Re: Are there any tools that can compare two source files

Sarath Kumar <sarath_kumar@mentorg.com> wrote:
: Generalizing the problem refers to the problem of finding the
: semantic equivalence of two programs. Is this possible?? As the
: theorists go this is very tough and not possible in polynomial time.


: If there is one such tool then send them down, i will love to look
: at it.


: Satyanandam Gullapudi wrote:
:> I am looking for some tool which is more than simple text diff. I am
:> looking for a tool which can generate the structure trees for the
:> source file and compare them. It should not throw errors if the
:> structure is just re-arragned.
: [Seems to me that, like with many NP-complete problems, even though
: it's impractical to get a perfect result, it could be very useful to
: get an approximate result. -John]


Not only is semantic equivalence not possible to test in polynomial
time, but it is equivalent to the halting problem (which can be viewed
as a test for a specific semantics).


There are however tests for equivalent syntactic structure. UC
Berkeley has a very interesting system MOSS (Measure of Software
Similarity) that many universities use to catch plagiarism on
programming homework assignments. ;-)


Tom Payne

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