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  • Android - Efficient way to draw tiles in OpenGL ES

    - by Maecky
    Hi, I am trying to write efficient code to render a tile based map in android. I load for each tile the corresponding bitmap (just one time) and then create the according tiles. I have designed a class to do this: public class VertexQuad { private float[] mCoordArr; private float[] mColArr; private float[] mTexCoordArr; private int mTextureName; private static short mCounter = 0; private short mIndex; As you can see, each tile has it's x,y location, a color array, texture coordinates and a texture name. Now, I want to render all my created tiles. To reduce the openGL api calls (I read somewhere that the state changes are costly and therefore I want to keep them to a minimum), I first want to hand ALL the coordinate-arrays, color-arrays and texture-coordinates over to OpenGL. After that I run two for loops. The first one iterates over the textures and binds the texture. The second for loop iterates over all Tiles and puts all tiles with the corresponding texture into an IndexBuffer. After the second for loop has finished, I call gl.gl_drawElements() whith the corresponding index buffer, to draw all tiles with the texture associated. For the next texture I do the same again. Now I run into some problems: Allocating and filling the FloatBuffers at the start of each rendering cycle costs very much time. I just run a test, where i wanted to put 400 coordinates into a FloatBuffer which took me about 200ms. My questions now are: Is there a better way, handling the coordinate and color structures? How is this correctly done, this is obviously not the optimal way? ;) thanks in advance, regards Markus

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  • What term is used to describe running frequent batch jobs to emulate near real time

    - by Steven Tolkin
    Suppose users of application A want to see the data updated by application B as frequently as possible. Unfortunately app A or app B cannot use message queues, and they cannot share a database. So app B writes a file, and a batch job periodically checks to see if the file is there, and if load loads it into app A. Is there a name for this concept? A very explicit and geeky description: "running very frequent batch jobs in a tight loop to emulate near real time". This concept is similar to "polling". However polling has the connotation of being very frequent, multiple times per second, whereas the most often you would run a batch job would be every few minutes. A related question -- what is the tightest loop that is reasonable. Is it 1 minute of 5 minutes or ...? Recall that the batch jobs are started by a batch job scheduler (e.g. Autosys, Control M, CA ESP, Spring Batch etc.) and so running a job too frequently would causes overhead and clutter.

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  • Faster 2D Collision detection

    - by eShredder
    Recently I've been working on a fast-paced 2d shooter and I came across a mighty problem. Collision detection. Sure, it is working, but it is very slow. My goal is: Have lots of enemies on screen and have them to not touch each other. All of the enemies are chasing the player entity. Most of them have the same speed so sooner or later they all end up taking the same space while chasing the player. This really drops the fun factor since, for the player, it looks like you are being chased by one enemy only. To prevent them to take the same space I added a collision detection (a very basic 2D detection, the only method I know of) which is. Enemy class update method Loop through all enemies (continue; if the loop points at this object) If enemy object intersects with this object Push enemy object away from this enemy object This works fine. As long as I only have <200 enemy entities that is. When I get closer to 300-350 enemy entities my frame rate begins to drop heavily. First I thought it was bad rendering so I removed their draw call. This did not help at all so of course I realised it was the update method. The only heavy part in their update method is this each-enemy-loops-through-every-enemy part. When I get closer to 300 enemies the game does a 90000 (300x300) step itteration. My my~ I'm sure there must be another way to aproach this collision detection. Though I have no idea how. The pages I find is about how to actually do the collision between two objects or how to check collision between an object and a tile. I already know those two things. tl;dr? How do I aproach collision detection between LOTS of entities? Quick edit: If it is to any help, I'm using C# XNA.

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  • Question on methods in Object Oriented Programming

    - by mal
    I’m learning Java at the minute (first language), and as a project I’m looking at developing a simple puzzle game. My question relates to the methods within a class. I have my Block type class; it has its many attributes, set methods, get methods and just plain methods. There are quite a few. Then I have my main board class. At the moment it does most of the logic, positioning of sprites collision detection and then draws the sprites etc... As I am learning to program as much as I’m learning to program games I’m curious to know how much code is typically acceptable within a given method. Is there such thing as having too many methods? All my draw functionality happens in one method, should I break this into a few ‘sub’ methods? My thinking is if I find at a later stage that the for loop I’m using to cycle through the array of sprites searching for collisions in the spriteCollision() method is inefficient I code a new method and just replace the old method calls with the new one, leaving the old code intact. Is it bad practice to have a method that contains one if statement, and place the call for that method in the for loop? I’m very much in the early stages of coding/designing and I need all the help I can get! I find it a little intimidating when people are talking about throwing together a prototype in a day too! Can’t wait until I’m that good!

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  • Tail-recursive implementation of take-while

    - by Giorgio
    I am trying to write a tail-recursive implementation of the function take-while in Scheme (but this exercise can be done in another language as well). My first attempt was (define (take-while p xs) (if (or (null? xs) (not (p (car xs)))) '() (cons (car xs) (take-while p (cdr xs))))) which works correctly but is not tail-recursive. My next attempt was (define (take-while-tr p xs) (let loop ((acc '()) (ys xs)) (if (or (null? ys) (not (p (car ys)))) (reverse acc) (loop (cons (car ys) acc) (cdr ys))))) which is tail recursive but needs a call to reverse as a last step in order to return the result list in the proper order. I cannot come up with a solution that is tail-recursive, does not use reverse, only uses lists as data structure (using a functional data structure like a Haskell's sequence which allows to append elements is not an option), has complexity linear in the size of the prefix, or at least does not have quadratic complexity (thanks to delnan for pointing this out). Is there an alternative solution satisfying all the properties above? My intuition tells me that it is impossible to accumulate the prefix of a list in a tail-recursive fashion while maintaining the original order between the elements (i.e. without the need of using reverse to adjust the result) but I am not able to prove this. Note The solution using reverse satisfies conditions 1, 3, 4.

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  • Algorithm for procedural city generation?

    - by Zove Games
    I am planning on making a (simple) procedural city generator using Java. I need ideas on whan algorithm to use for the layout, and the actual buildings. The city will mostly have skyscrapers, not really much complex stuff. For the layout I already have a simple algorithm implemented: Create a Map with java.awt.Point keys and Integer values. Fill it with all the points in the city's bounds with the value as -1 (unnassigned) Shuffle the map, and assign the 1st 10 of the keys IDs (from 1-10) Loop until all points have IDs: Loop though all points: Assign points next to an assigned point IDs of the point next to them, if 2 or more points border the point, then randomly choose which ID the point will get. You will end up with 10 random regions. Make roads bordering these regions. Fill the inside of each region with a randomly spaced and randomly rotated grid PROBLEM: This is not the fastest way to do it. What algorithm should I use for the layout. And what should I use to make each building's design? I don't even know how I'm going to do that yet (fractals maybe). I just need some ideas, not actual code.

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  • What would be the fastest way of storing or calculating legal move sets for chess pieces?

    - by ioSamurai
    For example if a move is attempted I could just loop through a list of legal moves and compare the x,y but I have to write logic to calculate those at least every time the piece is moved. Or, I can store in an array [,] and then check if x and y are not 0 then it is a legal move and then I save the data like this [0][1][0][0] etc etc for each row where 1 is a legal move, but I still have to populate it. I wonder what the fastest way to store and read a legal move on a piece object for calculation. I could use matrix math as well I suppose but I don't know. Basically I want to persist the rules for a given piece so I can assign a piece object a little template of all it's possible moves considering it is starting from it's current location, which should be just one table of data. But is it faster to loop or write LINQ queries or store arrays and matrices? public class Move { public int x; public int y; } public class ChessPiece : Move { private List<Move> possibleMoves { get; set; } public bool LegalMove(int x, int y){ foreach(var p in possibleMoves) { if(p.x == x && p.y == y) { return true; } } } } Anyone know?

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  • Win8 x64 Laptop (Samsung) unable to boot after installing Ubuntu

    - by user285872
    I posted here a while back and no one was able to help me so I am going to try to explain my problem better. I have a Samsung series 7 Ultrabook and I connected a USB optical drive with an Ubuntu 14.04 installation disc. I did not set or change any of my partitions, however, as I mainly wanted to just be able to boot from the disc and fool around with Ubuntu. Upon restarting my computer I get a blue-screen message saying: Recovery Your PC needs to be repiared The Boot configuration date file is missing some required information. File: \BCD Error Code: 0xc000000d You'll need to use the recovery tools on your installing media. If you don't have any installation media (like a disc or USB device), contact your system administrator or PC manufacturer. However I am never given the option to even try to boot to anything. When I turn my computer on the optical drive spins and then after a moment or two comes to a halt. I turned off safeboot and switched it to CSM (I believe that is what it is called) mode, and that makes it so when I turn my computer on it takes me to a Windows Recovery screen. I am able to change the date I want to recover and view all the applications installed, however upon recovering Windows says "All boot options are tried. Press key to recover with factory image using Recovery or any other keys for next boot loop iteration." It seems to be stuck in a loop. Can someone please help me?! I'm so confused and nothing is working!

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  • Do i need to restore iptable rules everytime on boot?

    - by capdragon
    Every time i reboot i loose the iptables rules that took me sooo long to enter. I know i can save them and restore them on boot but is there anyway to save them forever? Do i really need to restore them on boot every time? Seriously? The problem is I have a HUGE list of IPs in which i use a while loop to load them in. This can take upwards of 10 minutes. This is my home FTP server. It's a small vm with 1gb ram and very little processing power. There are so many IPs because I've pretty much given up on the Asian continent. I don't need them to be hitting up my ftp server everyday with brute force. I also block gov. monitors, trackers and spammers. This is the while loop i use to load in the list. grep INPUT block.list | while read LISTA; do sudo iptables -A $LISTA; done

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  • Do Loops kind of Reset every time you go through it?... [closed]

    - by JacKeown
    #include <iostream> using namespace std; int main (void) { cout << " 1\t2\t3\t4\t5\t6\t7\t8\t9" << endl << "" << endl; for (int c = 1; c < 10; c++) { cout << c << "| "; for (int i = 1; i < 10; i++) { cout << i * c << '\t'; } cout << endl; } return 0; } Hey so this code produces a times table...I found it on Google Code's C++ class online...I'm confused about why "i" in the second for loop resets to 1 every time you go through that loop...or is it being declared again in the first parameter? Thanks in advance!

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  • How do you coordinate with co-workers to give a balanced interview?

    - by goldierox
    My company has been conducting a lot of interviews lately for candidates with various experience levels, ranging from interns to senior candidates. We put our candidates through five 45 minute interview sessions where we try to ask a range of questions. One person always asks the same questions that test logic and communication. The rest typically split time between a whiteboard coding question and a discussion of previous projects, technologies the interviewee has worked with, and what he/she is looking for a job. Generally, we know the range of questions that other people on the loop will ask. Sometimes we switch things up and end up having redundancies. Today, 3 interviewers asked tree-related questions. Other times, we've all honed in on the same project on a resume and have had the interviewee talk about it with everyone. I think a smooth interview process would help us learn more about the candidate while giving the impression to the candidate that we have our act together as a team. How do you coordinate with others in the interview loop to give a balanced interview?

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  • Efficiency of iterators and alternatives? [migrated]

    - by user48037
    I have the following code for my game tiles: std::vector<GameObject_Tile*>::iterator it; for(int y = 0; y < GAME_TILES_Y; y++) { for(int x = 0; x < GAME_TILES_X; x++) { for (it = gameTiles[x][y].tiles.begin() ; it != gameTiles[x][y].tiles.end(); ++it) {}}} tiles is: struct Game_Tile { // More specific object types will be added here eventually vector<GameObject_Tile*> tiles; }; My problem is that if I change the vector to just be a single GameObject_Tile* instead and remove the iterator line in the loop I go from about 200fps to 450fps. Some context: The vector/pointer only contains one object in both scenarios. I will eventually need to store multiple, but for testing I just set it to a single pointer. The loop goes through 2,300 objects each frame and draws them. I would like to point out that if I remove the Draw (not seen int he example) method, I gain about 30 frames in both scenarios, the issue is the iteration. So I am wondering why having this as a vector being looped through by an iterator (to get at a single object) is costing me over 200 frames when compared to it being a single pointer? The 200+ frames faster code is: std::vector<GameObject_Tile*>::iterator it; for(int y = 0; y < GAME_TILES_Y; y++) { for(int x = 0; x < GAME_TILES_X; x++) { //gameTiles[x][y].tiles is used as a pointer here instead of using *it }} tiles is: struct Game_Tile { // More specific object types will be added here eventually GameObject_Tile* tiles; };

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  • Maze not being random.

    - by Matt Habel
    Hey there, I am building a program that generates a maze so I can later translate the path to my graphical part. I have most of it working, however, every time you can just take the east and south routes, and you'll get to the end. Even if I set the width as high as 64, so the maze is 64*64, I'm able to choose those 2 options and get to the end every time. I really don't understand why it is doing that. The code is below, it's fairly easy to understand. import random width = 8 def check(x,y): """Figures out the directions that Gen can move while""" if x-1 == -1: maze[x][y][3] = 0 if x+1 == width + 1: maze[x][y][1] = 0 if y+1 == width + 1: maze[x][y][2] = 0 if y-1 == -1: maze[x][y][0] = 0 if x + 1 in range(0,width) and visited[x+1][y] == False: maze[x][y][1] = 2 if x - 1 in range(0,width) and visited[x-1][y] == False: maze[x][y][3] = 2 if y + 1 in range(0,width) and visited[x][y+1] == False: maze[x][y][2] = 2 if y - 1 in range(0,width) and visited[x][y-1] == False: maze[x][y][0] = 2 def possibleDirs(x,y): """Figures out the ways that the person can move in each square""" dirs = [] walls = maze[x][y] if walls[0] == 1: dirs.append('n') if walls[1] == 1: dirs.append('e') if walls[2] == 1: dirs.append('s') if walls[3] == 1: dirs.append('w') return dirs def Gen(x,y): """Generates the maze using a depth-first search and recursive backtracking.""" visited[x][y] = True dirs = [] check(x,y) if maze[x][y][0] == 2: dirs.append(0) if maze[x][y][1] == 2: dirs.append(1) if maze[x][y][2] == 2: dirs.append(2) if maze[x][y][3] == 2: dirs.append(3) print dirs if len(dirs): #Randonly selects a derection for the current square to move past.append(current[:]) pos = random.choice(dirs) maze[x][y][pos] = 1 if pos == 0: current[1] -= 1 maze[x][y-1][2] = 1 if pos == 1: current[0] += 1 maze[x+1][y][3] = 1 if pos == 2: current[1] += 1 maze[x][y+1][0] = 1 if pos == 3: current[0] -= 1 maze[x-1][y][1] = 1 else: #If there's nowhere to go, go back one square lastPlace = past.pop() current[0] = lastPlace[0] current[1] = lastPlace[1] #Build the initial values for the maze to be replaced later maze = [] visited = [] past = [] #Generate empty 2d list with a value for each of the xy coordinates for i in range(0,width): maze.append([]) for q in range(0, width): maze[i].append([]) for n in range(0, 4): maze[i][q].append(4) #Makes a list of falses for all the non visited places for x in range(0, width): visited.append([]) for y in range(0, width): visited[x].append(False) dirs = [] print dirs current = [0,0] #Generates the maze so every single square has been filled. I'm not sure how this works, as it is possible to only go south and east to get to the final position. while current != [width-1, width-1]: Gen(current[0], current[1]) #Getting the ways the person can move in each square for i in range(0,width): dirs.append([]) for n in range(0,width): dirs[i].append([]) dirs[i][n] = possibleDirs(i,n) print dirs print visited pos = [0,0] #The user input part of the maze while pos != [width - 1, width - 1]: dirs = [] print pos if maze[pos[0]][pos[1]][0] == 1: dirs.append('n') if maze[pos[0]][pos[1]][1] == 1: dirs.append('e') if maze[pos[0]][pos[1]][2] == 1: dirs.append('s') if maze[pos[0]][pos[1]][3] == 1: dirs.append('w') print dirs path = raw_input("What direction do you want to go: ") if path not in dirs: print "You can't go that way!" continue elif path.lower() == 'n': pos[1] -= 1 elif path.lower() == 'e': pos[0] += 1 elif path.lower() == 's': pos[1] += 1 elif path.lower() == 'w': pos[0] -= 1 print"Good job!" As you can see, I think the problem is at the point where I generate the maze, however, when I just have it go until the current point is at the end, it doesn't fill every maze and is usually just one straight path. Thanks for helping. Update: I have changed the for loop that generates the maze to a simple while loop and it seems to work much better. It seems that when the for loop ran, it didn't go recursively, however, in the while loop it's perfectly fine. However, now all the squares do not fill out.

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  • Any tool to make git build every commit to a branch in a seperate repository?

    - by Wayne
    A git tool that meets the specs below is needed. Does one already exists? If not, I will create a script and make it available on GitHub for others to use or contribute. Is there a completely different and better way to solve the need to build/test every commit to a branch in a git repository? Not just to the latest but each one back to a certain staring point. Background: Our development environment uses a separate continuous integration server which is wonderful. However, it is still necessary to do full builds locally on each developer's PC to make sure the commit won't "break the build" when pushed to the CI server. Unfortunately, with auto unit tests, those build force the developer to wait 10 or 15 minutes for a build every time. To solve this we have setup a "mirror" git repository on each developer PC. So we develop in the main repository but anytime a local full build is needed. We run a couple commands in a in the mirror repository to fetch, checkout the commit we want to build, and build. It's works extremely lovely so we can continue working in the main one with the build going in parallel. There's only one main concern now. We want to make sure every single commit builds and tests fine. But we often get busy and neglect to build several fresh commits. Then if it the build fails you have to do a bisect or manually figure build each interim commit to figure out which one broke. Requirements for this tool. The tool will look at another repo, origin by default, fetch and compare all commits that are in branches to 2 lists of commits. One list must hold successfully built commits and the other lists commits that failed. It identifies any commit or commits not yet in either list and begins to build them in a loop in the order that they were committed. It stops on the first one that fails. The tool appropriately adds each commit to either the successful or failed list after it as attempted to build each one. The tool will ignore any "legacy" commits which are prior to the oldest commit in the success list. This logic makes the starting point possible in the next point. Starting Point. The tool building a specific commit so that, if successful it gets added to the success list. If it is the earliest commit in the success list, it becomes the "starting point" so that none of the commits prior to that are examined for builds. Only linear tree support? Much like bisect, this tool works best on a commit tree which is, at least from it's starting point, linear without any merges. That is, it should be a tree which was built and updated entirely via rebase and fast forward commits. If it fails on one commit in a branch it will stop without building the rest that followed after that one. Instead if will just move on to another branch, if any. The tool must do these steps once by default but allow a parameter to loop with an option to set how many seconds between loops. Other tools like Hudson or CruiseControl could do more fancy scheduling options. The tool must have good defaults but allow optional control. Which repo? origin by default. Which branches? all of them by default. What tool? by default an executable file to be provided by the user named "buildtest", "buildtest.sh" "buildtest.cmd", or buildtest.exe" in the root folder of the repository. Loop delay? run once by default with option to loop after a number of seconds between iterations.

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  • How do I make these fields autopopulate from the database?

    - by dmanexe
    I have an array, which holds values like this: $items_pool = Array ( [0] => Array ( [id] => 1 [quantity] => 1 ) [1] => Array ( [id] => 2 [quantity] => 1 ) [2] => Array ( [id] => 72 [quantity] => 6 ) [3] => Array ( [id] => 4 [quantity] => 1 ) [4] => Array ( [id] => 5 [quantity] => 1 ) [5] => Array ( [id] => 7 [quantity] => 1 ) [6] => Array ( [id] => 8 [quantity] => 1 ) [7] => Array ( [id] => 9 [quantity] => 1 ) [8] => Array ( [id] => 19 [quantity] => 1 ) [9] => Array ( [id] => 20 [quantity] => 1 ) [10] => Array ( [id] => 22 [quantity] => 1 ) [11] => Array ( [id] => 29 [quantity] => 0 ) ) Next, I have a form that I am trying to populate. It loops through the item database, prints out all the possible items, and checks the ones that are already present in $items_pool. <?php foreach ($items['items_poolpackage']->result() as $item): ?> <input type="checkbox" name="measure[<?=$item->id?>][checkmark]" value="<?=$item->id?>"> <?php endforeach; ?> I know what logically I'm trying to accomplish here, but I can't figure out the programming. What I'm looking for, written loosely is something like this (not real code): <input type="checkbox" name="measure[<?=$item->id?>][checkmark]" value="<?=$item->id?>" <?php if ($items_pool['$item->id']) { echo "SELECTED"; } else { }?>> Specifically this conditional loop through the array, through all the key values (the ID) and if there's a match, the checkbox is selected. <?php if ($items_pool['$item->id']) { echo "SELECTED"; } else { }?> I understand from a loop structured like this that it may mean a lot of 'extra' processing. TL;DR - I need to echo within a loop if the item going through the loop exists within another array.

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  • Dispatcher Timer Problem

    - by will
    I am trying to make a game in silverlight that also has widgets in it. To do this I am using a dispatcher timer running a game loop that updates graphics etc. In this I have a variable that has to be accessed by both by the constantly running game loop and UI event code. At first look it seemed that the gameloop had its own local copy of currentUnit (the variable), despite the variable being declared globally. I am trying to update currentUnit with an event by the widget part of the app, but the timer's version of the variable is not being updated. What can I do get the currentUnit in the gameloop loop to be updated whenever I update currentUnit via a click event? Here is the code for setting currentUnit as part of a click event DataContractJsonSerializer serializer = new DataContractJsonSerializer(typeof(Unit)); currentUnit = serializer.ReadObject(e.Result) as Unit; txtName.Text = currentUnit.name; Canvas.SetLeft(txtName, 100 - (int)Math.Ceiling(txtName.ActualWidth) / 2); txtX.Text = "" + currentUnit.x; txtY.Text = "" + currentUnit.y; txtX.Text = "" + currentUnit.owner; txtY.Text = "" + currentUnit.moved; txtName.Text = "" + currentUnit.GetHashCode(); And here is a snippet from the gameLoop loop //deal with phase changes and showing stuff if (txtPhase.Text == "Move" && movementPanel.Visibility == Visibility.Collapsed) { if (currentUnit != null) { if (currentUnit.owner) { if (currentUnit.moved) { txtMoved.Text = "This Unit has Already Moved!"; movementPanel.Visibility = Visibility.Collapsed; } else { txtMoved.Text = "" + currentUnit.GetHashCode(); movementPanel.Visibility = Visibility.Visible; } } else { txtMoved.Text = "bam"; movementPanel.Visibility = Visibility.Collapsed; } } else { txtMoved.Text = "slam"; movementPanel.Visibility = Visibility.Collapsed; } //loadUnitList(); } Here is the code for my unit class. using System; public class Unit { public int id { get; set; } public string name { get; set; } public string image { get; set; } public int x { get; set; } public int y { get; set; } public bool owner { get; set; } public int rotation { get; set; } public double movement { get; set; } public string type { get; set; } public bool moved { get; set; } public bool fired { get; set; } } Overall, any simple types, like a double is being 'updated' correctly, yet a complex of my own type (Unit) seems to be holding a local copy. Please help, I've asked other places and no one has had an answer for me!

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  • Looping through siblings of a specific row/setting up function

    - by Matt
    Trying to work through my javascript book I am referencing to learn the language and got stuck on looping through siblings of a specific row. W3schools and W3 didnt have what i was looking for. Below is a function walk-through... It reads: Create the countRecords() function. The purpose of this function is to count the number of visible rows in the data table after the table headings. The total is then displayed in the table cell with the id "records". Add the follow commands to the function: a. Create a object named headRow that points to the table row with the id "titleRow". Create a variable named rowCount, setting its initial value to 0. b. Create a for loop that uses familial references starting with the first sibling of headRow and moving to the next sibling until there are no siblings left. Within the for loop. test whether the node name of the currentnext sibling until there are no sibilings left. Within the for loop test whether the node name of the current node is equal to "TR". If it is, test wheter the value of its display style is equal to an empty text string. If it is (indicating that it is visible in the document) increate the value of the rowCount variable by 1. c. Change the text of the "records" table cell to the value of the rowCount variable. Don't use innerHTML. Create a text node that contains the value of the rowCount variable and assign it to a variable called txt. Create a variable called record to store the reference to the element "records" table cell. d. Insert an if condition that test whether the "records" cell has any child nodes. If it does, replace the replace the text node of the "record" table cell with the created text node (txt). If it doesn't append the text node to the cell. var headRow; // part a var rowCount = 0; //part b this is where I get lost. I know I need to access the id titleRow but unsure how to set my loop up specifically for this headRow = document.getElementById("titleRow"); for(var i=0; i<headrow.length; i++) { if (something is not equal == "TH") { make code happen here } if (is "TR" == ""){ rowCount = +1; } //part c var txt = document.createTextNode(rowCount); var record = document.getElementsById("records") //part d holding off on this part until I get a,b,c figured out. The HTML supporting snippet: <table id="filters"> <tr><th colspan="2">Filter Product List</th></tr> <tr> <td>Records: </td> <td id="records"></td> </tr> <table id="prodTable"> <tr><th colspan="8">Digital Cameras</th></tr> <tr id="titleRow"> <th>Model</th> <th>Manufacturer</th> <th>Resolution</th> <th>Zoom</th> <th>Media</th> <th>Video</th> <th>Microphone</th> </tr> Thanks for the help!

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  • Why is processing a sorted array faster than an unsorted array?

    - by GManNickG
    Here is a piece of code that shows some very peculiar performance. For some strange reason, sorting the data miraculously speeds up the code by almost 6x: #include <algorithm> #include <ctime> #include <iostream> int main() { // generate data const unsigned arraySize = 32768; int data[arraySize]; for (unsigned c = 0; c < arraySize; ++c) data[c] = std::rand() % 256; // !!! with this, the next loop runs faster std::sort(data, data + arraySize); // test clock_t start = clock(); long long sum = 0; for (unsigned i = 0; i < 100000; ++i) { // primary loop for (unsigned c = 0; c < arraySize; ++c) { if (data[c] >= 128) sum += data[c]; } } double elapsedTime = static_cast<double>(clock() - start) / CLOCKS_PER_SEC; std::cout << elapsedTime << std::endl; std::cout << "sum = " << sum << std::endl; } Without std::sort(data, data + arraySize);, the code runs in 11.54 seconds. With the sorted data, the code runs in 1.93 seconds. Initially I thought this might be just a language or compiler anomaly. So I tried it Java... import java.util.Arrays; import java.util.Random; public class Main { public static void main(String[] args) { // generate data int arraySize = 32768; int data[] = new int[arraySize]; Random rnd = new Random(0); for (int c = 0; c < arraySize; ++c) data[c] = rnd.nextInt() % 256; // !!! with this, the next loop runs faster Arrays.sort(data); // test long start = System.nanoTime(); long sum = 0; for (int i = 0; i < 100000; ++i) { // primary loop for (int c = 0; c < arraySize; ++c) { if (data[c] >= 128) sum += data[c]; } } System.out.println((System.nanoTime() - start) / 1000000000.0); System.out.println("sum = " + sum); } } with a similar but less extreme result. My first thought was that sorting brings the data into cache, but my next thought was how silly that is because the array was just generated. What is going on? Why is a sorted array faster than an unsorted array? The code is summing up some independent terms, the order should not matter.

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  • Identifier is undefined

    - by hawk
    I wrote the following code in C++ using VS2012 Express. void ac_search( uint num_patterns, uint pattern_length, const char *patterns, uint num_records, uint record_length, const char *records, int *matches, Node* trie) { // Irrelevant code omitted. } vector<int> ac_benchmark_search( uint num_patterns, uint pattern_length, const char *patterns, uint num_records, uint record_length, const char *records, double &time) { // Prepare the container for the results vector<int> matches(num_records * num_patterns); Trie T; Node* trie = T.addWord(records, num_records, record_length); // error line ac_search(num_patterns, pattern_length, patterns, num_records, record_length, records, matches.data(), trie); // Irrelevant code omitted. return matches; } I get the error identifier "ac_search" is undefined at the function invoking line. I am a bit confused here. because the function ac_search is declared as a global (not inside any container). Why can't I call it at this place? Am I missing something? Update I tried ignore irrelevant code and then included it gradually and found that everything is fine until I include the outer loop of ac_search I get the aforementioned error. here is updated code of the function ac_search: void ac_cpu_string_search(uint num_patterns, uint pattern_length, const char *patterns, uint num_records, uint record_length, const char *records, int *matches, Node* trie) { // Loop over all records //for (uint record_number = 0; record_number < num_records; ++record_number) //{ // // Loop over all patterns for (uint pattern_number = 0; pattern_number < num_patterns; ++pattern_number) { // Execute string search const char *ptr_record = &records[record_number * record_length]; const char *ptr_match = std::strstr(ptr_record, &patterns[pattern_number * pattern_length]); // If pattern was found, then calculate offset, otherwise result is -1 if (ptr_match) { matches[record_number * num_patterns + pattern_number] = static_cast<int>(std::distance(ptr_record, ptr_match)); } else { matches[record_number * num_patterns + pattern_number] = -1; } // } //} } Update 2 I think the error has something to do with the function addWord which belongs to the class Trie. When I commented out this function, I did not get the error anymore. Node* Trie::addWord(const char *records, uint num_records, uint record_length) { // Loop over all records for (uint record_number = 0; record_number < num_records; ++record_number) { const char *ptr_record = &records[record_number * record_length]; string s = ptr_record; Node* current = root; if ( s.length() == 0 ) { current->setWordMarker(); // an empty word return; } for ( int i = 0; i < s.length(); i++ ) { Node* child = current->findChild(s[i]); if ( child != NULL ) { current = child; } else { Node* tmp = new Node(); tmp->setContent(s[i]); current->appendChild(tmp); current = tmp; } if ( i == s.length() - 1 ) current->setWordMarker(); } return current; } void ac_search( uint num_patterns, uint pattern_length, const char *patterns, uint num_records, uint record_length, const char *records, int *matches, Node* trie) { // Irrelevant code omitted. } vector<int> ac_benchmark_search( uint num_patterns, uint pattern_length, const char *patterns, uint num_records, uint record_length, const char *records, double &time) { // Prepare the container for the results vector<int> matches(num_records * num_patterns); Trie T; Node* trie = T.addWord(records, num_records, record_length); // error line ac_search(num_patterns, pattern_length, patterns, num_records, record_length, records, matches.data(), trie); // Irrelevant code omitted. return matches; }

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  • Calling Object Methods in Code

    - by Mister R2
    I'm a bit new to PHP, and I'm more experienced with strongly-typed languages such as JAVA, C# or C++.I'm currently writing a web tool in PHP, and I am having an issue trying to do what I want. The simple idea of what I want to do in code is run through some emails I used PHP-IMAP to get. I then create email objects (a class I defined), and put them in an array. Later on the code, however, I cycle through those emails to display them. However, as you might have guessed I'd have an issue with, I try to use an Email Class object method in that later loop -- and I'm pretty sure PHP doesn't know that the variables in the array happen to be Email Class objects! I wrote a toString method, and I want to call it in the loop. While I don't need to do this for the final version of this tool, I would like to find out what I'm missing. This is the class and the loop where I'm calling the method: include 'imap_email_interface.php'; class ImapEmail implements imap_email_interface { // Email data var $msgno; var $to; var $from; var $subject; var $body; var $attachment; // Email behavior /* PHP 4 ~ legacy constructor */ public function ImapEmail($message_number) { $this->__construct(); $this->msgno = $message_number; } /* PHP 5 Constructor */ public function __construct($message_number) { $this->msgno = $message_number; } public function send($send_to) { // Not Yet Needed! Seriously! } public function setHeaderDirectly($TO, $FROM, $SUBJECT) { $this->to = $TO; $this->from = $FROM; $this->subject = $SUBJECT; } public function setHeaderIndirectly($HEADER) { if (isset($HEADER->to[0]->personal)) $this->to = '"'.$HEADER->to[0]->personal.'", '.$HEADER->to[0]->mailbox.'@'.$HEADER->to[0]->host; else $this->to = $HEADER->to[0]->mailbox.'@'.$HEADER->to[0]->host; $this->from = '"'.$HEADER->from[0]->personal.'", '.$HEADER->from[0]->mailbox.'@'.$HEADER->from[0]->host; $this->subject = $HEADER->subject; } public function setBody($BODY) { $this->body = $BODY; } public function setAttachment($ATTCH) { $this->attachment = $ATTCH; } public function toString() { $str = '[TO]: ' . $this->to . '<br />' . '[FROM]: ' . $this->from . '<br />' . '[SUBJECT]: ' . $this->subject . '<br />'; $str .= '[Attachment]: '.$this->attachment.'<br />'; return $str; } } ?> The Loop: foreach ($orderFileEmails as $x) { $x->toString(); echo '<br /><br />'; } Any ideas?

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  • texture colours opengl

    - by user1324894
    Hi I am making a simple 2D game in c++ and for the map I am doing texture mapping by using tiles and assigning textures to those tiles. However, when I run the programme the textures become black and white when I want them to be the colour they are in the .png image. This is my code: int worldMap[10][10] = { {0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0}, {0,0,0,0,0,0,0,0,0,0}, }; void background() { glClearColor(0.0,0.0,0.0,0.0); /**********************************************************************************************/ // Texture loading object nv::Image img; // Return true on success if(img.loadImageFromFile("Image_Loading/field.png")) { glGenTextures(1, &myTexture); glBindTexture(GL_TEXTURE_2D, myTexture); glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE); glTexImage2D(GL_TEXTURE_2D, 0, img.getInternalFormat(), img.getWidth(), img.getHeight(), 0, img.getFormat(), img.getType(), img.getLevel(0)); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT ); glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT ); glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAX_ANISOTROPY_EXT, 16.0f); } else MessageBox(NULL, "Failed to load texture", "End of the world", MB_OK | MB_ICONINFORMATION); /**********************************************************************************************/ } void drawTiles (void) { //our function to draw the tiles for (int i = 0; i < 10; i++) //loop through the height of the map { for (int j = 0; j < 10; j++) //loop through the width of the map { if (worldMap[i][j] == 0) //if the map at this position contains a 0 { glBindTexture( GL_TEXTURE_2D, myTexture ); //bind our grass texture to our shape } glPushMatrix(); //push the matrix so that our translations only affect this tile glTranslatef(j, -i, 0); //translate the tile to where it should belong glBegin (GL_QUADS); //begin drawing our quads glTexCoord2d(10, 0); glVertex2f((-10 + mapX),(-10 + mapY)); //with our vertices we have to assign a texcoord glTexCoord2d(10, 0); glVertex2f((10 + mapX),(-10 + mapY)); //so that our texture has some points to draw to glTexCoord2d(10, 10); glVertex2f((10 + mapX),(10 + mapY)); glTexCoord2d(0, 10); glVertex2f((-10 + mapX),(10 + mapY)); glEnd(); glPopMatrix(); //pop the matrix } //end first loop } //end second loop } void display() { glClearColor (0.0,0.0,0.0,1.0); glClear(GL_COLOR_BUFFER_BIT); /**********************************************************************************************/ glMatrixMode( GL_PROJECTION ); glLoadIdentity(); gluOrtho2D( -5, 5, -5, 5); glMatrixMode( GL_MODELVIEW ); glEnable(GL_TEXTURE_2D); glBindTexture(GL_TEXTURE_2D, myTexture); glEnable(GL_BLEND); glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); drawTiles(); glDisable(GL_TEXTURE_2D); glDisable(GL_BLEND); /**********************************************************************************************/ } void character () { glBegin(GL_POLYGON); glVertex2f((-0.5+characterX),(-0.5 +characterY)); glVertex2f((-0.5+characterX),(0.5+characterY)); glVertex2f((0.5+characterX),(0.5+characterY)); glVertex2f((0.5+characterX),(-0.5+characterY)); glTranslatef(characterX, characterY, 0.0f); glEnd(); } Can anybody help please?

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  • Find out when all processes in (void) is done?

    - by Emil
    Hey. I need to know how you can find out when all processes (loaded) from a - (void) are done, if it's possible. Why? I'm loading in data for a UITableView, and I need to know when a Loading... view can be replaced with the UITableView, and when I can start creating the cells. This is my code: - (void) reloadData { NSAutoreleasePool *releasePool = [[NSAutoreleasePool alloc] init]; NSLog(@"Reloading data."); NSURL *urlPosts = [NSURL URLWithString:[NSString stringWithFormat:@"%@", URL]]; NSError *lookupError = nil; NSString *data = [[NSString alloc] initWithContentsOfURL:urlPosts encoding:NSUTF8StringEncoding error:&lookupError]; postsData = [data componentsSeparatedByString:@"~"]; [data release], data = nil; urlPosts = nil; self.numberOfPosts = [[postsData objectAtIndex:0] intValue]; self.postsArrayID = [[postsData objectAtIndex:1] componentsSeparatedByString:@"#"]; self.postsArrayDate = [[postsData objectAtIndex:2] componentsSeparatedByString:@"#"]; self.postsArrayTitle = [[postsData objectAtIndex:3] componentsSeparatedByString:@"#"]; self.postsArrayComments = [[postsData objectAtIndex:4] componentsSeparatedByString:@"#"]; self.postsArrayImgSrc = [[postsData objectAtIndex:5] componentsSeparatedByString:@"#"]; NSMutableArray *writeToPlist = [NSMutableArray array]; NSMutableArray *writeToNoImagePlist = [NSMutableArray array]; NSMutableArray *imagesStored = [NSMutableArray arrayWithContentsOfFile:[rootPath stringByAppendingPathComponent:@"imagesStored.plist"]]; int loop = 0; for (NSString *postID in postsArrayID) { if ([imagesStored containsObject:[NSString stringWithFormat:@"%@.png", postID]]){ NSLog(@"Allready stored, jump to next. ID: %@", postID); continue; } NSLog(@"%@.png", postID); NSData *imageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:[postsArrayImgSrc objectAtIndex:loop]]]; // If image contains anything, set cellImage to image. If image is empty, try one more time or use noImage.png, set in IB if (imageData == nil){ NSLog(@"imageData is empty before trying .jpeg"); // If image == nil, try to replace .jpg with .jpeg, and if that worked, set cellImage to that image. If that is also nil, use noImage.png, set in IB. imageData = [NSData dataWithContentsOfURL:[NSURL URLWithString:[[postsArrayImgSrc objectAtIndex:loop] stringByReplacingOccurrencesOfString:@".jpg" withString:@".jpeg"]]]; } if (imageData != nil){ NSLog(@"imageData is NOT empty when creating file"); [fileManager createFileAtPath:[rootPath stringByAppendingPathComponent:[NSString stringWithFormat:@"images/%@.png", postID]] contents:imageData attributes:nil]; [writeToPlist addObject:[NSString stringWithFormat:@"%@.png", postID]]; } else { [writeToNoImagePlist addObject:[NSString stringWithFormat:@"%@", postID]]; } imageData = nil; loop++; NSLog(@"imagePlist: %@\nnoImagePlist: %@", writeToPlist, writeToNoImagePlist); } NSMutableArray *writeToAllPlist = [NSMutableArray arrayWithArray:writeToPlist]; [writeToPlist addObjectsFromArray:[NSArray arrayWithContentsOfFile:nowPlist]]; [writeToAllPlist addObjectsFromArray:[NSArray arrayWithContentsOfFile:[rootPath stringByAppendingPathComponent:@"imagesStored.plist"]]]; [writeToNoImagePlist addObjectsFromArray:[NSArray arrayWithContentsOfFile:[rootPath stringByAppendingPathComponent:@"noImage.plist"]]]; [writeToPlist writeToFile:nowPlist atomically:YES]; [writeToAllPlist writeToFile:[rootPath stringByAppendingPathComponent:@"imagesStored.plist"] atomically:YES]; [writeToNoImagePlist writeToFile:[rootPath stringByAppendingPathComponent:@"noImage.plist"] atomically:YES]; [releasePool release]; }

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  • Help with Java Program for Prime numbers

    - by Ben
    Hello everyone, I was wondering if you can help me with this program. I have been struggling with it for hours and have just trashed my code because the TA doesn't like how I executed it. I am completely hopeless and if anyone can help me out step by step, I would greatly appreciate it. In this project you will write a Java program that reads a positive integer n from standard input, then prints out the first n prime numbers. We say that an integer m is divisible by a non-zero integer d if there exists an integer k such that m = k d , i.e. if d divides evenly into m. Equivalently, m is divisible by d if the remainder of m upon (integer) division by d is zero. We would also express this by saying that d is a divisor of m. A positive integer p is called prime if its only positive divisors are 1 and p. The one exception to this rule is the number 1 itself, which is considered to be non-prime. A positive integer that is not prime is called composite. Euclid showed that there are infinitely many prime numbers. The prime and composite sequences begin as follows: Primes: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, … Composites: 1, 4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 24, 25, 26, 27, 28, … There are many ways to test a number for primality, but perhaps the simplest is to simply do trial divisions. Begin by dividing m by 2, and if it divides evenly, then m is not prime. Otherwise, divide by 3, then 4, then 5, etc. If at any point m is found to be divisible by a number d in the range 2 d m-1, then halt, and conclude that m is composite. Otherwise, conclude that m is prime. A moment’s thought shows that one need not do any trial divisions by numbers d which are themselves composite. For instance, if a trial division by 2 fails (i.e. has non-zero remainder, so m is odd), then a trial division by 4, 6, or 8, or any even number, must also fail. Thus to test a number m for primality, one need only do trial divisions by prime numbers less than m. Furthermore, it is not necessary to go all the way up to m-1. One need only do trial divisions of m by primes p in the range 2 p m . To see this, suppose m 1 is composite. Then there exist positive integers a and b such that 1 < a < m, 1 < b < m, and m = ab . But if both a m and b m , then ab m, contradicting that m = ab . Hence one of a or b must be less than or equal to m . To implement this process in java you will write a function called isPrime() with the following signature: static boolean isPrime(int m, int[] P) This function will return true or false according to whether m is prime or composite. The array argument P will contain a sufficient number of primes to do the testing. Specifically, at the time isPrime() is called, array P must contain (at least) all primes p in the range 2 p m . For instance, to test m = 53 for primality, one must do successive trial divisions by 2, 3, 5, and 7. We go no further since 11 53 . Thus a precondition for the function call isPrime(53, P) is that P[0] = 2 , P[1] = 3 , P[2] = 5, and P[3] = 7 . The return value in this case would be true since all these divisions fail. Similarly to test m =143 , one must do trial divisions by 2, 3, 5, 7, and 11 (since 13 143 ). The precondition for the function call isPrime(143, P) is therefore P[0] = 2 , P[1] = 3 , P[2] = 5, P[3] = 7 , and P[4] =11. The return value in this case would be false since 11 divides 143. Function isPrime() should contain a loop that steps through array P, doing trial divisions. This loop should terminate when 2 either a trial division succeeds, in which case false is returned, or until the next prime in P is greater than m , in which case true is returned. Function main() in this project will read the command line argument n, allocate an int array of length n, fill the array with primes, then print the contents of the array to stdout according to the format described below. In the context of function main(), we will refer to this array as Primes[]. Thus array Primes[] plays a dual role in this project. On the one hand, it is used to collect, store, and print the output data. On the other hand, it is passed to function isPrime() to test new integers for primality. Whenever isPrime() returns true, the newly discovered prime will be placed at the appropriate position in array Primes[]. This process works since, as explained above, the primes needed to test an integer m range only up to m , and all of these primes (and more) will already be stored in array Primes[] when m is tested. Of course it will be necessary to initialize Primes[0] = 2 manually, then proceed to test 3, 4, … for primality using function isPrime(). The following is an outline of the steps to be performed in function main(). • Check that the user supplied exactly one command line argument which can be interpreted as a positive integer n. If the command line argument is not a single positive integer, your program will print a usage message as specified in the examples below, then exit. • Allocate array Primes[] of length n and initialize Primes[0] = 2 . • Enter a loop which will discover subsequent primes and store them as Primes[1] , Primes[2], Primes[3] , ……, Primes[n -1] . This loop should contain an inner loop which walks through successive integers and tests them for primality by calling function isPrime() with appropriate arguments. • Print the contents of array Primes[] to stdout, 10 to a line separated by single spaces. In other words Primes[0] through Primes[9] will go on line 1, Primes[10] though Primes[19] will go on line 2, and so on. Note that if n is not a multiple of 10, then the last line of output will contain fewer than 10 primes. Your program, which will be called Prime.java, will produce output identical to that of the sample runs below. (As usual % signifies the unix prompt.) % java Prime Usage: java Prime [PositiveInteger] % java Prime xyz Usage: java Prime [PositiveInteger] % java Prime 10 20 Usage: java Prime [PositiveInteger] % java Prime 75 2 3 5 7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 101 103 107 109 113 127 131 137 139 149 151 157 163 167 173 179 181 191 193 197 199 211 223 227 229 233 239 241 251 257 263 269 271 277 281 283 293 307 311 313 317 331 337 347 349 353 359 367 373 379 % 3 As you can see, inappropriate command line argument(s) generate a usage message which is similar to that of many unix commands. (Try doing the more command with no arguments to see such a message.) Your program will include a function called Usage() having signature static void Usage() that prints this message to stderr, then exits. Thus your program will contain three functions in all: main(), isPrime(), and Usage(). Each should be preceded by a comment block giving it’s name, a short description of it’s operation, and any necessary preconditions (such as those for isPrime().) See examples on the webpage.

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  • C++ Multithreading with pthread is blocking (including sockets)

    - by Sebastian Büttner
    I am trying to implement a multi threaded application with pthread. I did implement a thread class which looks like the following and I call it later twice (or even more), but it seems to block instead of execute the threads parallel. Here is what I got until now: The Thread Class is an abstract class which has the abstract method "exec" which should contain the thread code in a derive class (I did a sample of this, named DerivedThread) Thread.hpp #ifndef THREAD_H_ #define THREAD_H_ #include <pthread.h> class Thread { public: Thread(); void start(); void join(); virtual int exec() = 0; int exit_code(); private: static void* thread_router(void* arg); void exec_thread(); pthread_t pth_; int code_; }; #endif /* THREAD_H_ */ And Thread.cpp #include <iostream> #include "Thread.hpp" /*****************************/ using namespace std; Thread::Thread(): code_(0) { cout << "[Thread] Init" << endl; } void Thread::start() { cout << "[Thread] Created Thread" << endl; pthread_create( &pth_, NULL, Thread::thread_router, reinterpret_cast<void*>(this)); } void Thread::join() { cout << "[Thread] Join Thread" << endl; pthread_join(pth_, NULL); } int Thread::exit_code() { return code_; } void Thread::exec_thread() { cout << "[Thread] Execute" << endl; code_ = exec(); } void* Thread::thread_router(void* arg) { cout << "[Thread] exec_thread function in thread" << endl; reinterpret_cast<Thread*>(arg)->exec_thread(); return NULL; } DerivedThread.hpp #include "Thread.hpp" class DerivedThread : public Thread { public: DerivedThread(); virtual ~DerivedThread(); int exec(); void Close() = 0; DerivedThread.cpp [...] #include "DerivedThread.cpp" [...] int DerivedThread::exec() { //code to be executed do { cout << "Thread executed" << endl; usleep(1000000); } while (true); //dummy, just to let it run for a while } [...] Basically, I am calling this like the here: DerivedThread *thread; cout << "Creating Thread" << endl; thread = new DerivedThread(); cout << "Created thread, starting..." << endl; thread->start(); cout << "Started thread" << endl; cout << "Creating 2nd Thread" << endl; thread = new DerivedThread(); cout << "Created 2nd thread, starting..." << endl; thread->start(); cout << "Started 2nd thread" << endl; What is working great if I am only starting one of these Threads , but if I start multiple which should run together (not synced, only parallel) . But I discovered, that the thread is created, then as it tries to execute it (via start) the problem seems to block until the thread has closed. After that the next Thread is processed. I thought that pthread would do it unblocked for me, so what did I wrong? A sample output might be: Creating Thread [Thread] Thread Init Created thread, starting... [Thread] Created thread [Thread] exec_thread function in thread [Thread] Execute Thread executed Thread executed Thread executed Thread executed Thread executed Thread executed Thread executed .... Until Thread 1 is not terminated, a Thread 2 won't be created not executed. The process above is executed in an other class. Just for the information: I am trying to create a multi threaded server. The concept is like this: MultiThreadedServer Class has a main loop, like this one: ::inet::ServerSock *sock; //just a simple self made wrapper class for sockets DerivedThread *thread; for (;;) { sock = new ::inet::ServerSock(); this->Socket->accept( *sock ); cout << "Creating Thread" << endl; //Threads (according to code sample above) thread = new DerivedThread(sock); //I did not mentoine the parameter before as it was not neccesary, in fact, I pass the socket handle with the connected socket to the thread cout << "Created thread, starting..." << endl; thread->start(); cout << "Started thread" << endl; } So I thought that this would loop over and over and wait for new connections to accept. and when a new client arrives, I am creating a new thread and give the thread the connected socket as a parameter. In the DerivedThread::exec I am doing the handling for the connected client. Like: [...] do { [...] if (this-sock_-read( Buffer, sizeof(PacketStruc) ) 0) { cout << "[Handler_Base] Recv Packet" << endl; //handle the packet } else { Connected = false; } delete Buffer; } while ( Connected ); So I loop in the created thread as long as the client keeps the connection. I think, that the socket may cause the blocking behaviour. Edit: I figured out, that it is not the read() loop in the DerivedThread Class as I simply replaced it with a loop over a simple cout-usleep part. It did also only execute the first one and after first thread finished, the 2nd one was executed. Many thanks and best regards, Sebastian

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  • Creating a dynamic, extensible C# Expando Object

    - by Rick Strahl
    I love dynamic functionality in a strongly typed language because it offers us the best of both worlds. In C# (or any of the main .NET languages) we now have the dynamic type that provides a host of dynamic features for the static C# language. One place where I've found dynamic to be incredibly useful is in building extensible types or types that expose traditionally non-object data (like dictionaries) in easier to use and more readable syntax. I wrote about a couple of these for accessing old school ADO.NET DataRows and DataReaders more easily for example. These classes are dynamic wrappers that provide easier syntax and auto-type conversions which greatly simplifies code clutter and increases clarity in existing code. ExpandoObject in .NET 4.0 Another great use case for dynamic objects is the ability to create extensible objects - objects that start out with a set of static members and then can add additional properties and even methods dynamically. The .NET 4.0 framework actually includes an ExpandoObject class which provides a very dynamic object that allows you to add properties and methods on the fly and then access them again. For example with ExpandoObject you can do stuff like this:dynamic expand = new ExpandoObject(); expand.Name = "Rick"; expand.HelloWorld = (Func<string, string>) ((string name) => { return "Hello " + name; }); Console.WriteLine(expand.Name); Console.WriteLine(expand.HelloWorld("Dufus")); Internally ExpandoObject uses a Dictionary like structure and interface to store properties and methods and then allows you to add and access properties and methods easily. As cool as ExpandoObject is it has a few shortcomings too: It's a sealed type so you can't use it as a base class It only works off 'properties' in the internal Dictionary - you can't expose existing type data It doesn't serialize to XML or with DataContractSerializer/DataContractJsonSerializer Expando - A truly extensible Object ExpandoObject is nice if you just need a dynamic container for a dictionary like structure. However, if you want to build an extensible object that starts out with a set of strongly typed properties and then allows you to extend it, ExpandoObject does not work because it's a sealed class that can't be inherited. I started thinking about this very scenario for one of my applications I'm building for a customer. In this system we are connecting to various different user stores. Each user store has the same basic requirements for username, password, name etc. But then each store also has a number of extended properties that is available to each application. In the real world scenario the data is loaded from the database in a data reader and the known properties are assigned from the known fields in the database. All unknown fields are then 'added' to the expando object dynamically. In the past I've done this very thing with a separate property - Properties - just like I do for this class. But the property and dictionary syntax is not ideal and tedious to work with. I started thinking about how to represent these extra property structures. One way certainly would be to add a Dictionary, or an ExpandoObject to hold all those extra properties. But wouldn't it be nice if the application could actually extend an existing object that looks something like this as you can with the Expando object:public class User : Westwind.Utilities.Dynamic.Expando { public string Email { get; set; } public string Password { get; set; } public string Name { get; set; } public bool Active { get; set; } public DateTime? ExpiresOn { get; set; } } and then simply start extending the properties of this object dynamically? Using the Expando object I describe later you can now do the following:[TestMethod] public void UserExampleTest() { var user = new User(); // Set strongly typed properties user.Email = "[email protected]"; user.Password = "nonya123"; user.Name = "Rickochet"; user.Active = true; // Now add dynamic properties dynamic duser = user; duser.Entered = DateTime.Now; duser.Accesses = 1; // you can also add dynamic props via indexer user["NickName"] = "AntiSocialX"; duser["WebSite"] = "http://www.west-wind.com/weblog"; // Access strong type through dynamic ref Assert.AreEqual(user.Name,duser.Name); // Access strong type through indexer Assert.AreEqual(user.Password,user["Password"]); // access dyanmically added value through indexer Assert.AreEqual(duser.Entered,user["Entered"]); // access index added value through dynamic Assert.AreEqual(user["NickName"],duser.NickName); // loop through all properties dynamic AND strong type properties (true) foreach (var prop in user.GetProperties(true)) { object val = prop.Value; if (val == null) val = "null"; Console.WriteLine(prop.Key + ": " + val.ToString()); } } As you can see this code somewhat blurs the line between a static and dynamic type. You start with a strongly typed object that has a fixed set of properties. You can then cast the object to dynamic (as I discussed in my last post) and add additional properties to the object. You can also use an indexer to add dynamic properties to the object. To access the strongly typed properties you can use either the strongly typed instance, the indexer or the dynamic cast of the object. Personally I think it's kinda cool to have an easy way to access strongly typed properties by string which can make some data scenarios much easier. To access the 'dynamically added' properties you can use either the indexer on the strongly typed object, or property syntax on the dynamic cast. Using the dynamic type allows all three modes to work on both strongly typed and dynamic properties. Finally you can iterate over all properties, both dynamic and strongly typed if you chose. Lots of flexibility. Note also that by default the Expando object works against the (this) instance meaning it extends the current object. You can also pass in a separate instance to the constructor in which case that object will be used to iterate over to find properties rather than this. Using this approach provides some really interesting functionality when use the dynamic type. To use this we have to add an explicit constructor to the Expando subclass:public class User : Westwind.Utilities.Dynamic.Expando { public string Email { get; set; } public string Password { get; set; } public string Name { get; set; } public bool Active { get; set; } public DateTime? ExpiresOn { get; set; } public User() : base() { } // only required if you want to mix in seperate instance public User(object instance) : base(instance) { } } to allow the instance to be passed. When you do you can now do:[TestMethod] public void ExpandoMixinTest() { // have Expando work on Addresses var user = new User( new Address() ); // cast to dynamicAccessToPropertyTest dynamic duser = user; // Set strongly typed properties duser.Email = "[email protected]"; user.Password = "nonya123"; // Set properties on address object duser.Address = "32 Kaiea"; //duser.Phone = "808-123-2131"; // set dynamic properties duser.NonExistantProperty = "This works too"; // shows default value Address.Phone value Console.WriteLine(duser.Phone); } Using the dynamic cast in this case allows you to access *three* different 'objects': The strong type properties, the dynamically added properties in the dictionary and the properties of the instance passed in! Effectively this gives you a way to simulate multiple inheritance (which is scary - so be very careful with this, but you can do it). How Expando works Behind the scenes Expando is a DynamicObject subclass as I discussed in my last post. By implementing a few of DynamicObject's methods you can basically create a type that can trap 'property missing' and 'method missing' operations. When you access a non-existant property a known method is fired that our code can intercept and provide a value for. Internally Expando uses a custom dictionary implementation to hold the dynamic properties you might add to your expandable object. Let's look at code first. The code for the Expando type is straight forward and given what it provides relatively short. Here it is.using System; using System.Collections.Generic; using System.Linq; using System.Dynamic; using System.Reflection; namespace Westwind.Utilities.Dynamic { /// <summary> /// Class that provides extensible properties and methods. This /// dynamic object stores 'extra' properties in a dictionary or /// checks the actual properties of the instance. /// /// This means you can subclass this expando and retrieve either /// native properties or properties from values in the dictionary. /// /// This type allows you three ways to access its properties: /// /// Directly: any explicitly declared properties are accessible /// Dynamic: dynamic cast allows access to dictionary and native properties/methods /// Dictionary: Any of the extended properties are accessible via IDictionary interface /// </summary> [Serializable] public class Expando : DynamicObject, IDynamicMetaObjectProvider { /// <summary> /// Instance of object passed in /// </summary> object Instance; /// <summary> /// Cached type of the instance /// </summary> Type InstanceType; PropertyInfo[] InstancePropertyInfo { get { if (_InstancePropertyInfo == null && Instance != null) _InstancePropertyInfo = Instance.GetType().GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.DeclaredOnly); return _InstancePropertyInfo; } } PropertyInfo[] _InstancePropertyInfo; /// <summary> /// String Dictionary that contains the extra dynamic values /// stored on this object/instance /// </summary> /// <remarks>Using PropertyBag to support XML Serialization of the dictionary</remarks> public PropertyBag Properties = new PropertyBag(); //public Dictionary<string,object> Properties = new Dictionary<string, object>(); /// <summary> /// This constructor just works off the internal dictionary and any /// public properties of this object. /// /// Note you can subclass Expando. /// </summary> public Expando() { Initialize(this); } /// <summary> /// Allows passing in an existing instance variable to 'extend'. /// </summary> /// <remarks> /// You can pass in null here if you don't want to /// check native properties and only check the Dictionary! /// </remarks> /// <param name="instance"></param> public Expando(object instance) { Initialize(instance); } protected virtual void Initialize(object instance) { Instance = instance; if (instance != null) InstanceType = instance.GetType(); } /// <summary> /// Try to retrieve a member by name first from instance properties /// followed by the collection entries. /// </summary> /// <param name="binder"></param> /// <param name="result"></param> /// <returns></returns> public override bool TryGetMember(GetMemberBinder binder, out object result) { result = null; // first check the Properties collection for member if (Properties.Keys.Contains(binder.Name)) { result = Properties[binder.Name]; return true; } // Next check for Public properties via Reflection if (Instance != null) { try { return GetProperty(Instance, binder.Name, out result); } catch { } } // failed to retrieve a property result = null; return false; } /// <summary> /// Property setter implementation tries to retrieve value from instance /// first then into this object /// </summary> /// <param name="binder"></param> /// <param name="value"></param> /// <returns></returns> public override bool TrySetMember(SetMemberBinder binder, object value) { // first check to see if there's a native property to set if (Instance != null) { try { bool result = SetProperty(Instance, binder.Name, value); if (result) return true; } catch { } } // no match - set or add to dictionary Properties[binder.Name] = value; return true; } /// <summary> /// Dynamic invocation method. Currently allows only for Reflection based /// operation (no ability to add methods dynamically). /// </summary> /// <param name="binder"></param> /// <param name="args"></param> /// <param name="result"></param> /// <returns></returns> public override bool TryInvokeMember(InvokeMemberBinder binder, object[] args, out object result) { if (Instance != null) { try { // check instance passed in for methods to invoke if (InvokeMethod(Instance, binder.Name, args, out result)) return true; } catch { } } result = null; return false; } /// <summary> /// Reflection Helper method to retrieve a property /// </summary> /// <param name="instance"></param> /// <param name="name"></param> /// <param name="result"></param> /// <returns></returns> protected bool GetProperty(object instance, string name, out object result) { if (instance == null) instance = this; var miArray = InstanceType.GetMember(name, BindingFlags.Public | BindingFlags.GetProperty | BindingFlags.Instance); if (miArray != null && miArray.Length > 0) { var mi = miArray[0]; if (mi.MemberType == MemberTypes.Property) { result = ((PropertyInfo)mi).GetValue(instance,null); return true; } } result = null; return false; } /// <summary> /// Reflection helper method to set a property value /// </summary> /// <param name="instance"></param> /// <param name="name"></param> /// <param name="value"></param> /// <returns></returns> protected bool SetProperty(object instance, string name, object value) { if (instance == null) instance = this; var miArray = InstanceType.GetMember(name, BindingFlags.Public | BindingFlags.SetProperty | BindingFlags.Instance); if (miArray != null && miArray.Length > 0) { var mi = miArray[0]; if (mi.MemberType == MemberTypes.Property) { ((PropertyInfo)mi).SetValue(Instance, value, null); return true; } } return false; } /// <summary> /// Reflection helper method to invoke a method /// </summary> /// <param name="instance"></param> /// <param name="name"></param> /// <param name="args"></param> /// <param name="result"></param> /// <returns></returns> protected bool InvokeMethod(object instance, string name, object[] args, out object result) { if (instance == null) instance = this; // Look at the instanceType var miArray = InstanceType.GetMember(name, BindingFlags.InvokeMethod | BindingFlags.Public | BindingFlags.Instance); if (miArray != null && miArray.Length > 0) { var mi = miArray[0] as MethodInfo; result = mi.Invoke(Instance, args); return true; } result = null; return false; } /// <summary> /// Convenience method that provides a string Indexer /// to the Properties collection AND the strongly typed /// properties of the object by name. /// /// // dynamic /// exp["Address"] = "112 nowhere lane"; /// // strong /// var name = exp["StronglyTypedProperty"] as string; /// </summary> /// <remarks> /// The getter checks the Properties dictionary first /// then looks in PropertyInfo for properties. /// The setter checks the instance properties before /// checking the Properties dictionary. /// </remarks> /// <param name="key"></param> /// /// <returns></returns> public object this[string key] { get { try { // try to get from properties collection first return Properties[key]; } catch (KeyNotFoundException ex) { // try reflection on instanceType object result = null; if (GetProperty(Instance, key, out result)) return result; // nope doesn't exist throw; } } set { if (Properties.ContainsKey(key)) { Properties[key] = value; return; } // check instance for existance of type first var miArray = InstanceType.GetMember(key, BindingFlags.Public | BindingFlags.GetProperty); if (miArray != null && miArray.Length > 0) SetProperty(Instance, key, value); else Properties[key] = value; } } /// <summary> /// Returns and the properties of /// </summary> /// <param name="includeProperties"></param> /// <returns></returns> public IEnumerable<KeyValuePair<string,object>> GetProperties(bool includeInstanceProperties = false) { if (includeInstanceProperties && Instance != null) { foreach (var prop in this.InstancePropertyInfo) yield return new KeyValuePair<string, object>(prop.Name, prop.GetValue(Instance, null)); } foreach (var key in this.Properties.Keys) yield return new KeyValuePair<string, object>(key, this.Properties[key]); } /// <summary> /// Checks whether a property exists in the Property collection /// or as a property on the instance /// </summary> /// <param name="item"></param> /// <returns></returns> public bool Contains(KeyValuePair<string, object> item, bool includeInstanceProperties = false) { bool res = Properties.ContainsKey(item.Key); if (res) return true; if (includeInstanceProperties && Instance != null) { foreach (var prop in this.InstancePropertyInfo) { if (prop.Name == item.Key) return true; } } return false; } } } Although the Expando class supports an indexer, it doesn't actually implement IDictionary or even IEnumerable. It only provides the indexer and Contains() and GetProperties() methods, that work against the Properties dictionary AND the internal instance. The reason for not implementing IDictionary is that a) it doesn't add much value since you can access the Properties dictionary directly and that b) I wanted to keep the interface to class very lean so that it can serve as an entity type if desired. Implementing these IDictionary (or even IEnumerable) causes LINQ extension methods to pop up on the type which obscures the property interface and would only confuse the purpose of the type. IDictionary and IEnumerable are also problematic for XML and JSON Serialization - the XML Serializer doesn't serialize IDictionary<string,object>, nor does the DataContractSerializer. The JavaScriptSerializer does serialize, but it treats the entire object like a dictionary and doesn't serialize the strongly typed properties of the type, only the dictionary values which is also not desirable. Hence the decision to stick with only implementing the indexer to support the user["CustomProperty"] functionality and leaving iteration functions to the publicly exposed Properties dictionary. Note that the Dictionary used here is a custom PropertyBag class I created to allow for serialization to work. One important aspect for my apps is that whatever custom properties get added they have to be accessible to AJAX clients since the particular app I'm working on is a SIngle Page Web app where most of the Web access is through JSON AJAX calls. PropertyBag can serialize to XML and one way serialize to JSON using the JavaScript serializer (not the DCS serializers though). The key components that make Expando work in this code are the Properties Dictionary and the TryGetMember() and TrySetMember() methods. The Properties collection is public so if you choose you can explicitly access the collection to get better performance or to manipulate the members in internal code (like loading up dynamic values form a database). Notice that TryGetMember() and TrySetMember() both work against the dictionary AND the internal instance to retrieve and set properties. This means that user["Name"] works against native properties of the object as does user["Name"] = "RogaDugDog". What's your Use Case? This is still an early prototype but I've plugged it into one of my customer's applications and so far it's working very well. The key features for me were the ability to easily extend the type with values coming from a database and exposing those values in a nice and easy to use manner. I'm also finding that using this type of object for ViewModels works very well to add custom properties to view models. I suspect there will be lots of uses for this - I've been using the extra dictionary approach to extensibility for years - using a dynamic type to make the syntax cleaner is just a bonus here. What can you think of to use this for? Resources Source Code and Tests (GitHub) Also integrated in Westwind.Utilities of the West Wind Web Toolkit West Wind Utilities NuGet© Rick Strahl, West Wind Technologies, 2005-2012Posted in CSharp  .NET  Dynamic Types   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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