Writing an Othello program [2] is an appealing and interesting challenge. Beside the dedicated Othello programmers Gunnar Andersson , Michael Buro , Mark Brockington , Paul Hsieh , and Andrea Zinno , to name a few, many chess programmers were and are busy in this domain as well.
Larry Atkin and Peter W. Frey wrote the commercial program Odin in the early 80s as well [4]. In Othello, similar to chess, search implementations are dominated by alpha-beta and variants so far.
In Othello, there is no concept of standing pat or quiescence , and null move pruning does not work. Despite material as decisive feature in Othello, it is also a volatile one and difficult to evaluate. Othello programmers often use piece-square tables , mobility and take various other features , pattern , and heuristics into account, considering strategic elements like the importance of the edge squares.
Paul Rosenbloom's program Iago of the early 80s used edge stability, internal stability [17] , current mobility and potential mobility, weighted by coefficients as suggested by Hans Berliner [18] [19]. In conjunction with probability based pruning aka ProbCut , Michael Buro elaborately addresses the evaluation function [20] [21] [22].
Othello is very bitboard friendly. Generator sets are the own pieces, propagator sets the opponent ones. The fill result, after a final direction shift similar as fill based sliding piece attacks in chess, needs an intersection with empty squares to determine the target squares per direction. Beside the target square coordinate, move encoding may incorporate a direction set one Byte with one distinct bit per direction for all eight directions with anchor squares, and possibly the number of pieces to flip, may be even as set for more reliable move ordering and faster make move.
An MMX implementation of Dumb7Fill in inline assembly by Gunnar Andersson [24] demonstrates determining mobility, while the implementation by co-author Toshihiko Okuhara in their program Zebra [25] looks parallel prefixed [26]. For 8x8 boards, Victor Allis estimated the number of legal positions in Othello is at most 10 28 , and it has a game-tree complexity of approximately 10 58 [29]. We use Graphics. The text is rendered with an outline, which is why we first stroke it and then fill the same text over top of the stroke.
Finally, we connect a global Pointer. We use a global listener here instead of listening on a particular layer because we want the user to be able to click anywhere to restart the game. When you finish your game, you should see something like this:. You can see the code up to this point by looking at the input branch. Playing the sound is quite simple. Just modify GameView. Thus each platform will look for sounds in its preferred format before falling back to.
You can see the code up to this point by looking at the audio branch. But the game seems a little dull. Note that if you plan to build the HTML version of your game, follow the instructions for adding TriplePlay to your html module as well. Now we can use the TriplePlay Animator class to bring our pieces to life. Add it to Reversi. We pass it the paint signal which is a signal emitted by our game on every frame with a Clock that contains timing information.
The animator uses that to process animations on every frame. Now we can use the animator to put our pieces onto the board with a bit more flare. This creates an animation which smoothly scales the piece from 2x to 1x using a bounceOut interpolator which smoothly transitions to its target value, but then bounces back a bit and cycles through a few bounces each decayed from the last.
The graph of the bounceOut interpolator looks like this. We also create an animation which delays a certain amount of time ms in this case and then plays our click sound. Be sure to remove the click. This ensures that even though four setPiece calls come in in rapid succession when the game first starts, the animations for each of them proceed one after another. This is why we setVisible false on our layers immediately after getting them from addPiece. So we make them invisible and the first thing the animation does is make them visible again, and then it starts tweening their scale.
In showPlays make the following change:. In the absence of barriers the Animator runs all the animations it knows about in parallel. When a player makes their move, the pieces that are flipped over as a result of that move are flipped immediately, without regard to animation scheduling. This new shader will tweak the stock shader a bit and apply a specific 3D transform to the quad being rendered which rotates it along a y-axis-aligned vector with the eye or camera at a specified screen coordinate location.
We also create an Animation. This allows a tween animation to change that value as an animation progresses. Then we create our animation sequence. The first thing we do is to use an action to configure the eye on the FlipBatch and configure the ImageLayer displaying our potential move with the FlipBatch.
Finally we clear out the batch, and add a barrier so that each of these animations proceeds one after another. If we tried to run multiple flip animations in parallel, the code that changes FlipBatch. This would make things look weird for all the layers except the last one.
You can see the code up to this point by looking at the bling branch. Now we have a Reversi game that, programmer art aside, we could show to our friends without feeling too embarrassed. The docs are there when you need to look things up. Now go forth and make awesome games! Addendum : the tutorial is complete and I pushed all the code to Github, and then I discovered an annoying bug.
But a layer with visibility set to false is not drawn at all. Home Docs Overview. WHITE ; pieces. BLACK ; pieces. WHITE ; turn. ArrayList ; import java. The program should ask for user configuration once it initializes the board and then it prints the board using the user configuration.
The last step is to ask for a move from the used and if it matches with the available moves printed before then it prints a message of the move is valid, then it prints the board for the last time using the valid move.
My code works fine till it prints the configured board, but after then I am getting some weird output here. In the following program input should be of the form: U- unoccupied,B- occupied by black,W-occupied by white. Ok, here's one simple observation for you.
It looks like you changed checkLegalMovesAvailable so that it now always returns true , correct? So here's a question for you: Does that make sense? If so, then perhaps it shouldn't return anything at all, and its callers should always treat it as if it returned true.
If not, then perhaps you should re-think your logic, and figure out under which circumstances it should return true vs. Does that make sense? So they're both in the range Only 8 of the 9 combinations are valid. But then in checkLegalInDirection , you keep looking further and further in that same direction without ever checking to see if you're still in bounds.
I suspect that's causing some real problems that you've been seeing. That's fine, but at the end, you need to check that the final square is empty, as opposed to your own color. That check is missing. See if you can make some progress on these fixes. That should keep you busy for a bit. If you're still having problems after that, I might be able to look at it again. Ok, here's another change for you which should solve several problems.
When searching for available moves, you're checking the board for squares that already have a player's piece on them, then you're looking in all directions to see if there's a move in that direction. This is backwards from how one would normally do it, and it will also cause problems duplicate moves.
As you can see, that position is a double-move, since legal captures exist in two different directions from the same position. Your current approach would list this move twice.
It would find it first starting from one of the X positions, and then it would find it again when it encounters the second X position. We can fix this bug, and solve your move-ordering problem, with a easy fix which might actually simplify your program.
Currently, you examine each square on the board to see if it's the player's color.
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