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• How to diagnose network speed drops

  - by Luis Alvarado

  Here is the image of System Monitor first: The graph shows the cycle the connection goes through. After 10 to 15 seconds it drops to 0 KB/S, then goes up to the Max speed (120 KB/S) then it repeats. dmesg shows the following during that time: [ 6066.757211] wlan0: send auth to 00:26:5a:b5:05:7b (try 1/3) [ 6066.804405] wlan0: authenticated [ 6066.804578] rt2800pci 0000:02:01.0 wlan0: disabling HT/VHT due to WEP/TKIP use [ 6066.805016] wlan0: associate with 00:26:5a:b5:05:7b (try 1/3) [ 6066.809218] wlan0: RX AssocResp from 00:26:5a:b5:05:7b (capab=0x431 status=0 aid=1) [ 6066.809581] wlan0: associated [ 6066.810203] bridge-eth0: disabling the bridge on dev down [ 6066.810239] bridge-eth0: down [ 6066.810254] bridge-eth0: detached [ 6066.810309] /dev/vmnet: open called by PID 1679 (vmnet-bridge) [ 6066.810322] /dev/vmnet: hub 0 does not exist, allocating memory. [ 6066.810355] /dev/vmnet: port on hub 0 successfully opened [ 6066.810366] bridge-wlan0: device is wireless, enabling SMAC [ 6066.810369] bridge-wlan0: up [ 6066.810372] bridge-wlan0: attached [ 6067.010285] userif-2: sent link down event. [ 6067.010290] userif-2: sent link up event. This also repeats with Wired or Wireless connections. How can I diagnose this changes in the network efficiently.

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• Integration error in high velocity

  - by Elektito

  I've implemented a simple simulation of two planets (simple 2D disks really) in which the only force is gravity and there is also collision detection/response (collisions are completely elastic). I can launch one planet into orbit of the other just fine. The collision detection code though does not work so well. I noticed that when one planet hits the other in a free fall it speeds backward and goes much higher than its original position. Some poking around convinced me that the simplistic Euler integration is causing the error. Consider this case. One object has a mass of 1kg and the other has a mass equal to earth. Say the object is 10 meters above ground. Assume that our dt (delta t) is 1 second. The object goes to the height of 9 meters at the end of the first iteration, 7 at the end of the second, 4 at the end of the third and 0 at the end of the fourth iteration. At this points it hits the ground and bounces back with the speed of 10 meters per second. The problem is with dt=1, on the first iteration it bounces back to a height of 10. It takes several more steps to make the object change its course. So my question is, what integration method can I use which fixes this problem. Should I split dt to smaller pieces when velocity is high? Or should I use another method altogether? What method do you suggest? EDIT: You can see the source code here at github:https://github.com/elektito/diskworld/

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• Find meeting point of 2 objects in 2D, knowing (constant) speed and slope

  - by Axonn

  I have a gun which fires a projectile which has to hit an enemy. The problem is that the gun has to be automatic, i.e. - choose the angle in which it has to shoot so that the projectile hits the enemy dead in the center. It's been a looooong time since school, and my physics skills are a bit rusty, but they're there. I've been thinking to somehow apply the v = d/t formula to find the time needed for the projectile or enemy to reach a certain point. But the problem is that I can't find the common point for both the projectile and enemy. Yes, I can find a certain point for the projectile, and another for the enemy, but I would need lots of tries to find where the point coincides, which is stupid. There has to be a way to link them together but I can't figure it out. I prepared some drawings and samples: A simple version of my Flash game, dumbed down to the basics, just some shapes: http://axonnsd.org/W/P001/MathSandBox.swf - click the mouse anywhere to fire a projectile. Or, here is an image which describes my problem: So... who has any ideas about how to find x3/y3 - thus leading me to find the angle in which the weapon has to tilt in order to fire a projectile to meet the enemy? EDIT I think it would be clearer if I also mention that I know: the speed of both Enemy and Projectile and the Enemy travels on a straight vertical line.

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• Financial institutions build predictive models using Oracle R Enterprise to speed model deployment

  - by Mark Hornick

  See the Oracle press release, Financial Institutions Leverage Metadata Driven Modeling Capability Built on the Oracle R Enterprise Platform to Accelerate Model Deployment and Streamline Governance for a description where a "unified environment for analytics data management and model lifecycle management brings the power and flexibility of the open source R statistical platform, delivered via the in-database Oracle R Enterprise engine to support open standards compliance." Through its integration with Oracle R Enterprise, Oracle Financial Services Analytical Applications provides "productivity, management, and governance benefits to financial institutions, including the ability to: Centrally manage and control models in a single, enterprise model repository, allowing for consistent management and application of security and IT governance policies across enterprise assets Reuse models and rapidly integrate with applications by exposing models as services Accelerate development with seeded models and common modeling and statistical techniques available out-of-the-box Cut risk and speed model deployment by testing and tuning models with production data while working within a safe sandbox Support compliance with regulatory requirements by carrying out comprehensive stress testing, which captures the effects of adverse risk events that are not estimated by standard statistical and business models. This approach supplements the modeling process and supports compliance with the Pillar I and the Internal Capital Adequacy Assessment Process stress testing requirements of the Basel II Accord Improve performance by deploying and running models co-resident with data. Oracle R Enterprise engines run in database, virtually eliminating the need to move data to and from client machines, thereby reducing latency and improving security"

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• Speed up ADF Mobile Deployment to Android with Keystore

  - by Shay Shmeltzer

  As you might have noticed from my latest ADF Mobile entries, I'm doing most of my ADF Mobile development on a windows machine and testing on an Android device. Unfortunately the Android/windows experience is not as fast as the iOS/Mac one. However, there is one thing I learned today that can make this a bit less painful in terms of the speed to deploy and test your application - and this is to use the "Release" mode when deploying your application instead of the "Debug" mode. To do this you'll first need to define a keystore, but as Joe from our Mobile team showed me today, this is quite easy. Here are the steps: Open a command line in your JDK bin directory (I just used the JDK that comes with the JDeveloper install). Issue the following command: keytool –genkey –v –keystore <Keystore Name>.keystore –alias <Alias Name> -keyalg RSA –keysize 2048 –validity 10000 Both keystore name and alias names are strings that you decide on. The keytool utility will then prompt you with various questions that you'll need to answer. Once this is done, the next step is to configure your JDeveloper preferences->ADF Mobile to add this keystore there under the release tab:  Then for your application specific deployment profile - switch the build mode from debug to release. The end result is a much smaller mobile application (for example from 60 to 21mb) and a much faster deployment cycle (for me it is about twice as fast as before).

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• Ubuntu One has high CPU usage but no syncing

  - by Peter

  over the weekend I updated my computer to Windows 8. So far Ubuntu One was running smoothly, but ever since the update (clean, new install) Ubuntu doesn't sync any more. In Windows 7 it would start to sync at full internet speed as soon as I drop a file. But now in Windows 8, as soon as I drop a new file into the Ubuntu One folder, CPU usage goes up to about 50 % and no network traffic occurs. This stays like that for a couple of minutes, CPU usage goes back to normal and then the client says that all is in sync - which isn't true. Is it too early for Windows 8? Do others have the same problem or is there something I can do about it? I try a couple of different things, and realized that if the file size is 20 MB the files get uploaded. The original file was 1.5 GB. I also didn't work with 200, 100 and 50 MB large files. But even with 20 MB large files, the upload is very slow and not steady. The log give plenty of this error: - twisted - ERROR - Failure: exceptions.TypeError About which I don't know the meaning. By the way, the account works just fine on the Ubuntu 12.04 partition. Any help is greatly appreciated. -Peter

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• Client and Server game update speed

  - by user20686

  I am working on a simple two player networked asteroids game using XNA and the Lidgren networking library. For this set up I have a Lidgren server maintaining what I want to be the true state of the game, and the XNA game is the Lidgren client. The client sends key inputs to the server, and the server process the key inputs against game logic, sending back updates. (This seemed like a better idea then sending local positions to the server.) The client also processes the key inputs on its own, so as to not have any visible lag, and then interpolates between the local position and remote position. Based on what I have been reading this is the correct way to smooth out a networked game. The only thing I don’t get is what value to use as the time deltas. Currently every message the server sends it also sends a delta-time update with it, which is time between the last update. The client then saves this delta time to use for its local position updates, so they can be using roughly the same time deltas to calculate position updates. I know the XNA game update gets called 60 times a second, so I set my server to update the game state at the same speed. This will probably only work as long as the game is working on a fixed time step and will probably cause problems if I want to change that in the future. The server sends updates to clients on another thread, which runs at 10 updates per second to cut down on bandwidth. I do not see noticeable lag in movement and over time if no user input is received the local and remote positions converge on each other as they should. I am also not currently calculating for any latency as I am trying to go one step at a time. So my question is should the XNA client be using its current game time to update the local game state and not being using time deltas sent by the server? If I should be using the clients time delta between updates how do I keep it in-line with how fast the server is updating its game state?

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• Pathfinding results in false path costs that are too high

  - by user2144536

  I'm trying to implement pathfinding in a game I'm programming using this method. I'm implementing it with recursion but some of the values after the immediate circle of tiles around the player are way off. For some reason I cannot find the problem with it. This is a screen cap of the problem: The pathfinding values are displayed in the center of every tile. Clipped blocks are displayed with the value of 'c' because the values were too high and were covering up the next value. The red circle is the first value that is incorrect. The code below is the recursive method. //tileX is the coordinates of the current tile, val is the current pathfinding value, used[][] is a boolean //array to keep track of which tiles' values have already been assigned public void pathFind(int tileX, int tileY, int val, boolean[][] used) { //increment pathfinding value int curVal = val + 1; //set current tile to true if it hasn't been already used[tileX][tileY] = true; //booleans to know which tiles the recursive call needs to be used on boolean topLeftUsed = false, topUsed = false, topRightUsed = false, leftUsed = false, rightUsed = false, botomLeftUsed = false, botomUsed = false, botomRightUsed = false; //set value of top left tile if necessary if(tileX - 1 >= 0 && tileY - 1 >= 0) { //isClipped(int x, int y) returns true if the coordinates givin are in a tile that can't be walked through (IE walls) //occupied[][] is an array that keeps track of which tiles have an enemy in them // //if the tile is not clipped and not occupied set the pathfinding value if(isClipped((tileX - 1) * 50 + 25, (tileY - 1) * 50 + 25) == false && occupied[tileX - 1][tileY - 1] == false && !(used[tileX - 1][tileY - 1])) { pathFindingValues[tileX - 1][tileY - 1] = curVal; topLeftUsed = true; used[tileX - 1][tileY - 1] = true; } //if it is occupied set it to an arbitrary high number so enemies find alternate routes if the best is clogged if(occupied[tileX - 1][tileY - 1] == true) pathFindingValues[tileX - 1][tileY - 1] = 1000000000; //if it is clipped set it to an arbitrary higher number so enemies don't travel through walls if(isClipped((tileX - 1) * 50 + 25, (tileY - 1) * 50 + 25) == true) pathFindingValues[tileX - 1][tileY - 1] = 2000000000; } //top middle if(tileY - 1 >= 0 ) { if(isClipped(tileX * 50 + 25, (tileY - 1) * 50 + 25) == false && occupied[tileX][tileY - 1] == false && !(used[tileX][tileY - 1])) { pathFindingValues[tileX][tileY - 1] = curVal; topUsed = true; used[tileX][tileY - 1] = true; } if(occupied[tileX][tileY - 1] == true) pathFindingValues[tileX][tileY - 1] = 1000000000; if(isClipped(tileX * 50 + 25, (tileY - 1) * 50 + 25) == true) pathFindingValues[tileX][tileY - 1] = 2000000000; } //top right if(tileX + 1 <= used.length && tileY - 1 >= 0) { if(isClipped((tileX + 1) * 50 + 25, (tileY - 1) * 50 + 25) == false && occupied[tileX + 1][tileY - 1] == false && !(used[tileX + 1][tileY - 1])) { pathFindingValues[tileX + 1][tileY - 1] = curVal; topRightUsed = true; used[tileX + 1][tileY - 1] = true; } if(occupied[tileX + 1][tileY - 1] == true) pathFindingValues[tileX + 1][tileY - 1] = 1000000000; if(isClipped((tileX + 1) * 50 + 25, (tileY - 1) * 50 + 25) == true) pathFindingValues[tileX + 1][tileY - 1] = 2000000000; } //left if(tileX - 1 >= 0) { if(isClipped((tileX - 1) * 50 + 25, (tileY) * 50 + 25) == false && occupied[tileX - 1][tileY] == false && !(used[tileX - 1][tileY])) { pathFindingValues[tileX - 1][tileY] = curVal; leftUsed = true; used[tileX - 1][tileY] = true; } if(occupied[tileX - 1][tileY] == true) pathFindingValues[tileX - 1][tileY] = 1000000000; if(isClipped((tileX - 1) * 50 + 25, (tileY) * 50 + 25) == true) pathFindingValues[tileX - 1][tileY] = 2000000000; } //right if(tileX + 1 <= used.length) { if(isClipped((tileX + 1) * 50 + 25, (tileY) * 50 + 25) == false && occupied[tileX + 1][tileY] == false && !(used[tileX + 1][tileY])) { pathFindingValues[tileX + 1][tileY] = curVal; rightUsed = true; used[tileX + 1][tileY] = true; } if(occupied[tileX + 1][tileY] == true) pathFindingValues[tileX + 1][tileY] = 1000000000; if(isClipped((tileX + 1) * 50 + 25, (tileY) * 50 + 25) == true) pathFindingValues[tileX + 1][tileY] = 2000000000; } //botom left if(tileX - 1 >= 0 && tileY + 1 <= used[0].length) { if(isClipped((tileX - 1) * 50 + 25, (tileY + 1) * 50 + 25) == false && occupied[tileX - 1][tileY + 1] == false && !(used[tileX - 1][tileY + 1])) { pathFindingValues[tileX - 1][tileY + 1] = curVal; botomLeftUsed = true; used[tileX - 1][tileY + 1] = true; } if(occupied[tileX - 1][tileY + 1] == true) pathFindingValues[tileX - 1][tileY + 1] = 1000000000; if(isClipped((tileX - 1) * 50 + 25, (tileY + 1) * 50 + 25) == true) pathFindingValues[tileX - 1][tileY + 1] = 2000000000; } //botom middle if(tileY + 1 <= used[0].length) { if(isClipped((tileX) * 50 + 25, (tileY + 1) * 50 + 25) == false && occupied[tileX][tileY + 1] == false && !(used[tileX][tileY + 1])) { pathFindingValues[tileX][tileY + 1] = curVal; botomUsed = true; used[tileX][tileY + 1] = true; } if(occupied[tileX][tileY + 1] == true) pathFindingValues[tileX][tileY + 1] = 1000000000; if(isClipped((tileX) * 50 + 25, (tileY + 1) * 50 + 25) == true) pathFindingValues[tileX][tileY + 1] = 2000000000; } //botom right if(tileX + 1 <= used.length && tileY + 1 <= used[0].length) { if(isClipped((tileX + 1) * 50 + 25, (tileY + 1) * 50 + 25) == false && occupied[tileX + 1][tileY + 1] == false && !(used[tileX + 1][tileY + 1])) { pathFindingValues[tileX + 1][tileY + 1] = curVal; botomRightUsed = true; used[tileX + 1][tileY + 1] = true; } if(occupied[tileX + 1][tileY + 1] == true) pathFindingValues[tileX + 1][tileY + 1] = 1000000000; if(isClipped((tileX + 1) * 50 + 25, (tileY + 1) * 50 + 25) == true) pathFindingValues[tileX + 1][tileY + 1] = 2000000000; } //call the method on the tiles that need it if(tileX - 1 >= 0 && tileY - 1 >= 0 && topLeftUsed) pathFind(tileX - 1, tileY - 1, curVal, used); if(tileY - 1 >= 0 && topUsed) pathFind(tileX , tileY - 1, curVal, used); if(tileX + 1 <= used.length && tileY - 1 >= 0 && topRightUsed) pathFind(tileX + 1, tileY - 1, curVal, used); if(tileX - 1 >= 0 && leftUsed) pathFind(tileX - 1, tileY, curVal, used); if(tileX + 1 <= used.length && rightUsed) pathFind(tileX + 1, tileY, curVal, used); if(tileX - 1 >= 0 && tileY + 1 <= used[0].length && botomLeftUsed) pathFind(tileX - 1, tileY + 1, curVal, used); if(tileY + 1 <= used[0].length && botomUsed) pathFind(tileX, tileY + 1, curVal, used); if(tileX + 1 <= used.length && tileY + 1 <= used[0].length && botomRightUsed) pathFind(tileX + 1, tileY + 1, curVal, used); }

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• Is there a javascript library that contains a rich set of very high level commonly used functions?

  - by bobo

  I find that many high level functions are missing in most well-known javascript libraries such as jquery, YUI...etc. Taking string manipulation as an example, startsWith, endsWith, contains, lTrim, rTrim, trim, isNullOrEmpty...etc. These function are actually very common ones. I would like to know if there exists a javascript library/ plugin of a javascript library that fills these gaps (including but not limited to string manipulation)? It would be great if the library does not override the prototype.

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• Php profiling on production server or other options

  - by absentx

  Alright I need some help here. I am commonly asked to speed up certain sections of some websites that I program for. I have yet to be able to figure out how to use a good php diagnosis/profiling tool. Some things to consider: The sites I am working on are already built, getting a testing server set up locally is just a huge pain..I have to rewrite include paths and just so many things. This is a results oriented deal and spending days to get a site fully working on a testing platform so I can debug one page probably isn't an option. I can write tons of php, but I have no clue how to interact or mess with servers. So every tutorial I read about setting up xdebug or xhprof all seem to involve getting something installed on a production server that I don't have access to or have no clue how to work with. So are there any solutions out there that will show me where my php is slow without having to do all sorts of server stuff that I just don't know how to do? Xhprof seems to be the closest to useable for me but from what I can tell it still has to be installed on a server. If anyone can just point me in the right direction on this I would be very grateful. Maybe getting these things put on the server isn't a big deal...but I have never interacted with server command lines or anything like that. I suppose I should start sometime but I really have no idea where to start. Plus I realize that profiling on a live platform is not the greatest idea either but I feel I am in a tough spot. I have speed issues to solve and setting up a local environment while a great idea, just doesn't seem real practical at the moment.

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• Accelerating 2d object collision with other objects [on hold]

  - by Silent Cave

  Making my very first attempt at game programming with SDL/OpenGL. So I made an object Actor witch can move in all four sides with acceleration. And there are bunch of other rectangles to collide to. the image Movement and collision detection alghorythms work just fine by itself, but when combined to prevent the green rectangle from crossing black rectangles, it gives me a kind of funny resault. Let me show you the code first: from Actor.h class Actor{ public: SDL_Rect * dim; alphaColor * col; float speed; float xlGrav, xrGrav, yuGrav, ydGrav; float acceleration; bool left,right,up,down; Actor(SDL_Rect * dim,alphaColor * col, float speed, float acceleration); bool colides(const SDL_Rect & rect); bool check_for_collisions(const std::vector<SDL_Rect*> & gameObjects ); }; from actor.cpp bool Actor::colides(const SDL_Rect & rect){ if (dim->x + dim->w < rect.x) return false; if (dim->x > rect.x + rect.w) return false; if (dim->y + dim->h < rect.y) return false; if (dim->y > rect.y + rect.h) return false; return true; } movement logic from main.cpp if (actor->left){ if(actor->xlGrav < actor->speed){ actor->xlGrav += actor->speed*actor->acceleration; }else actor->xlGrav = actor->speed; actor->dim->x -= actor->xlGrav; if(actor->check_for_collisions(gameObjects)){ actor->dim->x += actor->xlGrav; actor->xlGrav = 0; } } if (!actor->left){ if(actor->xlGrav - actor->speed*actor->acceleration > 0){ actor->xlGrav -= actor->speed*actor->acceleration; }else actor->xlGrav = 0; actor->dim->x -= actor->xlGrav; if(actor->check_for_collisions(gameObjects)){ actor->dim->x += actor->xlGrav; actor->xlGrav = 0; } } if (actor->right){ if(actor->xrGrav < actor->speed){ actor->xrGrav += actor->speed*actor->acceleration; }else actor->xrGrav = actor->speed; actor->dim->x += actor->xrGrav; if(actor->check_for_collisions(gameObjects)){ actor->dim->x -= actor->xrGrav; actor->xrGrav = 0; } } if (!actor->right){ if(actor->xrGrav - actor->speed*actor->acceleration > 0){ actor->xrGrav -= actor->speed*actor->acceleration; }else actor->xrGrav = 0; actor->dim->x += actor->xrGrav; if(actor->check_for_collisions(gameObjects)){ actor->dim->x -= actor->xrGrav; actor->xrGrav = 0; } } if (actor->up){ if(actor->yuGrav < actor->speed){ actor->yuGrav += actor->speed*actor->acceleration; }else actor->yuGrav = actor->speed; actor->dim->y -= actor->yuGrav; if(actor->check_for_collisions(gameObjects)){ actor->dim->y += actor->yuGrav; actor->yuGrav = 0; } } if (!actor->up){ if(actor->yuGrav - actor->speed*actor->acceleration > 0){ actor->yuGrav -= actor->speed*actor->acceleration; }else actor->yuGrav = 0; actor->dim->y -= actor->yuGrav; if(actor->check_for_collisions(gameObjects)){ actor->dim->y += actor->yuGrav; actor->yuGrav = 0; } } if (actor->down){ if(actor->ydGrav < actor->speed){ actor->ydGrav += actor->speed*actor->acceleration; }else actor->ydGrav = actor->speed; actor->dim->y += actor->ydGrav; if(actor->check_for_collisions(gameObjects)){ actor->dim->y -= actor->ydGrav; actor->ydGrav = 0; } } if (!actor->down){ if(actor->ydGrav - actor->speed*actor->acceleration > 0){ actor->ydGrav -= actor->speed*actor->acceleration; }else actor->ydGrav = 0; actor->dim->y += actor->ydGrav; if(actor->check_for_collisions(gameObjects)){ actor->dim->y -= actor->ydGrav; actor->ydGrav = 0; } } So, if the green box approaches an obstacle from up or left, everything goes as planned - object stops, and it's acceleration drops to zero. But if it comes from bottom or right, it enters into obstacles inner space and starts strangely dance, I'd rather say move in inverted controls. What do I fail to see?

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• Applications: The Mathematics of Movement, Part 3

  - by TechTwaddle

  Previously: Part 1, Part 2 As promised in the previous post, this post will cover two variations of the marble move program. The first one, Infinite Move, keeps the marble moving towards the click point, rebounding it off the screen edges and changing its direction when the user clicks again. The second version, Finite Move, is the same as first except that the marble does not move forever. It moves towards the click point, rebounds off the screen edges and slowly comes to rest. The amount of time that it moves depends on the distance between the click point and marble. Infinite Move This case is simple (actually both cases are simple). In this case all we need is the direction information which is exactly what the unit vector stores. So when the user clicks, you calculate the unit vector towards the click point and then keep updating the marbles position like crazy. And, of course, there is no stop condition. There’s a little more additional code in the bounds checking conditions. Whenever the marble goes off the screen boundaries, we need to reverse its direction.  Here is the code for mouse up event and UpdatePosition() method, //stores the unit vector double unitX = 0, unitY = 0; double speed = 6; //speed times the unit vector double incrX = 0, incrY = 0; private void Form1_MouseUp(object sender, MouseEventArgs e) {     double x = e.X - marble1.x;     double y = e.Y - marble1.y;     //calculate distance between click point and current marble position     double lenSqrd = x * x + y * y;     double len = Math.Sqrt(lenSqrd);     //unit vector along the same direction (from marble towards click point)     unitX = x / len;     unitY = y / len;     timer1.Enabled = true; } private void UpdatePosition() {     //amount by which to increment marble position     incrX = speed * unitX;     incrY = speed * unitY;     marble1.x += incrX;     marble1.y += incrY;     //check for bounds     if ((int)marble1.x < MinX + marbleWidth / 2)     {         marble1.x = MinX + marbleWidth / 2;         unitX *= -1;     }     else if ((int)marble1.x > (MaxX - marbleWidth / 2))     {         marble1.x = MaxX - marbleWidth / 2;         unitX *= -1;     }     if ((int)marble1.y < MinY + marbleHeight / 2)     {         marble1.y = MinY + marbleHeight / 2;         unitY *= -1;     }     else if ((int)marble1.y > (MaxY - marbleHeight / 2))     {         marble1.y = MaxY - marbleHeight / 2;         unitY *= -1;     } } So whenever the user clicks we calculate the unit vector along that direction and also the amount by which the marble position needs to be incremented. The speed in this case is fixed at 6. You can experiment with different values. And under bounds checking, whenever the marble position goes out of bounds along the x or y direction we reverse the direction of the unit vector along that direction. Here’s a video of it running;   Finite Move The code for finite move is almost exactly same as that of Infinite Move, except for the difference that the speed is not fixed and there is an end condition, so the marble comes to rest after a while. Code follows, //unit vector along the direction of click point double unitX = 0, unitY = 0; //speed of the marble double speed = 0; private void Form1_MouseUp(object sender, MouseEventArgs e) {     double x = 0, y = 0;     double lengthSqrd = 0, length = 0;     x = e.X - marble1.x;     y = e.Y - marble1.y;     lengthSqrd = x * x + y * y;     //length in pixels (between click point and current marble pos)     length = Math.Sqrt(lengthSqrd);     //unit vector along the same direction as vector(x, y)     unitX = x / length;     unitY = y / length;     speed = length / 12;     timer1.Enabled = true; } private void UpdatePosition() {     marble1.x += speed * unitX;     marble1.y += speed * unitY;     //check for bounds     if ((int)marble1.x < MinX + marbleWidth / 2)     {         marble1.x = MinX + marbleWidth / 2;         unitX *= -1;     }     else if ((int)marble1.x > (MaxX - marbleWidth / 2))     {         marble1.x = MaxX - marbleWidth / 2;         unitX *= -1;     }     if ((int)marble1.y < MinY + marbleHeight / 2)     {         marble1.y = MinY + marbleHeight / 2;         unitY *= -1;     }     else if ((int)marble1.y > (MaxY - marbleHeight / 2))     {         marble1.y = MaxY - marbleHeight / 2;         unitY *= -1;     }     //reduce speed by 3% in every loop     speed = speed * 0.97f;     if ((int)speed <= 0)     {         timer1.Enabled = false;     } } So the only difference is that the speed is calculated as a function of length when the mouse up event occurs. Again, this can be experimented with. Bounds checking is same as before. In the update and draw cycle, we reduce the speed by 3% in every cycle. Since speed is calculated as a function of length, speed = length/12, the amount of time it takes speed to reach zero is directly proportional to length. Note that the speed is in ‘pixels per 40ms’ because the timeout value of the timer is 40ms.  The readability can be improved by representing speed in ‘pixels per second’. This would require you to add some more calculations to the code, which I leave out as an exercise. Here’s a video of this second version,

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• Question regarding Readability vs Processing Time

  - by Jordy

  I am creating a flowchart for a program with multiple sequential steps. Every step should be performed if the previous step is succesful. I use a c-based programming language so the lay-out would be something like this: METHOD 1: if(step_one_succeeded()) { if(step_two_succeeded()) { if(step_three_succeeded()) { //etc. etc. } } } If my program would have 15+ steps, the resulting code would be terribly unfriendly to read. So I changed my design and implemented a global errorcode that I keep passing by reference, make everything more readable. The resulting code would be something like this: METHOD 2: int _no_error = 0; step_one(_no_error); if(_no_error == 0) step_two(_no_error); if(_no_error == 0) step_three(_no_error); if(_no_error == 0) step_two(_no_error); The cyclomatic complexibility stays the same. Now let's say there are N number of steps. And let's assume that checking a condition is 1 clock long and performing a step doesn't take up time. The processing speed of Method1 can be anywhere between 1 and N. The processing speed of Method2 however is always equal to N-1. So Method1 will be faster most of the time. Which brings me to my question, is it bad practice to sacrifice time in order to make the code more readable? And why (not)?

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• Long 'Wait' Time for three php/CSS files. Is something blocking them?

  - by William Pitcher

  I have been speed optimizing a Wordpress site to little effect. There are three files CSS-related php files from the Wordpress theme that are delaying page loads on the site. One of the three files is basically one line of custom CSS from the custom CSS feature in the theme. You can see what I am talking about with this Pingdom speed test: The yellow is 'Wait'. There are no slow items in the cut-off portion of the image. The full results are here: Pingdom Results Page 1. Any thoughts on what might be causing this? I understand that I have blocking CSS or JS files, but I don't see anything that would be causing that long of a wait. When I ran the P3 Plugin Profiler, Wordpress and all plugins appeared fine -- it is the theme that is taking all the time. GTmetrix recommends avoiding dynamic queries. I assume all the ver=3.61 references are to the version of Wordpress (which I am using). I noticed that my Wordpress sites using other themes don't make this query (at least not over and over). 2. Is this typical coding practice? 3. How much negative impact do these query-strings have -- a little or a lot? I tried searching for similar questions here, please excuse me if I missed something. Sometimes, I know just enough to be dangerous.

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• High Tq values for HAProxy

  - by Will

  I just took over administration of a new environment. A known issue is that the environment is known for high response times (20+ seconds), so I figured I'd turn on haproxy logging and see what is going on. I figured I'd see slow load times in the app servers, but I'm actually seeing high Tq values in HAProxy. The HAProxy is on EC2 and is NOT behind ELB. Sep 5 14:22:00 haproxy-apps01 haproxy[24695]: 76.14.153.221:3371 [05/Sep/2012:14:21:49.780] http-in default_apps/fe04-c 10936/0/0/55/10991 200 488 - - ---- 111/111/0/1/0 0/0 "GET /event_times/next?callback=jQuery170189312373075111_1346854917562&_=1346854918453 HTTP/1.1" As you can see, this one has a Tq of about 10 seconds. Not all the Tq's are high (1+ seconds), but a good percentage of them are (approx 35%). Normally when I see this behavior, I'd expect there to be network issues, but this is an incredibly high percentage of visitors to be having an issue like this, so I'm wondering if anybody has seen this or have any hints on diagnosing if the issue could possibly be on this box?

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• Find which php scripts cause high CPU with php-cgi

  - by Oli

  Background: I maintain a server for a client who has half a dozen Wordpress sites on. They all have the W3 Total Cache plugin installed and eAcellerator is installed (might be APC). All the PHP sites run through a single batch of fastcgi php-cgi processes (it's actually php-fpm but I'm not sure if that makes a difference). Problem: php-cgi's CPU usage is quite high. Not terminally high but high enough to raise an eyebrow. The client wants to add more sites in the future and I want to avoid becoming CPU limited if I can help it. Question: Is there any way I can find the scripts or even just requests that are causing the high CPU. I realise I might not be able to do anything with the results but it would give me a chance.

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• Good book for building high performance web sites?

  - by Arne Evertsson

  Any recommendations for a book about building and running high performance, high-availability web sites on Linux?

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• How much traffic is high-traffic [closed]

  - by Jack

  My primary interest is in gathering information about the technology used behind public facing websites. Much of the information I read arbitrarily differentiates between high-traffic vs the unstated non-high-traffic websites. This troubles me because I don't have a good grasp of how much traffic is high-traffic. Can anyone help me with this, is there a good rule of thumb? Please don't tell me it depends ;)

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• High fan speed with no reason

  - by Klaus

  For a few weeks, the fans of my Lenovo B590 laptop, running on Xubuntu 14, turn to high speed a few minutes after it is turned on. The fans won't speed down until I turn the computer off. This is quite strange, since This didn't happen before The temperatures are quite low (are they ?) $sensors Adapter: Virtual device temp1: +36.0°C (crit = +88.0°C) temp2: +30.0°C (crit = +126.0°C) coretemp-isa-0000 Adapter: ISA adapter Physical id 0: +37.0°C (high = +72.0°C, crit = +90.0°C) Core 0: +34.0°C (high = +72.0°C, crit = +90.0°C) Core 1: +31.0°C (high = +72.0°C, crit = +90.0°C) thinkpad-isa-0000 Adapter: ISA adapter fan1: 0 RPM pkg-temp-0-virtual-0 Adapter: Virtual device temp1: +37.0°C $sudo hddtemp /dev/sda /dev/sda: ST500LT012-9WS142: 33°C The computer is under low load: top - 08:30:15 up 16 min, 2 users, load average: 0.28, 0.23, 0.23 Tasks: 197 total, 1 running, 196 sleeping, 0 stopped, 0 zombie %Cpu(s): 0.8 us, 0.5 sy, 0.0 ni, 98.7 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 st KiB Mem: 3607944 total, 1973956 used, 1633988 free, 99660 buffers KiB Swap: 3744764 total, 0 used, 3744764 free. 789936 cached Mem The BIOS is up to date (and there are no fan settings in it) The fan is clean and dust-free Why would the BIOS turn the fans to high speed where there seem to be no reason for that ? It seems that we cannot control the fan manually with this model, so I guess the only solution is to understand why this happens.

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• Teaching high school kids ASP.NET programming

  - by dotneteer

  During the 2011 Microsoft MVP Global Summit, I have been talking to people about teaching kids ASP.NET programming. I want to work with volunteer organizations to provide kids volunteer opportunities while learning technical skills that can be applied elsewhere. The goal is to teach motivated kids enough skill to be productive with no more than 6 hours of instruction. Based on my prior teaching experience of college extension courses and involvement with high school math and science competitions, I think this is quite doable with classic ASP but a challenge with ASP.NET. I don’t want to use ASP because it does not provide a good path into the future. After some considerations, I think this is possible with ASP.NET and here are my thoughts: · Create a framework within ASP.NET for kids programming. · Use existing editor. No extra compiler and intelligence work needed. · Using a subset of C# like a scripting language. Teaches data type, expression, statements, if/for/while/switch blocks and functions. Use existing classes but no class creation and OOP. · Linear rendering model. No complicated life cycle. · Bare-metal html with some MVC style helpers for widget creation; ASP.NET control is optional. I want to teach kids to understand something and avoid black boxes as much as possible. · Use SQL for CRUD with a helper class. Again, I want to teach understanding rather than black boxes. · Provide a template to encourage clean separation of concern. · Provide a conversion utility to convert the code that uses template to ASP.NET MVC. This will allow kids with AP Computer Science knowledge to step up to ASP.NET MVC. Let me know if you have thoughts or can help.

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• Extract High Quality Icons from Files Using a Free Tool

  - by Lori Kaufman

  If you need to extract an icon from a program file or other type of file (such as .dll files), there are many free tools available that make the task easy. However, very few will extract high quality icon images from the files. Most free icon extraction tools will extract smaller icon image sizes, such as 16×16, 32×32, or 48×48 pixels. Some icons come in larger sizes, such as icons used in Windows. There is a free, small utility, called BeCyIconGrabber, that allows you to view and save icons and cursors of any size contained in .exe, .dll, .icl, .ocx, .cpl, .src, .ico, and .cur files. You can save the extracted icons individually as a .png file, .bmp file, .ico file, or .cur file, or in groups within resource libraries, i.e., .dll or .icl files. BeCyIconGrabber can be downloaded as an installable file or as a portable executable that does not need to be installed. We downloaded the portable file. How To Properly Scan a Photograph (And Get An Even Better Image) The HTG Guide to Hiding Your Data in a TrueCrypt Hidden Volume Make Your Own Windows 8 Start Button with Zero Memory Usage

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• XNA Easy Storage XBOX 360 High Scores

  - by user1003211

  To followup from a previous query - I need some help with the implementation of easystorage high scores, which is bringing up some errors on the xbox. I get the prompt screen, a savedevice is selected and a file are all created! However the file remains empty, (I've tried prepopulating but still get errors). The full portions of the scoring code can be found here: http://pastebin.com/74v897Yt The current issue in particular is in LoadHighScores() - "There is an error in XML document (0, 0)." under line data = (HighScoreData)serializer.Deserialize(stream); I'm not sure whether this line is correct either: HighScoreData data = new HighScoreData(); public static HighScoreData LoadHighScores(string container, string filename) { HighScoreData data = new HighScoreData(); if (Global.SaveDevice.FileExists(container, filename)) { Global.SaveDevice.Load(container, filename, stream => { File.Open(Global.fileName_options, FileMode.OpenOrCreate, FileAccess.Read); try { // Read the data from the file XmlSerializer serializer = new XmlSerializer(typeof(HighScoreData)); data = (HighScoreData)serializer.Deserialize(stream); } finally { // Close the file stream.Close(); // stream.Dispose(); } }); } return (data); } I call: PromptMe(); when the Start button is pressed at the beginning. I call: if (Global.SaveDevice.IsReady){entries = LoadHighScores(HighScoresContainer, HighScoresFilename);} during the menu screen to try and display the highscore screen. I call: SaveHighScore(); when game ends. I've tried altering the struct code to a class but still no luck. Any help greatly appreciated.

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• High-Level Application Architecture Question

  - by Jesse Bunch

  So I'm really wanting to improve how I architect the software I code. I want to focus on maintainability and clean code. As you might guess, I've been reading a lot of resources on this topic and all it's doing is making it harder for me to settle on an architecture because I can never tell if my design is the one that the more experienced programmer would've chosen. So I have these requirements: I should connect to one vendor and download form submissions from their API. We'll call them the CompanyA. I should then map those submissions to a schema fit for submitting to another vendor for integration with the email service provider. We'll call them the CompanyB. I should then submit those responses to the ESP (CompanyB) and then instruct the ESP to send that submitter an email. So basically, I'm copying data from one web service to another and then performing an action at the latter web service. I've identified a couple high-level services: The service that downloads data from CompanyA. I called this the CompanyAIntegrator. The service that submits the data to CompanyB. I called this CompanyBIntegrator. So my questions are these: Is this a good design? I've tried to separate the concerns and am planning to use the facade pattern to make the integrators interchangeable if the vendors change in the future. Are my naming conventions accurate and meaningful to you (who knows nothing specific of the project)? Now that I have these services, where should I do the work of taking output from the CompanyAIntegrator and getting it in the format for input to the CompanyBIntegrator? Is this OK to be done in main()? Do you have any general pointers on how you'd code something like this? I imagine this scenario is common to us engineers---especially those working in agencies. Thanks for any help you can give. Learning how to architect well is really mind-cluttering.

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• check what process was causing the problem of high cpu load

  - by linuxk

  I'm running nginx wordpress server in KVM using 12.04 server x86. It was running very well about 4 month until 2 hours ago. I found that my website is down and no ping response. Virt-manager logged high cpu load(plz see the picture below) before unexpected shut down. I want to know what process caused unexpected shutdown. The following log files make me think my server is attacked. Any suggestions and help would be appreciated. kern.log and syslog showed me same output. Nov 11 03:54:11 www kernel: [1344541.156239] [UFW BLOCK] IN=eth0 OUT= MAC= SRC=0.0.0.0 DST=224.0. 0.1 LEN=32 TOS=0x00 PREC=0xC0 TTL=1 ID=0 DF PROTO=2 Nov 11 03:54:11 www kernel: [1344541.156315] [UFW BLOCK] IN=eth0 OUT= MAC= SRC=0101:080a:2334:c90 0:0100:0000:0000:0000 DST=ff02:0000:0000:0000:0000:0000:0000:0001 LEN=72 TC=0 HOPLIMIT=1 FLOWLBL=0 PROTO=ICMPv6 TYPE=130 CODE=0 /nginx/access.log showed me 119.235.237.17 - - [11/Nov/2012:03:45:29 +0900] "GET /blog HTTP/1.1" 200 30493 "-" "Yeti/1.0 (NHN Corp.; http://help.naver.com/robots/)" my-server-ip - - [11/Nov/2012:11:05:30 +0900] "POST /wp-cron.php?doing_wp_cron=13 HTTP/1.0" 499 0 "-" "WordPress/3.4.2; http://mywebsite.com" Server turned on in here. 119.235.237.16 - - [11/Nov/2012:11:05:30 +0900] "GET /blog HTTP/1.1" 200 32935 "-" "Yeti/1.0 (NHN Corp.; http://help.naver.com/robots/)"

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• High Performance SQL Views Using WITH(NOLOCK)

  - by gt0084e1

  Every now and then you find a simple way to make everything much faster. We often find customers creating data warehouses or OLAP cubes even though they have a relatively small amount of data (a few gigs) compared to their server memory. If you have more server memory than the size of your database or working set, nearly any aggregate query should run in a second or less. In some situations there may be high traffic on from the transactional application and SQL server may wait for several other queries to run before giving you your results. The purpose of this is make sure you don’t get two versions of the truth. In an ATM system, you want to give the bank balance after the withdrawal, not before or you may get a very unhappy customer. So by default databases are rightly very conservative about this kind of thing. Unfortunately this split-second precision comes at a cost. The performance of the query may not be acceptable by today’s standards because the database has to maintain locks on the server. Fortunately, SQL Server gives you a simple way to ask for the current version of the data without the pending transactions. To better facilitate reporting, you can create a view that includes these directives. CREATE VIEW CategoriesAndProducts AS SELECT * FROM dbo.Categories WITH(NOLOCK) INNER JOIN dbo.Products WITH(NOLOCK) ON dbo.Categories.CategoryID = dbo.Products.CategoryID In some cases quires that are taking minutes end up taking seconds. Much easier than moving the data to a separate database and it’s still pretty much real time give or take a few milliseconds. You’ve been warned not to use this for bank balances though. More from Data Stream

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