Implementation of digital pheromones in PSO accelerated by commodity Graphics Hardware

In this paper, a model for Graphics Processing Unit (GPU) implementation of Particle Swarm Optimization (PSO) using digital pheromones to coordinate swarms within ndimensional design spaces is presented. Previous work by the authors demonstrated the capability of digital pheromones within PSO for searching n-dimensional design spaces with improved accuracy, efficiency and reliability in both serial and parallel computing environments using traditional CPUs. Modern GPUs have proven to outperform the number of floating point operations when compared to CPUs through inherent data parallel architecture and higher bandwidth capabilities. The advent of programmable graphics hardware in the recent times further provided a suitable platform for scientific computing particularly in the field of design optimization. However, the data parallel architecture of GPUs requires a specialized formulation for leveraging its computational capabilities. When the objective function computations are appropriately formulated for GPUs, it is theorized that the solution efficiency (speed) can be significantly increased while maintaining solution accuracy. The development of this method together with a number of multi-modal unconstrained test problems are tested and presented in this paper

Digital Pheromone Implementation of PSO with Velocity Vector Accelerated by Commodity Graphics Hardware

In this paper, a model for Graphics Processing Unit (GPU) implementation of Particle Swarm Optimization (PSO) using digital pheromones to coordinate swarms within ndimensional design spaces is presented. Particularly, the velocity vector computations are carried out on graphics hardware. Previous work by the authors demonstrated the capability of digital pheromones within PSO for searching n-dimensional design spaces with improved accuracy, efficiency and reliability in serial, parallel and GPU computing environments. The GPU implementation was limited to computing the objective function values alone. Modern GPUs have proven to outperform the number of floating point operations when compared to CPUs through inherent data parallel architecture and higher bandwidth capabilities. This paper presents a method to implement velocity vector computations on a GPU along with objective function evaluations. Three different modes of implementation are studied and presented - First, CPU-CPU where objective function and velocity vector are calculated on CPU alone. Second, GPU-CPU where objective function is computed on the GPU and velocity vector is computed on GPU. Third, GPU-GPU where objective function and velocity vector are both evaluated on the GPU. The results from these three implementations are presented followed by conclusions and recommendations on the best approach for utilizing the full potential of GPUs for PSO

Chronic intermittent hypoxia induces oxidative stress and decreases NO production in the carotid artery of rats

Obstructive sleep apnea (OSA) syndrome is a risk factor of hypertension and stroke. Chronic intermittent hypoxia (CIH) leads to oxidative stress and tissue injury. We examined the hypothesis that CIH-induced oxidative stress plays a pathophysiological role in the endothelial dysfunction in rat carotid artery. Adult Sprague-Dawley rats were exposed to IH treatment mimicking a severe OSA condition for 14 days. The carotid arteries were harvested for the malondialdehyde assay, PCR and Western-blotting analysis, and the measurement of nitric oxide (NO) with electrochemistry. Levels of malondialdehyde were significantly elevated in the hypoxic group when compared to the normoxic control. Also, the mRNA expressions of NADPH oxidase (gp91phox, p22phox) were markedly increased in the hypoxic group, indicating an involvement in the CIH-induced oxidative stress. In addition, the protein level of phosphorylated eNOS (ser1177) and the NO levels were notably lowered in the hypoxic group. These results suggest that oxidative stress induced by the CIH treatment deteriorates the endothelial function of the carotid artery with decreased NO bioavailability. These data may be clinically relevant to the increased risk for cerebrovascular disease in OSA patients