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• Is my way of doing threads in Android correct?

  - by Charlie

  Hi, I'm writing a live wallpaper, and I'm forking off two separate threads in my main wallpaper service. One updates, and the other draws. I was under the impression that once you call thread.start(), it took care of everything for you, but after some trial and error, it seems that if I want my update and draw threads to keep running, I have to manually keep calling their run() methods? In other words, instead of calling start() on both threads and forgetting, I have to manually set up a delayed handler event that calls thread.run() on both the update and draw threads every 16 milliseconds. Is this the correct way of having a long running thread? Also, to kill threads, I'm just setting them to be daemons, then nulling them out. Is this method ok? Most examples I see use some sort of join() / interrupt() in a while loop...I don't understand that one...

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• strange bug - how to pause a java program?

  - by TerraNova993

  I'm trying to: display a text in a jLabel, wait for two seconds, then write a new text in the jLabel this should be simple, but I get a strange bug: the first text is never written, the application just waits for 2 seconds and then displays the final text. here is the example code: private void testButtonActionPerformed(java.awt.event.ActionEvent evt) { displayLabel.setText("Clicked!"); // first method with System timer /* long t0= System.currentTimeMillis(); long t1= System.currentTimeMillis(); do{ t1 = System.currentTimeMillis(); } while ((t1 - t0) < (2000)); */ // second method with thread.sleep() try { Thread.currentThread().sleep(2000); } catch (InterruptedException e) {} displayLabel.setText("STOP"); } with this code, the text "Clicked!" is never displayed. I just get a 2 seconds - pause and then the "STOP" text. I tried to use System timer with a loop, or Thread.sleep(), but both methods give the same result.

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• C++: static function member shared between threads, can block all?

  - by mhambra

  Hi all, I have a class, which has static function defined to work with C-style extern C { static void callback(foo bar) { } }. // static is defined in header. Three objects (each in separate pthread) are instantiated from this class, each of them has own loop (in class constructor), which can receive the callback. The pointer to function is passed as: x = init_function(h, queue_id, &callback, NULL); while(1) { loop_function(x); } So each thread has the same pointer to &callback. Callback function can block for minutes. Each thread object, excluding the one which got the blocking callback, can call callback again. If the callback function exists only once, then any thread attempting to callback will also block. This would give me an undesired bug, circa is interesting to ask: can anything in C++ become acting this way? Maybe, due to extern { } or some pointer usage?

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• Multithreaded update of multiple ProgressBars

  - by ClaudeS

  I have developped an application that can process data (in my case image algorithms performed on videos). I have developed different ProcessingMethods. Sometimes several videos are processed in parallel. Each process runs in a seperate thread. I have a GUI with several ProgressBars, one for each thread that is processing data. What is a good way to update the ProgressBar? Today my GUI is creating all the processing threads and one progressBars for each thread. Then I pass those progressBars to the threads, which pass them to the ProcessingMethod. The ProcessingMethod will then update the progressbar (using Invoke(..)). I have different processingMethods. Within each of these methods I have copy-paste code to update the progressBar. Although I am a new to programming, I know copy-paste is not good. What is a good way to make it better?

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• Debug.writeline locks

  - by Carra

  My program frequently stops with a deadlock. When I do a break-all and look at the threads I see that three threads are stuck in our logging function: public class Logging { public static void WriteClientLog(LogLevel logLevel, string message) { #if DEBUG System.Diagnostics.Debug.WriteLine(String.Format("{0} {1}", DateTime.Now.ToString("HH:mm:ss"), message)); //LOCK #endif //...Log4net logging } } If I let the program continue the threads are still stuck on that line. I can't see where this can lock. The debug class, string class & datetime class seem to be thread safe. The error goes away when I remove the "#if DEBUG System... #endif" code but I'm curious why this behavior happens. Thread one: public void CleanCache() { Logging.WriteClientLog(LogLevel.Debug, "Start clean cache.");//Stuck } Thread two: private void AliveThread() { Logging.WriteClientLog(LogLevel.Debug, "Check connection");//Stuck }

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• How do I ensure data consistency in this concurrent situation?

  - by MalcomTucker

  The problem is this: I have multiple competing threads (100+) that need to access one database table Each thread will pass a String name - where that name exists in the table, the database should return the id for the row, where the name doesn't already exist, the name should be inserted and the id returned. There can only ever be one instance of name in the database - ie. name must be unique How do I ensure that thread one doesn't insert name1 at the same time as thread two also tries to insert name1? In other words, how do I guarantee the uniqueness of name in a concurrent environment? This also needs to be as efficient as possible - this has the potential to be a serious bottleneck. I am using MySQL and Java. Thanks

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• Is it possible to creating a Service without starting it?

  - by ThaMe90

  Hello all, I wonder, is it possible to create a Service, set some data, and then start it? I haven't come across a thread specific to this problem, so I would like to know if it is possible (if it is known of course). My problem is that I have a Service which listens to a DatagramSocket, but the socket in question needs to be set after creation, but before the start of the Service. The setting of the socket happens through the use of a Broadcast (I broadcast 2 Strings which hold the IP-Address & Port and the BroadcastReceiver then constructs a socket for me). When the Service is started, a Thread will start to run and listen to the supposedly created socket. This, sadly, doesn't happen. The socket will remain null and I can't set it when the Thread is running (This is another issue I hope to tackle in the future, if anybody got any ideas about this, please notify me). So, is what I want possible, or should I come up with another construct for achieving this goal?

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• isAlive problem..Help to understand how it works

  - by max

  I get this error: "non-static method isAlive() cannot be referenced from a static context" what's wrong with this code..please. I'd like to detect if the thread is alive... Any help in terms of code will be highly appreciated..thanks max class RecThread extends Thread { public void run() { recFile = new File("recorded_track.wav"); // Output file type AudioFileFormat.Type fileType = null; fileType = AudioFileFormat.Type.WAVE; // if rcOn =1 thread is alive int rcOn; try { // starts recording targetDataLine.open(audioFormat); targetDataLine.start(); AudioSystem.write(new AudioInputStream(targetDataLine), fileType, recFile); if (RecThread.isAlive() == true) { rcOn =1; } else { rcOn =0; } } catch (Exception e) { showException(e); } // update actions recAction.setEnabled(true); stopRecAction.setEnabled(false); } }

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• How to debug ConcurrentModificationException?

  - by Dani

  I encountered ConcurrentModificationException and by looking at it I can't see the reason why it's happening; the area throwing the exception and all the places modifying the collection are surrounded by synchronized (this.locks.get(id)) { ... } // locks is a HashMap<String, Object>; I tried to catch the the pesky thread but all I could nail (by setting a breakpoint in the exception) is that the throwing thread owns the monitor while the other thread (there are two threads in the program) sleeps. How should I proceed? What do you usually do when you encounter similar threading issues?

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• C++11: thread_local or array of OpenCL 1.2 cl_kernel objects?

  - by user926918

  I need to run several C++11 threads (GCC 4.7.1) parallely in host. Each of them needs to use a device, say a GPU. As per OpenCL 1.2 spec (p. 357): All OpenCL API calls are thread-safe75 except clSetKernelArg. clSetKernelArg is safe to call from any host thread, and is safe to call re-entrantly so long as concurrent calls operate on different cl_kernel objects. However, the behavior of the cl_kernel object is undefined if clSetKernelArg is called from multiple host threads on the same cl_kernel object at the same time. An elegant way would be to use thread_local cl_kernel objects and the other way I can think of is to use an array of these objects such that i'th thread uses i'th object. As I have not implemented these earlier I was wondering if any of the two are good or are there better ways of getting things done. TIA, S

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• Disable Adding Item to Collection

  - by Wonko the Sane

  Hi All, I'm sure there's an "easy" answer to this, but for the moment it escapes me. In an MVVM application, I have a property that is a ObservableCollection, used for displaying some set of elements on the view. private readonly ObservableCollection<MyType> mMyCollection = new ObservableCollection<MyType>(); public ObservableCollection<MyType> MyCollection { get { return mMyCollection; } } I want to restrict consumers of this collection from simply using the property to add to the collection (i.e. I want to prevent this from the view): viewModel.MyCollection.Add(newThing); // want to prevent this! Instead, I want to force the use of a method to add items, because there may be another thread using that collection, and I don't want to modify the collection while that thread is processing it. public void AddToMyCollection(MyType newItem) { // Do some thread/task stuff here } Thanks, wTs

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• Volatile keyword

  - by Tiyoal

  Say I have two threads and an object. One thread assigns the object: public void assign(MyObject o) { myObject = o; } Another thread uses the object: public void use() { myObject.use(); } Does the variable myObject have to be declared as volatile? I am trying to understand when to use volatile and when not, and this is puzzling me. Is it possible that the second thread keeps a reference to an old object in its local memory cache? If not, why not? Thanks a lot.

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• The Scala way to use one actor per socket connection

  - by Stefan

  I am wondering how it is possible to avoid one socket connection pr. thread in Scala. I have thought a lot about it, but I always end up with some code which is listening for incoming data for each client connection. The problem is that I want to develop an application which should simultanously handle perhaps a couple of thousand connections. However I will of course not want to create a thread for each connection because of the lack of scalability and context switching. What would be the "right" way to do this. In my world it should be possible to have one actor for each connection without the need to block one thread per actor.

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• Java ME Runnable object takes up memory although not made an instance yet

  - by user1646684

  I am facing a strange problem with memory in Java ME. here is a part of my code: int variable=1; while (true) { if (variable==2) { display = Display.getDisplay(this); MyCanvas mc = new MyCanvas(this); // MyCanvas is a runnable object mcT = new Thread(mc); // new thread for MyCanvas mc.repaint(); display.setCurrent(mc); mcT.start(); // run thread } if (variable==1) { // Do some other stuff } } The problem is that although still the variable is set to 1, so it does not come through the if (variable==2) condition the program consumes 300kB more memory than when I delete the code after condition if (variable==2). As far as I know the code should by executed and the objects shall be created only when I set variable to value 2. But it consumes the memory also when the code after condition "if (variable==2)" is not executed. Why does this happen?

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• Java concurrency - Should block or yield?

  - by teto

  Hi, I have multiple threads each one with its own private concurrent queue and all they do is run an infinite loop retrieving messages from it. It could happen that one of the queues doesn't receive messages for a period of time (maybe a couple seconds), and also they could come in big bursts and fast processing is necessary. I would like to know what would be the most appropriate to do in the first case: use a blocking queue and block the thread until I have more input or do a Thread.yield()? I want to have as much CPU resources available as possible at a given time, as the number of concurrent threads may increase with time, but also I don't want the message processing to fall behind, as there is no guarantee of when the thread will be reescheduled for execution when doing a yield(). I know that hardware, operating system and other factors play an important role here, but setting that aside and looking at it from a Java (JVM?) point of view, what would be the most optimal?

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• assignment from incompatible pointer type

  - by Hristo

  I have set up the following struct: typedef struct _thread_node_t { pthread_t thread; struct thread_node_t *next; } thread_node_t; ... and then I have defined: // create thread to for incoming connection thread_node_t *thread_node = (thread_node_t*) malloc(sizeof(thread_node_t)); pthread_create(&(thread_node->thread), NULL, client_thread, &csFD); thread_node->next = thread_arr; // assignment from incompatible pointer type thread_arr = thread_node; where thread_arr is thread_node_t *thread_arr = NULL; I don't understand why the compiler is complaining. Maybe I'm misunderstanding something.

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• Program quits if pipe is closed

  - by givemelight

  I am trying to write to a pipe using C++. The following code gets called in an extra thread: void writeToPipe() { int outfifo; char buf[100]; char outfile[] = "out"; mknod(outfile, S_IFIFO | 0666, 0); if ((outfifo = open(outfile, O_WRONLY)) < 0) { perror("Opening output fifo failed"); return false; } int currentTimestamp = (int)time(0); int bufLen = sprintf(bug, "Time is %d.", currentTimestamp); write(outfifo, buf, bufLen); } The thread is called in main using: thread writeThread(writeToPipe); writeThread.detach(); If the pipe is not opened by another process, the C++ program just quits without an error. I don't know how to check if the pipe is opened.

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• Queues And Wait Handles in C#

  - by Michael Covelli

  I've had the following code in my application for some years and have never seen an issue from it. while ((PendingOrders.Count > 0) || (WaitHandle.WaitAny(CommandEventArr) != 1)) { lock (PendingOrders) { if (PendingOrders.Count > 0) { fbo = PendingOrders.Dequeue(); } else { fbo = null; } } // Do Some Work if fbo is != null } Where CommandEventArr is made up of the NewOrderEvent (an auto reset event) and the ExitEvent (a manual reset event). But I just realized today that its not thread safe at all. If this thread gets interrupted right after the first (PendingOrder.Count 0) check has returned false. And then the other thread both enqueues an order and sets the NewOrderEvent before I get a chance to wait on it, the body of the while loop will never run. What's the usual pattern used with a Queue and an AutoResetEvent to fix this and do what I'm trying to do with the code above?

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• [C++] Run codes for only 60 times each second.

  - by djzmo

  Hello there, I'm creating a directx application that relies on the system time (because it must be accurate), and I need to run lines of code for 60 times each second in the background (in a thread created by boost::thread). that's equal to 60 FPS (frame per second), but without depending on the main application frame rate. //................. void frameThread() { // I want to run codes inside this loop for *exactly* 60 times in a second. // In other words, every 16.67 (1000/60) milliseconds for(;;) { DoWork(); //......... } } int WINAPI WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR lpCmdLine, int nShowCmd) { initialize(); //.....stuffs boost::thread framethread(frameThread); //...... } Is there a way to do this? Any kind of help would be appreciated :)

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• What's the most performance effective way to have a webbrowser inside a class library ?

  - by Xaqron

  I'm developing a class library. Need some data from internet and this cannot be done with HttpWebRequest in my case so I wanna use WebBrowser component. WebBrowser is used for opening a single page and fetch some data from it, so WebBrowser life-time is very short. Running thread is MTA and no message pump or STA thread is available by default (class library is used by an ASP.NET application). How to create a WebBrowser object, run it with a STA thread, fetch data from a web page and finally dispose it with the least performance impact on the application ? I just need the idea/concept and will find details myself. Thanks guys

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• Dispatcher.CheckAccess() isn't working from my console application, is there a better way.

  - by zimmer62

  I wrote an application in WPF / VB and separated the business logic and UI into different projects. The business layer uses a serial port which runs on a different thread, Now that I'm trying to write a command line interface for the same business layer, it seems to fail when .Invoke() is called. (no error, just doesn't work) I'm pretty sure the reason I had to add in checkaccess and .invoke was because I have collections that would be changed during processing the serial port data and wanted the NotifyCollectionChanged to be handled by WPF data binding. (The reason I'm not 100% sure is because it was months ago I wrote that part and it all worked great from the GUI, now adding the console app has made me rethink some of this) I would like my business layer to run these processes on the thread they were created, I need this to work from both my GUI version and the command line version. Am I misusing the Dispatcher in my business layer? Is there a better way to handle an event from the serial port, and then return to the main thread to processes the data?

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• Building the Elusive Windows Phone Panorama Control

  When the Windows Phone 7 Developer SDK was released a couple of weeks ago at MIX10 many people noticed the SDK doesnt include a template for a Panorama control.   Here at Clarity we decided to build our own Panorama control for use in some of our prototypes and I figured I would share what we came up with. There have been a couple of implementations of the Panorama control making their way through the interwebs, but I didnt think any of them really nailed the experience that is shown in the simulation videos.   One of the key design principals in the UX Guide for Windows Phone 7 is the use of motion.  The WP7 OS is fairly stripped of extraneous design elements and makes heavy use of typography and motion to give users the necessary visual cues.  Subtle animations and wide layouts help give the user a sense of fluidity and consistency across the phone experience.  When building the panorama control I was fairly meticulous in recreating the motion as shown in the videos.  The effect that is shown in the application hubs of the phone is known as a Parallax Scrolling effect.  This this pseudo-3D technique has been around in the computer graphics world for quite some time. In essence, the background images move slower than foreground images, creating an illusion of depth in 2D.  Here is an example of the traditional use: http://www.mauriciostudio.com/.  One of the animation gems I've learned while building interactive software is the follow animation.  The premise is straightforward: instead of translating content 1:1 with the interaction point, let the content catch up to the mouse or finger.  The difference is subtle, but the impact on the smoothness of the interaction is huge.  That said, it became the foundation of how I achieved the effect shown below.   Source Code Available HERE Before I briefly describe the approach I took in creating this control..and Ill add some **asterisks ** to the code below as my coding skills arent up to snuff with the rest of my colleagues.  This code is meant to be an interpretation of the WP7 panorama control and is not intended to be used in a production application.  1.  Layout the XAML The UI consists of three main components :  The background image, the Title, and the Content.  You can imagine each  these UI Elements existing on their own plane with a corresponding Translate Transform to create the Parallax effect.  2.  Storyboards + Procedural Animations = Sexy As I mentioned above, creating a fluid experience was at the top of my priorities while building this control.  To recreate the smooth scroll effect shown in the video we need to add some place holder storyboards that we can manipulate in code to simulate the inertia and snapping.  Using the easing functions built into Silverlight helps create a very pleasant interaction.    3.  Handle the Manipulation Events With Silverlight 3 we have some new touch event handlers.  The new Manipulation events makes handling the interactivity pretty straight forward.  There are two event handlers that need to be hooked up to enable the dragging and motion effects: the ManipulationDelta event :  (the most relevant code is highlighted in pink) Here we are doing some simple math with the Manipulation Deltas and setting the TO values of the animations appropriately. Modifying the storyboards dynamically in code helps to create a natural feel.something that cant easily be done with storyboards alone.   And secondly, the ManipulationCompleted event:  Here we take the Final Velocities from the Manipulation Completed Event and apply them to the Storyboards to create the snapping and scrolling effects.  Most of this code is determining what the next position of the viewport will be.  The interesting part (shown in pink) is determining the duration of the animation based on the calculated velocity of the flick gesture.  By using velocity as a variable in determining the duration of the animation we can produce a slow animation for a soft flick and a fast animation for a strong flick. Challenges to the Reader There are a couple of things I didnt have time to implement into this control.  And I would love to see other WPF/Silverlight approaches.  1.  A good mechanism for deciphering when the user is manipulating the content within the panorama control and the panorama itself.   In other words, being able to accurately determine what is a flick and what is click. 2.  Dynamically Sizing the panorama control based on the width of its content.  Right now each control panel is 400px, ideally the Panel items would be measured and then panorama control would update its size accordingly.  3.  Background and content wrapping.  The WP7 UX guidelines specify that the content and background should wrap at the end of the list.  In my code I restrict the drag at the ends of the list (like the iPhone).  It would be interesting to see how this would effect the scroll experience.     Well, Its been fun building this control and if you use it Id love to know what you think.  You can download the Source HERE or from the Expression Gallery  Erik Klimczak  | [email protected] | twitter.com/eklimczDid 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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• The Inkremental Architect&acute;s Napkin - #4 - Make increments tangible

  - by Ralf Westphal

  Originally posted on: http://geekswithblogs.net/theArchitectsNapkin/archive/2014/06/12/the-inkremental-architectacutes-napkin---4---make-increments-tangible.aspxThe driver of software development are increments, small increments, tiny increments. With an increment being a slice of the overall requirement scope thin enough to implement and get feedback from a product owner within 2 days max. Such an increment might concern Functionality or Quality.[1] To make such high frequency delivery of increments possible, the transition from talking to coding needs to be as easy as possible. A user story or some other documentation of what´s supposed to get implemented until tomorrow evening at latest is one side of the medal. The other is where to put the logic in all of the code base. To implement an increment, only logic statements are needed. Functionality like Quality are just about expressions and control flow statements. Think of Assembler code without the CALL/RET instructions. That´s all is needed. Forget about functions, forget about classes. To make a user happy none of that is really needed. It´s just about the right expressions and conditional executions paths plus some memory allocation. Automatic function inlining of compilers which makes it clear how unimportant functions are for delivering value to users at runtime. But why then are there functions? Because they were invented for optimization purposes. We need them for better Evolvability and Production Efficiency. Nothing more, nothing less. No software has become faster, more secure, more scalable, more functional because we gathered logic under the roof of a function or two or a thousand. Functions make logic easier to understand. Functions make us faster in producing logic. Functions make it easier to keep logic consistent. Functions help to conserve memory. That said, functions are important. They are even the pivotal element of software development. We can´t code without them - whether you write a function yourself or not. Because there´s always at least one function in play: the Entry Point of a program. In Ruby the simplest program looks like this:puts "Hello, world!" In C# more is necessary:class Program { public static void Main () { System.Console.Write("Hello, world!"); } } C# makes the Entry Point function explicit, not so Ruby. But still it´s there. So you can think of logic always running in some function. Which brings me back to increments: In order to make the transition from talking to code as easy as possible, it has to be crystal clear into which function you should put the logic. Product owners might be content once there is a sticky note a user story on the Scrum or Kanban board. But developers need an idea of what that sticky note means in term of functions. Because with a function in hand, with a signature to run tests against, they have something to focus on. All´s well once there is a function behind whose signature logic can be piled up. Then testing frameworks can be used to check if the logic is correct. Then practices like TDD can help to drive the implementation. That´s why most code katas define exactly how the API of a solution should look like. It´s a function, maybe two or three, not more. A requirement like “Write a function f which takes this as parameters and produces such and such output by doing x” makes a developer comfortable. Yes, there are all kinds of details to think about, like which algorithm or technology to use, or what kind of state and side effects to consider. Even a single function not only must deliver on Functionality, but also on Quality and Evolvability. Nevertheless, once it´s clear which function to put logic in, you have a tangible starting point. So, yes, what I´m suggesting is to find a single function to put all the logic in that´s necessary to deliver on a the requirements of an increment. Or to put it the other way around: Slice requirements in a way that each increment´s logic can be located under the roof of a single function. Entry points Of course, the logic of a software will always be spread across many, many functions. But there´s always an Entry Point. That´s the most important function for each increment, because that´s the root to put integration or even acceptance tests on. A batch program like the above hello-world application only has a single Entry Point. All logic is reached from there, regardless how deep it´s nested in classes. But a program with a user interface like this has at least two Entry Points: One is the main function called upon startup. The other is the button click event handler for “Show my score”. But maybe there are even more, like another Entry Point being a handler for the event fired when one of the choices gets selected; because then some logic could check if the button should be enabled because all questions got answered. Or another Entry Point for the logic to be executed when the program is close; because then the choices made should be persisted. You see, an Entry Point to me is a function which gets triggered by the user of a software. With batch programs that´s the main function. With GUI programs on the desktop that´s event handlers. With web programs that´s handlers for URL routes. And my basic suggestion to help you with slicing requirements for Spinning is: Slice them in a way so that each increment is related to only one Entry Point function.[2] Entry Points are the “outer functions” of a program. That´s where the environment triggers behavior. That´s where hardware meets software. Entry points always get called because something happened to hardware state, e.g. a key was pressed, a mouse button clicked, the system timer ticked, data arrived over a wire.[3] Viewed from the outside, software is just a collection of Entry Point functions made accessible via buttons to press, menu items to click, gestures, URLs to open, keys to enter. Collections of batch processors I´d thus say, we haven´t moved forward since the early days of software development. We´re still writing batch programs. Forget about “event-driven programming” with its fancy GUI applications. Software is just a collection of batch processors. Earlier it was just one per program, today it´s hundreds we bundle up into applications. Each batch processor is represented by an Entry Point as its root that works on a number of resources from which it reads data to process and to which it writes results. These resources can be the keyboard or main memory or a hard disk or a communication line or a display. Together many batch processors - large and small - form applications the user perceives as a single whole: Software development that way becomes quite simple: just implement one batch processor after another. Well, at least in principle ;-) Features Each batch processor entered through an Entry Point delivers value to the user. It´s an increment. Sometimes its logic is trivial, sometimes it´s very complex. Regardless, each Entry Point represents an increment. An Entry Point implemented thus is a step forward in terms of Agility. At the same time it´s a tangible unit for developers. Therefore, identifying the more or less numerous batch processors in a software system is a rewarding task for product owners and developers alike. That´s where user stories meet code. In this example the user story translates to the Entry Point triggered by clicking the login button on a dialog like this: The batch then retrieves what has been entered via keyboard, loads data from a user store, and finally outputs some kind of response on the screen, e.g. by displaying an error message or showing the next dialog. This is all very simple, but you see, there is not just one thing happening, but several. Get input (email address, password) Load user for email address If user not found report error Check password Hash password Compare hash to hash stored in user Show next dialog Viewed from 10,000 feet it´s all done by the Entry Point function. And of course that´s technically possible. It´s just a bunch of logic and calling a couple of API functions. However, I suggest to take these steps as distinct aspects of the overall requirement described by the user story. Such aspects of requirements I call Features. Features too are increments. Each provides some (small) value of its own to the user. Each can be checked individually by a product owner. Instead of implementing all the logic behind the Login() entry point at once you can move forward increment by increment, e.g. First implement the dialog, let the user enter any credentials, and log him/her in without any checks. Features 1 and 4. Then hard code a single user and check the email address. Features 2 and 2.1. Then check password without hashing it (or use a very simple hash like the length of the password). Features 3. and 3.2 Replace hard coded user with a persistent user directoy, but a very simple one, e.g. a CSV file. Refinement of feature 2. Calculate the real hash for the password. Feature 3.1. Switch to the final user directory technology. Each feature provides an opportunity to deliver results in a short amount of time and get feedback. If you´re in doubt whether you can implement the whole entry point function until tomorrow night, then just go for a couple of features or even just one. That´s also why I think, you should strive for wrapping feature logic into a function of its own. It´s a matter of Evolvability and Production Efficiency. A function per feature makes the code more readable, since the language of requirements analysis and design is carried over into implementation. It makes it easier to apply changes to features because it´s clear where their logic is located. And finally, of course, it lets you re-use features in different context (read: increments). Feature functions make it easier for you to think of features as Spinning increments, to implement them independently, to let the product owner check them for acceptance individually. Increments consist of features, entry point functions consist of feature functions. So you can view software as a hierarchy of requirements from broad to thin which map to a hierarchy of functions - with entry points at the top.   I like this image of software as a self-similar structure on many levels of abstraction where requirements and code match each other. That to me is true agile design: the core tenet of Agility to move forward in increments is carried over into implementation. Increments on paper are retained in code. This way developers can easily relate to product owners. Elusive and fuzzy requirements are not tangible. Software production is moving forward through requirements one increment at a time, and one function at a time. In closing Product owners and developers are different - but they need to work together towards a shared goal: working software. So their notions of software need to be made compatible, they need to be connected. The increments of the product owner - user stories and features - need to be mapped straightforwardly to something which is relevant to developers. To me that´s functions. Yes, functions, not classes nor components nor micro services. We´re talking about behavior, actions, activities, processes. Their natural representation is a function. Something has to be done. Logic has to be executed. That´s the purpose of functions. Later, classes and other containers are needed to stay on top of a growing amount of logic. But to connect developers and product owners functions are the appropriate glue. Functions which represent increments. Can there always be such a small increment be found to deliver until tomorrow evening? I boldly say yes. Yes, it´s always possible. But maybe you´ve to start thinking differently. Maybe the product owner needs to start thinking differently. Completion is not the goal anymore. Neither is checking the delivery of an increment through the user interface of a software. Product owners need to become comfortable using test beds for certain features. If it´s hard to slice requirements thin enough for Spinning the reason is too little knowledge of something. Maybe you don´t yet understand the problem domain well enough? Maybe you don´t yet feel comfortable with some tool or technology? Then it´s time to acknowledge this fact. Be honest about your not knowing. And instead of trying to deliver as a craftsman officially become a researcher. Research an check back with the product owner every day - until your understanding has grown to a level where you are able to define the next Spinning increment. ? Sometimes even thin requirement slices will cover several Entry Points, like “Add validation of email addresses to all relevant dialogs.” Validation then will it put into a dozen functons. Still, though, it´s important to determine which Entry Points exactly get affected. That´s much easier, if strive for keeping the number of Entry Points per increment to 1. ? If you like call Entry Point functions event handlers, because that´s what they are. They all handle events of some kind, whether that´s palpable in your code or note. A public void btnSave_Click(object sender, EventArgs e) {…} might look like an event handler to you, but public static void Main() {…} is one also - for then event “program started”. ?

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• Upcoming EMEA, APAC & US Events with MySQL in 2014

  - by Lenka Kasparova

  As an update to the previous announcement from Mar 25, 2014 please find below the updated list of events where MySQL Community team is attending and/or supporting. This time you can find not only EMEA & APAC ones but also conferences & events we are covering in the US & Canada. You are invited to meet our engineers at the events below.   EMEA  NEW!! BGOUG, Sandanski, Bulgaria, June 13, 2014  Georgi Kodinov will attend and speak at this local Oracle User Group event. Feel free to come. PHP Tour Lyon, Lyon, France, June 23-24, 2014 MySQL team is going to be part of this show as well, we are not going to have a booth here but very active networking by our french MySQL team around the event. Come to meet us and talk to us! NEW!! Converge Conference, Glasgow, Scotland, August 15-16, 2014  MySQL Community Manager, David Stokes attends with MySQL talk. NEW!! CakeFest, Madrid, Spain, August 21-24, 2014  A talk on "Scaling Your MySQL instances AND keeping your Sanity" will be given by the MySQL Community Manager, David Stokes. Froscon 2014, St.Augustin, Germany, August 23-24, 2014 Please visit our booth as well as watch the Froscon website for the schedule updates. NEW!! SymfonyLive, UK, London, September 25-26, 2014 MySQL Community Magers, David Stokes & Morgan Tocker submitted MySQL talks for this show. Schedule will be announced later on. DrupalCon Amsterdam, The Netherlands, September 29-Oct 3, 2014 Meet us at our booth at DrupalCon Amsterdam. For the schedule please watch the DrupalCon website. All Your Base, Oxford UK, October 17, 2014  Come to visit our MySQL booth and talk to our MySQL experts. NEW!! WebTechCon / IPC, Munich Germany, October 26-29, 2014 NEW!! DOAG, Nuremberg, Germany, November 18-20, 2014 There will be a full day of MySQL talks and one full day of MySQL workshop & sessions with live demo. This event is simply hard to miss! NEW!! Forum PHP Paris, France, November 21-22, 2014 More details: TBD NEW!! UK OUG, Liverpool, UK, December 8-10, 2014 MySQL will be part of the Oracle booth and we hope to get more space for MySQL talks.  USA NEW!! Texas Linux Fest, Austin, Texas, US, June 13-14, 2014 NEW!! SouthEast Linux Fest, Charlotte, US, June 20-22, 2014 NEW!! Debian Conference 2014, Portland, OR, US, August 23-31, 2014 NEW!! FossetCon, Orlando, US, September 11-13, 2014 NEW!! Oracle Open World, San Francisco, US, September 29-October 3, 2014 NEW!! MySQL Central @ Open/World, San Francisco, US, September 29-October 3, 2014 NEW!! PyTexas 2014, Dallas, TX, US, October 3-5, 2014 NEW!! All Things Open (replacing POSSCON), Raleigh, NC, October 23-24, 2014 NEW!! Ohio LinuxFest 2014, Columbus, Ohio, US, October 24-25, 2014 NEW!! ZendCon PHP, Santa Clara, US, October 27-30, 2014 NEW!! Kuali Days 2014, Indianapolis, US, November 10-13, 2014 NEW!! Live 360, Orlando, FL, US, November 17-20, 2014 APAC OpenSourceConference Japan, Hokkaido, June 13-14, 2014 MySQL is represented by Ryusuke Kajiyama with the talk on "MySQL Technology Updates". NEW!! db tech showcase, Osaka Japan, June 18-20, 2014 Three MySQL talks are scheduled for this show, "MySQL for Oracle DBA" & "MySQL Technology Updates" by Ryusuke Kajiyama. The last talk will be on MySQL Fabric by Yoshiaki Yamasaki. NEW!! PyCon Singapore, Singapore, June 18-20, 2014 Ryusuke Kajiyama will be talking about "Sharding and scale-out using Python-based MySQL Fabric". NEW!! COSCUP, Taipei, Taiwan, July 19-20, 2014 We are going to run a technical session on MySQL Workbench & one talk on how to make MySQL better MySQL. NEW!! PyCon New Zealand, Wellington, New Zealand, September 13-14, 2014 MySQL talks were submitted as well as one talk by Solaris Modernization team on Python & Solaris, watch the website for schedule updates. NEW!! PyCon Japan, Tokyo Japan, September 13-15, 2014 MySQL will be a MySQL session speaker, no schedule is announced yet. Ruby Kaigi, Tokyo, Japan, September 18-20, 2014 Another event MySQL supports and attends in APAC region. Ruby Kaigi is the international Ruby Conference in Japan, Tokyo. Ruby started in Japan, so Ruby Kaigi has excellent speakers and developers! MySQL team is going to be present at this conference with MySQL talks and active networking around the venue. NEW!! PyCon India, Bangalore, India, September 26-28, 2014 A MySQL talk on "MySQL Utilities scaling MySQL with Python" has been submitted, please watch the PyCon website for the schedule updates. NEW!! OpenSourceConference Japan, Tokyo, October 18-19, 2014 NEW!! OpenSource India, Bengaluru, India, November 7-8, 2014 NEW!! OpenSourceConference Japan, Fukuoka, November 14-15, 2014 You can check the MySQL wikis for updates on the conferences we are attending. Next time I hope to have more details for each event above (especially for the US ones).

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• Building the Elusive Windows Phone Panorama Control

  When the Windows Phone 7 Developer SDK was released a couple of weeks ago at MIX10 many people noticed the SDK doesnt include a template for a Panorama control.   Here at Clarity we decided to build our own Panorama control for use in some of our prototypes and I figured I would share what we came up with. There have been a couple of implementations of the Panorama control making their way through the interwebs, but I didnt think any of them really nailed the experience that is shown in the simulation videos.   One of the key design principals in the UX Guide for Windows Phone 7 is the use of motion.  The WP7 OS is fairly stripped of extraneous design elements and makes heavy use of typography and motion to give users the necessary visual cues.  Subtle animations and wide layouts help give the user a sense of fluidity and consistency across the phone experience.  When building the panorama control I was fairly meticulous in recreating the motion as shown in the videos.  The effect that is shown in the application hubs of the phone is known as a Parallax Scrolling effect.  This this pseudo-3D technique has been around in the computer graphics world for quite some time. In essence, the background images move slower than foreground images, creating an illusion of depth in 2D.  Here is an example of the traditional use: http://www.mauriciostudio.com/.  One of the animation gems I've learned while building interactive software is the follow animation.  The premise is straightforward: instead of translating content 1:1 with the interaction point, let the content catch up to the mouse or finger.  The difference is subtle, but the impact on the smoothness of the interaction is huge.  That said, it became the foundation of how I achieved the effect shown below.   Source Code Available HERE Before I briefly describe the approach I took in creating this control..and Ill add some **asterisks ** to the code below as my coding skills arent up to snuff with the rest of my colleagues.  This code is meant to be an interpretation of the WP7 panorama control and is not intended to be used in a production application.  1.  Layout the XAML The UI consists of three main components :  The background image, the Title, and the Content.  You can imagine each  these UI Elements existing on their own plane with a corresponding Translate Transform to create the Parallax effect.  2.  Storyboards + Procedural Animations = Sexy As I mentioned above, creating a fluid experience was at the top of my priorities while building this control.  To recreate the smooth scroll effect shown in the video we need to add some place holder storyboards that we can manipulate in code to simulate the inertia and snapping.  Using the easing functions built into Silverlight helps create a very pleasant interaction.    3.  Handle the Manipulation Events With Silverlight 3 we have some new touch event handlers.  The new Manipulation events makes handling the interactivity pretty straight forward.  There are two event handlers that need to be hooked up to enable the dragging and motion effects: the ManipulationDelta event :  (the most relevant code is highlighted in pink) Here we are doing some simple math with the Manipulation Deltas and setting the TO values of the animations appropriately. Modifying the storyboards dynamically in code helps to create a natural feel.something that cant easily be done with storyboards alone.   And secondly, the ManipulationCompleted event:  Here we take the Final Velocities from the Manipulation Completed Event and apply them to the Storyboards to create the snapping and scrolling effects.  Most of this code is determining what the next position of the viewport will be.  The interesting part (shown in pink) is determining the duration of the animation based on the calculated velocity of the flick gesture.  By using velocity as a variable in determining the duration of the animation we can produce a slow animation for a soft flick and a fast animation for a strong flick. Challenges to the Reader There are a couple of things I didnt have time to implement into this control.  And I would love to see other WPF/Silverlight approaches.  1.  A good mechanism for deciphering when the user is manipulating the content within the panorama control and the panorama itself.   In other words, being able to accurately determine what is a flick and what is click. 2.  Dynamically Sizing the panorama control based on the width of its content.  Right now each control panel is 400px, ideally the Panel items would be measured and then panorama control would update its size accordingly.  3.  Background and content wrapping.  The WP7 UX guidelines specify that the content and background should wrap at the end of the list.  In my code I restrict the drag at the ends of the list (like the iPhone).  It would be interesting to see how this would effect the scroll experience.     Well, Its been fun building this control and if you use it Id love to know what you think.  You can download the Source HERE or from the Expression Gallery  Erik Klimczak  | [email protected] | twitter.com/eklimczDid 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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