Comparison between SLOCs and number of files as size metrics for software evolution analysis 1

Transcription

1 Comparison between SLOCs and number of files as size metrics for software evolution analysis 1 Comparison between SLOCs and number of files as size metrics for software evolution analysis Israel Herraiz, Gregorio Robles, Jesús M. González-Barahona, Universidad Rey Juan Carlos {herraiz, grex, jgb}@gsyc.escet.urjc.es Andrea Capiluppi, University of Lincoln acapiluppi@lincoln.ac.uk Juan F. Ramil, The Open University J.F.Ramil@open.ac.uk CSMR 2006, Bari, March 23rd 2006

2 2 (cc) 2005 Israel Herraiz Some rights reserved. This presentation is licensed under a Creative Commons Attribution-ShareAlike License. To view a copy of full license, see

3 Introduction 3 Introduction Libre (free / open source) software systems can grow superlinearly, not conforming to Lehman s laws. Classical studies use number of modules (source code files) as base. Recent studies on libre software, SLOCs.

4 Goals 4 Goals Is it superlinear (or at least, non-sublinear) a common pattern in the libre software world? Does the results change using different metrics? In the long term, why are they growing faster than expected?

5 An example: the case of the Linux kernel 5 An example: the case of the Linux kernel

6 Selected population 6 Selected population Debian GNU/Linux distribution There are some studies on the size and evolution of this distribution. There are a list of packages sorted by size. Map from packages to projects.

7 Sample selection criteria 7 Sample selection criteria 30 months old projects. Control version system publicly available. The largest projects of Debian.

8 Sample selection criteria (cont.) 8 Details of the selected projects Name Modules SLOCs Num. of files First date Last Date Amaya Amaya Evolution evolution FreeBSD src Kaffe kaffe NetBSD src OpenBSD src Prc-Tools prc-tools Python python Wine wine wxwidgets wxwidgets XEmacs XEmacs XFree86 xc Linux

9 Data extraction and analysis 9 Data extraction and analysis By means of the GlueTheos and SlocCount tools, we obtained a snapshot of the source code each six months.

10 Results 10 Results High correlation between SLOCs and number of files. 10 out of 13 projects show non-sublinear growth.

11 Results 11 Correlation coefficients Project Equation n r 2 Amaya S = f Evolution S = f FreeBSD S = f p Kaffe S = f NetBSD S = f OpenBSD S = f Prc tools S = f Python S = f Wine S = f wxwidgets S = f XEmacs S = f XFree86 S = f Linux S = f

12 Results 12 Growth patterns Project Growth rate (SLOCs) Growth rate (# files) Category Amaya Linear Evolution Sublinear FreeBSD* Linear Kaffe Superlinear NetBSD* Superlinear OpenBSD* Superlinear Prc tools Superlinear Python Linear Wine Linear wxwidgets* Superlinear XEmacs Sublinear XFree Sublinear Linux* Superlinear

13 Results 13 Correlation SLOCs vs Files in the case of Linux 4.5e+06 SLOCs vs. files 4e e+06 3e e+06 2e e+06 1e

14 Results 14 Correlation SLOCs vs Files in the case of FreeBSD 1.8e+06 SLOCs vs. files 1.6e e e+06 1e

15 Results 15 Evolution of the size of FreeBSD (SLOCs) 1.8e+06 SLOCs 1.6e e e+06 1e

16 Results 16 Evolution of the size of FreeBSD (Num. of files) 6000 Files

17 Results 17 Evolution of the size of Linux (Num. of files) Total Files Sep-1991 Oct-1995 Sep-1996 Feb-1998 Nov-1999 Aug-2002 Dec-2004

18 Conclusions 18 Conclusions Most of the projects grow linear or superlinearly, not conforming to Lehman s laws. All the studied projects show the same pattern (sublinear, linear or superlinear), independently of the selected metric So, classical studies and more recent ones are comparable. Studies on the case of the Linux kernel that used SLOCs, are also validated using number of source code files.

19 Conclusions 19 Next steps To compare more metrics, in particular, syntactic with semantic metrics. Is it worthy to measure semantic metrics for the analysis of evolution of libre software? Effort and complexity measurements can help to explain superlinearity.

20 Many thanks for your attention 20 Many thanks for your attention Reach me at This presentation, some tools, and more papers on this topic available on Questions? Comments?