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  • Fast language for problem solving? [closed]

    - by Friend of Kim
    I learned PHP to make websites. After some years I've started using programming for solving what is difficult tasks for my level. Now I want to make a program that solves equations. (I want to write it myself, not use an API. Because I'm doing this for the sake of the challenge, not for the result..) Because of this, I'm going to learn a new and faster/better language. It's going to be C++, Java, Python or C#. What are the benefits of each language, and which language is best for speed compared to speed of writing and readability? Using C would be lightning fast, but the lack of OO is making for more complex code and reduces the readability, for example..

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  • accessing webpages from terminal

    - by August
    Using Ubuntu 12.04 . I know two methods to access the web-pages through terminal . They are lynx & elinkswhen i have tried to use them to access web-pages from terminal i didn't felt any kind of speed improvements . I am not sure whether its a usual thing or my speed (because its slow one ). so which way is the best to access the web-page terminal browsers or GUI browsers? and what else more i can get/lost from text terminals ?

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  • Particle system lifetimes in OpenGL ES 2

    - by user16547
    I don't know how to work with my particle's lifetimes. My design is simple: each particle has a position, a speed and a lifetime. At each frame, each particle should update its position like this: position.y = position.y + INCREMENT * speed.y However, I'm having difficulties in choosing my INCREMENT. If I set it to some sort of FRAME_COUNT, it looks fine until FRAME_COUNT has to be set back to 0. The effect will be that all particles start over at the same time, which I don't want to happen. I want my particles sort of live "independent" of each other. That's the reason I need a lifetime, but I don't know how to make use of it. I added a lifetime for each particle in the particle buffer, but I also need an individual increment that's updated on each frame, so that when PARTICLE_INCREMENT = PARTICLE_LIFETIME, each increment goes back to 0. How can I achieve something like that?

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  • Can my computer run Ubuntu? [duplicate]

    - by Harry B
    This question already has an answer here: How do I find out which version and derivative of Ubuntu is right for my hardware in terms of minimal system requirements? 2 answers Just want to check if my computer can run Ubuntu. It is an old IBM ThinkPad, so here are the basic stats I could find: IBM 28832ZU Processor Intel(R) Celeron(R) M processor 1300MHz Processor Speed 1.27 GHz Memory (RAM) 2048 MB Operating System Microsoft Windows XP Professional Operating System Version 5.1.2600 Intel Extreme Graphics 2M And here is some info pulled from the graphics panel NTEL(R) EXTREME GRAPHICS 2 FOR MOBILE REPORT Report Date: 06/28/2013 Report Time[hr:mm:ss]: 17:53:20 Driver Version: 6.14.10.3943 Operating System: Windows NT* 5.1.2600 Service Pack 2 Default Language: English DirectX* Version: 9.0 Physical Memory: 2038 MB Min. Graphics Memory: 8 MB Max. Graphics Memory: 64 MB Graphics Memory in use: 7 MB Processor: x86 family 6 Model 9 Stepping 5 Processor Speed: 1296 MHZ Device Revision: 2 Output Devices Connected to Graphics Accelerator * Active Notebook Displays:1

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  • Webcast: Extreme Analytics Without Limits

    - by Rob Reynolds
    Event Date: November 8, 2012 Event Time: 1 p.m. PT / 4 p.m. ET If you are a current Oracle Business Intelligence Applications customer, or thinking about implementing the BI Apps, please join us for this Webcast to learn how the combination of Oracle Exalytics In- Memory Machine and Oracle’s market leading analytic applications enables you to go beyond the traditional boundaries of data analysis and get the insight you need from massive volumes of data – all at the speed of thought. See how you can benefit from running your analytic applications on Oracle Exalytics to: Lower TCO Improve Operational Decision Making and Enhance Competitive Advantage Deliver Speed-of-thought Analysis – Anytime, Anywhere Click here to register.

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  • Generate Unique Abstract Backgrounds with Ablaze

    - by Jason Fitzpatrick
    If you want custom and unique backgrounds without having to code your own image-generating engine, Ablaze makes it simple (and fun) to create abstract images. You can customize a wide array of options in Ablaze including the base shape (ring, horizontal line, or random), number of particles, distance each particle travels, and the speed (if you increase the speed range you get more distinct lines and if you decrease it you get smoother smokier shapes). You can also seed the design with a color palette pulled from any image you provide (the sample above was seeded with a Wonder Woman comic panel). Tweak and reset the pattern generation as much as you want; when you create an abstract image worthy of your desktop just click the save button to grab a copy of it in PNG format. Ablaze [via Flowing Data] How To Create a Customized Windows 7 Installation Disc With Integrated Updates How to Get Pro Features in Windows Home Versions with Third Party Tools HTG Explains: Is ReadyBoost Worth Using?

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  • Object array updates one instance repeatedly [on hold]

    - by MGN001
    I'm making a 2D shooter, and the player object holds an array of bullets that represent how many shots the player can have on screen at once. At least, this is what I'm trying for. What's happening is that each time any of the objects in the array is called, it seems to update a single object in memory. So, if I fire and then fire again, the object "starts over" from where I shot from and moves twice as fast. I've spent weeks trying to fix this and I've managed nothing. Hopefully another pair of eyes will see something I've missed. Player.cpp #include "Player.h" const int startLives = 3; const int maxHealth = 2; const float speed = 1; const int maxVelocity = 500; const int topBound = WINDOW_HEIGHT / 5 * 3; const int slowRate = 500; const int accRate = 1000; const int maxBullets = 5; const float spriteWidth = 99; const float spriteHeight = 75; const Vector2f startPosition = { (WINDOW_WIDTH / 2) - (spriteWidth / 2), (WINDOW_HEIGHT / 4 * 3) - (spriteHeight / 2) }; Bullet bullets[maxBullets]; Bullet * bulletPointers[maxBullets]; SDL_Texture * playerHealthy; SDL_Texture * playerDamaged; SDL_Texture * currentSprite; SDL_Rect * rect; Vector2f position; Vector2f velocity; int Health; int Lives; Player::Player() { rect = new SDL_Rect(); } Player::~Player() { SDL_DestroyTexture(playerHealthy); SDL_DestroyTexture(playerDamaged); SDL_DestroyTexture(currentSprite); rect = NULL; } void Player::Initialize(SDL_Renderer * renderer) { SDL_Surface * temp; temp = IMG_Load(".\\Sprites\\player.png"); if (temp == NULL) { printf("Initialization Error: %s\n", IMG_GetError()); exit(PLAYER_INITIALIZATION_ERROR); } playerHealthy = SDL_CreateTextureFromSurface(renderer, temp); temp = IMG_Load(".\\Sprites\\playerDamaged.png"); if (temp == NULL) { printf("Initialization Error: %s\n", IMG_GetError()); exit(PLAYER_INITIALIZATION_ERROR); } playerDamaged = SDL_CreateTextureFromSurface(renderer, temp); temp = IMG_Load(".\\Sprites\\laserGreen.png"); if (temp == NULL) { printf("Initialization Error: %s\n", IMG_GetError()); exit(PLAYER_INITIALIZATION_ERROR); } SDL_Texture * bullet = SDL_CreateTextureFromSurface(renderer, temp); temp = IMG_Load(".\\Sprites\\laserGreenShot.png"); if (temp == NULL) { printf("Initialization Error: %s\n", IMG_GetError()); exit(PLAYER_INITIALIZATION_ERROR); } SDL_Texture * explosion = SDL_CreateTextureFromSurface(renderer, temp); for (int i = 0; i < maxBullets; i++) { bullets[i].Initialize(renderer, bullet, explosion); bulletPointers[i] = NULL; } temp = NULL; rect->h = spriteHeight; rect->w = spriteWidth; Reset(); } void Player::Update(Input input, float deltaTime) { if (abs(velocity.x) < slowRate * deltaTime) { velocity.x = 0; } else if (velocity.x > 0) { velocity.x -= slowRate * deltaTime; } else if (velocity.x < 0) { velocity.x += slowRate * deltaTime; } if (abs(velocity.y) < slowRate * deltaTime) { velocity.y = 0; } if (velocity.y > 0) { velocity.y -= slowRate * deltaTime; } else if (velocity.y < 0) { velocity.y += slowRate * deltaTime; } if (Health <= 0) { --Lives; Spawn(); } velocity.x += UnitVector(input.InputNew.movement).x * accRate * deltaTime; velocity.y += UnitVector(input.InputNew.movement).y * accRate * deltaTime; if (Magnitude(velocity) > maxVelocity) { velocity.x = UnitVector(velocity).x * maxVelocity; velocity.y = UnitVector(velocity).y * maxVelocity; } position.x += velocity.x * deltaTime * speed; position.y += velocity.y * deltaTime * speed; if (input.InputNew.JumpLeft && !input.InputOld.JumpLeft) { position.x -= spriteWidth; } if (input.InputNew.JumpRight && !input.InputOld.JumpRight) { position.x += spriteWidth; } Boundaries(); rect->x = position.x; rect->y = position.y; if (input.InputNew.Fire && !input.InputOld.Fire) { Fire(); } for (int i = 0; i < maxBullets; ++i) { if (bulletPointers[i] != NULL) { bullets[i].Update(deltaTime); if (bullets[i].getPosition().y < -33) { bulletPointers[i] = NULL; } } } } void Player::Draw(SDL_Renderer * renderer) { for (int i = 0; i < maxBullets; ++i) { if (bulletPointers[i] != NULL) { bullets[i].Draw(renderer); } } SDL_RenderCopy(renderer, currentSprite, NULL, rect); } void Player::Spawn() { position = startPosition; Health = maxHealth; currentSprite = playerHealthy; rect->x = position.x; rect->y = position.y; } void Player::Boundaries() { if (position.x < 0) { position.x = 0; velocity.x *= -1; } else if (position.x > WINDOW_WIDTH - spriteWidth) { position.x = WINDOW_WIDTH - spriteWidth; velocity.x *= -1; } if (position.y < topBound) { position.y = topBound; velocity.y *= -1; } else if (position.y > WINDOW_HEIGHT - spriteHeight) { position.y = WINDOW_HEIGHT - spriteHeight; velocity.y *= -1; } } int Player::getLives() { return Lives; } void Player::Reset() { Lives = startLives; Spawn(); } void Player::Fire() { for (int i = 0; i < maxBullets; ++i) { if (bulletPointers[i] == NULL) { bulletPointers[i] = &bullets[i]; bullets[i].Fire(position,velocity.x/2); break; } } } Bullet.cpp #include "Bullet.h" const int speed = 500; Vector2f bulletVelocity; float ExplosionMax = 0.5f; float ExplosionTimer; const Vector2f fireOffset = { 45.5f, 10.0f }; const Vector2f explosionOffset = { 23.5f, -27.0f }; const Vector2i bulletSize = { 9, 33 }; const Vector2i explosionSize = { 56, 54 }; Vector2f bulletPosition; SDL_Texture * bulletSprite; SDL_Texture * explosionSprite; SDL_Texture * bulletCurrentSprite; SDL_Rect * bulletRect; Bullet::Bullet() { } Bullet::~Bullet() { } void Bullet::Initialize(SDL_Renderer * renderer, SDL_Texture * bullet, SDL_Texture * explosion) { bulletSprite = bullet; explosionSprite = explosion; bulletRect = new SDL_Rect(); } void Bullet::Update(float deltaTime) { bulletPosition.y -= bulletVelocity.y * deltaTime; bulletPosition.x += bulletVelocity.x * deltaTime; bulletRect->x = static_cast<int>(bulletPosition.x); bulletRect->y = static_cast<int>(bulletPosition.y); } void Bullet::Draw(SDL_Renderer * renderer) { SDL_RenderCopy(renderer, bulletCurrentSprite, NULL, bulletRect); } void Bullet::Fire(Vector2f pos, float xSpeed) { bulletPosition.x = pos.x + fireOffset.x; bulletPosition.y = pos.y + fireOffset.y; bulletVelocity.x = xSpeed; bulletVelocity.y = speed; bulletCurrentSprite = bulletSprite; bulletRect->h = bulletSize.y; bulletRect->w = bulletSize.x; bulletRect->x = static_cast<int>(bulletPosition.x); bulletRect->y = static_cast<int>(bulletPosition.y); } Vector2f Bullet::getPosition() { return bulletPosition; } void Bullet::Hit() { bulletCurrentSprite = explosionSprite; bulletVelocity = { 0.0f, 0.0f }; ExplosionTimer = ExplosionMax; bulletPosition.x += explosionOffset.x; bulletPosition.y += explosionOffset.y; bulletRect->w = explosionSize.x; bulletRect->h = explosionSize.y; }

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  • How to calculate shot angle and velocity to hit a moving target?

    - by Guen
    I am developing a 2D Android game and I am making an aiming algorithm for AI projectiles to hit enemies either following a path, or free moving. At the moment it just calculates where the target will be after a distance and fires a projectile to meet it at that distance. Of course this means varying the projectile speed to meet the target. Does anyone have any tips for a simple-ish algorithm (optimal-ish) to calculate when the projectile needs to fire and where it needs to aim if it can only travel at a constant velocity? Say the projectile goes twice the speed of the target? The only way I can think of involves searching and seems quite large.

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  • Monday at Oracle OpenWorld 2012 - Must See Session: “Using the Right Tools, Techniques, and Technologies for Integration Projects”

    - by Lionel Dubreuil
    Don’t miss this “CON8669 - Using the Right Tools, Techniques, and Technologies for Integration Projects“ session with Timothy Hall - Sr. Director, Oracle: Date: Monday, Oct 1, Time: 3:15 PM - 4:15 PM Location: Moscone South - 308 Every integration project brings its own unique set of challenges. There are many tools and techniques to choose from. How do you ensure that you have a means of consistently and repeatedly making decisions about which tools, techniques, and technologies are used? In working with many customers around the globe, Oracle has developed a set of criteria to help evaluate a variety of common integration questions. This session explores these criteria and how they have been further organized into decision trees that offer a repeatable means for ensuring that project teams are given the same guidance from project to project. Using these techniques, the presentation shows how you can reduce risk and speed productivity for your projects Objectives for this session are to: Discuss common questions that arise at the start of integration projects Review various decision criteria and approaches for getting to a consistent set of answers Explore how these techniques can be used to reduce risk and speed productivity

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  • Monday at Oracle OpenWorld 2012 - Must See Session: “Using the Right Tools, Techniques, and Technologies for Integration Projects”

    - by Lionel Dubreuil
    Don’t miss this “CON8669 - Using the Right Tools, Techniques, and Technologies for Integration Projects“ session with Timothy Hall - Sr. Director, Oracle: Date: Monday, Oct 1, Time: 3:15 PM - 4:15 PM Location: Moscone South - 308 Every integration project brings its own unique set of challenges. There are many tools and techniques to choose from. How do you ensure that you have a means of consistently and repeatedly making decisions about which tools, techniques, and technologies are used? In working with many customers around the globe, Oracle has developed a set of criteria to help evaluate a variety of common integration questions. This session explores these criteria and how they have been further organized into decision trees that offer a repeatable means for ensuring that project teams are given the same guidance from project to project. Using these techniques, the presentation shows how you can reduce risk and speed productivity for your projects Objectives for this session are to: Discuss common questions that arise at the start of integration projects Review various decision criteria and approaches for getting to a consistent set of answers Explore how these techniques can be used to reduce risk and speed productivity

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  • Does low latency code sometimes have to be "ugly"?

    - by user997112
    (This is mainly aimed at those who have specific knowledge of low latency systems, to avoid people just answering with unsubstantiated opinions). Do you feel there is a trade-off between writing "nice" object orientated code and writing very fast low latency code? For instance, avoiding virtual functions in C++/the overhead of polymorphism etc- re-writing code which looks nasty, but is very fast etc? It stands to reason- who cares if it looks ugly (so long as its maintainable)- if you need speed, you need speed? I would be interested to hear from people who have worked in such areas.

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  • car race game collision condition.

    - by ashok patidar
    in this how can rotate car when it goes to collied with the track side. package { import flash.display.MovieClip; import flash.events.Event; import flash.events.KeyboardEvent; import flash.text.TextField; import flash.ui.Keyboard; import Math; /** * ... * @author Ashok */ public class F1race extends MovieClip { public var increment:Number = 0; //amount the car moves each frame public var posNeg:Number = 1; public var acceleration:Number = .05; //acceleration of the car, or the amount increment gets increased by. public var speed:Number = 0; //the speed of the car that will be displayed on screen public var maxSpeed:Number = 100; public var keyLeftPressed:Boolean; public var keyRightPressed:Boolean; public var keyUpPressed:Boolean; public var keyDownPressed:Boolean; public var spedometer:TextField = new TextField(); public var carRotation:Number ; public var txt_hit:TextField = new TextField(); public function F1race() { carRotation = carMC.rotation; trace(carMC.rotation); //addChild(spedometer); //spedometer.x = 0; //spedometer.y = 0; addChild(txt_hit); txt_hit.x = 0; txt_hit.y = 100; //rotation of the car addEventListener(Event.ENTER_FRAME, onEnterFrameFunction); stage.addEventListener(KeyboardEvent.KEY_DOWN, keyPressed,false); stage.addEventListener(KeyboardEvent.KEY_UP, keyReleased,false); carMC.addEventListener(Event.ENTER_FRAME, carOver_road) } public function carOver_road(event:Event):void { //trace(texture.hitTestPoint(carMC.x,carMC.y,true),"--"); /* if(!texture.hitTestPoint(carMC.x,carMC.y,true)) { txt_hit.text = "WRONG WAY"; if(increment!=0) { increment=1; } } else { txt_hit.text = ""; //increment++; }*/ if (roadless.hitTestPoint(carMC.x - carMC.width / 2, carMC.y,true)) { trace("left Hit" + carMC.rotation); //acceleration = .005; //if(carMC.rotation>90 || carMC.rotation>90 //carMC.rotation += 2; if ((carMC.rotation >= 90) && (carMC.rotation <= 180)) { carMC.rotation += 3; carMC.x += 3; } if ((carMC.rotation <= -90) && (carMC.rotation >= -180)) { carMC.rotation += 3; texture.y -= 3; } if ((carMC.rotation > -90) && (carMC.rotation <= -1)) { carMC.rotation += 3; texture.y -= 3; } if(increment<0) { increment += 1.5 * acceleration; } if(increment>0) { increment -= 1.5 * acceleration; } } if (roadless.hitTestPoint(carMC.x + carMC.width / 2, carMC.y,true)) { trace("left right"); //carMC.rotation -= 2; if(increment<0) { increment += 1.5 * acceleration; } if(increment>0) { increment -= 1.5 * acceleration; } } if (roadless.hitTestPoint(carMC.x, carMC.y- carMC.height / 2,true)) { trace("left right"); //carMC.rotation -= 2; if(increment<0) { increment += 1.5 * acceleration; } if(increment>0) { increment -= 1.5 * acceleration; } } if (roadless.hitTestPoint(carMC.x, carMC.y+ carMC.height / 2,true)) { trace("left right"); //carMC.rotation -= 2; if(increment<0) { increment += 1.5 * acceleration; } if(increment>0) { increment -= 1.5 * acceleration; } } if ((!roadless.hitTestPoint(carMC.x - carMC.width / 2, carMC.y, true)) && (!roadless.hitTestPoint(carMC.x, carMC.y- carMC.height / 2,true)) && (!roadless.hitTestPoint(carMC.x, carMC.y+ carMC.height / 2,true)) && (!roadless.hitTestPoint(carMC.x, carMC.y+ carMC.height / 2,true))) { //acceleration = .05; } } public function onEnterFrameFunction(events:Event):void { speed = Math.round((increment) * 5); spedometer.text = String(speed); if ((carMC.rotation < 180)&&(carMC.rotation >= 0)){ carRotation = carMC.rotation; posNeg = 1; } if ((carMC.rotation < 0)&&(carMC.rotation > -180)){ carRotation = -1 * carMC.rotation; posNeg = -1; } if (keyRightPressed) { carMC.rotation += .5 * increment; carMC.LWheel.rotation = 8; carMC.RWheel.rotation = 8; steering.gotoAndStop(2); } if (keyLeftPressed) { carMC.rotation -= .5 * increment; carMC.LWheel.rotation = -8; carMC.RWheel.rotation = -8; steering.gotoAndStop(3); } if (keyDownPressed) { steering.gotoAndStop(1); carMC.LWheel.rotation = 0; carMC.RWheel.rotation = 0; increment -= 0.5 * acceleration; texture.y -= ((90 - carRotation) / 90) * increment; roadless.y = texture.y; if (((carMC.rotation > 90)&&(carMC.rotation < 180))||((carMC.rotation < -90)&&(carMC.rotation > -180))) { texture.x += posNeg * (((((1 - (carRotation / 360)) * 360) - 180) / 90) * increment); roadless.x = texture.x; } if (((carMC.rotation <= 90)&&(carMC.rotation > 0))||((carMC.rotation >= -90)&&(carMC.rotation < -1))) { texture.x += posNeg * ((carRotation) / 90) * increment; roadless.x = texture.x; } increment -= 1 * acceleration; if ((Math.abs(speed)) < (Math.abs(maxSpeed))) { increment += acceleration; } if ((Math.abs(speed)) == (Math.abs(maxSpeed))) { trace("hello"); } } if (keyUpPressed) { steering.gotoAndStop(1); carMC.LWheel.rotation = 0; carMC.RWheel.rotation = 0; //trace(carMC.rotation); texture.y -= ((90 - carRotation) / 90) * increment; roadless.y = texture.y; if (((carMC.rotation > 90)&&(carMC.rotation < 180))||((carMC.rotation < -90)&&(carMC.rotation > -180))) { texture.x += posNeg * (((((1 - (carRotation / 360)) * 360) - 180) / 90) * increment); roadless.x = texture.x; } if (((carMC.rotation <= 90)&&(carMC.rotation > 0))||((carMC.rotation >= -90)&&(carMC.rotation < -1))) { texture.x += posNeg * ((carRotation) / 90) * increment; roadless.x = texture.x; } increment += 1 * acceleration; if ((Math.abs(speed)) < (Math.abs(maxSpeed))) { increment += acceleration; } } if ((!keyUpPressed) && (!keyDownPressed)){ /*if (increment > 0 && (!keyUpPressed)&& (!keyDownPressed)) { //texture.y -= ((90-carRotation)/90)*increment; increment -= 1.5 * acceleration; } if((increment==0)&&(!keyUpPressed)&& (!keyDownPressed)) { increment = 0; } if((increment<0)&&(!keyUpPressed)&& (!keyDownPressed)) { increment += 1.5 * acceleration; }*/ if (increment > 0) { increment -= 1.5 * acceleration; texture.y -= ((90 - carRotation) / 90) * increment; roadless.y = texture.y; if (((carMC.rotation > 90)&&(carMC.rotation < 180))||((carMC.rotation < -90)&&(carMC.rotation > -180))) { texture.x += posNeg * (((((1 - (carRotation / 360)) * 360) - 180) / 90) * increment); roadless.x = texture.x; } if (((carMC.rotation <= 90)&&(carMC.rotation > 0))||((carMC.rotation >= -90)&&(carMC.rotation < -1))) { texture.x += posNeg * ((carRotation) / 90) * increment; roadless.x = texture.x; } } if (increment == 0) { increment = 0; } if (increment < 0) { increment += 1.5 * acceleration; texture.y -= ((90 - carRotation) / 90) * increment; roadless.y = texture.y; if (((carMC.rotation > 90)&&(carMC.rotation < 180))||((carMC.rotation < -90)&&(carMC.rotation > -180))) { texture.x += posNeg * (((((1 - (carRotation / 360)) * 360) - 180) / 90) * increment); roadless.x = texture.x; } if (((carMC.rotation <= 90)&&(carMC.rotation > 0))||((carMC.rotation >= -90)&&(carMC.rotation < -1))) { texture.x += posNeg * ((carRotation) / 90) * increment; roadless.x = texture.x; } } } } public function keyPressed(event:KeyboardEvent):void { trace("keyPressed"); if (event.keyCode == Keyboard.LEFT) { keyLeftPressed = true; } if (event.keyCode == Keyboard.RIGHT) { keyRightPressed = true; } if (event.keyCode == Keyboard.UP) { keyUpPressed = true; } if (event.keyCode == Keyboard.DOWN) { keyDownPressed = true; } } public function keyReleased(event:KeyboardEvent):void { trace("keyReleased..."); //increment -= 1.5 * acceleration; //increment--; if (event.keyCode == Keyboard.LEFT) { keyLeftPressed = false; } if (event.keyCode == Keyboard.RIGHT) { keyRightPressed = false; } if (event.keyCode == Keyboard.UP) { keyUpPressed = false; } if (event.keyCode == Keyboard.DOWN) { keyDownPressed = false; } } } }

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  • How many bits for sequence number using Go-Back-N protocol.

    - by Mike
    Hi Everyone, I'm a regular over at Stack Overflow (Software developer) that is trying to get through a networking course. I got a homework problem I'd like to have a sanity check on. Here is what I got. Q: A 3000-km-long T1 trunk is used to transmit 64-byte frames using Go-Back-N protocol. If the propagation speed is 6 microseconds/km, how many bits should the sequence numbers be? My Answer: For this questions what we need to do is lay the base knowledge. What we are trying to find is the size of the largest sequence number we should us using Go-Back-N. To figure this out we need to figure out how many packets can fit into our link at a time and then subtract one from that number. This will ensure that we never have two packets with the same sequence number at the same time in the link. Length of link: 3,000km Speed: 6 microseconds / km Frame size: 64 bytes T1 transmission speed: 1544kb/s (http://ckp.made-it.com/t1234.html) Propagation time = 6 microseconds / km * 3000 km = 18,000 microseconds (18ms). Convert 1544kb to bytes = 1544 * 1024 = 1581056 bytes Transmission time = 64 bytes / 1581056bytes / second = 0.000040479 seconds (0.4ms) So then if we take the 18ms propagation time and divide it by the 0.4ms transmission time we will see that we are going to be able to stuff ( 18 / 0.4) 45 packets into the link at a time. That means that our sequence number should be 2 ^ 45 bits long! Am I going in the right direction with this? Thanks, Mike

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  • Alternative to robocopy /MIR

    - by Robin Day
    We run a number of web apps that store a lot of local data in small xml files. One part of our backup / recovery strategy is to produce a local mirror of the file system via a VPN to the hosting centre. The VPN connection is only via a 12Mbps ADSL and whilst there are a lot of files and directories, the actual number of files that changes is quite small. Although the bandwidth is probably an issue, I'm seeing results such as the output below. The robocopy /MIR took 5 hours to run yet only 30 mins to actually perform the copy. Does anyone have any suggestions as to ways to improve this. The 5 hours is now bordering on too slow and if we can't find a way to speed this up then we're going to have to come up with a completely different solution. Total Copied Skipped Mismatch FAILED Extras Dirs : 17625 6618 11007 0 0 0 Files : 1112430 1223 1111207 0 0 0 Bytes : 57.451 g 192.25 m 57.263 g 0 0 0 Times : 5:01:23 0:35:55 0:00:00 4:25:27 Speed : 93509 Bytes/sec. Speed : 5.350 MegaBytes/min. Ended : Fri Apr 16 05:54:23 2010

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  • iPod touch has extremely slow wifi, drops packets - only on my router

    - by mskfisher
    I just purchased an iPod Touch. I am having a lot of trouble with its speeds on my Tenda W311R, but it has no speed problems on my neighbor's Netgear router. It will connect and authenticate to my network, but the Speed Test app from speedtest.net shows rates near 20-50 kbps. If I run the speed test immediately after powering the iPod on, it will get speeds of 10-20 Mbps, like it should - but the speeds slow down to the kbps range abut 10-15 seconds afterward. I get the same behavior with encryption and without encryption, and regardless of N, G, or B compatibility settings in the router. I've tried rebooting the iPod and resetting the network settings, but it's still slow. I've tried pinging the iPod from another computer, and it shows about 40% packet loss: $ ping 192.168.0.111 PING 192.168.0.111 (192.168.0.111): 56 data bytes 64 bytes from 192.168.0.111: icmp_seq=0 ttl=64 time=14.188 ms 64 bytes from 192.168.0.111: icmp_seq=1 ttl=64 time=11.556 ms 64 bytes from 192.168.0.111: icmp_seq=2 ttl=64 time=5.675 ms 64 bytes from 192.168.0.111: icmp_seq=3 ttl=64 time=5.721 ms Request timeout for icmp_seq 4 64 bytes from 192.168.0.111: icmp_seq=5 ttl=64 time=6.491 ms Request timeout for icmp_seq 6 64 bytes from 192.168.0.111: icmp_seq=7 ttl=64 time=8.065 ms Request timeout for icmp_seq 8 Request timeout for icmp_seq 9 Request timeout for icmp_seq 10 64 bytes from 192.168.0.111: icmp_seq=11 ttl=64 time=9.605 ms Signal strength is good - I'm never more than 20 feet from my access point, and it exhibits the same behavior if I'm standing next to the router. It works just well enough to receive text, but videos don't work at all. App downloads are hit and miss. I've tweaked just about all of the settings I can see to tweak, and I'm at a loss. I have also been searching Google for the past three days, all to no avail. Any suggestions?

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  • Max. Bandwidth Cannot be Reached

    - by Poyraz Sagtekin
    I have a question regarding the bandwidth usage. I don't think it's a very technical question but I really want to know the reason behind the problem. I'm having my education in one of my university's campuses. There is a 200mbps bandwidth availability for approx. 2100 students. Our main campus has 25,000 students and 2gbps bandwidth and there is no problem with the internet connection speed in main campus. However, in my campus, we are having difficulties with the internet connection speed. I went to IT department of my university and they've showed me some graphics about the bandwidth usage. The usage of the bandwidth has never reached 200mbps and it generally is around 130-140mbps. According to this information, maximum bandwidth is never made by the users but the browsing speed is not very convincing. What can be the problem? Maybe this is a silly question but I really want to know the reason. They told me that they've reached 180mbps before.

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  • How to wire 20 computers and 20 phones and 1 server into LAN?

    - by John Smith
    I have currently 3 switches Two Netgear JFS524 with 24 slots, One Belkin with 16 slots. Server DSL Internet Router. Main question is how to connect switches together, two Netgear's are next to each other, yet one is about 100 feet away and holds about 5 computer and 5 phones. If i connect them with only 1 wire will that limit bandwidth? e.g. all 23 computers will be limited to speed of one CAT5e cable? If i connect switches with 2 cables will this give speed boost? What's the ideal scenario should i just move the third switch next to other two? Will the speed of computer connected to white switch be same as computer connected to top switch? Will moving white switch right next top switch and having 16 wires comming 100 feet instead of 1 wire comming 100 feet make it faster? EDIT 1: I actually have NETGEAR ProSafe GS105 Gigabit switch its only has 4 ports in it though, you think i can have use of it in current setup? Like connect all 3 switches and server into it and keep internet router and phone server on one of the slower switches EDIT 2: Everyone mention gigabit switches, but will they do any difference with 10/100 network cards? I then have to use gigabit cards in every computer too? I could in server perhaps, but users will be 10/100

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  • USB keyboard stopped working in Ubuntu with error -71

    - by tapan
    I have a usb keyboard which was working perfectly till now (about a year since i have been regularly using ubuntu). It suddenly stopped working. It stopped working when I connected a USB HDD. Now the keyboard works randomly .. working for a while and then stops working for a longer time. Here is the dmesg output : [ 705.817076] usb 5-1: device not accepting address 8, error -71 [ 705.928032] usb 5-1: new low speed USB device using uhci_hcd and address 9 [ 706.336060] usb 5-1: device not accepting address 9, error -71 [ 706.448055] usb 5-1: new low speed USB device using uhci_hcd and address 10 [ 706.568044] usb 5-1: device descriptor read/64, error -71 [ 706.792049] usb 5-1: device descriptor read/64, error -71 [ 707.008060] usb 5-1: new low speed USB device using uhci_hcd and address 11 [ 707.128041] usb 5-1: device descriptor read/64, error -71 [ 707.352052] usb 5-1: device descriptor read/64, error -71 [ 707.456068] hub 5-0:1.0: unable to enumerate USB device on port 1 Based on the suggestions here i tried the following two things: echo -1 > /sys/module/usbcore/parameters/autosuspend echo Y > /sys/module/usbcore/parameters/old_scheme_first However, i am still facing the same problem. Can anyone help me out with this ? I'm using Ubuntu 10.04 Lucid Lynx.

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  • Cisco Catalyst 3750 connected to Cisco ASA 5505 and dropping packets

    - by Bo102010
    (Cross posted from Super User per suggestion there) At the office, I have inherited a network that I am still trying to fully comprehend. I have a problem today with a new connection between: A port on a Cisco Catalyst 3750 [WS-C3750G-48TS-S running C3750-IPSERVICESK9-M version 12.2(53)SE1] A port on a Cisco ASA 5505 [ASA Software version 8.3(2)] The 3750 is home to a Vlan that has a few ports assigned to it. interface Vlan3 description Internal network (172.18.160.0/24) ip address 172.18.160.1 255.255.255.0 I have a host (outside of my control) that needs to be in this VLAN (i.e it must have an address 172.18.160.something/24) that also needs to access the Internet. To accomplish this, I ran a link from the Catalyst (Gi1/0/13) to the ASA (Ethernet 0/5). I configured the Catalyst port like so: interface GigabitEthernet1/0/13 description To ASA, 172.18.160.69 switchport access vlan 3 switchport mode access speed 100 duplex full I configured the ASA like so: interface Vlan1 nameif inside security-level 100 ip address 172.18.160.69 255.255.255.0 interface Ethernet0/5 speed 100 duplex full Then I plugged the host into Ethernet 0/4 on the ASA and instructed its owner to make its default gateway 172.18.160.69. I made a NAT rule in the ASA and set up some rules, and it's able to access the Internet without issue. However, I noticed that the Catalyst reports a ton of packets being dropped toward the ASA. Catalyst3750#show interfaces GigabitEthernet 1/0/13 | include counters|drops Last clearing of "show interface" counters 00:28:13 Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 136909347 This is a huge number of drops, since there's not much traffic on this VLAN at all. I tried these things: Make sure speed and duplex agree on both sides (100 Mbps / Full) Set no cdp enable on the Catalyst Gi10/13 Set no keepalive on the Catalyst Gi10/13 Checked for excessive CPU usage on both Checked for excessive traffic on both Am I missing something? Any help would be appreciated.

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  • Improving abysmal 802.11n wireless network

    - by concept
    I am in desperate need of help to improve the abysmal performance of my 802.11n wireless network. At best I get 30Mbs (this is an internet download) from a technology that boasts 300Mbs, even worse is the LAN where to date best i have ever gotten is 1Mbs. It is literally quicker to copy the file to a USB and walk it to the other computer. Infrastructure is this AP 802.11n only broadcasting at both 2.4GHz and 5GHz Mac with 802.11a/b/g/n card is connected to the AP via 5GHz Linux with 802.11a/b/g/n card is connected to AP via 2.4GHz I have conducted the following tests (results at end of post) Internet based speed test wired and wireless LAN file copy wired and wireless I have read: http://nutsaboutnets.com/troubleshooting-wi-fi-problems/ http://www.smallnetbuilder.com/wireless/wireless-basics/30664-5-ways-to-fix-slow-80211n-- speed http colon //www.wi-fiplanet dot com/tutorials/7-tips-to-increase-wi-fi-performance.html Slow file transfer on network between two 802.11n laptops (connected directly together via access point) Wireless Network Performance Issues Slower than expected 802.11n wireless network speeds I have made the following optimizations AP broadcasts only 802.11n on both 2.4GHz and 5GHz frequencies 2.4GHz is on a channel with least interference (live in an apartment with lots of APs), this did make a 10Mb/sec improvement Our AP is the only one transmitting on the 5GHz freq. Security: WPA Personal WPA2 AES encryption Bandwidth: 20MHz / 40MHz (i assume this to be channel bonding) I have tried the following with 0 improvement Dropped the Fragment Threshold to 512 Dropped the Request To Send (RTS) Threshold to 512 and 1 Even thought of buying a frequency spectrum analyzer, until i saw the cost of them!!! Speed test results Linux Wired: DOWNLOAD 128.40Mb/s UPLOAD 10.62Mb/s www dot speedtest dot net/my-result/2948381853 Mac Wired: DOWNLOAD 118.02Mb/s UPLOAD 10.56Mb/s www dot speedtest dot net/my-result/2948384406 Linux Wireless: DOWNLOAD 23.99Mb/s UPLOAD 10.31Mb/s www.speedtest dot net/my-result/2948394990 Mac Wireless: DOWNLOAD 22.55Mb/s UPLOAD 10.36Mb/s www.speedtest dot net/my-result/2948396489 LAN NFS 53,345,087 bytes (51Mb) file Linux Mac NFS Wired: 65.6959 Mb/sec Linux Mac NFS Wireless: .9443 Mb/sec All help is appreciated, even testing methods will be accepted.

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  • Disk IO slow on ESXi, even slower on a VM (freeNAS + iSCSI)

    - by varesa
    I have a server with ESXi 5 and iSCSI attached network storage(4x1Tb Raid-Z on freenas 8.0.4). Those two machines are connected to each other with Gigabit ethernet. The raid-z volume is divided into three parts: two zvols, shared with iscsi, and one directly on top of zfs, shared with nfs and similar. I ssh'd into the freeNAS box, and did some testing on the disks. I used ddto test the third part of the disks (straight on top of ZFS). I copied a 4GB (2x the amount of RAM) block from /dev/zero to the disk, and the speed was 80MB/s. Other of the iSCSI shared zvols is a datastore for the ESXi. I did similar test with time dd .. there. Since the dd there did not give the speed, I divided the amount of data transfered by the time show by time. The result was around 30-40 MB/s. Thats about half of the speed from the freeNAS host! Then I tested the IO on a VM running on the same ESXi host. The VM was a light CentOS 6.0 machine, which was not really doing anything else at that time. There were no other VMs running on the server at the time, and the other two "parts" of the disk array were not used. A similar dd test gave me result of about 15-20 MB/s. That is again about half of the result on a lower level! Of course the is some overhead in raid-z - zfs - zvolume - iSCSI - VMFS - VM, but I don't expect it to be that big. I belive there must be something wrong in my system. I have heard about bad performance of freeNAS's iSCSI, is that it? I have not managed to get any other "big" SAN OS to run on the box (NexentaSTOR, openfiler). Can you see any obvious problems with my setup?

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  • Is dual-channel RAM operation independent for each bank?

    - by user553702
    For dual-channel usage of DDR3 SDRAM, what happens if one bank has DIMMs in both channels but the other bank has only one DIMM in one channel? Will the bank with the paired DIMMs operate at the dual-channel rate while the bank with the unpaired DIMM operates at the single-channel rate? Or does having a bank with an unpaired DIMM force all of the RAM to operate as single-channel? For example, if I initially have only one bank populated with paired 4GB sticks operating as dual-channel, what happens if I then add a single 8GB stick to the other channel leaving the last DIMM slot empty? Will this stop the 4GB sticks from being dual-channel? In addition, what happens if each bank has DIMMs of different clock speeds? Does each dual-channel bank operate at an independent speed, or does all of the RAM operate at the slowest DIMM's speed? For example, in the above scenario, what would happen if the 8GB stick I added is slower than the original 4GB sticks in the other bank? Will the (paired) 4GB sticks then operate at a slower speed than before?

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  • MySQL Server Is Slow

    - by user2853965746
    I have two MySQL servers and one was just recently setup. The one I just recently setup is a bit slower than my older one, which kind of bothers me because I don't want my clients to be upset with the speed difference when I launch the new one. The older server runs on Ubuntu (~13.04 I believe) and the new one is on Debian 6. Both servers are 2GB ram, but my newer server is has an SSD, so I thought it might be the same speed if not faster. Anyway, the speed difference isn't too much (both are still under a second, but still noticeable). Whenever I select 50 rows from the user table on my older server (SELECT * FROM users LIMIT 50), I get the results in 0.003 s. There is 100,000+ accounts in that table. Whenever running the same command on the same table with only six dev accounts, it takes 0.069 s. It may not seem like a lot, but it's noticeable when you're used to a fast response. I added skip-name-resolve to the config and it didn't seem to help. Basically I'm asking if anyone knows what can cause a MySQL server to be slow in Debian 6? Should I just drop it and switch to Ubuntu like the older server (I don't think the OS is the problem, but you never know)? The older server is under a lot of use too, it's used a lot for web api's on my website. A lot of connections and stuff, and it still remains fast.

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