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• A Case for Women in Technology

  - by Denise McInerney

  Pragmatic Works and the PASS Women in Tech chapter are co-sponsoring a webinar series featuring women speakers. I presented a session on “A Case for Women in Technology” explaining why we are all affected by the lack of women studying and working in tech. The recording is available here. And here are the slides from that presentation: The presentation includes a link to a trailer for an upcoming documentary. This short video makes a good case for why we need more women creating technology. There are many organizations doing good and important work on this issue. Here are some of them: National Center for Women & Information Technology Catalyst Anita Borg Institute Girls Inc Girls Who Code Code.org Black Girls Code Teaching Kids Programming Digigirlz IGNITE She++ The Ada Initiative PASS WIT Here are the publications I referenced in my slides: Women in IT: The Facts Why Diversity Matters Women in IT: By the Numbers NCWIT Scorecard

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• Parallelism in .NET – Part 7, Some Differences between PLINQ and LINQ to Objects

  - by Reed

  In my previous post on Declarative Data Parallelism, I mentioned that PLINQ extends LINQ to Objects to support parallel operations.  Although nearly all of the same operations are supported, there are some differences between PLINQ and LINQ to Objects.  By introducing Parallelism to our declarative model, we add some extra complexity.  This, in turn, adds some extra requirements that must be addressed. In order to illustrate the main differences, and why they exist, let’s begin by discussing some differences in how the two technologies operate, and look at the underlying types involved in LINQ to Objects and PLINQ . LINQ to Objects is mainly built upon a single class: Enumerable.  The Enumerable class is a static class that defines a large set of extension methods, nearly all of which work upon an IEnumerable<T>.  Many of these methods return a new IEnumerable<T>, allowing the methods to be chained together into a fluent style interface.  This is what allows us to write statements that chain together, and lead to the nice declarative programming model of LINQ: double min = collection .Where(item => item.SomeProperty > 6 && item.SomeProperty < 24) .Min(item => item.PerformComputation()); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Other LINQ variants work in a similar fashion.  For example, most data-oriented LINQ providers are built upon an implementation of IQueryable<T>, which allows the database provider to turn a LINQ statement into an underlying SQL query, to be performed directly on the remote database. PLINQ is similar, but instead of being built upon the Enumerable class, most of PLINQ is built upon a new static class: ParallelEnumerable.  When using PLINQ, you typically begin with any collection which implements IEnumerable<T>, and convert it to a new type using an extension method defined on ParallelEnumerable: AsParallel().  This method takes any IEnumerable<T>, and converts it into a ParallelQuery<T>, the core class for PLINQ.  There is a similar ParallelQuery class for working with non-generic IEnumerable implementations. This brings us to our first subtle, but important difference between PLINQ and LINQ – PLINQ always works upon specific types, which must be explicitly created. Typically, the type you’ll use with PLINQ is ParallelQuery<T>, but it can sometimes be a ParallelQuery or an OrderedParallelQuery<T>.  Instead of dealing with an interface, implemented by an unknown class, we’re dealing with a specific class type.  This works seamlessly from a usage standpoint – ParallelQuery<T> implements IEnumerable<T>, so you can always “switch back” to an IEnumerable<T>.  The difference only arises at the beginning of our parallelization.  When we’re using LINQ, and we want to process a normal collection via PLINQ, we need to explicitly convert the collection into a ParallelQuery<T> by calling AsParallel().  There is an important consideration here – AsParallel() does not need to be called on your specific collection, but rather any IEnumerable<T>.  This allows you to place it anywhere in the chain of methods involved in a LINQ statement, not just at the beginning.  This can be useful if you have an operation which will not parallelize well or is not thread safe.  For example, the following is perfectly valid, and similar to our previous examples: double min = collection .AsParallel() .Select(item => item.SomeOperation()) .Where(item => item.SomeProperty > 6 && item.SomeProperty < 24) .Min(item => item.PerformComputation()); However, if SomeOperation() is not thread safe, we could just as easily do: double min = collection .Select(item => item.SomeOperation()) .AsParallel() .Where(item => item.SomeProperty > 6 && item.SomeProperty < 24) .Min(item => item.PerformComputation()); In this case, we’re using standard LINQ to Objects for the Select(…) method, then converting the results of that map routine to a ParallelQuery<T>, and processing our filter (the Where method) and our aggregation (the Min method) in parallel. PLINQ also provides us with a way to convert a ParallelQuery<T> back into a standard IEnumerable<T>, forcing sequential processing via standard LINQ to Objects.  If SomeOperation() was thread-safe, but PerformComputation() was not thread-safe, we would need to handle this by using the AsEnumerable() method: double min = collection .AsParallel() .Select(item => item.SomeOperation()) .Where(item => item.SomeProperty > 6 && item.SomeProperty < 24) .AsEnumerable() .Min(item => item.PerformComputation()); Here, we’re converting our collection into a ParallelQuery<T>, doing our map operation (the Select(…) method) and our filtering in parallel, then converting the collection back into a standard IEnumerable<T>, which causes our aggregation via Min() to be performed sequentially. This could also be written as two statements, as well, which would allow us to use the language integrated syntax for the first portion: var tempCollection = from item in collection.AsParallel() let e = item.SomeOperation() where (e.SomeProperty > 6 && e.SomeProperty < 24) select e; double min = tempCollection.AsEnumerable().Min(item => item.PerformComputation()); This allows us to use the standard LINQ style language integrated query syntax, but control whether it’s performed in parallel or serial by adding AsParallel() and AsEnumerable() appropriately. The second important difference between PLINQ and LINQ deals with order preservation.  PLINQ, by default, does not preserve the order of of source collection. This is by design.  In order to process a collection in parallel, the system needs to naturally deal with multiple elements at the same time.  Maintaining the original ordering of the sequence adds overhead, which is, in many cases, unnecessary.  Therefore, by default, the system is allowed to completely change the order of your sequence during processing.  If you are doing a standard query operation, this is usually not an issue.  However, there are times when keeping a specific ordering in place is important.  If this is required, you can explicitly request the ordering be preserved throughout all operations done on a ParallelQuery<T> by using the AsOrdered() extension method.  This will cause our sequence ordering to be preserved. For example, suppose we wanted to take a collection, perform an expensive operation which converts it to a new type, and display the first 100 elements.  In LINQ to Objects, our code might look something like: // Using IEnumerable<SourceClass> collection IEnumerable<ResultClass> results = collection .Select(e => e.CreateResult()) .Take(100); If we just converted this to a parallel query naively, like so: IEnumerable<ResultClass> results = collection .AsParallel() .Select(e => e.CreateResult()) .Take(100); We could very easily get a very different, and non-reproducable, set of results, since the ordering of elements in the input collection is not preserved.  To get the same results as our original query, we need to use: IEnumerable<ResultClass> results = collection .AsParallel() .AsOrdered() .Select(e => e.CreateResult()) .Take(100); This requests that PLINQ process our sequence in a way that verifies that our resulting collection is ordered as if it were processed serially.  This will cause our query to run slower, since there is overhead involved in maintaining the ordering.  However, in this case, it is required, since the ordering is required for correctness. PLINQ is incredibly useful.  It allows us to easily take nearly any LINQ to Objects query and run it in parallel, using the same methods and syntax we’ve used previously.  There are some important differences in operation that must be considered, however – it is not a free pass to parallelize everything.  When using PLINQ in order to parallelize your routines declaratively, the same guideline I mentioned before still applies: Parallelization is something that should be handled with care and forethought, added by design, and not just introduced casually.

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• how to implemet a nice scanline effect using libgdx

  - by Alexandre GUIDET

  I am working on an old school platformer based on libgdx. My first attempt is to make a little texture and fill a rect above the whole screen, but it seems that I am messing arround with the orthographic camera (I use two camera, one for the tilemap and one to project the scanline filter). Sometime the texture is stuck on the tilemap and sometime it is too large and cover the whole screen in black. Is my approach correct using two camera? Does someone have a solution to achieve this retro effect using libgdx (see maldita castilla)? Thanks

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• Parallelism in .NET – Part 2, Simple Imperative Data Parallelism

  - by Reed

  In my discussion of Decomposition of the problem space, I mentioned that Data Decomposition is often the simplest abstraction to use when trying to parallelize a routine.  If a problem can be decomposed based off the data, we will often want to use what MSDN refers to as Data Parallelism as our strategy for implementing our routine.  The Task Parallel Library in .NET 4 makes implementing Data Parallelism, for most cases, very simple. Data Parallelism is the main technique we use to parallelize a routine which can be decomposed based off data.  Data Parallelism refers to taking a single collection of data, and having a single operation be performed concurrently on elements in the collection.  One side note here: Data Parallelism is also sometimes referred to as the Loop Parallelism Pattern or Loop-level Parallelism.  In general, for this series, I will try to use the terminology used in the MSDN Documentation for the Task Parallel Library.  This should make it easier to investigate these topics in more detail. Once we’ve determined we have a problem that, potentially, can be decomposed based on data, implementation using Data Parallelism in the TPL is quite simple.  Let’s take our example from the Data Decomposition discussion – a simple contrast stretching filter.  Here, we have a collection of data (pixels), and we need to run a simple operation on each element of the pixel.  Once we know the minimum and maximum values, we most likely would have some simple code like the following: for (int row=0; row < pixelData.GetUpperBound(0); ++row) { for (int col=0; col < pixelData.GetUpperBound(1); ++col) { pixelData[row, col] = AdjustContrast(pixelData[row, col], minPixel, maxPixel); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This simple routine loops through a two dimensional array of pixelData, and calls the AdjustContrast routine on each pixel. As I mentioned, when you’re decomposing a problem space, most iteration statements are potentially candidates for data decomposition.  Here, we’re using two for loops – one looping through rows in the image, and a second nested loop iterating through the columns.  We then perform one, independent operation on each element based on those loop positions. This is a prime candidate – we have no shared data, no dependencies on anything but the pixel which we want to change.  Since we’re using a for loop, we can easily parallelize this using the Parallel.For method in the TPL: Parallel.For(0, pixelData.GetUpperBound(0), row => { for (int col=0; col < pixelData.GetUpperBound(1); ++col) { pixelData[row, col] = AdjustContrast(pixelData[row, col], minPixel, maxPixel); } }); Here, by simply changing our first for loop to a call to Parallel.For, we can parallelize this portion of our routine.  Parallel.For works, as do many methods in the TPL, by creating a delegate and using it as an argument to a method.  In this case, our for loop iteration block becomes a delegate creating via a lambda expression.  This lets you write code that, superficially, looks similar to the familiar for loop, but functions quite differently at runtime. We could easily do this to our second for loop as well, but that may not be a good idea.  There is a balance to be struck when writing parallel code.  We want to have enough work items to keep all of our processors busy, but the more we partition our data, the more overhead we introduce.  In this case, we have an image of data – most likely hundreds of pixels in both dimensions.  By just parallelizing our first loop, each row of pixels can be run as a single task.  With hundreds of rows of data, we are providing fine enough granularity to keep all of our processors busy. If we parallelize both loops, we’re potentially creating millions of independent tasks.  This introduces extra overhead with no extra gain, and will actually reduce our overall performance.  This leads to my first guideline when writing parallel code: Partition your problem into enough tasks to keep each processor busy throughout the operation, but not more than necessary to keep each processor busy. Also note that I parallelized the outer loop.  I could have just as easily partitioned the inner loop.  However, partitioning the inner loop would have led to many more discrete work items, each with a smaller amount of work (operate on one pixel instead of one row of pixels).  My second guideline when writing parallel code reflects this: Partition your problem in a way to place the most work possible into each task. This typically means, in practice, that you will want to parallelize the routine at the “highest” point possible in the routine, typically the outermost loop.  If you’re looking at parallelizing methods which call other methods, you’ll want to try to partition your work high up in the stack – as you get into lower level methods, the performance impact of parallelizing your routines may not overcome the overhead introduced. Parallel.For works great for situations where we know the number of elements we’re going to process in advance.  If we’re iterating through an IList<T> or an array, this is a typical approach.  However, there are other iteration statements common in C#.  In many situations, we’ll use foreach instead of a for loop.  This can be more understandable and easier to read, but also has the advantage of working with collections which only implement IEnumerable<T>, where we do not know the number of elements involved in advance. As an example, lets take the following situation.  Say we have a collection of Customers, and we want to iterate through each customer, check some information about the customer, and if a certain case is met, send an email to the customer and update our instance to reflect this change.  Normally, this might look something like: foreach(var customer in customers) { // Run some process that takes some time... DateTime lastContact = theStore.GetLastContact(customer); TimeSpan timeSinceContact = DateTime.Now - lastContact; // If it's been more than two weeks, send an email, and update... if (timeSinceContact.Days > 14) { theStore.EmailCustomer(customer); customer.LastEmailContact = DateTime.Now; } } Here, we’re doing a fair amount of work for each customer in our collection, but we don’t know how many customers exist.  If we assume that theStore.GetLastContact(customer) and theStore.EmailCustomer(customer) are both side-effect free, thread safe operations, we could parallelize this using Parallel.ForEach: Parallel.ForEach(customers, customer => { // Run some process that takes some time... DateTime lastContact = theStore.GetLastContact(customer); TimeSpan timeSinceContact = DateTime.Now - lastContact; // If it's been more than two weeks, send an email, and update... if (timeSinceContact.Days > 14) { theStore.EmailCustomer(customer); customer.LastEmailContact = DateTime.Now; } }); Just like Parallel.For, we rework our loop into a method call accepting a delegate created via a lambda expression.  This keeps our new code very similar to our original iteration statement, however, this will now execute in parallel.  The same guidelines apply with Parallel.ForEach as with Parallel.For. The other iteration statements, do and while, do not have direct equivalents in the Task Parallel Library.  These, however, are very easy to implement using Parallel.ForEach and the yield keyword. Most applications can benefit from implementing some form of Data Parallelism.  Iterating through collections and performing “work” is a very common pattern in nearly every application.  When the problem can be decomposed by data, we often can parallelize the workload by merely changing foreach statements to Parallel.ForEach method calls, and for loops to Parallel.For method calls.  Any time your program operates on a collection, and does a set of work on each item in the collection where that work is not dependent on other information, you very likely have an opportunity to parallelize your routine.

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• Think Centre 71, Ubuntu 12 ... Error 1962: No operating system found

  - by johnboy7

  Brought a new Think Centre Edge 71 because The Lenovo ThinkCentre Edge71 desktop has been awarded the status of Certified for Ubuntu. Source. Spent the the past 2 days trying to get *any*Ubuntu 12.04 64bit to install and boot. All give me the same answer: Error 1962: No operating system found Here are a few of the links I've tried: Just installed Ubuntu 12.04. When booting, all I get is a black screen with cursor. Some of the links report to solve the problem. None have worked. http://ubuntuforums.org/showthread.php?t=1901748 Is there a relative simple way to install and boot Ubuntu 12.04 64bit on a Think Centre Edge 71?? I mean it is Certified for Ubuntu?

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• This Week in Geek History: Morse Code, Mars Rovers, J.R.R. Tolkien’s Birthday

  - by Jason Fitzpatrick

  Every week we bring you interesting facts from the history of Geekdom. This week in Geek History witnessed the first successful demonstration of the electric telegraph, the safe landing of the Spirit rover on the surface of Mars, and the birth of famed fantasy author J.R.R. Tolkien. Latest Features How-To Geek ETC How To Boot 10 Different Live CDs From 1 USB Flash Drive The 20 Best How-To Geek Linux Articles of 2010 The 50 Best How-To Geek Windows Articles of 2010 The 20 Best How-To Geek Explainer Topics for 2010 How to Disable Caps Lock Key in Windows 7 or Vista How to Use the Avira Rescue CD to Clean Your Infected PC The Deep – Awesome Use of Metal Objects as Deep Sea Creatures [Video] Convert or View Documents Online Easily with Zoho, No Account Required Build a Floor Scrubbing Robot out of Computer Fans and a Frisbee Serene Blue Windows Wallpaper for Your Desktop 2011 International Space Station Calendar Available for Download (Free) Ultimate Elimination – Lego Black Ops [Video]

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• Parallelism in .NET – Part 4, Imperative Data Parallelism: Aggregation

  - by Reed

  In the article on simple data parallelism, I described how to perform an operation on an entire collection of elements in parallel.  Often, this is not adequate, as the parallel operation is going to be performing some form of aggregation. Simple examples of this might include taking the sum of the results of processing a function on each element in the collection, or finding the minimum of the collection given some criteria.  This can be done using the techniques described in simple data parallelism, however, special care needs to be taken into account to synchronize the shared data appropriately.  The Task Parallel Library has tools to assist in this synchronization. The main issue with aggregation when parallelizing a routine is that you need to handle synchronization of data.  Since multiple threads will need to write to a shared portion of data.  Suppose, for example, that we wanted to parallelize a simple loop that looked for the minimum value within a dataset: double min = double.MaxValue; foreach(var item in collection) { double value = item.PerformComputation(); min = System.Math.Min(min, value); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } This seems like a good candidate for parallelization, but there is a problem here.  If we just wrap this into a call to Parallel.ForEach, we’ll introduce a critical race condition, and get the wrong answer.  Let’s look at what happens here: // Buggy code! Do not use! double min = double.MaxValue; Parallel.ForEach(collection, item => { double value = item.PerformComputation(); min = System.Math.Min(min, value); }); This code has a fatal flaw: min will be checked, then set, by multiple threads simultaneously.  Two threads may perform the check at the same time, and set the wrong value for min.  Say we get a value of 1 in thread 1, and a value of 2 in thread 2, and these two elements are the first two to run.  If both hit the min check line at the same time, both will determine that min should change, to 1 and 2 respectively.  If element 1 happens to set the variable first, then element 2 sets the min variable, we’ll detect a min value of 2 instead of 1.  This can lead to wrong answers. Unfortunately, fixing this, with the Parallel.ForEach call we’re using, would require adding locking.  We would need to rewrite this like: // Safe, but slow double min = double.MaxValue; // Make a "lock" object object syncObject = new object(); Parallel.ForEach(collection, item => { double value = item.PerformComputation(); lock(syncObject) min = System.Math.Min(min, value); }); This will potentially add a huge amount of overhead to our calculation.  Since we can potentially block while waiting on the lock for every single iteration, we will most likely slow this down to where it is actually quite a bit slower than our serial implementation.  The problem is the lock statement – any time you use lock(object), you’re almost assuring reduced performance in a parallel situation.  This leads to two observations I’ll make: When parallelizing a routine, try to avoid locks. That being said: Always add any and all required synchronization to avoid race conditions. These two observations tend to be opposing forces – we often need to synchronize our algorithms, but we also want to avoid the synchronization when possible.  Looking at our routine, there is no way to directly avoid this lock, since each element is potentially being run on a separate thread, and this lock is necessary in order for our routine to function correctly every time. However, this isn’t the only way to design this routine to implement this algorithm.  Realize that, although our collection may have thousands or even millions of elements, we have a limited number of Processing Elements (PE).  Processing Element is the standard term for a hardware element which can process and execute instructions.  This typically is a core in your processor, but many modern systems have multiple hardware execution threads per core.  The Task Parallel Library will not execute the work for each item in the collection as a separate work item. Instead, when Parallel.ForEach executes, it will partition the collection into larger “chunks” which get processed on different threads via the ThreadPool.  This helps reduce the threading overhead, and help the overall speed.  In general, the Parallel class will only use one thread per PE in the system. Given the fact that there are typically fewer threads than work items, we can rethink our algorithm design.  We can parallelize our algorithm more effectively by approaching it differently.  Because the basic aggregation we are doing here (Min) is communitive, we do not need to perform this in a given order.  We knew this to be true already – otherwise, we wouldn’t have been able to parallelize this routine in the first place.  With this in mind, we can treat each thread’s work independently, allowing each thread to serially process many elements with no locking, then, after all the threads are complete, “merge” together the results. This can be accomplished via a different set of overloads in the Parallel class: Parallel.ForEach<TSource,TLocal>.  The idea behind these overloads is to allow each thread to begin by initializing some local state (TLocal).  The thread will then process an entire set of items in the source collection, providing that state to the delegate which processes an individual item.  Finally, at the end, a separate delegate is run which allows you to handle merging that local state into your final results. To rewriting our routine using Parallel.ForEach<TSource,TLocal>, we need to provide three delegates instead of one.  The most basic version of this function is declared as: public static ParallelLoopResult ForEach<TSource, TLocal>( IEnumerable<TSource> source, Func<TLocal> localInit, Func<TSource, ParallelLoopState, TLocal, TLocal> body, Action<TLocal> localFinally ) The first delegate (the localInit argument) is defined as Func<TLocal>.  This delegate initializes our local state.  It should return some object we can use to track the results of a single thread’s operations. The second delegate (the body argument) is where our main processing occurs, although now, instead of being an Action<T>, we actually provide a Func<TSource, ParallelLoopState, TLocal, TLocal> delegate.  This delegate will receive three arguments: our original element from the collection (TSource), a ParallelLoopState which we can use for early termination, and the instance of our local state we created (TLocal).  It should do whatever processing you wish to occur per element, then return the value of the local state after processing is completed. The third delegate (the localFinally argument) is defined as Action<TLocal>.  This delegate is passed our local state after it’s been processed by all of the elements this thread will handle.  This is where you can merge your final results together.  This may require synchronization, but now, instead of synchronizing once per element (potentially millions of times), you’ll only have to synchronize once per thread, which is an ideal situation. Now that I’ve explained how this works, lets look at the code: // Safe, and fast! double min = double.MaxValue; // Make a "lock" object object syncObject = new object(); Parallel.ForEach( collection, // First, we provide a local state initialization delegate. () => double.MaxValue, // Next, we supply the body, which takes the original item, loop state, // and local state, and returns a new local state (item, loopState, localState) => { double value = item.PerformComputation(); return System.Math.Min(localState, value); }, // Finally, we provide an Action<TLocal>, to "merge" results together localState => { // This requires locking, but it's only once per used thread lock(syncObj) min = System.Math.Min(min, localState); } ); Although this is a bit more complicated than the previous version, it is now both thread-safe, and has minimal locking.  This same approach can be used by Parallel.For, although now, it’s Parallel.For<TLocal>.  When working with Parallel.For<TLocal>, you use the same triplet of delegates, with the same purpose and results. Also, many times, you can completely avoid locking by using a method of the Interlocked class to perform the final aggregation in an atomic operation.  The MSDN example demonstrating this same technique using Parallel.For uses the Interlocked class instead of a lock, since they are doing a sum operation on a long variable, which is possible via Interlocked.Add. By taking advantage of local state, we can use the Parallel class methods to parallelize algorithms such as aggregation, which, at first, may seem like poor candidates for parallelization.  Doing so requires careful consideration, and often requires a slight redesign of the algorithm, but the performance gains can be significant if handled in a way to avoid excessive synchronization.

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• Parallelism in .NET – Part 11, Divide and Conquer via Parallel.Invoke

  - by Reed

  Many algorithms are easily written to work via recursion.  For example, most data-oriented tasks where a tree of data must be processed are much more easily handled by starting at the root, and recursively “walking” the tree.  Some algorithms work this way on flat data structures, such as arrays, as well.  This is a form of divide and conquer: an algorithm design which is based around breaking up a set of work recursively, “dividing” the total work in each recursive step, and “conquering” the work when the remaining work is small enough to be solved easily. Recursive algorithms, especially ones based on a form of divide and conquer, are often a very good candidate for parallelization. This is apparent from a common sense standpoint.  Since we’re dividing up the total work in the algorithm, we have an obvious, built-in partitioning scheme.  Once partitioned, the data can be worked upon independently, so there is good, clean isolation of data. Implementing this type of algorithm is fairly simple.  The Parallel class in .NET 4 includes a method suited for this type of operation: Parallel.Invoke.  This method works by taking any number of delegates defined as an Action, and operating them all in parallel.  The method returns when every delegate has completed: Parallel.Invoke( () => { Console.WriteLine("Action 1 executing in thread {0}", Thread.CurrentThread.ManagedThreadId); }, () => { Console.WriteLine("Action 2 executing in thread {0}", Thread.CurrentThread.ManagedThreadId); }, () => { Console.WriteLine("Action 3 executing in thread {0}", Thread.CurrentThread.ManagedThreadId); } ); .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Running this simple example demonstrates the ease of using this method.  For example, on my system, I get three separate thread IDs when running the above code.  By allowing any number of delegates to be executed directly, concurrently, the Parallel.Invoke method provides us an easy way to parallelize any algorithm based on divide and conquer.  We can divide our work in each step, and execute each task in parallel, recursively. For example, suppose we wanted to implement our own quicksort routine.  The quicksort algorithm can be designed based on divide and conquer.  In each iteration, we pick a pivot point, and use that to partition the total array.  We swap the elements around the pivot, then recursively sort the lists on each side of the pivot.  For example, let’s look at this simple, sequential implementation of quicksort: public static void QuickSort<T>(T[] array) where T : IComparable<T> { QuickSortInternal(array, 0, array.Length - 1); } private static void QuickSortInternal<T>(T[] array, int left, int right) where T : IComparable<T> { if (left >= right) { return; } SwapElements(array, left, (left + right) / 2); int last = left; for (int current = left + 1; current <= right; ++current) { if (array[current].CompareTo(array[left]) < 0) { ++last; SwapElements(array, last, current); } } SwapElements(array, left, last); QuickSortInternal(array, left, last - 1); QuickSortInternal(array, last + 1, right); } static void SwapElements<T>(T[] array, int i, int j) { T temp = array[i]; array[i] = array[j]; array[j] = temp; } Here, we implement the quicksort algorithm in a very common, divide and conquer approach.  Running this against the built-in Array.Sort routine shows that we get the exact same answers (although the framework’s sort routine is slightly faster).  On my system, for example, I can use framework’s sort to sort ten million random doubles in about 7.3s, and this implementation takes about 9.3s on average. Looking at this routine, though, there is a clear opportunity to parallelize.  At the end of QuickSortInternal, we recursively call into QuickSortInternal with each partition of the array after the pivot is chosen.  This can be rewritten to use Parallel.Invoke by simply changing it to: // Code above is unchanged... SwapElements(array, left, last); Parallel.Invoke( () => QuickSortInternal(array, left, last - 1), () => QuickSortInternal(array, last + 1, right) ); } This routine will now run in parallel.  When executing, we now see the CPU usage across all cores spike while it executes.  However, there is a significant problem here – by parallelizing this routine, we took it from an execution time of 9.3s to an execution time of approximately 14 seconds!  We’re using more resources as seen in the CPU usage, but the overall result is a dramatic slowdown in overall processing time. This occurs because parallelization adds overhead.  Each time we split this array, we spawn two new tasks to parallelize this algorithm!  This is far, far too many tasks for our cores to operate upon at a single time.  In effect, we’re “over-parallelizing” this routine.  This is a common problem when working with divide and conquer algorithms, and leads to an important observation: When parallelizing a recursive routine, take special care not to add more tasks than necessary to fully utilize your system. This can be done with a few different approaches, in this case.  Typically, the way to handle this is to stop parallelizing the routine at a certain point, and revert back to the serial approach.  Since the first few recursions will all still be parallelized, our “deeper” recursive tasks will be running in parallel, and can take full advantage of the machine.  This also dramatically reduces the overhead added by parallelizing, since we’re only adding overhead for the first few recursive calls.  There are two basic approaches we can take here.  The first approach would be to look at the total work size, and if it’s smaller than a specific threshold, revert to our serial implementation.  In this case, we could just check right-left, and if it’s under a threshold, call the methods directly instead of using Parallel.Invoke. The second approach is to track how “deep” in the “tree” we are currently at, and if we are below some number of levels, stop parallelizing.  This approach is a more general-purpose approach, since it works on routines which parse trees as well as routines working off of a single array, but may not work as well if a poor partitioning strategy is chosen or the tree is not balanced evenly. This can be written very easily.  If we pass a maxDepth parameter into our internal routine, we can restrict the amount of times we parallelize by changing the recursive call to: // Code above is unchanged... SwapElements(array, left, last); if (maxDepth < 1) { QuickSortInternal(array, left, last - 1, maxDepth); QuickSortInternal(array, last + 1, right, maxDepth); } else { --maxDepth; Parallel.Invoke( () => QuickSortInternal(array, left, last - 1, maxDepth), () => QuickSortInternal(array, last + 1, right, maxDepth)); } We no longer allow this to parallelize indefinitely – only to a specific depth, at which time we revert to a serial implementation.  By starting the routine with a maxDepth equal to Environment.ProcessorCount, we can restrict the total amount of parallel operations significantly, but still provide adequate work for each processing core. With this final change, my timings are much better.  On average, I get the following timings: Framework via Array.Sort: 7.3 seconds Serial Quicksort Implementation: 9.3 seconds Naive Parallel Implementation: 14 seconds Parallel Implementation Restricting Depth: 4.7 seconds Finally, we are now faster than the framework’s Array.Sort implementation.

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• Unable to boot Windows 7 after installing Ubuntu

  - by Devendra

  I have Windows 7 on my machine and then installed Ubuntu 12.04 using a live CD. I can see both Windows 7 and Ubuntu in the grub menu, but when I select Windows 7 it shows a black screen for about 2 seconds and the returns to the Grub menu. But if I select Ubuntu it's working fine. This is the contents of the boot-repair log: Boot Info Script 0.61.full + Boot-Repair extra info [Boot-Info November 20th 2012] ============================= Boot Info Summary: =============================== => Grub2 (v2.00) is installed in the MBR of /dev/sda and looks at sector 1 of the same hard drive for core.img. core.img is at this location and looks in partition 1 for (,msdos6)/boot/grub. sda1: __________________________________________________________________________ File system: ntfs Boot sector type: Grub2 (v1.99-2.00) Boot sector info: Grub2 (v2.00) is installed in the boot sector of sda1 and looks at sector 388911128 of the same hard drive for core.img. core.img is at this location and looks in partition 1 for (,msdos6)/boot/grub. No errors found in the Boot Parameter Block. Operating System: Windows 7 Boot files: /bootmgr /Boot/BCD /Windows/System32/winload.exe sda2: __________________________________________________________________________ File system: ntfs Boot sector type: Windows Vista/7: NTFS Boot sector info: No errors found in the Boot Parameter Block. Operating System: Boot files: sda3: __________________________________________________________________________ File system: ntfs Boot sector type: Windows Vista/7: NTFS Boot sector info: No errors found in the Boot Parameter Block. Operating System: Boot files: sda4: __________________________________________________________________________ File system: Extended Partition Boot sector type: - Boot sector info: sda5: __________________________________________________________________________ File system: ntfs Boot sector type: Windows Vista/7: NTFS Boot sector info: According to the info in the boot sector, sda5 starts at sector 2048. Operating System: Boot files: sda6: __________________________________________________________________________ File system: ext4 Boot sector type: - Boot sector info: Operating System: Ubuntu 12.10 Boot files: /boot/grub/grub.cfg /etc/fstab /boot/grub/i386-pc/core.img sda7: __________________________________________________________________________ File system: swap Boot sector type: - Boot sector info: ============================ Drive/Partition Info: ============================= Drive: sda _____________________________________________________________________ Disk /dev/sda: 750.2 GB, 750156374016 bytes 255 heads, 63 sectors/track, 91201 cylinders, total 1465149168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes Partition Boot Start Sector End Sector # of Sectors Id System /dev/sda1 * 206,848 146,802,687 146,595,840 7 NTFS / exFAT / HPFS /dev/sda2 147,007,488 293,623,807 146,616,320 7 NTFS / exFAT / HPFS /dev/sda3 293,623,808 332,820,613 39,196,806 7 NTFS / exFAT / HPFS /dev/sda4 332,822,526 1,465,145,343 1,132,322,818 f W95 Extended (LBA) /dev/sda5 461,342,720 1,465,145,343 1,003,802,624 7 NTFS / exFAT / HPFS /dev/sda6 332,822,528 453,171,199 120,348,672 83 Linux /dev/sda7 453,173,248 461,338,623 8,165,376 82 Linux swap / Solaris "blkid" output: ________________________________________________________________ Device UUID TYPE LABEL /dev/sda1 F6AE2C13AE2BCB47 ntfs /dev/sda2 DC2273012272DFC6 ntfs /dev/sda3 1E76E43376E40D79 ntfs New Volume /dev/sda5 5ED60ACDD60AA57D ntfs /dev/sda6 9e70fd16-b48b-4f88-adcf-e443aef83124 ext4 /dev/sda7 52f3dd94-6be7-4a7b-a3ae-f43eb8810483 swap ================================ Mount points: ================================= Device Mount_Point Type Options /dev/sda6 / ext4 (rw,errors=remount-ro) =========================== sda6/boot/grub/grub.cfg: =========================== -------------------------------------------------------------------------------- # # DO NOT EDIT THIS FILE # # It is automatically generated by grub-mkconfig using templates # from /etc/grub.d and settings from /etc/default/grub # ### BEGIN /etc/grub.d/00_header ### if [ -s $prefix/grubenv ]; then set have_grubenv=true load_env fi set default="0" if [ x"${feature_menuentry_id}" = xy ]; then menuentry_id_option="--id" else menuentry_id_option="" fi export menuentry_id_option if [ "${prev_saved_entry}" ]; then set saved_entry="${prev_saved_entry}" save_env saved_entry set prev_saved_entry= save_env prev_saved_entry set boot_once=true fi function savedefault { if [ -z "${boot_once}" ]; then saved_entry="${chosen}" save_env saved_entry fi } function recordfail { set recordfail=1 if [ -n "${have_grubenv}" ]; then if [ -z "${boot_once}" ]; then save_env recordfail; fi; fi } function load_video { if [ x$feature_all_video_module = xy ]; then insmod all_video else insmod efi_gop insmod efi_uga insmod ieee1275_fb insmod vbe insmod vga insmod video_bochs insmod video_cirrus fi } if [ x$feature_default_font_path = xy ] ; then font=unicode else insmod part_msdos insmod ext2 set root='hd0,msdos6' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos6 --hint-efi=hd0,msdos6 --hint-baremetal=ahci0,msdos6 9e70fd16-b48b-4f88-adcf-e443aef83124 else search --no-floppy --fs-uuid --set=root 9e70fd16-b48b-4f88-adcf-e443aef83124 fi font="/usr/share/grub/unicode.pf2" fi if loadfont $font ; then set gfxmode=auto load_video insmod gfxterm set locale_dir=$prefix/locale set lang=en_IN insmod gettext fi terminal_output gfxterm if [ "${recordfail}" = 1 ]; then set timeout=10 else set timeout=10 fi ### END /etc/grub.d/00_header ### ### BEGIN /etc/grub.d/05_debian_theme ### set menu_color_normal=white/black set menu_color_highlight=black/light-gray if background_color 44,0,30; then clear fi ### END /etc/grub.d/05_debian_theme ### ### BEGIN /etc/grub.d/10_linux ### function gfxmode { set gfxpayload="${1}" if [ "${1}" = "keep" ]; then set vt_handoff=vt.handoff=7 else set vt_handoff= fi } if [ "${recordfail}" != 1 ]; then if [ -e ${prefix}/gfxblacklist.txt ]; then if hwmatch ${prefix}/gfxblacklist.txt 3; then if [ ${match} = 0 ]; then set linux_gfx_mode=keep else set linux_gfx_mode=text fi else set linux_gfx_mode=text fi else set linux_gfx_mode=keep fi else set linux_gfx_mode=text fi export linux_gfx_mode if [ "${linux_gfx_mode}" != "text" ]; then load_video; fi menuentry 'Ubuntu' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-9e70fd16-b48b-4f88-adcf-e443aef83124' { recordfail gfxmode $linux_gfx_mode insmod gzio insmod part_msdos insmod ext2 set root='hd0,msdos6' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos6 --hint-efi=hd0,msdos6 --hint-baremetal=ahci0,msdos6 9e70fd16-b48b-4f88-adcf-e443aef83124 else search --no-floppy --fs-uuid --set=root 9e70fd16-b48b-4f88-adcf-e443aef83124 fi linux /boot/vmlinuz-3.5.0-17-generic root=UUID=9e70fd16-b48b-4f88-adcf-e443aef83124 ro quiet splash $vt_handoff initrd /boot/initrd.img-3.5.0-17-generic } submenu 'Advanced options for Ubuntu' $menuentry_id_option 'gnulinux-advanced-9e70fd16-b48b-4f88-adcf-e443aef83124' { menuentry 'Ubuntu, with Linux 3.5.0-17-generic' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.5.0-17-generic-advanced-9e70fd16-b48b-4f88-adcf-e443aef83124' { recordfail gfxmode $linux_gfx_mode insmod gzio insmod part_msdos insmod ext2 set root='hd0,msdos6' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos6 --hint-efi=hd0,msdos6 --hint-baremetal=ahci0,msdos6 9e70fd16-b48b-4f88-adcf-e443aef83124 else search --no-floppy --fs-uuid --set=root 9e70fd16-b48b-4f88-adcf-e443aef83124 fi echo 'Loading Linux 3.5.0-17-generic ...' linux /boot/vmlinuz-3.5.0-17-generic root=UUID=9e70fd16-b48b-4f88-adcf-e443aef83124 ro quiet splash $vt_handoff echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.5.0-17-generic } menuentry 'Ubuntu, with Linux 3.5.0-17-generic (recovery mode)' --class ubuntu --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-3.5.0-17-generic-recovery-9e70fd16-b48b-4f88-adcf-e443aef83124' { recordfail insmod gzio insmod part_msdos insmod ext2 set root='hd0,msdos6' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos6 --hint-efi=hd0,msdos6 --hint-baremetal=ahci0,msdos6 9e70fd16-b48b-4f88-adcf-e443aef83124 else search --no-floppy --fs-uuid --set=root 9e70fd16-b48b-4f88-adcf-e443aef83124 fi echo 'Loading Linux 3.5.0-17-generic ...' linux /boot/vmlinuz-3.5.0-17-generic root=UUID=9e70fd16-b48b-4f88-adcf-e443aef83124 ro recovery nomodeset echo 'Loading initial ramdisk ...' initrd /boot/initrd.img-3.5.0-17-generic } } ### END /etc/grub.d/10_linux ### ### BEGIN /etc/grub.d/20_linux_xen ### ### END /etc/grub.d/20_linux_xen ### ### BEGIN /etc/grub.d/20_memtest86+ ### menuentry "Memory test (memtest86+)" { insmod part_msdos insmod ext2 set root='hd0,msdos6' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos6 --hint-efi=hd0,msdos6 --hint-baremetal=ahci0,msdos6 9e70fd16-b48b-4f88-adcf-e443aef83124 else search --no-floppy --fs-uuid --set=root 9e70fd16-b48b-4f88-adcf-e443aef83124 fi linux16 /boot/memtest86+.bin } menuentry "Memory test (memtest86+, serial console 115200)" { insmod part_msdos insmod ext2 set root='hd0,msdos6' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos6 --hint-efi=hd0,msdos6 --hint-baremetal=ahci0,msdos6 9e70fd16-b48b-4f88-adcf-e443aef83124 else search --no-floppy --fs-uuid --set=root 9e70fd16-b48b-4f88-adcf-e443aef83124 fi linux16 /boot/memtest86+.bin console=ttyS0,115200n8 } ### END /etc/grub.d/20_memtest86+ ### ### BEGIN /etc/grub.d/30_os-prober ### menuentry 'Windows 7 (loader) (on /dev/sda1)' --class windows --class os $menuentry_id_option 'osprober-chain-F6AE2C13AE2BCB47' { insmod part_msdos insmod ntfs set root='hd0,msdos1' if [ x$feature_platform_search_hint = xy ]; then search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 F6AE2C13AE2BCB47 else search --no-floppy --fs-uuid --set=root F6AE2C13AE2BCB47 fi chainloader +1 } ### END /etc/grub.d/30_os-prober ### ### BEGIN /etc/grub.d/30_uefi-firmware ### ### END /etc/grub.d/30_uefi-firmware ### ### BEGIN /etc/grub.d/40_custom ### # This file provides an easy way to add custom menu entries. Simply type the # menu entries you want to add after this comment. Be careful not to change # the 'exec tail' line above. ### END /etc/grub.d/40_custom ### ### BEGIN /etc/grub.d/41_custom ### if [ -f ${config_directory}/custom.cfg ]; then source ${config_directory}/custom.cfg elif [ -z "${config_directory}" -a -f $prefix/custom.cfg ]; then source $prefix/custom.cfg; fi ### END /etc/grub.d/41_custom ### -------------------------------------------------------------------------------- =============================== sda6/etc/fstab: ================================ -------------------------------------------------------------------------------- # /etc/fstab: static file system information. # # Use 'blkid' to print the universally unique identifier for a # device; this may be used with UUID= as a more robust way to name devices # that works even if disks are added and removed. See fstab(5). # # <file system> <mount point> <type> <options> <dump> <pass> # / was on /dev/sda6 during installation UUID=9e70fd16-b48b-4f88-adcf-e443aef83124 / ext4 errors=remount-ro 0 1 # swap was on /dev/sda7 during installation UUID=52f3dd94-6be7-4a7b-a3ae-f43eb8810483 none swap sw 0 0 -------------------------------------------------------------------------------- =================== sda6: Location of files loaded by Grub: ==================== GiB - GB File Fragment(s) 162.831275940 = 174.838751232 boot/grub/grub.cfg 1 163.036647797 = 175.059267584 boot/initrd.img-3.5.0-17-generic 1 206.871749878 = 222.126850048 boot/vmlinuz-3.5.0-17-generic 1 163.036647797 = 175.059267584 initrd.img 1 163.036647797 = 175.059267584 initrd.img.old 1 206.871749878 = 222.126850048 vmlinuz 1 =============================== StdErr Messages: =============================== cat: write error: Broken pipe cat: write error: Broken pipe ADDITIONAL INFORMATION : =================== log of boot-repair 2012-12-11__00h59 =================== boot-repair version : 3.195~ppa28~quantal boot-sav version : 3.195~ppa28~quantal glade2script version : 3.2.2~ppa45~quantal boot-sav-extra version : 3.195~ppa28~quantal boot-repair is executed in installed-session (Ubuntu 12.10, quantal, Ubuntu, x86_64) CPU op-mode(s): 32-bit, 64-bit BOOT_IMAGE=/boot/vmlinuz-3.5.0-17-generic root=UUID=9e70fd16-b48b-4f88-adcf-e443aef83124 ro quiet splash vt.handoff=7 =================== os-prober: /dev/sda6:The OS now in use - Ubuntu 12.10 CurrentSession:linux /dev/sda1:Windows 7 (loader):Windows:chain =================== blkid: /dev/sda1: UUID="F6AE2C13AE2BCB47" TYPE="ntfs" /dev/sda2: UUID="DC2273012272DFC6" TYPE="ntfs" /dev/sda3: LABEL="New Volume" UUID="1E76E43376E40D79" TYPE="ntfs" /dev/sda5: UUID="5ED60ACDD60AA57D" TYPE="ntfs" /dev/sda6: UUID="9e70fd16-b48b-4f88-adcf-e443aef83124" TYPE="ext4" /dev/sda7: UUID="52f3dd94-6be7-4a7b-a3ae-f43eb8810483" TYPE="swap" 1 disks with OS, 2 OS : 1 Linux, 0 MacOS, 1 Windows, 0 unknown type OS. Warning: extended partition does not start at a cylinder boundary. DOS and Linux will interpret the contents differently. =================== /etc/default/grub : # If you change this file, run 'update-grub' afterwards to update # /boot/grub/grub.cfg. # For full documentation of the options in this file, see: # info -f grub -n 'Simple configuration' GRUB_DEFAULT=0 #GRUB_HIDDEN_TIMEOUT=0 GRUB_HIDDEN_TIMEOUT_QUIET=true GRUB_TIMEOUT=10 GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian` GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" GRUB_CMDLINE_LINUX="" # Uncomment to enable BadRAM filtering, modify to suit your needs # This works with Linux (no patch required) and with any kernel that obtains # the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...) #GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef" # Uncomment to disable graphical terminal (grub-pc only) #GRUB_TERMINAL=console # The resolution used on graphical terminal # note that you can use only modes which your graphic card supports via VBE # you can see them in real GRUB with the command `vbeinfo' #GRUB_GFXMODE=640x480 # Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux #GRUB_DISABLE_LINUX_UUID=true # Uncomment to disable generation of recovery mode menu entries #GRUB_DISABLE_RECOVERY="true" # Uncomment to get a beep at grub start #GRUB_INIT_TUNE="480 440 1" =================== /etc/grub.d/ : drwxr-xr-x 2 root root 4096 Oct 17 20:29 grub.d total 72 -rwxr-xr-x 1 root root 7541 Oct 14 23:06 00_header -rwxr-xr-x 1 root root 5488 Oct 4 15:00 05_debian_theme -rwxr-xr-x 1 root root 10891 Oct 14 23:06 10_linux -rwxr-xr-x 1 root root 10258 Oct 14 23:06 20_linux_xen -rwxr-xr-x 1 root root 1688 Oct 11 19:40 20_memtest86+ -rwxr-xr-x 1 root root 10976 Oct 14 23:06 30_os-prober -rwxr-xr-x 1 root root 1426 Oct 14 23:06 30_uefi-firmware -rwxr-xr-x 1 root root 214 Oct 14 23:06 40_custom -rwxr-xr-x 1 root root 216 Oct 14 23:06 41_custom -rw-r--r-- 1 root root 483 Oct 14 23:06 README =================== UEFI/Legacy mode: This installed-session is not in EFI-mode. EFI in dmesg. Please report this message to [email protected] [ 0.000000] ACPI: UEFI 00000000bafe7000 0003E (v01 DELL QA09 00000002 PTL 00000002) [ 0.000000] ACPI: UEFI 00000000bafe6000 00042 (v01 PTL COMBUF 00000001 PTL 00000001) [ 0.000000] ACPI: UEFI 00000000bafe3000 00256 (v01 DELL QA09 00000002 PTL 00000002) SecureBoot disabled. =================== PARTITIONS & DISKS: sda6 : sda, not-sepboot, grubenv-ok grub2, grub-pc , update-grub, 64, with-boot, is-os, not--efi--part, fstab-without-boot, fstab-without-efi, no-nt, no-winload, no-recov-nor-hid, no-bmgr, notwinboot, apt-get, grub-install, with--usr, fstab-without-usr, not-sep-usr, standard, farbios, . sda1 : sda, not-sepboot, no-grubenv nogrub, no-docgrub, no-update-grub, 32, no-boot, is-os, not--efi--part, part-has-no-fstab, part-has-no-fstab, no-nt, haswinload, no-recov-nor-hid, bootmgr, is-winboot, nopakmgr, nogrubinstall, no---usr, part-has-no-fstab, not-sep-usr, standard, not-far, /mnt/boot-sav/sda1. sda2 : sda, not-sepboot, no-grubenv nogrub, no-docgrub, no-update-grub, 32, no-boot, no-os, not--efi--part, part-has-no-fstab, part-has-no-fstab, no-nt, no-winload, no-recov-nor-hid, no-bmgr, notwinboot, nopakmgr, nogrubinstall, no---usr, part-has-no-fstab, not-sep-usr, standard, farbios, /mnt/boot-sav/sda2. sda3 : sda, not-sepboot, no-grubenv nogrub, no-docgrub, no-update-grub, 32, no-boot, no-os, not--efi--part, part-has-no-fstab, part-has-no-fstab, no-nt, no-winload, no-recov-nor-hid, no-bmgr, notwinboot, nopakmgr, nogrubinstall, no---usr, part-has-no-fstab, not-sep-usr, standard, farbios, /mnt/boot-sav/sda3. sda5 : sda, not-sepboot, no-grubenv nogrub, no-docgrub, no-update-grub, 32, no-boot, no-os, not--efi--part, part-has-no-fstab, part-has-no-fstab, no-nt, no-winload, no-recov-nor-hid, no-bmgr, notwinboot, nopakmgr, nogrubinstall, no---usr, part-has-no-fstab, not-sep-usr, standard, farbios, /mnt/boot-sav/sda5. sda : not-GPT, BIOSboot-not-needed, has-no-EFIpart, not-usb, has-os, 2048 sectors * 512 bytes =================== parted -l: Model: ATA WDC WD7500BPKT-7 (scsi) Disk /dev/sda: 750GB Sector size (logical/physical): 512B/4096B Partition Table: msdos Number Start End Size Type File system Flags 1 106MB 75.2GB 75.1GB primary ntfs boot 2 75.3GB 150GB 75.1GB primary ntfs 3 150GB 170GB 20.1GB primary ntfs 4 170GB 750GB 580GB extended lba 6 170GB 232GB 61.6GB logical ext4 7 232GB 236GB 4181MB logical linux-swap(v1) 5 236GB 750GB 514GB logical ntfs =================== parted -lm: BYT; /dev/sda:750GB:scsi:512:4096:msdos:ATA WDC WD7500BPKT-7; 1:106MB:75.2GB:75.1GB:ntfs::boot; 2:75.3GB:150GB:75.1GB:ntfs::; 3:150GB:170GB:20.1GB:ntfs::; 4:170GB:750GB:580GB:::lba; 6:170GB:232GB:61.6GB:ext4::; 7:232GB:236GB:4181MB:linux-swap(v1)::; 5:236GB:750GB:514GB:ntfs::; =================== mount: /dev/sda6 on / type ext4 (rw,errors=remount-ro) proc on /proc type proc (rw,noexec,nosuid,nodev) sysfs on /sys type sysfs (rw,noexec,nosuid,nodev) none on /sys/fs/fuse/connections type fusectl (rw) none on /sys/kernel/debug type debugfs (rw) none on /sys/kernel/security type securityfs (rw) udev on /dev type devtmpfs (rw,mode=0755) devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620) tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755) none on /run/lock type tmpfs (rw,noexec,nosuid,nodev,size=5242880) none on /run/shm type tmpfs (rw,nosuid,nodev) none on /run/user type tmpfs (rw,noexec,nosuid,nodev,size=104857600,mode=0755) gvfsd-fuse on /run/user/dev/gvfs type fuse.gvfsd-fuse (rw,nosuid,nodev,user=dev) /dev/sda1 on /mnt/boot-sav/sda1 type fuseblk (rw,nosuid,nodev,allow_other,blksize=4096) /dev/sda2 on /mnt/boot-sav/sda2 type fuseblk (rw,nosuid,nodev,allow_other,blksize=4096) /dev/sda3 on /mnt/boot-sav/sda3 type fuseblk (rw,nosuid,nodev,allow_other,blksize=4096) /dev/sda5 on /mnt/boot-sav/sda5 type fuseblk (rw,nosuid,nodev,allow_other,blksize=4096) =================== ls: /sys/block/sda (filtered): alignment_offset bdi capability dev device discard_alignment events events_async events_poll_msecs ext_range holders inflight power queue range removable ro sda1 sda2 sda3 sda4 sda5 sda6 sda7 size slaves stat subsystem trace uevent /sys/block/sr0 (filtered): alignment_offset bdi capability dev device discard_alignment events events_async events_poll_msecs ext_range holders inflight power queue range removable ro size slaves stat subsystem trace uevent /dev (filtered): alarm ashmem autofs binder block bsg btrfs-control bus cdrom cdrw char console core cpu cpu_dma_latency disk dri dvd dvdrw ecryptfs fb0 fb1 fd full fuse hpet input kmsg kvm log mapper mcelog mei mem net network_latency network_throughput null oldmem port ppp psaux ptmx pts random rfkill rtc rtc0 sda sda1 sda2 sda3 sda4 sda5 sda6 sda7 sg0 sg1 shm snapshot snd sr0 stderr stdin stdout uinput urandom v4l vga_arbiter vhost-net video0 zero ls /dev/mapper: control =================== df -Th: Filesystem Type Size Used Avail Use% Mounted on /dev/sda6 ext4 57G 2.7G 51G 6% / udev devtmpfs 1.9G 12K 1.9G 1% /dev tmpfs tmpfs 770M 892K 769M 1% /run none tmpfs 5.0M 0 5.0M 0% /run/lock none tmpfs 1.9G 260K 1.9G 1% /run/shm none tmpfs 100M 44K 100M 1% /run/user /dev/sda1 fuseblk 70G 36G 35G 51% /mnt/boot-sav/sda1 /dev/sda2 fuseblk 70G 66G 4.8G 94% /mnt/boot-sav/sda2 /dev/sda3 fuseblk 19G 87M 19G 1% /mnt/boot-sav/sda3 /dev/sda5 fuseblk 479G 436G 44G 92% /mnt/boot-sav/sda5 =================== fdisk -l: Disk /dev/sda: 750.2 GB, 750156374016 bytes 255 heads, 63 sectors/track, 91201 cylinders, total 1465149168 sectors Units = sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 4096 bytes Disk identifier: 0x1dc69d0b Device Boot Start End Blocks Id System /dev/sda1 * 206848 146802687 73297920 7 HPFS/NTFS/exFAT /dev/sda2 147007488 293623807 73308160 7 HPFS/NTFS/exFAT /dev/sda3 293623808 332820613 19598403 7 HPFS/NTFS/exFAT /dev/sda4 332822526 1465145343 566161409 f W95 Ext'd (LBA) Partition 4 does not start on physical sector boundary. /dev/sda5 461342720 1465145343 501901312 7 HPFS/NTFS/exFAT /dev/sda6 332822528 453171199 60174336 83 Linux /dev/sda7 453173248 461338623 4082688 82 Linux swap / Solaris Partition table entries are not in disk order =================== Recommended repair Recommended-Repair This setting will reinstall the grub2 of sda6 into the MBR of sda. Additional repair will be performed: unhide-bootmenu-10s grub-install (GRUB) 2.00-7ubuntu11,grub-install (GRUB) 2. Reinstall the GRUB of sda6 into the MBR of sda Installation finished. No error reported. grub-install /dev/sda: exit code of grub-install /dev/sda:0 update-grub Generating grub.cfg ... Found linux image: /boot/vmlinuz-3.5.0-17-generic Found initrd image: /boot/initrd.img-3.5.0-17-generic Found memtest86+ image: /boot/memtest86+.bin Found Windows 7 (loader) on /dev/sda1 Unhide GRUB boot menu in sda6/boot/grub/grub.cfg Boot successfully repaired. You can now reboot your computer. The boot files of [The OS now in use - Ubuntu 12.10] are far from the start of the disk. Your BIOS may not detect them. You may want to retry after creating a /boot partition (EXT4, >200MB, start of the disk). This can be performed via tools such as gParted. Then select this partition via the [Separate /boot partition:] option of [Boot Repair]. (https://help.ubuntu.com/community/BootPartition)

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• Building and Deploying Windows Azure Web Sites using Git and GitHub for Windows

  - by shiju

  Microsoft Windows Azure team has released a new version of Windows Azure which is providing many excellent features. The new Windows Azure provides Web Sites which allows you to deploy up to 10 web sites  for free in a multitenant shared environment and you can easily upgrade this web site to a private, dedicated virtual server when the traffic is grows. The Meet Windows Azure Fact Sheet provides the following information about a Windows Azure Web Site: Windows Azure Web Sites enable developers to easily build and deploy websites with support for multiple frameworks and popular open source applications, including ASP.NET, PHP and Node.js. With just a few clicks, developers can take advantage of Windows Azure’s global scale without having to worry about operations, servers or infrastructure. It is easy to deploy existing sites, if they run on Internet Information Services (IIS) 7, or to build new sites, with a free offer of 10 websites upon signup, with the ability to scale up as needed with reserved instances. Windows Azure Web Sites includes support for the following: Multiple frameworks including ASP.NET, PHP and Node.js Popular open source software apps including WordPress, Joomla!, Drupal, Umbraco and DotNetNuke Windows Azure SQL Database and MySQL databases Multiple types of developer tools and protocols including Visual Studio, Git, FTP, Visual Studio Team Foundation Services and Microsoft WebMatrix Signup to Windows and Enable Azure Web Sites You can signup for a 90 days free trial account in Windows Azure from here. After creating an account in Windows Azure, go to https://account.windowsazure.com/ , and select to preview features to view the available previews. In the Web Sites section of the preview features, click “try it now” which will enables the web sites feature Create Web Site in Windows Azure To create a web sites, login to the Windows Azure portal, and select Web Sites from and click New icon from the left corner  Click WEB SITE, QUICK CREATE and put values for URL and REGION dropdown. You can see the all web sites from the dashboard of the Windows Azure portal Set up Git Publishing Select your web site from the dashboard, and select Set up Git publishing To enable Git publishing , you must give user name and password which will initialize a Git repository Clone Git Repository We can use GitHub for Windows to publish apps to non-GitHub repositories which is well explained by Phil Haack on his blog post. Here we are going to deploy the web site using GitHub for Windows. Let’s clone a Git repository using the Git Url which will be getting from the Windows Azure portal. Let’s copy the Git url and execute the “git clone” with the git url. You can use the Git Shell provided by GitHub for Windows. To get it, right on the GitHub for Windows, and select open shell here as shown in the below picture. When executing the Git Clone command, it will ask for a password where you have to give password which specified in the Windows Azure portal. After cloning the GIT repository, you can drag and drop the local Git repository folder to GitHub for Windows GUI. This will automatically add the Windows Azure Web Site repository onto GitHub for Windows where you can commit your changes and publish your web sites to Windows Azure. Publish the Web Site using GitHub for Windows We can add multiple framework level files including ASP.NET, PHP and Node.js, to the local repository folder can easily publish to Windows Azure from GitHub for Windows GUI. For this demo, let me just add a simple Node.js file named Server.js which handles few request handlers. 1: var http = require('http'); 2: var port=process.env.PORT; 3: var querystring = require('querystring'); 4: var utils = require('util'); 5: var url = require("url"); 6:   7: var server = http.createServer(function(req, res) { 8: switch (req.url) { //checking the request url 9: case '/': 10: homePageHandler (req, res); //handler for home page 11: break; 12: case '/register': 13: registerFormHandler (req, res);//hamdler for register 14: break; 15: default: 16: nofoundHandler (req, res);// handler for 404 not found 17: break; 18: } 19: }); 20: server.listen(port); 21: //function to display the html form 22: function homePageHandler (req, res) { 23: console.log('Request handler home was called.'); 24: res.writeHead(200, {'Content-Type': 'text/html'}); 25: var body = '<html>'+ 26: '<head>'+ 27: '<meta http-equiv="Content-Type" content="text/html; '+ 28: 'charset=UTF-8" />'+ 29: '</head>'+ 30: '<body>'+ 31: '<form action="/register" method="post">'+ 32: 'Name:<input type=text value="" name="name" size=15></br>'+ 33: 'Email:<input type=text value="" name="email" size=15></br>'+ 34: '<input type="submit" value="Submit" />'+ 35: '</form>'+ 36: '</body>'+ 37: '</html>'; 38: //response content 39: res.end(body); 40: } 41: //handler for Post request 42: function registerFormHandler (req, res) { 43: console.log('Request handler register was called.'); 44: var pathname = url.parse(req.url).pathname; 45: console.log("Request for " + pathname + " received."); 46: var postData = ""; 47: req.on('data', function(chunk) { 48: // append the current chunk of data to the postData variable 49: postData += chunk.toString(); 50: }); 51: req.on('end', function() { 52: // doing something with the posted data 53: res.writeHead(200, "OK", {'Content-Type': 'text/html'}); 54: // parse the posted data 55: var decodedBody = querystring.parse(postData); 56: // output the decoded data to the HTTP response 57: res.write('<html><head><title>Post data</title></head><body><pre>'); 58: res.write(utils.inspect(decodedBody)); 59: res.write('</pre></body></html>'); 60: res.end(); 61: }); 62: } 63: //Error handler for 404 no found 64: function nofoundHandler(req, res) { 65: console.log('Request handler nofound was called.'); 66: res.writeHead(404, {'Content-Type': 'text/plain'}); 67: res.end('404 Error - Request handler not found'); 68: } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } If there is any change in the local repository folder, GitHub for Windows will automatically detect the changes. In the above step, we have just added a Server.js file so that GitHub for Windows will detect the changes. Let’s commit the changes to the local repository before publishing the web site to Windows Azure. After committed the all changes, you can click publish button which will publish the all changes to Windows Azure repository. The following screen shot shows deployment history from the Windows Azure portal.   GitHub for Windows is providing a sync button which can use for synchronizing between local repository and Windows Azure repository after making any commit on the local repository after any changes. Our web site is running after the deployment using Git Summary Windows Azure Web Sites lets the developers to easily build and deploy websites with support for multiple framework including ASP.NET, PHP and Node.js and can easily deploy the Web Sites using Visual Studio, Git, FTP, Visual Studio Team Foundation Services and Microsoft WebMatrix. In this demo, we have deployed a Node.js Web Site to Windows Azure using Git. We can use GitHub for Windows to publish apps to non-GitHub repositories and can use to publish Web SItes to Windows Azure.

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• Alpha issue with SharpDX SpriteBatch in WPF

  - by Kingdom

  .Hi devs, I'm coding a game using SharpDX in a WPF context. void Load() { sb = new SpriteBatch(GraphicsDevice); t2d = Content.Load<Texture2D>("Sprite.png"); } void Draw() { sb.Begin(); sb.Draw(t2d, new Rectangle(0, 0, 64, 64), Color.White); sb.End(); } I made Sprite.png, an object with pink color (alpha = 0%) for the background. The output show me my object but with the pink square at more or less 50% rate! So if I try to draw more sprites, it's like a little poney dream. Note If I apply Color.Black on the Draw method, the sprite is like expected :|

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• Advice for creating fog of war on tilemap game XNA

  - by Sigh-AniDe

  I have created a 2D Tile Based game. The game has a single path that the sprite can move on. I want to create to make the entire screen black except for where the sprite is. The sprite has commands such as left where he keeps looking left, right where he keeps looking right and move forward where he moves in the direction he is looking. I want to make it such that when he looks left then the tile on the left of the sprites fog should be removed and so on for all the sides. What is the best way to do this? Is there any tutorials that you guys know of that i can take a look at? Thanks

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• Video Recording Not Working in ICS

  - by Nirav Ranpara

  I have implement code Record video in Android Phone . This code is working in 2.2 , 2.3 . not in ICS But when I checked in ICS code is not working ? here I posted code and xml file. videorecord.java import java.io.File; import java.io.IOException; import android.app.Activity; import android.app.AlertDialog; import android.content.Context; import android.content.DialogInterface; import android.content.Intent; import android.content.SharedPreferences; import android.hardware.Camera; import android.media.CamcorderProfile; import android.media.MediaRecorder; import android.os.Bundle; import android.os.CountDownTimer; import android.os.Environment; import android.util.Log; import android.view.Display; import android.view.KeyEvent; import android.view.SurfaceHolder; import android.view.SurfaceView; import android.view.View; import android.widget.EditText; import android.widget.FrameLayout; import android.widget.ImageView; import android.widget.LinearLayout; import android.widget.TextView; import android.widget.Toast; public class videorecord extends Activity{ SharedPreferences.Editor pre; String filename; CountDownTimer t; private Camera myCamera; private MyCameraSurfaceView myCameraSurfaceView; private MediaRecorder mediaRecorder; Integer cnt=0; LinearLayout myButton; TextView myButton1; SurfaceHolder surfaceHolder; boolean recording; private TextView txtcount; private ImageView btnplay; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); recording = false; setContentView(R.layout.videorecord); init(); myCamera = getCameraInstance(); if(myCamera == null){ } myCameraSurfaceView = new MyCameraSurfaceView(this, myCamera); FrameLayout myCameraPreview = (FrameLayout)findViewById(R.id.videoview); Display display = getWindowManager().getDefaultDisplay(); int width = display.getWidth(); int height = display.getHeight(); myCameraSurfaceView.setLayoutParams(new LinearLayout.LayoutParams(width, height-60)); myCameraPreview.addView(myCameraSurfaceView); myButton = (LinearLayout)findViewById(R.id.mybutton); btnplay.setOnClickListener(myButtonOnClickListener); } private void init() { txtcount = (TextView) findViewById(R.id.txtcounter); //myButton1 = (TextView) findViewById(R.id.mybutton1); btnplay = (ImageView)findViewById(R.id.btnplay); t = new CountDownTimer( Long.MAX_VALUE , 1000) { @Override public void onTick(long millisUntilFinished) { cnt++; String time = new Integer(cnt).toString(); long millis = cnt; int seconds = (int) (millis / 60); int minutes = seconds / 60; seconds = seconds % 60; txtcount.setText(String.format("%d:%02d:%02d", minutes, seconds,millis)); } @Override public void onFinish() { } }; } @Override public boolean onKeyDown(int keyCode, KeyEvent event) { if ((keyCode == KeyEvent.KEYCODE_BACK)) { if(recording) { new AlertDialog.Builder(videorecord.this).setTitle("Do you want to save Video ?") .setPositiveButton("OK", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int which) { filename(); //finish(); } }).setNegativeButton("Cancle", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int which) { // TODO Auto-generated method stub } }).show(); } else { if ((keyCode == KeyEvent.KEYCODE_BACK)) { //Intent homeIntent= new Intent(Intent.ACTION_MAIN); //homeIntent.addCategory(Intent.CATEGORY_HOME); //homeIntent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); //startActivity(homeIntent); //this.finishActivity(1); finish(); } //moveTaskToBack(true); // finish(); return super.onKeyDown(keyCode, event); } } else { // Toast.makeText(getApplicationContext(), "asd", Toast.LENGTH_LONG).show(); android.os.Process.killProcess(android.os.Process.myPid()) ; } return super.onKeyDown(keyCode, event); } ImageView.OnClickListener myButtonOnClickListener = new ImageView.OnClickListener(){ public void onClick(View v) { if(recording){ Log.e("Record error", "error in recording ."); mediaRecorder.stop(); t.cancel(); filename(); releaseMediaRecorder(); }else{ releaseCamera(); Log.e("Record Stop error", "error in recording ."); // if(!prepareMediaRecorder()){ prepareMediaRecorder(); finish(); } mediaRecorder.start(); recording = true; // myButton1.setText("STOP Recording"); // btnplay.setImageResource(android.R.drawable.ic_media_pause); btnplay.setImageResource(R.drawable.stoprec); t.start(); } }}; private Camera getCameraInstance(){ Camera c = null; try { c = Camera.open(); } catch (Exception e){ } return c; } private void filename() { AlertDialog.Builder alert = new AlertDialog.Builder(this); alert.setTitle("Save Video"); alert.setMessage("Enter File Name"); final EditText input = new EditText(this); alert.setView(input); alert.setPositiveButton("Ok", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int whichButton) { if(input.getText().length()>=1) { filename = input.getText().toString(); File sdcard = new File(Environment.getExternalStorageDirectory() + "/VideoRecord"); File from = new File(sdcard,"null.mp4"); File to = new File(sdcard,filename+".mp4"); from.renameTo(to); SharedPreferences sp = videorecord.this.getSharedPreferences("data", MODE_WORLD_WRITEABLE); pre = sp.edit(); pre.clear(); pre.commit(); pre.putString("lastvideo", filename+".mp4"); pre.commit(); //btnplay.setImageResource(android.R.drawable.ic_media_play); btnplay.setImageResource(R.drawable.startrec); // Intent intent = new Intent(videorecord.this,StopVidoWatch_Activity.class); // startActivity(intent); Intent myIntent = new Intent(getApplicationContext(), StopVidoWatch_Activity.class).setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); startActivity(myIntent); } else { filename(); } } }); alert.setNegativeButton("Cancel", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int whichButton) { // Intent intent = new Intent(videorecord.this,StopVidoWatch_Activity.class); // startActivity(intent); File file = new File(Environment.getExternalStorageDirectory() + "/VideoRecord/null.mp4"); //boolean deleted = file.delete(); file.delete(); finish(); } }); alert.show(); } private boolean prepareMediaRecorder(){ myCamera = getCameraInstance(); mediaRecorder = new MediaRecorder(); myCamera.unlock(); mediaRecorder.setCamera(myCamera); mediaRecorder.setAudioSource(MediaRecorder.AudioSource.CAMCORDER); mediaRecorder.setVideoSource(MediaRecorder.VideoSource.CAMERA); mediaRecorder.setProfile(CamcorderProfile.get(CamcorderProfile.QUALITY_HIGH)); File folder = new File(Environment.getExternalStorageDirectory() + "/VideoRecord"); boolean success = false; if (!folder.exists()) { success = folder.mkdir(); } if (!success) { } else { } mediaRecorder.setOutputFile("/sdcard/VideoRecord/"+filename+".mp4"); mediaRecorder.setMaxDuration(60000); mediaRecorder.setMaxFileSize(5000000); Display display = getWindowManager().getDefaultDisplay(); int width = display.getHeight(); int height = display.getWidth(); String s = new String(); s= s.valueOf(width); String s1 = new String(); s1= s1.valueOf(height); // Toast.makeText(videorecord.this, "Width : " + s , Toast.LENGTH_LONG).show(); // Toast.makeText(videorecord.this, "Height : " + s1 , Toast.LENGTH_LONG).show(); mediaRecorder.setVideoSize(height, width); mediaRecorder.setPreviewDisplay(myCameraSurfaceView.getHolder().getSurface()); try { mediaRecorder.prepare(); } catch (IllegalStateException e) { releaseMediaRecorder(); return false; } catch (IOException e) { releaseMediaRecorder(); return false; } return true; } @Override protected void onPause() { super.onPause(); releaseMediaRecorder(); releaseCamera(); } private void releaseMediaRecorder() { if (mediaRecorder != null) { mediaRecorder.reset(); mediaRecorder.release(); mediaRecorder = null; myCamera.lock(); } } private void releaseCamera(){ if (myCamera != null){ myCamera.release(); myCamera = null; } } public class MyCameraSurfaceView extends SurfaceView implements SurfaceHolder.Callback{ private SurfaceHolder mHolder; private Camera mCamera; public MyCameraSurfaceView(Context context, Camera camera) { super(context); mCamera = camera; mHolder = getHolder(); mHolder.addCallback(this); mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS); } public void surfaceChanged(SurfaceHolder holder, int format, int weight, int height) { if (mHolder.getSurface() == null){ return; } try { mCamera.stopPreview(); } catch (Exception e){ } try { mCamera.setPreviewDisplay(mHolder); mCamera.startPreview(); } catch (Exception e){ } } public void surfaceCreated(SurfaceHolder holder) { try { mCamera.setPreviewDisplay(holder); mCamera.startPreview(); } catch (IOException e) { } } public void surfaceDestroyed(SurfaceHolder holder) { } } } videorecord.xml <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <FrameLayout android:layout_width="fill_parent" android:layout_height="fill_parent" > <FrameLayout android:id="@+id/videoview" android:layout_width="fill_parent" android:layout_height="fill_parent"></FrameLayout> <LinearLayout android:id="@+id/mybutton" android:layout_width="fill_parent" android:layout_marginBottom="0dip" android:layout_height="wrap_content" android:orientation="horizontal" android:layout_weight="0" > <!-- <TextView android:text="START Recording" android:id="@+id/mybutton1" android:layout_height="wrap_content" android:layout_width="wrap_content" style="@style/savestyle" android:layout_weight="1" android:gravity="left" > </TextView> --> <ImageView android:layout_height="wrap_content" android:id="@+id/btnplay" android:padding="5dip" android:background="#A0000000" android:textColor="#ffffffff" android:layout_width="wrap_content" android:src="@drawable/startrec" /> </LinearLayout> <TextView android:text="00:00:00" android:id="@+id/txtcounter" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_gravity="right|bottom" android:padding="5dip" android:background="#A0000000" android:textColor="#ffffffff" /> </FrameLayout> <RelativeLayout android:layout_width="fill_parent" android:layout_height="fill_parent" android:background="@color/bgcolor" > <LinearLayout android:layout_above="@+id/mybutton" android:orientation="horizontal" android:layout_width="fill_parent" android:layout_height="fill_parent" > </LinearLayout> </RelativeLayout> </LinearLayout>

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• Ask How-To Geek: Tiling Windows, iOS Remote Desktop, and Getting a Handle on Windows 7 Libraries

  - by Jason Fitzpatrick

  This week we’re taking a look at how to tile application windows in Windows 7, remote controlling your desktop from iOS devices, and understanding exactly what Windows 7 libraries are. Once a week we dip into our reader mailbag and help readers solve their problems, sharing the useful solutions with you in the process. Read on to see the fixes for this week’s reader dilemmas. Latest Features How-To Geek ETC How To Colorize Black and White Vintage Photographs in Photoshop How To Get SSH Command-Line Access to Windows 7 Using Cygwin The How-To Geek Video Guide to Using Windows 7 Speech Recognition How To Create Your Own Custom ASCII Art from Any Image How To Process Camera Raw Without Paying for Adobe Photoshop How Do You Block Annoying Text Message (SMS) Spam? Battlestar Galactica – Caprica Map of the 12 Colonies (Wallpaper Also Available) View Enlarged Versions of Thumbnail Images with Thumbnail Zoom for Firefox IntoNow Identifies Any TV Show by Sound Walk Score Calculates a Neighborhood’s Pedestrian Friendliness Factor Fantasy World at Twilight Wallpaper Hack a Wireless Doorbell into a Snail Mail Indicator

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• How to use integrated Intel graphics instead of Nvidia graphics on MacBook Pro?

  - by Benjamin Geese

  I am running Ubuntu 12.04 64bit on MacBook Pro 15" 2010 (MacBookPro6,2) and I would like to use the integrated Intel graphics instead of the dedicated Nvidia graphics Ubuntu boots with on this machine. I am booting with UEFI, not REFIT or similar. I managed to switch to UEFI with the help of this page. This wiki page also contains tips on switching to Intel graphics which include some (for me) cryptic boot commands to grub. However if I follow the guide, my display stays just black. Currently, I am only looking for solution to use Intel graphics for Ubuntu to save power and keep my MacBook cool. Dynamic switching or stuff like that is not required.

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• Internet Explorer: Flash 1 item remaining- Movie Not Loaded

  A couple of days ago I started having an issue where if Id go to Youtube.com to look at a Flash movie, Id get to see only a black screen in the movie area. A right click on the movie and Id see Movie not loaded. In addition, the browser status bar reports 1 item remaining basically meaning, Im waiting for this movie to load. Of course, this never goes away. Heres how I fixed it: In Internet Explorer, choose Tools / Internet Options. In the Browsing History section, click the Delete button...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• Problems with graphics of Sony Vaio Z

  - by dpcat237

  Hello, I have problem with my Sony Vaio Z VPCZ1. It has physical selector of GPUs which Linux kernel not detect. So after GRUB I see black display (I tried different distributions of Ubuntu and other Linux OS). I read in Ubuntu 10.10 was solve same problem with hybrid graphics but not in my case ^^ I found solutions (not easy at do) for oldest models. But I'm not expert in Linux and before I prefer ask people with more experience. Somebody can help me? Someone installed Ubuntu in same laptop? PS. for more information I found different webs: http://goo.gl/ktvq Thanks Regards

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• Create Awesome Map-Based Wallpapers for Your Desktop with ‘Map –> Image’

  - by Asian Angel

  Are you tired of using the same old types of wallpapers on your desktop? Then add something fresh and unique to your desktop with custom-created map wallpapers from ‘Map – Image’. When you first visit the website it will show the default location of San Francisco (home of the developers). To get started simply enter your location in the search blank in the upper left corner and click the Go Button. Your chosen location will appear in a basic black and white format as shown here. 6 Start Menu Replacements for Windows 8 What Is the Purpose of the “Do Not Cover This Hole” Hole on Hard Drives? How To Log Into The Desktop, Add a Start Menu, and Disable Hot Corners in Windows 8

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• Ask How-To Geek: Speeding Up the Start Menu Search, Halting Auto-Rotating Android Screens, and Dropbox-powered Torrenting

  - by Jason Fitzpatrick

  This week we take a look at tweaking the Window’s start menu search for fast and focused searching, locking down a hyperactive Android screen, and fueling your torrenting habit through Dropbox. Once a week we dip into our reader mailbag to help readers solve their problems, sharing the useful solutions with you in the process. Read on to see our fixes for this week’s reader dilemmas. Latest Features How-To Geek ETC Inspire Geek Love with These Hilarious Geek Valentines How to Integrate Dropbox with Pages, Keynote, and Numbers on iPad RGB? CMYK? Alpha? What Are Image Channels and What Do They Mean? How to Recover that Photo, Picture or File You Deleted Accidentally How To Colorize Black and White Vintage Photographs in Photoshop How To Get SSH Command-Line Access to Windows 7 Using Cygwin Amazon Finally Adds Real Page Numbers to the Kindle Now You Can Print Google Docs and Gmail through Google Cloud Print AppBrain Enables Direct-to-Phone Installation Again Build a DIY Clapper to Hone Your Electronics Chops How to Kid Proof Your Computer’s Power and Reset Buttons Microsoft’s Windows Media Player Extension Adds H.264 Support Back to Google Chrome

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• NVIDIA graphics driver on Macbook Pro 10,1

  - by Boatzart

  I just installed 14.04 over my old 12.04 partition on my Macbook Pro 10,1 (which is dual-booting with OS X) by following the instructions here. The only difference is that I'm using rEFInd instead of rEFIt. The proprietary NVIDIA drivers worked great with 12.04, but now I'm unable to boot into Unity with it in 14.04. Generally, I just get a black screen after the Grub menu, though occasionally I get some kind of panic screen like this, where I see errors like: [drm: __gen6_gt_force_wake_mt_get] *ERROR* Timed out waiting for forcewake old ack to clear. [drm: __gen6_gt_wait_for_thread_c0] *ERROR* GT thread status wait timed out [drm: __intel_ring_setup_status_page] *ERROR* render ring: wait for SyncFlush to complete for TLB invalidation timed out etc. Using the nouveau drivers works fine, but everything feels sluggish so I would really like to get the NVIDIA drivers working. Has anyone successfully gotten the NVIDIA drivers working with the GT-650M Mac Edition?

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• Desktop Fun: Valentine’s Day 2011 Wallpaper Collection [Bonus Edition]

  - by Asian Angel

  First, we brought you fonts for your Valentine’s Day stationary needs followed by icon packs to help customize your desktop. Today we finish our romantic holiday trio out with a larger than normal size wallpaper collection Latest Features How-To Geek ETC How to Integrate Dropbox with Pages, Keynote, and Numbers on iPad RGB? CMYK? Alpha? What Are Image Channels and What Do They Mean? How to Recover that Photo, Picture or File You Deleted Accidentally How To Colorize Black and White Vintage Photographs in Photoshop How To Get SSH Command-Line Access to Windows 7 Using Cygwin The How-To Geek Video Guide to Using Windows 7 Speech Recognition Android Notifier Pushes Android Notices to Your Desktop Dead Space 2 Theme for Chrome and Iron Carl Sagan and Halo Reach Mashup – We Humans are Capable of Greatness [Video] Battle the Necromorphs Once Again on Your Desktop with the Dead Space 2 Theme for Windows 7 HTC Home Brings HTC’s Weather Widget to Your Windows Desktop Apps Uninstall Batch Removes Android Applications

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• Desktop Fun: Valentine’s Day Icon Packs

  - by Asian Angel

  Are you looking forward to Valentine’s Day? Then we have the perfect way for you to start customizing your desktop for the holiday with our Valentine’s Day Icon Packs collection Latest Features How-To Geek ETC How To Colorize Black and White Vintage Photographs in Photoshop How To Get SSH Command-Line Access to Windows 7 Using Cygwin The How-To Geek Video Guide to Using Windows 7 Speech Recognition How To Create Your Own Custom ASCII Art from Any Image How To Process Camera Raw Without Paying for Adobe Photoshop How Do You Block Annoying Text Message (SMS) Spam? Change Your MAC Address to Avoid Free Internet Restrictions Battlestar Galactica – Caprica Map of the 12 Colonies (Wallpaper Also Available) View Enlarged Versions of Thumbnail Images with Thumbnail Zoom for Firefox IntoNow Identifies Any TV Show by Sound Walk Score Calculates a Neighborhood’s Pedestrian Friendliness Factor Fantasy World at Twilight Wallpaper

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• My fresh installed ubuntu 12,4 won´t start without live usb drive

  - by Alexander Neira

  I just installed a fresh copy of ubuntu 12,04 in my netbook, through a live USB drive. I used the whole HDD and erased an existent win 7 partition. It installed everything and then asked me to reboot. When I did that, after rebooting, it only appeared the writer marker on top of a black screen and only that. Then, i plugged in again my usb drive and reboot. It loaded, but in the loading screen sent me (once) an error about the hard drive, that some file was missing (sorry i coulnd't write down the exact message). After that, I tried to re install ubuntu using my USB drive, but it sends me inmediately to the login screen. How do I solve this?

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• SharePoint Saturday Michigan 2010 Recap, Slides, and Photos

  - by Brian Jackett

  This past weekend I attended SharePoint Saturday Michigan (SPSMI) in Ann Arbor, Michigan.  For those unfamiliar, SharePoint Saturday is a community driven event where various speakers gather to present at a FREE conference on all topics related to SharePoint.  This made my third SharePoint Saturday attended and second I’ve spoken at.  I believe today it was announced that about 210 people total attended the event.  I was very happy with the turnout, especially the ratio of male to female attendees.  Typically with computer related conferences the ratio leans towards more males attending, but both Peter Serzo (one of conference organizers) and I both commented to each other that at the end of the day it appeared to be close to 40% women in the crowd.  So here’s my recap of the weekend. Arrival     Friday afternoon I drove up from Columbus, OH to Ann Arbor, MI and arrived around 4pm.  I was attempting to avoid the rush hour traffic and construction backups.  Turned out to be a good idea because other speakers coming up Friday got stuck on a highway which literally closed down in both directions due to a bad accident.  I was talking my friend Sean McDonough through the highway closing and this was the first time I had seen a solid black traffic line on Google Maps.  Most of us are familiar with Green, Yellow, and Red, but this line was black if that tells you how bad it got. Speaker “Dinner”     Fast forward a few hours and it was time for the speaker “dinner.”  I put “dinner” in quotes because with this night alone SPSMI set a new bar for nicest and most extravagant speaker appreciation events for SharePoint Saturday.  By tapping into some very influential contacts, the conference organizers were able to provide a truck limo (yep you heard right) with refreshments, access to an underground suite at the Palace of Auburn Hills, and courtside tickets to see the Detroit Pistons play that night.  Being a Michigan native I have to say that I was absolutely floored by this experience and very thankful to our conference organizers Peter, Sebastian, and Jesse along with Trillium Teamologies. Sessions     The actual conference started Saturday morning at 9am with the keynote by Rob Collie who is the Microsoft program manager for PowerPivot.  The day continued and I attended the following sessions: Mike Watson (@mikewat) – “SharePoint 2010 Fight Night: Devs vs. Admins” Karl Swedeberg (@kswedberg) – “A Walk on the Client Side with jQuery“ [my session] Brian Jackett (@briantjackett) - “Real World Deployment of SharePoint 2007 Solutions” Jeff Willinger (@jwillie) - “Social Computing and Collaboration Inside and Outside the 4 Walls” Paul Schaeflein (@paulschaeflein) – “PowerShell for the SharePoint Developer” My Presentation     I had a great time presenting my session on Deploying SharePoint 2007 Solutions, but it wasn’t without its fair share of technical issues.  As my session was right after lunch I came in to my room 10 mins early to set up my laptop, slides, and demos.  As a quick background note, a few months ago I got an upgraded laptop from my company Sogeti and have been dual booting it between XP (factory installed) and Windows Server 2008 R2 w/ Hyper-V.  As such I had prepared all of my demo virtual machines to run under Hyper-V.  About 3 minutes before my session was scheduled to start though it became apparent that I did not have the correct display drivers to connect Windows Server 2008 R2 to the projector…     As you can imagine this was a slight cause for concern as I was potentially going to be unable to give my presentation.  Luckily for me I usually prepare for such unforeseen issues and had my presentation and some spare VMs that would run on XP on my external hard drive.  Knowing this I rebooted my machine into XP and began my presentation without slides until about 5 mins into the session when everything was up and running on XP.  Despite this being the first time I gave this presentation I have to say it was one of my favorites I’ve given so far.  The audience was very engaged in the session and I received some great, positive feedback afterwards.  Thanks to all who attended my session, I appreciate it very much. Link to Presentation Files     For those of you who attended my session and would like my slides or demo PowerShell scripts they can be found on my SkyDrive at the link below.  Also, if you have a few minutes and wouldn’t mind rating my session I have this session posted on SpeakerRate.  As speakers we always appreciate any and all feedback attendees offer, so thank you if you are able to provide any. SkyDrive folder with session files Rate my SharePoint 2007 Solutions session   Picture Albums     For everyone else, here are my pictures from the weekend.  The first link is to my FaceBook album which will have tagging (recommend this one.)  The second is to my Live album if you care for higher resolution images. http://www.facebook.com/album.php?aid=2154482&id=21905041&l=a3fb72ee8c View Full Album Conclusion     A big thank you goes out to all of the organizers, speakers, sponsors, and attendees of SPSMI.  As I’ve said so many times, without each and every one of you these events wouldn’t be possible.  I thoroughly enjoyed this trip back to my home state and presenting a new session.  For those interested in my upcoming schedule I will be giving two sessions on PowerShell at SharePoint Saturday Charlotte in April, helping plan Stir Trek: Iron Man Edition in May, and I’m submitting sessions to Day of .Net Ann Arbor in May as well.  Beyond that I haven’t planned out any travels.  Thanks for reading my recap.  Look forward to more technical posts now that I have a short break in conferences.         -Frog Out   links: Michigan image

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• Demystifying Silverlight Dependency Properties

  - by dwahlin

  I have the opportunity to teach a lot of people about Silverlight (amongst other technologies) and one of the topics that definitely confuses people initially is the concept of dependency properties. I confess that when I first heard about them my initial thought was “Why do we need a specialized type of property?” While you can certainly use standard CLR properties in Silverlight applications, Silverlight relies heavily on dependency properties for just about everything it does behind the scenes. In fact, dependency properties are an essential part of the data binding, template, style and animation functionality available in Silverlight. They simply back standard CLR properties. In this post I wanted to put together a (hopefully) simple explanation of dependency properties and why you should care about them if you’re currently working with Silverlight or looking to move to it.   What are Dependency Properties? XAML provides a great way to define layout controls, user input controls, shapes, colors and data binding expressions in a declarative manner. There’s a lot that goes on behind the scenes in order to make XAML work and an important part of that magic is the use of dependency properties. If you want to bind data to a property, style it, animate it or transform it in XAML then the property involved has to be a dependency property to work properly. If you’ve ever positioned a control in a Canvas using Canvas.Left or placed a control in a specific Grid row using Grid.Row then you’ve used an attached property which is a specialized type of dependency property. Dependency properties play a key role in XAML and the overall Silverlight framework. Any property that you bind, style, template, animate or transform must be a dependency property in Silverlight applications. You can programmatically bind values to controls and work with standard CLR properties, but if you want to use the built-in binding expressions available in XAML (one of my favorite features) or the Binding class available through code then dependency properties are a necessity. Dependency properties aren’t needed in every situation, but if you want to customize your application very much you’ll eventually end up needing them. For example, if you create a custom user control and want to expose a property that consumers can use to change the background color, you have to define it as a dependency property if you want bindings, styles and other features to be available for use. Now that the overall purpose of dependency properties has been discussed let’s take a look at how you can create them. Creating Dependency Properties When .NET first came out you had to write backing fields for each property that you defined as shown next: Brush _ScheduleBackground; public Brush ScheduleBackground { get { return _ScheduleBackground; } set { _ScheduleBackground = value; } } Although .NET 2.0 added auto-implemented properties (for example: public Brush ScheduleBackground { get; set; }) where the compiler would automatically generate the backing field used by get and set blocks, the concept is still the same as shown in the above code; a property acts as a wrapper around a field. Silverlight dependency properties replace the _ScheduleBackground field shown in the previous code and act as the backing store for a standard CLR property. The following code shows an example of defining a dependency property named ScheduleBackgroundProperty: public static readonly DependencyProperty ScheduleBackgroundProperty = DependencyProperty.Register("ScheduleBackground", typeof(Brush), typeof(Scheduler), null);   Looking through the code the first thing that may stand out is that the definition for ScheduleBackgroundProperty is marked as static and readonly and that the property appears to be of type DependencyProperty. This is a standard pattern that you’ll use when working with dependency properties. You’ll also notice that the property explicitly adds the word “Property” to the name which is another standard you’ll see followed. In addition to defining the property, the code also makes a call to the static DependencyProperty.Register method and passes the name of the property to register (ScheduleBackground in this case) as a string. The type of the property, the type of the class that owns the property and a null value (more on the null value later) are also passed. In this example a class named Scheduler acts as the owner. The code handles registering the property as a dependency property with the call to Register(), but there’s a little more work that has to be done to allow a value to be assigned to and retrieved from the dependency property. The following code shows the complete code that you’ll typically use when creating a dependency property. You can find code snippets that greatly simplify the process of creating dependency properties out on the web. The MVVM Light download available from http://mvvmlight.codeplex.com comes with built-in dependency properties snippets as well. public static readonly DependencyProperty ScheduleBackgroundProperty = DependencyProperty.Register("ScheduleBackground", typeof(Brush), typeof(Scheduler), null); public Brush ScheduleBackground { get { return (Brush)GetValue(ScheduleBackgroundProperty); } set { SetValue(ScheduleBackgroundProperty, value); } } The standard CLR property code shown above should look familiar since it simply wraps the dependency property. However, you’ll notice that the get and set blocks call GetValue and SetValue methods respectively to perform the appropriate operation on the dependency property. GetValue and SetValue are members of the DependencyObject class which is another key component of the Silverlight framework. Silverlight controls and classes (TextBox, UserControl, CompositeTransform, DataGrid, etc.) ultimately derive from DependencyObject in their inheritance hierarchy so that they can support dependency properties. Dependency properties defined in Silverlight controls and other classes tend to follow the pattern of registering the property by calling Register() and then wrapping the dependency property in a standard CLR property (as shown above). They have a standard property that wraps a registered dependency property and allows a value to be assigned and retrieved. If you need to expose a new property on a custom control that supports data binding expressions in XAML then you’ll follow this same pattern. Dependency properties are extremely useful once you understand why they’re needed and how they’re defined. Detecting Changes and Setting Defaults When working with dependency properties there will be times when you want to assign a default value or detect when a property changes so that you can keep the user interface in-sync with the property value. Silverlight’s DependencyProperty.Register() method provides a fourth parameter that accepts a PropertyMetadata object instance. PropertyMetadata can be used to hook a callback method to a dependency property. The callback method is called when the property value changes. PropertyMetadata can also be used to assign a default value to the dependency property. By assigning a value of null for the final parameter passed to Register() you’re telling the property that you don’t care about any changes and don’t have a default value to apply. Here are the different constructor overloads available on the PropertyMetadata class: PropertyMetadata Constructor Overload Description PropertyMetadata(Object) Used to assign a default value to a dependency property. PropertyMetadata(PropertyChangedCallback) Used to assign a property changed callback method. PropertyMetadata(Object, PropertyChangedCalback) Used to assign a default property value and a property changed callback.   There are many situations where you need to know when a dependency property changes or where you want to apply a default. Performing either task is easily accomplished by creating a new instance of the PropertyMetadata class and passing the appropriate values to its constructor. The following code shows an enhanced version of the initial dependency property code shown earlier that demonstrates these concepts: public Brush ScheduleBackground { get { return (Brush)GetValue(ScheduleBackgroundProperty); } set { SetValue(ScheduleBackgroundProperty, value); } } public static readonly DependencyProperty ScheduleBackgroundProperty = DependencyProperty.Register("ScheduleBackground", typeof(Brush), typeof(Scheduler), new PropertyMetadata(new SolidColorBrush(Colors.LightGray), ScheduleBackgroundChanged)); private static void ScheduleBackgroundChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { var scheduler = d as Scheduler; scheduler.Background = e.NewValue as Brush; } The code wires ScheduleBackgroundProperty to a property change callback method named ScheduleBackgroundChanged. What’s interesting is that this callback method is static (as is the dependency property) so it gets passed the instance of the object that owns the property that has changed (otherwise we wouldn’t be able to get to the object instance). In this example the dependency object is cast to a Scheduler object and its Background property is assigned to the new value of the dependency property. The code also handles assigning a default value of LightGray to the dependency property by creating a new instance of a SolidColorBrush. To Sum Up In this post you’ve seen the role of dependency properties and how they can be defined in code. They play a big role in XAML and the overall Silverlight framework. You can think of dependency properties as being replacements for fields that you’d normally use with standard CLR properties. In addition to a discussion on how dependency properties are created, you also saw how to use the PropertyMetadata class to define default dependency property values and hook a dependency property to a callback method. The most important thing to understand with dependency properties (especially if you’re new to Silverlight) is that they’re needed if you want a property to support data binding, animations, transformations and styles properly. Any time you create a property on a custom control or user control that has these types of requirements you’ll want to pick a dependency property over of a standard CLR property with a backing field. There’s more that can be covered with dependency properties including a related property called an attached property….more to come.

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