Articles by Derek-Jones

Changes in optimization performance of gcc over time

September 16, 2012 | Derek-Jones

The SPEC benchmarks came out a year after the first release of gcc (in fact gcc was and still is one of the programs included in the benchmark). Compiling the SPEC programs using the gcc option -O2 (sometimes -O3) has always been the way to measure gcc performance, but after 25 ... [Read more...]

Descriptive statistics of some Agile feature characteristics

September 2, 2012 | Derek-Jones

The purpose of software engineering research is to figure out how software development works so that the software industry can improve its quality/timeliness (i.e., lower costs and improved customer satisfaction). Research is hampered by the fact that companies are not usually willing to make public good quality data ... [Read more...]

My no loops in R hair shirt

July 27, 2012 | Derek-Jones

Being professional involved with analyzing source code I get to work with a much larger number of programming languages than most people. There is a huge difference between knowing the intricate details of the semantics of a language and being able to fluently program in a language like a native ... [Read more...]

Success does not require understanding

July 23, 2012 | Derek-Jones

I took part in the second Data Science London Hackathon last weekend (also my second hackathon) and it was a very different experience compared to the first hackathon. Once again Carlos and his team really looked after us. The data was released 24 hours before the competition started and even though ... [Read more...]

EU rules that computer languages cannot be copyrighted

May 2, 2012 | Derek-Jones

The European Court of Justice has published its decision in SAS v WPL; the title of the press release says it all “The functionality of a computer program and the programming language cannot be protected by copyright”. To summarise the background, World Programming Ltd developed a system that was capable ... [Read more...]

Incompetence borne of excessive cleverness

April 29, 2012 | Derek-Jones

I have just got back from the 24 hour Data Science Global Hackathon; I was an on-site participant at Hub Westminster in London (thanks to Carlos and his team for doing such a great job looking after us all {around 50 turned up from the 100 who registered; the percentage was similar in ... [Read more...]

An academic programming language paper about R

April 27, 2012 | Derek-Jones

The R language has passed another milestone, a paper aimed at the academic programming language community (or at least one section of this community) has been written about it, Evaluating the Design of the R Language by Morandat, Hill, Osvald and Vitek. Hardly earth shattering news, but it may have ... [Read more...]

Go faster R for Google’s summer of code 2012

March 28, 2012 | Derek-Jones

The R Foundation has been accepted for Google’s summer of code and I thought I would suggest a few ideas for projects. My interests are in optimization and source code analysis, so obviously the suggestions involve these topics. There are an infinite number of possible optimizations that can be ... [Read more...]

Initial impressions of RangeLab

December 30, 2011 | Derek-Jones

I was rummaging around in the source of R looking for trouble, as one does, when I came across what I believed to be a less than optimally accurate floating-point algorithm (function R_pos_di in src/main/arithemtic.c). Analyzing the accuracy of floating-point code is notoriously difficult and ... [Read more...]

Learning R as a language

November 29, 2011 | Derek-Jones

Books written to teach a general purpose programming language are usually organized according to the features of the language and examples often show how a particular language feature is interpreted by a compiler. Books about domain specific languages are usually organized in a way that makes sense in the corresponding ... [Read more...]

Halstead’s metrics and flat-Earthers are still with us

August 18, 2011 | Derek-Jones

I recently discovered a fascinating series of technical reports from the 1970s in the Purdue University e-Pubs archive that shine a surprising light on what are now known as the Halstead metrics. The first surprises came from Halstead’s A Software Physics Analysis of Akiyama’s Debugging Data; surprising in ... [Read more...]

Searching for inaccurate literals in R

May 29, 2011 | Derek-Jones

In creating the numbers tool I wanted to be able to do two things, 1) obtain information about what source did by matching the numeric literals it contained against a database of ‘interesting’ values (now with over 14,000 entries) and 2) flag possible incorrect numeric literals (e.g., 3.1459265 when 3.14159265 had been intended in ... [Read more...]

Unused function parameters

May 8, 2011 | Derek-Jones

I have started redoing the source code measurements that appear in my C book, this time using a lot more source, upgraded versions of existing tools, plus some new tools such as Coccinelle and R. The intent is to make the code and data available in a form that is ... [Read more...]

Quality comparison of floating-point maths libraries

April 10, 2011 | Derek-Jones

What is the best way to compare the quality of floating-point math libraries (e.g., sin, cos and log)? The traditional approach for evaluating the quality of an algorithm implementing a mathematical function is based on mathematics; methods have been developed to calculate the maximum error between the calculated and ... [Read more...]

Empirical software engineering is five years old

March 31, 2011 | Derek-Jones

Science and engineering are built on theoretical models that are tested against measurements of ‘reality’. Until around 10 years ago there was very little software engineering ‘reality’ publicly available; companies rarely made source available and were generally unforthcoming about any bugs that had been discovered. What happened around 10 years ago was ... [Read more...]

Thinking in R: vectors

September 4, 2010 | Derek-Jones

While I have been using the R language/environment for over five years or so, whenever I needed to do some statistical calculations, until recently I was only a casual user. A few months ago I started to use R in more depth and made a conscious decision to try ...
[Read more...]
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