In the field of Materials Science, tomographic images play an important role in the analysis of composite materials.We present a computational environment that helps specialists in the field to carry out analysis and evaluation of samples of composite materials.This environment takes the form of a tailored Problem Solving Environment (PSE) and builds upon the SCiRun PSE.Its implementation is driven primarily by four major attributes: modularity, flexibility, interactivity and performance.Users can easily assemble networks of modules, with some of the modules being specifically designed for materials science analysis.These modules are flexible in terms of configuration, so yielding more flexibility to the setup of the networks, as well as in relation to the user interaction upon them once running.The implementation of data processing algorithms supporting critical modules rely on parallel programming.Furthermore, the quality of tomographic images under analysis is an issue of concern.

We present part of our recent work on performance enhancement of cluster file systems using shared disks over a SAN. This work is built around the proposal of pCFS, a file system specifically targeting those environments. In we presented the objectives and design principles of pCFS and a proof-of-concept implementation, carried out by modifying Red Hatpsilas GFS , showing significant improvements in operations over files shared among processes running in different nodes. pCFS differs from GFS in two main aspects: its use of cooperative caching and a finer grain of locking. The first aspect, which used the LAN to enhance performance in write sharing situations, was described elsewhere ; we now introduce a complementary strategy - locking file regions instead of the whole file - which enables us to use the SAN while delivering a high level of performance in those same write sharing situations. pCFS may apply inter-node locks to regions, allowing processes to operate in parallel with a minimum of coherency overhead among nodes; a process cannot access outside its region(s) and, when a writer unlocks a region, others can then lock it and be able to see modified data immediately. Through a set of experiments where a file is shared between processes running in different nodes, we show that the described approach allows a gain of, at least, an order of magnitude over plain GFS.

Parallel and Distributed Computing (EuroPar

This short paper describes the cooperative caching architecture of pCFS, a shared disk cluster file system (CFS) which aims to achieve high performance in a broad spectrum of I/O intensive applications ranging from computational access to large data sets to video streaming and databases, and includes an extended API for parallel I/O access. pCFS is targeted at small to medium sized clusters where data is stored in fibre channel shared devices on a storage area network (SAN) and exploits two interconnect fabrics: a SAN to access on-disk data, and a LAN, used both for the exchange of control information (related to locking and cache management) and for cooperative caching dataflow

We present our use of the Bochs PC emulator in a series of pratical assignments that, in a basic computer architecture course, introduce polling and interrupt-based input-output programming techniques.