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  • Why Content Should Be King of Your Business' Website

    You've no doubt heard that "content is king" on websites, but do you really know why? If your business website doesn't give visitors good, solid information they're going to leave your site and go to the next site that came up in their search engine results looking for the information you didn't provide. If they find it at your competitor's site, she'll probably get their business.

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  • Why lock statements don't scale

    - by Alex.Davies
    We are going to have to stop using lock statements one day. Just like we had to stop using goto statements. The problem is similar, they're pretty easy to follow in small programs, but code with locks isn't composable. That means that small pieces of program that work in isolation can't necessarily be put together and work together. Of course actors scale fine :) Why lock statements don't scale as software gets bigger Deadlocks. You have a program with lots of threads picking up lots of locks. You already know that if two of your threads both try to pick up a lock that the other already has, they will deadlock. Your program will come to a grinding halt, and there will be fire and brimstone. "Easy!" you say, "Just make sure all the threads pick up the locks in the same order." Yes, that works. But you've broken composability. Now, to add a new lock to your code, you have to consider all the other locks already in your code and check that they are taken in the right order. Algorithm buffs will have noticed this approach means it takes quadratic time to write a program. That's bad. Why lock statements don't scale as hardware gets bigger Memory bus contention There's another headache, one that most programmers don't usually need to think about, but is going to bite us in a big way in a few years. Locking needs exclusive use of the entire system's memory bus while taking out the lock. That's not too bad for a single or dual-core system, but already for quad-core systems it's a pretty large overhead. Have a look at this blog about the .NET 4 ThreadPool for some numbers and a weird analogy (see the author's comment). Not too bad yet, but I'm scared my 1000 core machine of the future is going to go slower than my machine today! I don't know the answer to this problem yet. Maybe some kind of per-core work queue system with hierarchical work stealing. Definitely hardware support. But what I do know is that using locks specifically prevents any solution to this. We should be abstracting our code away from the details of locks as soon as possible, so we can swap in whatever solution arrives when it does. NAct uses locks at the moment. But my advice is that you code using actors (which do scale well as software gets bigger). And when there's a better way of implementing actors that'll scale well as hardware gets bigger, only NAct needs to work out how to use it, and your program will go fast on it's own.

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  • Why Clonezilla needs to reinstall grub?

    - by Pablo
    By default CloneZilla Live will reinstall grub after restore. In my particular case I am restoring a disk image to same phisical disk without any partitioning/size change. I am expecting to have exact same state as I had right after backup. However, reinstalling grub will render my system to unbootable. If I remove that option [-g] then everything is fine. My question is in what cases and why CloneZilla ever need to re-install grub when restoring disk image?

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  • why I can not install Gphpedit

    - by Mohamed Samir Khalil
    why I can not install Gphpedit and I get this errors: Failed to fetch //http://security.ubuntu.com/ubuntu/pool/main/w/webkit/libjavascriptcoregtk-1.0-0_1.8.1-0ubuntu0.12.04.1_amd64.deb 404 Not Found [IP: 91.189.92.190 80] Failed to fetch //http://security.ubuntu.com/ubuntu/pool/main/w/webkit/libwebkitgtk-1.0-common_1.8.1-0ubuntu0.12.04.1_all.deb 404 Not Found [IP: 91.189.92.190 80] Failed to fetch //http://security.ubuntu.com/ubuntu/pool/main/w/webkit/libwebkitgtk-1.0-0_1.8.1-0ubuntu0.12.04.1_amd64.deb 404 Not Found [IP: 91.189.92.190 80]

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  • Why it is so difficult to find a good Ads SDK for Windows Phone 7

    - by help.net
    This post try to address an issue with the Microsoft Advertising SDK, the main fact that today Microsoft is still refusing access to the Ad Center worldwide. Yesterday they generously increase the number of free apps we can develop from 5 to 100. According to talks with other developers and the Windows Phone 7 team, I have the strong feeling the model of publishing free apps supported by apps is the right course to take today. This probably why Microsoft has moved to a bigger figure. Am I the only...(read more)

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  • Why should you document code?

    - by Edwin Tripp
    I am a graduate software developer for a financial company that uses an old COBOL-like language/flat-file record storage system. The code is completely undocumented, both code comments and overall system design and there is no help on the web (unused outside the industry). The current developers have been working on the system for between 10 and 30 years and are adamant that documentation is unnecessary as you can just read the code to work out what's going on and that you can't trust comments. Why should such a system be documented?

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  • Why Solid-State Drives Slow Down As You Fill Them Up

    - by Chris Hoffman
    The benchmarks are clear: Solid-state drives slow down as you fill them up. Fill your solid-state drive to near-capacity and its write performance will decrease dramatically. The reason why lies in the way SSDs and NAND Flash storage work. Filling the drive to capacity is one of the things you should never do with a solid-state drive. A nearly full solid-state drive will have much slower write operations, slowing down your computer.    

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  • Why do iterators in Python raise an exception?

    - by NullUserException
    Here's the syntax for iterators in Java (somewhat similar syntax in C#): Iterator it = sequence.iterator(); while (it.hasNext()) { System.out.println(it.next()); } Which makes sense. Here's the equivalent syntax in Python: it = iter(sequence) while True: try: value = it.next() except StopIteration: break print(value) I thought Exceptions were supposed to be used only in, well, exceptional circumstances. Why does Python use exceptions to stop iteration?

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  • Why was Scala not implemented with C or C++

    - by jpartogi
    Does anybody know why was Scala implemented in Java and .NET instead of C or C++? Most languages are implemented with Cor C++ [i.e Erlang, Python, PHP, Ruby, Perl]. What are the advantages for Scala implemented in Java and .NET other than giving access to Java and .NET libraries? UPDATE Woudln't Scala gain more benefit if it is implemented in C because it can be tuned better rather than relying on JVM?

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  • Why you need to learn async in .NET

    - by PSteele
    I had an opportunity to teach a quick class yesterday about what’s new in .NET 4.0.  One of the topics was the TPL (Task Parallel Library) and how it can make async programming easier.  I also stressed that this is the direction Microsoft is going with for C# 5.0 and learning the TPL will greatly benefit their understanding of the new async stuff.  We had a little time left over and I was able to show some code that uses the Async CTP to accomplish some stuff, but it wasn’t a simple demo that you could jump in to and understand so I thought I’d thrown one together and put it in a blog post. The entire solution file with all of the sample projects is located here. A Simple Example Let’s start with a super-simple example (WindowsApplication01 in the solution). I’ve got a form that displays a label and a button.  When the user clicks the button, I want to start displaying the current time for 15 seconds and then stop. What I’d like to write is this: lblTime.ForeColor = Color.Red; for (var x = 0; x < 15; x++) { lblTime.Text = DateTime.Now.ToString("HH:mm:ss"); Thread.Sleep(1000); } lblTime.ForeColor = SystemColors.ControlText; (Note that I also changed the label’s color while counting – not quite an ILM-level effect, but it adds something to the demo!) As I’m sure most of my readers are aware, you can’t write WinForms code this way.  WinForms apps, by default, only have one thread running and it’s main job is to process messages from the windows message pump (for a more thorough explanation, see my Visual Studio Magazine article on multithreading in WinForms).  If you put a Thread.Sleep in the middle of that code, your UI will be locked up and unresponsive for those 15 seconds.  Not a good UX and something that needs to be fixed.  Sure, I could throw an “Application.DoEvents()” in there, but that’s hacky. The Windows Timer Then I think, “I can solve that.  I’ll use the Windows Timer to handle the timing in the background and simply notify me when the time has changed”.  Let’s see how I could accomplish this with a Windows timer (WindowsApplication02 in the solution): public partial class Form1 : Form { private readonly Timer clockTimer; private int counter;   public Form1() { InitializeComponent(); clockTimer = new Timer {Interval = 1000}; clockTimer.Tick += UpdateLabel; }   private void UpdateLabel(object sender, EventArgs e) { lblTime.Text = DateTime.Now.ToString("HH:mm:ss"); counter++; if (counter == 15) { clockTimer.Enabled = false; lblTime.ForeColor = SystemColors.ControlText; } }   private void cmdStart_Click(object sender, EventArgs e) { lblTime.ForeColor = Color.Red; counter = 0; clockTimer.Start(); } } Holy cow – things got pretty complicated here.  I use the timer to fire off a Tick event every second.  Inside there, I can update the label.  Granted, I can’t use a simple for/loop and have to maintain a global counter for the number of iterations.  And my “end” code (when the loop is finished) is now buried inside the bottom of the Tick event (inside an “if” statement).  I do, however, get a responsive application that doesn’t hang or stop repainting while the 15 seconds are ticking away. But doesn’t .NET have something that makes background processing easier? The BackgroundWorker Next I try .NET’s BackgroundWorker component – it’s specifically designed to do processing in a background thread (leaving the UI thread free to process the windows message pump) and allows updates to be performed on the main UI thread (WindowsApplication03 in the solution): public partial class Form1 : Form { private readonly BackgroundWorker worker;   public Form1() { InitializeComponent(); worker = new BackgroundWorker {WorkerReportsProgress = true}; worker.DoWork += StartUpdating; worker.ProgressChanged += UpdateLabel; worker.RunWorkerCompleted += ResetLabelColor; }   private void StartUpdating(object sender, DoWorkEventArgs e) { var workerObject = (BackgroundWorker) sender; for (int x = 0; x < 15; x++) { workerObject.ReportProgress(0); Thread.Sleep(1000); } }   private void UpdateLabel(object sender, ProgressChangedEventArgs e) { lblTime.Text = DateTime.Now.ToString("HH:mm:ss"); }   private void ResetLabelColor(object sender, RunWorkerCompletedEventArgs e) { lblTime.ForeColor = SystemColors.ControlText; }   private void cmdStart_Click(object sender, EventArgs e) { lblTime.ForeColor = Color.Red; worker.RunWorkerAsync(); } } Well, this got a little better (I think).  At least I now have my simple for/next loop back.  Unfortunately, I’m still dealing with event handlers spread throughout my code to co-ordinate all of this stuff in the right order. Time to look into the future. The async way Using the Async CTP, I can go back to much simpler code (WindowsApplication04 in the solution): private async void cmdStart_Click(object sender, EventArgs e) { lblTime.ForeColor = Color.Red; for (var x = 0; x < 15; x++) { lblTime.Text = DateTime.Now.ToString("HH:mm:ss"); await TaskEx.Delay(1000); } lblTime.ForeColor = SystemColors.ControlText; } This code will run just like the Timer or BackgroundWorker versions – fully responsive during the updates – yet is way easier to implement.  In fact, it’s almost a line-for-line copy of the original version of this code.  All of the async plumbing is handled by the compiler and the framework.  My code goes back to representing the “what” of what I want to do, not the “how”. I urge you to download the Async CTP.  All you need is .NET 4.0 and Visual Studio 2010 sp1 – no need to set up a virtual machine with the VS2011 beta (unless, of course, you want to dive right in to the C# 5.0 stuff!).  Starting playing around with this today and see how much easier it will be in the future to write async-enabled applications.

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  • Design Patterns - Why the need for interfaces?

    - by Kyle Johnson
    OK. I am learning design patterns. Every time I see someone code an example of a design pattern they use interfaces. Here is an example: http://visualstudiomagazine.com/Articles/2013/06/18/the-facade-pattern-in-net.aspx?Page=1 Can someone explain to me why was the interfaces needed in this example to demonstrate the facade pattern? The program work if you pass in the classes to the facade instead of the interface. If I don't have interfaces does that mean

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  • Why can we recognize game engines?

    - by Bart van Heukelom
    About many games you can say "oh that's the Unreal engine for sure", "this was made by upgrading GTA 4", etc. We can often recognize the engine used for a game just by looking at its graphics (disregarding menus and such). I'm wondering, why is this? All game engines use the same 3D rendering technology that we all use, and the different games usually have a distinct art style, so what's left to recognize?

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  • Why does XCode convert PNGs to CgBI format?

    - by Gdeglin
    According to the research done here http://imageoptim.com/tweetbot.html, Xcode's conversion of PNGs to the proprietary Apple CgBI format does not create a noticeable performance improvement. Their claim is that the conversion only reduces PNG loading speed by 1 nanosecond. If this is true, why does apple bother with the CgBI format at all? Has anyone else benchmarked loading CgBI images vs regular PNG images on iOS devices to see if they perform differently?

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  • Why is iOS "jailbreaking" CPU specific? [closed]

    - by Ted Wong
    Recently, iOS 6 was "jailbroken" but only on the Apple A4 CPU. Why is the "jailbreaking" process specific to a CPU? From Wikipedia: ... "iOS jailbreaking is the process of removing the limitations imposed by Apple on devices running the iOS operating system through the use of hardware/software exploits – such devices include the iPhone, iPod touch, iPad, and second generation Apple TV. Jailbreaking allows iOS users to gain root access to the operating system""" ...

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  • Why Use !boolean_variable Over boolean_variable == false

    - by ell
    A comment on this question: Calling A Method that returns a boolean value inside a conditional statement says that you should use !boolean instead of boolean == false when testing conditions. Why? To me boolean == false is much more natural in English and is more explicit. I apologise if this is just a matter of style, but I was wondering if there was some other reason for this preference of !boolean?

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  • why do we need to put private members in headers

    - by Simon
    Private variables are a way to hide complexity and implementation details to the user of a class. This is a rather nice feature. But I do not understand why in c++ we need to put them in the header of a class. I see some annoying downsides to this: it clutters the header from the user it force recompilation of all client libraries whenever the internals are modified Is there a conceptual reason behind this requirement? Is it only to ease the work of the compiler?

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  • Why do we (really) program to interfaces?

    - by Kyle Burns
    One of the earliest lessons I was taught in Enterprise development was "always program against an interface".  This was back in the VB6 days and I quickly learned that no code would be allowed to move to the QA server unless my business objects and data access objects each are defined as an interface and have a matching implementation class.  Why?  "It's more reusable" was one answer.  "It doesn't tie you to a specific implementation" a slightly more knowing answer.  And let's not forget the discussion ending "it's a standard".  The problem with these responses was that senior people didn't really understand the reason we were doing the things we were doing and because of that, we were entirely unable to realize the intent behind the practice - we simply used interfaces and had a bunch of extra code to maintain to show for it. It wasn't until a few years later that I finally heard the term "Inversion of Control".  Simply put, "Inversion of Control" takes the creation of objects that used to be within the control (and therefore a responsibility of) of your component and moves it to some outside force.  For example, consider the following code which follows the old "always program against an interface" rule in the manner of many corporate development shops: 1: ICatalog catalog = new Catalog(); 2: Category[] categories = catalog.GetCategories(); In this example, I met the requirement of the rule by declaring the variable as ICatalog, but I didn't hit "it doesn't tie you to a specific implementation" because I explicitly created an instance of the concrete Catalog object.  If I want to test the functionality of the code I just wrote I have to have an environment in which Catalog can be created along with any of the resources upon which it depends (e.g. configuration files, database connections, etc) in order to test my functionality.  That's a lot of setup work and one of the things that I think ultimately discourages real buy-in of unit testing in many development shops. So how do I test my code without needing Catalog to work?  A very primitive approach I've seen is to change the line the instantiates catalog to read: 1: ICatalog catalog = new FakeCatalog();   once the test is run and passes, the code is switched back to the real thing.  This obviously poses a huge risk for introducing test code into production and in my opinion is worse than just keeping the dependency and its associated setup work.  Another popular approach is to make use of Factory methods which use an object whose "job" is to know how to obtain a valid instance of the object.  Using this approach, the code may look something like this: 1: ICatalog catalog = CatalogFactory.GetCatalog();   The code inside the factory is responsible for deciding "what kind" of catalog is needed.  This is a far better approach than the previous one, but it does make projects grow considerably because now in addition to the interface, the real implementation, and the fake implementation(s) for testing you have added a minimum of one factory (or at least a factory method) for each of your interfaces.  Once again, developers say "that's too complicated and has me writing a bunch of useless code" and quietly slip back into just creating a new Catalog and chalking any test failures up to "it will probably work on the server". This is where software intended specifically to facilitate Inversion of Control comes into play.  There are many libraries that take on the Inversion of Control responsibilities in .Net and most of them have many pros and cons.  From this point forward I'll discuss concepts from the standpoint of the Unity framework produced by Microsoft's Patterns and Practices team.  I'm primarily focusing on this library because it questions about it inspired this posting. At Unity's core and that of most any IoC framework is a catalog or registry of components.  This registry can be configured either through code or using the application's configuration file and in the most simple terms says "interface X maps to concrete implementation Y".  It can get much more complicated, but I want to keep things at the "what does it do" level instead of "how does it do it".  The object that exposes most of the Unity functionality is the UnityContainer.  This object exposes methods to configure the catalog as well as the Resolve<T> method which is used to obtain an instance of the type represented by T.  When using the Resolve<T> method, Unity does not necessarily have to just "new up" the requested object, but also can track dependencies of that object and ensure that the entire dependency chain is satisfied. There are three basic ways that I have seen Unity used within projects.  Those are through classes directly using the Unity container, classes requiring injection of dependencies, and classes making use of the Service Locator pattern. The first usage of Unity is when classes are aware of the Unity container and directly call its Resolve method whenever they need the services advertised by an interface.  The up side of this approach is that IoC is utilized, but the down side is that every class has to be aware that Unity is being used and tied directly to that implementation. Many developers don't like the idea of as close a tie to specific IoC implementation as is represented by using Unity within all of your classes and for the most part I agree that this isn't a good idea.  As an alternative, classes can be designed for Dependency Injection.  Dependency Injection is where a force outside the class itself manipulates the object to provide implementations of the interfaces that the class needs to interact with the outside world.  This is typically done either through constructor injection where the object has a constructor that accepts an instance of each interface it requires or through property setters accepting the service providers.  When using dependency, I lean toward the use of constructor injection because I view the constructor as being a much better way to "discover" what is required for the instance to be ready for use.  During resolution, Unity looks for an injection constructor and will attempt to resolve instances of each interface required by the constructor, throwing an exception of unable to meet the advertised needs of the class.  The up side of this approach is that the needs of the class are very clearly advertised and the class is unaware of which IoC container (if any) is being used.  The down side of this approach is that you're required to maintain the objects passed to the constructor as instance variables throughout the life of your object and that objects which coordinate with many external services require a lot of additional constructor arguments (this gets ugly and may indicate a need for refactoring). The final way that I've seen and used Unity is to make use of the ServiceLocator pattern, of which the Patterns and Practices team has also provided a Unity-compatible implementation.  When using the ServiceLocator, your class calls ServiceLocator.Retrieve in places where it would have called Resolve on the Unity container.  Like using Unity directly, it does tie you directly to the ServiceLocator implementation and makes your code aware that dependency injection is taking place, but it does have the up side of giving you the freedom to swap out the underlying IoC container if necessary.  I'm not hugely concerned with hiding IoC entirely from the class (I view this as a "nice to have"), so the single biggest problem that I see with the ServiceLocator approach is that it provides no way to proactively advertise needs in the way that constructor injection does, allowing more opportunity for difficult to track runtime errors. This blog entry has not been intended in any way to be a definitive work on IoC, but rather as something to spur thought about why we program to interfaces and some ways to reach the intended value of the practice instead of having it just complicate your code.  I hope that it helps somebody begin or continue a journey away from being a "Cargo Cult Programmer".

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  • Why SEO Hosting Reviews Are Important

    Read about why and how webmasters are finding out SEO Hosting Reviews to be able to find the ideal web host to make the most of their domains and sites. This is the new age of internet marketing and it begins with SEO Hosting.

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  • Why many designs ignore normalization in RDBMS?

    - by Yosi
    I got to see many designs that normalization wasn't the first consideration in decision making phase. In many cases those designs included more than 30 columns, and the main approach was "to put everything in the same place" According to what I remember normalization is one of the first, most important things, so why is it dropped so easily sometimes? Edit: Is it true that good architects and experts choose a denormalized design while non-experienced developers choose the opposite? What are the arguments against starting your design with normalization in mind?

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  • Metaobject protocol:Why is it known as an important concept

    - by sushant
    Metaobject protocol is protocol for metaobjects in a programming languages. Although I understand it on simple terms, I want to know the reason and a summary of real world usage patterns of this protocol. So, why exactly is metaobject and more importantly metaobject protocol is such a good idea. I want to know the problem which led to its evolution and also, its high power usage. Opinions as well as general overview/description/alternate explanations are also welcome.

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  • Why Hekaton In-Memory OLTP Truly is Revolutionary

    - by merrillaldrich
    I just returned from the PASS Summit in Charlotte, NC – which was excellent, among the best I have attended – and I have had Dr. David DeWitt’s talk rolling around in my head since he gave it on Thursday. (Dr. DeWitt starts at 27:00 at that link.) I probably cannot do it justice, but I wanted to recap why Hekaton really is revolutionary, and not just a marketing buzzword. I am normally skeptical of product announcements, and I find too often that real technical innovation can be overwhelmed by the...(read more)

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