Odesys Backgammon - Frequently Asked Questions

1. How does Odesys Backgammon work?
2. How strong is Odesys Backgammon?
3. How do I play online?
4. Are the dice random?
5. What is the difference between the levels of difficulty?
6. Why can't I double?
7. Can I turn the doubling cube off?
8. Rolls distribution

Note: If you do not find an answer to your question here, please write to us at support@odesys.com

1. How does Odesys Backgammon work?

As with most board games, the computer uses an evaluation function, which assigns a number, or score, to a given position on the board. After each roll, the AI compares all possible moves and plays the one with the highest score.

2. How strong is Odesys Backgammon?

The AI engine used in the Expert level scores 0.68 points per game (ppg) against PubEval* in cubeless games. This is a very strong result meaning it wins around 2/3 of the games. The Hard level is roughly equivalent to PubEval. In 5-point matches Expert performs even better, achieving win rate of 75% against Hard, mostly due to its superior cube strategy.

* PubEval is a common benchmark for computer Backgammon programs. It is considered to be as strong as an intermediate human player.

3. How do I play online?

To play online, finish or resign the current match, if any. When the title screen comes up, go to Menu->Options and change the "Game" setting to "Online". Enter your FIBS username and password in the respective fields at the bottom of the list. Please note that both username and password are case sensitive. If you do not have a FIBS account, you can create one at http://wap.odesys.com/fibsreg/

4. Are the dice random?

Yes, the dice are random, or pseudo-random to be precise, because they are in fact produced by an algorithm. That is how computers work.
For those familiar with the Java platform, the dice are implemented by the following line:

random.nextInt(6) + 1;

where random is an instance of java.util.Random, initialized by the system clock every time the game is started. The random number generator of course has no idea whose turn it is or at what stage of the game. For more related information please see the Roll distribution below.

5. What is the difference between the levels of difficulty?

Accurate board evaluation produces strong moves. The Easy level uses a simple, but not very accurate evaluation function, while the Expert level uses a much more complex, but also much more accurate evaluation function

6. Why can't I double?

There are certain cases when doubling is not allowed. You can only double at the beginning of your turn and before you roll. You cannot double if your opponent owns the doubling cube. You cannot double during a 1-point match or during the Crawford game in a multi-point match as described at http://www.bkgm.com/gloss/lookup.cgi?crawford+rule

7. Can I turn the doubling cube off?

Yes, the doubling cube can be turned off. Go to Options and set the "Match points" setting to 1. There is no doubling in 1-point matches.

8. Rolls distribution

We conducted an experiment in the Android emulator to verify that the rolls are well distributed and the random number generator works properly. The rate (in brackets) is the average number of times out of 36 that each roll appears. The distribution we observed after 3600000 is very close to ideal.

Double rolls
[1,1] = 99622 (0.99622)
[2,2] = 99920 (1.0003)
[3,3] = 100557 (1.00036)
[4,4] = 99878 (1.00054)
[5,5] = 99933 (0.99902)
[6,6] = 100431 (0.9999)

Mixed rolls
[1,2] = 199993 (1.99993)
[1,3] = 200570 (2.0057)
[2,3] = 200080 (2.0008)
[1,4] = 199730 (1.9973)
[2,4] = 199972 (1.99972)
[3,4] = 199769 (1.99769)
[1,5] = 199690 (1.9969)
[2,5] = 199369 (1.99369)
[3,5] = 200344 (2.00344)
[4,5] = 200046 (2.00046)
[1,6] = 200577 (2.00577)
[2,6] = 200331 (2.00331)
[3,6] = 199824 (1.99824)
[4,6] = 199861 (1.99861)
[5,6] = 200210 (2.0021)