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• What is the best way to exploit multicores when making multithread games?

  - by Keeper

  Many people suggest to write a program, and then start optimizing it. But I think that when it's coming to multithreading with multicore, a little think ahead is required. I've read about using threads, and experienced it myself during some courses at the university (still a student). The big question is simple, but a bit abstract: What thread related steps in game design do I need to take, before implementation? Now trying to be more specific. Let's say, as an example, that I'm making a small board game (like Monopoly) that I want to be multithreaded. My goal Is that this multithreaded game will exploit the best of the multicore system, lets say 4-6 cores (like in i7 processors). My answer to this question at the moment is, one thread for each of these four basic components: GUI User Input / Output AI (computer rival) Other game related calculations (like shortest path from A to B, or level up status change) I'm not an expert (yet!), and I'm sure there are better answers out there. Any suggestion, answer, different approach will be helpful. Some thoughts: Maybe splitting the main database is a good way.. (or total disaster.. )

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• A (slight) Change of Focus

  - by StuartBrierley

  When I started this blog in September 2009 I was working as a BizTalk developer for a financial institution based in the South West of England.  At the time I was developing using BizTalk Server 2004 and intended to use my blog to collate and share any useful information and experiences that I had using this version of BizTalk (and occasionally other technologies) in an effort to bring together as many useful details as I could in one place. Since then my circumstances have changed and I am no longer working in the financial industry using BizTalk 2004.  Instead I have recently started a new post in the logistics industry, in the North of England, as "IT Integration Manager".  The company I now work for has identified a need to boost their middleware/integration platform and have chosen BizTalk Server 2009 as their platform of choice; this is where I come in. To start with my role is to provide the expertise with BizTalk that they currently lack, design and direct the initial BizTalk 2009 implementation and act as lead developer on all pending BizTalk projects.  Following this it is my hope that we will be able to build on the initial BizTalk "proof of concept" and eventually implement a fully robust enterprise level BizTalk 2009 environment. As such, this blog is going to see a shift in focus from BizTalk 2004 to BizTalk 2009 and at least initially is likely to include posts on the design and installation of our BizTalk environment - assuming of course that I have the time to write them! The last post I made was the start of a chapter by chapter look at the book SOA Patterns with BizTalk Server 2009.  Due to my change of job I am currently "paused" half way through this book, and my lack of posts on the subject are directly as a result of the job move and the pending relocation of my family.  I am hoping to write about my overall opinion of this book sometime soon; so far it certainly looks like it will be a positive one. Thanks for reading; I'm off to manage some integration.

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• 3D physics engine for accurate collision handling on desktop/laptop computers (non-console)

  - by Georges Oates Larsen

  What are your suggestions for a physics engine that satisfies the following criteria? Capable of calculating collisions between multiple concave mesh-based colliders Handles many collisions going on at once (for instance one mesh being wedged between two others, which themselves may be wedged between two meshes) Does not allow for collider passthrough, even at high speeds. For instance, if I am applying force to a programmatically hinged object that makes it spin, I do not want it to pass through another rigidbody that it collides with while spinning. I have this problem using PhysX As implied before, reacts well to hinged objects, preferably has its own implementation of a hinge, but I am willing to program my own. The important part is that it has some sort of interface that guarantees accurate collision tracking even when dealing with these things Platform independent -- runs on mac as well as PC, also not tied down to specific graphics cards I think that's the best way to explain what I am looking for. Basically, I need SUPER reliable collisions. Something that can't be accomplished with a simple ray casting approach that sends a ray from the last position of the object to the current position (as this object may be potentially large and colliding with small objects via rotation) Bonus points for also including an OPEN SOURCE engine.

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• How to handle sorting of complex objects?

  - by AedonEtLIRA

  How would one sort a list of objects that have more than one sortable element? Suppose you have a simple object Car and car is a defined as such: class Car { public String make; public String model; public int year; public String color; // ... No methods, just a structure / container } I designed a simple framework that would allow for multiple SortOptions to be provided to a Sorter that would then sort the list. interface ISorter<T> { List<T> sort(List<T> items); void addSortOption(ISortOption<T> option); ISortOption<T>[] getSortOptions(); void setSortOption(ISortOption<T> option); } interface ISortOption<T> { String getLabel(); int compare(T t1, T t2); } Example use class SimpleStringSorter extends MergeSorter<String> { { addSorter(new AlphaSorter()); } private static final class AlphaSorter implements ISortOption<String> { // ... implementation of alpha compare and get label } } The issue with this solution is that it is not easily expandable. If car was to ever receive a new field, say, currentOwner. I would need to add the field, then track down the sorter class file, implement a new sort option class then recompile the application for redistribution. Is there an easier more expandable/practical way to sort data like this?

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• Endeca Information Discovery 3-Day Hands-on Training Boot-Camp

  - by Mike.Hallett(at)Oracle-BI&EPM

  For Oracle Partners, on October 15-17, 2012 in Paris, France: Register here. The Oracle Endeca Information Discovery (OEID) Boot-Camp is designed to give partners an understanding of OEID’s features, and how it complements the existing Oracle Business Intelligence suite. Participants will learn how to develop & implement solutions using a Data Discovery method.  Training is in English. What will be covered? The Oracle Endeca Information Discovery (OEID) Boot Camp is a three-day class with a combination of lecture and hands-on exercises, tailored to make participants aware of the Oracle Endeca Information Discovery platform, and to gain valuable skills for the implementation of projects.   Prerequisites You must bring a laptop with you for the Hands-on labs: Attendees should have experience and familiarity with the basic concepts of business intelligence and be OPN Partners with Gold or above membership.  This training is free to OPN Partners. Click here for more information. Where and When ? Monday, October 15th until Wednesday, October 17th included  9:00 - 18:00 Oracle France 15, boulevard Charles de Gaulle 92715 Colombes: Access Venue Map Register here  : NOTE there is a Limited number of seats, you will get confirmation within 2 weeks.

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• What technical details should a programmer of a web application consider before making the site public?

  - by Joel Coehoorn

  What things should a programmer implementing the technical details of a web application consider before making the site public? If Jeff Atwood can forget about HttpOnly cookies, sitemaps, and cross-site request forgeries all in the same site, what important thing could I be forgetting as well? I'm thinking about this from a web developer's perspective, such that someone else is creating the actual design and content for the site. So while usability and content may be more important than the platform, you the programmer have little say in that. What you do need to worry about is that your implementation of the platform is stable, performs well, is secure, and meets any other business goals (like not cost too much, take too long to build, and rank as well with Google as the content supports). Think of this from the perspective of a developer who's done some work for intranet-type applications in a fairly trusted environment, and is about to have his first shot and putting out a potentially popular site for the entire big bad world wide web. Also, I'm looking for something more specific than just a vague "web standards" response. I mean, HTML, JavaScript, and CSS over HTTP are pretty much a given, especially when I've already specified that you're a professional web developer. So going beyond that, Which standards? In what circumstances, and why? Provide a link to the standard's specification.

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• Challenge Ends on Friday!

  - by Yolande Poirier

  This is your last chance to win a JavaOne trip. Submit a project video and code for the IoT Developer Challenge by this Friday, May 30.  12 JavaOne trips will be awarded to 3 professional teams and one student team. Members of two student teams will win laptops and certification training vouchers. Ask your last minute questions on the coaching form or the Challenge forum. They will be answered promptly. Your project video should explain how your project works. Any common video format such as mp4, avi, mov is fine. Your project must use Java Embedded - whether it is Java SE Embedded or ME Embedded - with the hardware of your choice, including any devices, boards and IoT technology. The project will be judged based on the project implementation, innovation and business usefulness. More details on the IoT Developer Challenge website  Just for fun! Here is a video of Vinicius Senger giving a tour of his home lab, and showing his boards and gadgets. &lt;span id=&quot;XinhaEditingPostion&quot;&gt;&lt;/span&gt;

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• Single-Click Checkbox in RadGridView

  - by Anthony Trudeau

  Originally posted on: http://geekswithblogs.net/tonyt/archive/2014/06/05/156809.aspxThe Telerik RadGridView for WPF is a flexible visual control for displaying and manipulating tables of data. It’s not without it’s quirks though. I ran into one of those quirks recently. The behavior of the RadGridView requires that you first activate the cell for editing. That enables the editing controls underneath. Although that provides better editing capabilities, it also can be unintuitive. In my case I don’t want my users to have to click a checkbox value twice in order to change the value. This can be solved easily by setting the EditTriggers and AutoSelectOnEdit properties to CellClick and True respectively. Unfortunately, the story doesn’t end there. You would think you could set those properties in a style with a TargetType of GridViewCheckBoxColumn. You’d be wrong. <!-- This works --> <telerik:GridViewCheckBoxColumn Header="Flag #1"       DataMemberBinding="{Binding Flag1}"       EditTriggers="CellClick" AutoSelectOnEdit="True"/> <!-- This doesn’t work --> <Style TargetType="{x:Type telerik:GridViewCheckBoxColumn}">       <Setter Property="EditTriggers" Value="CellClick" />       <Setter Property="AutoSelectOnEdit" Value="True" /> </Style> Telerik told me that is the correct, expected behavior, because the columns in the RadGridView are not visual elements. Their explanation is that the Style property comes from the base class FrameworkContentElement, but the column objects aren’t visual elements. That may be an implementation truth, but that doesn’t make the behavior correct or expected. It’s unintuitive that the GridViewCheckBoxColumn exposes a Style property that cannot be used properly, but there it is. At least there’s a way to get the desired effect.

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• Questions before I revamp my rendering engine to use shaders (GLSL)

  - by stephelton

  I've written a fairly robust rendering engine using OpenGL ES 1.1 (fixed-function.) I've been looking into revamping the engine to use OpenGL ES 2.0, which necessitates that I use shaders. I've been absorbing information all day long and still have some questions. Firstly, lighting. The fixed-function pipeline is guaranteed to have at least 8 lights available. My current engine finds lights that are "close" to the primitives being drawn and enables them; I don't know how many lights are going to be enabled until I draw a given model. Nothing is dynamically allocated in GLSL, so I have to define in a shader some number of lights to be used, right? So if I want to stick with 8, should I write my general purpose shader to have 8 lights and then use uniforms to tell it how many / which lights to use? Which brings me to another question: should I be concerned with the amount of data I'm allocating in a shader? Recent video cards have hundreds of "stream processors." If I've got a fragment shader being used on some number of fragments in a given triangle, I assume they must each have their own stack to work on. Are read-only variables copied here, or read when needed? My initial goal is to rework my code so that it is virtually identical to the current implementation. What I have in mind is to create my own matrix stack so that I can implement something along the lines of push/popMatrix and apply all my translations, rotations, and scales to this matrix, then provide the matrix to the vertex shader so that it can make very quick vertex translations. Is this approach sound? Edit: My original intention was to ask if there was a tutorial that would explain the bare minimum necessary to jump from fixed-function to using shaders. Thanks!

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• WCF REST Error Handler

  - by Elton Stoneman

  I’ve put up on GitHub a sample WCF error handler for REST services, which returns proper HTTP status codes in response to service errors.   The code is very simple – a ServiceBehavior implementation which can be specified in config to tag the RestErrorHandler to a service. Any uncaught exceptions will be routed to the error handler, which sets the HTTP status code and description in the response, based on the type of exception.   The sample defines a ClientException which can be thrown in code to indicate a problem with the client’s request, and the response will be a status 400 with a friendly error message:       throw new ClientException("Invalid userId. Must be provided as a positive integer");   - responds:   Request URL http://localhost/Sixeyed.WcfRestErrorHandler.Sample/ErrorProneService.svc/lastLogin?userId=xyz   Error Status Code: 400, Description: Invalid userId. Must be provided as a positive integer   Any other uncaught exceptions are hidden from the client. The full details are logged with a GUID to identify the error, and the response to the client is a status 500 with a generic message giving them the GUID to follow up on:       var iUserId = 0;     var dbz = 1 / iUserId;   - logs the divide-by-zero error and responds:   Request URL http://localhost/Sixeyed.WcfRestErrorHandler.Sample/ErrorProneService.svc/dbz     Error Status Code: 500, Description: Something has gone wrong. Please contact our support team with helpdesk ID: C9C5A968-4AEA-48C7-B90A-DEC986F80DA5   The sample demonstrates two techniques for building the response. For client exceptions, a friendly HTML response is sent in the body as well as the status code and description. Personally I prefer not to do that – it doesn’t make sense to get a 400 error and find text/html when you’re expecting application/json, but it’s easy to do if that’s the functionality you want. The other option is to send an empty response, which the sample does with server exceptions.   The obvious extension is to have multiple exceptions representing all the status codes you want to provide, then your code is as simple as throwing the relevant exception – UnauthorizedException, ForbiddenExeption, NotImplementedException etc – anywhere in the stack, and it will be handled nicely.

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• Should all public methods in an abstract class be marked virtual?

  - by Justin Pihony

  I recently had to update an abstract base class on some OSS that I was using so that it was more testable by making them virtual (I could not use an interface as it combined two). This got me thinking whether I should mark all of the methods that I needed virtual, or if I should mark every public method/property virtual. I generally agree with Roy Osherove that every method should be made virtual, but I came across this article that got me thinking about whether this was necessary or not. I am going to limit this down to abstract classes for simplicity, however (whether all concrete public methods should be virtual is especially debatable, I am sure). I could see where you might want to allow a sub-class to use a method, but not want it overriding the implementation. However, as long as you trust that Liskov's Substitution Principle will be followed, then why would you not allow it to be overriden? By marking it abstract, you are forcing a certain override anyway, so, it seems to me that all public methods inside of an abstract class should indeed be marked virtual. However, I wanted to ask in case there was something I might not be thinking. Should all public methods within an abstract class be made virtual?

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• Floating point undesirable in highly critical code?

  - by Kirt Undercoffer

  Question 11 in the Software Quality section of "IEEE Computer Society Real-World Software Engineering Problems", Naveda, Seidman, lists fp computation as undesirable because "the accuracy of the computations cannot be guaranteed". This is in the context of computing acceleration for an emergency braking system for a high speed train. This thinking seems to be invoking possible errors in small differences between measurements of a moving object but small differences at slow speeds aren't a problem (or shouldn't be), small differences between two measurements at high speed are irrelevant - can there be a problem with small roundoff errors during deceleration for an emergency braking system? This problem has been observed with airplane braking systems resulting in hydroplaning but could this actually happen in the context of a high speed train? The concern about fp errors seems to not be well-founded in this context. Any insight? The fp is used for acceleration so perhaps the concern is inching over a speed limit? But fp should be just fine if they use a double in whatever implementation language. The actual problem in the text states: During the inspection of the code for the emergency braking system of a new high speed train (a highly critical, real-time application), the review team identifies several characteristics of the code. Which of these characteristics are generally viewed as undesirable? The code contains three recursive functions (well that one is obvious). The computation of acceleration uses floating point arithmetic. All other computations use integer arithmetic. The code contains one linked list that uses dynamic memory allocation (second obvious problem). All inputs are checked to determine that they are within expected bounds before they are used.

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• OpenGL doesn't draw (3.3+) [on hold]

  - by Dhiego Magalhães

  Brief: I've been following this tutorial about OpenGL for 2 days, and I still can't have a triangle drawn, so I'm asking for help here. The tutorial is turned to OpenGL version 3.3 programing, using vertex arrays, buffers, etc. The libraries are: GLFW3 and GLEW, and I setted them by myself. The screen keeps black all the time. Full code: link here (It's just like a Hello World opengl program) Further Details: I get no errors at all. I downloaded a software to test my video card, and it supports OpenGL 4.1+ Standard OpenGL code for drawing (from earlier version) such as this one works normally. I'm using Microsoft Visual Studio 10.0 I presume all the OpenGL implementation was dune right: I added Additional Dependences to the linker as glew32.lib, opengl32.lib, glfw3.lib. The glew.dll was placed at SysWOW64 - because I'm running window 64bits, and glew is 32. Notes: I've been working hard to find out what this is, but I can't find. I would appreciate if anyone could test this code for me, so I can know if I implemented something wrong, and that its not my code.

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• Messaging with KnockoutJs

  - by Aligned

  MVVM Light has Messaging that helps keep View Models decoupled, isolated, and keep the separation of concerns, while allowing them to communicate with each other. This is a very helpful feature. One View Model can send off a message and if anyone is listening for it, they will react, otherwise nothing will happen. I now want to do the same with KnockoutJs View Models. Here are some links on how to do this: http://stackoverflow.com/questions/9892124/whats-the-best-way-of-linking-synchronising-view-models-in-knockout http://www.knockmeout.net/2012/05/using-ko-native-pubsub.html ~ this is a great article describing the ko.subscribable type. http://jsfiddle.net/rniemeyer/z7KgM/ ~ shows how to do the subscription https://github.com/rniemeyer/knockout-postbox will be used to help with the PubSub (described in the blog post above) through the Nuget package. http://jsfiddle.net/rniemeyer/mg3hj/ of knockout-postbox   Implementation: Use syncWith for two-way synchronization. MainVM: self.selectedElement= ko.observable().syncWith (“selectedElement”); ElementListComponentVM example: self.selectedElement= ko.observable().syncWith(“selectedElement”); ko.selectedElement.subscribe(function(){ // do something with the seletion change }); ElementVMTwo: self.selectedElement= ko.observable().syncWith (“selectedElement”); // subscribe example ko.postbox.subscribe(“changeMessage”, function(newValue){ }); // or use subscribeTo this.visible = ko.observable().subscribeTo("section", function(newValue) { // do something here }); · Use ko.toJS to avoid both sides having the same reference (see the blog post). · unsubscribeFrom should be called when the dialog is hidden or closed · Use publishOn to automatically send out messages when an observable changes o ko.observable().publishOn(“section”);

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• Software Manager who makes developers do Project Management

  - by hdman

  I'm a software developer working in an embedded systems company. We have a Project Manager, who takes care of the overall project schedule (including electrical, quality, software and manufacturing) hence his software schedule is very brief. We also have a Software Manager, who's my boss. He makes me write and maintain the software schedule, design documents (high and low level design), SRS, change management, verification plans and reports, release management, reviews, and ofcourse the software. We only have one Test Engineer for the whole software team (10 members), and at any given time, there are a couple of projects going on. I'm spending 80% of my time making these documents. My boss comes from a Process background, and believes what we need is better documentation to improve software: (1) He considers the design to be paramount, coding is "just writing the design down", it shouldn't take too long, and "all the code should be written before the hardware is ready". (2) Doesn't understand the difference between a Central & Distributed Version control, even after we told him its easier to collaborate with a distributed model. (3) Doesn't understand code, and wants to understand every bug and its proposed solution. (4) Believes verification should be done by developer, and validation by the Tester. Thing is though, our verification only checks if implementation is correct (we don't write unit tests, its never considered in the schedule), and validation is black box testing, so the units tests are missing. I'm really confused. (1) Am I responsible for maintaining all these documents? It makes me feel like I'm doing the Software Project Management, in essence. (2) I don't really like creating documents, I want to solve problems and write code. In my experience, creating design documents only helps to an extent, its never the solution to better or faster code. (3) I feel the boss doesn't really care about making better products, but only about being a good manager in the eyes of the management. What can I do?

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• Gathering IP address and workstation information; does it belong in a state class?

  - by p.campbell

  I'm writing an enterprisey utility that collects exception information and writes to the Windows Event Log, sends an email, etc. This utility class will be used by all applications in the corporation: web, BizTalk, Windows Services, etc. Currently this class: holds state given to it via public properties calls out to .NET Framework methods to gather information about runtime details. Included are call to various properties and methods from System.Environment, Reflection details, etc. This implementation has the benefit of allowing all those callers not to have to make these same calls themselves. This means less code for the caller to forget, screw up, etc. Should this state class (please what's the phrase I'm looking for [like DTO]?) know how to resolve/determine runtime details (like the IP address and machine name that it's running on)? It seems to me on second thought that it's meant to be a class that should hold state, and not know how to call out to the .NET Framework to find information. var myEx = new AppProblem{MachineName="Riker"}; //Will get "Riker 10.0.0.1" from property MachineLongDesc Console.WriteLine("full machine details: " + myEx.MachineLongDesc); public class AppProblem { public string MachineName{get;set;} public string MachineLongDesc{ get{ if(string.IsNullOrEmpty(this.MachineName) { this.MachineName = Environment.MachineName; } return this.MachineName + " " + GetCurrentIP(); } } private string GetCurrentIP() { return System.Net.Dns.GetHostEntry(this.MachineName) .AddressList.First().ToString(); } } This code was written by hand from memory, and presented for simplicity, trying to illustrate the concept.

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• implementing dynamic query handler on historical data

  - by user2390183

  EDIT : Refined question to focus on the core issue Context: I have historical data about property (house) sales collected from various sources in a centralized/cloud data source (assume info collection is handled by a third party) Planning to develop an application to query and retrieve data from this centralized data source Example Queries: Simple : for given XYZ post code, what is average house price for 3 bed room house? Complex: What is estimated price for an house at "DD,Some Street,XYZ Post Code" (worked out from average values of historic data filtered by various characteristics of the house: house post code, no of bed rooms, total area, and other deeper insights like house building type, year of built, features)? In addition to average price, the application should support other property info ** maximum, or minimum price..etc and trend (graph) on a selected property attribute over a period of time**. Hence, the queries should not enforce the search based on a primary key or few fixed fields In other words, queries can be What is the change in 3 Bed Room house price (irrespective of location) over last 30 days? What kind of properties we can get for X price (irrespective of location or house type) The challenge I have is identifying the domain (BI/ Data Analytical or DB Design or DB Query Interface or DW related or something else) this problem (dynamic query on historic data) belong to, so that I can do further exploration My findings so far I could be wrong on the following, so please correct me if you think so I briefly read about BI/Data Analytics - I think it is heavy weight solution for my problem and has scalability issues. DB Design - As I understand RDBMS works well if you know Data model at design time. I am expecting attributes about property or other entity (user) that am going to bring in, would evolve quickly. hence maintenance would be an issue. As I am going to have multiple users executing query at same time, performance would be a bottleneck Other options like Graph DB (http://www.tinkerpop.com/) seems to be bit complex (they are good. but using those tools meant for generic purpose, make me think like assembly programming to solve my problem ) BigData related solution are to analyse data from multiple unrelated domains So, Any suggestion on the space this problem fit in ? (Especially if you have design/implementation experience of back-end for property listing or similar portals)

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• How do I drag my widgets without dragging other widgets?

  - by Cypher

  I have a bunch of drag-able widgets on screen. When I am dragging one of the widgets around, if I drag the mouse over another widget, that widget then gets "snagged" and is also dragged around. While this is kind of a neat thing and I can think of a few game ideas based on that alone, that was not intended. :-P Background Info I have a Widget class that is the basis for my user interface controls. It has a bunch of properties that define it's size, position, image information, etc. It also defines some events, OnMouseOver, OnMouseOut, OnMouseClick, etc. All of the event handler functions are virtual, so that child objects can override them and make use of their implementation without duplicating code. Widgets are not aware of each other. They cannot tell each other, "Hey, I'm dragging so bugger off!" Source Code Here's where the widget gets updated (every frame): public virtual void Update( MouseComponent mouse, KeyboardComponent keyboard ) { // update position if the widget is being dragged if ( this.IsDragging ) { this.Left -= (int)( mouse.LastPosition.X - mouse.Position.X ); this.Top -= (int)( mouse.LastPosition.Y - mouse.Position.Y ); } ... // define and throw other events if ( !this.WasMouseOver && this.IsMouseOver && mouse.IsButtonDown( MouseButton.Left ) ) { this.IsMouseDown = true; this.MouseDown( mouse, new EventArgs() ); } ... // define and throw other events } And here's the OnMouseDown event where the IsDraggable property gets set: public virtual void OnMouseDown( object sender, EventArgs args ) { if ( this.IsDraggable ) { this.IsDragging = true; } } Problem Looking at the source code, it's obvious why this is happening. The OnMouseDown event gets fired whenever the mouse is hovered over the Widget and when the left mouse button is "down" (but not necessarily in that order!). That means that even if I hold the mouse down somewhere else on screen, and simply move it over anything that IsDraggable, it will "hook" onto the mouse and go for a ride. So, now that it's obvious that I'm Doing It Wrong™, how do I do this correctly?

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• Does LINQ require significantly more processing cycles and memory than lower-level data iteration techniques?

  - by Matthew Patrick Cashatt

  Background I am recently in the process of enduring grueling tech interviews for positions that use the .NET stack, some of which include silly questions like this one, and some questions that are more valid. I recently came across an issue that may be valid but I want to check with the community here to be sure. When asked by an interviewer how I would count the frequency of words in a text document and rank the results, I answered that I would Use a stream object put the text file in memory as a string. Split the string into an array on spaces while ignoring punctuation. Use LINQ against the array to .GroupBy() and .Count(), then OrderBy() said count. I got this answer wrong for two reasons: Streaming an entire text file into memory could be disasterous. What if it was an entire encyclopedia? Instead I should stream one block at a time and begin building a hash table. LINQ is too expensive and requires too many processing cycles. I should have built a hash table instead and, for each iteration, only added a word to the hash table if it didn't otherwise exist and then increment it's count. The first reason seems, well, reasonable. But the second gives me more pause. I thought that one of the selling points of LINQ is that it simply abstracts away lower-level operations like hash tables but that, under the veil, it is still the same implementation. Question Aside from a few additional processing cycles to call any abstracted methods, does LINQ require significantly more processing cycles to accomplish a given data iteration task than a lower-level task (such as building a hash table) would?

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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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• Moving away from PHP and running towards server-side JavaScript [on hold]

  - by Sosukodo

  I've decided to start moving away from PHP and server-side JavaScript looks like an attractive replacement. However, I'm having a hard time wrapping my head around how others are using Node.js for web applications. I'm currently using Lighttpd with FastCGI PHP. The one thing I like about PHP is that I can "inline" my scripts in the document like so: <?php echo 'Hello, World!'; ?> My question is: Is there any server-side JavaScript solution that I can use in this manor? For instance, I'd love to be able to do this: <?js print('Hello, World!'); ?> Is there such a thing? I'm not looking for opinions about "which is better". I just want to know what's out there and I'll explore each of them on my own. The important thing is that I'd like to use it like I demonstrated above. Links to the software along with implementation examples will be considered above other answers.

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• Handling game logic events by behavior components

  - by chehob

  My question continues on topic discussed here I have tried implementing attribute/behavior design and here is a quick example demonstrating the issue. class HealthAttribute : public ActorAttribute { public: HealthAttribute( float val ) : mValue( val ) { } float Get( void ) const { return mValue; } void Set( float val ) { mValue = val; } private: float mValue; }; class HealthBehavior : public ActorBehavior { public: HealthBehavior( shared_ptr< HealthAttribute > health ) : pHealth( health ) { // Set OnDamage() to listen for game logic event "DamageEvent" } void OnDamage( IEventDataPtr pEventData ) { // Check DamageEvent target entity // ( compare my entity ID with event's target entity ID ) // If not my entity, do nothing // Else, modify health attribute with received DamageEvent data } protected: shared_ptr< HealthAttribute > pHealth; }; My question - is it possible to get rid of this annoying check for game logic events? In the current implementation when some entity must receive damage, game logic just fires off event that contains damage value and the entity id which should receive that damage. And all HealthBehaviors are subscribed to the DamageEvent type, which leads to any entity possesing HealthBehavior call OnDamage() even if he is not the addressee.

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• The idea of functionN in Scala / Functionaljava

  - by Luke Murphy

  From brain driven development It turns out, that every Function you’ll ever define in Scala, will become an instance of an Implementation which will feature a certain Function Trait. There is a whole bunch of that Function Traits, ranging from Function1 up to Function22. Since Functions are Objects in Scala and Scala is a statically typed language, it has to provide an appropriate type for every Function which comes with a different number of arguments. If you define a Function with two arguments, the compiler picks Function2 as the underlying type. Also, from Michael Froh's blog You need to make FunctionN classes for each number of parameters that you want? Yes, but you define the classes once and then you use them forever, or ideally they're already defined in a library (e.g. Functional Java defines classes F, F2, ..., F8, and the Scala standard library defines classes Function1, ..., Function22) So we have a list of function traits (Scala), and a list of interfaces (Functional-java) to enable us to have first class funtions. I am trying to understand exactly why this is the case. I know, in Java for example, when I write a method say, public int add(int a, int b){ return a + b; } That I cannot go ahead and write add(3,4,5); ( error would be something like : method add cannot be applied to give types ) We simply have to define an interface/trait for functions with different parameters, because of static typing?

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• Effective and simple matching for 2 unequal small-scale point sets

  - by Pavlo Dyban

  I need to match two sets of 3D points, however the number of points in each set can be different. It seems that most algorithms are designed to align images and trimmed to work with hundreds of thousands of points. My case are 50 to 150 points in each of the two sets. So far I have acquainted myself with Iterative Closest Point and Procrustes Matching algorithms. Implementing Procrustes algorithms seems like a total overkill for this small quantity. ICP has many implementations, but I haven't found any readily implemented version accounting for the so-called "outliers" - points without a matching pair. Besides the implementation expense, algorithms like Fractional and Sparse ICP use some statistics information to cancel points that are considered outliers. For series with 50 to 150 points statistic measures are often biased or statistic significance criteria are not met. I know of Assignment Problem in linear optimization, but it is not suitable for cases with unequal sets of points. Are there other, small-scale algorithms that solve the problem of matching 2 point sets? I am looking for algorithm names, scientific papers or C++ implementations. I need some hints to know where to start my search.

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• TXPAUSE : polite waiting for hardware transactional memory

  - by Dave

  Classic locks are an appropriate tool to prevent potentially conflicting operations A and B, invoked by different threads, from running at the same time. In a sense the locks cause either A to run before B or vice-versa. Similarly, we can replace the locks with hardware transactional memory, or use transactional lock elision to leverage potential disjoint access parallelism between A and B. But often we want A to wait until B has run. In a Pthreads environment we'd usually use locks in conjunction with condition variables to implement our "wait until" constraint. MONITOR-MWAIT is another way to wait for a memory location to change, but it only allows us to track one cache line and it's only available on x86. There's no similar "wait until" construct for hardware transactions. At the instruction-set level a simple way to express "wait until" in transactions would be to add a new TXPAUSE instruction that could be used within an active hardware transaction. TXPAUSE would politely stall the invoking thread, possibly surrendering or yielding compute resources, while at the same time continuing to track the transaction's address-set. Once a transaction has executed TXPAUSE it can only abort. Ideally that'd happen when some other thread modifies a variable that's in the transaction's read-set or write-set. And since we're aborting all writes would be discarded. In a sense this gives us multi-location MWAIT but with much more flexibility. We could also augment the TXPAUSE with a cycle-count bound to cap the time spent stalled. I should note that we can already enter a tight spin loop in a transaction to wait for updates to address-set to cause an abort. Assuming that the implementation monitors the address-set via cache-coherence probes, by waiting in this fashion we actually communicate via the probes, and not via memory values. That is the updating thread signals the waiter via probes instead of by traditional memory values. But TXPAUSE gives us a polite way to spin.

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