Posts tagged "software development"
Requirements... February 6, 2008
Some [More] Notes on the Abstraction Penalty for IA86 C++ Compilers February 25, 2008
Functional Programming in the ACM CS Curriculum July 9, 2008
Finally! July 24, 2008
Will the real whiteboard pattern stand up? July 29, 2008
OSGi vs. Log4j August 12, 2008
Just so wrong... August 21, 2008
OSGi vs. JRuby on Rails, pt. 1 December 7, 2008
OSGi vs. JRuby on Rails, pt. 2 December 8, 2008
JRuby already has OSGi metadata December 11, 2008
Scala problem #1 January 10, 2009
Adobe Flex Messaging (or BlazeDS) Vs. OSGi March 25, 2009
Steve Vinoski, REST, and distributed systems June 20, 2009
HTTPS Virtual Hosts in Apache July 2, 2009
API design and granfalloons July 9, 2009
GNU Screen July 9, 2009
Brilliant make rule July 20, 2009
Running JRuby in an OSGi container July 24, 2009
Requiescat in Pace: SpringSource dm Server June 6, 2010
Phantom Types in Java June 19, 2010
Quote o' the Week: Christopher Alexander June 24, 2010
Phantom Types in Java, Revisted July 5, 2010
Link o' the Day: Beej! July 24, 2010
Monads and regular expressions August 8, 2010
Quote o' the Week: It’s [Not] Faster Because It’s C October 12, 2010
Link o' the Day: Top 10 Performance Problems October 17, 2010
Subclassing and Java Generics, revisited November 3, 2010
Knights, knaves, and Program Construction November 11, 2010
Finger Trees November 25, 2010
Measured Finger Trees December 11, 2010
Equational programming December 25, 2010
Orthogonality January 6, 2011
The one problem with open source February 1, 2011
If I Only Changed the Software, Why Is the Phone on Fire? March 11, 2011
A few more comments about ...Why Is the Phone on Fire? March 14, 2011
SQL Combinators in Java April 13, 2011
Tony Morris on static types May 9, 2011
De re profanae May 22, 2011
Quote o' the Day: Software Awesomeness June 3, 2011
Some Lisp suggestions June 17, 2011
The Tappan Zee Bridge and software development August 19, 2011
Why I usually prefer the GPL October 24, 2011
Oracle JDBC API changes: things that make me sigh October 28, 2011
Systems programming November 1, 2011
Tip: Converting a CVS repository to git December 30, 2011
Quote o' the week: Don Stewart on the big picture February 3, 2012
Link o' the day: Java and memory February 9, 2012
The Clean Coder March 18, 2012
ASON March 27, 2012
Quote o' the day: OMG! Something from Steve Yegge! May 18, 2012
On the definition of object oriented programming July 14, 2012
Tom DeMarco on project control July 18, 2012
mmap and the Rust Foreign Function Interface June 12, 2013
A faster hashmap in Rust October 12, 2013
Best of mcguire: ruthless simplicity April 19, 2014
If you have a problem and you think, I'll use sed... June 7, 2014
Quote o' the day: On the use of ducks June 26, 2014
One stupid shell scripting trick everyone should know April 11, 2015
Reimplementing ashurbanipal.web in Rust July 14, 2015
Quicksort February 14, 2016
Quote o' the Day: Age and Syntax Directed Editing July 13, 2016
Laurence Tratt, writing An Editor for Composed Programs, came up with this interesting factoid regarding syntax-directed editing, a bizarre remnant of something horrible that the ’80s have to answer for:
Read more…Applied Formal Logic: Brute Force String Search June 19, 2017
Need is there, but tools are not.
– zzz95
Let’s play with Frama-C.
Read more…Applied Formal Logic: The bug in Quick Search June 23, 2017
In my last post, I presented a brief introduction to Frama-C and to the process of verifying properties about a very simple C function, a brute force string search. This time around, I intended to do roughly the same thing, using a slightly more complicated function, a faster string searching algorithm. Unfortunately, in doing so, I found a bug in the algorithm. Admittedly, the bug is rather minor and should not affect the actual behavior of an implementation in practice, but still, it is doing something it shouldn’t ought to be doing.
The string searching algorithm I am looking at this time is Quick Search, so named by Daniel M. Sunday in 1990 because it “is a simple, fast, practical algorithm [and] because it can be both coded and debugged quickly” (“A Very Fast Substring Search Algorithm” [PDF]. It is my personal favorite string search because it is, indeed, simple, fast, and practical. Let me quickly show why.
Read more…Applied Formal Logic: Correctness of Quick Search July 16, 2017
When last I left, I had verified that the implementation of Quick Search was safe: the modified algorithm didn’t access memory it shouldn’t, it didn’t have numeric overflows, and it didn’t modify anything outside of its own implementation. And, using Frama-C, the process hadn’t hardly been torturous or even particularly unpleasant at all. The most important tasks were describing the requirements for calling the two functions. Those requirements are…detailed…but nothing more than what an experienced C programmer would have in mind while writing or calling the functions. A final set of shiny set of annotations ensured that the loops and the variable modifications needed by them behaved themselves.
But I hadn’t done anything about proving that the function actually did what it claimed it was supposed to do. It’s not hard to understand (one of the reasons I like Quick Search), but the ANSI/ISO C Specification Language is unfamiliar and I didn’t know how to express what went on, where. Fortunately, Yannick Moy, a software engineer at AdaCore, came to my assistance with an excellent introduction to doing the same thing with SPARK, and Loïc Correnson, one of the creators of Frama-C, popped in with some excellent suggestions (and very flattering comments).
So now, for your software verification pleasure, here is my essay at proving the correctness of Quick Search. It pretty much follows the same pattern as Yannick’s, but I did come up with a slightly different postcondition for make_bad_shift.
Applied Formal Logic: Verifying Quicksort August 9, 2017
Have you ever tried to solve a problem, gotten stuck, backed off, tried again, changed approaches, failed, and then suddenly, with some approach that you’d already abandoned, solved the problem as sweetly as Penelope Doglington begging for part of your sandwich? I’ve had one of those weeks, and now I honestly don’t know what the problem was. Everything seems to be all better now.
So, here it is: my proof of Quicksort. The proof, which is mine, is mine. And therefore, my proof, which belongs to me, is as follows.
Read more…