Sandeep Kulkarni

I&C Journal 2022 Journal Article

An efficient approach to achieve compositionality using optimized multi-version object based transactional systems

• Chirag Juyal
• Sandeep Kulkarni
• Sweta Kumari
• Sathya Peri
• Archit Somani

In the modern era of multi-core systems, the main aim is to utilize the cores properly. This utilization can be done by concurrent programming. But developing a flawless and well-organized concurrent program is difficult. Software Transactional Memory Systems (STMs) are a convenient programming interface which assist the programmer to access the shared memory concurrently without worrying about consistency issues. Many STMs available in the literature execute read/write primitive operations on memory buffers. We represent them as Read-Write STMs or RWSTMs. Whereas, there exists some STMs which work on higher level operations. We refer these STMs as Object Based STMs or OSTMs. The literature of databases and RWSTMs say that maintaining multiple versions ensures greater concurrency. So, this paper proposes the notion of Optimized Multi-version Object Based STMs or OPT-MVOSTMs which encapsulates the idea of multiple versions in OSTMs to harness the greater concurrency efficiently.

TAAS Journal 2014 Journal Article

The Complexity of Adding Multitolerance

• Jingshu Chen
• Ali Ebnenasir
• Sandeep Kulkarni

We focus on the problem of adding multitolerance to an existing fault-intolerant program. A multitolerant program tolerates multiple classes of faults and provides a potentially different level of fault tolerance to each of them. We consider three levels of fault tolerance, namely failsafe (i.e., satisfy safety in the presence of faults), nonmasking (i.e., recover to legitimate states after the occurrence of faults), and masking (both). For the case where the program is subject to two classes of faults, we consider six categories of multitolerant programs—FF, FN, FM, MM, MN, and NN, where F, N, and M represent failsafe, nonmasking, and masking levels of tolerance provided to each class of fault. We show that the problem of adding FF, NN, and MN multitolerance can be solved in polynomial time (in the state space of the program). However, the problem is NP-complete for adding FN, MM, and FM multitolerance. We note that the hardness of adding MM and FM multitolerance is especially atypical given that MM and FM multitolerance can be added efficiently under more restricted scenarios where multiple faults occur simultaneously in the same computation. We also present heuristics for managing the complexity of MM multitolerance. Finally, we present real-world multitolerant programs and discuss the trade-off involved in design decisions while developing such programs.

TCS Journal 2013 Journal Article

MR4UM: A framework for adding fault tolerance to UML state diagrams

• Jingshu Chen
• Sandeep Kulkarni

Modern systems often need to address the challenges brought about by a changing environment and/or newly identified faults. The economic and practical issues dictate that the existing models and/or programs be reused while providing tolerance in the presence of faults. In this paper, we propose a framework, namely MR4UM, for applying model revision for the existing program design modeled in a UML state diagram to add tolerance to newly identified faults. In particular, MR4UM starts with program design modeled in a UML state diagram, and automatically transforms the design model in the UML state diagram to the corresponding program actions in the underlying computational model (UCM). Then, MR4UM applies the techniques of model revision to the program in the UCM and generates a fault-tolerant program in the UCM. Finally, MR4UM automatically converts the fault-tolerant program in the UCM into a fault-tolerant program design in the UML state diagram. We illustrate the stepwise procedure of MR4UM with two case studies: the adaptive cruise control program from an automotive system and the altitude switch program from an aircraft altitude control system.

TCS Journal 2011 Journal Article

Preface

• Shlomi Dolev
• Sandeep Kulkarni
• André Schiper