On Mon, Feb 01, 1999 at 10:40:46AM -0500, Mark Guzdial wrote:
> For example, he analyzes the reliability claims of Linux over commercial
> UNIX.  He says that raw defect rates are not a valid indicator -- much more
> interesting is "defect density": Defects per thousands of lines of code.
> Commercial UNIX is typically around 10 million LOC, while Linux is 1.5
> million.  
Hmm.. IMHO the 1.5 Million loc is the source of the kernel alone! The 10 
Million loc of "commercial Unix"  contain _everything_ that is delivered 
with a standard UNIX. (I think so... ).    

There is an interesting paper at

ftp://grilled.cs.wisc.edu/technical_papers/fuzz-revisited.ps


|Barton P. Miller and his colleagues tested the reliability of Unix utility
|programs in 1990 and 1995. Each time, GNU's utilities came out considerably 
|ahead. They tested seven commercial Unix systems as well as GNU. By 
|subjecting them to a random input stream, they could `crash (with core dump)
|or hang (infinite loop) over 40% (in the worst case) of the basic utility 
|programs ...'' 
|
|These researchers found that the commercial Unix systems had a failure rate
|that ranged from 15% to 43%. In contrast,
|the failure rate for GNU was only 7%. 
|
|Miller also said that, `the three commercial systems that we compared in
|both 1990 and 1995 noticeably improved in reliability, but still had 
|significant rates of failure (the basic utilities from GNU/Linux still 
|were noticeably better than those of the commercial systems).'' 
 

> If you consider defect density, the Linux reliability numbers are
> really bad.  
Linux is used by much more people. More usage, more bugs are found.

An other question: Some parts of the code are used by everyone
(e.g. the kernel scheduler), others (and these are the most of
the 1.5 Million lines of the kernel) are only device-drivers.
A Bug in a device-driver of a device used by only 30 people
is imho not as mission-critical as a bug in the kernel-scheduler.
And Bugs per LOC will be very different between these parts of the
Kernel.

Debian GNU/Linux contains *much* more than 10 million lines of code
but these are more than 1000 different programms. (even squeak will be 
part of debian soon).    

> Lewis believes that as the programming tasks get more complex,
> only commercial programmers will be able to put in the time and effort. 

Hmm... many of the main developers of the Linux kernel are paid
for it. (Alan Cox, Dave  Miller, etc....)

 Marcus

-- 
Marcus Denker                          Weechstr. 1 E103
marcus at ira.uka.de                      76131 Karlsruhe