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  • c# (wcf) architecture file and directory structure (and instantiation)

    - by stevenrosscampbell
    Hello and thanks for any assistance. I have a wcf service that I'm trying to properly modularize. I'm interested in finding out if there is a better way or implementing the file and directory structure along with instanciatation, is there a more appropriate way of abstraction that I may be missing? Is this the best approach? especially if performance and the ability to handle thousands of simultanious request? Currently I have this following structure: -Root\Service.cs public class Service : IService { public void CreateCustomer(Customer customer) { CustomerService customerService = new CustomerService(); customerService.Create(customer); } public void UpdateCustomer(Customer customer) { CustomerService customerService = new CustomerService(); customerService.Update(customer); } } -Root\Customer\CustomerService.cs pulbic class CustomerService { public void Create(Customer customer) { //DO SOMETHING } public void Update(Customer customer) { //DO SOMETHING } public void Delete(int customerId) { //DO SOMETHING } public Customer Retrieve(int customerId) { //DO SOMETHING } } Note: I do not include the Customer Object or the DataAccess libraries in this example as I am only concerned about the service. If you could either let me know what you think, if you know a better way, or a resource that could help out. Thanks Kindly. Steven

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  • Per-pixel per-component alpha blending in Windows

    - by Crend King
    I have a 24-bit bitmaps with R, G, B color channels and a 24-bit bitmap with R, G, B alpha channels. I want to alpha blend the first bitmap to a HDC in GDI or RenderTarget in Direct2D with the alpha channels respectively. For example, suppose for one pixel, the bitmap color is (192, 192, 192), the HDC color is (0, 255, 255) and the alpha channels are (30, 40, 50). The final HDC color should be (22, 245, 242). I know I can BitBlt the HDC to a memory HDC first, do alpha blending by manually calculating the color of each pixel and finally BitBlt back. I just want to avoid the additional blitting and leave APIs do their job (faster since they are in kernel space). The first idea comes to my mind is to split the source bitmap into 3 red-only, green-only and blue-only 8-bit bitmaps, do normal alpha blending, then composite the 3 output bitmaps into the HDC. But I don't find a way to do the splitting and composition natively in Windows (would Direct2D layer help?). Also, the splitting and compositing may require many additional copying. The performance overhead would be too high. Or maybe do the alpha blending in 3 passes. Each pass apply the blending for one channel, while maintaining the other 2 unchanged. Thanks for any comment. EDIT: I found this question, and the answer should be good reference to this problem. However, besides AC_SRC_OVER, there is no other blending operation supported. Why don't Microsoft improve their API?

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  • Using a .MDF SQL Server Database with ASP.NET Versus Using SQL Server

    - by Maxim Z.
    I'm currently writing a website in ASP.NET MVC, and my database (which doesn't have any data in it yet, it only has the correct tables) uses SQL Server 2008, which I have installed on my development machine. I connect to the database out of my application by using the Server Explorer, followed by LINQ to SQL mapping. Once I finish developing the site, I will move it over to my hosting service, which is a virtual hosting plan. I'm concerned about whether using the SQL Server setup that is currently working on my development machine will be hard to do on the production server, as I'll have to import all the database tables through the hosting control panel. I've noticed that it is possible to create a SQL Server database from inside Visual Studio. It is then stored in the App_Data directory. My questions are the following: Does it make sense to move my SQL Server DB out of SQL Server and into the App_Data directory as an .mdf file? If so, how can I move it? I believe this is called the Detach command, is it not? Are there any performance/security issues that can occur with a .mdf file like this? Would my intended setup work OK with a typical virtual hosting plan? I'm hoping that the .mdf database won't count against the limited number of SQL Server databases that can be created with my plan. I hope this question isn't too broad. Thanks in advance! Note: I'm just starting out with ASP.NET MVC and all this, so I might be completely misunderstanding how this is supposed to work.

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  • iPhone - User Defaults and UIImages

    - by Staros
    Hello, I've been developing an iPhone app for the last few months. Recently I wanted to up performance and cache a few of the images that are used in the UI. The images are downloaded randomly from the web by the user so I can't add specific images to the project. I'm also already using NSUserDefaults to save other info within the app. So now I'm attempting to save a dictionary of UIImages to my NSUserDefaults object and get... -[UIImage encodeWithCoder:]: unrecognized selector sent to instance I then decided to subclass UIImage with a class named UISaveableImage and implement NSCoding. So now I'm at... @implementation UISaveableImage -(void)encodeWithCoder:(NSCoder *)encoder { [encoder encodeObject:super forKey:@"image"]; } -(id)initWithCoder:(NSCoder *)decoder { if (self=[super init]){ super = [decoder decodeObjectForKey:@"image"]; } return self; } @end which isn't any better than where I started. If I was able to convert an UIImage to NSData I would be good, but all I can find are function like UIImagePNGRepresentation which require me to know what type of image this was. Something that UIImage doesn't allow me to do. Thoughts? I feel like I might have wandered down the wrong path...

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  • mySQL need to merge fields and get unique rows

    - by jiudev
    i have a database with +1 million rows and the stuktur looks like: CREATE TABLE IF NOT EXISTS `Performance` ( `id` int(11) NOT NULL AUTO_INCREMENT, `CIDs` varchar(100) DEFAULT NULL, `COLOR` varchar(100) DEFAULT NULL, `Name` varchar(255) DEFAULT NULL, `XT` bigint(16) DEFAULT NULL, `MP` varchar(100) DEFAULT NULL, PRIMARY KEY (`id`), KEY `CIDs` (`CIDs`), KEY `COLOR` (`COLOR`), KEY `Name` (`Name`), KEY `XT` (`XT`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8 AUTO_INCREMENT=0 ; insert into `Performance` (`id`, `CIDs`, `COLOR`, `Name`, `XT`, `MP`) VALUES (1, '1253374160', 'test test test test test', 'Load1', '89421331221', ''), (2, '1271672029', NULL, 'Load1', '19421331221', NULL), (3, '1188959688', NULL, 'Load2', '39421331221', NULL), (4, '1271672029', NULL, 'Load3', '49421341221', 'Description'), (5, '1271888888', NULL, 'Load4', '59421331221', 'Description'); The Output should look like: +----+------------+--------------------------+-------------+-------------+-------+-----------+---------+ | id | CIDs | COLOR | XT | MP | Name | PIDs | unqName | +----+------------+--------------------------+-------------+-------------+-------+-----------+---------+ | 1 | 1253374160 | test test test test test | 89421331221 | | Load1 | 1,2 | Load1 | | 3 | 1188959688 | NULL | 39421331221 | NULL | Load2 | 3 | Load2 | | 4 | 1271672029 | NULL | 49421341221 | Description | Load3 | 4,5 | Load3 | +----+------------+--------------------------+-------------+-------------+-------+-----------+---------+ any ideas, how i could do this as fast as possible? I have tried with some group by, but it takes some Minutes :/ Thanks Advance //edit: for the solution with the group by, i needed 4 subquerys :/ //edit2: as requested: select id, CIDs, COLOR, XT, MP, Name, concat(PIDs,",",GROUP_CONCAT(DISTINCT id)) as PIDs, IFNULL(Name,id) as unqName from ( select id, CIDs, COLOR, XT, MP, Name, concat(PIDs,",",GROUP_CONCAT(DISTINCT id)) as PIDs, IFNULL(MP,id) as unqMP from ( select id, CIDs, COLOR, XT, MP, Name, concat(PIDs,",",GROUP_CONCAT(DISTINCT id)) as PIDs, IFNULL(XT,id) as unqXT from ( select id, CIDs, COLOR, XT, MP, Name, GROUP_CONCAT(DISTINCT id) as PIDs, IFNULL(COLOR,id) as unqCOLOR from Performance group by unqCOLOR ) m group by unqXT ) x group by unqMP ) y group by unqName

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  • Winforms: How to speed up Invalidate()?

    - by Pedery
    I'm developing a retained mode drawing application in GDI+. The application can draw simple shapes to a canvas and perform basic editing. The math that does this is optimized to the last byte and is not an issue. I'm drawing on a panel that is using the built-in Controlstyles.DoubleBuffer. Now, my problem arises if I run my app maximized on a big monitor (HD in my case). If I try to draw a line from one corner of the (big) canvas to the diagonally oposite other, it will start to lag and the CPU goes high up. Each graphical object in my app has a boundingbox. Thus, when I invalidate the boundingbox of a line that goes from one corner of the maximized app to the oposite diagonal one, that boundingbox is virtually as big as the canvas. When a user is drawing a line, this invalidation of the boundingbox thus happens on the mousemove event, and there is a clear lag visible. This lag also exists if the line is the only object on the canvas. I've tried to optimize this in many ways. If I draw a shorter line, the CPU and the lag goes down. If I remove the Invalidate() and keep all other code, the app is quick. If I use a Region (that only spans the figure) to invalidate instead of the boundingbox, it is just as slow. If I split the boundingbox into a range of smaller boxes that lie back to back, thus reducing the invalidation area, no visible performance gain can be seen. Thus I'm at a loss here. How can I speed up the invalidation? On a side note, both Paint.Net and Mspaint suffers from the same shortcommings. Word and PowerPoint however, seem to be able to paint a line as described above with no lag and no CPU load at all. Thus it's possible to achieve the desired results, the question is how?

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  • Execute remote Lua Script

    - by Bruno Lee
    Hi, I want to make an application that executes a remote script. The user can create a script (probabily a LUA script) then stores it in the server. Then he can uses an API for execute the script. I was thinking that API could be a webservice. So my questions are: I need high performance to execute the script. So my first choice was LUA script. Someone has another sugestion? Cause I need high perfomance, I was thinking if the webservice is the best solution. Maybe I could create a TCP/IP Windows Service that hold the users request. It is important to say that I will have many user executing scripts at the same time. So I will have a concurrency problem. My scripts will query in a database. I will use Tokyo Cabinet or Tokio Tyrant. I think Tokio Tyrant is the only solution cause I will have many requests. For perfomance, Do I need to make a connection pooling? Is there anyway to share variables between webservices requests? To make the webservice or the Windows service i was thinking to use C++. Can someone help with these questions? thanks

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  • Memory mapped files and "soft" page faults. Unavoidable?

    - by Robert Oschler
    I have two applications (processes) running under Windows XP that share data via a memory mapped file. Despite all my efforts to eliminate per iteration memory allocations, I still get about 10 soft page faults per data transfer. I've tried every flag there is in CreateFileMapping() and CreateFileView() and it still happens. I'm beginning to wonder if it's just the way memory mapped files work. If anyone there knows the O/S implementation details behind memory mapped files I would appreciate comments on the following theory: If two processes share a memory mapped file and one process writes to it while another reads it, then the O/S marks the pages written to as invalid. When the other process goes to read the memory areas that now belong to invalidated pages, this causes a soft page fault (by design) and the O/S knows to reload the invalidated page. Also, the number of soft page faults is therefore directly proportional to the size of the data write. My experiments seem to bear out the above theory. When I share data I write one contiguous block of data. In other words, the entire shared memory area is overwritten each time. If I make the block bigger the number of soft page faults goes up correspondingly. So, if my theory is true, there is nothing I can do to eliminate the soft page faults short of not using memory mapped files because that is how they work (using soft page faults to maintain page consistency). What is ironic is that I chose to use a memory mapped file instead of a TCP socket connection because I thought it would be more efficient. Note, if the soft page faults are harmless please note that. I've heard that at some point if the number is excessive, the system's performance can be marred. If soft page faults intrinsically are not significantly harmful then if anyone has any guidelines as to what number per second is "excessive" I'd like to hear that. Thanks.

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  • What are the primitive Forth operators?

    - by Barry Brown
    I'm interested in implementing a Forth system, just so I can get some experience building a simple VM and runtime. When starting in Forth, one typically learns about the stack and its operators (DROP, DUP, SWAP, etc.) first, so it's natural to think of these as being among the primitive operators. But they're not. Each of them can be broken down into operators that directly manipulate memory and the stack pointers. Later one learns about store (!) and fetch (@) which can be used to implement DUP, SWAP, and so forth (ha!). So what are the primitive operators? Which ones must be implemented directly in the runtime environment from which all others can be built? I'm not interested in high-performance; I want something that I (and others) can learn from. Operator optimization can come later. (Yes, I'm aware that I can start with a Turing machine and go from there. That's a bit extreme.) Edit: What I'm aiming for is akin to bootstrapping an operating system or a new compiler. What do I need do implement, at minimum, so that I can construct the rest of the system out of those primitive building blocks? I won't implement this on bare hardware; as an educational exercise, I'd write my own minimal VM.

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  • Codility-like sites for code golfs

    - by Adam Matan
    Hi, I've run into codility.com new cool service after listening to one of the recent stackoverflow.com podcasts. In short, it presents the user with a programming riddle to solve, within a given time frame. The user writes code in an online editor, and has the ability to run the program and view the standard output. After final submission, the user sees its final score and which tests failed him. Quoting Joel Spolsky: You are given a programming problem, you can do it in Java, C++, C#, C, Pascal, Python and PHP, which is pretty cool, and you have 30 minutes. And it gives you an editor in a webpage. And you've got to just start typing your code. And it's going to time you, basically you have to do it in a certain amount of time. And it actually runs your code and determines the performance characteristics of your code. It is intended for job interview screenings, but the idea seems very cool for code-golfs and for practicing new languages. Do you know if there's any proper open replacement? Adam

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  • How to make Stack.Pop threadsafe

    - by user260197
    I am using the BlockingQueue code posted in this question, but realized I needed to use a Stack instead of a Queue given how my program runs. I converted it to use a Stack and renamed the class as needed. For performance I removed locking in Push, since my producer code is single threaded. My problem is how can thread working on the (now) thread safe Stack know when it is empty. Even if I add another thread safe wrapper around Count that locks on the underlying collection like Push and Pop do, I still run into the race condition that access Count and then Pop are not atomic. Possible solutions as I see them (which is preferred and am I missing any that would work better?): Consumer threads catch the InvalidOperationException thrown by Pop(). Pop() return a nullptr when _stack-Count == 0, however C++-CLI does not have the default() operator ala C#. Pop() returns a boolean and uses an output parameter to return the popped element. Here is the code I am using right now: generic <typename T> public ref class ThreadSafeStack { public: ThreadSafeStack() { _stack = gcnew Collections::Generic::Stack<T>(); } public: void Push(T element) { _stack->Push(element); } T Pop(void) { System::Threading::Monitor::Enter(_stack); try { return _stack->Pop(); } finally { System::Threading::Monitor::Exit(_stack); } } public: property int Count { int get(void) { System::Threading::Monitor::Enter(_stack); try { return _stack->Count; } finally { System::Threading::Monitor::Exit(_stack); } } } private: Collections::Generic::Stack<T> ^_stack; };

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  • Hibernate: order multiple one-to-many relations

    - by Markos Fragkakis
    I have a search screen, using JSF, JBoss Seam and Hibernate underneath. There are columns for A, B and C, where the relations are as follows: A (1< -- ) B (1< -- ) C A has a List< B and B has a List< C (both relations are one-to-many). The UI table supports ordering by any column (ASC or DESC), so I want the results of the query to be ordered. This is the reason I used Lists in the model. However, I got an exception that Hibernate cannot eagerly fetch multiple bags (it considers both lists to be bags). There is an interesting blog post here, and they identify the following solutions: Use @IndexColumn annotation (there is none in my DB, and what's more, I want the position of results to be determined by the ordering, not by an index column) Fetch lazily (for performance reasons, I need eager fetching) Change List to Set So, I changed the List to Set, which by the way is more correct, model-wise. First, if don't use @OrderBy, the PersistentSet returned by Hibernate wraps a HashSet, which has no ordering. Second, If I do use @OrderBy, the PersistentSet wraps a LinkedHashSet, which is what I would like, but the OrderBy property is hardcoded, so all other ordering I perform through the UI comes after it. I tried again with Sets, and used SortedSet (and its implementation, TreeSet), but I have some issues: I want ordering to take place in the DB, and not in-memory, which is what TreeSet does (either through a Comparator, or through the Comparable interface of the elements). Second, I found that there is the Hibernate annotation @Sort, which has a SortOrder.UNSORTED and you can also set a Comparator. I still haven't managed to make it compile, but I am still not convinced it is what I need. Any advice?

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  • Cloud-aware programming and help choosing a good framework

    - by Shoaibi
    How can i write a cloud-aware application? e.g. an application that takes benefit of being deployed on cloud. Is it same as an application that runs or a vps/dedicated server? if not then what are the differences? are there any design changes? What are the procedures that i need to take if i am to migrate an application to cloud-aware? Also i am about to implement a web application idea which would need features like security, performance, caching, and more importantly free. I have been comparing some frameworks and found that django has least RAM/CPU usage and works great in prefork+threaded mode, but i have also read that django based sites stop to respond with huge load of connections. Other frameworks that i have seen/know are Zend, CakePHP, Lithium/Cake3, CodeIgnitor, Symfony, Ruby on Rails.... So i would leave this to your opinion as well, suggest me a good free framework based on my needs. Finally thanks for reading the essay ;)

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  • Cross-platform game development: ease of development vs security

    - by alcuadrado
    Hi, I'm a member and contributor of the Argentum Online (AO) community, the first MMORPG from Argentina, which is Free Software; which, although it's not 3D, it's really addictive and has some dozens of thousands of users. Really unluckily AO was developed in Visual Basic (yes, you can laugh) but the former community, so imagine, the code not only sucks, it has zero portability. I'm planning, with some friends to rewrite the client, and as a GNU/Linux frantic, want to do it cross-platform. Some other people is doing the same with the server in Java. So my biggest problem is that we would like to use a rapid development language (like Java, Ruby or Python) but the client would be pretty insecure. Ruby/Python version would have all it's code available, and the Java one would be easily decompilable (yes, we have some crackers in the community) We have consider the option to implement the security module in C/C++ as a dynamic library, but it can be replaced with a custom one, so it's not really secure. We are also considering the option of doing the core application in C++ and the GUI in Ruby/Python. But haven't analysed all it's implications yet. But we really don't want to code the entire game in C/C++ as it doesn't need that much performance (the game is played at 18fps on average) and we want to develop it as fast as possible. So what would you choose in my case? Thank you!

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  • ajax delay load UserControl asp.net

    - by user196202
    regarding ajax delay load of usercontrols (or any controls) on Post at Encosia.com : http://encosia.com/2008/02/05/boost-aspnet-performance-with-deferred-content-loading/ I tried to implement it , but I noticed that it can be done only for simple controls or UserControls that Have simple asp.net controls (or html tags) . But when it involved with advanced dynamic ajax control (like ajaxControlToolkit or Telerik controls) that have javascripts inside them This method of injecting the html code to the .InnerHtml property of div tag (for example) IS NOT WORKING , and I red about it that The browser need to load the script on load and after that it won't iterperate the scripts injectd via .InnerHtml. So I attached here example of delay load project (from encosia.com by dave ward) with my modification (look at DefaultPopup.aspx and beforePopup.aspx and AfterPopup.aspx) Which I modified the RssReader to show listview with popup items (which is implemented via ACT HoverMenuExtender ) So in the regular way the popup items are shown right , but on the delay load which is done by creating virtual page for rendering the html and injecting it to .InnerHtml property – This ISN'T WORKING. So my question is : is there a way to do delay loading for controls which include scripts lik ACT and Telerik and others? And for the ajax templates – if I need to inject advanced control to the page – how I do it with your approach? Thanks very much (I can't attach here files so everyone please ask me by mail ([email protected]) and i'll send it to him. ) Zahi Kramer

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  • Creative ways to punish (or just curb) laziness in coworkers

    - by FerretallicA
    Like the subject suggests, what are some creative ways to curb laziness in co-workers? By laziness I'm talking about things like using variable names like "inttheemplrcd" instead of "intEmployerCode" or not keeping their projects synced with SVN, not just people who use the last of the sugar in the coffee room and don't refill the jar. So far the two most effective things I've done both involve the core library my company uses. Since most of our programs are in VB.net the lack of case sensitivity is abused a lot. I've got certain features of the library using Reflection to access data in the client apps, which has a negligible performance hit and introduces case sensitivity in a lot places where it is used. In instances where we have an agreed standard which is compromised by blatant laziness I take it a step further, like the DatabaseController class which will blatantly reject any DataTable passed to it which isn't named dtSomething (ie- must begin with dt and third letter must be capitalised). It's frustrating to have to resort to things like this but it has also gradually helped drill more attention to detail into their heads. Another is adding some code to the library's initialisation function to display a big and potentially embarrassing (only if seen by a client) message advising that the program is running in debug mode. We have had many instances where projects are sent to clients built in debug mode which has a lot of implications for us (especially with regard to error recovery) and doing that has made sure they always build to release before distributing. Any other creative (ie- not StyleCop etc) approaches like this?

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  • Load Images in WPF application

    - by LLS
    I am not familiar with WPF, and I just feel quite confusing. I am trying to create a little computer game, and there are elements I want to display dynamically. I use Image class and add the images to a canvas. But I'm not sure whether it's a good practice. I feel that adding controls to canvas seem to be a little wired. And I'm a little concerned about the performance, because I may need many images. The real problem is, I can't load the images from the image files. I see an example in a text book like this (XMAL): <Image Panel.ZIndex="0" Margin="0,0,0,0" Name ="image1"> <Image.Source> <BitmapImage UriSource="Bell.gif" /> </Image.Source> </Image> Where Bell.gif is added into the project. And I tried to copy this in code to create an image. new Image { Source = new BitmapImage(new Uri("Blockade.bmp"))} But I got invalid Uri exception. After some search in the Internet, I found that loading resources dynamically seems to be difficult. Can I load the files added to the project dynamically? If I use absolute path then it's OK. But I can't expect every computer will put the files in the same location. Can I use relative path? I tried new Image { Source = new BitmapImage(new Uri(@"Pictures\Blank Land.bmp", UriKind.Relative)) } But it doesn't work. (The image is blank) Thanks.

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  • What file format can represent an uncompressed raster image at 48 or 64 bits per pixel?

    - by finnw
    I am creating screenshots under Windows and using the LockBits function from GDI+ to extract the pixel data, which will then be written to a file. To maximise performance I am also: Using the same PixelFormat as the source bitmap, to avoid format conversion Using the ImageLockModeUserInputBuf flag to extract the pixel data into a pre-allocated buffer This pre-allocated buffer (pointed to by BitmapData::Scan0) is part of a memory-mapped file (to avoid copying the pixel data again.) I will also be writing the code that reads the file, so I can use (or invent) any format I wish. However I would prefer to use a well-known format that existing programs (ideally web browsers) are able to read, because that means I can visually confirm that the images are correct before writing the code for the other program (that reads the image.) I have implemented this successfully for the PixelFormat32bppRGB format, which matches the format of a 32bpp BMP file, so if I extract the pixel data directly into the memory-mapped BMP file and prefix it with a BMP header I get a valid BMP image file that can be opened in Paint and most browsers. Unfortunately one of the machines I am testing on returns pixels in PixelFormat64bppPARGB format (presumably this is influenced by the video adapter driver) and there is no corresponding BMP pixel format for this. Converting to a 16, 24 or 32bpp BMP format slows the program down considerably (as well as being lossy) so I am looking for a file format that can use this pixel format without conversion, so I can extract directly into the memory-mapped file as I have done with the 32bpp format. What raster image file formats support 48bpp and/or 64bpp?

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  • Why not systematically attach event in WPF instead of using delegate ?

    - by user310291
    For a button to handle event, we can add a delegate to the click property of the button: this.button1.Click += new System.EventHandler(this.button1_Click); But in WPF contrary to Winform, you can also attach a handler http://msdn.microsoft.com/en-us/magazine/cc785480.aspx So why not do so for the button ? Is performance better in first case maybe ? Update: I mean this Attached Events In order to enable elements to handle events that are declared in a different element, WPF supports something called attached events. Attached events are routed events that support a hookup in XAML on elements other than the type on which the event is declared. For example, if you want the Grid element to listen for a Button.Click event to bubble past, you would simply hook it up like the following: <Grid Button.Click="myButton_Click"> <Button Name="myButton" >Click Me</Button> </Grid> The resulting code in the compile-time-generated partial class now looks like this: #line 5 "..\..\Window1.xaml" ((System.Windows.Controls.Grid)(target)).AddHandler( System.Windows.Controls.Primitives.ButtonBase.ClickEvent, new System.Windows.RoutedEventHandler(this.myButton_Click));

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  • SQLite on iPhone - Techniques for tracking down multithreading-related bugs

    - by Jasarien
    Hey guys, I'm working with an Objective-C wrapper around SQLite that I didn't write, and documentation is sparse... It's not FMDB. The people writing this wrapper weren't aware of FMDB when writing this code. It seems that the code is suffering from a bug where database connections are being accessed from multiple threads -- which according to the SQLite documentation won't work if the if SQLite is compiled with SQLITE_THREADSAFE 2. I have tested the libsqlite3.dylib provided as part of the iPhone SDK and seen that it is compiled in this manner, using the sqlite_threadsafe() routine. Using the provided sqlite library, the code regularly hits SQLITE_BUSY and SQLITE_LOCKED return codes when performing routines. To combat this, I added some code to wait a couple of milliseconds and try again, with a maximum retry count of 50. The code didn't contain any retry logic prior to this. Now when a sqlite call returns SQLITE_BUSY or SQLITE_LOCKED, the retry loop is invoked and the retry returns SQLITE_MISUSE. Not good. Grasping at straws, I replaced the provided sqlite library with a version compiled by myself setting SQLITE_THREADSAFE to 1 - which according to the documentation means sqlite is safe to be used in a multithreaded environment, effectively serialising all of the operations. It incurs a performance hit, that which I haven't measured, but it ridded the app of the SQLITE_MISUSE happening and seemed to not need the retry logic as it never hit a busy or locked state. What I would rather do is fix the problem of accessing a single db connection from multiple threads, but I can't for the life of me find where it's occurring. So if anyone has any tips on locating multithreaded bugs I would be extremely appreciative. Thanks in advance.

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  • Python: How to execute a SQL file or command

    - by Mestika
    Hi, I have this Python script: import sys import getopt import timeit import random import os import re import ibm_db import time from string import maketrans runs=5 queries=50 file = open("results.txt", "a") for r in range(5): print "Run %s\n" % r os.system("python reads.py -r1 -pquery1.sql -q50 -sespec") file.write('END QUERY READ 01') file.close() os.system("python query_read_02.py") Everything here is working, it is creating the results.txt file, it run the os.system("python reads.py...") file and that file is doing everything it's suppose to, but the problem comes when go and run the query_read_02.py file. In this file, it should execute a SQL command or a SQL file on my database, so I can create an index and see what the performance of that input is, but how do i do it? I create the connection to the database in the reads.py file, but it's hard to create the queries in there because I doesn't keep track of which file it has reached, it just execute commands from what the parameters are. I hope I've explained myself clear enough, otherwise please let me know. I just want to execute a SQL command or file which each query_read_0x.py file. Sincerely Mestika

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  • Seeking reporting or templating tool to generate large formatted PDF reports from dataset

    - by Mr. Tacos
    Say I have some data in MySQL or a big ole CSV file. I also have a report. It's a PDF, call it 100 pages long. I need to generate variations on this PDF for slices of the data. More specific example: I have a CSV file with each StackOverflow user in a row and each column contains various statistics about that user. I have a report called "Your StackOverflow Performance". Its got lots of text, always the same, but each section contains something like: "You Vs. The Average StackOverflow Poster on this metric". I want a table that appears there that has the average data, which is the same in every run of the PDF, in one column. In the second column, I want your data, which is different for each PDF/row in the CSV file/user of StackOverflow. I'm pretty sure people use things like Crystal for this? Is there something in MS SQL Server that's good for this? An open source template language? I'm not even really sure if what I need is called a 'reporting' tool (since I don't really need to do any crunching, the data in this case is being crunched by a series of scripts and SPSS, I don't need bands and subbands and so on) or 'templating'. Is there even such a thing as templating PDFs? Natch, I'd be fine with something that generates output easily scriptable to PDF, like eps, but not something like HTML. The report formatting is fussy and done and externally determined and handed down from on high. It's print-oriented, not webby. Thanks in advance.

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  • Throttling outbound API calls generated by a Rails app

    - by Sharpie
    I am not a professional web developer, but I like to wrench on websites as a hobby. Recently, I have been playing with developing a Rails app as a project to help me learn the framework. The goal of my toy app is to harvest data from another service through their API and make it available for me to query using a search function. However, the service I want to pull data from imposes a rate limit on the number of API calls that may be executed per minute. I plan on having my app run a daily update which may generate a burst of API calls that far exceeds the limit provided by the external service. I wish to respect the performance of the external site and so would like to throttle the rate at which my app executes the calls. I have done a little bit of searching and the overwhelming amount of tutorial material and pre-built libraries I have found cover throttling inbound API calls to a web app and I can find little discussion of controlling the flow of outbound calls. Being both an amateur web developer and a rails newbie, it is entirely possible that I have been executing the wrong searches in the wrong places. Therefore my questions are: Is there a nice website out there aggregating Rails tutorials that has material related to throttling outbound API requests? Are there any ruby gems or other libraries that would help me throttle the requests? I have some ideas of how I might go about writing a throttling system using a queue-based worker like DelayedJob or Resque to manage the API calls, but I would rather spend my weekends building the rest of the site if there is a good pre-built solution out there already.

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  • Shared value in parallel python

    - by Jonathan
    Hey all- I'm using ParallelPython to develop a performance-critical script. I'd like to share one value between the 8 processes running on the system. Please excuse the trivial example but this illustrates my question. def findMin(listOfElements): for el in listOfElements: if el < min: min = el import pp min = 0 myList = range(100000) job_server = pp.Server() f1 = job_server.submit(findMin, myList[0:25000]) f2 = job_server.submit(findMin, myList[25000:50000]) f3 = job_server.submit(findMin, myList[50000:75000]) f4 = job_server.submit(findMin, myList[75000:100000]) The pp docs don't seem to describe a way to share data across processes. Is it possible? If so, is there a standard locking mechanism (like in the threading module) to confirm that only one update is done at a time? l = Lock() if(el < min): l.acquire if(el < min): min = el l.release I understand I could keep a local min and compare the 4 in the main thread once returned, but by sharing the value I can do some better pruning of my BFS binary tree and potentially save a lot of loop iterations. Thanks- Jonathan

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  • Linux Lightweight Distro and X Windows for Development

    - by Fernando Barrocal
    Heyall... I want to build a lightweight linux configuration to use for development. The first idea is to use it inside a Virtual Machine under Windows, or old Laptops with 1Gb RAM top. Maybe even a distributable environment for developers. So the whole idea is to use a LAMP server, Java Application Server (Tomcat or Jetty) and X Windows (any Window manager, from FVWM to Enlightment), Eclipse, maybe jEdit and of course Firefox. Edit: I am changing this post to compile a possible list of distros and window managers that can be used to configure a real lightweight development environment. I am using as base personal experiences on this matter. Info about the distros can be easily found in their sites. So please, focus on personal use of those systems Distros Ubuntu / Xubuntu Pros: Personal Experience in old systems or low RAM environment - @Schroeder, @SCdF Several sugestions based on personal knowledge - @Kyle, @Peter Hoffmann Gentoo Pros: Not targeted to Desktop Users - @paan Don't come with a huge ammount of applications - @paan Slackware Pros: Suggested as best performance in a wise install/configuration - @Ryan Damn Small Linux Pros: Main focus is the lightweight factor - 50MB LiveCD - @Ryan Debian Pros: Very versatile, can be configured for both heavy and lightweight computers - @Ryan APT as package manager - @Kyle Based on compatibility and usability - @Kyle -- Fell Free to add Prós and Cons on this, so we can compile a good Reference. -- X Windows suggestion keep coming about XFCE. If others are to add here, open a session for it Like the distro one :)

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