Acta Informatica最新文献

{"title":"Correction: A natural deduction system for the Byzantine Generals Oral Messages algorithm","authors":"Dennis M. Volpano","doi":"10.1007/s00236-026-00545-y","DOIUrl":"10.1007/s00236-026-00545-y","url":null,"abstract":"","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"63 3","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00236-026-00545-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148465957","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Multi-points cyber defense ((1+epsilon )) and ((1+epsilon )^{k-k'})-approximation","authors":"Pimukthee Jaikla,&nbsp;Sanpawat Kantabutra","doi":"10.1007/s00236-026-00541-2","DOIUrl":"10.1007/s00236-026-00541-2","url":null,"abstract":"<div><p>Given a system and a set of strongest security measures, a system administrator wants to optimally place these strongest security measures in appropriate places in the system to minimize the maximum damage caused by a potential attacker who comes with a budget <i>B</i>. In this article we model this scenario as follows. Let <i>T</i> be a network in the system with cost and prize assignments to edges and nodes, respectively. The problem of determining <i>k</i> appropriate edges for the <i>k</i> strongest security measures in the security system was shown to be <i>coNP</i>-hard, implying that a deterministic polynomial time algorithm most likely does not exist. We propose three methods to solve this problem. Here <span>(d=deg(r))</span> is the root degree, <i>n</i> is the number of non-root vertices, <span>(c_{max})</span> is the maximum edge cost, and <span>(L=sum _{vne r} p(v))</span> is the total prize over all non-root nodes. First, conditioned on some reasonable assumptions and given any error constant <span>(frac{1}{B}le epsilon le 1)</span>, a polynomial time (<span>(1+epsilon )</span>)-approximation algorithm with a time bound <span>(O(d^2n(c_{max}n)^2))</span> is given. This approximation algorithm is fast and gives a reasonably good result. Second, given <span>(Ble c_{max}n)</span>, a <span>(O(d^2n(c_{max}n)^2))</span> time algorithm is shown to give the exact solution to the problem. Third, given an error rate <span>(epsilon &gt; 0)</span> and an accuracy parameter <span>(k' le k)</span>, the <span>((1+epsilon )^{k-k'})</span> polynomial time approximation scheme is shown to solve the problem. The third approximation scheme has the running time of <span>(O((k-k')frac{1}{epsilon ^2}n^4log L))</span>. Consequently, we resolve the open problem posed by Mukdasanit and Kantabutra [18] concerning the case of placing <i>k</i> infinite costs on <i>k</i> edges.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"63 3","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148380760","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"CSB: A Counting and Sampling tool for Bit-vectors","authors":"Arijit Shaw,&nbsp;Kuldeep S. Meel","doi":"10.1007/s00236-026-00535-0","DOIUrl":"10.1007/s00236-026-00535-0","url":null,"abstract":"<div><p>Satisfiability modulo theory (SMT) solvers have significantly advanced automated reasoning due to their effectiveness in solving problems across various fields. With the advancement in SMT solvers, there is growing interest in exploring capabilities beyond mere satisfiability, similar to the progression observed in Boolean satisfiability solvers that expanded into counting and sampling. In this study, we investigate the following question: <i>Can we rely on modern CNF model counters and CNF samplers to extend modern SMT solvers to handle the problems of counting and sampling over bit-vectors?</i> The main contribution of this work is the development of an efficient and user-friendly tool, <span>(textsf{csb})</span>, that solves a bunch of problems around model counting and sampling on the theory of bit-vectors, namely exact and approximate projected and non-projected model counting, along with the almost-uniform and uniform-like sampling. In the case of exact counting, projected counting, and uniform sampling, <span>(textsf{csb})</span> is the first tool to solve the problem—although all these problems have a lot of applications. Our tool <span>(textsf{csb})</span> converts the bit-vector formula into a CNF formula using bit-blasting techniques before applying CNF model counters or samplers to perform counting or sampling. It keeps track of the variable mapping between the bitvector and CNF formula and passes that information to the CNF counter. We built our tool on top of SMT solver <span>(textsf{STP})</span> by integrating approximate model counter <span>(textsf{ApproxMC})</span>, exact model counter <span>(textsf{Ganak})</span>, almost-uniform sampler <span>(textsf{UniGen})</span>, and uniform-like sampler <span>(textsf{CMSGen})</span> in it. Our experiments demonstrate significant performance improvements over existing methods.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"63 3","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-06-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148323767","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A natural deduction system for the Byzantine Generals Oral Messages algorithm","authors":"Dennis M. Volpano","doi":"10.1007/s00236-026-00540-3","DOIUrl":"10.1007/s00236-026-00540-3","url":null,"abstract":"<div><p>The Oral Messages algorithm OM(<i>m</i>) is an algorithm that uses <i>m</i> message relay rounds to solve the Byzantine Generals Problem [5]. It is a landmark result, however its original specification is informal and its correctness proof sketchy, making both hard to understand. The proof is rewritten here using a natural deduction system formulated directly from the message flows described for OM(<i>m</i>) in [5]. The system comprises only two inference rules which can be used to explain the original algorithm via derivations. The rules are shown complete relative to OM(<i>m</i>) and sound in the sense they cannot be used to derive consensus when it is impossible [8]. The completeness proof provides more details than the original correctness proof, clearly showing the role of <i>m</i>, the risk it creates, and why the algorithm succeeds under well-known constraints.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"63 3","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00236-026-00540-3.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148261907","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A couple of simple algorithms for k-dispersion","authors":"Ke Chen,&nbsp;Adrian Dumitrescu","doi":"10.1007/s00236-026-00534-1","DOIUrl":"10.1007/s00236-026-00534-1","url":null,"abstract":"<div><p>Given a set <i>P</i> of <i>n</i> points in <span>(mathbb {R}^d)</span>, and a positive integer <span>(k le n)</span>, the <i>k</i>-dispersion problem is that of selecting <i>k</i> of the given points so that the minimum inter-point distance among them is maximized (under Euclidean distances). Among others, we show the following: </p><ol>\u0000 <li>\u0000 <span>(I)</span>\u0000 \u0000 <p>Given a set <i>P</i> of <i>n</i> points in the plane, and a positive integer <span>(k ge 2)</span>, the <i>k</i>-dispersion problem can be solved by an algorithm running in <span>(Oleft( n^{k-1} log {n}right) )</span> time. This extends an earlier result for <span>(k=3)</span>, due to Horiyama, Nakano, Saitoh, Suetsugu, Suzuki, Uehara, Uno, and Wasa [20] to arbitrary <i>k</i>. In particular, it improves on previous running times for small <i>k</i>.</p>\u0000 \u0000 </li>\u0000 <li>\u0000 <span>(II)</span>\u0000 \u0000 <p>Given a set <i>P</i> of <i>n</i> points in <span>(mathbb {R}^3)</span>, and a positive integer <span>(k ge 2)</span>, the <i>k</i>-dispersion problem can be solved by an algorithm running in </p><div><div><span>$$ {left{ begin{array}{ll} Oleft( n^{k-1} log {n}right) text {time}, &amp; text {if } k text { is even}; Oleft( n^{k-1} log ^2{n}right) text {time}, &amp; text {if } k text { is odd}. end{array}right. } $$</span></div></div><p> For <span>(k ge 4)</span>, no combinatorial algorithm running in <span>(o(n^k))</span> time was known for this problem.</p>\u0000 \u0000 </li>\u0000 <li>\u0000 <span>(III)</span>\u0000 \u0000 <p>Let <i>P</i> be a set of <i>n</i> random points uniformly distributed in <span>([0,1]^2)</span>. Then under suitable conditions, a 0.99-approximation for <i>k</i>-dispersion can be computed in <i>O</i>(<i>n</i>) time with high probability.</p>\u0000 \u0000 </li>\u0000 </ol></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"63 3","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00236-026-00534-1.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148261906","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Upper bound for output patterns of energy-bounded boolean circuits, and its applications","authors":"Jayalal Sarma,&nbsp;Kei Uchizawa","doi":"10.1007/s00236-026-00539-w","DOIUrl":"10.1007/s00236-026-00539-w","url":null,"abstract":"<div><p>Consider a Boolean circuit over a basis <span>({ wedge , vee , lnot })</span>, where <span>(wedge )</span> and <span>(vee )</span> are the conjunction of unbounded fan-in and disjunction of unbounded fan-in, respectively, and <span>(lnot )</span> is the negation. The energy complexity of a circuit is defined as the number of gates outputting ones in the circuit, where the maximum is taken over all the input assignments. \u0000We prove that the number of output patterns (the set of possible outputs of all the internal gates in the circuit) in a circuit of energy <i>e</i> is at most <span>(2^{e log e + 4e})</span> vastly improving the trivial bound of <span>(sum _{i=0}^e {s atopwithdelims ()i})</span>. where <i>s</i> is the size of the circuit, which contrasts with our observation that a threshold circuit achieves the trivial bound. Building on this tool, we prove the following three applications: (i) Any Boolean circuit <i>C</i> of energy <i>e</i> can be converted to a depth-3 circuit of size <span>(s2^{elog e + 4e})</span>. (ii) The problem of counting output patterns of a given circuit is known to be <span>(#textrm{P})</span>-complete in general, but is fixed-parameter tractable when parameterized by energy <i>e</i> (over the basis <span>(mathcal {B}_2 = {wedge _2,vee _2,lnot })</span>). We also show other FPT algorithms; (iii) If a function <span>(f:{0,1}^n times {0,1}^n rightarrow {0,1})</span> is computed by a circuit of energy <i>e</i>, then the unbounded-error communication complexity <i>U</i>(<i>f</i>) is at most <span>(O(e log e))</span>.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"63 3","pages":""},"PeriodicalIF":1.2,"publicationDate":"2026-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148261908","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Open packing in interval graphs","authors":"M. Shalu,&nbsp;V. K. Kirubakaran","doi":"10.1007/s00236-026-00537-y","DOIUrl":"10.1007/s00236-026-00537-y","url":null,"abstract":"<div><p>Total domination and open packing form a primal-dual pair of problems. A vertex subset <i>S</i> of a graph <i>G</i> is called an open packing in <i>G</i> if no pair of distinct vertices in <i>S</i> have a common neighbor in <i>G</i>. The cardinality of a maximum open packing in <i>G</i> is called the open packing number, <span>(rho ^o(G))</span>, of <i>G</i> which is a lower bound for the total domination number of <i>G</i>. Given a graph <i>G</i> and a positive integer <i>k</i>, the problem <span>Open Packing</span> tests whether <i>G</i> has an open packing of size at least <i>k</i>. It is known that <span>Open Packing</span> is NP-complete for split graphs (and so for chordal graphs) [1]. In this work, we use a dynamic programming based approach to show that a maximum open packing in interval graphs (a subclass of chordal graphs) can be found in <span>(O(n^3))</span> time.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"63 2","pages":""},"PeriodicalIF":0.5,"publicationDate":"2026-06-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148237077","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Expressivity of asynchronous TeamLTL and HyperLTL","authors":"Juha Kontinen,&nbsp;Max Sandström,&nbsp;Jonni Virtema","doi":"10.1007/s00236-025-00514-x","DOIUrl":"10.1007/s00236-025-00514-x","url":null,"abstract":"<div><p>Linear temporal logic (LTL) is used in system verification to write formal specifications for reactive systems. However, some relevant properties, e.g. non-inference in information flow security, cannot be expressed in LTL. A class of such properties that has recently received ample attention is known as hyperproperties. There are two major streams in the research regarding capturing hyperproperties, namely hyperlogics, which extend LTL with trace quantifiers (HyperLTL), and logics that employ team semantics, extending truth to sets of traces. In this article we explore the relation between asynchronous LTL under set-based team semantics (TeamLTL) and HyperLTL. In particular we consider the extensions of TeamLTL with the Boolean disjunction and a fragment of the extension of TeamLTL with the Boolean negation, where the negation cannot occur in the right-hand side of the strong release operator or within the global operator. We show that TeamLTL extended with the Boolean disjunction is equi-expressive with the positive Boolean closure of HyperLTL restricted to one universal quantifier, while the right-downward closed fragment of TeamLTL extended with the Boolean negation is expressively equivalent with the Boolean closure of HyperLTL restricted to one universal quantifier. Furthermore, we show that formulae of TeamLTL extended with the Boolean negation are equivalent with sentences of first-order logic interpreted over grid structures.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"63 2","pages":""},"PeriodicalIF":0.5,"publicationDate":"2026-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00236-025-00514-x.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148010107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Simple linear time algorithm for sorting strings in omega-order with applications","authors":"Ruixi Luo,&nbsp;Taikun Zhu,&nbsp;Kai Jin","doi":"10.1007/s00236-026-00530-5","DOIUrl":"10.1007/s00236-026-00530-5","url":null,"abstract":"<div><p>We present a simple linear time algorithm for the following sorting problem: Given <i>n</i> words <span>(A_1,ldots ,A_n)</span>, find a permutation <span>({pi _1,ldots ,pi _n})</span> of <span>(1,ldots ,n)</span> so that <span>((A_{pi _1})^omega le ldots le (A_{pi _n})^omega)</span>, where <span>((A)^omega)</span> denotes the infinitely repeating string <span>(AAAldots)</span>. Let <i>L</i> denote the total length of the given strings. We note that the running time of our algorithm is <i>O</i>(<i>L</i>) even if the size of alphabet is beyond <i>O</i>(1). We also present an <span>(O(L+n log n))</span> time algorithm for the restricted model where we are only allowed to compare symbols. In other words, the main result of this paper is that the time complexity of sorting <span>(A_1,ldots, A_n)</span> in omega-order is the same as that of sorting them in lexicographic order under all common models (bounded alphabet, unbounded alphabet, compare-based model). Our main results find applications in related problems such as rearranging and concatenating given words so that the result is lexicographically smallest or largest.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"63 2","pages":""},"PeriodicalIF":0.5,"publicationDate":"2026-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00236-026-00530-5.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147737774","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A lazy and modular approach to int-blasting","authors":"Max Barth,&nbsp;Matthias Heizmann,&nbsp;Jochen Hoenicke","doi":"10.1007/s00236-026-00529-y","DOIUrl":"10.1007/s00236-026-00529-y","url":null,"abstract":"<div><p>Bit-vector operations are ubiquitous in programming languages and formal verification, but their complex semantics pose challenges for SMT solvers. Although bit-blasting—translating bit-vectors to Boolean variables—is widely used, it struggles with arithmetic bit-vector operations on large bit-widths (e.g., 64-bit or 256-bit variables) due to exponential blowup. Int-blasting, which maps bit-vectors to integer arithmetic, offers a scalable alternative for arithmetic bit-vector operations, but introduces many modulo operations of which some are redundant. This article presents a modular three-step translation from bit-vector formulas to integer formulas, designed to keep the amount of modulo operations low, while preserving correctness. In the first step, we translate bit-vector operations to integer operations. Thereby, we introduce the two functions <span>(texttt {bv2nat})</span> and <span>(texttt {nat2bv}_k)</span> as explicit operators in the SMT-LIB theory of bit-vectors. Each integer operation is wrapped by <span>(texttt {bv2nat})</span> and <span>(texttt {nat2bv}_k)</span>. Hence, the sort of all bit-vector terms is preserved. Therefore, the first translation step is an equivalence transformation. In the second step, we simplify the formula by replacing the composition <span>(texttt {bv2nat} circ texttt {nat2bv}_k)</span> with a modulo operation. These modulo operations are added lazily, i.e., if the modulo does not change the result of the operation, it is omitted. In our experiments this reduced the average amount of modulo operations by 51%. In the third step, we introduce lemmas to precisely capture the meaning of <span>(texttt {bv2nat})</span> and <span>(texttt {nat2bv}_k)</span>. We prove that these lemmas suffice to solve bit-vector formulas. Furthermore, we illustrate that these lemmas are also sufficient for bit-vector formulas with quantifiers, arrays and uninterpreted functions. We implement our translation in <span>SMTInterpol</span> and evaluate it on 19570 SMT-LIB benchmarks. Results show that our lazy int-blasting solves 15% more tasks than an eager int-blasting, with 35% faster average runtime and 12% lower memory usage.</p></div>","PeriodicalId":7189,"journal":{"name":"Acta Informatica","volume":"63 2","pages":""},"PeriodicalIF":0.5,"publicationDate":"2026-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00236-026-00529-y.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"147643135","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"计算机科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}