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  • .NET 3.5 DataGridView Wont Save To Database

    - by Jimbo
    I have created a test Winforms application in Visual Studio 2008 (SP1) to see just how "RAD" C# and .NET 3.5 can be. So far I have mixed emotions. Added a service-based database to my application (MyDB.mdf) and added two tables - Contact (id [identity], name [varchar] and number [varchar] columns) and Group (id [identity] and name [varchar] columns) Added a DataSource, selected "Database" as the source, used the default connection string as the connection (which points to my database) and selected "All Tables" to be included in the data source and saved as MyDBDataSet Expanded the data source showing my two tables, selected the "Group" table and chose to display it as a DataGridView (from the dropdown option on the right of each entity) and dragged it onto Form1, thus creating a groupBindingNavigator, groupBindingSource, groupTableAdapter, tableAdapterManager, myDBDataset and groupDataGridView Press F5 to test the application, enter the name "Test" under the DataGridView's "name" column and click "Save" on the navigator which has autogenerated code to save the data that looks like this: private void groupBindingNavigatorSaveItem_Click(object sender, EventArgs e) { this.Validate(); this.groupBindingSource.EndEdit(); this.tableAdapterManager.UpdateAll(this.myDBDataSet); } Stop the application and have a look at the database data, you will see no data saved there in the "Group" table. I dont know why and cant find out how to fix it! Googled for about 30 minutes with no luck. The code is auto-generated with the controls, so you'd think that it would work too :)

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  • What is the best Design/Way to keep user connected ?

    - by Fasih Hansmukh
    Am working on a POC for self learning in which I want to keep my user connected in LIVE pattern. For example, A game in which 4 user can play at a time , here I need to keep this user connected to my game . M not good at Socket type of programming and love to do that in Services way.What i wana know is 'What is the best way of doing this'. According to my initial Brain Storming, I have decided that I will use SilverLight(In Browser Or Out of Browser) as Front end [I have no issue in that]. I m more concern in back end. Either I make an handler or make a WCF service or use full duplex service and use pooling mechanism for that. As a random thought I come up with a Timer type logic that will fire every after 10 seconds at clients end and get status like Is it now Its turn to roll a dice Home many user left (in case if some of them left) What are connected user status in game like there score/points ect and update game view according to this at his end Kindly place your best answers here that will help me to learn this. Regards and thanks in Advance EDIT: Starting Bounty as i need more feedback. FH

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  • Resources and techniques/methods for SCJP preparation ?

    - by BenoitParis
    I am passing the SCJP 6 exam in a month. I have the "SCJP Sun Certified Programmer for Java 6 Exam 310-065" book. It seems great for the exam. But I want your advice on this. Getting the closest possible to 100% would be great. I have found a site that answered some of the questions you ask yourself when you go trough the book. Here is it : http://www.janeg.ca/java2.html As you can see it was written for Java 2 :/ I have written another specific question here on StackOverflow about the usefulness of JVM specification and Java compiler code for the SCJP. Will Update the results here. Here it is. Please share the resources you used in preparing the exam. Please also specify any resources that you think might help. Any type of resource is welcome: books, code, specs, sites, wikies, papers, online tests, grandmas... Please also share on any method/technique that helped you prepare the exam. Please also comment on the return you got from the resource and the method (for the learning process and for points in the exam) I'll begin: Book : "SCJP Sun Certified Programmer for Java 6 Exam 310-065". Seems like the official book for the preparation. Technique : Writing code in a text editor and compiling it with javac to test a question. NO IDEs! It helps you get a a straight answer to a question you have. It helps you pay attention to every word in the code (and this is very important in the SCJP) EDIT: Added dimension: Are there good, up-to-date online tests?

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  • R plotting multiple histograms on single plot to .pdf as a part of R batch script

    - by Bryce Thomas
    I am writing R scripts which play just a small role in a chain of commands I am executing from a terminal. Basically, I do much of my data manipulation in a Python script and then pipe the output to my R script for plotting. So, from the terminal I execute commands which look something like $python whatever.py | R CMD BATCH do_some_plotting.R. This workflow has been working well for me so far, though I have now reached a point where I want to overlay multiple histograms on the same plot, inspired by this answer to another user's question on Stackoverflow. Inside my R script, my plotting code looks like this: pdf("my_output.pdf") plot(hist(d$original,breaks="FD",prob=TRUE), col=rgb(0,0,1,1/4),xlim=c(0,4000),main="original - This plot is in beta") plot(hist(d$minus_thirty_minutes,breaks="FD",prob=TRUE), col=rgb(1,0,0,1/4),add=T,xlim=c(0,4000),main="minus_thirty_minutes - This plot is in beta") Notably, I am using add=T, which is presumably meant to specify that the second plot should be overlaid on top of the first. When my script has finished, the result I am getting is not two histograms overlaid on top of each other, but rather a 3-page PDF whose 3 individual plots contain the titles: i) Histogram of d$original ii) original - This plot is in beta iii) Histogram of d$minus_thirty_minutes So there's two points here I'm looking to clarify. Firstly, even if the plots weren't overlaid, I would expect just a 2-page PDF, not a 3-page PDF. Can someone explain why I am getting a 3-page PDF? Secondly, is there a correction I can make here somewhere to get just the two histograms plotted, and both of them on the same plot (i.e. 1-page PDF)? The other Stackoverflow question/answer I linked to in the first paragraph did mention that alpha-blending isn't supported on all devices, and so I'm curious whether this has anything to do with it. Either way, it would be good to know if there is a R-based solution to my problem or whether I'm going to have to pipe my data into a different language/plotting engine.

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  • Elo rating system: start value

    - by Marco W.
    I've implemented an Elo rating system in a game. There is no limit for the number players. Players can join the game constantly so the number of players probably rises gradually. How the Elo values are exactly calculated isn't important because of this fact: If team A beats team B then A's Elo win equals B's Elo loss. Hence I've got a problem concerning the starting values for my rating system: Should I use the starting value "0" for every player? The sum of all Elo values would be constant. But since the number of players is increasing there would be some kind of Elo deflation, wouldn't it? Should I use any starting value greater than 0? In this case, the sum of all Elo values would constantly increase. So there could be an Elo inflation. The problem: Elo points lose value but the starting value keeps always the same. What should I do? Can you help me? Thanks in advance!

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  • Move camera to fit 3D scene

    - by Burre
    Hi there. I'm looking for an algorithm to fit a bounding box inside a viewport (in my case a DirectX scene). I know about algorithms for centering a bounding sphere in a orthographic camera but would need the same for a bounding box and a perspective camera. I have most of the data: I have the up-vector for the camera I have the center point of the bounding box I have the look-at vector (direction and distance) from the camera point to the box center I have projected the points on a plane perpendicular to the camera and retrieved the coefficients describing how much the max/min X and Y coords are within or outside the viewing plane. Problems I have: Center of the bounding box isn't necessarily in the center of the viewport (that is, it's bounding rectangle after projection). Since the field of view "skew" the projection (see http://en.wikipedia.org/wiki/File:Perspective-foreshortening.svg) I cannot simply use the coefficients as a scale factor to move the camera because it will overshoot/undershoot the desired camera position How do I find the camera position so that it fills the viewport as pixel perfect as possible (exception being if the aspect ratio is far from 1.0, it only needs to fill one of the screen axis)? I've tried some other things: Using a bounding sphere and Tangent to find a scale factor to move the camera. This doesn't work well, because, it doesn't take into account the perspective projection, and secondly spheres are bad bounding volumes for my use because I have a lot of flat and long geometries. Iterating calls to the function to get a smaller and smaller error in the camera position. This has worked somewhat, but I can sometimes run into weird edge cases where the camera position overshoots too much and the error factor increases. Also, when doing this I didn't recenter the model based on the position of the bounding rectangle. I couldn't find a solid, robust way to do that reliably. Help please!

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  • setting the openCV configuration in an openGL project produce several errors

    - by GolSa
    I have a win32 solution which is set for openGL; it works well; but I want to write a function which use functions of openCV; I set the configuration for openCV for both X86 and X64;;I commented the openCV function and just to test the correctness of configuration, I run it; but when I want to run it on X64 I faced with the error below: Error 1 error C2065: 'GWL_HINSTANCE' : undeclared identifier D:\matrix\matrixProjection\src\ControllerMain.cpp 35 1 matrixProjection Error 2 error C2664: 'CreateDialogParamW' : cannot convert parameter 4 from 'BOOL (__cdecl *)(HWND,UINT,WPARAM,LPARAM)' to 'DLGPROC' D:\matrix\matrixProjection\src\DialogWindow.cpp 47 1 matrixProjection Error 2 points to this line of code: HWND DialogWindow::create() { /*-->this line*/ handle = ::CreateDialogParam(instance, MAKEINTRESOURCE(id), parentHandle, Win::dialogProcedure, (LPARAM)controller); return handle; } but on Debug Win32 configure, it runs; I used openGL32 in my project; is there any probability to be the cause? is there any X64 version for openGL? I know that there is something needed in X64 mode which my solution can not handle it; I googled a lot about it but I did not find any solution; How can I solve that?

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  • How to split up levels? (cocos2d,box2d,iphone) to save CPU and memory?

    - by cocos2dbeginner
    Hi, so I'm going to create large levels. But there's a problem: There's much unseen space (it's a jump'n run like mario bros.) and this will use memory + cpu. so how could I split up my levels? I'm using Box2D+ cocos2d for iphone. Any ideas? Mayby just set the visible property to NO? But it would be still in the memory :(. But what with the box2d bodies? Destroy and recreate them would be to heavy for the FPS, because I have physics built in which should not be recreated. Should I make fix points where i want to split the level up, than if the player is 200 px away it should preload it. and if the player is 200 px away from the last part of the level I unload it. But there would be the problem with the physics, because on the start of the level it has a unique movement and later if i destroy and recreate it it would do the same. but i don't want that. other ideas?

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  • Resource placement (optimal strategy)

    - by blackened
    I know that this is not exactly the right place to ask this question, but maybe a wise guy comes across and has the solution. I'm trying to write a computer game and I need an algorithm to solve this question: The game is played between 2 players. Each side has 1.000 dollars. There are three "boxes" and each player writes down the amount of money he is going to place into those boxes. Then these amounts are compared. Whoever placed more money in a box scores 1 point (if draw half point each). Whoever scores more points wins his opponents 1.000 dollars. Example game: Player A: [500, 500, 0] Player B: [333, 333, 334] Player A wins because he won Box A and Box B (but lost Box C). Question: What is the optimal strategy to place the money? I have more questions to ask (algorithm related, not math related) but I need to know the answer to this one first. Update (1): After some more research I've learned that these type of problems/games are called Colonel Blotto Games. I did my best and found few (highly technical) documents on the subject. Cutting it short, the problem I have (as described above) is called simple Blotto Game (only three battlefields with symmetric resources). The difficult ones are the ones with, say, 10+ battle fields with non-symmetric resources. All the documents I've read say that the simple Blotto game is easy to solve. The thing is, none of them actually say what that "easy" solution is.

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  • Cocoa - calling a VIEW method from the CONTROLLER

    - by eemerge
    Hello everyone, Got a little problem i asked about it before but maybe i didnt ask properly. I have a cocoa application, which amongst other things, must do the following task: - load some images from the disk, store them in an array and display them in a custom view. In the Interface Builder i have a CustomView and an OBJECT that points to TexturesController.h The custom view is a custom class, TextureBrowser. Below is the code for the controller and view: TexturesController #import <Cocoa/Cocoa.h> @class TextureBrowser; @interface TexturesController : NSObject { IBOutlet NSTextField *logWindow; IBOutlet TextureBrowser *textureView; NSMutableArray *textureList; } @property textureView; -(IBAction)loadTextures:(id)sender; -(IBAction)showTexturesInfo:(id)sender; @end TextureBrowser @interface TextureBrowser : NSView { NSMutableArray *textures; } @property NSMutableArray *textures; -(void)loadTextureList:(NSMutableArray *)source; @end These are just the headers. Now , what i need to do is: when loadTextures from the TexturesController is called, after i load the images i want to send this data to the view (TextureBrowser), for example, store it in the NSMutableArray *textures. I tried using the -(void)loadTextureList:(NSMutableArray*)source method from the view, but in the TextureController.m i get a warning : No -loadTextureList method found This is how i call the method : [textureView loadTextureList: textureList]; And even if i run it with the warning left there, the array in the view class doesnt get initialised. Maybe im missing something...maybe someone can give a simple example of what i need to do and how to do it (code). Thanks in advance.

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  • Unable to plot graph using matplotlib

    - by Aman Deep Gautam
    I have the following code which searches all the directory in the current directory and then takes data from those files to plot the graph. The data is read correctly as verified by printing but there are no points plotted on graph. import argparse import os import matplotlib.pyplot as plt #find the present working directory pwd=os.path.dirname(os.path.abspath(__file__)) #find all the folders in the present working directory. dirs = [f for f in os.listdir('.') if os.path.isdir(f)] plt.figure() plt.xlim(0, 20000) plt.ylim(0, 1) for directory in dirs: os.chdir(os.path.join(pwd, directory)); chd_dir = os.path.dirname(os.path.abspath(__file__)) files = [ fl for fl in os.listdir('.') if os.path.isfile(fl) ] print files for f in files: f_obj = open(os.path.join(chd_dir, f), 'r') list_x = [] list_y = [] for i in xrange(0,4): f_obj.next() for line in f_obj: temp_list = line.split() print temp_list list_y.append(temp_list[0]) list_x.append(temp_list[1]) print 'final_lsit' print list_x print list_y plt.plot(list_x, list_y, 'r.') f_obj.close() os.chdir(pwd) plt.savefig("test.jpg") The input files look like the following: 5 865 14709 15573 14709 1.32667e-06 664 0.815601 14719 1.55333e-06 674 0.813277 14729 1.82667e-06 684 0.810185 14739 1.4e-06 694 0.808459 Can anybody help me with why this is happening? Being new I would like to know some tutorial where I can get help with kind of plotting as the tutorial I was following made me end up here. Any help appreciated.

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  • Can we have a component-scoped bean in a JSF2 composite component?

    - by Pradyumna
    Hi, I was wondering how I could create "component-scoped" beans, or so-to-say, "local variables inside a composite component" that are private to the instance of the composite component, and live as long as that instance lives. Below are more details, explained with an example: Suppose there is a "calculator" component - something that allows users to type in a mathematical expression, and evaluates its value. Optionally, it also plots the associated function. I can make a composite component that has: a text box for accepting the math expression two buttons called "Evaluate", and "Plot" another nested component that plots the function It is evidently a self-contained piece of function; so that somebody who wants to use it may just say <math:expressionEvaluator /> But obviously, the implementation would need a java object - something that evaluates the expression, something that computes the plot points, etc. - and I imagine it can be a bean - scoped just for this instance of this component, not a view-scoped or request-scoped bean that is shared across all instances of the component. How do I create such a bean? Is that even possible with composite components?

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  • Yii Framework Tutorial - file not found

    - by Heshan Perera
    I am in the process of learning the Yii Framework. I have been following this Tutorial. I have followed all the steps and have by index page loading. In my index.php page I point to two other pages located in protected/views/message The following is the code in my index.php located in the message folder mentioned above. <html> <body> <h1>Welcome</h1> <p> To view our message go to... <?php echo CHtml::link('Here', '/message/show')?> </p> <p> To edit our message go to... <?php echo CHtml::link('Here', '/message/edit')?> </p> </body> </html> "message" is the ID I gave when generating the model and controller through the yii shell application. The problem is, after the above page loads, and I click on any one of the above URLs, it points to "localhost:8080/message/show" and "localhost:8080/message/edit" , whereas the real location of these files is "localhost:8080/test/protected/views/message/..." What could I be doing wrong ?

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  • Pointing class property to another class with vectors

    - by jmclem
    I've got a simple class, and another class that has a property that points to the first class: #include <iostream> #include <vector> using namespace std; class first{ public: int var1; }; class second{ public: first* classvar; }; Then, i've got a void that's supposed to point "classvar" to the intended iteration of the class "first". void fill(vector<second>& sec, vector<first>& fir){ sec[0].classvar = &fir[0]; } Finally the main(). Create and fill a vector of class "first", create "second" vector, and run the fill function. int main(){ vector<first> a(1); a[0].var1 = 1000; vector<second> b(1); fill(b, a); cout << b[0].classvar.var1 << '\n'; system("PAUSE"); return 0; } This gives me the following error: 1>c:\...\main.cpp(29) : error C2228: left of '.var1' must have class/struct/union 1> type is 'first *' And I can't figure out why it reads the "classvar" as the whole vector instead of just the single instance. Should I do this cout << b[0].classvar[0].var1 << '\n'; it reads perfectly. Can anyone figure out the problem? Thanks in advance

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  • How do you tell that your unit tests are correct?

    - by Jacob Adams
    I've only done minor unit testing at various points in my career. Whenever I start diving into it again, it always troubles me how to prove that my tests are correct. How can I tell that there isn't a bug in my unit test? Usually I end up running the app, proving it works, then using the unit test as a sort of regression test. What is the recommended approach and/or what is the approach you take to this problem? Edit: I also realize that you could write small, granular unit tests that would be easy to understand. However, if you assume that small, granular code is flawless and bulletproof, you could just write small, granular programs and not need unit testing. Edit2: For the arguments "unit testing is for making sure your changes don't break anything" and "this will only happen if the test has the exact same flaw as the code", what if the test overfits? It's possible to pass both good and bad code with a bad test. My main question is what good is unit testing since if your tests can be flawed you can't really improve your confidence in your code, can't really prove your refactoring worked, and can't really prove that you met the specification?

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  • Easiest way to remove Keys from a 2D Array?

    - by dbemerlin
    Hi, I have an Array that looks like this: array( 0 => array( 'key1' => 'a', 'key2' => 'b', 'key3' => 'c' ), 1 => array( 'key1' => 'c', 'key2' => 'b', 'key3' => 'a' ), ... ) I need a function to get an array containing just a (variable) number of keys, i.e. reduce_array(array('key1', 'key3')); should return: array( 0 => array( 'key1' => 'a', 'key3' => 'c' ), 1 => array( 'key1' => 'c', 'key3' => 'a' ), ... ) What is the easiest way to do this? If possible without any additional helper function like array_filter or array_map as my coworkers already complain about me using too many functions. The source array will always have the given keys so it's not required to check for existance. Bonus points if the values are unique (the keys will always be related to each other, meaning that if key1 has value a then the other key(s) will always have value b). My current solution which works but is quite clumsy (even the name is horrible but can't find a better one): function get_unique_values_from_array_by_keys(array $array, array $keys) { $result = array(); $found = array(); if (count($keys) > 0) { foreach ($array as $item) { if (in_array($item[$keys[0]], $found)) continue; array_push($found, $item[$keys[0]]); $result_item = array(); foreach ($keys as $key) { $result_item[$key] = $item[$key]; } array_push($result, $result_item); } } return $result; } Addition: PHP Version is 5.1.6.

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  • Lambda Functions in PHP aren't Logical

    - by Chacha102
    Note: I have condensed this article into my person wiki: http://wiki.chacha102.com/Lambda - Enjoy I am having some troubles with Lambda style functions in PHP. First, This Works: $foo = function(){ echo "bar"; }; $foo(); Second, This Works: class Bar{ public function foo(){ echo "Bar"; } Third, This works: $foo = new stdClass; $foo->bar = function(){ echo "bar"; }; $test = $foo->bar; $test(); But, this does not work: $foo = new stdClass; $foo->bar = function(){ echo "bar"; }; $foo->bar(); And, this does not work class Bar{ public function foo(){ echo "Bar"; } $foo = new Bar; $foo->foo = function(){ echo "foo"; }; $foo->foo(); // echo's bar instead of Foo. My Question is Why?, and how can I assure that both this: $foo->bar = function(){ echo "test"; }; $foo->bar(); and this $foo = new Bar; $foo->bar(); are called properly? Extra Points if you can point to documentation stating why this problem occurs.

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  • How to determine loading status of images not attached to the DOM

    - by Rookwood
    I am working on a bit of javascript to plot data on a <canvas. The data points are marked by one of several different (small) image files. I am attempting to have the plot method wait until all the images are loaded. My best attempt thus far is such: var icon = { left : { air : new Image(), bone : new Image(), }, right : { air: new Image(), bone : new Image(), }, }; icon.left.air.src = option.imgPath + 'left.air.png'; icon.right.air.src = option.imgPath + 'right.air.png'; icon.left.bone.src = option.imgPath + 'left.bone.png'; icon.right.bone.src = option.imgPath + 'right.bone.png'; function main() { Canvas.draw(); // Make sure our image icons are loaded before we try to plot $(icon.left.air).load(function() { $(icon.right.air).load(function() { $(icon.left.bone).load(function() { $(icon.right.bone).load(function() { Data.plot(); }); }); }); }); } This works as expected most of the time. On occasion, it will fail and no data will be plotted. Inserting several console.log() statements shows that the script will silently stop working through the series of .load() statements, though code that comes after will be executed. My questions are as follows: Am I approaching this the right way? Is there a way to attach an event to my icon object that will fire once all of the images inside are loaded? This is a jquery plugin, so obviously jquery-based solutions are just as acceptable as vanilla javascript.

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  • Easily measure elapsed time

    - by hap497
    I am trying to use time() to measure various points of my program. What I don't understand is why the values in the before and after are the same? I understand this is not the best way to profile my program, I just want to see how long something take. printf("**MyProgram::before time= %ld\n", time(NULL)); doSomthing(); doSomthingLong(); printf("**MyProgram::after time= %ld\n", time(NULL)); I have tried: struct timeval diff, startTV, endTV; gettimeofday(&startTV, NULL); doSomething(); doSomethingLong(); gettimeofday(&endTV, NULL); timersub(&endTV, &startTV, &diff); printf("**time taken = %ld %ld\n", diff.tv_sec, diff.tv_usec); How do I read a result of **time taken = 0 26339? Does that mean 26,339 nanoseconds = 26.3 msec? What about **time taken = 4 45025, does that mean 4 seconds and 25 msec?

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  • OpenGL 3.3 different colours with fragment shader [solved]

    - by Andrew Seymour
    I'm an OpenGL newbie. I'm trying to colour 3 circles but only 3 white circles are appearing. n is 3 in this example. Each vertice has 5 points, 2 for position and 3 for color Here is where I think a problem may lie: glEnableVertexAttribArray(0); glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer); glVertexAttribPointer( 0, 2, GL_FLOAT, GL_FALSE, 5*sizeof(float), (void*)0 ); glEnableVertexAttribArray(1); glVertexAttribPointer( 1, 3, GL_FLOAT, GL_FALSE, 5*sizeof(float), (void*)(2*sizeof(float)) ); glDrawElements(GL_TRIANGLES, 20 * 3 * n, GL_UNSIGNED_INT, 0); glDisableVertexAttribArray(0); glDisableVertexAttribArray(1); My shaders: #version 330 core in vec3 Color; out vec4 outColor; void main() { outColor = vec4(Color, 1.0); } #version 330 core layout(location = 0) in vec2 position; layout(location = 1) in vec3 color out vec3 Color void main(){ gl_Position = vec4(position, 0.0, 1.0); Color = color; } Thanks for taking a look Andy EDIT: layout(location = 1) in vec3 color out vec3 Color layout(location = 1) in vec3 color; out vec3 Color;

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  • Memory leaks after using typeinfo::name()

    - by icabod
    I have a program in which, partly for informational logging, I output the names of some classes as they are used (specifically I add an entry to a log saying along the lines of Messages::CSomeClass transmitted to 127.0.0.1). I do this with code similar to the following: std::string getMessageName(void) const { return std::string(typeid(*this).name()); } And yes, before anyone points it out, I realise that the output of typeinfo::name is implementation-specific. According to MSDN The type_info::name member function returns a const char* to a null-terminated string representing the human-readable name of the type. The memory pointed to is cached and should never be directly deallocated. However, when I exit my program in the debugger, any "new" use of typeinfo::name() shows up as a memory leak. If I output the information for 2 classes, I get 2 memory leaks, and so on. This hints that the cached data is never being freed. While this is not a major issue, it looks messy, and after a long debugging session it could easily hide genuine memory leaks. I have looked around and found some useful information (one SO answer gives some interesting information about how typeinfo may be implemented), but I'm wondering if this memory should normally be freed by the system, or if there is something i can do to "not notice" the leaks when debugging. I do have a back-up plan, which is to code the getMessageName method myself and not rely on typeinfo::name, but I'd like to know anyway if there's something I've missed.

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  • Wicket application + Apache + mod_jk - AJP queues are filling up!

    - by nojyarg
    Dear community, We are having a Wicket-based Java application deployed in a production server cluster using Apache (2.2.3) with mod_jk (1.2.30) as load balancing component w/ sticky session and Jboss 5 as application container for the Java application. We are inconsistently seeing an issue in our production environment where our AJP queues between Apache and Jboss as shown in the JMX console fill up with requests to the point where the application server is no longer taking on any new requests. When looking at all involved system components (overall traffic, load db, process list db, load of all clustered application server nodes) nothing points towards a capacity issue which would explain why the calls are being stalled in the AJP queue. Instead all systems appear sufficiently idle. So far, our only remedy to this issue is to restart the appservers and the load balancer which only occasionally clears the AJP queues. We are trying to figure out why the queues are filling up to the point that no calls get returned to the end user although the system is not under a high load. Has anyone else experienced similar problems? Are there any other system metrics we should monitor that could explain the queuing behavior? Is this potentially a mod_jk issue? If so, is it advisable to swap mod_jk with mod_cluster to resolve the issue? Any advice is highly appreciated. If I can provide additional information for the sake of troubleshooting I would be more than willing to do so. /Ben

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  • Does the pointer to free() have to point to beginning of the memory block, or can it point to the interior?

    - by Lambert
    The question is in the title... I searched but couldn't find anything. Edit: I don't really see any need to explain this, but because people think that what I'm saying makes no sense (and that I'm asking the wrong questions), here's the problem: Since people seem to be very interested in the "root" cause of all the problem rather than the actual question asked (since that apparently helps things get solved better, let's see if it does), here's the problem: I'm trying to make a D runtime library based on NTDLL.dll, so that I can use that library for subsystems other than the Win32 subsystem. So that forces me to only link with NTDLL.dll. Yes, I'm aware that the functions are "undocumented" and could change at any time (even though I'd bet a hundred dollars that wcstombs will still do the same exact thing 20 years from now, if it still exists). Yes, I know people (especially Microsoft) don't like developers linking to that library, and that I'll probably get criticized for the right here. And yes, those two points above mean that programs like chkdsk and defragmenters that run before the Win32 subsystem aren't even supposed to be created in the first place, because it's literally impossible to link with anything like kernel32.dll or msvcrt.dll and still have NT-native executables, so we developers should just pretend that those stages are meant to be forever out of our reaches. But no, I doubt that anyone here would like me to paste a few thousand lines of code and help me look through them and try to figure out why memory allocations that aren't failing are being rejected by the source code I'm modifying. So that's why I asked about a different problem than the "root" cause, even though that's supposedly known to be the best practice by the community. If things still don't make sense, feel free to post comments below! :)

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  • Defend PHP; convince me it isn't horrible

    - by Jason L
    I made a tongue-in-cheek comment in another question thread calling PHP a terrible language and it got down-voted like crazy. Apparently there are lots of people here who love PHP. So I'm genuinely curious. What am I missing? What makes PHP a good language? Here are my reasons for disliking it: PHP has inconsistent naming of built-in and library functions. Predictable naming patterns are important in any design. PHP has inconsistent parameter ordering of built-in functions, eg array_map vs. array_filter which is annoying in the simple cases and raises all sorts of unexpected behaviour or worse. The PHP developers constantly deprecate built-in functions and lower-level functionality. A good example is when they deprecated pass-by-reference for functions. This created a nightmare for anyone doing, say, function callbacks. A lack of consideration in redesign. The above deprecation eliminated the ability to, in many cases, provide default keyword values for functions. They fixed this in PHP 5, but they deprecated the pass-by-reference in PHP 4! Poor execution of name spaces (formerly no name spaces at all). Now that name spaces exist, what do we use as the dereference character? Backslash! The character used universally for escaping, even in PHP! Overly-broad implicit type conversion leads to bugs. I have no problem with implicit conversions of, say, float to integer or back again. But PHP (last I checked) will happily attempt to magically convert an array to an integer. Poor recursion performance. Recursion is a fundamentally important tool for writing in any language; it can make complex algorithms far simpler. Poor support is inexcusable. Functions are case insensitive. I have no idea what they were thinking on this one. A programming language is a way to specify behavior to both a computer and a reader of the code without ambiguity. Case insensitivity introduces much ambiguity. PHP encourages (practically requires) a coupling of processing with presentation. Yes, you can write PHP that doesn't do so, but it's actually easier to write code in the incorrect (from a sound design perspective) manner. PHP performance is abysmal without caching. Does anyone sell a commercial caching product for PHP? Oh, look, the designers of PHP do. Worst of all, PHP convinces people that designing web applications is easy. And it does indeed make much of the effort involved much easier. But the fact is, designing a web application that is both secure and efficient is a very difficult task. By convincing so many to take up programming, PHP has taught an entire subgroup of programmers bad habits and bad design. It's given them access to capabilities that they lack the understanding to use safely. This has led to PHP's reputation as being insecure. (However, I will readily admit that PHP is no more or less secure than any other web programming language.) What is it that I'm missing about PHP? I'm seeing an organically-grown, poorly-managed mess of a language that's spawning poor programmers. So convince me otherwise!

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  • Problems with Threading in Python 2.5, KeyError: 51, Help debugging?

    - by vignesh-k
    I have a python script which runs a particular script large number of times (for monte carlo purpose) and the way I have scripted it is that, I queue up the script the desired number of times it should be run then I spawn threads and each thread runs the script once and again when its done. Once the script in a particular thread is finished, the output is written to a file by accessing a lock (so my guess was that only one thread accesses the lock at a given time). Once the lock is released by one thread, the next thread accesses it and adds its output to the previously written file and rewrites it. I am not facing a problem when the number of iterations is small like 10 or 20 but when its large like 50 or 150, python returns a KeyError: 51 telling me element doesn't exist and the error it points out to is within the lock which puzzles me since only one thread should access the lock at once and I do not expect an error. This is the class I use: class errorclass(threading.Thread): def __init__(self, queue): self.__queue=queue threading.Thread.__init__(self) def run(self): while 1: item = self.__queue.get() if item is None: break result = myfunction() lock = threading.RLock() lock.acquire() ADD entries from current thread to entries in file and REWRITE FILE lock.release() queue = Queue.Queue() for i in range(threads): errorclass(queue).start() for i in range(desired iterations): queue.put(i) for i in range(threads): queue.put(None) Python returns with KeyError: 51 for large number of desired iterations during the adding/write file operation after lock access, I am wondering if this is the correct way to use the lock since every thread has a lock operation rather than every thread accessing a shared lock? What would be the way to rectify this?

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