Salvador Abreu

The Final Frontier: Confidentiality and Privacy in the Cloud

The boundary between the trusted inside and the untrusted outside blurs when a company adopts cloud computing. The organizations applications-and data-are no longer onsite, fundamentally changing the definition of a malicious insider.

Applications of Declarative Programming and Knowledge Management

Invited Talk.- A Guide for Manual Construction of Difference-List Procedures.- Constraints.- Linear Weighted-Task-Sum - Scheduling Prioritized Tasks on a Single Resource.- Efficient Edge-Finding on Unary Resources with Optional Activities.- Encoding of Planning Problems and Their Optimizations in Linear Logic.- Constraint-Based Timetabling System for the German University in Cairo.- Databases and Data Mining.- Squash: A Tool for Analyzing, Tuning and Refactoring Relational Database Applications.- Relational Models for Tabling Logic Programs in a Database.- Integrating XQuery and Logic Programming.- Causal Subgroup Analysis for Detecting Confounding.- Using Declarative Specifications of Domain Knowledge for Descriptive Data Mining.- Extensions of Logic Programming.- Integrating Temporal Annotations in a Modular Logic Language.- Visual Generalized Rule Programming Model for Prolog with Hybrid Operators.- The Kiel Curry System KiCS.- Narrowing for First Order Functional Logic Programs with Call-Time Choice Semantics.- Java Type Unification with Wildcards.- System Demonstrations.- Testing Relativised Uniform Equivalence under Answer-Set Projection in the System cc???.- spock: A Debugging Support Tool for Logic Programs under the Answer-Set Semantics.

Objective: In Minimum Context

The current proposals for the inclusion of modules in the ISO Prolog standard are not very consensual. Since a program-structuring feature is required for a production programming language, several alternatives have been explored over the years.

On the implementation of gnu prolog

GNU Prolog is a general-purpose implementation of the Prolog language, which distinguishes itself from most other systems by being, above all else, a native-code compiler which produces stand-alone executables which do not rely on any bytecode emulator or meta-interpreter. Other aspects which stand out include the explicit organization of the Prolog system as a multipass compiler, where intermediate representations are materialized, in Unix compiler tradition. GNU Prolog also includes an extensible and high-performance finite-domain constraint solver, integrated with the Prolog language but implemented using independent lower-level mechanisms. This paper discusses the main issues involved in designing and implementing GNU Prolog : requirements, system organization, performance, and portability issues as well as its position with respect to other Prolog system implementations and the ISO standardization initiative.

Targeting the Cell Broadband Engine for constraint-based local search

We investigated the use of the Cell Broadband Engine (Cell/BE) for constraint‐based local search and combinatorial optimization applications. We presented a parallel version of a constraint‐based local search algorithm that was chosen because it fits very well the Cell/BE architecture because it requires neither shared memory nor communication among processors. The performance study on several large optimization benchmarks shows mostly linear time speedups, sometimes even super linear. These experiments were carried out on a dual‐Cell IBM (Armonk, NY, USA) blade with 16 processors. Besides getting speedups, the execution times exhibit a much smaller variance that benefits applications where a timely reply is critical. Copyright

Parallel Constraint-Based Local Search on the Cell/BE Multicore Architecture

We investigate the use of the Cell Broadband Engine (Cell/BE) for Combinatorial Optimization applications. We present a parallel version of a constraint-based Local Search algorithm which was chosen because it fits very well the Cell/BE architecture since it requires neither shared memory nor communication between processors. The performance study on several large optimization benchmarks shows mostly linear time speedups, even sometimes super-linear. These experiments were done on a Dual-Cell IBM Blade with 16 processors. Besides getting speedups, the execution times exhibit a much smaller variance, which benefits applications where a timely reply is critical.

Large-scale parallelism for constraint-based local search: the costas array case study

We present the parallel implementation of a constraint-based Local Search algorithm and investigate its performance on several hardware platforms with several hundreds or thousands of cores. We chose as the basis for these experiments the Adaptive Search method, an efficient sequential Local Search method for Constraint Satisfaction Problems (CSP). After preliminary experiments on some CSPLib benchmarks, we detail the modeling and solving of a hard combinatorial problem related to radar and sonar applications: the Costas Array Problem. Performance evaluation on some classical CSP benchmarks shows that speedups are very good for a few tens of cores, and good up to a few hundreds of cores. However for a hard combinatorial search problem such as the Costas Array Problem, performance evaluation of the sequential version shows results outperforming previous Local Search implementations, while the parallel version shows nearly linear speedups up to 8,192 cores. The proposed parallel scheme is simple and based on independent multi-walks with no communication between processes during search. We also investigated a cooperative multi-walk scheme where processes share simple information, but this scheme does not seem to improve performance.

A Logic-Based Information System

In this article we present the University of Evoras Integrated Information System (SIIUE), which is meant to model most of the information necessary for the management and day-to-day operation of an institution such as a public University. SIIUE is centered around a logicbased representation of all intervenients and processes, which is used to generate the more efficient and specific representations for the actual use. This includes extended SQL, PHP3 and Java code generation. SIIUE also interacts with an etherogenous set of partial information systems, both to supply and collect information.

A Parametric Framework for Cooperative Parallel Local Search

In this paper we address the problem of parallelizing local search. We propose a general framework where different local search engines cooperate (through communication) in the quest for a solution. Several parameters allow the user to instantiate and customize the framework, like the degree of intensification and diversification. We implemented a prototype in the X10 programming language based on the adaptive search method. We decided to use X10 in order to benefit from its ease of use and the architectural independence from parallel resources which it offers. Initial experiments prove the approach to be successful, as it outperforms previous systems as the number of processes increases.

Unbalanced tree search on a manycore system using the GPI programming model

The recent developments in computer architectures progress towards systems with large core count (Manycore) which expose more parallelism to applications. Some applications named irregular and unbalanced applications demand a dynamic and asynchronous load balance implementation to utilize the full performance a Manycore system. For example, the recently established Graph500 benchmark aims at such applications. The UTS benchmark characterizes the performance of such irregular and unbalanced computations with a tree-structured search space that requires continuous dynamic load balancing. GPI is a PGAS API that delivers the full performance of RDMA-enabled networks directly to the application. Its programming model focuses the use of one-sided asynchronous communication, overlapping computation and communication. In this paper we address the dynamic load balancing requirements of unbalanced applications using the GPI programming model. Using the UTS benchmark, we detail the implementation of a work stealing algorithm using GPI and present the performance results. Our performance evaluation shows significant improvements when compared with the optimized MPI version with a maximum performance of 9.5 billion nodes per second on 3072 cores.