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• How do client-server cooperation based games like Diablo 3 work?

  - by edgar

  Diablo 3 cooperates with Blizzard servers even during single player games. In fact, Blizzard has had problems with the games "melting their servers." I would like to ask: How do the client and the server communicate? What details does the client leave to the server, and vice versa? What details are redundant - both the client and the server know - and how often do they disagree? The previous paragraph contains the important questions, but I have a few more that I must explain my motivation towards. I am interested in the programming of botting. Ethical botting - I don't plan on actually abusing the automation to run 24/7. I just find it to be a great programming challenge to glean information from a game, and then make decisions from that information. I am stuck in the starting gate. The unofficial questions from this post would be: How can I make a bot (language, tools, libraries)? Can I get information through the communication between client and server, rather than the brute force pixel detection easily used in more static games? There probably is a trust issue, and to that all I can say is that I promise not to abuse the answers. But please feel free to answer any of the questions you feel comfortable with. Thank you!

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• Find non-ascii characters from a UTF-8 string

  - by user10607

  I need to find the non-ASCII characters from a UTF-8 string. my understanding: UTF-8 is a superset of character encoding in which 0-127 are ascii characters. So if in a UTF-8 string , a characters value is Not between 0-127, then it is not a ascii character , right? Please correct me if i'm wrong here. On the above understanding i have written following code in C : Note: I'm using the Ubuntu gcc compiler to run C code utf-string is xvab c long i; char arr[] = "xvab c"; printf("length : %lu \n", sizeof(arr)); for(i=0; i<sizeof(arr); i++){ char ch = arr[i]; if (isascii(ch)) printf("Ascii character %c\n", ch); else printf("Not ascii character %c\n", ch); } Which prints the output like: length : 9 Ascii character x Not ascii character Not ascii character ? Not ascii character ? Ascii character a Ascii character b Ascii character Ascii character c Ascii character To naked eye length of xvab c seems to be 6, but in code it is coming as 9 ? Correct answer for the xvab c is 1 ...i.e it has only 1 non-ascii character , but in above output it is coming as 3 (times Not ascii character). How can i find the non-ascii character from UTF-8 string, correctly. Please guide on the subject.

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• Object inheritance and method parameters/return types - Please check my logic

  - by user2368481

  I'm preparing for a test and doing practice questions, this one in particular I am unsure I did correctly: We are given a very simple UML diagram to demonstrate inheritance: I hope this is clear, it shows that W inherits from V and so on: |-----Y V <|----- W<|-----| |-----X<|----Z and this code: public X method1(){....} method2(new Y()); method2(method1()); method2(method3()); The questions and my answers: Q: What types of objects could method1 actually return? A: X and Z, since the method definition includes X as the return type and since Z is a kind of X is would be OK to return either. Q: What could the parameter type of method2 be? A: Since method2 in the code accepts Y, X and Z (as the return from method1), the parameter type must be either V or W, as Y,X and Z inherit from both of these. Q: What could return type of method3 be? A: Return type of method3 must be V or W as this would be consistent with answer 2.

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• Checking preconditions or not

  - by Robert Dailey

  I've been wanting to find a solid answer to the question of whether or not to have runtime checks to validate input for the purposes of ensuring a client has stuck to their end of the agreement in design by contract. For example, consider a simple class constructor: class Foo { public: Foo( BarHandle bar ) { FooHandle handle = GetFooHandle( bar ); if( handle == NULL ) { throw std::exception( "invalid FooHandle" ); } } }; I would argue in this case that a user should not attempt to construct a Foo without a valid BarHandle. It doesn't seem right to verify that bar is valid inside of Foo's constructor. If I simply document that Foo's constructor requires a valid BarHandle, isn't that enough? Is this a proper way to enforce my precondition in design by contract? So far, everything I've read has mixed opinions on this. It seems like 50% of people would say to verify that bar is valid, the other 50% would say that I shouldn't do it, for example consider a case where the user verifies their BarHandle is correct, but a second (and unnecessary) check is also being done inside of Foo's constructor.

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• Configuring permissions with Bastille

  - by Lucio

  I was using Bastille to improve the security of OS and I found the next question there I don't know if I should answer for YES or NOT: Questions: Would you like to set more restrictive permissions on the administration utilities? Explanation: In general, the default file permissions set by most vendors are fairly secure. To make them more secure, though, you can remove non-root user access to some administrator functions. If you choose this option, you'll be changing the permissions on some common system administration utilities so that they're not readable or executable by users other than root. These utilities (which include linuxconf, fsck, ipconfig, runlevel and portmap) are ones that most users could never have a need to access. This option will increase your system security, but there's a chance it will inconvenience your users. My users: When I installed Ubuntu I had create a user (admin), then I was able to create another user (people) but I cannot change the permissions of this user. Questions: The user there I am using like admin it's not the root, right? The effects of this option will affect to the two users (admin & people) or just to people?

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• How can rotating release managers improve a project's velocity and stability?

  - by Yannis Rizos

  The Wikipedia article on Parrot VM includes this unreferenced claim: Core committers take turns producing releases in a revolving schedule, where no single committer is responsible for multiple releases in a row. This practice has improved the project's velocity and stability. Parrot's Release Manager role documentation doesn't offer any further insight into the process, and I couldn't find any reference for the claim. My first thoughts were that rotating release managers seems like a good idea, sharing the responsibility between as many people as possible, and having a certain degree of polyphony in releases. Is it, though? Rotating release managers has been proposed for Launchpad, and there were some interesting counterarguments: Release management is something that requires a good understanding of all parts of the code and the authority to make calls under pressure if issues come up during the release itself The less change we can have to the release process the better from an operational perspective Don't really want an engineer to have to learn all this stuff on the job as well as have other things to take care of (regular development responsibilities) Any change of timezones of the releases would need to be approved with the SAs and: I think this would be a great idea (mainly because of my lust for power), but I also think that there should be some way making sure that a release manager doesn't get overwhelmed if something disastrous happens during release week, maybe by have a deputy release manager at the same time (maybe just falling back to Francis or Kiko would be sufficient). The practice doesn't appear to be very common, and the counterarguments seem reasonalbe and convincing. I'm quite confused on how it would improve a project's velocity and stability, is there something I'm missing, or is this just a bad edit on the Wikipedia article? Worth noting that the top voted answer in the related "Is rotating the lead developer a good or bad idea?" question boldly notes: Don't rotate.

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• Javascript Canvas Drawing Efficiency

  - by jujumbura

  I have just recently started some experiments with game development in Javascript/HTML5, and so far it has been going pretty well. I have a simple test scene running with some basic input handling, and a hundred-ish drawImage() calls with a few transforms. This all runs great on Chrome, but unfortunately, it already chugs on Firefox. I am using a very large canvas ( 1920 x 1080 ), but it doesn't seem like I should be hitting my limit already. So on that note, I was hoping to ask a few questions: 1) What exactly is done on the CPU vs. the GPU in terms of canvas and drawImage()? I'm afraid the answer is probably "it depends on the browser", but can anybody give me some rules of thumb? I naively imagined that each drawImage call results in a textured quad on the GPU with the canvas effectively being a render target, but I'm wondering if I'm pretty far off base there... 2) I have seen posts here and there with people saying not to use the translate(), rotate(), scale() functions when drawing on the canvas. Am I adding a lot of overhead just by adding a translate() call, as opposed to passing in the x,y to drawImage()? Some people suggest using "transate3d", etc., which are CSS properties, but I'm not sure how to use them within a scene. Can they be used for animated sprites within a single canvas? 3) I have also seen a lot of posts with people mentioning that pre-building canvases and then re-using them is a lot faster than issuing all the individual draw calls again. I am guessing that my background should definitely be pre-built into a canvas, but how far should I take this? Should I maintain an individual canvas for each sprite, to cache all static image data when not animating? Thank you much for your advice!

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• What are the most necessary non-language specific things a programmer needs to know?

  - by Josh

  I've been thinking about this a lot lately. Right now I work at a little web company, am almost done with school, and have written an iPhone app, but I'm not sure what else I need to focus my learning energies on. I've decided I want to do software programming, so I've been actively reading everything I can get my hands on that deals with Objective-C / C++ (Cocoa, OpenGL, etc). But those are not the things I'm talking about. I know I need to "master" a language or two. What I'm talking about are the other "things". Things such as learning and using source control, design patterns, etc. What thing (or things, just one per response), would you say I should concurrently be focusing on? You can consider in your answer that I'm wanting to do the aforementioned career path, but you don't have to. I just want a nice list of things to research, and actually use in my career. Also, can someone help me with tagging this? I'm not sure what exactly would be a good tag for such a question.

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• Empty interface to combine multiple interfaces

  - by user1109519

  Suppose you have two interfaces: interface Readable { public void read(); } interface Writable { public void write(); } In some cases the implementing objects can only support one of these but in a lot of cases the implementations will support both interfaces. The people who use the interfaces will have to do something like: // can't write to it without explicit casting Readable myObject = new MyObject(); // can't read from it without explicit casting Writable myObject = new MyObject(); // tight coupling to actual implementation MyObject myObject = new MyObject(); None of these options is terribly convenient, even more so when considering that you want this as a method parameter. One solution would be to declare a wrapping interface: interface TheWholeShabam extends Readable, Writable {} But this has one specific problem: all implementations that support both Readable and Writable have to implement TheWholeShabam if they want to be compatible with people using the interface. Even though it offers nothing apart from the guaranteed presence of both interfaces. Is there a clean solution to this problem or should I go for the wrapper interface? UPDATE It is in fact often necessary to have an object that is both readable and writable so simply seperating the concerns in the arguments is not always a clean solution. UPDATE2 (extracted as answer so it's easier to comment on) UPDATE3 Please beware that the primary usecase for this is not streams (although they too must be supported). Streams make a very specific distinction between input and output and there is a clear separation of responsibilities. Rather, think of something like a bytebuffer where you need one object you can write to and read from, one object that has a very specific state attached to it. These objects exist because they are very useful for some things like asynchronous I/O, encodings,...

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• Which forum software has the most advanced community/GetSatisfaction type features?

  - by Gaia

  I need to assemble a GetSatisfaction/Lithium/Jive type support forum/community. The first is not available in the desired language and the last two are priced for the enterprise market. I did research some other options (open source or SaaS) but they all seem to be either: kind of dead (open source options) too focused in gathering ideas/feedback (uservoice) strictly support without the community/voting features (zendesk) I need an open forum (people powered support/UGC with community/voting features). Therefore I will have to do some of the work on my own. I want to piece things (plugins/mods/etc) on top of a standard forum platform to give it the features I need. For this purpose, I want to use a mature product with widespread userbase, active community and lots of plugin options. I believe most will agree that my options therefore are: vBulletin phpBB SMF Here are the questions: Which one of the three above offers the easier path towards the desired goal? Which one of the three above has the most advanced features related to the desired goal? Of course I dont expect anyone to know these answers cut and dry. I am hoping to hear some experiences and see some examples. Also, it would be great if both those questions had the same answer, but I am not going to get my hopes up... PS: I wish I could add the tags "phpbb" and "smf" ;)

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• Software licensing template that gives room for restricting usage to certain industries/uses of software/source

  - by BSara

  *Why this question is not a duplicate of the questions specified as such: I did not ask if there was a license that restricted specific uses and I did not ask if I could rewrite every line of any open source project. I asked very specifically: "Does there exist X? If not, can I Y with Z?". As far as I can tell, the two questions that were specified as duplicates do not answer my specific question. Please remove the duplicate status placed on the question. I'm developing some software that I would like to be "semi" open source. I would like to allow for anyone to use my software/source unless they are using the software/source for certain purposes. For example, I don't want to allow usage of the software/source if it is being used to create, distribute, view or otherwise support pornography, illegal purposes, etc. I'm no lawyer and couldn't ever hope to write a license myself nor do I have to time to figure how to best do this. My question is this: Does there exist a freely available license or a template for a license that I can use to license my software under they conditions explained above just like one can use the Creative Commons licenses? If not, am I allowed to just alter one of Creative Commons licenses to meet my needs?

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• Tree Surgeon 2.0 - The future on the T4 Express

  - by Malcolm Anderson

  If you've never been a fan of TreeSurgeon (http://treesurgeon.codeplex.com/) then skip this post.However, if have been there have been some interesting developments over the last couple of years.The biggest one is T4Recently Bill Simser wrote a detailed post about the potential future of tree surgeon, called "Tree Surgeon - Alive and Kicking or Dead and Buried" He raised the question:Times have changed. Since that last release in 2008 so much has changed for .NET developers. The question is, today is the project still viable? Do we still need a tool to generate a project tree given that we have things like scaffolding systems, NuGet, and T4 templates. Or should we just give the project its rightful and respectful send off as its had a good life and has outlived its usefulness.For myself, the answer is, keep it.I've spent the last couple of years doing agile engineering coaching and architecture and from my experience, I can tell you, there are a lot of shops out there that would benefit from having Tree Surgeon as a viable product.  Many would benefit simply from having the software engineering information that is embedded in the tree surgeon site be floating around their conversation.Little things like, keep all of your software needed to run the build, with the build in the version control system.Have your developers and the build system using the same build.Have a one-touch buildSeparate your code from your interfacePut unit tests in first, not lastI've seen companies with great developers suffer from the problems that naturally come from builds taking 3 and 4 hours to run.  It takes work to get that build down to 10 minutes, but the benefits are always worth it.  Tree Surgeon gives you a leg up, by starting you off with a project that you can drop into your Continuous Integration system, right out of the box.Well, it used to be right out of the box.  Today, you have to play with the project to make it work for you, but even with the issues (it hasn't been updated since 2008) it still gives you a framework, with logical separations that you can build from.If you have used Tree Surgeon in the past, take a few minutes and drop a comment about what difference it made in your development style, and what you are doing differently today because of it.

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• What's the best way to manage error logging for exceptions?

  - by Peter Boughton

  Introduction If an error occurs on a website or system, it is of course useful to log it, and show the user a polite message with a reference code for the error. And if you have lots of systems, you don't want this information dotted around - it is good to have a single centralised place for it. At the simplest level, all that's needed is an incrementing id and a serialized dump of the error details. (And possibly the "centralised place" being an email inbox.) At the other end of the spectrum is perhaps a fully normalised database that also allows you to press a button and see a graph of errors per day, or identifying what the most common type of error on system X is, whether server A has more database connection errors than server B, and so on. What I'm referring to here is logging code-level errors/exceptions by a remote system - not "human-based" issue tracking, such as done with Jira,Trac,etc. Questions I'm looking for thoughts from developers who have used this type of system, specifically with regards to: What are essential features you couldn't do without? What are good to have features that really save you time? What features might seem a good idea, but aren't actually that useful? For example, I'd say a "show duplicates" function that identifies multiple occurrence of an error (without worrying about 'unimportant' details that might differ) is pretty essential. A button to "create an issue in [Jira/etc] for this error" sounds like a good time-saver. Just to re-iterate, what I'm after is practical experiences from people that have used such systems, preferably backed-up with why a feature is awesome/terrible. (If you're going to theorise anyway, at the very least mark your answer as such.)

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• When to use PHP or ASP.NET? [closed]

  - by loyalpenguin

  I have worked extensively in developing web applications using PHP and ASP.NET, but one of the questions that I'm constantly asked by customers is whether to move forward with a php website or an asp.net website. So naturally the first thing that comes to mind is to answer the question like this: PHP is open-source and ASP.NET is from Microsoft. Usually after something like that is said the customer has a blank look on there face. Apparently the fact that one is open source and the other isn't doesn't really faze them. And for good reason, because when I first heard it, it really doesn't tell me much. I know from working with both that each have their + and - when it comes to developing websites. NOTE: THIS QUESTION IS NOT TO QUESTION WHICH IS BETTER TO DEVELOP WITH. THIS QUESTION IS INTENDED TO BE OBJECTIVE. My question is what are differences between ASP.NET and PHP as far as Features Security Extendability Frameworks Average Development Time And when one is generally used over the other for certain types of projects. I am trying to compile a list of facts to be able to compare with the customer what developement platform is better for there particular project. I have done a simple search on google and a ton of articles come up, but the problem is the majority are usually biased towards PHP or ASP.NET. Also if you can maybe provide examples from experience when one technology was more preferable than the other that would be awesome.

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• How Can I Effectively Interview an Oracle Candidate?

  - by Tim Medora

  First, I browsed through SO for matching questions and didn't find one, but please point me in the right direction if this exact question has already been asked. I work with and around programmers of various skill levels on various platforms. I would consider my skills to be strong in terms of relational database design, query development, and basic performance tuning and administration. I'm mid-level when it comes to database theory. My team is looking to me to ensure that we have the best talent on staff, in this case, an engineer experienced in Oracle administration. To me, a well-rounded database administrator, regardless of platform, should also be competent in developing against the database so that is also a requirement. However my database skills are centralized around SQL Server 200x with experience in a few other products like SAP MaxDB, Access, and FoxPro. How can I thoroughly assess the skills of an Oracle engineer? I can ask high-level database theory questions and talk about routine tasks that are common across platforms, but I want to dig deep enough that I can be confident in the people I hire. Normally, I would alternate very specific questions that have a right/wrong answer with architectural questions that might have several valid answers. Does anyone have an interview template, specific questions, or any other knowledge that they can share? Even knowing the meaningful Oracle-related certifications would be a help. Thank you. EDIT: All the answers have been very helpful so far and I have given upvotes to everyone. I'm surprised that there are already 3 close votes on this question as "off topic". To be clear, I am specifically asking how a MS SQL Server engineer (like myself) can effectively interview a person with different but symbiotic skills. The question has already received specific, technical answers which have improved my own database design and programming skills. If this is more appropriate as a community wiki, please convert it.

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• What are `Developmental Milestones` for programming skills?

  - by Holmes

  I studied in the field of Computer Science for 6 years, bachelor's degree and master's degree. I have studied all the basic programming like C, Java, VB, C#, Python, and etc. When I have free times, I will learn new programming languages and follow new programming trends by myself , such as PHP, HTML5, CSS5, LESS, Bootstrap, Symfony2, and GitHub. So, if someone wants me to write some instructions using these languages, I'm certain that I can do it, not so good but I can get a job done. However, I don't have any favorite programming language. Moreover, I also have studied about algorithms, database, and etc. Everything I just wrote so far seems that I know a lot in this field. In fact, I feel I am very stupid. I cannot answer 80% of the questions on SO. In spite of those languages??, I have studied. Perhaps it is because I have never worked before. As there is the Developmental Milestones for children, which refers to how a child becomes able to do more complex things as they get older, I would like to evaluate the same thing but for programming skills. What are the set of functional skills or age-specific tasks that most programmers can do at a certain age range? In order to evaluate myself, I would like to ask your opinions that all of the skills I mentioned above, are they enough for programmers to know when they are 25 years old? What are your suggestions in order to improve the skills in this field?

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• How to understand computer science as a whole?

  - by MrCellophane

  I am a college student in Computer Science, I have been studying CS for a long time. But even till today, I still feel so confused about a lot of things. First of all, I have solid foundation in alg, data structure, and OOP, but I don't have a clear understanding of the whole system of the subject. I studied database, alg, data structure, OOP, network, software engineering, OS, and a lot of courses. I know what they are, but I don't know how to connect them together. Is there a way to have a clear understanding of the architecture of the subject? And is there a way to know what technology is used to do what? For example, in interviews, when people ask me alg, data str, Java, OS or any other specific field, I could answer, but when they ask some other very general about the field, I have no idea. Well, I know my question maybe a little bit confusing, but what my situation is I don't even know how to ask a clear question. I don't know my question, it's totally a mess in my head. Is there a way to make it clear?

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• What are the requirements to test a website using jquery.get() ? [migrated]

  - by Frankie

  I am working on a simple website. It has to search quite a few text files in different sub-folders. The rest of the page uses jquery, so I would like to use it for this also. The function I am looking at is .get() for downloading the files. So my main question is, can I test this on my local computer (Ubuntu Linux) or do I have to have it uploaded to a server? Also, if there's a better way to go about this, that would be nice to know. However, I'm more worried about getting it working. Thanks, Frankie PS: Heres the JS/jQuery code for downloading the files to an array. g_lists = new Array(); $(":checkbox").each(function(i){ if ($(this).attr("name") != "0") { var path = "../" + $(this).attr("name") + ".txt"; $("#bot").append("<br />" + path); // debug $.get(path, function(data){ g_lists[i] = data; $("#bot").html(data); }); } else { g_lists[i] = ""; } }); Edit: Just a note about the path variable. I think it's correct, but I'm not 100% sure. I'm new to web development. Here's some examples it produces and the directory tree of the site. Maybe it will help, can't hurt. . +-- include ¦   +-- jquery.js ¦   +-- load.js +-- index.xhtml +-- style.css +-- txt    +-- Scripting_Tools    +-- Editors.txt    +-- Other.txt Examples of path: ../txt/Scripting_Tools/Editors.txt ../txt/Scripting_Tools/Other.txt Well I'm a new user, so I can't "answer" my own question, so I'll just post it here: After asking for help on a IRC chat channel specific to jQuery, I was told I could use this on a local host. To do this I installed Apache web server, and copied my site into it's directory. More information on setting it up can be found here: http://www.howtoforge.com/ubuntu_debian_lamp_server Then to run the site I navigated my browser to "localhost" and everything works.

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• Team Software Development using Ruby on Rails

  - by Panoy

  I used to work alone on small to medium sized programming projects before and have no experience working in a team environment. Currently, there will be 3 of us in an in-house software development team that is tasked to develop a number of software for an academic institution. We have decided to use the web for the majority of the projects and are planning to choose Ruby on Rails for this and I would like to ask for your inputs, advices and approaches with regards to software development as a team using the RoR web framework. One thing that has really confounded me is how you divide the programming tasks of a project if there are 3 of you that are really doing the coding. It’s obvious that we as developers approach a problem in a modular way and finish it one after another. If the project consists of 3 modules, should each one of us focus on each of those modules? Would it be faster that way? How about if the 3 of us would focus on one module first (that’s what I really prefer). Is using a distributed version control system such as Git the answer to this type of problem? Please don’t forget to put your tips and experiences with regards to team software development. Cheers!

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• Loadbalancing Questions

  - by Van Holtz

  I have been learning networking for about 4 months. Wrote a single standalone Multiplayer server and succeeded with authoritative approach. Now I want to extend it by splitting the single server into clusters to allow even more players to log in to avoid latency issues. Now I have protyped the Loadbalancing server and its running pretty good so far. This is my architecture, I have a master server which acts as a proxy, every sub servers(chat, login, game) connect to the master server as well as all the clients. when a client connects, Client Request: Send Request - MS(Master) - Decides which SS(SubServer) to forward to - Forwards Request to SS - SS - Analyze Message - Send Response to MS - Decides which Client to forward to - Forwards Response to Client Well, it looks like its going through lots of stages. it takes double the time to process the message than a single server approach. i feel like my model isnt the best or i may be wrong. is there any better model or the one they use in professional games? I still want a Master-SubServer approach. I just want to clarify that I'm going in the right direction before writing all my codes. Thanks for any answer :)

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• How to improve Minecraft-esque voxel world performance?

  - by SomeXnaChump

  After playing Minecraft I marveled a bit at its large worlds but at the same time I found them extremely slow to navigate, even with a quad core and meaty graphics card. Now I assume Minecraft is fairly slow because: A) It's written in Java, and as most of the spatial partitioning and memory management activities happen in there, it would naturally be slower than a native C++ version. B) It doesn't partition its world very well. I could be wrong on both assumptions; however it got me thinking about the best way to manage large voxel worlds. As it is a true 3D world, where a block can exist in any part of the world, it is basically a big 3D array [x][y][z], where each block in the world has a type (i.e BlockType.Empty = 0, BlockType.Dirt = 1 etc.) Now, I am assuming to make this sort of world perform well you would need to: A) Use a tree of some variety (oct/kd/bsp) to split all the cubes out; it seems like an oct/kd would be the better option as you can just partition on a per cube level not a per triangle level. B) Use some algorithm to work out which blocks can currently be seen, as blocks closer to the user could obfuscate the blocks behind, making it pointless to render them. C) Keep the block object themselves lightweight, so it is quick to add and remove them from the trees. I guess there is no right answer to this, but I would be interested to see peoples' opinions on the subject. How would you improve performance in a large voxel-based world?

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• Algorithmic problem - quickly finding all #'s where value %x is some given value

  - by Steve B.

  Problem I'm trying to solve, apologies in advance for the length: Given a large number of stored records, each with a unique (String) field S. I'd like to be able to find through an indexed query all records where Hash(S) % N == K for any arbitrary N, K (e.g. given a million strings, find all strings where HashCode(s) % 17 = 5. Is there some way of memoizing this so that we can quickly answer any question of this form without doing the % on every value? The motivation for this is a system of N distributed nodes, where each record has to be assigned to at least one node. The nodes are numbered 0 - (K-1) , and each node has to load up all of the records that match it's number: If we have 3 nodes Node 0 loads all records where Hash % 3 ==0 Node 1 loads all records where Hash % 3 ==1 Node 2 loads all records where Hash % 3 ==2 adding a 4th node, obviously all the assignments have to be recomputed - Node 0 loads all records where Hash % 4 ==0 ... etc I'd like to easily find these records through an indexed query without having to compute the mod individually. The best I've been able to come up with so far: If we take the prime factors of N (p1 * p2 * ... ) if N % M == I then p % M == I % p for all of N's prime factors e.g. 10 nodes : N % 10 == 6 then N % 2 = 0 == 6 %2 N % 5 = 1 == 6 %5 so storing an array of the "%" of N for the first "reasonable" number of primes for my data set should be helpful. For example in the above example we store the hash and the primes HASH PRIMES (array of %2, %3, %5, %7, ... ]) 16 [0 1 1 2 .. ] so looking for N%10 == 6 is equivalent to looking for all values where array[1]==1 and array[2] == 1. However, this breaks at the first prime larger than the highest number I'm storing in the factor table. Is there a better way?

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• Friday Tips #6, Part 2

  - by Chris Kawalek

  Here is a question about updating Oracle VM: Question: How can I perform Oracle VM 3 server updates from Oracle VM Manager? Answer by Gregory King, Principal Best Practices Consultant, Oracle VM Product Management: Server Update Manager is a built-in feature of the Oracle VM Manager. Basically, Server Update Manager automatically configures YUM updates on all the Oracle VM Servers, pointing each to our Unbreakable Linux Network (ULN) update channel for Oracle VM. The servers periodically check with our Oracle YUM repository and notify the Oracle VM Manager that an update is available for each server. Actual server updates must be triggered by the Oracle VM administrator – they are not executed automatically. At this point, you can use the Oracle VM Manager to put a server into maintenance mode which live migrates all the running Oracle VM Guests to other Oracle VM Servers in the server pool. Once all the Oracle VM Guests have been migrated, the Oracle VM administrator can trigger the update on the server. The entire process is documented in the Installation and Upgrade Guide of Oracle VM Documentation so I won’t spend time detailing the steps. However, configuring the Server Update Manager is exceedingly simple. Simply navigate to the Tools and Resources tab in the Oracle VM Manager, select the link for Server Update Manager and ensure the following values are added to the text boxes as shown in the illustration below: YUM Base URL: http://public-yum.oracle.com/repo/OracleVM/OVM3/latest/x86_64 YUM GPG Key: file:///etc/pki/rpm-gpg/RPM-GPG-KEY-oracle Every server in the pool will be automatically configured for YUM updates once you choose the Apply button. Many thanks to Greg and Rick for providing the answers to this week's questions. If you want to ask us something, hit up Twitter and use hashtag #AskOracleVirtualization. See you next week! -Chris 

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• How do I require use of the 5 GHz band when connecting to a Wireless N access point?

  - by cqcallaw

  What is says in the topic: there's a Wireless N access point to which I'd like to connect using the 5 GHz band exclusively. How does one accomplish this? Using the directive band=a in the connection configuration file in /etc/NetworkManager/system-connections doesn't seem to affect anything (/var/log/syslog still shows attempts by wpa_supplicant to connect using the 2.4 GHz band), and running iwconfig wlan0 freq 5G per this question results in the following error: Error for wireless request "Set Frequency" (8B04) : SET failed on device wlan0 ; Invalid argument. [Edit] I'm hoping the answer won't depend on the hardware in use, but here's some information about the hardware, just in case: System is an Asus ZenBook Prime UX31A-DB51, running Ubuntu 12.04. lspci output: 00:00.0 Host bridge: Intel Corporation Ivy Bridge DRAM Controller (rev 09) 00:02.0 VGA compatible controller: Intel Corporation Ivy Bridge Graphics Controller (rev 09) 00:04.0 Signal processing controller: Intel Corporation Device 0153 (rev 09) 00:14.0 USB controller: Intel Corporation Panther Point USB xHCI Host Controller (rev 04) 00:16.0 Communication controller: Intel Corporation Panther Point MEI Controller #1 (rev 04) 00:1a.0 USB controller: Intel Corporation Panther Point USB Enhanced Host Controller #2 (rev 04) 00:1b.0 Audio device: Intel Corporation Panther Point High Definition Audio Controller (rev 04) 00:1c.0 PCI bridge: Intel Corporation Panther Point PCI Express Root Port 1 (rev c4) 00:1c.1 PCI bridge: Intel Corporation Panther Point PCI Express Root Port 2 (rev c4) 00:1d.0 USB controller: Intel Corporation Panther Point USB Enhanced Host Controller #1 (rev 04) 00:1f.0 ISA bridge: Intel Corporation Panther Point LPC Controller (rev 04) 00:1f.2 SATA controller: Intel Corporation Panther Point 6 port SATA Controller [AHCI mode] (rev 04) 00:1f.3 SMBus: Intel Corporation Panther Point SMBus Controller (rev 04) 00:1f.6 Signal processing controller: Intel Corporation Panther Point Thermal Management Controller (rev 04) 02:00.0 Network controller: Intel Corporation Centrino Advanced-N 6235 (rev 24) The driver for the wireless interface is iwlwifi.

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• Logic / Render phases with a single thread

  - by DevilWithin

  The question I have may generate different opinions from different developers, but I'd still like to have an answer on this. Its all about the updating and rendering steps of the game loop, and their use under multi and single threaded environments. Currently, there is one thread running, which takes care of sequentially executing events , logic and rendering. Sometimes, the logic part may wish to change the game state to something else, and in between do some loading of files. The result is that the game hangs completely while loading, and then proceeds to normal rendering of the new state. To go around this, i could make another thread, do the loading there while the main thread renders a smooth loading animation, and then proceed normally. The real question is about if i don't create another thread. I could refresh the screen from the logic thread, and provide some basic loading screen, which could be not so smoothly updated while the files load. In fact, this approach is not loved by a lot of developers, as it scrambles render code in the logic step, which may cause problems of different sorts.. Hope its clear!

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