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  • How to solve linear recurrences involving two functions?

    - by Aditya Bahuguna
    Actually I came across a question in Dynamic Programming where we need to find the number of ways to tile a 2 X N area with tiles of given dimensions.. Here is the problem statement Now after a bit of recurrence solving I came out with these. F(n) = F(n-1) + F(n-2) + 2G(n-1), and G(n) = G(n-1) + F(n-1) I know how to solve LR model where one function is there.For large N as is the case in the above problem we can do the matrix exponentiation and achieve O(k^3log(N)) time where k is the minimum number such that for all km F(n) does not depend on F(n-k). The method of solving linear recurrence with matrix exponentiation as it is given in that blog. Now for the LR involving two functions can anyone suggest an approach feasible enough for large N.

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  • Banshee won't sync OGG format to my iphone

    - by Daze
    I have a jailbroken iphone 3g with 16 gigs of memory and I've been putting my music on it from banshee lately and have been having almost no issue. Unfortunately, I just added a few albums to my Banshee library and tried to sync them to my iphone, but every time I try, i see a hundred or so errors saying that the device doesn't support the ogg format and there was no converter found. I'm still pretty much a newb at this stuff, so please help me and dumb down your answer. I'm running 12.04 and again, using an iphone 3g with no sim card, but it's been jailbroken and is used primarily for it's music function.

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  • How to Create Reports in Microsoft Access 2010

    Reports are great ways to present information to parties who want to see relevant data in an organized format that can be easily analyzed. Microsoft Access 2010 allows you to create reports that not only make data more digestible, but also more presentable thanks to their professional look. A report's function comes from its ability to pull in or extract information from single or multiple tables or queries. It could be considered similar to a query in this sense, but what sets it apart is the way in which it presents the information in an easy to use format that you can define to fit your n...

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  • Creating a 2D Line Branch (Part 2)

    - by Danran
    Yesterday i asked this question on how to create a 2D line branch; Creating a 2D Line Branch And thanks to the answered provided, i now have this nice looking main branch; *coloured to show the different segments in the final item. Now is the time now to branch things off as discussed in the article; http://drilian.com/2009/02/25/lightning-bolts/ Again however i am confused as to the meaning of the following pseudo code; splitEnd = Rotate(direction, randomSmallAngle)*lengthScale + midPoint; I'm unsure how to actually rotate this correctly. In all honesty i'm abit unsure what to-do completely at this part, "splitEnd" will be a Vector3, so whatever happens in the rotate function must then return some form of directional rotation which is then * by a scale to create length and then added to the midPoint. I'm not sure. If someone could explain what i'm meant to be doing in this part that would be really grateful.

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  • MEF to the rescue in Task-it

    One of the frameworks that I chose to leverage in the development of my Silverlight 4 Task-It application is MEF, the Managed Extensibility Framework. Actually, that decision came while I was at a Silverlight Deep Dive session on the Microsoft campus in Redmond, WA, and came at the recommendation of John Papa (Microsoft Silverlight Evangelist) and Glenn Block (the MEF Maniac). If you are not familiar with MEF, its primary function is to provide a framework for extensibility in Silverlight applications, however, what I found is that MEF's capabilities go beyond just this. As a matter of fact, Microsoft announced at MIX this week that its new Silverlight Analytics Framework would use MEF for composition. You can read about Telerik's support for this new framework here: Telerik is First to Announce Support for Microsoft Silverlight Analytics Framework MEF used to be just one of many frameworks out there that could ...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • How is this recursion properly working when it is iterated through [on hold]

    - by Rakso Zrobin
    Here is my code right now: hasht= {"A":["B", "D", "E"], "B":["C"], "C":["D", "E"], "D":["C", "E"], "E":["B"]} paths=[] def recusive(start, finish, started=true): if start==finish and !started: return start else: for i in hasht[start]: path= start+ recusive(i,finish,false) paths.append(path) print (recusive("C","C",1)) print paths # [CDC, CDEBC, CEBC] I am trying to generate a table like the one on the bottom, but am running into the problem of the string and the array not being able to concatenate. When I just return however, it returns CDC and works, however, exiting the function as return is meant to do. I am wondering how I can improve my code here to (1) make it work, (2) why my logic was faulty. For example, I understand that it generates say [DC], but I am confused as to how to go around that. perhaps index the value returned?

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  • What are the pros and cons of a non-fixed-interval update loop?

    - by akonsu
    I am studying various approaches to implementing a game loop and I have found this article. In the article the author implements a loop which, if the processing falls behind in time, skips frame renderings and just updates the game in a loop (the last variant called "Constant Game Speed independent of Variable FPS"). I do not understand why it is acceptable to call update_game() in a loop without making sure the update function is called at a particular interval. I do not see any value in doing this. I would think that in my game I want to be sure the game is updated periodically with a known period. So maybe it is worthwhile to have two threads, one would call update periodically, and the other one would redraw the game, also periodically? Would this be a good and practical approach? Of course I would need to synchronise the threads.

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  • How to document and teach others "optimized beyond recognition" computationally intensive code?

    - by rwong
    Occasionally there is the 1% of code that is computationally intensive enough that needs the heaviest kind of low-level optimization. Examples are video processing, image processing, and all kinds of signal processing, in general. The goals are to document, and to teach the optimization techniques, so that the code does not become unmaintainable and prone to removal by newer developers. (*) (*) Notwithstanding the possibility that the particular optimization is completely useless in some unforeseeable future CPUs, such that the code will be deleted anyway. Considering that software offerings (commercial or open-source) retain their competitive advantage by having the fastest code and making use of the newest CPU architecture, software writers often need to tweak their code to make it run faster while getting the same output for a certain task, whlist tolerating a small amount of rounding errors. Typically, a software writer can keep many versions of a function as a documentation of each optimization / algorithm rewrite that takes place. How does one make these versions available for others to study their optimization techniques?

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  • Redirect error in Google Webmaster Tools report

    - by Aurelio De Rosa
    I built a CMS and I used it to create the following website http://www.tkdmontecatini.com . After some days, Google Webmaster Tools started to give me several "Redirect error" on some pages like the follows: http://www.tkdmontecatini.com/it/photogallery http://www.tkdmontecatini.com/it/pagina/9/Informazioni/Corsi/Chi-Siamo http://www.tkdmontecatini.com/it/pagina/2/Informazioni/Eventi/Eventi The funny things are: If I access those links from a browser, it's all right and I've not redirect loops or other similar issues If I use the "Fetch as Googlebot" function, I get a great "Success" result Question: Any idea of why this happens and how can I fix it?

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  • OpenGL Get Rotated X and Y of quad

    - by matejkramny
    I am developing a game in 2D using LWJGL library. So far I have a rotating box. I have done basic Rectangle collision, but it doesn't work for rotated rectangles. Does OpenGL have a function that returns the vertices of rotated rectangle? Or is there another way of doing this using trigonometry? I had researched how to do this and everything I found was using some matrix that I don't understand so I am asking if there is another way of doing this. For clarification, I am trying to find out the true (rotated) X,Y of each point of the rectangle. Let's say, the first point of a rectangle (top,left) has x=10 y=10.. Width and height is 100 pixels. When I rotate the rectangle using glRotatef() the x and y stay the same. The rotation is happening inside OpenGL. I need to extract the x,y of the rectangle so I can detect collisions properly.

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  • Application won't run when installed in "/opt"

    - by Sam Hewitt
    I've developed a program for the App Developer Showdown, with quickly, in python, and it works as expected when I package and install it normally -in /usr. However when packaged for installation in /opt it doesn't run -and I'm not getting (or can't find) an error message of any sort, as to what the problem might be. I was wondering if someone here has the answer. The app does require root access -using gksudo- to function. I'm fairly new to programming, but not to Linux. Thanks, Sam Launchpad: https://launchpad.net/aplomb

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  • State Pattern - should a state know about its context?

    - by Extrakun
    I am referring to the state pattern as described in this link. In the example class diagram, a context has numerous states. However, it does not show how does a state communicates with a context (perhaps an input in a state has impact on a setting in the context). The two examples on the page shows either passing the context to the state via a function, or storing a reference to the context. Are those advisable? Are there other ways for a state to communicate with a context? Update to an edit: For instance, I am doing a remote control which can have several states. Say, the context has a setting for Volume, and I am in one of the states which allow me to tweak the volume. How should the state communicates with the context that the volume is being changed?

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  • Resize images to specific height value in ImageMagick?

    - by Jason
    I've looked around for this, and can't find an easily implemented solution. Currently I'm working on an application that deals with panoramas. As they come out of the batch stitch process, the dimensions average 18000x4000. Using ImageMagick, how can I downscale those images to a specific height value while maintaining aspect ratio? According to the manual, the convert operation takes in both height and width to resize to while maintaining the same aspect ratio. What I'd like is to put in 600 and 1000 in my existing resize script function and have both a regular viewable image as well as a reduced size.

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  • Is there such a thing as having too many private functions/methods?

    - by shovonr
    I understand the importance of well documented code. But I also understand the importance of self-documenting code. The easier it is to visually read a particular function, the faster we can move on during software maintenance. With that said, I like to separate big functions into other smaller ones. But I do so to a point where a class can have upwards of five of them just to serve one public method. Now multiply five private methods by five public ones, and you get around twenty-five hidden methods that are probably going to be called only once by those public ones. Sure, it's now easier to read those public methods, but I can't help but think that having too many functions is bad practice.

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  • how to really master a programming language

    - by cprogcr
    I know that learning a language, you can simply buy a book, follow the examples, and whenever possible try the exercises. But what I'm really looking is how to master the language once you've learned it. Now I know that experience is one major factor, but what about learning the internals of the language, what is the underlying structure, etc. There are articles out there saying read this book, read that book, make this game and that game. But to me this doesn't mean to master a language. I want to be able to read other people's code and understand it, no matter how hard that is. To understand when to use a function and when another, etc etc. The list could go on and on but I believe I've made the point. :) And finally, take whatever language as an example if needed, though best would be if C was taken as an example.

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  • How do I pass vertex and color positions to OpenGL shaders?

    - by smoth190
    I've been trying to get this to work for the past two days, telling myself I wouldn't ask for help. I think you can see where that got me... I thought I'd try my hand at a little OpenGL, because DirectX is complex and depressing. I picked OpenGL 3.x, because even with my OpenGL 4 graphics card, all my friends don't have that, and I like to let them use my programs. There aren't really any great tutorials for OpenGL 3, most are just "type this and this will happen--the end". I'm trying to just draw a simple triangle, and so far, all I have is a blank screen with my clear color (when I set the draw type to GL_POINTS I just get a black dot). I have no idea what the problem is, so I'll just slap down the code: Here is the function that creates the triangle: void CEntityRenderable::CreateBuffers() { m_vertices = new Vertex3D[3]; m_vertexCount = 3; m_vertices[0].x = -1.0f; m_vertices[0].y = -1.0f; m_vertices[0].z = -5.0f; m_vertices[0].r = 1.0f; m_vertices[0].g = 0.0f; m_vertices[0].b = 0.0f; m_vertices[0].a = 1.0f; m_vertices[1].x = 1.0f; m_vertices[1].y = -1.0f; m_vertices[1].z = -5.0f; m_vertices[1].r = 1.0f; m_vertices[1].g = 0.0f; m_vertices[1].b = 0.0f; m_vertices[1].a = 1.0f; m_vertices[2].x = 0.0f; m_vertices[2].y = 1.0f; m_vertices[2].z = -5.0f; m_vertices[2].r = 1.0f; m_vertices[2].g = 0.0f; m_vertices[2].b = 0.0f; m_vertices[2].a = 1.0f; //Create the VAO glGenVertexArrays(1, &m_vaoID); //Bind the VAO glBindVertexArray(m_vaoID); //Create a vertex buffer glGenBuffers(1, &m_vboID); //Bind the buffer glBindBuffer(GL_ARRAY_BUFFER, m_vboID); //Set the buffers data glBufferData(GL_ARRAY_BUFFER, sizeof(m_vertices), m_vertices, GL_STATIC_DRAW); //Set its usage glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex3D), 0); glVertexAttribPointer(1, 4, GL_FLOAT, GL_TRUE, sizeof(Vertex3D), (void*)(3*sizeof(float))); //Enable glEnableVertexAttribArray(0); glEnableVertexAttribArray(1); //Check for errors if(glGetError() != GL_NO_ERROR) { Error("Failed to create VBO: %s", gluErrorString(glGetError())); } //Unbind... glBindVertexArray(0); } The Vertex3D struct is as such... struct Vertex3D { Vertex3D() : x(0), y(0), z(0), r(0), g(0), b(0), a(1) {} float x, y, z; float r, g, b, a; }; And finally the render function: void CEntityRenderable::RenderEntity() { //Render... glBindVertexArray(m_vaoID); //Use our attribs glDrawArrays(GL_POINTS, 0, m_vertexCount); glBindVertexArray(0); //unbind OnRender(); } (And yes, I am binding and unbinding the shader. That is just in a different place) I think my problem is that I haven't fully wrapped my mind around this whole VertexAttribArray thing (the only thing I like better in DirectX was input layouts D:). This is my vertex shader: #version 330 //Matrices uniform mat4 projectionMatrix; uniform mat4 viewMatrix; uniform mat4 modelMatrix; //In values layout(location = 0) in vec3 position; layout(location = 1) in vec3 color; //Out values out vec3 frag_color; //Main shader void main(void) { //Position in world gl_Position = vec4(position, 1.0); //gl_Position = projectionMatrix * viewMatrix * modelMatrix * vec4(in_Position, 1.0); //No color changes frag_color = color; } As you can see, I've disable the matrices, because that just makes debugging this thing so much harder. I tried to debug using glslDevil, but my program just crashes right before the shaders are created... so I gave up with that. This is my first shot at OpenGL since the good old days of LWJGL, but that was when I didn't even know what a shader was. Thanks for your help :)

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  • Junkyard Jumbotron Creates a Massive Display from Multiple Screens

    - by Jason Fitzpatrick
    Junkyard Jumbotron is a web-based service that performs a rather unique function. It allows you to turn any number of screens into a massive collective display for showcasing photos. You’ll need screens of some sort (any will work: old CRT monitors, iPads, cell phones) and a way to get them online. Each screen needs to be able to access the web; Junkyard Jumbotron takes care of the rest. Check out the video above to see it in action or visit the link below to read more. Junkyard Jumbotron [via BoingBoing] Internet Explorer 9 Released: Here’s What You Need To KnowHTG Explains: How Does Email Work?How To Make a Youtube Video Into an Animated GIF

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  • How should I write new code when the old codebase and the environment uses lots of globals in PHP

    - by Nicola Peluchetti
    I'm working in the Wordpress environment which itself heavily relies on globals and the codebase I'm maintaining introduces some more. I want this to change and so I'm trying to think how should I handle this. For the globals our code has introduced I think I will set them as dependencies in the constructor or in getter / setter so that I don't rely on them being globals and then refactor the old codebase little by little so that we have no globals. With Wordpress globals I was thinking to wrap all WP globals inside a Wrapper class and hide them in there. Like this class WpGlobals { public static function getDb() { global $wpdb; return $wpdb; } } Would this be of any help? The idea is that I centralize all globals in one class and do not scatter them through the code, so that if Wordpress kills one of them I need to modify code only in one place. What would you do?

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  • Dash doesn't recognize that application is installed

    - by Calixte
    I've installed Geary from the software center, but I can't launch it from the Dash nor did I manage to create an app icon on the Launcher. The Software center has no problem seeing that the app is installed (see screenshot) Running the command "geary" will launch the app. Is there any way I can force the Dash to function properly? Thanks, Calixte PS: Does anyone know what this problem is related to? I tried re-installing the app and restarting the computer but that has no effect at all. I have practically installed nothing on this computer, so I can't imagine what app could interfere with the Dash

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  • Detecting tile with height in isometric game

    - by Carlos Navarro
    I'm trying to create an isometric tile-based game (for iPhone) and I'm having trouble with height in tiles. What I currently do (without heights) is apply some mathematic transformations to my 2D-matrix (which represent the tiles) so that I know where in the screen (x,y) should I place the isometric tile. Then, when the user clicks somewhere in the screen, I take that values and pass them through a function (kind of f^-1) to get which tile it belongs to. This works perfectly. My problem is: imagine that I want some tiles to have a different height from others. In order to draw the tile itself its pretty simple, since the z-coordinate has no transformation in the isometric approach used in games (z'=z). BUT what if I want to calculate the tile coordinate (defined by X-tile and Y-tile) from the touch coordinates (x,y)? Any guess?

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  • most efficient AABB vs Ray collision algorithms

    - by Asher Einhorn
    Is there a known 'most efficient' algorithm for AABB vs Ray collision detection? I recently stumbled accross Arvo's AABB vs Sphere collision algorithm, and I am wondering if there is a similarly noteworthy algorithm for this. One must have condition for this algorithm is that I need to have the option of querying the result for the distance from the ray's origin to the point of collision. having said this, if there is another, faster algorithm which does not return distance, then in addition to posting one that does, also posting that algorithm would be very helpful indeed. Please also state what the function's return argument is, and how you use it to return distance or a 'no-collision' case. For example, does it have an out parameter for the distance as well as a bool return value? or does it simply return a float with the distance, vs a value of -1 for no collision? (For those that don't know: AABB = Axis Aligned Bounding Box)

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  • How much C/C++ knowledge is needed for Objective-C/iPhone development?

    - by BFree
    First, a little background. I'm a .Net developer (C#) and have over 5 years experience in both web development and desktop applications. I've been wanting to look into iPhone development for some time now, but for one reason or another always got side tracked. I finally have a potential project on the horizon, and I'm now going full steam ahead learning this stuff. My question is this: I haven't done any C/C++ programming since my schooling days, I've been living in managed land ever since. How much knowledge if any is needed to be successful as an iOS developer? Obviously memory management is something that I'll have to be conscious about (although with iOS 5 there seems to be something called ARC which should make my life easier), but what else? I'm not just talking about the C API (for example, in order to get the sin of a number, I call the sin() function), that's what Google is for. I'm talking about fundamental C/C++ idioms that the average C# developer is unaware of.

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  • k-d tree implementation [closed]

    - by user466441
    when i run my code and debugged,i got this error - this 0x00093584 {_Myproxy=0x00000000 _Mynextiter=0x00000000 } std::_Iterator_base12 * const - _Myproxy 0x00000000 {_Mycont=??? _Myfirstiter=??? } std::_Container_proxy * _Mycont CXX0017: Error: symbol "" not found _Myfirstiter CXX0030: Error: expression cannot be evaluated + _Mynextiter 0x00000000 {_Myproxy=??? _Mynextiter=??? } std::_Iterator_base12 * but i dont know what does it means,code is this #include<iostream> #include<vector> #include<algorithm> using namespace std; struct point { float x,y; }; vector<point>pointleft(4); vector<point>pointright(4); //we are going to implement two comparison function for x and y coordinates,we need it in calculation of median (we should sort vector //by x or y according to depth informaton,is depth even or odd. bool sortby_X(point &a,point &b) { return a.x<b.x; } bool sortby_Y(point &a,point &b) { return a.y<b.y; } //so i am going to implement to median finding algorithm,one for finding median by x and another find median by y point medianx(vector<point>points) { point temp; sort(points.begin(),points.end(),sortby_X); temp=points[(points.size()/2)]; return temp; } point mediany(vector<point>points) { point temp; sort(points.begin(),points.end(),sortby_Y); temp=points[(points.size()/2)]; return temp; } //now construct basic tree structure struct Tree { float x,y; Tree(point a) { x=a.x; y=a.y; } Tree *left; Tree *right; }; Tree * build_kd( Tree *root,vector<point>points,int depth) { point temp; if(points.size()==1)// that point is as a leaf { if(root==NULL) root=new Tree(points[0]); return root; } if(depth%2==0) { temp=medianx(points); root=new Tree(temp); for(int i=0;i<points.size();i++) { if (points[i].x<temp.x) pointleft[i]=points[i]; else pointright[i]=points[i]; } } else { temp=mediany(points); root=new Tree(temp); for(int i=0;i<points.size();i++) { if(points[i].y<temp.y) pointleft[i]=points[i]; else pointright[i]=points[i]; } } return build_kd(root->left,pointleft,depth+1); return build_kd(root->right,pointright,depth+1); } void print(Tree *root) { while(root!=NULL) { cout<<root->x<<" " <<root->y; print(root->left); print(root->right); } } int main() { int depth=0; Tree *root=NULL; vector<point>points(4); float x,y; int n=4; for(int i=0;i<n;i++) { cin>>x>>y; points[i].x=x; points[i].y=y; } root=build_kd(root,points,depth); print(root); return 0; } i am trying ti implement in c++ this pseudo code tuple function build_kd_tree(int depth, set points): if points contains only one point: return that point as a leaf. if depth is even: Calculate the median x-value. Create a set of points (pointsLeft) that have x-values less than the median. Create a set of points (pointsRight) that have x-values greater than or equal to the median. else: Calculate the median y-value. Create a set of points (pointsLeft) that have y-values less than the median. Create a set of points (pointsRight) that have y-values greater than or equal to the median. treeLeft = build_kd_tree(depth + 1, pointsLeft) treeRight = build_kd_tree(depth + 1, pointsRight) return(median, treeLeft, treeRight) please help me what this error means?

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  • Keypress Left is called twice in Update when key is pressed only once

    - by Simran kaur
    I have a piece of code that is changing the position of player when left key is pressed. It is inside of Update() function. I know, Update is called multiple times, but since I have an ifstatement to check if left arrow is pressed, it should update only once. I have tested using print statement that once pressed, it gets called twice. Problem: Position updated twice when key is pressed only once. Below given is the structure of my code: void Update() { if (Input.GetKeyDown (KeyCode.LeftArrow)) { print ("PRESSEEEEEEEEEEEEEEEEEEDDDDDDDDDDDDDD"); } } I looked up on web and what was suggested id this: if (Event.current.type == EventType.KeyDown && Event.current.keyCode == KeyCode.LeftArrow) { print("pressed"); } But, It gives me an error that says: Object reference not set to instance of an object How can I fix this?

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  • Getting the masked URL values in Mediawiki

    - by Kalai
    I have successfully masked the URL in Mediawiki. By using the following scripts in .htaccess and localsettings.php files in Mediawiki, i.e.: .htaccess: Options +FollowSymLinks RewriteEngine on RewriteCond %{REQUEST_FILENAME} !-f RewriteCond %{REQUEST_FILENAME} !-d RewriteRule ^(.*)/(.*)$ /mediawiki/index.php?title=$1&actions=$2 [L] Localsettings.php: $wgScriptPath = "/lib/mediawiki"; $wgArticlePath = "/lib/mediawiki/$1/$2"; It is working fine with required URL. But my problem is I want to consider the second parameter as a querystring for my pages. But I could not get the second parameter in my file. I tried with $wgrequest function but it is only giving the first parameter as title. I tried with $_REQUEST also, it is sometimes give the value of $_REQUEST['actions']. But many times not. I cant understand what is the problem.

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