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  • Why is it possible to have an interface without a return type in PHP?

    - by streetparade
    Why is it possible to create an interface without specifying a return type? Why doesn't this make this interface unusable? This makes it more Clear: Interface run { public function getInteger(); } class MyString implements run { public function myNumber() { } public function getInteger() { return "Not a number"; } } In Java every Interface has a return type like Integer, String or Void I know that PHP is unfortunately a loosely typed Language but isn't there a Solution to that Problem? Is it possible to define an Interface with a return type like Integer?

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  • designing the database if depending on dynamic columns

    - by phani_yelugula
    In my project,"admin" can create text fields dynamically (using jsp +javascript) and enter can enter data in text fields for saving.in the back end i have to save them in database. here the problem is 1)how we can create columns dynamically depending on the textfields admin is creating. like if he is creating 5textfields then we should create 5 columns in database,if he going with 10 we should do 10 columns. im doing this in mysql,jsp,struts,hibernate

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  • How can I make the small icon(16x16)?

    - by Cora
    Hi All, I found it difficult to make small icons look clear and clean. For instance, I made the 16x16 size icons, they looked ok in PS or AI, but after saved them as some other image types, they are not that clear at all. Is that because i used wrong color or wrong tools? I wonder if there are some special tools for making extremely small icons. So any options? How i can make them look more clear and clean? Thanks a lot!

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  • what service class to use to incapsulate method

    - by xbsxbs
    I have to write a simple method extractArticle() that returns Article object which is extracted from Message object. I have MessageService and ArticleService classes intended to handle tasks like this. What service class is more correctly to use to incapsulate extractArticle() funcionality? $article = MessageService::extractArticle(Message $message); or $article = ArticleService::extractArticleFromMessage(Message $message);

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  • Windows Game Loop 50% CPU on Dual Core

    - by Dave18
    The game loop alone is using 50% of CPU Usage, I haven't done any rendering work yet. What i'm doing here? while(true) { if(PeekMessage(&msg,NULL,0,0,PM_REMOVE)) { if(msg.message == WM_QUIT || msg.message == WM_CLOSE || msg.message == WM_DESTROY) break; TranslateMessage(&msg); DispatchMessage(&msg); } else { //Run game code, break out of loop when the game is over } }

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  • [WPF] When Should I Retrieve Values from Textbox?

    - by they_soft
    Suppose I have a Window with TextBoxes I want to use the values. Right now I'm thinking of either: 1) Updating each associated value once the cursor is out of focus, and once the user presses Ok I start the program 2) Once the user presses Ok, I retrieve all the values at once then start the program I'm not sure which one is better though. First alternative seems more modular, but there's more semantic coupling since I each new box is supposed to be updating its respective value. I realize this isn't all that important, but I'm trying to understand when to centralize and when not to. Other better approachers are appreciated too.

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  • Best way to create 100% width middle column with css

    - by nick
    Hey everyone, I have a pretty standard css layout where I use a container div that is 980px wide to hold everything. The only problem is that I want to have a 1900px wide banner half way down the page that is centered in the middle and is 100% width of the page. Is there any way to do this without getting rid of the container div? so I am wanting ____________________ | | | | | | | | | | | | |___| |___| | | | | |___ ___| | | | | | | | | | | | | | | | | |___|___________|___| < 980px > container < 100% page width > Anyone know how to get that 1900px banner centered in the middle without deleting my container div? THANKS!!

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  • How to create many div's with 100% height?

    - by ChrisBenyamin
    I need a html document, that contains multiple div's with 100% height (screen filling) one below the other. I have tried to apply every element a height of 100%, but that won't work seamless nor clean. Maybe there is a option with JavaScript? I don't have an idea. Please suggest me your solutions. chris

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  • DESIGNING FOR WIN PHONE 7

    Designing applications for the Win Phone 7 is very similar to designing for print. In my opinion, it feels like a cross between a tri-fold brochure and a poster. I based my prototype designs on Microsofts Metro style guide, with typography as the main focus and stunning imagery for support. Its nice to have fixed factors regulating the design, making it a fun and fresh design experience. Microsoft provides a UI Design Guidelines document that outlines layout sizes, background image size, recommended typefaces and spacing. You know what you are designing for and you know how it will look and act on the win phone 7 platform. Although applications are not required to strictly adhere to the Metro style guide I feel it makes the best use of the panorama view  and navigation. With strong examples of this UI concept in place like their Zune-like music + videos hub, I found it fairly easy to put together a few quick app mockups (see below). In addition to design guidelines, using a ready built design templates, or a win phone 7 specific panorama control like the one by Clarity Consulting will make the process of bringing your designs to life much more efficient. Likes, Dislikes, and Challenges I think the idea of the hub is completely intuitive. This concept clearly breaks down info into more manageable pieces, and greatly helps with organization when designing for the phone. I like the chromeless appearance, allowing the core functionality of the application to take precedence over gradients, textures, bevels, drop shadows, and the complicated animations you see on the web. Although I understand the Win Phone 7 guidelines are a work in progress, I found a few contradictions. I also noticed that certain design specifications did not translate well to the phone emulator . If you use their guidelines as suggested best practices and not as fixed definitions you will have more success. Multi-directional vs Linear The main challenge I had was stepping away from familiar navigational examples seen in other mobile phones. I had to keep reminding myself that the content to the right and to the left of what I was working on didnt necessarily have to have a direct link to one another. I started thinking multi-directional as opposed to linear. Win phone 7 vs IPhone The Metro styling of the Win Phone 7 is similar to the Zune HD and the Windows Media Center UI and offers a different interface paradigm than the IPhone. When navigating an application it feels like you are panning a long seamless page of information in contrast to the multiple panels of an IPhone. I think there is less of an opportunity to overdesign your application, which happens often with IPhone applications. While both interfaces are simple and sleek, win phone 7 really gets down to the basics. IPhone sets a high standard for designing for touch, designing for win phone 7 could improve on that user experience with a consistent and strategic use of white space and staying away from a menu and icon heavy UI. Design Examples for Win Phone 7 Applications Here are some concepts for both generic and brand specific applications for Win Phone 7: View Full Album Resources to get you going with your own Win Phone 7 design: Helpful design templates for Win Phone 7  http://www.shazaml.com/archives/windows-phone-7-ui-templates Here is the interaction design guide for Win Phone 7 http://go.microsoft.com/?linkid=9713252 Windows has a project template for Blend 4 and Visual Studio 2010 RC1 http://developer.windowsphone.com/ Clarity Consulting developed a panorama control for Win Phone 7 http://blogs.claritycon.com/blogs/design/archive/2010/03/30/building-the-elusive-windows-phone-panorama-control.aspxDid you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • DESIGNING FOR WIN PHONE 7

    Designing applications for the Win Phone 7 is very similar to designing for print. In my opinion, it feels like a cross between a tri-fold brochure and a poster. I based my prototype designs on Microsofts Metro style guide, with typography as the main focus and stunning imagery for support. Its nice to have fixed factors regulating the design, making it a fun and fresh design experience. Microsoft provides a UI Design Guidelines document that outlines layout sizes, background image size, recommended typefaces and spacing. You know what you are designing for and you know how it will look and act on the win phone 7 platform. Although applications are not required to strictly adhere to the Metro style guide I feel it makes the best use of the panorama view  and navigation. With strong examples of this UI concept in place like their Zune-like music + videos hub, I found it fairly easy to put together a few quick app mockups (see below). In addition to design guidelines, using a ready built design templates, or a win phone 7 specific panorama control like the one by Clarity Consulting will make the process of bringing your designs to life much more efficient. Likes, Dislikes, and Challenges I think the idea of the hub is completely intuitive. This concept clearly breaks down info into more manageable pieces, and greatly helps with organization when designing for the phone. I like the chromeless appearance, allowing the core functionality of the application to take precedence over gradients, textures, bevels, drop shadows, and the complicated animations you see on the web. Although I understand the Win Phone 7 guidelines are a work in progress, I found a few contradictions. I also noticed that certain design specifications did not translate well to the phone emulator . If you use their guidelines as suggested best practices and not as fixed definitions you will have more success. Multi-directional vs Linear The main challenge I had was stepping away from familiar navigational examples seen in other mobile phones. I had to keep reminding myself that the content to the right and to the left of what I was working on didnt necessarily have to have a direct link to one another. I started thinking multi-directional as opposed to linear. Win phone 7 vs IPhone The Metro styling of the Win Phone 7 is similar to the Zune HD and the Windows Media Center UI and offers a different interface paradigm than the IPhone. When navigating an application it feels like you are panning a long seamless page of information in contrast to the multiple panels of an IPhone. I think there is less of an opportunity to overdesign your application, which happens often with IPhone applications. While both interfaces are simple and sleek, win phone 7 really gets down to the basics. IPhone sets a high standard for designing for touch, designing for win phone 7 could improve on that user experience with a consistent and strategic use of white space and staying away from a menu and icon heavy UI. Design Examples for Win Phone 7 Applications Here are some concepts for both generic and brand specific applications for Win Phone 7: View Full Album Resources to get you going with your own Win Phone 7 design: Helpful design templates for Win Phone 7  http://www.shazaml.com/archives/windows-phone-7-ui-templates Here is the interaction design guide for Win Phone 7 http://go.microsoft.com/?linkid=9713252 Windows has a project template for Blend 4 and Visual Studio 2010 RC1 http://developer.windowsphone.com/ Clarity Consulting developed a panorama control for Win Phone 7 http://blogs.claritycon.com/blogs/design/archive/2010/03/30/building-the-elusive-windows-phone-panorama-control.aspxDid you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • Apps UX Launches Blueprints for Mobile User Experiences

    - by mvaughan
    By Misha Vaughan, Oracle Applications User ExperienceAt Oracle OpenWorld 2012 this year, the Oracle Applications User Experience (Apps UX) team announced the release of Mobile User Experience Functional Design Patterns. These patterns are designed to work directly with Oracle’s Fusion Middleware, specifically, ADF Mobile.  The Oracle Application Development Framework for mobile users enables developers to build one application that can be deployed to multiple mobile device platforms. These same mobile design patterns provide the guidance for Oracle teams to develop Fusion Mobile expenses. Application developers can use Oracle’s mobile design patterns to design iPhone, Android, or browser-based smartphone applications. We are sharing our mobile design patterns and their baked-in, scientifically proven usability to enable Oracle customers and partners to build mobile applications quickly.A different way of thinking and designing. Lynn Rampoldi-Hnilo, Senior Manager of Mobile User Experiences for Apps UX, says mobile design has to be compelling. “It needs to be optimized for the device, and be visually rich and simple,” she said. “What is really key is that you are designing for a user’s most personal device, the device that they will have with them at all times of the day.”Katy Massucco, director of the overall design patterns site, said: “You need to start with a simplified task flow. Everything should be a natural interaction. The action should be relevant and leveraging the device. It should be seamless.”She suggests that developers identify the essential tasks that a user would want to do while mobile. “They need to understand the user and the context,” she added. ?A sample inline action design patternWhat people are sayingReactions to the release of the design patterns have been positive. Debra Lilley, Oracle ACE Director and Fusion User Experience Advocate (FXA), has already demo’ed Fusion Mobile Expenses widely.  Fellow Oracle Ace Director Ronald van Luttikhuizen, called it a “cool demo by @debralilley of the new mobile expenses app.” FXA member Floyd Teter says he is already cooking up some plans for using mobile design patterns.  We hope to see those ideas at Collaborate or ODTUG in 2013. For another perspective on why user experience is such an important focus for mobile applications, check out this video by John King, Director, and Monty Latiolais, President, both from ODTUG, or the Oracle Development Tools User Group.In a separate interview by e-mail, Latiolais wrote: “I enjoy the fact we can take something that, in the past, has been largely subjective, and now apply to it a scientifically proven look and feel. Trusting Oracle’s UX Design Patterns, the presentation really can become one less thing to worry about. As someone with limited ADF experience, that is extremely beneficial.”?King, who was also interviewed by e-mail, wrote: “User Experience is about making the task at hand as easy and error-free as possible. Oracle's UX labs worked hard to make the User Experience in the new Fusion Applications as good as possible; ADF makes adding tested, consistent, user experiences a declarative exercise by leveraging that work. As we move applications onto mobile platforms, user experience is the driving factor. Customers are "spoiled" by a bevy of fantastic applications, and ours cannot disappoint them. Creating applications that enable users to quickly and effectively accomplish whatever task is at hand takes thought and practice. Developers must become ’power users’ and then create applications that they and their users will love.”

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  • Construction Paper, Legos, and Architectural Modeling

    I can remember as a kid playing with construction paper and Legos to explore my imagination. Through my exploration I was able to build airplanes, footballs, guns, and more, out of paper. Additionally I could create entire cities, robots, or anything else I could image out of Legos.  These toys, I now realize were in fact tools that gave me an opportunity to explore my ideas in the physical world through the use of modeling.  My imagination was allowed to run wild as I, unknowingly at the time, made design decisions that directly affected the models I was building from the raw materials.  To prove my point further, I can remember building a paper airplane that seemed to go nowhere when I tried to throw it. So I decided to attach a paper clip to the plane before I decided to throw it the next time to test my concept that by adding more weight to the plane that it would fly better and for longer distances. The paper airplane allowed me to model my design decision through the use of creating an artifact in that I created a paper airplane that was carrying extra weight through the incorporation of the paper clip in to the design. Also, I remember using Legos to build all sorts of creations, and these creations became artifacts of my imagination. As I further and further defined my Lego creations through the process of playing I was able to create elaborate artifacts of my imagination. These artifacts represented design decision I had made in the evolution of my creation through my child like design process. In some form or fashion the artifacts I created as a kid are very similar to the artifacts that I create when I model a software architectural concept or a software design in that the process of making decisions is directly translated in to a tangible model in the form of an architectural model. Architectural models have been defined as artifacts that depict design decisions of a system’s architecture.  The act of creating architectural models is the act of architectural modeling. Furthermore, architectural modeling is the process of creating a physical model based architectural concepts and documenting these design decisions. In the process of creating models, the standard notation used is Architectural modeling notation. This notation is the primary method of capturing the essence of design decisions regarding architecture.  Modeling notations can vary based on the need and intent of a project; typically they range from natural language to a diagram based notation. Currently, Unified Markup Language (UML) is the industry standard in terms of architectural modeling notation  because allows for architectures to be defined through a series of boxes, lines, arrows and other basic symbols that encapsulate design designs in to virtual components, connectors, configurations and interfaces.  Furthermore UML allows for additional break down of models through the use of natural language as to explain each section of the model in plain English. One of the major factors in architectural modeling is to define what is to be modeled. As a basic rule of thumb, I tend to model architecture based on the complexity of systems or sub sub-systems of architecture. Another key factor is the level of detail that is actually needed for a model. For example if I am modeling a system for a CEO to view then the low level details will be omitted. In comparison, if I was modeling a system for another engineer to actually implement I would include as much detailed information as I could to help the engineer implement my design.

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  • is Microsoft LC random generator patented?

    - by user396672
    I need a very simple pseudo random generator (no any specific quality requirements) and I found Microsoft's variant of LCG algorithm used for rand() C runtime library function fit my needs (gcc's one seems too complex). I found the algorithm here: http://rosettacode.org/wiki/Linear_congruential_generator#C However, I worry the algorithm (including its "magic numbers" i.e coefficients) may by patented or restricted for use in some another way. Is it allowed to use this algorithm without any licence or patent restrictions or not? I can't use library rand() because I need my results to be exactly reproducible on different platforms

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  • Could I be going crazy with Event Handlers? Am I going the "wrong way" with my design?

    - by sensae
    I guess I've decided that I really like event handlers. I may be suffering a bit from analysis paralysis, but I'm concerned about making my design unwieldy or running into some other unforeseen consequence to my design decisions. My game engine currently does basic sprite-based rendering with a panning overhead camera. My design looks a bit like this: SceneHandler Contains a list of classes that implement the SceneListener interface (currently only Sprites). Calls render() once per tick, and sends onCameraUpdate(); messages to SceneListeners. InputHandler Polls the input once per tick, and sends a simple "onKeyPressed" message to InputListeners. I have a Camera InputListener which holds a SceneHandler instance and triggers updateCamera(); events based on what the input is. AgentHandler Calls default actions on any Agents (AI) once per tick, and will check a stack for any new events that are registered, dispatching them to specific Agents as needed. So I have basic sprite objects that can move around a scene and use rudimentary steering behaviors to travel. I've gotten onto collision detection, and this is where I'm not sure the direction my design is going is good. Is it a good practice to have many, small event handlers? I imagine going the way I am that I'd have to implement some kind of CollisionHandler. Would I be better off with a more consolidated EntityHandler which handles AI, collision updates, and other entity interactions in one class? Or will I be fine just implementing many different event handling subsystems which pass messages to each other based on what kind of event it is? Should I write an EntityHandler which is simply responsible for coordinating all these sub event handlers? I realize in some cases, such as my InputHandler and SceneHandler, those are very specific types of events. A large portion of my game code won't care about input, and a large portion won't care about updates that happen purely in the rendering of the scene. Thus I feel my isolation of those systems is justified. However, I'm asking this question specifically approaching game logic type events.

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  • Issue with VS 2008 designer and usercontrol.

    - by Ram
    Hello, I have created a custom data grid control. I dragged it on windows form and set its properties like column and all & ran the project. It built successfully and I am able to view the grid control on the form. Now if i try to view that form in designer, I am getting following error.. Object reference not set to an instance of an object. Instances of this error (1) 1. Hide Call Stack at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.GetMemberTargetObject(XmlElementData xmlElementData, String& member) at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.CreateAssignStatement(XmlElementData xmlElement) at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.XmlElementData.get_CodeDomElement() at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.EndElement(String prefix, String name, String urn) at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.Parse(XmlReader reader) at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.ParseXml(String xmlStream, CodeStatementCollection statementCollection, String fileName, String methodName) at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomParser.OnMethodPopulateStatements(Object sender, EventArgs e) at System.CodeDom.CodeMemberMethod.get_Statements() at System.ComponentModel.Design.Serialization.TypeCodeDomSerializer.Deserialize(IDesignerSerializationManager manager, CodeTypeDeclaration declaration) at System.ComponentModel.Design.Serialization.CodeDomDesignerLoader.PerformLoad(IDesignerSerializationManager manager) at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomDesignerLoader.PerformLoad(IDesignerSerializationManager serializationManager) at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomDesignerLoader.DeferredLoadHandler.Microsoft.VisualStudio.TextManager.Interop.IVsTextBufferDataEvents.OnLoadCompleted(Int32 fReload) If I ignore the exception, form appears blank with no sign of grid control on it. However I can see the code for the grid in the designer file. Any pointer on this would be a great help.

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  • VS 2008 designer and usercontrol.

    - by Ram
    Hello, I have created a custom data grid control. I dragged it on windows form and set its properties like column and all & ran the project. It built successfully and I am able to view the grid control on the form. Now if i try to view that form in designer, I am getting following error.. Object reference not set to an instance of an object. Instances of this error (1) 1. Hide Call Stack at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.GetMemberTargetObject(XmlElementData xmlElementData, String& member) at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.CreateAssignStatement(XmlElementData xmlElement) at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.XmlElementData.get_CodeDomElement() at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.EndElement(String prefix, String name, String urn) at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.Parse(XmlReader reader) at Microsoft.VisualStudio.Design.Serialization.CodeDom.XML.CodeDomXmlProcessor.ParseXml(String xmlStream, CodeStatementCollection statementCollection, String fileName, String methodName) at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomParser.OnMethodPopulateStatements(Object sender, EventArgs e) at System.CodeDom.CodeMemberMethod.get_Statements() at System.ComponentModel.Design.Serialization.TypeCodeDomSerializer.Deserialize(IDesignerSerializationManager manager, CodeTypeDeclaration declaration) at System.ComponentModel.Design.Serialization.CodeDomDesignerLoader.PerformLoad(IDesignerSerializationManager manager) at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomDesignerLoader.PerformLoad(IDesignerSerializationManager serializationManager) at Microsoft.VisualStudio.Design.Serialization.CodeDom.VSCodeDomDesignerLoader.DeferredLoadHandler.Microsoft.VisualStudio.TextManager.Interop.IVsTextBufferDataEvents.OnLoadCompleted(Int32 fReload) If I ignore the exception, form appears blank with no sign of grid control on it. However I can see the code for the grid in the designer file. Any pointer on this would be a great help. I have customized grid for my custom requirements like I have added custom text box n all. I have defined 3 constructors public GridControl() public GridControl(IContainer container) protected GridControl(SerializationInfo info, StreamingContext context)

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  • Why does adding Crossover to my Genetic Algorithm gives me worse results?

    - by MahlerFive
    I have implemented a Genetic Algorithm to solve the Traveling Salesman Problem (TSP). When I use only mutation, I find better solutions than when I add in crossover. I know that normal crossover methods do not work for TSP, so I implemented both the Ordered Crossover and the PMX Crossover methods, and both suffer from bad results. Here are the other parameters I'm using: Mutation: Single Swap Mutation or Inverted Subsequence Mutation (as described by Tiendil here) with mutation rates tested between 1% and 25%. Selection: Roulette Wheel Selection Fitness function: 1 / distance of tour Population size: Tested 100, 200, 500, I also run the GA 5 times so that I have a variety of starting populations. Stop Condition: 2500 generations With the same dataset of 26 points, I usually get results of about 500-600 distance using purely mutation with high mutation rates. When adding crossover my results are usually in the 800 distance range. The other confusing thing is that I have also implemented a very simple Hill-Climbing algorithm to solve the problem and when I run that 1000 times (faster than running the GA 5 times) I get results around 410-450 distance, and I would expect to get better results using a GA. Any ideas as to why my GA performing worse when I add crossover? And why is it performing much worse than a simple Hill-Climb algorithm which should get stuck on local maxima as it has no way of exploring once it finds a local max?

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  • Why does adding Crossover to my Genetic Algorithm give me worse results?

    - by MahlerFive
    I have implemented a Genetic Algorithm to solve the Traveling Salesman Problem (TSP). When I use only mutation, I find better solutions than when I add in crossover. I know that normal crossover methods do not work for TSP, so I implemented both the Ordered Crossover and the PMX Crossover methods, and both suffer from bad results. Here are the other parameters I'm using: Mutation: Single Swap Mutation or Inverted Subsequence Mutation (as described by Tiendil here) with mutation rates tested between 1% and 25%. Selection: Roulette Wheel Selection Fitness function: 1 / distance of tour Population size: Tested 100, 200, 500, I also run the GA 5 times so that I have a variety of starting populations. Stop Condition: 2500 generations With the same dataset of 26 points, I usually get results of about 500-600 distance using purely mutation with high mutation rates. When adding crossover my results are usually in the 800 distance range. The other confusing thing is that I have also implemented a very simple Hill-Climbing algorithm to solve the problem and when I run that 1000 times (faster than running the GA 5 times) I get results around 410-450 distance, and I would expect to get better results using a GA. Any ideas as to why my GA performing worse when I add crossover? And why is it performing much worse than a simple Hill-Climb algorithm which should get stuck on local maxima as it has no way of exploring once it finds a local max?

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  • Is there any algorithm that can solve ANY traditional sudoku puzzles, WITHOUT guessing (or similar techniques)?

    - by justin
    Is there any algorithm that solves ANY traditional sudoku puzzle, WITHOUT guessing? Here Guessing means trying an candidate and see how far it goes, if a contradiction is found with the guess, backtracking to the guessing step and try another candidate; when all candidates are exhausted without success, backtracking to the previous guessing step (if there is one; otherwise the puzzle proofs invalid.), etc. EDIT1: Thank you for your replies. traditional sudoku means 81-box sudoku, without any other constraints. Let us say the we know the solution is unique, is there any algorithm that can GUARANTEE to solve it without backtracking? Backtracking is a universal tool, I have nothing wrong with it but, using a universal tool to solve sudoku decreases the value and fun in deciphering (manually, or by computer) sudoku puzzles. How can a human being solve the so called "the hardest sudoku in the world", does he need to guess? I heard some researcher accidentally found that their algorithm for some data analysis can solve all sudoku. Is that true, do they have to guess too?

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  • Technical Article: Oracle Magazine Java Developer of the Year Adam Bien on Java EE 6 Simplicity by Design

    - by janice.heiss(at)oracle.com
    Java Champion and Oracle Magazine Java Developer of the Year, Adam Bien, offers his unique perspective on how to leverage new Java EE 6 features to build simple and maintainable applications in a new article in Oracle Magazine. Bien examines different Java EE 6 architectures and design approaches in an effort to help developers build efficient, simple, and maintainable applications.From the article: "Java EE 6 consists of a set of independent APIs released together under the Java EE name. Although these APIs are independent, they fit together surprisingly well. For a given application, you could use only JavaServer Faces (JSF) 2.0, you could use Enterprise JavaBeans (EJB) 3.1 for transactional services, or you could use Contexts and Dependency Injection (CDI) with Java Persistence API (JPA) 2.0 and the Bean Validation model to implement transactions.""With a pragmatic mix of available Java EE 6 APIs, you can entirely eliminate the need to implement infrastructure services such as transactions, threading, throttling, or monitoring in your application. The real challenge is in selecting the right subset of APIs that minimizes overhead and complexity while making sure you don't have to reinvent the wheel with custom code. As a general rule, you should strive to use existing Java SE and Java EE services before expanding your search to find alternatives." Read the entire article here.

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  • How to design highly scalable web services in Java?

    - by Kshitiz Sharma
    I am creating some Web Services that would have 2000 concurrent users. The services are offered for free and are hence expected to get a large user base. In the future it may be required to scale up to 50,000 users. There are already a few other questions that address the issue like - Building highly scalable web services However my requirements differ from the question above. For example - My application does not have a user interface, so images, CSS, javascript are not an issue. It is in Java so suggestions like using HipHop to translate PHP to native code are useless. Hence I decided to ask my question separately. This is my project setup - Rest based Web services using Apache CXF Hibernate 3.0 (With relevant optimizations like lazy loading and custom HQL for tune up) Tomcat 6.0 MySql 5.5 My questions are - Are there alternatives to Mysql that offer better performance for what I'm trying to do? What are some general things to abide by in order to scale a Java based web application? I am thinking of putting my Application in two tomcat instances with httpd redirecting the request to appropriate tomcat on basis of load. Is this the right approach? Separate tomcat instances can help but then database becomes the bottleneck since both applications access the same database? I am a programmer not a Db Admin, how difficult would it be to cluster a Mysql database (or, to cluster whatever database offered as an alternative to 1)? How effective are caching solutions like EHCache? Any other general best practices? Some clarifications - Could you partition the data? Yes we could but we're trying to avoid it. We need to run a lot of data mining algorithms and the design would evolve over time so we can't be sure what lines of partition should be there.

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  • What is the best approach for database design with lots of columns?

    - by Pratyush
    I am writing a query based financial application. It lets the user to write complicated equations (much like WHERE part of an SQL query) and find companies matching those criteria. For the above, I currently have more than 500 columns in the database table (each column representing a financial field). Example of Columns are: company_name, sales_annual_00, sales_annual_01, sales_annual_02, sales_annual_03, sales_annual_04, protit_annual_00, profit_annual1...(over 500 such columns). The number of rows is around 5000. Going forward, I would like to further increase the number of columns/financial-fields. For the above I would like to get help regarding: 1) What is the best database design approach? Is it ok to have these many number of columns? 2) How can it be normalized? (User can use any of these fields in search criteria). 3) Is it ok to stick with MySQL, or modern document based databases like MongoDB should be better for it? P.S. (Update): I have been using MySQL till now and a running example of the usage is at: http://screener.in/companies/89/Formula-- In above there around 500 fields/columns to create your query on, however, I seek to increase that number to much more in future.

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