Search Results

Search found 1725 results on 69 pages for 'compute shader'.

Page 58/69 | < Previous Page | 54 55 56 57 58 59 60 61 62 63 64 65  | Next Page >

• Consumer Oriented Search In Oracle Endeca Information Discovery - Part 2

  - by Bob Zurek

  As discussed in my last blog posting on this topic, Information Discovery, a core capability of the Oracle Endeca Information Discovery solution enables businesses to search, discover and navigate through a wide variety of big data including structured, unstructured and semi-structured data. With search as a core advanced capabilities of our product it is important to understand some of the key differences and capabilities in the underlying data store of Oracle Endeca Information Discovery and that is our Endeca Server. In the last post on this subject, we talked about Exploratory Search capabilities along with support for cascading relevance. Additional search capabilities in the Endeca Server, which differentiate from simple keyword based "search boxes" in other Information Discovery products also include: The Endeca Server Supports Set Search.  The Endeca Server is organized around set retrieval, which means that it looks at groups of results (all the documents that match a search), as well as the relationship of each individual result to the set. Other approaches only compute the relevance of a document by comparing the document to the search query – not by comparing the document to all the others. For example, a search for “U.S.” in another approach might match to the title of a document and get a high ranking. But what if it were a collection of government documents in which “U.S.” appeared in many titles, making that clue less meaningful? A set analysis would reveal this and be used to adjust relevance accordingly. The Endeca Server Supports Second-Order Relvance. Unlike simple search interfaces in traditional BI tools, which provide limited relevance ranking, such as a list of results based on key word matching, Endeca enables users to determine the most salient terms to divide up the result. Determining this second-order relevance is the key to providing effective guidance. Support for Queries and Filters. Search is the most common query type, but hardly complete, and users need to express a wide range of queries. Oracle Endeca Information Discovery also includes navigation, interactive visualizations, analytics, range filters, geospatial filters, and other query types that are more commonly associated with BI tools. Unlike other approaches, these queries operate across structured, semi-structured and unstructured content stored in the Endeca Server. Furthermore, this set is easily extensible because the core engine allows for pluggable features to be added. Like a search engine, queries are answered with a results list, ranked to put the most likely matches first. Unlike “black box” relevance solutions, which generalize one strategy for everyone, we believe that optimal relevance strategies vary across domains. Therefore, it provides line-of-business owners with a set of relevance modules that let them tune the best results based on their content. The Endeca Server query result sets are summarized, which gives users guidance on how to refine and explore further. Summaries include Guided Navigation® (a form of faceted search), maps, charts, graphs, tag clouds, concept clusters, and clarification dialogs. Users don’t explicitly ask for these summaries; Oracle Endeca Information Discovery analytic applications provide the right ones, based on configurable controls and rules. For example, the analytic application might guide a procurement agent filtering for in-stock parts by visualizing the results on a map and calculating their average fulfillment time. Furthermore, the user can interact with summaries and filters without resorting to writing complex SQL queries. The user can simply just click to add filters. Within Oracle Endeca Information Discovery, all parts of the summaries are clickable and searchable. We are living in a search driven society where business users really seem to enjoy entering information into a search box. We do this everyday as consumers and therefore, we have gotten used to looking for that box. However, the key to getting the right results is to guide that user in a way that provides additional Discovery, beyond what they may have anticipated. This is why these important and advanced features of search inside the Endeca Server have been so important. They have helped to guide our great customers to success. 

  Read the article

• Approach for packing 2D shapes while minimizing total enclosing area

  - by Dennis

  Not sure on my tags for this question, but in short .... I need to solve a problem of packing industrial parts into crates while minimizing total containing area. These parts are motors, or pumps, or custom-made components, and they have quite unusual shapes. For some, it may be possible to assume that a part === rectangular cuboid, but some are not so simple, i.e. they assume a shape more of that of a hammer or letter T. With those, (assuming 2D shape), by alternating direction of top & bottom, one can pack more objects into the same space, than if all tops were in the same direction. Crude example below with letter "T"-shaped parts: ***** xxxxx ***** x ***** *** ooo * x vs * x vs * x vs * x o * x * xxxxx * x * x o xxxxx xxx Right now we are solving the problem by something like this: using CAD software, make actual models of how things fit in crate boxes make estimates of actual crate dimensions & write them into Excel file (1) is crazy amount of work and as the result we have just a limited amount of possible entries in (2), the Excel file. The good things is that programming this is relatively easy. Given a combination of products to go into crates, we do a lookup, and if entry exists in the Excel (or Database), we bring it out. If it doesn't, we say "sorry, no data!". I don't necessarily want to go full force on making up some crazy algorithm that given geometrical part description can align, rotate, and figure out best part packing into a crate, given its shape, but maybe I do.. Question Well, here is my question: assuming that I can represent my parts as 2D (to be determined how), and that some parts look like letter T, and some parts look like rectangles, which algorithm can I use to give me a good estimate on the dimensions of the encompassing area, while ensuring that the parts are packed in a minimal possible area, to minimize crating/shipping costs? Are there approximation algorithms? Seeing how this can get complex, is there an existing library I could use? My thought / Approach My naive approach would be to define a way to describe position of parts, and place the first part, compute total enclosing area & dimensions. Then place 2nd part in 0 degree orientation, repeat, place it at 180 degree orientation, repeat (for my case I don't think 90 degree rotations will be meaningful due to long lengths of parts). Proceed using brute force "tacking on" other parts to the enclosing area until all parts are processed. I may have to shift some parts a tad (see 3rd pictorial example above with letters T). This adds a layer of 2D complexity rather than 1D. I am not sure how to approach this. One idea I have is genetic algorithms, but I think those will take up too much processing power and time. I will need to look out for shape collisions, as well as adding extra padding space, since we are talking about real parts with irregularities rather than perfect imaginary blocks. I'm afraid this can get geometrically messy fairly fast, and I'd rather keep things simple, if I can. But what if the best (practical) solution is to pack things into different crate boxes rather than just one? This can get a bit more tricky. There is human element involved as well, i.e. like parts can go into same box and are thus a constraint to be considered. Some parts that are not the same are sometimes grouped together for shipping and can be considered as a common grouped item. Sometimes customers want things shipped their way, which adds human element to constraints. so there will have to be some customization.

  Read the article

• Indexed Drawing in OpenGL not working

  - by user2050846

  I am trying to render 2 types of primitives- - points ( a Point Cloud ) - triangles ( a Mesh ) I am rendering points simply without any index arrays and they are getting rendered fine. To render the meshes I am using indexed drawing with the face list array having the indices of the vertices to be rendered as Triangles. Vertices and their corresponding vertex colors are stored in their corresponding buffers. But the indexed drawing command do not draw anything. The code is as follows- Main Display Function: void display() { simple->enable(); simple->bindUniform("MV",modelview); simple->bindUniform("P", projection); // rendering Point Cloud glBindVertexArray(vao); // Vertex buffer Point Cloud glBindBuffer(GL_ARRAY_BUFFER,vertexbuffer); glEnableVertexAttribArray(0); glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,0,0); // Color Buffer point Cloud glBindBuffer(GL_ARRAY_BUFFER,colorbuffer); glEnableVertexAttribArray(1); glVertexAttribPointer(1,3,GL_FLOAT,GL_FALSE,0,0); // Render Colored Point Cloud //glDrawArrays(GL_POINTS,0,model->vertexCount); glDisableVertexAttribArray(0); glDisableVertexAttribArray(1); // ---------------- END---------------------// //// Floor Rendering glBindBuffer(GL_ARRAY_BUFFER,fl); glEnableVertexAttribArray(0); glEnableVertexAttribArray(1); glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,0,0); glVertexAttribPointer(1,4,GL_FLOAT,GL_FALSE,0,(void *)48); glDrawArrays(GL_QUADS,0,4); glDisableVertexAttribArray(0); glDisableVertexAttribArray(1); // -----------------END---------------------// //Rendering the Meshes //////////// PART OF CODE THAT IS NOT DRAWING ANYTHING //////////////////// glBindVertexArray(vid); for(int i=0;i<NUM_MESHES;i++) { glBindBuffer(GL_ARRAY_BUFFER,mVertex[i]); glEnableVertexAttribArray(0); glEnableVertexAttribArray(1); glVertexAttribPointer(0,3,GL_FLOAT,GL_FALSE,0,0); glVertexAttribPointer(1,3,GL_FLOAT,GL_FALSE,0,(void *)(meshes[i]->vertexCount*sizeof(glm::vec3))); //glDrawArrays(GL_TRIANGLES,0,meshes[i]->vertexCount); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,mFace[i]); //cout<<gluErrorString(glGetError()); glDrawElements(GL_TRIANGLES,meshes[i]->faceCount*3,GL_FLOAT,(void *)0); glDisableVertexAttribArray(0); glDisableVertexAttribArray(1); } glUseProgram(0); glutSwapBuffers(); glutPostRedisplay(); } Point Cloud Buffer Allocation Initialization: void initGLPointCloud() { glGenBuffers(1,&vertexbuffer); glGenBuffers(1,&colorbuffer); glGenBuffers(1,&fl); //Populates the position buffer glBindBuffer(GL_ARRAY_BUFFER,vertexbuffer); glBufferData(GL_ARRAY_BUFFER, model->vertexCount * sizeof (glm::vec3), &model->positions[0], GL_STATIC_DRAW); //Populates the color buffer glBindBuffer(GL_ARRAY_BUFFER, colorbuffer); glBufferData(GL_ARRAY_BUFFER, model->vertexCount * sizeof (glm::vec3), &model->colors[0], GL_STATIC_DRAW); model->FreeMemory(); // To free the not needed memory, as the data has been already // copied on graphic card, and wont be used again. glBindBuffer(GL_ARRAY_BUFFER,0); } Meshes Buffer Initialization: void initGLMeshes(int i) { glBindBuffer(GL_ARRAY_BUFFER,mVertex[i]); glBufferData(GL_ARRAY_BUFFER,meshes[i]->vertexCount*sizeof(glm::vec3)*2,NULL,GL_STATIC_DRAW); glBufferSubData(GL_ARRAY_BUFFER,0,meshes[i]->vertexCount*sizeof(glm::vec3),&meshes[i]->positions[0]); glBufferSubData(GL_ARRAY_BUFFER,meshes[i]->vertexCount*sizeof(glm::vec3),meshes[i]->vertexCount*sizeof(glm::vec3),&meshes[i]->colors[0]); glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,mFace[i]); glBufferData(GL_ELEMENT_ARRAY_BUFFER,meshes[i]->faceCount*sizeof(glm::vec3), &meshes[i]->faces[0],GL_STATIC_DRAW); meshes[i]->FreeMemory(); //glBindBuffer(GL_ELEMENT_ARRAY_BUFFER,0); } Initialize the Rendering, load and create shader and calls the mesh and PCD initializers. void initRender() { simple= new GLSLShader("shaders/simple.vert","shaders/simple.frag"); //Point Cloud //Sets up VAO glGenVertexArrays(1, &vao); glBindVertexArray(vao); initGLPointCloud(); //floorData glBindBuffer(GL_ARRAY_BUFFER, fl); glBufferData(GL_ARRAY_BUFFER, sizeof(floorData), &floorData[0], GL_STATIC_DRAW); glBindBuffer(GL_ARRAY_BUFFER,0); glBindVertexArray(0); //Meshes for(int i=0;i<NUM_MESHES;i++) { if(i==0) // SET up the new vertex array state for indexed Drawing { glGenVertexArrays(1, &vid); glBindVertexArray(vid); glGenBuffers(NUM_MESHES,mVertex); glGenBuffers(NUM_MESHES,mColor); glGenBuffers(NUM_MESHES,mFace); } initGLMeshes(i); } glEnable(GL_DEPTH_TEST); } Any help would be much appreciated, I have been breaking my head on this problem since 3 days, and still it is unsolved.

  Read the article

• C# XNA 4.0 multitextured cube

  - by chron

  So I am following this tutorial on how to draw a cube in XNA and I ran into a problem. Ok so my shader can only have texture right? I need to have a texture on the front and back of my cube. So I thought I could just have both textures stored in one texture. Problem is I do not know how to map out my UV coords to do so. (I tried dividing by 2 and such with no luck...). I am really new to this (not programming, just game development and some concepts), but how could I get UV coordinates for both halfs of the texture. private void ConstructCube(Vector3 Position,Vector3 Size) { _vertices = new VertexPositionNormalTexture[50]; // Calculate the position of the vertices on the top face. Vector3 topLeftFront = Position + new Vector3(-1.0f, 1.0f, -1.0f) * Size; Vector3 topLeftBack = Position + new Vector3(-1.0f, 1.0f, 1.0f) * Size; Vector3 topRightFront = Position + new Vector3(1.0f, 1.0f, -1.0f) * Size; Vector3 topRightBack = Position + new Vector3(1.0f, 1.0f, 1.0f) * Size; // Calculate the position of the vertices on the bottom face. Vector3 btmLeftFront = Position + new Vector3(-1.0f, -1.0f, -1.0f) * Size; Vector3 btmLeftBack = Position + new Vector3(-1.0f, -1.0f, 1.0f) * Size; Vector3 btmRightFront = Position + new Vector3(1.0f, -1.0f, -1.0f) * Size; Vector3 btmRightBack = Position + new Vector3(1.0f, -1.0f, 1.0f) * Size; // Normal vectors for each face (needed for lighting / display) Vector3 normalFront = new Vector3(0.0f, 0.0f, 1.0f) * Size; Vector3 normalBack = new Vector3(0.0f, 0.0f, -1.0f) * Size; Vector3 normalTop = new Vector3(0.0f, 1.0f, 0.0f) * Size; Vector3 normalBottom = new Vector3(0.0f, -1.0f, 0.0f) * Size; Vector3 normalLeft = new Vector3(-1.0f, 0.0f, 0.0f) * Size; Vector3 normalRight = new Vector3(1.0f, 0.0f, 0.0f) * Size; // UV texture coordinates Vector2 textureTopLeft = new Vector2(1.0f * Size.X, 0.0f * Size.Y); Vector2 textureTopRight = new Vector2(0.0f * Size.X, 0.0f * Size.Y); Vector2 textureBottomLeft = new Vector2(1.0f * Size.X, 1.0f * Size.Y); Vector2 textureBottomRight = new Vector2(0.0f * Size.X, 1.0f * Size.Y); // Add the vertices for the FRONT face. _vertices[0] = new VertexPositionNormalTexture(topLeftFront, normalFront, textureTopLeft); _vertices[1] = new VertexPositionNormalTexture(btmLeftFront, normalFront, textureBottomLeft); _vertices[2] = new VertexPositionNormalTexture(topRightFront, normalFront, textureTopRight); _vertices[3] = new VertexPositionNormalTexture(btmLeftFront, normalFront, textureBottomLeft); _vertices[4] = new VertexPositionNormalTexture(btmRightFront, normalFront, textureBottomRight); _vertices[5] = new VertexPositionNormalTexture(topRightFront, normalFront, textureTopRight); // Add the vertices for the BACK face. _vertices[6] = new VertexPositionNormalTexture(topLeftBack, normalBack, textureTopRight); _vertices[7] = new VertexPositionNormalTexture(topRightBack, normalBack, textureTopLeft); _vertices[8] = new VertexPositionNormalTexture(btmLeftBack, normalBack, textureBottomRight); _vertices[9] = new VertexPositionNormalTexture(btmLeftBack, normalBack, textureBottomRight); _vertices[10] = new VertexPositionNormalTexture(topRightBack, normalBack, textureTopLeft); _vertices[11] = new VertexPositionNormalTexture(btmRightBack, normalBack, textureBottomLeft); // Add the vertices for the TOP face. _vertices[12] = new VertexPositionNormalTexture(topLeftFront, normalTop, textureBottomLeft); _vertices[13] = new VertexPositionNormalTexture(topRightBack, normalTop, textureTopRight); _vertices[14] = new VertexPositionNormalTexture(topLeftBack, normalTop, textureTopLeft); _vertices[15] = new VertexPositionNormalTexture(topLeftFront, normalTop, textureBottomLeft); _vertices[16] = new VertexPositionNormalTexture(topRightFront, normalTop, textureBottomRight); _vertices[17] = new VertexPositionNormalTexture(topRightBack, normalTop, textureTopRight); // Add the vertices for the BOTTOM face. _vertices[18] = new VertexPositionNormalTexture(btmLeftFront, normalBottom, textureTopLeft); _vertices[19] = new VertexPositionNormalTexture(btmLeftBack, normalBottom, textureBottomLeft); _vertices[20] = new VertexPositionNormalTexture(btmRightBack, normalBottom, textureBottomRight); _vertices[21] = new VertexPositionNormalTexture(btmLeftFront, normalBottom, textureTopLeft); _vertices[22] = new VertexPositionNormalTexture(btmRightBack, normalBottom, textureBottomRight); _vertices[23] = new VertexPositionNormalTexture(btmRightFront, normalBottom, textureTopRight); // Add the vertices for the LEFT face. _vertices[24] = new VertexPositionNormalTexture(topLeftFront, normalLeft, textureTopRight); _vertices[25] = new VertexPositionNormalTexture(btmLeftBack, normalLeft, textureBottomLeft ); _vertices[26] = new VertexPositionNormalTexture(btmLeftFront, normalLeft, textureBottomRight ); _vertices[27] = new VertexPositionNormalTexture(topLeftBack, normalLeft, textureTopLeft); _vertices[28] = new VertexPositionNormalTexture(btmLeftBack, normalLeft, textureBottomLeft ); _vertices[29] = new VertexPositionNormalTexture(topLeftFront, normalLeft, textureTopRight ); // Add the vertices for the RIGHT face. _vertices[30] = new VertexPositionNormalTexture(topRightFront, normalRight, textureTopLeft); _vertices[31] = new VertexPositionNormalTexture(btmRightFront, normalRight, textureBottomLeft); _vertices[32] = new VertexPositionNormalTexture(btmRightBack, normalRight, textureBottomRight); _vertices[33] = new VertexPositionNormalTexture(topRightBack, normalRight, textureTopRight); _vertices[34] = new VertexPositionNormalTexture(topRightFront, normalRight, textureTopLeft); _vertices[35] = new VertexPositionNormalTexture(btmRightBack, normalRight, textureBottomRight); done = true; }

  Read the article

• WPF / C#: Transforming coordinates from an image control to the image source

  - by Gabriel

  I'm trying to learn WPF, so here's a simple question, I hope: I have a window that contains an Image element bound to a separate data object with user-configurable Stretch property <Image Name="imageCtrl" Source="{Binding MyImage}" Stretch="{Binding ImageStretch}" /> When the user moves the mouse over the image, I would like to determine the coordinates of the mouse with respect to the original image (before stretching/cropping that occurs when it is displayed in the control), and then do something with those coordinates (update the image). I know I can add an event-handler to the MouseMove event over the Image control, but I'm not sure how best to transform the coordinates: void imageCtrl_MouseMove(object sender, MouseEventArgs e) { Point locationInControl = e.GetPosition(imageCtrl); Point locationInImage = ??? updateImage(locationInImage); } Now I know I could compare the size of Source to the ActualSize of the control, and then switch on imageCtrl.Stretch to compute the scalars and offsets on X and Y, and do the transform myself. But WPF has all the information already, and this seems like functionality that might be built-in to the WPF libraries somewhere. So I'm wondering: is there a short and sweet solution? Or do I need to write this myself? EDIT I'm appending my current, not-so-short-and-sweet solution. Its not that bad, but I'd be somewhat suprised if WPF didn't provide this functionality automatically: Point ImgControlCoordsToPixelCoords(Point locInCtrl, double imgCtrlActualWidth, double imgCtrlActualHeight) { if (ImageStretch == Stretch.None) return locInCtrl; Size renderSize = new Size(imgCtrlActualWidth, imgCtrlActualHeight); Size sourceSize = bitmap.Size; double xZoom = renderSize.Width / sourceSize.Width; double yZoom = renderSize.Height / sourceSize.Height; if (ImageStretch == Stretch.Fill) return new Point(locInCtrl.X / xZoom, locInCtrl.Y / yZoom); double zoom; if (ImageStretch == Stretch.Uniform) zoom = Math.Min(xZoom, yZoom); else // (imageCtrl.Stretch == Stretch.UniformToFill) zoom = Math.Max(xZoom, yZoom); return new Point(locInCtrl.X / zoom, locInCtrl.Y / zoom); }

  Read the article

• Boosting my GA with Neural Networks and/or Reinforcement Learning

  - by AlexT

  As I have mentioned in previous questions I am writing a maze solving application to help me learn about more theoretical CS subjects, after some trouble I've got a Genetic Algorithm working that can evolve a set of rules (handled by boolean values) in order to find a good solution through a maze. That being said, the GA alone is okay, but I'd like to beef it up with a Neural Network, even though I have no real working knowledge of Neural Networks (no formal theoretical CS education). After doing a bit of reading on the subject I found that a Neural Network could be used to train a genome in order to improve results. Let's say I have a genome (group of genes), such as 1 0 0 1 0 1 0 1 0 1 1 1 0 0... How could I use a Neural Network (I'm assuming MLP?) to train and improve my genome? In addition to this as I know nothing about Neural Networks I've been looking into implementing some form of Reinforcement Learning, using my maze matrix (2 dimensional array), although I'm a bit stuck on what the following algorithm wants from me: (from http://people.revoledu.com/kardi/tutorial/ReinforcementLearning/Q-Learning-Algorithm.htm) 1. Set parameter , and environment reward matrix R 2. Initialize matrix Q as zero matrix 3. For each episode: * Select random initial state * Do while not reach goal state o Select one among all possible actions for the current state o Using this possible action, consider to go to the next state o Get maximum Q value of this next state based on all possible actions o Compute o Set the next state as the current state End Do End For The big problem for me is implementing a reward matrix R and what a Q matrix exactly is, and getting the Q value. I use a multi-dimensional array for my maze and enum states for every move. How would this be used in a Q-Learning algorithm? If someone could help out by explaining what I would need to do to implement the following, preferably in Java although C# would be nice too, possibly with some source code examples it'd be appreciated.

  Read the article

• java client program to send digest authentication request using HttpClient API

  - by Rajesh

  I have restlet sample client program which sends the digest request. Similar to this I need java client program which sends a digest request using HttpClient api. Can anybody send me sample code. Thanks in advance. Reference reference = new Reference("http://localhost:8092/authenticate"); Client client = new Client(Protocol.HTTP); Request request = new Request(Method.GET, reference); Response response = client.handle(request); System.out.println("response: "+response.getStatus()); Form form = new Form(); form.add("username", "rajesh"); form.add("uri", reference.getPath()); // Loop over the challengeRequest objects sent by the server. for (ChallengeRequest challengeRequest : response .getChallengeRequests()) { // Get the data from the server's response. if (ChallengeScheme.HTTP_DIGEST .equals(challengeRequest.getScheme())) { Series<Parameter> params = challengeRequest.getParameters(); form.add(params.getFirst("nonce")); form.add(params.getFirst("realm")); form.add(params.getFirst("domain")); form.add(params.getFirst("algorithm")); form.add(params.getFirst("qop")); } } // Compute the required data String a1 = Engine.getInstance().toMd5( "rajesh" + ":" + form.getFirstValue("realm") + ":" + "rajesh"); String a2 = Engine.getInstance().toMd5( request.getMethod() + ":" + form.getFirstValue("uri")); form.add("response", Engine.getInstance().toMd5( a1 + ":" + form.getFirstValue("nonce") + ":" + a2)); ChallengeResponse challengeResponse = new ChallengeResponse( ChallengeScheme.HTTP_DIGEST, "", ""); challengeResponse.setCredentialComponents(form); // Send the completed request request.setChallengeResponse(challengeResponse); response = client.handle(request); // Should be 200. System.out.println(response.getStatus());

  Read the article

• Eigenvector computation using OpenCV

  - by Andriyev

  Hi I have this matrix A, representing similarities of pixel intensities of an image. For example: Consider a 10 x 10 image. Matrix A in this case would be of dimension 100 x 100, and element A(i,j) would have a value in the range 0 to 1, representing the similarity of pixel i to j in terms of intensity. I am using OpenCV for image processing and the development environment is C on Linux. Objective is to compute the Eigenvectors of matrix A and I have used the following approach: static CvMat mat, *eigenVec, *eigenVal; static double A[100][100]={}, Ain1D[10000]={}; int cnt=0; //Converting matrix A into a one dimensional array //Reason: That is how cvMat requires it for(i = 0;i < affnDim;i++){ for(j = 0;j < affnDim;j++){ Ain1D[cnt++] = A[i][j]; } } mat = cvMat(100, 100, CV_32FC1, Ain1D); cvEigenVV(&mat, eigenVec, eigenVal, 1e-300); for(i=0;i < 100;i++){ val1 = cvmGet(eigenVal,i,0); //Fetching Eigen Value for(j=0;j < 100;j++){ matX[i][j] = cvmGet(eigenVec,i,j); //Fetching each component of Eigenvector i } } Problem: After execution I get nearly all components of all the Eigenvectors to be zero. I tried different images and also tried populating A with random values between 0 and 1, but the same result. Few of the top eigenvalues returned look like the following: 9805401476911479666115491135488.000000 -9805401476911479666115491135488.000000 -89222871725331592641813413888.000000 89222862280598626902522986496.000000 5255391142666987110400.000000 I am now thinking on the lines of using cvSVD() which performs singular value decomposition of real floating-point matrix and might yield me the eigenvectors. But before that I thought of asking it here. Is there anything absurd in my current approach? Am I using the right API i.e. cvEigenVV() for the right input matrix (my matrix A is a floating point matrix)? cheers

  Read the article

• the problem of "cvEigenVV"

  - by gg-anny

  Hi!When I compile the program,VC2005 always tell :"error C2198: 'cvEigenVV' : too few arguments for call". Part of the code below: void draw_oxfd_feature( IplImage* img, struct feature* feat, CvScalar color ) { double m[4] = { feat-a, feat-b, feat-b, feat-c }; double v[4] = { 0 }; double e[2] = { 0 }; CvMat M; CvMat V; CvMat E; double alpha, l1, l2; /* compute axes and orientation of ellipse surrounding affine region */ cvInitMatHeader( &M, 2, 2, CV_64FC1, m, CV_AUTOSTEP ); cvInitMatHeader( &V, 2, 2, CV_64FC1, v, CV_AUTOSTEP ); cvInitMatHeader( &E, 2, 1, CV_64FC1, e, CV_AUTOSTEP ); cvEigenVV( &M, &V, &E, DBL_EPSILON ); l1 = 1 / sqrt( e[1] ); l2 = 1 / sqrt( e[0] ); alpha = -atan2( v[1], v[0] ); alpha *= 180 / CV_PI; cvEllipse( img, cvPoint( feat-x, feat-y ), cvSize( l2, l1 ), alpha, 0, 360, CV_RGB(0,0,0), 3, 8, 0 ); cvEllipse( img, cvPoint( feat-x, feat-y ), cvSize( l2, l1 ), alpha, 0, 360, color, 1, 8, 0 ); cvLine( img, cvPoint( feat-x+2, feat-y ), cvPoint( feat-x-2, feat-y ), color, 1, 8, 0 ); cvLine( img, cvPoint( feat-x, feat-y+2 ), cvPoint( feat-x, feat-y-2 ), color, 1, 8, 0 ); // cvCircle(img,cvPoint(cvRound( feat-x ),cvRound( feat-y )),2, color, CV_FILLED, 8, 0); cvCircle(img,cvPoint( cvRound( feat-x ), cvRound( feat-y )), 2,CV_RGB(0,255,0), CV_FILLED, 8, 0 ); } How to solve the problem?Thank you!

  Read the article

• Code Golf: Leibniz formula for Pi

  - by Greg Beech

  I recently posted one of my favourite interview whiteboard coding questions in "What's your more controversial programming opinion", which is to write a function that computes Pi using the Leibniz formula. It can be approached in a number of different ways, and the exit condition takes a bit of thought, so I thought it might make an interesting code golf question. Shortest code wins! Given that Pi can be estimated using the function 4 * (1 - 1/3 + 1/5 - 1/7 + ...) with more terms giving greater accuracy, write a function that calculates Pi to within 0.00001. Edit: 3 Jan 2008 As suggested in the comments I changed the exit condition to be within 0.00001 as that's what I really meant (an accuracy 5 decimal places is much harder due to rounding and so I wouldn't want to ask that in an interview, whereas within 0.00001 is an easier to understand and implement exit condition). Also, to answer the comments, I guess my intention was that the solution should compute the number of iterations, or check when it had done enough, but there's nothing to prevent you from pre-computing the number of iterations and using that number. I really asked the question out of interest to see what people would come up with.

  Read the article

• infinite loop shutting down ensime

  - by Jeff Bowman

  When I run M-X ensime-disconnect I get the following forever: string matching regex `\"((?:[^\"\\]|\\.)*)\"' expected but `^@' found and I see this exception when I use C-c C-c Uncaught exception in com.ensime.server.SocketHandler@769aba32 java.net.SocketException: Broken pipe at java.net.SocketOutputStream.socketWrite0(Native Method) at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:109) at java.net.SocketOutputStream.write(SocketOutputStream.java:153) at sun.nio.cs.StreamEncoder.writeBytes(StreamEncoder.java:220) at sun.nio.cs.StreamEncoder.implFlushBuffer(StreamEncoder.java:290) at sun.nio.cs.StreamEncoder.implFlush(StreamEncoder.java:294) at sun.nio.cs.StreamEncoder.flush(StreamEncoder.java:140) at java.io.OutputStreamWriter.flush(OutputStreamWriter.java:229) at java.io.BufferedWriter.flush(BufferedWriter.java:253) at com.ensime.server.SocketHandler.write(server.scala:118) at com.ensime.server.SocketHandler$$anonfun$act$1$$anonfun$apply$mcV$sp$1.apply(server.scala:132) at com.ensime.server.SocketHandler$$anonfun$act$1$$anonfun$apply$mcV$sp$1.apply(server.scala:127) at scala.actors.Actor$class.receive(Actor.scala:456) at com.ensime.server.SocketHandler.receive(server.scala:67) at com.ensime.server.SocketHandler$$anonfun$act$1.apply$mcV$sp(server.scala:127) at com.ensime.server.SocketHandler$$anonfun$act$1.apply(server.scala:127) at com.ensime.server.SocketHandler$$anonfun$act$1.apply(server.scala:127) at scala.actors.Reactor$class.seq(Reactor.scala:262) at com.ensime.server.SocketHandler.seq(server.scala:67) at scala.actors.Reactor$$anon$3.andThen(Reactor.scala:240) at scala.actors.Combinators$class.loop(Combinators.scala:26) at com.ensime.server.SocketHandler.loop(server.scala:67) at scala.actors.Combinators$$anonfun$loop$1.apply(Combinators.scala:26) at scala.actors.Combinators$$anonfun$loop$1.apply(Combinators.scala:26) at scala.actors.Reactor$$anonfun$seq$1$$anonfun$apply$1.apply(Reactor.scala:259) at scala.actors.ReactorTask.run(ReactorTask.scala:36) at scala.actors.ReactorTask.compute(ReactorTask.scala:74) at scala.concurrent.forkjoin.RecursiveAction.exec(RecursiveAction.java:147) at scala.concurrent.forkjoin.ForkJoinTask.quietlyExec(ForkJoinTask.java:422) at scala.concurrent.forkjoin.ForkJoinWorkerThread.mainLoop(ForkJoinWorkerThread.java:340) at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:325) Is there something else I'm missing in my config or I should check on? Thanks, Jeff

  Read the article

• Combinations into pairs

  - by Will

  I'm working on a directed network problem and trying to compute all valid paths between two points. I need a way to look at paths up to 30 "trips" (represented by an [origin, destination] pair) in length. The full route is then composed of a series of these pairs: route = [[start, city2], [city2, city3], [city3, city4], [city4, city5], [city5, city6], [city6, city7], [city7, city8], [city8, stop]] So far my best solution is as follows: def numRoutes(graph, start, stop, minStops, maxStops): routes = [] route = [[start, stop]] if distance(graph, route) != "NO SUCH ROUTE" and len(route) >= minStops and len(route) <= maxStops: routes.append(route) if maxStops >= 2: for city2 in routesFromCity(graph, start): route = [[start, city2],[city2, stop]] if distance(graph, route) != "NO SUCH ROUTE" and len(route) >= minStops and len(route) <= maxStops: routes.append(route) if maxStops >= 3: for city2 in routesFromCity(graph, start): for city3 in routesFromCity(graph, city2): route = [[start, city2], [city2, city3], [city3, stop]] if distance(graph, route) != "NO SUCH ROUTE" and len(route) >= minStops and len(route) <= maxStops: routes.append(route) if maxStops >= 4: for city2 in routesFromCity(graph, start): for city3 in routesFromCity(graph, city2): for city4 in routesFromCity(graph, city3): route = [[start, city2], [city2, city3], [city3, city4], [city4, stop]] if distance(graph, route) != "NO SUCH ROUTE" and len(route) >= minStops and len(route) <= maxStops: routes.append(route) if maxStops >= 5: for city2 in routesFromCity(graph, start): for city3 in routesFromCity(graph, city2): for city4 in routesFromCity(graph, city3): for city5 in routesFromCity(graph, city4): route = [[start, city2], [city2, city3], [city3, city4], [city4, city5], [city5, stop]] if distance(graph, route) != "NO SUCH ROUTE" and len(route) >= minStops and len(route) <= maxStops: routes.append(route) return routes Where numRoutes is fed my network graph where numbers represent distances: [[0, 5, 0, 5, 7], [0, 0, 4, 0, 0], [0, 0, 0, 8, 2], [0, 0, 8, 0, 6], [0, 3, 0, 0, 0]] a start city, an end city and the parameters for the length of the routes. distance checks if a route is viable and routesFromCity returns the attached nodes to each fed in city. I have a feeling there's a far more efficient way to generate all of the routes especially as I move toward many more steps, but I can't seem to get anything else to work.

  Read the article

• Transforming coordinates from an image control to the image source in WPF

  - by Gabriel

  I'm trying to learn WPF, so here's a simple question, I hope: I have a window that contains an Image element bound to a separate data object with user-configurable Stretch property <Image Name="imageCtrl" Source="{Binding MyImage}" Stretch="{Binding ImageStretch}" /> When the user moves the mouse over the image, I would like to determine the coordinates of the mouse with respect to the original image (before stretching/cropping that occurs when it is displayed in the control), and then do something with those coordinates (update the image). I know I can add an event-handler to the MouseMove event over the Image control, but I'm not sure how best to transform the coordinates: void imageCtrl_MouseMove(object sender, MouseEventArgs e) { Point locationInControl = e.GetPosition(imageCtrl); Point locationInImage = ??? updateImage(locationInImage); } Now I know I could compare the size of Source to the ActualSize of the control, and then switch on imageCtrl.Stretch to compute the scalars and offsets on X and Y, and do the transform myself. But WPF has all the information already, and this seems like functionality that might be built-in to the WPF libraries somewhere. So I'm wondering: is there a short and sweet solution? Or do I need to write this myself? EDIT I'm appending my current, not-so-short-and-sweet solution. Its not that bad, but I'd be somewhat suprised if WPF didn't provide this functionality automatically: Point ImgControlCoordsToPixelCoords(Point locInCtrl, double imgCtrlActualWidth, double imgCtrlActualHeight) { if (ImageStretch == Stretch.None) return locInCtrl; Size renderSize = new Size(imgCtrlActualWidth, imgCtrlActualHeight); Size sourceSize = bitmap.Size; double xZoom = renderSize.Width / sourceSize.Width; double yZoom = renderSize.Height / sourceSize.Height; if (ImageStretch == Stretch.Fill) return new Point(locInCtrl.X / xZoom, locInCtrl.Y / yZoom); double zoom; if (ImageStretch == Stretch.Uniform) zoom = Math.Min(xZoom, yZoom); else // (imageCtrl.Stretch == Stretch.UniformToFill) zoom = Math.Max(xZoom, yZoom); return new Point(locInCtrl.X / zoom, locInCtrl.Y / zoom); }

  Read the article

• Explicit behavior with checks vs. implicit behavior

  - by Silviu

  I'm not sure how to construct the question but I'm interested to know what do you guys think of the following situations and which one would you prefer. We're working at a client-server application with winforms. And we have a control that has some fields automatically calculated upon filling another field. So we're having a field currency which when filled by the user would determine an automatic filling of another field, maybe more fields. When the user fills the currency field, a Currency object would be retrieved from a cache based on the string introduced by the user. If entered currency is not found in the cache a null reference is returned by the cache object. Further down when asking the application layer to compute the other fields based on the currency, given a null currency a null specific field would be returned. This way the default, implicit behavior is to clear all fields. Which is the expected behavior. What i would call the explicit implementation would be to verify that the Currency object is null in which case the depending fields are cleared explicitly. I think that the latter version is more clear, less error prone and more testable. But it implies a form of redundancy. The former version is not as clear and it implies a certain behavior from the application layer which is not expressed in the tests. Maybe in the lower layer tests but when the need arises to modify the lower layers, so that given a null currency something else should be returned, i don't think a test that says just that without a motivation is going to be an impediment for introducing a bug in upper layers. What do you guys think?

  Read the article

• Computed width with decimal values in Firefox, but without decimals in Webkit

  - by jävi

  Hello one more time! I have a strange problem working with HTML,CSS in different browsers: Firefox 3.6 and Webkit browsers (Chrome & Safari). My HTML looks like this: <div class="ln-letters"> <a href="#" class="all">ALL</a> <a href="#" class="a">A</a> <a href="#" class="b">B</a> <a href="#" class="c">C</a> </div> And my CSS is... .ln-letters a { font-family: 'Lucida Grande'; font-size:14px; display:block; float:left; padding:0px 7px; border-left:1px solid silver; border-right:none; text-decoration:none; } So as you can guess, each anchor gets a different width depending on its inner text. For example the first element with the text 'ALL' will be bigger (more width) than the others. Now the problem is that in Firefox (using Firebug) I can see that the computed width for the first element is 26.5667px, while in Chrome (using Chrome's developer tools) the computed width for the same element is exactly 27px. Therefore the div.ln-letters ends with different widths in each browser and that is causing me some troubles. Question is: there is any workaround to avoid Firefox computing decimal values? Or the opposite: to force Chrome to compute decimal values? Thank you in advance!

  Read the article

• Making pascal's triangle with mpz_t's

  - by SDLFunTimes

  Hey, I'm trying to convert a function I wrote to generate an array of longs that respresents Pascal's triangles into a function that returns an array of mpz_t's. However with the following code: mpz_t* make_triangle(int rows, int* count) { //compute triangle size using 1 + 2 + 3 + ... n = n(n + 1) / 2 *count = (rows * (rows + 1)) / 2; mpz_t* triangle = malloc((*count) * sizeof(mpz_t)); //fill in first two rows mpz_t one; mpz_init(one); mpz_set_si(one, 1); triangle[0] = one; triangle[1] = one; triangle[2] = one; int nums_to_fill = 1; int position = 3; int last_row_pos; int r, i; for(r = 3; r <= rows; r++) { //left most side triangle[position] = one; position++; //inner numbers mpz_t new_num; mpz_init(new_num); last_row_pos = ((r - 1) * (r - 2)) / 2; for(i = 0; i < nums_to_fill; i++) { mpz_add(new_num, triangle[last_row_pos + i], triangle[last_row_pos + i + 1]); triangle[position] = new_num; mpz_clear(new_num); position++; } nums_to_fill++; //right most side triangle[position] = one; position++; } return triangle; } I'm getting errors saying: incompatible types in assignment for all lines where a position in the triangle is being set (i.e.: triangle[position] = one;). Does anyone know what I might be doing wrong?

  Read the article

• Django Admin Page missing CSS

  - by super9

  I saw this question and recommendation from Django Projects here but still can't get this to work. My Django Admin pages are not displaying the CSS at all. This is my current configuration. settings.py ADMIN_MEDIA_PREFIX = '/media/admin/' httpd.conf <VirtualHost *:80> DocumentRoot /home/django/sgel ServerName ec2-***-**-***-***.ap-**********-1.compute.amazonaws.com ErrorLog /home/django/sgel/logs/apache_error.log CustomLog /home/django/sgel/logs/apache_access.log combined WSGIScriptAlias / /home/django/sgel/apache/django.wsgi <Directory /home/django/sgel/media> Order deny,allow Allow from all </Directory> <Directory /home/django/sgel/apache> Order deny,allow Allow from all </Directory> LogLevel warn Alias /media/ /home/django/sgel/media/ </VirtualHost> <VirtualHost *:80> ServerName sgel.com Redirect permanent / http://www.sgel.com/ </VirtualHost> In addition, I also ran the following to create (I think) the symbolic link ln -s /home/djangotest/sgel/media/admin/ /usr/lib/python2.6/site-packages/django/contrib/admin/media/ UPDATE In my httpd.conf file, User django Group django When I run ls -l in my /media directory drwxr-xr-x 2 root root 4096 Apr 4 11:03 admin -rw-r--r-- 1 root root 9 Apr 8 09:02 test.txt Should that root user be django instead? UPDATE 2 When I enter ls -la in my /media/admin folder total 12 drwxr-xr-x 2 root root 4096 Apr 13 03:33 . drwxr-xr-x 3 root root 4096 Apr 8 09:02 .. lrwxrwxrwx 1 root root 60 Apr 13 03:33 media -> /usr/lib/python2.6/site-packages/django/contrib/admin/media/ The thing is, when I navigate to /usr/lib/python2.6/site-packages/django/contrib/admin/media/, the folder was empty. So I copied the CSS, IMG and JS folders from my Django installation into /usr/lib/python2.6/site-packages/django/contrib/admin/media/ and it still didn't work

  Read the article

• fast similarity detection

  - by reinierpost

  I have a large collection of objects and I need to figure out the similarities between them. To be exact: given two objects I can compute their dissimilarity as a number, a metric - higher values mean less similarity and 0 means the objects have identical contents. The cost of computing this number is proportional to the size of the smaller object (each object has a given size). I need the ability to quickly find, given an object, the set of objects similar to it. To be exact: I need to produce a data structure that maps any object o to the set of objects no more dissimilar to o than d, for some dissimilarity value d, such that listing the objects in the set takes no more time than if they were in an array or linked list (and perhaps they actually are). Typically, the set will be very much smaller than the total number of objects, so it is really worthwhile to perform this computation. It's good enough if the data structure assumes a fixed d, but if it works for an arbitrary d, even better. Have you seen this problem before, or something similar to it? What is a good solution? To be exact: a straightforward solution involves computing the dissimilarities between all pairs of objects, but this is slow - O(n2) where n is the number of objects. Is there a general solution with lower complexity?

  Read the article

• 3x3 Sobel operator and gradient features

  - by pithyless

  Reading a paper, I'm having difficulty understanding the algorithm described: Given a black and white digital image of a handwriting sample, cut out a single character to analyze. Since this can be any size, the algorithm needs to take this into account (if it will be easier, we can assume the size is 2^n x 2^m). Now, the description states given this image we will convert it to a 512-bit feature (a 512-bit hash) as follows: (192 bits) computes the gradient of the image by convolving it with a 3x3 Sobel operator. The direction of the gradient at every edge is quantized to 12 directions. (192 bits) The structural feature generator takes the gradient map and looks in a neighborhood for certain combinations of gradient values. (used to compute 8 distinct features that represent lines and corners in the image) (128 bits) Concavity generator uses an 8-point star operator to find coarse concavities in 4 directions, holes, and lagrge-scale strokes. The image feature maps are normalized with a 4x4 grid. I'm for now struggling with how to take an arbitrary image, split into 16 sections, and using a 3x3 Sobel operator to come up with 12 bits for each section. (But if you have some insight into the other parts, feel free to comment :)

  Read the article

• Bitwise Interval Arithmetic

  - by KennyTM

  I've recently read an interesting thread on the D newsgroup, which basically asks, Given two signed integers a ∈ [amin, amax], b ∈ [bmin, bmax], what is the tightest interval of a | b? I'm think if interval arithmetics can be applied on general bitwise operators (assuming infinite bits). The bitwise-NOT and shifts are trivial since they just corresponds to -1 − x and 2n x. But bitwise-AND/OR are a lot trickier, due to the mix of bitwise and arithmetic properties. Is there a polynomial-time algorithm to compute the intervals of bitwise-AND/OR? Note: Assume all bitwise operations run in linear time (of number of bits), and test/set a bit is constant time. The brute-force algorithm runs in exponential time. Because ~(a | b) = ~a & ~b and a ^ b = (a | b) & ~(a & b), solving the bitwise-AND and -NOT problem implies bitwise-OR and -XOR are done. Although the content of that thread suggests min{a | b} = max(amin, bmin), it is not the tightest bound. Just consider [2, 3] | [8, 9] = [10, 11].)

  Read the article

• Posting xml from classic asp to asp.net

  - by Chris Dunaway

  I apologize if this has been asked before. I searched and didn't find anything that matched my situation. Also bear in mind I am fairly new to asp/asp.net development. My current project is a relatively simple e-commerce site. The customer will connect to the site, select products, input shipping and billing information, payment information (credit card) and submit the order. The project is being split into two parts: The store front which includes displaying the items and taking the customer's shipping and billing information and the payment site which will collect the customers credit card, compute tax, and save the order into the company's system. The reason that the site was split up, was that our side (payment side) already has facilities for credit card handling and tax computation. There may also be some regulatory issues that the store front side does not want to deal with (which we already do). I'm working on the payment portion of the app and I am using asp.net. The store front side is being written in classic asp (not my decision). Each part will be hosted on different servers. The problem I am having is transferring the contents of the "shopping cart" to our app so that we can collect the cc info and submit the order. We had thought that the classic asp could somehow post an xml fragment which contains the billing/shipping info and the items selected. Our side would display a summary of the order, securely collect the credit card info, and submit the order to our system. But I have been unable to post or send the xml from a classic asp on one server, to our asp.net application on another. It all works just fine when I test on the same server. How can I post (or otherwise transfer) the shopping cart data from classic asp to asp.net across server boundaries and transfer control to the asp.net application? As I said, I am new to web development, so this is proving quite a challenge for me. Thanks

  Read the article

• Static Data Structures on Embedded Devices (Android in particular)

  - by Mark

  I've started working on some Android applications and have a question regarding how people normally deal with situations where you have a static data set and have an application where that data is needed in memory as one of the standard java collections or as an array. In my current specific issue i have a spreadsheet with some pre-calculated data. It consists of ~100 rows and 3 columns. 1 Column is a string, 1 column is a float, 1 column is an integer. I need access to this data as an array in java. It seems like i could: 1) Encode in XML - This would be cpu intensive to decode in my experience. 2) build into SQLite database - seems like a lot of overhead for static access to data i only need array style access to in ram. 3) Build into binary blob and read in. (never done this in java, i miss void *) 4) Build a python script to take the CSV version of my data and spit out a java function that adds the values to my desired structure with hard coded values. 5) Store a string array via androids resource mechanism and compute the other 2 columns on application load. In my case the computation would require a lot of calls to Math.log, Math.pow and Math.floor which i'd rather not have to do for load time and battery usage reasons. I mostly work in low power embedded applications in C and as such #4 is what i'm used to doing in these situations. It just seems like it should be far easier to gain access to static data structures in java/android. Perhaps I'm just being too battery usage conscious and in my single case i imagine the answer is that it doesn't matter much, but if every application took that stance it could begin to matter. What approaches do people usually take in this situation? Anything I missed?

  Read the article

• Two strange efficiency problems in Mathematica

  - by Jess Riedel

  FIRST PROBLEM I have timed how long it takes to compute the following statements (where V[x] is a time-intensive function call): Alice = Table[V[i],{i,1,300},{1000}]; Bob = Table[Table[V[i],{i,1,300}],{1000}]^tr; Chris_pre = Table[V[i],{i,1,300}]; Chris = Table[Chris_pre,{1000}]^tr; Alice, Bob, and Chris are identical matricies computed 3 slightly different ways. I find that Chris is computed 1000 times faster than Alice and Bob. It is not surprising that Alice is computed 1000 times slower because, naively, the function V must be called 1000 more times than when Chris is computed. But it is very surprising that Bob is so slow, since he is computed identically to Chris except that Chris stores the intermediate step Chris_pre. Why does Bob evaluate so slowly? SECOND PROBLEM Suppose I want to compile a function in Mathematica of the form f(x)=x+y where "y" is a constant fixed at compile time (but which I prefer not to directly replace in the code with its numerical because I want to be able to easily change it). If y's actual value is y=7.3, and I define f1=Compile[{x},x+y] f2=Compile[{x},x+7.3] then f1 runs 50% slower than f2. How do I make Mathematica replace "y" with "7.3" when f1 is compiled, so that f1 runs as fast as f2? Many thanks!

  Read the article

• Execution time in nano seconds and related issues

  - by anup

  Hi All, I am using the following code to compute execution time in milli-secs. struct timespec tp; if (clock_gettime (CLOCK_REALTIME, &tp) == 0) return ((tp.tv_sec * 1000000000) + tp.tv_nsec); else return ; Can you please tell me whether this is correct? Let's name this function comptime_nano(). Now, I write the following code in main() to check execution times of following operations. unsigned long int a, b, s1, s3; a = (unsigned long int)(1) << 63; b = (unsigned long int)(1) << 63; btime = comptime_nano(); s1 = b >> 30; atime = comptime_nano(); printf ("Time =%ld for %lu\n", (atime - btime), s1); btime = comptime_nano(); s3 = a >> 1; atime = comptime_nano(); printf ("Time =%ld for %lu\n", (atime - btime), s3); To my surprise, the first operation takes about roughly 4 times more time than the second. Again, if I change the relative ordering of these operations, the respective timings change drastically. Please comment...

  Read the article

• Required Working Precision for the BBP Algorithm?

  - by brainfsck

  Hello, I'm looking to compute the nth digit of Pi in a low-memory environment. As I don't have decimals available to me, this integer-only BBP algorithm in Python has been a great starting point. I only need to calculate one digit of Pi at a time. How can I determine the lowest I can set D, the "number of digits of working precision"? D=4 gives me many correct digits, but a few digits will be off by one. For example, computing digit 393 with precision of 4 gives me 0xafda, from which I extract the digit 0xa. However, the correct digit is 0xb. No matter how high I set D, it seems that testing a sufficient number of digits finds an one where the formula returns an incorrect value. I've tried upping the precision when the digit is "close" to another, e.g. 0x3fff or 0x1000, but cannot find any good definition of "close"; for instance, calculating at digit 9798 gives me 0xcde6 , which is not very close to 0xd000, but the correct digit is 0xd. Can anyone help me figure out how much working precision is needed to calculate a given digit using this algorithm? Thank you,

  Read the article

< Previous Page | 54 55 56 57 58 59 60 61 62 63 64 65  | Next Page >