Mohamed A. El-Zawawy

Mohamed A. El-Zawawy, Mohammad N. Alanazi

Static alias analysis of different type of programming languages has been drawing researcher attention. However most of the results of existing techniques for alias analysis are not precise enough compared to needs of modern compilers. Probabilistic versions of these results, in which result elements are associated with occurrence probabilities, are required in optimizations techniques of modern compilers. This paper presents a new probabilistic approach for alias analysis of parallel programs. The treated parallelism model is that of SPMD where in SPMD, a program is executed using a fixed number of program threads running on distributed machines on different data. The analyzed programs are assumed to be in the static single assignment (SSA) form which is a program representation form facilitating program analysis. The proposed technique has the form of simply-strictured system of inference rules. This enables using the system in applications like Proof-Carrying Code (PPC) which is a general technique for proving the safety characteristics of modern programs.

Mohamed A. El-Zawawy, Mohammad N. Alanazi

Execution of concurrent programs implies frequent switching between different thread contexts. This property perplexes analyzing and reasoning about concurrent programs. Trace simplification is a technique that aims at alleviating this problem via transforming a concurrent program trace (execution) into a semantically equivalent one. The resulted trace typically includes less number of context switches than that in the original trace. This paper presents a new static approach for trace simplification. This approach is based on a connectivity analysis that calculates for each trace-point connectivity and context-switching information. The paper also presents a novel operational semantics for concurrent programs. The semantics is used to prove the correctness and efficiency of the proposed techniques for connectivity analysis and trace simplification. The results of experiments testing the proposed technique on problems treated by previous work for trace simplification are also shown in the paper. The results prove the efficiency and effectiveness of the proposed method.

Mohamed A. El-Zawawy

This paper presents a new technique for data slicing of distributed programs running on a hierarchy of machines. Data slicing can be realized as a program transformation that partitions heaps of machines in a hierarchy into independent regions. Inside each region of each machine, pointers preserve the original pointer structures in the original heap hierarchy. Each heap component of the base type (e.g., the integer type) goes only to a region of one of the heaps. The proposed technique has the shape of a system of inference rules. In addition, this paper presents a simply structure type system to decide type soundness of distributed programs. Using this type system, a mathematical proof that the proposed slicing technique preserves typing properties is outlined in this paper as well.

Mohamed A. El-Zawawy, Eisa A. Aleisa

Context-oriented programming (COP) is a new technique for programming that allows changing the context in which commands execute as a program executes. Compared to object-oriented programming (aspect-oriented programming), COP is more flexible (modular and structured). This paper presents a precise syntax-directed operational semantics for context-oriented programming with layers, as realized by COP languages like ContextJ* and ContextL. Our language model is built on Java enriched with layer concepts and activation and deactivation of layer scopes. The paper also presents a static type system that guarantees that typed programs do not get stuck. Using the means of the proposed semantics, the mathematical correctness of the type system is presented in the paper.