Incremental file reorganization schemes

Issued as Final project report, Project no. G-36-66

A Survey on Array Storage, Query Languages, and Systems

Since scientific investigation is one of the most important providers of massive amounts of ordered data, there is a renewed interest in array data processing in the context of Big Data. To the best of our knowledge, a unified resource that summarizes and analyzes array processing research over its long existence is currently missing. In this survey, we provide a guide for past, present, and future research in array processing. The survey is organized along three main topics. Array storage discusses all the aspects related to array partitioning into chunks. The identification of a reduced set of array operators to form the foundation for an array query language is analyzed across multiple such proposals. Lastly, we survey real systems for array processing. The result is a thorough survey on array data storage and processing that should be consulted by anyone interested in this research topic, independent of experience level. The survey is not complete though. We greatly appreciate pointers towards any work we might have forgotten to mention.Comment: 44 page

Concurrent Context-Free Framework for Conceptual Similarity Problem using Reverse Dictionary

Semantic search is one of the most prominent options to search the required and relevant content from the web. But most of them are doing key word and phrase wise similarity search. It may or may not find the relevant information because they directly search with that phrase. But, in most of the cases documents may conceptually equal instead of term wise. Reverse dictionary can solve such type of problems. This will take meaning of the word and it will return related keywords with respective ranks. But main problem here is building such dictionaries is time and memory consuming. Cost effective solutions are required to reduce search time and in-memory requirements. This paper focuses on such aspects by utilizing concurrent programming and efficient index structures and builds a framework to Conceptual similarity problem using reverse dictionary. Simulation results shows that proposed approach can take less time when compared to existing approaches

STANSE: Bug-finding Framework for C Programs

Regular paper accepted at the MEMICS 2011 workshop. The paper deals with static analysis. It also describes a framework and tool called Stanse

Data-centric concurrency control on the java programming language

Dissertação para obtenção do Grau de Mestre em Engenharia InformáticaThe multi-core paradigm has propelled shared-memory concurrent programming to an important role in software development. Its use is however limited by the constructs that provide a layer of abstraction for synchronizing access to shared resources. Reasoning with these constructs is not trivial due to their concurrent nature. Data-races and deadlocks occur in concurrent programs, encumbering the programmer and further reducing his productivity. Even though the constructs should be as unobtrusive and intuitive as possible, performance must also be kept high compared to legacy lock-based mechanism. Failure to guarantee similar performance will hinder a system from adoption. Recent research attempts to address these issues. However, the current state of the art in concurrency control mechanisms is mostly code-centric and not intuitive. Its codecentric nature requires the specification of the zones in the code that require synchronization,contributing to the decentralization of concurrency bugs and error-proneness of the programmer. On the other hand, the only data-centric approach, AJ [VTD06], exposes excessive detail to the programmer and fails to provide complete deadlock-freedom. Given this state of the art, our proposal intends to provide the programmer a set of unobtrusive data-centric constructs. These will guarantee desirable security properties: composability, atomicity, and deadlock-freedom in all scenarios. For that purpose, a lower level mechanism (ResourceGroups) will be used. The model proposed resides on the known concept of atomic variables, the basis for our concurrency control mechanism. To infer the efficiency of our work, it is compared to Java synchronized blocks, transactional memory and AJ, where our system demonstrates a competitive performance and an equivalent level of expressivity.RepComp project(PTDC/EIA-EIA/108963/2008

The Table Generating Routines of a Data Description Language Processor

The Data Description Language Processor, designed by J. A. Ramirez, is the compiler for a modified version of the Data Description Language (DDL), written by D. P. Smith. Two main phases exist in the DDL Processor: 1) The Syntactic Analysis phase and 2) The Code Generation phase The former phase checks the DDL source for local and global syntactic flaws before passing control to the latter. In order to speed up execution of phase 2, internal tables (one symbol and several data tables), containing encoded versions of the DDL source input, are constructed. The tables, created during syntax analysis, will facilitate global syntax checking (verifying all DDL statement references to be valid), and will permit code generation to operate more quickly by providing it with the essence of the source data and, hence, negate the necessity of a second pass over the source input