Venkatesh Choppella

Synthesis of High-Performance Parallel Programs for a Class of ab Initio Quantum Chemistry Models

This paper provides an overview of a program synthesis system for a class of quantum chemistry computations. These computations are expressible as a set of tensor contractions and arise in electronic structure modeling. The input to the system is a a high-level specification of the computation, from which the system can synthesize high-performance parallel code tailored to the characteristics of the target architecture. Several components of the synthesis system are described, focusing on performance optimization issues that they address.

Automatic code generation for many-body electronic structure methods: the tensor contraction engine‡‡

As both electronic structure methods and the computers on which they are run become increasingly complex, the task of producing robust, reliable, high-performance implementations of methods at a rapid pace becomes increasingly daunting. In this paper we present an overview of the Tensor Contraction Engine (TCE), a unique effort to address issues of both productivity and performance through automatic code generation. The TCE is designed to take equations for many-body methods in a convenient high-level form and acts like an optimizing compiler, producing an implementation tuned to the target computer system and even to the specific chemical problem of interest. We provide examples to illustrate the TCE approach, including the ability to target different parallel programming models, and the effects of particular optimizations.

Requirements for and Evaluation of RMI Protocols for Scientific Computing

Distributed software component architectures provide promising approach to the problem of building large scale, scientific Grid applications [18]. Communication in these component architectures is based on Remote Method Invocation (RMI) protocols that allow one software component to invoke the functionality of another. Examples include Java remote method invocation (Java RMI)[25] and the new Simple Object Access Protocol (SOAP) [15]. SOAP has the advantage that many programming languages and component frameworks can support it. This paper describes experiments showing that SOAP by itself is not efficient enough for large scale scientific applications. However, when it is embedded in multi-protocol RMI framework, SOAP can be effectively used as a universal control protocol, that can be swapped out by faster, more special purpose protocols when large data transfer speeds are needed.

Efficient synthesis of out-of-core algorithms using a nonlinear optimization solver

Summary form only given. We address the problem of efficient out-of-core code generation for a special class of imperfectly nested loops encoding tensor contractions. These loops operate on arrays too large to fit in physical memory. The problem involves determining optimal tiling and placement of disk I/O statements. This entails a search in an explosively large parameter space. We formulate the problem as a nonlinear optimization problem and use a discrete constraint solver to generate optimized out-of-core code. Measurements on sequential and parallel versions of the generated code demonstrate the effectiveness of the proposed approach.

Alipi: a framework for re-narrating web pages

We propose Alipi, a distributed and participatory approach for re-narrating web pages for the purpose of rendering the content more accessible. This model supports alternative descriptions for a web page or parts of it via rewriting or re-narration for a given target audience by volunteers. The goal is to render the Web accessible to people across varied abilities, age, economic situation, language and geographic locations. We present the motivation, architecture and prototype implementation of Alipi.

Identifying cost-effective common subexpressions to reduce operation count in tensor contraction evaluations

Complex tensor contraction expressions arise in accurate electronic structure models in quantum chemistry, such as the coupled cluster method. Transformations using algebraic properties of commutativity and associativity can be used to significantly decrease the number of arithmetic operations required for evaluation of these expressions. Operation minimization is an important optimization step for the Tensor Contraction Engine, a tool being developed for the automatic transformation of high-level tensor contraction expressions into efficient programs. The identification of common subexpressions among a set of tensor contraction expressions can result in a reduction of the total number of operations required to evaluate the tensor contractions. In this paper, we develop an effective algorithm for common subexpression identification and demonstrate its effectiveness on tensor contraction expressions for coupled cluster equations.

Decomposition of Sequential Behavior UsingInterface Specification and Complementation

Decomposition of system behavior along functional boundaries into interacting sequential components is a key step in top-down system design. In this paper, we present sequential decomposition, a method for factoring sequential components from a system specification based on interface specifications of the components. The resulting components can be independently synthesized, or realized using off-the-shelf components. We introduce interface specification language (ISL), based on finite-state machine semantics, to specify the input/output behavior of synchronous sub-systems. A component is factored from a system by embedding an implementation of the complement of its interface into the system description. The composition of a machine with its complement is shown to be isomorphic to the machine, and the composition of a machine with an implementation of its component is shown to be a safe interaction. We apply sequential decomposition to a non-trivial example, a special-purpose computer with Scheme programming language primitives as its instructions.

An Aspect Oriented Approach for Renarrating Web Content

The ability to modify the existing published web pages is what we are calling Renarration of the web. Such a mechanism is useful for improving accessibility and personalization of the content currently on the web. There are many techniques in place for enabling both Web Accessibility and Web Personalization. In this paper we propose a novel approach: an Aspects inspired design of renarration. Aspects have traditionally been applied to programming. Here we reinterpret concepts like Join Points, Point-cuts and Advices and apply them to web documents. To validate our approach, we designed a framework called Rennaration Studio that is built using microservices based architecture pattern and implemented using Pythons flask platform. We demonstrate the feasibility of our proposal by renarrating different Aspects (text, language, phonetics) of two specific web documents.

DISCOVIR: A Framework for Designing Interfaces and Structuring Content for Virtual Labs

As education and technology merge, the opportunity for teaching and learning expand even more. However, the juxtaposition of the latest technologies has also raised concern for academic institutions as to which technologies are most effective in terms of cost, reach, richness, and, most importantly, learning. In this paper, we present a novel development framework, which we call as DISCOVIR, for asynchronous virtual lab development. Our aim is to simplify the process of developing the content for a virtual lab and to make the resulting labs more consistent for the learners (students). We incorporate the popular Model View Controller architecture, in building the user interface for the virtual lab. It allows the lab developers to focus completely on the quality of the content while the look and the feel for the resultant lab is provided in the form of customizable themes. We define an HTML5 based semantic structure for writing the lab content. It ensures long term sustainability of the lab and supports semantic search capabilities. Our model makes no prior assumptions or requisites in terms of expertise and tools required to use it in practice. A lab developer is free to use any html editor on any operating system to build his lab. It requires no costly software installations and runs locally without a web server support. Our proposed model is currently being used by 16 of the 28 virtual labs from IIIT, Hyderabad.

CORP: A Browser Policy to Mitigate Web Infiltration Attacks

Cross origin interactions constitute the core of today’s collaborative Word Wide Web. They are, however, also the cause of malicious behaviour like Cross-Site Request Forgery (CSRF), clickjacking, and cross-site timing attacks, which we collectively refer as Web Infiltration attacks. These attacks are a rampant source of information stealth and privacy intrusion on the web. Existing browser security policies like Same Origin Policy, either ignore this class of attacks or, like Content Security Policy, insufficiently deal with them.