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  • javascript fixed timestep gameloop with requestanimation frame

    - by coffeecup
    hello i just started to read through several articles, including http://gafferongames.com/game-physics/fix-your-timestep/ ...://gamedev.stackexchange.com/questions/1589/fixed-time-step-vs-variable-time-step/ ...//dewitters.koonsolo.com/gameloop.html ...://nokarma.org/2011/02/02/javascript-game-development-the-game-loop/index.html my understanding of this is that i need the currentTime and the timeStep size and integrate all states to the next state the time which is left is then passed into the render function to do interpolation i tried to implement glenn fiedlers "the final touch", whats troubling me is that each FrameTime is about 15 (ms) and the update loop runs at about 1500 fps which seems a little bit off? heres my code this.t = 0 this.dt = 0.01 this.currTime = new Date().getTime() this.accumulator = 0.0 this.animate() animate: function(){ var newTime = new Date().getTime() , frameTime = newTime - this.currTime , alpha if ( frameTime > 0.25 ) frameTime = 0.25 this.currTime = newTime this.accumulator += frameTime while (this.accumulator >= this.dt ) { this.prev_state = this.curr_state this.update(this.t,this.dt) this.t += this.dt this.accumulator -= this.dt } alpha = this.accumulator / this.dt this.render( this.t, this.dt, alpha) requestAnimationFrame( this.animate ) } also i would like to know, are there differences between glenn fiedlers implementation and the last solution presented here ? gameloop1 gameloop2 [ sorry couldnt post more than 2 links.. ] edit : i looked into it again and adjusted the values this.currTime = new Date().getTime() this.accumulator = 0 this.p_t = 0 this.p_step = 1000/100 this.animate() animate: function(){ var newTime = new Date().getTime() , frameTime = newTime - this.currTime , alpha if(frameTime > 25) frameTime = 25 this.currTime = newTime this.accumulator += frameTime while(this.accumulator >= this.p_step){ // prevstate = currState this.update() this.p_t+=this.p_step this.accumulator -= this.p_step } alpha = this.accumulator / this.p_step this.render(alpha) requestAnimationFrame( this.animate ) now i can set the physics update rate, render runs at 60 fps and physics update at 100 fps, maybe someone could confirm this because its the first time i'm playing around with game development :-)

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  • Game software design

    - by L. De Leo
    I have been working on a simple implementation of a card game in object oriented Python/HTML/Javascript and building on the top of Django. At this point the game is in its final stage of development but, while spotting a big issue about how I was keeping the application state (basically using a global variable), I reached the point that I'm stuck. The thing is that ignoring the design flaw, in a single-threaded environment such as under the Django development server, the game works perfectly. While I tried to design classes cleanly and keep methods short I now have in front of me an issue that has been keeping me busy for the last 2 days and that countless print statements and visual debugging hasn't helped me spot. The reason I think has to do with some side-effects of functions and to solve it I've been wondering if maybe refactoring the code entirely with static classes that keep no state and just passing the state around might be a good option to keep side-effects under control. Or maybe trying to program it in a functional programming style (although I'm not sure Python allows for a purely functional style). I feel that now there's already too many layers that the software (which I plan to make incredibly more complex by adding non trivial features) has already become unmanageable. How would you suggest I re-take control of my code-base that (despite being still only at < 1000 LOC) seems to have taken a life of its own?

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  • Curing the Database-Application mismatch

    - by Phil Factor
    If an application requires access to a database, then you have to be able to deploy it so as to be version-compatible with the database, in phase. If you can deploy both together, then the application and database must normally be deployed at the same version in which they, together, passed integration and functional testing.  When a single database supports more than one application, then the problem gets more interesting. I’ll need to be more precise here. It is actually the application-interface definition of the database that needs to be in a compatible ‘version’.  Most databases that get into production have no separate application-interface; in other words they are ‘close-coupled’.  For this vast majority, the whole database is the application-interface, and applications are free to wander through the bowels of the database scot-free.  If you’ve spurned the perceived wisdom of application architects to have a defined application-interface within the database that is based on views and stored procedures, any version-mismatch will be as sensitive as a kitten.  A team that creates an application that makes direct access to base tables in a database will have to put a lot of energy into keeping Database and Application in sync, to say nothing of having to tackle issues such as security and audit. It is not the obvious route to development nirvana. I’ve been in countless tense meetings with application developers who initially bridle instinctively at the apparent restrictions of being ‘banned’ from the base tables or routines of a database.  There is no good technical reason for needing that sort of access that I’ve ever come across.  Everything that the application wants can be delivered via a set of views and procedures, and with far less pain for all concerned: This is the application-interface.  If more than zero developers are creating a database-driven application, then the project will benefit from the loose-coupling that an application interface brings. What is important here is that the database development role is separated from the application development role, even if it is the same developer performing both roles. The idea of an application-interface with a database is as old as I can remember. The big corporate or government databases generally supported several applications, and there was little option. When a new application wanted access to an existing corporate database, the developers, and myself as technical architect, would have to meet with hatchet-faced DBAs and production staff to work out an interface. Sure, they would talk up the effort involved for budgetary reasons, but it was routine work, because it decoupled the database from its supporting applications. We’d be given our own stored procedures. One of them, I still remember, had ninety-two parameters. All database access was encapsulated in one application-module. If you have a stable defined application-interface with the database (Yes, one for each application usually) you need to keep the external definitions of the components of this interface in version control, linked with the application source,  and carefully track and negotiate any changes between database developers and application developers.  Essentially, the application development team owns the interface definition, and the onus is on the Database developers to implement it and maintain it, in conformance.  Internally, the database can then make all sorts of changes and refactoring, as long as source control is maintained.  If the application interface passes all the comprehensive integration and functional tests for the particular version they were designed for, nothing is broken. Your performance-testing can ‘hang’ on the same interface, since databases are judged on the performance of the application, not an ‘internal’ database process. The database developers have responsibility for maintaining the application-interface, but not its definition,  as they refactor the database. This is easily tested on a daily basis since the tests are normally automated. In this setting, the deployment can proceed if the more stable application-interface, rather than the continuously-changing database, passes all tests for the version of the application. Normally, if all goes well, a database with a well-designed application interface can evolve gracefully without changing the external appearance of the interface, and this is confirmed by integration tests that check the interface, and which hopefully don’t need to be altered at all often.  If the application is rapidly changing its ‘domain model’  in the light of an increased understanding of the application domain, then it can change the interface definitions and the database developers need only implement the interface rather than refactor the underlying database.  The test team will also have to redo the functional and integration tests which are, of course ‘written to’ the definition.  The Database developers will find it easier if these tests are done before their re-wiring  job to implement the new interface. If, at the other extreme, an application receives no further development work but survives unchanged, the database can continue to change and develop to keep pace with the requirements of the other applications it supports, and needs only to take care that the application interface is never broken. Testing is easy since your automated scripts to test the interface do not need to change. The database developers will, of course, maintain their own source control for the database, and will be likely to maintain versions for all major releases. However, this will not need to be shared with the applications that the database servers. On the other hand, the definition of the application interfaces should be within the application source. Changes in it have to be subject to change-control procedures, as they will require a chain of tests. Once you allow, instead of an application-interface, an intimate relationship between application and database, we are in the realms of impedance mismatch, over and above the obvious security problems.  Part of this impedance problem is a difference in development practices. Whereas the application has to be regularly built and integrated, this isn’t necessarily the case with the database.  An RDBMS is inherently multi-user and self-integrating. If the developers work together on the database, then a subsequent integration of the database on a staging server doesn’t often bring nasty surprises. A separate database-integration process is only needed if the database is deliberately built in a way that mimics the application development process, but which hampers the normal database-development techniques.  This process is like demanding a official walking with a red flag in front of a motor car.  In order to closely coordinate databases with applications, entire databases have to be ‘versioned’, so that an application version can be matched with a database version to produce a working build without errors.  There is no natural process to ‘version’ databases.  Each development project will have to define a system for maintaining the version level. A curious paradox occurs in development when there is no formal application-interface. When the strains and cracks happen, the extra meetings, bureaucracy, and activity required to maintain accurate deployments looks to IT management like work. They see activity, and it looks good. Work means progress.  Management then smile on the design choices made. In IT, good design work doesn’t necessarily look good, and vice versa.

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  • Debugging/Logging Techniques for End Users

    - by James Burgess
    I searched a bit, but didn't find anything particularly pertinent to my problem - so please do excuse me if I missed something! A few months back I inherited the source to a fairly-popular indie game project and have been working, along with another developer, on the code-base. We recently made our first release since taking over the development but we're a little stuck. A few users are experiencing slowdowns/lagging in the current version, as compared to the previous version, and we are not able to reproduce these issues in any of our various development environments (debug, release, different OSes, different machines, etc.). What I'd like to know is how can we go about implementing some form of logging/debugging mechanism into the game, that users can enable and send the reports to us for examination? We're not able to distribute debug binaries using the MSVS 2010 runtimes, due to the licensing - and wouldn't want to, for a variety of reasons. We'd really like to get to the bottom of this issue, even if just to find out it's nothing to do with our code base but everything to do with their system configuration. At the moment, we just have no leads - and the community isn't a very technically-savvy one, so we're unable to rely on 'expert' bug reports or investigations. I've seen the debug logging mechanism used in other applications and games for everything from logging simple errors to crash dumps. We're really at a loss at this stage as to how to address these issues, having been over every commit to the repository from the previous to the current version and not finding any real issues.

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  • How to implement a birds eye view of 2D Grid Map using Android

    - by IM_Adan
    I'm a true beginner with using the android platform and I'm having difficulties on implementing a 2D grid system for a tower defense type game. Where I can place towers on a specific tile and enemies will be able to traverse through tiles etc. What I would like is a practical explanation of how I could tackle this. A step by step guide for dummies. This is what I believe are the necessary steps to take, I think I might be wrong but I hope someone could help me out. Calculate the Width and Height of the view I'm working with. Based on that, determine the number of tiles required and their dimensions, (Still not sure how I would do this) Create each tile as a Rectangle object and draw these rectangle on a canvas I would really be grateful if someone could steer me in the right direction on how to implement a 2D Grid Map using android. I hope the answer to this questions helps the TRUE beginners out there like me. I have looked at the following links below yet I still feel that I don't trully understand what's going on. For XNA: 2D Grid based game - how should I draw grid lines? How to Create a Grid for a 2D Game? Also a quick note: All my previous game development has been in Java, mostly using Java SE and Swing. I also have good understanding of the game development process, it is only android thats confusing me :S

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  • Alternatives to a leveling system

    - by Bane
    I'm currently designing a rough prototype of a mecha fighting game. These are the basics I came up with: Multiplayer (matchmaking for up to 10 people, for now) Browser based (HTML5) 2D (<canvas>) Persistent (as in, players have accounts and don't have to use a new mech each time they start a match) Players earn money upon destroying another mech, which is used to buy parts (guns, armor, boosters, etc) Simplicity (both of the game itself, and of the development of said game) No "leveling" (as in, players don't get awarded with XP) The last part is bothering me. At first, I wanted to have players gain experience points (XP) when destroying other mechs, but gaining two things at once (money and XP) seemed to be in conflict with my last point, which is simplicity. If I were to have a leveling system, that would require additional development. But, the biggest problem is that I simply couldn't fit it anywhere! Adding levels would require adding meaning to these levels, and most of the things that I hoped to achieve could already be achieved with the money mechanic I introduced. So I decided to drop leveling off completely. That, in turn, removed a fairly popular and robust mean of progression in games from my game (not that I would use it well anyway). Is there another way of progression in games, aside from leveling and XP points, that wouldn't get rendered redundant by my money mechanic, would be somehow meaningful (even on a symbolic level), and wouldn't be in conflict with my last point, which is simplicity?

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  • Porting Ruby/NCruses Rogue-Like to .NET and FlatRedBall

    - by ashes999
    I created an awesome rogue-like game in Ruby. For the GUI, I used NCurses. Since I'm using FlatRedBall as my engine of choice for Silverlight game development, I want to port this game over. What is the best way to efficiently doing this, and what are the pitfalls I should expect? For example, Ruby is object-oriented, like C#, and I should be able to just convert (rewrite) classes one by one. However, I will run into issues like: NCurses API. I need to possibly create my own notions of a "Window", or else rewrite GUI code. It's one class, but it's BIG. Mix-Ins. These are essentially aspect-oriented development. There are a couple of solutions in .NET, like dynamic classes. What else? Also, I should mention that I want to create a C# application out of this. As much as possible, I'll dump reusable and helper code, algorithms, etc. into separate projects and generate reusable DLLs.

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  • Is there a portal dedicated to HTML5 games?

    - by Bane
    Just to get something straight; by "portal", I mean a website that frequently publishes a certain type of games, has a blog, some articles, maybe some tutorials and so on. All of these things are not required (except the game publishing part, of course), for example, I consider Miniclip to be a flash game portal. The reason for defining this term is because I'm not sure if other people use it in this context. I recently (less than a year ago) got into HTML5 game development, nothing serious, just my own small projects that I didn't really show to a lot of people, and that certainly didn't end up somewhere on the web (although, I am planning to make a website for my next game). I am interested in the existence of an online portal where indie devs (or non-indie ones, doesn't really matter that much) can publish their own games, sort of like "by devs for devs", also a place where you can find some simple tutorials on basic HTML5 game development and so on... I doubt something like this exists for several reasons: You can't really commercialize an HTML5 game without a strong server-side and microtransactions The code can be easily copied HTML5 is simply new, and things need time to get their own portals somewhere... If a thing like this does not exist, I think I might get into making one some day...

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  • Lighting-Reflectance Models & Licensing Issues

    - by codey
    Generally, or specifically, is there any licensing issue with using any of the well known lighting/reflectance models (i.e. the BRDFs or other distribution or approximation functions): Phong, Blinn–Phong, Cook–Torrance, Blinn-Torrance-Sparrow, Lambert, Minnaert, Oren–Nayar, Ward, Strauss, Ashikhmin-Shirley and common modifications where applicable, such as: Beckmann distribution, Blinn distribution, Schlick's approximation, etc. in your shader code utilised in a commercial product? Or is it a non-issue?

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  • 2D/Isometric map algorithm

    - by Icarus Cocksson
    First of all, I don't have much experience on game development but I do have experience on development. I do know how to make a map, but I don't know if my solution is a normal or a hacky solution. I don't want to waste my time coding things, and realise they're utterly crap and lose my motivation. Let's imagine the following map. (2D - top view - A square) X: 0 to 500 Y: 0 to 500 My character currently stands at X:250,Y:400, somewhere near center of 100px above bottom and I can control him with my keyboard buttons. LEFT button does X--, UP button does Y-- etc. This one is kid's play. I'm asking this because I know there are some engines that automate this task. For example, games like Diablo 3 uses an engine. You can pretty much drag drop a rock to map, and it is automatically being placed here - making player unable to pass through/detect the collision. But what the engine exactly does in the background? Generates a map like mine, places a rock at the center, and checks it like: unmovableObjects = array('50,50'); //we placed a rock at 50,50 location if(Map.hasUnmovableObject(CurrentPlayerX, CurrentPlayerY)) { //unable to move } else { //able to move } My question is: Is this how 2D/Isometric maps are being generated or there is a different and more complex logic behind them?

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  • Tools for creating assets? [closed]

    - by Agent_9191
    There are similar questions about finding existing resources that are free for use (free sprites/images, music, sound), but I'm interested in creating the resources myself. What tools do you use for asset creation/modification? Please only put one tool per answer. Also try to include the following information: Product Name Link to website Type of assets is can create (2D images, 3D images, audio, etc) OS(s) supported Cost License (if free/open source) General summary

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  • Which software to keep track of my project?

    - by Exa
    I'm about to start the first real phase of my game development which will consist of the acquisition of information, resources and the definition of where I want to go and what I will need for that. I just want to make sure that I'm prepared as best as possible before I actually start development. I don't like the thought of using Microsoft Word or Excel for my project management... I already worked with MS Project but I don't think it fits my needs. I need a software where I can easily maintain project steps, milestones, important issues, information about technologies and engines I use, as well as simple notes and thoughts I just want to write down. I usually prefer a whiteboard for stuff like that but unfortunately it's not a persistent way of storing. ;) Also writing it down the old-school way is something I can think of, but only for quick notes... Which software do you use for that? Are there commonly used programs? Is there any free software at all?

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  • Jump handling and gravity

    - by sprawl
    I'm new to game development and am looking for some help on improving my jump handling for a simple side scrolling game I've made. I would like to make the jump last longer if the key is held down for the full length of the jump, otherwise if the key is tapped, make the jump not as long. Currently, how I'm handling the jumping is the following: Player.prototype.jump = function () { // Player pressed jump key if (this.isJumping === true) { // Set sprite to jump state this.settings.slice = 250; if (this.isFalling === true) { // Player let go of jump key, increase rate of fall this.settings.y -= this.velocity; this.velocity -= this.settings.gravity * 2; } else { // Player is holding down jump key this.settings.y -= this.velocity; this.velocity -= this.settings.gravity; } } if (this.settings.y >= 240) { // Player is on the ground this.isJumping = false; this.isFalling = false; this.velocity = this.settings.maxVelocity; this.settings.y = 240; } } I'm setting isJumping on keydown and isFalling on keyup. While it works okay for simple use, I'm looking for a better way handle jumping and gravity. It's a bit buggy if the gravity is increased (which is why I had to put the last y setting in the last if condition in there) on keyup, so I'd like to know a better way to do it. Where are some resources I could look at that would help me better understand how to handle jumping and gravity? What's a better approach to handling this? Like I said, I'm new to game development so I could be doing it completely wrong. Any help would be appreciated.

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  • Is there an alternative to SDL 1.3 for a C++ game that should run on iOS and Android?

    - by futlib
    I've used SDL for many desktop games, always as the cross-platform glue for: Creating a window Processing input Rendering images Rendering fonts Playing sounds/music It has never disappointed me at those tasks. But when it comes to graphics, I prefer to work with the OpenGL API directly, even though all of our games are 2D. In the project I'm currently working on, I've made sure to only use the API subset supported by both OpenGL 1.3 and OpenGL 1.0, so making the thing run on Android should be easy, I thought. Turns out there is no official Android or iOS port of SDL yet. However, there's one in SDL 1.3, which is still in development. SDL 1.3 doesn't seem very appealing to me for three reasons: It's been in development for at least 4 years, and I have no idea when it will be done, not to mention stable. It's not ported to as many platforms as SDL 1.2. From what I've seen, it uses OpenGL for drawing, so I suppose the community will move away from directly using OpenGL. So I'm wondering if I should use a different library for our current project - it doesn't matter much if I need to port my existing code from SDL 1.2 to SDL 1.3 or to some other library. We're planning to release on Windows, Mac OS X, Linux, iOS and Android, so good support for these platforms is essential. Is there anything stable that does what I want?

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  • Investment scheme for a PC game the project

    - by Alex Kamen
    Good day everyone, I am working on a PC game project that has 3 phases planned, micro, macro and mmo versions [if confused, see a brief description at the bottom]. I have found a potential investor for the micro version of the game, but naturally, he requested a detailed plan of how the game will pay back. And the problem is that micro version itself is not supposed to be monetized much, other than some ads and limited in-game currency utilization. The idea is that with this combat demo already at hand, it should be possible to get a really large enough investment (millions of dollars) and use it to pay back the initial small one (thousands of dollars) and take the project into macro phase, which will really make profit. This way, everybody is going to win, provided that I can deliver the end-product. Yet while I am confident of that both the conception of the macro and the real game-play of the micro versions are going to be appealing, I don’t know how to obtain any guarantee of that I will be able to get funded once I have the prototype ready. And without that, I won’t receive the funds for the prototype in the first place! To summarize, my question is: how to figure out my future possibilities of getting funded once I have combat demo out, basically “whom to write to and what”. Ideally, I would like some sort of a preliminary agreement with a game publisher, something that would basically state “If the developer provides the product in time and in quality corresponding to the specifications given, the publisher guarantees to allocate funds for distribution and further development, thereby acquiring the right to X part of all future profits”. Does this sound sane? It’s just that I don’t want to sell all of my rights out straight away by taking a big outside investment while the project is in such early stage. I would appreciate if you would share your thoughts on this kind of scheme, and be sure to ask questions as I am sure I must have forgotten to mention a ton of important things, like the fact that initial funds are going to be spent on outsourcing (living in Siberia is really just great). [here’s a brief outline of what each version will feature] [micro] 1) turn based tactical combat rules 2) character development 3) arena/tournament system [macro] 4) ai-ruled dynamic interactive worlds 5) global map adventuring 6) strategic rpg + god simulator gameplay [mmo] 7) Persistent worlds system 8) Social structures system (“guilds/clans”) 9) god-simulation on the mmo scale P.S. Obviously, these features are incremental, so that mmo version has all 9.

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  • What is going on in this SAT/vector projection code?

    - by ssb
    I'm looking at the example XNA SAT collision code presented here: http://www.xnadevelopment.com/tutorials/rotatedrectanglecollisions/rotatedrectanglecollisions.shtml See the following code: private int GenerateScalar(Vector2 theRectangleCorner, Vector2 theAxis) { //Using the formula for Vector projection. Take the corner being passed in //and project it onto the given Axis float aNumerator = (theRectangleCorner.X * theAxis.X) + (theRectangleCorner.Y * theAxis.Y); float aDenominator = (theAxis.X * theAxis.X) + (theAxis.Y * theAxis.Y); float aDivisionResult = aNumerator / aDenominator; Vector2 aCornerProjected = new Vector2(aDivisionResult * theAxis.X, aDivisionResult * theAxis.Y); //Now that we have our projected Vector, calculate a scalar of that projection //that can be used to more easily do comparisons float aScalar = (theAxis.X * aCornerProjected.X) + (theAxis.Y * aCornerProjected.Y); return (int)aScalar; } I think the problems I'm having with this come mostly from translating physics concepts into data structures. For example, earlier in the code there is a calculation of the axes to be used, and these are stored as Vector2, and they are found by subtracting one point from another, however these points are also stored as Vector2s. So are the axes being stored as slopes in a single Vector2? Next, what exactly does the Vector2 produced by the vector projection code represent? That is, I know it represents the projected vector, but as it pertains to a Vector2, what does this represent? A point on a line? Finally, what does the scalar at the end actually represent? It's fine to tell me that you're getting a scalar value of the projected vector, but none of the information I can find online seems to tell me about a scalar of a vector as it's used in this context. I don't see angles or magnitudes with these vectors so I'm a little disoriented when it comes to thinking in terms of physics. If this final scalar calculation is just a dot product, how is that directly applicable to SAT from here on? Is this what I use to calculate maximum/minimum values for overlap? I guess I'm just having trouble figuring out exactly what the dot product is representing in this particular context. Clearly I'm not quite up to date on my elementary physics, but any explanations would be greatly appreciated.

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  • Clutter for game GUI

    - by tjameson
    I'm pretty new to game development, having only written a simple 3d game for a class project, but I'd like to get started on a bigger project. I'm writing an MMORPG to run in both the browser (WebGL) and natively (OpenGL ES 2). In choosing a GUI toolkit, I'm trying to find a style that work work natively and would be simple to emulate in WebGL. I am considering using D or Go for writing my game, so interfacing with C++ libraries will be difficult, if not impossible. Of course, the language isn't the end goal here, so if using C++ will save considerable time, I'll bite the bullet and use that. In order to reduce the amount of code I'll have to write for the browser, I'm considering using something simple like Clutter for basic abstractions, which I think will be pretty easy to emulate (layered canvases maybe?). Does anyone have experience using Clutter for a 3d game? Note: I haven't used any game development libraries, and I only have limited experience with GUI libraries. I do have HTML+CSS experience, so maybe librocket is a viable solution?

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  • OpenXDK Questions

    - by iamcreasy
    I was strolling around XBox development. Apart form buying a DevKit from Microsoft, another thing got my attention is called, OpenXDK which stands for Open XBox Development Kit. From their main site its pretty obvious that there hasn't been any update since 2005 but digging a little deeper, I found that in their project repository is was being updated. Last time stamp was 2009-02-15. Quick google search said, its not actually really on a good place to poke around. Many and MANY features are absent. Being a hobby project I perfectly understand. But, those results are quite old. The question is, is there anybody who has any experience with OpenXDK? If is, that is it possible to shade some light on this? about its limitations? Is this a mature project? How's the latest version and what's it capable of doing? Or should I just stay away from it?

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  • What are the functions of modern game publishers? [closed]

    - by ApoorvaJ
    According to the Wikipedia page on Video game publishers, they are responsible for "their product's manufacturing and marketing, including market research and all aspects of advertising." From what I've read, they also arrange for the development funding. In the following questions, I'm asking about AAA, indie and mobile publishers: Do today's publishers fulfill any other functions? Is there any good reading material on these topics?

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  • What helped YOU learn C++? [on hold]

    - by Tips48
    So here's my attempt to not get this question closed for too subjective :P I'm a young programmer, specifically interested in Game Development. I've written my first couple games in Java, which I would consider my self intermediate-Advanced in. As I start to prepare myself for college and (hopefully) internships, I've noticed that learning C/C++ is essential to the industry. I've decided to start with C++, and so I read a couple of books that I saw were suggested. Anyway, now I have a decent understanding of the basics, but I really want to enhance my language knowledge. Instead of just asking for things to do, I was wondering what were some exercises that you did that really helped you understand the language? Preferably they would be near the beginner level. I understand that they obviously won't be directly related to Game Development, but it be nice if there were some things that I could transfer over eventually. (Specifically, I struggle with memory (pointers, etc) since there is no such concept in Java) Thanks! - Tips P.S.: Here's to hoping this isn't to subjective :P

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  • creating objects in list

    - by prince23
    List myList = new List { new Users{ Name="Kumar", Gender="M", Age=75, Parent="All"}, new Users{ Name="Suresh",Gender="M", Age=50, Parent="Kumar"}, new Users{ Name="Bennette", Gender="F",Age=45, Parent="Kumar"}, new Users{ Name="kian", Gender="M",Age=20, Parent="Suresh"}, new Users{ Name="Nathani", Gender="M",Age=15, Parent="Suresh"}, new Users{ Name="Peter", Gender="M",Age=90, Parent="All"}, new Users{ Name="Mica", Age=56, Gender="M",Parent="Peter"}, new Users{ Name="Linderman", Gender="M",Age=51, Parent="Peter"}, new Users{ Name="john", Age=25, Gender="M",Parent="Mica"}, new Users{ Name="tom", Gender="M",Age=21, Parent="Mica"}, new Users{ Name="Ando", Age=64, Gender="M",Parent="All"}, new Users{ Name="Maya", Age=24, Gender="M",Parent="Ando"}, new Users{ Name="Niki Sanders", Gender="F",Age=2, Parent="Maya"}, new Users{ Name="Angela Patrelli", Gender="F",Age=3, Parent="Maya"}, }; now i need to format the data like here i need to check the parent based on the parent i will be creating objects under the parent objects now { Name="Kumar", Gender="M", Age=75, Parent="All" } this is the top level as a property Parent ="all" now under parent object kumar here we again create a new object to store these information under object(kumar who is the parent) new Users{ Name="Suresh",Gender="M", Age=50, Parent="Kumar"}, new Users{ Name="Bennette", Gender="F",Age=45, Parent="Kumar"}, what i need to do here is i need to check the parent based on the parent create further objects under it ex: i need to achive like this. looking for the syntax how i can do it. public class SampleProjectData { public static ObservableCollection<Product> GetSampleData() { DateTime dtS = DateTime.Now; ObservableCollection<Product> teams = new ObservableCollection<Product>(); teams.Add(new Product() { PDName = "Product1", OverallStartTime = dtS, OverallEndTime = dtS + TimeSpan.FromDays(3), }); Project emp = new Project() { PName = "Project1", OverallStartTime = dtS + TimeSpan.FromDays(1), OverallEndTime = dtS + TimeSpan.FromDays(6) }; emp.Tasks.Add(new Task() { StartTime = dtS, EndTime = dtS + TimeSpan.FromDays(2), TaskName = "John's Task 3" }); emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(3), EndTime = dtS + TimeSpan.FromDays(4), TaskName = "John's Task 2" }); teams[0].Projects.Add(emp); emp = new Project() { PName = "Project2", OverallStartTime = dtS + TimeSpan.FromDays(1.5), OverallEndTime = dtS + TimeSpan.FromDays(5.5) }; emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(1), EndTime = dtS + TimeSpan.FromDays(4), TaskName = "Victor's Task" }); teams[0].Projects.Add(emp); emp = new Project() { PName = "Project3", OverallStartTime = dtS + TimeSpan.FromDays(2), OverallEndTime = dtS + TimeSpan.FromDays(5) }; emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(1), EndTime = dtS + TimeSpan.FromDays(4), TaskName = "Jason's Task 1" }); emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(7), EndTime = dtS + TimeSpan.FromDays(9), TaskName = "Jason's Task 2" }); teams[0].Projects.Add(emp); teams.Add(new Product() { PDName = "Product2", OverallStartTime = dtS, OverallEndTime = dtS + TimeSpan.FromDays(3) }); emp = new Project() { PName = "Project4", OverallStartTime = dtS + TimeSpan.FromDays(0.5), OverallEndTime = dtS + TimeSpan.FromDays(3.5) }; emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(1.5), EndTime = dtS + TimeSpan.FromDays(4), TaskName = "Vicky's Task" }); teams[1].Projects.Add(emp); emp = new Project() { PName = "Project5", OverallStartTime = dtS + TimeSpan.FromDays(2), OverallEndTime = dtS + TimeSpan.FromDays(6) }; emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(2.2), EndTime = dtS + TimeSpan.FromDays(3.8), TaskName = "Oleg's Task 1" }); emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(5), EndTime = dtS + TimeSpan.FromDays(6), TaskName = "Oleg's Task 2" }); emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(8), EndTime = dtS + TimeSpan.FromDays(9.6), TaskName = "Oleg's Task 3" }); teams[1].Projects.Add(emp); emp = new Project() { PName = "Project6", OverallStartTime = dtS + TimeSpan.FromDays(2.5), OverallEndTime = dtS + TimeSpan.FromDays(4.5) }; emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(0.8), EndTime = dtS + TimeSpan.FromDays(2), TaskName = "Kim's Task" }); teams[1].Projects.Add(emp); teams.Add(new Product() { PDName = "Product3", OverallStartTime = dtS, OverallEndTime = dtS + TimeSpan.FromDays(3) }); emp = new Project() { PName = "Project7", OverallStartTime = dtS + TimeSpan.FromDays(5), OverallEndTime = dtS + TimeSpan.FromDays(7.5) }; emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(1.5), EndTime = dtS + TimeSpan.FromDays(4), TaskName = "Balaji's Task 1" }); emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(5), EndTime = dtS + TimeSpan.FromDays(8), TaskName = "Balaji's Task 2" }); teams[2].Projects.Add(emp); emp = new Project() { PName = "Project8", OverallStartTime = dtS + TimeSpan.FromDays(3), OverallEndTime = dtS + TimeSpan.FromDays(6.3) }; emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(1.75), EndTime = dtS + TimeSpan.FromDays(2.25), TaskName = "Li's Task" }); teams[2].Projects.Add(emp); emp = new Project() { PName = "Project9", OverallStartTime = dtS + TimeSpan.FromDays(2), OverallEndTime = dtS + TimeSpan.FromDays(6) }; emp.Tasks.Add(new Task() { StartTime = dtS + TimeSpan.FromDays(2), EndTime = dtS + TimeSpan.FromDays(3), TaskName = "Stacy's Task" }); teams[2].Projects.Add(emp); return teams; } } above is an sample data where i am grouping them with static data in the same way i need **to for teh data which is cmg from DB and i need to store them list** all these three data are comig from different services. and i am storing them in a list now i have three tables data Product , Project, Task. all the data are coming from webservies. i have created three list where i am storing the data in list. List<Project>objpro= new List<Project>(); List<Product>objproduct= new List<Product>(); LIst<Task>objTask= new List<Task>(); **now what i need to do is i need to do the mapping between these tables. if you see above. i have object of Product under Product i have added object of Project and then under project object i have added task object.** now from the above data which is stored in the list i need to do the same mapping between class. and group the data. public class Product : INotifyPropertyChanged { public Product() { this.Projects = new ObservableCollection<Project>(); } public string PDName { get; set; } public ObservableCollection<Project> Projects { get; set; } private DateTime _st; public DateTime OverallStartTime { get { return _st; } set { if (this._st != value) { TimeSpan dur = this._et - this._st; this._st = value; this.OnPropertyChanged("OverallStartTime"); this.OverallEndTime = value + dur; } } } private DateTime _et; public DateTime OverallEndTime { get { return _et; } set { if (this._et != value) { this._et = value; this.OnPropertyChanged("OverallEndTime"); } } } #region INotifyPropertyChanged Members protected void OnPropertyChanged(string name) { if (this.PropertyChanged != null) this.PropertyChanged(this, new PropertyChangedEventArgs(name)); } public event PropertyChangedEventHandler PropertyChanged; #endregion } public class Project : INotifyPropertyChanged { public Project() { this.Tasks = new ObservableCollection<Task>(); } public string PName { get; set; } public ObservableCollection<Task> Tasks { get; set; } DateTime _st; public DateTime OverallStartTime { get { return _st; } set { if (this._st != value) { TimeSpan dur = this._et - this._st; this._st = value; this.OnPropertyChanged("OverallStartTime"); this.OverallEndTime = value + dur; } } } DateTime _et; public DateTime OverallEndTime { get { return _et; } set { if (this._et != value) { this._et = value; this.OnPropertyChanged("OverallEndTime"); } } } #region INotifyPropertyChanged Members protected void OnPropertyChanged(string name) { if (this.PropertyChanged != null) this.PropertyChanged(this, new PropertyChangedEventArgs(name)); } public event PropertyChangedEventHandler PropertyChanged; #endregion } public class Task : INotifyPropertyChanged { public string TaskName { get; set; } DateTime _st; public DateTime StartTime { get { return _st; } set { if (this._st != value) { TimeSpan dur = this._et - this._st; this._st = value; this.OnPropertyChanged("StartTime"); this.EndTime = value + dur; } } } private DateTime _et; public DateTime EndTime { get { return _et; } set { if (this._et != value) { this._et = value; this.OnPropertyChanged("EndTime"); } } } #region INotifyPropertyChanged Members protected void OnPropertyChanged(string name) { if (this.PropertyChanged != null) this.PropertyChanged(this, new PropertyChangedEventArgs(name)); } public event PropertyChangedEventHandler PropertyChanged; #endregion } hope my question is clear

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  • Writing an OS for Motorola 68K processor. Can I emulate it? And can I test-drive OS development?

    - by ulver
    Next term, I'll need to write a basic operating system for Motorola 68K processor as part of a course lab material. Is there a Linux emulator of a basic hardware setup with that processor? So my partners and I can debug quicker on our computers instead of physically restarting the board and stuff. Is it possible to apply test-driven development technique to OS development? Code will be mostly assembly and C. What will be the main difficulties with trying to test-drive this? Any advice on how to do it?

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  • Cant bind data to a table view

    - by sudhakarilla
    Hi, I have retrieved data from Json URL and displayed it in a table view. I have also inlcuced a button in table view. On clicking the button the data must be transferred to a another table view. The problem is that i could send the data to a view and could display it on a label. But i couldnt bind the dat to table view ... Here's some of the code snippets... Buy Button... -(IBAction)Buybutton{ /* UIAlertView *alert =[[UIAlertView alloc]initWithTitle:@"thank u" message:@"products" delegate:nil cancelButtonTitle:@"ok" otherButtonTitles:nil]; [alert show]; [alert release];*/ Product *selectedProduct = [[data products]objectAtIndex:0]; CartViewController *cartviewcontroller = [[[CartViewController alloc] initWithNibName:@"CartViewController" bundle:nil]autorelease]; cartviewcontroller.product= selectedProduct; //NSString *productname=[product ProductName]; //[currentproducts setproduct:productname]; [self.view addSubview:cartviewcontroller.view]; } CartView... // Implement viewDidLoad to do additional setup after loading the view, typically from a nib. - (void)viewDidLoad { [super viewDidLoad]; data = [GlobalData SharedData]; NSMutableArray *prod =[[NSMutableArray alloc]init]; prod = [data products]; for(NSDictionary *product in prod) { Cart *myprod = [[Cart alloc]init]; myprod.Description = [product Description]; myprod.ProductImage =[product ProductImage]; myprod.ProductName = [product ProductName]; myprod.SalePrice = [product SalePrice]; [data.carts addObject:myprod]; [myprod release]; } Cart *cart = [[data carts]objectAtIndex:0]; NSString *productname=[cart ProductName]; self.label.text =productname; NSLog(@"carts"); } (NSInteger)numberOfSectionsInTableView:(UITableView *)tableView { return 1; } (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return [data.carts count]; } -(CGFloat)tableView:(UITableView *)tableView heightForRowAtIndexPath:(NSIndexPath *)indexPath { return 75; } (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { NSLog(@"cellforrow"); static NSString *CellIdentifier = @"Cell"; ProductCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if(cell ==nil) { cell = [[[ProductCell alloc]initWithFrame:CGRectZero reuseIdentifier:CellIdentifier]autorelease]; } NSUInteger row = [indexPath row]; Cart *cart = [[data carts]objectAtIndex:row]; cell.productNameLabel.text = [cart ProductName]; /*NSString *sale = [[NSString alloc]initWithFormat:@"SalePrice:%@",[cart SalePrice]]; cell.salePriceLabel.text = sale; cell.DescriptionLabel.text = [cart Description]; NSMutableString imageUrl =[NSMutableString string]; [imageUrl appendFormat:@"http://demo.s2commerce.net/DesktopModules/S2Commerce/Images/Products/%@",[product ProductImage]]; NSLog(@"imageurl:%@",imageUrl); NSString mapURL = [imageUrl stringByReplacingPercentEscapesUsingEncoding:NSASCIIStringEncoding]; NSData* imageData = [[NSData alloc]initWithContentsOfURL:[NSURL URLWithString:mapURL]]; UIImage* image = [[UIImage alloc]initWithData:imageData]; cell.productImageview.image = image; [imageData release]; [image release];*/ return cell; } I am also getting the following error in the console 2010-06-11 18:34:29.169 navigation[4109:207] * -[CartViewController tableView:numberOfRowsInSection:]: message sent to deallocated instance 0xcb4d4f90

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  • Need help to properly remove duplicates in NHibernate

    - by Michael D. Kirkpatrick
    Here is the problem I am having. I have a database with over 100 records in it. I am paging through the data to get 9 results at a time. When I added a check to see if items are active, it caused the results to start doubling up. A little background: "Product" is the actual product line "ProductSkus" are the actual products that exist in the product line When there is more then 1 ProductSku within Product, it causes a duplicate entry to be returned. See the NHibernate Query below: result = this.Session.CreateCriteria<Model.Product>() .Add(Expression.Eq("IsActive", true)) .AddOrder(new Order("Name", true)) .SetFirstResult(indexNumber).SetMaxResults(maxNumber) // This part of the query duplicates the products .CreateAlias("ProductSkus", "ProdSkus", JoinType.InnerJoin) .Add(Expression.Eq("ProdSkus.IsActive", true)) .CreateAlias("ProductToSubcategory", "ProdToSubcat") .CreateAlias("ProdToSubcat.ProductSubcategory", "ProdSubcat") .Add(Expression.Eq("ProdSubcat.ID", subCatId)) // This part takes out the duplicate products - Removes too many items... // Turns out that with .SetFirstResult(indexNumber).SetMaxResults(maxNumber) // it gets 9 records back then the duplicates are removed. // Example: // Total Records over 100 // Max = 9 // 4 Duplicates removed // Yields 5 records when there should be 9 // Why??? This line is ran in NHibernate on the data after it has been extracted from the SQL server. .SetResultTransformer(new NHibernate.Transform.DistinctRootEntityResultTransformer()) .List<Model.Product>(); I added the DistinctRootEntityResultTransformer to clean up the duplicates. The problem is that it pulls 9 records back that contains duplicates. DistinctRootEntityResultTransformer then cleans up the duplicates in the 9 records. I am basically needing a distinct statement to be ran on the SQL server to begin with. However, distinct on SQL is not going to work since NHibernate by default wants to add every field from every table in the select part of the statement. I am only using the fields that belong to the root table to begin with (Model.Product). If I can tell NHibernate to not add the fields to the joined tables into the select part of the statement along with adding Distinct, it would work. I use NHibernare Profiler to see the actual query: SELECT top 9 this_.ID as ID351_3_, this_.Name as Name351_3_, this_.Description as Descript3_351_3_, this_.IsActive as IsActive351_3_, this_.ManufacturerID as Manufact5_351_3_, prodskus1_.ID as ID373_0_, prodskus1_.Description as Descript2_373_0_, prodskus1_.PartNumber as PartNumber373_0_, prodskus1_.Price as Price373_0_, prodskus1_.IsKit as IsKit373_0_, prodskus1_.IsActive as IsActive373_0_, prodskus1_.IsFeaturedProduct as IsFeatur7_373_0_, prodskus1_.DateAdded as DateAdded373_0_, prodskus1_.Weight as Weight373_0_, prodskus1_.TimesViewed as TimesVi10_373_0_, prodskus1_.TimesOrdered as TimesOr11_373_0_, prodskus1_.ProductID as ProductID373_0_, prodskus1_.OverSizedBoxID as OverSiz13_373_0_, prodtosubc2_.ID as ID362_1_, prodtosubc2_.MasterSubcategory as MasterSu2_362_1_, prodtosubc2_.ProductID as ProductID362_1_, prodtosubc2_.ProductSubcategoryID as ProductS4_362_1_, prodsubcat3_.ID as ID352_2_, prodsubcat3_.Name as Name352_2_, prodsubcat3_.ProductCategoryID as ProductC3_352_2_, prodsubcat3_.ImageID as ImageID352_2_, prodsubcat3_.TriggerShow as TriggerS5_352_2_ FROM Product this_ inner join ProductSku prodskus1_ on this_.ID = prodskus1_.ProductID and (prodskus1_.IsActive = 1) inner join ProductToSubcategory prodtosubc2_ on this_.ID = prodtosubc2_.ProductID inner join ProductSubcategory prodsubcat3_ on prodtosubc2_.ProductSubcategoryID = prodsubcat3_.ID WHERE this_.IsActive = 1 /* @p0 */ and prodskus1_.IsActive = 1 /* @p1 */ and prodsubcat3_.ID = 3 /* @p2 */ ORDER BY this_.Name asc If I hand modify the query and run it directly on the SQL server I get the result set I want (I removed all the extra fields in the select section and added DISTINCT): SELECT DISTINCT top 9 this_.ID as ID351_3_, this_.Name as Name351_3_, this_.Description as Descript3_351_3_, this_.IsActive as IsActive351_3_, this_.ManufacturerID as Manufact5_351_3_, FROM Product this_ inner join ProductSku prodskus1_ on this_.ID = prodskus1_.ProductID and (prodskus1_.IsActive = 1) inner join ProductToSubcategory prodtosubc2_ on this_.ID = prodtosubc2_.ProductID inner join ProductSubcategory prodsubcat3_ on prodtosubc2_.ProductSubcategoryID = prodsubcat3_.ID WHERE this_.IsActive = 1 /* @p0 */ and prodskus1_.IsActive = 1 /* @p1 */ and prodsubcat3_.ID = 3 /* @p2 */ ORDER BY this_.Name asc The big question I now must ask is... What must I change in the NHibernate Query to ultimately get the exact same result? Thanks in advance.

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  • Towards Database Continuous Delivery – What Next after Continuous Integration? A Checklist

    - by Ben Rees
    .dbd-banner p{ font-size:0.75em; padding:0 0 10px; margin:0 } .dbd-banner p span{ color:#675C6D; } .dbd-banner p:last-child{ padding:0; } @media ALL and (max-width:640px){ .dbd-banner{ background:#f0f0f0; padding:5px; color:#333; margin-top: 5px; } } -- Database delivery patterns & practices STAGE 4 AUTOMATED DEPLOYMENT If you’ve been fortunate enough to get to the stage where you’ve implemented some sort of continuous integration process for your database updates, then hopefully you’re seeing the benefits of that investment – constant feedback on changes your devs are making, advanced warning of data loss (prior to the production release on Saturday night!), a nice suite of automated tests to check business logic, so you know it’s going to work when it goes live, and so on. But what next? What can you do to improve your delivery process further, moving towards a full continuous delivery process for your database? In this article I describe some of the issues you might need to tackle on the next stage of this journey, and how to plan to overcome those obstacles before they appear. Our Database Delivery Learning Program consists of four stages, really three – source controlling a database, running continuous integration processes, then how to set up automated deployment (the middle stage is split in two – basic and advanced continuous integration, making four stages in total). If you’ve managed to work through the first three of these stages – source control, basic, then advanced CI, then you should have a solid change management process set up where, every time one of your team checks in a change to your database (whether schema or static reference data), this change gets fully tested automatically by your CI server. But this is only part of the story. Great, we know that our updates work, that the upgrade process works, that the upgrade isn’t going to wipe our 4Tb of production data with a single DROP TABLE. But – how do you get this (fully tested) release live? Continuous delivery means being always ready to release your software at any point in time. There’s a significant gap between your latest version being tested, and it being easily releasable. Just a quick note on terminology – there’s a nice piece here from Atlassian on the difference between continuous integration, continuous delivery and continuous deployment. This piece also gives a nice description of the benefits of continuous delivery. These benefits have been summed up by Jez Humble at Thoughtworks as: “Continuous delivery is a set of principles and practices to reduce the cost, time, and risk of delivering incremental changes to users” There’s another really useful piece here on Simple-Talk about the need for continuous delivery and how it applies to the database written by Phil Factor – specifically the extra needs and complexities of implementing a full CD solution for the database (compared to just implementing CD for, say, a web app). So, hopefully you’re convinced of moving on the the next stage! The next step after CI is to get some sort of automated deployment (or “release management”) process set up. But what should I do next? What do I need to plan and think about for getting my automated database deployment process set up? Can’t I just install one of the many release management tools available and hey presto, I’m ready! If only it were that simple. Below I list some of the areas that it’s worth spending a little time on, where a little planning and prep could go a long way. It’s also worth pointing out, that this should really be an evolving process. Depending on your starting point of course, it can be a long journey from your current setup to a full continuous delivery pipeline. If you’ve got a CI mechanism in place, you’re certainly a long way down that path. Nevertheless, we’d recommend evolving your process incrementally. Pages 157 and 129-141 of the book on Continuous Delivery (by Jez Humble and Dave Farley) have some great guidance on building up a pipeline incrementally: http://www.amazon.com/Continuous-Delivery-Deployment-Automation-Addison-Wesley/dp/0321601912 For now, in this post, we’ll look at the following areas for your checklist: You and Your Team Environments The Deployment Process Rollback and Recovery Development Practices You and Your Team It’s a cliché in the DevOps community that “It’s not all about processes and tools, really it’s all about a culture”. As stated in this DevOps report from Puppet Labs: “DevOps processes and tooling contribute to high performance, but these practices alone aren’t enough to achieve organizational success. The most common barriers to DevOps adoption are cultural: lack of manager or team buy-in, or the value of DevOps isn’t understood outside of a specific group”. Like most clichés, there’s truth in there – if you want to set up a database continuous delivery process, you need to get your boss, your department, your company (if relevant) onside. Why? Because it’s an investment with the benefits coming way down the line. But the benefits are huge – for HP, in the book A Practical Approach to Large-Scale Agile Development: How HP Transformed LaserJet FutureSmart Firmware, these are summarized as: -2008 to present: overall development costs reduced by 40% -Number of programs under development increased by 140% -Development costs per program down 78% -Firmware resources now driving innovation increased by a factor of 8 (from 5% working on new features to 40% But what does this mean? It means that, when moving to the next stage, to make that extra investment in automating your deployment process, it helps a lot if everyone is convinced that this is a good thing. That they understand the benefits of automated deployment and are willing to make the effort to transform to a new way of working. Incidentally, if you’re ever struggling to convince someone of the value I’d strongly recommend just buying them a copy of this book – a great read, and a very practical guide to how it can really work at a large org. I’ve spoken to many customers who have implemented database CI who describe their deployment process as “The point where automation breaks down. Up to that point, the CI process runs, untouched by human hand, but as soon as that’s finished we revert to manual.” This deployment process can involve, for example, a DBA manually comparing an environment (say, QA) to production, creating the upgrade scripts, reading through them, checking them against an Excel document emailed to him/her the night before, turning to page 29 in his/her notebook to double-check how replication is switched off and on for deployments, and so on and so on. Painful, error-prone and lengthy. But the point is, if this is something like your deployment process, telling your DBA “We’re changing everything you do and your toolset next week, to automate most of your role – that’s okay isn’t it?” isn’t likely to go down well. There’s some work here to bring him/her onside – to explain what you’re doing, why there will still be control of the deployment process and so on. Or of course, if you’re the DBA looking after this process, you have to do a similar job in reverse. You may have researched and worked out how you’d like to change your methodology to start automating your painful release process, but do the dev team know this? What if they have to start producing different artifacts for you? Will they be happy with this? Worth talking to them, to find out. As well as talking to your DBA/dev team, the other group to get involved before implementation is your manager. And possibly your manager’s manager too. As mentioned, unless there’s buy-in “from the top”, you’re going to hit problems when the implementation starts to get rocky (and what tool/process implementations don’t get rocky?!). You need to have support from someone senior in your organisation – someone you can turn to when you need help with a delayed implementation, lack of resources or lack of progress. Actions: Get your DBA involved (or whoever looks after live deployments) and discuss what you’re planning to do or, if you’re the DBA yourself, get the dev team up-to-speed with your plans, Get your boss involved too and make sure he/she is bought in to the investment. Environments Where are you going to deploy to? And really this question is – what environments do you want set up for your deployment pipeline? Assume everyone has “Production”, but do you have a QA environment? Dedicated development environments for each dev? Proper pre-production? I’ve seen every setup under the sun, and there is often a big difference between “What we want, to do continuous delivery properly” and “What we’re currently stuck with”. Some of these differences are: What we want What we’ve got Each developer with their own dedicated database environment A single shared “development” environment, used by everyone at once An Integration box used to test the integration of all check-ins via the CI process, along with a full suite of unit-tests running on that machine In fact if you have a CI process running, you’re likely to have some sort of integration server running (even if you don’t call it that!). Whether you have a full suite of unit tests running is a different question… Separate QA environment used explicitly for manual testing prior to release “We just test on the dev environments, or maybe pre-production” A proper pre-production (or “staging”) box that matches production as closely as possible Hopefully a pre-production box of some sort. But does it match production closely!? A production environment reproducible from source control A production box which has drifted significantly from anything in source control The big question is – how much time and effort are you going to invest in fixing these issues? In reality this just involves figuring out which new databases you’re going to create and where they’ll be hosted – VMs? Cloud-based? What about size/data issues – what data are you going to include on dev environments? Does it need to be masked to protect access to production data? And often the amount of work here really depends on whether you’re working on a new, greenfield project, or trying to update an existing, brownfield application. There’s a world if difference between starting from scratch with 4 or 5 clean environments (reproducible from source control of course!), and trying to re-purpose and tweak a set of existing databases, with all of their surrounding processes and quirks. But for a proper release management process, ideally you have: Dedicated development databases, An Integration server used for testing continuous integration and running unit tests. [NB: This is the point at which deployments are automatic, without human intervention. Each deployment after this point is a one-click (but human) action], QA – QA engineers use a one-click deployment process to automatically* deploy chosen releases to QA for testing, Pre-production. The environment you use to test the production release process, Production. * A note on the use of the word “automatic” – when carrying out automated deployments this does not mean that the deployment is happening without human intervention (i.e. that something is just deploying over and over again). It means that the process of carrying out the deployment is automatic in that it’s not a person manually running through a checklist or set of actions. The deployment still requires a single-click from a user. Actions: Get your environments set up and ready, Set access permissions appropriately, Make sure everyone understands what the environments will be used for (it’s not a “free-for-all” with all environments to be accessed, played with and changed by development). The Deployment Process As described earlier, most existing database deployment processes are pretty manual. The following is a description of a process we hear very often when we ask customers “How do your database changes get live? How does your manual process work?” Check pre-production matches production (use a schema compare tool, like SQL Compare). Sometimes done by taking a backup from production and restoring in to pre-prod, Again, use a schema compare tool to find the differences between the latest version of the database ready to go live (i.e. what the team have been developing). This generates a script, User (generally, the DBA), reviews the script. This often involves manually checking updates against a spreadsheet or similar, Run the script on pre-production, and check there are no errors (i.e. it upgrades pre-production to what you hoped), If all working, run the script on production.* * this assumes there’s no problem with production drifting away from pre-production in the interim time period (i.e. someone has hacked something in to the production box without going through the proper change management process). This difference could undermine the validity of your pre-production deployment test. Red Gate is currently working on a free tool to detect this problem – sign up here at www.sqllighthouse.com, if you’re interested in testing early versions. There are several variations on this process – some better, some much worse! How do you automate this? In particular, step 3 – surely you can’t automate a DBA checking through a script, that everything is in order!? The key point here is to plan what you want in your new deployment process. There are so many options. At one extreme, pure continuous deployment – whenever a dev checks something in to source control, the CI process runs (including extensive and thorough testing!), before the deployment process keys in and automatically deploys that change to the live box. Not for the faint hearted – and really not something we recommend. At the other extreme, you might be more comfortable with a semi-automated process – the pre-production/production matching process is automated (with an error thrown if these environments don’t match), followed by a manual intervention, allowing for script approval by the DBA. One he/she clicks “Okay, I’m happy for that to go live”, the latter stages automatically take the script through to live. And anything in between of course – and other variations. But we’d strongly recommended sitting down with a whiteboard and your team, and spending a couple of hours mapping out “What do we do now?”, “What do we actually want?”, “What will satisfy our needs for continuous delivery, but still maintaining some sort of continuous control over the process?” NB: Most of what we’re discussing here is about production deployments. It’s important to note that you will also need to map out a deployment process for earlier environments (for example QA). However, these are likely to be less onerous, and many customers opt for a much more automated process for these boxes. Actions: Sit down with your team and a whiteboard, and draw out the answers to the questions above for your production deployments – “What do we do now?”, “What do we actually want?”, “What will satisfy our needs for continuous delivery, but still maintaining some sort of continuous control over the process?” Repeat for earlier environments (QA and so on). Rollback and Recovery If only every deployment went according to plan! Unfortunately they don’t – and when things go wrong, you need a rollback or recovery plan for what you’re going to do in that situation. Once you move in to a more automated database deployment process, you’re far more likely to be deploying more frequently than before. No longer once every 6 months, maybe now once per week, or even daily. Hence the need for a quick rollback or recovery process becomes paramount, and should be planned for. NB: These are mainly scenarios for handling rollbacks after the transaction has been committed. If a failure is detected during the transaction, the whole transaction can just be rolled back, no problem. There are various options, which we’ll explore in subsequent articles, things like: Immediately restore from backup, Have a pre-tested rollback script (remembering that really this is a “roll-forward” script – there’s not really such a thing as a rollback script for a database!) Have fallback environments – for example, using a blue-green deployment pattern. Different options have pros and cons – some are easier to set up, some require more investment in infrastructure; and of course some work better than others (the key issue with using backups, is loss of the interim transaction data that has been added between the failed deployment and the restore). The best mechanism will be primarily dependent on how your application works and how much you need a cast-iron failsafe mechanism. Actions: Work out an appropriate rollback strategy based on how your application and business works, your appetite for investment and requirements for a completely failsafe process. Development Practices This is perhaps the more difficult area for people to tackle. The process by which you can deploy database updates is actually intrinsically linked with the patterns and practices used to develop that database and linked application. So you need to decide whether you want to implement some changes to the way your developers actually develop the database (particularly schema changes) to make the deployment process easier. A good example is the pattern “Branch by abstraction”. Explained nicely here, by Martin Fowler, this is a process that can be used to make significant database changes (e.g. splitting a table) in a step-wise manner so that you can always roll back, without data loss – by making incremental updates to the database backward compatible. Slides 103-108 of the following slidedeck, from Niek Bartholomeus explain the process: https://speakerdeck.com/niekbartho/orchestration-in-meatspace As these slides show, by making a significant schema change in multiple steps – where each step can be rolled back without any loss of new data – this affords the release team the opportunity to have zero-downtime deployments with considerably less stress (because if an increment goes wrong, they can roll back easily). There are plenty more great patterns that can be implemented – the book Refactoring Databases, by Scott Ambler and Pramod Sadalage is a great read, if this is a direction you want to go in: http://www.amazon.com/Refactoring-Databases-Evolutionary-paperback-Addison-Wesley/dp/0321774515 But the question is – how much of this investment are you willing to make? How often are you making significant schema changes that would require these best practices? Again, there’s a difference here between migrating old projects and starting afresh – with the latter it’s much easier to instigate best practice from the start. Actions: For your business, work out how far down the path you want to go, amending your database development patterns to “best practice”. It’s a trade-off between implementing quality processes, and the necessity to do so (depending on how often you make complex changes). Socialise these changes with your development group. No-one likes having “best practice” changes imposed on them, so good to introduce these ideas and the rationale behind them early.   Summary The next stages of implementing a continuous delivery pipeline for your database changes (once you have CI up and running) require a little pre-planning, if you want to get the most out of the work, and for the implementation to go smoothly. We’ve covered some of the checklist of areas to consider – mainly in the areas of “Getting the team ready for the changes that are coming” and “Planning our your pipeline, environments, patterns and practices for development”, though there will be more detail, depending on where you’re coming from – and where you want to get to. This article is part of our database delivery patterns & practices series on Simple Talk. Find more articles for version control, automated testing, continuous integration & deployment.

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