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  • How to crete a Java Iterator that throws IOException

    - by Antonio
    I'd like to implement an iterator that retrieves objects from disk/network. Iterator itr = getRemoteIterator(); while(itr.hasNext()) { Object element = itr.next(); System.out.print(element + " "); } However the problem is that hasNext() and next() methods of the Iterator object does not allow to throw IOException. Is there any other standard interface work around this issue? Desired code is: public interface RemoteIterator<E> { boolean hasNext() throws IOException; E next() throws IOException; void remove(); }

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  • Explicitly persist states in Workflow 4.0 rather than everything.

    - by jlafay
    I have ran into an issue with my SQL instance store attached to a WorkflowApplication that is running. When I exit my application I'm calling an Unload() on the WF app to persist it. I didn't think about it during design time, but it does makes sense, it's persisting an arg that was passed in to the WorkflowApplication constructor when instanced. When the application runs, everything in the workflow works as expected. When I call Unload() I get an unhandled exception that states that the arg is not serializable and needs [DataContractAttribute]. What's passed into the workflow is my applications custom logger object that I wrote so that the WF can log to disk in a uniform way that I prefer. How do I prevent the workflow app from persisting this one argument and persist everything else? I'm sure something can be done with extensions but I'm having a hard time finding info on them or finding persistence examples for my scenario.

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  • Push notification or thread with timer

    - by neha
    Hi all, In my application, I'm having functionality like twitter that when you have not refreshed your screen, and if there're new messages then you get this message that "You have n new messages" and a refresh button, which on press will refresh the screen. I'm basically fetching all the data from an xml with some url. In case of thread, I need to call a timer after some time period which might affect the app performance. Can anybody please suggest wheather what will be better to use push notifications or thread with timer? Thanx in advance.

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  • Why is this loop over mysql resultset slow? (1.4ms per cycle)

    - by pawpro
    The $res contains around 488k rows the whole loop takes 61s! that's over 1.25ms per cycle! What is taking all that time? while($row = $res->fetch_assoc()) { $clist[$row['upload_id']][$row['dialcode_id']][$row['carrier_id']]['std'] = $row['cost_std']; $clist[$row['upload_id']][$row['dialcode_id']][$row['carrier_id']]['ecn'] = $row['cost_ecn']; $clist[$row['upload_id']][$row['dialcode_id']][$row['carrier_id']]['wnd'] = $row['cost_wnd']; $dialcode_destination[$row['upload_id']][$row['carrier_id']][$row['dialcode_id']]['other_destination'] = $row['destination_id']; $dialcode_destination[$row['upload_id']][$row['carrier_id']][$row['dialcode_id']]['carrier_destination'] = $row['carrier_destination_id']; } Now resultset of 10 rows, smaller arrays and performance 30 times higher (0.041ms) not the fastest still but better. while($row = $res->fetch_assoc()) { $customer[$row['id']]['name'] = $row['name']; $customer[$row['id']]['code'] = $row['customer']; }

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  • Using function arguments as local variables

    - by Rubys
    Something like this (yes, this doesn't deal with some edge cases - that's not the point): int CountDigits(int num) { int count = 1; while (num >= 10) { count++; num /= 10; } return count; } What's your opinion about this? That is, using function arguments as local variables. Both are placed on the stack, and pretty much identical performance wise, I'm wondering about the best-practices aspects of this. I feel like an idiot when I add an additional and quite redundant line to that function consisting of int numCopy = num, however it does bug me. What do you think? Should this be avoided?

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  • using arrays to get best memory alignment and cache use, is it necessary?

    - by Alberto Toglia
    I'm all about performance these days cause I'm developing my first game engine. I'm no c++ expert but after some research I discovered the importance of the cache and the memory alignment. Basically what I found is that it is recommended to have memory well aligned specially if you need to access them together, for example in a loop. Now, In my project I'm doing my Game Object Manager, and I was thinking to have an array of GameObjects references. meaning I would have the actual memory of my objects one after the other. static const size_t MaxNumberGameObjects = 20; GameObject mGameObjects[MaxNumberGameObjects]; But, as I will be having a list of components per object -Component based design- (Mesh, RigidBody, Transformation, etc), will I be gaining something with the array at all? Anyway, I have seen some people just using a simple std::map for storing game objects. So what do you guys think? Am I better off using a pure component model?

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  • Tiny C Compiler and Virus warnings...

    - by NoMoreZealots
    I wanted to try out the TCC and got the Win32 Binary zip file from the website. upon decompressing it I tried to compile the "hello_win.c" source from the example directory. As soon as the compiler tried to write to the disk McAfee Popped up a dialog box and identified a Trojan named "Generic.dx." Has anyone else experience this? Dropping a virus into a compiler would be a sneaky, but brilliant, delivery mechanizism. I just want to know if this is a legit threat.

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  • How do I change the class of an object to a subclass of its current class in C++?

    - by Jared P
    I have an array of pointers to a base class, so that I can make those pointers point to (different) subclasses of the base class, but still interact with them. (really only a couple of methods which I made virtual and overloaded) I'm wondering if I can avoid using the pointers, and instead just make an array of the base class, but have some way to set the class to the subclass of my choosing. I know there must be something there specifying the class, as it needs to use that to look up the function pointer for virtual methods. By the way, the subclasses all have the same ivars and layout. Note: the design is actually based on using a template argument instead of a variable, due to performance increases, so really the abstract base class is just the interface for the subclasses, which are all the same except for their compiled code. Thanks

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  • Is scala functional programming slower than traditional coding?

    - by Fred Haslam
    In one of my first attempts to create functional code, I ran into a performance issue. I started with a common task - multiply the elements of two arrays and sum up the results: var first:Array[Float] ... var second:Array[Float] ... var sum=0f; for(ix<-0 until first.length) sum += first(ix) * second(ix); Here is how I reformed the work: sum = first.zip(second).map{ case (a,b) => a*b }.reduceLeft(_+_) When I benchmarked the two approaches, the second method takes 40 times as long to complete! Why does the second method take so much longer? How can I reform the work to be both speed efficient and use functional programming style?

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  • Selecting a value from multiple dictionaries inside an enumeration

    - by johaanfaust
    If I have an enumeration of dictionaries IEnumerable<IDictionary<string, float>> enumeration can I perform a Linq query on it so that I can select by a value from each dictionary in the enumeration using the same key? I can do this in a loop: float f; foreach (var dictionary in enumeration) { if (dictionary.TryGetValue("some key", out f)) { Console.WriteLine(f); } } (The eventual plan is to compare the performance of the query verses the equivalent nested looping statements (the enumeration itself is formed from either another query or an equivalent set of loops).)

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  • Response.Redirect exception

    - by Tedd Hansen
    Executing the line: Response.Redirect("Whateva.aspx", true); Results in: A first chance exception of type 'System.Threading.ThreadAbortException' occurred in mscorlib.dll An exception of type 'System.Threading.ThreadAbortException' occurred in mscorlib.dll but was not handled in user code The exception is because of the "true" part, telling it to end the current request immediately. Is this how it should be? If we consider: Exceptions are generally considered heavy, and many times the reason for ending the request early is to avoid processing the rest of the page. Exceptions show up in performance monitoring, so monitoring the solution will show a false number of exceptions. Is there an alternative way to achieve the same?

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  • Parallelism on two duo-core processor system

    - by Qin
    I wrote a Java program that draw the Mandelbrot image. To make it interesting, I divided the for loop that calculates the color of each pixel into 2 halves; each half will be executed as a thread thus parallelizing the task. On a two core one cpu system, the performance of using two thread approach vs just one main thread is nearly two fold. My question is on a two dual-core processor system, will the parallelized task be split among different processor instead of just utilize the two core on one processor? I suppose the former scenario will be slower than the latter one simply because the latency of communicating between 2 CPU over the motherboard wires. Any ideas? Thanks

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  • Why SQL functions are faster than UDF

    - by Zerotoinfinite
    Though it's a quite subjective question but I feel it necessary to share on this forum. I have personally experienced that when I create a UDF (even if that is not complex) and use it into my SQL it drastically decrease the performance. But when I use SQL inbuild function they happen to work pretty faster. Conversion , logical & string functions are clear example of that. So, my question is "Why SQL in build functions are faster than UDF"? and it would be an advantage if someone can guide me how can I judge/manipulate function cost either mathematically or logically.

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  • IDL-like parser that turns a document definition into powerful classes?

    - by paniq
    I am looking for an IDL-like (or whatever) translator which turns a DOM- or JSON-like document definition into classes which are accessible from both C++ and Python, within the same application expose document properties as ints, floats, strings, binary blobs and compounds: array, string dict (both nestable) (basically the JSON type feature set) allow changes to be tracked to refresh views of an editing UI provide a change history to enable undo/redo operations can be serialized to and from JSON (can also be some kind of binary format) allow to keep large data chunks on disk, with parts only loaded on demand provide non-blocking thread-safe read/write access to exchange data with realtime threads allow multiple editors in different processes (or even on different machines) to view and modify the document The thing that comes closest so far is the Blender 2.5 DNA/RNA system, but it's not available as a separate library, and badly documented. I'm most of all trying to make sure that such a lib does not exist yet, so I know my time is not wasted when I start to design and write such a thing. It's supposed to provide a great foundation to write editing UI components.

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  • How to add an existing folder to a Visual Studio project?

    - by Earlz
    I have a web application project made in Visual Studio 2008. Well, I added a jquery folder and added it to source control and other such things. I forgot to add it to the visual studio project though. How do I add the existing folder now? I've tried just creating a new folder and naming it jquery but it gave me a cryptic error "the directory is already on the disk ... if you want to see this directory then check the Show All Files option in the project file" Yet I looked and saw no such option. Is the only way around this to rename jquery to jquery2 and then create a new folder via visual studio named jquery and copy all my files into it?

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  • What is the best platform/language for a 3D game in a web browser?

    - by CodeJustin.com
    I have enjoyed making 2D games in various langues (actionscript 3.0, java, python, others) but now I'm ready to move into 3D and to really get me amped up while learning 3D development I'm going to attempt to make a 3D multiplayer game (I already have server written in python). I'm looking for a platform that will run a 3D game well in the browser on low end computers with low end internet. What first came to mind was try Java or use flash/silver light with a 3D framework but I wanted to ask the good people of stackoverflow since performance is a big part of my needs and also good documentation is a plus since I'm just starting 3D development. (the programming language does not matter)

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  • Which are the current/emerging desktop development technologies worth looking into?

    - by heeboir
    Greetings, With all the existing development towards web development and emerging technologies in that area, I'm left wondering; what is a state of the art way to implement desktop applications in this day and age? If you were to start a new application of considerable size from scratch what technology would you invest your efforts in (focusing on cross platform portability, decent performance and interoperability with existing standards)? I've looked into the Adobe Air platform which appears quite impressive but seems rather limited to support a large application. Would something like Java/SWT still be the sensible choice? Do things like GWT fit the bill? Thanks P.S. I'm leaving my question a bit open-ended in an effort to gather diverse answers. Surely this a subjective matter and there is no right and wrong answer.

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  • Restricting deletion with NHibernate

    - by FrontSvin
    I'm using NHibernate (fluent) to access an old third-party database with a bunch of tables, that are not related in any explicit way. That is a child tables does have parentID columns which contains the primary key of the parent table, but there are no foreign key relations ensuring these relations. Ideally I would like to add some foreign keys, but cannot touch the database schema. My application works fine, but I would really like impose a referential integrity rule that would prohibit deletion of parent objects if they have children, e.i. something similar 'ON DELETE RESTRICT' but maintained by NHibernate. Any ideas on how to approach this would be appreciated. Should I look into the OnDelete() method on the IInterceptor interface, or are there other ways to solve this? Of course any solution will come with a performance penalty, but I can live with that.

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  • Does HTML5 only replace the video aspects of Flash/Silverlight?

    - by John
    I see a lot of talk how HTML5 video tag will kill Flash. But while video is the most widely used part of Flash/SL, it's only a small part of their technical abilities. For instance you can write a game using full 3D graphics and socket connections in Flex, and serious business applications, etc. Is the thinking that Javascript will kill those parts of Flash/Flex/SL? Because while that seems feasible now for even quite rich web-apps, what about any kind of high-performance app like real-time graphics?

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  • Looking for a source code management system with a good GUI client

    - by Anders Öhrt
    We are currently using CS-RCS Pro for source code management, and are looking for to replace this due to performance issues. It is based on client side file access with no own protocol, which makes it painfully slow to use over a slow VPN line since it always rewrites the whole history of a file. It does however have a GUI client which is very simple and gives a great overview. We have three main requirements in a SCM: Fast. It must have a server side service or some other smart way so working with files with a large history is fast. A good Windows GUI client (not Explorer shell integration, not VS or Eclipse IDE integration), so working with files and branches is easy. The possibility to have several branches checked out at once in different directories. Does anyone have a recommendation of a SCM which fulfills there requirements?

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  • How to reduce this IF-Else ladder in c#

    - by Rohit
    This is the IF -Else ladder which I have created to focus first visible control on my form.According to the requirement any control can be hidden on the form.So i had to find first visible control and focus it. if (ddlTranscriptionMethod.Visible) { ddlTranscriptionMethod.Focus(); } else if (ddlSpeechRecognition.Visible) { ddlSpeechRecognition.Focus(); } else if (!SliderControl1.SliderDisable) { SliderControl1.Focus(); } else if (ddlESignature.Visible) { ddlESignature.Focus(); } else { if (tblDistributionMethods.Visible) { if (chkViaFax.Visible) { chkViaFax.Focus(); } else if (chkViaInterface.Visible) { chkViaInterface.Focus(); } else if (chkViaPrint.Visible) { chkViaPrint.Focus(); } else { chkViaSelfService.Focus(); } } } Is there any other way of doing this. I thought using LINQ will hog the performance as i have to tranverse the whole page collection. I am deep on page which has masterpages.Please suggest.

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  • Class.Class vs Namespace.Class for top level general use class libraries?

    - by Joan Venge
    Which one is more acceptable (best-practice)?: namespace NP public static class IO public static class Xml ... // extension methods using NP; IO.GetAvailableResources (); vs public static class NP public static class IO public static class Xml ... // extension methods NP.IO.GetAvailableResources (); Also for #2, the code size is managed by having partial classes so each nested class can be in a separate file, same for extension methods (except that there is no nested class for them) I prefer #2, for a couple of reasons like being able to use type names that are already commonly used, like IO, that I don't want to replace or collide. Which one do you prefer? Any pros and cons for each? What's the best practice for this case? EDIT: Also would there be a performance difference between the two?

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  • Is select() Ok to implemnet single socket read/write timeout ?

    - by chmike
    I have an application processing network communication with blocking calls. Each thread manages a single connection. I've added a timeout on the read and write operation by using select prior to read or write on the socket. Select is known to be inefficient when dealing with large number of sockets. But is it ok, in term of performance to use it with a single socket or are there more efficient methods to add timeout support on single sockets calls ? The benefit of select is to be portable.

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  • A non-blocking server with java.io

    - by Jon
    Everybody knows that java IO is blocking, and java NIO is non-blocking. In IO you will have to use the thread per client pattern, in NIO you can use one thread for all clients. Now my question follows: is it possible to make a non-blocking design using only the Java IO api. (not NIO) I was thinking about a pattern like this (obviously very simplified); List<Socket> li; for (Socket s : li) { InputStream in = s.getInputStream(); byte[] data = in.available(); in.read(data); // processData(data); (decoding packets, encoding outgoing packets } Also note that the client will always be ready for reading data. What are your opinions on this? Will this be suitable for a server that should at least hold a few hundred of clients without major performance issues?

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  • Separate one-off code paths

    - by DeadMG
    I'm implementing an application with different code paths that shall be chosen once at startup and then fixed forevermore for that execution- for example, choosing D3D11 or D3D9 rendering path. Obviously I don't want to duplicate all my other code. Is run-time inheritance (no virtual inheritance) a fair solution? I don't want to waste a bunch of performance making virtual lookups when the type was fixed long ago. Not just that, but it makes me nervous that the functions can't be inlined and whether or not it affects RVO and NRVO and such. Am I just being over-concerned about this?

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