Information Processing Letters最新文献

{"title":"Efficient Implementations of Square-root Vélu's Formulas","authors":"Jianming Lin ,&nbsp;Weize Wang ,&nbsp;Chang-An Zhao ,&nbsp;Yuhao Zheng","doi":"10.1016/j.ipl.2025.106580","DOIUrl":"10.1016/j.ipl.2025.106580","url":null,"abstract":"<div><div>In the implementation of isogeny-based cryptographic schemes, Vélu's formulas are essential for constructing and evaluating isogenies. Bernstein et al. proposed an approach known as √élu, which computes an <em>ℓ</em>-isogeny at a cost of <span><math><mover><mrow><mi>O</mi></mrow><mrow><mo>˜</mo></mrow></mover><mo>(</mo><msqrt><mrow><mi>ℓ</mi></mrow></msqrt><mo>)</mo></math></span> finite field operations. This paper presents two improvements to enhance the efficiency of the implementation of √élu as follows: optimizing the index system required in √élu and speeding up the computations of the sums of products used in polynomial multiplications over a finite field <span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span> with characteristic <em>p</em>. To optimize the index system, we modify it to enhance the utilization of <em>x</em>-coordinates and combine it with the technique of redundant representation, which can ultimately reduce the number of <span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span>-multiplications. The speedup of the sums of products is to employ two techniques: lazy reduction (abbreviated as LZYR) and generalized interleaved Montgomery multiplication (abbreviated as INTL). These techniques aim to minimize the underlying operations. We provide an optimized C and assembly implementation of √élu. For the computational cost (in terms of <span><math><msub><mrow><mi>F</mi></mrow><mrow><mi>p</mi></mrow></msub></math></span>-multiplications) of each isogeny involved in CTIDH2048 (resp. SQIsign), exploiting our modified index system (including the combination with redundant representation) obtains a saving up to 5.78% (resp. 5.39%) compared to the previous work. In terms of the performance (reported in CPU clock cycles) of isogeny computations in CTIDH512, applying our index system combined with INTL (resp. our index system combined with LZYR) offers an improvement up to 16.05% (resp. 10.96%) compared to the previous implementation. As for executing an isogeny group action in CTIDH512, our experimental results also demonstrate a reduction of 3.73% (resp. 1.83%) clock cycles by utilizing our index system combined with INTL (resp. our index system combined with LZYR).</div></div>","PeriodicalId":56290,"journal":{"name":"Information Processing Letters","volume":"190 ","pages":"Article 106580"},"PeriodicalIF":0.7,"publicationDate":"2025-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143833606","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":"The longest common subsequence problem for small alphabets in the word RAM model","authors":"Rodrigo Alexander Castro Campos","doi":"10.1016/j.ipl.2025.106579","DOIUrl":"10.1016/j.ipl.2025.106579","url":null,"abstract":"<div><div>Given two strings of lengths <em>m</em> and <em>n</em>, with <span><math><mi>m</mi><mo>≤</mo><mi>n</mi></math></span>, the longest common subsequence problem consists of computing a common subsequence of maximum length by deleting symbols from both strings. While the <span><math><mi>O</mi><mo>(</mo><mi>m</mi><mi>n</mi><mo>)</mo></math></span> algorithm devised in 1974 is optimal in the most general setting, algorithms that depend on parameters other than <em>m</em> and <em>n</em> have been proposed since then. In the word RAM model, let <em>w</em> be the word size, <em>s</em> be the alphabet size, <em>d</em> be the number of dominant symbol matches between the strings, and <em>p</em> be the length of the longest common subsequence. Fast algorithms for this problem have complexities <span><math><mi>O</mi><mo>(</mo><mi>m</mi><mi>n</mi><mo>/</mo><mi>log</mi><mo>⁡</mo><mi>n</mi><mo>)</mo></math></span>, <span><math><mi>O</mi><mo>(</mo><mi>m</mi><mi>n</mi><mo>/</mo><mi>w</mi><mo>)</mo></math></span>, <span><math><mi>O</mi><mo>(</mo><mi>n</mi><mi>s</mi><mo>+</mo><mi>min</mi><mo>⁡</mo><mo>(</mo><mi>p</mi><mo>(</mo><mi>n</mi><mo>−</mo><mi>p</mi><mo>)</mo><mo>,</mo><mi>p</mi><mi>m</mi><mo>)</mo><mo>)</mo></math></span>, <span><math><mi>O</mi><mo>(</mo><mi>n</mi><mi>log</mi><mo>⁡</mo><mi>s</mi><mo>+</mo><mi>d</mi><mi>log</mi><mo>⁡</mo><mi>log</mi><mo>⁡</mo><mi>min</mi><mo>⁡</mo><mo>(</mo><mi>d</mi><mo>,</mo><mi>m</mi><mi>n</mi><mo>/</mo><mi>d</mi><mo>)</mo><mo>)</mo></math></span>, <span><math><mi>O</mi><mo>(</mo><mi>n</mi><mi>s</mi><mo>+</mo><mi>min</mi><mo>⁡</mo><mo>(</mo><mi>d</mi><mi>s</mi><mo>,</mo><mi>p</mi><mi>m</mi><mo>)</mo><mo>)</mo></math></span>, and <span><math><mi>O</mi><mo>(</mo><mi>n</mi><mi>s</mi><mo>+</mo><mi>s</mi><msup><mrow><mo>!</mo></mrow><mrow><mn>2</mn></mrow></msup><mi>s</mi><mo>+</mo><mi>d</mi><mi>log</mi><mo>⁡</mo><mi>s</mi><mo>)</mo></math></span>. In this work, we present an <span><math><mi>O</mi><mo>(</mo><mi>n</mi><mo>(</mo><mi>s</mi><mo>+</mo><msup><mrow><mi>log</mi></mrow><mrow><mo>⁎</mo></mrow></msup><mo>⁡</mo><mi>n</mi><mo>)</mo><mo>+</mo><mi>min</mi><mo>⁡</mo><mo>(</mo><mi>d</mi><mi>log</mi><mo>⁡</mo><mi>s</mi><mo>,</mo><mi>p</mi><mi>m</mi><mo>)</mo><mo>)</mo></math></span> algorithm when <span><math><mi>s</mi><mo>∈</mo><mi>O</mi><mo>(</mo><mi>w</mi><mo>)</mo></math></span>, and also an <span><math><mi>O</mi><mo>(</mo><mi>n</mi><mo>(</mo><mi>s</mi><mo>+</mo><msup><mrow><mi>log</mi></mrow><mrow><mo>⁎</mo></mrow></msup><mo>⁡</mo><mi>n</mi><mo>)</mo><mo>+</mo><mi>d</mi><mo>)</mo></math></span> algorithm when <span><math><mi>s</mi><mo>≤</mo><mi>w</mi></math></span> which uses bitwise instructions that became recently available in modern processors.</div></div>","PeriodicalId":56290,"journal":{"name":"Information Processing Letters","volume":"190 ","pages":"Article 106579"},"PeriodicalIF":0.7,"publicationDate":"2025-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143833605","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":"Fair and truthful allocations under leveled valuations","authors":"George Christodoulou ,&nbsp;Vasilis Christoforidis","doi":"10.1016/j.ipl.2025.106577","DOIUrl":"10.1016/j.ipl.2025.106577","url":null,"abstract":"<div><div>We study the problem of fairly allocating indivisible goods among agents which are equipped with <em>leveled</em> valuation functions. Such preferences, that have been studied before in economics and fair division literature, capture a simple and intuitive economic behavior; larger bundles are always preferred to smaller ones. We provide a fine-grained analysis for various subclasses of leveled valuations focusing on two extensively studied notions of fairness, (approximate) MMS and EFX. In particular, we present a general positive result, showing the existence of 2/3-MMS allocations under valuations that are both leveled and submodular. We also show how some of our ideas can be used beyond the class of leveled valuations; for the case of two submodular (not necessarily leveled) agents we show that there always exists a 2/3-MMS allocation, complementing a recent impossibility result. Then, we switch to the case of subadditive and fractionally subadditive leveled agents, where we are able to show tight (lower and upper) bounds of 1/2 on the approximation factor of MMS. Moreover, we show the existence of exact EFX allocations under general leveled valuations via a simple protocol that in addition satisfies several natural economic properties. Finally, we take a mechanism design approach and we propose protocols that are both truthful and approximately fair under leveled valuations.</div></div>","PeriodicalId":56290,"journal":{"name":"Information Processing Letters","volume":"190 ","pages":"Article 106577"},"PeriodicalIF":0.7,"publicationDate":"2025-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143768168","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 note on the method of equal shares","authors":"Luis Sánchez-Fernández","doi":"10.1016/j.ipl.2025.106576","DOIUrl":"10.1016/j.ipl.2025.106576","url":null,"abstract":"<div><div>The Method of Equal Shares (ES) is a popular approval-based multi-winner voting rule, which was originally proposed by Peters and Skowron. It satisfies several well-known representation axioms, like extended justified representation (EJR) and priceability, and it can be computed in polynomial time. Further, it has already been employed in several real participatory budgeting elections. In this note, we prove that ES is an instance of the EJR-Exact family of voting rules that also satisfy EJR and were proposed by Aziz et al. 2018 before the work of Peters and Skowron.</div></div>","PeriodicalId":56290,"journal":{"name":"Information Processing Letters","volume":"190 ","pages":"Article 106576"},"PeriodicalIF":0.7,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143682684","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 note on the complexity of one-sided crossing minimization of trees","authors":"Alexander Dobler","doi":"10.1016/j.ipl.2025.106575","DOIUrl":"10.1016/j.ipl.2025.106575","url":null,"abstract":"<div><div>In 2011, Harrigan and Healy claimed that one-sided crossing minimization can be solved in polynomial time on trees <span><span>[1]</span></span>. We point out a counterexample to their claims, and show that one-sided crossing minimization is <figure><img></figure>-hard for trees.</div></div>","PeriodicalId":56290,"journal":{"name":"Information Processing Letters","volume":"190 ","pages":"Article 106575"},"PeriodicalIF":0.7,"publicationDate":"2025-03-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143682683","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":"On the complexity of some restricted variants of Quotient Pigeon and a weak variant of Kőnig","authors":"Takashi Ishizuka","doi":"10.1016/j.ipl.2025.106574","DOIUrl":"10.1016/j.ipl.2025.106574","url":null,"abstract":"<div><div>One of the most famous <span>TFNP</span> subclasses is <span>PPP</span>, which is the set of all search problems whose totality is guaranteed by the pigeonhole principle. The author's recent preprint <span><span>[1]</span></span> has introduced a <span>TFNP</span> problem related to the pigeonhole principle over a quotient set, called <span>Quotient Pigeon</span>, and shown that the problem <span>Quotient Pigeon</span> is not only <span>PPP</span>-hard but also <span>PLS</span>-hard. In this paper, we formulate other computational problems related to the pigeonhole principle over a quotient set via an explicit representation of the equivalence classes. Our new formulation introduces a non-trivial <span><math><mtext>PPP</mtext><mo>∩</mo><msub><mrow><mtext>PPA</mtext></mrow><mrow><mi>k</mi></mrow></msub></math></span>-complete problem for every <span><math><mi>k</mi><mo>≥</mo><mn>2</mn></math></span>. Furthermore, we consider the computational complexity of a computational problem related to Kőnig's lemma, which is a weaker variant of the problem formulated by Pasarkar et al. <span><span>[2]</span></span>. We show that our weaker variant is <span>PPAD</span>-hard and is in <span><math><mtext>PPP</mtext><mo>∩</mo><mtext>PPA</mtext></math></span>.</div></div>","PeriodicalId":56290,"journal":{"name":"Information Processing Letters","volume":"190 ","pages":"Article 106574"},"PeriodicalIF":0.7,"publicationDate":"2025-03-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143601479","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":"Friends-and-strangers is PSPACE-complete","authors":"Chao Yang ,&nbsp;Zhujun Zhang","doi":"10.1016/j.ipl.2025.106573","DOIUrl":"10.1016/j.ipl.2025.106573","url":null,"abstract":"<div><div>The friends-and-strangers problem is defined on two graphs <em>X</em> and <em>Y</em> of the same order <em>n</em>, where <em>X</em> is the location graph on a set of locations <span><math><mi>V</mi><mo>(</mo><mi>X</mi><mo>)</mo></math></span> and <em>Y</em> is the friendship graph on a set of people <span><math><mi>V</mi><mo>(</mo><mi>Y</mi><mo>)</mo></math></span>. A configuration is a bijection from <span><math><mi>V</mi><mo>(</mo><mi>X</mi><mo>)</mo></math></span> to <span><math><mi>V</mi><mo>(</mo><mi>Y</mi><mo>)</mo></math></span>, representing an arrangement of <em>n</em> people at <em>n</em> locations. The friends-and-stranger problem investigates the connectivity of two arbitrary configurations by a sequence of swaps of two people that are neighbors (i.e., adjacent in <em>X</em>) and friends (i.e., adjacent in <em>Y</em>). In this paper, we show that the friends-and-strangers problem with subcubic planar location graphs <em>X</em> is <span>PSPACE</span>-complete by a reduction from the <span>Ncl</span> (non-deterministic constraint logic) problem.</div></div>","PeriodicalId":56290,"journal":{"name":"Information Processing Letters","volume":"190 ","pages":"Article 106573"},"PeriodicalIF":0.7,"publicationDate":"2025-03-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143534766","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 simple 4-approximation algorithm for maximum agreement forests on multiple unrooted binary trees","authors":"Jordan Dempsey ,&nbsp;Leo van Iersel ,&nbsp;Mark Jones ,&nbsp;Norbert Zeh","doi":"10.1016/j.ipl.2025.106572","DOIUrl":"10.1016/j.ipl.2025.106572","url":null,"abstract":"<div><div>Maximum agreement forests have been used as a measure of dissimilarity of two or more phylogenetic trees on a given set of taxa. An agreement forest is a set of trees that can be obtained from each of the input trees by deleting edges and suppressing degree-2 vertices. A maximum agreement forest is such a forest with the minimum number of components. We present a simple 4-approximation algorithm for computing a maximum agreement forest of multiple unrooted binary trees. This algorithm applies LP rounding to an extension of a recent ILP formulation of the maximum agreement forest problem on two trees by Van Wersch et al. <span><span>[13]</span></span>. We achieve the same approximation ratio as the algorithm by Chen et al. <span><span>[3]</span></span>, but our algorithm is extremely simple. We also prove that no algorithm based on the ILP formulation by Van Wersch et al. can achieve an approximation ratio of <span><math><mn>4</mn><mo>−</mo><mi>ε</mi></math></span>, for any <span><math><mi>ε</mi><mo>&gt;</mo><mn>0</mn></math></span>, even on two trees. To this end, we prove that the integrality gap of the ILP approaches 4 as the size of the two input trees grows.</div></div>","PeriodicalId":56290,"journal":{"name":"Information Processing Letters","volume":"190 ","pages":"Article 106572"},"PeriodicalIF":0.7,"publicationDate":"2025-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143534765","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":"Lower bound proof for the size of BDDs representing a shifted addition","authors":"Jan Kleinekathöfer,&nbsp;Alireza Mahzoon,&nbsp;Rolf Drechsler","doi":"10.1016/j.ipl.2025.106571","DOIUrl":"10.1016/j.ipl.2025.106571","url":null,"abstract":"<div><div><em>Decision Diagrams</em> (DDs) are among the most popular representations for Boolean functions. They are widely used in the synthesis and verification of digital circuits. The size (i.e., number of nodes) and computation time (required time for performing operations) are two important parameters that determine the efficiency of a DD in different applications. It has been proven that some DDs can represent specific functions in polynomial space or perform certain operations in polynomial time. For example, <em>Binary Decision Diagrams</em> (BDDs) are capable of representing a wide variety of functions (e.g. integer addition) in polynomial space with respect to the input size. However, there are also some functions (e.g., integer multiplication) for which the exponential lower-bounds have been proven for the BDD sizes.</div><div>In this paper, we investigate the space complexity of representing an integer addition, where one of the operands is shifted to the right by an arbitrary value. We call this function the shifted addition. This function is widely used in many digital circuits, e.g., floating point adders. We prove that the size of the BDD representing a shifted addition has exponential space complexity with respect to the input size. It is an important step towards clarifying the reasons behind the failure of BDD-based verification and synthesis when they are applied to the circuits containing shifted addition, e.g., floating point adders.</div></div>","PeriodicalId":56290,"journal":{"name":"Information Processing Letters","volume":"190 ","pages":"Article 106571"},"PeriodicalIF":0.7,"publicationDate":"2025-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143427877","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":"Faster algorithms and a smaller kernel for Cliques or Trees Vertex Deletion","authors":"Dekel Tsur","doi":"10.1016/j.ipl.2025.106570","DOIUrl":"10.1016/j.ipl.2025.106570","url":null,"abstract":"<div><div>In the <span>Cliques or Trees Vertex Deletion</span> problem, the input is a graph <em>G</em> and an integer <em>k</em>, and the goal is to decide whether there is a set of at most <em>k</em> vertices whose removal from <em>G</em> result in a graph in which every connected component is either a clique or a tree. In this paper we give an <span><math><msup><mrow><mi>O</mi></mrow><mrow><mo>⁎</mo></mrow></msup><mo>(</mo><msup><mrow><mn>3.46</mn></mrow><mrow><mi>k</mi></mrow></msup><mo>)</mo></math></span>-time deterministic algorithm, an <span><math><msup><mrow><mi>O</mi></mrow><mrow><mo>⁎</mo></mrow></msup><mo>(</mo><msup><mrow><mn>3.103</mn></mrow><mrow><mi>k</mi></mrow></msup><mo>)</mo></math></span>-time randomized algorithm, and a kernel with <span><math><mi>O</mi><mo>(</mo><msup><mrow><mi>k</mi></mrow><mrow><mn>4</mn></mrow></msup><mo>)</mo></math></span> vertices for <span>Cliques or Trees Vertex Deletion</span>.</div></div>","PeriodicalId":56290,"journal":{"name":"Information Processing Letters","volume":"190 ","pages":"Article 106570"},"PeriodicalIF":0.7,"publicationDate":"2025-02-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143420534","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}