[SUMMARY] Game of Life (#193)

Great job everyone on the response this week. (To view the images
inline go to http://rubyquiz.strd6.com/quizzes/193/#summary )

Despite all the commonalities, a two dimensional array and a simple
state machine, these solutions have something for everyone.

Jesus's solution is straightforward and comes with some nice pre-set
configurations: a glider and two oscillators. Like my solution Jesus
uses a 'poor mans' animation of printing the grid directly out to the
console.

![Game of Life - Jesus][1]

snex's solution uses an OpenGL display. Check it out if you are
interested in calling OpenGL from Ruby. My suggestion for improving
Object Oriented class design here is to [Tell, Don't Ask][2]. The
Board is asking the Cell for it's data and then changing it's state.
This functionality would be best pushed into the Cell class so the
Board can tell the Cell "Do your thing!"

![Game of Life - snex][3]

Patrick uses Ruby/Tk and focuses on performance. In place of a two
dimensional Array a single dimension is used. Additionally, instead of
iterating through the neighbor count with a loop they are all placed
explicitly in the code to remove loop overhead. The wrap() method may
not be necessary as Ruby's % operator handles -1 % size as expected at
size-1. With all of these tuning tweaks Patrick was able to go from a
time of 12s to a time of 1.3s about a 10x speed improvement. Patrick's
summary of the changes also say how some of the attempted
modifications actually worsened performance, like using a single bit
set. This illustrates the importance of measurement and trying
multiple approaches until acceptable performance is reached.

James submitted a solution that can reads in patterns from files and
can display either on the screen or by saving a sequence of images to
the disc. To prevent unnecessary computation James's solution keeps
track of a list of active locations and processes those each update.

![Game of Life - James][4]

Andrea submitted a complex and compact solution involving mixing in
Enumerable to the Grid class and a pinch of meta-programming for the
'born', 'die', and 'unchanged' methods. The next generation cells are
created by duplicating the Arrays and creating new Cells in the each
method. This keeps the effects of state changes from interfering with
the previous calculations. Afterwards the cell array is switched to
the new array for the process to begin again.

![Game of Life - Andrea][5]

Daniel (me) submitted a solution using/abusing ruby 1.9 Fibers.
Figuring out exactly when execution leaves the Fiber and what data
comes back in was a bit of a challenge, but after wrestling with it
for a while it started to click. Take a look if you are interested in
learning some more about Fibers. There are also many good tutorials on
the net.

Great turnout this week everyone, let's keep it up!

[1]: http://rubyquiz.strd6.com/quizzes/193/jesus.png
[2]: http://www.pragprog.com/articles/tell-dont-ask
[3]: http://rubyquiz.strd6.com/quizzes/193/snex.png
[4]: http://rubyquiz.strd6.com/quizzes/193/james.png
[5]: http://rubyquiz.strd6.com/quizzes/193/andrea.png