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  • Is true multithreading really necessary?

    - by Jonathan Graef
    So yeah, I'm creating a programming language. And the language allows multiple threads. But, all threads are synchronized with a global interpreter lock, which means only one thread is allowed to execute at a time. The only way to get the threads to switch off is to explicitly tell the current thread to wait, which allows another thread to execute. Parallel processing is of course possible by spawning multiple processes, but the variables and objects in one process cannot be accessed from another. However the language does have a fairly efficient IPC interface for communicating between processes. My question is: Would there ever be a reason to have multiple, unsynchronized threads within a single process (thus circumventing the GIL)? Why not just put thread.wait() statements in key positions in the program logic (presuming thread.wait() isn't a CPU hog, of course)? I understand that certain other languages that use a GIL have processor scheduling issues (cough Python), but they have all been resolved.

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  • null values vs "empty" singleton for optional fields

    - by Uko
    First of all I'm developing a parser for an XML-based format for 3D graphics called XGL. But this question can be applied to any situation when you have fields in your class that are optional i.e. the value of this field can be missing. As I was taking a Scala course on coursera there was an interesting pattern when you create an abstract class with all the methods you need and then create a normal fully functional subclass and an "empty" singleton subclass that always returns false for isEmpty method and throws exceptions for the other ones. So my question is: is it better to just assign null if the optional field's value is missing or make a hierarchy described above and assign it an empty singleton implementation?

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  • Creating user UI using Flixel

    - by Jamie Read
    I am new to game development but familiar with programming languages. I have started using Flixel and have a working Breakout game with score and lives. What I am trying to do is add a Start Screen before actually loading the game. I have a create function that adds all the game elements to the stage: override public function create():void // all game elements { How can I add this pre-load Start Screen? I'm not sure if I have to add in the code to this create function or somewhere else and what code to actually add. Eventually I would also like to add saving, loading, options and upgrades too. So any advice with that would be great. Here is my main game.as: package { import org.flixel.*; public class Game extends FlxGame { private const resolution:FlxPoint = new FlxPoint(640, 480); private const zoom:uint = 2; private const fps:uint = 60; public function Game() { super(resolution.x / zoom, resolution.y / zoom, PlayState, zoom); FlxG.flashFramerate = fps; } } } Thanks.

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  • Map Library: Client-side or Server-side?

    - by Mahdi
    As I have already asked here, I have to implement a Multi-Platform Map application. Now I have Mapstraction as an option which uses Javascript to implement the desired functionality. My question is, "Is there any reason/benefit to implement such a library (let say, Adapters) in Server-side (in my case, PHP)?" As these maps are all based on Javascript, there is a big reason to use Javascript again to make the adapter also, so it would not be dependent to PHP, Java, or .NET for example. But is that all? I wish to hear your ideas and comments also. :)

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  • How to expose game data in the game without a singelton?

    - by zardon
    I'm quite new to cocos2d and games programming, and am currently I am writing a game that is currently in Prototype stage. Everything is going okay, but I've realized a potentially big problem and I am not sure how to solve it. I am using a singelton to store a bunch of arrays for everything, a global list of planets, a global list of troops, a global list of products, etc. And only now I'm realizing that all of this will be in memory and this is the wrong way to do it. I am not storing files or anything on the disk just yet, with exception to a save/load state, which is a capture of everything. My game makes use of a map which allows you to select a planet, then it will give you a breakdown of that planets troops and resources, Lets use this scenario: My game has 20 planets. On which you can have 20 troops. Straight away that's an array of 400! This does not add the NPC, which is another 10. So, 20x10 = 200 So, now we have 600 all in arrays inside a Singelton. This is obviously very bad, and very wrong. Especially as the game scales in the amount of data. But I need to expose pretty much everything, especially on the map page, and I am not sure how else to do it. I've been told that I can use a controller for the map page which has the information I need for each planet, and other controllers for other items I require global display for. I've also thought about storing each planet's data in a save file, using initWithCoder however there could be a boatload of files on the user's device? I really don't want to use a database, mainly because I would need to translate NSObjects and non-NSObjects like CGRects and CGPoints and Colors into/from SQL. I am open to other ideas on how to store and read game data to prevent using a singelton to store everything, everywhere. Thanks for your time.

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  • How do I explain the importance of NUNIT Test cases to my Colleagues [duplicate]

    - by JNL
    This question already has an answer here: How to explain the value of unit testing 6 answers I am currently working in Software Development for applications including lot of Mathematical Calculations. As a result there are lot of test cases that we need to consider. We donot have any NUNIT Test case system, I am wonderring how should I get the advantages of implementing the NUNIT testing in front of my colleagues and my boss. I am pretty sure, it would be of great help for our team. Any help regarding the same, will be higly appreciated.

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  • How to Detect Sprites in a SpriteSheet?

    - by IAE
    I'm currently writing a Sprite Sheet Unpacker such as Alferds Spritesheet Unpacker. Now, before this is sent to gamedev, this isn't necessarily about games. I would like to know how to detect a sprite within a spriitesheet, or more abstactly, a shape inside of an image. Given this sprite sheet: I want to detect and extract all individual sprites. I've followed the algorithm detailed in Alferd's Blog Post which goes like: Determine predominant color and dub it the BackgroundColor Iterate over each pixel and check ColorAtXY == BackgroundColor If false, we've found a sprite. Keep going right until we find a BackgroundColor again, backtrack one, go down and repeat until a BackgroundColor is reached. Create a box from location to ending location. Repeat this until all sprites are boxed up. Combined overlapping boxes (or within a very short distance) The resulting non-overlapping boxes should contain the sprite. This implementation is fine, especially for small sprite sheets. However, I find the performance too poor for larger sprite sheets and I would like to know what algorithms or techniques can be leveraged to increase the finding of sprites. A second implementation I considered, but have not tested yet, is to find the first pixel, then use a backtracking algorithm to find every connected pixel. This should find a contiguous sprite (breaks down if the sprite is something like an explosion where particles are no longer part of the main sprite). The cool thing is that I can immediately remove a detected sprite from the sprite sheet. Any other suggestions?

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  • Should I incorporate exit cost into choosing a solution

    - by Mr Happy
    I'm currently choosing between two viable software designs/solutions. Solution 1 is easy to implement, but will lock some data in a propriaty format, and will be hard to change later. Solution 2 is hard to implement, but will be a lot easier to change later on. Should I go YAGNI on this or should I incorporate the exit cost in the decision making? Or asked differently, is the exit cost part of the TCO? I'm thinking of going back to the customer with this to ask wether or not he thinks the exit costs are relevant, but I'd like to know what the community thinks first. P.S. Is exit cost the correct term?

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  • Which data structure you will use to for a witness list?

    - by mateen
    I'm making a game where the plot is a bank robbery. Lots of people witness that robbery. The game will load a list of suspects, while the players (witnesses) will have to identify the suspects of this robbery. The game should load a list of suspects to identify the one as quickly as possible. Admin can add/remove suspects in the lists and two or more lists of suspects can also be merged into one (to show it to the player). The question is which data structure will be suitable to develop the lists?

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  • Developing a live video-streaming website

    - by cawecoy
    I'm a computer science student and know a little about some technology to start developing my website, like PHP, RubyOnRails and Python, and MySQL and PostgreSQL for Database. I need to know what are the best (secure, stable, low-price, etc) to get started, based on my business information: My website will be a live video-streaming one, similar to livestream.com We need to provide a secure service for our customers. They need to have a page to create and configure their own Live-Streaming-Videos, get statistics, etc. We work with Wowza Media Server ruuning on an Apache Server In addition, I would like to know some good practices for this kind of website development, as I am new to this. Thanks in advance!

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  • Best approach to accessing multiple data source in a web application

    - by ced
    I've a base web application developed with .net technologies (asp.net) used into our LAN by 30 users simultanousley. From this web application I've developed two verticalization used from online users. In future i expect hundreds users simultanousley. Our company has different locations. Each site use its own database. The web application needs to retrieve information from all existing databases. Currently there are 3 database, but it's not excluded in the future expansion of new offices. My question then is: What is the best strategy for a web application to retrieve information from different databases (which have the same schema) whereas the main objective performance data access and high fault tolerance? There are case studies in the literature that I can take as an example? Do you know some good documents to study? Do you have any tips to implement this task so efficient? Intuitively I would say that two possible strategy are: perform queries from different sources in real time and aggregate data on the fly; create a repository that contains the union of the entities of interest and perform queries directly on repository;

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  • What is the ideal length of a method?

    - by iPhoneDeveloper
    In object-oriented programming, there is no exact rule on the maximum length of a method , but I still found these two qutes somewhat contradicting each other, so I would like to hear what you think. In Clean Code: A Handbook of Agile Software Craftsmanship, Robert Martin says: The first rule of functions is that they should be small. The second rule of functions is that they should be smaller than that. Functions should not be 100 lines long. Functions should hardly ever be 20 lines long. and he gives an example from Java code he sees from Kent Beck: Every function in his program was just two, or three, or four lines long. Each was transparently obvious. Each told a story. And each led you to the next in a compelling order. That’s how short your functions should be! This sounds great, but on the other hand, in Code Complete, Steve McConnell says something very different: The routine should be allowed to grow organically up to 100-200 lines, decades of evidence say that routines of such length no more error prone then shorter routines. And he gives a reference to a study that says routines 65 lines or long are cheaper to develop. So while there are diverging opinions about the matter, is there a functional best-practice towards determining the ideal length of a method for you?

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  • Identifying the best pattern

    - by Daniel Grillo
    I'm developing a software to program a device. I have some commands like Reset, Read_Version, Read_memory, Write_memory, Erase_memory. Reset and Read_Version are fixed. They don't need parameters. Read_memory and Erase_memory need the same parameters that are Length and Address. Write_memory needs Lenght, Address and Data. For each command, I have the same steps in sequence, that are something like this sendCommand, waitForResponse, treatResponse. I'm having difficulty to identify which pattern should I use. Factory, Template Method, Strategy or other pattern.

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  • What every beginner should know about website development? [closed]

    - by user975234
    I am a novice at building websites and considering to make one. But there is a lot of confusion that's going on right now. I guess every beginner faces them. Few questions that come up are: I have an idea and a need a website. That's all i know right now. But how do i start ? HTML is for sure the basic language but there are a hell of other technologies too. What is actually asp, php, ruby etc? How do i choose the right one from them? Other than asp, php there is javascript and other languages under the same belt. What are they used for? Hosting. When i am choosing the host, what considerations i have to keep in mind ? What support do i need from them (other than getting some important space obviously!). I am considering of making the website in ruby on rails. I don't know about php and what effect it would have if i choose ruby over php. I thought about ruby just because its new and i dont want to learn some thing "not new"! :P Moreover what is a framework and how does a framework effect my development process? These three questions are just to explain my "confusion" better. There is obviously a lot more to it. Just to try to answer how the flow of website development goes keeping in mind my questions!

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  • In-Game Encyclopedias

    - by SHiNKiROU
    There are some games where there is an in-game encyclopedia where you can know many things about characters and settings of the game. For example, the Codex in Mass Effect. I want to know if it is exclusive to Bioware, and get inspired about other encyclopedia systems. What are some other examples of in-game encyclopedias? How effective is it? I also want some examples where the in-game encyclopedia is not effective at all or an ignored feature

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  • What are the reasons for MMOs to have level caps [on hold]

    - by SamStephens
    In many MMOs players character progression is artificially capped, e.g. by level 60 or 90 or 100 or whatever. Why do MMOs have these level caps in the first place? Why not just allow characters to continue to arbitrary levels with a mathematically designed leveling system that keeps the leveling experience interesting and endless? Answers to this question may help us to see the reason behind the feature and decide if and how this should be implemented in our MMOs.

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  • More Tables or More Databases?

    - by BuckWoody
    I got an e-mail from someone that has an interesting situation. He has 15,000 customers, and he asks if he should have a database for their data per customer. Without a LOT more data it’s impossible to say, of course, but there are some general concepts to keep in mind. Whenever you’re segmenting data, it’s all about boundary choices. You have not only boundaries around how big the data will get, but things like how many objects (tables, stored procedures and so on) that will be involved, if there are any cross-sections of data (do they share location or product information) and – very important – what are the security requirements? From the answer to these types of questions, you now have the choice of making multiple tables in a single database, or using multiple databases. A database carries some overhead – it needs a certain amount of memory for locking and so on. But it has a very clean boundary – everything from objects to security can be kept apart. Having multiple users in the same database is possible as well, using things like a Schema. But keeping 15,000 schemas can be challenging as well. My recommendation in complex situations like this is similar to a post on decisions that I did earlier – I lay out the choices on a spreadsheet in rows, and then my requirements at the top in the columns. I  give each choice a number based on how well it meets each requirement. At the end, the highest number wins. And many times it’s a mix – perhaps this person could segment customers into larger regions or districts or products, in a database. Within that database might be multiple schemas for the customers. Of course, he needs to query across all customers, that becomes another requirement. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • Relationship between Repository and Unit of Work

    - by NullOrEmpty
    I am going to implement a repository, and I would like to use the UOW pattern since the consumer of the repository could do several operations, and I want to commit them at once. After read several articles about the matter, I still don't get how to relate this two elements, depending on the article it is being done in a way u other. Sometimes the UOW is something internal to the repository: public class Repository { UnitOfWork _uow; public Repository() { _uow = IoC.Get<UnitOfWork>(); } public void Save(Entity e) { _uow.Track(e); } public void SubmittChanges() { SaveInStorage(_uow.GetChanges()); } } And sometimes it is external: public class Repository { public void Save(Entity e, UnitOfWork uow) { uow.Track(e); } public void SubmittChanges(UnitOfWork uow) { SaveInStorage(uow.GetChanges()); } } Other times, is the UOW whom references the Repository public class UnitOfWork { Repository _repository; public UnitOfWork(Repository repository) { _repository = repository; } public void Save(Entity e) { this.Track(e); } public void SubmittChanges() { _repository.Save(this.GetChanges()); } } How are these two elements related? UOW tracks the elements that needs be changed, and repository contains the logic to persist those changes, but... who call who? Does the last make more sense? Also, who manages the connection? If several operations have to be done in the repository, I think using the same connection and even transaction is more sound, so maybe put the connection object inside the UOW and this one inside the repository makes sense as well. Cheers

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  • designing classes with similar goal but widely different decisional core

    - by Stefano Borini
    I am puzzled on how to model this situation. Suppose you have an algorithm operating in a loop. At every loop, a procedure P must take place, whose role is to modify an input data I into an output data O, such that O = P(I). In reality, there are different flavors of P, say P1, P2, P3 and so on. The choice of which P to run is user dependent, but all P have the same finality, produce O from I. This called well for a base class PBase with a method PBase::apply, with specific reimplementations of P1::apply(I), P2::apply(I), and P3::apply(I). The actual P class gets instantiated in a factory method, and the loop stays simple. Now, I have a case of P4 which follows the same principle, but this time needs additional data from the loop (such as the current iteration, and the average value of O during the previous iterations). How would you redesign for this case?

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  • Is reliance on parametrized queries the only way to protect against SQL injection?

    - by Chris Walton
    All I have seen on SQL injection attacks seems to suggest that parametrized queries, particularly ones in stored procedures, are the only way to protect against such attacks. While I was working (back in the Dark Ages) stored procedures were viewed as poor practice, mainly because they were seen as less maintainable; less testable; highly coupled; and locked a system into one vendor; (this question covers some other reasons). Although when I was working, projects were virtually unaware of the possibility of such attacks; various rules were adopted to secure the database against corruption of various sorts. These rules can be summarised as: No client/application had direct access to the database tables. All accesses to all tables were through views (and all the updates to the base tables were done through triggers). All data items had a domain specified. No data item was permitted to be nullable - this had implications that had the DBAs grinding their teeth on occasion; but was enforced. Roles and permissions were set up appropriately - for instance, a restricted role to give only views the right to change the data. So is a set of (enforced) rules such as this (though not necessarily this particular set) an appropriate alternative to parametrized queries in preventing SQL injection attacks? If not, why not? Can a database be secured against such attacks by database (only) specific measures? EDIT Emphasis of the question changed slightly, in the light of the initial responses received. Base question unchanged. EDIT2 The approach of relying on paramaterized queries seems to be only a peripheral step in defense against attacks on systems. It seems to me that more fundamental defenses are both desirable, and may render reliance on such queries not necessary, or less critical, even to defend specifically against injection attacks. The approach implicit in my question was based on "armouring" the database and I had no idea whether it was a viable option. Further research has suggested that there are such approaches. I have found the following sources that provide some pointers to this type of approach: http://database-programmer.blogspot.com http://thehelsinkideclaration.blogspot.com The principle features I have taken from these sources is: An extensive data dictionary, combined with an extensive security data dictionary Generation of triggers, queries and constraints from the data dictionary Minimize Code and maximize data While the answers I have had so far are very useful and point out difficulties arising from disregarding paramaterized queries, ultimately they do not answer my original question(s) (now emphasised in bold).

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  • Pattern for a class that does only one thing

    - by Heinzi
    Let's say I have a procedure that does stuff: void doStuff(initalParams) { ... } Now I discover that "doing stuff" is quite a compex operation. The procedure becomes large, I split it up into multiple smaller procedures and soon I realize that having some kind of state would be useful while doing stuff, so that I need to pass less parameters between the small procedures. So, I factor it out into its own class: class StuffDoer { private someInternalState; public Start(initalParams) { ... } // some private helper procedures here ... } And then I call it like this: new StuffDoer().Start(initialParams); or like this: new StuffDoer(initialParams).Start(); And this is what feels wrong. When using the .NET or Java API, I always never call new SomeApiClass().Start(...);, which makes me suspect that I'm doing it wrong. Sure, I could make StuffDoer's constructor private and add a static helper method: public static DoStuff(initalParams) { new StuffDoer().Start(initialParams); } But then I'd have a class whose external interface consists of only one static method, which also feels weird. Hence my question: Is there a well-established pattern for this type of classes that have only one entry point and have no "externally recognizable" state, i.e., instance state is only required during execution of that one entry point?

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  • How to have operations with character/items in binary with concrete operations?

    - by Piperoman
    I have the next problem. A item can have a lot of states: NORMAL = 0000000 DRY = 0000001 HOT = 0000010 BURNING = 0000100 WET = 0001000 COLD = 0010000 FROZEN = 0100000 POISONED= 1000000 A item can have some states at same time but not all of them Is impossible to be dry and wet at same time. If you COLD a WET item, it turns into FROZEN. If you HOT a WET item, it turns into NORMAL A item can be BURNING and POISON Etc. I have tried to set binary flags to states, and use AND to combine different states, checking before if it is possible or not to do it, or change to another status. Does there exist a concrete approach to solve this problem efficiently without having an interminable switch that checks every state with every new state? It is relatively easy to check 2 different states, but if there exists a third state it is not trivial to do.

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  • What is the best way to diagrammatically represent a system threading architecture?

    - by thegreendroid
    I am yet to find the perfect way to diagrammatically represent the overall threading architecture for a system (using UML or otherwise). I am after a diagramming technique that would show all the threads in a given system and how they interact with each other. There are a few similar questions - Drawing Thread Interaction, UML Diagrams of Multithreaded Applications and Intuitive UML Approach to Depict Threads but they don't fully answer my question. What are some of the techniques that you've found useful to depict the overall threading architecture for a system?

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  • Why does Clang/LLVM warn me about using default in a switch statement where all enumerated cases are covered?

    - by Thomas Catterall
    Consider the following enum and switch statement: typedef enum { MaskValueUno, MaskValueDos } testingMask; void myFunction(testingMask theMask) { switch theMask { case MaskValueUno: {}// deal with it case MaskValueDos: {}// deal with it default: {} //deal with an unexpected or uninitialized value } }; I'm an Objective-C programmer, but I've written this in pure C for a wider audience. Clang/LLVM 4.1 with -Weverything warns me at the default line: Default label in switch which covers all enumeration values Now, I can sort of see why this is there: in a perfect world, the only values entering in the argument theMask would be in the enum, so no default is necessary. But what if some hack comes along and throws an uninitialized int into my beautiful function? My function will be provided as a drop in library, and I have no control over what could go in there. Using default is a very neat way of handling this. Why do the LLVM gods deem this behaviour unworthy of their infernal device? Should I be preceding this by an if statement to check the argument?

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  • Relationships in a Chen ERD

    - by Nibroc A Rehpotsirhc
    I am working on a Chen ERD to model our organizations merchandise. Our central entity is a Style. We have supplemental entities of Color and Season. I am defining our assortment as the relationship between these three entities, and this relationship itself will have attributes and is defined by the three entities which participate in the mandatory relationship. The rules are; Many Styles can be offered in a Season, and a Style can be offered in many Seasons. Within a Season, a Style can be offered in Many Colors. I then have 2 other entities, one of which I believe is a weak entity, Climate, and the other may be weak, but I am not sure, this being Transaction Channel. I am thinking of these as relationships off of a relationship? Meaning, for a given Style/Color combination offered in a Season, it can be available through 1 or more Transaction Channels. Additionally, within a season, a given Style/Color combination can be intended for 1 or more Climates. Is it valid to have relationships off of relationships? Or does this requirement dictate that I should think of this Style/Color/Season relationship as an entity itself, and define the relationships to Climate and Transaction Channel off of this entity?

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