Search Results

Search found 16947 results on 678 pages for 'kernel programming'.

Page 639/678 | < Previous Page | 635 636 637 638 639 640 641 642 643 644 645 646  | Next Page >

• How should I plan the inheritance structure for my game?

  - by Eric Thoma

  I am trying to write a platform shooter in C++ with a really good class structure for robustness. The game itself is secondary; it is the learning process of writing it that is primary. I am implementing an inheritance tree for all of the objects in my game, but I find myself unsure on some decisions. One specific issue that it bugging me is this: I have an Actor that is simply defined as anything in the game world. Under Actor is Character. Both of these classes are abstract. Under Character is the Philosopher, who is the main character that the user commands. Also under Character is NPC, which uses an AI module with stock routines for friendly, enemy and (maybe) neutral alignments. So under NPC I want to have three subclasses: FriendlyNPC, EnemyNPC and NeutralNPC. These classes are not abstract, and will often be subclassed in order to make different types of NPC's, like Engineer, Scientist and the most evil Programmer. Still, if I want to implement a generic NPC named Kevin, it would nice to be able to put him in without making a new class for him. I could just instantiate a FriendlyNPC and pass some values for the AI machine and for the dialogue; that would be ideal. But what if Kevin is the one benevolent Programmer in the whole world? Now we must make a class for him (but what should it be called?). Now we have a character that should inherit from Programmer (as Kevin has all the same abilities but just uses the friendly AI functions) but also should inherit from FriendlyNPC. Programmer and FriendlyNPC branched away from each other on the inheritance tree, so inheriting from both of them would have conflicts, because some of the same functions have been implemented in different ways on the two of them. 1) Is there a better way to order these classes to avoid these conflicts? Having three subclasses; Friendly, Enemy and Neutral; from each type of NPC; Engineer, Scientist, and Programmer; would amount to a huge number of classes. I would share specific implementation details, but I am writing the game slowly, piece by piece, and so I haven't implemented past Character yet. 2) Is there a place where I can learn these programming paradigms? I am already trying to take advantage of some good design patterns, like MVC architecture and Mediator objects. The whole point of this project is to write something in good style. It is difficult to tell what should become a subclass and what should become a state (i.e. Friendly boolean v. Friendly class). Having many states slows down code with if statements and makes classes long and unwieldy. On the other hand, having a class for everything isn't practical. 3) Are there good rules of thumb or resources to learn more about this? 4) Finally, where does templating come in to this? How should I coordinate templates into my class structure? I have never actually taken advantage of templating honestly, but I hear that it increases modularity, which means good code.

  Read the article

• Mastering snow and Java development at jDays in Gothenburg

  - by JavaCecilia

  Last weekend, I took the train from Stockholm to Gothenburg to attend and present at the new Java developer conference jDays. It was professionally arranged in the Swedish exhibition hall close to the amusement park Liseberg and we got a great deal out of the top-level presenters and hallway discussions. Understanding and Improving Your Java Process Our main purpose was to spread information on JVM and our monitoring tools for Java processes, so I held a crash course in the most important terms and concepts if you want to affect the performance of your Java process. From the beginning - the JVM specification to interpretation of heap usage graphs. For correct analysis, you also need to understand something about process memory - you need space for the Java heap (-Xms for initial size and -Xmx for max heap size), but the process memory also contain the thread stacks (to a size of -Xss), JVM internal data structures used for keeping track of Java objects on the heap, method compilation/optimization, native libraries, etc. If you get long pause times, make sure to monitor your application, see the allocation rate and frequency of pause times.My colleague Klara Ward then held a presentation on the Java Mission Control product, the profiling and diagnostics tools suite for HotSpot, coming soon. The room was packed and very appreciated, Klara demonstrated four different scenarios, e.g. how to diagnose and fix latencies due to lock contention for logging.My German colleague, OpenJDK ambassador Dalibor Topic travelled to Sweden to do the second keynote on "Make the Future Java". He let us in on the coming features and roadmaps of Java, now delivering major versions on a two-year schedule (Java 7 2011, Java 8 2013, etc). Also letting us in on where to download early versions of 8, to report problems early on. Software Development in teams Being a scout leader, I'm drilled in different team building and workshop techniques, creating strong groups - of course, I had to attend Henrik Berglund's session on building successful teams. He spoke about the importance of clear goals, autonomy and agreed processes. Thomas Sundberg ended the conference by doing live remote pair programming with Alex in Rumania and a concrete tips for people wanting to try it out (for local collaboration, remember to wash and change clothes). Memory Master Keynote The conference keynote was delivered by the Swedish memory master Mattias Ribbing, showing off by remembering the order of a deck of cards he'd seen once. He made it interactive by forcing the audience to learn a memory mastering technique of remembering ten ordered things by heart, asking us to shout out the order backwards and we made it! I desperately need this - bought the book, will get back on the subject. Continuous Delivery The most impressive presenter was Axel Fontaine on Continuous Delivery. Very well prepared slides with key images of his message and moved about the stage like a rock star. The topic is of course highly interesting, how to create an infrastructure enabling immediate feedback to developers and ability to release your product several times per day. Tomek Kaczanowski delivered a funny and useful presentation on good and bad tests, providing comic relief with poorly written tests and the useful rules of thumb how to rewrite them. To conclude, we had a great time and hope to see you at jDays next year :)

  Read the article

• Strings in .NET are Enumerable

  - by Scott Dorman

  It seems like there is always some confusion concerning strings in .NET. This is both from developers who are new to the Framework and those that have been working with it for quite some time. Strings in the .NET Framework are represented by the System.String class, which encapsulates the data manipulation, sorting, and searching methods you most commonly perform on string data. In the .NET Framework, you can use System.String (which is the actual type name or the language alias (for C#, string). They are equivalent so use whichever naming convention you prefer but be consistent. Common usage (and my preference) is to use the language alias (string) when referring to the data type and String (the actual type name) when accessing the static members of the class. Many mainstream programming languages (like C and C++) treat strings as a null terminated array of characters. The .NET Framework, however, treats strings as an immutable sequence of Unicode characters which cannot be modified after it has been created. Because strings are immutable, all operations which modify the string contents are actually creating new string instances and returning those. They never modify the original string data. There is one important word in the preceding paragraph which many people tend to miss: sequence. In .NET, strings are treated as a sequence…in fact, they are treated as an enumerable sequence. This can be verified if you look at the class declaration for System.String, as seen below: // Summary:// Represents text as a series of Unicode characters.public sealed class String : IEnumerable, IComparable, IComparable<string>, IEquatable<string> The first interface that String implements is IEnumerable, which has the following definition: // Summary:// Exposes the enumerator, which supports a simple iteration over a non-generic// collection.public interface IEnumerable{ // Summary: // Returns an enumerator that iterates through a collection. // // Returns: // An System.Collections.IEnumerator object that can be used to iterate through // the collection. IEnumerator GetEnumerator();} As a side note, System.Array also implements IEnumerable. Why is that important to know? Simply put, it means that any operation you can perform on an array can also be performed on a string. This allows you to write code such as the following: string s = "The quick brown fox";foreach (var c in s){ System.Diagnostics.Debug.WriteLine(c);}for (int i = 0; i < s.Length; i++){ System.Diagnostics.Debug.WriteLine(s[i]);} If you executed those lines of code in a running application, you would see the following output in the Visual Studio Output window: In the case of a string, these enumerable or array operations return a char (System.Char) rather than a string. That might lead you to believe that you can get around the string immutability restriction by simply treating strings as an array and assigning a new character to a specific index location inside the string, like this: string s = "The quick brown fox";s[2] = 'a';   However, if you were to write such code, the compiler will promptly tell you that you can’t do it: This preserves the notion that strings are immutable and cannot be changed once they are created. (Incidentally, there is no built in way to replace a single character like this. It can be done but it would require converting the string to a character array, changing the appropriate indexed location, and then creating a new string.)

  Read the article

• What Color is your Jetpack ?

  - by JoshReuben

  I’m a programmer, Im approaching 40, and I’m fairly decent at my job – I’ll keep doing what I’m doing for as long as they let me!   So what are your career options if you know how to code? A Programmer could be ..   An Algorithm developer Pros Interesting High barriers of entry, potential for startup competitive factor Cons Do you have the skill, qualifications? What are working conditions n this mystery niche ? micro-focus An Academic Pros Low pressure Job security – or is this an illusion ? Cons Low Pay Need a PhD A Software Architect Pros: strategic, rather than tactical Setting technology platform and high level vision You say how it should work, others have to figure out why its not working the way its supposed to ! broad view – you are paid to learn (how do you con people into paying for you to learn ??) Cons: Glorified developer – more often than not! competitive – everyone wants to do it ! loose touch with underlying tech in tough times, first guy to get the axe ! A Software Engineer Pros: interesting, always more to learn fun I can do it Fallback Cons: Nothing new under the sun – been there, done that Dealing with poor requirements, deadlines, other peoples code, overtime C#, XAML, Web - Low barriers of entry –> à race to the bottom A Team leader Pros: Setting code standards and proposing technology choices Cons: Glorified developer – more often than not! Inspecting other peoples code and debugging the problems they cannot fix Dealing with mugbies and prima donas Responsible for QA of others A Project Manager Pros No need for debugging other peoples code Cons Low barrier of entry High pressure Responsible for QA of others Loosing touch with technology A lot of bullshit meetings Have to be an asshole A Product Manager Pros No need for debugging other peoples code Learning new skillset of sales and marketing Cons Travel (I'm a family man) May need to know the bs details of an uninteresting product things I want to work with: AI, algorithms, Numerical Computing, Mathematica, C++ AMP – unfortunately, the work here is few & far between. VS & TFS Extensibility, DSLs (Workflow , Lightswitch), Code Generation – one day, code will write code ! Unity3D, WebGL – fun, fun, fun ! Modern Web – Knockout, SignalR, MVC, Node.Js ??? (tentative – I'll wait until things stabilize as this area is undergoing a pre-Cambrian explosion) Things I don’t want to work with: (but will if I'm asked to !) C# – same old, same old – not learning anything new here Old code – blech ! Environment with code & fix mentality , ad hoc requirements, excessive overtime Pc support, System administration – even after 20 years, people still ask you to do this sometimes ! debugging – my skills are just not there yet Oracle Old tech: VB 6, XSLT, WinForms, Net 3.51 or less Old style Web dev Information Systems: ASP.NET webforms, Reporting services / crystal reports, SQL Server CRUD with manual data layer, XAML MVVM – variations of the same concept, ad nauseaum. Low barriers of entry –> race to the bottom.  Metro – an elegant API coupled to a horrendous UX – I'll wait for market penetration viability before investing further in this.   Conclusion So if you are in a slump, take heart: Programming is a great career choice compared to every other job !

  Read the article

• Welcome To The Nashorn Blog

  - by jlaskey

  Welcome to all.  Time to break the ice and instantiate The Nashorn Blog.  I hope to contribute routinely, but we are very busy, at this point, preparing for the next development milestone and, of course, getting ready for open source. So, if there are long gaps between postings please forgive. We're just coming back from JavaOne and are stoked by the positive response to all the Nashorn sessions. It was great for the team to have the front and centre slide from Georges Saab early in the keynote. It seems we have support coming from all directions. Most of the session videos are posted. Check out the links. Nashorn: Optimizing JavaScript and Dynamic Language Execution on the JVM. Unfortunately, Marcus - the code generation juggernaut,  got saddled with the first session of the first day. Still, he had a decent turnout. The talk focused on issues relating to optimizations we did to get good performance from the JVM. Much yet to be done but looking good. Nashorn: JavaScript on the JVM. This was the main talk about Nashorn. I delivered the little bit of this and a little bit of that session with an overview, a follow up on the open source announcement, a run through a few of the Nashorn features and some demos. The room was SRO, about 250±. High points: Sam Pullara, from Twitter, came forward to describe how painless it was to get Mustache.js up and running (20x over Rhino), and,  John Ceccarelli, from NetBeans came forward to describe how Nashorn has become an integral part of Netbeans. A healthy Q & A at the end was very encouraging. Meet the Nashorn JavaScript Team. Michel, Attila, Marcus and myself hosted a Q & A. There was only a handful of people in the room (we assume it was because of a conflicting session ;-) .) Most of the questions centred around Node.jar, which leads me to believe, Nashorn + Node.jar is what has the most interest. Akhil, Mr. Node.jar, sitting in the audience, fielded the Node.jar questions. Nashorn, Node, and Java Persistence. Doug Clarke, Akhil and myself, discussed the title topics, followed by a lengthy Q & A (security had to hustle us out.) 80 or so in the room. Lots of questions about Node.jar. It was great to see Doug's use of Nashorn + JPA. Nashorn in action, with such elegance and grace. Putting the Metaobject Protocol to Work: Nashorn’s Java Bindings. Attila discussed how he applied Dynalink to Nashorn. Good turn out for this session as well. I have a feeling that once people discover and embrace this hidden gem, great things will happen for all languages running on the JVM. Finally, there were quite a few JavaOne sessions that focused on non-Java languages and their impact on the JVM. I've always believed that one's tool belt should carry a variety of programming languages, not just for domain/task applicability, but also to enhance your thinking and approaches to problem solving. For the most part, future blog entries will focus on 'how to' in Nashorn, but if you have any suggestions for topics you want discussed, please drop a line.  Cheers. 

  Read the article

• Rotation of viewplatform in Java3D

  - by user29163

  I have just started with Java3D programming. I thought I had built up some basic intuition about how the scene graph works, but something that should work, does not work. I made a simple program for rotating a pyramid around the y-axis. This was done just by adding a RotationInterpolator R to the TransformGroup above the pyramid. Then I thought hey, can I now remove the RotationInterpolator from this TransformGroup, then add it to the TransformGroup above my ViewPlatform leaf. This should work if I have understood how things work. Adding the RotationInterpolator to this TransformGroup, should make the children of this TransformGroup rotate, and the ViewingPlatform is a child of the TransformGroup. Any ideas on where my reasoning is flawed? Here is the code for setting up the universe, and the view branchgroup. import java.awt.*; import java.awt.event.*; import javax.media.j3d.*; import javax.vecmath.*; public class UniverseBuilder { // User-specified canvas Canvas3D canvas; // Scene graph elements to which the user may want access VirtualUniverse universe; Locale locale; TransformGroup vpTrans; View view; public UniverseBuilder(Canvas3D c) { this.canvas = c; // Establish a virtual universe that has a single // hi-res Locale universe = new VirtualUniverse(); locale = new Locale(universe); // Create a PhysicalBody and PhysicalEnvironment object PhysicalBody body = new PhysicalBody(); PhysicalEnvironment environment = new PhysicalEnvironment(); // Create a View and attach the Canvas3D and the physical // body and environment to the view. view = new View(); view.addCanvas3D(c); view.setPhysicalBody(body); view.setPhysicalEnvironment(environment); // Create a BranchGroup node for the view platform BranchGroup vpRoot = new BranchGroup(); // Create a ViewPlatform object, and its associated // TransformGroup object, and attach it to the root of the // subgraph. Attach the view to the view platform. Transform3D t = new Transform3D(); Transform3D s = new Transform3D(); t.set(new Vector3f(0.0f, 0.0f, 10.0f)); t.rotX(-Math.PI/4); s.set(new Vector3f(0.0f, 0.0f, 10.0f)); //forandre verdier her for å endre viewing position t.mul(s); ViewPlatform vp = new ViewPlatform(); vpTrans = new TransformGroup(t); vpTrans.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE); // Rotator stuff Transform3D yAxis = new Transform3D(); //yAxis.rotY(Math.PI/2); Alpha rotationAlpha = new Alpha( -1, Alpha.INCREASING_ENABLE, 0, 0,4000, 0, 0, 0, 0, 0); RotationInterpolator rotator = new RotationInterpolator( rotationAlpha, vpTrans, yAxis, 0.0f, (float) Math.PI*2.0f); RotationInterpolator rotator2 = new RotationInterpolator( rotationAlpha, vpTrans); BoundingSphere bounds = new BoundingSphere(new Point3d(0.0,0.0,0.0), 1000.0); rotator.setSchedulingBounds(bounds); vpTrans.addChild(rotator); vpTrans.addChild(vp); vpRoot.addChild(vpTrans); view.attachViewPlatform(vp); // Attach the branch graph to the universe, via the // Locale. The scene graph is now live! locale.addBranchGraph(vpRoot); } public void addBranchGraph(BranchGroup bg) { locale.addBranchGraph(bg); } }

  Read the article

• problem on my site [closed]

  - by ali

  Errors found while checking this document as XHTML How and from where repaired ,please help my hello, I have a problem on my site, was discovered by the program (A1 website analyzer) you can fix my site? Because I really do not know about the programming language, if it please email me and thank you please see this link it http://jigsaw.w3.org/css-validator/validator?uri=http://www.moneybillion.com/#errors Validation Output: 19 Errors Line 193, Column 261: there is no attribute "data-count" …ass="twitter-share-button" data-count="horizontal" data-via="elibeto1199"Twee…? You have used the attribute named above in your document, but the document type you are using does not support that attribute for this element. This error is often caused by incorrect use of the "Strict" document type with a document that uses frames (e.g. you must use the "Transitional" document type to get the "target" attribute), or by using vendor proprietary extensions such as "marginheight" (this is usually fixed by using CSS to achieve the desired effect instead). This error may also result if the element itself is not supported in the document type you are using, as an undefined element will have no supported attributes; in this case, see the element-undefined error message for further information. How to fix: check the spelling and case of the element and attribute, (Remember XHTML is all lower-case) and/or check that they are both allowed in the chosen document type, and/or use CSS instead of this attribute. If you received this error when using the element to incorporate flash media in a Web page, see the FAQ item on valid flash. Line 193, Column 283: there is no attribute "data-via" …ton" data-count="horizontal" data-via="elibeto1199"Tweet This error may also result if the element itself is not supported in the document type you are using, as an undefined element will have no supported attributes; in this case, see the element-undefined error message for further information. How to fix: check the spelling and case of the element and attribute, (Remember XHTML is all lower-case) and/or check that they are both allowed in the chosen document type, and/or use CSS instead of this attribute. If you received this error when using the element to incorporate flash media in a Web page, see the FAQ item on valid flash. Line 193, Column 393: required attribute "type" not specified …ript" src="//platform.twitter.com/widgets.js"var facebook = {? The attribute given above is required for an element that you've used, but you have omitted it. For instance, in most HTML and XHTML document types the "type" attribute is required on the "script" element and the "alt" attribute is required for the "img" element. Typical values for type are type="text/css" for and type="text/javascript" for . Line 194, Column 23: element "data:post.url" undefined url : "",? You have used the element named above in your document, but the document type you are using does not define an element of that name. This error is often caused by: incorrect use of the "Strict" document type with a document that uses frames (e.g. you must use the "Frameset" document type to get the "" element), by using vendor proprietary extensions such as "" or "" (this is usually fixed by using CSS to achieve the desired effect instead). by using upper-case tags in XHTML (in XHTML attributes and elements must be all lower-case). Line 197, Column 62: required attribute "type" not specified src="http://orkut-share.googlecode.com/svn/trunk/facebook.js"?

  Read the article

• Best approach to depth streaming via existing codec

  - by Kevin

  I'm working on a development system (and game) intended for games set mostly in static third-person views. We produce our scenery by CG and photographic techniques. Our background art is rendered off-line by a production-grade renderer. To allow the runtime imagery to properly interact with the background art, I wrote a program to convert from depth output by Mental Ray into a texture, and a pixel shader to draw a quad such that the Z data comes from the texture. This technique is working out very well, but now we've decided that some of the camera angle changes between scenes should be animated. The animation itself is straightforward to produce from our CG models. We intend to encode it to some HD video codec such as H.264. The problem is that in order to maintain our runtime imagery on the screen, the depth buffer will need to be loaded for each video frame. Due to the bandwidth, the video's depth data will need to be compressed efficiently. I've looked into methods for performing temporal compression of depth info and found an interesting research paper here: http://web4.cs.ucl.ac.uk/staff/j.kautz/publications/depth-streaming.pdf The method establishes a mapping between 16-bit depth values and YCbCr values. The mapping is tuned to the properties of existing video codecs in order to maximize precision of the decoded depths after the YCbCr has undergone video compression. It allows an existing, unmodified video codec to be used on the backend. I'm looking at how to pull this off with the least possible work. (This design change was unplanned.) Our game engine itself is native C++, presently for Win32 and DirectX, although we've worked hard to keep platform dependence segregated because we intend other ports. We don't have motion video facilities in the engine yet but will ultimately need that anyway for cinematics. I was planning on using some off-the-shelf motion video solution we can plug into our engine, and haven't chosen one yet. This new added requirement makes selecting one harder since, among other things, we'll now need to bypass colourspace conversion on one of the streams, and also will need to be playing two streams simultaneously in lockstep, on top of in some cases audio on one of them (for the cinematics). I'm also wondering if it's possible (or even useful) to do the conversion from YCbCr to depth in a pixel shader, or if it's better to just do it in CPU and separately load the resulting depth values into a locked tex. The conversion unfortunately does involve branching logic per-pixel. (There are more naive mappings that don't need branching, but they produce inferior results.) It could be reduced to a table lookup but the table would be 32MB. Programming is second-nature to me but I'm not that experienced with pix shaders and have zero knowledge of off-the-shelf video solutions. I'd therefore be interested in advice from others who may have dealt more with depth streaming, pixel shaders, and/or off-the-shelf codecs, regarding how feasible the proposed application is and what off-the-shelf video systems out there would best get along with this usage case.

  Read the article

• Multithreading 2D gravity calculations

  - by Postman

  I'm building a space exploration game and I've currently started working on gravity ( In C# with XNA). The gravity still needs tweaking, but before I can do that, I need to address some performance issues with my physics calculations. This is using 100 objects, normally rendering 1000 of them with no physics calculations gets well over 300 FPS (which is my FPS cap), but any more than 10 or so objects brings the game (and the single thread it runs on) to its knees when doing physics calculations. I checked my thread usage and the first thread was killing itself from all the work, so I figured I just needed to do the physics calculation on another thread. However when I try to run the Gravity.cs class's Update method on another thread, even if Gravity's Update method has nothing in it, the game is still down to 2 FPS. Gravity.cs public void Update() { foreach (KeyValuePair<string, Entity> e in entityEngine.Entities) { Vector2 Force = new Vector2(); foreach (KeyValuePair<string, Entity> e2 in entityEngine.Entities) { if (e2.Key != e.Key) { float distance = Vector2.Distance(entityEngine.Entities[e.Key].Position, entityEngine.Entities[e2.Key].Position); if (distance > (entityEngine.Entities[e.Key].Texture.Width / 2 + entityEngine.Entities[e2.Key].Texture.Width / 2)) { double angle = Math.Atan2(entityEngine.Entities[e2.Key].Position.Y - entityEngine.Entities[e.Key].Position.Y, entityEngine.Entities[e2.Key].Position.X - entityEngine.Entities[e.Key].Position.X); float mult = 0.1f * (entityEngine.Entities[e.Key].Mass * entityEngine.Entities[e2.Key].Mass) / distance * distance; Vector2 VecForce = new Vector2((float)Math.Cos(angle), (float)Math.Sin(angle)); VecForce.Normalize(); Force = Vector2.Add(Force, VecForce * mult); } } } entityEngine.Entities[e.Key].Position += Force; } } Yeah, I know. It's a nested foreach loop, but I don't know how else to do the gravity calculation, and this seems to work, it's just so intensive that it needs its own thread. (Even if someone knows a super efficient way to do these calculations, I'd still like to know how I COULD do it on multiple threads instead) EntityEngine.cs (manages an instance of Gravity.cs) public class EntityEngine { public Dictionary<string, Entity> Entities = new Dictionary<string, Entity>(); public Gravity gravity; private Thread T; public EntityEngine() { gravity = new Gravity(this); } public void Update() { foreach (KeyValuePair<string, Entity> e in Entities) { Entities[e.Key].Update(); } T = new Thread(new ThreadStart(gravity.Update)); T.IsBackground = true; T.Start(); } } EntityEngine is created in Game1.cs, and its Update() method is called within Game1.cs. I need my physics calculation in Gravity.cs to run every time the game updates, in a separate thread so that the calculation doesn't slow the game down to horribly low (0-2) FPS. How would I go about making this threading work? (any suggestions for an improved Planetary Gravity system are welcome if anyone has them) I'm also not looking for a lesson in why I shouldn't use threading or the dangers of using it incorrectly, I'm looking for a straight answer on how to do it. I've already spent an hour googling this very question with little results that I understood or were helpful. I don't mean to come off rude, but it always seems hard as a programming noob to get a straight meaningful answer, I usually rather get an answer so complex I'd easily be able to solve my issue if I understood it, or someone saying why I shouldn't do what I want to do and offering no alternatives (that are helpful). Thank you for the help!

  Read the article

• Oracle at ARM TechCon

  - by Tori Wieldt

  ARM TechCon is a technical conference for hardware and software engineers, Oct. 30-Nov 1 in Santa Clara, California. Days two and three of the conference will be geared towards systems designers and software developers, those interested in building ARM processor-based modules, boards, and systems. It will cover all of the hardware and software, tools, ranging from low-power design, networking and connectivity, open source software, and security. Oracle is a sponsor of ARM TechCon, and will present three Java sessions and a hands-on-lab:  "Do You Like Coffee with Your Dessert? Java and the Raspberry Pi" - The Raspberry Pi, an ARM-powered single board computer running a full Linux distro off an SD card has caused a huge wave of interest among developers. This session looks at how Java can be used on a device such as this. Using Java SE for embedded devices and a port of JavaFX, the presentation includes a variety of demonstrations of what the Raspberry Pi is capable of. The Raspberry Pi also provides GPIO line access, and the session covers how this can be used from Java applications. Prepare to be amazed at what this tiny board can do. (Angela Caicedo, Java Evangelist) "Modernizing the Explosion of Advanced Microcontrollers with Embedded Java" - This session explains why Oracle Java ME Embedded is the right choice for building small, connected, and intelligent embedded solutions, such as industrial control applications, smart sensing, wireless connectivity, e-health, or general machine-to-machine (M2M) functionality---extending your business to new areas, driving efficiency, and reducing cost. The new Oracle Java ME Embedded product brings the benefits of Java technology to microcontroller platforms. It is a full-featured, complete, compliant software runtime with value-add features targeted to the embedded space and has the ability to interface with additional hardware components, remote manageability, and over-the-air software updates. It is accompanied by a feature-rich set of tools free of charge. (Fareed Suliman, Java Product Manager) "Embedded Java in Smart Energy and Healthcare" - This session covers embedded Java products and technologies that enable smart and connect devices in the Smart Energy and Healthcare/Medical industries. (speaker Kevin Lee) "Java SE Embedded Development on ARM Made Easy" - This Hands-on Lab aims to show that developers already familiar with the Java develop/debug/deploy lifecycle can apply those same skills to develop Java applications, using Java SE Embedded, on embedded devices. (speaker Jim Connors) In the Oracle booth #603, you can see the following demos: Industry Solutions with JavaThis exhibit consists of a number of industry solutions and how they can be powered by Java technology deployed on embedded systems.  Examples in consumer devices, home gateways, mobile health, smart energy, industrial control, and tablets all powered by applications running on the Java platform are shown.  Some of the solutions demonstrate the ability of Java to connect intelligent devices at the edge of the network to the datacenter or the cloud as a total end-to-end platform.Java in M2M with QualcommThis station will exhibit a new M2M solutions platform co-developed by Oracle and Qualcomm that enables wireless communications for embedded smart devices powered by Java, and share the types of industry solutions that are possible.  In addition, a new platform for wearable devices based on the ARM Cortex M3 platform is exhibited.Why Java for Embedded?Demonstration platforms will show how traditional development environments, tools, and Java programming skills can be used to create applications for embedded devices.  The advantages that Java provides because of  the runtime's abstraction of software from hardware, modularity and scalability, security, and application portability and manageability are shared with attendees. Drop by and see why Java is an optimal applications platform for embedded systems.

  Read the article

• Trouble rotating viewplatform in Java3D [closed]

  - by user29163

  I have just started with Java3D programming. I thought I had built up some basic intuition about how the scene graph works, but something that should work, does not work. I made a simple program for rotating a pyramid around the y-axis. This was done just by adding a RotationInterpolator R to the TransformGroup above the pyramid. Then I thought hey, can I now remove the RotationInterpolator from this TransformGroup, then add it to the TransformGroup above my ViewPlatform leaf. This should work if I have understood how things work. Adding the RotationInterpolator to this TransformGroup, should make the children of this TransformGroup rotate, and the ViewingPlatform is a child of the TransformGroup. Any ideas on where my reasoning is flawed? Here is the code for setting up the universe, and the view branchgroup. import java.awt.*; import java.awt.event.*; import javax.media.j3d.*; import javax.vecmath.*; public class UniverseBuilder { // User-specified canvas Canvas3D canvas; // Scene graph elements to which the user may want access VirtualUniverse universe; Locale locale; TransformGroup vpTrans; View view; public UniverseBuilder(Canvas3D c) { this.canvas = c; // Establish a virtual universe that has a single // hi-res Locale universe = new VirtualUniverse(); locale = new Locale(universe); // Create a PhysicalBody and PhysicalEnvironment object PhysicalBody body = new PhysicalBody(); PhysicalEnvironment environment = new PhysicalEnvironment(); // Create a View and attach the Canvas3D and the physical // body and environment to the view. view = new View(); view.addCanvas3D(c); view.setPhysicalBody(body); view.setPhysicalEnvironment(environment); // Create a BranchGroup node for the view platform BranchGroup vpRoot = new BranchGroup(); // Create a ViewPlatform object, and its associated // TransformGroup object, and attach it to the root of the // subgraph. Attach the view to the view platform. Transform3D t = new Transform3D(); Transform3D s = new Transform3D(); t.set(new Vector3f(0.0f, 0.0f, 10.0f)); t.rotX(-Math.PI/4); s.set(new Vector3f(0.0f, 0.0f, 10.0f)); //forandre verdier her for å endre viewing position t.mul(s); ViewPlatform vp = new ViewPlatform(); vpTrans = new TransformGroup(t); vpTrans.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE); // Rotator stuff Transform3D yAxis = new Transform3D(); //yAxis.rotY(Math.PI/2); Alpha rotationAlpha = new Alpha( -1, Alpha.INCREASING_ENABLE, 0, 0,4000, 0, 0, 0, 0, 0); RotationInterpolator rotator = new RotationInterpolator( rotationAlpha, vpTrans, yAxis, 0.0f, (float) Math.PI*2.0f); RotationInterpolator rotator2 = new RotationInterpolator( rotationAlpha, vpTrans); BoundingSphere bounds = new BoundingSphere(new Point3d(0.0,0.0,0.0), 1000.0); rotator.setSchedulingBounds(bounds); vpTrans.addChild(rotator); vpTrans.addChild(vp); vpRoot.addChild(vpTrans); view.attachViewPlatform(vp); // Attach the branch graph to the universe, via the // Locale. The scene graph is now live! locale.addBranchGraph(vpRoot); } public void addBranchGraph(BranchGroup bg) { locale.addBranchGraph(bg); } }

  Read the article

• Removing occurrences of characters in a string

  - by DmainEvent

  I am reading this book, programming Interviews exposed by John Wiley and sons and in chapter 6 they are discussing removing all instances of characters in a src string using a removal string... so removeChars(string str, string remove) In there writeup they sey the steps to accomplish this are to have a boolean lookup array with all values initially set to false, then loop through each character in remove setting the corresponding value in the lookup array to true (note: this could also be a hash if the possible character set where huge like Unicode-16 or something like that or if str and remove are both relatively small... < 100 characters I suppose). You then iterate through the str with a source and destination index, copying each character only if its corresponding value in the lookup array is false... Which makes sense... I don't understand the code that they use however... They have for(src = 0; src < len; ++src){ flags[r[src]] == true; } which is turning the flag value at the remove string indexed at src to true... so if you start out with PLEASE HELP as your str and LEA as your remove you will be setting in your flag table at 0,1,2... t|t|t but after that you will get an out of bounds exception because r doesn't have have anything greater than 2 in it... even using there example you get an out of bounds exception... Am is there code example unworkable? Entire function string removeChars( string str, string remove ){ char[] s = str.toCharArray(); char[] r = remove.toCharArray(); bool[] flags = new bool[128]; // assumes ASCII! int len = s.Length; int src, dst; // Set flags for characters to be removed for( src = 0; src < len; ++src ){ flags[r[src]] = true; } src = 0; dst = 0; // Now loop through all the characters, // copying only if they aren’t flagged while( src < len ){ if( !flags[ (int)s[src] ] ){ s[dst++] = s[src]; } ++src; } return new string( s, 0, dst ); } as you can see, r comes from the remove string. So in my example the remove string has only a size of 3 while my str string has a size of 11. len is equal to the length of the str string. So it would be 11. How can I loop through the r string since it is only size 3? I haven't compiled the code so I can loop through it, but just looking at it I know it won't work. I am thinking they wanted to loop through the r string... in other words they got the length of the wrong string here.

  Read the article

• Framework for Everything - Where to begin? [Longer post]

  - by SquaredSoft

  Back story of this question, feel free to skip down for the specific question Hello, I've been very interested in the idea of abstract programming the last few years. I've made about 30 attempts at creating a piece of software that is capable of almost anything you throw at it. I've undertook some attempts at this that have taken upwards of a year, while getting close, never releasing it beyond my compiler. This has been something I've always tried wrapping my head around, and something is always missing. With the title, I'm sure you're assuming, "Yes of course you noob! You can't account for everything!" To which I have to reply, "Why not?" To give you some background into what I'm talking about, this all started with doing maybe a shade of gray hat SEO software. I found myself constantly having to create similar, but slightly different sets of code. I've gone through as many iterations of way to communicate on http as the universe has particles. "How many times am I going to have to write this multi-threaded class?" is something I found myself asking a lot. Sure, I could create a class library, and just work with that, but I always felt I could optimize what I had, which often was a large undertaking and typically involved frequent use of the CRTL+A keyboard shortcut, mixed with the delete button. It dawned on me that it was time to invest in a plugin system. This would allow me to simply add snippets of code. as time went on, and I could subversion stuff out, and distribute small chunks of code, rather than something that encompasses only a specific function or design. This comes with its own complexity, of course, and by the time I had finished the software scope for this addition, it hit me that I would want to add to everything in the software, not just a new http method, or automation code for a specific website. Great, we're getting more abstract. However, the software that I have in my mind comes down to a quite a few questions regarding its execution. I have to have some parameters to what I am going to do. After writing what the perfect software would do in my mind, I came up with this as a list of requirements: Should be able to use networking A "Macro" or "Expression system" which would allow people to do something like : =First(=ParseToList(=GetUrl("http://www.google.com?q=helloworld!"), Template.Google)) Multithreaded Able to add UI elements through some type of XML -- People can make their own addons etc. Can use third party API through the plugins, such as Microsoft CRM, Exchange, etc. This would allow the software to essentially be used for everything. Really, any task you wish to automate, in a simple way. Making the UI was as also extremely hard. How do you do all of this? Its very difficult. So my question: With so many attempts at this, I'm out of ideas how to successfully complete this. I have a very specific idea in my mind, but I keep failing to execute it. I'm a self taught programmer. I've been doing it for years, and work professionally in it, but I've never encountered something that would be as complex and in-depth as a system which essentially does everything. Where would you start? What are the best practices for design? How can I avoid constantly having to go back and optimize my software. What can I do to generalize this and draw everything out to completion. These are things I struggle with. P.s., I'm using c# as my main language. I feel like in this example, I might be hitting the outer limit of the language, although, I don't know if that is the case, or if I'm just a bad programmer. Thanks for your time.

  Read the article

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

  - by Dennis

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

  Read the article

• Class design issue

  - by user2865206

  I'm new to OOP and a lot of times I become stumped in situations similar to this example: Task: Generate an XML document that contains information about a person. Assume the information is readily available in a database. Here is an example of the structure: <Person> <Name>John Doe</Name> <Age>21</Age> <Address> <Street>100 Main St.</Street> <City>Sylvania</City> <State>OH</State> </Address> <Relatives> <Parents> <Mother> <Name>Jane Doe</Name> </Mother> <Father> <Name>John Doe Sr.</Name> </Father> </Parents> <Siblings> <Brother> <Name>Jeff Doe</Name> </Brother> <Brother> <Name>Steven Doe</Name> </Brother> </Siblings> </Relatives> </Person> Ok lets create a class for each tag (ie: Person, Name, Age, Address) Lets assume each class is only responsible for itself and the elements directly contained Each class will know (have defined by default) the classes that are directly contained within them Each class will have a process() function that will add itself and its childeren to the XML document we are creating When a child is drawn, as in the previous line, we will have them call process() as well Now we are in a recursive loop where each object draws their childeren until all are drawn But what if only some of the tags need to be drawn, and the rest are optional? Some are optional based on if the data exists (if we have it, we must draw it), and some are optional based on the preferences of the user generating the document How do we make sure each object has the data it needs to draw itself and it's childeren? We can pass down a massive array through every object, but that seems shitty doesnt it? We could have each object query the database for it, but thats a lot of queries, and how does it know what it's query is? What if we want to get rid of a tag later? There is no way to reference them. I've been thinking about this for 20 hours now. I feel like I am misunderstanding a design principle or am just approaching this all wrong. How would you go about programming something like this? I suppose this problem could apply to any senario where there are classes that create other classes, but the classes created need information to run. How do I get the information to them in a way that doesn't seem fucky? Thanks for all of your time, this has been kicking my ass.

  Read the article

• Dependency Injection Introduction

  - by MarkPearl

  I recently was going over a great book called “Dependency Injection in .Net” by Mark Seeman. So far I have really enjoyed the book and would recommend anyone looking to get into DI to give it a read. Today I thought I would blog about the first example Mark gives in his book to illustrate some of the benefits that DI provides. The ones he lists are Late binding Extensibility Parallel Development Maintainability Testability To illustrate some of these benefits he gives a HelloWorld example using DI that illustrates some of the basic principles. It goes something like this… class Program { static void Main(string[] args) { var writer = new ConsoleMessageWriter(); var salutation = new Salutation(writer); salutation.Exclaim(); Console.ReadLine(); } } public interface IMessageWriter { void Write(string message); } public class ConsoleMessageWriter : IMessageWriter { public void Write(string message) { Console.WriteLine(message); } } public class Salutation { private readonly IMessageWriter _writer; public Salutation(IMessageWriter writer) { _writer = writer; } public void Exclaim() { _writer.Write("Hello World"); } }   If you had asked me a few years ago if I had thought this was a good approach to solving the HelloWorld problem I would have resounded “No”. How could the above be better than the following…. class Program { static void Main(string[] args) { Console.WriteLine("Hello World"); Console.ReadLine(); } }  Today, my mind-set has changed because of the pain of past programs. So often we can look at a small snippet of code and make judgements when we need to keep in mind that we will most probably be implementing these patterns in projects with hundreds of thousands of lines of code and in projects that we have tests that we don’t want to break and that’s where the first solution outshines the latter. Let’s see if the first example achieves some of the outcomes that were listed as benefits of DI. Could I test the first solution easily? Yes… We could write something like the following using NUnit and RhinoMocks… [TestFixture] public class SalutationTests { [Test] public void ExclaimWillWriteCorrectMessageToMessageWriter() { var writerMock = MockRepository.GenerateMock<IMessageWriter>(); var sut = new Salutation(writerMock); sut.Exclaim(); writerMock.AssertWasCalled(x => x.Write("Hello World")); } }   This would test the existing code fine. Let’s say we then wanted to extend the original solution so that we had a secure message writer. We could write a class like the following… public class SecureMessageWriter : IMessageWriter { private readonly IMessageWriter _writer; private readonly string _secretPassword; public SecureMessageWriter(IMessageWriter writer, string secretPassword) { _writer = writer; _secretPassword = secretPassword; } public void Write(string message) { if (_secretPassword == "Mark") { _writer.Write(message); } else { _writer.Write("Unauthenticated"); } } }   And then extend our implementation of the program as follows… class Program { static void Main(string[] args) { var writer = new SecureMessageWriter(new ConsoleMessageWriter(), "Mark"); var salutation = new Salutation(writer); salutation.Exclaim(); Console.ReadLine(); } }   Our application has now been successfully extended and yet we did very little code change. In addition, our existing tests did not break and we would just need add tests for the extended functionality. Would this approach allow parallel development? Well, I am in two camps on parallel development but with some planning ahead of time it would allow for it as you would simply need to decide on the interface signature and could then have teams develop different sections programming to that interface. So,this was really just a quick intro to some of the basic concepts of DI that Mark introduces very successfully in his book. I am hoping to blog about this further as I continue through the book to list some of the more complex implementations of containers.

  Read the article

• Modernizr Rocks HTML5

  - by Laila

  HTML5 is a moving target.  At the moment, we don't know what will be in future versions.  In most circumstances, this really matters to the developer. When you're using Adobe Air, you can be reasonably sure what works, what is there, and what isn't, since you have a version of the browser built-in. With Metro, you can assume that you're going to be using at least IE 10.   If, however,  you are using HTML5 in a web application, then you are going to rely heavily on Feature Detection.  Feature-Detection is a collection of techniques that tell you, via JavaScript, whether the current browser has this feature natively implemented or not Feature Detection isn't just there for the esoteric stuff such as  Geo-location,  progress bars,  <canvas> support,  the new <input> types, Audio, Video, web workers or storage, but is required even for semantic markup, since old browsers make a pigs ear out of rendering this.  Feature detection can't rely just on reading the browser version and inferring from that what works. Instead, you must use JavaScript to check that an HTML5 feature is there before using it.  The problem with relying on the user-agent is that it takes a lot of historical data  to work out what version does what, and, anyway, the user-agent can be, and sometimes is, spoofed. The open-source library Modernizr  is just about the most essential  JavaScript library for anyone using HTML5, because it provides APIs to test for most of the CSS3 and HTML5 features before you use them, and is intelligent enough to alter semantic markup into 'legacy' 'markup  using shims  on page-load  for old browsers. It also allows you to check what video Codecs are installed for playing video. It also provides media queries  and conditional resource-loading (formerly YepNope.js.).  Generally, Modernizr gives you the choice of what you do about browsers that don't support the feature that you want. Often, the best choice is graceful degradation, but the resource-loading feature allows you to dynamically load JavaScript Shims to replace the standard API for missing or defective HTML5 functionality, called 'PolyFills'.  As the Modernizr site says 'Yes, not only can you use HTML5 today, but you can use it in the past, too!' The evolutionary progress of HTML5  requires a more defensive style of JavaScript programming where the programmer adopts a mindset of fearing the worst ( IE 6)  rather than assuming the best, whilst exploiting as many of the new HTML features as possible for the requirements of the site or HTML application.  Why would anyone want the distraction of developing their own techniques to do this when  Modernizr exists to do this for you? Laila

  Read the article

• Does *every* project benefit from written specifications?

  - by nikie

  I know this is holy war territory, so please read the question to the end before answering. There are many cases where written specifications make a lot of sense. For example, if you're a contractor and you want to get paid, you need written specs. If you're working in a team with 20 persons, you need written specs. If you're writing a programming language compiler or interpreter (and it's not perl), you'll usually write a formal specification. I don't doubt that there are many more cases where written specifications are a really good idea. I just think that there are cases where there's so little benefit in written specs, that it doesn't outweigh the costs of writing and maintaining them. EDIT: The close votes say that "it is difficult to say what is asked here", so let me clarify: The usefulness of written, detailed specifications is often claimed like a dogma. (If you want examples, look at the comments.) But I don't see the use of them for the kind of development I'm doing. So what is asked here is: How would written specifications help me? Background information: I work for a small company that's developing vertical market software. If our product is easier to use and has better performance than the competition, it sells. If it's harder to use, even if it behaves 100% as the specification says, it doesn't sell. So there are no "external forces" for having written specs. The advantage would have to be somewhere in the development process. Now, I can see how frozen specifications would make a developer's life easier. But we'll never have frozen specs. If we see in the middle of development that feature X is not intuitive to use the way it's specified, then we can only choose between changing the specification or developing a product that won't sell. You'll probably ask by now: How do you know when you're done? Well, we're continually improving our product. The competition does the same. So (hopefully) we're never done. We keep improving the software, and when we reach a point when the benefits of the improvements we've added since the last release outweigh the costs of an update, we create a new release that is then tested, localized, documented and deployed. This also means that there's rarely any schedule pressure. Nobody has to do overtime to make a deadline. If the feature isn't done by the time we want to release the next version, it'll simply go into the next version. The next question might be: How do your developers know what they're supposed to implement? The answer is: They have a lot of domain knowledge. They know the customers business well enough, so a high-level description of the feature (or even just the problem that the customer needs solved) is enough to implement it. If it's not clear, the developer creates a few fake screens to get feedback from marketing/management or customers, but this is nowhere near the level of detail of actual specifications. This might be inefficient for larger teams, but for a small team with low turnover it works quite well. It has the additional benefit that the developer in question often comes up with a better solution than the person writing the specs might have. This question is already getting very long, but let me address one last point: Testing. Like I said in the beginning, if our software behaves 100% like the spec says, it still can be crap. In fact, if it's so unintuitive that you need a spec to know how to test it, it probably is crap. It makes sense to have fixed, written tests for some core functionality and for regression bugs, but again, this is nowhere near a full written spec of how the software should behave when. The main test is: hand the software to a user who doesn't know it yet and tell him to use the new feature X. If she can figure out how to use it and it works, it works.

  Read the article

• XNA - 3D AABB collision detection and response

  - by fastinvsqrt

  I've been fiddling around with 3D AABB collision in my voxel engine for the last couple of days, and every method I've come up with thus far has been almost correct, but each one never quite worked exactly the way I hoped it would. Currently what I do is get two bounding boxes for my entity, one modified by the X translation component and the other by the Z component, and check if each collides with any of the surrounding chunks (chunks have their own octrees that are populated only with blocks that support collision). If there is a collision, then I cast out rays into that chunk to get the shortest collision distance, and set the translation component to that distance if the component is greater than the distance. The problem is that sometimes collisions aren't even registered. Here's a video on YouTube that I created showing what I mean. I suspect the problem may be with the rays that I cast to get the collision distance not being where I think they are, but I'm not entirely sure what would be wrong with them if they are indeed the problem. Here is my code for collision detection and response in the X direction (the Z direction is basically the same): // create the XZ offset vector Vector3 offsXZ = new Vector3( ( _translation.X > 0.0f ) ? SizeX / 2.0f : ( _translation.X < 0.0f ) ? -SizeX / 2.0f : 0.0f, 0.0f, ( _translation.Z > 0.0f ) ? SizeZ / 2.0f : ( _translation.Z < 0.0f ) ? -SizeZ / 2.0f : 0.0f ); // X physics BoundingBox boxx = GetBounds( _translation.X, 0.0f, 0.0f ); if ( _translation.X > 0.0f ) { foreach ( Chunk chunk in surrounding ) { if ( chunk.Collides( boxx ) ) { float dist = GetShortestCollisionDistance( chunk, Vector3.Right, offsXZ ) - 0.0001f; if ( dist < _translation.X ) { _translation.X = dist; } } } } else if ( _translation.X < 0.0f ) { foreach ( Chunk chunk in surrounding ) { if ( chunk.Collides( boxx ) ) { float dist = GetShortestCollisionDistance( chunk, Vector3.Left, offsXZ ) - 0.0001f; if ( dist < -_translation.X ) { _translation.X = -dist; } } } } And here is my implementation for GetShortestCollisionDistance: private float GetShortestCollisionDistance( Chunk chunk, Vector3 rayDir, Vector3 offs ) { int startY = (int)( -SizeY / 2.0f ); int endY = (int)( SizeY / 2.0f ); int incY = (int)Cube.Size; float dist = Chunk.Size; for ( int y = startY; y <= endY; y += incY ) { // Position is the center of the entity's bounding box Ray ray = new Ray( new Vector3( Position.X + offs.X, Position.Y + offs.Y + y, Position.Z + offs.Z ), rayDir ); // Chunk.GetIntersections(Ray) returns Dictionary<Block, float?> foreach ( var pair in chunk.GetIntersections( ray ) ) { if ( pair.Value.HasValue && pair.Value.Value < dist ) { dist = pair.Value.Value; } } } return dist; } I realize some of this code can be consolidated to help with speed, but my main concern right now is to get this bit of physics programming to actually work.

  Read the article

• Come up with a real-world problem in which only the best solution will do (a problem from Introduction to algorithms) [closed]

  - by Mike

  EDITED (I realized that the question certainly needs a context) The problem 1.1-5 in the book of Thomas Cormen et al Introduction to algorithms is: "Come up with a real-world problem in which only the best solution will do. Then come up with one in which a solution that is “approximately” the best is good enough." I'm interested in its first statement. And (from my understanding) it is asked to name a real-world problem where only the exact solution will work as opposed to a real-world problem where good-enough solution will be ok. So what is the difference between the exact and good enough solution. Consider some physics problem for example the simulation of the fulid flow in the permeable medium. To make this simulation happen some simplyfing assumptions have to be made when deriving a mathematical model. Otherwise the model becomes at least complex and unsolvable. Virtually any particle in the universe has its influence on the fluid flow. But not all particles are equal. Those that form the permeable medium are much more influental than the ones located light years away. Then when the mathematical model needs to be solved an exact solution can rarely be found unless the mathematical model is simple enough (wich probably means the model isn't close to reality). We take an approximate numerical method and after hours of coding and days of verification come up with the program or algorithm which is a solution. And if the model and an algorithm give results close to a real problem by some degree that is good enough soultion. Its worth noting the difference between exact solution algorithm and exact computation result. When considering real-world problems and real-world computation machines I believe all physical problems solutions where any calculations are taken can not be exact because universal physical constants are represented approximately in the computer. Any numbers are represented with the limited precision, at least limited by amount of memory available to computing machine. I can imagine plenty of problems where good-enough, good to some degree solution will work, like train scheduling, automated trading, satellite orbit calculation, health care expert systems. In that cases exact solutions can't be derived due to constraints on computation time, limitations in computer memory or due to the nature of problems. I googled this question and like what this guy suggests: there're kinds of mathematical problems that need exact solutions (little note here: because the question is taken from the book "Introduction to algorithms" the term "solution" means an algorithm or a program, which in this case gives exact answer on each input). But that's probably more of theoretical interest. So I would like to narrow down the question to: What are the real-world practical problems where only the best (exact) solution algorithm or program will do (but not the good-enough solution)? There are problems like breaking of cryptographic ciphers where only exact solution matters in practice and again in practice the process of deciphering without knowing a secret should take reasonable amount of time. Returning to the original question this is the problem where good-enough (fast-enough) solution will do there's no practical need in instant crack though it's desired. So the quality of "best" can be understood in any sense: exact, fastest, requiring least memory, having minimal possible network traffic etc. And still I want this question to be theoretical if possible. In a sense that there may be example of computer X that has limited resource R of amount Y where the best solution to problem P is the one that takes not more than available Y for inputs of size N*Y. But that's the problem of finding solution for P on computer X which is... well, good enough. My final thought that we live in a world where it is required from programming solutions to practical purposes to be good enough. In rare cases really very very good but still not the best ones. Isn't it? :) If it's not can you provide an example? Or can you name any such unsolved problem of practical interest?

  Read the article

• How to parse a CSV file containing serialized PHP? [migrated]

  - by garbetjie

  I've just started dabbling in Perl, to try and gain some exposure to different programming languages - so forgive me if some of the following code is horrendous. I needed a quick and dirty CSV parser that could receive a CSV file, and split it into file batches containing "X" number of CSV lines (taking into account that entries could contain embedded newlines). I came up with a working solution, and it was going along just fine. However, as one of the CSV files that I'm trying to split, I came across one that contains serialized PHP code. This seems to break the CSV parsing. As soon as I remove the serialization - the CSV file is parsed correctly. Are there any tricks I need to know when it comes to parsing serialized data in CSV files? Here is a shortened sample of the code: use strict; use warnings; my $csv = Text::CSV_XS->new({ eol => $/, always_quote => 1, binary => 1 }); my $out; my $in; open $in, "<:encoding(utf8)", "infile.csv" or die("cannot open input file $inputfile"); open $out, ">outfile.000"; binmode($out, ":utf8"); while (my $line = $csv->getline($in)) { $lines++; $csv->print($out, $line); } I'm never able to get into the while loop shown above. As soon as I remove the serialized data, I suddenly am able to get into the loop. Edit: An example of a line that is causing me trouble (taken straight from Vim - hence the ^M): "26","other","1","20,000 Subscriber Plan","Some text here.^M\ Some more text","on","","18","","0","","0","0","recurring","0","","payment","totalsend","0","tsadmin","R34bL9oq","37","0","0","","","","","","","","","","","","","","","","","","","","","","","0","0","0","a:18:{i:0;s:1:\"3\";i:1;s:1:\"2\";i:2;s:2:\"59\";i:3;s:2:\"60\";i:4;s:2:\"61\";i:5;s:2:\"62\";i:6;s:2:\"63\";i:7;s:2:\"64\";i:8;s:2:\"65\";i:9;s:2:\"66\";i:10;s:2:\"67\";i:11;s:2:\"68\";i:12;s:2:\"69\";i:13;s:2:\"70\";i:14;s:2:\"71\";i:15;s:2:\"72\";i:16;s:2:\"73\";i:17;s:2:\"74\";}","","","0","0","","0","0","0.0000","0.0000","0","","","0.00","","6","1" "27","other","1","35,000 Subscriber Plan","Some test here.^M\ Some more text","on","","18","","0","","0","0","recurring","0","","payment","totalsend","0","tsadmin","R34bL9oq","38","0","0","","","","","","","","","","","","","","","","","","","","","","","0","0","0","a:18:{i:0;s:1:\"3\";i:1;s:1:\"2\";i:2;s:2:\"59\";i:3;s:2:\"60\";i:4;s:2:\"61\";i:5;s:2:\"62\";i:6;s:2:\"63\";i:7;s:2:\"64\";i:8;s:2:\"65\";i:9;s:2:\"66\";i:10;s:2:\"67\";i:11;s:2:\"68\";i:12;s:2:\"69\";i:13;s:2:\"70\";i:14;s:2:\"71\";i:15;s:2:\"72\";i:16;s:2:\"73\";i:17;s:2:\"74\";}","","","0","0","","0","0","0.0000","0.0000","0","","","0.00","","7","1" "28","other","1","50,000 Subscriber Plan","Some text here.^M\ Some more text","on","","18","","0","","0","0","recurring","0","","payment","totalsend","0","tsadmin","R34bL9oq","39","0","0","","","","","","","","","","","","","","","","","","","","","","","0","0","0","a:18:{i:0;s:1:\"3\";i:1;s:1:\"2\";i:2;s:2:\"59\";i:3;s:2:\"60\";i:4;s:2:\"61\";i:5;s:2:\"62\";i:6;s:2:\"63\";i:7;s:2:\"64\";i:8;s:2:\"65\";i:9;s:2:\"66\";i:10;s:2:\"67\";i:11;s:2:\"68\";i:12;s:2:\"69\";i:13;s:2:\"70\";i:14;s:2:\"71\";i:15;s:2:\"72\";i:16;s:2:\"73\";i:17;s:2:\"74\";}","","","0","0","","0","0","0.0000","0.0000","0","","","0.00","","8","1""73","other","8","10,000,000","","","","0","","0","","0","0","recurring","0","","payment","","0","","","75","0","10000000","","","","","","","","","","","","","","","","","","","","","","","0","0","0","a:17:{i:0;s:1:\"3\";i:1;s:1:\"2\";i:2;s:2:\"59\";i:3;s:2:\"60\";i:4;s:2:\"61\";i:5;s:2:\"62\";i:6;s:2:\"63\";i:7;s:2:\"64\";i:8;s:2:\"65\";i:9;s:2:\"66\";i:10;s:2:\"67\";i:11;s:2:\"68\";i:12;s:2:\"69\";i:13;s:2:\"70\";i:14;s:2:\"71\";i:15;s:2:\"72\";i:16;s:2:\"74\";}","","","0","0","","0","0","0.0000","0.0000","0","","","0.00","","14","0"

  Read the article

• A* algorithm very slow

  - by Amaranth

  I have an programming a RTS game (I use XNA with C#). The pathfinding is working fine, except that when it has a lot of node to search in, there is a lag period of one or two seconds, it happens mainly when there is no path to the target destination, since it that situation there is more nodes to explore. I have the same problem when the path is shorter but selected more than 3 units (can't take the same path since the selected units can be in different part of the map). private List<NodeInfo> FindPath(Unit u, NodeInfo start, NodeInfo end) { Map map = GameInfo.GetInstance().GameMap; _nearestToTarget = start; start.MoveCost = 0; Vector2 endPosition = map.getTileByPos(end.X, end.Y).Position; //getTileByPos simply gets the tile in a 2D array with the X and Y indexes start.EstimatedRemainingCost = (int)(endPosition - map.getTileByPos(start.X, start.Y).Position).Length(); start.Parent = null; List<NodeInfo> openedNodes = new List<NodeInfo>(); ; List<NodeInfo> closedNodes = new List<NodeInfo>(); Point[] movements = GetMovements(u.UnitType); openedNodes.Add(start); while (!closedNodes.Contains(end) && openedNodes.Count > 0) { //Loop in nodes to find lowest cost NodeInfo currentNode = FindLowestCostOpenedNode(openedNodes); openedNodes.Remove(currentNode); closedNodes.Add(currentNode); Vector2 previousMouvement; if (currentNode.Parent == null) { previousMouvement = ConvertRotationToDirectionVector(u.Rotation); } else { previousMouvement = map.getTileByPos(currentNode.X, currentNode.Y).Position - map.getTileByPos(currentNode.Parent.X, currentNode.Parent.Y).Position; previousMouvement.Normalize(); } //For each neighbor foreach (Point movement in movements) { Point exploredGridPos = new Point(currentNode.X + movement.X, currentNode.Y + movement.Y); //Checks if valid move and checks if not if closed nodes list if (ValidNavigableNode(u.UnitType, new Point(currentNode.X, currentNode.Y), exploredGridPos) && !closedNodes.Contains(_gridMap[exploredGridPos.Y, exploredGridPos.X])) { NodeInfo exploredNode = _gridMap[exploredGridPos.Y, exploredGridPos.X]; Tile.TileType exploredTerrain = map.getTileByPos(exploredGridPos.X, exploredGridPos.Y).TerrainType; if(openedNodes.Contains(exploredNode)) { int newCost = currentNode.MoveCost + GetMoveCost(previousMouvement, movement, exploredTerrain); if (newCost < exploredNode.MoveCost) { exploredNode.Parent = currentNode; exploredNode.MoveCost = newCost; //Find nearest tile to the target (in case doesn't find path to target) //Only compares the node to the current nearest FindNearest(exploredNode); } } else { exploredNode.Parent = currentNode; exploredNode.MoveCost = currentNode.MoveCost + GetMoveCost(previousMouvement, movement, exploredTerrain); Vector2 exploredNodeWorldPos = map.getTileByPos(exploredGridPos.X, exploredGridPos.Y).Position; exploredNode.EstimatedRemainingCost = (int)(endPosition - exploredNodeWorldPos).Length(); //Find nearest tile to the target (in case doesn't find path to target) //Only compares the node to the current nearest FindNearest(exploredNode); openedNodes.Add(exploredNode); } } } } return closedNodes; } After that, I simply check if the end node is contained in the returned nodes. If so, I add the end node and each parent until I reach the start. If not, I add the nearestToTarget and each parent until I reach the start. I added a condition before calling FindPath so that only one unit can call a find path each frame (60 frame per second), but it makes no difference. I thought maybe I could solve this by allowing the find path to run in background while the game continues to run correctly, even if it takes a few frame (it is currently sequential sonce it is called in the update() of the unit if there's a target location but no path), but I don't really know how... I also though about sorting my opened nodes list by cost so I don't have to loop them, but I don't know if that would have an effect on the performance... Would there be other solutions? P.S. In the code, when I get the Move Cost, I check if the unit has to turn to perform the move, and the terrain type, nothing hard to do.

  Read the article

• Entity System with C++ templates

  - by tommaisey

  I've been getting interested in the Entity/Component style of game programming, and I've come up with a design in C++ which I'd like a critique of. I decided to go with a fairly pure Entity system, where entities are simply an ID number. Components are stored in a series of vectors - one for each Component type. However, I didn't want to have to add boilerplate code for every new Component type I added to the game. Nor did I want to use macros to do this, which frankly scare me. So I've come up with a system based on templates and type hinting. But there are some potential issues I'd like to check before I spend ages writing this (I'm a slow coder!) All Components derive from a Component base class. This base class has a protected constructor, that takes a string parameter. When you write a new derived Component class, you must initialise the base with the name of your new class in a string. When you first instantiate a new DerivedComponent, it adds the string to a static hashmap inside Component mapped to a unique integer id. When you subsequently instantiate more Components of the same type, no action is taken. The result (I think) should be a static hashmap with the name of each class derived from Component that you instantiate at least once, mapped to a unique id, which can by obtained with the static method Component::getTypeId ("DerivedComponent"). Phew. The next important part is TypedComponentList<typename PropertyType>. This is basically just a wrapper to an std::vector<typename PropertyType> with some useful methods. It also contains a hashmap of entity ID numbers to slots in the array so we can find Components by their entity owner. Crucially TypedComponentList<> is derived from the non-template class ComponentList. This allows me to maintain a list of pointers to ComponentList in my main ComponentManager, which actually point to TypedComponentLists with different template parameters (sneaky). The Component manager has template functions such as: template <typename ComponentType> void addProperty (ComponentType& component, int componentTypeId, int entityId) and: template <typename ComponentType> TypedComponentList<ComponentType>* getComponentList (int componentTypeId) which deal with casting from ComponentList to the correct TypedComponentList for you. So to get a list of a particular type of Component you call: TypedComponentList<MyComponent>* list = componentManager.getComponentList<MyComponent> (Component::getTypeId("MyComponent")); Which I'll admit looks pretty ugly. Bad points of the design: If a user of the code writes a new Component class but supplies the wrong string to the base constructor, the whole system will fail. Each time a new Component is instantiated, we must check a hashed string to see if that component type has bee instantiated before. Will probably generate a lot of assembly because of the extensive use of templates. I don't know how well the compiler will be able to minimise this. You could consider the whole system a bit complex - perhaps premature optimisation? But I want to use this code again and again, so I want it to be performant. Good points of the design: Components are stored in typed vectors but they can also be found by using their entity owner id as a hash. This means we can iterate them fast, and minimise cache misses, but also skip straight to the component we need if necessary. We can freely add Components of different types to the system without having to add and manage new Component vectors by hand. What do you think? Do the good points outweigh the bad?

  Read the article

• Making user input/math on data fast, unlike excel type programs

  - by proGrammar

  I'm creating a research platform solely for myself to do some research on data. Programs like excel are terribly slow for me so I'm trying to come up with another solution. Originally I used excel. A1 was the cell that contained the data and all other cells in use calculated something on A1, or on other cells, that all could be in the end traced to A1. A1 was like an element of an array, I then I incremented it to go through all my data. This was way too slow. So the only other option I found originally was to hand code in c# the calculations inside a loop. Then I simply recompiled each time I changed my math. This was terribly slow to do and I had to order everything correctly so things would update correctly (dependencies). I could have also used events, but hand coding events for each cell like calculation would also be very slow. Next I created an application to read Excel and to perfectly imitate it. Which is what I now use. Basically I write formulas onto a fraction of my data to get live results inside excel. Then my program reads excel, writes another c# program, compiles it, and runs that program which runs my excel created formulas through a lot more data a whole lot faster. The advantage being my application dependency sorts everything (or I could use events) so I don't have to (like excel does) And of course the speed. But now its not a single application anymore. Instead its 2 applications, one which only reads my formulas and writes another program. The other one being the result which only lives for a short while before I do other runs through my data with different formulas / settings. So I can't see multiple results at one time without introducing even more programs like a database or at least having the 2 applications talking to each other. My idea was to have a dll that would be written, compiled, loaded, and unloaded again and again. So a self-updating program, sort of. But apparently that's not possible without another appdomain which means data has to be marshaled to be moved between the appdomains. Which would slow things down, not for summaries, but for other stuff I need to do with all my data. I'm also forgetting to mention a huge problem with restarting an application again and again which is having to reload ALL my data into memory again and again. But its still a whole lot faster than excel. I'm really super puzzled as to what people do when they want to research data fast. I'm completely unable to have a program accept user input and having it fast. My understanding is that it would have to do things like excel which is to evaluate strings again and again. So my only option is to repeatedly compile applications. Do I have a correct understanding on computer science? I've only just began programming, and didn't think I would have to learn much to do some simple math on data. My understanding is its either compiling my user defined stuff to a program or evaluating them from a string or something stupid again and again. And my only option is to probably switch operating systems or something to be able to have a program compile and run itself without stopping (writing/compiling dll, loading dll to program, unloading, and repeating). Can someone give me some idea on how computers work? Is anything better possible? Like a running program, that can accept user input and compile it and then unload it later? I mean heck operating systems dont need to be RESTARTED with every change to user input. What is this the cave man days? Sorry, it's just so super frustrating not knowing what one can do, and can't do. If only I could understand and learn this stuff fast enough.

  Read the article

• I need help with 2D collision response (of stacking rotating polygons, with friction and gravity, for a game)

  - by Register Sole

  Hi I am looking for suggestions on how to write a collision response for game programming purpose (so not a scientific simulation). I am dealing with 2D polygons that are rotating, and I want them to be able to stack. I also want friction and gravity. I have a detection mechanism that returns the separating axis, how long the polygons are overlapping, and up to 2 points of contact. For the response, I am currently using an impulse-based response, which main idea is: find the separating axis, length of overlap, and the point of contact (if there are two, pick a random point between to simulate averaged force. i believe there are better ways than this) separate the object (modifying their positions, taking into account of their masses. i do not separate them completely though, to keep track that they are colliding to reduce jitter) calculate normal force based on the coefficient of restitution as if there is no friction. calculate friction, as if there is no normal force. I also assume that the direction of the friction is the same throughout the collision. apply the two forces (which result in a rather inaccurate result, since each force is calculated as if the other is not present. for non-rotating bodies though, this method is exact) I am aware that this method requires the coefficient of friction to be sufficiently small due to the assumption that the direction of friction stays the same in a collision. Also, the result is visually satisfying if gravity is not present. However, when there is gravity, objects on ground jitter and drift (even with zero coefficient of restitution)! It also happens for stacking objects. Larger coefficient of restitution and gravity increase the jittering. I hope you can help me with this. Some things i would like to know more about is how to handle collision with two point of contacts (how to end up having an object sitting still on the ground?), how to reduce, and prevent if possible, jitter and drift (do people use the most accurate method possible, or is there a trick to overcome this?), and how to handle multiple objects collision (for example, in the case of stacking objects, how do I check collisions between all of them and keep them all stable at every frame so they don't jitter?). A total reformulation of my algorithm is also welcomed, as long as it works. Another thing to note is that I am not making a Physics game, so I only need a visually satisfying response (though a realistic response is preferable, if it is not performance-heavy). But surely jittering and drifting objects on flat ground are not at all acceptable. In addition, I am a Physics student, so feel free to talk about impulse and whatever needed. Finally, I'm sorry for the long post. I tried to be as concise as I can. Thank you for reading it! EDIT It seems what I didn't manage to come up all this time is to separate resting contact as a class of its own and how to solve them. Currently reading the paper suggested by Jedediah. More suggestions on the topic are welcome :) CASE CLOSED After reading various papers referenced in the paper, successfully implemented simultaneous impulse method (referring to the original paper by Erin Catto, [Catt05]). Thanks maaaan!! The paper is wonderful. The current system is visibly much better than the previous. Still haven't separated resting contact as a class of its own though, which brings me to my next question. Love you all! Haha (sorry, I'm just so happy thanks to you).

  Read the article

< Previous Page | 635 636 637 638 639 640 641 642 643 644 645 646  | Next Page >