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• MongoDB usage best practices

  - by andresv

  The project I'm working on uses MongoDB for some stuff so I'm creating some documents to help developers speedup the learning curve and also avoid mistakes and help them write clean & reliable code. This is my first version of it, so I'm pretty sure I will be adding more stuff to it, so stay tuned! C# Official driver notes The 10gen official MongoDB driver should always be referenced in projects by using NUGET. Do not manually download and reference assemblies in any project. C# driver quickstart guide: http://www.mongodb.org/display/DOCS/CSharp+Driver+Quickstart Reference links C# Language Center: http://www.mongodb.org/display/DOCS/CSharp+Language+Center MongoDB Server Documentation: http://www.mongodb.org/display/DOCS/Home MongoDB Server Downloads: http://www.mongodb.org/downloads MongoDB client drivers download: http://www.mongodb.org/display/DOCS/Drivers MongoDB Community content: http://www.mongodb.org/display/DOCS/CSharp+Community+Projects Tutorials Tutorial MongoDB con ASP.NET MVC - Ejemplo Práctico (Spanish):http://geeks.ms/blogs/gperez/archive/2011/12/02/tutorial-mongodb-con-asp-net-mvc-ejemplo-pr-225-ctico.aspx MongoDB and C#:http://www.codeproject.com/Articles/87757/MongoDB-and-C C# driver LINQ tutorial:http://www.mongodb.org/display/DOCS/CSharp+Driver+LINQ+Tutorial C# driver reference: http://www.mongodb.org/display/DOCS/CSharp+Driver+Tutorial Safe Mode Connection The C# driver supports two connection modes: safe and unsafe. Safe connection mode (only applies to methods that modify data in a database like Inserts, Deletes and Updates. While the current driver defaults to unsafe mode (safeMode == false) it's recommended to always enable safe mode, and force unsafe mode on specific things we know aren't critical. When safe mode is enabled, the driver internal code calls the MongoDB "getLastError" function to ensure the last operation is completed before returning control the the caller. For more information on using safe mode and their implicancies on performance and data reliability see: http://www.mongodb.org/display/DOCS/getLastError+Command If safe mode is not enabled, all data modification calls to the database are executed asynchronously (fire & forget) without waiting for the result of the operation. This mode could be useful for creating / updating non-critical data like performance counters, usage logging and so on. It's important to know that not using safe mode implies that data loss can occur without any notification to the caller. As with any wait operation, enabling safe mode also implies dealing with timeouts. For more information about C# driver safe mode configuration see: http://www.mongodb.org/display/DOCS/CSharp+getLastError+and+SafeMode The safe mode configuration can be specified at different levels: Connection string: mongodb://hostname/?safe=true Database: when obtaining a database instance using the server.GetDatabase(name, safeMode) method Collection: when obtaining a collection instance using the database.GetCollection(name, safeMode) method Operation: for example, when executing the collection.Insert(document, safeMode) method Some useful SafeMode article: http://stackoverflow.com/questions/4604868/mongodb-c-sharp-safemode-official-driver Exception Handling The driver ensures that an exception will be thrown in case of something going wrong, in case of using safe mode (as said above, when not using safe mode no exception will be thrown no matter what the outcome of the operation is). As explained here https://groups.google.com/forum/?fromgroups#!topic/mongodb-user/mS6jIq5FUiM there is no need to check for any returned value from a driver method inserting data. With updates the situation is similar to any other relational database: if an update command doesn't affect any records, the call will suceed anyway (no exception thrown) and you manually have to check for something like "records affected". For MongoDB, an Update operation will return an instance of the "SafeModeResult" class, and you can verify the "DocumentsAffected" property to ensure the intended document was indeed updated. Note: Please remember that an Update method might return a null instance instead of an "SafeModeResult" instance when safe mode is not enabled. Useful Community Articles Comments about how MongoDB works and how that might affect your application: http://ethangunderson.com/blog/two-reasons-to-not-use-mongodb/ FourSquare using MongoDB had serious scalability problems: http://mashable.com/2010/10/07/mongodb-foursquare/ Is MongoDB a replacement for Memcached? http://www.quora.com/Is-MongoDB-a-good-replacement-for-Memcached/answer/Rick-Branson MongoDB Introduction, shell, when not to use, maintenance, upgrade, backups, memory, sharding, etc: http://www.markus-gattol.name/ws/mongodb.html MongoDB Collection level locking support: https://jira.mongodb.org/browse/SERVER-1240 MongoDB performance tips: http://www.quora.com/MongoDB/What-are-some-best-practices-for-optimal-performance-of-MongoDB-particularly-for-queries-that-involve-multiple-documents Lessons learned migrating from SQL Server to MongoDB: http://www.wireclub.com/development/TqnkQwQ8CxUYTVT90/read MongoDB replication performance: http://benshepheard.blogspot.com.ar/2011/01/mongodb-replication-performance.html

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• Silverlight Firestarter thoughts, and thanks to one and all!

  - by Dave Campbell

  A few metrics that of course got out of hand, but some may find interesting:   1/2 My share of the MVP of the Year award in February of 2009 with Laurent Bugnion 2 Number of degrees I hold: B.S., M.S. Electrical Engineering 3 Number of years in the U.S. Army 3.5 Number of years SilverlighCream has been posted 4 Number of times awarded MVP 6 Number of professional positions I've worked: Antenna Rigger, Boilermaker, Musician, Electronic Technician, Hardware Engineer, Software Engineer 16 Number of companies I've worked for during my career as an Engineer 19 Age at which I turned my first line of code 28 Age at which I hit the workforce as an Engineer 33 Number of years working as an Engineer 43 Number of years writing code 62 Number of years since instantiation 116 Number of tags to search SilverlightCream with 645 Number of blogs I view to find articles (at this moment) 664 Number of articles tagged wp7dev at SilverlightCream right now 700 Number of Twitter followers for WynApse 981 Number of individual bloggers in the SilverlightCream database 1002 Number of SilverlightCream blogposts 1100 Number of people live in Redmond for the Firestarter (I think) 1428 Number of total blogposts at GeeksWithBlogs (not counting this one) 4200 Number of Feedburner subscribers (approximately) 6500 Number of Twitter followers for SilverlightNews (approximately) 7087 Number of posts tagged and aggregated at SilverlightCream right now 13000 Number of people registered to watch the Firestarter online (I think) The overwhelming feeling I have returning from the Silverlight Firestarter: Priceless There is absolutely no way that I could personally thank everyone that over the last few years has held their hand out and offered me a step up to get to the point that Scott Guthrie called me out in his keynote. So I'm just going to hit the highlights here... Scott Guthrie Thanks for not only being the level you are at Microsoft, but for being so approachable, easy to talk to, willing to help everyone, and above all knowledgable. My first level manager at my last position asked if Visual Studio was a graphics program... and you step up to a laptop at a conference and type "File->New Program" ... 'nuff said... oh yeah, thanks for the shoutout! John Papa Thanks for being a good friend, ramroding the Firestarter, being a great guy to be around, and for the poster... holy crap is that cool. Tim Heuer Thanks for all you did as a great DE in Phoenix, and for helping out so many of us, of course being a great guy, and for the poster as well... I think you and John shared that task. In no order at all my buddy Michael Washington, Laurent Bugnion (the other half of the first Silverlight MVP of the Year) Tim Sneath, Mike Harsh, Chad Campbell and Bryant Likes (from back in the day), Adam Kinney, Jesse Liberty, Jeff Paries, Pete Brown, András Velvárt, David Kelly, Michael Palermo, Scott Cate, Erik Mork, and on and on... don't feel bad if your name didn't appear, I have simply too many supporters to name. Silverlight Firestarter Indeed All the people mentioned here, and all the MVPs knew Silverlight was NOT dead, but because of a very unfortunate circumstance, the popular media opinion became that. Consequently the Firestarter exploded from a laid-back event to a global conference. People worked their ass off getting bits ready and presentations using those bits. All to stem the flow of misinformation. All involved please accept my personal thanks for an absolutely awesome job. I had the priviledge of watching the 'prep' on Wednesday afternoon, and was blown away the first time I saw the 3D demo... and have been blown away every time I've seen it since. Not to mention all the other goodness in Silverlight 5. Yes I hit 1000 on my blog, but more importantly, all of you are blogging and using Silverlight, and Microsoft hit one completely out of the park... no... they knocked it out of the neighborhood with the Firestarter. It was amazing to be there for it, and it will be awesome to use the new bits as we get them. Keep reading, there's tons more to come with Silverlight and SilverlightCream following along behind. As usual, this old hacker is humbled to be allowed to play with all the cool kids... Thanks one and all for everything, and Stay in the 'Light

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• WCF RIA Services DomainContext Abstraction Strategies–Say That 10 Times!

  - by dwahlin

  The DomainContext available with WCF RIA Services provides a lot of functionality that can help track object state and handle making calls from a Silverlight client to a DomainService. One of the questions I get quite often in our Silverlight training classes (and see often in various forums and other areas) is how the DomainContext can be abstracted out of ViewModel classes when using the MVVM pattern in Silverlight applications. It’s not something that’s super obvious at first especially if you don’t work with delegates a lot, but it can definitely be done. There are various techniques and strategies that can be used but I thought I’d share some of the core techniques I find useful. To start, let’s assume you have the following ViewModel class (this is from my Silverlight Firestarter talk available to watch online here if you’re interested in getting started with WCF RIA Services): public class AdminViewModel : ViewModelBase { BookClubContext _Context = new BookClubContext(); public AdminViewModel() { if (!DesignerProperties.IsInDesignTool) { LoadBooks(); } } private void LoadBooks() { _Context.Load(_Context.GetBooksQuery(), LoadBooksCallback, null); } private void LoadBooksCallback(LoadOperation<Book> books) { Books = new ObservableCollection<Book>(books.Entities); } } Notice that BookClubContext is being used directly in the ViewModel class. There’s nothing wrong with that of course, but if other ViewModel objects need to load books then code would be duplicated across classes. Plus, the ViewModel has direct knowledge of how to load data and I like to make it more loosely-coupled. To do this I create what I call a “Service Agent” class. This class is responsible for getting data from the DomainService and returning it to a ViewModel. It only knows how to get and return data but doesn’t know how data should be stored and isn’t used with data binding operations. An example of a simple ServiceAgent class is shown next. Notice that I’m using the Action<T> delegate to handle callbacks from the ServiceAgent to the ViewModel object. Because LoadBooks accepts an Action<ObservableCollection<Book>>, the callback method in the ViewModel must accept ObservableCollection<Book> as a parameter. The callback is initiated by calling the Invoke method exposed by Action<T>: public class ServiceAgent { BookClubContext _Context = new BookClubContext(); public void LoadBooks(Action<ObservableCollection<Book>> callback) { _Context.Load(_Context.GetBooksQuery(), LoadBooksCallback, callback); } public void LoadBooksCallback(LoadOperation<Book> lo) { //Check for errors of course...keeping this brief var books = new ObservableCollection<Book>(lo.Entities); var action = (Action<ObservableCollection<Book>>)lo.UserState; action.Invoke(books); } } This can be simplified by taking advantage of lambda expressions. Notice that in the following code I don’t have a separate callback method and don’t have to worry about passing any user state or casting any user state (the user state is the 3rd parameter in the _Context.Load method call shown above). public class ServiceAgent { BookClubContext _Context = new BookClubContext(); public void LoadBooks(Action<ObservableCollection<Book>> callback) { _Context.Load(_Context.GetBooksQuery(), (lo) => { var books = new ObservableCollection<Book>(lo.Entities); callback.Invoke(books); }, null); } } A ViewModel class can then call into the ServiceAgent to retrieve books yet never know anything about the DomainContext object or even know how data is loaded behind the scenes: public class AdminViewModel : ViewModelBase { ServiceAgent _ServiceAgent = new ServiceAgent(); public AdminViewModel() { if (!DesignerProperties.IsInDesignTool) { LoadBooks(); } } private void LoadBooks() { _ServiceAgent.LoadBooks(LoadBooksCallback); } private void LoadBooksCallback(ObservableCollection<Book> books) { Books = books } } You could also handle the LoadBooksCallback method using a lambda if you wanted to minimize code just like I did earlier with the LoadBooks method in the ServiceAgent class.  If you’re into Dependency Injection (DI), you could create an interface for the ServiceAgent type, reference it in the ViewModel and then inject in the object to use at runtime. There are certainly other techniques and strategies that can be used, but the code shown here provides an introductory look at the topic that should help get you started abstracting the DomainContext out of your ViewModel classes when using WCF RIA Services in Silverlight applications.

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• Using Lambdas for return values in Rhino.Mocks

  - by PSteele

  In a recent StackOverflow question, someone showed some sample code they’d like to be able to use.  The particular syntax they used isn’t supported by Rhino.Mocks, but it was an interesting idea that I thought could be easily implemented with an extension method. Background When stubbing a method return value, Rhino.Mocks supports the following syntax: dependency.Stub(s => s.GetSomething()).Return(new Order()); The method signature is generic and therefore you get compile-time type checking that the object you’re returning matches the return value defined by the “GetSomething” method. You could also have Rhino.Mocks execute arbitrary code using the “Do” method: dependency.Stub(s => s.GetSomething()).Do((Func<Order>) (() => new Order())); This requires the cast though.  It works, but isn’t as clean as the original poster wanted.  They showed a simple example of something they’d like to see: dependency.Stub(s => s.GetSomething()).Return(() => new Order()); Very clean, simple and no casting required.  While Rhino.Mocks doesn’t support this syntax, it’s easy to add it via an extension method. The Rhino.Mocks “Stub” method returns an IMethodOptions<T>.  We just need to accept a Func<T> and use that as the return value.  At first, this would seem straightforward: public static IMethodOptions<T> Return<T>(this IMethodOptions<T> opts, Func<T> factory) { opts.Return(factory()); return opts; } And this would work and would provide the syntax the user was looking for.  But the problem with this is that you loose the late-bound semantics of a lambda.  The Func<T> is executed immediately and stored as the return value.  At the point you’re setting up your mocks and stubs (the “Arrange” part of “Arrange, Act, Assert”), you may not want the lambda executing – you probably want it delayed until the method is actually executed and Rhino.Mocks plugs in your return value. So let’s make a few small tweaks: public static IMethodOptions<T> Return<T>(this IMethodOptions<T> opts, Func<T> factory) { opts.Return(default(T)); // required for Rhino.Mocks on non-void methods opts.WhenCalled(mi => mi.ReturnValue = factory()); return opts; } As you can see, we still need to set up some kind of return value or Rhino.Mocks will complain as soon as it intercepts a call to our stubbed method.  We use the “WhenCalled” method to set the return value equal to the execution of our lambda.  This gives us the delayed execution we’re looking for and a nice syntax for lambda-based return values in Rhino.Mocks. Technorati Tags: .NET,Rhino.Mocks,Mocking,Extension Methods

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• Logging WebSocket Frames using Chrome Developer Tools, Net-internals and Wireshark (TOTD #184)

  - by arungupta

  TOTD #183 explained how to build a WebSocket-driven application using GlassFish 4. This Tip Of The Day (TOTD) will explain how do view/debug on-the-wire messages, or frames as they are called in WebSocket parlance, over this upgraded connection. This blog will use the application built in TOTD #183. First of all, make sure you are using a browser that supports WebSocket. If you recall from TOTD #183 then WebSocket is combination of Protocol and JavaScript API. A browser supporting WebSocket, or not, means they understand your web pages with the WebSocket JavaScript. caniuse.com/websockets provide a current status of WebSocket support in different browsers. Most of the major browsers such as Chrome, Firefox, Safari already support WebSocket for the past few versions. As of this writing, IE still does not support WebSocket however its planned for a future release. Viewing WebSocket farmes require special settings because all the communication happens over an upgraded HTTP connection over a single TCP connection. If you are building your application using Java, then there are two common ways to debug WebSocket messages today. Other language libraries provide different mechanisms to log the messages. Lets get started! Chrome Developer Tools provide information about the initial handshake only. This can be viewed in the Network tab and selecting the endpoint hosting the WebSocket endpoint. You can also click on "WebSockets" on the bottom-right to show only the WebSocket endpoints. Click on "Frames" in the right panel to view the actual frames being exchanged between the client and server. The frames are not refreshed when new messages are sent or received. You need to refresh the panel by clicking on the endpoint again. To see more detailed information about the WebSocket frames, you need to type "chrome://net-internals" in a new tab. Click on "Sockets" in the left navigation bar and then on "View live sockets" to see the page. Select the box with the address to your WebSocket endpoint and see some basic information about connection and bytes exchanged between the client and the endpoint. Clicking on the blue text "source dependency ..." shows more details about the handshake. If you are interested in viewing the exact payload of WebSocket messages then you need a network sniffer. These tools are used to snoop network traffic and provide a lot more details about the raw messages exchanged over the network. However because they provide lot more information so they need to be configured in order to view the relevant information. Wireshark (nee Ethereal) is a pretty standard tool for sniffing network traffic and will be used here. For this blog purpose, we'll assume that the WebSocket endpoint is hosted on the local machine. These tools do allow to sniff traffic across the network though. Wireshark is quite a comprehensive tool and we'll capture traffic on the loopback address. Start wireshark, select "loopback" and click on "Start". By default, all traffic information on the loopback address is displayed. That includes tons of TCP protocol messages, applications running on your local machines (like GlassFish or Dropbox on mine), and many others. Specify "http" as the filter in the top-left. Invoke the application built in TOTD #183 and click on "Say Hello" button once. The output in wireshark looks like Here is a description of the messages exchanged: Message #4: Initial HTTP request of the JSP page Message #6: Response returning the JSP page Message #16: HTTP Upgrade request Message #18: Upgrade request accepted Message #20: Request favicon Message #22: Responding with favicon not found Message #24: Browser making a WebSocket request to the endpoint Message #26: WebSocket endpoint responding back You can also use Fiddler to debug your WebSocket messages. How are you viewing your WebSocket messages ? Here are some references for you: JSR 356: Java API for WebSocket - Specification (Early Draft) and Implementation (already integrated in GlassFish 4 promoted builds) TOTD #183 - Getting Started with WebSocket in GlassFish Subsequent blogs will discuss the following topics (not necessary in that order) ... Binary data as payload Custom payloads using encoder/decoder Error handling Interface-driven WebSocket endpoint Java client API Client and Server configuration Security Subprotocols Extensions Other topics from the API

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• Editor's Notebook - Social Aura: Insights from the Oracle Social Media Summit

  - by user462779

  Panelists talk social marketing at the Oracle Social Media Summit On November 14, I traveled to Las Vegas for the first-ever Oracle Social Media Summit. The two day event featured an impressive collection of social media luminaries including: David Kirkpatrick (founder and CEO of Techonomy Media and author of The Facebook Effect), John Yi (Head of Marketing Partnerships, Facebook), Matt Dickman (EVP of Social Business Innovation, Weber Shandwick), and Lyndsay Iorio (Social Media & Communications Manager, NBC Sports Group) among others. It was also a great opportunity to talk shop with some of our new Vitrue and Involver colleagues who have been returning great social media results even before their companies were acquired by Oracle. I was live tweeting the event from @OracleProfit which was great for those who wanted to follow along with the proceedings from the comfort of their office or blackjack table. But I've also found over the years that live tweeting an event is a handy way to take notes: I can sift back through my record of what people said or thoughts I had at the time and organize the Twitter messages into some kind of summary account of the proceedings. I've had nearly a month to reflect on the presentations and conversations at the event and a few key topics have emerged: David Kirkpatrick's comment during the opening presentation really set the stage for the conversations that followed. Especially if you are a marketer or publisher, the idea that you are in a one-way broadcast relationship with your audience is a thing of the past. "Rising above the noise" does not mean reaching for a megaphone, ALL CAPS, or exclamation marks. Hype will not motivate social media denizens to do anything but unfollow and tune you out. But knowing your audience, creating quality content and/or offers for them, treating them with respect, and making an authentic effort to please them: that's what I believe is now necessary. And Kirkpatrick's comment early in the day really made the point. Later in the day, our friends @Vitrue demonstrated this point by elaborating on a comment by Facebook's John Yi. If a social strategy is comprised of nothing more than cutting/pasting the same message into different social media properties, you're missing the opportunity to have an actual conversation. That's not shouting at your audience, but it does feel like an empty gesture. Walter Benjamin, perplexed by auraless Twitter messages Not to get too far afield, but 20th century cultural critic Walter Benjamin has a concept that is useful for understanding the dynamics of the empty social media gesture: Aura. In his work The Work of Art in the Age of Mechanical Reproduction, Benjamin struggled to understand the difference he percieved between the value of a hand-made art object (a painting, wood cutting, sculpture, etc.) and a photograph. For Benjamin, aura is similar to the "soul" of an artwork--the intangible essence that is created when an artist picks up a tool and puts creative energy and effort into a work. I'll defer to Wikipedia: "He argues that the "sphere of authenticity is outside the technical" so that the original artwork is independent of the copy, yet through the act of reproduction something is taken from the original by changing its context. He also introduces the idea of the "aura" of a work and its absence in a reproduction." So make sure you put aura into your social interactions. Don't just mechanically reproduce them. Keeping aura in your interactions requires the intervention of an actual human being. That's why @NoahHorton's comment about content curation struck me as incredibly important. Maybe it's just my own prejudice, being in the content curation business myself. And it's not to totally discount machine-aided content management systems, content recommendation engines, and other tech-driven tools for building an exceptional content experience. It's just that without that human interaction--that editor who reviews the analytics and responds to user feedback--interactions over social media feel a bit empty. It is SOCIAL media, right? (We'll leave the conversation about social machines for another day). At the end of the day, experimentation is key. Just like trying to find that right joke to tell at the beginning of your presentation or that good opening like at a cocktail party, social media messages and interactions can take some trial and error. Don't be afraid to try things, tinker with incomplete ideas, abandon things that don't work, and engage in the conversation. And make sure your heart is in it, otherwise your audience can tell. And finally:

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• Get to Know a Candidate (16 of 25): Stewart Alexander&ndash;Socialist Party USA

  - by Brian Lanham

  DISCLAIMER: This is not a post about “Romney” or “Obama”. This is not a post for whom I am voting. Information sourced for Wikipedia. Alexander is an American democratic socialist politician and a resident of California. Alexander was the Peace and Freedom Party candidate for Lieutenant Governor in 2006. He received 43,319 votes, 0.5% of the total. In August 2010, Alexander declared his candidacy for the President of the United States with the Socialist Party and Green Party. In January 2011, Alexander also declared his candidacy for the presidential nomination of the Peace and Freedom Party. Stewart Alexis Alexander was born to Stewart Alexander, a brick mason and minister, and Ann E. McClenney, a nurse and housewife.  While in the Air Force Reserve, Alexander worked as a full-time retail clerk at Safeway Stores and then began attending college at California State University, Dominguez Hills. Stewart began working overtime as a stocking clerk with Safeway to support himself through school. During this period he married to Freda Alexander, his first wife. They had one son. He was honorably discharged in October 1976 and married for the second time. He left Safeway in 1978 and for a brief period worked as a licensed general contractor. In 1980, he went to work for Lockheed Aircraft but quit the following year.  Returning to Los Angeles, he became involved in several civic organizations, including most notably the NAACP (he became the Labor and Industry Chairman for the Inglewood South Bay Branch of the NAACP). In 1986 he moved back to Los Angeles and hosted a weekly talk show on KTYM Radio until 1989. The show dealt with social issues affecting Los Angeles such as gangs, drugs, and redevelopment, interviewing government officials from all levels of government and community leaders throughout California. He also worked with Delores Daniels of the NAACP on the radio and in the street. The Socialist Party USA (SPUSA) is a multi-tendency democratic-socialist party in the United States. The party states that it is the rightful continuation and successor to the tradition of the Socialist Party of America, which had lasted from 1901 to 1972. The party is officially committed to left-wing democratic socialism. The Socialist Party USA, along with its predecessors, has received varying degrees of support, when its candidates have competed against those from the Republican and Democratic parties. Some attribute this to the party having to compete with the financial dominance of the two major parties, as well as the limitations of the United States' legislatively and judicially entrenched two-party system. The Party supports third-party candidates, particularly socialists, and opposes the candidates of the two major parties. Opposing both capitalism and "authoritarian Communism", the Party advocates bringing big business under public ownership and democratic workers' self-management. The party opposes unaccountable bureaucratic control of Soviet communism. Alexander has Ballot Access in: CO, FL, NY, OH (write-in access in: IN, TX) Learn more about Stewart Alexander and Socialist Party USA on Wikipedia.

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• Hidden exceptions

  - by user12617285

  Occasionally you may find yourself in a Java application environment where exceptions in your code are being caught by the application framework and either silently swallowed or converted into a generic exception. Either way, the potentially useful details of your original exception are inaccessible. Wouldn't it be nice if there was a VM option that showed the stack trace for every exception thrown, whether or not it's caught? In fact, HotSpot includes such an option: -XX:+TraceExceptions. However, this option is only available in a debug build of HotSpot (search globals.hpp for TraceExceptions). And based on a quick skim of the HotSpot source code, this option only prints the exception class and message. A more useful capability would be to have the complete stack trace printed as well as the code location catching the exception. This is what the various TraceException* options in in Maxine do (and more). That said, there is a way to achieve a limited version of the same thing with a stock standard JVM. It involves the use of the -Xbootclasspath/p non-standard option. The trick is to modify the source of java.lang.Exception by inserting the following: private static final boolean logging = System.getProperty("TraceExceptions") != null; private void log() { if (logging && sun.misc.VM.isBooted()) { printStackTrace(); } } Then every constructor simply needs to be modified to call log() just before returning: public Exception(String message) { super(message); log(); } public Exception(String message, Throwable cause) { super(message, cause); log(); } // etc... You now need to compile the modified Exception.java source and prepend the resulting class to the boot class path as well as add -DTraceExceptions to your java command line. Here's a console session showing these steps: % mkdir boot % javac -d boot Exception.java % java -DTraceExceptions -Xbootclasspath/p:boot -cp com.oracle.max.vm/bin test.output.HelloWorld java.util.zip.ZipException: error in opening zip file at java.util.zip.ZipFile.open(Native Method) at java.util.zip.ZipFile.(ZipFile.java:127) at java.util.jar.JarFile.(JarFile.java:135) at java.util.jar.JarFile.(JarFile.java:72) at sun.misc.URLClassPath$JarLoader.getJarFile(URLClassPath.java:646) at sun.misc.URLClassPath$JarLoader.access$600(URLClassPath.java:540) at sun.misc.URLClassPath$JarLoader$1.run(URLClassPath.java:607) at java.security.AccessController.doPrivileged(Native Method) at sun.misc.URLClassPath$JarLoader.ensureOpen(URLClassPath.java:599) at sun.misc.URLClassPath$JarLoader.(URLClassPath.java:583) at sun.misc.URLClassPath$3.run(URLClassPath.java:333) at java.security.AccessController.doPrivileged(Native Method) at sun.misc.URLClassPath.getLoader(URLClassPath.java:322) at sun.misc.URLClassPath.getLoader(URLClassPath.java:299) at sun.misc.URLClassPath.getResource(URLClassPath.java:168) at java.net.URLClassLoader$1.run(URLClassLoader.java:194) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:190) at sun.misc.Launcher$ExtClassLoader.findClass(Launcher.java:229) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at java.lang.ClassLoader.loadClass(ClassLoader.java:295) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:247) java.security.PrivilegedActionException at java.security.AccessController.doPrivileged(Native Method) at sun.misc.URLClassPath$JarLoader.ensureOpen(URLClassPath.java:599) at sun.misc.URLClassPath$JarLoader.(URLClassPath.java:583) at sun.misc.URLClassPath$3.run(URLClassPath.java:333) at java.security.AccessController.doPrivileged(Native Method) at sun.misc.URLClassPath.getLoader(URLClassPath.java:322) ... It's worth pointing out that this is not as useful as direct VM support for tracing exceptions. It has (at least) the following limitations: The trace is shown for every exception, whether it is thrown or not. It only applies to subclasses of java.lang.Exception as there appears to be bootstrap issues when the modification is applied to Throwable.java. It does not show you where the exception was caught. It involves overriding a class in rt.jar, something should never be done in a non-development environment.

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• JRE not working on firefox

  - by user1488595

  I am attempting to get JRE 7 run in firefox in ubuntu 12.04, 32 bit. I've tried to follow this article: www.liberiangeek.net/2012/04/install-oracle-java-runtime-jre-7-in-ubuntu-12-04-precise-pangolin/ . I've also tried this repository: www.webupd8.org/2012/06/how-to-install-oracle-java-7-in-debian.html As well as installing JDK, which contains JRE, by following this article: www.liberiangeek.net/2012/04/install-oracle-java-jdk-7-in-ubuntu-12-04-precise-pangolin/ With all above method of installation, I get the following error in firefox console when I run applet with firefox: java.io.IOException: Cannot run program "/usr/lib/jvm/jre1.7.0/bin/java": error=13, Permission denied at java.lang.ProcessBuilder.start(Unknown Source) at sun.plugin2.jvm.JVMLauncher.start(Unknown Source) at sun.plugin2.main.server.JVMInstance.startImpl(Unknown Source) at sun.plugin2.main.server.JVMInstance.start(Unknown Source) at sun.plugin2.main.server.JVMManager.getOrCreateBestJVMInstance(Unknown Source) at sun.plugin2.main.server.JVMManager.startAppletImpl(Unknown Source) at sun.plugin2.main.server.JVMManager.startApplet(Unknown Source) at sun.plugin2.main.server.JVMManager.startApplet(Unknown Source) at sun.plugin2.main.server.MozillaPlugin.maybeStartApplet(Unknown Source) at sun.plugin2.main.server.MozillaPlugin.setWindow(Unknown Source) Caused by: java.io.IOException: error=13, Permission denied at java.lang.UNIXProcess.forkAndExec(Native Method) at java.lang.UNIXProcess.(Unknown Source) at java.lang.ProcessImpl.start(Unknown Source) ... 10 more java.io.IOException at sun.plugin2.main.server.JVMInstance.startImpl(Unknown Source) at sun.plugin2.main.server.JVMInstance.start(Unknown Source) at sun.plugin2.main.server.JVMManager.getOrCreateBestJVMInstance(Unknown Source) at sun.plugin2.main.server.JVMManager.startAppletImpl(Unknown Source) at sun.plugin2.main.server.JVMManager.startApplet(Unknown Source) at sun.plugin2.main.server.JVMManager.startApplet(Unknown Source) at sun.plugin2.main.server.MozillaPlugin.maybeStartApplet(Unknown Source) at sun.plugin2.main.server.MozillaPlugin.setWindow(Unknown Source) Caused by: java.io.IOException: Cannot run program "/usr/lib/jvm/jre1.7.0/bin/java": error=13, Permission denied at java.lang.ProcessBuilder.start(Unknown Source) at sun.plugin2.jvm.JVMLauncher.start(Unknown Source) ... 8 more Caused by: java.io.IOException: error=13, Permission denied at java.lang.UNIXProcess.forkAndExec(Native Method) at java.lang.UNIXProcess.(Unknown Source) at java.lang.ProcessImpl.start(Unknown Source) ... 10 more Exception in thread "main" java.lang.RuntimeException: java.io.IOException at sun.plugin2.main.server.JVMManager.getOrCreateBestJVMInstance(Unknown Source) at sun.plugin2.main.server.JVMManager.startAppletImpl(Unknown Source) at sun.plugin2.main.server.JVMManager.startApplet(Unknown Source) at sun.plugin2.main.server.JVMManager.startApplet(Unknown Source) at sun.plugin2.main.server.MozillaPlugin.maybeStartApplet(Unknown Source) at sun.plugin2.main.server.MozillaPlugin.setWindow(Unknown Source) Caused by: java.io.IOException at sun.plugin2.main.server.JVMInstance.startImpl(Unknown Source) at sun.plugin2.main.server.JVMInstance.start(Unknown Source) ... 6 more Caused by: java.io.IOException: Cannot run program "/usr/lib/jvm/jre1.7.0/bin/java": error=13, Permission denied at java.lang.ProcessBuilder.start(Unknown Source) at sun.plugin2.jvm.JVMLauncher.start(Unknown Source) ... 8 more Caused by: java.io.IOException: error=13, Permission denied at java.lang.UNIXProcess.forkAndExec(Native Method) at java.lang.UNIXProcess.(Unknown Source) at java.lang.ProcessImpl.start(Unknown Source) ... 10 more I've tried to type: sudo chmod 777 /usr/lib/jvm/jre1.7.0/bin/java It did not work. I also tried to run Eclipse, which requires JRE to run. It did not work originally(it works now), returning the following error: java.lang.UnsatisfiedLinkError: Could not load SWT library. Reasons: no swt-gtk-3740 in java.library.path no swt-gtk in java.library.path Can't load library: /home/username/.swt/lib/linux/x86/libswt-gtk-3740.so Can't load library: /home/usename/.swt/lib/linux/x86/libswt-gtk.so at org.eclipse.swt.internal.Library.loadLibrary(Library.java:285) By running "ln -s /usr/lib/jni/libswt-* ~/.swt/lib/linux/x86/" (Thanks, stackoverflow.com/questions/10970754/cant-open-eclipse-in-ubuntu-12-04-java-lang-unsatisfiedlinkerror-could-not-l), Eclipse works again. I have been googling this for days, without luck. Any response would be appreciated.

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• Override ToString() in your Classes

  - by psheriff

  One of the reasons I love teaching is because of the questions that I get from attendees. I was giving a presentation at DevConnections and was showing a collection of Product objects. When I hovered over the variable that contained the collection, it looked like Figure 2. As you can see in the collection, I have actual product names of my videos from www.pdsa.com/videos being displayed. To get your data to appear in the data tips you must override the ToString() method in your class. To illustrate this, take the following simple Product class shown below: public class Product{  public string ProductName { get; set; }  public int ProductId { get; set; }} This class does not have an override of the ToString() method so if you create a collection of Product objects you will end up with data tips that look like Figure 1. Below is the code I used to create a collection of Product objects. I have shortened the code in this blog, but you can get the full source code for this sample by following the instructions at the bottom of this blog entry. List<Product> coll = new List<Product>();Product prod; prod = new Product()  { ProductName = "From Zero to HTML 5 in 60 Minutes",     ProductId = 1 };coll.Add(prod);prod = new Product()   { ProductName = "Architecting Applications …",     ProductId = 2 };coll.Add(prod);prod = new Product()  { ProductName = "Introduction to Windows Phone Development",    ProductId = 3 };coll.Add(prod);prod = new Product()   { ProductName = "Architecting a Business  …",     ProductId = 4 };coll.Add(prod);......   Figure 1: Class without overriding ToString() Now, go back to the Product class and add an override of the ToString() method as shown in the code listed below: public class Product{  public string ProductName { get; set; }  public int ProductId { get; set; }   public override string ToString()  {    return ProductName;  }} In this simple sample, I am just returning the ProductName property. However, you can create a whole string of information if you wish to display more data in your data tips. Just concatenate any properties you want from your class and return that string. When you now run the application and hover over the collection object you will now see something that looks like Figure 2. Figure 2: Overriding ToString() in your Class Another place the ToString() override comes in handy is if you forget to use a DisplayMemberPath in your ListBox or ComboBox. The ToString() method is called automatically when a class is bound to a list control. Summary You should always override the ToString() method in your classes as this will help you when debugging your application. Seeing relevant data immediately in the data tip without having to drill down one more layer and maybe scroll through a complete list of properties should help speed up your development process. NOTE: You can download the sample code for this article by visiting my website at http://www.pdsa.com/downloads. Select “Tips & Tricks”, then select “Override ToString” from the drop down list.  

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• Recent improvements in Console Performance

  - by loren.konkus

  Recently, the WebLogic Server development and support organizations have worked with a number of customers to quantify and improve the performance of the Administration Console in large, distributed configurations where there is significant latency in the communications between the administration server and managed servers. These improvements fall into two categories: Constraining the amount of time that the Console stalls waiting for communication Reducing and streamlining the amount of data required for an update A few releases ago, we added support for a configurable domain-wide mbean "Invocation Timeout" value on the Console's configuration: general, advanced section for a domain. The default value for this setting is 0, which means wait indefinitely and was chosen for compatibility with the behavior of previous releases. This configuration setting applies to all mbean communications between the admin server and managed servers, and is the first line of defense against being blocked by a stalled or completely overloaded managed server. Each site should choose an appropriate timeout value for their environment and network latency. In the next release of WebLogic Server, we've added an additional console preference, "Management Operation Timeout", to the Console's shared preference page. This setting further constrains how long certain console pages will wait for slowly responding servers before returning partial results. While not all Console pages support this yet, key pages such as the Servers Configuration and Control table pages and the Deployments Control pages have been updated to support this. For example, if a user requests a Servers Table page and a Management Operation Timeout occurs, the table is displayed with both local configuration and remote runtime information from the responding managed servers and only local configuration information for servers that did not yet respond. This means that a troublesome managed server does not impede your ability to manage your domain using the Console. To support these changes, these Console pages have been re-written to use the Work Management feature of WebLogic Server to interact with each server or deployment concurrently, which further improves the responsiveness of these pages. The basic algorithm for these pages is: For each configuration mbean (ie, Servers) populate rows with configuration attributes from the fast, local mbean server Find a WorkManager For each server, Create a Work instance to obtain runtime mbean attributes for the server Schedule Work instance in the WorkManager Call WorkManager.waitForAll to wait WorkItems to finish, constrained by Management Operation Timeout For each WorkItem, if the runtime information obtained was not complete, add a message indicating which server has incomplete data Display collected data in table In addition to these changes to constrain how long the console waits for communication, a number of other changes have been made to reduce the amount and scope of managed server interactions for key pages. For example, in previous releases the Deployments Control table looked at the status of a deployment on every managed server, even those servers that the deployment was not currently targeted on. (This was done to handle an edge case where a deployment's target configuration was changed while it remained running on previously targeted servers.) We decided supporting that edge case did not warrant the performance impact for all, and instead only look at the status of a deployment on the servers it is targeted to. Comprehensive status continues to be available if a user clicks on the 'status' field for a deployment. Finally, changes have been made to the System Status portlet to reduce its impact on Console page display times. Obtaining health information for this display requires several mbean interactions with managed servers. In previous releases, this mbean interaction occurred with every display, and any delay or impediment in these interactions was reflected in the display time for every page. To reduce this impact, we've made several changes in this portlet: Using Work Management to obtain health concurrently Applying the operation timeout configuration to constrain how long we will wait Caching health information to reduce the cost during rapid navigation from page to page and only obtaining new health information if the previous information is over 30 seconds old. Eliminating heath collection if this portlet is minimized. Together, these Console changes have resulted in significant performance improvements for the customers with large configurations and high latency that we have worked with during their development, and some lesser performance improvements for those with small configurations and very fast networks. These changes will be included in the 11g Rel 1 patch set 2 (10.3.3.0) release of WebLogic Server.

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• Free RAM disappears - Memory leak?

  - by Izzy

  On a fresh started system, free reports about 1.5G used RAM (8G RAM alltogether, Ubuntu 12.04 with lightdm and plasma desktop, one konsole window started). Having the apps running I use, it still consumes not more than 2G. However, having the system running for a couple of days, more and more of my free RAM disappears -- without showing up in the list of used apps: while smem --pie=name reports less than 20% used (and 80% being available), everything else says differently. free -m for example reports on about day 7: total used free shared buffers cached Mem: 7459 7013 446 0 178 997 -/+ buffers/cache: 5836 1623 Swap: 9536 296 9240 (so you can see, it's not the buffers or the cache). Today this finally ended with the system crashing completely: the windows manager being gone, apps "hanging in the air" (frameless) -- and a popup notifying me about "too many open files". Syslog reports: kernel: [856738.020829] VFS: file-max limit 752838 reached So I closed those applications I was able to close, and killed X using Ctrl-Alt-backspace. X tried to come up again after that with failsafeX, but was unable to do so as it could no longer detect its configuration. So I switched to a console using Ctrl-Alt-F2, captured all information I could think of (vmstat, free, smem, proc/meminfo, lsof, ps aux), and finally rebooted. X again came up with failsafeX; this time I told it to "recover from my backed-up configuration", then switched to a console and successfully used startx to bring up the graphical environment. I have no real clue to what is causing this issue -- though it must have to do either with X itself, or with some user processes running on X -- as after killing X, free -m output looked like this: total used free shared buffers cached Mem: 7459 2677 4781 0 62 419 -/+ buffers/cache: 2195 5263 Swap: 9536 59 9477 (~3.5GB being freed) -- to compare with the output after a fresh start: total used free shared buffers cached Mem: 7459 1483 5975 0 63 730 -/+ buffers/cache: 689 6769 Swap: 9536 0 9536 Two more helpful outputs are provided by memstat -u. Shortly before the crash: User Count Swap USS PSS RSS mail 1 0 200 207 616 whoopsie 1 764 740 817 2300 colord 1 3200 836 894 2156 root 62 70404 352996 382260 569920 izzy 80 177508 1465416 1519266 1851840 After having X killed: User Count Swap USS PSS RSS mail 1 0 184 188 356 izzy 1 1400 708 739 1080 whoopsie 1 848 668 826 1772 colord 1 3204 804 888 1728 root 62 54876 131708 149950 267860 And after a restart, back in X: User Count Swap USS PSS RSS mail 1 0 212 217 628 whoopsie 1 0 1536 1880 5096 colord 1 0 3740 4217 7936 root 54 0 148668 180911 345132 izzy 47 0 370928 437562 915056 Edit: Just added two graphs from my monitoring system. Interesting to see: everytime when there's a "jump" in memory consumption, CPU peaks as well. Just found this right now -- and it reminds me of another indicator pointing to X itself: Often when returning to my machine and unlocking the screen, I found something doing heavvy work on my CPU. Checking with top, it always turned out to be /usr/bin/X :0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch -background none. So after this long explanation, finally my questions: What could be the possible causes? How can I better identify involved processes/applications? What steps could be taken to avoid this behaviour -- short from rebooting the machine all X days? I was running 8.04 (Hardy) for about 5 years on my old machine, never having experienced the like (always more than 100 days uptime, before rebooting for e.g. kernel updates). This now is a complete new machine with a fresh install of 8.04. In case it matters, some specs: AMD A4-3400 APU with Radeon(tm) HD Graphics, using the open-source ati/radeon driver (so no fglrx installed), 8GB RAM, WDC WD1002FAEX-0 hdd (1TB), Asus F1A75-V Evo mainboard. Ubuntu 12.04 64-bit with KDE4/Plasma. Apps usually open more or less permanently include Evolution, Firefox, konsole (with Midnight Commander running inside, about 4 tabs), and LibreOffice -- plus occasionally Calibre, Gimp and Moneyplex (banking software I'm already using for almost 20 years now, in a version which did fine on Hardy).

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• Big Data – Operational Databases Supporting Big Data – Columnar, Graph and Spatial Database – Day 14 of 21

  - by Pinal Dave

  In yesterday’s blog post we learned the importance of the Key-Value Pair Databases and Document Databases in the Big Data Story. In this article we will understand the role of Columnar, Graph and Spatial Database supporting Big Data Story. Now we will see a few of the examples of the operational databases. Relational Databases (The day before yesterday’s post) NoSQL Databases (The day before yesterday’s post) Key-Value Pair Databases (Yesterday’s post) Document Databases (Yesterday’s post) Columnar Databases (Tomorrow’s post) Graph Databases (Today’s post) Spatial Databases (Today’s post) Columnar Databases  Relational Database is a row store database or a row oriented database. Columnar databases are column oriented or column store databases. As we discussed earlier in Big Data we have different kinds of data and we need to store different kinds of data in the database. When we have columnar database it is very easy to do so as we can just add a new column to the columnar database. HBase is one of the most popular columnar databases. It uses Hadoop file system and MapReduce for its core data storage. However, remember this is not a good solution for every application. This is particularly good for the database where there is high volume incremental data is gathered and processed. Graph Databases For a highly interconnected data it is suitable to use Graph Database. This database has node relationship structure. Nodes and relationships contain a Key Value Pair where data is stored. The major advantage of this database is that it supports faster navigation among various relationships. For example, Facebook uses a graph database to list and demonstrate various relationships between users. Neo4J is one of the most popular open source graph database. One of the major dis-advantage of the Graph Database is that it is not possible to self-reference (self joins in the RDBMS terms) and there might be real world scenarios where this might be required and graph database does not support it. Spatial Databases  We all use Foursquare, Google+ as well Facebook Check-ins for location aware check-ins. All the location aware applications figure out the position of the phone with the help of Global Positioning System (GPS). Think about it, so many different users at different location in the world and checking-in all together. Additionally, the applications now feature reach and users are demanding more and more information from them, for example like movies, coffee shop or places see. They are all running with the help of Spatial Databases. Spatial data are standardize by the Open Geospatial Consortium known as OGC. Spatial data helps answering many interesting questions like “Distance between two locations, area of interesting places etc.” When we think of it, it is very clear that handing spatial data and returning meaningful result is one big task when there are millions of users moving dynamically from one place to another place & requesting various spatial information. PostGIS/OpenGIS suite is very popular spatial database. It runs as a layer implementation on the RDBMS PostgreSQL. This makes it totally unique as it offers best from both the worlds. Courtesy: mushroom network Tomorrow In tomorrow’s blog post we will discuss about very important components of the Big Data Ecosystem – Hive. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Big Data, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL

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• Heading out to Dallas GiveCamp 2011

  - by dotgeek

  The day has finally arrived for twelve local charities here in the Dallas area, when they’ll get some help from various local Developers with their website initiative needs at this years Dallas GiveCamp. I’m really looking forward to helping out at this year event and what I hope will be the start of many more GiveCamps to follow. Similar to Habitat for Humanity, where people gather to help build and improve homes for people in need, GiveCamp brings together programmers and equips them with the virtual tools they need to build and improve their existing websites. Tonight is when things will kickoff for this weekends events and teams will start working on their various projects. The building continues on through the night then and all the way through until Sunday afternoon. The end goal for the teams and charities is to have a completed and working website for each charity to begin using and turn over all the production code and digital assets to them. None of this would be possible with out the great sponsors we have returning once again and their donations of various products to help these charities out with their projects, like Telerik's CMS product Sitefinity 4.0, paired with a year of hosting from Verio to mention just a few of them. Just like the skilled builders who might help train volunteers in the use of a nail gun in building a house. Training is also available here on site for the Developers and these local Charities. Giving them all the skills in how to manage and use these products, from site development and then into actual production is a key to the success of this weekends event.     Tonight's training sessions will kick off with a real treat from Giovanni Gallucci, as he speaks about Social Media for NPOs and then later Gabe Sumner from Telerik will begin a training session on Sitefinity for Developers. These training sessions will continue through out the weekend with .Net Nuke and Mojo Portal sessions also planned as well. If you’re a developer and would like to help out in the future, then check in your area and with your local User Groups to find out if you already have a GiveCamp near you to help out. If you don’t have one available, then consider starting up a local GiveCamp and then you too can help Code it Forward. About GiveCamp GiveCamp is a weekend-long event where software developers, designers, and database administrators donate their time to create custom software for non-profit organizations. This custom software could be a new website for the nonprofit organization, a small data-collection application to keep track of members, or a application for the Red Cross that automatically emails a blood donor three months after they’ve donated blood to remind them that they are now eligible to donate again. The only limitation is that the project should be scoped to be able to be completed in a weekend. During GiveCamp, developers are welcome to go home in the evenings or camp out all weekend long. There are usually food and drink provided at the event. There are sometimes even game systems set up for when you and your need a little break! Overall, it’s a great opportunity for people to work together, developing new friendships, and doing something important for their community. At GiveCamp, there is an expectation of “What Happens at GiveCamp, Stays at GiveCamp”. Therefore, all source code must be turned over to the charities at the end of the weekend (developers cannot ask for payment) and the charities are responsible for maintaining the code moving forward (charities cannot expect the developers to maintain the codebase).

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• Subterranean IL: Compiling C# exception handlers

  - by Simon Cooper

  An exception handler in C# combines the IL catch and finally exception handling clauses into a single try statement: try { Console.WriteLine("Try block") // ... } catch (IOException) { Console.WriteLine("IOException catch") // ... } catch (Exception e) { Console.WriteLine("Exception catch") // ... } finally { Console.WriteLine("Finally block") // ... } How does this get compiled into IL? Initial implementation If you remember from my earlier post, finally clauses must be specified with their own .try clause. So, for the initial implementation, we take the try/catch/finally, and simply split it up into two .try clauses (I have to use label syntax for this): StartTry: ldstr "Try block" call void [mscorlib]System.Console::WriteLine(string) // ... leave.s End EndTry: StartIOECatch: ldstr "IOException catch" call void [mscorlib]System.Console::WriteLine(string) // ... leave.s End EndIOECatch: StartECatch: ldstr "Exception catch" call void [mscorlib]System.Console::WriteLine(string) // ... leave.s End EndECatch: StartFinally: ldstr "Finally block" call void [mscorlib]System.Console::WriteLine(string) // ... endfinally EndFinally: End: // ... .try StartTry to EndTry catch [mscorlib]System.IO.IOException handler StartIOECatch to EndIOECatch catch [mscorlib]System.Exception handler StartECatch to EndECatch .try StartTry to EndTry finally handler StartFinally to EndFinally However, the resulting program isn't verifiable, and doesn't run: [IL]: Error: Shared try has finally or fault handler. Nested try blocks What's with the verification error? Well, it's a condition of IL verification that all exception handling regions (try, catch, filter, finally, fault) of a single .try clause have to be completely contained within any outer exception region, and they can't overlap with any other exception handling clause. In other words, IL exception handling clauses must to be representable in the scoped syntax, and in this example, we're overlapping catch and finally clauses. Not only is this example not verifiable, it isn't semantically correct. The finally handler is specified round the .try. What happens if you were able to run this code, and an exception was thrown? Program execution enters top of try block, and exception is thrown within it CLR searches for an exception handler, finds catch Because control flow is leaving .try, finally block is run The catch block is run leave.s End inside the catch handler branches to End label. We're actually running the finally before the catch! What we do about it What we actually need to do is put the catch clauses inside the finally clause, as this will ensure the finally gets executed at the correct time (this time using scoped syntax): .try { .try { ldstr "Try block" call void [mscorlib]System.Console::WriteLine(string) // ... leave.s End } catch [mscorlib]System.IO.IOException { ldstr "IOException catch" call void [mscorlib]System.Console::WriteLine(string) // ... leave.s End } catch [mscorlib]System.Exception { ldstr "Exception catch" call void [mscorlib]System.Console::WriteLine(string) // ... leave.s End } } finally { ldstr "Finally block" call void [mscorlib]System.Console::WriteLine(string) // ... endfinally } End: ret Returning from methods There is a further semantic mismatch that the C# compiler has to deal with; in C#, you are allowed to return from within an exception handling block: public int HandleMethod() { try { // ... return 0; } catch (Exception) { // ... return -1; } } However, you can't ret inside an exception handling block in IL. So the C# compiler does a leave.s to a ret outside the exception handling area, loading/storing any return value to a local variable along the way (as leave.s clears the stack): .method public instance int32 HandleMethod() { .locals init ( int32 retVal ) .try { // ... ldc.i4.0 stloc.0 leave.s End } catch [mscorlib]System.Exception { // ... ldc.i4.m1 stloc.0 leave.s End } End: ldloc.0 ret } Conclusion As you can see, the C# compiler has quite a few hoops to jump through to translate C# code into semantically-correct IL, and hides the numerous conditions on IL exception handling blocks from the C# programmer. Next up: catch-all blocks, and how the runtime deals with non-Exception exceptions.

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• Flow-Design Cheat Sheet &ndash; Part II, Translation

  - by Ralf Westphal

  In my previous post I summarized the notation for Flow-Design (FD) diagrams. Now is the time to show you how to translate those diagrams into code. Hopefully you feel how different this is from UML. UML leaves you alone with your sequence diagram or component diagram or activity diagram. They leave it to you how to translate your elaborate design into code. Or maybe UML thinks it´s so easy no further explanations are needed? I don´t know. I just know that, as soon as people stop designing with UML and start coding, things end up to be very different from the design. And that´s bad. That degrades graphical designs to just time waste on paper (or some designer). I even believe that´s the reason why most programmers view textual source code as the only and single source of truth. Design and code usually do not match. FD is trying to change that. It wants to make true design a first class method in every developers toolchest. For that the first prerequisite is to be able to easily translate any design into code. Mechanically, without thinking. Even a compiler could do it :-) (More of that in some other article.) Translating to Methods The first translation I want to show you is for small designs. When you start using FD you should translate your diagrams like this. Functional units become methods. That´s it. An input-pin becomes a method parameter, an output-pin becomes a return value: The above is a part. But a board can be translated likewise and calls the nested FUs in order: In any case be sure to keep the board method clear of any and all business logic. It should not contain any control structures like if, switch, or a loop. Boards do just one thing: calling nested functional units in proper sequence. What about multiple input-pins? Try to avoid them. Replace them with a join returning a tuple: What about multiple output-pins? Try to avoid them. Or return a tuple. Or use out-parameters: But as I said, this simple translation is for simple designs only. Splits and joins are easily done with method translation: All pretty straightforward, isn´t it. But what about wires, named pins, entry points, explicit dependencies? I suggest you don´t use this kind of translation when your designs need these features. Translating to methods is for small scale designs like you might do once you´re working on the implementation of a part of a larger design. Or maybe for a code kata you´re doing in your local coding dojo. Instead of doing TDD try doing FD and translate your design into methods. You´ll see that way it´s much easier to work collaboratively on designs, remember them more easily, keep them clean, and lessen the need for refactoring. Translating to Events [coming soon]

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• CacheAdapter 2.4 – Bug fixes and minor functional update

  - by Glav

  Note: If you are unfamiliar with the CacheAdapter library and what it does, you can read all about its awesome ability to utilise memory, Asp.Net Web, Windows Azure AppFabric and memcached caching implementations via a single unified, simple to use API from here and here.. The CacheAdapter library is receiving an update to version 2.4 and is currently available on Nuget here. Update: The CacheAdapter has actualy just had a minor revision to 2.4.1. This significantly increases the performance and reliability in memcached scenario under more extreme loads. General to moderate usage wont see any noticeable difference though. Bugs This latest version fixes a big that is only present in the memcached implementation and is only seen in rare, intermittent times (making i particularly hard to find). The bug is where a cache node would be removed from the farm when errors in deserialization of cached objects would occur due to serialised data not being read from the stream in entirety. The code also contains enhancements to better surface serialization exceptions to aid in the debugging process. This is also specifically targeted at the memcached implementation. This is important when moving from something like memory or Asp.Web caching mechanisms to memcached where the serialization rules are not as lenient. There are a few other minor bug fixes, code cleanup and a little refactoring. Minor feature addition In addition to this bug fix, many people have asked for a single setting to either enable or disable the cache.In this version, you can disable the cache by setting the IsCacheEnabled flag to false in the application configuration file. Something like the example below: <Glav.CacheAdapter.MainConfig> <setting name="CacheToUse" serializeAs="String"> <value>memcached</value> </setting> <setting name="DistributedCacheServers" serializeAs="String"> <value>localhost:11211</value> </setting> <setting name="IsCacheEnabled" serializeAs="String"> <value>False</value> </setting> </Glav.CacheAdapter.MainConfig> Your reasons to use this feature may vary (perhaps some performance testing or problem diagnosis). At any rate, disabling the cache will cause every attempt to retrieve data from the cache, resulting in a cache miss and returning null. If you are using the ICacheProvider with the delegate/Func<T> syntax to populate the cache, this delegate method will get executed every single time. For example, when the cache is disabled, the following delegate/Func<T> code will be executed every time: var data1 = cacheProvider.Get<SomeData>("cache-key", DateTime.Now.AddHours(1), () => { // With the cache disabled, this data access code is executed every attempt to // get this data via the CacheProvider. var someData = new SomeData() { SomeText = "cache example1", SomeNumber = 1 }; return someData; }); One final note: If you access the cache directly via the ICache instance, instead of the higher level ICacheProvider API, you bypass this setting and still access the underlying cache implementation. Only the ICacheProvider instance observes the IsCacheEnabled setting. Thanks to those individuals who have used this library and provided feedback. Ifyou have any suggestions or ideas, please submit them to the issue register on bitbucket (which is where you can grab all the source code from too)

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• Antenna Aligner Part 4: Role'ing in the deep

  - by Chris George

  Since last time I've been trying to sort out the general workflow of the app. It's fundamentally not hard, there is a list of transmitters, you select a transmitter and it shows the compass view. Having done quite a bit of ajax/asp.net/html in the past, I immediately started off by creating two divs within my 'page', one for the list, one for the compass. Then using the onClick event in the list, this will switch the display attribute on the divs. This seemed to work, but did lead to some dodgy transitional redrawing artefacts which I was not happy with. So after some Googling I realised I was doing it all wrong! JQuery mobile has the concept of giving an object in html a data-role. By giving a div the attribute data-role="page" it is then treated as a separate page on the mobile device. Within the code, this is referenced like a html anchor in the form #mypage. Using this system, page transitions such as fade or slide are automatically applied which adds to the whole authenticity of the app! Here is a simple example: . <a href="#'compasspage">compass</a> . <div data-role="page" id="compasspage" data-add-back-btn="true"> But I don't want just a static link, I want to dynamically create my list, and get each list elements to switch to the compass page with the right information. So here is the jquery that I used to dynamically inject new <li> rows into the <ul> block. $('ul').append($('<li/>', {    //here appendin `<li>`     'data-role': "list-divider" }).append($('<a/>', {    //here appending `<a>` into `<li>`     'href': '#compasspage',     'data-transition': 'none',     'onclick': 'selectTx(' + i + ')',     'html': buttonHtml }))); $('ul').listview('refresh'); This is called within a for loop so the first 5 appropriate transmitters are used. There are several things of interest to note here. Firstly, I could not find a more elegant way to tell the target page which transmitter I've clicked on, so I have used the onclick event as well as the href attribute. The onclick event fires 'selectTx' which simply sets a global member variable to the specific index number I've clicked on. Yes it's not nice, but it works. Secondly, the data-transition attribute is set to 'none'. I wanted the transition between the pages to be a whooshy slidey effect. However this worked going to the compass page, but returning to the list page gave some undesirable visual artefacts (flickering, redrawing etc.). So I decided to remove the transitions all together, which was a shame. Thirdly, rather than embedding loads of html into the append command, I removed this out into a variable 'buttonHtml'. Doing this really tidied up my code. Until next time!

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• SQLAuthority News – Advantages of Distance Learning

  - by Pinal Dave

  Distance education is extremely popular – almost overnight, it seems.  Almost everyone has taken an online course, or knows someone who has, or is considering joining an online school.  There are many advantages and disadvantages to attending an online school – but the same can be said of attending a physical school!  Let’s take a look at the top reasons to use distance education. 1) Flexibility.  Physical universities are usually willing to make some concessions to student – like night classes, study hours, and online networks.  However, nothing is going to beat the flexibility of distance education.  You can attend classes and take notes anytime, anywhere, wearing anything you’d like! 2) Affordability.  We don’t need to get into hard numbers to understand how an expensive university can be.  Students are taking on more and more debt just to get an education.  Many of these fees pay for room, board, and facilities.   Distance education cuts out all these costs, and makes attending school much more affordable for the average student. 3) Try before you buy.  Did you know that the average college student changes his or her major 10 times before they graduate?  You can imagine that this kind of indecision plays a huge part in WHEN you graduate – not being able to make up your mind can cost you big bucks if you have to stay in school for extra years!  Distance education allows you to take different classes from a wide range of disciplines.  Do you want to study forensic science or English literature?  Now you don’t have to pay for classes you can’t afford just to find out. 4) Pace yourself.  Some students struggle in a traditional classroom setting – classes can be taught too fast, too slow, or there are too many distractions.  Distance education allows mature students to set the pace themselves.  They can rewatch lectures they didn’t catch the first time, or go through classes quickly if they are already familiar with the material – cutting out the chance of burning out or getting bored. 5) Lifelong learning.  Maybe you already have a degree, but would like to learn more about your field, or a related field, or maybe even about something completely unrelated – just because you are curious!  Distance education allows you to learn whatever you want ,whenever you want (and yes, wearing anything you’d like!). 6) Attend whatever college you want.  Because of the popularity of distance education, physical campuses are getting in on the game by offering online courses – often just uploaded versions of classes already taught at their campus.  Ever wanted to attend Harvard, but knew you couldn’t get in?  Take a class online!  Of course, you probably should not attempt to lie and say you have a Harvard degree, but Ivy League colleges are prestigious because they are the best in their field – take advantage of the best by taking an online course! I am a big believer in continuing education, whether it is online courses, returning to school, or even take informal classes online.  Distance education can be a great way to accomplish these goals and become a lifelong learner. My friends at provides training through virtual classrooms for students who want to avoid travelling. Distance learning course allows IT aspirants to connect with trainers using the internet.  I encourage everyone to check it out! Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQL Training, T SQL, Technology

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• Synchronous Actions

  - by Dan Krasinski-Oracle

  Since the introduction of SMF, svcadm(1M) has had the ability to enable or disable a service instance and wait for that service instance to reach a final state.  With Oracle Solaris 11.2, we’ve expanded the set of administrative actions which can be invoked synchronously. Now all subcommands of svcadm(1M) have synchronous behavior. Let’s take a look at the new usage: Usage: svcadm [-v] [cmd [args ... ]] svcadm enable [-rt] [-s [-T timeout]] <service> ... enable and online service(s) svcadm disable [-t] [-s [-T timeout]] <service> ... disable and offline service(s) svcadm restart [-s [-T timeout]] <service> ... restart specified service(s) svcadm refresh [-s [-T timeout]] <service> ... re-read service configuration svcadm mark [-It] [-s [-T timeout]] <state> <service> ... set maintenance state svcadm clear [-s [-T timeout]] <service> ... clear maintenance state svcadm milestone [-d] [-s [-T timeout]] <milestone> advance to a service milestone svcadm delegate [-s] <restarter> <svc> ... delegate service to a restarter As you can see, each subcommand now has a ‘-s’ flag. That flag tells svcadm(1M) to wait for the subcommand to complete before returning. For enables, that means waiting until the instance is either ‘online’ or in the ‘maintenance’ state. For disable, the instance must reach the ‘disabled’ state. Other subcommands complete when: restart A restart is considered complete once the instance has gone offline after running the ‘stop’ method, and then has either returned to the ‘online’ state or has entered the ‘maintenance’ state. refresh If an instance is in the ‘online’ state, a refresh is considered complete once the ‘refresh’ method for the instance has finished. mark maintenance Marking an instance for maintenance completes when the instance has reached the ‘maintenance’ state. mark degraded Marking an instance as degraded completes when the instance has reached the ‘degraded’ state from the ‘online’ state. milestone A milestone transition can occur in one of two directions. Either the transition moves from a lower milestone to a higher one, or from a higher one to a lower one. When moving to a higher milestone, the transition is considered complete when the instance representing that milestone reaches the ‘online’ state. The transition to a lower milestone, on the other hand, completes only when all instances which are part of higher milestones have reached the ‘disabled’ state. That’s not the whole story. svcadm(1M) will also try to determine if the actions initiated by a particular subcommand cannot complete. Trying to enable an instance which does not have its dependencies satisfied, for example, will cause svcadm(1M) to terminate before that instance reaches the ‘online’ state. You’ll also notice the optional ‘-T’ flag which can be used in conjunction with the ‘-s’ flag. This flag sets a timeout, in seconds, after which svcadm gives up on waiting for the subcommand to complete and terminates. This is useful in many cases, but in particular when the start method for an instance has an infinite timeout but might get stuck waiting for some resource that may never become available. For the C-oriented, each of these administrative actions has a corresponding function in libscf(3SCF), with names like smf_enable_instance_synchronous(3SCF) and smf_restart_instance_synchronous(3SCF).  Take a look at smf_enable_instance_synchronous(3SCF) for details.

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• Designing An ACL Based Permission System

  - by ryanzec

  I am trying to create a permissions system where everything is going to be stored in MySQL (or some database) and pulled using PHP for a project management system I am building.  I am right now trying to do it is an ACL kind of way.  There are a number key features I want to be able to support: 1.  Being able to assign permissions without being tied to a specific object. The reason for this is that I want to be able to selectively show/hide elements of the UI based on permissions at a point where I am not directly looking at a domain object instance.  For instance, a button to create a new project should only should only be shown to users that have the pm.project.create permission but obviously you can assign a create permission to an domain object instance (as it is already created). 2.  Not have to assign permissions for every single object. Obviously creating permissions entries for every single object (projects, tickets, comments, etc…) would become a nightmare to maintain so I want to have some level of permission inheritance. *3.  Be able to filter queries based on permissions. This would be a really nice to have but I am not sure if it is possible.  What I mean by this is say I have a page that list all projects.  I want the query that pulls all projects to incorporate the ACL so that it would not show projects that the current user does not have pm.project.read access to.  This would have to be incorporated into the main query as if it is a process that is done after that main query (which I know I could do) certain features like pagination become much more difficult. Right now this is my basic design for the tables: AclEntities id - the primary key key - the unique identifier for the domain object (usually the primary key of that object) parentId - the parent of the domain object (like the project object if this was a ticket object) aclDomainObjectId - metadata about the domain object AclDomainObjects id - primary key title - simple string to unique identify the domain object(ie. project, ticket, comment, etc…) fullyQualifiedClassName - the fully qualified class name for use in code (I am using namespaces) There would also be tables mapping AclEntities to Users and UserGroups. I also have this interface that all acl entity based object have to implement: IAclEntity getAclKey() - to the the unique key for this specific instance of the acl domain object (generally return the primary key or a concatenated string of a composite primary key) getAclTitle() - to get the unique title for the domain object (generally just returning a static string) getAclDisplayString() - get the string that represents this entity (generally one or more field on the object) getAclParentEntity() - get the parent acl entity object (or null if no parent) getAclEntity() - get the acl enitty object for this instance of the domain object (or null if one has not been created yet) hasPermission($permissionString, $user = null) - whether or not the user has the permission for this instance of the domain object static getFromAclEntityId($aclEntityId) - get a specific instance of the domain object from an acl entity id. Do any of these features I am looking for seems hard to support or are just way off base? Am I missing or not taking in account anything in my implementation? Is performance something I should keep in mind?

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• Strings in .NET are Enumerable

  - by Scott Dorman

  It seems like there is always some confusion concerning strings in .NET. This is both from developers who are new to the Framework and those that have been working with it for quite some time. Strings in the .NET Framework are represented by the System.String class, which encapsulates the data manipulation, sorting, and searching methods you most commonly perform on string data. In the .NET Framework, you can use System.String (which is the actual type name or the language alias (for C#, string). They are equivalent so use whichever naming convention you prefer but be consistent. Common usage (and my preference) is to use the language alias (string) when referring to the data type and String (the actual type name) when accessing the static members of the class. Many mainstream programming languages (like C and C++) treat strings as a null terminated array of characters. The .NET Framework, however, treats strings as an immutable sequence of Unicode characters which cannot be modified after it has been created. Because strings are immutable, all operations which modify the string contents are actually creating new string instances and returning those. They never modify the original string data. There is one important word in the preceding paragraph which many people tend to miss: sequence. In .NET, strings are treated as a sequence…in fact, they are treated as an enumerable sequence. This can be verified if you look at the class declaration for System.String, as seen below: // Summary:// Represents text as a series of Unicode characters.public sealed class String : IEnumerable, IComparable, IComparable<string>, IEquatable<string> The first interface that String implements is IEnumerable, which has the following definition: // Summary:// Exposes the enumerator, which supports a simple iteration over a non-generic// collection.public interface IEnumerable{ // Summary: // Returns an enumerator that iterates through a collection. // // Returns: // An System.Collections.IEnumerator object that can be used to iterate through // the collection. IEnumerator GetEnumerator();} As a side note, System.Array also implements IEnumerable. Why is that important to know? Simply put, it means that any operation you can perform on an array can also be performed on a string. This allows you to write code such as the following: string s = "The quick brown fox";foreach (var c in s){ System.Diagnostics.Debug.WriteLine(c);}for (int i = 0; i < s.Length; i++){ System.Diagnostics.Debug.WriteLine(s[i]);} If you executed those lines of code in a running application, you would see the following output in the Visual Studio Output window: In the case of a string, these enumerable or array operations return a char (System.Char) rather than a string. That might lead you to believe that you can get around the string immutability restriction by simply treating strings as an array and assigning a new character to a specific index location inside the string, like this: string s = "The quick brown fox";s[2] = 'a';   However, if you were to write such code, the compiler will promptly tell you that you can’t do it: This preserves the notion that strings are immutable and cannot be changed once they are created. (Incidentally, there is no built in way to replace a single character like this. It can be done but it would require converting the string to a character array, changing the appropriate indexed location, and then creating a new string.)

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• Arcball Problems with UDK

  - by opdude

  I'm trying to re-create an arcball example from a Nehe, where an object can be rotated in a more realistic way while floating in the air (in my game the object is attached to the player at a distance like for example the Physics Gun) however I'm having trouble getting this to work with UDK. I have created an LGArcBall which follows the example from Nehe and I've compared outputs from this with the example code. I think where my problem lies is what I do to the Quaternion that is returned from the LGArcBall. Currently I am taking the returned Quaternion converting it to a rotation matrix. Getting the product of the last rotation (set when the object is first clicked) and then returning that into a Rotator and setting that to the objects rotation. If you could point me in the right direction that would be great, my code can be found below. class LGArcBall extends Object; var Quat StartRotation; var Vector StartVector; var float AdjustWidth, AdjustHeight, Epsilon; function SetBounds(float NewWidth, float NewHeight) { AdjustWidth = 1.0f / ((NewWidth - 1.0f) * 0.5f); AdjustHeight = 1.0f / ((NewHeight - 1.0f) * 0.5f); } function StartDrag(Vector2D startPoint, Quat rotation) { StartVector = MapToSphere(startPoint); } function Quat Update(Vector2D currentPoint) { local Vector currentVector, perp; local Quat newRot; //Map the new point to the sphere currentVector = MapToSphere(currentPoint); //Compute the vector perpendicular to the start and current perp = startVector cross currentVector; //Make sure our length is larger than Epsilon if (VSize(perp) > Epsilon) { //Return the perpendicular vector as the transform newRot.X = perp.X; newRot.Y = perp.Y; newRot.Z = perp.Z; //In the quaternion values, w is cosine (theta / 2), where //theta is the rotation angle newRot.W = startVector dot currentVector; } else { //The two vectors coincide, so return an identity transform newRot.X = 0.0f; newRot.Y = 0.0f; newRot.Z = 0.0f; newRot.W = 0.0f; } return newRot; } function Vector MapToSphere(Vector2D point) { local float x, y, length, norm; local Vector result; //Transform the mouse coords to [-1..1] //and inverse the Y coord x = (point.X * AdjustWidth) - 1.0f; y = 1.0f - (point.Y * AdjustHeight); length = (x * x) + (y * y); //If the point is mapped outside of the sphere //( length > radius squared) if (length > 1.0f) { norm = 1.0f / Sqrt(length); //Return the "normalized" vector, a point on the sphere result.X = x * norm; result.Y = y * norm; result.Z = 0.0f; } else //It's inside of the sphere { //Return a vector to the point mapped inside the sphere //sqrt(radius squared - length) result.X = x; result.Y = y; result.Z = Sqrt(1.0f - length); } return result; } DefaultProperties { Epsilon = 0.000001f } I'm then attempting to rotate that object when the mouse is dragged, with the following update code in my PlayerController. //Get Mouse Position MousePosition.X = LGMouseInterfacePlayerInput(PlayerInput).MousePosition.X; MousePosition.Y = LGMouseInterfacePlayerInput(PlayerInput).MousePosition.Y; newQuat = ArcBall.Update(MousePosition); rotMatrix = MakeRotationMatrix(QuatToRotator(newQuat)); rotMatrix = rotMatrix * LastRot; LGMoveableActor(movingPawn.CurrentUseableObject).SetPhysics(EPhysics.PHYS_Rotating); LGMoveableActor(movingPawn.CurrentUseableObject).SetRotation(MatrixGetRotator(rotMatrix));

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• Antenna Aligner Part 4: Role'ing in the deep

  - by Chris George

  Since last time I've been trying to sort out the general workflow of the app. It's fundamentally not hard, there is a list of transmitters, you select a transmitter and it shows the compass view. Having done quite a bit of ajax/asp.net/html in the past, I immediately started off by creating two divs within my 'page', one for the list, one for the compass. Then using the onClick event in the list, this will switch the display attribute on the divs. This seemed to work, but did lead to some dodgy transitional redrawing artefacts which I was not happy with. So after some Googling I realised I was doing it all wrong! JQuery mobile has the concept of giving an object in html a data-role. By giving a div the attribute data-role="page" it is then treated as a separate page on the mobile device. Within the code, this is referenced like a html anchor in the form #mypage. Using this system, page transitions such as fade or slide are automatically applied which adds to the whole authenticity of the app! Here is a simple example: . <a href="#'compasspage">compass</a> . <div data-role="page" id="compasspage" data-add-back-btn="true"> But I don't want just a static link, I want to dynamically create my list, and get each list elements to switch to the compass page with the right information. So here is the jquery that I used to dynamically inject new <li> rows into the <ul> block. $('ul').append($('<li/>', {    //here appendin `<li>`     'data-role': "list-divider" }).append($('<a/>', {    //here appending `<a>` into `<li>`     'href': '#compasspage',     'data-transition': 'none',     'onclick': 'selectTx(' + i + ')',     'html': buttonHtml }))); $('ul').listview('refresh'); This is called within a for loop so the first 5 appropriate transmitters are used. There are several things of interest to note here. Firstly, I could not find a more elegant way to tell the target page which transmitter I've clicked on, so I have used the onclick event as well as the href attribute. The onclick event fires 'selectTx' which simply sets a global member variable to the specific index number I've clicked on. Yes it's not nice, but it works. Secondly, the data-transition attribute is set to 'none'. I wanted the transition between the pages to be a whooshy slidey effect. However this worked going to the compass page, but returning to the list page gave some undesirable visual artefacts (flickering, redrawing etc.). So I decided to remove the transitions all together, which was a shame. Thirdly, rather than embedding loads of html into the append command, I removed this out into a variable 'buttonHtml'. Doing this really tidied up my code. Until next time!

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• Best triple head display setup

  - by dgel

  I'm currently running Ubuntu 12.04 with a darn good triple head display setup. I've got a VisionTek 900530 Radeon HD 5450 512MB DDR3 PCI Express video card that has two DVI outputs and one Mini DisplayPort that I have connected to a HDMI adapter. I'm running three identical Asus 1920x1080 monitors that each have a DVI, VGA, and HDMI input. I'm using the xorg-edgers ppa, so I'm using the open source radeon driver version 6.99.99. I tried using the ATI binary fglrx driver, but I wasn't able to get the three monitors working properly- the monitor connected via HDMI / DisplayPort wouldn't run at full resolution. The setup is almost perfect: Compiz runs fine and is quite snappy. I'm not able to use that great compiz feature where you can drag a window to the side of a display and it will half maximize. I occasionally experience display corruption weirdness with Unity and need to restart it. When I use a dropdown menu in LibreOffice it often pops the menu down in another window. For example, if I'm using the center monitor and click the Insert menu, the menu pulls down on the monitor to my right, forcing me to chase it. If I chase down the menu and choose Manual Break, the dialog appears over on my left monitor. This absurdity is mildly entertaining but has lost its novelty. I've decided to build a new system and have spared no expense- latest i7 processor, SSD, etc. I really like the performance of the Nvidia binary drivers, so I put two ZOTAC ZT-40707-10L GeForce GT 440 in the system, figuring I'd have four DVI outputs and an awesome triple (or even eventually quad) head setup. Unfortunately it appears that I didn't do sufficient research before my purchase. It seems that Nvidia TwinView only supports two monitors on one card (I guess that's why they call it TwinView...). I messed around with running two X servers, but I really don't want that- being able to drag windows to any monitor is critical. It doesn't sound like Xinerama is an option because from what I understand it simply doesn't support Compiz. I've seen a BaseMosaic option that can be used with the Nvidia drivers that appears to support an almost unlimited number of heads- unfortunately me cheap little cards don't support it. I'm also not sure whether you'll still have all nice maximizing and snapping that TwinView provides, or whether Ubuntu will only see it as one massive display. I put my old trusty ATI card into my new system and installed 12.10. I'm using the opensource radeon drivers again because even in 12.10 I can't get the fglrx binary drivers to do triple head. Unfortunately, even with an unbelievably powerful system the experience is extremely sluggish (much more so than my experience in 12.04). The menu scattering problem appears to be fixed, but I get a lot of nasty Unity display corruption. So finally, my question is this: What hardware / drivers should I use? I'm willing to buy (almost) any video card(s). I have two PCI-Express 3.0 slots on my motherboard (which has an integrated Intel HD card). I'm willing to use ATI or Nvidia cards and willing to run Ubuntu 12.04.1 or 12.10. I'm not a gamer, but do want beautiful and snappy Compiz effects. Does anyone out there have the perfect triple head setup in 12.04 or 12.10? What hardware / drivers are you using? I have those two Nvidia cards but will probably be returning them unless someone knows a way to use them together for a triple head setup. Since I'm having pretty good luck with a single ATI card providing three displays, should I just buy a beefier one with the hopes that it will fix the horrible sluggishness I'm experiencing in 12.10?

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