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  • What is a good practice for 2D scene graph partitioning for culling?

    - by DevilWithin
    I need to know an efficient way to cull the scene graph objects, to render exclusively the ones in the view, and as fast as possible. I am thinking of doing it the following way, having in each object a local boundingbox which holds the object bounds, and a global boundingbox which holds the bounds of the object and all children. When a camera is moved, the render list is updated by traversing the global boundingboxes. When only the object is being moved, it tries to enlarge or shrink the ancestors global boundingboxes, and in the end updating or not the renderlist. What do you think of this approach? Do you think it will provide a fast and efficient culling? Also, because the render list is a contiguous list, it could accelerate the rendering, right? Any further tips for a 2D scene graphs are highly appreciated!

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  • Depth buffer values reset on change shader?

    - by bobobobo
    I have 2 different shaders, and when I change the shader (glUseProgram), it seems that the depth information is lost, because everything drawn with the 2nd shader appears completely on top of anything drawn by the first shader. If I switch the order of shader use/drawing, then it's the same (the last drawn object always appears on top of the first drawn object if there is a shader change between the 2 objects, even if the last drawn object is further away)

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  • How to load Image in C# and set properties of the Picture Box

    - by SAMIR BHOGAYTA
    Create a C# application drag a picture Box, four buttons and open file dialog on the form. Write code on btn_browse Button click ----------------------------------------- private void btn_browse_Click(object sender, System.EventArgs e) { try { OpenFileDialog open = new OpenFileDialog(); open.Filter = "Image Files(*.jpg; *.jpeg; *.gif; *.bmp)|*.jpg; *.jpeg; *.gif; *.bmp"; if (open.ShowDialog()==DialogResult.OK) { pictureBox1.Image = new Bitmap(open.FileName); } } catch (Exception) { throw new ApplicationException("Failed loading image"); } } Write code on btn_StretchImage Button click ------------------------------------------------ private void btn_StretchImage_Click(object sender, System.EventArgs e) { pictureBox1.SizeMode = System.Windows.Forms.PictureBoxSizeMode.StretchImage; } Write code on btn_AutoSize Button click ------------------------------------------------- private void btn_AutoSize_Click(object sender, System.EventArgs e) { pictureBox1.SizeMode = System.Windows.Forms.PictureBoxSizeMode.AutoSize; } Write code on btn_CenterImage Button click -------------------------------------------------- private void btn_CenterImage_Click(object sender, System.EventArgs e) { pictureBox1.SizeMode = System.Windows.Forms.PictureBoxSizeMode.CenterImage; }

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  • Faster, Simpler access to Azure Tables with Enzo Azure API

    - by Herve Roggero
    After developing the latest version of Enzo Cloud Backup I took the time to create an API that would simplify access to Azure Tables (the Enzo Azure API). At first, my goal was to make the code simpler compared to the Microsoft Azure SDK. But as it turns out it is also a little faster; and when using the specialized methods (the fetch strategies) it is much faster out of the box than the Microsoft SDK, unless you start creating complex parallel and resilient routines yourself. Last but not least, I decided to add a few extension methods that I think you will find attractive, such as the ability to transform a list of entities into a DataTable. So let’s review each area in more details. Simpler Code My first objective was to make the API much easier to use than the Azure SDK. I wanted to reduce the amount of code necessary to fetch entities, remove the code needed to add automatic retries and handle transient conditions, and give additional control, such as a way to cancel operations, obtain basic statistics on the calls, and control the maximum number of REST calls the API generates in an attempt to avoid throttling conditions in the first place (something you cannot do with the Azure SDK at this time). Strongly Typed Before diving into the code, the following examples rely on a strongly typed class called MyData. The way MyData is defined for the Azure SDK is similar to the Enzo Azure API, with the exception that they inherit from different classes. With the Azure SDK, classes that represent entities must inherit from TableServiceEntity, while classes with the Enzo Azure API must inherit from BaseAzureTable or implement a specific interface. // With the SDK public class MyData1 : TableServiceEntity {     public string Message { get; set; }     public string Level { get; set; }     public string Severity { get; set; } } //  With the Enzo Azure API public class MyData2 : BaseAzureTable {     public string Message { get; set; }     public string Level { get; set; }     public string Severity { get; set; } } Simpler Code Now that the classes representing an Azure Table entity are defined, let’s review the methods that the Azure SDK would look like when fetching all the entities from an Azure Table (note the use of a few variables: the _tableName variable stores the name of the Azure Table, and the ConnectionString property returns the connection string for the Storage Account containing the table): // With the Azure SDK public List<MyData1> FetchAllEntities() {      CloudStorageAccount storageAccount = CloudStorageAccount.Parse(ConnectionString);      CloudTableClient tableClient = storageAccount.CreateCloudTableClient();      TableServiceContext serviceContext = tableClient.GetDataServiceContext();      CloudTableQuery<MyData1> partitionQuery =         (from e in serviceContext.CreateQuery<MyData1>(_tableName)         select new MyData1()         {            PartitionKey = e.PartitionKey,            RowKey = e.RowKey,            Timestamp = e.Timestamp,            Message = e.Message,            Level = e.Level,            Severity = e.Severity            }).AsTableServiceQuery<MyData1>();        return partitionQuery.ToList();  } This code gives you automatic retries because the AsTableServiceQuery does that for you. Also, note that this method is strongly-typed because it is using LINQ. Although this doesn’t look like too much code at first glance, you are actually mapping the strongly-typed object manually. So for larger entities, with dozens of properties, your code will grow. And from a maintenance standpoint, when a new property is added, you may need to change the mapping code. You will also note that the mapping being performed is optional; it is desired when you want to retrieve specific properties of the entities (not all) to reduce the network traffic. If you do not specify the properties you want, all the properties will be returned; in this example we are returning the Message, Level and Severity properties (in addition to the required PartitionKey, RowKey and Timestamp). The Enzo Azure API does the mapping automatically and also handles automatic reties when fetching entities. The equivalent code to fetch all the entities (with the same three properties) from the same Azure Table looks like this: // With the Enzo Azure API public List<MyData2> FetchAllEntities() {        AzureTable at = new AzureTable(_accountName, _accountKey, _ssl, _tableName);        List<MyData2> res = at.Fetch<MyData2>("", "Message,Level,Severity");        return res; } As you can see, the Enzo Azure API returns the entities already strongly typed, so there is no need to map the output. Also, the Enzo Azure API makes it easy to specify the list of properties to return, and to specify a filter as well (no filter was provided in this example; the filter is passed as the first parameter).  Fetch Strategies Both approaches discussed above fetch the data sequentially. In addition to the linear/sequential fetch methods, the Enzo Azure API provides specific fetch strategies. Fetch strategies are designed to prepare a set of REST calls, executed in parallel, in a way that performs faster that if you were to fetch the data sequentially. For example, if the PartitionKey is a GUID string, you could prepare multiple calls, providing appropriate filters ([‘a’, ‘b’[, [‘b’, ‘c’[, [‘c’, ‘d[, …), and send those calls in parallel. As you can imagine, the code necessary to create these requests would be fairly large. With the Enzo Azure API, two strategies are provided out of the box: the GUID and List strategies. If you are interested in how these strategies work, see the Enzo Azure API Online Help. Here is an example code that performs parallel requests using the GUID strategy (which executes more than 2 t o3 times faster than the sequential methods discussed previously): public List<MyData2> FetchAllEntitiesGUID() {     AzureTable at = new AzureTable(_accountName, _accountKey, _ssl, _tableName);     List<MyData2> res = at.FetchWithGuid<MyData2>("", "Message,Level,Severity");     return res; } Faster Results With Sequential Fetch Methods Developing a faster API wasn’t a primary objective; but it appears that the performance tests performed with the Enzo Azure API deliver the data a little faster out of the box (5%-10% on average, and sometimes to up 50% faster) with the sequential fetch methods. Although the amount of data is the same regardless of the approach (and the REST calls are almost exactly identical), the object mapping approach is different. So it is likely that the slight performance increase is due to a lighter API. Using LINQ offers many advantages and tremendous flexibility; nevertheless when fetching data it seems that the Enzo Azure API delivers faster.  For example, the same code previously discussed delivered the following results when fetching 3,000 entities (about 1KB each). The average elapsed time shows that the Azure SDK returned the 3000 entities in about 5.9 seconds on average, while the Enzo Azure API took 4.2 seconds on average (39% improvement). With Fetch Strategies When using the fetch strategies we are no longer comparing apples to apples; the Azure SDK is not designed to implement fetch strategies out of the box, so you would need to code the strategies yourself. Nevertheless I wanted to provide out of the box capabilities, and as a result you see a test that returned about 10,000 entities (1KB each entity), and an average execution time over 5 runs. The Azure SDK implemented a sequential fetch while the Enzo Azure API implemented the List fetch strategy. The fetch strategy was 2.3 times faster. Note that the following test hit a limit on my network bandwidth quickly (3.56Mbps), so the results of the fetch strategy is significantly below what it could be with a higher bandwidth. Additional Methods The API wouldn’t be complete without support for a few important methods other than the fetch methods discussed previously. The Enzo Azure API offers these additional capabilities: - Support for batch updates, deletes and inserts - Conversion of entities to DataRow, and List<> to a DataTable - Extension methods for Delete, Merge, Update, Insert - Support for asynchronous calls and cancellation - Support for fetch statistics (total bytes, total REST calls, retries…) For more information, visit http://www.bluesyntax.net or go directly to the Enzo Azure API page (http://www.bluesyntax.net/EnzoAzureAPI.aspx). About Herve Roggero Herve Roggero, Windows Azure MVP, is the founder of Blue Syntax Consulting, a company specialized in cloud computing products and services. Herve's experience includes software development, architecture, database administration and senior management with both global corporations and startup companies. Herve holds multiple certifications, including an MCDBA, MCSE, MCSD. He also holds a Master's degree in Business Administration from Indiana University. Herve is the co-author of "PRO SQL Azure" from Apress and runs the Azure Florida Association (on LinkedIn: http://www.linkedin.com/groups?gid=4177626). For more information on Blue Syntax Consulting, visit www.bluesyntax.net.

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  • concurrency::extent<N> from amp.h

    - by Daniel Moth
    Overview We saw in a previous post how index<N> represents a point in N-dimensional space and in this post we'll see how to define the N-dimensional space itself. With C++ AMP, an N-dimensional space can be specified with the template class extent<N> where you define the size of each dimension. From a look and feel perspective, you'd expect the programmatic interface of a point type and size type to be similar (even though the concepts are different). Indeed, exactly like index<N>, extent<N> is essentially a coordinate vector of N integers ordered from most- to least- significant, BUT each integer represents the size for that dimension (and hence cannot be negative). So, if you read the description of index, you won't be surprised with the below description of extent<N> There is the rank field returning the value of N you passed as the template parameter. You can construct one extent from another (via the copy constructor or the assignment operator), you can construct it by passing an integer array, or via convenience constructor overloads for 1- 2- and 3- dimension extents. Note that the parameterless constructor creates an extent of the specified rank with all bounds initialized to 0. You can access the components of the extent through the subscript operator (passing it an integer). You can perform some arithmetic operations between extent objects through operator overloading, i.e. ==, !=, +=, -=, +, -. There are operator overloads so that you can perform operations between an extent and an integer: -- (pre- and post- decrement), ++ (pre- and post- increment), %=, *=, /=, +=, –= and, finally, there are additional overloads for plus and minus (+,-) between extent<N> and index<N> objects, returning a new extent object as the result. In addition to the usual suspects, extent offers a contains function that tests if an index is within the bounds of the extent (assuming an origin of zero). It also has a size function that returns the total linear size of this extent<N> in units of elements. Example code extent<2> e(3, 4); _ASSERT(e.rank == 2); _ASSERT(e.size() == 3 * 4); e += 3; e[1] += 6; e = e + index<2>(3,-4); _ASSERT(e == extent<2>(9, 9)); _ASSERT( e.contains(index<2>(8, 8))); _ASSERT(!e.contains(index<2>(8, 9))); grid<N> Our upcoming pre-release bits also have a similar type to extent, grid<N>. The way you create a grid is by passing it an extent, e.g. extent<3> e(4,2,6); grid<3> g(e); I am not going to dive deeper into grid, suffice for now to think of grid<N> simply as an alias for the extent<N> object, that you create when you encounter a function that expects a grid object instead of an extent object. Usage The extent class on its own simply defines the size of the N-dimensional space. We'll see in future posts that when you create containers (arrays) and wrappers (array_views) for your data, it is an extent<N> object that you'll need to use to create those (and use an index<N> object to index into them). We'll also see that it is a grid<N> object that you pass to the new parallel_for_each function that I'll cover in the next post. Comments about this post by Daniel Moth welcome at the original blog.

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  • What level of detail to use in an interface members descriptions?

    - by famousgarkin
    I am extracting interfaces from some classes in .NET, and I am not completely sure about what level of detail of description to use for some of the interface members (properties, methods). An example: interface ISomeInterface { /// <summary> /// Checks if the object is checked out. /// </summary> /// <returns> /// Returns true if the object is checked out, or if the object locking is not enabled, /// otherwise returns false. /// </returns> bool IsObjectCheckedOut(); } class SomeImplementation : ISomeInterface { public bool IsObjectCheckedOut() { // An implementation of the method that returns true if the object is checked out, // or if the object locking is not enabled } } The part in question is the <returns>...</returns> section of the IsObjectCheckedOut description in the interface. Is it ok to include such a detail about return value in the interface itself, as the code that will work with the interface should know exactly what that method will do? All the current implementations of the method will do just that. But is it ok to limit the possible other/future implementations by description this way? Or should this not be included in the interface description, as there is no way to actually ensure that other/future implementations will do exactly this? Is it better to be as general as possible regarding the interface in such circumstances? I am currently inclined to the latter option.

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  • When should one use "out" parameters?

    - by qegal
    In Objective-C, there are several methods like initWithContentsOfFile:encoding:error: where one passes in a reference to an NSError object for the error: parameter. In this example, the value of the NSError object passed in can change based on what goes on at runtime when the method is being called and whether the body of the method was executed in a certain way successfully. In a way I think of this NSError object as sort of like a second return value from the method, and only differs from an object anObject in the statement return anObject; in that when this statement is called, execution leaves the method. So my question is, not only in the context of error handling in Objective-C, but in general, when should one use an "out" parameter in place of returning said value in a return statement?

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  • Searching for context in Silverlight applications

    - by PeterTweed
    A common behavior in business applications that have developed through the ages is for a user to be able to get information or execute commands in relation to some information/function displayed by right clicking the object in question and popping up a context menu that offers relevant options to choose. The Silverlight Toolkit April 2010 release introduced the context menu object.  This can be added to other UI objects and display options for the user to choose.  The menu items can be enabled or disabled as per your application logic and icons can be added to the menu items to add visual effect.  This post will walk you through how to use the context menu object from the Silverlight Toolkit. Steps: 1. Create a new Silverlight 4 application 2. Copy the following namespace definition to the user control object of the MainPage.xaml file: xmlns:my="clr-namespace:System.Windows.Controls;assembly=System.Windows.Controls.Input.Toolkit"   3. Copy the following XAML into the LayoutRoot grid in MainPage.xaml:          <Border CornerRadius="15" Background="Blue" Width="400" Height="100">             <TextBlock Foreground="White" FontSize="20" Text="Context Menu In This Border...." HorizontalAlignment="Center" VerticalAlignment="Center" >             </TextBlock>             <my:ContextMenuService.ContextMenu>                 <my:ContextMenu >                     <my:MenuItem                 Header="Copy"                 Click="CopyMenuItem_Click" Name="copyMenuItem">                         <my:MenuItem.Icon>                             <Image Source="copy-icon-small.png"/>                         </my:MenuItem.Icon>                     </my:MenuItem>                     <my:Separator/>                     <my:MenuItem Name="pasteMenuItem"                 Header="Paste"                 Click="PasteMenuItem_Click">                         <my:MenuItem.Icon>                             <Image Source="paste-icon-small.png"/>                         </my:MenuItem.Icon>                     </my:MenuItem>                 </my:ContextMenu>             </my:ContextMenuService.ContextMenu>         </Border>   The above code associates a context menu with two menu items and a separator between them to the border object.  The menu items has icons associated with them to add visual appeal.  The menu items have click event handlers that will be added in the MainPage.xaml.cs code behind in a later step. 4. Add two icon sized images to the ClientBin directory of the web project hosting the Silverlight application, named copy-icon-small.png and paste-icon-small.jpg respectively.  I used copy and paste icons as the names suggest. 5. Add the following code to the class in MainPage.xaml.cs file:         private void CopyMenuItem_Click(object sender, RoutedEventArgs e)         {             MessageBox.Show("Copy selected");         }           private void PasteMenuItem_Click(object sender, RoutedEventArgs e)         {             MessageBox.Show("Paste selected");         }   This code adds the event handlers for the menu items defined in step 3. 6. Run the application, right click on the border and select a menu option and see the appropriate message box displayed. Congratulations it’s that easy!   Take the Slalom Challenge at www.slalomchallenge.com!

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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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  • Translate along local axis

    - by Aaron
    I have an object with a position matrix and a rotation matrix (derived from a quaternion, but I digress). I'm able to translate this object along world-relative vectors, but I'm trying to figure out how to translate it along local-relative vectors. So if the object is tilted 45 degrees around its Z-axis the vector (1, 0, 0) would make it move to the upper right. For world-space translations I simply turn the movement vector into a matrix and multiply it by the position matrix: position_mat = translation_mat * position_mat. For local-space translations I'd think I'd have to use the rotation matrix into that formula, but I see the object spin around instead when I apply a translation over time no matter where I multiply the rotation matrix.

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  • How to get Rosegarden to work with timidity?

    - by molybtek
    I'm having problems getting Rosegarden to play midi using Timidity on Ubuntu 11.10 amd64. I've tried mapping the MIDI playback device to one of the Timidity port that was automatically created on start up and that failed. I've also tried manually starting timidity using the -iA option, and mapping the Rosegarden's MIDI playback device to one of the new ports, and that still failed. When I close Rosegarden, I can hear one or two notes get played. Would anyone know how I can get Rosegarden to work again. Thanks.

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  • Geometry Shader : points + Triangles

    - by CmasterG
    I have different Shaders and for each Shader a instance of the ShaderClass class, which initializes the Shaders, Renders the Shaders, etc. I use most of the Shaderclasses without Geometry Shader, but in one Shader Class i also use a Geometry Shader. The problem is, that when I render one object with the Shaderclass that uses the Geometry shader, all other object are rendered with the same geometry that I create in the Geometry Shader. Can you help me? Is it possible that I have to use a Geometry Shader for each object, when I use one for one object? I use DirectX 11 with C++.

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  • More efficient in range checking

    - by Mob
    I am going to use a specific example in my question, but overall it is pretty general. I use java and libgdx. I have a ship that moves through space. In space there is debris that the ship can tractor beam in and and harvest. Debris is stored in a list, and the object contains it own x and y values. So currently there is no way to to find the debris's location without first looking at the debris object. Now at any given time there can be a huge (1000+) amount of debris in space, and I figure that calculating the distance between the ship and every single piece of debris and comparing it to maximum tractor beam length is rather inefficient. I have thought of dividing space into sectors, and have each sector contain a list of every object in it. This way I could only check nearby sectors. However this essentially doubles memory for the list. (I would reference the same object so it wouldn't double overall. I am not CS major, but I doubt this would be hugely significant.) This also means anytime an object moves it has to calculate which sector it is in, again not a huge problem. I also don't know if I can use some sort of 2D MAP that uses x and y values as keys. But since I am using float locations this sounds more trouble than its worth. I am kind of new to programming games, and I imagined there would be some eloquent solution to this issue.

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  • Best practice for organizing/storing character/monster data in an RPG?

    - by eclecto
    Synopsis: Attempting to build a cross-platform RPG app in Adobe Flash Builder and am trying to figure out the best class hierarchy and the best way to store the static data used to build each of the individual "hero" and "monster" types. My programming experience, particularly in AS3, is embarrassingly small. My ultra-alpha method is to include a "_class" object in the constructor for each instance. The _class, in turn, is a static Object pulled from a class created specifically for that purpose, so things look something like this: // Character.as package { public class Character extends Sprite { public var _strength:int; // etc. public function Character(_class:Object) { _strength = _class._strength; // etc. } } } // MonsterClasses.as package { public final class MonsterClasses extends Object { public static const Monster1:Object={ _strength:50, // etc. } // etc. } } // Some other class in which characters/monsters are created. // Create a new instance of Character var myMonster = new Character(MonsterClasses.Monster1); Another option I've toyed with is the idea of making each character class/monster type its own subclass of Character, but I'm not sure if it would be efficient or even make sense considering that these classes would only be used to store variables and would add no new methods. On the other hand, it would make creating instances as simple as var myMonster = new Monster1; and potentially cut down on the overhead of having to read a class containing the data for, at a conservative preliminary estimate, over 150 monsters just to fish out the one monster I want (assuming, and I really have no idea, that such a thing might cause any kind of slowdown in execution). But long story short, I want a system that's both efficient at compile time and easy to work with during coding. Should I stick with what I've got or try a different method? As a subquestion, I'm also assuming here that the best way to store data that will be bundled with the final game and not read externally is simply to declare everything in AS3. Seems to me that if I used, say, XML or JSON I'd have to use the associated AS3 classes and methods to pull in the data, parse it, and convert it to AS3 object(s) anyway, so it would be inefficient. Right?

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  • [EF + Oracle] Inserting Data (1/2)

    - by JTorrecilla
    Prologue Following EF series (I ,II y III) in this chapter we will see how to create DB record from EF. Inserting Data Like we indicated in the 2º post: “One Entity matches with a DB record, and one property match with a Table Column”. To start, we need to create an object from one of the Entities: 1: EMPLEADOS empleado = new EMPLEADOS(); Also like, I told previously, Exists the possibility to use the Static Function defined by VS for each Entity: Once we have created the object, we can Access to it properties to fill like a common class:   1: empleado.NOMBRE = "Javier Torrecilla";   After finish of fill our Entity properties, it must be needed to add the object to the appropriate ObjectSet in the ObjectContext: 1: enti.EMPLEADOS.AddObject(empleado); or 1: enti.AddToEMPLEADOS(empleado); Both methods will do the same action, create an insert statement. Have we finished? No. Any Entity has a property called “EntityState”. This prop is an Enum from “EntityState”, which has the following: Detached: the Entity is created, but not added to the Context. Unchanged: There is no pending changes in the Entity. Added: The entity is added to the ObjectSet, but it is not yet sent to the DB. Deleted: The object is deleted form the ObjectSet, but not yet from the DB. Modified: There is Pending Changes to confirm. Let’s see, the several values of the property during the Creation steps: 1. While the Object is created and we are filling the props: EntityState.Detached; 2. After adding to the ObjectSet: EntityState.Added. This not indicated that the record is in the DB 3. Saving the Data: To sabe the data in the DB, we are going to call “SaveChanges” method of the Object Context. After invoke it, the property will be EntityState.Unchanged.   What does SaveChanges Method? This function will synchronize and send all pending changes to DB. It will add, modify or delete all Entities, whose EntityState property, is setted to Added, Deleted or Modified. After finishing, all added or modified entities will be change the State to “Unchanged”, and deleted Entities must take the “Detached” state.

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  • How best to look up objects by label?

    - by dsollen
    I am writing the server backed by a pre-written API. I'm going to get a number of strings representing ports, signals, paths, etc etc etc. I need to look up the object associated with a given label, these objects are all in memory (no sql magic to do this for me). My question is, how best do I associate a given unique label with the mutable object it represents? I have enough objects that looking through every signal or every port to find the one that matches is possible, but may be slightly too slow. To be honest the direct 'look at every object' method is probably good enough for so small a body of objects and anything else is premature optimization, but I still am curious what the proper solution would be if I thought my signals were going to grow a bit larger. As I see it there are two options available. First would be to to create a 'store' that is a simple map between object and label. I could have it so that every time I call addObject the object is automatically saved into a hashmap or the like. This works, but relies on my properly adding and deleting each object so the map doesn't grow indefinitely. The biggest issue to me is that this involves having some hidden static map in my ModelObject class that just feels...wrong somehow. The other option is to have some method that can interpret the labels. All of these labels are derived from the underlying objects. So I can look at the signal label, for instance, and say "these 20 characters are the port" to figure out what port I need. This would allow me to quickly figure out what I need. However, if the label method is changed the translateLabelToObject method needs to be updated as well or everything breaks. Which solution is cleaner, or possibly a cleaner solution than either of above? For the record I'm working with sufficient number of variables to make direct comparison a little slow, but not enough to be concerned about memory overhead, written in java. All objects that have labels I need to look up extend the same parent class.

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  • F# Objects &ndash; Part 3 &ndash; it&rsquo;s time to overload&hellip;

    - by MarkPearl
    Okay, some basic examples of overloading in F# Overloading Constructors Assume you have a F# object called person… type Person (firstname : string, lastname : string) = member v.Fullname = firstname + " " + lastname   This only has one constructor. To add additional constructors to the object by explicitly declaring them using the method member new. type Person (firstname : string, lastname : string) = new () = Person("Unknown", "Unknown") member v.Fullname = firstname + " " + lastname   In the code above I added another constructor to the Person object that takes no parameters and then refers to the primary constructor. Using the same technique in the code below I have created another constructor that accepts only the firstname as a parameter to create an object. type Person (firstname : string, lastname : string) = new () = Person("Unknown", "Unknown") new (firstname : string) = Person(firstname, "Unknown") member v.Fullname = firstname + " " + lastname   Overloading Operators So, you can overload operators of objects in F# as well… let’s look at example code… type Person(name : string) = member v.name = name static member (+) (person1 : Person , person2 : Person) = Person(person1.name + " " + person2.name)   In the code above we have overloaded the “+” operator. Whenever we add to Person objects together, it will now create a new object with the combined names…

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  • Use a SQL Database for a Desktop Game

    - by sharethis
    Developing a Game Engine I am planning a computer game and its engine. There will be a 3 dimensional world with first person view and it will be single player for now. The programming language is C++ and it uses OpenGL. Data Centered Design Decision My design decision is to use a data centered architecture where there is a global event manager and a global data manager. There are many components like physics, input, sound, renderer, ai, ... Each component can trigger and listen to events. Moreover, each component can read, edit, create and remove data. The question is about the data manager. Whether to Use a Relational Database Should I use a SQL Database, e.g. SQLite or MySQL, to store the game data? This contains virtually all game content like items, characters, inventories, ... Except of meshes and textures which are even more performance related, so I will keep them in memory. Is a SQL database fast enough to use it for realtime reading and writing game informations, like the position of a moving character? I also need to care about cross-platform compatibility. Aside from keeping everything in memory, what alternatives do I have? Advantages Would Be The advantages of using a relational database like MySQL would be the data orientated structure which allows fast computation. I would not need objects for representing entities. I could easily query data of objects near the player needed for rendering. And I don't have to take care about data of objects far away. Moreover there would be no need for savegames since the hole game state is saved in the database. Last but not least, expanding the game to an online game would be relative easy because there already is a place where the hole game state is stored.

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  • How can I test linkable/executable files that require re-hosting or retargeting?

    - by hagubear
    Due to data protection, I cannot discuss fine details of the work itself so apologies PROBLEM CASE Sometimes my software projects require merging/integration with third party (customer or other suppliers) software. these software are often in linkable executables or object code (requires that my source code is retargeted and linked with it). When I get the executables or object code, I cannot validate its operation fully without integrating it with my system. My initial idea is that executables are not meant to be unit tested, they are meant to be linkable with other system, but what is the guarantee that post-linkage and integration behaviour will be okay? There is also no sufficient documentation available (from the customer) to indicate how to go about integrating the executables or object files. I know this is philosophical question, but apparently not enough research could be found at this moment to conclude to a solution. I was hoping that people could help me go to the right direction by suggesting approaches. To start, I have found out that Avionics OEM software is often rehosted and retargeted by third parties e.g. simulator makers. I wonder how they test them. Surely, the source code will not be supplied due to IPR rgulations. UPDATE I have received reasonable and very useful suggestions regarding this area. My current struggle has shifted into testing 3rd party OBJECT code that needs to be linked with my own source code (retargeted) on my host machine. How can I even test object code? Surely, I need to link them first to even think about doing anything. Is it the post-link behaviour that needs to be determined and scripted (using perl,Tcl, etc.) so that inputs and outputs could be verified? No clue!! :( thanks,

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  • How to ensure that a member variable is initialized before calling a class method

    - by Omkar Ekbote
    There's a class with a parametrized constructor that initializes a member variable. All public methods of the class then use this member variable to do something. I want to ensure that the caller always creates an object using the parametrized constructor (there is also a setter for this member variable) and then call that object's methods. In essence, it should be impossible for the caller to call any method without setting a value to the member variable (either by using the parametrized constructor or the setter). Currently, a caller can simply make an object using the default constructor and then call that object's method - I want to avoid checking whether or not the member variable is set in each and every one of the 20-odd methods of the class (and throw an exception if it is not). Though a runtime solution is acceptable (better than the one I mentioned above); a compile-time solution is preferable so that any developer will not be allowed to make that mistake and then waste hours debuggging it!

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