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  • Why Swift is 100 times slower than C in this image processing test?

    - by xiaobai
    Like many other developers I have been very excited at the new Swift language from Apple. Apple has boasted its speed is faster than Objective C and can be used to write operating system. And from what I learned so far, it's a very type-safe language and able to have precisely control over the exact data type (like integer length). So it does look like having good potential handling performance critical tasks, like image processing, right? That's what I thought before I carried out a quick test. The result really surprised me. Here is a much simplified image alpha blending code snippet in C: test.c: #include <stdio.h> #include <stdint.h> #include <string.h> uint8_t pixels[640*480]; uint8_t alpha[640*480]; uint8_t blended[640*480]; void blend(uint8_t* px, uint8_t* al, uint8_t* result, int size) { for(int i=0; i<size; i++) { result[i] = (uint8_t)(((uint16_t)px[i]) *al[i] /255); } } int main(void) { memset(pixels, 128, 640*480); memset(alpha, 128, 640*480); memset(blended, 255, 640*480); // Test 10 frames for(int i=0; i<10; i++) { blend(pixels, alpha, blended, 640*480); } return 0; } I compiled it on my Macbook Air 2011 with the following command: gcc -O3 test.c -o test The 10 frame processing time is about 0.01s. In other words, it takes the C code 1ms to process one frame: $ time ./test real 0m0.010s user 0m0.006s sys 0m0.003s Then I have a Swift version of the same code: test.swift: let pixels = UInt8[](count: 640*480, repeatedValue: 128) let alpha = UInt8[](count: 640*480, repeatedValue: 128) let blended = UInt8[](count: 640*480, repeatedValue: 255) func blend(px: UInt8[], al: UInt8[], result: UInt8[], size: Int) { for(var i=0; i<size; i++) { var b = (UInt16)(px[i]) * (UInt16)(al[i]) result[i] = (UInt8)(b/255) } } for i in 0..10 { blend(pixels, alpha, blended, 640*480) } The build command line is: xcrun swift -O3 test.swift -o test Here I use the same O3 level optimization flag to make the comparison hopefully fair. However, the resulting speed is 100 time slower: $ time ./test real 0m1.172s user 0m1.146s sys 0m0.006s In other words, it takes Swift ~120ms to processing one frame which takes C just 1 ms. I also verified the memory initialization time in both test code are very small compared to the blend processing function time. What happened?

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  • What are the requirements for running .net application on windows ce5?

    - by citronas
    What are the requirements for running .net framework targeted application on Windows CE 5? When I try to start an application that I developed for Windows Mobile 6, I'm getting an error Cannot find 'Projectname' (or one of its components) Make sure the path and filename are correct and that all the required libraries are available My app is a simple hello world app. What could cause that such error message? Is there a way to dertimine which .net compact framework version is running on my system?

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  • C++ Newbie Question

    - by JavaMan
    I am from a Java background and is learning C++. I encountered the following C++ code: String source = String::New("'Hello' + ', World'"); As what I understand so far, this should be a call to static member function 'New' of class 'String'. But, I've searched through the whole header file defining 'String', there is not any static member named 'New' in the String class or its super classes. Is there any special meaning attached to String class or the New member function in C++?

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  • Ruby parse order

    - by bresc
    Hi, given this code: class Foo def bar return Bar.new end end class Bar ... end I get this error: NameError: uninitialized constant Bar This obviously works if I put Bar before Foo but that is not a real solution though. Any ideas on how to solve this without considering the order? Many thanks.

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  • generate PHP classes from XSD?

    - by Qwerty
    Is there in the world analogues of JavaBeans or JAXB for PHP? Is it possible to generate PHP classes from XML schema? It's common practice to publish API's as XSD schemas. Java and C# guys can get advantage of this by generating classes right from XSD. Is there same tool for PHP?

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  • What is the best way to go about obscuring Java code?

    - by Waltzy
    Well, I'm planning on releasing a Jar into the world but would prefer if the code was not readably available to anyone with a Java Decompiler as I want to control access to the program with usernames / auth codes etc. After some Googling I haven't found any software to do this for me, so I was wondering what steps to take from here; if anyone can point me at any software or information on methodologies of obscurification I would be grateful. Cheers again Stack Overflow.

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  • example for Singleton pattern

    - by JavaUser
    Hi, Please give me a real time example for singleton pattern . Different threads accessing a shared file is singleton or not ? Since each thread access the same instance of the file not individual instances of their own .

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  • Which conventions, events, etc. should I look into attending?

    - by perlox
    I am a student programmer and relatively new to the industry. Once I get out into the real world and have money to blow, which events/conventions/conferences/etc. should I look into attending? Which do you consider a must-attend-at-least-once-in-your-life-as-a-developer type of event? Just to clarify, any language, company, size, are acceptable. I'm mostly looking to generate a list of highly regarded conferences for a variety of different fields/interests.

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  • How is management of requirements for embedded software different from business applications ?

    - by Chakra
    For business software we usually document the business flow and functional and non functional specs as SRS, Use cases or user stories. One of the critical requirements is UI design which may get prototyped. How do people in the real world document and manage requirements for embedded software for automobile systems ? How are they different from the business applications in terms of requirements management ? Thanks, Chak.

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  • How to blit() in android?

    - by Lo'oris
    I'm used to handle graphics with old-school libraries (allegro, GD, pygame), where if I want to copy a part of a bitmap into another... I just use blit. I'm trying to figure out how to do that in android, and I got very confused. So... we have these Canvas that are write-only, and Bitmaps that are read-only? It seems too stupid to be real, there must be something I'm missing, but I really can't figure it out.

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  • Operation precedence on postgress

    - by user24691
    I have set new division on postgress pg_operator table because i want tath when is division by zero return 0. i have write this: create operator / ( procedure = zero_division, leftarg = double precision, rightarg = double precision); where zero_division is: CREATE OR REPLACE FUNCTION zero_division(double precision, double precision) RETURNS double precision AS 'select case when $2 = 0 then 0 else $1 / $2::real end;' LANGUAGE sql IMMUTABLE COST 100; when i run value/ 0 i get error of division.

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  • Cocos2d score resetting is messing up (long post warning)

    - by Jhon Doe
    The score is not resetting right at all,I am trying to make a high score counter where every time you passed previous high score it will update.However, right now it is resetting during the game. For example if I had high score of 2 during the game it will take 3 points just to put it up to 3 as high score instead of keep going up until it is game over. I have came to the conclusion that I need to reset it in gameoverlayer so it won't reset during game. I have been trying to to do this but no luck. hello world ./h #import "cocos2d.h" // HelloWorldLayer @interface HelloWorldLayer : CCLayer { int _score; int _oldScore; CCLabelTTF *_scoreLabel; } @property (nonatomic, assign) CCLabelTTF *scoreLabel; hello world init ./m _score = [[NSUserDefaults standardUserDefaults] integerForKey:@"score"]; _oldScore = -1; self.scoreLabel = [CCLabelTTF labelWithString:@"" dimensions:CGSizeMake(100, 50) alignment:UITextAlignmentRight fontName:@"Marker Felt" fontSize:32]; _scoreLabel.position = ccp(winSize.width - _scoreLabel.contentSize.width, _scoreLabel.contentSize.height); _scoreLabel.color = ccc3(255,0,0); [self addChild:_scoreLabel z:1]; hello world implement ./m - (void)update:(ccTime)dt { NSMutableArray *projectilesToDelete = [[NSMutableArray alloc] init]; CGRect projectileRect = CGRectMake( projectile.position.x - (projectile.contentSize.width/2), projectile.position.y - (projectile.contentSize.height/2), projectile.contentSize.width, projectile.contentSize.height); BOOL monsterHit = FALSE; NSMutableArray *targetsToDelete = [[NSMutableArray alloc] init]; for (CCSprite *target in _targets) { CGRect targetRect = CGRectMake( target.position.x - (target.contentSize.width/2), target.position.y - (target.contentSize.height/2), target.contentSize.width, target.contentSize.height); if (CGRectIntersectsRect(projectileRect, targetRect)) { CCParticleFire* explosion = [[CCParticleFire alloc] initWithTotalParticles:200]; explosion.texture =[[CCTextureCache sharedTextureCache] addImage:@"sun.png"]; explosion.autoRemoveOnFinish = YES; explosion.startSize = 20.0f; explosion.speed = 70.0f; explosion.anchorPoint = ccp(0.5f,0.5f); explosion.position = target.position; explosion.duration = 1.0f; [self addChild:explosion z:11]; [explosion release]; monsterHit = TRUE; Monster *monster = (Monster *)target; monster.hp--; if (monster.hp <= 0) { [targetsToDelete addObject:target]; [[SimpleAudioEngine sharedEngine] playEffect:@"splash.wav"]; _score ++; } break; } } for (CCSprite *target in targetsToDelete) { [_targets removeObject:target]; [self removeChild:target cleanup:YES]; } if (targetsToDelete.count > 0) { [ projectilesToDelete addObject:projectile]; } [targetsToDelete release]; if (_score > _oldScore) { _oldScore = _score; [_scoreLabel setString:[NSString stringWithFormat:@"score%d", _score]]; [[NSUserDefaults standardUserDefaults] setInteger:_oldScore forKey:@"score"]; _score = 0; } } - (void)update:(ccTime)dt { NSMutableArray *projectilesToDelete = [[NSMutableArray alloc] init]; CGRect projectileRect = CGRectMake( projectile.position.x - (projectile.contentSize.width/2), projectile.position.y - (projectile.contentSize.height/2), projectile.contentSize.width, projectile.contentSize.height); BOOL monsterHit = FALSE; NSMutableArray *targetsToDelete = [[NSMutableArray alloc] init]; for (CCSprite *target in _targets) { CGRect targetRect = CGRectMake( target.position.x - (target.contentSize.width/2), target.position.y - (target.contentSize.height/2), target.contentSize.width, target.contentSize.height); if (CGRectIntersectsRect(projectileRect, targetRect)) { CCParticleFire* explosion = [[CCParticleFire alloc] initWithTotalParticles:200]; explosion.texture =[[CCTextureCache sharedTextureCache] addImage:@"sun.png"]; explosion.autoRemoveOnFinish = YES; explosion.startSize = 20.0f; explosion.speed = 70.0f; explosion.anchorPoint = ccp(0.5f,0.5f); explosion.position = target.position; explosion.duration = 1.0f; [self addChild:explosion z:11]; [explosion release]; monsterHit = TRUE; Monster *monster = (Monster *)target; monster.hp--; if (monster.hp <= 0) { [targetsToDelete addObject:target]; [[SimpleAudioEngine sharedEngine] playEffect:@"splash.wav"]; _score ++; } break; } } for (CCSprite *target in targetsToDelete) { [_targets removeObject:target]; [self removeChild:target cleanup:YES]; } if (targetsToDelete.count > 0) { [projectilesToDelete addObject:projectile]; } [targetsToDelete release]; if (_score > _oldScore) { _oldScore = _score; [_scoreLabel setString:[NSString stringWithFormat:@"score%d", _score]]; [[NSUserDefaults standardUserDefaults] setInteger:_oldScore forKey:@"score"]; _score = 0; } The game overlayer .h file game over @interface GameOverLayer : CCLayerColor { CCLabelTTF *_label; CCSprite * background; int _score; int _oldScore; } @property (nonatomic, retain) CCLabelTTF *label; @end @interface GameOverScene : CCScene { GameOverLayer *_layer; } @property (nonatomic, retain) GameOverLayer *layer; @end .m file gameover #import "GameOverLayer.h" #import "HelloWorldLayer.h" #import "MainMenuScene.h" @implementation GameOverScene @synthesize layer = _layer; - (id)init { if ((self = [super init])) { self.layer = [GameOverLayer node]; [self addChild:_layer]; } return self; } - (void)dealloc { [_layer release]; _layer = nil; [super dealloc]; } @end @implementation GameOverLayer @synthesize label = _label; -(id) init { if( (self=[super initWithColor:ccc4(0,0,0,0)] )) { CGSize winSize = [[CCDirector sharedDirector] winSize]; self.label = [CCLabelTTF labelWithString:@"" fontName:@"Arial" fontSize:32]; _label.color = ccc3(225,0,0); _label.position = ccp(winSize.width/2, winSize.height/2); [self addChild:_label]; [self runAction:[CCSequence actions: [CCDelayTime actionWithDuration:3], [CCCallFunc actionWithTarget:self selector:@selector(gameOverDone)], nil]]; _score=0; }

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  • Is there a nice way of having static generic parameters is Java?

    - by Chris
    Hello, recently I'm writing some functions that I take from Haskell and translate into Java. One of the main problems I have is I cannot easily create a static property with a generic type. Let me explain by a little example... // An interface to implement functions public interface Func<P, R> { public R apply(P p); } // What I want to do... (incorrect in Java) public class ... { public static <T> Func<T, T> identity = new Func<T, T>() { public T apply(T p) { return p; } } } // What I do right now public class ... { private static Func<Object, Object> identity = new Func<Object, Object>() { public Object apply(Object p) { return p; } } @SuppressWarnings("unchecked") public static <T> Func<T, T> getIdentity() { return (Func<T, T>)identity; } } Are there any easier ways to do something like that? What kind of problems might arise if the syntax I used would be valid?

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  • Perl ENV variable contains newline and tab

    - by Michael
    Say I have an environment variable myvar myvar=\tapple\n when the following command will print out this variable perl -e 'print "$ENV{myvar}"' I will literally have \tapple\n, however, I want those control chars to be evaluated and not escaped. How would I achieve it? In the real world $ENV residing in substitution, but I hope the answer will cover that.

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  • How much memory is my iphone app using (from Simulator)

    - by Jonathan
    I know this has something to do with Instruments, but well it's kind of confusing and searching for Instruments on Google doesn't help much. I'd like to know how well my app runs, like how much memory it uses. I just don't know where to find something like: "As close as we can tell from the simulator you'll app will currently be using xx MBs of RAM on a real iphone device." I need help on how to get this information.

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  • URL redirection if wrong url

    - by xRobot
    I have this method in my book model: def get_absolute_url(self): return "/book/%s/%s/%i/%i/" % ( self.book_title, self.book_editor, self.book_pages, self.id) So the urls of each book are like this: example.com/book/the-bible/gesu-crist/938/12/ I want that if there is an error in the url, then I get redirected to the real url by using book.id in the end of the url. For example if I go to: example.com/book/A-bible/gesu-crist/938/12/ the I will get redirected to: example.com/book/the-bible/gesu-crist/938/12/ How can I do that ?

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  • Use of malloc() and free() in C++

    - by Matt H
    Is there any reason to use malloc and free in C++ over their more modern counterparts? Occasionally I see this, and I can't see why some people do it. Are there any advantages/disadvantage, or is there no real difference, except that it's just better to use C++ constructs in C++?

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  • iPhone. Particle system performance

    - by e40pud
    I try to draw rain and snow as particle system using Core Graphics. In simulator rendering proceeded fine but when I run my app on real device rendering is slow down. So, advise me please approaches to increase particle system drawing performance on iPhone. May be I should use OpenGL for this or CoreAnimation?

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  • Activity visible size

    - by Tsimmi
    Hi! How can I know the visible size of my activity? I'm trying to get the Activity real size, not the height and width from getHeight() and getWidth(), witch gives me the screen full size. Thanks

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