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• Training v. Teaching

  - by Chris Gardner

  Originally posted on: http://geekswithblogs.net/freestylecoding/archive/2014/05/28/training-v.-teaching.aspxAs some of you may know, I recently accepted a position to teach an undergraduate course at my alma mater. Yesterday, I had my first day in an academic classroom. I immediately noticed a difference with the interactions between the students. They don't act like students in a professional training or conference talk. I wanted to use this opportunity to enumerate some of those differences. The immediate thing I noticed was the lack of open environment. This is not to say the class was hostile towards me. I am used to entering the room, bantering with audience, loosening everyone a bit, and flowing into the discussion. A purely academic audience does not banter. At least, they do not banter on day one. I think I can attribute this to two factors. This first is a greater perception of authority. In a training or conference environment, I am an equal with the audience. This is true even if I am being a subject matter expert. We're all professionals. We're all there to learn from each other, share our stories, and enjoy the journey. In the academic classroom, there was a distinct class difference. I had forgotten about this distinction; I had the professional familiarity with the staff by the time I completed my masters. This leads to the other distinction. These was an expectation of performance. At conference and professional training, there is generally no (immediate) grading. This may be a preparation for a certification exam, but I'm not the one responsible for delivering the exam. This was not the case in the academic classroom. These students are battling for points, and I am the sole arbiter. These students are less likely to let the material wash over them, applying the material to their past experiences. They were down taking notes. I don't want to leave the impression that there was no interact in the classroom. I spent a good deal of time doing problems with the class on the whiteboard. I tried to get the class to help me work out the steps. This opened up a few of them. After every conference or training class, I always get a few people that will email me afterward to continue the conversation. I am very curious to see if anybody comes to my office hours tomorrow. However, that is a curiosity that will have to wait until tomorrow.

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• Portland Silverlight User Group: WP7 &amp; XNA &ndash; I survived.

  - by George Clingerman

  Last night I gave a talk to the Portland Silverlight User Group. http://www.portlandsilverlight.net/Meetings/Details/15 And I survived (which you should have probably already figured out since you’re reading this post AND that’s what I titled it…) Really though it was a fantastic time and I had a lot of fun! I was a little nervous getting ready for it, but I’m always a little nervous getting ready for things. I had the game all written,  I knew the general flow for what the talk was going to be. I read over Scott Hanselman’s 11 Top Tips for a Successful Technical presentation (which has become something I do EVERY time I’m preparing for a talk). I gave myself a brief list of points I wanted to make sure I covered or worked into the talk. But then I was ready and I waited. I hate the waiting. It makes me nervous. Once I was up in front of the room though with my laptop open and some XNA code in front of me, my nerves go away. Then I’m ready. I know XNA, I love talking about XNA and I love sharing what I know and hearing questions that make me think. And hopefully that came through while I was talking. I had a freaking blast. The swag went quickly (and I was even able to hand out some XNA 2.0 books that have been around forever!) and the pizza was been gobbled down. I started the talk at about 6:10 and managed to cover a very brief intro to programming against the game loop (it’s a different concept and one that seems to trip a lot of people up getting started with game development) and then rolled into making a basic 2D game for Windows Phone 7 using XNA. And I finished the whole thing before 8:30. Wahoo! I’m planning on posting the source code and assets on my site so those should be coming soon. And to make things even better, they recorded the whole thing on video so everyone will get to see me pretend I can speak! Just wait till you hear the new song I wrote for this talk…

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• Questions to ask to ensure someone understands programming? (and iOS)

  - by Stephen J

  So, I've been tutoring my friend for 2 years. Most people learn programming on their own in 3-6 months, (sans algorithms). It's confusing 'cause he'll run anywhere I tell him to, understands how to read C and C++ honestly better than the average college student, and he'll modify and repeat anything I do... but for the love of god he doesn't move on to new things and he still has test anxiety. I've recently realized he's copied and toyed with existing, but not once gained an understanding of why. I was under the impression he was learning fast because he could write it, but when you say "Make a function that takes an NSString" and he says "How?" and I say "The same way you make ANY function that takes any parameter, NSString is just a type like int" and all I hear is "No, it's an NSString, it's a special thing." and we get into an arguing match 'cause I'm like "It's just a class like any other class, you've used them for months now" and blah... I've subconsciously avoided comprehension questions because of this. Anyway, if you have him copy a program and say "Just initialize it" "Where?" "I don't care, didLoad or initWithCoder or Awake from nib, anywhere it gets initialized" and "No, it has to be exactly where you had it!" "No it doesn't!" I'm sick of this, but he won't give up. So I'm done avoiding these yelling matches and becoming a sadist from now on. I would like some help in finding questions to ask him that force him to understand what he's doing. I'd like some help and any resources I can find. CQuestions looked like a good site, but now I need some iPhone stuff. For example: *What do properties do? How are they changed? How do you change the name of the getter? *Why are Booleans inefficent? What advantage does int have over a boolean and how does the bit-shift operator help? *What does Copy do to a string? *What's the difference between a view controller and a uiview? *Write a program from memory that displays blah on screen, and flashes each view one by one. From beginner up to intermediate, hobbyist with some algebra at most. I'm just looking for resources to work with. I left in backstory so you know to "twist" the questions so he doesn't know he's supposed to init a variable here or there, but has to figure it out, and learn why it goes "here" or that "anywhere is fine as long as it's". Sample programs, anything. I'm relatively open about this because, being a programmer, I seriously doubt he's the only one who has this issue. I'd like to know how others have overcome similar. What made things "click"? for you? Did you have a hard time finding answers on Google, and how did you learn a better way to find what you were looking for? (He's so exact, he'll search for how to write a checkers program with color X and Y inside a uiview, as his search string, instead of breaking it up into components, I need help with that too, and believe it is related). This type of problem has to remind one of us of someone they know. So, Exercises to force them to think? Ways we overcame this thing in the past? I greatly appreciate any help.

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• Missing Fields and Default Values

  - by PointsToShare

  © 2011 By: Dov Trietsch. All rights reserved Dealing with Missing Fields and Default Values New fields and new default values are not propagated throughout the list. They only apply to new and updated items and not to items already entered. They are only prospective. We need to be able to deal with this issue. Here is a scenario. The user has an old list with old items and adds a new field. The field is not created for any of the old items. Trying to get its value raises an Argument Exception. Here is another: a default value is added to a field. All the old items, where the field was not assigned a value, do not get the new default value. The two can also happen in tandem – a new field is added with a default. The older items have neither. Even better, if the user changes the default value, the old items still carry the old defaults. Let’s go a bit further. You have already written code for the list, be it an event receiver, a feature receiver, a console app or a command extension, in which you span all the fields and run on selected items – some new (no problem) and some old (problems aplenty). Had you written defensive code, you would be able to handle the situation, including similar changes in the future. So, without further ado, here’s how. Instead of just getting the value of a field in an item – item[field].ToString() – use the function below. I use ItemValue(item, fieldname, “mud in your eye”) and if “mud in your eye” is what I get, I know that the item did not have the field.   /// <summary> /// Return the column value or a default value /// </summary> private static string ItemValue(SPItem item, string column, string defaultValue) {     try     {         return item[column].ToString();     }     catch (NullReferenceException ex)     {         return defaultValue;     }     catch (ArgumentException ex)     {         return defaultValue;     } } I also use a similar function to return the default and a funny default-default to ascertain that the default does not exist. Here it is:  /// <summary> /// return a fields default or the "default" default. /// </summary> public static string GetFieldDefault(SPField fld, string defValue) {     try     {         // -- Check if default exists.         return fld.DefaultValue.ToString();     }     catch (NullReferenceException ex)     {         return defValue;     }     catch (ArgumentException ex)     {         return defValue;     } } How is this defensive? You have trapped an expected error and dealt with it. Therefore the program did not stop cold in its track and the required code ran to its end. Now, take a further step - write to a log (See Logging – a log blog). Read your own log every now and then, and act accordingly. That’s all Folks!

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• What to do when you inherit an unmaintainable codebase?

  - by GordonM

  I'm currently working at a company with 2 other PHP developers aside from me, and 1 junior developer. The senior developer who originally built the system we're all working on has resigned and will only be here for a matter of weeks. The other developer, who is the only other guy who knows anything about the system, is unhappy here and is looking for a new job. I'm very real danger of being left behind as the only experienced developer on this codebase. Since I've joined this company I've tried to push for better coding standards, project documentation, etc and I do think I've made some headway, but the vast majority of the code is simply unmaintainable and uncommented. A lot of this has to do with the need to get things done fast at points in the project before I joined, but now the technical debt is enormous, even with the two developers who do understand the system on board. Without them, it will simply be impossible to do anything with it. The senior developer is working on trying to at least comment all his code before he leaves but I think the codebase is simply too vast to properly document in the remaining time. Besides, when he does comment it still doesn't make things as clear as it could. If the system was better organized and documented I could probably start refactoring it incrementally, but the whole thing is so tightly coupled that it's very difficult to make any changes in one module without having unintended knock-on effects in other modules. Naturally, there's no unit tests either, and I honestly don't think this codebase could possibly be unit tested anyway given how it's implemented. There also never seems to be enough time to get things done even with 3 developers and 1 junior developer. With one developer and one junior, neither of which had significant input into the early design of the system, I don't see how we could possibly get anything done with keeping the current system working, implementing new features as needed and developing a replacement for the current codebase that is better organized. Is there an approach I can take to cope with this situation, or should I be getting my own CV in order as well at this point? If it was just me and the junior designer who would be left I'd go for the latter option almost without question. However, there's a team of front-end developers and content managers as well, and I'm worried what would become of them if I left and put them in a position where there would be no developers at all. The department might just be closed down altogether under such circumstances, and then I'd have their unemployment on my conscience as well!

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• Migrating to Natty (or any other future versions of ubuntu)

  - by Nik

  I am hoping that this question would help other ubuntu users when migrating to a newer version of ubuntu. This should have all the info that they need. So please when you answer try to phrase them into points for easy understanding. I understand that some questions that I ask might have been asked before by other users. In that case just provide the links to those questions. I am running ubuntu 10.10 Maverick Meerkat in case that is important. I can say for sure that a clean install is definitely better than an upgrade since it gives you an opportunity to clean your system and get a fresh start. However some of us like to retain certain software configuration or files etc. The questions are as follows, How do you save the configuration files of certain application like for instance Thunderbird, firefox, etc...so that you can basically paste in the new version of ubuntu? (Thunderbird for instance has all my mail, so I definitely would like to backup its configuration and then use it the new installation that I do) I have some applications like MATLAB and Maple (Based on JAVA) installed. When I migrate, can I just copy the entire installation folder to the new version of ubuntu? Would it still work as now if I do that? When doing a backup which folders should be backed up? Obviously your personal files would be backup. But other than that, is it necessary to back up stuff in the home folder, /usr/bin etc? I have BURG installed. I am guessing that would be erased when I do a clean install along with the program's configuration and everything. How can I do a backup of it? I am dual booting my ubuntu alongside with Windows 7. When I perform the clean install of ubuntu, would GRUB (bootloader) be removed and in anyway jeopardize my windows installation? Over time I have added a lot of PPA which are of course compatible with my current ubuntu version. How do I make a backup of all my PPA and would they be compatible to the newer version of ubuntu when I restore them? I hope this covers all the questions or doubts that a user might face when thinking about performing a clean install of his system. If I missed anything please mention it as a comment and I will add it to my answer.

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• DTLoggedExec 1.1.2008.4 Released!

  - by Davide Mauri

  Today I've relased the latest version of my DTExec replacement tool, DTLoggedExec. The main changes are the following: Used a new strategy for version numbers. Now it will follow the following pattern Major.Minor.TargetSQLServerVersion.Revision Added support for Auto Configurations Fixed a bug that reported incorrect number of errors and warnings to Log Providers Fixed a buf that prevented correct casting of values when using /Set and /Param options Errors and Warnings are now counted more precisely. Updated database and log import scripts to categorize logs by projects and sections. E.g.: Project: MyBIProject; Sections: Staging, Datawarehouse Removed unused report stored procedures from database Updated Samples: 12 samples are now available to show ALL DTLoggedExec features From this version only SSIS 2008 will be supported http://dtloggedexec.codeplex.com/releases/view/62218  It useful to say something more on a couple of specific points: From this version only SSIS 2008 will be supportedYes, Integration Services 2005 are not supported anymore. The latest version capable of running SSIS 2005 Packages is the 1.0.0.2. Updated database and log import scripts to categorize logs by projects and sectionsWhen you import a log file, you can now assign it to a Project and to a Section of that project. In this way it's easier to gather statistical information for an entire project or a subsection of it. This also allows to store logged data of package belonging to different projects in the same database. For example:  Updated SamplesA complete set of samples that shows how to use all DTLoggedExec features are now shipped with the product. Enjoy! Added support for Auto ConfigurationsThis point will have a post on its own, since it's quite important and is by far the biggest new feature introduced in this release. To explain it in a few words, I can just say that you don't need to waste time with complex DTS configuration files or options, since a package will configure itself automatically. You just need to write a single statement as a parameter for DTLoggedExec. This feature can simplify deployment *a lot* :)   I the next days I'll write the mentioned post on Auto-Configurations and i'll update the documentation available on theDTLoggedExec website:   http://dtloggedexec.davidemauri.it/MainPage.ashx

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• Lenovo Thinkpad X1 Carbon support

  - by Robottinosino

  I am considering selling my Mac to get money towards a Lenovo Thinkpad X1 because what I really want to do is to be running an Ubuntu system all the time. Is this machine completely supported in Ubuntu, with no tiny little feature missing just because I am "going Linux"? Optional user story section, skip to the question below if you don't have time: I have a friend who bought a "works on Ubuntu" system a year ago and has hated the fact ever since: battery lasts less than if he boots in Windows (which he despises) and he ascribes that to "no good OS/harware integration and support for advanced chipset power management features", odd behaviour on suspend/resume/hibernate (says: "when it works 90% of the time and the other 10% it makes you lose your work is as good as broken - 90% is the same as 0% he says), some occasional graphics card glitches he can perfectly well live with and has almost grown affectionate to, and finally, and that is what would make him undo his choice if he could, bad "input device drivers". He says: trackpoint and trackpad just "feel different", "so much better" on Windows and that was impossible to know from the website brochure. That story makes me very doubtful... but I want to abandon this "walled garden" of prison that is my Mac and go Ubuntu all the way, no doubt about that! My dilemma at this time is just: "I don't want to live with those eternal frustrations for sure"! Here's a directly answerable phrasing of my question: Is the Lenovo Thinkpad X1 supported on Ubuntu? Yes/no, which version? Which hardware features are not supported? Provide a list Optionally: sort the list in descending order of frustration from your experience Optionally: mention if there are acceptable workarounds to the "out-of-the-box" condition described in the earlier points and whether this ameliorates frustration at least to "tolerable" levels Comment: the Ubuntu hardware certification page is so not-for-end-users it's unreal. Whoa. What would make it end-user friendly is: Link to "buy here and you'll be just fine, this is the right configuration for you, it'll work as long as you press BUY on that page and don't browse further" Remove mentions of may and might not work. Just tell it straight: press buy here and you will get a working system with the exception of A, B, C (so that I can decide whether the philosophical "freedom pleasure" I get from escaping an Apple world is enough to off-balance the loss, for instance, of Bluetooth capabilities (something that I of course use on my Mac) but "could" lose to use free (as in freedom) software The certification page fails to dispel doubts in me as an end-user. I don't feel "eased into Ubuntu", I feel "partially informed".

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• Is Innovation Dead?

  - by wulfers

  My question is has innovation died?  For large businesses that do not have a vibrant, and fearless leadership (see Apple under Steve jobs), I think is has.  If you look at the organizational charts for many of the large corporate megaliths you will see a plethora of middle managers who are so risk averse that innovation (any change involves risk) is choked off since there are no innovation champions in the middle layers.  And innovation driven top down can only happen when you have a visionary in the top ranks, and that is also very rare.So where is actual innovation happening, at the bottom layer, the people who live in the trenches…   The people who live for a challenge. So how can big business leverage this innovation layer?  Remove the middle management layer.   Provide an innovation champion who has an R&D budget and is tasked with working with the bottom layer of a company, the engineers, developers  and business analysts that live on the edge (Where the corporate tires meet the road). Here are two innovation failures I will tell you about, and both have been impacted by a company so risk averse it is starting to fail in its primary business ventures: This company initiated an innovation process several years ago.  The process was driven companywide with team managers being the central points of collection of innovative ideas.  These managers were given no budget to do anything with these ideas.  There was no process or incentive for these managers to drive it about their team.  This lasted close to a year and the innovation program slowly slipped into oblivion…. A second example:  This same company failed an attempt to market a consumer product in a line where there was already a major market leader.  This product was under development for several years and needed to provide some major device differentiation form the current market leader.  This same company had a large Lead Technologist community made up of real innovators in all areas of technology.  Did this same company leverage the skills and experience of this internal community,   NO!!! So to wrap this up, if large companies really want to survive, then they need to start acting like a small company.  Support those innovators and risk takers!  Reward them by implementing their innovative ideas.  Champion (from the top down) innovation (found at the bottom) in your companies.  Remember if you stand still you are really falling behind.Do it now!  Take a risk!

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• BIDS Helper 1.6 Beta Release (now with SQL 2012 support!)

  - by Darren Gosbell

  The beta for BIDS Helper 1.6 was just released. We have not updated the version notification just yet as we would like to get some feedback on people's experiences with the SQL 2012 version. So if you are using SQL 2012, go grab it and let us know how you go (you can post a comment on this blog post or on the BIDS Helper site itself). This is the first release that supports SQL 2012 and consequently also the first release that runs in Visual Studio 2010. A big thanks to Greg Galloway for doing the bulk of the work on this release. Please note that if you are doing an xcopy deploy that you will need to unblock the files you download or you will get a cryptic error message. This appears to be caused by a security update to either Visual Studio or the .Net framework – the xcopy deploy instructions have been updated to show you how to do this. Below are the notes from the release page. ====== This beta release is the first to support SQL Server 2012 (in addition to SQL Server 2005, 2008, and 2008 R2). Since it is marked as a beta release, we are looking for bug reports in the next few months as you use BIDS Helper on real projects. In addition to getting all existing BIDS Helper functionality working appropriately in SQL Server 2012 (SSDT), the following features are new... Analysis Services Tabular Smart Diff Tabular Actions Editor Tabular HideMemberIf Tabular Pre-Build Fixes and Updates The Unused Datasets feature for Reporting Services now accounts for new features in Reporting Services 2008 R2 like Lookups and new features in Reporting Services 2012. SSIS: emit an informational message when a variable has an expression defined and EvaluateAsExpression = False SSAS: roles reports points to wrong server SSIS - Variable Copy / Move broken in v1.5 "Unused DataSets Report" not showing up in Context menu on VS2005 if Solution Folders used SSAS Tabular: Create a UI for managing actions SSAS Tabular: Smart Diff improvements for new schema and Tabular models SSIS: Copy/Move Variable Erroring due to custom Control Flow item Icon SSIS Performance Visualization Index out of range fixing bugs in AggManager when aggregation design IDs don't match names The exe downloads are a self extracting installer, the zip downloads allow for an xcopy deploy. Make sure to note the updated xcopy deploy instructions for SQL Server 2012.

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• Ray Picking Problems

  - by A Name I Haven't Decided On

  I've read so many answers on here about how to do Ray Picking, that I thought I had the idea of it down. But when I try to implement it in my game, I get garbage. I'm working with LWJGL. Here's the code: public static Ray getPick(int mouseX, int mouseY){ glPushMatrix(); //Setting up the Mouse Clip Vector4f mouseClip = new Vector4f((float)mouseX * 2 / 960f - 1, 1 - (float)mouseY * 2 / 640f ,0 ,1); //Loading Matrices FloatBuffer modMatrix = BufferUtils.createFloatBuffer(16); FloatBuffer projMatrix = BufferUtils.createFloatBuffer(16); glGetFloat(GL_MODELVIEW_MATRIX, modMatrix); glGetFloat(GL_PROJECTION_MATRIX, projMatrix); //Assigning Matrices Matrix4f proj = new Matrix4f(); Matrix4f model = new Matrix4f(); model.load(modMatrix); proj.load(projMatrix); //Multiplying the Projection Matrix by the Model View Matrix Matrix4f tempView = new Matrix4f(); Matrix4f.mul(proj, model, tempView); tempView.invert(); //Getting the Camera Position in World Space. The 4th Column of the Model View Matrix. model.invert(); Point cameraPos = new Point(model.m30, model.m31, model.m32); //Theoretically getting the vector the Picking Ray goes Vector4f rayVector = new Vector4f(); Matrix4f.transform(tempView, mouseClip, rayVector); rayVector.translate((float)-cameraPos.getX(),(float) -cameraPos.getY(),(float) -cameraPos.getZ(), 0f); rayVector.normalise(); glPopMatrix(); //This Basically Spits out a value that changes as the Camera moves. //When the Mouse moves, the values change around 0.001 points from screen edge to edge. System.out.format("Vector: %f %f %f%n", rayVector.x, rayVector.y, rayVector.z); //return new Ray(cameraPos, rayVector); return null; } I don't really know why this isn't working. I was hoping some more experienced eyes might be able to help me out. I can get the camera position like a champ, it's the vector the rays going in that I can't seem to get right. Thanks.

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• Play the Microsoft Game “Are You Certifiable?”

  - by Mysticgeek

  Want to know if you have what it takes to be certified by Microsoft? Today we check out an enjoyable way to practice and test your IT knowledge of Microsoft products.  There are two modes, one where you log in with your Live account so you can save your progress, and play additional levels.   If you log in with your Live account, it’s obvious that Microsoft wants to sell you some certification courses, so just be aware of that. Or Guest Play where you can only play one episode and scores are not saved.   Playing the Game We’ll take a look at the Guest Play just so you get a sense of what the game is about. Enter in a username and pick an avatar… Then read the instructions…we won’t go over them all here, there are a lot of options and points are scored by correct answers, amount of time it takes to answer them, you get vouchers to play a question before answers are shown…etc. Once you start playing, you get certification questions, you can take as much time to read the question as you want, then hit the Answer button when you’re ready. Now you have four answers to choose from…notice the time clicking down, so you want to try to answer as quickly as possible. After selecting the answer, you’re told if it is correct or not, then given an answer explaination, along with your score. You can flag the topic so it comes up again, which is a good way to get repetition of various topics, which really helps when taking the cert tests. If you get an answer wrong, you still get an answer explanation which is cool, so you can learn and better understand the topic. Conclusion This game is definitely not for everyone, only those who are curious or want a fun way to practice for Microsoft certifications. If you are interested in a cert from Microsoft, it’s a fun way to practice up. Play Are You Certifiable? Similar Articles Productive Geek Tips Geek Fun: Play Alien Arena the Free FPS GameFriday Fun: Get Your Mario OnFriday Fun: Play Bubble QuodFriday Fun: 13 Days in HellFriday Fun: Open Doors TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 Download Free iPad Wallpapers at iPad Decor Get Your Delicious Bookmarks In Firefox’s Awesome Bar Manage Photos Across Different Social Sites With Dropico Test Drive Windows 7 Online Download Wallpapers From National Geographic Site Spyware Blaster v4.3

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• The long road to bug-free software

  - by Tony Davis

  The past decade has seen a burgeoning interest in functional programming languages such as Haskell or, in the Microsoft world, F#. Though still on the periphery of mainstream programming, functional programming concepts are gradually seeping into the imperative C# language (for example, Lambda expressions have their root in functional programming). One of the more interesting concepts from functional programming languages is the use of formal methods, the lofty ideal behind which is bug-free software. The idea is that we write a specification that describes exactly how our function (say) should behave. We then prove that our function conforms to it, and in doing so have proved beyond any doubt that it is free from bugs. All programmers already use one form of specification, specifically their programming language's type system. If a value has a specific type then, in a type-safe language, the compiler guarantees that value cannot be an instance of a different type. Many extensions to existing type systems, such as generics in Java and .NET, extend the range of programs that can be type-checked. Unfortunately, type systems can only prevent some bugs. To take a classic problem of retrieving an index value from an array, since the type system doesn't specify the length of the array, the compiler has no way of knowing that a request for the "value of index 4" from an array of only two elements is "unsafe". We restore safety via exception handling, but the ideal type system will prevent us from doing anything that is unsafe in the first place and this is where we start to borrow ideas from a language such as Haskell, with its concept of "dependent types". If the type of an array includes its length, we can ensure that any index accesses into the array are valid. The problem is that we now need to carry around the length of arrays and the values of indices throughout our code so that it can be type-checked. In general, writing the specification to prove a positive property, even for a problem very amenable to specification, such as a simple sorting algorithm, turns out to be very hard and the specification will be different for every program. Extend this to writing a specification for, say, Microsoft Word and we can see that the specification would end up being no simpler, and therefore no less buggy, than the implementation. Fortunately, it is easier to write a specification that proves that a program doesn't have certain, specific and undesirable properties, such as infinite loops or accesses to the wrong bit of memory. If we can write the specifications to prove that a program is immune to such problems, we could reuse them in many places. The problem is the lack of specification "provers" that can do this without a lot of manual intervention (i.e. hints from the programmer). All this might feel a very long way off, but computing power and our understanding of the theory of "provers" advances quickly, and Microsoft is doing some of it already. Via their Terminator research project they have started to prove that their device drivers will always terminate, and in so doing have suddenly eliminated a vast range of possible bugs. This is a huge step forward from saying, "we've tested it lots and it seems fine". What do you think? What might be good targets for specification and verification? SQL could be one: the cost of a bug in SQL Server is quite high given how many important systems rely on it, so there's a good incentive to eliminate bugs, even at high initial cost. [Many thanks to Mike Williamson for guidance and useful conversations during the writing of this piece] Cheers, Tony.

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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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• Using HTML5 Today part 3&ndash; Using Polyfills

  - by Steve Albers

  Shims helps when adding semantic tags to older IE browsers, but there is a huge range of other new HTML5 features that having varying support on browsers.  Polyfills are JavaScript code and/or browser plug-ins that can provide older or less featured browsers with API support.  The best polyfills will detect the whether the current browser has native support, and only adds the functionality if necessary.  The Douglas Crockford JSON2.js library is an example of this approach: if the browser already supports the JSON object, nothing changes.  If JSON is not available, the library adds a JSON property in the global object. This approach provides some big benefits: It lets you add great new HTML5 features to your web sites sooner. It lets the developer focus on writing to the up-and-coming standard rather than proprietary APIs. Where most one-off legacy code fixes tends to break down over time, well done polyfills will stop executing over time (as customer browsers natively support the feature) meaning polyfill code may not need to be tested against new browsers since they will execute the native methods instead. Your should also remember that Polyfills represent an entirely separate code path (and sometimes plug-in) that requires testing for support.  Also Polyfills tend to run on older browsers, which often have slower JavaScript performance.  As a result you might find that performance on older browsers is not comparable. When looking for Polyfills you can start by checking the Modernizr GitHub wiki or the HTML5 Please site. For an example of a polyfill consider a page that writes a few geometric shapes on a <canvas> <script src="jquery-1.7.1.min.js"><script> <script> $(document).ready(function () { drawCanvas(); }); function drawCanvas() { var context = $("canvas")[0].getContext('2d'); //background context.fillStyle = "#8B0000"; context.fillRect(5, 5, 300, 100); // emptybox context.strokeStyle = "#B0C4DE"; context.lineWidth = 4; context.strokeRect(20, 15, 80, 80); // circle context.arc(160, 55, 40, 0, Math.PI * 2, false); context.fillStyle = "#4B0082"; context.fill(); </script>   The result is a simple static canvas with a box & a circle:   …to enable this functionality on a pre-canvas browser we can find a polyfill.  A check on html5please.com references  FlashCanvas.  Pull down the zip and extract the files (flashcanvas.js, flash10canvas.swf, etc) to a directory on your site.  Then based on the documentation you need to add a single line to your original HTML file: <!--[if lt IE 9]><script src="flashcanvas.js"></script><![endif]—> …and you have canvas functionality!  The IE conditional comments ensure that the library is only loaded in browsers where it is useful, improving page load & processing time. Like all Polyfills, you should test to verify the functionality matches your expectations across browsers you need to support.  For instance the Flash Canvas home page advertises 70% support of HTML5 Canvas spec tests.

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• Accessing Controls Within A Gridview

  - by Bunch

  Sometimes you need to access a control within a GridView, but it isn’t quite as straight forward as just using FindControl to grab the control like you can in a FormView. Since the GridView builds multiple rows the key is to specify the row. In this example there is a GridView with a control for a player’s errors. If the errors is greater than 9 the GridView should display the control (lblErrors) in red so it stands out. Here is the GridView: <asp:GridView ID="gvFielding" runat="server" DataSourceID="sqlFielding" DataKeyNames="PlayerID" AutoGenerateColumns="false" >     <Columns>         <asp:BoundField DataField="PlayerName" HeaderText="Player Name" />         <asp:BoundField DataField="PlayerNumber" HeaderText="Player Number" />         <asp:TemplateField HeaderText="Errors">             <ItemTemplate>                 <asp:Label ID="lblErrors" runat="server" Text='<%# EVAL("Errors") %>'  />             </ItemTemplate>         </asp:TemplateField>     </Columns> </asp:GridView> In the code behind you can add the code to change the label’s ForeColor property to red based on the amount of errors. In this case 10 or more errors triggers the color change. Protected Sub gvFielding_DataBound(ByVal sender As Object, ByVal e As System.EventArgs) Handles gvFielding.DataBound     Dim errorLabel As Label     Dim errors As Integer     Dim i As Integer = 0     For Each row As GridViewRow In gvFielding.Rows         errorLabel = gvFielding.Rows(i).FindControl("lblErrors")         If Not errorLabel.Text = Nothing Then             Integer.TryParse(errorLabel.Text, errors)             If errors > 9 Then                 errorLabel.ForeColor = Drawing.Color.Red             End If         End If         i += 1     Next End Sub The main points in the DataBound sub is use a For Each statement to loop through the rows and to increment the variable i so you loop through every row. That way you check each one and if the value is greater than 9 the label changes to red. The If Not errorLabel.Text = Nothing line is there as a check in case no data comes back at all for Errors. Technorati Tags: GridView,ASP.Net,VB.Net

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• How do I create weapon attachments?

  - by Tron86

  My question is; I am developing a game for XNA and I am trying to create a weapon attachment for my player model. My player model loads the .md3 format and reads tags for attachment points. I am able to get the tag of my model's hand. And I am also able to get the tag of my weapon's handle. Each tag I am able to get the rotation and position of and this is how I am calculating it: Model.worldMatrix = Matrix.CreateScale(Model.scale) * Matrix.CreateRotationX(-MathHelper.PiOver2) * Matrix.CreateRotationY(MathHelper.PiOver2); Pretty simple, the player model has a scale and its orientation(it loads on its side so I just use a 90 degree X axis rotation, and a Y axis rotation to face away from the camera). I then calculate the torso tag on the lower body, which gives me a local coordinate at the waist. Then I take that matrix and calculate the tag_weapon in the upper body. This gives me the hand position in local space. I also get the rotation matrix from that tag that I store for later use. All this seems to work fine. Now I move onto my weapon: Matrix weaponWorld = Matrix.CreateScale(CurrentWeapon.scale) * Matrix.CreateRotationX(-MathHelper.PiOver2) * TagRotationMatrix * Matrix.CreateTranslation(HandTag.Position) * Matrix.CreateRotationY(PlayerRotation) * Matrix.CreateTranslation(CollisionBody.Position) * You may notice the weapon matrix gets rotated by 90 degress on the X axis as well. This is because they load in on their sides. Once again this seems pretty simple and follows the SRT order I keep reading about. My TagRotation matrix is the hand's rotation. HandTag.Position is its position in local space. CreateRotationY(PlayerRotation) is the player's rotation in world space, and the CollisionBody.Position is the player's world location. Everything seems to be in order, and almost works in game. However when the gun spawns and follows the player's hand it seems to be flipped on an axis every couple frames. Almost like the X or Y axis is being inversed then put right back. Its hard to explain and I am totally stumped. Even removing all my X axis fixes does nothing to solve the problem. Hopefully I explained everything enough as I am a bit new to this! Thanks!

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• Code Design question, circular reference across classes?

  - by dsollen

  I have no code here, as this is more of a design question (I assume this is still the best place to ask it). I have a very simple server in java which stores a mapping between certain values and UUID which are to be used by many systems across multiple platforms. It accepts a connection from a client and creates a clientSocket which stores the socket and all the other relevant data unique to that connection. Each clientSocket will run in their own thread and will block on the socket waiting for a read. I expect very little strain on this system, it will rarely get called, but when it does get a call it will need to respond quickly and due to the risk of it having a peak time with multiple calls coming in at once threaded is still better. Each thread has a reference to a Mapper class which stores the mapping of UUID which it's reporting to others (with proper synchronization of course). This all works until I have to add a new UUID to the list. When this happens I want to report to all clients that care about that particular UUID that a new one was added. I can't multicast (limitation of the system I'm running on) so I'm having each socket send the message to the client through the established socket. However, since each thread only knows about the socket it's waiting on I didn't have a clear method of looking up every thread/socket that cares about the data to inform them of the new UUID. Polling is out mostly because it seems a little too convoluted to try to maintain a list of newly added UUID. My solution as of now is to have the 'parent' class which creates the mapper class and spawns all the threads pass itself as an argument to the mapper. Then when the mapper creates a new UUID it can make a call to the parent class telling it to send out updates to all the other sockets that care about the change. I'm concerned that this may be a bad design due to the use of a circular reference; parent has a reference to mapper (to pass it to new ClientSocket threads) and mapper points to parent. It doesn't really feel like a bad design to me but I wanted to check since circular references are suppose to be bad. Note: I realize this means that the thread associated with whatever socket originally received the request that spawned the creation of a UUID is going to pay the 'cost' of outputting to all the other clients that care about the new UUID. I don't care about this; as I said I suspect the client to receive only intermittent messages. It's unlikely for one socket to receive multiple messages at one time, and there won't be that many sockets so it shouldn't take too long to send messages to each of them. Perhaps later I'll fix the fact that I'm saddling higher work load on whatever unfortunate thread gets the first request; but for now I think it's fine.

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• Oracle Application in DMZ (Demilitarized Zone)

  - by PRajkumar

   Business Needs Large Organizations want to expose their Oracle Application services outside their private network (HTTP/HTTPS and SSL). Usually these exposures must exist to promote external communication. So they want to separate an external network from directly referencing an internal network   Business Challenges ·         Business does not want to compromise with security information ·         Business cannot expose internal domain or internal URL information   Business Solution DMZ is the solution of this problem. In Oracle application we can achieve this by following way –   ·         Oracle Application consists of fleet nodes (FND_NODES) so first decide which node have to expose to public ·         To expose the node to public use the profile “Node Trust Level” ·         Set node to Public/Private (Normal -> private, External -> public) ·         Set "Responsibility Trust Level" profile to decide whether to expose Application Responsibility to inside or outside firewall         Solution Features   ·         Exposed web services can be accessed by both internal and external users ·         Configurable and can be very easily rolled out ·         Internal network and business data is secured from outside traffic ·         Unauthorized access to internal network from outside is prohibited ·         No need for VPN and Secure FTP server   Benefits  ·       Large Organizations having Oracle Application can expose their web services like (HTTP/HTTPS and SSL) to the internet without compromise with security information and without exposing their internal domain   Possible Week Points  ·         If external firewall is compromised, then external application server is also compromised, exposing an attack on E-Business Suite database ·         There’s nothing to prevent internal users from attacking internal application server, also exposing an attack on E-Business Suite database   Reference Links  ·         https://blogs.oracle.com/manojmadhusoodanan/tags/dmz

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• Part 5: Choose the right tool - or - why

  - by volker.eckardt(at)oracle.com

  Consider the following client request “Please create a report for us to list expenses”. Which Oracle EBS tool would you choose? There are plenty of options available: Oracle Reports, or BI Publisher with PDF or Excel layout, or Discoverer, or BI Publisher Stand Alone, or PDF online generation, or Oracle WebADI, or Plain SQL*Plus as Concurrent Program, or Online review option … Assuming, you as development lead have to decide, you may decide by available skill set in your development team. However, is this a good decision? An important question to influence the decision is the “Why” question: why do you need this report, what process is behind, what exactly you like to achieve? We see often data created or printed, although it would be much better to get the data in Excel, and upload changes via WebADI directly. There are more points that should drive your decision: How many of such requirements you have got? Has this technique been used in the project already? Are there related reusable’s you may gain from? How difficult is it to maintain your solution? Can you merge this report with another one, to reduce test and maintenance work? In addition, also your own development standards should guide you a bit to come to a good decision. In one of my own projects, we discussed such topics in our weekly team meeting. By utilizing the team knowledge best, you may come to a better decision, and additionally, your team supports your decision. Unfortunately, I have rarely seen dedicated team trainings or planned knowledge transfer to support such processes. Often the pressure to deliver on time is too high to have discussion and decision time left. But exactly this can help keeping maintenance costs low by limiting the number of alternative solutions for similar requirements. Lastly, design decisions should be documented to allow another person taking this over easily. Decisions shall be reviewed and updated regularly, to reflect related procedures or Oracle products respective product versions. Summary: Oracle EBS offers plenty of alternatives to implement customizations. Create and maintain a decision tree to support the design process. Do not leave the decision just on developer side. Limit the number of alternative solutions as best as possible; choose one which is the most appropriate also from future maintenance perspective.

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• Android Array Lag?

  - by Mike

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

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

  - by Berin Loritsch

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

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• Why I lose certain values from array?

  - by blankon91

  I've the code to input the values dynamically, when I use it to add the values for the first time, it's fine, but when I want to edit it, the old values didn't inserted on sql query but the new values inserted Here is the example: http://i.stack.imgur.com/dwugS.jpg here is the code: ============the function================= sub ShowItemfgEdit(query,selItemName,defValue,num,cdisable) response.write "<select " & cdisable & " num=""" & num & """ id=""itemCombo"" name=""" & selItemName & """ class=""label"" onchange=""varUsage.ChangeSatuanDt(this)"">" if NOT query.BOF then query.moveFirst WHILE NOT query.EOF tulis = "" if trim(defValue) = trim(query("ckdbarang")) then tulis = "selected" end if response.write "<option value=""" & trim(query("ckdbarang")) & """" & tulis & ">" & trim(query("ckdbarang")) & " - " & trim(query("vnamabarang")) query.moveNext WEND end if response.write "</select>" end sub ============calling the function================ <td class="rb" align="left"><% call ShowItemfgEdit(qGetItemfgGrp,"fitem",qGetUsageDt("ckdfg"),countLine,readonlyfg) %></td> ==============post the value====================== <input type="hidden" name="fitem" value=""> ================get the value=================== for i = 1 to request.form("hdnOrderNum") if request.form("selOrdItem_" & i) <> "" then 'bla...blaa...blaa... ckdfg = trim(request.form("fitem_" & i)) '<==here is the problem objCommand.commandText = "INSERT INTO IcTrPakaiDt " &_ "(id, id_h, ckdunitkey, cnopakai, dtglpakai, ckdbarang, ckdgudang, nqty1, nqty2, csatuan1, csatuan2, nqtypakai, csatuanpakai, vketerangan, cJnsPakai, ckdprodkey, ckdfg, ncountstart, ncountstop, ncounttotal) " &_ " VALUES " &_ " (" & idDt & ",'" & idHd & "','" & selLoc & "','" & nopakai & "','" & cDate(request.form("hdnUsageDate")) & "','" & trim(ckdbarang) & "','" & trim(ckdgudang) & "'," & nqty1 & "," & nqty2 & ",'" & trim(csatuan1) & "','" & trim(csatuan2) & "'," & nqtypakai & ",'" & csatuanpakai & "','" & trim(keteranganItem) & "','" & trim(cjnspakai) & "','" & ckdprodkey & "','" &ckdfg& "'," & cnt1 & "," & cnt2 & "," & totalcnt & ")" set qInsertPakaiDt = objCommand.Execute end if next problem: old value of ckdfg didn't inserted to query, but the new value inserted. How to fix this bug?

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• Why is the framerate (fps) capped at 60?

  - by dennmat

  ISSUE I recently moved a project from my laptop to my desktop(machine info below). On my laptop the exact same code displays the fps(and ms/f) correctly. On my desktop it does not. What I mean by this is on the laptop it will display 300 fps(for example) where on my desktop it will show only up to 60. If I add 100 objects to the game on the laptop I'll see my frame rate drop accordingly; the same test on the desktop results in no change and the frames stay at 60. It takes a lot(~300) entities before I'll see a frame drop on the desktop, then it will descend. It seems as though its "theoretical" frames would be 400 or 500 but will never actually get to that and only do 60 until there's too much to handle at 60. This 60 frame cap is coming from no where. I'm not doing any frame limiting myself. It seems like something external is limiting my loop iterations on the desktop, but for the last couple days I've been scratching my head trying to figure out how to debug this. SETUPS Desktop: Visual Studio Express 2012 Windows 7 Ultimate 64-bit Laptop: Visual Studio Express 2010 Windows 7 Ultimate 64-bit The libraries(allegro, box2d) are the same versions on both setups. CODE Main Loop: while(!abort) { frameTime = al_get_time(); if (frameTime - lastTime >= 1.0) { lastFps = fps/(frameTime - lastTime); lastTime = frameTime; avgMspf = cumMspf/fps; cumMspf = 0.0; fps = 0; } /** DRAWING/UPDATE CODE **/ fps++; cumMspf += al_get_time() - frameTime; } Note: There is no blocking code in the loop at any point. Where I'm at My understanding of al_get_time() is that it can return different resolutions depending on the system. However the resolution is never worse than seconds, and the double is represented as [seconds].[finer-resolution] and seeing as I'm only checking for a whole second al_get_time() shouldn't be responsible. My project settings and compiler options are the same. And I promise its the same code on both machines. My googling really didn't help me much, and although technically it's not that big of a deal. I'd really like to figure this out or perhaps have it explained, whichever comes first. Even just an idea of how to go about figuring out possible causes, because I'm out of ideas. Any help at all is greatly appreciated. EDIT: Thanks All. For any others that find this to disable vSync(windows only) in opengl: First get "wglext.h". It's all over the web. Then you can use a tool like GLee or just write your own quick extensions manager like: bool WGLExtensionSupported(const char *extension_name) { PFNWGLGETEXTENSIONSSTRINGEXTPROC _wglGetExtensionsStringEXT = NULL; _wglGetExtensionsStringEXT = (PFNWGLGETEXTENSIONSSTRINGEXTPROC) wglGetProcAddress("wglGetExtensionsStringEXT"); if (strstr(_wglGetExtensionsStringEXT(), extension_name) == NULL) { return false; } return true; } and then create and setup your function pointers: PFNWGLSWAPINTERVALEXTPROC wglSwapIntervalEXT = NULL; PFNWGLGETSWAPINTERVALEXTPROC wglGetSwapIntervalEXT = NULL; if (WGLExtensionSupported("WGL_EXT_swap_control")) { // Extension is supported, init pointers. wglSwapIntervalEXT = (PFNWGLSWAPINTERVALEXTPROC) wglGetProcAddress("wglSwapIntervalEXT"); // this is another function from WGL_EXT_swap_control extension wglGetSwapIntervalEXT = (PFNWGLGETSWAPINTERVALEXTPROC) wglGetProcAddress("wglGetSwapIntervalEXT"); } Then just call wglSwapIntervalEXT(0) to disable vSync and 1 to enable vSync. I found the reason this is windows only is that openGl actually doesn't deal with anything other than rendering it leaves the rest up to the OS and Hardware. Thanks everyone saved me a lot of time!

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• Is this over-abstraction? (And is there a name for it?)

  - by mwhite

  I work on a large Django application that uses CouchDB as a database and couchdbkit for mapping CouchDB documents to objects in Python, similar to Django's default ORM. It has dozens of model classes and a hundred or two CouchDB views. The application allows users to register a "domain", which gives them a unique URL containing the domain name that gives them access to a project whose data has no overlap with the data of other domains. Each document that is part of a domain has its domain property set to that domain's name. As far as relationships between the documents go, all domains are effectively mutually exclusive subsets of the data, except for a few edge cases (some users can be members of more than one domain, and there are some administrative reports that include all domains, etc.). The code is full of explicit references to the domain name, and I'm wondering if it would be worth the added complexity to abstract this out. I'd also like to know if there's a name for the sort of bound property approach I'm taking here. Basically, I have something like this in mind: Before in models.py class User(Document): domain = StringProperty() class Group(Document): domain = StringProperty() name = StringProperty() user_ids = StringListProperty() # method that returns related document set def users(self): return [User.get(id) for id in self.user_ids] # method that queries a couch view optimized for a specific lookup @classmethod def by_name(cls, domain, name): # the view method is provided by couchdbkit and handles # wrapping json CouchDB results as Python objects, and # can take various parameters modifying behavior return cls.view('groups/by_name', key=[domain, name]) # method that creates a related document def get_new_user(self): user = User(domain=self.domain) user.save() self.user_ids.append(user._id) return user in views.py: from models import User, Group # there are tons of views like this, (request, domain, ...) def create_new_user_in_group(request, domain, group_name): group = Group.by_name(domain, group_name)[0] user = User(domain=domain) user.save() group.user_ids.append(user._id) group.save() in group/by_name/map.js: function (doc) { if (doc.doc_type == "Group") { emit([doc.domain, doc.name], null); } } After models.py class DomainDocument(Document): domain = StringProperty() @classmethod def domain_view(cls, *args, **kwargs): kwargs['key'] = [cls.domain.default] + kwargs['key'] return super(DomainDocument, cls).view(*args, **kwargs) @classmethod def get(cls, *args, **kwargs, validate_domain=True): ret = super(DomainDocument, cls).get(*args, **kwargs) if validate_domain and ret.domain != cls.domain.default: raise Exception() return ret def models(self): # a mapping of all models in the application. accessing one returns the equivalent of class BoundUser(User): domain = StringProperty(default=self.domain) class User(DomainDocument): pass class Group(DomainDocument): name = StringProperty() user_ids = StringListProperty() def users(self): return [self.models.User.get(id) for id in self.user_ids] @classmethod def by_name(cls, name): return cls.domain_view('groups/by_name', key=[name]) def get_new_user(self): user = self.models.User() user.save() views.py @domain_view # decorator that sets request.models to the same sort of object that is returned by DomainDocument.models and removes the domain argument from the URL router def create_new_user_in_group(request, group_name): group = request.models.Group.by_name(group_name) user = request.models.User() user.save() group.user_ids.append(user._id) group.save() (Might be better to leave the abstraction leaky here in order to avoid having to deal with a couchapp-style //! include of a wrapper for emit that prepends doc.domain to the key or some other similar solution.) function (doc) { if (doc.doc_type == "Group") { emit([doc.name], null); } } Pros and Cons So what are the pros and cons of this? Pros: DRYer prevents you from creating related documents but forgetting to set the domain. prevents you from accidentally writing a django view - couch view execution path that leads to a security breach doesn't prevent you from accessing underlying self.domain and normal Document.view() method potentially gets rid of the need for a lot of sanity checks verifying whether two documents whose domains we expect to be equal are. Cons: adds some complexity hides what's really happening requires no model modules to have classes with the same name, or you would need to add sub-attributes to self.models for modules. However, requiring project-wide unique class names for models should actually be fine because they correspond to the doc_type property couchdbkit uses to decide which class to instantiate them as, which should be unique. removes explicit dependency documentation (from group.models import Group)

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