The ability to solve large-scale problems efficiently is one of the intrinsic values of a grid system. To maximize the throughput of the grid system, matching the submitted tasks to suitable resources is essential. This problem has been identified as the task matching problem. The task matching problem has been studied extensively in the past. Among other nature-inspired algorithms, Particle Swarm Optimization (PSO) has been used more commonly for the task matching problem and has shown promising results. Throughout the literature, the global PSO (gbest) has been chosen as the standard topology, while few other works have considered the local best (ring) topology for the task matching problem. As a result, there is a lack of research investigating the effectiveness of other topologies for the task matching problem. This knowledge gap has motivated our research to elucidate the impact of different PSO topologies on the task matching problem. We observed that the fully connected topology performed best (makespan) in many sets of experiments, but only slightly. Additionally, it was evident from the results that the pyramid topology achieved a slight edge over the other topologies in terms of makespan when all experiments were considered. However, each topology worked better on some problems and not as well on other problems. In addition, the population size significantly impacts the balance between the exploration and the exploitation search process.

When parallel programs are executed on multiprocessors with private caches, a set of data may be repeatedly used and modified by different threads. Such data sharing can often result in cache thrashing, which degrades memory performance. This paper presents and evaluates a loop restructuring method to reduce or even eliminate cache thrashing caused by true data sharing in nested parallel loops. This method uses a compiler analysis which applies linear algebra and the theory of numbers to the subscript expressions of array references. Due to this method's simplicity, it can be efficiently implemented in any parallel compiler. Experimental results show quite significant performance improvements over existing static and dynamic scheduling methods.