bodom_lx at task3 dot cc

Elements and Concepts – A brief overview

Introduction

This document contains some basic concepts and definitions about software testing. It has been written for studying a part of the Software Engineering Project course at my University. It is composed by a summary of the intersection of more than 10 different sources, all of which are cited. If you feel that some contents of this publication belong to your intellectual property and it is not cited, please contact the author who is willing to correct any mistake.

The first part of the paper focuses on the definition of the most important key aspects of software testing. Then some information about input partitioning are given. What follows is a research about code coverage and two useful and famous tools, Control-flow coverage and Data-flow analysis. A complete example on using those tools is then given. The second half of the document also contains the definition of the most important software testing practices.

The goal of this tiny document is to clarify key terms and therefore become a base start for the reader to go in deep with the interested topics. Another goal is to give a simple but clear example about data flow analysis, as I realized that not all the people understand the examples around the Net.

Software Testing

Software Testing is an empirical investigation conducted to provide stakeholders with information about the quality of the product or service under test, with respect to the context in which it is intended to operate. Software Testing also provides an objective, independent view of the software to allow the business to appreciate and understand the risks at implementation of the software. Test techniques include, but are not limited to, the process of executing a program or application with the intent of finding software bugs. It can also be stated as the process of validating and verifying that a software program/application/product meets the business and technical requirements that guided its design and development, so that it works as expected and can be implemented with the same characteristics. ¹

Read more…

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For people having Intel graphic chipset under Gnu/Linux, performance using 3D applications or Compiz-* window manager effects has always been a problem. Intel drivers for Xorg never gave problems but have also never been brilliant. I always looked around searching for xorg.conf tuning configuration entries.
Today I was simply browsing Ubuntu Wiki and discovered the UxaTesting page. I wanted to know something about UXA and Intel drivers, so I found a Wikipedia definition:

In computing, UXA is the reimplementation of the EXA graphics acceleration architecture of the X.Org Server developed by Intel. Its major difference with EXA is the use of GEM, replacing Translation Table Maps.

Yeah cool, the official Xorg Wiki Intel Graphics Driver page Gives also some more information, so if you’ve got one of these chipsets (you can verify using lspci | grep VGA ):

• i810 and variants thereof
• i815
• i830M
• 845G
• i852GM
• 855GM
• 865G
• 915G and variants (GMA 900)
• E7221
• 945G and variants (GMA 950)
• 946GME
• G33
• Q33
• Q35
• 965G/Q
• G35
• G41
• G43
• G/GM/Q45

You may want to try out the new acceleration method by adding this line


Option "AccelMethod" "uxa"


To your /etc/X11/xorg.conf file, in section “Device”.

Please note that:

1. UXA is not yet stable as EXA. Try it out, signal your experience on the Ubuntu wiki page and fill out a bug if necessary
2. You will need at least Xorg server 1.6.0
3. You will need at least xf86-video-intel-2.6.2 drivers
4. I don’t think this is mandatory, but please tell me if you encounter differences when updating to 2.6.30.x kernel. I already have 2.6.30.0 on Sid so I don’t know if with a previous version this is working

On Debian Sid I just had to add the Option line to my xorg.conf file.
The performance differences are noticeable and incredible. Everything runs faster and smoother.
My glxgears output went from 60 FPS (using EXA) to 425 FPS (using UXA).
This is a 700% performance improvement!

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I’m currently pressed by my University life, that’s because I don’t post often.
There are 3 big projects for this semester: a C compiler, a dynamic website using Java Servlets and JSP and the most interesting one: a C++ program for Software Engineering Project course.
I’m working with other two collegues on a task manager for people using the Pomodoro Technique by Francesco Cirillo.
The project is called Pomotux and is under development following strong software engineering methodologies (Scrum@Xp). Pomotux is under construction since 2 months and uses technologies such as SQLite to store and play with tasks. The interesting fact regarding our data structure choice is that we are also using a framework for obtaining ORM, called LiteSQL.

LiteSQL is a C++ library that integrates C++ objects tightly to relational database and thus provides an object persistence layer

LiteSQL is still young and immature but powerful enough for our scope. We are also happy to provide feedback to their developers, that are ready to help us. They even wrote a patch for us!
Pomotux is reaching an unexpected stability. Unexpected because it is written by 3 young people that come from a light Java experience and saw C++ 3 months ago. It works under Linux and its graphical interface uses QT 4.5.0. It should work on any *NIX variant that meets dependencies, but also under Windows with some light modifications.
It will support just the basic features of the technique (unfortunately we don’t have the time to fully work on it) but it’s ready for expansions such as team support and statistics.
We will be happy to release the sources as soon as we finish the course, hoping that people will find it useful and that some serious programmers take it and make it the perfect tool for Pomodorians I will also contact the author of the Pomodoro Technique when we release it.

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After the study of pointers versus references, the second natural question that comes in head of a ex Java developer turning to C++ is:

“What are the difference between static and dynamic memory allocation in C++?”

which can be translated as:

“When should I use the stack and when do I have to use the heap in C++?”

that can be further simplified to:

“When should I use the new operator in C++?”

I could simply summarize the answer to: “Use stack when possible”, but I think that this time there is the need of more explanations. Let’s have the following model for a process in the system:

A simplified model for a process

I’m not really interested in an real representation of a process (see Modern Operating Systems by A. S. Tanenbaum for a very good explanation on processes), but focus on the stack and on the heap.
In reality the heap is a software abstraction but you can also imagine it like the stack.
In C++ programs there are also several other memory areas in which objects and non-object values may be stored (see this article on GotW for further details).

Why then choose between stack or heap? Quoting my publication on object-oriented memory management in Java:

Stack-based variables have their extent determined by their scope, so the former is constrained by the structure of the code at compile-time .

Sometimes there is a need for the variables with unconstrained extent in order to cope with
problems where lifetime of a variable can only be known at run-time.
In this case heap-based variables, whose extent is strictly under control of the programmer, are used. [..]

I promise that I will update my 17 pages about OO-memory management to cover also C++ by the end of June. By the way, following some forums, wikipedia, my publication and GotW, I also summarized pros and cons of stack and heap use in C++:

Update 2009-07-03
After 4 months of heavy GUI and Database C++ programming, here are my thoughts: if you are planning to write a program with something more than a couple of objects interacting, using associations and therefore, objects as attributes, use the heap. Every serious program, even if not really big, uses heap for object allocation. Just take care to delete the objects when you don’t need them anymore. Objects on the heap are dynamically allocated and it is more comfortable to pass them through other objects using pointers. The use of the heap assures the live of objects even if the method that generated them runs out of scope ( =dies ). If you also plan to write GUIs, solid toolkits like QT recommend the use of heap to create graphical objects.

In some Operating Systems, stack is also very limited while heap is usually not.

Here are listed the sources I used for writing this article:

• http://www.velocityreviews.com/forums/t278261-stack-vs-heap.html
• http://www.computing.net/answers/programming/stackheap-c/2293.html
• http://www.codeguru.com/forum/showthread.php?p=1186307#post1186307
• http://www.codeguru.com/forum/showthread.php?t=350945
• http://www.gotw.ca/gotw/009.htm
• http://en.wikipedia.org/wiki/Process_(computing)#Representation
• http://task3.cc/object-oriented-memory-management/

Hope that this article helped you to clearly understand the differences between stack and heap allocation in C++, write me if there are other issues or you need more explanations!

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É con grande piacere che annuncio il lancio di www.trasportiamoci.it, nato dalla collaborazione di 6 persone (tra le quali il sottoscritto) interessate a risolvere problematiche legate al trasporto oranizzato.
Riporto qui parte della lettera che verrá presto inviata a quotidiani, enti e chi piú ne ha piú ne metta:

Nasce in questi giorni il sito www.trasportiamoci.it, una concreta risposta ai problemi del traffico, dell’inquinamento e delle gravose spese per il trasporto privato.

Il nostro sito offre la possibilità ai cittadini viaggiatori di accordarsi per condividere gli spostamenti in automobile, fornendo una bacheca virtuale di domande e offerte di spostamenti.

Cosa si vuole ottenere con ciò?

• Una riduzione delle vetture circolanti riempiendo i posti altrimenti lasciati vuoti e un conseguente alleggerimento delle emissioni di CO2
• Un risparmio per automobilisti e viaggiatori che, unendosi, dividono le spese di pedaggi e carburante
• Un servizio utile e pulito basato sulla coscienza ambientale e sulla cooperazione tra la cittadinanza

Il sito è intuitivo e facile da usare: offre la possibilità di cercare un passaggio (con una semplice ricerca da città a città) o offrire i posti lasciati vuoti a potenziali compagni di viaggio, il tutto per una nuova forma di viaggio, la condivisione e la cooperazione.

Il tutto gratuitamente, permettendo di contattare offerenti e richiedenti attraverso mail o telefono in tutta Italia, per strade meno trafficate e aria più pulita.

É sufficiente iscriversi

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BD-shell (a.k.a. bdsh) is a tiny Unix shell written in C. It’s a project required for the Operating System Course at my University.
It is written using a clean coding style, following xP coding standard philosophy.
Version 1.0 is the release that satisfies all the course requirements!

Quick Jump:
Features
Download
License

Features

Cool Features

• Lightweight
• Implements real Job Control
• Clear and understandable code, ideal for Academic (and personal) studies
• Makes use of various system calls, signals, signal handlers, user input handling, data structures implementation
• Free Software!

Cool Features NOT present (but may be in future)

• No command history present
• No command/filename auto completion
• No wildcars
• No command piping, just a single command can be launched at a time
• Put everything else here.

Download:

• 2008-09-14 – version 1.0.0.
  • fixed synchronization bug in putJobBackground() that made not notify background processes requesting input (in some situations)

  Known Bugs:

  • Lots of! I consider bdsh-1.0.0 stable because it covers ALL requirements of the course and does them whell on various Unix systems. So it works, but commands like “in non_existent_file cat” won’t work and will crash it!

  What will be next?

  • I don’t know. I may consider a 1.0.1 release to fix future bugs. I may also think to add cool features to make the shell complete. I hope I will have the time for it. You can also do it by yourself and send me the code

License:

BD-shell is released under The Gnu GPL version 3! This is different from the license of the contents of the blog

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see <http ://www.gnu.org/licenses/>>.

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