures?

Several different measures for digraph width have appeared in the last few
years. However, none of them shares all the "nice" properties of treewidth:
First, being \emph{algorithmically useful} i.e. admitting polynomial-time
algorithms for all $\MS1$-definable problems on digraphs of bounded width. And,
second, having nice \emph{structural properties} i.e. being monotone under
taking subdigraphs and some form of arc contractions. As for the former,
(undirected) $\MS1$ seems to be the least common denominator of all reasonably
expressive logical languages on digraphs that can speak about the edge/arc
relation on the vertex set.The latter property is a necessary condition for a
width measure to be characterizable by some version of the cops-and-robber game
characterizing the ordinary treewidth. Our main result is that \emph{any
reasonable} algorithmically useful and structurally nice digraph measure cannot
be substantially different from the treewidth of the underlying undirected
graph. Moreover, we introduce \emph{directed topological minors} and argue that
they are the weakest useful notion of minors for digraphs
On the (non-)existence of polynomial kernels for Pl-free edge
  modification problems

Given a graph G = (V,E) and an integer k, an edge modification problem for a
graph property P consists in deciding whether there exists a set of edges F of
size at most k such that the graph H = (V,E \vartriangle F) satisfies the
property P. In the P edge-completion problem, the set F of edges is constrained
to be disjoint from E; in the P edge-deletion problem, F is a subset of E; no
constraint is imposed on F in the P edge-edition problem. A number of
optimization problems can be expressed in terms of graph modification problems
which have been extensively studied in the context of parameterized complexity.
When parameterized by the size k of the edge set F, it has been proved that if
P is an hereditary property characterized by a finite set of forbidden induced
subgraphs, then the three P edge-modification problems are FPT. It was then
natural to ask whether these problems also admit a polynomial size kernel.
Using recent lower bound techniques, Kratsch and Wahlstrom answered this
question negatively. However, the problem remains open on many natural graph
classes characterized by forbidden induced subgraphs. Kratsch and Wahlstrom
asked whether the result holds when the forbidden subgraphs are paths or cycles
and pointed out that the problem is already open in the case of P4-free graphs
(i.e. cographs). This paper provides positive and negative results in that line
of research. We prove that parameterized cograph edge modification problems
have cubic vertex kernels whereas polynomial kernels are unlikely to exist for
the Pl-free and Cl-free edge-deletion problems for large enough l
Exponential Time Complexity of Weighted Counting of Independent Sets

We consider weighted counting of independent sets using a rational weight x:
Given a graph with n vertices, count its independent sets such that each set of
size k contributes x^k. This is equivalent to computation of the partition
function of the lattice gas with hard-core self-repulsion and hard-core pair
interaction. We show the following conditional lower bounds: If counting the
satisfying assignments of a 3-CNF formula in n variables (#3SAT) needs time
2^{\Omega(n)} (i.e. there is a c>0 such that no algorithm can solve #3SAT in
time 2^{cn}), counting the independent sets of size n/3 of an n-vertex graph
needs time 2^{\Omega(n)} and weighted counting of independent sets needs time
2^{\Omega(n/log^3 n)} for all rational weights x\neq 0.
  We have two technical ingredients: The first is a reduction from 3SAT to
independent sets that preserves the number of solutions and increases the
instance size only by a constant factor. Second, we devise a combination of
vertex cloning and path addition. This graph transformation allows us to adapt
a recent technique by Dell, Husfeldt, and Wahlen which enables interpolation by
a family of reductions, each of which increases the instance size only
polylogarithmically.Comment: Introduction revised, differences between versions of counting
  independent sets stated more precisely, minor improvements. 14 page
Small Vertex Cover makes Petri Net Coverability and Boundedness Easier

The coverability and boundedness problems for Petri nets are known to be
Expspace-complete. Given a Petri net, we associate a graph with it. With the
vertex cover number k of this graph and the maximum arc weight W as parameters,
we show that coverability and boundedness are in ParaPspace. This means that
these problems can be solved in space O(ef(k,W)poly(n)), where ef(k,W) is some
exponential function and poly(n) is some polynomial in the size of the input.
We then extend the ParaPspace result to model checking a logic that can express
some generalizations of coverability and boundedness.Comment: Full version of the paper appearing in IPEC 201
Parameterized Complexity Results in Symmetry Breaking

Symmetry is a common feature of many combinatorial problems. Unfortunately
eliminating all symmetry from a problem is often computationally intractable.
This paper argues that recent parameterized complexity results provide insight
into that intractability and help identify special cases in which symmetry can
be dealt with more tractablyComment: Invited talk at IPEC 2010, 5th International Symposium on
  Parameterized and Exact Computation, December 13-15, 2010, Chennai, India
  http://www.imsc.res.in/ipe
Cluster Editing: Kernelization based on Edge Cuts

Kernelization algorithms for the {\sc cluster editing} problem have been a
popular topic in the recent research in parameterized computation. Thus far
most kernelization algorithms for this problem are based on the concept of {\it
critical cliques}. In this paper, we present new observations and new
techniques for the study of kernelization algorithms for the {\sc cluster
editing} problem. Our techniques are based on the study of the relationship
between {\sc cluster editing} and graph edge-cuts. As an application, we
present an ${\cal O}(n^2)$-time algorithm that constructs a $2k$ kernel for the
{\it weighted} version of the {\sc cluster editing} problem. Our result meets
the best kernel size for the unweighted version for the {\sc cluster editing}
problem, and significantly improves the previous best kernel of quadratic size
for the weighted version of the problem
Non-oblivious Strategy Improvement

We study strategy improvement algorithms for mean-payoff and parity games. We
describe a structural property of these games, and we show that these
structures can affect the behaviour of strategy improvement. We show how
awareness of these structures can be used to accelerate strategy improvement
algorithms. We call our algorithms non-oblivious because they remember
properties of the game that they have discovered in previous iterations. We
show that non-oblivious strategy improvement algorithms perform well on
examples that are known to be hard for oblivious strategy improvement. Hence,
we argue that previous strategy improvement algorithms fail because they ignore
the structural properties of the game that they are solving
A quasipolynomial cut-elimination procedure in deep inference via atomic flows and threshold formulae

Jeřábek showed in 2008 that cuts in propositional-logic deep-inference proofs can be eliminated in quasipolynomial time. The proof is an indirect one relying on a result of Atserias, Galesi and Pudlák about monotone sequent calculus and a correspondence between this system and cut-free deep-inference proofs. In this paper we give a direct proof of Jeřábek’s result: we give a quasipolynomial-time cut-elimination procedure in propositional-logic deep inference. The main new ingredient is the use of a computational trace of deep-inference proofs called atomic flows, which are both very simple (they trace only structural rules and forget logical rules) and strong enough to faithfully represent the cut-elimination
On the Continuous CNN Problem

In the (discrete) CNN problem, online requests appear as points in
$\mathbb{R}^2$. Each request must be served before the next one is revealed. We
have a server that can serve a request simply by aligning either its $x$ or $y$
coordinate with the request. The goal of the online algorithm is to minimize
the total $L_1$ distance traveled by the server to serve all the requests. The
best known competitive ratio for the discrete version is 879 (due to Sitters
and Stougie).
  We study the continuous version, in which, the request can move continuously
in $\mathbb{R}^2$ and the server must continuously serve the request. A simple
adversarial argument shows that the lower bound on the competitive ratio of any
online algorithm for the continuous CNN problem is 3. Our main contribution is
an online algorithm with competitive ratio $3+2 \sqrt{3} \approx 6.464$. Our
analysis is tight. The continuous version generalizes the discrete orthogonal
CNN problem, in which every request must be $x$ or $y$ aligned with the
previous request. Therefore, Our result improves upon the previous best
competitive ratio of 9 (due to Iwama and Yonezawa)
On the intersection of tolerance and cocomparability graphs.

It has been conjectured by Golumbic and Monma in 1984 that the intersection of tolerance and cocomparability graphs coincides with bounded tolerance graphs. Since cocomparability graphs can be efficiently recognized, a positive answer to this conjecture in the general case would enable us to efficiently distinguish between tolerance and bounded tolerance graphs, although it is NP-complete to recognize each of these classes of graphs separately. The conjecture has been proved under some – rather strong – structural assumptions on the input graph; in particular, it has been proved for complements of trees, and later extended to complements of bipartite graphs, and these are the only known results so far. Furthermore, it is known that the intersection of tolerance and cocomparability graphs is contained in the class of trapezoid graphs. In this article we prove that the above conjecture is true for every graph G, whose tolerance representation satisfies a slight assumption; note here that this assumption concerns only the given tolerance representation R of G, rather than any structural property of G. This assumption on the representation is guaranteed by a wide variety of graph classes; for example, our results immediately imply the correctness of the conjecture for complements of triangle-free graphs (which also implies the above-mentioned correctness for complements of bipartite graphs). Our proofs are algorithmic, in the sense that, given a tolerance representation R of a graph G, we describe an algorithm to transform R into a bounded tolerance representation R  ∗  of G. Furthermore, we conjecture that any minimal tolerance graph G that is not a bounded tolerance graph, has a tolerance representation with exactly one unbounded vertex. Our results imply the non-trivial result that, in order to prove the conjecture of Golumbic and Monma, it suffices to prove our conjecture. In addition, there already exists evidence in the literature that our conjecture is true. \u
Solving Two-Stage Stochastic Steiner Tree Problems by Two-Stage Branch-and-Cut

We consider the Steiner tree problem under a two-stage stochastic model with recourse and finitely many scenarios. In this prob- lem, edges are purchased in the first stage when only probabilistic infor- mation on the set of terminals and the future edge costs is known. In the second stage, one of the given scenarios is realized and additional edges are puchased in order to interconnect the set of (now known) ter- minals. The goal is to decide on the set of edges to be purchased in the first stage while minimizing the overall expected cost of the solution. We provide a new semi-directed cut-set based integer programming formula- tion, which is stronger than the previously known undirected model. We suggest a two-stage branch-and-cut (B&C) approach in which L-shaped and integer-L-shaped cuts are generated. In our computational study we compare the performance of two variants of our algorithm with that of a B&C algorithm for the extensive form of the deterministic equiva- lent (EF). We show that, as the number of scenarios increases, the new approach significantly outperforms the (EF) approach
Improving the performance of facial expression recognition using dynamic, subtle and regional features

Human facial expression is a complex process characterized of dynamic, subtle and regional emotional features. State-of-the-art approaches on facial expression recognition (FER) have not fully utilized this kind of features to improve the recognition performance. This paper proposes an approach to overcome this limitation using patch-based ‘salient’ Gabor features. A set of 3D patches are extracted to represent the subtle and regional features, and then inputted into patch matching operations for capturing the dynamic features. Experimental results show a significant performance improvement of the proposed approach due to the use of the dynamic features. Performance comparison with pervious work also confirms that the proposed approach achieves the highest CRR reported to date on the JAFFE database and a top-level performance on the Cohn-Kanade (CK) database
An Axiomatic Characterization of Continuous-Outcome Market Makers

Most existing market maker mechanisms for prediction markets are designed for events with a finite number of outcomes. All known attempts on designing market makers for forecasting continuous-outcome events resulted in mechanisms with undesirable properties. In this paper, we take an axiomatic approach to study whether it is possible for continuous-outcome market makers to satisfy certain desirable properties simultaneously. We define a general class of continuous-outcome market makers, which allows traders to express their information on any continuous subspace of their choice. We characterize desirable properties of these market makers using formal axioms. Our main result is an impossibility theorem showing that if a market maker offers binary-payoff contracts, either the market maker has unbounded worst case loss or the contract prices will stop being responsive, making future trades no longer profitable. In addition, we analyze a mechanism that does not belong to our framework. This mechanism has a worst case loss linear in the number of submitted orders, but encourages some undesirable strategic behavior.Engineering and Applied Science
Developing trust networks based on user tagging information for recommendation making

Recommender systems are one of the recent inventions to deal with ever growing information overload. Collaborative filtering seems to be the most popular technique in recommender systems. With sufficient background information of item ratings, its performance is promising enough. But research shows that it performs very poor in a cold start situation where previous rating data is sparse. As an alternative, trust can be used for neighbor formation to generate automated recommendation. User assigned explicit trust rating such as how much they trust each other is used for this purpose. However, reliable explicit trust data is not always available. In this paper we propose a new method of developing trust networks based on user’s interest similarity in the absence of explicit trust data. To identify the interest similarity, we have used user’s personalized tagging information. This trust network can be used to find the neighbors to make automated recommendations. Our experiment result shows that the proposed trust based method outperforms the traditional collaborative filtering approach which uses users rating data. Its performance improves even further when we utilize trust propagation techniques to broaden the range of neighborhood
Hash Functions and Gröbner Bases Cryptanalysis

<p>Hash functions are being used as building blocks in such diverse primitives as commitment schemes, message authentication codes and digital signatures. These primitives have important applications by themselves, and they are also used in the construction of more complex protocols such as electronic voting systems, online auctions, public-key distribution, mutual authentication handshakes and more. Part of the work presented in this thesis has contributed to the \SHA-3 contest" for developing the new standard for hash functions organized by the National Institute of Standards and Technology. We constructed the candidate Edon-R, which is a hash function based on quasigroup string transformation. Edon-R was designed to be much more efficient than SHA-2 cryptographic hash functions, while at the same time offering same or better security. Most notably Edon-R was the most efficient hash function submitted to the contest.</p><p>Another contribution to the contest was our cryptanalysis of the second round SHA-3 candidate Hamsi. In our work we studied Hamsi's resistance to differential and higher-order differential cryptanalysis, with focus on the 256-bit version of Hamsi. Our main results are efficient distinguishers and near-collisions for its full (3-round) compression function, and distinguishers for its full (6-round) finalization function, indicating that Hamsi's building blocks do not behave ideally.</p><p>Another important part of this thesis is the application of Gröbner bases. In the last decade, Gröbner bases have shown to be a valuable tool for algebraic cryptanalysis. The idea is to set up a system of multivariate equations such that the solution of the system reveals some secret information of the cryptographic primitive. The system is then solved with Gröbner bases computation. Staying close to the topic of hash functions, we have applied this tool for cryptanalysis and construction of multivariate digital signature schemes, which is a major hash function application. The result of this is our cryptanalysis of the public-key cryptosystem MQQ, where we show exactly why the multivariate quadratic equation system is so easy to solve in practice. The knowledge we gained from finding the underlying weakness of the MQQ scheme was used to construct a digital signature scheme. The resulting scheme, MQQ-SIG, is a provably CMA resistant multivariate quadratic digital signature scheme based on multivariate quadratic quasigroups. The scheme is designed to be very fast both in hardware and in software. Compared to some other multivariate quadratic digital signature schemes, MQQ-SIG is much better in signing and private key size, while worse in key generation, verification and public key size. This means that MQQ-SIG is a good alternative for protocols where the constrained environment is on the side of the signer.</p>PhD i telematikkPhD in Telematic
Protocol Requirements for Self-organizing Artifacts: Towards an Ambient
  Intelligence

We discuss which properties common-use artifacts should have to collaborate
without human intervention. We conceive how devices, such as mobile phones,
PDAs, and home appliances, could be seamlessly integrated to provide an
"ambient intelligence" that responds to the user's desires without requiring
explicit programming or commands. While the hardware and software technology to
build such systems already exists, as yet there is no standard protocol that
can learn new meanings. We propose the first steps in the development of such a
protocol, which would need to be adaptive, extensible, and open to the
community, while promoting self-organization. We argue that devices,
interacting through "game-like" moves, can learn to agree about how to
communicate, with whom to cooperate, and how to delegate and coordinate
specialized tasks. Thus, they may evolve a distributed cognition or collective
intelligence capable of tackling complex tasks.Comment: To be presented at 5th International Conference on Complex System