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Checkers AI Algorithm

- by John

I am making an AI for my checkers game and I'm trying to make it as hard as possible. Here is the current criteria for a move on the hardest difficulty: 1: Look For A Block: This is when a piece is being threatened and another piece can be moved in behind it to protect it. Here is an example: Black Moves |W| |W| |W| |W| | | |W| |W| |W| |W| |W| | | |W| |W| | | | | |W| | | | | | | | | |B| | | | | |B| | | |B| |B| |B| |B| |B| |B| | | |B| |B| |B| |B| White Blocks |W| |W| |W| |W| | | |W| | | |W| |W| |W| |W| |W| |W| | | | | |W| | | | | | | | | |B| | | | | |B| | | |B| |B| |B| |B| |B| |B| | | |B| |B| |B| |B| 2: Move pieces out of danger: if any piece is being threatened, and a piece cannot block for that piece, then it will attempt to move out of the way. If the piece cannot move out of the way without still being in danger, the computer ignores the piece. 3: If the computer player owns any kings, it will attempt to 'hunt down' enemy pieces on the board, if no moves can be made that won't in danger the king or any other pieces, the computer ignores this rule. 4: Any piece that is owned by the computer that is in column 1 or 6 will attempt to go to a side. When a piece is in column 0 or 7, it is in a very strategic position because it cannot get captured while it is in either of these columns 5: It makes an educated random move, the move will not indanger the piece that is moving or any piece that is on the board. 6: If none of the above are possible it makes a random move. This question is not really specific to any language but if all examples could be in Java that would be great, considering this app is written in android. Does anyone see any room for improvement in this algorithm? Anything that would make it better at playing checkers?

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C# XNA: Effecient mesh building algorithm for voxel based terrain ("top" outside layer only, non-destructible)

- by Tim Hatch

To put this bluntly, for non-destructible/non-constructible voxel style terrain, are generated meshes handled much better than instancing? Is there another method to achieve millions of visible quad faces per scene with ease? If generated meshes per chunk is the way to go, what kind of algorithm might I want to use based on only EVER needing the outer layer rendered? I'm using 3D Perlin Noise for terrain generation (for overhangs/caves/etc). The layout is fantastic, but even for around 20k visible faces, it's quite slow using instancing (whether it's one big draw call or multiple smaller chunks). I've simplified it to the point of removing non-visible cubes and only having the top faces of my cube-like terrain be rendered, but with 20k quad instances, it's still pretty sluggish (30fps on my machine). My goal is for the world to be made using quite small cubes. Where multiple games (IE: Minecraft) have the player 1x1 cube in width/length and 2 high, I'm shooting for 6x6 width/length and 9 high. With a lot of advantages as far as gameplay goes, it also means I could quite easily have a single scene with millions of truly visible quads. So, I have been trying to look into changing my method from instancing to mesh generation on a chunk by chunk basis. Do video cards handle this type of processing better than separate quads/cubes through instancing? What kind of existing algorithms should I be looking into? I've seen references to marching cubes a few times now, but I haven't spent much time investigating it since I don't know if it's the better route for my situation or not. I'm also starting to doubt my need of using 3D Perlin noise for terrain generation since I won't want the kind of depth it would seem best at. I just like the idea of overhangs and occasional cave-like structures, but could find no better 'surface only' algorithms to cover that. If anyone has any better suggestions there, feel free to throw them at me too. Thanks, Mythics

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Which algorithm used in Advance Wars type turn based games

- by Jan de Lange

Has anyone tried to develop, or know of an algorithm such as used in a typical turn based game like Advance Wars, where the number of objects and the number of moves per object may be too large to search through up to a reasonable depth like one would do in a game with a smaller search base like chess? There is some path-finding needed to to engage into combat, harvest, or move to an object, so that in the next move such actions are possible. With this you can build a search tree for each item, resulting in a large tree for all items. With a cost function one can determine the best moves. Then the board flips over to the player role (min/max) and the computer searches the best player move, and flips back etc. upto a number of cycles deep. Finally it has found the best move and now it's the players turn. But he may be asleep by now... So how is this done in practice? I have found several good sources on A*, DFS, BFS, evaluation / cost functions etc. But as of yet I do not see how I can put it all together.

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Flood fill algorithm for Game of Go

- by Jackson Borghi

I'm having a hell of a time trying to figure out how to make captured stones disappear. I've read everywhere that I should use the flood fill algorithm, but I haven't had any luck with that so far. Any help would be amazing! Here is my code: package Go; import static java.lang.Math.*; import static stdlib.StdDraw.*; import java.awt.Color; public class Go2 { public static Color opposite(Color player) { if (player == WHITE) { return BLACK; } return WHITE; } public static void drawGame(Color[][] board) { Color[][][] unit = new Color[400][19][19]; for (int h = 0; h < 400; h++) { for (int x = 0; x < 19; x++) { for (int y = 0; y < 19; y++) { unit[h][x][y] = YELLOW; } } } setXscale(0, 19); setYscale(0, 19); clear(YELLOW); setPenColor(BLACK); line(0, 0, 0, 19); line(19, 19, 19, 0); line(0, 19, 19, 19); line(0, 0, 19, 0); for (double i = 0; i < 19; i++) { line(0.0, i, 19, i); line(i, 0.0, i, 19); } for (int x = 0; x < 19; x++) { for (int y = 0; y < 19; y++) { if (board[x][y] != YELLOW) { setPenColor(board[x][y]); filledCircle(x, y, 0.47); setPenColor(GRAY); circle(x, y, 0.47); } } } int h = 0; } public static void main(String[] args) { int px; int py; Color[][] temp = new Color[19][19]; Color[][] board = new Color[19][19]; Color player = WHITE; for (int i = 0; i < 19; i++) { for (int h = 0; h < 19; h++) { board[i][h] = YELLOW; temp[i][h] = YELLOW; } } while (true) { drawGame(board); while (!mousePressed()) { } px = (int) round(mouseX()); py = (int) round(mouseY()); board[px][py] = player; while (mousePressed()) { } floodFill(px, py, player, board, temp); System.out.print("XXXXX = "+ temp[px][py]); if (checkTemp(temp, board, px, py)) { for (int x = 0; x < 19; x++) { for (int y = 0; y < 19; y++) { if (temp[x][y] == GRAY) { board[x][y] = YELLOW; } } } } player = opposite(player); } } private static boolean checkTemp(Color[][] temp, Color[][] board, int x, int y) { if (x < 19 && x > -1 && y < 19 && y > -1) { if (temp[x + 1][y] == YELLOW || temp[x - 1][y] == YELLOW || temp[x][y - 1] == YELLOW || temp[x][y + 1] == YELLOW) { return false; } } if (x == 18) { if (temp[x - 1][y] == YELLOW || temp[x][y - 1] == YELLOW || temp[x][y + 1] == YELLOW) { return false; } } if (y == 18) { if (temp[x + 1][y] == YELLOW || temp[x - 1][y] == YELLOW || temp[x][y - 1] == YELLOW) { return false; } } if (y == 0) { if (temp[x + 1][y] == YELLOW || temp[x - 1][y] == YELLOW || temp[x][y + 1] == YELLOW) { return false; } } if (x == 0) { if (temp[x + 1][y] == YELLOW || temp[x][y - 1] == YELLOW || temp[x][y + 1] == YELLOW) { return false; } } else { if (x < 19) { if (temp[x + 1][y] == GRAY) { checkTemp(temp, board, x + 1, y); } } if (x >= 0) { if (temp[x - 1][y] == GRAY) { checkTemp(temp, board, x - 1, y); } } if (y < 19) { if (temp[x][y + 1] == GRAY) { checkTemp(temp, board, x, y + 1); } } if (y >= 0) { if (temp[x][y - 1] == GRAY) { checkTemp(temp, board, x, y - 1); } } } return true; } private static void floodFill(int x, int y, Color player, Color[][] board, Color[][] temp) { if (board[x][y] != player) { return; } else { temp[x][y] = GRAY; System.out.println("x = " + x + " y = " + y); if (x < 19) { floodFill(x + 1, y, player, board, temp); } if (x >= 0) { floodFill(x - 1, y, player, board, temp); } if (y < 19) { floodFill(x, y + 1, player, board, temp); } if (y >= 0) { floodFill(x, y - 1, player, board, temp); } } } }

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FloodFill Algorithm for Game of Go

- by Jackson Borghi

I'm having a hell of a time trying to figure out how to make captured stones disappear. I've read everywhere that I should use the FloodFill algorithm, but I havent had any luck with that so far. Any help would be amazing! Here is my code: package Go; import static java.lang.Math.; import static stdlib.StdDraw.; import java.awt.Color; public class Go2 { public static Color opposite(Color player) { if (player == WHITE) { return BLACK; } return WHITE; } public static void drawGame(Color[][] board) { Color[][][] unit = new Color[400][19][19]; for (int h = 0; h < 400; h++) { for (int x = 0; x < 19; x++) { for (int y = 0; y < 19; y++) { unit[h][x][y] = YELLOW; } } } setXscale(0, 19); setYscale(0, 19); clear(YELLOW); setPenColor(BLACK); line(0, 0, 0, 19); line(19, 19, 19, 0); line(0, 19, 19, 19); line(0, 0, 19, 0); for (double i = 0; i < 19; i++) { line(0.0, i, 19, i); line(i, 0.0, i, 19); } for (int x = 0; x < 19; x++) { for (int y = 0; y < 19; y++) { if (board[x][y] != YELLOW) { setPenColor(board[x][y]); filledCircle(x, y, 0.47); setPenColor(GRAY); circle(x, y, 0.47); } } } int h = 0; } public static void main(String[] args) { int px; int py; Color[][] temp = new Color[19][19]; Color[][] board = new Color[19][19]; Color player = WHITE; for (int i = 0; i < 19; i++) { for (int h = 0; h < 19; h++) { board[i][h] = YELLOW; temp[i][h] = YELLOW; } } while (true) { drawGame(board); while (!mousePressed()) { } px = (int) round(mouseX()); py = (int) round(mouseY()); board[px][py] = player; while (mousePressed()) { } floodFill(px, py, player, board, temp); System.out.print("XXXXX = "+ temp[px][py]); if (checkTemp(temp, board, px, py)) { for (int x = 0; x < 19; x++) { for (int y = 0; y < 19; y++) { if (temp[x][y] == GRAY) { board[x][y] = YELLOW; } } } } player = opposite(player); } } private static boolean checkTemp(Color[][] temp, Color[][] board, int x, int y) { if (x < 19 && x > -1 && y < 19 && y > -1) { if (temp[x + 1][y] == YELLOW || temp[x - 1][y] == YELLOW || temp[x][y - 1] == YELLOW || temp[x][y + 1] == YELLOW) { return false; } } if (x == 18) { if (temp[x - 1][y] == YELLOW || temp[x][y - 1] == YELLOW || temp[x][y + 1] == YELLOW) { return false; } } if (y == 18) { if (temp[x + 1][y] == YELLOW || temp[x - 1][y] == YELLOW || temp[x][y - 1] == YELLOW) { return false; } } if (y == 0) { if (temp[x + 1][y] == YELLOW || temp[x - 1][y] == YELLOW || temp[x][y + 1] == YELLOW) { return false; } } if (x == 0) { if (temp[x + 1][y] == YELLOW || temp[x][y - 1] == YELLOW || temp[x][y + 1] == YELLOW) { return false; } } else { if (x < 19) { if (temp[x + 1][y] == GRAY) { checkTemp(temp, board, x + 1, y); } } if (x >= 0) { if (temp[x - 1][y] == GRAY) { checkTemp(temp, board, x - 1, y); } } if (y < 19) { if (temp[x][y + 1] == GRAY) { checkTemp(temp, board, x, y + 1); } } if (y >= 0) { if (temp[x][y - 1] == GRAY) { checkTemp(temp, board, x, y - 1); } } } return true; } private static void floodFill(int x, int y, Color player, Color[][] board, Color[][] temp) { if (board[x][y] != player) { return; } else { temp[x][y] = GRAY; System.out.println("x = " + x + " y = " + y); if (x < 19) { floodFill(x + 1, y, player, board, temp); } if (x >= 0) { floodFill(x - 1, y, player, board, temp); } if (y < 19) { floodFill(x, y + 1, player, board, temp); } if (y >= 0) { floodFill(x, y - 1, player, board, temp); } } } }

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Algorithm for spreading labels in a visually appealing and intuitive way

- by mac

Short version Is there a design pattern for distributing vehicle labels in a non-overlapping fashion, placing them as close as possible to the vehicle they refer to? If not, is any of the method I suggest viable? How would you implement this yourself? Extended version In the game I'm writing I have a bird-eye vision of my airborne vehicles. I also have next to each of the vehicles a small label with key-data about the vehicle. This is an actual screenshot: Now, since the vehicles could be flying at different altitudes, their icons could overlap. However I would like to never have their labels overlapping (or a label from vehicle 'A' overlap the icon of vehicle 'B'). Currently, I can detect collisions between sprites and I simply push away the offending label in a direction opposite to the otherwise-overlapped sprite. This works in most situations, but when the airspace get crowded, the label can get pushed very far away from its vehicle, even if there was an alternate "smarter" alternative. For example I get: B - label A -----------label C - label where it would be better (= label closer to the vehicle) to get: B - label label - A C - label EDIT: It also has to be considered that beside the overlapping vehicles case, there might be other configurations in which vehicles'labels could overlap (the ASCII-art examples show for example three very close vehicles in which the label of A would overlap the icon of B and C). I have two ideas on how to improve the present situation, but before spending time implementing them, I thought to turn to the community for advice (after all it seems like a "common enough problem" that a design pattern for it could exist). For what it's worth, here's the two ideas I was thinking to: Slot-isation of label space In this scenario I would divide all the screen into "slots" for the labels. Then, each vehicle would always have its label placed in the closest empty one (empty = no other sprites at that location. Spiralling search From the location of the vehicle on the screen, I would try to place the label at increasing angles and then at increasing radiuses, until a non-overlapping location is found. Something down the line of: try 0°, 10px try 10°, 10px try 20°, 10px ... try 350°, 10px try 0°, 20px try 10°, 20px ...

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AABB Sweeping, algorithm to solve "stacking box" problem

- by Ivo Wetzel

I'm currently working on a simple AABB collision system and after some fiddling the sweeping of a single box vs. another and the calculation of the response velocity needed to push them apart works flawlessly. Now on to the new problem, imagine I'm having a stack of boxes which are falling towards a ground box which isn't moving: Each of these boxes has a vertical velocity for the "gravity" value, let's say this velocity is 5. Now, the result is that they all fall into each other: The reason is obvious, since all the boxes have a downward velocity of 5, this results in no collisions when calculating the relative velocity between the boxes during sweeping. Note: The red ground box here is static (always 0 velocity, can utilize spatial partitioning ), and all dynamic static collisions are resolved first, thus the fact that the boxes stop correctly at this ground box. So, this seems to be simply an issue with the order the boxes are sweept against each other. I imagine that sorting the boxes based on their x and y velocities and then sweeping these groups correctly against each other may resolve this issues. So, I'm looking for algorithms / examples on how to implement such a system. The code can be found here: https://github.com/BonsaiDen/aabb The two files which are of interest are [box/Dynamic.lua][3] and [box/Manager.lua][4]. The project is using Love2D in case you want to run it.

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Derive a algorithm to match best position

- by Farooq Arshed

I have pieces in my game which have stats and cost assigned to them and they can only be placed at a certain location. Lets say I have 50 pieces. e.g. Piece1 = 100 stats, 10 cost, Position A. Piece2 = 120 stats, 5 cost, Position B. Piece3 = 500 stats, 50 cost, Position C. Piece4 = 200 stats, 25 cost, Position A. and so on.. I have a board on which 12 pieces have to be allocated and have to remain inside the board cost. e.g. A board has A,B,C ... J,K,L positions and X Cost assigned to it. I have to figure out a way to place best possible piece in the correct position and should remain within the cost specified by the board. Any help would be appreciated.

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Algorithm for approximating sihlouette image as polygon

- by jack

I want to be able to analyze a texture in real time and approximate a polygon to represent a silhouette. Imagine a person standing in front of a green screen and I want to approximately trace around their outline and get a 2D polygon as the result. Are there algorithms to do this and are they fast enough to work frame-to-frame in a game? (I have found algorithms to triangulate polygons, but I am having trouble knowing what to search for that describes my goal.)

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Best algorithm for recursive adjacent tiles?

- by OhMrBigshot

In my game I have a set of tiles placed in a 2D array marked by their Xs and Zs ([1,1],[1,2], etc). Now, I want a sort of "Paint Bucket" mechanism: Selecting a tile will destroy all adjacent tiles until a condition stops it, let's say, if it hits an object with hasFlag. Here's what I have so far, I'm sure it's pretty bad, it also freezes everything sometimes: void destroyAdjacentTiles(int x, int z) { int GridSize = Cubes.GetLength(0); int minX = x == 0 ? x : x-1; int maxX = x == GridSize - 1 ? x : x+1; int minZ = z == 0 ? z : z-1; int maxZ = z == GridSize - 1 ? z : z+1; Debug.Log(string.Format("Cube: {0}, {1}; X {2}-{3}; Z {4}-{5}", x, z, minX, maxX, minZ, maxZ)); for (int curX = minX; curX <= maxX; curX++) { for (int curZ = minZ; curZ <= maxZ; curZ++) { if (Cubes[curX, curZ] != Cubes[x, z]) { Debug.Log(string.Format(" Checking: {0}, {1}", curX, curZ)); if (Cubes[curX,curZ] && Cubes[curX,curZ].GetComponent<CubeBehavior>().hasFlag) { Destroy(Cubes[curX,curZ]); destroyAdjacentTiles(curX, curZ); } } } } }

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Algorithm to find average position

- by Simran kaur

In the given diagram, I have the extreme left and right points, that is -2 and 4 in this case. So, obviously, I can calculate the width which is 6 in this case. What we know: The number of partitions:3 in this case The partition number at at any point i.e which one is 1st,second or third partition (numbered starting from left) What I want: The position of the purple line drawn which is positio of average of a particular partition So, basically I just want a generalized formula to calculate position of the average at any point.

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2D/Isometric map algorithm

- by Icarus Cocksson

First of all, I don't have much experience on game development but I do have experience on development. I do know how to make a map, but I don't know if my solution is a normal or a hacky solution. I don't want to waste my time coding things, and realise they're utterly crap and lose my motivation. Let's imagine the following map. (2D - top view - A square) X: 0 to 500 Y: 0 to 500 My character currently stands at X:250,Y:400, somewhere near center of 100px above bottom and I can control him with my keyboard buttons. LEFT button does X--, UP button does Y-- etc. This one is kid's play. I'm asking this because I know there are some engines that automate this task. For example, games like Diablo 3 uses an engine. You can pretty much drag drop a rock to map, and it is automatically being placed here - making player unable to pass through/detect the collision. But what the engine exactly does in the background? Generates a map like mine, places a rock at the center, and checks it like: unmovableObjects = array('50,50'); //we placed a rock at 50,50 location if(Map.hasUnmovableObject(CurrentPlayerX, CurrentPlayerY)) { //unable to move } else { //able to move } My question is: Is this how 2D/Isometric maps are being generated or there is a different and more complex logic behind them?

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Need ideas for an algorithm to draw irregular blotchy shapes

- by Yttermayn

I'm looking to draw irregular shapes on an x,y grid, and I'd like to come up with a simple, fast method if possible. My only idea so far is to draw a bunch of circles of random sizes very near each other, but at a random distance apart from a more or less central coordinate, then fill in any blank spaces. I realize this is a clunky, inelegant method, hopefully it will give you a rough idea of the kinds of rounded, random blotchy shapesI'm shooting for. Please suggest methods to accomplish this, I'm not so much interested in code. I can noodle that part out myself. Thanks!

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What's wrong with this turn to face algorithm?

- by Chan

I implement a torpedo object that chases a rotating planet. Specifically, it will turn toward the planet each update. Initially my implement was: void move() { vector3<float> to_target = target - get_position(); to_target.normalize(); position += (to_target * speed); } which works perfectly for torpedo that is a solid sphere. Now my torpedo is actually a model, which has a forward vector, so using this method looks odd because it doesn't actually turn toward but jump toward. So I revised it a bit to get, double get_rotation_angle(vector3<float> u, vector3<float> v) const { u.normalize(); v.normalize(); double cosine_theta = u.dot(v); // domain of arccosine is [-1, 1] if (cosine_theta > 1) { cosine_theta = 1; } if (cosine_theta < -1) { cosine_theta = -1; } return math3d::to_degree(acos(cosine_theta)); } vector3<float> get_rotation_axis(vector3<float> u, vector3<float> v) const { u.normalize(); v.normalize(); // fix linear case if (u == v || u == -v) { v[0] += 0.05; v[1] += 0.0; v[2] += 0.05; v.normalize(); } vector3<float> axis = u.cross(v); return axis.normal(); } void turn_to_face() { vector3<float> to_target = (target - position); vector3<float> axis = get_rotation_axis(get_forward(), to_target); double angle = get_rotation_angle(get_forward(), to_target); double distance = math3d::distance(position, target); gl_matrix_mode(GL_MODELVIEW); gl_push_matrix(); { gl_load_identity(); gl_translate_f(position.get_x(), position.get_y(), position.get_z()); gl_rotate_f(angle, axis.get_x(), axis.get_y(), axis.get_z()); gl_get_float_v(GL_MODELVIEW_MATRIX, OM); } gl_pop_matrix(); move(); } void move() { vector3<float> to_target = target - get_position(); to_target.normalize(); position += (get_forward() * speed); } The logic is simple, I find the rotation axis by cross product, the angle to rotate by dot product, then turn toward the target position each update. Unfortunately, it looks extremely odds since the rotation happens too fast that it always turns back and forth. The forward vector for torpedo is from the ModelView matrix, the third column A: MODELVIEW MATRIX -------------------------------------------------- R U A T -------------------------------------------------- 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 -------------------------------------------------- Any suggestion or idea would be greatly appreciated.

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Algorithm to shift the car

- by Simran kaur

I have a track that can be divided into n number of tracks and a car as GamObject. The track has transforms such that some part of the track's width lies in negative x axis and other in positive. Requirement: One move should cross one track. On every move(left or right), I want the car to reach exact centre of the next track on either sides i.e left or right. My code: Problem: : Because of negative values , somewhere I am missing out something that is making car move not in desirable positions and that's because of negative values only. variable tracks is the number of tracks the whole track is divided in. variable dist is the total width of the complete track. On left movement: if (Input.GetKeyDown (KeyCode.LeftArrow)) { if (this.transform.position.x < r.renderer.bounds.min.x + box.size.x) { this.transform.position = new Vector3 (r.renderer.bounds.min.x + Mathf.FloorToInt(box.size.x), this.transform.position.y, this.transform.position.z); } else { int tracknumber = Mathf.RoundToInt(dist - transform.position.x)/tracks; float averagedistance = (tracknumber*(dist/tracks) + (tracknumber-1)*(dist/tracks))/2; if(transform.position.x > averagedistoftracks) { amountofmovement = amountofmovement + (transform.position.x - averagedistance); } else { amountofmovement = amountofmovement - (averagedistance - transform.position.x); } this.transform.position = new Vector3 (this.transform.position.x - amountofmovement, this.transform.position.y, this.transform.position.z); } }

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Pixel alignment algorithm

- by user42325

I have a set of square blocks, I want to draw them in a window. I am sure the coordinates calculation is correct. But on the screen, some squares' edge overlap with other, some are not. I remember the problem is caused by accuracy of pixels. I remember there's a specific topic related to this kind of problem in 2D image rendering. But I don't remember what exactly it is, and how to solve it. Look at this screenshot. Each block should have a fixed width margin. But in the image, the vertical white line have different width.Though, the horizontal lines looks fine.

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Distributed website server redundancy

- by Keith Lion

Assume a website infrastructure is very complicated and is fully distributed (probably like most large web companies). Am I right in thinking that although there are all these extra web servers to handle multiple client requests, there is still a single "machine" whereby users must enter? I am guessing this machine will be the one physically associated to the IP address? I ask because I need to know whether, in places where distributed systems exist, there is still a single point of failure- usually the control node or, in this example, the machine connected to the public internet? Surely there cannot be two machines connected to the internet, as they would have to have different IP addresses? This "machine" may not be a server per se, but maybe it is a piece of cisco equipment. I just need to know whether, in the real world, these distributed systems still have a particular section where they depend on the integrity of one electronic device?

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Efficient algorithm for creating an ideal distribution of groups into containers?

- by Inshim

I have groups of students that need to be allocated into classrooms of a fixed capacity (say, 100 chairs in each). Each group must only be allocated to a single classroom, even if it is larger than the capacity (ie there can be an overflow, with students standing up) I need an algorithm to make the allocations with minimum overflows and under-capacity classrooms. A naive algorithm to do this allocation is horrendously slow when having ~200 groups, with a distribution of about half of them being under 20% of the classroom size. Any ideas where I can find at least some good starting point for making this algorithm lightning fast? Thanks!

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What are the functionalities of Distributed File systems and Distributed Storage Systems?

- by Berkay

i'm reading cloud vendors solutions for the distributed storage systems such as Amazon Dynamo and Google Big Table. and really confused in two terms : what is Distrubuted file systems for in cloud ? what is Distributed storage systems for? what are differences of these terms and functionalities ? if i understand these terms i will create the general architecture of the cloud vendors, any good tutorial or web page will be appreciated. Thanks

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Distributed Database Services?

- by Cameron

I'm working on a database-driven web service with clients in the US and Australia. We're currently hosted in the US, however our Australian clients are experiencing lag. The lag is primarily due to the fact that the pages launch AJAX queries which require some db work to be done on our database in the US and these take a while to perform a round trip. Ideally, we're looking for some kind of distributed database system which replicates our main US database in Australia (and possibly other locations if we choose to expand later on). Does anyone have any suggestions for services which offer something like this? Something like a CDN (CacheFly etc), which is web-based, simple to set up etc but for databases instead of static files. Ideally it would be completely transparent to the application and abstract away all the distributed database management, syncs etc.

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Distributed file systems

- by Neeraj

I need to implement a distributed storage system for a set of nodes(devices) connected in a mesh network. So what basically my design goals are: The storage system should be capable of handling dynamic entry and exit of nodes. Replication (for fault tolerance). For this i am thinking of using a Distributed file system. Every node could access data in the other nodes in a transparent manner. Are there some simple, easily pluggable opensource implementations? Thanks for your thoughts!

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Distributed filesystem for automated offline data mirroring

- by Petr Pudlák

I'd like to achieve the following setup: Every time I connect my laptop to a local network, my partition gets automatically mirrored to a partition on my local server. I only want to mirror what has changed from the last time. (I understand that it is not a proper backup solution since there is no history of the changes, it'd be more like a non-persistent network RAID.) Is there a distributed file system that allows such a setup? I've done some searching and it seems to me that most distributed file-systems are focused on data availability and distribution, not duplicating them. I'd be thankful for suggestions. Edit: Sorry, I forgot to mention: I'm using Linux.

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Can I use a plaintext diff algorithm for tracking XML changes?

- by rinogo

Hi all! Interesting question for you here. I'm working in Flex/AS3 on (for simplicity) an XML editor. I need to provide undo/redo functionality. Of course, one solution is to store the entire source text with each edit. However, to conserve memory, I'd like to store the diffs instead (these diffs will also be used to transmit updates to the server for auto-saving). My question is - can I use a plaintext diff algorithm for tracking these XML changes? My research on the internet indicates that I cannot do so. However, I'm obviously missing something. Plaintext diff provides functionality that is purportedly: diff(text, text') - diffs patch(text, diffs) - text' XML is simply text, so why can't I just use diff() and patch() to transform the text reliably? For example: Let's say that I'm a poet. When I write poetry, I use lots of funky punctuation... You know, like <, /, and . (You might see where I'm going with this...) If I'm writing my poetry in an application that uses diffs to provide undo/redo functionality, does my poetry become garbled when I undo/redo my edits? It's just text! Why does it make a difference to the algorithm? I obviously don't get something here...Thanks for explaining! :) -Rich

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Fast distributed filesystem for a large amounts of data with metadata in database

- by undefined hero

My project uses several processing machines and one storage machine. Currently storage organized with a MSSQL filetable shared folder. Every file in storage have some metadata in database. Processing machines executes tasks for which they needed files from storage and their metadata. After completing task, processing machine puts resulting data back in storage. From there its taken by another processing machine, which also generates some file and put it back in storage. And etc. Everything was fine, but as number of processing machines increases, I found myself bottlenecked myself with storage machines hard drive performance. So I want processing machines to put files in distributed FS. to lift load from storage machines, from which they can take data from each other, not only storage machine. Can You suggest a particular distributed FS which meets my needs? Or there is another way to solve this problem, without it? Amounts of data in FS in one time are like several terabytes. (storage can handle this, but processors cannot). Data consistence is critical. Read write policy is: once file is written - its constant and may be only removed, but not modified. My current platform is Windows, but I'm ready to switch it, if there is a substantially more convenient solution on another one.

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O(log n) algorithm for computing rank of union of two sorted lists?

- by Eternal Learner

Given two sorted lists, each containing n real numbers, is there a O(log?n) time algorithm to compute the element of rank i (where i coresponds to index in increasing order) in the union of the two lists, assuming the elements of the two lists are distinct? I can think of using a Merge procedure to merge the 2 lists and then find the A[i] element in constant time. But the Merge would take O(n) time. How do we solve it in O(log n) time?

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