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  • How to calculate the state of a graph?

    - by zcb
    Given a graph G=(V,E), each node i is associated with 'Ci' number of objects. At each step, for every node i, the Ci objects will be taken away by the neighbors of i equally. After K steps, output the number of objects of the top five nodes which has the most objects. Some Constrains: |V|<10^5, |E|<2*10^5, K<10^7, Ci<1000 My current idea is: represent the transformation in each step with a matrix. This problem is converted to the calculation of the power of matrix. But this solution is much too slow considering |V| can be 10^5. Is there any faster way to do it?

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  • I want to make a wrapped acces type for certain internals of one of classes and I have some performa

    - by Alex
    I am writing an abstract matrix class (and some concrete subclasses) for use on very differing hardwares/architectures, etc. and I want to write a row and column type that provides a transparent reference to the rows and columns of the matrix. However, I want to tune for performance, so I'd like this class to be essentially a compiler construct. In other words, I'm willing to sacrifice some dev time to making the overhead of these classes as small as possible. I assume all (small) methods would want to be virtual? Keep the structure small? Any other suggestions?

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  • XNA 3D model collision is inaccurate

    - by Daniel Lopez
    I am creating a classic game in 3d that deals with asteriods and you have to shoot them and avoid being hit from them. I can generate the asteroids just fine and the ship can shoot bullets just fine. But the asteroids always hit the ship even it doesn't look they are even close. I know 2D collision very well but not 3D so can someone please shed some light to my problem. Thanks in advance. Code For ModelRenderer: using System; using System.Collections.Generic; using System.Linq; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Audio; using Microsoft.Xna.Framework.Content; using Microsoft.Xna.Framework.GamerServices; using Microsoft.Xna.Framework.Graphics; using Microsoft.Xna.Framework.Input; using Microsoft.Xna.Framework.Media; namespace _3D_Asteroids { class ModelRenderer { private float aspectratio; private Model model; private Vector3 camerapos; private Vector3 modelpos; private Matrix rotationy; float radiansy = 0; private bool isalive; public ModelRenderer(Model m, float AspectRatio, Vector3 initial_pos, Vector3 initialcamerapos) { isalive = true; model = m; if (model.Meshes.Count == 0) { throw new Exception("Invalid model because it contains zero meshes!"); } modelpos = initial_pos; camerapos = initialcamerapos; aspectratio = AspectRatio; return; } public float RadiusOfSphere { get { return model.Meshes[0].BoundingSphere.Radius; } } public BoundingBox BoxBounds { get { return BoundingBox.CreateFromSphere(model.Meshes[0].BoundingSphere); } } public BoundingSphere SphereBounds { get { return model.Meshes[0].BoundingSphere; } } public Vector3 CameraPosition { set { camerapos = value; } get { return camerapos; } } public bool IsAlive { get { return isalive; } } public Vector3 ModelPosition { set { modelpos = value; } get { return modelpos; } } public void RotateY(float radians) { radiansy += radians; rotationy = Matrix.CreateRotationY(radiansy); } public Matrix RotationY { set { rotationy = value; } get { return rotationy; } } public float AspectRatio { set { aspectratio = value; } get { return aspectratio; } } public void Kill() { isalive = false; } public void Draw(float scale) { Matrix world; if (rotationy == new Matrix(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)) { world = Matrix.CreateScale(scale) * Matrix.CreateTranslation(modelpos); } else { world = rotationy * Matrix.CreateScale(scale) * Matrix.CreateTranslation(modelpos); } Matrix view = Matrix.CreateLookAt(camerapos, Vector3.Zero, Vector3.Up); Matrix projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.ToRadians(45.0f), this.AspectRatio, 1f, 100000f); foreach (ModelMesh mesh in model.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.World = world; effect.View = view; effect.Projection = projection; } mesh.Draw(); } } public void Draw() { Matrix world; if (rotationy == new Matrix(0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0)) { world = Matrix.CreateTranslation(modelpos); } else { world = rotationy * Matrix.CreateTranslation(modelpos); } Matrix view = Matrix.CreateLookAt(camerapos, Vector3.Zero, Vector3.Up); Matrix projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.ToRadians(45.0f), this.AspectRatio, 1f, 100000f); foreach (ModelMesh mesh in model.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.World = world; effect.View = view; effect.Projection = projection; } mesh.Draw(); } } } Code For Game1: using System; using System.Collections.Generic; using System.Linq; using Microsoft.Xna.Framework; using Microsoft.Xna.Framework.Audio; using Microsoft.Xna.Framework.Content; using Microsoft.Xna.Framework.GamerServices; using Microsoft.Xna.Framework.Graphics; using Microsoft.Xna.Framework.Input; using Microsoft.Xna.Framework.Media; namespace _3D_Asteroids { /// <summary> /// This is the main type for your game /// </summary> public class Game1 : Microsoft.Xna.Framework.Game { GraphicsDeviceManager graphics; int score = 0, lives = 5; SpriteBatch spriteBatch; GameState gstate = GameState.OnMenuScreen; Menu menu = new Menu(Color.Yellow, Color.White); SpriteFont font; Texture2D background; ModelRenderer ship; Model b, a; List<ModelRenderer> bullets = new List<ModelRenderer>(); List<ModelRenderer> asteriods = new List<ModelRenderer>(); float time = 0.0f; int framecount = 0; SoundEffect effect; public Game1() { graphics = new GraphicsDeviceManager(this); graphics.PreferredBackBufferWidth = 1280; graphics.PreferredBackBufferHeight = 796; graphics.ApplyChanges(); Content.RootDirectory = "Content"; } /// <summary> /// Allows the game to perform any initialization it needs to before starting to run. /// This is where it can query for any required services and load any non-graphic /// related content. Calling base.Initialize will enumerate through any components /// and initialize them as well. /// </summary> protected override void Initialize() { // TODO: Add your initialization logic here base.Initialize(); } /// <summary> /// LoadContent will be called once per game and is the place to load /// all of your content. /// </summary> protected override void LoadContent() { // Create a new SpriteBatch, which can be used to draw textures. spriteBatch = new SpriteBatch(GraphicsDevice); font = Content.Load<SpriteFont>("Fonts\\Lucida Console"); background = Content.Load<Texture2D>("Textures\\B1_stars"); Model p1 = Content.Load<Model>("Models\\p1_wedge"); b = Content.Load<Model>("Models\\pea_proj"); a = Content.Load<Model>("Models\\asteroid1"); effect = Content.Load<SoundEffect>("Audio\\tx0_fire1"); ship = new ModelRenderer(p1, GraphicsDevice.Viewport.AspectRatio, new Vector3(0, 0, 0), new Vector3(0, 0, 9000)); } /// <summary> /// UnloadContent will be called once per game and is the place to unload /// all content. /// </summary> protected override void UnloadContent() { } /// <summary> /// Allows the game to run logic such as updating the world, /// checking for collisions, gathering input, and playing audio. /// </summary> /// <param name="gameTime">Provides a snapshot of timing values.</param> protected override void Update(GameTime gameTime) { KeyboardState state = Keyboard.GetState(PlayerIndex.One); switch (gstate) { case GameState.OnMenuScreen: { if (state.IsKeyDown(Keys.Enter)) { switch (menu.SelectedChoice) { case MenuChoices.Play: { gstate = GameState.GameStarted; break; } case MenuChoices.Exit: { this.Exit(); break; } } } if (state.IsKeyDown(Keys.Down)) { menu.MoveSelectedMenuChoiceDown(gameTime); } else if(state.IsKeyDown(Keys.Up)) { menu.MoveSelectedMenuChoiceUp(gameTime); } else { menu.KeysReleased(); } break; } case GameState.GameStarted: { foreach (ModelRenderer bullet in bullets) { if (bullet.ModelPosition.X < (ship.ModelPosition.X + 4000) && bullet.ModelPosition.Z < (ship.ModelPosition.X + 4000) && bullet.ModelPosition.X > (ship.ModelPosition.Z - 4000) && bullet.ModelPosition.Z > (ship.ModelPosition.Z - 4000)) { bullet.ModelPosition += (bullet.RotationY.Forward * 120); } else if (collidedwithasteriod(bullet)) { bullet.Kill(); } else { bullet.Kill(); } } foreach (ModelRenderer asteroid in asteriods) { if (ship.SphereBounds.Intersects(asteroid.BoxBounds)) { lives -= 1; asteroid.Kill(); // This always hits no matter where the ship goes. } else { asteroid.ModelPosition -= (asteroid.RotationY.Forward * 50); } } for (int index = 0; index < asteriods.Count; index++) { if (asteriods[index].IsAlive == false) { asteriods.RemoveAt(index); } } for (int index = 0; index < bullets.Count; index++) { if (bullets[index].IsAlive == false) { bullets.RemoveAt(index); } } if (state.IsKeyDown(Keys.Left)) { ship.RotateY(0.1f); if (state.IsKeyDown(Keys.Space)) { if (time < 17) { firebullet(); //effect.Play(); } } else { time = 0; } } else if (state.IsKeyDown(Keys.Right)) { ship.RotateY(-0.1f); if (state.IsKeyDown(Keys.Space)) { if (time < 17) { firebullet(); //effect.Play(); } } else { time = 0; } } else if (state.IsKeyDown(Keys.Up)) { ship.ModelPosition += (ship.RotationY.Forward * 50); if (state.IsKeyDown(Keys.Space)) { if (time < 17) { firebullet(); //effect.Play(); } } else { time = 0; } } else if (state.IsKeyDown(Keys.Space)) { time += gameTime.ElapsedGameTime.Milliseconds; if (time < 17) { firebullet(); //effect.Play(); } } else { time = 0.0f; } if ((framecount % 60) == 0) { createasteroid(); framecount = 0; } framecount++; break; } } base.Update(gameTime); } void firebullet() { if (bullets.Count < 3) { ModelRenderer bullet = new ModelRenderer(b, GraphicsDevice.Viewport.AspectRatio, ship.ModelPosition, new Vector3(0, 0, 9000)); bullet.RotationY = ship.RotationY; bullets.Add(bullet); } } void createasteroid() { if (asteriods.Count < 2) { Random random = new Random(); float z = random.Next(-13000, -11000); float x = random.Next(-9000, -8000); Random random2 = new Random(); int degrees = random.Next(0, 45); float radians = MathHelper.ToRadians(degrees); ModelRenderer asteroid = new ModelRenderer(a, GraphicsDevice.Viewport.AspectRatio, new Vector3(x, 0, z), new Vector3(0,0, 9000)); asteroid.RotateY(radians); asteriods.Add(asteroid); } } /// <summary> /// This is called when the game should draw itself. /// </summary> /// <param name="gameTime">Provides a snapshot of timing values.</param> protected override void Draw(GameTime gameTime) { GraphicsDevice.Clear(Color.CornflowerBlue); switch (gstate) { case GameState.OnMenuScreen: { spriteBatch.Begin(); spriteBatch.Draw(background, Vector2.Zero, Color.White); menu.DrawMenu(ref spriteBatch, font, new Vector2(GraphicsDevice.Viewport.Width / 2, GraphicsDevice.Viewport.Height / 2) - new Vector2(50f), 100f); spriteBatch.End(); break; } case GameState.GameStarted: { spriteBatch.Begin(); spriteBatch.Draw(background, Vector2.Zero, Color.White); spriteBatch.DrawString(font, "Score: " + score.ToString() + "\nLives: " + lives.ToString(), Vector2.Zero, Color.White); spriteBatch.End(); ship.Draw(); foreach (ModelRenderer bullet in bullets) { bullet.Draw(); } foreach (ModelRenderer asteroid in asteriods) { asteroid.Draw(0.1f); } break; } } base.Draw(gameTime); } bool collidedwithasteriod(ModelRenderer bullet) { foreach (ModelRenderer asteroid in asteriods) { if (bullet.SphereBounds.Intersects(asteroid.BoxBounds)) { score += 10; asteroid.Kill(); return true; } } return false; } } } }

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  • Problem with memset after an instance of a user defined class is created and a file is opened

    - by Liberalkid
    I'm having a weird problem with memset, that was something to do with a class I'm creating before it and a file I'm opening in the constructor. The class I'm working with normally reads in an array and transforms it into another array, but that's not important. The class I'm working with is: #include <vector> #include <algorithm> using namespace std; class PreProcess { public: PreProcess(char* fileName,char* outFileName); void SortedOrder(); private: vector< vector<double > > matrix; void SortRow(vector<double> &row); char* newFileName; vector< pair<double,int> > rowSorted; }; The other functions aren't important, because I've stopped calling them and the problem persists. Essentially I've narrowed it down to my constructor: PreProcess::PreProcess(char* fileName,char* outFileName):newFileName(outFileName){ ifstream input(fileName); input.close(); //this statement is inconsequential } I also read in the file in my constructor, but I've found that the problem persists if I don't read in the matrix and just open the file. Essentially I've narrowed it down to if I comment out those two lines the memset works properly, otherwise it doesn't. Now to the context of the problem I'm having with it: I wrote my own simple wrapper class for matrices. It doesn't have much functionality, I just need 2D arrays in the next part of my project and having a class handle everything makes more sense to me. The header file: #include <iostream> using namespace std; class Matrix{ public: Matrix(int r,int c); int &operator()(int i,int j) {//I know I should check my bounds here return matrix[i*columns+j]; } ~Matrix(); const void Display(); private: int *matrix; const int rows; const int columns; }; Driver: #include "Matrix.h" #include <string> using namespace std; Matrix::Matrix(int r,int c):rows(r),columns(c) { matrix=new int[rows*columns]; memset(matrix,0,sizeof(matrix)); } const void Matrix::Display(){ for(int i=0;i<rows;i++){ for(int j=0;j<columns;j++) cout << (*this)(i,j) << " "; cout << endl; } } Matrix::~Matrix() { delete matrix; } My main program runs: PreProcess test1(argv[1],argv[2]); //test1.SortedOrder(); Matrix test(10,10); test.Display(); And when I run this with the input line uncommented I get: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 -1371727776 32698 -1 0 0 0 0 0 6332656 0 -1 -1 0 0 6332672 0 0 0 0 0 0 0 0 0 0 0 0 0 -1371732704 32698 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 I really don't have a clue what's going on in memory to cause this, on a side note if I replace memset with: for(int i=0;i<rows*columns;i++) *(matrix+i) &= 0x0; Then it works perfectly, it also works if I don't open the file. If it helps I'm running GCC 64-bit version 4.2.4 on Ubuntu.I assume there's some functionality of memset that I'm not properly understanding.

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  • SQL Query for generating matrix like output querying related table in SQL Server

    - by Nagesh
    I have three tables: Product ProductID ProductName 1 Cycle 2 Scooter 3 Car Customer CustomerID CustomerName 101 Ronald 102 Michelle 103 Armstrong 104 Schmidt 105 Peterson Transactions TID ProductID CustomerID TranDate Amount 10001 1 101 01-Jan-11 25000.00 10002 2 101 02-Jan-11 98547.52 10003 1 102 03-Feb-11 15000.00 10004 3 102 07-Jan-11 36571.85 10005 2 105 09-Feb-11 82658.23 10006 2 104 10-Feb-11 54000.25 10007 3 103 20-Feb-11 80115.50 10008 3 104 22-Feb-11 45000.65 I have written a query to group the transactions like this: SELECT P.ProductName AS Product, C.CustName AS Customer, SUM(T.Amount) AS Amount FROM Transactions AS T INNER JOIN Product AS P ON T.ProductID = P.ProductID INNER JOIN Customer AS C ON T.CustomerID = C.CustomerID WHERE T.TranDate BETWEEN '2011-01-01' AND '2011-03-31' GROUP BY P.ProductName, C.CustName ORDER BY P.ProductName which gives the result like this: Product Customer Amount Car Armstrong 80115.50 Car Michelle 36571.85 Car Schmidt 45000.65 Cycle Michelle 15000.00 Cycle Ronald 25000.00 Scooter Peterson 82658.23 Scooter Ronald 98547.52 Scooter Schmidt 54000.25 I need result of query in MATRIX form like this: Customer |------------ Amounts --------------- Name |Car Cycle Scooter Totals Armstrong 80115.50 0.00 0.00 80115.50 Michelle 36571.85 15000.00 0.00 51571.85 Ronald 0.00 25000.00 98547.52 123547.52 Peterson 0.00 0.00 82658.23 82658.23 Schmidt 45000.65 0.00 54000.25 99000.90 Please help me to acheive the above result in SQL Server 2005. Using mulitple views or even temporory tables is fine for me.

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  • FFT and IFFT on 3D matrix (Matlab)

    - by SteffenDM
    I have a movie with 70 grayscale frames in MATLAB. I have put them in a 3-D matrix, so the dimensions are X, Y and time. I want to determine the frequencies in the time dimension, so I have to calculate the FFT for every point in the 3rd dimension. This is not a problem but I have to return the images to the original form with ifft. In a normal situation this would be true: X = ifft(fft(X)), but this is not the case it seems in MATLAB when you work with multidimensional data. This is the code I use: for i = 1:length y(:, :, i) = [img1{i, level}]; %# take each picture from an cell array and put it end %# and put it in 3D array y2 = ifft(fft(y, NFFT,3), NFFT, 3); %# NFFT = 128, the 3 is the dimension in which i want %# to calculate the FFT and IFFT y is 480x640x70, so there are 70 images of 640x480 pixels. If I use only fft, y2 is 480x640x128 (this is normal because we want 128 points with NFFT). If I use fft and ifft, y2 is 480x640x128 pixels. This is not normal, the 128 should be 70 again. I tried to do it in just one dimension by using 2 for loops and this works fine. The for loops take to much time, though.

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  • Memory allocation for a matrix in C

    - by Snogzvwtr
    Why is the following code resulting in Segmentation fault? (I'm trying to create two matrices of the same size, one with static and the other with dynamic allocation) #include <stdio.h> #include <stdlib.h> //Segmentation fault! int main(){ #define X 5000 #define Y 6000 int i; int a[X][Y]; int** b = (int**) malloc(sizeof(int*) * X); for(i=0; i<X; i++){ b[i] = malloc (sizeof(int) * Y); } } Weirdly enough, if I comment out one of the matrix definitions, the code runs fine. Like this: #include <stdio.h> #include <stdlib.h> //No Segmentation fault! int main(){ #define X 5000 #define Y 6000 int i; //int a[X][Y]; int** b = (int**) malloc(sizeof(int*) * X); for(i=0; i<X; i++){ b[i] = malloc (sizeof(int) * Y); } } or #include <stdio.h> #include <stdlib.h> //No Segmentation fault! int main(){ #define X 5000 #define Y 6000 int i; int a[X][Y]; //int** b = (int**) malloc(sizeof(int*) * X); //for(i=0; i<X; i++){ // b[i] = malloc (sizeof(int) * Y); //} } I'm running gcc on Linux on a 32-bit machine.

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  • Set all nonzero matrix elements to 1 (while keeping the others 0)

    - by Tomas Lycken
    I have a mesh grid defined as [X, Y, Z] = meshgrid(-100:100, -100:100, 25); % z will have more values later and two shapes (ovals, in this case): x_offset_1 = 40; x_offset_2 = -x_offset_1; o1 = ((X-x_offset_1).^2./(2*Z).^2+Y.^2./Z.^2 <= 1); o2 = ((X-x_offset_2).^2./(2*Z).^2+Y.^2./Z.^2 <= 1); Now, I want to find all points that are nonzero in either oval. I tried union = o1+o2; but since I simply add them, the overlapping region will have a value of 2 instead of the desired 1. How can I set all nonzero entries in the matrix to 1, regardless of their previous value? (I tried normalized_union = union./union;, but then I end up with NaN in all 0 elements because I'm dividing by zero...) Follow-up question: I got a perfect answer to my original question, but now I have a follow-up question on the same problem. I'm going to define a filled disc, c = (X.^2+Y.^2<R^2) that will also overlap with the two ovals. How do I find all the points that are inside the circle, but not inside any of the ovals?

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  • Join and sum not compatible matrices through data.table

    - by leodido
    My goal is to "sum" two not compatible matrices (matrices with different dimensions) using (and preserving) row and column names. I've figured this approach: convert the matrices to data.table objects, join them and then sum columns vectors. An example: > M1 1 3 4 5 7 8 1 0 0 1 0 0 0 3 0 0 0 0 0 0 4 1 0 0 0 0 0 5 0 0 0 0 0 0 7 0 0 0 0 1 0 8 0 0 0 0 0 0 > M2 1 3 4 5 8 1 0 0 1 0 0 3 0 0 0 0 0 4 1 0 0 0 0 5 0 0 0 0 0 8 0 0 0 0 0 > M1 %ms% M2 1 3 4 5 7 8 1 0 0 2 0 0 0 3 0 0 0 0 0 0 4 2 0 0 0 0 0 5 0 0 0 0 0 0 7 0 0 0 0 1 0 8 0 0 0 0 0 0 This is my code: M1 <- matrix(c(0,0,1,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0), byrow = TRUE, ncol = 6) colnames(M1) <- c(1,3,4,5,7,8) M2 <- matrix(c(0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0), byrow = TRUE, ncol = 5) colnames(M2) <- c(1,3,4,5,8) # to data.table objects DT1 <- data.table(M1, keep.rownames = TRUE, key = "rn") DT2 <- data.table(M2, keep.rownames = TRUE, key = "rn") # join and sum of common columns if (nrow(DT1) > nrow(DT2)) { A <- DT2[DT1, roll = TRUE] A[, list(X1 = X1 + X1.1, X3 = X3 + X3.1, X4 = X4 + X4.1, X5 = X5 + X5.1, X7, X8 = X8 + X8.1), by = rn] } That outputs: rn X1 X3 X4 X5 X7 X8 1: 1 0 0 2 0 0 0 2: 3 0 0 0 0 0 0 3: 4 2 0 0 0 0 0 4: 5 0 0 0 0 0 0 5: 7 0 0 0 0 1 0 6: 8 0 0 0 0 0 0 Then I can convert back this data.table to a matrix and fix row and column names. The questions are: how to generalize this procedure? I need a way to automatically create list(X1 = X1 + X1.1, X3 = X3 + X3.1, X4 = X4 + X4.1, X5 = X5 + X5.1, X7, X8 = X8 + X8.1) because i want to apply this function to matrices which dimensions (and row/columns names) are not known in advance. In summary I need a merge procedure that behaves as described. there are other strategies/implementations that achieve the same goal that are, at the same time, faster and generalized? (hoping that some data.table monster help me) to what kind of join (inner, outer, etc. etc.) is assimilable this procedure? Thanks in advance. p.s.: I'm using data.table version 1.8.2 EDIT - SOLUTIONS @Aaron solution. No external libraries, only base R. It works also on list of matrices. add_matrices_1 <- function(...) { a <- list(...) cols <- sort(unique(unlist(lapply(a, colnames)))) rows <- sort(unique(unlist(lapply(a, rownames)))) out <- array(0, dim = c(length(rows), length(cols)), dimnames = list(rows,cols)) for (m in a) out[rownames(m), colnames(m)] <- out[rownames(m), colnames(m)] + m out } @MadScone solution. Used reshape2 package. It works only on two matrices per call. add_matrices_2 <- function(m1, m2) { m <- acast(rbind(melt(M1), melt(M2)), Var1~Var2, fun.aggregate = sum) mn <- unique(colnames(m1), colnames(m2)) rownames(m) <- mn colnames(m) <- mn m } BENCHMARK (100 runs with microbenchmark package) Unit: microseconds expr min lq median uq max 1 add_matrices_1 196.009 257.5865 282.027 291.2735 549.397 2 add_matrices_2 13737.851 14697.9790 14864.778 16285.7650 25567.448 No need to comment the benchmark: @Aaron solution wins. I'll continue to investigate a similar solution for data.table objects. I'll add other solutions eventually reported or discovered.

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  • Converting switch statements to more elegant solution.

    - by masfenix
    I have a 9 x 9 matrix. (think of suduko). 4 2 1 6 8 1 8 5 8 3 1 5 8 1 1 7 5 8 1 1 4 0 5 6 7 0 4 6 2 5 5 4 4 8 1 2 6 8 8 2 8 1 6 3 5 8 4 2 6 4 7 4 1 1 1 3 5 3 8 8 5 2 2 2 6 6 0 8 8 8 0 6 8 7 2 3 3 1 1 7 4 now I wanna be able to get a "quadrant". for example (according to my code) the quadrant 2 , 2 returns the following: 5 4 4 2 8 1 6 4 7 If you've noticed, this is the matrix from the very center of the 9 x 9. I've split everything up in to pairs of "3" if you know what i mean. the first "ROW" is from 0 - 3, the second from 3 - 6, the third for 6 - 9.. I hope this makes sense ( I am open to alternate ways to go about this) anyways, heres my code. I dont really like this way, even though it works. I do want speed though beccause i am making a suduko solver. //a quadrant returns the mini 3 x 3 //row 1 has three quads,"1", "2", 3" //row 2 has three quads "1", "2", "3" etc public int[,] GetQuadrant(int rnum, int qnum) { int[,] returnMatrix = new int[3, 3]; int colBegin, colEnd, rowBegin, rowEnd, row, column; //this is so we can keep track of the new matrix row = 0; column = 0; switch (qnum) { case 1: colBegin = 0; colEnd = 3; break; case 2: colBegin = 3; colEnd = 6; break; case 3: colBegin = 6; colEnd = 9; break; default: colBegin = 0; colEnd = 0; break; } switch (rnum) { case 1: rowBegin = 0; rowEnd = 3; break; case 2: rowBegin = 3; rowEnd = 6; break; case 3: rowBegin = 6; rowEnd = 9; break; default: rowBegin = 0; rowEnd = 0; break; } for (int i = rowBegin ; i < rowEnd; i++) { for (int j = colBegin; j < colEnd; j++) { returnMatrix[row, column] = _matrix[i, j]; column++; } column = 0; row++; } return returnMatrix; }

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  • Where can I find BLAS example code (in Fortran)?

    - by Feynman
    I have been searching for decent documentation on blas, and I have found some 315 pages of dense material that ctrl-f does not work on. It provides all the information regarding what input arguments the routines take, but there are a LOT of input arguments and I could really use some example code. I am unable to locate any. I know there has to be some or no one would be able to use these libraries! Specifically, I use ATLAS installed via macports on a mac osx 10.5.8 and I use gfortran from gcc 4.4 (also installed via macports). I am coding in Fortran 90. I am still quite new to Fortran, but I have a fair amount of experience with mathematica, matlab, perl, and shell scripting. I would like to be able to initialize and multiply a dense complex vector by a dense symmetric (but not hermitian) complex matrix. The elements of the matrix are defined through a mathematical function of the indices--call it f(i,j). Could anyone provide some code or a link to some code?

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  • python matrices - list index out of range

    - by user1888493
    I am writing a function, that takes a matrix as input, such as the one below. Then the it returns the matrix' inverse, where all the 1s are changed to 0s and all the 0s changed to 1s, while keeping the diagonal from top left to bottom right 0s. An example input: g1 = [[0, 1, 1, 0], [1, 0, 0, 1], [1, 0, 0, 1], [0, 1, 1, 0]] the function should output this: g1 = [[0, 0, 0, 1], [0, 0, 1, 0], [0, 1, 0, 0], [1, 0, 0, 0]] When I run the program, it raises a list index out of range error. I'm sure this happens, because the loops I have set up are trying to access values that do not exist. But how do I allow an input of unknown row and column size? I only know how to do this with a single list, but a list of lists? Following you see the transforming function, but not the test function that calls it: def inverse_graph(graph): # take in graph # change all zeros to ones and ones to zeros r, c = 0, 0 # row, column equal zero while (graph[r][c] == 0 or graph[r][c] == 1): # while the current row has a value. while (graph[r][c] == 0 or graph[r][c] == 1): # while the current column has a value if (graph[r][c] == 0): graph[r][c] = 1 elif (graph[r][c] == 1): graph[r][c] = 0 c+=1 c=0 r+=1 c=0 r=0 # sets diagonal to zeros while (g1[r][c] == 0 or g1[r][c] == 1): g1[r][c]=0 c+=1 r+=1 return graph

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  • 2D Rendering with OpenGL ES 2.0 on Android (matrices not working)

    - by TranquilMarmot
    So I'm trying to render two moving quads, each at different locations. My shaders are as simple as possible (vertices are only transformed by the modelview-projection matrix, there's only one color). Whenever I try and render something, I only end up with slivers of color! I've only done work with 3D rendering in OpenGL before so I'm having issues with 2D stuff. Here's my basic rendering loop, simplified a bit (I'm using the Matrix manipulation methods provided by android.opengl.Matrix and program is a custom class I created that just calls GLES20.glUniformMatrix4fv()): Matrix.orthoM(projection, 0, 0, windowWidth, 0, windowHeight, -1, 1); program.setUniformMatrix4f("Projection", projection); At this point, I render the quads (this is repeated for each quad): Matrix.setIdentityM(modelview, 0); Matrix.translateM(modelview, 0, quadX, quadY, 0); program.setUniformMatrix4f("ModelView", modelview); quad.render(); // calls glDrawArrays and all I see is a sliver of the color each quad is! I'm at my wits end here, I've tried everything I can think of and I'm at the point where I'm screaming at my computer and tossing phones across the room. Anybody got any pointers? Am I using ortho wrong? I'm 100% sure I'm rendering everything at a Z value of 0. I tried using frustumM instead of orthoM, which made it so that I could see the quads but they would get totally skewed whenever they got moved, which makes sense if I correctly understand the way frustum works (it's more for 3D rendering, anyway). If it makes any difference, I defined my viewport with GLES20.glViewport(0, 0, windowWidth, windowHeight); Where windowWidth and windowHeight are the same values that are pased to orthoM It might be worth noting that the android.opengl.Matrix methods take in an offset as the second parameter so that multiple matrices can be shoved into one array, so that'w what the first 0 is for For reference, here's my vertex shader code: uniform mat4 ModelView; uniform mat4 Projection; attribute vec4 vPosition; void main() { mat4 mvp = Projection * ModelView; gl_Position = vPosition * mvp; } I tried swapping Projection * ModelView with ModelView * Projection but now I just get some really funky looking shapes... EDIT Okay, I finally figured it out! (Note: Since I'm new here (longtime lurker!) I can't answer my own question for a few hours, so as soon as I can I'll move this into an actual answer to the question) I changed Matrix.orthoM(projection, 0, 0, windowWidth, 0, windowHeight, -1, 1); to float ratio = windowWwidth / windowHeight; Matrix.orthoM(projection, 0, 0, ratio, 0, 1, -1, 1); I then had to scale my projection matrix to make it a lot smaller with Matrix.scaleM(projection, 0, 0.05f, 0.05f, 1.0f);. I then added an offset to the modelview translations to simulate a camera so that I could center on my action (so Matrix.translateM(modelview, 0, quadX, quadY, 0); was changed to Matrix.translateM(modelview, 0, quadX + camX, quadY + camY, 0);) Thanks for the help, all!

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  • xna orbit camera troubles

    - by user17753
    I have a Model named cube to which I load in LoadContent(): cube = Content.Load<Model>("untitled");. In the Draw Method I call DrawModel: private void DrawModel(Model m, Matrix world) { foreach (ModelMesh mesh in m.Meshes) { foreach (BasicEffect effect in mesh.Effects) { effect.EnableDefaultLighting(); effect.View = camera.View; effect.Projection = camera.Projection; effect.World = world; } mesh.Draw(); } } camera is of the Camera type, a class I've setup. Right now it is instantiated in the initialization section with the graphics aspect ratio and the translation (world) vector of the model, and the Draw loop calls the camera.UpdateCamera(); before drawing the models. class Camera { #region Fields private Matrix view; // View Matrix for Camera private Matrix projection; // Projection Matrix for Camera private Vector3 position; // Position of Camera private Vector3 target; // Point camera is "aimed" at private float aspectRatio; //Aspect Ratio for projection private float speed; //Speed of camera private Vector3 camup = Vector3.Up; #endregion #region Accessors /// <summary> /// View Matrix of the Camera -- Read Only /// </summary> public Matrix View { get { return view; } } /// <summary> /// Projection Matrix of the Camera -- Read Only /// </summary> public Matrix Projection { get { return projection; } } #endregion /// <summary> /// Creates a new Camera. /// </summary> /// <param name="AspectRatio">Aspect Ratio to use for the projection.</param> /// <param name="Position">Target coord to aim camera at.</param> public Camera(float AspectRatio, Vector3 Target) { target = Target; aspectRatio = AspectRatio; ResetCamera(); } private void Rotate(Vector3 Axis, float Amount) { position = Vector3.Transform(position - target, Matrix.CreateFromAxisAngle(Axis, Amount)) + target; } /// <summary> /// Resets Default Values of the Camera /// </summary> private void ResetCamera() { speed = 0.05f; position = target + new Vector3(0f, 20f, 20f); projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver4, aspectRatio, 0.5f, 100f); CalculateViewMatrix(); } /// <summary> /// Updates the Camera. Should be first thing done in Draw loop /// </summary> public void UpdateCamera() { Rotate(Vector3.Right, speed); CalculateViewMatrix(); } /// <summary> /// Calculates the View Matrix for the camera /// </summary> private void CalculateViewMatrix() { view = Matrix.CreateLookAt(position,target, camup); } I'm trying to create the camera so that it can orbit the center of the model. For a test I am calling Rotate(Vector3.Right, speed); but it rotates almost right but gets to a point where it "flips." If I rotate along a different axis Rotate(Vector3.Up, speed); everything seems OK in that direction. So I guess, can someone tell me what I'm not accounting for in the above code I wrote? Or point me to an example of an orbiting camera that can be fixed on an arbitrary point?

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  • Why does multiplying a double by -1 not give the negative of the current answer

    - by Ankur
    I am trying to multiply a double value by -1 to get the negative value. It continues to give me a positive value double man = Double.parseDouble(mantissa); double exp; if(sign.equals("plus")){ exp = Double.parseDouble(exponent); } else { exp = Double.parseDouble(exponent); exp = exp*-1; } System.out.println(man+" - "+sign+" - "+exp); The printed result is 13.93 - minus - 2.0 which is correct except that 2.0 should be -2.0

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  • Modifying multiplying calculation to use delta time

    - by Bart van Heukelom
    function(deltaTime) { x = x * 0.9; } This function is called in a game loop. First assume that it's running at a constant 30 FPS, so deltaTime is always 1/30. Now the game is changed so deltaTime isn't always 1/30 but becomes variable. How can I incorporate deltaTime in the calculation of x to keep the "effect per second" the same?

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  • Memory read/write access efficiency

    - by wolfPack88
    I've heard conflicting information from different sources, and I'm not really sure which one to believe. As such, I'll post what I understand and ask for corrections. Let's say I want to use a 2D matrix. There are three ways that I can do this (at least that I know of). 1: int i; char **matrix; matrix = malloc(50 * sizeof(char *)); for(i = 0; i < 50; i++) matrix[i] = malloc(50); 2: int i; int rowSize = 50; int pointerSize = 50 * sizeof(char *); int dataSize = 50 * 50; char **matrix; matrix = malloc(dataSize + pointerSize); char *pData = matrix + pointerSize - rowSize; for(i = 0; i < 50; i++) { pData += rowSize; matrix[i] = pData; } 3: //instead of accessing matrix[i][j] here, we would access matrix[i * 50 + j] char *matrix = malloc(50 * 50); In terms of memory usage, my understanding is that 3 is the most efficient, 2 is next, and 1 is least efficient, for the reasons below: 3: There is only one pointer and one allocation, and therefore, minimal overhead. 2: Once again, there is only one allocation, but there are now 51 pointers. This means there is 50 * sizeof(char *) more overhead. 1: There are 51 allocations and 51 pointers, causing the most overhead of all options. In terms of performance, once again my understanding is that 3 is the most efficient, 2 is next, and 1 is least efficient. Reasons being: 3: Only one memory access is needed. We will have to do a multiplication and an addition as opposed to two additions (as in the case of a pointer to a pointer), but memory access is slow enough that this doesn't matter. 2: We need two memory accesses; once to get a char *, and then to the appropriate char. Only two additions are performed here (once to get to the correct char * pointer from the original memory location, and once to get to the correct char variable from wherever the char * points to), so multiplication (which is slower than addition) is not required. However, on modern CPUs, multiplication is faster than memory access, so this point is moot. 1: Same issues as 2, but now the memory isn't contiguous. This causes cache misses and extra page table lookups, making it the least efficient of the lot. First and foremost: Is this correct? Second: Is there an option 4 that I am missing that would be even more efficient?

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  • iPhone OpenGL ES - How to Pick

    - by Ali Nadalizadeh
    I'm working on an OpenGL ES1 app which displays a 2D grid and allows user to navigate and scale/rotate it. I need to know the exact translation of View Touch coordinates into my opengl world and grid cell. Are there any helpers to do the reverse of last few transforms which I do for navigation ? or I should calculate and do the matrix stuff by hand ?

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  • Graph representation benchmarking

    - by Carlucho
    Currently am developing a program that solves (if possible) any given labyrinth of dimensions from 3X4 to 26x30. I represent the graph using both adj matrix (sparse) and adj list. I would like to know how to output the total time taken by the DFS to find the solution using one and then the other method. Programatically, how could i produce such benchmark?

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  • Matrices of "long"s in Java/COLT?

    - by Darren Wilkinson
    I'm very new to Java/COLT so apologies if this is a dumb question... But, is it possible to define (2d) matrices of type "long" using the cern.colt.matrix stuff? If so, how?! I can find an abstract class for "Object" and a concrete implementation for "double", but then I am stuck... Thanks,

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