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• Complete Beginner to Game Programming and Unreal Engine 4, Looking For Advice [on hold]

  - by onemic

  I am currently a 2nd year programming student(Just finished my first year so I will be starting my second year in September) and have mainly learned C and C++ in my classes. In terms of what I know of C++, I know about general inheritance, polymorphism, overloading operators, iterators, a little bit about templates(only class and function templates) etc. but not of the more advanced topics like linked lists and other sequential containers(containers in general I guess), enumerations, most of the standard library(other than like strings and vectors), and probably a bunch of other stuff I dont even know about yet. I subscribed to Unreal Engine 4 as I was very intrigued by their Unreal Tournament announcement earlier this month, especially after hearing that UE4 is going completely C++. Of course my end goal in doing this programming program is to eventually go into game/graphics programming. Since it's my summer off, I thought what better way then to actually apply some of my skills to a personal project so I actually have a firmer understanding of C++ past what my professors tell me. My questions are this: What would be the best way to start off making a small personal game in UE4 as a project for the summer? What should I be aiming for, especially for someone that is still learning C++? Should I focus on making a simple 2D game rather than a 3D one to get started? Seeing the Flappy Chicken showcase intrigued me because before I thought the UE engine was pretty much pigeonholed into being for FPS games What should my expectations be going into UE4 and a game engine for the first time?(UE4 will be my first foray into making a game) What can I expect to gain from making things in UE4, in terms of making games and in terms of further fleshing out my knowledge of C++? Would you recommend I start off 100% using C++ for scripting or using the visual blueprints? Since I'm not a designer, how would I be able to add objects and designs to my game? For someone at my level is retaining the UE4 subscription worth it or is it better to cancel and resub when I learn enough about UE4 and C++? Lastly is there anything to be gained in terms of knowledge/insight through me looking at the source code for UE4? I opened it in VS2013, but noticed that most of the files were C# files and not cpp's. Thanks in advance for taking the time to answer.

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• Criteria for a programming language to be considered "mature"

  - by Giorgio

  I was recently reading an answer to this question, and I was struck by the statement "The language is mature". So I was wondering what we actually mean when we say that "A programming language is mature"? Normally, a programming language is initially developed out of a need, e.g. Try out / implement a new programming paradigm or a new combination of features that cannot be found in existing languages. Try to solve a problem or overcome a limitation of an existing language. Create a language for teaching programming. Create a language that solves a particular class of problems (e.g. concurrency). Create a language and an API for a special application field, e.g. the web (in this case the language might reuse a well-known paradigm, but the whole API must be new). Create a language to push your competitor out of the market (in this case the creator might want the new language to be very similar to an existing one, in order to attract developers to the new programming language and platform). Regardless of what the original motivation and scenario in which a language has been created, eventually some languages are considered mature. In my intuition, this means that the language has achieved (at least one of) its goals, e.g. "We can now use language X as a reliable tool for writing web applications." This is however a bit vague, so I wanted to ask what you consider the most important criteria (if any) that are applied when saying that a language is mature. IMPORTANT NOTE This question is (on purpose) language-agnostic because I am only interested in general criteria. Please write only language-agnostic answers and comments! I am not asking whether any specific "language X is mature" or "which programming languages can be considered mature", or whether "language X is more mature than language Y": please avoid posting any opinions or reference about any specific languages because these are out of the scope of this question. EDIT To make the question more precise, by criteria I mean such things as "tool support", "adoption by the industry", "stability", "rich API", "large user community", "successful application record", "standardization", "clean and uniform semantics", and so on.

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• Best way to determine surface normal for a group of pixels?

  - by Paul Renton

  One of my current endeavors is creating a 2D destructible terrain engine for iOS Cocos2D (See https://github.com/crebstar/PWNDestructibleTerrain ). It is in an infant stages no doubt, but I have made significant progress since starting a couple weeks ago. However, I have run into a bit of a performance road block with calculating surface normals. Note: For my destructible terrain engine, an alpha of 0 is considered to not be solid ground. The method posted below works just great given small rectangles, such as n < 30. Anything above 30 causes a dip in the frame rate. If you approach 100x100 then you might as well read a book while the sprite attempts to traverse the terrain. At the moment this is the best I can come up with for altering the angle on a sprite as it roams across terrain (to get the angle for a sprite's orientation just take dot product of 100 * normal * (1,0) vector). -(CGPoint)getAverageSurfaceNormalAt:(CGPoint)pt withRect:(CGRect)area { float avgX = 0; float avgY = 0; ccColor4B color = ccc4(0, 0, 0, 0); CGPoint normal; float len; for (int w = area.size.width; w >= -area.size.width; w--) { for (int h = area.size.height; h >= -area.size.height; h--) { CGPoint pixPt = ccp(w + pt.x, h + pt.y); if ([self pixelAt:pixPt colorCache:&color]) { if (color.a != 0) { avgX -= w; avgY -= h; } // end inner if } // end outer if } // end inner for } // end outer for len = sqrtf(avgX * avgX + avgY * avgY); if (len == 0) { normal = ccp(avgX, avgY); } else { normal = ccp(avgX/len, avgY/len); } // end if return normal; } // end get My problem is I have sprites that require larger rectangles in order for their movement to look realistic. I considered doing a cache of all surface normals, but this lead to issues of knowing when to recalculate the surface normals and these calculations also being quite expensive (also how large should the blocks be?). Another smaller issue is I don't know how to properly treat the case when length is = 0. So I am stuck... Any advice from the community would be greatly appreciated! Is my method the best possible one? Or should I rethink the algorithm? I am new to game development and always looking to learn new tips and tricks.

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• Is there a factory pattern to prevent multiple instances for same object (instance that is Equal) good design?

  - by dsollen

  I have a number of objects storing state. There are essentially two types of fields. The ones that uniquely define what the object is (what node, what edge etc), and the others that store state describing how these things are connected (this node is connected to these edges, this edge is part of these paths) etc. My model is updating the state variables using package methods, so all these objects act as immutable to anyone not in Model scope. All Objects extend one base type. I've toyed with the idea of a Factory approach which accepts a Builder object and constructs the applicable object. However, if an instance of the object already exists (ie would return true if I created the object defined by the builder and passed it to the equal method for the existing instance) the factory returns the current object instead of creating a new instance. Because the Equal method would only compare what uniquely defines the type of object (this is node A to node B) but won't check the dynamic state stuff (node A is currently connected to nodes C and E) this would be a way of ensuring anyone that wants my Node A automatically knows its state connections. More importantly it would prevent aliasing nightmares of someone trying to pass an instance of node A with different state then the node A in my model has. I've never heard of this pattern before, and it's a bit odd. I would have to do some overriding of serialization methods to make it work (ensure that when I read in a serilized object I add it to my facotry list of known instances, and/or return an existing factory in its place), as well as using a weakHashMap as if it was a weakHashSet to know whether an instance exists without worrying about a quasi-memory leak occuring. I don't know if this is too confusing or prone to its own obscure bugs. One thing I know is that plugins interface with lowest level hardware. The plugins have to be able to return state that is different than my memory; to tell my memory when its own state is inconsistent. I believe this is possible despite their fetching objects that exist in my memory; we allow building of objects without checking their consistency with the model until the addToModel is called anyways; and the existing plugins design was written before all this extra state existed and worked fine without ever being aware of it. Should I just be using some other design to avoid this crazyness? (I have another question to that affect that I'm posting).

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• Java @Contented annotation to help reduce false sharing

  - by Dave

  See this posting by Aleksey Shipilev for details -- @Contended is something we've wanted for a long time. The JVM provides automatic layout and placement of fields. Usually it'll (a) sort fields by descending size to improve footprint, and (b) pack reference fields so the garbage collector can process a contiguous run of reference fields when tracing. @Contended gives the program a way to provide more explicit guidance with respect to concurrency and false sharing. Using this facility we can sequester hot frequently written shared fields away from other mostly read-only or cold fields. The simple rule is that read-sharing is cheap, and write-sharing is very expensive. We can also pack fields together that tend to be written together by the same thread at about the same time. More generally, we're trying to influence relative field placement to minimize coherency misses. Fields that are accessed closely together in time should be placed proximally in space to promote cache locality. That is, temporal locality should condition spatial locality. Fields accessed together in time should be nearby in space. That having been said, we have to be careful to avoid false sharing and excessive invalidation from coherence traffic. As such, we try to cluster or otherwise sequester fields that tend to written at approximately the same time by the same thread onto the same cache line. Note that there's a tension at play: if we try too hard to minimize single-threaded capacity misses then we can end up with excessive coherency misses running in a parallel environment. Theres no single optimal layout for both single-thread and multithreaded environments. And the ideal layout problem itself is NP-hard. Ideally, a JVM would employ hardware monitoring facilities to detect sharing behavior and change the layout on the fly. That's a bit difficult as we don't yet have the right plumbing to provide efficient and expedient information to the JVM. Hint: we need to disintermediate the OS and hypervisor. Another challenge is that raw field offsets are used in the unsafe facility, so we'd need to address that issue, possibly with an extra level of indirection. Finally, I'd like to be able to pack final fields together as well, as those are known to be read-only.

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• Drawing flaming letters in 3D with OpenGL ES 2.0

  - by Chiquis

  I am a bit confused about how to achieve this. What I want is to "draw with flames". I have achieved this with textures successfully, but now my concern is about doing this with particles to achieve the flaming effect. Am I supposed to create a path along which I should add many particle emitters that will be emitting flame particles? I understand the concept for 2D, but for 3D are the particles always supposed to be facing the user? Something else I'm worried about is the performance hit that will occur by having that many particle emitters, because there can be many letters and drawings at the same time, and each of these elements will have many particle emitters. More detailed explanation: I have a path of points, which is my model. Imagine a dotted letter "S" for example. I want make the "S" be on fire. The "S" is just an example it can be a circle, triangle, a line, pretty much any path described by my set of points. For achieving this fire effect I thought about using particles. So I am using a program called "Particle Designer" to create a fire style particle emitter. This emitter looks perfect on 2D on the iphone screen dimensions. So then I thought that I could probably draw an S or any other figure if i place many particle emitters next to each other following the path described. To move from the 2D version to the 3D version I thought about, scaling the emitter (with a scale matrix multiplication in its model matrix) and then moving it to a point in my 3D world. I did this and it works. So now I have 1 particle emitter in the 3D world. My question is, is this how you would achieve a flaming letter? Is this too inefficient if i expect to have many flaming paths on my world? Am i supposed to rotate the particle's quad so that its always looking at the user? (the last one is because i noticed that if u look at it from the side the particles start to flatten out)

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• How do you conquer the challenge of designing for large screen real-estate?

  - by Berin Loritsch

  This question is a bit more subjective, but I'm hoping to get some new perspective. I'm so used to designing for a certain screen size (typically 1024x768) that I find that size to not be a problem. Expanding the size to 1280x1024 doesn't buy you enough screen real estate to make an appreciable difference, but will give me a little more breathing room. Basically, I just expand my "grid size" and the same basic design for the slightly smaller screen still works. However, in the last couple of projects my clients were all using 1080p (1920x1080) screens and they wanted solutions to use as much of that real estate as possible. 1920 pixels across provides just under twice the width I am used to, and the wide screen makes some of my old go to design approaches not to work as well. The problem I'm running into is that when presented with so much space, I'm confronted with some major problems. How many columns should I use? The wide format lends itself to a 3 column split with a 2:1:1 split (i.e. the content column bigger than the other two). However, if I go with three columns what do I do with that extra column? How do I make efficient use of the screen real estate? There's a temptation to put everything on the screen at once, but too much information actually makes the application harder to use. White space is important to help make sense of complex information, but too much makes related concepts look too separate. I'm usually working with web applications that have complex data, and visualization and presentation is key to making sense of the raw data. When your user also has a large screen (at least 24"), some information is out of eye sight and you need to move the pointer a long distance. How do you make sure everything that's needed stays within the visual hot points? Simple sites like blogs actually do better when the width is constrained, which results in a lot of wasted real estate. I kind of wonder if having the text box and the text preview side by side would be a big benefit for the admin side of that type of screen? (1:1 two column split). For your answers, I know almost everything in design is "it depends". What I'm looking for is: General principles you use How your approach to design has changed I'm finding that i have to retrain myself how to work with this different format. Every bump in resolution I've worked through to date has been about 25%: 640 to 800 (25% increase), 800 to 1024 (28% increase), and 1024 to 1280 (25% increase). However, the jump from 1280 to 1920 is a good 50% increase in space--the equivalent from jumping from 640 straight to 1024. There was no commonly used middle size to help learn lessons more gradually.

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• TechEd 2010 Day Three: The Database Designer (Isn't)

  - by BuckWoody

  Yesterday at TechEd 2010 here in New Orleans I worked the front-booth, answering general SQL Server questions for the masses. I was actually a little surprised to find most of the questions I got were from folks that wanted to know more about Stream Insight and Master Data Services. In past conferences I've been asked a lot of "free consulting" questions, about problems folks have had from older products. I don't mind that a bit - in fact, I'm always happy to help in any way I can. But this time people are really interested in the new features in the product, and I like that they are thinking ahead, not just having to solve problems in production. My presentation was on "Database Design in an Hour". We had the usual fun, and SideShow Bob made an appearance - I kid you not. The guy in the back of the room looked just like Sideshow Bob, so I quickly held a "bes thair" contest, and he won. Duing the presentation, I explain the tools you can use to design databases. I also explain that the "Database Designer" tool in SQL Server Management Studio (SSMS) isn't truly a desinger - it uses non-standard notation, doesn't have a meta-data dictionary, and worst of all, it works at the physical level. In other words, whatever you do in SSMS will automatically change the field/table/relationship structures in the database. We fixed this in SSMS 2008 and higher by adding an option to block that, but the tool is not a good design function nonetheless. To be fair, no one I know of at Microsoft recommends that it is - but I was shocked to hear so many developers in the room defending it as a good tool. I think the main issue for someone who doesn't have to work with Relational Systems a great deal is that it can be difficult to figure out Foreign Keys. The syntax makes them look "backwards", so it's just easier to grab a field and place it on the table you want to point to. There are options. You can download a couple of free tools (CA has a community edition of ER-WIN, Quest has one, and Embarcadero also has one) and if you design more than one or two databases a year, it may be worth buying a true design tool. For years I used Visio, but we changed it so that it doesn't forward-engineer (create the DDL) any more, so it isn't a true design tool either. So investigate those free and not-so-free tools. You'll find they help you in your job - but stay away from the Database Designer in SSMS. Or I'll send Sideshow Bob over there to straighten you out. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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• Android Array Lag?

  - by Mike

  I am making a platform game for Android. It is sort of a tile based game. I added bullets and enemies with AI and a bunch of tile types. I created a simple map with no Enemies. Everything was running well and smooth until I shot a bunch of bullets randomly everywhere. A couple of hundreds of bullets later, the FPS lowered. I made a test to find out if the bullets were the problem so I made another simple map with just a tile to stand on and left it for a while. Minutes later, I played around with it a bit to check if the FPS changed and it didnt. I reloaded the same map and shot a lot of bullets. Minutes later, the FPS was visibly lower even after the number of bullets were zero. Points to note: Programmed FPS is 30 Tested on a Samsung Galaxy Y and Samsung Galaxy W Any tile, enemy, bullet that is off screen is not drawn to prevent lag Bullets collide with Tiles (if they dont collide with in 450 frames, they are removed from the array) I used List bullets = new ListArray(); I used bullets.add(new Bullet(x, y, params...)); I used for(...){ if(...){ bullets.remove(i); } } Code for bullet: private void drawBullets(Canvas canvas) { for (int i = 0; i < bullets.size(); i++) { Bullet b = bullets.get(i); b.update(canvas); //updates physics if (b.t > blm) { //if the bullet is past its expiry bullets.remove(i); i--; } else { if (svx((b.x)) > 0 && svx(b.x) < width && svy((b.y)) > 0 && svy(b.y) < height) { // if bullet is not off screen b.draw(canvas); // draw the bullet } } } } I tried searching for solutions and references but I have no luck. I'm guessing that the lag has something to do with the Array and the Bullets or Classes that I've loaded? I'm not sure! Someone please help! Thanks in advance! :)

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• Should i continue my self-taught coding practice or learn how to do coding professionally?

  - by G1i1ch

  Lately I've been getting professional work, hanging out with other programmers, and making friends in the industry. The only thing is I'm 100% self-taught. It's caused my style to extremely deviate from the style of those that are properly trained. It's the techniques and organization of my code that's different. It's a mixture of several things I do. I tend to blend several programming paradigms together. Like Functional and OO. I lean to the Functional side more than OO, but I see the use of OO when something would make more sense as an abstract entity. Like a game object. Next I also go the simple route when doing something. When in contrast, it seems like sometimes the code I see from professional programmers is complicated for the sake of it! I use lots of closures. And lastly, I'm not the best commenter. I find it easier just to read through my code than reading the comment. And most cases I just end up reading the code even if there are comments. Plus I've been told that, because of how simply I write my code, it's very easy to read it. I hear professionally trained programmers go on and on about things like unit tests. Something I've never used before so I haven't even the faintest idea of what they are or how they work. Lots and lots of underscores "_", which aren't really my taste. Most of the techniques I use are straight from me, or a few books I've read. Don't know anything about MVC, I've heard a lot about it though with things like backbone.js. I think it's a way to organize an application. It just confuses me though because by now I've made my own organizational structures. It's a bit of a pain. I can't use template applications at all when learning something new like with Ubuntu's Quickly. I have trouble understanding code that I can tell is from someone trained. Complete OO programming really leaves a bad taste in my mouth, yet that seems to be what EVERYONE else is strictly using. It's left me not that confident in the look of my code, or wondering whether I'll cause sparks when joining a company or maybe contributing to open source projects. In fact I'm rather scared of the fact that people will eventually be checking out my code. Is this just something normal any programmer goes through or should I really look to change up my techniques?

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• Legal concerns with orchestrating a music submission contest

  - by Amplify91

  My team and I are getting pretty far along in the development of our latest game and have been thinking about audio. We decided to host an audio submission contest where we will offer a little cash and some equity stake in the game as prizes. We are also giving away copies of the game to participants. We hope not only to find audio for our game, but to meet some cool sound artists and promote the game a bit through the process. First of all, is this even a good idea? What are some potential dangers in doing this? Will it even be well received among artists? Secondly, I wrote up some Terms and Conditions in my best legal-speak to try to protect us and clarify how the contest will be run. Are these sufficient to make sure everyone involved is treated fairly and is legally protected? They are as follows: All submissions (The Submission) must be licensed under a Creative Commons Attribution 3.0 Unported License (CC-BY-3.0) By applying a CC-BY-3.0 license, you (The Submitter) expressly give Detour Games (and all members wherein) permission to copy, distribute, transmit, modify, adapt, and make commercial use of The Submission. The Submitter must own all rights to The Submission and be within their rights to license it as specified and submit it. The Submitter claims responsibility for the legality of The Submission. If The Submission is found to infringe on the rights of a person or entity other than those of The Submitter, Detour Games will not be held liable as all responsibility and liability for the legality of The Submission is that of The Submitter's. No more than two free copies of The Game per submitter. All flat cash prizes will only be disbursed pending the success of our first $5,000 Kickstarter campaign. These prizes will be disbursed 30 days after Detour Games receives the Kickstarter funds. All equity prizes (percentage of profits) are defined as the given percent of total profits after costs for a period of one year (12 months) after the release of RAW. These prizes will be disbursed semi-annually. All prize money will be disbursed through either an electronic fund transfer through a service such as PayPal or by a mailed money order. It is The Submitter's responsibility to cooperate with Detour Games in the disbursement of the funds. Detour Games reserves the right to change these Terms and Conditions at any time without notice. By participating in the contest, The Submitter agrees to and accepts all terms and conditions listed. What else could I do (legally) to protect everyone involved?

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• Website directory structure regarding subdomains, www, and "global" content

  - by Pawnguy7

  I am trying to make a homemade HTTP server. It occurs to me, though, I never fully understood what you might call "relativity" among web pages. I have come across that www. is a subdomain, and I understand its original purpose. IT sounds like, in general, you would redirect (is that 301 or 302?) it to a... non-subdomain, sort of. As in, redirecting www.example.com to example.com. I am not entirely sure how to make this work when retrieving files for an HTTP server though. I would assume that example.com would be the root, and www manifests as a folder within it. I am unsure. There is also the question of multi-level subdomains, e.g. subdomain2.subdomain1.example.com. It seems to me they are structured "backwards", where you go from the root left in folder structure. In this situation, subdomain2 is a directory within subdomain1, which is a directory in the root. Finally, it occurs to me I might want a sort of global location. For example, maybe all subdomains still use an image as a logo. It makes more sense to me that there is one image, rather than each having a copy. In the same way, albiet more doubtfully, you might have global CSS (though that is a bit contrary to the idea of a subdomain in the first place), or a javascript that is commonly used. (more efficient than each having its copy and better for organization purposes). Finally, mabye you have a global 404 page. I think this might be the case where you have user-created subdomains (say bloggername.example.com), where example.com still has a default 404 when either a subdomain does not exist or page does not exists under a valid blogger. I am confused on what the directory structure for this should be. To summarize: Should and how it have a global files not in a subdirectory, how should www. be handled, (or how a now www or other subdomain should be handled), and the pattern for root/subdomain, as well as subdomain within subdomains (order-wise). Sorry this is multiple questions, but I feel at the root they are all related to the directory.

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• Object Oriented Design of a Small Java Game

  - by user2733436

  This is the problem i am dealing with. I have to make a simple game of NIM. I am learning java using a book so far i have only coded programs that deal with 2 classes. This program would have about 4 classes i guess including the main class. My problem is i am having a difficult time designing classes how they will interact with each other. I really want to think and use a object oriented approach. So the first thing i did was design the Pile CLASS as it seemed the easiest and made the most sense to me in terms of what methods go in it. Here is what i have got down for the Pile Class so far. package Nim; import java.util.Random; public class Pile { private int initialSize; public Pile(){ } Random rand = new Random(); public void setPile(){ initialSize = (rand.nextInt(100-10)+10); } public void reducePile(int x){ initialSize = initialSize - x; } public int getPile(){ return initialSize; } public boolean hasStick(){ if(initialSize>0){ return true; } else { return false; } } } Now i need help in designing the Player Class. By that i mean i am not asking for anyone to write code for me as that defeats the purpose of learning i was just wondering how would i design the player class and what would go on it. My guess is that the player class would contain method for choosing move for computer and also receiving the move human user makes. Lastly i am guessing in the Game class i am guessing the turns would be handeled. I am really lost right now so i was wondering if someone can help me think through this problem it would be great. Starting with the player class would be appreciated. I know there are some solutions for this problem online but i refuse to look at because i want to develop my own approach to such problems and i am confident if i can get through this problem i can solve other problems. I apologize if this question is a bit poor but in specific i need help in designing the Player class.

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• Are there any good Java/JVM libraries for my Expression Tree architecture?

  - by Snuggy

  My team and I are developing an enterprise-level application and I have devised an architecture for it that's best described as an "Expression Tree". The basic idea is that the leaf nodes of the tree are very simple expressions (perhaps simple values or strings). Nodes closer to the trunk will get more and more complex, taking the simpler nodes as their inputs and returning more complex results for their parents. Looking at it the other way, the application performs some task, and for this it creates a root expression. The root expression divides its input into smaller units and creates child expressions, which when evaluated it can use to build it's own result. The subdividing process continues until the simplest leaf nodes. There are two very important aspects of this architecture: It must be possible to manipulate nodes of the tree after it is built. The nodes may be given new input values to work with and any change in result for that node needs to be propagated back up the tree to the root node. The application must make best use of available processors and ultimately be scalable to other computers in a grid or in the cloud. Nodes in the tree will often be updating concurrently and notifying other interested nodes in the tree when they get a new value. Unfortunately, I'm not at liberty to discuss my actual application, but to aid understanding a little bit, you might imagine a kind of spreadsheet application being implemented with a similar architecture, where changes to cells in the table are propagated all over the place to other cells that need the result. The spreadsheet could get so massive that applying multi-core multi-computer distributed system to solve it would be of benefit. I've got my prototype "Expression Engine" working nicely on a single multi-core PC but I've started to run into a few concurrency issues (as expected because I haven't been taking too much care so far) so it's now time to start thinking about migrating the Engine to a more robust library, and that leads to a number of related questions: Is there any precedent for my "Expression Tree" architecture that I could research? What programming concepts should I consider. I realise this approach has many similarities to a functional programming style, and I'm already aware of the concepts of using futures and actors. Are there any others? Are there any languages or libraries that I should study? This question is inspired by my accidental discovery of Scala and the Akka library (which has good support for Actors, Futures, Distributed workloads etc.) and I'm wondering if there is anything else I should be looking at as well?

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• Should Item Grouping/Filter be in the ViewModel or View layer?

  - by ronag

  I'm in a situation where I have a list of items that need to be displayed depending on their properties. What I'm unsure of is where is the best place to put the filtering/grouping logic of the viewmodel state? Currently I have it in my view using converters, but I'm unsure whether I should have the logic in the viewmodel? e.g. ViewModel Layer: class ItemViewModel { DateTime LastAccessed { get; set; } bool IsActive { get; set; } } class ContainerViewModel { ObservableCollection<Item> Items {get; set;} } View Layer: <TextView Text="Active Items"/> <List ItemsSource={Binding Items, Converter=GroupActiveItemsByDay}/> <TextView Text="Active Items"/> <List ItemsSource={Binding Items, Converter=GroupInActiveItemsByDay}/> or should I build it like this? ViewModel Layer: class ContainerViewModel { ObservableCollection<IGrouping<string, Item>> ActiveItemsByGroup {get; set;} ObservableCollection<IGrouping<string, Item>> InActiveItemsByGroup {get; set;} } View Layer: <TextView Text="Active Items"/> <List ItemsSource={Binding ActiveItemsGroupByDate }/> <TextView Text="Active Items"/> <List ItemsSource={Binding InActiveItemsGroupByDate }/> Or maybe something in between? ViewModel Layer: class ContainerViewModel { ObservableCollection<IGrouping<string, Item>> ActiveItems {get; set;} ObservableCollection<IGrouping<string, Item>> InActiveItems {get; set;} } View Layer: <TextView Text="Active Items"/> <List ItemsSource={Binding ActiveItems, Converter=GroupByDate }/> <TextView Text="Active Items"/> <List ItemsSource={Binding InActiveItems, Converter=GroupByDate }/> I guess my question is what is good practice in terms as to what logic to put into the ViewModel and what logic to put into the Binding in the View, as they seem to overlap a bit?

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• Why is Java the lingua franca at so many institutions?

  - by Billy ONeal

  EDIT: This question at first seems to be bashing Java, and I guess at this point it is a bit. However, the bigger point I am trying to make is why any one single language is chosen as the one end all be all solution to all problems. Java happens to be the one that's used so that's the one I had to beat on here, but I'm not intentionality ripping Java a new one :) I don't like Java in most academic settings. I'm not saying the language itself is bad -- it has several extremely desirable aspects, most importantly the ability to run without recompilation on most any platform. Nothing wrong with using the language for Your Next App ^TM. (Not something I would personally do, but that's more because I have less experience with it, rather than it's design being poor) I think it is a waste that high level CS courses are taught using Java as a language. Too many of my co-students cannot program worth a damn, because they don't know how to work in a non-garbage-collected world. They don't fundamentally understand the machines they are programming for. When someone can work outside of a garbage collected world, they can work inside of one, but not vice versa. GC is a tool, not a crutch. But the way it is used to teach computer science students is a as a crutch. Computer science should not teach an entire suite of courses tailored to a single language. Students leave with the idea that all good design is idiomatic Java design, and that Object Oriented Design is the ONE TRUE WAY THAT IS THE ONLY WAY THINGS CAN BE DONE. Other languages, at least one of them not being a garbage collected language, should be used in teaching, in order to give the graduate a better understanding of the machines. It is an embarrassment that somebody with a PHD in CS from a respected institution cannot program their way out of a paper bag. What's worse, is that when I talk to those CS professors who actually do understand how things operate, they share feelings like this, that we're doing a disservice to our students by doing everything in Java. (Note that the above would be the same if I replaced it with any other language, generally using a single language is the problem, not Java itself) In total, I feel I can no longer respect any kind of degree at all -- when I can't see those around me able to program their way out of fizzbuzz problems. Why/how did it get to be this way?

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• Advantages to Multiple Methods over Switch

  - by tandu

  I received a code review from a senior developer today asking "By the way, what is your objection to dispatching functions by way of a switch statement?" I have read in many places about how pumping an argument through switch to call methods is bad OOP, not as extensible, etc. However, I can't really come up with a definitive answer for him. I would like to settle this for myself once and for all. Here are our competing code suggestions (php used as an example, but can apply more universally): class Switch { public function go($arg) { switch ($arg) { case "one": echo "one\n"; break; case "two": echo "two\n"; break; case "three": echo "three\n"; break; default: throw new Exception("Unknown call: $arg"); break; } } } class Oop { public function go_one() { echo "one\n"; } public function go_two() { echo "two\n"; } public function go_three() { echo "three\n"; } public function __call($_, $__) { throw new Exception("Unknown call $_ with arguments: " . print_r($__, true)); } } Part of his argument was "It (switch method) has a much cleaner way of handling default cases than what you have in the generic __call() magic method." I disagree about the cleanliness and in fact prefer call, but I would like to hear what others have to say. Arguments I can come up with in support of Oop scheme: A bit cleaner in terms of the code you have to write (less, easier to read, less keywords to consider) Not all actions delegated to a single method. Not much difference in execution here, but at least the text is more compartmentalized. In the same vein, another method can be added anywhere in the class instead of a specific spot. Methods are namespaced, which is nice. Does not apply here, but consider a case where Switch::go() operated on a member rather than a parameter. You would have to change the member first, then call the method. For Oop you can call the methods independently at any time. Arguments I can come up with in support of Switch scheme: For the sake of argument, cleaner method of dealing with a default (unknown) request Seems less magical, which might make unfamiliar developers feel more comfortable Anyone have anything to add for either side? I'd like to have a good answer for him.

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• Rebuilding a Mac Mini (early 2009)

  - by Kelly Jones

  This weekend I decided to rebuild the family’s Mac Mini.  It’s the early 2009 model and I hadn’t done it since we got it in March of 2009.  Even worse, I had done the import data step (or whatever Apple calls it) which brought over all of the data files and apps from our previous Mac.  AND that install goes back to before 2005, as far as I can remember.  SO, to say that “cruft” had built up in the operating system, is probably a bit of an understatement. The rebuild went pretty smoothly, especially since I had a couple of spare hard drives.  I hooked up a spare USB drive and formatted it for use with the Mac.  I then used Carbon Copy to clone the internal hard drive onto the USB drive.  (Carbon Copy is a great little app that I used several years ago and I was happy to see it was not only still around, but updated as well.) Once I had my backup, I shut down the Mac and replaced the internal hard drive.  I had purchased the hard drive last fall to use with my work laptop, but I got a new work laptop (with awesome dual SSDs) so I wasn’t using it anymore.  The replacement drive (Seagate Momentus 7200.4 ST9500420AS 500GB 7200 RPM 2.5" SATA 3.0Gb/s Internal Notebook Hard Drive) has more than double the original’s capacity and is also faster.  I’ll have to keep an eye on the temperature, since that 7200 drive will run hotter. Opening the Mac Mini is not for the easily intimidated!  That cool little case is quite the pain to open.  Luckily, OWC put a video together here.  After replacing the drive, I then installed a clean copy of OS 10.5 using the DVDs that came with the Mac.  After the OS, it was time to reinstall the apps.  I downloaded some of the freeware, just to make sure I had the latest versions.  For the rest, I just copied from the backup cloned drive to the new drive.  (I love the way most Mac apps are written – with almost everything contained within a “package” that I can just copy from one drive to another.  MUCH better than the Windows way of using shared DLLs and the registry to store critical pieces that the app needs in order to run!) The whole process took longer than I would have preferred, but it was long overdue.  It definitely “feels” faster, especially boot time and application launches.

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• Simulate 'Shock absorbtion' with tire rubber in PhysX (2.8.x)

  - by Mungoid

  This is a kinda tricky question and I fear there is no easy enough solution, but I figured I'd hit SE up before giving up on it and just doing what I can. A machine I am working on has no suspension or shocks or springs of any sort in the real machine, so you would think that when it drives over bumps, it would shake like crazy but because its tires (6 of them) are quite large they seem to absorb a lot of shock from the bumps. Part of this is because the machine is around 30k lbs and it just smashes/compresses any bumps in the ground down (This is another issue im still working on) and the other part is that the tires seem to have a lot of flex to them with a lot of air as well. So my current task is to simulate shock absorption in physx without visibly separating the tires from the spindle/axle.. I have been messing with all kinds of NxMaterial, NxSpring, Joints, etc. and have had no luck getting this to work. The main problem is that the spindle attached to the tire is directly in the center and the axle is basically solidly attached to the chassis, so if i give it any spring or suspension travel, that spindle on the tires will move upwards or downwards, looking very odd because now its not any longer in the center of the tire. I tried giving it a higher restitution but that just makes it bouncy without any shock absorption. Another avenue I am messing with is to actively smooth the terrain in front of the tires so that before it hits a bumpy patch, that patch is smoothed and it doesn't bounce. The only issue with this is that it is pretty expensive to do with 6 tires, high tesselation of the terrain and other complex things going on at the same time in this simulation. I am still working on this but I am hoping to mix and match a few different aspects to get the best possible outcome. This is a bit of a complex issue so I'm not expecting anyone to have a definitive answer, just hoping someone may think of something I haven't =-) -Side note: Yes i know PhysX 2.8.x is quite outdated but we have to stick with it for this implementation. We are in the process of going to another physics engine but it is out of scope to apply that engine to this project.

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• Working with Windows and Unix

  - by user554629

  Beware of new line characters One of the most frequent issues we encounter in Tech Support is the corruption of files that are transferred between Windows and Unix.   The transfer can occur at any stage, but ultimately involves a transfer of a file using an ftp client that is running on Windows;  it could be ftp or filezilla. Windows uses two characters to mark the end of a line in a text file (CR/LF),carriage return, linefeed.   Unix uses a single character (CR). In all situations, it is best to use binary mode transfer for all files, including ascii text files. Common problems: upload a core file from unix to windows using ftp in ascii mode.The file is going to be larger on Windows than Unix.ftp doesn't know if this is a text file with real line-ends, it takes every ascii CR and transmits two ascii characters CR/LF.The core file, tar file, library ... will be corrupted when transferred to Oracle. download a shell script to Windows, and transfer it to Unix using ftpIf the file is edited on Windows, the unix script line-end chars will be doubled.Unix doesn't know how to handle that, and will likely tell you the script is not executable.Why?  The first line of a shell script ( called "sh-bang" ), identifies the command interpreter the unix shell should use for this script.   Common examples:#/bin/sh#/bin/ksh#/bin/bash#/bin/perl#/bin/sh^M    # will not be understood.#/bin/env ksh # special syntax.  Find ksh and run it dos2unix is a common utility found on most unix platforms, that repairs the issue of Windows LineEnd characters in unix script files.   I've written my own flavor of this utility for use in Tech Support and build environments, that is a bit easier to use, and has some nice side-effects. accepts a list of files:   dos2unix *.sh repairs the file in-place.  Doesn't generate a new file you have to name retains the same timestamp;  it is the encoding that changed, not the file content. Here are the versions of dos2unix for each of the environments we work in.They are compressed with gzip, to avoid the ftp ascii transfer trap,and because I am quite limited in the number of files I can upload to this blog. AIX Linux Solaris sparc  Windows 

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• How best to look up objects by label?

  - by dsollen

  I am writing the server backed by a pre-written API. I'm going to get a number of strings representing ports, signals, paths, etc etc etc. I need to look up the object associated with a given label, these objects are all in memory (no sql magic to do this for me). My question is, how best do I associate a given unique label with the mutable object it represents? I have enough objects that looking through every signal or every port to find the one that matches is possible, but may be slightly too slow. To be honest the direct 'look at every object' method is probably good enough for so small a body of objects and anything else is premature optimization, but I still am curious what the proper solution would be if I thought my signals were going to grow a bit larger. As I see it there are two options available. First would be to to create a 'store' that is a simple map between object and label. I could have it so that every time I call addObject the object is automatically saved into a hashmap or the like. This works, but relies on my properly adding and deleting each object so the map doesn't grow indefinitely. The biggest issue to me is that this involves having some hidden static map in my ModelObject class that just feels...wrong somehow. The other option is to have some method that can interpret the labels. All of these labels are derived from the underlying objects. So I can look at the signal label, for instance, and say "these 20 characters are the port" to figure out what port I need. This would allow me to quickly figure out what I need. However, if the label method is changed the translateLabelToObject method needs to be updated as well or everything breaks. Which solution is cleaner, or possibly a cleaner solution than either of above? For the record I'm working with sufficient number of variables to make direct comparison a little slow, but not enough to be concerned about memory overhead, written in java. All objects that have labels I need to look up extend the same parent class.

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• Building a Store Locator ASP.NET Application Using Google Maps API

  The past couple of projects I've been working on have included the use of the Google Maps API and geocoding service in websites for various reasons. I decided to tie together some of the lessons learned, build an ASP.NETstore locator demo, and write about it on 4Guys. Last week I published the first article in what I think will be a three-part series: Building a Store Locator ASP.NET Application Using Google Maps (Part 1). Part 1 walks through creating a demo where a user can type in an address and any stores within a (roughly) 15 mile area will be displayed in a grid.The article begins with a look at the database used to power the store locator (namely, a single table that contains one row for every location, with each location storing its store number, address, and, most important, latitude and longitude coordinates) and then turns to usingGoogle's geocoding service to translatea user-entered address into latitude and longitude coordinates. The latitude and longitude coordinates are used to find nearby stores, which are then displayed in a grid. Part 2 looks at enhancing the search results to include a map with markers indicating the position of each nearby store location. The Google Maps API, along with a bit of client-side script and server-side logic, make this actually pretty straightforward and easy to implement. Here's a screen shot of the improved store locator results. Part 3, which I plan on publishing next week, looks at how to enhance the map by using information windows to display address information when clicking a marker. Additionally, I'll show how to use custom icons for the markers so that instead of having the same marker for each nearby location the markers will be images numbered 1, 2, 3, and so on, which will correspond to a number assigned to each search result in the grid. The idea here is that by numbering the search results in the grid and the markers on the map visitors will quickly be able to see what marker corresponds to what search result. This article and demo has been a lot of fun to write and create, and I hope you enjoy reading it, too. Building a Store Locator ASP.NET Application Using Google Maps API (Part 1) Building a Store Locator ASP.NET Application Using Google Maps API (Part 2) Happy Programming!Did 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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• iPhone app development pricing [closed]

  - by AlexMorley-Finch

  I currently manage a website design and development company that integrates itself with print work too. I've been co manager for a couple of months now, however business is slow at the moment. I got an email today from a potential client asking if we do iPhone app development. Obviously we do not. But, seeing as there aren't many other project on the go at the moment, why not give it a go? Searching Google was my first option. I did a bit of background scrubbing. Discovered that I need certain developer tools etc. This can be arranged easily enough. The reason I came to Stack Exchange is for answers to these questions. I am a competant programmer and have had experience in Java, PHP, JavaScript, C++ and C#. So how long would it take me to come to grips with Objective-C? Assuming an 8 hour working day. Not only the language but also the iPhone interface libraries (if any exist) and other native libraries? The potential client said the app will be a catalogue. So I'm assuming either the data will be pulled online or in some kind of local database. I know the requirements are vague but does anyone have any idea of how mug time this would take? To learn the language, design the architecture and code? 40 Hours? 80 Hours? My final question kind of depends on the first two. But obviously the potential client wants a quote. And I have got no idea how much an app costs. I did some research and found a huge range in differences. The majority of the cost would cone from the time to develops the app! So to summarise. How long would it take me to be comfortable coding Objective-C, taking into consideration my past knowledge? I'm assuming a day or two to fully understand but you really don't know. How long would it take me to develop an app? How much should I charge (approx) for the development of this app?

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• Boot error aftter clean Ubuntu 13.04 install: [Reboot and select proper boot device]

  - by IcarusNM

  I am having the same problem as this guy where a fresh Ubuntu install completes beautifully but will not boot. I get the ASUS (?) "Reboot and select proper boot device" error, first with Xubuntu 13.10 and after finally giving up there, and Xubuntu 13.4, I am back to regular Ubuntu 13.4. ASUS motherboard Z77, Intel chipset. Standard internal SATA 500GB HD. 64-bit. All-new hardware less than 3 months old. It was running Ubuntu 12.04LTC great until I tried this upgrade. I have re-installed from scratch every which way: with LVM, without LVM; with the default partitions, with my own partitions. With ext3 or ext4. Alongside; replace; upgrade. No difference. On the last two tries, I have booted afterward from the same USB stick, downloaded and run boot-repair, and now I guess I am off to the boot-repair support email with my URLs from that. It did all kinds of cool stuff but ultimately made no difference. I never got anything like this with Ubuntu 12.04. I've now probably re-installed Ubuntu 13.04 ten times slightly different ways. I finally found how to skip the language packs, so at least that sped things up! :) This starts from the ubuntu-13.04-desktop-amd64.iso and UNetbootin as suggested on the official instructions for USB thumb drive creation from OSX. That part all works fine (booting the USB on the PC and trying Ubuntu and/or installing from there on the PC HD.) I have no CD drive on this PC, but I suppose I could get one. I would rather find some Linux install that works from USB like I've always done. After running boot-repair twice, in the ASUS BIOS I now see three different UEFI boot options in the priority list, and they are all labeled exactly the same: ubuntu (P6: WDC WD5000AAKX-00U6AA0) Then there's a non-UEFI option: P6: WDC WD5000AAKX-00U6AA0 (476940MB) And a fifth option appeared after the first boot-repair: Windows Boot Manager (P6: WDC WD5000AAKX-00U6AA0) I have tried all 5 of these, and I get exactly the same error. I have never had Windows installed on this HD. ASUS is calling it Windows Boot Manaer but I presume that's a mistaken label for whatever boot-repair did. I can boot on USB and run GParted and it looks great. The partitions all look normal. I found another case of this online with no solution posted. I can't find much about it online. Needs a Master Boot Record wipe/redo?? I'm not sure how.

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• is a factory pattern to prevent multuple instances for same object (instance that is Equal) good design?

  - by dsollen

  I have a number of objects storing state. There are essentially two types of fields. The ones that uniquly define what the object is (what node, what edge etc), and the oens that store state describing how these things are connected (this node is connected to these edges, this edge is part of these paths) etc. My model is updating the state variables using package methdos, so these objects all act as immutable to anyone not in Model scope. All Objects extend one base type. I've toyed with the idea of a Factory approch which accepts a Builder object and construct the applicable object. However, if an instance of the object already exists (ie would return true if I created the object defined by the builder and passed it to the equal method for the existing instance) the factory returns the current object instead of creating a new instance. Because the Equal method would only compare what uniquly defines the type of object (this is node A nto node B) but won't check the dynamic state stuff (node A is currently connected to nodes C and E) this would be a way of ensuring anyone that wants my Node A automatically knows it's state connections. More importantly it would prevent aliasing nightmares of someone trying to pass an instance of node A with different state then the node A in my model has. I've never heard of this pattern before, and it's a bit odd. I would have to do some overiding of serlization methods to make it work (ensure when I read in a serilized object I add it to my facotry list of known instances, and/or return an existing factory in it's place), as well as using a weakHashMap as if it was a weakHashSet to know rather an instance exists without worrying about a quasi-memory leak occuring. I don't know if this is too confusing or prone to it's own obscure bugs. One thing I know is that plugins interface with lowest level hardware. The plugins have to be able to return state taht is different then my memory; to tell my memory when it's own state is inconsistent. I believe this is possible despit their fetching objects that exist in my memory; we allow building of objects without checking their consistency with the model until the addToModel is called anyways; and the existing plugins design was written before all this extra state existed and worked fine without ever being aware of it. Should I just be using some other design to avoid this crazyness? (I have another question to that affect I'm posting).

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