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  • Large sparse (stiff) ODE system needed for testing

    - by macydanim
    I hope this is the right place for this question. I have been working on a sparse stiff implicit ODE solver and have finished the code so far. I now tested the solver with the Van der Pol equation, and another stiff problem, which is of dimension 4. But to perform better tests I am searching for a bigger system. I'm thinking of the order N = 100...1000, if possible stiff and sparse. Does anybody have an example I could use? I really don't know where to search.

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  • Developing an ELO like point system for a multiplayer gaming site

    - by Alejandro Piad
    I'm currently working on a gaming site where users will submit virtual players for different games, like Chess, Nash, Backgammon, Go, etc. The idea is that users don't compete themselves, but through their virtual players. There will be leagues, tournaments, and other competition formats. The question is which would be a good rating system for users in this environment. Take into account that every user may have many different virtual players playing in many different games. As a general guideline I would like to guarantee the following properties: Users who have a lot of mediocre players should not score higher than users with a few very good players. A user with a high rating should not be penalized if he adds a new bad player, until he has had enough time to improve his player. Users who don't play often should not score higher than users who play every day. Thanks in advance.

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  • Physics System ignores collision in some rare cases

    - by Gajoo
    I've been developing a simple physics engine for my game. since the game physics is very simple I've decided to increase accuracy a little bit. Instead of formal integration methods like fourier or RK4, I'm directly computing the results after delta time "dt". based on the very first laws of physics : dx = 0.5 * a * dt^2 + v0 * dt dv = a * dt where a is acceleration and v0 is object's previous velocity. Also to handle collisions I've used a method which is somehow different from those I've seen so far. I'm detecting all the collision in the given time frame, stepping the world forward to the nearest collision, resolving it and again check for possible collisions. As I said the world consist of very simple objects, so I'm not loosing any performance due to multiple collision checking. First I'm checking if the ball collides with any walls around it (which is working perfectly) and then I'm checking if it collides with the edges of the walls (yellow points in the picture). the algorithm seems to work without any problem except some rare cases, in which the collision with points are ignored. I've tested everything and all the variables seem to be what they should but after leaving the system work for a minute or two the system the ball passes through one of those points. Here is collision portion of my code, hopefully one of you guys can give me a hint where to look for a potential bug! void PhysicalWorld::checkForPointCollision(Vec2 acceleration, PhysicsComponent& ball, Vec2& collisionNormal, float& collisionTime, Vec2 target) { // this function checks if there will be any collision between a circle and a point // ball contains informations about the circle (it's current velocity, position and radius) // collisionNormal is an output variable // collisionTime is also an output varialbe // target is the point I want to check for collisions Vec2 V = ball.mVelocity; Vec2 A = acceleration; Vec2 P = ball.mPosition - target; float wallWidth = mMap->getWallWidth() / (mMap->getWallWidth() + mMap->getHallWidth()) / 2; float r = ball.mRadius / (mMap->getWallWidth() + mMap->getHallWidth()); // r is ball radius scaled to match actual rendered object. if (A.any()) // todo : I need to first correctly solve the collisions in case there is no acceleration return; if (V.any()) // if object is not moving there will be no collisions! { float D = P.x * V.y - P.y * V.x; float Delta = r*r*V.length2() - D*D; if(Delta < eps) return; Delta = sqrt(Delta); float sgnvy = V.y > 0 ? 1: (V.y < 0?-1:0); Vec2 c1(( D*V.y+sgnvy*V.x*Delta) / V.length2(), (-D*V.x+fabs(V.y)*Delta) / V.length2()); Vec2 c2(( D*V.y-sgnvy*V.x*Delta) / V.length2(), (-D*V.x-fabs(V.y)*Delta) / V.length2()); float t1 = (c1.x - P.x) / V.x; float t2 = (c2.x - P.x) / V.x; if(t1 > eps && t1 <= collisionTime) { collisionTime = t1; collisionNormal = c1; } if(t2 > eps && t2 <= collisionTime) { collisionTime = t2; collisionNormal = c2; } } } // this function should step the world forward by dt. it doesn't check for collision of any two balls (components) // it just checks if there is a collision between the current component and 4 points forming a rectangle around it. void PhysicalWorld::step(float dt) { for (unsigned i=0;i<mObjects.size();i++) { PhysicsComponent &current = *mObjects[i]; Vec2 acceleration = current.mForces * current.mInvMass; float rt=dt; // stores how much more the world should advance while(rt > eps) { float collisionTime = rt; Vec2 collisionNormal = Vec2(0,0); float halfWallWidth = mMap->getWallWidth() / (mMap->getWallWidth() + mMap->getHallWidth()) / 2; // we check if there is any collision with any of those 4 points around the ball // if there is a collision both collisionNormal and collisionTime variables will change // after these functions collisionTime will be exactly the value of nearest collision (if any) // and if there was, collisionNormal will report in which direction the ball should return. checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2(floor(current.mPosition.x) + halfWallWidth,floor(current.mPosition.y) + halfWallWidth)); checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2(floor(current.mPosition.x) + halfWallWidth, ceil(current.mPosition.y) - halfWallWidth)); checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2( ceil(current.mPosition.x) - halfWallWidth,floor(current.mPosition.y) + halfWallWidth)); checkForPointCollision(acceleration,current,collisionNormal,collisionTime,Vec2( ceil(current.mPosition.x) - halfWallWidth, ceil(current.mPosition.y) - halfWallWidth)); // either if there is a collision or if there is not we step the forward since we are sure there will be no collision before collisionTime current.mPosition += collisionTime * (collisionTime * acceleration * 0.5 + current.mVelocity); current.mVelocity += collisionTime * acceleration; // if the ball collided with anything collisionNormal should be at least none zero in one of it's axis if (collisionNormal.any()) { collisionNormal *= Dot(collisionNormal, current.mVelocity) / collisionNormal.length2(); current.mVelocity -= 2 * collisionNormal; // simply reverse velocity along collision normal direction } rt -= collisionTime; } // reset all forces for current object so it'll be ready for later game event current.mForces.zero(); } }

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  • Dynamic obstacles avoidance in navigation mesh system

    - by Variable
    I've built my path finding system with unreal engine, somehow the path finding part works just fine while i can't find a proper way to solve dynamic obstacles avoidance problem. My characters are walking allover the map and collide with each other while they moving. I try to steering them when collision occurs, but this doesn't work well. For example, two characters block on the road while the third one's path is right in the middle of them and he'll get stuck. Can someone tell me the most popular way of doing dynamic avoidance? Thanks a lot.

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  • I'm getting unrelated system messages in terminal?

    - by Zed
    For some reason from time to time I keep getting this weird system messages in my working terminal emulator, unrelated to anything I do.For example: [000:000] Browser XEmbed support present: 1 [000:000] Browser toolkit is Gtk2. [000:001] Using Gtk2 toolkit [000:033] Starting client channel. [000:048] Read port file, port=33359 [000:050] Initiated connection to GoogleTalkPlugin [000:154] Socket connection established [000:154] ScheduleOnlineCheck: Online check in 5000ms [000:203] Got cookie response, socket is authorized [000:203] AUTHORIZED; socket handshake complete [005:216] HandleOnlineCheck: Starting check [005:216] HandleOnlineCheck: OK; current state: 3 Failed to open VDPAU backend libvdpau_nvidia.so: cannot open shared object file: No such file or directory After some investigation I concluded that those messages ARE from firefox.However, I didn't start Firefox from terminal. or nsBuiltinDecoderStateMachine::RunStateMachine queuing nsBuiltinDecoder::PlaybackEnded nsBuiltinDecoder::PlaybackEnded mPlayState=3 nsBuiltinDecoderStateMachine::RunStateMachine queuing nsBuiltinDecoder::PlaybackEnded nsBuiltinDecoder::PlaybackEnded mPlayState=3 I have no clue how this ends up in working terminal, any thoughts ?

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  • Is extensive documentation a code smell?

    - by Griffin
    Every library, open-source project, and SDK/API I've ever come across has come packaged with a (usually large) documentation file, and this seems contradictory to the wide-spread belief that good code needs little to no comments. What separates documentation from this programming methodology? a one to two page overview of a package seems reasonable, but elegant code combined with standard intelisense should have theoretically deprecated the practice of documentation by now IMO. I feel like companies only create detailed documentation and tutorials because its what they've always done. Why should developers have to constantly be searching through online documentation in order to learn how to do things when such information should be intrinsic to the classes, methods and namespaces?

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  • How did programmers resolve their problems before the internet?

    - by 9a3eedi
    When programming, anytime I get stuck, perhaps with a compiler error that doesn't make sense, or from a GUI function that didn't do what I expected, I automatically google my problem, find someone else that faced the same thing, and read what's going on and why I'm getting the problem. Before the internet, how did people handle these situations? People used to read books and manuals more, I know. But books don't explain everything, like the odd compiler problem that you get sometimes, or nothing showing up on your screen despite you clearly writing correct OpenGL code. How did people cope when facing challenges? Did they simply "bash their head" on the wall till they figured it out? Is there something people used to do regularly on the side that gave them the ability to get themselves unstuck more easily? Were libraries/compilers much simpler back then? I've been asking this question because I sometimes feel guilty depending on Google so much when I'm pretty sure programmers before my time were more independent when it comes to facing these matters.

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  • On-the-fly graphical representation of code

    - by dukeofgaming
    I know about Omondo's plugin for live code-UML synchronization in Eclipse, but I was wondering if there was any other tool/IDE/IDE-extension that has some form of live graphical code representaiton (structural, flow, call-stacks, dependencies, etc.). I'm essentially looking for richer visual feedback on code while programming, not really looking for purely graphical code editors, though round-trips would be nice (edit graphically, code gets modified; edit code, representation gets modified). If you don't know about any graphical live documentation tool for code, maybe someone that can coexist with code, such as MySQL Workbench or Enterprise Architect.

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  • Historical origins of Scala implicits

    - by Frank
    Scala has been called complex with its rich feature set by many of my colleagues and some even blamed all those new features of it. While most programmers are aware of the OO-features, and at least the decent ones also know about functional programming, there is one feature in particular in Scala for which I am not aware of its historical origins. Given that a major mantra of our profession is to not reinvent the wheel, I am rather confident, that Scala does not have any actual unheard-of-before features, but I stand to be corrected on this one if necessary. To get to the actual question, while I am aware of the origins of most of Scala's features I have never seen something like its implicit declarations before. Are there other (older!) languages out there which also provide this feature? Does it make sense to distinguish the different cases of implicits (as they may originate from different sources), namely implict conversions and implicit parameters?

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  • What php programmer should know?

    - by emchinee
    I've dig the database here and didn't found any answer for my question. What is a standard for a php programmer to know? I mean, literally, what group of language functions, mechanisms, variables should person know to consider oneself a (good) php programmer? (I know 'being good' is beyond language syntax, still I'm considering syntax of plain php only) To give an example what I mean: functions to control http sessions, cookies functions to control connection with databases functions to control file handling functions to control xml etc.. I omit phrases like 'security' or 'patterns' or 'framework' intentionally as it applies to every programming language. Hope I made myself clear, any input appreciated :) Note: Michael J.V. is right claiming that databases are independent from language, so to put my question more precisely and emphasise differences: Practises or security, are some ideas to implement (there is no 'Pattern' object with 'Decorator()' method, is there?) while using databases means knowing a mysqli and a set of its methods.

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  • Nested languages code smell

    - by l0b0
    Many projects combine languages, for example on the web with the ubiquitous SQL + server-side language + markup du jour + JavaScript + CSS mix (often in a single function). Bash and other shell code is mixed with Perl and Python on the server side, evaled and sometimes even passed through sed before execution. Many languages support runtime execution of arbitrary code strings, and in some it seems to be fairly common practice. In addition to advice about security and separation of concerns, what other issues are there with this type of programming, what can be done to minimize it, and is it ever defensible (except in the "PHB on the shoulder" situation)?

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  • Scrum for Team System v3 RTM available

    - by Enrique Lima
    If you are using the Scrum for Team System (aka Conchango Scrum Template), it has hit RTM and it is available for download.  First you will need to register and then you will ne able to access the goods. There is also a very well laid out Getting Started with v3 guide, put together by Crispin Parker. Note:  Very important to know and consider, is the fact there is no upgrade or migration strategy laid out from v2.2.  So you are left to your own devices on that one.  There are plenty of discussions going on as far as making it happen.  Don’t get me wrong v2.2 work items will be present and you will be able to use them, just don’t expect the v3 template to trigger when  adding new work items. For now, get TFS in place, install the template and start fresh.  The Workbench should be released soon too, and that makes it a great component to this solution.

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  • Would you use (a dialect of) LISP for a real-world application? Where and why?

    - by Anto
    LISP (and dialects such as Scheme, Common LISP and Clojure) haven't gained much industry support even though they are quite decent programming languages. (At the moment though it seems like they are gaining some traction). Now, this is not directly related to the question, which is would you use a LISP dialect for a production program? What kind of program and why? Usages of the kind of being integrated into some other code (e.g. C) are included as well, but note that it is what you mean in your answer. Broad concepts are preferred but specific applications are okey as well.

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  • Artist, Looking to lean how to program games, where do I start? [on hold]

    - by Christopher Hindson
    I have bean an artist for many years now I am very comfortable with using Photoshop and Flash but I want to learn how to but together my own games, I bean doing my own research into this and at the moment I am at little bit stuck on witch direction to go down. So my question is witch programming language should I learn? I have already bean looking into this what i understand is that Gamemaker with its built in language (GML) is one of the most friendly to people who are new to the game making world. I have played around with this program and was pretty happy with it but I want more also you can use Unity with language such as C and javascript and then games built with Java witch looks interesting. One more thing before you send your answer in at this moment in time I would only be able to make 2D game but 3D isn't out of the picture.

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  • Should data structures be integrated into the language (as in Python) or be provided in the standard library (as in Java)?

    - by Anto
    In Python, and most likely many other programming languages, common data structures can be found as an integrated part of the core language with their own dedicated syntax. If we put LISP's integrated list syntax aside, I can't think of any other languages that I know which provides some kind of data structure above the array as an integrated part of their syntax, though all of them (but C, I guess) seem to provide them in the standard library. From a language design perspective, what are your opinions on having a specific syntax for data structures in the core language? Is it a good idea, and does the purpose of the language (etc.) change how good this could be of a choice? Edit: I'm sorry for (apparently) causing some confusion about which data structures I mean. I talk about the basic and commonly used ones, but still not the most basic ones. This excludes trees (too complex, uncommon), stacks (too seldom used), arrays (too simple) but includes e.g. sets, lists and hashmaps.

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  • Is writing software in the absence of requirements a skill to possess or a situation I should avoid?

    - by Brian Reindel
    I find that some software developers are very adept at this, and often times are praised for their ability to deliver a working concept with abstract requirements. Frankly, this drives me crazy, and I don't like "making it up" as I go. I used to think this was problematic, but I've started to sense a shift, and I'm wondering if I need to adjust my thought (and programming) process when given very little direction. Should I begin to acquire this ability as a skill, or stick to the idea that requirement's gathering and business rules are the first priority?

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  • Knowing so much but application is a problem?

    - by Moaz ELdeen
    In my work, my friends always tell me, you know so much about computer science, electronics engineering,..etc. But I have difficulty in applying them and my code is crap. How to solve that problem? Will I be better or programming isn't my career? For example, yes I know OCTree that is used for space partitioning in games and it is used for optimization, did I implement it? No, but I know about it in principle.. Do I know algorithms like Sorting, Searching,..etc? Yes, and I know them pretty well, but didn't implement them.. When I get a task, I struggle in applying the things that I know...

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  • "Waiting for Sound System to respond." error dialog

    - by Paulo Truta
    Hello guys. I'm having a nasty problem with the Sound Menu on my Ubuntu 10.10 Installation. What happens is that the sound control icon is blocked, and i can't control the master volume. If i try to get to the Sound Preferences i get a little Pop-Up Window saying: "Waiting for Sound System to respond...". Don't know what to do... Apart of that, sound works great. Thanks a lot ;) PS: I made 2 screenshot uploads. Hope it helps.

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  • HD video editing system with Truecrypt

    - by Rob
    I'm looking to do hi-def video editing and transcoding on an unencrypted standard partition, with Truecrypt on the system partition for sensitive data. I'm aiming to keep certain data private but still have performance where needed. Goals: Maximum, unimpacted, performance possible for hi-def video editing, encryption of video not required Encrypt system partition, using Truecrypt, for web/email privacy, etc. in the event of loss In other words I want to selectively encrypt the hard drive - i.e. make the system partition encrypted but not impact the original maximum performance that would be available to me for hi-def/HD video editing. The thinking is to use an unencrypted partition for the video and set up video applications to point at that. Assuming that they would use that partition only for their workspace and not the encrypted system partition, then I should expect to not get any performance hit. Would I be correct? I guess it might depend on the application, if that app is hard-wired to use the system partition always for temporary storage during editing and transcoding, or if it has to be installed on the C: system partition always. So some real data on how various apps behave in the respect would be useful, e.g. Adobe, Cyberlink, Nero etc. etc. I have a Intel i7 Quad-core (8 threads) 1.6Ghz (up to 2.8Ghz turbo-boost) 4Gb, 7200rpm SATA, nvidia HP laptop. I've read the excellent posting about the general performance impact of truecrypt but the benchmarks weren't specific enough for my needs where I'm dealing with HD-video and using a non-encrypted partition to maintain max performance.

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  • What tools should I consider if my strategy is to make a game available to as many platforms as possible?

    - by Kenji Kina
    We're planning on developing a 2D, grid-based puzzle game, and although it's still very early in the planning stages, we'd like to make our decisions well from the beginning. Our strategy will be to make the game available to as many platforms as possible, for example PCs (Windows, Mac and/or Linux), mobile phones (iPhone and/or Android based phones), game consoles (XBLA and/or PSN) PC will have an emphasis, but I believe that's the most flexible platform so that shouldn't be a problem. So, what programming language, game engine, frameworks and all around tools would be best suited for our goal? P.S.: I'm betting a set of tools won't cover ALL of them, and that there will still be some kind of "translating" effort for some platforms, but we'd like to know what the most far reaching are.

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  • What language yields most rapid development of a SOAP client application

    - by mathematician1975
    I have written a SOAP client application. It started off as Perl but I needed it to have proper multithreaded capabilities, so I rewrote it in C++ which was a horrendous experience and the development time was many many times more than that of the Perl bot. I need to implement a new SOAP client and I was wondering what peoples opinions were about choice of language with regards to fastest development time. C++ is clearly not well suited to web services type programming so there is no way I am going to write in C++ again.

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  • Version hash to solve Event Sourcing problems

    - by SystematicFrank
    The basic examples I have seen about Event Sourcing do not deal with out of order events, clock offsets in different systems and late events from system partitions. I am wondering if more polished Event Sourcing implementations rely on a version stamp of modified objects? For example, assuming that the system is rendering the entity Client with version id ABCD1234. If the user modifies the entity, the system will create an event with the modified fields AND the version id reference to which version it applies. Later the event responder would detect out of order events and merge them.

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  • Icons missing from launcher, system settings, folders

    - by Giannis Rizos
    Various icons from launcher are missing. The first one is from Home folder menu the second from Terminal the last one from Desktop Switcher. This happened after I upgraded to 11.10 from 11.04. I have created a New (Untitled Folder) folder in my desktop and the icon is missing too. The same occurs in System Settings menu too. Some icons like Appearance, Keyboard Layout are missing too. Sorry but I can't post a screenshot due to my reputation. Any suggestions?

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  • What technologies are used for Game development now days?

    - by Monika Michael
    Whenever I ask a question about game development in an online forum I always get suggestions like learning line drawing algorithms, bit level image manipulation and video decompression etc. However looking at games like God of War 3, I find it hard to believe that these games could be developed using such low level techniques. The sheer awesomeness of such games defy any comprehensible(for me) programming methodology. Besides the gaming hardware is really a monster now days. So it stands to reason that the developers would work at a higher level of abstraction. What is the latest development methodology in the gaming industry? How is it that a team of 30-35 developers (of which most is management and marketing fluff) able to make such mind boggling games?

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  • "PHP: Good Parts"-ish book / reference

    - by julkiewicz
    Before I had my first proper contact with Javascript I read an excellent book "Javascript: The Good Parts" by Douglas Crockford. I was hoping for something similar in case of PHP. My first thought was this book: "PHP: The Good Parts" from O'Reilly However after I read the reviews it seems it totally misses the point. I am looking for a resource that would: concentrate on known shortcommings of PHP, give concrete examples, be as exhaustive as possible I already see that things can go wrong. If you want to close this question: Please consider this, I looked through SO, and Programmers for materials. I obviously found this question: http://stackoverflow.com/questions/90924/what-is-the-best-php-programming-book It's general, mine is specific. Moreover I'm reading the top recommendation "PHP Objects, Patterns, and Practice" right now. I find it insufficient -- it doesn't address the bad practices as much as I would like it to. tl;dr My question is NOT a general PHP book request.

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