GNU Backgammon
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Setting up a position

Think about the friday night chouette where there was this tough choice between two move candidates. Which move was better? Or what about that match score cube decision from the weekend tournament. Wouldn’t it be nice to be able to set up the position in GNU Backgammon and ask for its opinion? This is possible in GNU Backgammon, and it’s one of the features that really can give you the answer to a lot of questions, and in that way give you a better understanding of the game.

Entering Edit mode

To set up a position, you have to be in Edit mode. To enter Edit mode you simply click the Edit button in the tool bar. There is currently no keyboard shortcut or menu item for entering edit mode. The Edit button is a toggle button and you will stay in edit mode untill you release the button by clicking it again.

If your Edit button in the toolbar is disabled it is because there is no game or match in progress. With the current state of GNU Backgammon there must be a game or match in progress to be able to enter edit mode. (This may change in the future.) If there is no game in progress and you want to set up a position, you can simply start a new game or match by clicking New in the toolbar.

When you are in edit mode you will see the the text (Editing) in the match information box below the board.


Setting up a position is basically done by editing the current position. The editing it self is controled by clicking different areas of the board and may not be obvious at the

Clearing the board

In edit mode you can easly clear the board by clicking in one of the bearoff trays. It’s often easier to start setting up a position with a empty board, so this feature is really handy. When you click on one of the bearoff tray, all checkers will be moved to the bearaoff.

[embedded Image]

Figure: Click in the one of the areas marked with a red ellipse to clear the board.

You can also just as easy generate the initial position by clicking the opposite trays when in edit mode. Clicking in one of these trays puts all checkers back to the initial position.

[embedded Image]

Figure: Click in the one of the areas marked with a red ellipse to get to the initial position.

Note that the bearoff trays change side when the board is displayed with clockwise movement.

Quick edit

The default method of editing a position is called Quick edit. It’s based on clicking on the point where you want to place checkers. The number of checkers placed on the point is depending on where you click, for example if you want to place 3 checkers on a point, clicking on the location where the third checker would go places 3 checkers. This method should be familiar to Snowie users that like to play games online.

Clicking with the left button places checkers for player1, clicking with the right button places checkers for player2. Macintosh users with a one-button mouse should use Option-click to emulate a right click. If you want to place more than 5 checkers, click multiple times on the tip of the point. To clear a point, click on the border of the board below or above the point - depending on if the point is in the lower or top half of the board. The bar works just like normal points - the more you click to the middle of the bar, the more checkers will be placed there.

FIXME example and figure.

Drag and drop

There is also a different way of editing the checker positions. You can drag and drop checkers around the board while you’re holding down the CTRL key on your keyboard. Press the CTRL key and hold it down. Then left-click the checker you want to drag to another point and drag it with the mouse, (while holding down the CTRL key and the left mouse button), to the destination point. You can drag checkers to open points or to points where you have checkers of the same colour. You can also ‘hit’ opponent blots with the drag and drop edit method.

This method of editing comes handy when there is just a small adjustment to be done in the position.

Setting the player on turn

The player on turn can be set by clicking the small checker icons below the board. See figure below.

[embedded Image] Figure: Clicking the White checker image will set White on turn, clicking the Black image will set Black in turn.

Note that setting the turn sets the turn before the dice has been rolled. If there is a dice present at the board, setting the turn will remove the dice rolled. In this way you can set up a position to be a cube decision evaluation instead of a move decision evaluation.

The turn can also be set by the menu by selecting Game→Set turn→Player name. Both these methods for setting the player on turn can also be used without being in edit mode.

Setting the dice

You can set the dice for a player by clicking in the middle part of the board where you usually click when you roll the dice while playing. Click in the middle of the right playing area to set the dice for player 0, the bottom player. Click the left dice rolling area to set the dice for player 1, the top player. Once you click one of these areas the dice selection widget will appear and you can select a dice roll by clicking on a dice pair.

[embedded Image] Figure: Click inside the red rectangle to set the dice for Black. Click inside the green rectangle to set the dice for White.

Setting the dice in edit mode sets both dice and the player on turn. Setting the dice for player 0, will make player 0 on turn with that specific dice roll to play.

This method for setting the dice roll only works in edit mode. If you’re not in edit mode you can set the dice by selecting Game→Set dice… for the menu, however this will set the dice for the player on turn.

Setting the cube

Setting the cube is quite simple while you’re in edit mode. Simply click the cube in the board and the cube selection widget appears.

Selecting a cube in the first row, where the number is displayed up-side-down, the top player will be the cube owner. The value of the cube will be the value of the cube you click in the widget. Note that the unturned cube is the leftmost cube labeled 64, just as it usually is on real doubling cube.

Setting the score

Very often in backgammon the match score does matter on how the position is evaluated. GNU Backgammon’s evaluation algorithms does take the score into account. You can therefore adjust the match length and the score of each player while you’re in edit mode.

FIXME Figure here

In the figure you see that the score fields are editable while you’re in edit mode. Insert the desired match score for each player in these fields. Player 0, the top player, has the left score field and player 1, the buttom player, has the right score. You can also set the match score in the match field to the right. There is also a checkbox to tick whenever the position is from a Crawford game.

If you want the computer to do a money game evaluation of the position, you should set the match score to 0 (zero).

Exiting Edit mode

Before you can start analysing the position you have to exit edit mode. This is done by releasing the Edit button in the toolbar by clicking it. Note that editing a position destroys your game record with no warning, so it might be an idea to save your match if you want to keep it.

Analysing the position

After you have successfully set up the position you desire, you can now analyse the position. You can click Hint in the toolbar to get the best move or cube decision in the same way as described in the chapter called Playing a game or match. Hint, rollouts and evaluations done from the hint window will not be saved if you try to save the position. If you want to analyse the position and then be able to save the position and the analysis results you should rather do a move and then click back to the move and then select Analyse→Analyse move from the menu. You can then work in the analysis pane on the right side instead of in the hint window.

You can enter chequers on a point by clicking on the point. Notice the amount of chequers you add on a point, depends on where on that point you click. Left mouse button, black chequers and right mouse button, red chequers. (assuming you didn’t change the colours). You will get used to this editing. and it makes it much faster to set up a position.

FIXME This chapter should be more complete

setting_up_a_position.txt · Last modified: 2013/02/08 08:19
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