Learning from Sudoku Solvers (2007)

2 days ago 1

Ron Jeffries attempts to create a sudoku solver - here, here, here, here and here. (You really ought to read these articles. They are ummm...{cough} ...err.... enlightening.)
Peter Norvig creates a Sudoku Solver.
Compare. Learn.
Update: Discussion on reddit
somewhat peripherally related but similiar (this about the bowling game) discussion
The devgrind post
Update 2:
(Oct 2009) Peter Norvig spoke about this post in Peter Seibel's book, "Coders at Work". My reaction..
Update 3:
Peter Siebel author of "Coders at Work" weighs in. Some gems there.
"One thing I noticed, reading through Jeffries’s blog posts, was that he got fixated on the problem of how to represent a Sudoku board. He immediately started writing tests of the low-level details of a few functions for manipulating a data structure representing the 9×9 Sudoku board and a few functions for getting at the rows, columns, and boxes of the board. (“Boxes” are what Sudoku players call the 3×3 squares subsquares of the 9×9 board.)
Then he basically wandered around for the rest of his five blog postings fiddling with the representation, making it more “object oriented” and then fixing up the tests to work with the new representation and so on until eventually, it seems, he just got bored and gave up, having made only one minor stab at the problem of actually solving puzzles.
I suspect, having done a small amount of TDD myself, that this is actually a pattern that arises when a programmer tries to apply TDD to a problem they just don’t know how to solve. If I was a high-priced consultant/trainer like Jeffries, I’d probably give this pattern a pithy name like “Going in Circles Means You Don’t Know What You’re Doing”.
.....
(Norvig has) 7 definitions in 12 lines of code and he’s done with data representation. I’m not sure how much code Jeffries ended up with. In his fourth installment he had about 81 lines devoted to providing slightly less functionality than Norvig provided in the code we just looked at. In the fifth (and mercifully final) installment, he started adding classes and subclasses and moving things around but never presented all the code again. Safe to say it ended up quite a lot more than 12 lines; if he’s lucky it stayed under 120.