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  • Implementing the procducer-consumer with .NET 4.0 new

    - by bitbonk
    With alle the new paralell programming features in .NET 4.0, what would be a a simple and fast way to implement the producer-consumer pattern (where at least one thread is producing and enqueuing task items and one other thread executes (dequeues) these tasks). Can we benfit from all these new APIs? What is your preferred implementation of this pattern?

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  • If I allocate memory in one thread in C++ can I de-allocate it in another

    - by Shane MacLaughlin
    If I allocate memory in one thread in C++ (either new or malloc) can I de-allocate it in another, or must both occur in the same thread? Ideally, I'd like to avoid this in the first place, but I'm curious to know is it legal, illegal or implementation dependent. Edit: The compilers I'm currently using include VS2003, VS2008 and Embedded C++ 4.0, targetting XP, Vista, Windows 7 and various flavours of Windows CE / PocketPC & Mobile. So basically all Microsoft but across an array of esoteric platforms.

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  • C# SQL: What is the best way to implement a dynamic table?

    - by SirMoreno
    I want to allow the user to add columns to a table in the UI. The UI: Columns Name:__ Columns Type: Number/String/Date My Question is how to build the SQL tables and C# objects so the implementation will be efficient and scalable. My thought is to build two SQL tables: TBL 1 - ColumnsDefinition: ColId, ColName, ColType[Text] TBL 2 - ColumnsValues: RowId, ColId, Value [Text] I want the solution to be efficient in DB space, and I want to allow the user to sort the dynamic columns. I work on .NET 3.5 MSSQL 2008. Thanks.

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  • approximating log10[x^k0 + k1]

    - by Yale Zhang
    Greetings. I'm trying to approximate the function Log10[x^k0 + k1], where .21 < k0 < 21, 0 < k1 < ~2000, and x is integer < 2^14. k0 & k1 are constant. For practical purposes, you can assume k0 = 2.12, k1 = 2660. The desired accuracy is 5*10^-4 relative error. This function is virtually identical to Log[x], except near 0, where it differs a lot. I already have came up with a SIMD implementation that is ~1.15x faster than a simple lookup table, but would like to improve it if possible, which I think is very hard due to lack of efficient instructions. My SIMD implementation uses 16bit fixed point arithmetic to evaluate a 3rd degree polynomial (I use least squares fit). The polynomial uses different coefficients for different input ranges. There are 8 ranges, and range i spans (64)2^i to (64)2^(i + 1). The rational behind this is the derivatives of Log[x] drop rapidly with x, meaning a polynomial will fit it more accurately since polynomials are an exact fit for functions that have a derivative of 0 beyond a certain order. SIMD table lookups are done very efficiently with a single _mm_shuffle_epi8(). I use SSE's float to int conversion to get the exponent and significand used for the fixed point approximation. I also software pipelined the loop to get ~1.25x speedup, so further code optimizations are probably unlikely. What I'm asking is if there's a more efficient approximation at a higher level? For example: Can this function be decomposed into functions with a limited domain like log2((2^x) * significand) = x + log2(significand) hence eliminating the need to deal with different ranges (table lookups). The main problem I think is adding the k1 term kills all those nice log properties that we know and love, making it not possible. Or is it? Iterative method? don't think so because the Newton method for log[x] is already a complicated expression Exploiting locality of neighboring pixels? - if the range of the 8 inputs fall in the same approximation range, then I can look up a single coefficient, instead of looking up separate coefficients for each element. Thus, I can use this as a fast common case, and use a slower, general code path when it isn't. But for my data, the range needs to be ~2000 before this property hold 70% of the time, which doesn't seem to make this method competitive. Please, give me some opinion, especially if you're an applied mathematician, even if you say it can't be done. Thanks.

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  • Saving data in custom class via AppDelegate

    - by redspike
    I can't seem to save data to a custom instance object in my AppDelegate. My custom class is very simple and is as follows: Person.h ... @interface Person : NSObject { int _age; } - (void) setAge: (int) age; - (int) age; @end Person.m #import "Person.h" @implementation Person - (void) setAge:(int) age { _age = age; } - (int) age { return _age; } @end I then create an instance of Person in the AppDelegate class: AppDelegate.h @class Person; @interface AccuTaxAppDelegate : NSObject <UIApplicationDelegate> { ... Person *person; } ... @property (nonatomic, retain) Person *person; @end AppDelegate.m ... #import "Person.h" @implementation AccuTaxAppDelegate ... @synthesize person; - (void)applicationDidFinishLaunching:(UIApplication *)application { // Override point for customization after app launch [window addSubview:[navigationController view]]; [window makeKeyAndVisible]; } - (void)applicationWillTerminate:(UIApplication *)application { // Save data if appropriate } #pragma mark - #pragma mark Memory management - (void)dealloc { [navigationController release]; [window release]; [person release]; [super dealloc]; } @end Finally, in my ViewController code I grab a handle on AppDelegate and then grab the person instance, but when I try to save the age it doesn't seem to work: MyViewController ... - (void)textFieldDidEndEditing:(UITextField *)textField { NSString *textAge = [textField text]; int age = [textAge intValue]; NSLog(@"Age from text field::%i", age); AppDelegate *appDelegate = (AppDelegate *)[UIApplication sharedApplication].delegate; Person *myPerson = (Person *)[appDelegate person]; NSLog(@"Age before setting: %i", [myPerson age]); [myPerson setAge:age]; NSLog(@"Age after setting: %i", [myPerson age]); [textAge release]; } ... The output of the above NSLogs are: [Session started at 2010-05-04 18:29:22 +0100.] 2010-05-04 18:29:28.260 AccuTax[16235:207] Age in text field:25 2010-05-04 18:29:28.262 AccuTax[16235:207] Age before setting: 0 2010-05-04 18:29:28.263 AccuTax[16235:207] Age after setting: 0 Any ideas why 'age' isn't being stored? I'm relatively new to Obj-C so please forgive me if I'm missing something very simple!

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  • Why does C# allow abstract class with no abstract members?

    - by fatcat1111
    The C# spec, section 10.1.1.1, states: An abstract class is permitted (but not required) to contain abstract members. This allows me to create classes like this: public abstract class A { public void Main() { // it's full of logic! } } This is really a concrete class; it's only abstract in so far as one can't instantiate it. If inheritors don't actually have to provide implementation, then why call it abstract?

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  • ModelMap usage in Spring

    - by Anna
    What are the benifits of using ModelMap instead of a simple Map in Spring MVC. I see in the code implementation that they put the datatype of the attribute added in the map as key instead to be made available on the form. Can anyone explain with an example.

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  • How do you hook a C++ compiled dll function to a sql database?

    - by Thomas
    I want to do something like: lastName SIMILARTO(lastName, 'Schwarseneger', 2) where lastName is the field in the database, 'Schwarseneger' is the value that lastName field is being compared to and 2 is the maximum number of characters (edit distance) that can differ between the lastName field, and the entered value. I can implement the SIMILARTO function in C++ using the Levenshtein distance (http://en.wikipedia.org/wiki/Levenshtein_distance), but how do hook the function in a dll to a mySQL implementation?

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  • Is it possible to use Boehm garbage collector only for the part of the program?

    - by bialix
    I've read article in LinuxJournal about Boehm-Demers-Weiser garbage collector library. I'm interesting to use it in my library instead of my own reference counting implementation. I have only one question: is it possible to use gc only for my shared library and still use malloc/free in the main application? I'm not quite understand how gc checks the heap so I'm worrying about performance of gc in that case and possible side effects.

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  • UINavigationBar Background Image Problem

    - by tobi
    i have set my navigationbar background with this code in my App delegate: @implementation UINavigationBar (UINavigationBarCategory) - (void)drawRect:(CGRect)rect { UIImage *backgroundImage = [UIImage imageNamed: @"Nav-rightpane.png"]; CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, self.frame.size.width, self.frame.size.height), backgroundImage.CGImage); } @end This works perfect but now i must change the background to the default at UIPopoverController. Any idea for this? Thanks

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  • Is there any open source AI engine?

    - by Andrei Savu
    I am searching for an open source AI engine implemented in C/C++, ActionScript or Java with no success. Do you know any open source implementation? Update: Thanks for answers! I had no idea how vast the AI field is. I am working on a sample application. I want to add intelligent behavior over a physics engine. I need some sort ai engine designed for games.

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  • Java Interger: what is faster comparison or subtraction?

    - by Vladimir
    I've found that java.lang.Ingteger implementation of compareTo method looks as follows: public int compareTo(Integer anotherInteger) { int thisVal = this.value; int anotherVal = anotherInteger.value; return (thisVal<anotherVal ? -1 : (thisVal==anotherVal ? 0 : 1)); } The question is why use comparison instead of subtraction: return thisVal - anotherVal;

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  • OpenID on stackoverlow.com [closed]

    - by Thomas Paine
    I'm trying to login to stackoverlow with openID and I am receiving an error from google saying "Request-URI Too Large". Is this an issue with google or an issue with stackoverlow's implementation of OpenID? My OpenID url: http://54.org/thomas The URL

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  • No pre-built ActionBar for Android pre-3.0?

    - by Ollie C
    I note the release a few days ago of the static library bringing fragments to Android versions prior to 3.0, but does this library include the ActionBar? I suspect not. I assume that for an app that will work on pre-3.0 versions, that it needs a hand-built ActionBar implementation for versions up to 2.3 and then to use the OS default ActionBar in v3.0? for some reason I assumed the library had ActionBar in it, but as I dig further I'm not finding any evidence of its presence.

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  • Delphi Unit local variables - how to make each instance unique?

    - by Justin
    Ok, this, I'm sure is something simple that is easy to do. The problem : I've inherited scary spaghetti code and am slowly trying to better it when new features need adding - generally when a refactor makes adding the new feature neater. I've got a bunch of code I'm packing into a single unit which, in different places in the application, controls the same physical thing in the outside world. The control appears in several places in the application and operates slightly differently in each instance. What I've done is to create a unit with all of the features I need which I can simply drop, as a frame, into each form that requires it. Each form then uses the unit's interface methods to customise the behaviour for each instance. The problem within the problem : In the unit in question (the frame) I have a variable declared in the IMPLEMENTATION section - local to the unit. I also have a procedure, declared in the TYPE section which takes an argument and assigns that argument to the local variable in question - each form passes a unique variable to each instance of the frame/unit. What I want it to do is for each instance of the frame to keep its own version of that variable, different from the others, and use that to define how it operates. What seems to be happening, however, is that all instances are using the same value, even if I explicitly pass each instance a different variable. ie: Unit FlexibleUnit; interface uses //the uses stuff type TFlexibleUnit=class(TFrame) //declarations including procedure makeThisInstanceX(passMeTheVar:integer); private // public // end; implementation uses //the uses var myLocalVar; procedure makeThisInstanceX(passMeTheVar:integer); begin myLocalVar:=passMeTheVar; end; //other procedures using myLocalVar //etc to the end; Now somewhere in another Form I've dropped this Frame onto the Design pane, sometimes two of these frames on one Form, and have it declared in the proper places, etc. Each is unique in that : ThisFlexibleUnit : TFlexibleUnit; ThatFlexibleUnit : TFlexibleUnit; and when I do a: ThisFlexibleUnit.makeThisInstanceX(var1); //want to behave in way "var1" ThatFlexibleUnit.makeThisInstanceX(var2); //want to behave in way "var2" it seems that they both share the same variable "myLocalVar". Am I doing this wrong, in principle? If this is the correct method then it's a matter of debugging what I have (which is too huge to post) but if this is not correct in principle then is there a way to do what I am suggesting? Thanks in advance, Stack Overflow - you guys (and gals!) are legendary.

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  • Learning to compile in xcode

    - by 00PS
    I have started using c++ extensively in school and now my programs are getting to the point where have more than 1 file (i.e. header, driver, implementation file). I don't know enough about software development to understand or get a grasp of how to setup the build process by looking at apple's guides. Could someone walk me through how to compile a simple c++ project with a header and two c++ files in xcode? Do I first need to make a makefile??

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  • Is a Multi-DAL Approach the way to go here?

    - by Krisc
    Working on the data access / model layer in this little MVC2 project and trying to think things out to future projects. I have a database with some basic tables and I have classes in the model layer that represent them. I obviously need something to connect the two. The easiest is to provide some sort of 'provider' that can run operations on the database and return objects. But this is for a website that would potentially be used "a lot" (I know, very general) so I want to cache results from the data layer and keep the cache updated as new data is generated. This question deals with how best to approach this problem of dual DALS. One that returns cached data when possible and goes to the data layer when there is a cache miss. But more importantly, how to integrate the core provider (thing that goes into database) with the caching layer so that it too can rely on cached objects rather than creating new ones. Right now I have the following interfaces: IDataProvider is used to reach the database. It doesn't concern itself with the meaning of the objects it produces, but simply the way to produce them. interface IDataProvider{ // Select, Update, Create, et cetera access IEnumerable<Entry> GetEntries(); Entry GetEntryById(int id); } IDataManager is a layer that sits on top of the IDataProvider layer and manages the cache interface IDataManager : IDataProvider{ void ClearCache(); } Note that in practice the IDataManager implementation will have useful helper functions to add objects to their related cache stores. (In the future I may define other functions on the interface) I guess what I am looking for is the best way to approach a loop back from the IDataProvider implementations so that they can access the cache. Or a different approach entirely may be in order? I am not very interested in 3rd party products at the moment as I am interested in the design of these things much more than this specific implementation. Edit: I realize the title may be a bit misleading. I apologize for that... not sure what to call this question.

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