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Showing papers by "Santonu Sarkar published in 2015"


Journal ArticleDOI
TL;DR: Sodium-ion battery (NIB) cathode performance based on ammonium vanadate is demonstrated here as having high capacity, long cycle life and good rate capability, and density functional theory calculation is envisioned for the NH4V4O10 cathode.
Abstract: Sodium-ion battery (NIB) cathode performance based on ammonium vanadate is demonstrated here as having high capacity, long cycle life and good rate capability. The simple preparation process and morphology study enable us to explore this electrode as suitable NIB cathode. Furthermore, density functional theory (DFT) calculation is envisioned for the NH4V4O10 cathode, and three possible sodium arrangements in the structure are depicted for the first time. Relevant NIB-related properties such as average voltage, lattice constants, and atomic coordinates have been derived, and the estimated values are in good agreement with the current experimental values. A screening study shows ammonium vanadate electrodes prepared on carbon coat onto Al-current collector exhibits a better electrochemical performance toward sodium, with a sustained reversible capacity and outstanding rate capability. With the current cathode with nanobelt morphology, a reversible capacity of 190 mAh g–1 is attained at a charging rate of 20...

59 citations


Journal ArticleDOI
TL;DR: A comprehensive and structured survey of the scheduling algorithms proposed so far is presented here using a novel multidimensional classification framework and identifies various open issues and directions for future research.
Abstract: A MapReduce scheduling algorithm plays a critical role in managing large clusters of hardware nodes and meeting multiple quality requirements by controlling the order and distribution of users, jobs, and tasks execution. A comprehensive and structured survey of the scheduling algorithms proposed so far is presented here using a novel multidimensional classification framework. These dimensions are (i) meeting quality requirements, (ii) scheduling entities, and (iii) adapting to dynamic environments; each dimension has its own taxonomy. An empirical evaluation framework for these algorithms is recommended. This survey identifies various open issues and directions for future research.

58 citations


Journal ArticleDOI
TL;DR: In this paper, the authors explore attack scenarios that call for securing the hypervisor, exploiting co-residency of VMs, VM image management, mitigating insider threats, securing storage in clouds, abusing lightweight software-as-a-service clients, and protecting data propagation in clouds.
Abstract: In response to the revival of virtualized technology by Rosenblum and Garfinkel [2005], NIST defined cloud computing, a new paradigm in service computing infrastructures. In cloud environments, the basic security mechanism is ingrained in virtualization—that is, the execution of instructions at different privilege levels. Despite its obvious benefits, the caveat is that a crashed virtual machine (VM) is much harder to recover than a crashed workstation. When crashed, a VM is nothing but a giant corrupt binary file and quite unrecoverable by standard disk-based forensics. Therefore, VM crashes should be avoided at all costs. Security is one of the major contributors to such VM crashes. This includes compromising the hypervisor, cloud storage, images of VMs used infrequently, and remote cloud client used by the customer as well as threat from malicious insiders. Although using secure infrastructures such as private clouds alleviate several of these security problems, most cloud users end up using cheaper options such as third-party infrastructures (i.e., private clouds), thus a thorough discussion of all known security issues is pertinent. Hence, in this article, we discuss ongoing research in cloud security in order of the attack scenarios exploited most often in the cloud environment. We explore attack scenarios that call for securing the hypervisor, exploiting co-residency of VMs, VM image management, mitigating insider threats, securing storage in clouds, abusing lightweight software-as-a-service clients, and protecting data propagation in clouds. Wearing a practitioner's glasses, we explore the relevance of each attack scenario to a service company like Infosys. At the same time, we draw parallels between cloud security research and implementation of security solutions in the form of enterprise security suites for the cloud. We discuss the state of practice in the form of enterprise security suites that include cryptographic solutions, access control policies in the cloud, new techniques for attack detection, and security quality assurance in clouds.

19 citations


Patent
12 Jun 2015
TL;DR: In this paper, the authors determine the possible Service Level Agreement (SLA) violation during migrating a workload from a physical environment to a virtualized environment and also migrating a virtual machine (VM) from one physical machine to another within a virtualised environment.
Abstract: This technique determines the possible Service Level Agreement (SLA) violation during migrating a workload from a physical environment to a virtualized environment and also migrating a virtual machine (VM) from one physical machine to another within a virtualized environment. This technique uses capacity factor, i.e. the ratio of host physical machine (host PM) capacity and target physical machine (target PM) capacity, to determine the service rate change in the target PM compared to host PM and eventually calculates the VM utilization and response time in the target PM. It then checks if the VM utilization and response time in the target PM lies within the SLA limit. It further checks if the migration in the target virtualized PM is violating a predefined target PM utilization threshold or not and finally causes the migration in the target physical machine if all the SLA parameters are satisfied.

11 citations


Proceedings ArticleDOI
18 Feb 2015
TL;DR: A novel profile guided approach to optimize branch divergence while transforming a serial program to a data-parallel program for GPUs is proposed, based on the observation that branches inside some data parallel loops although divergent, exhibit repetitive regular patterns of outcomes.
Abstract: GPUs offer a powerful bulk synchronous programming model for exploiting data parallelism; however, branch divergence amongst executing warps can lead to serious performance degradation due to execution serialization. We propose a novel profile guided approach to optimize branch divergence while transforming a serial program to a data-parallel program for GPUs. Our approach is based on the observation that branches inside some data parallel loops although divergent, exhibit repetitive regular patterns of outcomes. By exploiting such patterns, loop iterations can be aligned so that the corresponding iterations traverse the same branch path. These aligned iterations when executed as a warp in a GPU, become convergent. We propose a new metric based on the repetitive pattern characteristics that indicates whether a data-parallel loop is worth restructuring. When tested our approach on the well-known Rodinia benchmark, we found that it is possible to achieve upto 48% performance improvement by loop restructuring suggested by the patterns and our metrics.

6 citations


Patent
Sayantan Mitra1, Santonu Sarkar1
04 Feb 2015
TL;DR: In this paper, a static analysis and a dynamic analysis of an application is presented, in a heterogeneous system, with the goal of achieving a desired speedup of the application based on the identified set of parameters.
Abstract: The present disclosure includes, in a heterogeneous system, receiving a desired speedup of an application as input and performing a static analysis and a dynamic analysis of the application. The dynamic analysis of the application comprises, identifying a set of parameters including, an end-to-end execution time of the application, an execution time of data parallel loops in the application, an execution time of non-data parallel loops in the application, and an amount of physical memory used by each data structure in each data parallel loop. Dynamic analysis also includes calculating and providing the feasibility of achieving the desired speedup of the application based on the identified set of parameters, and satisfaction of each of, an initialization invariant, a data-parallel invariant and a data transfer invariant.

4 citations


Proceedings ArticleDOI
04 Jan 2015
TL;DR: This paper investigates which power management setting can be used to improve the energy efficiency of IO-intensive MapReduce jobs by performing a thorough empirical study and indicates that a constant CPU frequency can reduce the energy consumption of an IO- intensive job, while improving its performance.
Abstract: Map-Reduce is a popular data-parallel programming model for varied analysis of huge volumes of data. While a multicore and many CPU HPC infrastructure can be used to improve parallelism of map-reduce tasks, IO-bandwidth limitations may make them ineffective. IO-intensive activities are essential in any MapReduce cluster. In HPC nodes, IO-intensive jobs get queued at the IO-resources while the CPU remain underutilized, resulting in a poor performance, high power consumption and thus, energy inefficiency. In this paper, we investigate which power management setting can be used to improve the energy efficiency of IO-intensive MapReduce jobs by performing a thorough empirical study. Our analysis indicates that a constant CPU frequency can reduce the energy consumption of an IO-intensive job, while improving its performance. Consequently, we build a set of regression models to predict the energy consumption of IO-intensive jobs at a CPU frequency for a given input data volume. We obtained same set of models, with different coefficients, for two different types of IO-intensive jobs, which substantiates the suitability of identified models. These models predict respective outcomes with 80% accuracy for 80% of the new test cases.

3 citations


Proceedings ArticleDOI
01 Oct 2015
TL;DR: It is concluded that peer review of code may have a distinct dynamic that is facilitated by developers working in relative isolation.
Abstract: As large scale software development has become more collaborative, and software teams more globally distributed, several studies have explored how developer interaction influences software development outcomes. The emphasis so far has been largely on outcomes like defect count, the time to close modification requests etc. In the paper, we examine data from the Chromium project to understand how different aspects of developer discussion relate to the closure time of reviews. On the basis of analyzing reviews discussed by 2000+ developers, our results indicate that quicker closure of reviews owned by a developer relates to higher reception of information and insights from peers. However, we also find evidence that higher engagement in collaboration by a developer is associated with slower closure of the reviews she owns. Within the scope of our study, these results lead us to conclude that peer review of code may have a distinct dynamic that is facilitated by developers working in relative isolation.

3 citations


Patent
Nidhi Tiwari1, Santonu Sarkar1
21 Aug 2015
TL;DR: In this paper, the authors proposed a technique to improve the energy efficiency of MapReduce system by using system performance model without changing any component of the system, which involves determining presence of any hardware bottleneck in any node of a Hadoop system.
Abstract: This technique improves energy efficiency of MapReduce system by using system performance model without changing any component of the MapReduce system. This involves determining presence of any hardware bottleneck in any node of MapReduce system based on a system performance model and if any hardware bottleneck is present in any node, then the maximum bandwidth value of hardware associated with the bottleneck of each node is determined. Thereafter, an energy efficient value of Central Processing Unit (CPU) frequency of each node having the bottleneck is determined by using the system performance model and the maximum bandwidth value of hardware associated with the bottleneck. Further, the CPU frequency of each node having the bottleneck is set at the energy efficient value determined in the earlier step.

2 citations


Proceedings ArticleDOI
18 May 2015
TL;DR: This empirical study analyzed a corpus of 19,000+ papers written by 21,000+.
Abstract: For researchers and practitioners of a relatively young discipline like software engineering, an enduring concern is to identify the acorns that will grow into oaks -- ideas remaining most current in the long run. Additionally, it is interesting to know how the ideas have risen in importance, and fallen, perhaps to rise again. We analyzed a corpus of 19,000+ papers written by 21,000+ authors across 16 software engineering publication venues from 1975 to 2010, to empirically determine the half-life of software engineering research topics. We adapted existing measures of half-life as well as defined a specific measure based on publication and citation counts. The results from this empirical study are a presented in this paper.

1 citations


Patent
24 Aug 2015
TL;DR: In this article, a method and system for monitoring health of virtual environment includes receiving input data for one or more virtual machines in the virtual environment, a number of entitled CPU cycles for each of the virtual machines based on the input data are determined.
Abstract: A method and system for monitoring health of virtual environment includes receiving input data for one or more virtual machines in the virtual environment. A number of entitled CPU cycles for each of the virtual machines based on the input data are determined. A number of actual CPU cycles obtained by each of the virtual machines based on the input data are computed. The number of entitled CPU cycles is compared with the number of actual CPU cycles for each of the virtual machines. A health status of the virtual machines based on the comparison is displayed.