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  • How to visualize code?

    - by gablin
    I've mostly only had to read my own code. As such, I've had no need to visualize the code as I already know how each and every class and module communicate with one another. But the few times I've had to read someone else's code - let us now assume we are talking about at least one larger module which contains several internal classes - I've almost always found myself wishing "This would have been so much easier to understand if I could just visualize it!" So what are the common methods or tools for enabling this? Which do you use, and why do you prefer them over the others? I've heard stuff like UML, module and class diagrams, but I imagine there are more. Furthermore, any of these is most likely better than anything I can devise on my own. EDIT: For those who answer with "Use pen and paper and just draw it": This isn't very helpful unless you explain this further. What exactly am I supposed to draw? A box for each class? Should I include the public methods? What about its fields? How should I draw connections that explain how one class uses another? What about modules? What if the language isn't object-oriented but functional or logical, or even just imperative (C, for instance)? What about global variables and functions? Is there an already-standardized way of drawing this, or do I need to think up of a method of my own? You get the drift.

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  • How to configure KDE default settings for a new user of a group?

    - by Adobe
    I'm a sys admin on Kubuntu 11.10 machine. Where do I configure the basic config for a new user (say belonging to group "users")? Edit 1: I want to configure langauages - currently my new users get English and Bulgarian Languages. I want them to get English and Russian - and also to set Alt-CapsLock - to be the input-language-switching-combination. Edit 2: How do I configure things in /usr/share/kde4 When I do kdesudo systemsettings and save configurations - only root settings got changed - not the /usr/share/kde4 ones. Edit 3: New user gets the /etc/skel files controlling bash behaviour-appearence. What about the KDE new user's default files - where are they stored? Edit 4: Oh, I found some hints: kde4-config --path config gives a list of folders (separated by the colon) where KDE looks for configs. My machine responded with: /home/boris/.kde/share/config/ /etc/kde4/ /usr/share/kubuntu-default-settings/kde4-profile/default/share/config/ /usr/share/kde4/config/ /usr/share/desktop-base/profiles/kde-profile/share/config/ It looks like third line is where KDE takes the default options. So I found these zilions of settings - but no GUI way to configure it ((. Edit 5: Finally, I've created a dummy user, configured it, and wrote a script which gives it's settings to a given user(s). The trick - is to chown after one transfered the dot files from one user to another. I've tested it - it works fine.

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  • Server-side Architecture for Online Game

    - by Draiken
    basically I have a game client that has communicate with a server for almost every action it takes, the game is in Java (using LWJGL) and right now I will start making the server. The base of the game is normally one client communicating with the server alone, but I will require later on for several clients to work together for some functionalities. I've already read how authentication server should be sepparated and I intend on doing it. The problem is I am completely inexperienced in this kind of server-side programming, all I've ever programmed were JSF web applications. I imagine I'll do socket connections for pretty much every game communication since HTML is very slow, but I still don't really know where to start on my server. I would appreciate reading material or guidelines on where to start, what architecture should the game server have and maybe some suggestions on frameworks that could help me getting the client-server communication. I've looked into JNAG but I have no experience with this kind of thing, so I can't really tell if it is a solid and good messaging layer. Any help is appreciated... Thanks ! EDIT: Just a little more information about the game. It is intended to be a very complex game with several functionalities, making some functionalities a "program" inside the program. It is not an usual game, like FPS or RPG but I intend on having a lot of users using these many different "programs" inside the game. If I wasn't clear enough, I'd really appreciate people that have already developed games with java client/server architecture, how they communicated, any frameworks, apis, messaging systems, etc. It is not a question of lack of knowledge of language, more a question for advice, so I don't end up creating something that works, but in the later stages will have to be rewriten for any kind of limiting reason. PS: sorry if my english is not perfect...

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  • Is error suppression acceptable in role of logic mechanism?

    - by Rarst
    This came up in code review at work in context of PHP and @ operator. However I want to try keep this in more generic form, since few question about it I found on SO got bogged down in technical specifics. Accessing array field, which is not set, results in error message and is commonly handled by following logic (pseudo code): if field value is set output field value Code in question was doing it like: start ignoring errors output field value stop ignoring errors The reasoning for latter was that it's more compact and readable code in this specific case. I feel that those benefits do not justify misuse (IMO) of language mechanics. Is such code is being "clever" in a bad way? Is discarding possible error (for any reason) acceptable practice over explicitly handling it (even if that leads to more extensive and/or intensive code)? Is it acceptable for programming operators to cross boundaries of intended use (like in this case using error handling for controlling output)? Edit I wanted to keep it more generic, but specific code being discussed was like this: if ( isset($array['field']) ) { echo '<li>' . $array['field'] . '</li>'; } vs the following example: echo '<li>' . @$array['field'] . '</li>';

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  • With the outcome of the Oracle vs Google trial, does that mean Mono is now safe from Microsoft [closed]

    - by Evan Plaice
    According to the an article on ArsTechnica the judge of the case ruled that APIs are not patent-able. He referred to the structure of modules/methods/classes/functions as being like libraries/books/chapters. To patent an API would be putting a patent on thought itself. It's the internal implementations that really matter. With that in mind, Mono (C# clone for Linux/Mac) has always been viewed tentatively because, even though C# and the CLI are ECMA standards, Microsoft holds a patent on the technology. Microsoft holds a covenant not to sue open source developers based on their patents but has maintained the ability to pull the plug on the Mono development team if they felt the project was a threat. With the recent ruling, is Mono finally out of the woods. A firm precedent has been established that patents can't be applied to APIs. From what I understand, none of the Mono implementation is copied verbatim, only the API structure and functionality. It's a topic I have been personally interested in for years now as I have spent a lot of time developing cross-platform C# libraries in MonoDevelop. I acknowledge that this is a controversial topic, if you have opinions that's what commenting is for. Try to keep the answers factual and based on established sources.

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  • best way to send messages to all subscribers with multiple subscriptions and multiple providers

    - by coding_idiot
    I'm writing an application in which - Many users can subsribe to posts made by another users. So for a single publisher there can be many subscribers. When a message is posted by an user X, all users who have subscribed to messages of User X will be sent an email. How to achieve this ? I'm thinking of using publish-subscribe pattern. And then I came through JMS. Which is the best JMS implementation to use according to your experience ? Or else what else solution do you propose to the given problem ? Shall I go for a straight-forward solution ?: User x posts a message, I find all users (from database) who subscribe to user x and then for every user, I call the sendEmail() method. [EDIT] My intention here is not to send-emails. I'm really sorry if it wasn't clear. I also have to send kind of system-notifications apart from Email to all subscribers. Right now, I've implemented the email-sending as a threadPool

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  • To PHP or Not to PHP? [closed]

    - by Vad
    Should I learn PHP in depth for my smaller projects or not? My main knowledge is Java/JavaScript for the web. My old small projects were written in classic ASP. However, ASP had its days. Now I am looking into going deeper with another scripting language which I can use for small website projects. Though I know PHP on a basic level I never liked PHP. But I have to admit it is so widely used that I better start liking it. And all hosting services offer mostly PHP solutions. However, there is quite a number of issues with PHP when I google for it. Developers seem to not like it a lot. I wish I would use server-side JavaScript for all my needs, but hosting is an issue plus many small businesses already want to improve their existing PHP sites. And lastly, say I want to create a web app for distribution. PHP sounds like the best bet. Or am I wrong?

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  • Languages with a clear distinction between subroutines that are purely functional, mutating, state-changing, etc?

    - by CPX
    Lately I've become more and more frustrated that in most modern programming languages I've worked with (C/C++, C#, F#, Ruby, Python, JS and more) there is very little, if any, language support for determining what a subroutine will actually do. Consider the following simple pseudo-code: var x = DoSomethingWith(y); How do I determine what the call to DoSomethingWith(y) will actually do? Will it mutate y, or will it return a copy of y? Does it depend on global or local state, or is it only dependent on y? Will it change the global or local state? How does closure affect the outcome of the call? In all languages I've encountered, almost none of these questions can be answered by merely looking at the signature of the subroutine, and there is almost never any compile-time or run-time support either. Usually, the only way is to put your trust in the author of the API, and hope that the documentation and/or naming conventions reveal what the subroutine will actually do. My question is this: Does there exist any languages today that make symbolic distinctions between these types of scenarios, and places compile-time constraints on what code you can actually write? (There is of course some support for this in most modern languages, such as different levels of scope and closure, the separation between static and instance code, lambda functions, et cetera. But too often these seem to come into conflict with each other. For instance, a lambda function will usually either be purely functional, and simply return a value based on input parameters, or mutate the input parameters in some way. But it is usually possible to access static variables from a lambda function, which in turn can give you access to instance variables, and then it all breaks apart.)

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

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

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

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

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  • How to implement behavior in a component-based game architecture?

    - by ghostonline
    I am starting to implement player and enemy AI in a game, but I am confused about how to best implement this in a component-based game architecture. Say I have a following player character that can be stationary, running and swinging a sword. A player can transit to the swing sword state from both the stationary and running state, but then the swing must be completed before the player can resume standing or running around. During the swing, the player cannot walk around. As I see it, I have two implementation approaches: Create a single AI-component containing all player logic (either decoupled from the actual component or embedded as a PlayerAIComponent). I can easily how to enforce the state restrictions without creating coupling between individual components making up the player entity. However, the AI-component cannot be broken up. If I have, for example, an enemy that can only stand and walk around or only walks around and occasionally swing a sword, I have to create new AI-components. Break the behavior up in components, each identifying a specific state. I then get a StandComponent, WalkComponent and SwingComponent. To enforce the transition rules, I have to couple each component. SwingComponent must disable StandComponent and WalkComponent for the duration of the swing. When I have an enemy that only stands around, swinging a sword occasionally, I have to make sure SwingComponent only disables WalkComponent if it is present. Although this allows for better mix-and-matching components, it can lead to a maintainability nightmare as each time a dependency is added, the existing components must be updated to play nicely with the new requirements the dependency places on the character. The ideal situation would be that a designer can build new enemies/players by dragging components into a container, without having to touch a single line of engine or script code. Although I am not sure script coding can be avoided, I want to keep it as simple as possible. Summing it all up: Should I lob all AI logic into one component or break up each logic state into separate components to create entity variants more easily?

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  • Question regarding Readability vs Processing Time

    - by Jordy
    I am creating a flowchart for a program with multiple sequential steps. Every step should be performed if the previous step is succesful. I use a c-based programming language so the lay-out would be something like this: METHOD 1: if(step_one_succeeded()) { if(step_two_succeeded()) { if(step_three_succeeded()) { //etc. etc. } } } If my program would have 15+ steps, the resulting code would be terribly unfriendly to read. So I changed my design and implemented a global errorcode that I keep passing by reference, make everything more readable. The resulting code would be something like this: METHOD 2: int _no_error = 0; step_one(_no_error); if(_no_error == 0) step_two(_no_error); if(_no_error == 0) step_three(_no_error); if(_no_error == 0) step_two(_no_error); The cyclomatic complexibility stays the same. Now let's say there are N number of steps. And let's assume that checking a condition is 1 clock long and performing a step doesn't take up time. The processing speed of Method1 can be anywhere between 1 and N. The processing speed of Method2 however is always equal to N-1. So Method1 will be faster most of the time. Which brings me to my question, is it bad practice to sacrifice time in order to make the code more readable? And why (not)?

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  • Best multi-platform mobile development tool, or use iPhone tools?

    - by Jesse Millikan
    I may be building a mobile app for a client soon. Their primary focus is the iPhone, but my boss would like to be able to target multiple platforms if it's feasible. The app will probably be a large but technically simple business application backed by a web service. So, here's the question as I see it: What is currently the strongest cross-platform mobile development tool that supports iOS? Would you choose it over native development tools? If you choose native, contrast it with a cross-platform tool you've used. In addition, For a project of the type we're expecting, what's the level of effort for your chosen tool versus other tools? What's the actual level of support of the tool for other platforms and their unique look and feel, capabilities, etc.? How thorough is the documentation of the product? How well do you like the development experience itself, e.g. the language, tools, documentation? Is it something you would choose to do long-term? I'll put a bounty out unless I get fantastic answers.

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  • Laptop keyboard and touchpad disabled on startup

    - by JAM
    I use Ubuntu 14.04 LTS on my Toshiba Satellite L775D laptop. 14.04 is the only operating system installed. I am new to Linux and only barely scratching the surface of doing things in terminal. When I boot my laptop keyboard and touchpad are disabled (99.99% of the time) if I do nothing. The only direct effect I can have is to keep pressing the "numlock" key during boot when I notice the "numlock" light goes off. If I do this then I have a 95% chance of the keyboard and touchpad working when I am in the operating system. I am able to use my wireless mouse regardless. I have not seen any messages during boot. Previously I have tried playing with input method settings and utilities as well as language support settings. This same problem exists with the 12.... and 13... versions of ubuntu. With everything I have tried (from looking at other posts/suggestions) it seems I can have only a temporary effect. Please help me find a permanent solution to this problem. thank you.

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  • Game Messaging System Design

    - by you786
    I'm making a simple game, and have decided to try to implement a messaging system. The system basically looks like this: Entity generates message - message is posted to global message queue - messageManager notifies every object of the new message through onMessageReceived(Message msg) - if object wants, it acts on the message. The way I'm making message objects is like this: //base message class, never actually instantiated abstract class Message{ Entity sender; } PlayerDiedMessage extends Message{ int livesLeft; } Now my SoundManagerEntity can do something like this in its onMessageReceived() method public void messageReceived(Message msg){ if(msg instanceof PlayerDiedMessage){ PlayerDiedMessage diedMessage = (PlayerDiedMessage) msg; if(diedMessage.livesLeft == 0) playSound(SOUND_DEATH); } } The pros to this approach: Very simple and easy to implement The message can contain as much as information as you want, because you can just create a new Message subclass that has whatever info necessary. The cons: I can't figure out how I can recycle Message objects to a object pool, unless I have a different pool for each subclass of Message. So I have lots and lots of object creation/memory allocation over time. Can't send a message to a specific recipient, but I haven't needed that yet in my game so I don't mind it too much. What am I missing here? There must be a better implementation or some idea that I'm missing.

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  • How do you avoid name similarities between your classes and the native ones?

    - by Oscar
    I just ran into an "interesting problem", which I would like your opinion about: I am developing a system and for many reasons (meaning: abstraction, technology independence, etc) we create our own types for exchanging information. For instance: if there is a method which is called SendEmail and is invoked by the business logic, it way have a parameter of type OurCompany.EMailMessage, which is an object which is completely technology independent and contains only "business relevant data" (for instance, no information abut head encoding). Inside the SendEmail function, we get this information from our EMailMEssage object and create a MailMessage (this one is technolgy specific) object so it can be sent over the network. As you can already notice, our class has a very similar name to the "native" language class. The problem is: this is exactly what they are, email messages, so it is hard to find another meaningful name for them. Do you have this problem often? How do you manage it? Edit: @mgkrebbs just commented about using fully qualified names. This is our current approach, but a little bit too verbose, IMHO. I would like something cleaner, if possible.

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

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

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

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

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  • Installation causing broken packages

    - by AWE
    Here I come I am so determined to use Ubuntu that I paid a professional to install it for me (dualboot). When I got it I got a lot of things from the software center. Skype did not have a download button so I googled it and Ubuntu help told me to do this: sudo add-apt-repository "deb http://archive.canonical.com/ $(lsb_release -sc) partner" and then this: sudo apt-get update && sudo apt-get install skype The terminal told me "that this is potentially harmful..." but I thought it was Ubuntu language meaning "are you sure?" Now items cannot be installed or removed until the package catalog is repaired, so I want to repair it but the package operation fails. "sudo aptitude -f install" - command not found Synaptic package manager tells me that I have two broken packages, libc6 and libc6-dev but doesn't help, only makes life complicated. What the *#$%&!!! I don't want to be forced to become a computer scientist just to be able to use a free source os. P.s. the sound stopped working

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  • Unable to debug an encodded javascript?

    - by miles away
    I’m having some problems debugging an encoded javacscript. This script I’m referring to given in this link over here. The encoding here is simple and it works by shifting the unicodes values to whatever Codekey was use during encoding. The code that does the decoding is given here in plain English below:- <script language="javascript"> function dF(s){ var s1=unescape(s.substr(0,s.length-1)); var t=''; for(i=0;i<s1.length;i++)t+=String.fromCharCode(s1.charCodeAt(i)-s.substr(s.length-1,1)); document.write(unescape(t)); } </script> I’m interested in knowing or understanding the values (e.g s1,t). Like for example when the value of i=0 what values would the following attributes / method would hold s1.charCodeAt(i) and s.substr(s.length-1,1) The reason I’m doing this is to understand as to how a CodeKey function really works. I don’t see anything in the code above which tells it to decode on the basis of codekey value. The only thing I can point in the encoding text is the last character which is set to 1 , 2 ,3 or 4 depending upon the codekey selected during encoding process. One can verify using the link I have given above. However, to debug, I’m using firebug addon with the script running as localhost on my wamp server. I’m able to put a breakpoint on the js using firebug but I’m unable to retrieve any of the user defined parameters or functions I mentioned above. I want to know under this context what would be best way to debug this encoded js.

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  • The advantages & disadvantages to be had from using a Web Framework?

    - by JHarley1
    Hello, This question is focused on extracting the advantages and disadvantages of using Web based Frameworks: such as Cake PHP, Zend, jQuery, ASP.NET). This question is completely language agnostic. Let me start with the notion of "Standing on the shoulders of Giants". Advantages: Empowers Developers - by taking features that would have previously have taken 100's of lines of code and compressing them into one simple function call empowers developers to integrate more complex features into their Web Sites. Allow for Quicker development of applications - this is very relevant for people that need websites created in a very small window (has anyone any examples of this?) Lower Costs - allows programmers to pass cost savings onto the customer, a whole new range of customers generated that wanted a website but previously could not afford the higher development costs. Disadvantages: Lost Understanding - by relying on the features of a framework a developer is in danger of loosing understanding on how things work (underneath the hood). The configuration cliff - once you go further than the configuration of your framework your productivity drops right off, it can be difficult to implement features outside of a frameworks configuration. Developer tramlines - you (the developer) has to do things the way that the developer want you to do things. Security issues - giving people these tools to develop professional looking websites fast is a potential risk, people can quickly create professional looking websites for fraudulent companies. I wonder what people make of my points, and whether any body disagrees with them? Also if people have additional points I would be grateful. Many Thanks, J

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

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

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  • Dealing with Fine-Grained Cache Entries in Coherence

    - by jpurdy
    On occasion we have seen significant memory overhead when using very small cache entries. Consider the case where there is a small key (say a synthetic key stored in a long) and a small value (perhaps a number or short string). With most backing maps, each cache entry will require an instance of Map.Entry, and in the case of a LocalCache backing map (used for expiry and eviction), there is additional metadata stored (such as last access time). Given the size of this data (usually a few dozen bytes) and the granularity of Java memory allocation (often a minimum of 32 bytes per object, depending on the specific JVM implementation), it is easily possible to end up with the case where the cache entry appears to be a couple dozen bytes but ends up occupying several hundred bytes of actual heap, resulting in anywhere from a 5x to 10x increase in stated memory requirements. In most cases, this increase applies to only a few small NamedCaches, and is inconsequential -- but in some cases it might apply to one or more very large NamedCaches, in which case it may dominate memory sizing calculations. Ultimately, the requirement is to avoid the per-entry overhead, which can be done either at the application level by grouping multiple logical entries into single cache entries, or at the backing map level, again by combining multiple entries into a smaller number of larger heap objects. At the application level, it may be possible to combine objects based on parent-child or sibling relationships (basically the same requirements that would apply to using partition affinity). If there is no natural relationship, it may still be possible to combine objects, effectively using a Coherence NamedCache as a "map of maps". This forces the application to first find a collection of objects (by performing a partial hash) and then to look within that collection for the desired object. This is most naturally implemented as a collection of entry processors to avoid pulling unnecessary data back to the client (and also to encapsulate that logic within a service layer). At the backing map level, the NIO storage option keeps keys on heap, and so has limited benefit for this situation. The Elastic Data features of Coherence naturally combine entries into larger heap objects, with the caveat that only data -- and not indexes -- can be stored in Elastic Data.

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  • Web Crawler for Learnign Topics on Wikipedia

    - by Chris Okyen
    When I want to learn a vast topic on wikipedia, I don't know where to start. For instance say I want to learn about Binary Stars, I then have to know other things linked on that pages and linked pages on all the linked pages and so on for the specified number of levels. I want to write a web crawler like HTTracker or something similiar, that will display a heiarchy of the links on a certain page and the links on those linked pages.I wish to use as much prewritten code as possible. Here is an example: Pretending we are bending the rules by grabing links from only the first sentence of each pages The example archives and "processes" two levels deep The page is Ternary operation The First Level In mathematics a ternary operation is an N-ary operation The Second Level Under Mathmatics: Mathematics (from Greek µ???µa máthema, “knowledge, study, learning”) is the abstract study of topics encompassing quantity, structure, space, change and others; it has no generally accepted definition. Under N-ary In logic,mathematics, and computer science, the arity i/'ær?ti/ of a function or operation is the number of arguments or operands that the function takes Under Operation In its simplest meaning in mathematics and logic, an operation is an action or procedure which produces a new value from one or more input values ------------------------------------------------------------------------- I need some way to determine what oder to approach all these wiki pages to learn the concept ( in this case ternary operations )... Following along with this exmpakle, one way to show the path to read would a printout flowout like so: This shows that the first sentence of the Mathematics page doesn't link to the first sentence of pages linked on ternary page two levels deep. (Please tell me how I should explain this ) --- In otherwords, the child node of the top pages first sentence, ternary_operation, does not have any child nodes that reference the children of the top pages other children nodes- N-ary and operation. Thus it is safe to read this first. Since N-ary has a link to operations we shoudl read the operation page second and finally read the N-ary page last. Again, I wish to use as much prewritten code as possible, and was wondering what language to use and what would be the simpliest way to go about doing this if there isn't already somethign out there? Thank You!

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  • Unit testing to prove balanced tree

    - by Darrel Hoffman
    I've just built a self-balancing tree (red-black) in Java (language should be irrelevant for this question though), and I'm trying to come up with a good means of testing that it's properly balanced. I've tested all the basic tree operations, but I can't think of a way to test that it is indeed well and truly balanced. I've tried inserting a large dictionary of words, both pre-sorted and un-sorted. With a balanced tree, those should take roughly the same amount of time, but an unbalanced tree would take significantly longer on the already-sorted list. But I don't know how to go about testing for that in any reasonable, reproducible way. (I've tried doing millisecond tests on these, but there's no noticeable difference - probably because my source data is too small.) Is there a better way to be sure that the tree is really balanced? Say, by looking at the tree after it's created and seeing how deep it goes? (That is, without modifying the tree itself by adding a depth field to each node, which is just wasteful if you don't need it for anything other than testing.)

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