Article author here: I do mention the idea of using a chess engine to improve compression. I propose a simple scheme and calculate&#x2F;estimate my scheme would compress moves in a reasonably played game to about 3.9 bits each on average. I am sure it&#x27;s possible to do better, but I suspect you&#x27;d hit diminishing returns before you get close to 3 bits.<p>I really should have included something about adding an opening book as I thought about that quite a lot. My conclusion was that an opening book is not going to be a really dramatic win. A simple scheme might encode say 64K opening sequences using 2 bytes, and save an average of perhaps 10 (half) moves. So a saving of 10*4 - 16 = 24 bits, spread over an average of 80 (half) moves. So about 0.3 bits per move.<p>You might question my estimate of 10 half moves max, but it&#x27;s an educated guess. One thing I&#x27;ve discovered whilst working on my chess database is that the standard tabiya positions are reached by huge numbers of different transposition possibilities. See my blog post at<p><a href="https:&#x2F;&#x2F;triplehappy.wordpress.com&#x2F;2013&#x2F;11&#x2F;13&#x2F;statistics-and-transpositions&#x2F;" rel="nofollow">https:&#x2F;&#x2F;triplehappy.wordpress.com&#x2F;2013&#x2F;11&#x2F;13&#x2F;statistics-and-...</a><p>This means that the standard canonical way of reaching a well known position doesn&#x27;t serve as a good proxy for the start of all the games that include that position.