From: "Eric I." <rubytraining@...>
Date: 2007-10-09T11:30:03+09:00
Subject: Re: Itinerary for a Traveling Salesman (#142)

My solution is split across a few files, so rather than pasting it all
into this posting, I'll offer a link instead:

    http://learnruby.com/examples/ruby-quiz-142.tgz

To run it for a grid of 7x7, say, you'd issue the command:

    ruby find_route.rb 7

Like James Edward Gray's solution, I created a generic GA class that
didn't have any specific coding for routes and grids.  And the Route
class has some methods to create routes from other routes that
correspond to various GA operators.  But there's also an interface
class that allows the GA class to deal with routes.

I implemented both of the suggested operations -- exchange and
reverse.  And I wanted an operation that combined two routes, and so I
used the one that I saw in James Koppel's solution -- partner guided
reorder.  I also allow one to specify the relative frequency with
which the various operators are randomly chosen.

And I do keep track of each route's ancestory, to look for possible
patterns as to which operations tended to be the most useful, for use
in tuning the operator frequencies.

Finally, if RMagick is available, it generates a GIF image of the best
route found.

It was interesting to see how easy a GA was to implement given Ruby's
nice set of Array/Enumerable methods.  It was a very nice Ruby Quiz as
it sucked me into spending more time on it than I would have liked.

Eric

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