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• Is acoustic fingerprinting too broad for one audio file only?

  - by IBG

  We were looking for some topics related to audio analysis and found acoustic fingerprinting. As it is, it seems like the most famous application for it is for identification of music. Enter our manager, who requested us to research and possible find an algorithm or existing code that we can use for this very simple approach (like it's easy, source codes don't show up like mushrooms): Always-on app for listening Compare the audio patterns to a single audio file (assume sound is a simple beep) If beep is detected, send notification to server With a flow this simple, do you think acoustic fingerprinting is a broad approach to use? Should we stop and take another approach? Where to best start? We haven't started anything yet (on the development side) on this regard, so I want to get other opinion if this is pursuit is worth it or moot.

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• "Can't open display" even after access with xhost

  - by Yann

  I'm trying to run a graphical program remotely, without using ssh. I've set the display variable on the server (let's say server.com, Linux, not ubuntu, and no su rights) to point to my workstation (workstation.com, ubuntu 10.04) setenv DISPLAY workstation.com:0 Then on my workstation I've tried both xhost +server.com and xhost + Then I ssh into the server (to test things): ssh [email protected] and try to run xclock, and get the following error: Error: Can't open display: workstation.com:0 I've looked at /etc/ssh/ssh_config on the workstation and I should be forwarding correctly: X11Forwarding yes. How do I go about troubleshooting this? What logs on the workstation document these failed attempts? To explain why I'm doing this: I want to run a batch job on a server to debug an MPI-based parallel program. I want to run xterm as the batch job executable, per the instructions provided by the system admins. This setup use to work. I reinstalled things on my workstation and since then I frequently get one-time message along the lines The authenticity of host 'hostname (XXX.XXX.XXX.XX)' can't be established. My attempt to fix the above was to move my ~/.ssh/known_hosts file to a back up on both server and host, and then to ssh from each to the other with the flag -o StrictHostKeyChecking=no. I no longer get that message, but I was wondering does this play a part in why X11 forwarding is not working?

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• How do I keep a 3D model on the screen in OpenGL?

  - by NoobScratcher

  I'm trying to keep a 3D model on the screen by placing my glDrawElement functions inside the draw function with the declarations at the top of .cpp. When I render the model, the model attaches it self to the current vertex buffer object. This is because my whole graphical user interface is in 2D quads except the window frame. Is there a way to avoid this from happening? or any common causes of this? Creating the file object: int index = IndexAssigner(1, 1); //make a fileobject and store list and the index of that list in a c string ifstream file (list[index].c_str() ); //Make another string //string line; points.push_back(Point()); Point p; int face[4]; Model rendering code: int numfloats = 4; float* point=reinterpret_cast<float*>(&points[0]); int num_bytes=numfloats*sizeof(float); cout << "Size Of Point" << sizeof(Point) << endl; GLuint vertexbuffer; glGenVertexArrays(1, &vao[3]); glGenBuffers(1, &vertexbuffer); glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer); glBufferData(GL_ARRAY_BUFFER, points.size()*sizeof(points), points.data(), GL_STATIC_DRAW); glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, num_bytes, &points[0]); glEnableClientState(GL_VERTEX_ARRAY); glVertexPointer(3, GL_FLOAT, points.size(), &points[0]); glEnableClientState(GL_INDEX_ARRAY); glIndexPointer(GL_FLOAT, faces.size(), faces.data()); glEnableVertexAttribArray(0); glDrawElements(GL_QUADS, points.size(), GL_UNSIGNED_INT, points.data()); glDrawElements(GL_QUADS, faces.size(), GL_UNSIGNED_INT, faces.data());

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• Twitter Customer Sentiment Analysis

  - by Liam McLennan

  The breakable toy that I am currently working on is a twitter customer sentiment analyser. It scrapes twitter for tweets relating to a particular organisation, applies a machine learning algorithm to determine if the content of tweet is positive or negative, and generates reports of the sentiment data over time, correlated to dates, events and news feeds. I’m having lots of fun building this, but I would also like to learn if there is a market for quantified sentiment data. So that I can start to show people what I have in mind I have created a mockup of the simplest and most important report. It shows customer sentiment over time, with important events highlighted. As the user moves their mouse to the right (forward in time) the source data area scrolls up to display the tweets from that time. The tweets are colour coded based on sentiment rating. After I started working on this project I discovered that a team of students have already built something similar. It is a lot of fun to enter your employers name and see what it says.

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• What is the logic behind this C Program?

  - by iamanimesh19

  Here is a small piece of program (14 lines of program) which counts the number of bits set in a number. Input-Output -- 0--0(0000000), 5--2(0000101), 7--3(0000111) int CountBits (unsigned int x) { static unsigned int mask[] = { 0x55555555, 0x33333333, 0x0F0F0F0F, 0x00FF00FF, 0x0000FFFF } ; int i ; int shift ; /* Number of positions to shift to right*/ for (i =0, shift =1; i < 5; i ++, shift *= 2) x = (x & mask[i ])+ ( ( x >> shift) & mask[i]); return x; } Can someone explain the algorithm used here/why this works?

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• Interview question ranking FizzBuzz (1), implementing malloc (10)

  - by blrs

  I'd like to have your opinion on the difficulty of the following interview question: Find the subarray with maximum sum in an array of integers in O(n) time. This trivial sounding problem was made famous by Jon Bentley in his Programming Pearls where he uses it to demonstrate algorithm design techniques. On a scale of 1-10, 1 being the FizzBuzz (or HoppityHop) test and 10 being implement the C stdlib function malloc(), how would you rank the above problem? I think the people who can best answer this question are those who have read Programming Pearls and have tried to solve this problem on their own. To motivate those who haven't, 'Programming Pearls' gets featured many times in the 'Top 10 programming books' list.

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• Implementing ASP.NET 4.0 Page.MetaDescription Property

  Before ASP.NET 4.0, you had to manually code your meta description tags. The meta description tag, though no longer used by major search engines in their ranking algorithm, is still an important factor for increasing website traffic. Bear in mind that searchers coming from search engines (such as Google) will only click on the results provided if the meta description is relevant to the query. If you want to increase your organic traffic (traffic coming from search engines) then one thing that you can easily improve are the meta descriptions. In ASP.NET 4.0, this can be easily implemented using...

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• Developing an AI opponent for Monopoly

  - by Bernhard Zürn

  i want to develop an AI opponent for the Board Game Monopoly. I want to implement the whole Game with Prolog (XPCE). The probability for a field on the Board being hit, can be computed with Markov Chains. I already know some "best practices" like "after 50% of the playing time it does not make sense to buy out of jail because in jail you get renting fees for your fields but you don't have to pay for other fields as long as you stay in prison". The interesting question always is: buy a streetfield ? buy houses / hotels ? how much ? so i think i would have to compute some kind of future liquidity .. does anyone know how to pack that into an algorithm or how to translate it to prolog ?

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• How to tile multiple procedurally generated textures?

  - by Burhuc

  I'm trying to develop a procedural tile generator for a game, mostly for the ground tiles, instead of using "hand-drawn" tiles. To achieve this I'm using Perlin noise and a sine wave with multiple parameters, which already gives me pretty nice results. I don't want to generate 1 tile and repeat that one forever for one ground type, but I want to avoid recurrences, so I'm generating n different tiles. The problem I'm having now is that I want to tile the generated textures (smooth transitions). At the moment I have this: 4 256x256 textures. I thought a simple method would be to just add the positions of the different tiles to the noise generation algorithm, so that, when creating the 4 256x256 textures, it would behave like it would create a 512x512 texture, but that somehow didn't work as intented. So how can I tile those textures?

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• Map, Set use cases in a general web app

  - by user2541902

  I am currently working on my own Java web app (to be shown in interview to get a Java job). So I've not worked on Java in professional environment, so no guidance. I have database, entity classes, JPA relationships. Use cases are like, user has albums, album has pics, user has locations, location has co-ordinates etc. I used List (ArrayList) everywhere. I can do anything with List and DB, get some entry, find etc. For example, I will keep the list of users in List, then use queries to get some entry (why would I keep them in Map with id/email as key?). I know very well the working and features, implementing classes of Map, Set. I can use them for solving some algorithm, processing some data etc. In interviews, I get asked have you worked with these, where have you used them etc. So, Please tell me cases where they should be used (DB or any popular real use case).

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• Algorithms for positioning rectangles evenly spaced with unknown connecting lines

  - by MacGyver

  I'm new to game development, but I'm trying to figure out a good algorithm for positioning rectangles (of any width and height) in a given surface area, and connecting them with any variation of lines. Two rectangles will never have more than one line connecting them. Where would I begin working on a problem like this? This is only a 2 dimensional surface. I read about graph theory, and it seems like this is a close representation of that. The rectangles would be considered a node, and the lines connecting them would be considered an edge in graph theory.

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• Whole continent simulation [on hold]

  - by user2309021

  Let's suppose I am planning to create a simulation of an entire continent at some point in the past (let's say, around 0 A.D). Is it feasible to spawn a hundred million actors that interact with each other and their environments? Having them reproduce, extract resources, etc? The fact is that I actually want to create a simulation that allows me to zoom in from a view of the entire continent up to a single village, and interact with it. (Think as if you could keep zooming in the campaign map of any Total War game and the transition to the battle map was seamless, not a change of the "game mode"). By the way, I have never made a game in my entire life (I have programmed normal desktop applications, though), so I am really having trouble wrapping my head around how to implement such a thing. Even while thinking about how to implement a simple population simulator, without a graphical interface, I think that the O(n) complexity of traversing an array and telling all people to get one year older each time the program ticks is kind of stupid. Any kind help would be greatly appreciated :) EDIT: After being put on hold, I shall specify a question. How would you implement a simulation of all basic human dynamics (reproduction, resource consumption) in an entire continent (with millions of people)?

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• Optimization of time-varying parameters

  - by brama

  I need to find an optimal set of "n" parameter values that minimize an objective function (a 2-hr simulation of a system). I have looked at genetic algorithm and simulated annealing methods, but was wondering if there are any better algorithms and guidance on their merits and limitations. With the above optimization methods I can find the optimal parameter values that hold true for the entire simulation duration. Incase, I want to find the optimal "time varying" parameter values (parameter values change with time during the 2-hr simulation), are there any methods/ideas other than making each time varying parameter value a variable to optimize? Any thoughts?

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• How to make my sprite jump properly?

  - by Matthew Morgan

  I'm currently working on a 2D platformer in XNA. I have, however been having some trouble with creating a fully functional jumping algorithm. This is what I have so far: if (keystate.IsKeyDown(Keys.W)) if (onGround = true) //"onground" is true when the collision between the main sprite and the ground is detected { spritePosition.Y = velocity.Y = -5; } So, the problem I am now having is that as soon as the jump starts the variable "onGround" = false and the sprite is brought back the ground by the simple gravity I have implemented. The other problem I have is creating a limit to the height after which the sprite should automatically return to the ground. Any advice or suggestions would be greatly appreciated.

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• What is the program "Additional Drivers" (jockey-gtk) talking me about?

  - by Robert Vila

  The program says: "No proprietary drivers are in use on this system" But it doesn't say if it is talking about graphical drivers only or what. Then, it lists two drivers: NVIDIA accelerated graphics driver (version 173). NVIDIA accelerated graphics driver (version current) [recomended] Both have exactly the same description. What is the difference then? When I select the 1st one, it says: "This river is not activated",and there's a button to "activate" it. When I select the 2nd one, it says: "This river is activated but it is not currently in use", and the button is to "remove". So which one is in use? Why or what for should I have activated (enabled) and not in use? If it is in use it is activated? What is the difference between activate and remove? and what is the relationship between installed, activated, in use, enabled and removed, disabled, inactive and not-installed? Why can I activate the inactivated and remove (but not deactivate) the activated that is not in use? All this is very puzzling... What other drivers can I use for an Apple MacBook pro 3,1 and how? I see that there's a nouveau and I heard that there was going to be a new open source even better. > -display > description: VGA compatible controller > product: G84 [GeForce 8600M GT] > vendor: nVidia Corporation

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• View space lighting in deferred shading

  - by kochol

  I implemented a simple deferred shading renderer. I use 3 G-Buffer for storing position (R32F), normal (G16R16F) and albedo (ARGB8). I use sphere map algorithm to store normals in world space. Currently I use inverse of view * projection matrix to calculate the position of each pixel from stored depth value. First I want to avoid per pixel matrix multiplication for calculating the position. Is there another way to store and calculate position in G-Buffer without the need of matrix multiplication Store the normal in view space Every lighting in my engine is in world space and I want do the lighting in view space to speed up my lighting pass. I want an optimized lighting pass for my deferred engine.

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• Bomb timer adventure game win32 c++ [on hold]

  - by user3491746

  I'm working on an adventure game in win32 and opengl for my 2nd year university project for class. I am pretty much finished my game but I'm stuck on the concept of how to program a timer which outputs hh : mm : ss -- but which countdown, not up. I've made a clock which counts up using vector matrices and the segxseg matrix algorithm but I cannot figure out how to make a clock (it can be simple even text using wsprintf) that counts down in that format. Can anyone possible give me an example or some literature that I can read on how to do this? Please dont suggest for me to use another environment, I've already been working here for 2 months on this game, and I'm pretty much done so i'm at no point to switch over. Can anyone show me how I can take a shot at this component of my project? Thanks a bunch! Anything that I can get is appreciated.

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• What classes are useful for an aspiring software developer? [closed]

  - by Anonymouse

  I'm a freshman in college trying to graduate in 3 years with a Math/CS dual major, and I don't have a lot of time to be fooling around with useless classes. I've tested out of most of my gen eds and science-y courses, but I need to know: what math and cs courses are most important for someone interested in algorithm development? Math courses already taken: Calc I-III,Linear Algebra, Discrete Math. CS courses taken: Java. Math courses I'm planning to take: ODE, Linear Algebra II, Vector calc, Logic, (Analysis or Algebra), Stats, probability CS courses I'm planning to take: C(required), Data Structures, Numerical Methods, Intro to Analysis of Algorithms. Which is better, analysis or algebra? Did I take enough CS courses? Am I missing out on anything? Thanks.

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• How do I balance program CPU reverse compatibility whist still being able to use cutting edge features?

  - by TheLQ

  As I learn more about C and C++ I'm starting to wonder: How can a compiler use newer features of processors without limiting it just to people with, for example, Intel Core i7's? Think about it: new processors come out every year with lots of new technologies. However you can't just only target them since a significant portion of the market will not upgrade to the latest and greatest processors for a long time. I'm more or less wondering how this is handled in general by C and C++ devs and compilers. Do compilers make code similar to if SSE is supported, do this using it, else do that using the slower way or do developers have to implement their algorithm twice, or what? More or less how do you release software that takes advantage of newer processor technologies while still keeping a low common denominator?

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• Petstore using Java EE 6 ? Almost!

  - by arungupta

  Antonio Goncalves, a Java Champion, JUG leader, and a well-known author, has started building a Petstore-like application using Java EE 6. The complete end-to-end sample application will build a eCommerce website and follows the Java EE 6 design principles of simple and easy-to-use to its core. Its using several technologies from the platform such as JPA 2.0, CDI 1.0, Bean Validation 1.0, EJB Lite 3.1, JSF 2.0, and JAX-RS 1.1. The two goals of the project are: • use Java EE 6 and just Java EE 6 : no external framework or dependency • make it simple : no complex business algorithm The application works with GlassFish and JBoss today and there are plans to add support for TomEE. Download the source code from github.com/agoncal/agoncal-application-petstore-ee6. And feel free to fork if you want to use a fancy toolkit as the front-end or show some nicer back-end integration. Some other sources of similar end-to-end applications are: • Java EE 6 Tutorial • Java EE 6 Galleria • Java EE 6 Hands-on Lab

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• Can certain system-hungry modules be disabled in Ubuntu?

  - by Ole Thomsen Buus

  Hi, Let me add some context: I am currently using Ubuntu 9.10 64-bit (Desktop) on a relatively powerful stationary PC (Intel Core i7 920, 12GB ram). My purpose is highspeed imaging with a pointgrey Grashopper machine-vision camera (for research, PhD project). This camera is capable of 200 fps at full VGA (640x480) resolution. The camera is connected using Firewire (1394b) and the drivers and software from Pointgrey works great. I have developed a console C++ application that can grap a certain number of frames to preallocated memory and after this also save the grapped frames to harddrive. Currently it works fine but sometimes I am observing a few framedrops (1-3). When this happens I reset the experiment and repeat the recording and usually i am lucky the second time with no framedrops (the camera-driver has a internal framecounter that I am using). Question: I usually go to tty1 and use "sudo service gdm stop" to disable the graphical frontend. It seems to release some memory though that is not my main concern. My concern is CPU resources. Are there other system hungry modules that can be disabled temporarily such that the CPU gets less busy on Ubuntu 9.10? At some point in the future I will update to 10.10. Should I perhaps option for the server edition instead? Thanks.

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• Generating HTML Help files based on XML documentation

  - by geekrutherford

  Since discovering the XML commenting features built into .NET years ago I have been using it to help make my code more readable and simpler for other developers to understand exactly what the code is doing. Entering /// preceding a line of code causes Visual Studio to insert "summary" tags.  It also results in additional tags being generated if you are commenting a method with parameters and a return type. I already knew that Intellisense would pick up these comments and display them when coding and selecting properties, methods, etc. from a class.  I also knew that you could set Visual Studio to generate an XML file containing said comments.  Only recently did I begin to wonder if I could generate some kind of readable help files based on these comments I so diligently added. After searching the web I came across NDoc, an open source project which creates documentation for you based on the XML files generated by Visual Studio.  Unfortunately, NDoc has become stale and no longer supported (last release was back in 2005). Fortunately there is a little known tool from Microsoft themselves called "Sandcastle Help File Builder".  This nifty little tool gives you a graphical interface that allows you to specify multiple DLL and XML files from which to generate a MSDN like HTML Help File for your own projects! You can check it out here: http://shfb.codeplex.com/ If you are curious how to set Visual Studio to generate the above reference XML documentation files simply go to your projects property page and edit as shown below (my paths are specific, you can leave yours at the default values):

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• Removing surrounding noises from voice recording

  - by Peak Reconstruction Wavelength

  I have a wave file whose frequency spectrum looks like this. http://i.stack.imgur.com/2rRaS.png It contains audio, which I want to keep while removing the rest. The problem is that the surround noise changes, just those distinct voice patterns remain. I marked the voice patterns for clarity: http://i.stack.imgur.com/eLkBl.png What could an algorithm look like / a workflow in adobe audition look like that removes everything but the voice patterns? I think that the main characteristic is the line-shaped form over time. Loudness alone is not enough as the noise is loud aswell.

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• Good books or tutorials on building projects without an IDE?

  - by CodexArcanum

  While I'm certainly under no illusions that building software without an IDE is possible, I don't actually know much about doing it well. I've been using graphical tools like Visual Studio or Code::Blocks so long that I'm pretty well lost without them. And that really stinks when I want to change environments or languages. I couldn't really do anything in D until someone made a Visual Studio plugin, and now that I'm trying to do more development on Mac, I can't use D again because the XCode plugins don't work. I'm sick of being lost when I see a .make file and having no idea what I'm supposed to do with a folder full of source files. People can't be compiling them one by one using the console and then linking them one by one. You'd spend more time typing file names than code. So what are the automation and productivity tools of the non-IDE user? How do you manage a project when you're writing all the code in emacs or vim or nano or whatever? I would love it if there was a book or a guide online that spells some of this out.

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• What is the R Language?

  - by TATWORTH

  I encountered the R Language recently with O'Reilly books and while from the context I knew it was a language for dealing with statistics, doing a web search for the support web site was futile. However I have now located the web site and it is at http://www.r-project.org/R is a free language available for a number of platforms including windows. CRAN mirrors are available at a number of locations worldwide.Here is the official description:"R is a language and environment for statistical computing and graphics. It is a GNU project which is similar to the S language and environment which was developed at Bell Laboratories (formerly AT&T, now Lucent Technologies) by John Chambers and colleagues. R can be considered as a different implementation of S. There are some important differences, but much code written for S runs unaltered under R. R provides a wide variety of statistical (linear and nonlinear modelling, classical statistical tests, time-series analysis, classification, clustering, ...) and graphical techniques, and is highly extensible. The S language is often the vehicle of choice for research in statistical methodology, and R provides an Open Source route to participation in that activity. One of R's strengths is the ease with which well-designed publication-quality plots can be produced, including mathematical symbols and formulae where needed. Great care has been taken over the defaults for the minor design choices in graphics, but the user retains full control. R is available as Free Software under the terms of the Free Software Foundation's GNU General Public License in source code form. It compiles and runs on a wide variety of UNIX platforms and similar systems (including FreeBSD and Linux), Windows and MacOS."

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