A three-year research project about water grid technology (“WATERGRID research project”) is led by ARIN – the company managing water distribution in the city of Naples – in a partnership with IBM and with the University of Naples. Objectives of the project's initial phase include designing and prototyping a subsystem for grid modelling, optimization and simulation (GMOS). The GMOS subsystem implements state-of-the-art software kernels for the simulation of water distribution networks, including modules for the calibration of the hydraulic model and for an optimal partitioning of the grid. This paper illustrates general findings in applying model-driven software engineering to the architecture and design of the GMOS subsystem which largely abstract from the specific nature of the distribution grid as they could equally apply to the modelling, optimization and simulation of gas and electricity distribution networks.

A pseudorandom number generator, based on a linear-feedback shift-register sequence, is presented. The very long period of the generator, 2/sup 1279/-1, makes it useful in modern statistical simulations. The proposed generator overcomes the limitations of multiplicative-congruential generators with modulus 2/sup 31/-1. The properties of linear-feedback shift-register sequences are reviewed, and a sequence of order p=1279 is proposed as a source of pseudorandom numbers. Results of the vectorization of shift register algorithm and of statistical tests are presented.>

Virtual storage management allows an efficient use of computer memory through the cooperative actions of the computer hardware and the operating system which are completely transparent to application programs. However, when program data exceed the available memory space, the program elapsed time may be dominated by the time spent in paging I/O operations. The data transfer rate, as determined by the operating system implementation of demand paging, may be small when compared with the maximum I/O bandwidth that the I/O hardware could support.