Backgammon, Part 11


The yahoo game has 4 clear behavior patterns in the start game:

1) Only move to new points if White can make a block without leaving a blot.
2) Hit opponent blots when possible.
3) Move to existing blocks if possible.
4) Move the stones out from White’s back field, leave blots if unavoidable.

In the mid-game:

1) If Red moves the stones on point-24 forward, put White’s stones behind them.
2) If Red has blots in his home field, it’s ok for White to leave blots, too.
3) Bring stones into White’s home field.
4) Cover blots if possible.
5) Leave at least 1 stone behind Red’s stones until switching to a running game.
6) If White has blots in his home field, don’t hit Red’s blots.

The key with pattern 5 is that White wants to jockey for the running game, while keeping open the chance of hitting Red’s blots if it looks like a good idea. So, as long as the computer has other stones available to move for rolls that come up 5’s and 6’s, it will leave the “back game anchor” in place. However, if there aren’t any other choices, White will use the 5 or 6 to bring the anchor forward and go to a running game.

In the end game:

1) Stones that are in the home field get moved closer to the tray first.
2) High rolls are used to bring the closest stones outside of the home field in home.
3) If bearing off, try to bear off at least one stone.
4) Bring stones in from point-6 if nothing else is available.

For pattern 3, if the computer has a stone on point-5 and nothing on 3, and rolls a 2-3, it will take the 5-point stone to the tray, rather than moving in two stones from point 6 (which is actually what you should do in a normal game).

These patterns do lead to some stupid choices occasionally. In order to hit a blot, it will sometimes leave an unprotected blot in it’s own home field where you can land on it. Or, if you put White on the bar while you’re bearing off, for a running game, White will often use one die to get back on the board, but instead of using the second die for running the same stone back home, it will move a stone in its home field closer to the tray. It’s this last goof that causes the computer to lose with a “gammon” (no stones borne off) or a “backgammon” (no stones borne off and one stone still in Red’s home field).

The computer does get “lucky” in about 3 games out of 10, and I have lost with a gammon because I was playing a back game and waiting for a blot to open up (which never happens). But, more often than not it misses clear chances for escaping from its back field when I’m preparing to build up a rolling wall. (I.e. – White has a blot on point-1, and I have blocks on points 2, 4, 5, 6, 8, 9. It rolls a 2-6, but instead of escaping, it jockeys its stones in the home field to be closer to the tray. In the next turn I block point-3 and then go on to win the game). About half of the games I win are ones where White stupidly uses a blot to put me on the bar, and then I hit the same blot to put it on the bar instead, while I have a full 6-point-wide wall on my side. With a better AI, my win rate might be closer to 4 of 10.

Then again, as I’ve complained before, the dice in the yahoo game aren’t random. Double 6’s come up way, way too often, and in the start game phase I keep seeing the same roll combinations game after game. There’s a lot of things that I think could have been done better. But, what do you expect to get for free?

To be continued.

Advertisements
Leave a comment

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: