Waldemar Grabski

Distributed algorithm for empty vehicles management in personal rapid transit (PRT) network

Summary In this paper, an original heuristic algorithm of empty vehicles management in personal rapid transit network is presented. The algorithm is used for the delivery of empty vehicles for waiting passengers, for balancing the distribution of empty vehicles within the network, and for providing an empty space for vehicles approaching a station. Each of these tasks involves a decision on the trip that has to be done by a selected empty vehicle from its actual location to some determined destination. The decisions are based on a multi-parameter function involving a set of factors and thresholds. An important feature of the algorithm is that it does not use any central database of passenger input (demand) and locations of free vehicles. Instead, it is based on the local exchange of data between stations: on their states and on the vehicles they expect. Therefore, it seems well-tailored for a distributed implementation. The algorithm is uniform, meaning that the same basic procedure is used for multiple tasks using a task-specific set of parameters. Copyright

Personal Rapid Transit (PRT) Computer Network Simulation and Analysis of Flow Capacity

Transportation problems of large urban conurbations inspire search for new transportation systems that meet high environmental standards, are relatively cheap and are user friendly. The latter element also includes the needs of disabled and elderly people. This article concerns a new transportation system - Personal Rapid Transit (PRT). In this article, the attention is focused on the analysis of the efficiency of the PRT transport network. The simulator of vehicle movement in PRT network as well as algorithms for traffic management and control are presented. The proposal of its physical implementation is also included.

System modeling in the COSMA environment

The aim of this paper is to demonstrate how the COSMA environment can be used for system modeling. This environment is a set of tools based on Concurrent State Machines paradigm and is developed in the Institute of Computer Science at the Warsaw University of Technology. Our demonstration example is a distributed brake control system dedicated for a railway transport. The paper shortly introduces COSMA. Next it shows how the example model can be validated by our temporal logic analyzer.

Data Model Design in Automatic Transit System (PRT) Simulation Software

Simulation has become a very important factor in the field of Automated Transit Network – Personal Rapid Transit (ATN-PRT) design. Multiple traffic conditions, as well as model structure and movement parameters lead to increase in the number of simulation experiments which must be performed to evaluate ATN control algorithms. This article aims to show some guidelines for design of such simulation systems, with particular emphasis on data model design in object oriented programming (OOP) for massive simulations. These guidelines are presented in the context of Feniks Personal Rapid Transit (PRT) simulator development, but are also valid for other graph-based simulation software.

Adapting Eclat algorithm to parallel environments with Charm++ library

In this paper we describe Eclat algorithm that is adapted to deal with growing data repositories. The presented solution utilizes Master-Slave scheme to distribute data mining tasks among available computation nodes. Several improvements have been proposed and successfully implemented using Charm++ library. This paper introduces optimization techniques to reduce communication cost and synchronization overhead. It also discusses results of the performance of parallel Eclat algorithm against different databases and compares it with parallel Apriori algorithm. The proposed approach has been illustrated with many experiments and measurements performed using multiprocessor and multithreaded computer platform.

Parallelization of Apriori algorithm using Charm++ library

This paper deals with the problem of adapting sequential frequent item sets mining algorithm to parallel processing. The original Bodons Apriori algorithm has been partitioned into loosely coupled tasks and prepared to be executed on several computation nodes using Charm++ library. Variety of optimization methods have been proposed and successfully implemented in parallel environment. The work provides enhancements to achieve good efficiency during parallelization of existing solutions, e.g.: how to organize communication between tasks. The presented approach has been illustrated with many experiments and measurements performed on parallelized algorithm.

CODE GENERATION FOR CSM/ECSM MODELS IN COSMA ENVIRONMENT

The COSMA software environment, developed in the Institute of Computer Science, WUT,was designed primarily for model checking of reactive systems specified in terms of ConcurrentState Machines (CSM). However, COSMA supports also Extended CSM (ECSM).The extensions allow for using complex data types and pieces of C/C++ code, attributedto CSM states and/or transitions. Because of these extensions, ECSM models cannot beverified by model checking, but they can be used as an intermediate step in code generation.The underlying CSM represent then the flow of control within cooperating components andthe communication among them while the extensions specify the data structures and thedetails of their processing.The paper discusses the code generation from ECSM diagrams. The approach is illustratedwith an example.