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  • C#/.NET Little Wonders: The Concurrent Collections (1 of 3)

    - by James Michael Hare
    Once again we consider some of the lesser known classes and keywords of C#.  In the next few weeks, we will discuss the concurrent collections and how they have changed the face of concurrent programming. This week’s post will begin with a general introduction and discuss the ConcurrentStack<T> and ConcurrentQueue<T>.  Then in the following post we’ll discuss the ConcurrentDictionary<T> and ConcurrentBag<T>.  Finally, we shall close on the third post with a discussion of the BlockingCollection<T>. For more of the "Little Wonders" posts, see the index here. A brief history of collections In the beginning was the .NET 1.0 Framework.  And out of this framework emerged the System.Collections namespace, and it was good.  It contained all the basic things a growing programming language needs like the ArrayList and Hashtable collections.  The main problem, of course, with these original collections is that they held items of type object which means you had to be disciplined enough to use them correctly or you could end up with runtime errors if you got an object of a type you weren't expecting. Then came .NET 2.0 and generics and our world changed forever!  With generics the C# language finally got an equivalent of the very powerful C++ templates.  As such, the System.Collections.Generic was born and we got type-safe versions of all are favorite collections.  The List<T> succeeded the ArrayList and the Dictionary<TKey,TValue> succeeded the Hashtable and so on.  The new versions of the library were not only safer because they checked types at compile-time, in many cases they were more performant as well.  So much so that it's Microsoft's recommendation that the System.Collections original collections only be used for backwards compatibility. So we as developers came to know and love the generic collections and took them into our hearts and embraced them.  The problem is, thread safety in both the original collections and the generic collections can be problematic, for very different reasons. Now, if you are only doing single-threaded development you may not care – after all, no locking is required.  Even if you do have multiple threads, if a collection is “load-once, read-many” you don’t need to do anything to protect that container from multi-threaded access, as illustrated below: 1: public static class OrderTypeTranslator 2: { 3: // because this dictionary is loaded once before it is ever accessed, we don't need to synchronize 4: // multi-threaded read access 5: private static readonly Dictionary<string, char> _translator = new Dictionary<string, char> 6: { 7: {"New", 'N'}, 8: {"Update", 'U'}, 9: {"Cancel", 'X'} 10: }; 11:  12: // the only public interface into the dictionary is for reading, so inherently thread-safe 13: public static char? Translate(string orderType) 14: { 15: char charValue; 16: if (_translator.TryGetValue(orderType, out charValue)) 17: { 18: return charValue; 19: } 20:  21: return null; 22: } 23: } Unfortunately, most of our computer science problems cannot get by with just single-threaded applications or with multi-threading in a load-once manner.  Looking at  today's trends, it's clear to see that computers are not so much getting faster because of faster processor speeds -- we've nearly reached the limits we can push through with today's technologies -- but more because we're adding more cores to the boxes.  With this new hardware paradigm, it is even more important to use multi-threaded applications to take full advantage of parallel processing to achieve higher application speeds. So let's look at how to use collections in a thread-safe manner. Using historical collections in a concurrent fashion The early .NET collections (System.Collections) had a Synchronized() static method that could be used to wrap the early collections to make them completely thread-safe.  This paradigm was dropped in the generic collections (System.Collections.Generic) because having a synchronized wrapper resulted in atomic locks for all operations, which could prove overkill in many multithreading situations.  Thus the paradigm shifted to having the user of the collection specify their own locking, usually with an external object: 1: public class OrderAggregator 2: { 3: private static readonly Dictionary<string, List<Order>> _orders = new Dictionary<string, List<Order>>(); 4: private static readonly _orderLock = new object(); 5:  6: public void Add(string accountNumber, Order newOrder) 7: { 8: List<Order> ordersForAccount; 9:  10: // a complex operation like this should all be protected 11: lock (_orderLock) 12: { 13: if (!_orders.TryGetValue(accountNumber, out ordersForAccount)) 14: { 15: _orders.Add(accountNumber, ordersForAccount = new List<Order>()); 16: } 17:  18: ordersForAccount.Add(newOrder); 19: } 20: } 21: } Notice how we’re performing several operations on the dictionary under one lock.  With the Synchronized() static methods of the early collections, you wouldn’t be able to specify this level of locking (a more macro-level).  So in the generic collections, it was decided that if a user needed synchronization, they could implement their own locking scheme instead so that they could provide synchronization as needed. The need for better concurrent access to collections Here’s the problem: it’s relatively easy to write a collection that locks itself down completely for access, but anything more complex than that can be difficult and error-prone to write, and much less to make it perform efficiently!  For example, what if you have a Dictionary that has frequent reads but in-frequent updates?  Do you want to lock down the entire Dictionary for every access?  This would be overkill and would prevent concurrent reads.  In such cases you could use something like a ReaderWriterLockSlim which allows for multiple readers in a lock, and then once a writer grabs the lock it blocks all further readers until the writer is done (in a nutshell).  This is all very complex stuff to consider. Fortunately, this is where the Concurrent Collections come in.  The Parallel Computing Platform team at Microsoft went through great pains to determine how to make a set of concurrent collections that would have the best performance characteristics for general case multi-threaded use. Now, as in all things involving threading, you should always make sure you evaluate all your container options based on the particular usage scenario and the degree of parallelism you wish to acheive. This article should not be taken to understand that these collections are always supperior to the generic collections. Each fills a particular need for a particular situation. Understanding what each container is optimized for is key to the success of your application whether it be single-threaded or multi-threaded. General points to consider with the concurrent collections The MSDN points out that the concurrent collections all support the ICollection interface. However, since the collections are already synchronized, the IsSynchronized property always returns false, and SyncRoot always returns null.  Thus you should not attempt to use these properties for synchronization purposes. Note that since the concurrent collections also may have different operations than the traditional data structures you may be used to.  Now you may ask why they did this, but it was done out of necessity to keep operations safe and atomic.  For example, in order to do a Pop() on a stack you have to know the stack is non-empty, but between the time you check the stack’s IsEmpty property and then do the Pop() another thread may have come in and made the stack empty!  This is why some of the traditional operations have been changed to make them safe for concurrent use. In addition, some properties and methods in the concurrent collections achieve concurrency by creating a snapshot of the collection, which means that some operations that were traditionally O(1) may now be O(n) in the concurrent models.  I’ll try to point these out as we talk about each collection so you can be aware of any potential performance impacts.  Finally, all the concurrent containers are safe for enumeration even while being modified, but some of the containers support this in different ways (snapshot vs. dirty iteration).  Once again I’ll highlight how thread-safe enumeration works for each collection. ConcurrentStack<T>: The thread-safe LIFO container The ConcurrentStack<T> is the thread-safe counterpart to the System.Collections.Generic.Stack<T>, which as you may remember is your standard last-in-first-out container.  If you think of algorithms that favor stack usage (for example, depth-first searches of graphs and trees) then you can see how using a thread-safe stack would be of benefit. The ConcurrentStack<T> achieves thread-safe access by using System.Threading.Interlocked operations.  This means that the multi-threaded access to the stack requires no traditional locking and is very, very fast! For the most part, the ConcurrentStack<T> behaves like it’s Stack<T> counterpart with a few differences: Pop() was removed in favor of TryPop() Returns true if an item existed and was popped and false if empty. PushRange() and TryPopRange() were added Allows you to push multiple items and pop multiple items atomically. Count takes a snapshot of the stack and then counts the items. This means it is a O(n) operation, if you just want to check for an empty stack, call IsEmpty instead which is O(1). ToArray() and GetEnumerator() both also take snapshots. This means that iteration over a stack will give you a static view at the time of the call and will not reflect updates. Pushing on a ConcurrentStack<T> works just like you’d expect except for the aforementioned PushRange() method that was added to allow you to push a range of items concurrently. 1: var stack = new ConcurrentStack<string>(); 2:  3: // adding to stack is much the same as before 4: stack.Push("First"); 5:  6: // but you can also push multiple items in one atomic operation (no interleaves) 7: stack.PushRange(new [] { "Second", "Third", "Fourth" }); For looking at the top item of the stack (without removing it) the Peek() method has been removed in favor of a TryPeek().  This is because in order to do a peek the stack must be non-empty, but between the time you check for empty and the time you execute the peek the stack contents may have changed.  Thus the TryPeek() was created to be an atomic check for empty, and then peek if not empty: 1: // to look at top item of stack without removing it, can use TryPeek. 2: // Note that there is no Peek(), this is because you need to check for empty first. TryPeek does. 3: string item; 4: if (stack.TryPeek(out item)) 5: { 6: Console.WriteLine("Top item was " + item); 7: } 8: else 9: { 10: Console.WriteLine("Stack was empty."); 11: } Finally, to remove items from the stack, we have the TryPop() for single, and TryPopRange() for multiple items.  Just like the TryPeek(), these operations replace Pop() since we need to ensure atomically that the stack is non-empty before we pop from it: 1: // to remove items, use TryPop or TryPopRange to get multiple items atomically (no interleaves) 2: if (stack.TryPop(out item)) 3: { 4: Console.WriteLine("Popped " + item); 5: } 6:  7: // TryPopRange will only pop up to the number of spaces in the array, the actual number popped is returned. 8: var poppedItems = new string[2]; 9: int numPopped = stack.TryPopRange(poppedItems); 10:  11: foreach (var theItem in poppedItems.Take(numPopped)) 12: { 13: Console.WriteLine("Popped " + theItem); 14: } Finally, note that as stated before, GetEnumerator() and ToArray() gets a snapshot of the data at the time of the call.  That means if you are enumerating the stack you will get a snapshot of the stack at the time of the call.  This is illustrated below: 1: var stack = new ConcurrentStack<string>(); 2:  3: // adding to stack is much the same as before 4: stack.Push("First"); 5:  6: var results = stack.GetEnumerator(); 7:  8: // but you can also push multiple items in one atomic operation (no interleaves) 9: stack.PushRange(new [] { "Second", "Third", "Fourth" }); 10:  11: while(results.MoveNext()) 12: { 13: Console.WriteLine("Stack only has: " + results.Current); 14: } The only item that will be printed out in the above code is "First" because the snapshot was taken before the other items were added. This may sound like an issue, but it’s really for safety and is more correct.  You don’t want to enumerate a stack and have half a view of the stack before an update and half a view of the stack after an update, after all.  In addition, note that this is still thread-safe, whereas iterating through a non-concurrent collection while updating it in the old collections would cause an exception. ConcurrentQueue<T>: The thread-safe FIFO container The ConcurrentQueue<T> is the thread-safe counterpart of the System.Collections.Generic.Queue<T> class.  The concurrent queue uses an underlying list of small arrays and lock-free System.Threading.Interlocked operations on the head and tail arrays.  Once again, this allows us to do thread-safe operations without the need for heavy locks! The ConcurrentQueue<T> (like the ConcurrentStack<T>) has some departures from the non-concurrent counterpart.  Most notably: Dequeue() was removed in favor of TryDequeue(). Returns true if an item existed and was dequeued and false if empty. Count does not take a snapshot It subtracts the head and tail index to get the count.  This results overall in a O(1) complexity which is quite good.  It’s still recommended, however, that for empty checks you call IsEmpty instead of comparing Count to zero. ToArray() and GetEnumerator() both take snapshots. This means that iteration over a queue will give you a static view at the time of the call and will not reflect updates. The Enqueue() method on the ConcurrentQueue<T> works much the same as the generic Queue<T>: 1: var queue = new ConcurrentQueue<string>(); 2:  3: // adding to queue is much the same as before 4: queue.Enqueue("First"); 5: queue.Enqueue("Second"); 6: queue.Enqueue("Third"); For front item access, the TryPeek() method must be used to attempt to see the first item if the queue.  There is no Peek() method since, as you’ll remember, we can only peek on a non-empty queue, so we must have an atomic TryPeek() that checks for empty and then returns the first item if the queue is non-empty. 1: // to look at first item in queue without removing it, can use TryPeek. 2: // Note that there is no Peek(), this is because you need to check for empty first. TryPeek does. 3: string item; 4: if (queue.TryPeek(out item)) 5: { 6: Console.WriteLine("First item was " + item); 7: } 8: else 9: { 10: Console.WriteLine("Queue was empty."); 11: } Then, to remove items you use TryDequeue().  Once again this is for the same reason we have TryPeek() and not Peek(): 1: // to remove items, use TryDequeue. If queue is empty returns false. 2: if (queue.TryDequeue(out item)) 3: { 4: Console.WriteLine("Dequeued first item " + item); 5: } Just like the concurrent stack, the ConcurrentQueue<T> takes a snapshot when you call ToArray() or GetEnumerator() which means that subsequent updates to the queue will not be seen when you iterate over the results.  Thus once again the code below will only show the first item, since the other items were added after the snapshot. 1: var queue = new ConcurrentQueue<string>(); 2:  3: // adding to queue is much the same as before 4: queue.Enqueue("First"); 5:  6: var iterator = queue.GetEnumerator(); 7:  8: queue.Enqueue("Second"); 9: queue.Enqueue("Third"); 10:  11: // only shows First 12: while (iterator.MoveNext()) 13: { 14: Console.WriteLine("Dequeued item " + iterator.Current); 15: } Using collections concurrently You’ll notice in the examples above I stuck to using single-threaded examples so as to make them deterministic and the results obvious.  Of course, if we used these collections in a truly multi-threaded way the results would be less deterministic, but would still be thread-safe and with no locking on your part required! For example, say you have an order processor that takes an IEnumerable<Order> and handles each other in a multi-threaded fashion, then groups the responses together in a concurrent collection for aggregation.  This can be done easily with the TPL’s Parallel.ForEach(): 1: public static IEnumerable<OrderResult> ProcessOrders(IEnumerable<Order> orderList) 2: { 3: var proxy = new OrderProxy(); 4: var results = new ConcurrentQueue<OrderResult>(); 5:  6: // notice that we can process all these in parallel and put the results 7: // into our concurrent collection without needing any external locking! 8: Parallel.ForEach(orderList, 9: order => 10: { 11: var result = proxy.PlaceOrder(order); 12:  13: results.Enqueue(result); 14: }); 15:  16: return results; 17: } Summary Obviously, if you do not need multi-threaded safety, you don’t need to use these collections, but when you do need multi-threaded collections these are just the ticket! The plethora of features (I always think of the movie The Three Amigos when I say plethora) built into these containers and the amazing way they acheive thread-safe access in an efficient manner is wonderful to behold. Stay tuned next week where we’ll continue our discussion with the ConcurrentBag<T> and the ConcurrentDictionary<TKey,TValue>. For some excellent information on the performance of the concurrent collections and how they perform compared to a traditional brute-force locking strategy, see this wonderful whitepaper by the Microsoft Parallel Computing Platform team here.   Tweet Technorati Tags: C#,.NET,Concurrent Collections,Collections,Multi-Threading,Little Wonders,BlackRabbitCoder,James Michael Hare

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  • Use Extension method to write cleaner code

    - by Fredrik N
    This blog post will show you step by step to refactoring some code to be more readable (at least what I think). Patrik Löwnedahl gave me some of the ideas when we where talking about making code much cleaner. The following is an simple application that will have a list of movies (Normal and Transfer). The task of the application is to calculate the total sum of each movie and also display the price of each movie. class Program { enum MovieType { Normal, Transfer } static void Main(string[] args) { var movies = GetMovies(); int totalPriceOfNormalMovie = 0; int totalPriceOfTransferMovie = 0; foreach (var movie in movies) { if (movie == MovieType.Normal) { totalPriceOfNormalMovie += 2; Console.WriteLine("$2"); } else if (movie == MovieType.Transfer) { totalPriceOfTransferMovie += 3; Console.WriteLine("$3"); } } } private static IEnumerable<MovieType> GetMovies() { return new List<MovieType>() { MovieType.Normal, MovieType.Transfer, MovieType.Normal }; } } .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; } In the code above I’m using an enum, a good way to add types (isn’t it ;)). I also use one foreach loop to calculate the price, the loop has a condition statement to check what kind of movie is added to the list of movies. I want to reuse the foreach only to increase performance and let it do two things (isn’t that smart of me?! ;)). First of all I can admit, I’m not a big fan of enum. Enum often results in ugly condition statements and can be hard to maintain (if a new type is added we need to check all the code in our app to see if we use the enum somewhere else). I don’t often care about pre-optimizations when it comes to write code (of course I have performance in mind). I rather prefer to use two foreach to let them do one things instead of two. So based on what I don’t like and Martin Fowler’s Refactoring catalog, I’m going to refactoring this code to what I will call a more elegant and cleaner code. First of all I’m going to use Split Loop to make sure the foreach will do one thing not two, it will results in two foreach (Don’t care about performance here, if the results will results in bad performance, you can refactoring later, but computers are so fast to day, so iterating through a list is not often so time consuming.) Note: The foreach actually do four things, will come to is later. var movies = GetMovies(); int totalPriceOfNormalMovie = 0; int totalPriceOfTransferMovie = 0; foreach (var movie in movies) { if (movie == MovieType.Normal) { totalPriceOfNormalMovie += 2; Console.WriteLine("$2"); } } foreach (var movie in movies) { if (movie == MovieType.Transfer) { totalPriceOfTransferMovie += 3; Console.WriteLine("$3"); } } .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; } To remove the condition statement we can use the Where extension method added to the IEnumerable<T> and is located in the System.Linq namespace: foreach (var movie in movies.Where( m => m == MovieType.Normal)) { totalPriceOfNormalMovie += 2; Console.WriteLine("$2"); } foreach (var movie in movies.Where( m => m == MovieType.Transfer)) { totalPriceOfTransferMovie += 3; Console.WriteLine("$3"); } .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; } The above code will still do two things, calculate the total price, and display the price of the movie. I will not take care of it at the moment, instead I will focus on the enum and try to remove them. One way to remove enum is by using the Replace Conditional with Polymorphism. So I will create two classes, one base class called Movie, and one called MovieTransfer. The Movie class will have a property called Price, the Movie will now hold the price:   public class Movie { public virtual int Price { get { return 2; } } } public class MovieTransfer : Movie { public override int Price { get { return 3; } } } .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; } The following code has no enum and will use the new Movie classes instead: class Program { static void Main(string[] args) { var movies = GetMovies(); int totalPriceOfNormalMovie = 0; int totalPriceOfTransferMovie = 0; foreach (var movie in movies.Where( m => m is Movie)) { totalPriceOfNormalMovie += movie.Price; Console.WriteLine(movie.Price); } foreach (var movie in movies.Where( m => m is MovieTransfer)) { totalPriceOfTransferMovie += movie.Price; Console.WriteLine(movie.Price); } } private static IEnumerable<Movie> GetMovies() { return new List<Movie>() { new Movie(), new MovieTransfer(), new Movie() }; } } .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 you take a look at the foreach now, you can see it still actually do two things, calculate the price and display the price. We can do some more refactoring here by using the Sum extension method to calculate the total price of the movies:   static void Main(string[] args) { var movies = GetMovies(); int totalPriceOfNormalMovie = movies.Where(m => m is Movie) .Sum(m => m.Price); int totalPriceOfTransferMovie = movies.Where(m => m is MovieTransfer) .Sum(m => m.Price); foreach (var movie in movies.Where( m => m is Movie)) Console.WriteLine(movie.Price); foreach (var movie in movies.Where( m => m is MovieTransfer)) Console.WriteLine(movie.Price); } .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; } Now when the Movie object will hold the price, there is no need to use two separate foreach to display the price of the movies in the list, so we can use only one instead: foreach (var movie in movies) Console.WriteLine(movie.Price); .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 we want to increase the Maintainability index we can use the Extract Method to move the Sum of the prices into two separate methods. The name of the method will explain what we are doing: static void Main(string[] args) { var movies = GetMovies(); int totalPriceOfMovie = TotalPriceOfMovie(movies); int totalPriceOfTransferMovie = TotalPriceOfMovieTransfer(movies); foreach (var movie in movies) Console.WriteLine(movie.Price); } private static int TotalPriceOfMovieTransfer(IEnumerable<Movie> movies) { return movies.Where(m => m is MovieTransfer) .Sum(m => m.Price); } private static int TotalPriceOfMovie(IEnumerable<Movie> movies) { return movies.Where(m => m is Movie) .Sum(m => m.Price); } .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; } Now to the last thing, I love the ForEach method of the List<T>, but the IEnumerable<T> doesn’t have it, so I created my own ForEach extension, here is the code of the ForEach extension method: public static class LoopExtensions { public static void ForEach<T>(this IEnumerable<T> values, Action<T> action) { Contract.Requires(values != null); Contract.Requires(action != null); foreach (var v in values) action(v); } } .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; } I will now replace the foreach by using this ForEach method: static void Main(string[] args) { var movies = GetMovies(); int totalPriceOfMovie = TotalPriceOfMovie(movies); int totalPriceOfTransferMovie = TotalPriceOfMovieTransfer(movies); movies.ForEach(m => Console.WriteLine(m.Price)); } .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; } The ForEach on the movies will now display the price of the movie, but maybe we want to display the name of the movie etc, so we can use Extract Method by moving the lamdba expression into a method instead, and let the method explains what we are displaying: movies.ForEach(DisplayMovieInfo); private static void DisplayMovieInfo(Movie movie) { Console.WriteLine(movie.Price); } .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; } Now the refactoring is done! Here is the complete code:   class Program { static void Main(string[] args) { var movies = GetMovies(); int totalPriceOfMovie = TotalPriceOfMovie(movies); int totalPriceOfTransferMovie = TotalPriceOfMovieTransfer(movies); movies.ForEach(DisplayMovieInfo); } private static void DisplayMovieInfo(Movie movie) { Console.WriteLine(movie.Price); } private static int TotalPriceOfMovieTransfer(IEnumerable<Movie> movies) { return movies.Where(m => m is MovieTransfer) .Sum(m => m.Price); } private static int TotalPriceOfMovie(IEnumerable<Movie> movies) { return movies.Where(m => m is Movie) .Sum(m => m.Price); } private static IEnumerable<Movie> GetMovies() { return new List<Movie>() { new Movie(), new MovieTransfer(), new Movie() }; } } public class Movie { public virtual int Price { get { return 2; } } } public class MovieTransfer : Movie { public override int Price { get { return 3; } } } pulbic static class LoopExtensions { public static void ForEach<T>(this IEnumerable<T> values, Action<T> action) { Contract.Requires(values != null); Contract.Requires(action != null); foreach (var v in values) action(v); } } .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; } I think the new code is much cleaner than the first one, and I love the ForEach extension on the IEnumerable<T>, I can use it for different kind of things, for example: movies.Where(m => m is Movie) .ForEach(DoSomething); .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; } By using the Where and ForEach extension method, some if statements can be removed and will make the code much cleaner. But the beauty is in the eye of the beholder. What would you have done different, what do you think will make the first example in the blog post look much cleaner than my results, comments are welcome! If you want to know when I will publish a new blog post, you can follow me on twitter: http://www.twitter.com/fredrikn

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  • Class member functions instantiated by traits [policies, actually]

    - by Jive Dadson
    I am reluctant to say I can't figure this out, but I can't figure this out. I've googled and searched Stack Overflow, and come up empty. The abstract, and possibly overly vague form of the question is, how can I use the traits-pattern to instantiate member functions? [Update: I used the wrong term here. It should be "policies" rather than "traits." Traits describe existing classes. Policies prescribe synthetic classes.] The question came up while modernizing a set of multivariate function optimizers that I wrote more than 10 years ago. The optimizers all operate by selecting a straight-line path through the parameter space away from the current best point (the "update"), then finding a better point on that line (the "line search"), then testing for the "done" condition, and if not done, iterating. There are different methods for doing the update, the line-search, and conceivably for the done test, and other things. Mix and match. Different update formulae require different state-variable data. For example, the LMQN update requires a vector, and the BFGS update requires a matrix. If evaluating gradients is cheap, the line-search should do so. If not, it should use function evaluations only. Some methods require more accurate line-searches than others. Those are just some examples. The original version instantiates several of the combinations by means of virtual functions. Some traits are selected by setting mode bits that are tested at runtime. Yuck. It would be trivial to define the traits with #define's and the member functions with #ifdef's and macros. But that's so twenty years ago. It bugs me that I cannot figure out a whiz-bang modern way. If there were only one trait that varied, I could use the curiously recurring template pattern. But I see no way to extend that to arbitrary combinations of traits. I tried doing it using boost::enable_if, etc.. The specialized state information was easy. I managed to get the functions done, but only by resorting to non-friend external functions that have the this-pointer as a parameter. I never even figured out how to make the functions friends, much less member functions. The compiler (VC++ 2008) always complained that things didn't match. I would yell, "SFINAE, you moron!" but the moron is probably me. Perhaps tag-dispatch is the key. I haven't gotten very deeply into that. Surely it's possible, right? If so, what is best practice? UPDATE: Here's another try at explaining it. I want the user to be able to fill out an order (manifest) for a custom optimizer, something like ordering off of a Chinese menu - one from column A, one from column B, etc.. Waiter, from column A (updaters), I'll have the BFGS update with Cholesky-decompositon sauce. From column B (line-searchers), I'll have the cubic interpolation line-search with an eta of 0.4 and a rho of 1e-4, please. Etc... UPDATE: Okay, okay. Here's the playing-around that I've done. I offer it reluctantly, because I suspect it's a completely wrong-headed approach. It runs okay under vc++ 2008. #include <boost/utility.hpp> #include <boost/type_traits/integral_constant.hpp> namespace dj { struct CBFGS { void bar() {printf("CBFGS::bar %d\n", data);} CBFGS(): data(1234){} int data; }; template<class T> struct is_CBFGS: boost::false_type{}; template<> struct is_CBFGS<CBFGS>: boost::true_type{}; struct LMQN {LMQN(): data(54.321){} void bar() {printf("LMQN::bar %lf\n", data);} double data; }; template<class T> struct is_LMQN: boost::false_type{}; template<> struct is_LMQN<LMQN> : boost::true_type{}; // "Order form" struct default_optimizer_traits { typedef CBFGS update_type; // Selection from column A - updaters }; template<class traits> class Optimizer; template<class traits> void foo(typename boost::enable_if<is_LMQN<typename traits::update_type>, Optimizer<traits> >::type& self) { printf(" LMQN %lf\n", self.data); } template<class traits> void foo(typename boost::enable_if<is_CBFGS<typename traits::update_type>, Optimizer<traits> >::type& self) { printf("CBFGS %d\n", self.data); } template<class traits = default_optimizer_traits> class Optimizer{ friend typename traits::update_type; //friend void dj::foo<traits>(typename Optimizer<traits> & self); // How? public: //void foo(void); // How??? void foo() { dj::foo<traits>(*this); } void bar() { data.bar(); } //protected: // How? typedef typename traits::update_type update_type; update_type data; }; } // namespace dj int main() { dj::Optimizer<> opt; opt.foo(); opt.bar(); std::getchar(); return 0; }

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  • Using Handlebars.js issue

    - by Roland
    I'm having a small issue when I'm compiling a template with Handlebars.js . I have a JSON text file which contains an big array with objects : Source ; and I'm using XMLHTTPRequest to get it and then parse it so I can use it when compiling the template. So far the template has the following structure : <div class="product-listing-wrapper"> <div class="product-listing"> <div class="left-side-content"> <div class="thumb-wrapper"> <img src="{{ThumbnailUrl}}"> </div> <div class="google-maps-wrapper"> <div class="google-coordonates-wrapper"> <div class="google-coordonates"> <p>{{LatLon.Lat}}</p> <p>{{LatLon.Lon}}</p> </div> </div> <div class="google-maps-button"> <a class="google-maps" href="#" data-latitude="{{LatLon.Lat}}" data-longitude="{{LatLon.Lon}}">Google Maps</a> </div> </div> </div> <div class="right-side-content"></div> </div> And the following block of code would be the way I'm handling the JS part : $(document).ready(function() { /* Default Javascript Options ~a javascript object which contains all the variables that will be passed to the cluster class */ var default_cluster_options = { animations : ['flash', 'bounce', 'shake', 'tada', 'swing', 'wobble', 'wiggle', 'pulse', 'flip', 'flipInX', 'flipOutX', 'flipInY', 'flipOutY', 'fadeIn', 'fadeInUp', 'fadeInDown', 'fadeInLeft', 'fadeInRight', 'fadeInUpBig', 'fadeInDownBig', 'fadeInLeftBig', 'fadeInRightBig', 'fadeOut', 'fadeOutUp', 'fadeOutDown', 'fadeOutLeft', 'fadeOutRight', 'fadeOutUpBig', 'fadeOutDownBig', 'fadeOutLeftBig', 'fadeOutRightBig', 'bounceIn', 'bounceInUp', 'bounceInDown', 'bounceInLeft', 'bounceInRight', 'bounceOut', 'bounceOutUp', 'bounceOutDown', 'bounceOutLeft', 'bounceOutRight', 'rotateIn', 'rotateInDownLeft', 'rotateInDownRight', 'rotateInUpLeft', 'rotateInUpRight', 'rotateOut', 'rotateOutDownLeft', 'rotateOutDownRight', 'rotateOutUpLeft', 'rotateOutUpRight', 'lightSpeedIn', 'lightSpeedOut', 'hinge', 'rollIn', 'rollOut'], json_data_url : 'data.json', template_data_url : 'template.php', base_maps_api_url : 'https://maps.googleapis.com/maps/api/js?sensor=false', cluser_wrapper_id : '#content-wrapper', maps_wrapper_class : '.google-maps', }; /* Cluster ~main class, handles all javascript operations */ var Cluster = function(environment, cluster_options) { var self = this; this.options = $.extend({}, default_cluster_options, cluster_options); this.environment = environment; this.animations = this.options.animations; this.json_data_url = this.options.json_data_url; this.template_data_url = this.options.template_data_url; this.base_maps_api_url = this.options.base_maps_api_url; this.cluser_wrapper_id = this.options.cluser_wrapper_id; this.maps_wrapper_class = this.options.maps_wrapper_class; this.test_environment_mode(this.environment); this.initiate_environment(); this.test_xmlhttprequest_availability(); this.initiate_gmaps_lib_load(self.base_maps_api_url); this.initiate_data_processing(); }; /* Test Environment Mode ~adds a modernizr test which looks wheater the cluster class is initiated in development or not */ Cluster.prototype.test_environment_mode = function(environment) { var self = this; return Modernizr.addTest('test_environment', function() { return (typeof environment !== 'undefined' && environment !== null && environment === "Development") ? true : false; }); }; /* Test XMLHTTPRequest Availability ~adds a modernizr test which looks wheater the xmlhttprequest class is available or not in the browser, exception makes IE */ Cluster.prototype.test_xmlhttprequest_availability = function() { return Modernizr.addTest('test_xmlhttprequest', function() { return (typeof window.XMLHttpRequest === 'undefined' || window.XMLHttpRequest === null) ? true : false; }); }; /* Initiate Environment ~depending on what the modernizr test returns it puts LESS in the development mode or not */ Cluster.prototype.initiate_environment = function() { return (Modernizr.test_environment) ? (less.env = "development", less.watch()) : true; }; Cluster.prototype.initiate_gmaps_lib_load = function(lib_url) { return Modernizr.load(lib_url); }; /* Initiate XHR Request ~prototype function that creates an xmlhttprequest for processing json data from an separate json text file */ Cluster.prototype.initiate_xhr_request = function(url, mime_type) { var request, data; var self = this; (Modernizr.test_xmlhttprequest) ? request = new ActiveXObject('Microsoft.XMLHTTP') : request = new XMLHttpRequest(); request.onreadystatechange = function() { if(request.readyState == 4 && request.status == 200) { data = request.responseText; } }; request.open("GET", url, false); request.overrideMimeType(mime_type); request.send(); return data; }; Cluster.prototype.initiate_google_maps_action = function() { var self = this; return $(this.maps_wrapper_class).each(function(index, element) { return $(element).on('click', function(ev) { var html = $('<div id="map-canvas" class="map-canvas"></div>'); var latitude = $(element).attr('data-latitude'); var longitude = $(element).attr('data-longitude'); log("LAT : " + latitude); log("LON : " + longitude); $.lightbox(html, { "width": 900, "height": 250, "onOpen" : function() { } }); ev.preventDefault(); }); }); }; Cluster.prototype.initiate_data_processing = function() { var self = this; var json_data = JSON.parse(self.initiate_xhr_request(self.json_data_url, 'application/json; charset=ISO-8859-1')); var source_data = self.initiate_xhr_request(self.template_data_url, 'text/html'); var template = Handlebars.compile(source_data); for(var i = 0; i < json_data.length; i++ ) { var result = template(json_data[i]); $(result).appendTo(self.cluser_wrapper_id); } self.initiate_google_maps_action(); }; /* Cluster ~initiate the cluster class */ var cluster = new Cluster("Development"); }); My problem would be that I don't think I'm iterating the JSON object right or I'm using the template the wrong way because if you check this link : http://rolandgroza.com/labs/valtech/ ; you will see that there are some numbers there ( which represents latitude and longitude ) but they are all the same and if you take only a brief look at the JSON object each number is different. So what am I doing wrong that it makes the same number repeat ? Or what should I do to fix it ? I must notice that I've just started working with templates so I have little knowledge it.

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  • Help getting frame rate (fps) up in Python + Pygame

    - by Jordan Magnuson
    I am working on a little card-swapping world-travel game that I sort of envision as a cross between Bejeweled and the 10 Days geography board games. So far the coding has been going okay, but the frame rate is pretty bad... currently I'm getting low 20's on my Core 2 Duo. This is a problem since I'm creating the game for Intel's March developer competition, which is squarely aimed at netbooks packing underpowered Atom processors. Here's a screen from the game: ![www.necessarygames.com/my_games/betraveled/betraveled-fps.png][1] I am very new to Python and Pygame (this is the first thing I've used them for), and am sadly lacking in formal CS training... which is to say that I think there are probably A LOT of bad practices going on in my code, and A LOT that could be optimized. If some of you older Python hands wouldn't mind taking a look at my code and seeing if you can't find any obvious areas for optimization, I would be extremely grateful. You can download the full source code here: http://www.necessarygames.com/my_games/betraveled/betraveled_src0328.zip Compiled exe here: www.necessarygames.com/my_games/betraveled/betraveled_src0328.zip One thing I am concerned about is my event manager, which I feel may have some performance wholes in it, and another thing is my rendering... I'm pretty much just blitting everything to the screen all the time (see the render routines in my game_components.py below); I recently found out that you should only update the areas of the screen that have changed, but I'm still foggy on how that accomplished exactly... could this be a huge performance issue? Any thoughts are much appreciated! As usual, I'm happy to "tip" you for your time and energy via PayPal. Jordan Here are some bits of the source: Main.py #Remote imports import pygame from pygame.locals import * #Local imports import config import rooms from event_manager import * from events import * class RoomController(object): """Controls which room is currently active (eg Title Screen)""" def __init__(self, screen, ev_manager): self.room = None self.screen = screen self.ev_manager = ev_manager self.ev_manager.register_listener(self) self.room = self.set_room(config.room) def set_room(self, room_const): #Unregister old room from ev_manager if self.room: self.room.ev_manager.unregister_listener(self.room) self.room = None #Set new room based on const if room_const == config.TITLE_SCREEN: return rooms.TitleScreen(self.screen, self.ev_manager) elif room_const == config.GAME_MODE_ROOM: return rooms.GameModeRoom(self.screen, self.ev_manager) elif room_const == config.GAME_ROOM: return rooms.GameRoom(self.screen, self.ev_manager) elif room_const == config.HIGH_SCORES_ROOM: return rooms.HighScoresRoom(self.screen, self.ev_manager) def notify(self, event): if isinstance(event, ChangeRoomRequest): if event.game_mode: config.game_mode = event.game_mode self.room = self.set_room(event.new_room) def render(self, surface): self.room.render(surface) #Run game def main(): pygame.init() screen = pygame.display.set_mode(config.screen_size) ev_manager = EventManager() spinner = CPUSpinnerController(ev_manager) room_controller = RoomController(screen, ev_manager) pygame_event_controller = PyGameEventController(ev_manager) spinner.run() # this runs the main function if this script is called to run. # If it is imported as a module, we don't run the main function. if __name__ == "__main__": main() event_manager.py #Remote imports import pygame from pygame.locals import * #Local imports import config from events import * def debug( msg ): print "Debug Message: " + str(msg) class EventManager: #This object is responsible for coordinating most communication #between the Model, View, and Controller. def __init__(self): from weakref import WeakKeyDictionary self.listeners = WeakKeyDictionary() self.eventQueue= [] self.gui_app = None #---------------------------------------------------------------------- def register_listener(self, listener): self.listeners[listener] = 1 #---------------------------------------------------------------------- def unregister_listener(self, listener): if listener in self.listeners: del self.listeners[listener] #---------------------------------------------------------------------- def post(self, event): if isinstance(event, MouseButtonLeftEvent): debug(event.name) #NOTE: copying the list like this before iterating over it, EVERY tick, is highly inefficient, #but currently has to be done because of how new listeners are added to the queue while it is running #(eg when popping cards from a deck). Should be changed. See: http://dr0id.homepage.bluewin.ch/pygame_tutorial08.html #and search for "Watch the iteration" for listener in list(self.listeners): #NOTE: If the weakref has died, it will be #automatically removed, so we don't have #to worry about it. listener.notify(event) #------------------------------------------------------------------------------ class PyGameEventController: """...""" def __init__(self, ev_manager): self.ev_manager = ev_manager self.ev_manager.register_listener(self) self.input_freeze = False #---------------------------------------------------------------------- def notify(self, incoming_event): if isinstance(incoming_event, UserInputFreeze): self.input_freeze = True elif isinstance(incoming_event, UserInputUnFreeze): self.input_freeze = False elif isinstance(incoming_event, TickEvent): #Share some time with other processes, so we don't hog the cpu pygame.time.wait(5) #Handle Pygame Events for event in pygame.event.get(): #If this event manager has an associated PGU GUI app, notify it of the event if self.ev_manager.gui_app: self.ev_manager.gui_app.event(event) #Standard event handling for everything else ev = None if event.type == QUIT: ev = QuitEvent() elif event.type == pygame.MOUSEBUTTONDOWN and not self.input_freeze: if event.button == 1: #Button 1 pos = pygame.mouse.get_pos() ev = MouseButtonLeftEvent(pos) elif event.type == pygame.MOUSEMOTION: pos = pygame.mouse.get_pos() ev = MouseMoveEvent(pos) #Post event to event manager if ev: self.ev_manager.post(ev) #------------------------------------------------------------------------------ class CPUSpinnerController: def __init__(self, ev_manager): self.ev_manager = ev_manager self.ev_manager.register_listener(self) self.clock = pygame.time.Clock() self.cumu_time = 0 self.keep_going = True #---------------------------------------------------------------------- def run(self): if not self.keep_going: raise Exception('dead spinner') while self.keep_going: time_passed = self.clock.tick() fps = self.clock.get_fps() self.cumu_time += time_passed self.ev_manager.post(TickEvent(time_passed, fps)) if self.cumu_time >= 1000: self.cumu_time = 0 self.ev_manager.post(SecondEvent()) pygame.quit() #---------------------------------------------------------------------- def notify(self, event): if isinstance(event, QuitEvent): #this will stop the while loop from running self.keep_going = False rooms.py #Remote imports import pygame #Local imports import config import continents from game_components import * from my_gui import * from pgu import high class Room(object): def __init__(self, screen, ev_manager): self.screen = screen self.ev_manager = ev_manager self.ev_manager.register_listener(self) def notify(self, event): if isinstance(event, TickEvent): pygame.display.set_caption('FPS: ' + str(int(event.fps))) self.render(self.screen) pygame.display.update() def get_highs_table(self): fname = 'high_scores.txt' highs_table = None config.all_highs = high.Highs(fname) if config.game_mode == config.TIME_CHALLENGE: if config.difficulty == config.EASY: highs_table = config.all_highs['time_challenge_easy'] if config.difficulty == config.MED_DIF: highs_table = config.all_highs['time_challenge_med'] if config.difficulty == config.HARD: highs_table = config.all_highs['time_challenge_hard'] if config.difficulty == config.SUPER: highs_table = config.all_highs['time_challenge_super'] elif config.game_mode == config.PLAN_AHEAD: pass return highs_table class TitleScreen(Room): def __init__(self, screen, ev_manager): Room.__init__(self, screen, ev_manager) self.background = pygame.image.load('assets/images/interface/background.jpg').convert() #Initialize #--------------------------------------- self.gui_form = gui.Form() self.gui_app = gui.App(config.gui_theme) self.ev_manager.gui_app = self.gui_app c = gui.Container(align=0,valign=0) #Quit Button #--------------------------------------- b = StartGameButton(ev_manager=self.ev_manager) c.add(b, 0, 0) self.gui_app.init(c) def render(self, surface): surface.blit(self.background, (0, 0)) #GUI self.gui_app.paint(surface) class GameModeRoom(Room): def __init__(self, screen, ev_manager): Room.__init__(self, screen, ev_manager) self.background = pygame.image.load('assets/images/interface/background.jpg').convert() self.create_gui() #Create pgu gui elements def create_gui(self): #Setup #--------------------------------------- self.gui_form = gui.Form() self.gui_app = gui.App(config.gui_theme) self.ev_manager.gui_app = self.gui_app c = gui.Container(align=0,valign=-1) #Mode Relaxed Button #--------------------------------------- b = GameModeRelaxedButton(ev_manager=self.ev_manager) self.b = b print b.rect c.add(b, 0, 200) #Mode Time Challenge Button #--------------------------------------- b = TimeChallengeButton(ev_manager=self.ev_manager) self.b = b print b.rect c.add(b, 0, 250) #Mode Think Ahead Button #--------------------------------------- # b = PlanAheadButton(ev_manager=self.ev_manager) # self.b = b # print b.rect # c.add(b, 0, 300) #Initialize #--------------------------------------- self.gui_app.init(c) def render(self, surface): surface.blit(self.background, (0, 0)) #GUI self.gui_app.paint(surface) class GameRoom(Room): def __init__(self, screen, ev_manager): Room.__init__(self, screen, ev_manager) #Game mode #--------------------------------------- self.new_board_timer = None self.game_mode = config.game_mode config.current_highs = self.get_highs_table() self.highs_dialog = None self.game_over = False #Images #--------------------------------------- self.background = pygame.image.load('assets/images/interface/game screen2-1.jpg').convert() self.logo = pygame.image.load('assets/images/interface/logo_small.png').convert_alpha() self.game_over_text = pygame.image.load('assets/images/interface/text_game_over.png').convert_alpha() self.trip_complete_text = pygame.image.load('assets/images/interface/text_trip_complete.png').convert_alpha() self.zoom_game_over = None self.zoom_trip_complete = None self.fade_out = None #Text #--------------------------------------- self.font = pygame.font.Font(config.font_sans, config.interface_font_size) #Create game components #--------------------------------------- self.continent = self.set_continent(config.continent) self.board = Board(config.board_size, self.ev_manager) self.deck = Deck(self.ev_manager, self.continent) self.map = Map(self.continent) self.longest_trip = 0 #Set pos of game components #--------------------------------------- board_pos = (SCREEN_MARGIN[0], 109) self.board.set_pos(board_pos) map_pos = (config.screen_size[0] - self.map.size[0] - SCREEN_MARGIN[0], 57); self.map.set_pos(map_pos) #Trackers #--------------------------------------- self.game_clock = Chrono(self.ev_manager) self.swap_counter = 0 self.level = 0 #Create gui #--------------------------------------- self.create_gui() #Create initial board #--------------------------------------- self.new_board = self.deck.deal_new_board(self.board) self.ev_manager.post(NewBoardComplete(self.new_board)) def set_continent(self, continent_const): #Set continent based on const if continent_const == config.EUROPE: return continents.Europe() if continent_const == config.AFRICA: return continents.Africa() else: raise Exception('Continent constant not recognized') #Create pgu gui elements def create_gui(self): #Setup #--------------------------------------- self.gui_form = gui.Form() self.gui_app = gui.App(config.gui_theme) self.ev_manager.gui_app = self.gui_app c = gui.Container(align=-1,valign=-1) #Timer Progress bar #--------------------------------------- self.timer_bar = None self.time_increase = None self.minutes_left = None self.seconds_left = None self.timer_text = None if self.game_mode == config.TIME_CHALLENGE: self.time_increase = config.time_challenge_start_time self.timer_bar = gui.ProgressBar(config.time_challenge_start_time,0,config.max_time_bank,width=306) c.add(self.timer_bar, 172, 57) #Connections Progress bar #--------------------------------------- self.connections_bar = None self.connections_bar = gui.ProgressBar(0,0,config.longest_trip_needed,width=306) c.add(self.connections_bar, 172, 83) #Quit Button #--------------------------------------- b = QuitButton(ev_manager=self.ev_manager) c.add(b, 950, 20) #Generate Board Button #--------------------------------------- b = GenerateBoardButton(ev_manager=self.ev_manager, room=self) c.add(b, 500, 20) #Board Size? #--------------------------------------- bs = SetBoardSizeContainer(config.BOARD_LARGE, ev_manager=self.ev_manager, board=self.board) c.add(bs, 640, 20) #Fill Board? #--------------------------------------- t = FillBoardCheckbox(config.fill_board, ev_manager=self.ev_manager) c.add(t, 740, 20) #Darkness? #--------------------------------------- t = UseDarknessCheckbox(config.use_darkness, ev_manager=self.ev_manager) c.add(t, 840, 20) #Initialize #--------------------------------------- self.gui_app.init(c) def advance_level(self): self.level += 1 print 'Advancing to next level' print 'New level: ' + str(self.level) if self.timer_bar: print 'Time increase: ' + str(self.time_increase) self.timer_bar.value += self.time_increase self.time_increase = max(config.min_advance_time, int(self.time_increase * 0.9)) self.board = self.new_board self.new_board = None self.zoom_trip_complete = None self.game_clock.unpause() def notify(self, event): #Tick event if isinstance(event, TickEvent): pygame.display.set_caption('FPS: ' + str(int(event.fps))) self.render(self.screen) pygame.display.update() #Wait to deal new board when advancing levels if self.zoom_trip_complete and self.zoom_trip_complete.finished: self.zoom_trip_complete = None self.ev_manager.post(UnfreezeCards()) self.new_board = self.deck.deal_new_board(self.board) self.ev_manager.post(NewBoardComplete(self.new_board)) #New high score? if self.zoom_game_over and self.zoom_game_over.finished and not self.highs_dialog: if config.current_highs.check(self.level) != None: self.zoom_game_over.visible = False data = 'time:' + str(self.game_clock.time) + ',swaps:' + str(self.swap_counter) self.highs_dialog = HighScoreDialog(score=self.level, data=data, ev_manager=self.ev_manager) self.highs_dialog.open() elif not self.fade_out: self.fade_out = FadeOut(self.ev_manager, config.TITLE_SCREEN) #Second event elif isinstance(event, SecondEvent): if self.timer_bar: if not self.game_clock.paused: self.timer_bar.value -= 1 if self.timer_bar.value <= 0 and not self.game_over: self.ev_manager.post(GameOver()) self.minutes_left = self.timer_bar.value / 60 self.seconds_left = self.timer_bar.value % 60 if self.seconds_left < 10: leading_zero = '0' else: leading_zero = '' self.timer_text = ''.join(['Time Left: ', str(self.minutes_left), ':', leading_zero, str(self.seconds_left)]) #Game over elif isinstance(event, GameOver): self.game_over = True self.zoom_game_over = ZoomImage(self.ev_manager, self.game_over_text) #Trip complete event elif isinstance(event, TripComplete): print 'You did it!' self.game_clock.pause() self.zoom_trip_complete = ZoomImage(self.ev_manager, self.trip_complete_text) self.new_board_timer = Timer(self.ev_manager, 2) self.ev_manager.post(FreezeCards()) print 'Room posted newboardcomplete' #Board Refresh Complete elif isinstance(event, BoardRefreshComplete): if event.board == self.board: print 'Longest trip needed: ' + str(config.longest_trip_needed) print 'Your longest trip: ' + str(self.board.longest_trip) if self.board.longest_trip >= config.longest_trip_needed: self.ev_manager.post(TripComplete()) elif event.board == self.new_board: self.advance_level() self.connections_bar.value = self.board.longest_trip self.connection_text = ' '.join(['Connections:', str(self.board.longest_trip), '/', str(config.longest_trip_needed)]) #CardSwapComplete elif isinstance(event, CardSwapComplete): self.swap_counter += 1 elif isinstance(event, ConfigChangeBoardSize): config.board_size = event.new_size elif isinstance(event, ConfigChangeCardSize): config.card_size = event.new_size elif isinstance(event, ConfigChangeFillBoard): config.fill_board = event.new_value elif isinstance(event, ConfigChangeDarkness): config.use_darkness = event.new_value def render(self, surface): #Background surface.blit(self.background, (0, 0)) #Map self.map.render(surface) #Board self.board.render(surface) #Logo surface.blit(self.logo, (10,10)) #Text connection_text = self.font.render(self.connection_text, True, BLACK) surface.blit(connection_text, (25, 84)) if self.timer_text: timer_text = self.font.render(self.timer_text, True, BLACK) surface.blit(timer_text, (25, 64)) #GUI self.gui_app.paint(surface) if self.zoom_trip_complete: self.zoom_trip_complete.render(surface) if self.zoom_game_over: self.zoom_game_over.render(surface) if self.fade_out: self.fade_out.render(surface) class HighScoresRoom(Room): def __init__(self, screen, ev_manager): Room.__init__(self, screen, ev_manager) self.background = pygame.image.load('assets/images/interface/background.jpg').convert() #Initialize #--------------------------------------- self.gui_app = gui.App(config.gui_theme) self.ev_manager.gui_app = self.gui_app c = gui.Container(align=0,valign=0) #High Scores Table #--------------------------------------- hst = HighScoresTable() c.add(hst, 0, 0) self.gui_app.init(c) def render(self, surface): surface.blit(self.background, (0, 0)) #GUI self.gui_app.paint(surface) game_components.py #Remote imports import pygame from pygame.locals import * import random import operator from copy import copy from math import sqrt, floor #Local imports import config from events import * from matrix import Matrix from textrect import render_textrect, TextRectException from hyphen import hyphenator from textwrap2 import TextWrapper ############################## #CONSTANTS ############################## SCREEN_MARGIN = (10, 10) #Colors BLACK = (0, 0, 0) WHITE = (255, 255, 255) RED = (255, 0, 0) YELLOW = (255, 200, 0) #Directions LEFT = -1 RIGHT = 1 UP = 2 DOWN = -2 #Cards CARD_MARGIN = (10, 10) CARD_PADDING = (2, 2) #Card types BLANK = 0 COUNTRY = 1 TRANSPORT = 2 #Transport types PLANE = 0 TRAIN = 1 CAR = 2 SHIP = 3 class Timer(object): def __init__(self, ev_manager, time_left): self.ev_manager = ev_manager self.ev_manager.register_listener(self) self.time_left = time_left self.paused = False def __repr__(self): return str(self.time_left) def pause(self): self.paused = True def unpause(self): self.paused = False def notify(self, event): #Pause Event if isinstance(event, Pause): self.pause() #Unpause Event elif isinstance(event, Unpause): self.unpause() #Second Event elif isinstance(event, SecondEvent): if not self.paused: self.time_left -= 1 class Chrono(object): def __init__(self, ev_manager, start_time=0): self.ev_manager = ev_manager self.ev_manager.register_listener(self) self.time = start_time self.paused = False def __repr__(self): return str(self.time_left) def pause(self): self.paused = True def unpause(self): self.paused = False def notify(self, event): #Pause Event if isinstance(event, Pause): self.pause() #Unpause Event elif isinstance(event, Unpause): self.unpause() #Second Event elif isinstance(event, SecondEvent): if not self.paused: self.time += 1 class Map(object): def __init__(self, continent): self.map_image = pygame.image.load(continent.map).convert_alpha() self.map_text = pygame.image.load(continent.map_text).convert_alpha() self.pos = (0, 0) self.set_color() self.map_image = pygame.transform.smoothscale(self.map_image, config.map_size) self.size = self.map_image.get_size() def set_pos(self, pos): self.pos = pos def set_color(self): image_pixel_array = pygame.PixelArray(self.map_image) image_pixel_array.replace(config.GRAY1, config.COLOR1) image_pixel_array.replace(config.GRAY2, config.COLOR2) image_pixel_array.replace(config.GRAY3, config.COLOR3) image_pixel_array.replace(config.GRAY4, config.COLOR4) image_pixel_array.replace(config.GRAY5, config.COLOR5)

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  • Slowdowns when reading from an urlconnection's inputstream (even with byte[] and buffers)

    - by user342677
    Ok so after spending two days trying to figure out the problem, and reading about dizillion articles, i finally decided to man up and ask to for some advice(my first time here). Now to the issue at hand - I am writing a program which will parse api data from a game, namely battle logs. There will be A LOT of entries in the database(20+ million) and so the parsing speed for each battle log page matters quite a bit. The pages to be parsed look like this: http://api.erepublik.com/v1/feeds/battle_logs/10000/0. (see source code if using chrome, it doesnt display the page right). It has 1000 hit entries, followed by a little battle info(lastpage will have <1000 obviously). On average, a page contains 175000 characters, UTF-8 encoding, xml format(v 1.0). Program will run locally on a good PC, memory is virtually unlimited(so that creating byte[250000] is quite ok). The format never changes, which is quite convenient. Now, I started off as usual: //global vars,class declaration skipped public WebObject(String url_string, int connection_timeout, int read_timeout, boolean redirects_allowed, String user_agent) throws java.net.MalformedURLException, java.io.IOException { // Open a URL connection java.net.URL url = new java.net.URL(url_string); java.net.URLConnection uconn = url.openConnection(); if (!(uconn instanceof java.net.HttpURLConnection)) { throw new java.lang.IllegalArgumentException("URL protocol must be HTTP"); } conn = (java.net.HttpURLConnection) uconn; conn.setConnectTimeout(connection_timeout); conn.setReadTimeout(read_timeout); conn.setInstanceFollowRedirects(redirects_allowed); conn.setRequestProperty("User-agent", user_agent); } public void executeConnection() throws IOException { try { is = conn.getInputStream(); //global var l = conn.getContentLength(); //global var } catch (Exception e) { //handling code skipped } } //getContentStream and getLength methods which just return'is' and 'l' are skipped Here is where the fun part began. I ran some profiling (using System.currentTimeMillis()) to find out what takes long ,and what doesnt. The call to this method takes only 200ms on avg public InputStream getWebPageAsStream(int battle_id, int page) throws Exception { String url = "http://api.erepublik.com/v1/feeds/battle_logs/" + battle_id + "/" + page; WebObject wobj = new WebObject(url, 10000, 10000, true, "Mozilla/5.0 " + "(Windows; U; Windows NT 5.1; en-US; rv:1.9.2.3) Gecko/20100401 Firefox/3.6.3 ( .NET CLR 3.5.30729)"); wobj.executeConnection(); l = wobj.getContentLength(); // global variable return wobj.getContentStream(); //returns 'is' stream } 200ms is quite expected from a network operation, and i am fine with it. BUT when i parse the inputStream in any way(read it into string/use java XML parser/read it into another ByteArrayStream) the process takes over 1000ms! for example, this code takes 1000ms IF i pass the stream i got('is') above from getContentStream() directly to this method: public static Document convertToXML(InputStream is) throws ParserConfigurationException, IOException, SAXException { DocumentBuilderFactory dbf = DocumentBuilderFactory.newInstance(); DocumentBuilder db = dbf.newDocumentBuilder(); Document doc = db.parse(is); doc.getDocumentElement().normalize(); return doc; } this code too, takes around 920ms IF the initial InputStream 'is' is passed in(dont read into the code itself - it just extracts the data i need by directly counting the characters, which can be done thanks to the rigid api feed format): public static parsedBattlePage convertBattleToXMLWithoutDOM(InputStream is) throws IOException { // Point A BufferedReader br = new BufferedReader(new InputStreamReader(is)); LinkedList ll = new LinkedList(); String str = br.readLine(); while (str != null) { ll.add(str); str = br.readLine(); } if (((String) ll.get(1)).indexOf("error") != -1) { return new parsedBattlePage(null, null, true, -1); } //Point B Iterator it = ll.iterator(); it.next(); it.next(); it.next(); it.next(); String[][] hits_arr = new String[1000][4]; String t_str = (String) it.next(); String tmp = null; int j = 0; for (int i = 0; t_str.indexOf("time") != -1; i++) { hits_arr[i][0] = t_str.substring(12, t_str.length() - 11); tmp = (String) it.next(); hits_arr[i][1] = tmp.substring(14, tmp.length() - 9); tmp = (String) it.next(); hits_arr[i][2] = tmp.substring(15, tmp.length() - 10); tmp = (String) it.next(); hits_arr[i][3] = tmp.substring(18, tmp.length() - 13); it.next(); it.next(); t_str = (String) it.next(); j++; } String[] b_info_arr = new String[9]; int[] space_nums = {13, 10, 13, 11, 11, 12, 5, 10, 13}; for (int i = 0; i < space_nums.length; i++) { tmp = (String) it.next(); b_info_arr[i] = tmp.substring(space_nums[i] + 4, tmp.length() - space_nums[i] - 1); } //Point C return new parsedBattlePage(hits_arr, b_info_arr, false, j); } I have tried replacing the default BufferedReader with BufferedReader br = new BufferedReader(new InputStreamReader(is), 250000); This didnt change much. My second try was to replace the code between A and B with: Iterator it = IOUtils.lineIterator(is, "UTF-8"); Same result, except this time A-B was 0ms, and B-C was 1000ms, so then every call to it.next() must have been consuming some significant time.(IOUtils is from apache-commons-io library). And here is the culprit - the time taken to parse the stream to string, be it by an iterator or BufferedReader in ALL cases was about 1000ms, while the rest of the code took 0ms(e.g. irrelevant). This means that parsing the stream to LinkedList, or iterating over it, for some reason was eating up a lot of my system resources. question was - why? Is it just the way java is made...no...thats just stupid, so I did another experiment. In my main method I added after the getWebPageAsStream(): //Point A ba = new byte[l]; // 'l' comes from wobj.getContentLength above bytesRead = is.read(ba); //'is' is our URLConnection original InputStream offset = bytesRead; while (bytesRead != -1) { bytesRead = is.read(ba, offset - 1, l - offset); offset += bytesRead; } //Point B InputStream is2 = new ByteArrayInputStream(ba); //Now just working with 'is2' - the "copied" stream The InputStream-byte[] conversion took again 1000ms - this is the way many ppl suggested to read an InputStream, and stil it is slow. And guess what - the 2 parser methods above (convertToXML() and convertBattlePagetoXMLWithoutDOM(), when passed 'is2' instead of 'is' took, in all 4 cases, under 50ms to complete. I read a suggestion that the stream waits for connection to close before unblocking, so i tried using HttpComponentsClient 4.0 (http://hc.apache.org/httpcomponents-client/index.html) instead, but the initial InputStream took just as long to parse. e.g. this code: public InputStream getWebPageAsStream2(int battle_id, int page) throws Exception { String url = "http://api.erepublik.com/v1/feeds/battle_logs/" + battle_id + "/" + page; HttpClient httpclient = new DefaultHttpClient(); HttpGet httpget = new HttpGet(url); HttpParams p = new BasicHttpParams(); HttpConnectionParams.setSocketBufferSize(p, 250000); HttpConnectionParams.setStaleCheckingEnabled(p, false); HttpConnectionParams.setConnectionTimeout(p, 5000); httpget.setParams(p); HttpResponse response = httpclient.execute(httpget); HttpEntity entity = response.getEntity(); l = (int) entity.getContentLength(); return entity.getContent(); } took even longer to process(50ms more for just the network) and the stream parsing times remained the same. Obviously it can be instantiated so as to not create HttpClient and properties every time(faster network time), but the stream issue wont be affected by that. So we come to the center problem - why does the initial URLConnection InputStream(or HttpClient InputStream) take so long to process, while any stream of same size and content created locally is orders of magnitude faster? I mean, the initial response is already somewhere in RAM, and I cant see any good reasong why it is processed so slowly compared to when a same stream is just created from a byte[]. Considering I have to parse million of entries and thousands of pages like that, a total processing time of almost 1.5s/page seems WAY WAY too long. Any ideas? P.S. Please ask in any more code is required - the only thing I do after parsing is make a PreparedStatement and put the entries into JavaDB in packs of 1000+, and the perfomance is ok ~ 200ms/1000entries, prb could be optimized with more cache but I didnt look into it much.

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