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  • Detecting/Repairing NSConnection failure

    - by anthony
    I would like to use NSConnection/NSDistributedObject for interprocess communication. I would like the client to be able to handle the case where the server is only occasionally reachable. How can I determine if sending a message to the NSConnection will fail or has failed? Currently if my server (the process that has vended the remote object) dies, the client will crash if it sends a selector to the remote object. Ideally I'd like to have a wrapper for the remote object that can lazily instantiate (or reinstantiate) the connection, and return a default value in the case where the connection could not be instantiated, or the connection has failed. I don't really know the correct way to do this using objective c. Here's some pseudocode representing this logic: if myConnection is null: instantiate myConnection if MyConnection is null: return defaultValue try return [myConnection someMethod] catch myConnection = null return defaultValue

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  • C# XPath id() not working?

    - by Iggyhopper
    I'm using C# and I'm stumped. Does it just not support id()? I have a large XML file, about 4-5 of them at ~400kb, so I need some speed and performance wherever I can get it. I use XmlDocument.SelectSingleNode("id('blahblahblah')") and it doesn't get the node by id. Am I going crazy or is it that C# XPath just doesn't support id()?

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  • Recommended textbook for machine-level programming?

    - by Norman Ramsey
    I'm looking at textbooks for an undergraduate course in machine-level programming. If the perfect book existed, this is what it would look like: Uses examples written in C or assembly language, or both. Covers machine-level operations such as two's-complement integer arithmetic, bitwise operations, and floating-point arithmetic. Explains how caches work and how they affect performance. Explains machine instructions or assembly instructions. Bonus if the example assembly language includes x86; triple bonus if it includes x86-64 (aka AMD64). Explains how C values and data structures are represented using hardware registers and memory. Explains how C control structures are translated into assembly language using conditional and unconditional branch instructions. Explains something about procedure calling conventions and how procedure calls are implemented at the machine level. Books I might be interested in would probably have the words "machine organization" or "computer architecture" in the title. Here are some books I'm considering but am not quite happy with: Computer Systems: A Programmer's Perspective by Randy Bryant and Dave O'Hallaron. This is quite a nice book, but it's a book for a broad, shallow course in systems programming, and it contains a great deal of material my students don't need. Also, it is just out in a second edition, which will make it expensive. Computer Organization and Design: The Hardware/Software Interface by Dave Patterson and John Hennessy. This is also a very nice book, but it contains way more information about how the hardware works than my students need. Also, the exercises look boring. Finally, it has a show-stopping bug: it is based very heavily on MIPS hardware and the use of a MIPS simulator. My students need to learn how to use DDD, and I can't see getting this to work on a simulator. Not to mention that I can't see them cross-compiling their code for the simulator, and so on and so forth. Another flaw is that the book mentions the x86 architecture only to sneer at it. I am entirely sympathetic to this point of view, but news flash! You guys lost! Write Great Code Vol I: Understanding the Machine by Randall Hyde. I haven't evaluated this book as thoroughly as the other two. It has a lot of what I need, but the translation from high-level language to assembler is deferred to Volume Two, which has mixed reviews. My students will be annoyed if I make them buy a two-volume series, even if the price of those two volumes is smaller than the price of other books. I would really welcome other suggestions of books that would help students in a class where they are to learn how C-language data structures and code are translated to machine-level data structures and code and where they learn how to think about performance, with an emphasis on the cache.

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  • Can we change dynamically the interval of "schedule" ?

    - by micropsari
    Hello, I'm making a game on iPhone using cocos2d, and I have a question. In my init method I'm doing this : [self schedule:@selector(newMonster:) interval:1]; It create a new monster every second. But I'd like that the interval change over time. For example : -The 10 first seconds of the game: a new monster appears every 1 second. -Then for 10 seconds: a new monster appears every 0.8 second. -And after every 0.5 second... How can I do that? Thanks !

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  • java.util.zip - ZipInputStream v.s. ZipFile

    - by lucho
    Hello, community! I have some general questions regarding the java.util.zip library. What we basically do is an import and an export of many small components. Previously these components were imported and exported using a single big file, e.g.: <component-type-a id="1"/> <component-type-a id="2"/> <component-type-a id="N"/> <component-type-b id="1"/> <component-type-b id="2"/> <component-type-b id="N"/> Please note that the order of the components during import is relevant. Now every component should occupy its own file which should be externally versioned, QA-ed, bla, bla. We decided that the output of our export should be a zip file (with all these files in) and the input of our import should be a similar zip file. We do not want to explode the zip in our system. We do not want opening separate streams for each of the small files. My current questions: Q1. May the ZipInputStream guarantee that the zip entries (the little files) will be read in the same order in which they were inserted by our export that uses ZipOutputStream? I assume reading is something like: ZipInputStream zis = new ZipInputStream(new BufferedInputStream(fis)); ZipEntry entry; while((entry = zis.getNextEntry()) != null) { //read from zis until available } I know that the central zip directory is put at the end of the zip file but nevertheless the file entries inside have sequential order. I also know that relying on the order is an ugly idea but I just want to have all the facts in mind. Q2. If I use ZipFile (which I prefer) what is the performance impact of calling getInputStream() hundreds of times? Will it be much slower than the ZipInputStream solution? The zip is opened only once and ZipFile is backed by RandomAccessFile - is this correct? I assume reading is something like: ZipFile zipfile = new ZipFile(argv[0]); Enumeration e = zipfile.entries();//TODO: assure the order of the entries while(e.hasMoreElements()) { entry = (ZipEntry) e.nextElement(); is = zipfile.getInputStream(entry)); } Q3. Are the input streams retrieved from the same ZipFile thread safe (e.g. may I read different entries in different threads simultaneously)? Any performance penalties? Thanks for your answers!

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  • Best approach to write huge xml data to file?

    - by Kayes
    Hi. I'm currently exporting a database table with huge data (100000+ records) into an xml file using XmlTextWriter class and I'm writing directly to a file on the physical drive. _XmlTextWriterObject = new XmlTextWriter(_xmlFilePath, null); While my code runs ok, my question is that is it the best approach? Or should I write the whole xml in memory stream first and then write the xml document in physical file from memory stream? And what are the effects on memory/ performance in both cases?

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  • Memory leak appears only when multiprocessing

    - by Sandro
    I am trying to use python's multiprocessing library to hopefully gain some performance. Specifically I am using its map function. Now, for some reason when I swap it out with its single threaded counterpart I don't get any memory leaks over time. But using the multiprocessing version of map causes my memory to go through the roof. For the record I am doing something which can easily hog up loads of memory, but what would the difference be between the two to cause such a stark difference?

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  • Using memcached as a session storage with CodeIgniter

    - by Alex N.
    I am researching possibilities of using memcached as a session storage for a system built on CodeIgniter. Has anybody done this before(that's probably a stupid question :) and if so what's your experience folks? Have you used any existing libraries/extensions? As far as performance improvement what have you seen? Any caveats?

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  • Postgres: Convert varchar to text

    - by williamjones
    I screwed up and created a column as a varchar(255) where that is no longer sufficient. I've read that varchar has no performance benefits over text on Postgres, and so would like to convert the varchar to a text column in a safe way that preserves the data. What's the best way for me to do this?

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  • Can I create a UITableViewController that inherits from a custom subclass of UIViewController?

    - by prendio2
    I have common functionality that I need to access from all screens of my app: a right bar button item and associated action. So as not to repeat the code I would like to set this up in a custom UIViewController and have all my view controllers inherit from it. - (void)viewDidLoad { UIBarButtonItem *rightBarButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemPlay target:self action:@selector(lightsCamera)]; self.navigationItem.rightBarButtonItem = rightBarButton; } - (void)lightsCamera { … } However, I have a number of UITableViewControllers however and I would like to know if it is possible for them to inherit the functionality too?

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  • WCF v.s. legacy ASP.Net Web Services

    - by George2
    Duplicate: although this is a good discussion, this is a duplicate of Web Services — WCF vs. Standard. Please consider adding any new information to the earlier question and closing this one. Could anyone recommend me some documents to describe why WCF is better than legacy ASP.Net web services? I am especially interested in performance and security. Thanks!

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  • Concise way to getattr() and use it if not None in Python

    - by MTsoul
    I am finding myself doing the following a bit too often: attr = getattr(obj, 'attr', None) if attr is not None: attr() # Do something, either attr(), or func(attr), or whatever else: # Do something else Is there a more pythonic way of writing that? Is this better? (At least not in performance, IMO.) try: obj.attr() # or whatever except AttributeError: # Do something else

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  • Why is this code's execution speed so different?

    - by Steve Watkins
    In Internet Explorer 7, this code executes consistently in 47 ms: function updateObjectValues() { $('.objects').html(12345678); // ~500 DIVs } however, this code executes consistently in 157 ms: function updateObjectValues() { $('.objects').html('12345678'); // ~500 DIVs } Passing a number is over 3x faster than a string. Why are these results so dramatically different? And, is there any way to help the performance of the string?

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  • what is the proper way to do logging in csv file?

    - by user2003548
    i want to log some information of every single request send to a busy http server in a formatted form,use log module would create some thing i don't want to: [I 131104 15:31:29 Sys:34] i think of csv format but i don't know how to customize it,and python got csv module,but read the manual import csv with open('some.csv', 'w', newline='') as f: writer = csv.writer(f) writer.writerows(someiterable) since it would open and close a file each time, i am afraid in this way would slow down the whole server performance, what could i do?

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  • keyDown works but i get beeps

    - by Oscar
    I just got my keydown method to work. But i get system beep everytime i press key. i have no idea whats wrong. Googled for hours and all people say is that if you have your keyDown method you should also implement the acceptsFirstResponder. did that to and it still doesn't work. #import <Cocoa/Cocoa.h> #import "PaddleView.h" #import "BallView.h" @interface GameController : NSView { PaddleView *leftPaddle; PaddleView *rightPaddle; BallView * ball; CGPoint ballVelocity; int gameState; int player1Score; int player2Score; } @property (retain) IBOutlet PaddleView *leftPaddle; @property (retain) IBOutlet PaddleView *rightPaddle; @property (retain) IBOutlet BallView *ball; - (void)reset:(BOOL)newGame; @end #import "GameController.h" #define GameStateRunning 1 #define GameStatePause 2 #define BallSpeedX 0.2 #define BallSpeedY 0.3 #define CompMoveSpeed 15 #define ScoreToWin 5 @implementation GameController @synthesize leftPaddle, rightPaddle, ball; - (id)initWithCoder:(NSCoder *)aDecoder { self = [super initWithCoder:aDecoder]; if(self) { gameState = GameStatePause; ballVelocity = CGPointMake(BallSpeedX, BallSpeedY); [NSTimer scheduledTimerWithTimeInterval:0.001 target:self selector:@selector(gameLoop) userInfo:nil repeats:YES]; } return self; } - (void)gameLoop { if(gameState == GameStateRunning) { [ball setFrameOrigin:CGPointMake(ball.frame.origin.x + ballVelocity.x, ball.frame.origin.y + ballVelocity.y)]; if(ball.frame.origin.x + 15 > self.frame.size.width || ball.frame.origin.x < 0) { ballVelocity.x =- ballVelocity.x; } if(ball.frame.origin.y + 35 > self.frame.size.height || ball.frame.origin.y < 0) { ballVelocity.y =- ballVelocity.y; } } if(CGRectIntersectsRect(ball.frame, leftPaddle.frame)) { if(ball.frame.origin.x > leftPaddle.frame.origin.x) { ballVelocity.x =- ballVelocity.x; } } if(CGRectIntersectsRect(ball.frame, rightPaddle.frame)) { if(ball.frame.origin.x +15 > rightPaddle.frame.origin.x) { ballVelocity.x =- ballVelocity.x; } } if(ball.frame.origin.x <= self.frame.size.width / 2) { if(ball.frame.origin.y < leftPaddle.frame.origin.y + 75 && leftPaddle.frame.origin.y > 0) { [leftPaddle setFrameOrigin:CGPointMake(leftPaddle.frame.origin.x, leftPaddle.frame.origin.y - CompMoveSpeed)]; } if(ball.frame.origin.y > leftPaddle.frame.origin.y +75 && leftPaddle.frame.origin.y < 700 - leftPaddle.frame.size.height ) { [leftPaddle setFrameOrigin:CGPointMake(leftPaddle.frame.origin.x, leftPaddle.frame.origin.y + CompMoveSpeed)]; } } if(ball.frame.origin.x <= 0) { player2Score++; [self reset:(player2Score >= ScoreToWin)]; } if(ball.frame.origin.x + 15 > self.frame.size.width) { player1Score++; [self reset:(player1Score >= ScoreToWin)]; } } - (void)reset:(BOOL)newGame { gameState = GameStatePause; [ball setFrameOrigin:CGPointMake((self.frame.size.width + 7.5) / 2, (self.frame.size.height + 7.5)/2)]; if(newGame) { if(player1Score > player2Score) { NSLog(@"Player 1 Wins!"); } else { NSLog(@"Player 2 Wins!"); } player1Score = 0; player2Score = 0; } else { NSLog(@"Press key to serve"); } NSLog(@"Player 1: %d",player1Score); NSLog(@"Player 2: %d",player2Score); } - (void)moveRightPaddleUp { if(rightPaddle.frame.origin.y < 700 - rightPaddle.frame.size.height) { [rightPaddle setFrameOrigin:CGPointMake(rightPaddle.frame.origin.x, rightPaddle.frame.origin.y + 20)]; } } - (void)moveRightPaddleDown { if(rightPaddle.frame.origin.y > 0) { [rightPaddle setFrameOrigin:CGPointMake(rightPaddle.frame.origin.x, rightPaddle.frame.origin.y - 20)]; } } - (BOOL)acceptsFirstResponder { return YES; } - (void)keyDown:(NSEvent *)theEvent { if ([theEvent modifierFlags] & NSNumericPadKeyMask) { NSString *theArrow = [theEvent charactersIgnoringModifiers]; unichar keyChar = 0; if ( [theArrow length] == 0 ) { return; // reject dead keys } if ( [theArrow length] == 1 ) { keyChar = [theArrow characterAtIndex:0]; if ( keyChar == NSLeftArrowFunctionKey ) { gameState = GameStateRunning; } if ( keyChar == NSRightArrowFunctionKey ) { } if ( keyChar == NSUpArrowFunctionKey ) { [self moveRightPaddleUp]; } if ( keyChar == NSDownArrowFunctionKey ) { [self moveRightPaddleDown]; } [super keyDown:theEvent]; } } else { [super keyDown:theEvent]; } } - (void)drawRect:(NSRect)dirtyRect { } - (void)dealloc { [ball release]; [rightPaddle release]; [leftPaddle release]; [super dealloc]; } @end

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  • What is the difference between these two different lines of Objective-C, and why does one work and n

    - by jrtc27
    If I try and release tempSeedsArray after seedsArray = tempSeedsArray , I get an EXEC_BAD_ACCESS, and Instruments shows that tempSeedsArray has been released twice. Here is my viewWillAppear method: - (void)viewWillAppear:(BOOL)animated { NSString *arrayFilePath = [[NSBundle mainBundle] pathForResource:@"SeedsArray" ofType:@"plist"]; NSLog(@"HIT!"); NSMutableArray *tempSeedsArray = [[NSMutableArray alloc] initWithContentsOfFile:arrayFilePath]; seedsArray = tempSeedsArray; NSLog(@"%u", [seedsArray retainCount]); [seedsArray sortUsingSelector:@selector(localizedCaseInsensitiveCompare:)]; [super viewWillAppear:animated]; } seedsArray is an NSMutableArray set as a nonatomic and a retain property, and is synthesised. However, if I change seedsArray = tempSeedsArray to self.seedsArray = tempSeedsArray (or [self seedsArray] = tempSeedsArray etc.), I can release tempSeedsArray. Could someone please explain simply to me why this is, as I am very confused! Thanks

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