Posts Tagged ‘Language usage’

An academic programming language paper about R

April 27th, 2012 1 comment

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 some impact on how R is viewed by nonusers of the language (the many R users in finance probably don’t care that R seems to have been labeled as the language for doing statistics). The paper is well written and contains some very interesting information as well as a few mistakes, although it will probably read like gobbledygook to anybody not familiar with academic programming language research. What follows has something of the form of an R users guide to reading this paper, plus some commentary.

The paper has roughly three parts, the first gives an overview of R, the second is a formal definition of a subset and the third an initial report of an analysis of R usage. For me and I imagine you dear reader the really interesting stuff is in the third section.

When giving a language overview to people who know other computer languages it makes sense to leverage that knowledge, this is why the discussion has a world view from the perspective of languages rarely associated with R: Scheme, Haskell and CLOS. I found some of the discussion of R constructs to be much more informative and less confusing than that in nearly all R books/tutorials I have read, but then they are written from a detailed operational programming language perspective. One criticism of this overview is that it does not give any hint as to why R has such a large following (saying that users found it more useful than these languages would send the wrong kind of signal ;-).

What is a formal description of a subset of R (i.e., done purely using mathematics) doing in the second part? Well, until recently very little academic software engineering was empirically based and was populated by people I would classify as failed mathematicians without the common sense needed to be engineers. Things are starting to change but research that measures things, particularly people, is still regarded as not being respectable in some quarters. In this case the formal definition is playing the role of a virility symbol showing that the authors are obviously regular guys who happen to be indulging in a bit of empirical research.

A surprising number of papers measuring the usage of real software contain formal definitions of a subset of the language being measured. Subsets are used because handling the complete language is a big project that usually involves one or more people getting a PhD out of the work. The subset chosen have to look plausible to readers who understand the mathematics but not the programming language, broadly handle all the major constructs but not get involved with all the fiddly details that need years of work and many pages to describe.

The third part contains the real research, which is really about one implementation of R and the characteristics of R source in the CRAN and Bioconductor repositories, and contains lots of interesting information. Note: the authors are incorrect to aim nearly all of the criticisms in this subsection at R, these really apply to the current implementation of R and might not apply to a different implementation.

In a previous post I suggested some possibilities for speeding up the execution of R programs that depended on R usage characteristics. The Morandat paper goes a long way towards providing numbers for some of these usage characteristics (e.g., 37% of function parameters are assigned to and 36% of vectors contain a single value).

What do we learn from this first batch of measurements? R users rarely use many of the more complicated features (e.g., object oriented constructs {and this paper has been accepted at the European Conference on Object-Oriented Programming}), a result usually seen for other languages. I was a bit surprised that R programs were only 40% smaller than equivalent C programs. I think part of the reason is that some of the problems used for benchmarking are not the kind that would usually be solved using R and I did not see any ‘typical’ R programs being coded up in C for comparison, another possibility is that the authors were not thinking in R when writing the code.

One big measurement topic the authors missed is comparing their general findings with usage measurements of other languages. I think they will find lots of similar patterns of usage.

The complaint that R has been defined by the successive releases of its only implementation, rather than a written specification, applies to all widely used languages, at least in their early days. Back in the day a major reason for creating language standards for Pascal and then C was so that other implementations could be created; the handful of major languages whose specification was written before the first implementation (e.g., PL/1, Ada) have/are dieing out. Are multiple implementations needed in an Open Source world? The answer seems to be no for Perl and yes for PHP, Ruby etc. The effort needed to create a written specification for the R language might be better invested improving the efficiency of the current implementation so that a better alternative is not needed.

Needless to say the authors suggested committing the fatal programming language research mistake.

The authors have created an interesting set of tools for static and dynamic analysis of R and I look forward to reading more about their findings in future papers.

Language usage in Google’s ngram viewer

January 5th, 2011 No comments

I thought I would join the fun that people are having with Google’s new ngram viewer. The raw data (only a subset for bigrams and longer ngrams) was also enticing, but at 35+ gigabytes for the compressed 1/2/3-grams of English-all I decided to forgo the longer n-grams.

We all know that in the dim and distant past most programmers wrote in machine code, but it was not until 1980 that “source code” appeared more frequently in books that “machine code”.

Source code/machine code phrase usage in books.

Computer language popularity is a perennial question. Fortran and Cobol address very different markets and I would have expected their usage to follow similar patterns, with “COBOL” having the obvious usage pattern for them both to follow. Instead, both “FORTRAN” and “Fortran” peaked within 10 years, with one staying there for another 20 years before declining and the other still going strong in 2000 (and still ahead of “PHP” and “Python” in 2000; neither shown to keep the clutter down). I am surprised to see “Prolog” usage being so much greater than “Lisp” and I would have expected “Lisp” to have a stronger presence in the 1970s.

I think the C++ crowd will be surprised to see that in 2000 usage was not much greater than what “FORTRAN” had enjoyed for 20 years.

Programming language names appearing in books.

“C”, as in language, usage is obviously different to reliably measure. I have tried the obvious bigrams. Looking at some of the book matches for the phrase “in C” shows that the OCR process has sometimes inserted spaces that probably did not exist in the original, the effect being to split words and create incorrect bigrams. The phrase “in C” would also appear in books on music.

Phrases in which C might appear in books.

I have put the three words “Java”/”SQL”/”BASIC” in a separate plot because their usage swamps that of the other languages. Java obviously has multiple non-computer related uses and subtracting the estimated background usage suggests a language usage similar to that of “SQL”. There is too much noise for the usage of “Basic” to tell us much.

Very popular language words appearing in books.

One way of comparing C/C++ language usage is to look source code usage where they are likely to differ. I/O, in the form of printf/scanf and stdio/iostream, is one obvious choice and while the expected C usage starts to declines in the 1990s the C++ usage just shows a stead growth (perhaps the <</>> usage, which does not appear in the Google viewer, has a dramatic growth during this time period).

Surprisingly #define also follows a similar pattern of decline. Even allowing for the rabid anti-macro rhetoric of the C++ in-crowd I would not have expected such a rapid decline. Perhaps this is some artifact of the book selection process used by Google; but then "namespace" shows a healthy growth around this time period.

The growth of "inline" over such a long period of time is a mystery. Perhaps some of this usage does not relate to a keyword appearing within source code examples but to text along the lines of "put this inline to make it faster".

C/C++ keywords and library names.

What usage should we expect for the last decade? A greater usage of "PHP" and "Python" is an obvious call to make, along with the continuing growth of SQL, I think "UML" will also feature prominently. Will "C++" show a decline in favor or "Java" and what about "C#"? We will have to wait and see.