Tadashi Dohi

Tadashi Dohi
Hiroshima University | HU · Department of Information Engineering

Ph.D.

About

516
Publications
23,059
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
4,256
Citations

Publications

Publications (516)
Chapter
This chapter introduces the moment-based epistemic uncertainty propagation in Markov models. The epistemic uncertainty in Markov models introduces the uncertainty of model parameters, and it can be propagated by regarding parameters as random variables. The idea behind the moment-based approach is to approximate the multiple integration with a seri...
Article
This article considers the parametric sensitivity of a software rejuvenation model for transaction systems whose system behavior is described by a quasi-birth-and-death (QBD) process with Markovian arrivals, and the software rejuvenation model is represented by a Markov regenerative process (MRGP). The stationary analysis of the MRGP model is based...
Article
The paper proposes a simulation-based procedure to determine the system reliability of a lamp problem. Suppose we have k lamps to light up a room, and each lamp can light a circular area of radius r. The system reliability is the probability that there is no dark area in the room during time t. We obtain the system reliability function and the expe...
Article
Full-text available
This paper focuses on the so-called proportional intensity-based software reliability models (PI-SRMs), which are extensions of the common non-homogeneous Poisson process (NHPP)-based SRMs, and describe the probabilistic behavior of software fault-detection process by incorporating the time-dependent software metrics data observed in the developmen...
Preprint
This paper focuses on the so-called proportional intensity-based software reliability models (PI-SRMs), which are extensions of the common non homogeneous Poisson process (NHPP)-based SRMs, and describe the probabilistic behavior of software fault-detection process by incorporating the time-dependent software metrics data observed in the developmen...
Article
With the growing demand for high reliability and safety software, software reliability prediction has attracted more and more attention to identifying potential faults in software. Software reliability growth models (SRGMs) are the most commonly used prediction models in practical software reliability engineering. However, their unrealistic assumpt...
Article
In this paper, we summarize the so-called Burr-type software reliability models (SRMs) based on the non-homogeneous Poisson process (NHPP) and comprehensively evaluate the model performances by comparing them with the existing NHPP-based SRMs. Two kinds of software fault count data are considered; fault-detection time-domain data and fault-detectio...
Article
In this paper, we focus on a pure birth process to describe software fault counts, called the geometric de-eutrophication software reliability model (SRM), and provide some useful results to handle the software fault count group data. Two types of SRMs are considered; Moranda SRM (1975) and Gaudoin-Soler SRM (1992), where the former is a modificati...
Article
In this paper we revisit a checkpoint/restart model by Slim et al (A new flexible 542 checkpoint/restart model, INRIA Technical Report, 6751, Centre 543 de recherche INRIA Grenoble, 2008) and derive the workload-dependent optimal checkpoint placement policies. Two cases are considered, where the system overhead parameters are independent and depend...
Article
Utilization data (a kind of incomplete data) is defined as the fraction of a fixed period in which the system is busy. In computer systems, utilization data is very common and easily observable, such as CPU utilization. Unlike inter-arrival times and waiting times, it is more significant to consider the parameter estimation of transaction-based sys...
Article
With the rapid increase of software scale and complexity, the cost of traditional software testing methods will increase faster than the scale of software. In order to improve test efficiency, it is particularly important to automatically generate high-quality test cases. This paper introduces a framework for automatic test data generation based on...
Article
This paper focuses on the age replacement problems under the assumption that the arrival of opportunities follows a stochastic point process. The opportunity is a chance to make the replacement, and one can replace a unit with a low cost at the opportunity. In this paper, the opportunity-based age replacement models by Dekker and Dijkstra (1992) an...
Article
Phase-type (PH) fitting is a technique to approximate any general distribution as a PH distribution, which is a probability distribution representing an absorbing time of a Markov chain. Since the PH distribution is described as a discrete- or continuous-time Markov chain (CTMC), the PH fitting can provide approximate Markov models to any non-expon...
Article
Full-text available
Software reliability models (SRMs) are widely used for quantitative evaluation of software reliability by estimating model parameters from failure data observed in the testing phase. In particular, non-homogeneous Poisson process (NHPP)-based SRMs are the most popular because of their mathematical tractability. In this paper, we focus on the parame...
Article
Full-text available
In software reliability engineering, software-rejuvenation and -checkpointing techniques are widely used for enhancing system reliability and strengthening data protection. In this paper, a stochastic framework composed of a composite stochastic Petri reward net and its resulting non-Markovian availability model is presented to capture the dynamic...
Article
This paper discusses how to compute the parametric sensitivity function in continuous-time Markov chains (CTMC). The sensitivity function is the first derivative of the steady-state probability vector regarding a CTMC parameter. Since the sensitivity function is given as a solution of linear equations with a sparse matrix, several linear equation s...
Article
In this paper, we consider a two-unit parallel redundant system with deterioration on a lattice, where each unit has multi-stage deterioration levels, say, n levels. The transition from one deterioration level to the subsequent level occurs following the well-known Marshall-Olkin bivariate exponential distribution. We derive the closed form of the...
Article
Intrusion tolerance is an ability to keep the correct service by masking the intrusion based on fault-tolerant techniques. With the rapid development of virtualization, the virtual machine (VM)-based intrusion tolerance scheme has been developed according to the concept of state machine replication with Byzantine fault tolerant technique. In this a...
Article
In this paper, we present non-Markovian availability models for capturing the dynamics of system behavior of an operational software system that undergoes aperiodic time-based software rejuvenation and checkpointing. Two availability models with rejuvenation are considered taking account of the procedure after the completion of rollback recovery op...
Article
The emergence of the smart grid has brought great innovation in the new distribution power system, facilitated a green and sustainable energy-based society, and mitigated the growing energy crisis. The smart grid is regarded as the next generation electrical power grid. It not only improves the power distribution systems with the techniques of dist...
Article
In this article, we consider data-driven approaches for software reliability evaluation without specifying the fault count distribution, where the underlying stochastic process to describe software fault-counts in the system testing is given by a non-homogeneous Poisson process. A comprehensive non-parametric method based on the kernel estimation i...
Article
Purpose In this paper, the authors propose two construction methods to estimate confidence intervals of the time-based optimal software rejuvenation policy and its associated maximum system availability via a parametric bootstrap method. Through simulation experiments the authors investigate their asymptotic behaviors and statistical properties. D...
Article
A software release game was formulated by Zeephongsekul and Chiera [Zeephongsekul, P. & Chiera, C. (1995). Optimal software release policy based on a two-person game of timing. Journal of Applied Probability 32: 470–481] and was reconsidered by Dohi et al. [Dohi, T., Teraoka, Y., & Osaki, S. (2000). Software release games. Journal of Optimization T...
Article
Full-text available
The phenomenon of software aging refers to the continuing degradation of software system performance with the operation time and is usually caused by the aging-related bugs such as the memory leak and the accumulation of round-off errors. Software rejuvenation acts as one of the proactive fault management techniques against the software aging. In t...
Article
This paper presents a stochastic framework, consisting of stochastic reward net (SRN) for capturing the transient behaviors of the system and its related non-Markovian state transition diagram, to model an operational software system that undergoes aperiodic time-based rejuvenation and checkpointing schemes, and further to investigate whether there...
Article
In this paper, we extend the existing opportunity-based age replacement policies by taking account of dependency between the failure time and the arrival time of a replacement opportunity for one-unit system. Based on the bivariate probability distribution function of the failure time and the arrival time of the opportunity, we focus on two opportu...
Article
Utilization data are defined as time series data consisting of time fractions of busy periods in fixed time intervals and are practically used to represent server conditions such as CPU utilization. In general, it is more challenging to estimate model parameters from utilization data, since we do not know exact job arrival time and service time fro...
Article
Full-text available
In the management of software testing, testing-recourse allocation is one of the most important problems due to the tradeoff between development cost and reliability of released software. This paper presents the model-based approach to design the testing-resource allocation. In particular, we employ the architecture-based software reliability model...
Article
Software testing-resource allocation plays a significant role in software project management. During the last two decades, a number of software-resource allocation problems have been formulated from various points of view, by taking account of several optimization criteria with constraints. First, we consider three optimization problems with constr...
Article
Software aging often affects the performance of software systems and may eventually cause them to fail. A complementary approach to handle transient software failures due to the software aging is called software rejuvenation. It is a preventive and proactive solution that is particularly useful for counteracting the phenomenon of software aging. In...
Article
Full-text available
Component importance analysis is to measure the effect on system reliability of component reliabilities, and is used to the system design from the reliability point of view. On the other hand, to guarantee high reliability of real-time computing systems, redundancy has been widely applied, which plays an important role in enhancing system reliabili...
Article
Full-text available
The determination of the software release time for a new software product is the most critical issue for designing and controlling software development processes. This paper presents an innovative technique to predict the optimal software release time using a neural network. In our approach, a three-layer perceptron neural network with multiple out...
Article
Full-text available
Non-Homogeneous Gamma Process (NHGP) is characterized by an arbitrary trend function and a gamma renewal distribution. In this paper, we estimate the confidence intervals of model parameters of NHGP via two parametric bootstrap methods: simulation-based approach and re-sampling-based approach. For each bootstrap method, we apply three methods to co...
Article
Full-text available
Mobile cloud computing (MCC) is a state-of-the-art architecture that integrates the cloud computing into the mobile environment, and overcomes obstacles such as processing capability, battery life, storage, and availability. Also the MCC is expected to be a key technology for cyber physical systems by connecting to vehicular systems, medical system...
Article
Full-text available
Purpose The purpose of this paper is to present a novel method to estimate the optimal software testing time which minimizes the relevant expected software cost via a refined neural network approach with the grouped data, where the multi-stage look ahead prediction is carried out with a simple three-layer perceptron neural network with multiple ou...
Chapter
This chapter introduces the model-based performance evaluation for security measures of an intrusion tolerant system. The intrusion tolerant system is a promising architecture to prevent security failures such as DoS attack and falsification. In this chapter, we focus on the specific intrusion tolerant system called SITAR which is developed at MCNC...
Chapter
Taking account of border effects in communication network areas is one of the most important problems to quantify accurately the performance/dependability of wireless ad hoc networks (WAHNs), because the assumption on uniformity of network node density is often unrealistic to describe the actual communication areas. This problem appears in both mod...
Poster
Full-text available
Call for Papers http://ijmems.in/ijmems--announcements.html
Article
This paper proposes an approach to estimate an optimal software rejuvenation schedule minimizing an expected total software cost per unit time. Based on a non-parametric predictive inference (NPI) approach, we derive the upper and lower bounds of the predictive expected software cost via the predictive survival function from system failure time dat...
Article
Software rejuvenation is one of the proactive fault management techniques to prevent system performance degradation, which may lead to the system failure caused by software aging. In the design of software rejuvenation, it is important to determine the optimal timing of triggering the rejuvenation in terms of the system overhead. In this paper, we...
Article
Full-text available
Software fault prediction is one of the most fundamental but significant management techniques in software dependability assessment. In this paper we concern the software fault prediction using a multilayer-perceptron neural network, where the underlying software fault count data are transformed to the Gaussian data, by means of the well-known Box-...
Article
In this paper we develop statistical inference approaches for three age replacement policies; classical age replacement, opportunity-based age replacement first and opportunity-based age replacement last, when the failure time distribution of an item is unknown. More specifically, we utilize the sample moments of the failure time distribution and e...
Article
When reliability and maintenance issues are dealt for real applications, we often encounter a number of problems related to modeling and optimization. Reliability and maintenance modeling with optimization plays an essential role for the quantitative analysis, and is considered as a significant application domain in Computational Science. We report...
Conference Paper
Computer security has become an increasingly important hot topic in computer and communication industry, since it is important to support critical business process and to protect personal and sensitive information. Computer security is to keep security attributes (confidentiality, integrity and availability) of computer systems, which face the thre...
Article
In this paper we consider an operational software system with multi-stage degradation levels due to software aging, and derive the optimal dynamic software rejuvenation policy maximizing the steady-state system availability, via the semi-Markov decision process. Also, we develop a reinforcement learning algorithm based on Q-learning as an on-line a...
Article
A trend renewal process is characterized by a counting process and a renewal process which are mutually transformed with each other by a trend function, and plays a significant role to represent a sub-class of general repair models. In this paper we develop another nonparametric estimation method for trend renewal processes, where the form of failu...
Conference Paper
In this paper, we present a novel method to estimate the optimal software release timing which minimizes the relevant expected cost via artificial neural networks (ANNs), where software bug count data are available at each testing date. First, we opt for data transform methods from the Poisson count data to the Gaussian data. Second, ANNs with mult...
Chapter
Full-text available
This chapter provides a comprehensive survey of PH (phase-type) distribution and MAP (Markovian arrival process) fitting. The PH distribution and MAP are widely used in analytical model-based performance evaluation because they can approximate non-Markovian models with arbitrary accuracy as Markovian models. Among a number of past research results...
Article
Full-text available
This article presents parameter estimation of phase-type (PH) distribution. PH distribution is widely used in model-based performance evaluation such as reliability and queueing system, and is defied by an absorbing continuous-time Markov chain (CTMC). Since non-Markovian model can be approximated by a CTMC by replacing general distributions with P...
Article
Nonparametric software reliability analysis is a challenging issue to predict software reliability under incomplete knowledge on software fault-detection time distribution, because the underlying stochastic model is a function of only software fault data and is not predictable in principle for unknown patterns in future long term. Sofer and Miller...