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Mutual visibility by robots with persistent memory 1

13th International Workshop on Frontiers in Algorithmics, FAW 2019

作者： Bhagat, Subhash Mukhopadhyaya, Krishnendu Advanced Computing and Microelectronics Unit Indian Statistical Institute Kolkata India

ISBN: (数字)9783030181260

ISBN: (纸本)9783030181253

This paper addresses one of the fundamental geometric formation problems, namely the mutual visibility problem, for a set of semi-synchronous, opaque robots occupying distinct positions in the Euclidean plane. Since robots are opaque, if three robots lie on a line, the middle robot obstructs the visions of the two other robots. The mutual visibility problem requires the robots to coordinate their movements to form a configuration, within finite time and without collision, in which no three robots are collinear. We assume that robots are endowed with constant bits of persistent memory. We consider the computational model [4] in which the persistent memory is used by the robots only to remember their previous internal states. This piece of information is not communicated or visible to the other robots. Except from this persistent memory, robots are oblivious i.e., they do not carry forward any other information from their previous computational cycles. The paper presents a distributed algorithm to solve the mutual visibility problem for a set of semi-synchronous robots using only 1 bit of persistent memory. The proposed algorithm also provides a self-stabilizing solution to the problem. The algorithm does not impose any other restriction on the capability of the robots and guarantees collision-free movements for the robots. © Springer Nature Switzerland AG 2019.

关键词： Robots

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Largest triangle inside a terrain 31

Largest triangle inside a terrain

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31st Canadian Conference on Computational Geometry, CCCG 2019

作者： Das, Arun Kumar Das, Sandip Mukherjee, Joydeep Advanced Computing and Microelectronics Unit Indian Statistical Institute Calcutta India

In this paper, we present an O(n2) time algorithm to find a largest area triangle contained inside a terrain with n vertices. We also present an O(n log n) time 1/2-factor approximation for the same. © CCCG 2019....

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Relay Selection in Millimeter Wave D2D Communications Through Obstacle Learning

Relay Selection in Millimeter Wave D2D Communications Throug...

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International Communication Systems and Networks and Workshops, COMSNETS

作者： Subhojit Sarkar Sasthi C. Ghosh Advanced Computing and Microelectronics Unit Indian Statistical Institute Kolkata India

ISBN: (数字)9781728131870

ISBN: (纸本)9781728131887

There has been growing interest in device to device (D2D) millimeterwave (mmwave) communication, due to the promising high speeds and immense amounts of unused bandwidth available. However, mmwaves suffer from unusually high attenuation, through free space, and especially through obstacles. The accepted way to avoid such attenuation is to break up the transmission path into multiple short hops, such that there are no obstacles between nodes. We extend the possibility of using a global positioning system (GPS) based, location aware, centralized approach to the problem of relay selection. Satellite imagery can be used to avoid static obstacles in the transmission path. However, satellite imagery cannot acquire smaller obstacles ones like bushes, trees and signboards. Moreover, depending on the size of the obstacle with respect to the heights of the mmwave base station (BS) and an user equipment (UE), presence of an obstacle does not guarantee obstruction. We propose a simple learning based approach to detect the presence of static as well as dynamic obstacles, without resorting to satellite imagery. We then use this knowledge to efficiently select an appropriate relay for a UE, lowering the chance of allocating an obstacle prone link. Finally we compare our relay selection algorithm with an existing algorithm and show that there is a significant improvement in the quality of link allocation.

关键词： Relays Long Term Evolution Global Positioning System Satellites Interference Attenuation Millimeter wave communication

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Tuning 2D magnetism in Fe3+XGeTe2 films by element doping

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National Science Review 2022年第6期9卷 163-170页

作者： Shanshan Liu Zihan Li Ke Yang Enze Zhang Awadhesh Narayan Xiaoqian Zhang Jiayi Zhu Wenqing Liu Zhiming Liao Masaki Kudo Takaaki Toriyama Yunkun Yang Qiang Li Linfeng Ai Ce Huang Jiabao Sun Xiaojiao Guo Wenzhong Bao Qingsong Deng Yanhui Chen Lifeng Yin Jian Shen Xiaodong Han Syo Matsumura Jin Zou Yongbing Xu Xiaodong Xu Hua Wu Faxian Xiu State Key Laboratory of Surface Physics and Department of Physics Fudan University Institute for Nanoelectronic Devices and Quantum Computing Fudan University College of Science University of Shanghai for Science and Technology Laboratory for Computational Physical Sciences(MOE) Fudan University Solid State and Structural Chemistry Unit Indian Institute of Science School of Electronic Science and Engineering Nanjing University Department of Physics University of Washington Department of Electronic Engineering Royal Holloway University of London Materials Engineering The University of Queensland Beijing Key Laboratory of Microstructure and Property of Advanced Materials Institute of Microstructure and Property of Advanced Materials Beijing University of Technology The Ultramicroscopy Research Center Kyushu University State Key Laboratory of ASIC and System School of Microelectronics Fudan University Collaborative Innovation Center of Advanced Microstructures Department of Applied Quantum Physics and Nuclear Engineering Kyushu University Centre for Microscopy and Microanalysis The University of Queensland Shanghai Research Center for Quantum Sciences

Two-dimensional（2D） ferromagnetic materials have been discovered with tunable magnetism and orbital-driven nodal-line features. Controlling the 2D magnetism in exfoliated nanoflakes via electric/magnetic fields enables a boosted Curie temperature（TC） or phase transitions. One of the challenges, however, is the realization of high TC2D magnets that are tunable, robust and suitable for large scale fabrication. Here, we report molecular-beam epitaxy growth of wafer-scale Fe3+XGeTe2films with TCabove room temperature. By controlling the Fe composition in Fe3+XGeTe2, a continuously modulated TCin a broad range of 185–320 K has been achieved. This widely tunable TCis attributed to the doped interlayer Fe that provides a 40% enhancement around the optimal composition X = 2. We further fabricated magnetic tunneling junction device arrays that exhibit clear tunneling signals. Our results show an effective and reliable approach, i.e. element doping, to producing robust and tunable ferromagnetism beyond room temperature in a large-scale 2D Fe3+XGeTe2fashion.

关键词： 2D ferromagnetic material Fe3+XGeTe2 film element doping above room temperature TC tunability

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Faster search of clustered marked states with lackadaisical quantum walks

arXiv

引用

arXiv 2021年

作者： Saha, Amit Majumdar, Ritajit Saha, Debasri Chakrabarti, Amlan Sur-Kolay, Susmita A. K. Choudhury School of Information Technology University of Calcutta India Advanced Computing & Microelectronics Unit Indian Statistical Institute India Atos Pune India

The nature of discrete-time quantum walk in the presence of multiple marked states has been studied by Nahimovs and Rivosh. They introduced an exceptional configuration of clustered marked states i.e., if the marked states are arranged in a √k × √k cluster within a √N × √N grid, where k = n2 and n an odd integer. They showed that finding a single marked state among the multiple ones using quantum walk with AKR (Ambainis, Kempe and Rivosh) coin requires Ω(√N − √k) time. Furthermore, Nahimov and Rivosh also showed that the Grover's coin can find the same configuration of marked state both faster and with higher probability compared to that with the AKR coin. In this article, we show that using lackadaisical quantum walk, a variant of a three-state discrete-time quantum walk on a line, the success probability of finding all the clustered marked states of this exceptional configuration is nearly 1 with smaller run-time. We also show that the weights of the self-loop suggested for multiple marked states in the state-of-the-art works are not optimal for this exceptional configuration of clustered mark states. We propose a range of weights of the self-loop from which only one can give the desired result for this configuration. © 2021, CC BY.

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Proactive Microservice Placement and Migration for Mobile Edge computing

Proactive Microservice Placement and Migration for Mobile Ed...

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IEEE/ACM Symposium on Edge computing (SEC)

作者： Kaustabha Ray Ansuman Banerjee Nanjangud C. Narendra Advanced Computing and Microelectronics Unit Indian Statistical Institute Ericsson Research Bangalore India

ISBN: (数字)9781728159430

ISBN: (纸本)9781728159447

In recent times, Mobile Edge computing (MEC) has emerged as a new paradigm allowing low-latency access to services deployed on edge nodes offering computation, storage and communication facilities. Vendors deploy their services on MEC servers to improve performance and mitigate network latencies often encountered in accessing cloud services. A service placement policy determines which services are deployed on which MEC servers. A number of mechanisms exist in literature to determine the optimal placement of services considering different performance metrics. However, for applications designed as microservice workflow architectures, service placement schemes need to be re-examined through a different lens owing to the inherent interdependencies which exist between microservices. Indeed, the dynamic environment, with stochastic user movement and service invocations, along with a large placement configuration space makes microservice placement in MEC a challenging task. Additionally, owing to user mobility, a placement scheme may need to be recalibrated, triggering service migrations to maintain the advantages offered by MEC. Existing microservice placement and migration schemes consider on-demand strategies. In this work, we take a different route and propose a Reinforcement Learning based proactive mechanism for microservice placement and migration. We use the San Francisco Taxi dataset to validate our approach. Experimental results show the effectiveness of our approach in comparison to other state-of-the-art methods.

关键词： Measurement Reinforcement learning Servers Task analysis Public transportation Edge computing Lenses

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Efficient decoding of surface code syndromes for error correction in quantum computing

arXiv

引用

arXiv 2021年

作者： Bhoumik, Debasmita Sen, Pinaki Majumdar, Ritajit Sur-Kolay, Susmita Kumar, Latesh K.J. Iyengar, Sundaraja Sitharama Advanced Computing & Microelectronics Unit Indian Statistical Institute Kolkata India Department of Electrical Engineering National Institute of Technology Agartala India KFSCIS Florida International University MiamiFL United States

Errors in surface code have typically been decoded by Minimum Weight Perfect Matching (MWPM) based method. Recently, neural-network-based Machine Learning (ML) techniques have been employed for this purpose. Here we propose a two-level (low and high) ML-based decoding scheme, where the first level corrects errors on physical qubits and the second one corrects any existing logical errors, for different noise models. Our results show that our proposed decoding method achieves ∼ 10× and ∼ 2× higher values of pseudo-threshold and threshold respectively, than for MWPM. We show that usage of more sophisticated ML models with higher training/testing time, do not provide significant improvement in the decoder performance. Finally, data generation for training the ML decoder requires significant overhead hence lower volume of training data is desirable. We have shown that our decoder maintains a good performance with the train-test-ratio as low as 40: 60. © 2021, CC BY.

关键词： Error correction

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Distributed Relay Selection in Presence of Dynamic Obstacles in Millimeter Wave D2D Communication

Distributed Relay Selection in Presence of Dynamic Obstacles...

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IEEE International Conference on Communications (ICC)

作者： Durgesh Singh Arpan Chattopadhyay Sasthi C. Ghosh Advanced Computing& Microelectronics Unit Indian Statistical Institute Kolkata India Department of Electrical Engineering Indian Institute of Technology Delhi

ISBN: (数字)9781728150895

ISBN: (纸本)9781728150901

Millimeter wave (mmWave) device to device (D2D) communication is highly susceptible to obstacles due to severe penetration losses and requires almost a line of sight (LOS) communication path. D2D channel condition is local to devices/user equipments (UEs) and hence is not directly visible to the base station (BS). Thus quality of the D2D channel needs to be propagated to BS by UEs which may incur some delay. Hence the solution provided by BS to UEs using this gathered channel information might become less useful to establish communication due to moving obstacles. These types of obstacles might not be known in advance and hence may cause unpredictable fluctuations to the D2D channel quality. Hence we seek to learn the D2D channels using the finite horizon partially observable Markov decision process (POMDP) framework to model the uncertainty in such kind of network environments with dynamic obstacles. The objective is to minimize delay when channel quality deteriorates, by making UEs choose locally the best possible decision between i) to continue on the current relay link on which communication is taking place or ii) to switch to another good relay by exploring other possible UEs in its locality. We derive an optimal threshold policy which tells the UE to take appropriate decision locally. Later, we give a simplified and easy to implement stationary threshold policy which counts the number of successive acknowledgement failures, based on which UE make appropriate decision locally. Through extensive simulation, we demonstrate that our approach outperforms recent algorithms.

关键词： Relays Device-to-device communication Packet loss Delays Uncertainty Switches

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Finding a Largest-Area Triangle in a Terrain in Near-Linear Time

arXiv

引用

arXiv 2021年

作者： Cabello, Sergio Das, Arun Kumar Das, Sandip Mukherjee, Joydeep Faculty of Mathematics and Physics University of Ljubljana Slovenia Institute of Mathematics Physics and Mechanics Slovenia Advanced Computing and Microelectronics Unit Indian Statistical Institute India Dept. of Computer Science Ramakrishna Mission Vivekananda Educational and Research Institute India

A terrain is an x-monotone polygon whose lower boundary is a single line segment. We present an algorithm to find in a terrain a triangle of largest area in O(n log n) time, where n is the number of vertices defining the terrain. The best previous algorithm for this problem has a running time of O(n2). Copyright © 2021, The Authors. All rights reserved.

关键词： Trees (mathematics)

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Current Comparator-Based Reconfigurable Adder and Multiplier on Hybrid Memristive Crossbar

Current Comparator-Based Reconfigurable Adder and Multiplier...

引用

IEEE Computer Society Annual Symposium on VLSI

作者： Manobendra Nath Mondal Susmita Sur-Kolay Bhargab B. Bhattacharya Advanced Computing and Microelectronics Unit Indian Statistical Institute Kolkata India Dept. of CSE Indian Institute of Technology Kharagpur India

ISBN: (数字)9781728157757

ISBN: (纸本)9781728157764

Memristors have shown significant promise both in logic synthesis and memory-subsystem design. A 2D-crossbar of memristors can be used to store multi-valued memory states by utilizing the analog variation of current-induced resistance through memristor cells. The integration of CMOS components with memristor cells can further widen their design space for handling various complex systems. A crossbar built with CMOS-memristor hybridization supports a potential platform that enables computation-in-memory (CIM). In this work we propose a logic system based on differential currents for implementing an ADDER and a MULTIPLIER on a hybrid-memristor crossbar network. Simulation studies demonstrate that the proposed design reduces both memristor cost and computation-cycle time compared to previous approaches.

关键词： Memristors Adders Computer architecture Wires Common Information Model (computing) Logic gates Voltage control

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