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  • Pushing to an array not working as expected

    - by Ross Attrill
    When I execute the code below, my array 'tasks' ends up with the same last row from the dbi call repeated for each row in the database. require 'dbi' require 'PP' dbh = DBI.connect('DBI:ODBC:Driver={SQL Server Native Client 10.0};Server=localhost,1433;Database=db;Uid=db;Pwd=mypass', 'db', 'mypass') sth = dbh.prepare('select * from TASK') sth.execute tasks = Array.new while row=sth.fetch do p row tasks.push(row) end pp(tasks) sth.finish So if I have two rows in my TASK table, then instead of getting this in the tasks array: [[1, "Task 1"], [2, "Task 2"]] I get this [[2, "Task 2"], [2, "Task 2"]] What am I doing wrong?

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  • Set postion in customized list field in blackberry

    - by arunabha
    I want three list field items to be displayed, from bottom to top. I am able to display three list field items, but they display from top to bottom. I have tried setting the position, but it isn't working. import java.util.Vector; import net.rim.device.api.system.Bitmap; import net.rim.device.api.system.Display; import net.rim.device.api.ui.ContextMenu; import net.rim.device.api.ui.DrawStyle; import net.rim.device.api.ui.Field; import net.rim.device.api.ui.Font; import net.rim.device.api.ui.Graphics; import net.rim.device.api.ui.Manager; import net.rim.device.api.ui.MenuItem; import net.rim.device.api.ui.UiApplication; import net.rim.device.api.ui.component.BitmapField; import net.rim.device.api.ui.component.Dialog; import net.rim.device.api.ui.component.LabelField; import net.rim.device.api.ui.component.ListField; import net.rim.device.api.ui.component.ListFieldCallback; import net.rim.device.api.ui.component.NullField; import net.rim.device.api.ui.container.FullScreen; import net.rim.device.api.ui.container.MainScreen; import net.rim.device.api.util.Arrays; import net.rim.device.api.ui.component.ListField; /** * @author Jason Emerick */ public class TaskListField extends UiApplication { //statics ------------------------------------------------------------------ public static void main(String[] args) { TaskListField theApp = new TaskListField(); theApp.enterEventDispatcher(); } public TaskListField() { pushScreen(new TaskList()); } } /*class List extends FullScreen { TaskList tl; List(){ super(); TaskList tl=new TaskList(); } }*/ class TaskList extends MainScreen implements ListFieldCallback { private Vector rows; private Bitmap p1; private Bitmap p2; private Bitmap p3; String Task; ListField listnew=new ListField(); public TaskList() { super(); listnew.setRowHeight(50); //setEmptyString("Hooray, no tasks here!", DrawStyle.HCENTER); listnew.setCallback(this); p1 = Bitmap.getBitmapResource("1.png"); p2 = Bitmap.getBitmapResource("2.png"); p3 = Bitmap.getBitmapResource("3.png"); rows = new Vector(); for (int x = 0; x < 3; x++) { TableRowManager row = new TableRowManager(); if (x== 0) { Task="On Air Now"; } if (x== 1) { Task="Music Channel"; } if (x==2) { Task="News Channel"; } // SET THE PRIORITY BITMAP FIELD // if high priority, display p1 bitmap if (x % 2 == 0) { row.add(new BitmapField(p1)); } // if priority is 2, set p2 bitmap else if (x % 3 == 0) { row.add(new BitmapField(p2)); } // if priority is 3, set p3 bitmap else { row.add(new BitmapField(p3)); } // SET THE TASK NAME LABELFIELD // if overdue, bold/underline LabelField task = new LabelField(Task, DrawStyle.ELLIPSIS); // if due today, bold if (x % 2 == 0) { task.setFont(Font.getDefault().derive( Font.BOLD)); } else { task.setFont(Font.getDefault().derive(Font.BOLD)); } row.add(task); LabelField task1 = new LabelField("Now Playing" + String.valueOf(x), DrawStyle.ELLIPSIS); // if due today, bold /* if (x % 2 == 0) { task.setFont(Font.getDefault().derive( Font.BOLD)); } else { task.setFont(Font.getDefault().derive(Font.BOLD)); }*/ Font myFont = Font.getDefault().derive(Font.PLAIN, 12); task1.setFont(myFont); row.add(task1); // SET THE DUE DATE/TIME row.add(new LabelField("", DrawStyle.ELLIPSIS | LabelField.USE_ALL_WIDTH | DrawStyle.RIGHT) { protected void paint(Graphics graphics) { graphics.setColor(0x00878787); super.paint(graphics); } }); rows.addElement(row); } listnew.setSize(rows.size()); this.add(listnew); } // ListFieldCallback Implementation public void drawListRow(ListField listField, Graphics g, int index, int y, int width) { //TaskList list =(TaskListField) listnew; TableRowManager rowManager = (TableRowManager)rows .elementAt(index); rowManager.drawRow(g, 0, y, width, listnew.getRowHeight()); } private class TableRowManager extends Manager { public TableRowManager() { super(0); } // Causes the fields within this row manager to be layed out then // painted. public void drawRow(Graphics g, int x, int y, int width, int height) { // Arrange the cell fields within this row manager. layout(0, 1); // Place this row manager within its enclosing list. setPosition(x,y); // Apply a translating/clipping transformation to the graphics // context so that this row paints in the right area. g.pushRegion(getExtent()); // Paint this manager's controlled fields. subpaint(g); g.setColor(0x00CACACA); g.drawLine(0, 0, getPreferredWidth(), 0); // Restore the graphics context. g.popContext(); } // Arrages this manager's controlled fields from left to right within // the enclosing table's columns. protected void sublayout(int width, int height) { // set the size and position of each field. int fontHeight = Font.getDefault().getHeight(); int preferredWidth = getPreferredWidth(); // start with the Bitmap Field of the priority icon /* Field field = getField(0); layoutChild(field, 0, 0); setPositionChild(field, 150, 300);*/ // set the task name label field /* field = getField(1); layoutChild(field, preferredWidth - 16, fontHeight + 1); setPositionChild(field, 34, 3); // set the list name label field field = getField(2); layoutChild(field, 150, fontHeight + 1); setPositionChild(field, 34, fontHeight + 6);*/ // set the due time name label field /* field = getField(3); layoutChild(field, 150, fontHeight + 1); setPositionChild(field,4,340);*/ /* layoutChild(listnew, preferredWidth, fontHeight); setPositionChild(listnew, 3, 396);*/ setExtent(360, 480); } // The preferred width of a row is defined by the list renderer. public int getPreferredWidth() { return getWidth(); } // The preferred height of a row is the "row height" as defined in the // enclosing list. public int getPreferredHeight() { return listnew.getRowHeight(); } } public Object get(ListField listField, int index) { // TODO Auto-generated method stub return null; } public int getPreferredWidth(ListField listField) { // TODO Auto-generated method stub return 0; } public int indexOfList(ListField listField, String prefix, int start) { // TODO Auto-generated method stub return 0; } }

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  • MvcExtensions – Bootstrapping

    - by kazimanzurrashid
    When you create a new ASP.NET MVC application you will find that the global.asax contains the following lines: namespace MvcApplication1 { // Note: For instructions on enabling IIS6 or IIS7 classic mode, // visit http://go.microsoft.com/?LinkId=9394801 public class MvcApplication : System.Web.HttpApplication { public static void RegisterRoutes(RouteCollection routes) { routes.IgnoreRoute("{resource}.axd/{*pathInfo}"); routes.MapRoute( "Default", // Route name "{controller}/{action}/{id}", // URL with parameters new { controller = "Home", action = "Index", id = UrlParameter.Optional } // Parameter defaults ); } protected void Application_Start() { AreaRegistration.RegisterAllAreas(); RegisterRoutes(RouteTable.Routes); } } } As the application grows, there are quite a lot of plumbing code gets into the global.asax which quickly becomes a design smell. Lets take a quick look at the code of one of the open source project that I recently visited: public static void RegisterRoutes(RouteCollection routes) { routes.IgnoreRoute("{resource}.axd/{*pathInfo}"); routes.MapRoute("Default","{controller}/{action}/{id}", new { controller = "Home", action = "Index", id = "" }); } protected override void OnApplicationStarted() { Error += OnError; EndRequest += OnEndRequest; var settings = new SparkSettings() .AddNamespace("System") .AddNamespace("System.Collections.Generic") .AddNamespace("System.Web.Mvc") .AddNamespace("System.Web.Mvc.Html") .AddNamespace("MvcContrib.FluentHtml") .AddNamespace("********") .AddNamespace("********.Web") .SetPageBaseType("ApplicationViewPage") .SetAutomaticEncoding(true); #if DEBUG settings.SetDebug(true); #endif var viewFactory = new SparkViewFactory(settings); ViewEngines.Engines.Add(viewFactory); #if !DEBUG PrecompileViews(viewFactory); #endif RegisterAllControllersIn("********.Web"); log4net.Config.XmlConfigurator.Configure(); RegisterRoutes(RouteTable.Routes); Factory.Load(new Components.WebDependencies()); ModelBinders.Binders.DefaultBinder = new Binders.GenericBinderResolver(Factory.TryGet<IModelBinder>); ValidatorConfiguration.Initialize("********"); HtmlValidationExtensions.Initialize(ValidatorConfiguration.Rules); } private void OnEndRequest(object sender, System.EventArgs e) { if (((HttpApplication)sender).Context.Handler is MvcHandler) { CreateKernel().Get<ISessionSource>().Close(); } } private void OnError(object sender, System.EventArgs e) { CreateKernel().Get<ISessionSource>().Close(); } protected override IKernel CreateKernel() { return Factory.Kernel; } private static void PrecompileViews(SparkViewFactory viewFactory) { var batch = new SparkBatchDescriptor(); batch.For<HomeController>().For<ManageController>(); viewFactory.Precompile(batch); } As you can see there are quite a few of things going on in the above code, Registering the ViewEngine, Compiling the Views, Registering the Routes/Controllers/Model Binders, Settings up Logger, Validations and as you can imagine the more it becomes complex the more things will get added in the application start. One of the goal of the MVCExtensions is to reduce the above design smell. Instead of writing all the plumbing code in the application start, it contains BootstrapperTask to register individual services. Out of the box, it contains BootstrapperTask to register Controllers, Controller Factory, Action Invoker, Action Filters, Model Binders, Model Metadata/Validation Providers, ValueProvideraFactory, ViewEngines etc and it is intelligent enough to automatically detect the above types and register into the ASP.NET MVC Framework. Other than the built-in tasks you can create your own custom task which will be automatically executed when the application starts. When the BootstrapperTasks are in action you will find the global.asax pretty much clean like the following: public class MvcApplication : UnityMvcApplication { public void ErrorLog_Filtering(object sender, ExceptionFilterEventArgs e) { Check.Argument.IsNotNull(e, "e"); HttpException exception = e.Exception.GetBaseException() as HttpException; if ((exception != null) && (exception.GetHttpCode() == (int)HttpStatusCode.NotFound)) { e.Dismiss(); } } } The above code is taken from my another open source project Shrinkr, as you can see the global.asax is longer cluttered with any plumbing code. One special thing you have noticed that it is inherited from the UnityMvcApplication rather than regular HttpApplication. There are separate version of this class for each IoC Container like NinjectMvcApplication, StructureMapMvcApplication etc. Other than executing the built-in tasks, the Shrinkr also has few custom tasks which gets executed when the application starts. For example, when the application starts, we want to ensure that the default users (which is specified in the web.config) are created. The following is the custom task that is used to create those default users: public class CreateDefaultUsers : BootstrapperTask { protected override TaskContinuation ExecuteCore(IServiceLocator serviceLocator) { IUserRepository userRepository = serviceLocator.GetInstance<IUserRepository>(); IUnitOfWork unitOfWork = serviceLocator.GetInstance<IUnitOfWork>(); IEnumerable<User> users = serviceLocator.GetInstance<Settings>().DefaultUsers; bool shouldCommit = false; foreach (User user in users) { if (userRepository.GetByName(user.Name) == null) { user.AllowApiAccess(ApiSetting.InfiniteLimit); userRepository.Add(user); shouldCommit = true; } } if (shouldCommit) { unitOfWork.Commit(); } return TaskContinuation.Continue; } } There are several other Tasks in the Shrinkr that we are also using which you will find in that project. To create a custom bootstrapping task you have create a new class which either implements the IBootstrapperTask interface or inherits from the abstract BootstrapperTask class, I would recommend to start with the BootstrapperTask as it already has the required code that you have to write in case if you choose the IBootstrapperTask interface. As you can see in the above code we are overriding the ExecuteCore to create the default users, the MVCExtensions is responsible for populating the  ServiceLocator prior calling this method and in this method we are using the service locator to get the dependencies that are required to create the users (I will cover the custom dependencies registration in the next post). Once the users are created, we are returning a special enum, TaskContinuation as the return value, the TaskContinuation can have three values Continue (default), Skip and Break. The reason behind of having this enum is, in some  special cases you might want to skip the next task in the chain or break the complete chain depending upon the currently running task, in those cases you will use the other two values instead of the Continue. The last thing I want to cover in the bootstrapping task is the Order. By default all the built-in tasks as well as newly created task order is set to the DefaultOrder(a static property), in some special cases you might want to execute it before/after all the other tasks, in those cases you will assign the Order in the Task constructor. For Example, in Shrinkr, we want to run few background services when the all the tasks are executed, so we assigned the order as DefaultOrder + 1. Here is the code of that Task: public class ConfigureBackgroundServices : BootstrapperTask { private IEnumerable<IBackgroundService> backgroundServices; public ConfigureBackgroundServices() { Order = DefaultOrder + 1; } protected override TaskContinuation ExecuteCore(IServiceLocator serviceLocator) { backgroundServices = serviceLocator.GetAllInstances<IBackgroundService>().ToList(); backgroundServices.Each(service => service.Start()); return TaskContinuation.Continue; } protected override void DisposeCore() { backgroundServices.Each(service => service.Stop()); } } That’s it for today, in the next post I will cover the custom service registration, so stay tuned.

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  • Logging connection strings

    If you some of the dynamic features of SSIS such as package configurations or property expressions then sometimes trying to work out were your connections are pointing can be a bit confusing. You will work out in the end but it can be useful to explicitly log this information so that when things go wrong you can just review the logs. You may wish to develop this idea further and encapsulate such logging into a custom task, but for now lets keep it simple and use the Script Task. The Script Task code below will raise an Information event showing the name and connection string for a connection. Imports System Imports Microsoft.SqlServer.Dts.Runtime Public Class ScriptMain Public Sub Main() Dim fireAgain As Boolean ' Get the connection string, we need to know the name of the connection Dim connectionName As String = "My OLE-DB Connection" Dim connectionString As String = Dts.Connections(connectionName).ConnectionString ' Format the message and log it via an information event Dim message As String = String.Format("Connection ""{0}"" has a connection string of ""{1}"".", _ connectionName, connectionString) Dts.Events.FireInformation(0, "Information", message, Nothing, 0, fireAgain) Dts.TaskResult = Dts.Results.Success End Sub End Class Building on that example it is probably more flexible to log all connections in a package as shown in the next example. Imports System Imports Microsoft.SqlServer.Dts.Runtime Public Class ScriptMain Public Sub Main() Dim fireAgain As Boolean ' Loop through all connections in the package For Each connection As ConnectionManager In Dts.Connections ' Get the connection string and log it via an information event Dim message As String = String.Format("Connection ""{0}"" has a connection string of ""{1}"".", _ connection.Name, connection.ConnectionString) Dts.Events.FireInformation(0, "Information", message, Nothing, 0, fireAgain) Next Dts.TaskResult = Dts.Results.Success End Sub End Class By using the Information event it makes it readily available in the designer, for example the Visual Studio Output window (Ctrl+Alt+O) or the package designer Execution Results tab, and also allows you to readily control the logging by choosing which events to log in the normal way. Now before somebody starts commenting that this is a security risk, I would like to highlight good practice for building connection managers. Firstly the Password property, or any other similar sensitive property is always defined as write-only, and secondly the connection string property only uses the public properties to assemble the connection string value when requested. In other words the connection string will never contain the password. I have seen a couple of cases where this is not true, but that was just bad development by third-parties, you won’t find anything like that in the box from Microsoft.   Whilst writing this code it made me wish that there was a custom log entry that you could just turn on that did this for you, but alas connection managers do not even seem to support custom events. It did however remind me of a very useful event that is often overlooked and fits rather well alongside connection string logging, the Execute SQL Task’s custom ExecuteSQLExecutingQuery event. To quote the help reference Custom Messages for Logging - Provides information about the execution phases of the SQL statement. Log entries are written when the task acquires connection to the database, when the task starts to prepare the SQL statement, and after the execution of the SQL statement is completed. The log entry for the prepare phase includes the SQL statement that the task uses. It is the last part that is so useful, how often have you used an expression to derive a SQL statement and you want to log that to make sure the correct SQL is being returned? You need to turn it one, by default no custom log events are captured, but I’ll refer you to a walkthrough on setting up the logging for ExecuteSQLExecutingQuery by Jamie.

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  • puppet rspec no such file to load -- rspec-puppet (LoadError)

    - by Vorsprung
    I have no prior experience at all of ruby. I am not interested in ruby (and so have no knowledge of rails etc) as such but am using puppet to manage a group of servers. I have written some modules and the rspec-puppet system looks like it would be very useful. However, I cannot get rspec-puppet to work I am using Ubuntu LTS 10.04 I have installed puppet rspec using the directions on their web page What I actually did apt-get install rubygems # (installs 1.8) gem install rspec-expectations gem install rspec-puppet I also installed librspec-ruby1.8 Then I ran rspec-puppet-init in a puppet module directory I'd already made (it's a working puppet module) I made a file as defined in the tutorial $ more spec/defines/rule_spec.rb require 'spec_helper' describe 'vanusers::rule' do let(:title) { 't1' } it { should contain_class('vanusers::JamieA') } end but when I try and run it there is a mysterious dependancy issue $ spec spec/defines/rule_spec.rb /home/jamie/git/puppet/modules/vanusers/spec/spec_helper.rb:1:in `require': no such file to load -- rspec-puppet (LoadError) from /home/jamie/git/puppet/modules/vanusers/spec/spec_helper.rb:1 from ./spec/defines/rule_spec.rb:1:in `require' from ./spec/defines/rule_spec.rb:1 from /usr/lib/ruby/1.8/spec/runner/example_group_runner.rb:15:in `load' from /usr/lib/ruby/1.8/spec/runner/example_group_runner.rb:15:in `load_files' from /usr/lib/ruby/1.8/spec/runner/example_group_runner.rb:14:in `each' from /usr/lib/ruby/1.8/spec/runner/example_group_runner.rb:14:in `load_files' from /usr/lib/ruby/1.8/spec/runner/options.rb:132:in `run_examples' from /usr/lib/ruby/1.8/spec/runner/command_line.rb:9:in `run' from /usr/bin/spec:3 Here is the solution I came up with in the end:: apt-get install rubygems gem install rspec-expectations rspec-puppet puppet-lint puppetlabs_spec_helper so your path picks up the gem stuff export PATH=/var/lib/gems/1.8/bin:$PATH cd into module and rm spec/spec_helper.rb rspec-puppet-init replace Rakefile with require 'rake' require 'rspec/core/rake_task' require 'puppetlabs_spec_helper/rake_tasks' Then "rake spec" to run tests or "rake lint" to check files http://sysadvent.blogspot.co.uk/2013/12/day-22-getting-started-testing-your.html was an excellent source of info

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  • How Do I Implement parameterMaps for ADF Regions and Dynamic Regions?

    - by david.giammona
    parameterMap objects defined by managed beans can help reduce the number of child <parameter> elements listed under an ADF region or dynamic region page definition task flow binding. But more importantly, the parameterMap approach also allows greater flexibility in determining what input parameters are passed to an ADF region or dynamic region. This can be especially helpful when using dynamic regions where each task flow utilized can provide an entirely different set of input parameters. The parameterMap is specified within an ADF region or dynamic region page definition task flow binding as shown below: <taskFlow id="checkoutflow1" taskFlowId="/WEB-INF/checkout-flow.xml#checkout-flow" activation="deferred" xmlns="http://xmlns.oracle.com/adf/controller/binding" parametersMap="#{pageFlowScope.userInfoBean.parameterMap}"/> The parameter map object must implement the java.util.Map interface. The keys it specifies match the names of input parameters defined by the task flows utilized within the task flow binding. An example parameterMap object class is shown below: import java.util.HashMap; import java.util.Map; public class UserInfoBean { private Map<String, Object> parameterMap = new HashMap<String, Object>(); public Map getParameterMap() { parameterMap.put("isLoggedIn", getSecurity().isAuthenticated()); parameterMap.put("principalName", getSecurity().getPrincipalName()); return parameterMap; }

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  • ADF Taskflow Transaction Management

    - by raghu.yadav
    There are four transaction management properties available, please refer the guide http://download.oracle.com/docs/cd/E15523_01/web.1111/b31974/taskflows_complex.htm#BABICCGC for detail description. In short : 1) - does not participate in any transaction management 2) Always Use Existing Transaction - the bounded task flow participates in an existing transaction 3) Use Existing Transaction If Possible - bounded task flow either participates in an existing transaction or starts a new transaction 4) Always Begin New Transaction - new transaction starts when the bounded task flow is entered 2) Always Begin New Transaction : There is already a example exists by andre use existing transaction example

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  • C#/.NET Little Wonders: The ConcurrentDictionary

    - by James Michael Hare
    Once again we consider some of the lesser known classes and keywords of C#.  In this series of posts, we will discuss how the concurrent collections have been developed to help alleviate these multi-threading concerns.  Last week’s post began with a general introduction and discussed the ConcurrentStack<T> and ConcurrentQueue<T>.  Today's post discusses the ConcurrentDictionary<T> (originally I had intended to discuss ConcurrentBag this week as well, but ConcurrentDictionary had enough information to create a very full post on its own!).  Finally next week, we shall close with a discussion of the ConcurrentBag<T> and BlockingCollection<T>. For more of the "Little Wonders" posts, see the index here. Recap As you'll recall from the previous post, the original collections were object-based containers that accomplished synchronization through a Synchronized member.  While these were convenient because you didn't have to worry about writing your own synchronization logic, they were a bit too finely grained and if you needed to perform multiple operations under one lock, the automatic synchronization didn't buy much. With the advent of .NET 2.0, the original collections were succeeded by the generic collections which are fully type-safe, but eschew automatic synchronization.  This cuts both ways in that you have a lot more control as a developer over when and how fine-grained you want to synchronize, but on the other hand if you just want simple synchronization it creates more work. With .NET 4.0, we get the best of both worlds in generic collections.  A new breed of collections was born called the concurrent collections in the System.Collections.Concurrent namespace.  These amazing collections are fine-tuned to have best overall performance for situations requiring concurrent access.  They are not meant to replace the generic collections, but to simply be an alternative to creating your own locking mechanisms. Among those concurrent collections were the ConcurrentStack<T> and ConcurrentQueue<T> which provide classic LIFO and FIFO collections with a concurrent twist.  As we saw, some of the traditional methods that required calls to be made in a certain order (like checking for not IsEmpty before calling Pop()) were replaced in favor of an umbrella operation that combined both under one lock (like TryPop()). Now, let's take a look at the next in our series of concurrent collections!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. ConcurrentDictionary – the fully thread-safe dictionary The ConcurrentDictionary<TKey,TValue> is the thread-safe counterpart to the generic Dictionary<TKey, TValue> collection.  Obviously, both are designed for quick – O(1) – lookups of data based on a key.  If you think of algorithms where you need lightning fast lookups of data and don’t care whether the data is maintained in any particular ordering or not, the unsorted dictionaries are generally the best way to go. Note: as a side note, there are sorted implementations of IDictionary, namely SortedDictionary and SortedList which are stored as an ordered tree and a ordered list respectively.  While these are not as fast as the non-sorted dictionaries – they are O(log2 n) – they are a great combination of both speed and ordering -- and still greatly outperform a linear search. Now, once again keep in mind that if all you need to do is load a collection once and then allow multi-threaded reading you do not need any locking.  Examples of this tend to be situations where you load a lookup or translation table once at program start, then keep it in memory for read-only reference.  In such cases locking is completely non-productive. However, most of the time when we need a concurrent dictionary we are interleaving both reads and updates.  This is where the ConcurrentDictionary really shines!  It achieves its thread-safety with no common lock to improve efficiency.  It actually uses a series of locks to provide concurrent updates, and has lockless reads!  This means that the ConcurrentDictionary gets even more efficient the higher the ratio of reads-to-writes you have. ConcurrentDictionary and Dictionary differences For the most part, the ConcurrentDictionary<TKey,TValue> behaves like it’s Dictionary<TKey,TValue> counterpart with a few differences.  Some notable examples of which are: Add() does not exist in the concurrent dictionary. This means you must use TryAdd(), AddOrUpdate(), or GetOrAdd().  It also means that you can’t use a collection initializer with the concurrent dictionary. TryAdd() replaced Add() to attempt atomic, safe adds. Because Add() only succeeds if the item doesn’t already exist, we need an atomic operation to check if the item exists, and if not add it while still under an atomic lock. TryUpdate() was added to attempt atomic, safe updates. If we want to update an item, we must make sure it exists first and that the original value is what we expected it to be.  If all these are true, we can update the item under one atomic step. TryRemove() was added to attempt atomic, safe removes. To safely attempt to remove a value we need to see if the key exists first, this checks for existence and removes under an atomic lock. AddOrUpdate() was added to attempt an thread-safe “upsert”. There are many times where you want to insert into a dictionary if the key doesn’t exist, or update the value if it does.  This allows you to make a thread-safe add-or-update. GetOrAdd() was added to attempt an thread-safe query/insert. Sometimes, you want to query for whether an item exists in the cache, and if it doesn’t insert a starting value for it.  This allows you to get the value if it exists and insert if not. Count, Keys, Values properties take a snapshot of the dictionary. Accessing these properties may interfere with add and update performance and should be used with caution. ToArray() returns a static snapshot of the dictionary. That is, the dictionary is locked, and then copied to an array as a O(n) operation.  GetEnumerator() is thread-safe and efficient, but allows dirty reads. Because reads require no locking, you can safely iterate over the contents of the dictionary.  The only downside is that, depending on timing, you may get dirty reads. Dirty reads during iteration The last point on GetEnumerator() bears some explanation.  Picture a scenario in which you call GetEnumerator() (or iterate using a foreach, etc.) and then, during that iteration the dictionary gets updated.  This may not sound like a big deal, but it can lead to inconsistent results if used incorrectly.  The problem is that items you already iterated over that are updated a split second after don’t show the update, but items that you iterate over that were updated a split second before do show the update.  Thus you may get a combination of items that are “stale” because you iterated before the update, and “fresh” because they were updated after GetEnumerator() but before the iteration reached them. Let’s illustrate with an example, let’s say you load up a concurrent dictionary like this: 1: // load up a dictionary. 2: var dictionary = new ConcurrentDictionary<string, int>(); 3:  4: dictionary["A"] = 1; 5: dictionary["B"] = 2; 6: dictionary["C"] = 3; 7: dictionary["D"] = 4; 8: dictionary["E"] = 5; 9: dictionary["F"] = 6; Then you have one task (using the wonderful TPL!) to iterate using dirty reads: 1: // attempt iteration in a separate thread 2: var iterationTask = new Task(() => 3: { 4: // iterates using a dirty read 5: foreach (var pair in dictionary) 6: { 7: Console.WriteLine(pair.Key + ":" + pair.Value); 8: } 9: }); And one task to attempt updates in a separate thread (probably): 1: // attempt updates in a separate thread 2: var updateTask = new Task(() => 3: { 4: // iterates, and updates the value by one 5: foreach (var pair in dictionary) 6: { 7: dictionary[pair.Key] = pair.Value + 1; 8: } 9: }); Now that we’ve done this, we can fire up both tasks and wait for them to complete: 1: // start both tasks 2: updateTask.Start(); 3: iterationTask.Start(); 4:  5: // wait for both to complete. 6: Task.WaitAll(updateTask, iterationTask); Now, if I you didn’t know about the dirty reads, you may have expected to see the iteration before the updates (such as A:1, B:2, C:3, D:4, E:5, F:6).  However, because the reads are dirty, we will quite possibly get a combination of some updated, some original.  My own run netted this result: 1: F:6 2: E:6 3: D:5 4: C:4 5: B:3 6: A:2 Note that, of course, iteration is not in order because ConcurrentDictionary, like Dictionary, is unordered.  Also note that both E and F show the value 6.  This is because the output task reached F before the update, but the updates for the rest of the items occurred before their output (probably because console output is very slow, comparatively). If we want to always guarantee that we will get a consistent snapshot to iterate over (that is, at the point we ask for it we see precisely what is in the dictionary and no subsequent updates during iteration), we should iterate over a call to ToArray() instead: 1: // attempt iteration in a separate thread 2: var iterationTask = new Task(() => 3: { 4: // iterates using a dirty read 5: foreach (var pair in dictionary.ToArray()) 6: { 7: Console.WriteLine(pair.Key + ":" + pair.Value); 8: } 9: }); The atomic Try…() methods As you can imagine TryAdd() and TryRemove() have few surprises.  Both first check the existence of the item to determine if it can be added or removed based on whether or not the key currently exists in the dictionary: 1: // try add attempts an add and returns false if it already exists 2: if (dictionary.TryAdd("G", 7)) 3: Console.WriteLine("G did not exist, now inserted with 7"); 4: else 5: Console.WriteLine("G already existed, insert failed."); TryRemove() also has the virtue of returning the value portion of the removed entry matching the given key: 1: // attempt to remove the value, if it exists it is removed and the original is returned 2: int removedValue; 3: if (dictionary.TryRemove("C", out removedValue)) 4: Console.WriteLine("Removed C and its value was " + removedValue); 5: else 6: Console.WriteLine("C did not exist, remove failed."); Now TryUpdate() is an interesting creature.  You might think from it’s name that TryUpdate() first checks for an item’s existence, and then updates if the item exists, otherwise it returns false.  Well, note quite... It turns out when you call TryUpdate() on a concurrent dictionary, you pass it not only the new value you want it to have, but also the value you expected it to have before the update.  If the item exists in the dictionary, and it has the value you expected, it will update it to the new value atomically and return true.  If the item is not in the dictionary or does not have the value you expected, it is not modified and false is returned. 1: // attempt to update the value, if it exists and if it has the expected original value 2: if (dictionary.TryUpdate("G", 42, 7)) 3: Console.WriteLine("G existed and was 7, now it's 42."); 4: else 5: Console.WriteLine("G either didn't exist, or wasn't 7."); The composite Add methods The ConcurrentDictionary also has composite add methods that can be used to perform updates and gets, with an add if the item is not existing at the time of the update or get. The first of these, AddOrUpdate(), allows you to add a new item to the dictionary if it doesn’t exist, or update the existing item if it does.  For example, let’s say you are creating a dictionary of counts of stock ticker symbols you’ve subscribed to from a market data feed: 1: public sealed class SubscriptionManager 2: { 3: private readonly ConcurrentDictionary<string, int> _subscriptions = new ConcurrentDictionary<string, int>(); 4:  5: // adds a new subscription, or increments the count of the existing one. 6: public void AddSubscription(string tickerKey) 7: { 8: // add a new subscription with count of 1, or update existing count by 1 if exists 9: var resultCount = _subscriptions.AddOrUpdate(tickerKey, 1, (symbol, count) => count + 1); 10:  11: // now check the result to see if we just incremented the count, or inserted first count 12: if (resultCount == 1) 13: { 14: // subscribe to symbol... 15: } 16: } 17: } Notice the update value factory Func delegate.  If the key does not exist in the dictionary, the add value is used (in this case 1 representing the first subscription for this symbol), but if the key already exists, it passes the key and current value to the update delegate which computes the new value to be stored in the dictionary.  The return result of this operation is the value used (in our case: 1 if added, existing value + 1 if updated). Likewise, the GetOrAdd() allows you to attempt to retrieve a value from the dictionary, and if the value does not currently exist in the dictionary it will insert a value.  This can be handy in cases where perhaps you wish to cache data, and thus you would query the cache to see if the item exists, and if it doesn’t you would put the item into the cache for the first time: 1: public sealed class PriceCache 2: { 3: private readonly ConcurrentDictionary<string, double> _cache = new ConcurrentDictionary<string, double>(); 4:  5: // adds a new subscription, or increments the count of the existing one. 6: public double QueryPrice(string tickerKey) 7: { 8: // check for the price in the cache, if it doesn't exist it will call the delegate to create value. 9: return _cache.GetOrAdd(tickerKey, symbol => GetCurrentPrice(symbol)); 10: } 11:  12: private double GetCurrentPrice(string tickerKey) 13: { 14: // do code to calculate actual true price. 15: } 16: } There are other variations of these two methods which vary whether a value is provided or a factory delegate, but otherwise they work much the same. Oddities with the composite Add methods The AddOrUpdate() and GetOrAdd() methods are totally thread-safe, on this you may rely, but they are not atomic.  It is important to note that the methods that use delegates execute those delegates outside of the lock.  This was done intentionally so that a user delegate (of which the ConcurrentDictionary has no control of course) does not take too long and lock out other threads. This is not necessarily an issue, per se, but it is something you must consider in your design.  The main thing to consider is that your delegate may get called to generate an item, but that item may not be the one returned!  Consider this scenario: A calls GetOrAdd and sees that the key does not currently exist, so it calls the delegate.  Now thread B also calls GetOrAdd and also sees that the key does not currently exist, and for whatever reason in this race condition it’s delegate completes first and it adds its new value to the dictionary.  Now A is done and goes to get the lock, and now sees that the item now exists.  In this case even though it called the delegate to create the item, it will pitch it because an item arrived between the time it attempted to create one and it attempted to add it. Let’s illustrate, assume this totally contrived example program which has a dictionary of char to int.  And in this dictionary we want to store a char and it’s ordinal (that is, A = 1, B = 2, etc).  So for our value generator, we will simply increment the previous value in a thread-safe way (perhaps using Interlocked): 1: public static class Program 2: { 3: private static int _nextNumber = 0; 4:  5: // the holder of the char to ordinal 6: private static ConcurrentDictionary<char, int> _dictionary 7: = new ConcurrentDictionary<char, int>(); 8:  9: // get the next id value 10: public static int NextId 11: { 12: get { return Interlocked.Increment(ref _nextNumber); } 13: } Then, we add a method that will perform our insert: 1: public static void Inserter() 2: { 3: for (int i = 0; i < 26; i++) 4: { 5: _dictionary.GetOrAdd((char)('A' + i), key => NextId); 6: } 7: } Finally, we run our test by starting two tasks to do this work and get the results… 1: public static void Main() 2: { 3: // 3 tasks attempting to get/insert 4: var tasks = new List<Task> 5: { 6: new Task(Inserter), 7: new Task(Inserter) 8: }; 9:  10: tasks.ForEach(t => t.Start()); 11: Task.WaitAll(tasks.ToArray()); 12:  13: foreach (var pair in _dictionary.OrderBy(p => p.Key)) 14: { 15: Console.WriteLine(pair.Key + ":" + pair.Value); 16: } 17: } If you run this with only one task, you get the expected A:1, B:2, ..., Z:26.  But running this in parallel you will get something a bit more complex.  My run netted these results: 1: A:1 2: B:3 3: C:4 4: D:5 5: E:6 6: F:7 7: G:8 8: H:9 9: I:10 10: J:11 11: K:12 12: L:13 13: M:14 14: N:15 15: O:16 16: P:17 17: Q:18 18: R:19 19: S:20 20: T:21 21: U:22 22: V:23 23: W:24 24: X:25 25: Y:26 26: Z:27 Notice that B is 3?  This is most likely because both threads attempted to call GetOrAdd() at roughly the same time and both saw that B did not exist, thus they both called the generator and one thread got back 2 and the other got back 3.  However, only one of those threads can get the lock at a time for the actual insert, and thus the one that generated the 3 won and the 3 was inserted and the 2 got discarded.  This is why on these methods your factory delegates should be careful not to have any logic that would be unsafe if the value they generate will be pitched in favor of another item generated at roughly the same time.  As such, it is probably a good idea to keep those generators as stateless as possible. Summary The ConcurrentDictionary is a very efficient and thread-safe version of the Dictionary generic collection.  It has all the benefits of type-safety that it’s generic collection counterpart does, and in addition is extremely efficient especially when there are more reads than writes concurrently. Tweet Technorati Tags: C#, .NET, Concurrent Collections, Collections, Little Wonders, Black Rabbit Coder,James Michael Hare

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  • Add a non-Google Tasks List to Chrome

    - by Asian Angel
    Most people rely on a task list to help them remember what they need to do but not everyone wants one that is tied to a Google account. If you have been wanting an independent tasks list then join us as we look at the Tasks extension for Google Chrome. Tasks in Action As soon as you have finished installing the extension you are ready to start adding new tasks to your list. Enter your task into the “Text Area” and press “Enter” to add the task to the list. Note: Your tasks list will be retained (in the order you set) when you close and then reopen your browser. In just moments you can have your task list ready to go. Notice that there is also a “numerical indicator” attached to the “Toolbar Button” so that you will always know how many tasks you have left to complete. You can use the “drag and drop” function to rearrange your list into a more proper order if needed. When you are finished with a task all that you will need to do is click on the “Checkmark” to remove it from the list. If you need to make a new entry similar to an existing one simply right click and the text is automatically pasted into the “Text Area”. Make any desired changes and press “Enter” to add your new task to the list. Prefer to skip using the drop-down window? Click on “Tasks” at the top to open your list in a new tab instead. The tasks list looked very nice in our new tab. Being able to use the style that best suits your needs makes this a very convenient extension. Conclusion The Tasks extension is a perfect fit for anyone who needs a tasks list available but does not want to be tied down with an online account. Quick, simple and best of all hassle free. Links Download the Tasks extension (Google Chrome Extensions) Similar Articles Productive Geek Tips Turn Chrome’s New Tab Page into a Google Tasks PageAccess Google Tasks in Chrome the Easy WayHow to Make Google Chrome Your Default BrowserAdd a To-Do List to Chrome’s New Tab PageAccess Remember The Milk in Google Chrome the Easy Way TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 PCmover Professional Test Drive Mobile Phones Online With TryPhone Ben & Jerry’s Free Cone Day, 3/23/10 New Stinger from McAfee Helps Remove ‘FakeAlert’ Threats Google Apps Marketplace: Tools & Services For Google Apps Users Get News Quick and Precise With Newser Scan for Viruses in Ubuntu using ClamAV

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  • MS SQL dts to ssis migration error

    - by Manjot
    Hi, I have migrated some DTS packages to SSIS 2005 using "Migration" wizard. When I tried to run it, it fails saying you need a higher version of SSIS even though the destination SSIS server is on 9.0.4211 level. then I digged in the package using business intelligence studio and saw that one of the package subtasks is "Transform data task" (the dts version) and the package fails to run that. The storage location for this dts task is set to "Embedded in Task". I didn't touch it. why didn't it convert this task to an SSIS data flow task? any help please? Thansk in advance

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  • Kendo UI Mobile with Knockout for Master-Detail Views

    - by Steve Michelotti
    Lately I’ve been playing with Kendo UI Mobile to build iPhone apps. It’s similar to jQuery Mobile in that they are both HTML5/JavaScript based frameworks for buildings mobile apps. The primary thing that drew me to investigate Kendo UI was its innate ability to adaptively render a native looking app based on detecting the device it’s currently running on. In other words, it will render to look like a native iPhone app if it’s running on an iPhone and it will render to look like a native Droid app if it’s running on a Droid. This is in contrast to jQuery Mobile which looks the same on all devices and, therefore, it can never quite look native for whatever device it’s running on. My first impressions of Kendo UI were great. Using HTML5 data-* attributes to define “roles” for UI elements is easy, the rendering looked great, and the basic navigation was simple and intuitive. However, I ran into major confusion when trying to figure out how to “correctly” build master-detail views. Since I was already very family with KnockoutJS, I set out to use that framework in conjunction with Kendo UI Mobile to build the following simple scenario: I wanted to have a simple “Task Manager” application where my first screen just showed a list of tasks like this:   Then clicking on a specific task would navigate to a detail screen that would show all details of the specific task that was selected:   Basic navigation between views in Kendo UI is simple. The href of an <a> tag just needs to specify a hash tag followed by the ID of the view to navigate to as shown in this jsFiddle (notice the href of the <a> tag matches the id of the second view):   Direct link to jsFiddle: here. That is all well and good but the problem I encountered was: how to pass data between the views? Specifically, I need the detail view to display all the details of whichever task was selected. If I was doing this with my typical technique with KnockoutJS, I know exactly what I would do. First I would create a view model that had my collection of tasks and a property for the currently selected task like this: 1: function ViewModel() { 2: var self = this; 3: self.tasks = ko.observableArray(data); 4: self.selectedTask = ko.observable(null); 5: } Then I would bind my list of tasks to the unordered list - I would attach a “click” handler to each item (each <li> in the unordered list) so that it would select the “selectedTask” for the view model. The problem I found is this approach simply wouldn’t work for Kendo UI Mobile. It completely ignored the click handlers that I was trying to attach to the <a> tags – it just wanted to look at the href (at least that’s what I observed). But if I can’t intercept this, then *how* can I pass data or any context to the next view? The only thing I was able to find in the Kendo documentation is that you can pass query string arguments on the view name you’re specifying in the href. This enabled me to do the following: Specify the task ID in each href – something like this: <a href=”#taskDetail?id=3></a> Attach an “init method” (via the “data-show” attribute on the details view) that runs whenever the view is activated Inside this “init method”, grab the task ID passed from the query string to look up the item from my view model’s list of tasks in order to set the selected task I was able to get all that working with about 20 lines of JavaScript as shown in this jsFiddle. If you click on the Results tab, you can navigate between views and see the the detail screen is correctly binding to the selected item:   Direct link to jsFiddle: here.   With all that being done, I was very happy to get it working with the behavior I wanted. However, I have no idea if that is the “correct” way to do it or if there is a “better” way to do it. I know that Kendo UI comes with its own data binding framework but my preference is to be able to use (the well-documented) KnockoutJS since I’m already familiar with that framework rather than having to learn yet another new framework. While I think my solution above is probably “acceptable”, there are still a couple of things that bug me about it. First, it seems odd that I have to loop through my items to *find* my selected item based on the ID that was passed on the query string - normally, with Knockout I can just refer directly to my selected item from where it was used. Second, it didn’t feel exactly right that I had to rely on the “data-show” method of the details view to set my context – normally with Knockout, I could just attach a click handler to the <a> tag that was actually clicked by the user in order to set the “selected item.” I’m not sure if I’m being too picky. I know there are many people that have *way* more expertise in Kendo UI compared to me – I’d be curious to know if there are better ways to achieve the same results.

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  • Logging connection strings

    If you some of the dynamic features of SSIS such as package configurations or property expressions then sometimes trying to work out were your connections are pointing can be a bit confusing. You will work out in the end but it can be useful to explicitly log this information so that when things go wrong you can just review the logs. You may wish to develop this idea further and encapsulate such logging into a custom task, but for now lets keep it simple and use the Script Task. The Script Task code below will raise an Information event showing the name and connection string for a connection. Imports System Imports Microsoft.SqlServer.Dts.Runtime Public Class ScriptMain Public Sub Main() Dim fireAgain As Boolean ' Get the connection string, we need to know the name of the connection Dim connectionName As String = "My OLE-DB Connection" Dim connectionString As String = Dts.Connections(connectionName).ConnectionString ' Format the message and log it via an information event Dim message As String = String.Format("Connection ""{0}"" has a connection string of ""{1}"".", _ connectionName, connectionString) Dts.Events.FireInformation(0, "Information", message, Nothing, 0, fireAgain) Dts.TaskResult = Dts.Results.Success End Sub End Class Building on that example it is probably more flexible to log all connections in a package as shown in the next example. Imports System Imports Microsoft.SqlServer.Dts.Runtime Public Class ScriptMain Public Sub Main() Dim fireAgain As Boolean ' Loop through all connections in the package For Each connection As ConnectionManager In Dts.Connections ' Get the connection string and log it via an information event Dim message As String = String.Format("Connection ""{0}"" has a connection string of ""{1}"".", _ connection.Name, connection.ConnectionString) Dts.Events.FireInformation(0, "Information", message, Nothing, 0, fireAgain) Next Dts.TaskResult = Dts.Results.Success End Sub End Class By using the Information event it makes it readily available in the designer, for example the Visual Studio Output window (Ctrl+Alt+O) or the package designer Execution Results tab, and also allows you to readily control the logging by choosing which events to log in the normal way. Now before somebody starts commenting that this is a security risk, I would like to highlight good practice for building connection managers. Firstly the Password property, or any other similar sensitive property is always defined as write-only, and secondly the connection string property only uses the public properties to assemble the connection string value when requested. In other words the connection string will never contain the password. I have seen a couple of cases where this is not true, but that was just bad development by third-parties, you won’t find anything like that in the box from Microsoft.   Whilst writing this code it made me wish that there was a custom log entry that you could just turn on that did this for you, but alas connection managers do not even seem to support custom events. It did however remind me of a very useful event that is often overlooked and fits rather well alongside connection string logging, the Execute SQL Task’s custom ExecuteSQLExecutingQuery event. To quote the help reference Custom Messages for Logging - Provides information about the execution phases of the SQL statement. Log entries are written when the task acquires connection to the database, when the task starts to prepare the SQL statement, and after the execution of the SQL statement is completed. The log entry for the prepare phase includes the SQL statement that the task uses. It is the last part that is so useful, how often have you used an expression to derive a SQL statement and you want to log that to make sure the correct SQL is being returned? You need to turn it one, by default no custom log events are captured, but I’ll refer you to a walkthrough on setting up the logging for ExecuteSQLExecutingQuery by Jamie.

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  • Load login shell inside user cronjob

    - by sa125
    I'm trying to run a rake task using a scheduled cronjob. My crontab looks something like this: 0 1 * * 1-7 /bin/bash -l -c "cd ~/jobs/rake && rake reports:create >> ~/jobs/logs/cron.log" Ruby on my account is provided by RVM, which is loaded via ~/.bashrc (before the no-interaction check): # load RVM env [[ -s $HOME/.rvm/scripts/rvm ]] && source $HOME/.rvm/scripts/rvm # If not running interactively, don't do anything [ -z "$PS1" ] && return # ... rest of logic Time and again, this task fails to run since RVM isn't loaded when the task is called (uses system's /usr/bin/ruby instead), and gem dependencies are missing. How can I make crontab load my shell environment before executing my scheduled jobs? thanks.

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  • Do you know when to send a done email in Scrum?

    - by Martin Hinshelwood
    At SSW we have always sent done emails to the owner/requestor to let them know that it is done. Others who are dependent on that tasks are CC’ed so they know they can proceed. But how does that fit into Scrum?   Update 14th April 2010 Rule added to Rules to better Scrum with TFS If you are working on a task: When you complete a Task that is part of a User Story you need to send a done email to the Owner of that Story. You only need to add the Task #, Summary and link to the item in WIWA. Remember that all your tasks should be under 4 hours, do spending lots of time on a Done Email for a Task would be counter productive. Add more information if required, for example you may have completed the task a different way than previously discussed.  Make sure that every User Story has an Owner as per the rules. If you are the owner of a story: When you complete a story you should send a comprehensive done email as per the rules when the story had been completed. Make sure you add a list of all of the Tasks that were completed as part of the story and the Done criteria that you completed. If your done criteria says: Built Successfully 30% Code Coverage All tests passed Then add an illustration to show this. Figure: Show that you have met your Done criteria where possible.   This is all designed to help you Scrum Team members (Product Owner, ScrumMaster and Team) validate the quality of the work that has been completed. Remember that you are not DONE until your team says you are done.   Technorati Tags: SSW,Scrum,SSW Rules

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  • How do I account for changed or forgotten tasks in an estimate?

    - by Andrew
    To handle task-level estimates and time reporting, I have been using (roughly) the technique that Steve McConnell describes in Chapter 10 of Software Estimation. Specifically, when the time comes for me to create task-level estimates (right before coding begins on a project), I determine the tasks at a fairly granular level so that, whenever possible, I have no tasks with a single-point, 50%-confidence estimate greater than four hours. That way, the task estimation process helps with constructing the software while helping me not to forget tasks during estimation. I come up with a range of hours possible for each task also, and using the statistical calculations that McConnell describes along with my historical accuracy data, I can generate estimates at other confidence levels when desired. I feel like this method has been working fairly well for me. We are required to put tasks and their estimates into TFS for tracking, so I use the estimates at the percentage of confidence I am told to use. I am unsure, however, what to do when I do forget a task, or I end up needing to do work that does not neatly fall within one of the tasks I estimated. Of course, trying to avoid this situation is best, but how do I account for forgotten/changed tasks? I want to have the best historical data I can to help me with future estimates, but right now, I basically am just calculating whether I made the 50%-confidence estimate and whether I made it inside the ranged estimate. I'll be happy to clarify what I'm asking if needed -- let me know what is unclear.

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  • How can I save state from script in a multithreaded engine?

    - by Peter Ren
    We are building a multithreaded game engine and we've encountered some problems as described below. The engine have 3 threads in total: script, render, and audio. Each frame, we update these 3 threads simultaneously. As these threads updating themselves, they produce some tasks and put them into a public storage area. As all the threads finish their update, each thread go and copy the tasks for themselves one by one. After all the threads finish their task copying, we make the threads process those tasks and update these threads simultaneously as described before. So this is the general idea of the task schedule part of our engine. Ok, well, all the task schedule part work well, but here's the problem: For the simplest, I'll take Camera as an example: local oldPos = camera:getPosition() -- ( 0, 0, 0 ) camera:setPosition( 1, 1, 1 ) -- Won't work now, cuz the render thread will process the task at the beginning of the next frame local newPos = camera:getPosition() -- Still ( 0, 0, 0 ) So that's the problem: If you intend to change a property of an object in another thread, you have to wait until that thread process this property-changing message. As a result, what you get from the object is still the information in the last frame. So, is there a way to solve this problem? Or are we build the task schedule part in a wrong way? Thanks for your answers :)

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  • Strategies for managUse of types in Python

    - by dave
    I'm a long time programmer in C# but have been coding in Python for the past year. One of the big hurdles for me was the lack of type definitions for variables and parameters. Whereas I totally get the idea of duck typing, I do find it frustrating that I can't tell the type of a variable just by looking at it. This is an issue when you look at someone else's code where they've used ambiguous names for method parameters (see edit below). In a few cases, I've added asserts to ensure parameters comply with an expected type but this goes against the whole duck typing thing. On some methods, I'll document the expected type of parameters (eg: list of user objects), but even this seems to go against the idea of just using an object and let the runtime deal with exceptions. What strategies do you use to avoid typing problems in Python? Edit: Example of the parameter naming issues: If our code base we have a task object (ORM object) and a task_obj object (higher level object that embeds a task). Needless to say, many methods accept a parameter named 'task'. The method might expect a task or a task_obj or some other construct such as a dictionary of task properties - it is not clear. It is them up to be to look at how that parameter is used in order to work out what the method expects.

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  • How to estimate tasks in scrum?

    - by Arian
    Let's say we have a backlog of User Stories, each with an estimated number of Story Points, and now we're doing the Sprint Planning. Now, the Stories should be broken down into tasks and many Scrum resources suggest that each task should be estimated in person-hours. Since all questions have been discussed by the team at this point, estimating a task should not take longer than a minute. However, since a task should not be longer than a day, assuming a three week sprint with 8 developers means 120 tasks, and taking two hours only for estimations seems to be a bit much to me. I know that experienced teams can skip or short-cut task estimations, but let's say we're not at that stage yet. In your experience, how many tasks are there in a sprint* and how long should it take to estimate all of them? (Estimating only half of them doesn't make much sense, does it?) (*) I know that depends on sprint length and team size, so let's assume 8 developers and three weeks.

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  • How do you accept arguments in the main.cpp file and reference another file?

    - by Jason H.
    I have a basic understanding of programming and I currently learning C++. I'm in the beginning phases of building my own CLI program for ubuntu. However, I have hit a few snags and I was wondering if I could get some clarification. The program I am working on is called "sat" and will be available via command line only. I have the main.cpp. However, my real question is more of a "best practices" for programming/organization. When my program "sat" is invoked I want it to take additional arguments. Here is an example: > sat task subtask I'm not sure if the task should be in its own task.cpp file for better organization or if it should be a function in the main.cpp? If the task should be in its own file how do you accept arguments in the main.cpp file and reference the other file? Any thoughts on which method is preferred and reference material to backup the reasoning?

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  • When designing a job queue, what should determine the scope of a job?

    - by Stuart Pegg
    We've got a job queue system that'll cheerfully process any kind of job given to it. We intend to use it to process jobs that each contain 2 tasks: Job (Pass information from one server to another) Fetch task (get the data, slowly) Send task (send the data, comparatively quickly) The difficulty we're having is that we don't know whether to break the tasks into separate jobs, or process the job in one go. Are there any best practices or useful references on this subject? Is there some obvious benefit to a method that we're missing? So far we can see these benefits for each method: Split Job lease length reflects job length: Rather than total of two Finer granularity on recovery: If we lose outgoing connectivity we can tell them all to retry The starting state of the second task is saved to job history: Helps with debugging (although similar logging could be added in single task method) Single Single job to be scheduled: Less processing overhead Data not stale on recovery: If the outgoing downtime is quite long, the pending Send jobs could be outdated

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  • Strategies for managing use of types in Python

    - by dave
    I'm a long time programmer in C# but have been coding in Python for the past year. One of the big hurdles for me was the lack of type definitions for variables and parameters. Whereas I totally get the idea of duck typing, I do find it frustrating that I can't tell the type of a variable just by looking at it. This is an issue when you look at someone else's code where they've used ambiguous names for method parameters (see edit below). In a few cases, I've added asserts to ensure parameters comply with an expected type but this goes against the whole duck typing thing. On some methods, I'll document the expected type of parameters (eg: list of user objects), but even this seems to go against the idea of just using an object and let the runtime deal with exceptions. What strategies do you use to avoid typing problems in Python? Edit: Example of the parameter naming issues: If our code base we have a task object (ORM object) and a task_obj object (higher level object that embeds a task). Needless to say, many methods accept a parameter named 'task'. The method might expect a task or a task_obj or some other construct such as a dictionary of task properties - it is not clear. It is them up to be to look at how that parameter is used in order to work out what the method expects.

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  • Alternatives to type casting in your domain

    - by Mr Happy
    In my Domain I have an entity Activity which has a list of ITasks. Each implementation of this task has it's own properties beside the implementation of ITask itself. Now each operation of the Activity entity (e.g. Execute()) only needs to loop over this list and call an ITask method (e.g. ExecuteTask()). Where I'm having trouble is when a specific tasks' properties need to be updated. How do I get an instance of that task? The options I see are: Get the Activity by Id and cast the task I need. This'll either sprinkle my code with: Tasks.OfType<SpecificTask>().Single(t => t.Id == taskId) or Tasks.Single(t => t.Id == taskId) as SpecificTask Make each task unique in the whole system (make each task an entity), and create a new repository for each ITask implementation I don't like either option, the first because I don't like casting: I'm using NHibernate and I'm sure this'll come back and bite me when I start using Lazy Loading (NHibernate currently uses proxies to implement this). I don't like the second option because there are/will be dozens of different kind of tasks. Which would mean I'd have to create as many repositories. Am I missing a third option here? Or are any of my objections to the two options not justified? How have you solved this problem in the past?

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  • Pair Programming, for or against? [on hold]

    - by user1037729
    I believe it has many advantages over individual programming: Pros By pairing senior with relatively junior staff, the more junior can get up to speed with both project and computing experience, and the senior will re-think the problem in order to communicate with the junior, thus re-checking his own thinking (rubber duck principle!). At least 2 people will know about any single piece of work, if one person is away the other can cover, or if some one leaves a project knowledge transfer is easier. Two brains on a complex task is more effective, communication keeps the work free flowing and provides redundancy in decision making. Code is effectively reviewed as its being written, no need for a separate reviewing phase which requires a context switch as someone who has not been working on the piece in question would be required to understand and review the related code. Reviewing code on your own which you haven't written or architected is not fun, hence counter productive. Cons Less bandwith for performing tasks, lets say we have 4 devs, pair programming requires 2 devs per task, so we would be doing 2 tasks concurrently as a posed to 4. I believe this "Con" does not stand up as the pair programmed task would complete sooner and comes with a review built in for free! Ie the pair programming task would be more efficient and thus free up resources earlier. Less flexibility to chop and change tasks as two developers are tied into a task, when flexibility is required this could be a problem.

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