IEICE Transactions on Information and Systems
Online ISSN : 1745-1361
Print ISSN : 0916-8532
Volume E104.D, Issue 3
Displaying 1-18 of 18 articles from this issue
Special Section on Foundations of Computer Science — New Trends of Theory of Computation and Algorithm —
• Atsuyoshi NAKAMURA
2021 Volume E104.D Issue 3 Pages 354
Published: March 01, 2021
Released on J-STAGE: March 01, 2021
JOURNAL FREE ACCESS
• Kento KIMURA, Kazuyuki AMANO, Tetsuya ARAKI
Article type: PAPER
2021 Volume E104.D Issue 3 Pages 355-361
Published: March 01, 2021
Released on J-STAGE: March 01, 2021
JOURNAL FREE ACCESS

Given a box of some specified size and a number of pieces of some specified shape, the anti-slide problem considers how to pack the pieces such that none of the pieces in the box can slide in any direction. The object is to find such a sparsest packing. In this paper, we consider the problem for the case of a two-dimensional square box using T-tetromino pieces. We show that, for a square box of side length n, the number of pieces in a sparsest packing is exactly $\lfloor 2n/3 \rfloor$ when n≢0 (mod 3), and is between 2n/3-1 and n-1 when n≡0 (mod 3).

• Hiroshi FUJIWARA, Yuta WANIKAWA, Hiroaki YAMAMOTO
Article type: PAPER
2021 Volume E104.D Issue 3 Pages 362-369
Published: March 01, 2021
Released on J-STAGE: March 01, 2021
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The performance of online algorithms for the bin packing problem is usually measured by the asymptotic approximation ratio. However, even if an online algorithm is explicitly described, it is in general difficult to obtain the exact value of the asymptotic approximation ratio. In this paper we show a theorem that gives the exact value of the asymptotic approximation ratio in a closed form when the item sizes and the online algorithm satisfy some conditions. Moreover, we demonstrate that our theorem serves as a powerful tool for the design of online algorithms combined with mathematical optimization.

• Ryoma SENDA, Yoshiaki TAKATA, Hiroyuki SEKI
Article type: PAPER
2021 Volume E104.D Issue 3 Pages 370-380
Published: March 01, 2021
Released on J-STAGE: March 01, 2021
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It is well-known that pushdown systems (PDS) effectively preserve regularity. This property implies the decidability of the reachability problem for PDS and has been applied to automatic program verification. The backward regularity preservation property was also shown for an extension of PDS by adding registers. This paper aims to show the forward regularity preservation property. First, we provide a concise definition of the register model called register pushdown systems (RPDS). Second, we show the forward regularity preservation property of RPDS by providing a saturation algorithm that constructs a register automaton (RA) recognizing $\post^{\ast}_\calP(L(\calA))$ where $\calA$ and $\calP$ are a given RA and an RPDS, respectively, and $\post^{\ast}_\calP$ is the forward image of the mapping induced by $\calP$. We also give an example of applying the proposed algorithm to malware detection.

• Hiroaki YAMAMOTO, Hiroshi FUJIWARA
Article type: PAPER
2021 Volume E104.D Issue 3 Pages 381-388
Published: March 01, 2021
Released on J-STAGE: March 01, 2021
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This paper presents a new method to translate a regular expression into a nondeterministic finite automaton (an NFA for short). Let r be a regular expression and let M be a Thompson automaton for r. We first introduce a labeled Thompson automaton defined by assigning two types of expressions which denote prefixes and suffixes of words in L(r) to each state of M. Then we give new ϵ-free NFAs constructed from a labeled Thompson automaton. These NFAs are called a prefix equation automaton and a suffix equation automaton. We show that a suffix equation automaton is isomorphic to an equation automaton defined by Antimirov. Furthermore we give an NFA called a unified equation automaton by joining two NFAs. Thus the number of states of a unified equation automaton can be smaller than that of an equation automaton.

• Yasuko MATSUI, Kenta OZEKI
Article type: LETTER
2021 Volume E104.D Issue 3 Pages 389-391
Published: March 01, 2021
Released on J-STAGE: March 01, 2021
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This paper deals with the problem of enumerating 3-edge-connected spanning subgraphs of an input plane graph. In 2018, Yamanaka et al. proposed two enumeration algorithms for such a problem. Their algorithm generates each 2-edge-connected spanning subgraph of a given plane graph with n vertices in O(n) time, and another one generates each k-edge-connected spanning subgraph of a general graph with m edges in O(mT) time, where T is the running time to check the k-edge connectivity of a graph. This paper focuses on the case of the 3-edge-connectivity in a plane graph. We give an algorithm which generates each 3-edge-connected spanning subgraph of the input plane graph in O(n2) time. This time complexity is the same as the algorithm by Yamanaka et al., but our algorithm is simpler than theirs.

• Hiroki MORIZUMI
Article type: LETTER
2021 Volume E104.D Issue 3 Pages 392-393
Published: March 01, 2021
Released on J-STAGE: March 01, 2021
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The circuit satisfiability problem has been intensively studied since Ryan Williams showed a connection between the problem and lower bounds for circuit complexity. In this letter, we present a #SAT algorithm for synchronous Boolean circuits of n inputs and s gates in time $2^{n\left(1 - \frac{1}{2^{O(s/n)}}\right)}$ if s=o(n log n).

Regular Section
• Pilsung KANG, Jongmin JO
Article type: PAPER
Subject area: Computer System
2021 Volume E104.D Issue 3 Pages 394-403
Published: March 01, 2021
Released on J-STAGE: March 01, 2021
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AI (artificial intelligence) has grown at an overwhelming speed for the last decade, to the extent that it has become one of the mainstream tools that drive the advancements in science and technology. Meanwhile, the paradigm of edge computing has emerged as one of the foremost areas in which applications using the AI technology are being most actively researched, due to its potential benefits and impact on today's widespread networked computing environments. In this paper, we evaluate two major entry-level offerings in the state-of-the-art edge device technology, which highlight increased computing power and specialized hardware support for AI applications. We perform a set of deep learning benchmarks on the devices to measure their performance. By comparing the performance with other GPU (graphics processing unit) accelerated systems in different platforms, we assess the computational capability of the modern edge devices featuring a significant amount of hardware parallelism.

• Takayuki OMORI, Katsuhisa MARUYAMA, Atsushi OHNISHI
Article type: PAPER
Subject area: Software System
2021 Volume E104.D Issue 3 Pages 404-418
Published: March 01, 2021
Released on J-STAGE: March 01, 2021
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History data of edit operations are more beneficial than those stored in version control systems since they provide detailed information on how source code was changed. Meanwhile, a large number of recorded edit operations discourage developers and researchers from roughly understanding the changes. To assist with this task, it is desirable that they easily obtain traceability links for changed program elements over two source code snapshots before and after a code change. In this paper, we propose a graph representation called Operation History Graph (OHG), which presents code change information with such traceability links that are inferred from the history of edit operations. An OHG instance is generated by parsing any source code snapshot restored by edit histories and combining resultant abstract syntax trees (ASTs) into a single graph structure. To improve the performance of building graph instances, we avoided simply maintaining every program element. Any program element presenting the inner-structure of methods and non-changed elements are omitted. In addition, we adopted a lightweight static analysis for type name resolving to reduce required memory resource in the analysis while the accuracy of name resolving is preserved. Moreover, we assign a specific ID to each node and edge in the graph instance so that a part of the graph data can be separately stored and loaded on demand. These decisions make it feasible to build, manipulate, and store the graph with limited computer resources. To demonstrate the usefulness of the proposed operation history graph and verify whether detected traceability links are sufficient to reveal actual changes of program elements, we implemented tools to generate and manipulate OHG instances. The evaluation on graph generation performance shows that our tool can reduce the required computer resource as compared to another tool authors previously proposed. Moreover, the evaluation on traceability shows that OHG provides traceability links with sufficient accuracy as compared to the baseline approach using GumTree.

• Sourav MISHRA, Subhajit CHAUDHURY, Hideaki IMAIZUMI, Toshihiko YAMASAK ...
Article type: PAPER
Subject area: Artificial Intelligence, Data Mining
2021 Volume E104.D Issue 3 Pages 419-429
Published: March 01, 2021
Released on J-STAGE: March 01, 2021
JOURNAL FREE ACCESS

Our paper attempts to critically assess the robustness of deep learning methods in dermatological evaluation. Although deep learning is being increasingly sought as a means to improve dermatological diagnostics, the performance of models and methods have been rarely investigated beyond studies done under ideal settings. We aim to look beyond results obtained on curated and ideal data corpus, by investigating resilience and performance on user-submitted data. Assessing via few imitated conditions, we have found the overall accuracy to drop and individual predictions change significantly in many cases despite of robust training.

• Feng ZHANG, Di LIU, Cong LIU
Article type: PAPER
Subject area: Educational Technology
2021 Volume E104.D Issue 3 Pages 430-440
Published: March 01, 2021
Released on J-STAGE: March 01, 2021
JOURNAL FREE ACCESS

The pervasive application of Small Private Online Course (SPOC) provides a powerful impetus for the reform of higher education. During the teaching process, a teacher needs to understand the difficulty of SPOC videos for students in real time to be more focused on the difficulties and key points of the course in a flipped classroom. However, existing educational data mining techniques pay little attention to the SPOC video difficulty clustering or classification. In this paper, we propose an approach to cluster SPOC videos based on the difficulty using video-watching data in a SPOC. Specifically, a bipartite graph that expresses the learning relationship between students and videos is constructed based on the number of video-watching times. Then, the SimRank++ algorithm is used to measure the similarity of the difficulty between any two videos. Finally, the spectral clustering algorithm is used to implement the video clustering based on the obtained similarity of difficulty. Experiments on a real data set in a SPOC show that the proposed approach has better clustering accuracy than other existing ones. This approach facilitates teachers learn about the overall difficulty of a SPOC video for students in real time, and therefore knowledge points can be explained more effectively in a flipped classroom.

• Akihito AIBA, Minoru YOSHIDA, Daichi KITAMURA, Shinnosuke TAKAMICHI, H ...
Article type: PAPER
Subject area: Speech and Hearing
2021 Volume E104.D Issue 3 Pages 441-449
Published: March 01, 2021
Released on J-STAGE: March 01, 2021
JOURNAL FREE ACCESS

We studied an acoustic anomaly detection system for equipments, where the outlier detection method based on recorded sounds is used. In a real environment, the SNR of the target sound against background noise is low, and there is the problem that it is necessary to catch slight changes in sound buried in noise. In this paper, we propose a system in which a sound source extraction process is provided at the preliminary stage of the outlier detection process. In the proposed system, nonnegative matrix factorization based on generalized Gaussian distribution (GGD-NMF) is used as a sound source extraction process. We evaluated the improvement of the anomaly detection performance in a low-SNR environment. In this experiment, SNR capable of detecting an anomaly was greatly improved by providing GGD-NMF for preprocessing.

• Shinobu KUDO, Shota ORIHASHI, Ryuichi TANIDA, Seishi TAKAMURA, Hideaki ...
Article type: PAPER
Subject area: Image Processing and Video Processing
2021 Volume E104.D Issue 3 Pages 450-460
Published: March 01, 2021
Released on J-STAGE: March 01, 2021
JOURNAL FREE ACCESS

Recently, image compression systems based on convolutional neural networks that use flexible nonlinear analysis and synthesis transformations have been developed to improve the restoration accuracy of decoded images. Although these methods that use objective metric such as peak signal-to-noise ratio and multi-scale structural similarity for optimization attain high objective results, such metric may not reflect human visual characteristics and thus degrade subjective image quality. A method using a framework called a generative adversarial network (GAN) has been reported as one of the methods aiming to improve the subjective image quality. It optimizes the distribution of restored images to be close to that of natural images; thus it suppresses visual artifacts such as blurring, ringing, and blocking. However, since methods of this type are optimized to focus on whether the restored image is subjectively natural or not, components that are not correlated with the original image are mixed into the restored image during the decoding process. Thus, even though the appearance looks natural, subjective similarity may be degraded. In this paper, we investigated why the conventional GAN-based compression techniques degrade subjective similarity, then tackled this problem by rethinking how to handle image generation in the GAN framework between image sources with different probability distributions. The paper describes a method to maximize mutual information between the coding features and the restored images. Experimental results show that the proposed mutual information amount is clearly correlated with subjective similarity and the method makes it possible to develop image compression systems with high subjective similarity.

• Haichuan YANG, Shangce GAO, Rong-Long WANG, Yuki TODO
Article type: LETTER
Subject area: Fundamentals of Information Systems
2021 Volume E104.D Issue 3 Pages 461-464
Published: March 01, 2021
Released on J-STAGE: March 01, 2021
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In 2019, a completely new algorithm, spherical evolution (SE), was proposed. The brand new search style in SE has been proved to have a strong search capability. In order to take advantage of SE, we propose a novel method called the ladder descent (LD) method to improve the SE' population update strategy and thereafter propose a ladder spherical evolution search (LSE) algorithm. With the number of iterations increasing, the range of parent individuals eligible to produce offspring gradually changes from the entire population to the current optimal individual, thereby enhancing the convergence ability of the algorithm. Experiment results on IEEE CEC2017 benchmark functions indicate the effectiveness of LSE.

• Ryousei TAKANO, Kuniyasu SUZAKI
Article type: LETTER
Subject area: Software System
2021 Volume E104.D Issue 3 Pages 465-468
Published: March 01, 2021
Released on J-STAGE: March 01, 2021
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A conventional data center that consists of monolithic-servers is confronted with limitations including lack of operational flexibility, low resource utilization, low maintainability, etc. Resource disaggregation is a promising solution to address the above issues. We propose a concept of disaggregated cloud data center architecture called Flow-in-Cloud (FiC) that enables an existing cluster computer system to expand an accelerator pool through a high-speed network. FlowOS-RM manages the entire pool resources, and deploys a user job on a dynamically constructed slice according to a user request. This slice consists of compute nodes and accelerators where each accelerator is attached to the corresponding compute node. This paper demonstrates the feasibility of FiC in a proof of concept experiment running a distributed deep learning application on the prototype system. The result successfully warrants the applicability of the proposed system.

• Muhammad MUDASIR QAZI, Rana ASIF REHMAN, Asadullah TARIQ, Byung-Seo KI ...
Article type: LETTER
Subject area: Information Network
2021 Volume E104.D Issue 3 Pages 469-472
Published: March 01, 2021
Released on J-STAGE: March 01, 2021
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Information-centric networking (ICN) provides an alternative to the traditional end-to-end communication model of the current Internet architecture by focusing on information dissemination and information retrieval. Named Data Networking (NDN) is one of the candidates that implements the idea of ICN on a practical level. Implementing NDN in wireless sensor networks (WSNs) will bring all the benefits of NDN to WSNs, making them more efficient. By applying the NDN paradigm directly to wireless multi-hop ad-hoc networks, various drawbacks are observed, such as packet flooding due to the broadcast nature of the wireless channel. To cope with these problems, in this paper, we propose an Interest called the accumulation-based forwarding scheme, as well as a novel content store architecture to increase its efficiency in terms of storing and searching data packets. We have performed extensive simulations using the ndnSIM simulator. Experimental results showed that the proposed scheme performs better when compared to another scheme in terms of the total number of Interests, the content store search time, and the network lifetime.

• Shuoyan LIU, Enze YANG, Kai FANG
Article type: LETTER
Subject area: Pattern Recognition
2021 Volume E104.D Issue 3 Pages 473-476
Published: March 01, 2021
Released on J-STAGE: March 01, 2021
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Abnormal behavior detection is now a widely concerned research field, especially for crowded scenes. However, most traditional unsupervised approaches often suffered from the problem when the normal events in the scenario with large visual variety. This paper proposes a self-learning probabilistic Latent Semantic Analysis, which aims at taking full advantage of the high-level abnormal information to solve problems. We select the informative observations to construct the “reference events” from the training sets as a high-level guidance cue. Specifically, the training set is randomly divided into two separate subsets. One is used to learn this model, which is defined as the initialization sequence of “reference events”. The other aims to update this model and the the infrequent samples are chosen into the “reference events”. Finally, we define anomalies using events that are least similar to “reference events”. The experimental result demonstrates that the proposed model can detect anomalies accurately and robustly in the real-world crowd environment.