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• What is "elegant" code?

  - by Breton

  I see a lot of lip service and talk about the most "elegant" way to do this or that. I think if you spend enough time programming you begin to obtain a sort of intuitive feel for what it is we call "elegance". But I'm curious. Even if we can look at a bit of code, and say instinctively "That's elegant", or "That's messy", I wonder if any of us really understands what that means. Is there a precise definition for this "elegance" we keep referring to? If there is, what is it? Now, what I mean by a precise definition, is a series of statements which can be used to derive questions about a peice of code, or a program as a whole, and determine objectively, or as objectively as possible, whether that code is "elegant" or not. May I assert, that perhaps no such definition exists, and it's all just personal preference. In this case, I ask you a slightly different question: Is there a better word for "elegance", or a better set of attributes to use for judging code quality that is perhaps more objective than merely appealing to individual intuition and taste? Perhaps code quality is a matter of taste, and the answer to both of my questions is "no". But I can't help but feel that we could be doing better than just expressing wishy washy feelings about our code quality. For example, user interface design is something that to a broad range of people looks for all the world like a field of study that oughtta be 100% subjective matter of taste. But this is shockingly and brutally not the case, and there are in fact many objective measures that can be applied to a user interface to determine its quality. A series of tests could be written to give a definitive and repeatable score to user interface quality. (See GOMS, for instance). Now, okay. is Elegance simply "code quality" or is it something more? Is it something that can be measured? Or is it a matter of taste? Does our profession have room for taste? Maybe I'm asking the wrong questions altogether. Help me out here. Bonus Round If there is such a thing as elegance in code, and that concept is useful, do you think that justifies classifying the field of programming as an "Art" capital A, or merely a "craft". Or is it just an engineering field populated by a bunch of wishful thinking humans? Consider this question in the light of your thoughts about the elegance question. Please note that there is a distinction between code which is considered "art" in itself, and code that was written merely in the service of creating an artful program. When I ask this question, I ask if the code itself justifies calling programming an art. Bounty Note I liked the answers to this question so much, I think I'd like to make a photographic essay book from it. Released as a free PDF, and published on some kind of on demand printing service of course, such as "zazz" or "tiggle" or "printley" or something . I'd like some more answers, please!

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• I create a JPanel and GridBagLayout within an object but when I get it in the main object, attributes are missing

  - by chickeneaterguy

  public oijoij() { String name = "Jackie"; int priority = 50; int minPriority = 90; setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); setBounds(100, 100, 450, 300); contentPane = new JPanel(); contentPane.setBorder(new EmptyBorder(5, 5, 5, 5)); contentPane.setLayout(new BorderLayout(0, 0)); setContentPane(contentPane); JPanel panel = new JPanel(); GridBagLayout gbc_panel = new GridBagLayout(); gbc_panel.columnWidths = new int[]{0,0,0}; gbc_panel.rowHeights = new int[]{0, 0, 0, 0, 0, 0}; gbc_panel.columnWeights = new double[]{0.0, 0.0, Double.MIN_VALUE}; gbc_panel.rowWeights = new double[]{0.0, 0.0, 0.0, 0.0, 0.0, Double.MIN_VALUE}; panel.setBorder(new LineBorder(new Color(0,0,0),1)); panel.setLayout(gbc_panel); panel.setAlignmentX(Component.LEFT_ALIGNMENT); panel.setMinimumSize(new Dimension(110,110)); panel.setPreferredSize(new Dimension(110, 110)); panel.setSize(new Dimension(110,110)); JLabel lblNewLabel = new JLabel("Process ID:"); GridBagConstraints gbc_lblNewLabel = new GridBagConstraints(); gbc_lblNewLabel.gridheight = 2; gbc_lblNewLabel.insets = new Insets(0, 0, 5, 5); gbc_lblNewLabel.gridx = 0; gbc_lblNewLabel.gridy = 0; panel.add(lblNewLabel, gbc_lblNewLabel); JLabel lblNewLabel_1 = new JLabel(name); GridBagConstraints gbc_lblNewLabel_1 = new GridBagConstraints(); gbc_lblNewLabel_1.gridheight = 2; gbc_lblNewLabel_1.insets = new Insets(0, 0, 5, 0); gbc_lblNewLabel_1.gridx = 1; gbc_lblNewLabel_1.gridy = 0; panel.add(lblNewLabel_1, gbc_lblNewLabel_1); JLabel lblNewLabel_2 = new JLabel("Priority:"); GridBagConstraints gbc_lblNewLabel_2 = new GridBagConstraints(); gbc_lblNewLabel_2.insets = new Insets(0, 0, 5, 5); gbc_lblNewLabel_2.gridx = 0; gbc_lblNewLabel_2.gridy = 2; panel.add(lblNewLabel_2, gbc_lblNewLabel_2); JLabel lblNum = new JLabel(Integer.toString(priority)); GridBagConstraints gbc_lblNum = new GridBagConstraints(); gbc_lblNum.insets = new Insets(0, 0, 5, 0); gbc_lblNum.gridx = 1; gbc_lblNum.gridy = 2; panel.add(lblNum, gbc_lblNum); JLabel lblNewLabel_3 = new JLabel("Min Priority:"); GridBagConstraints gbc_lblNewLabel_3 = new GridBagConstraints(); gbc_lblNewLabel_3.insets = new Insets(0, 0, 5, 5); gbc_lblNewLabel_3.gridx = 0; gbc_lblNewLabel_3.gridy = 3; panel.add(lblNewLabel_3, gbc_lblNewLabel_3); JLabel lblMp = new JLabel(Integer.toString(minPriority)); GridBagConstraints gbc_lblMp = new GridBagConstraints(); gbc_lblMp.insets = new Insets(0, 0, 5, 0); gbc_lblMp.gridx = 1; gbc_lblMp.gridy = 3; panel.add(lblMp, gbc_lblMp); JLabel lblTimeSlice = new JLabel("Time Slice:"); GridBagConstraints gbc_lblTimeSlice = new GridBagConstraints(); gbc_lblTimeSlice.insets = new Insets(0, 0, 0, 5); gbc_lblTimeSlice.gridx = 0; gbc_lblTimeSlice.gridy = 4; panel.add(lblTimeSlice, gbc_lblTimeSlice); Random r = new Random(System.currentTimeMillis()); panel.setBackground(new Color( r.nextInt(255 - 210) + 210, r.nextInt(255 - 210) + 210, r.nextInt(255 - 210) + 210)); } I have accessor methods for the GridBagLayout and the JPanel. When calling the functions in another file, it looks like I just get the JPanel (but without any labels or the layout or other GridBagLayout features). Help?

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• Lock-Free, Wait-Free and Wait-freedom algorithms for non-blocking multi-thread synchronization.

  - by GJ

  In multi thread programming we can find different terms for data transfer synchronization between two or more threads/tasks. When exactly we can say that some algorithem is: 1)Lock-Free 2)Wait-Free 3)Wait-Freedom I understand what means Lock-free but when we can say that some synchronization algorithm is Wait-Free or Wait-Freedom? I have made some code (ring buffer) for multi-thread synchronization and it use Lock-Free methods but: 1) Algorithm predicts maximum execution time of this routine. 2) Therad which call this routine at beginning set unique reference, what mean that is inside of this routine. 3) Other threads which are calling the same routine check this reference and if is set than count the CPU tick count (measure time) of first involved thread. If that time is to long interrupt the current work of involved thread and overrides him job. 4) Thread which not finished job because was interrupted from task scheduler (is reposed) at the end check the reference if not belongs to him repeat the job again. So this algorithm is not really Lock-free but there is no memory lock in use, and other involved threads can wait (or not) certain time before overide the job of reposed thread. Added RingBuffer.InsertLeft function: function TgjRingBuffer.InsertLeft(const link: pointer): integer; var AtStartReference: cardinal; CPUTimeStamp : int64; CurrentLeft : pointer; CurrentReference: cardinal; NewLeft : PReferencedPtr; Reference : cardinal; label TryAgain; begin Reference := GetThreadId + 1; //Reference.bit0 := 1 with rbRingBuffer^ do begin TryAgain: //Set Left.Reference with respect to all other cores :) CPUTimeStamp := GetCPUTimeStamp + LoopTicks; AtStartReference := Left.Reference OR 1; //Reference.bit0 := 1 repeat CurrentReference := Left.Reference; until (CurrentReference AND 1 = 0)or (GetCPUTimeStamp - CPUTimeStamp > 0); //No threads present in ring buffer or current thread timeout if ((CurrentReference AND 1 <> 0) and (AtStartReference <> CurrentReference)) or not CAS32(CurrentReference, Reference, Left.Reference) then goto TryAgain; //Calculate RingBuffer NewLeft address CurrentLeft := Left.Link; NewLeft := pointer(cardinal(CurrentLeft) - SizeOf(TReferencedPtr)); if cardinal(NewLeft) < cardinal(@Buffer) then NewLeft := EndBuffer; //Calcolate distance result := integer(Right.Link) - Integer(NewLeft); //Check buffer full if result = 0 then //Clear Reference if task still own reference if CAS32(Reference, 0, Left.Reference) then Exit else goto TryAgain; //Set NewLeft.Reference NewLeft^.Reference := Reference; SFence; //Try to set link and try to exchange NewLeft and clear Reference if task own reference if (Reference <> Left.Reference) or not CAS64(NewLeft^.Link, Reference, link, Reference, NewLeft^) or not CAS64(CurrentLeft, Reference, NewLeft, 0, Left) then goto TryAgain; //Calcolate result if result < 0 then result := Length - integer(cardinal(not Result) div SizeOf(TReferencedPtr)) else result := cardinal(result) div SizeOf(TReferencedPtr); end; //with end; { TgjRingBuffer.InsertLeft } RingBuffer unit you can find here: RingBuffer, CAS functions: FockFreePrimitives, and test program: RingBufferFlowTest Thanks in advance, GJ

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• APACHE2.2/WIN2003(32-bit)/PHP: How do I configure Apache to Run Background PHP Processes on Win 2003

  - by Captain Obvious

  I have a script, testforeground.php, that kicks off a background script, testbackground.php, then returns while the background script continues to run until it's finished. Both the foreground and background scripts write to the output file correctly when I run the foreground script from the command line using php-cgi: C:\>php-cgi testforeground.php The above command starts a php-cgi.exe process, then a php-win.exe process, then closes the php-cgi.exe almost immediately, while the php-win.exe continues until it's finished. The same script runs correctly but does not have permission to write to the output file when I run it from the command line using plain php: C:\>php testforeground.php AND when I run the same script from the browser, instead of php-cgi.exe, a single cmd.exe process opens and closes almost instantly, only the foreground script writes to the output file, and it doesn't appear that the 2nd process starts: http://XXX/testforeground.php Here is the server info: OS: Win 2003 32-bit HTTP: Apache 2.2.11 PHP: 5.2.13 Loaded Modules: core mod_win32 mpm_winnt http_core mod_so mod_actions mod_alias mod_asis mod_auth_basic mod_authn_default mod_authn_file mod_authz_default mod_authz_groupfile mod_authz_host mod_authz_user mod_autoindex mod_cgi mod_dir mod_env mod_include mod_isapi mod_log_config mod_mime mod_negotiation mod_setenvif mod_userdir mod_php5 Here's the foreground script: <?php ini_set("display_errors",1); error_reporting(E_ALL); echo "<pre>loading page</pre>"; function run_background_process() { file_put_contents("0testprocesses.txt","foreground start time = " . time() . "\n"); echo "<pre> foreground start time = " . time() . "</pre>"; $command = "start /B \"{$_SERVER['CMS_PHP_HOMEPATH']}\php-cgi.exe\" {$_SERVER['CMS_HOMEPATH']}/testbackground.php"; $rp = popen($command, 'r'); if(isset($rp)) { pclose($rp); } echo "<pre> foreground end time = " . time() . "</pre>"; file_put_contents("0testprocesses.txt","foreground end time = " . time() . "\n", FILE_APPEND); return true; } echo "<pre>calling run_background_process</pre>"; $output = run_background_process(); echo "<pre>output = $output</pre>"; echo "<pre>end of page</pre>"; ?> And the background script: <?php $start = "background start time = " . time() . "\n"; file_put_contents("0testprocesses.txt",$start, FILE_APPEND); sleep(10); $end = "background end time = " . time() . "\n"; file_put_contents("0testprocesses.txt", $end, FILE_APPEND); ?> I've confirmed that the above scripts work correctly using Apache 2.2.3 on Linux. I'm sure I just need to change some Apache and/or PHP config settings, but I'm not sure which ones. I've been muddling over this for too long already, so any help would be appreciated.

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• Rendering a view to a string in MVC, then redirecting -- workarounds?

  - by James S

  Hi -- I can't render a view to a string and then redirect, despite this answer from Feb (after version 1.0, I think) that claims it's possible. I thought I was doing something wrong, and then I read this answer from Haack in July that claims it's not possible. If somebody has it working and can help me get it working, that's great (and I'll post code, errors). However, I'm now at the point of needing workarounds. There are a few, but nothing ideal. Has anybody solved this, or have any comments on my ideas? This is to render email. While I can surely send the email outside of the web request (store info in a db and get it later), there are many types of emails and I don't want to store the template data (user object, a few other LINQ objects) in a db to let it get rendered later. I could create a simpler, serializable POCO and save that in the db, but why? ... I just want rendered text! I can create a new RedirectToAction object that checks if the headers have been sent (can't figure out how to do this -- try/catch?) and, if so, builds out a simple page with a meta redirect, a javascript redirect, and also a "click here" link. Within my controller, I can remember if I've rendered an email and, if so, manually do #2 by displaying a view. I can manually send the redirect headers before any potential email rendering. Then, rather than using the MVC infrastructure to redirecttoaction, I just call result.end. This seems easiest, but really messy. Anything else? EDIT: I've tried Dan's code (very similar to the code from Jan/Feb that I've already tried) and I'm still getting the same error. The only substantial difference I can see is that his example uses a view while I use a partial view. I'll try testing this later with a view. Here's what I've got: Controller public ActionResult Certifications(string email_intro) { //a lot of stuff ViewData["users"] = users; if (isPost()) { //create the viewmodel var view_model = new ViewModels.Emails.Certifications.Open(userContext) { emailIntro = email_intro }; //i've tried stopping this after just one iteration, in case the problem is due to calling it multiple times foreach (var user in users) { if (user.Email_Address.IsValidEmailAddress()) { //add more stuff to the view model specific to this user view_model.user = user; view_model.certification302Summary.subProcessesOwner = new SubProcess_Certifications(RecordUpdating.Role.Owner, null, null, user.User_ID, repository); //more here.... //if i comment out the next line, everything works ok SendEmail(view_model, this.ControllerContext); } } return RedirectToAction("Certifications"); } return View(); } SendEmail() public static void SendEmail(ViewModels.Emails.Certifications.Open model, ControllerContext context) { var vd = context.Controller.ViewData; vd["model"] = model; var renderer = new CustomRenderers(); //i fixed an error in your code here var text = renderer.RenderViewToString3(context, "~/Views/Emails/Certifications/Open.ascx", "", vd, null); var a = text; } CustomRenderers public class CustomRenderers { public virtual string RenderViewToString3(ControllerContext controllerContext, string viewPath, string masterPath, ViewDataDictionary viewData, TempDataDictionary tempData) { //copy/paste of dan's code } } Error [HttpException (0x80004005): Cannot redirect after HTTP headers have been sent.] System.Web.HttpResponse.Redirect(String url, Boolean endResponse) +8707691 Thanks, James

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• Implementing ZBar QR Code Reader in UIView

  - by Bobster4300

  I really need help here. I'm pretty new to iOS/Objective-C so sorry if the problem resolution is obvious or if my code is terrible. Be easy on me!! :-) I'm struggling to integrate ZBarSDK for reading QR Codes into an iPad app i'm building. If I use ZBarReaderController (of which there are plenty of tutorials and guides on implementing), it works fine. However I want to make the camera come up in a UIView as opposed to the fullscreen camera. Now I have gotten as far as making the camera view (readerView) come up in the UIView (ZBarReaderView) as expected, but I get an error when it scans a code. The error does not come up until a code is scanned making me believe this is either delegate related or something else. Here's the important parts of my code: (ZBarSDK.h is imported at the PCH file) SignInViewController.h #import <UIKit/UIKit.h> #import <AVFoundation/AVFoundation.h> @class AVCaptureSession, AVCaptureDevice; @interface SignInViewController : UIViewController < ZBarReaderDelegate > { ZBarReaderView *readerView; UITextView *resultText; } @property (nonatomic, retain) UIImagePickerController *imgPicker; @property (strong, nonatomic) IBOutlet UITextView *resultText; @property (strong, nonatomic) IBOutlet ZBarReaderView *readerView; -(IBAction)StartScan:(id) sender; SignInViewController.m #import "SignInViewController.h" @interface SignInViewController () @end @implementation SignInViewController @synthesize resultText, readerView; -(IBAction)StartScan:(id) sender { readerView = [ZBarReaderView new]; readerView.readerDelegate = self; readerView.tracksSymbols = NO; readerView.frame = CGRectMake(30,70,230,230); readerView.torchMode = 0; readerView.device = [self frontFacingCameraIfAvailable]; ZBarImageScanner *scanner = readerView.scanner; [scanner setSymbology: ZBAR_I25 config: ZBAR_CFG_ENABLE to: 0]; [self relocateReaderPopover:[self interfaceOrientation]]; [readerView start]; [self.view addSubview: readerView]; resultText.hidden=NO; } - (void) readerControllerDidFailToRead: (ZBarReaderController*) reader withRetry: (BOOL) retry{ NSLog(@"the image picker failing to read"); } - (void) imagePickerController: (UIImagePickerController*) reader didFinishPickingMediaWithInfo: (NSDictionary*) info { NSLog(@"the image picker is calling successfully %@",info); id<NSFastEnumeration> results = [info objectForKey: ZBarReaderControllerResults]; ZBarSymbol *symbol = nil; NSString *hiddenData; for(symbol in results) hiddenData=[NSString stringWithString:symbol.data]; NSLog(@"the symbols is the following %@",symbol.data); resultText.text=symbol.data; NSLog(@"BARCODE= %@",symbol.data); NSLog(@"SYMBOL : %@",hiddenData); resultText.text=hiddenData; } The error I get when a code is scanned: 2012-12-16 14:28:32.797 QRTestApp[7970:907] -[SignInViewController readerView:didReadSymbols:fromImage:]: unrecognized selector sent to instance 0x1e88b1c0 2012-12-16 14:28:32.799 QRTestApp[7970:907] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[SignInViewController readerView:didReadSymbols:fromImage:]: unrecognized selector sent to instance 0x1e88b1c0' I'm not too worried about what happens with the results just yet, just want to get over this error. Took me ages just to get the camera to come up in the UIView due to severe lack of tutorial or documentation on ZBarReaderView (for beginners anyway). Thanks all.

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• Issues writing to serial port on MAC OSX using unistd.h in c

  - by Schuyler

  I am trying to write to a bluetooth device on MAC OSX using the unistd.h Linux functions in c. I am connecting fine and writing the first few bytes with success. When I try to write other commands to it (there are bytes added to the write buffer every 15ms), I don't see any results even though the write() function returns 1 (write success). If you start a write and it doesn't finish by the time you try to start another write (since it is non-blocking), could that possibly screw up the initial write? (If so, is there any way to check if a write has completed?) That is the only thing I can think of since the writes are occurring fairly frequently and the first two are successfully sent. qwbyte() simply adds a byte to the output array and increments its length The open port function: BAMid = -1; struct termios options; struct termios originalTTYAttrs; // Open the serial port read/write, nonblocking, with no controlling terminal, and don't wait for a connection. BAMid = open(strPath, O_RDWR | O_NOCTTY | O_NONBLOCK); if (BAMid == -1) { printf("Error opening serial port %s - %s(%d).\n", strPath, strerror(errno), errno); goto error; } // Issue TIOCEXCL ioctl to prevent additional opens except by root-owned processes. if (ioctl(BAMid, TIOCEXCL) == -1) { printf("Error setting TIOCEXCL on %s - %s(%d).\n", strPath, strerror(errno), errno); goto error; } // Get the current options and save them so we can restore the default settings later. if (tcgetattr(BAMid, &originalTTYAttrs) == -1) { printf("Error getting tty attributes %s - %s(%d).\n", strPath, strerror(errno), errno); goto error; } // The serial port attributes such as timeouts and baud rate are set by modifying the termios // structure and then calling tcsetattr() to cause the changes to take effect. Note that the // changes will not become effective without the tcsetattr() call. options = originalTTYAttrs; // Set raw input (non-canonical) mode, with reads blocking until either a single character // has been received or a one second timeout expires. [should be moot since we are leaving it as nonblocking] cfmakeraw(&options); options.c_cc[VMIN] = 1; options.c_cc[VTIME] = 10; cfsetspeed(&options, B57600); // Set 57600 baud options.c_cflag |= CS8; // Use 8 bit words // Cause the new options to take effect immediately. if (tcsetattr(BAMid, TCSANOW, &options) == -1) { printf("Error setting tty attributes %s - %s(%d).\n", strPath, strerror(errno), errno); goto error; } //flush old transmissions if (tcflush(BAMid,TCIOFLUSH) == -1) { printf("Error flushing BAM serial port - %s(%d).\n", strerror(errno), errno); } oBufLength = 0; // Ask it to start if (! qwbyte(CmdStart) ) { goto error; } if (! qwbyte(CmdFull) ) { goto error; } //this transmit works txbytes(); printf("success opening port!"); return -1; // Failure path error: if (BAMid != -1) { close(BAMid); } printf("returning an error--%d",errno); return errno; } The write function (txbytes): int i, bufSize, numBytes; if(oBufLength != 0) { //if the output array isn't empty //duplicating the output array and its size so it can //be overwritten while this write is occuring printf("about to transmit: "); for(i = 0; i < oBufLength; i++) { printf(" %u",oBuf[i]); tempBuf[i] = oBuf[i]; } printf("\n"); bufSize = oBufLength; oBufLength = 0; numBytes = write(BAMid, &tempBuf, bufSize); printf("bytes written = %d\n",numBytes); if (numBytes == -1) { printf("Error writing to port - %s(%d).\n", strerror(errno), errno); } return (numBytes 0); } else { return 0; }

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• Problem with memset after an instance of a user defined class is created and a file is opened

  - by Liberalkid

  I'm having a weird problem with memset, that was something to do with a class I'm creating before it and a file I'm opening in the constructor. The class I'm working with normally reads in an array and transforms it into another array, but that's not important. The class I'm working with is: #include <vector> #include <algorithm> using namespace std; class PreProcess { public: PreProcess(char* fileName,char* outFileName); void SortedOrder(); private: vector< vector<double > > matrix; void SortRow(vector<double> &row); char* newFileName; vector< pair<double,int> > rowSorted; }; The other functions aren't important, because I've stopped calling them and the problem persists. Essentially I've narrowed it down to my constructor: PreProcess::PreProcess(char* fileName,char* outFileName):newFileName(outFileName){ ifstream input(fileName); input.close(); //this statement is inconsequential } I also read in the file in my constructor, but I've found that the problem persists if I don't read in the matrix and just open the file. Essentially I've narrowed it down to if I comment out those two lines the memset works properly, otherwise it doesn't. Now to the context of the problem I'm having with it: I wrote my own simple wrapper class for matrices. It doesn't have much functionality, I just need 2D arrays in the next part of my project and having a class handle everything makes more sense to me. The header file: #include <iostream> using namespace std; class Matrix{ public: Matrix(int r,int c); int &operator()(int i,int j) {//I know I should check my bounds here return matrix[i*columns+j]; } ~Matrix(); const void Display(); private: int *matrix; const int rows; const int columns; }; Driver: #include "Matrix.h" #include <string> using namespace std; Matrix::Matrix(int r,int c):rows(r),columns(c) { matrix=new int[rows*columns]; memset(matrix,0,sizeof(matrix)); } const void Matrix::Display(){ for(int i=0;i<rows;i++){ for(int j=0;j<columns;j++) cout << (*this)(i,j) << " "; cout << endl; } } Matrix::~Matrix() { delete matrix; } My main program runs: PreProcess test1(argv[1],argv[2]); //test1.SortedOrder(); Matrix test(10,10); test.Display(); And when I run this with the input line uncommented I get: 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 -1371727776 32698 -1 0 0 0 0 0 6332656 0 -1 -1 0 0 6332672 0 0 0 0 0 0 0 0 0 0 0 0 0 -1371732704 32698 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 I really don't have a clue what's going on in memory to cause this, on a side note if I replace memset with: for(int i=0;i<rows*columns;i++) *(matrix+i) &= 0x0; Then it works perfectly, it also works if I don't open the file. If it helps I'm running GCC 64-bit version 4.2.4 on Ubuntu.I assume there's some functionality of memset that I'm not properly understanding.

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• Qt - reloading widget contents

  - by bullettime

  I'm trying to modify the fridge magnets example by adding a button that will reload the widget where the draggable labels are drawn, reflecting any changes made to the text file it reads. I defined another class that would contain the button and the DragWidget object, so there would be an instance of this class instead of DragWidget in main(): class wrapWidget: public QWidget { public: wrapWidget(); }; wrapWidget::wrapWidget() { QGridLayout *gridlayout = new QGridLayout(); DragWidget *w = new DragWidget(); QPushButton *b = new QPushButton("refresh"); gridlayout ->addWidget(w,0,0); gridlayout ->addWidget(b,1,0); setLayout(gridlayout ); connect(b,SIGNAL(clicked()),w,SLOT(draw())); } The call to connect is where I'm trying to do the refresh thing. In the original fridge magnets example, all the label drawing code was inside the constructor of the DragWidget class. I moved that code to a public method that I named 'draw()', and called this method from the constructor instead. Here's DragWidget definition and implementation: #include <QWidget> QT_BEGIN_NAMESPACE class QDragEnterEvent; class QDropEvent; QT_END_NAMESPACE class DragWidget : public QWidget { public: DragWidget(QWidget *parent = 0); public slots: void draw(); protected: void dragEnterEvent(QDragEnterEvent *event); void dragMoveEvent(QDragMoveEvent *event); void dropEvent(QDropEvent *event); void mousePressEvent(QMouseEvent *event); void paintEvent(QPaintEvent *event); }; DragWidget::DragWidget(QWidget *parent) : QWidget(parent) { draw(); QPalette newPalette = palette(); newPalette.setColor(QPalette::Window, Qt::white); setPalette(newPalette); setMinimumSize(400, 100);//qMax(200, y)); setWindowTitle(tr("Fridge Magnets")); setAcceptDrops(true); } void DragWidget::draw(){ QFile dictionaryFile(":/dictionary/words.txt"); dictionaryFile.open(QFile::ReadOnly); QTextStream inputStream(&dictionaryFile); int x = 5; int y = 5; while (!inputStream.atEnd()) { QString word; inputStream >> word; if (!word.isEmpty()) { DragLabel *wordLabel = new DragLabel(word, this); wordLabel->move(x, y); wordLabel->show(); wordLabel->setAttribute(Qt::WA_DeleteOnClose); x += wordLabel->width() + 2; if (x >= 245) { x = 5; y += wordLabel->height() + 2; } } } } I thought that maybe calling draw() as a slot would be enough to reload the labels, but it didn't work. Putting the draw() call inside the widget's overriden paintEvent() instead of the constructor didn't work out as well, the program would end up in an infinite loop. What I did was obviously not the right way of doing it, so what should I be doing instead?

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• Why is my code returning a Null Object Refrence error when using WatIn?

  - by Fuzz Evans

  I keep getting a Null Object Refrence Error, but can't tell why. I have a CSV file that contains 100 urls. The file is read into an array called "lines". public partial class Form1 : System.Windows.Forms.Form { string[] lines; public Form1() ... private void ReadLinksIntoMemory() { //this reads the chosen csv file into our "lines" array //and splits on comma's and new lines to create new objects within the array using (StreamReader sr = new StreamReader(@"C:\temp.csv")) { //reads everything in our csv into 1 long line string fileContents = sr.ReadToEnd(); //splits the 1 long line read in into multiple objects of the lines array lines = fileContents.Split(new string[] { ",", Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries); sr.Dispose(); } } The next part is where I get the null object error. When I try to use WatIn to go to the first item in the lines array it says I'm referencing a null object. private void GoToEditLinks() { for (int i = 0; i < lines.Length; i++) { //go to each link sequentially myIE.GoTo(lines[i].ToString()); //sleep so we can make sure the page loads System.Threading.Thread.Sleep(5000); } } When I debug the code it says that the GoTo request calls lines which is null. It seems like I need to declare the array, but don't I need to tell it an exact size to do that? Example: lines = new string[10] I thought I could use the lines.Length to tell it how big to make the array but that didn't work. What is weird to me is I can use the following code without problem: //returns the accurate number of urls that were in the CSV we read in earlier txtbx1.text = lines.Length; //or //this returns the last entry in the csv, as well as the last entry in the array TextBox2.Text = lines[lines.Length - 1]; I am confused why the array clearly has items in it, they can be called to fill a text box, but when I try to call them in my for loop it says its a null reference? UPDATE: By placing my cursor on both calls to lines and pressing f12 I find they both go to the same instance. The thought next is that I am not calling ReadLinksIntoMemory in time, below is my code: private void button1_Click(object sender, EventArgs e) { button1.Enabled = false; ReadLinksIntoMemory(); GoToEditLinks(); button1.Enabled = true; } Unless I'm mistaken the code says that the ReadLinksIntoMemory method must complete before GoToEditLinks can be called? If ReadLinksIntoMemory didn't finish in time I shouldn't be able to fill my text boxes with the lines array length and/or last entry. UPDATE: Stepping into the method GoToEditLinks() I see that lines is null before it calls: myIE.GoTo(lines[i]); but when it hits the goto command the value changes from null to the url it is suppose to go to, but at that same time it gives me the null object error? UPDATE: I added a IsNullOrEmpty check method and lines array passes it without any issue. I'm beginning to think it is an issue with WatIn and the myIE.GoTo command. I think this is the stack trace/call stack? Program.exe!Program.Form1.GoToEditLinks() Line 284 C# Program.exe!Program.Form1.button1_Click(object sender, System.EventArgs e) Line 191 + 0x8 bytes C# [External Code] Program.exe!Program.Program.Main() Line 18 + 0x1d bytes C# [External Code]

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• Rx IObservable buffering to smooth out bursts of events

  - by Dan

  I have an Observable sequence that produces events in rapid bursts (ie: five events one right after another, then a long delay, then another quick burst of events, etc.). I want to smooth out these bursts by inserting a short delay between events. Imagine the following diagram as an example: Raw: --oooo--------------ooooo-----oo----------------ooo| Buffered: --o--o--o--o--------o--o--o--o--o--o--o---------o--o--o| My current approach is to generate a metronome-like timer via Observable.Interval() that signals when it's ok to pull another event from the raw stream. The problem is that I can't figure out how to then combine that timer with my raw unbuffered observable sequence. IObservable.Zip() is close to doing what I want, but it only works so long as the raw stream is producing events faster than the timer. As soon as there is a significant lull in the raw stream, the timer builds up a series of unwanted events that then immediately pair up with the next burst of events from the raw stream. Ideally, I want an IObservable extension method with the following function signature that produces the bevaior I've outlined above. Now, come to my rescue StackOverflow :) public static IObservable<T> Buffered(this IObservable<T> src, TimeSpan minDelay) PS. I'm brand new to Rx, so my apologies if this is a trivially simple question... 1. Simple yet flawed approach Here's my initial naive and simplistic solution that has quite a few problems: public static IObservable<T> Buffered<T>(this IObservable<T> source, TimeSpan minDelay) { Queue<T> q = new Queue<T>(); source.Subscribe(x => q.Enqueue(x)); return Observable.Interval(minDelay).Where(_ => q.Count > 0).Select(_ => q.Dequeue()); } The first obvious problem with this is that the IDisposable returned by the inner subscription to the raw source is lost and therefore the subscription can't be terminated. Calling Dispose on the IDisposable returned by this method kills the timer, but not the underlying raw event feed that is now needlessly filling the queue with nobody left to pull events from the queue. The second problem is that there's no way for exceptions or end-of-stream notifications to be propogated through from the raw event stream to the buffered stream - they are simply ignored when subscribing to the raw source. And last but not least, now I've got code that wakes up periodically regardless of whether there is actually any work to do, which I'd prefer to avoid in this wonderful new reactive world. 2. Way overly complex appoach To solve the problems encountered in my initial simplistic approach, I wrote a much more complicated function that behaves much like IObservable.Delay() (I used .NET Reflector to read that code and used it as the basis of my function). Unfortunately, a lot of the boilerplate logic such as AnonymousObservable is not publicly accessible outside the system.reactive code, so I had to copy and paste a lot of code. This solution appears to work, but given its complexity, I'm less confident that its bug free. I just can't believe that there isn't a way to accomplish this using some combination of the standard Reactive extensions. I hate feeling like I'm needlessly reinventing the wheel, and the pattern I'm trying to build seems like a fairly standard one.

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• DSP - Problems using the inverse Fast Fourier Transform

  - by Trap

  I've been playing around a little with the Exocortex implementation of the FFT, but I'm having some problems. First, after calculating the inverse FFT of an unchanged frequency spectrum obtained by a previous forward FFT, one would expect to get the original signal back, but this is not the case. I had to figure out that I needed to scale the FFT output to about 1 / fftLength to get the amplitudes ok. Why is this? Second, whenever I modify the amplitudes of the frequency bins before calling the iFFT the signal gets distorted at low frequencies. However, this does not happen if I attenuate all the bins by the same factor. Let me put a very simplified example of the output buffer of a 4-sample FFT: // Bin 0 (DC) FFTOut[0] = 0.0000610351563 FFTOut[1] = 0.0 // Bin 1 FFTOut[2] = 0.000331878662 FFTOut[3] = 0.000629425049 // Central bin FFTOut[4] = -0.0000381469727 FFTOut[5] = 0.0 // Bin 3, this is a negative frequency bin. FFTOut[6] = 0.000331878662 FFTOut[7] = -0.000629425049 The output is composed of pairs of floats, each representing the real and imaginay parts of a single bin. So, bin 0 (array indexes 0, 1) would represent the real and imaginary parts of the DC frequency. As you can see, bins 1 and 3 both have the same values, (except for the sign of the Im part), so I guess these are the negative frequency values, and finally indexes (4, 5) would be the central frequency bin. To attenuate the frequency bin 1 this is what I do: // Attenuate the 'positive' bin FFTOut[2] *= 0.5; FFTOut[3] *= 0.5; // Attenuate its corresponding negative bin. FFTOut[6] *= 0.5; FFTOut[7] *= 0.5; For the actual tests I'm using a 1024-length FFT and I always provide all the samples so no 0-padding is needed. // Attenuate var halfSize = fftWindowLength / 2; float leftFreq = 0f; float rightFreq = 22050f; for( var c = 1; c < halfSize; c++ ) { var freq = c * (44100d / halfSize); // Calc. positive and negative frequency locations. var k = c * 2; var nk = (fftWindowLength - c) * 2; // This kind of attenuation corresponds to a high-pass filter. // The attenuation at the transition band is linearly applied, could // this be the cause of the distortion of low frequencies? var attn = (freq < leftFreq) ? 0 : (freq < rightFreq) ? ((freq - leftFreq) / (rightFreq - leftFreq)) : 1; mFFTOut[ k ] *= (float)attn; mFFTOut[ k + 1 ] *= (float)attn; mFFTOut[ nk ] *= (float)attn; mFFTOut[ nk + 1 ] *= (float)attn; } Obviously I'm doing something wrong but can't figure out what or where.

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• Portable scripting language for a multi-server admin?

  - by Aaron

  Please Note: Portable as in portableapps.com, not the traditional definition. Originally posted on stackoverflow.com, asking here at another user's suggestion. I'm a DBA and sysadmin, mostly for Windows machines running SQL Server. I'm looking for a programming/scripting language for Windows that doesn't require Admin access or an installer, needing no install process other than expanding it into a folder. My intent is to have a language for automation on which I can standardize. Up to this point, I've been using a combination of batch files and Unix shell, using sh.exe from UnxUtils but it's far from a perfect solution. I've evaluated a handful of options, all of them have at least one serious shortcoming or another. I have a strong preference for something open source or dual license, but I'm more interested in finding the right tool than anything else. Not interested that anything that relies on Cygwin or Java, but at this point I'd be fine with something that needs .NET. Requirements: Manageable footprint (1-100 files, under 30 MB installed) Run on Windows XP and Server (2003+) No installer (exe, msi) Works with external pipes, processes, and files Support for MS SQL Server or ODBC connections Bonus Points: Open Source FFI for calling functions in native DLLs GUI support (native or gtk, wx, fltk, etc) Linux, AIX, and/or OS X support Dynamic, object oriented and/or functional, interpreted or bytecode compiled; interactive development Able to package or compile scripts into executables So far I've tried: Ruby: 148 MB on disk, 23000 files Portable Python: 54 MB on disk, 2800 files Strawberry Perl: 123 MB on disk, 3600 files REBOL: Great, except closed source and no MSSQL or ODBC in free version Squeak Smalltalk: Great, except poor support for scripting ---- cut: points of clarification ---- Why all the limitations? I realize some of my criteria seem arbitrarily confining. It's primarily a product my environment. I work as a SQL Server DBA and backup Unix admin at a division of a large company. In addition to near a hundred boxes running some version or another of SQL Server on Windows, I also support the SQL Server Express Edition installs on over a thousand machines in the field. Because of our security policies, I don't login rights on every machine. Often enough, an issue comes up and I'm given local Admin for some period of time. Often enough, it's some box I've never touched and don't have my own environment setup yet. I may have temporary admin rights on the box, but I'm not the admin for the machine- I'm just the DBA. I've no interest in stepping on the toes of the Windows admins, nor do I want to take over any of their duties. If I bring up "installing" something, suddenly it becomes a matter of interest for Production Control and the Windows admins; if I'm copying up a script, no one minds. The distinction may not mean much to the readers, but if someone gets the wrong idea I've suddenly got a long wait and significant overhead before I can get the tool installed and get the problem solved. That's why I want something that can be copied and run in the manner of a portable app. What about the small footprint? My company has three divisions, each in a different geographical location, and one of them is a new acquisition. We have different production control/security policies in each division. I support our MSSQL databases in all three divisions. The field machines are spread around the US, sometimes connecting to the VPN over very slow links. Installing Ruby \using psexec has taken a long time over these connections. In these instances, the bigger time waster seems to be archives with thousands and thousands of files rather than their sheer size. You could say I'm spoiled by Unix, where the admins usually have at least some modern scripting language installed; I'd use PowerShell, but I don't know it well and more importantly it isn't everywhere I need to work. It's a regular occurrence that I need to write, deploy and execute some script on short notice on some machine I've never on which logged in. Since having Ruby or something similar installed on every machine I'll ever need to touch is effectively impossible because of the approvals, time and and Windows admin labor needed I makes more sense find a solution that allows me to work on my own terms.

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• Fatal error on a non-object

  - by Chris Leah

  Hey, so I have created a function to check the DB for unique entries, but when I call the function it doesn't seem to work and gives me a fatal error any ideas ? Thanks :) //Check for unique entries function checkUnique($table, $field, $compared) { $query = $mysqli->query('SELECT '.$mysqli->real_escape_string($field).' FROM '.$mysqli->real_escape_string($table).' WHERE "'.$mysqli->real_escape_string($field).'" = "'.$mysqli->real_escape_string($compared).'"'); if(!$query){ return TRUE; } else { return FALSE; } } The page calling it..... //Start session session_start(); //Check if the session is already set, if so re-direct to the game if(isset($_SESSION['id'], $_SESSION['logged_in'])){ Header('Location: ../main/index.php'); }; //Require database connection require_once('../global/includes/db.php'); require_once('../global/functions/functions.php'); //Check if the form has been submitted if (isset($_POST['signup'])){ //Validate input if (!empty($_POST['username']) && !empty($_POST['password']) && $_POST['password']==$_POST['password_confirm'] && !empty($_POST['email']) && validateEmail($_POST['email']) == TRUE && checkUnique('users', 'email', $_POST['email']) == TRUE && checkUnique('users', 'username', $_POST['username']) == TRUE) { //Insert user to the database $insert_user = $mysqli->query('INSERT INTO (`username, `password`, `email`, `verification_key`) VALUES ("'.$mysqli->real_escape_string($_POST['username']).'", "'.$mysqli-real_escape_string(md5($_POST['password'])).'", "'.$mysqli->real_escape_string($_POST['email']).'", "'.randomString('alnum', 32). '"') or die($mysqli->error()); //Get user information $getUser = $mysqli->query('SELECT id, username, email, verification_key FROM users WHERE username = "'.$mysqli->real_escape_string($_POST['username']).'"' or die($mysqli->error())); //Check if the $getUser returns true if ($getUser->num_rows == 1) { //Fetch associated fields to this user $row = $getUser->fetch_assoc(); //Set mail() variables $headers = 'From: [email protected]'."\r\n". 'Reply-To: [email protected]'."\r\n". 'X-Mailer: PHP/'.phpversion(); $subject = 'Activate your account (Music Battles.net)'; //Set verification email message $message = 'Dear '.$row['username'].', I would like to welcome you to Music Battles. Although in order to enjoy the gmae you must first activate your account. \n\n Click the following link: http://www.musicbattles.net/home/confirm.php?id='.$row['id'].'key='.$row['verification_key'].'\n Thanks for signing up, enjoy the game! \n Music Battles Team'; //Attempts to send the email if (mail($row['email'], $subject, $message, $headers)) { $msg = '<p class="success">Accound has been created, please go activate it from your email.</p>'; } else { $error = '<p class="error">The account was created but your email was not sent.</p>'; } } else { $error = '<p class="error">Your account was not created.</p>'; } } else { $error = '<p class="error">One or more fields contain non or invalid data.</p>'; } } Erorr.... Fatal error: Call to a member function query() on a non-object in /home/mbattles/public_html/global/functions/functions.php on line 5

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• Unable to start ServiceIntent android

  - by Mj1992

  I don't know why my service class is not working although it was working fine before. I've the following service class. public class MyIntentService extends IntentService { private static PowerManager.WakeLock sWakeLock; private static final Object LOCK = MyIntentService.class; public MyIntentService() { super("MuazzamService"); } @Override protected void onHandleIntent(Intent intent) { try { String action = intent.getAction(); <-- breakpoint if (action.equals("com.google.android.c2dm.intent.REGISTRATION")) <-- passes by { handleRegistration(intent); } else if (action.equals("com.google.android.c2dm.intent.RECEIVE")) { handleMessage(intent); } } finally { synchronized(LOCK) { sWakeLock.release(); } } } private void handleRegistration(Intent intent) { try { String registrationId = intent.getStringExtra("registration_id"); String error = intent.getStringExtra("error"); String unregistered = intent.getStringExtra("unregistered"); if (registrationId != null) { this.SendRegistrationIDViaHttp(registrationId); Log.i("Regid",registrationId); } if (unregistered != null) {} if (error != null) { if ("SERVICE_NOT_AVAILABLE".equals(error)) { Log.e("ServiceNoAvail",error); } else { Log.i("Error In Recieveing regid", "Received error: " + error); } } } catch(Exception e) { Log.e("ErrorHai(MIS0)",e.toString()); e.printStackTrace(); } } private void SendRegistrationIDViaHttp(String regID) { HttpClient httpclient = new DefaultHttpClient(); try { HttpGet httpget = new HttpGet("http://10.116.27.107/php/GCM/AndroidRequest.php?registrationID="+regID+"&[email protected]"); //test purposes k liye muazzam HttpResponse response = httpclient.execute(httpget); HttpEntity entity=response.getEntity(); if(entity!=null) { InputStream inputStream=entity.getContent(); String result= convertStreamToString(inputStream); Log.i("finalAnswer",result); // Toast.makeText(getApplicationContext(),regID, Toast.LENGTH_LONG).show(); } } catch (ClientProtocolException e) { Log.e("errorhai",e.getMessage()); e.printStackTrace(); } catch (IOException e) { Log.e("errorhai",e.getMessage()); e.printStackTrace(); } } private static String convertStreamToString(InputStream is) { BufferedReader reader = new BufferedReader(new InputStreamReader(is)); StringBuilder sb = new StringBuilder(); String line = null; try { while ((line = reader.readLine()) != null) { sb.append(line + "\n"); } } catch (IOException e) { Log.e("ErrorHai(MIS)",e.toString()); e.printStackTrace(); } finally { try { is.close(); } catch (IOException e) { Log.e("ErrorHai(MIS2)",e.toString()); e.printStackTrace(); } } return sb.toString(); } private void handleMessage(Intent intent) { try { String score = intent.getStringExtra("score"); String time = intent.getStringExtra("time"); Toast.makeText(getApplicationContext(), "hjhhjjhjhjh", Toast.LENGTH_LONG).show(); Log.e("GetExtraScore",score.toString()); Log.e("GetExtratime",time.toString()); } catch(NullPointerException e) { Log.e("je bat",e.getMessage()); } } static void runIntentInService(Context context,Intent intent){ synchronized(LOCK) { if (sWakeLock == null) { PowerManager pm = (PowerManager) context.getSystemService(Context.POWER_SERVICE); sWakeLock = pm.newWakeLock(PowerManager.PARTIAL_WAKE_LOCK, "my_wakelock"); } } sWakeLock.acquire(); intent.setClassName(context, MyIntentService.class.getName()); context.startService(intent); } } and here's how I am calling the service as mentioned in the android docs. Intent registrationIntent = new Intent("com.google.android.c2dm.intent.REGISTER"); registrationIntent.putExtra("app", PendingIntent.getBroadcast(this, 0, new Intent(), 0)); registrationIntent.putExtra("sender",Sender_ID); startService(registrationIntent); I've declared the service in the manifest file inside the application tag. <service android:name="com.pack.gcm.MyIntentService" android:enabled="true"/> I placed a breakpoint in my IntentService class but it never goes there.But if I declare my registrationIntent like this Intent registrationIntent = new Intent(getApplicationContext(),com.pack.gcm.MyIntentService); It works and goes to the breakpoint I've placed but intent.getAction() contains null and hence it doesn't go into the if condition placed after those lines. It says 07-08 02:10:03.755: W/ActivityManager(60): Unable to start service Intent { act=com.google.android.c2dm.intent.REGISTER (has extras) }: not found in the logcat.

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• is it right to call ejb bean from thread by ThreadPoolExecutor?

  - by kislo_metal

  I trying to call some ejb bean method from tread. and getting error : (as is glassfish v3) Log Level SEVERE Logger javax.enterprise.system.std.com.sun.enterprise.v3.services.impl Name-Value Pairs {_ThreadName=Thread-1, _ThreadID=42} Record Number 928 Message ID java.lang.NullPointerException at ua.co.rufous.server.broker.TempLicService.run(TempLicService.java Complete Message 35) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908) at java.lang.Thread.run(Thread.java:637) here is tread public class TempLicService implements Runnable { String hash; //it`s Stateful bean @EJB private LicActivatorLocal lActivator; public TempLicService(String hash) { this.hash= hash; } @Override public void run() { lActivator.proccessActivation(hash); } } my ThreadPoolExecutor public class RequestThreadPoolExecutor extends ThreadPoolExecutor { private boolean isPaused; private ReentrantLock pauseLock = new ReentrantLock(); private Condition unpaused = pauseLock.newCondition(); private static RequestThreadPoolExecutor threadPool; private RequestThreadPoolExecutor() { super(1, Integer.MAX_VALUE, 10, TimeUnit.SECONDS, new LinkedBlockingQueue<Runnable>()); System.out.println("RequestThreadPoolExecutor created"); } public static RequestThreadPoolExecutor getInstance() { if (threadPool == null) threadPool = new RequestThreadPoolExecutor(); return threadPool; } public void runService(Runnable task) { threadPool.execute(task); } protected void beforeExecute(Thread t, Runnable r) { super.beforeExecute(t, r); pauseLock.lock(); try { while (isPaused) unpaused.await(); } catch (InterruptedException ie) { t.interrupt(); } finally { pauseLock.unlock(); } } public void pause() { pauseLock.lock(); try { isPaused = true; } finally { pauseLock.unlock(); } } public void resume() { pauseLock.lock(); try { isPaused = false; unpaused.signalAll(); } finally { pauseLock.unlock(); } } public void shutDown() { threadPool.shutdown(); } //<<<<<< creating thread here public void runByHash(String hash) { Runnable service = new TempLicService(hash); threadPool.runService(service); } } and method where i call it (it is gwt servlet, but there is no proble to call thread that not contain ejb) : @Override public Boolean submitHash(String hash) { System.out.println("submiting hash"); try { if (tBoxService.getTempLicStatus(hash) == 1) { //<<< here is the call RequestThreadPoolExecutor.getInstance().runByHash(hash); return true; } } catch (NoResultException e) { e.printStackTrace(); } return false; } I need to organize some pool of submitting hash to server (calls of LicActivator bean), is ThreadPoolExecutor design good idea and why it is not working in my case? (as I know we can`t create thread inside bean, but could we call bean from different threads? ). If No, what is the bast practice for organize such request pool? Thanks. << Answer: I am using DI (EJB 3.1) soo i do not need any look up here. (application packed in ear and both modules in it (web module and ejb), it works perfect for me). But I can use it only in managed classes. So.. 2.Can I use manual look up in Tread ? Could I use Bean that extends ThreadPoolExecutor and calling another bean that implements Runnable ? Or it is not allowed ?

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• Custom event loop and UIKit controls. What extra magic Apple's event loop does?

  - by tequilatango

  Does anyone know or have good links that explain what iPhone's event loop does under the hood? We are using a custom event loop in our OpenGL-based iPhone game framework. It calls our game rendering system, calls presentRenderbuffer and pumps events using CFRunLoopRunInMode. See the code below for details. It works well when we are not using UIKit controls (as a proof, try Facetap, our first released game). However, when using UIKit controls, everything almost works, but not quite. Specifically, scrolling of UIKit controls doesn't work properly. For example, let's consider following scenario. We show UIImagePickerController on top of our own view. UIImagePickerController covers our custom view We also pause our own rendering, but keep on using the custom event loop. As said, everything works, except scrolling. Picking photos works. Drilling down to photo albums works and transition animations are smooth. When trying to scroll photo album view, the view follows your finger. Problem: when scrolling, scrolling stops immediately after you lift your finger. Normally, it continues smoothly based on the speed of your movement, but not when we are using the custom event loop. It seems that iPhone's event loop is doing some magic related to UIKit scrolling that we haven't implemented ourselves. Now, we can get UIKit controls to work just fine and dandy together with our own system by using Apple's event loop and calling our own rendering via NSTimer callbacks. However, I'd still like to understand, what is possibly happening inside iPhone's event loop that is not implemented in our custom event loop. - (void)customEventLoop { OBJC_METHOD; float excess = 0.0f; while(isRunning) { animationInterval = 1.0f / openGLapp->ticks_per_second(); // Calculate the target time to be used in this run of loop float wait = max(0.0, animationInterval - excess); Systemtime target = Systemtime::now().after_seconds(wait); Scope("event loop"); NSAutoreleasePool* pool = [[ NSAutoreleasePool alloc] init]; // Call our own render system and present render buffer [self drawView]; // Pump system events [self handleSystemEvents:target]; [pool release]; excess = target.seconds_to_now(); } } - (void)drawView { OBJC_METHOD; // call our own custom rendering bool bind = openGLapp->app_render(); // bind the buffer to be THE renderbuffer and present its contents if (bind) { opengl::bind_renderbuffer(renderbuffer); [context presentRenderbuffer:GL_RENDERBUFFER_OES]; } } - (void) handleSystemEvents:(Systemtime)target { OBJC_METHOD; SInt32 reason = 0; double time_left = target.seconds_since_now(); if (time_left <= 0.0) { while((reason = CFRunLoopRunInMode(kCFRunLoopDefaultMode, 0, TRUE)) == kCFRunLoopRunHandledSource) {} } else { float dt = time_left; while((reason = CFRunLoopRunInMode(kCFRunLoopDefaultMode, dt, FALSE)) == kCFRunLoopRunHandledSource) { double time_left = target.seconds_since_now(); if (time_left <= 0.0) break; dt = (float) time_left; } } }

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• Round-twice error in .NET's Double.ToString method

  - by Jeppe Stig Nielsen

  Mathematically, consider for this question the rational number 8725724278030350 / 2**48 where ** in the denominator denotes exponentiation, i.e. the denominator is 2 to the 48th power. (The fraction is not in lowest terms, reducible by 2.) This number is exactly representable as a System.Double. Its decimal expansion is 31.0000000000000'49'73799150320701301097869873046875 (exact) where the apostrophes do not represent missing digits but merely mark the boudaries where rounding to 15 resp. 17 digits is to be performed. Note the following: If this number is rounded to 15 digits, the result will be 31 (followed by thirteen 0s) because the next digits (49...) begin with a 4 (meaning round down). But if the number is first rounded to 17 digits and then rounded to 15 digits, the result could be 31.0000000000001. This is because the first rounding rounds up by increasing the 49... digits to 50 (terminates) (next digits were 73...), and the second rounding might then round up again (when the midpoint-rounding rule says "round away from zero"). (There are many more numbers with the above characteristics, of course.) Now, it turns out that .NET's standard string representation of this number is "31.0000000000001". The question: Isn't this a bug? By standard string representation we mean the String produced by the parameterles Double.ToString() instance method which is of course identical to what is produced by ToString("G"). An interesting thing to note is that if you cast the above number to System.Decimal then you get a decimal that is 31 exactly! See this Stack Overflow question for a discussion of the surprising fact that casting a Double to Decimal involves first rounding to 15 digits. This means that casting to Decimal makes a correct round to 15 digits, whereas calling ToSting() makes an incorrect one. To sum up, we have a floating-point number that, when output to the user, is 31.0000000000001, but when converted to Decimal (where 29 digits are available), becomes 31 exactly. This is unfortunate. Here's some C# code for you to verify the problem: static void Main() { const double evil = 31.0000000000000497; string exactString = DoubleConverter.ToExactString(evil); // Jon Skeet, http://csharpindepth.com/Articles/General/FloatingPoint.aspx Console.WriteLine("Exact value (Jon Skeet): {0}", exactString); // writes 31.00000000000004973799150320701301097869873046875 Console.WriteLine("General format (G): {0}", evil); // writes 31.0000000000001 Console.WriteLine("Round-trip format (R): {0:R}", evil); // writes 31.00000000000005 Console.WriteLine(); Console.WriteLine("Binary repr.: {0}", String.Join(", ", BitConverter.GetBytes(evil).Select(b => "0x" + b.ToString("X2")))); Console.WriteLine(); decimal converted = (decimal)evil; Console.WriteLine("Decimal version: {0}", converted); // writes 31 decimal preciseDecimal = decimal.Parse(exactString, CultureInfo.InvariantCulture); Console.WriteLine("Better decimal: {0}", preciseDecimal); // writes 31.000000000000049737991503207 } The above code uses Skeet's ToExactString method. If you don't want to use his stuff (can be found through the URL), just delete the code lines above dependent on exactString. You can still see how the Double in question (evil) is rounded and cast.

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• Forms bound to updateable ADO recordsets are not updateable when the source includes a JOIN

  - by Art

  I'm developing an application in Access 2007. It uses an .accdb front end connecting to an SQL Server 2005 backend. I use forms that are bound to ADO recordsets at runtime. For the sake of efficiency, the recordsets usually contain only one record, and are queried out on the server: Public Sub SetUpFormRecordset(cn As ADODB.Connection, rstIn As ADODB.Recordset, rstSource As String) Dim cmd As ADODB.Command Dim I As Long Set cmd = New ADODB.Command cn.Errors.Clear ' Recordsets based on command object Execute method are Read Only! With cmd Set .ActiveConnection = cn .CommandType = adCmdText .CommandText = rstSource End With With rstIn .CursorType = adOpenKeyset .LockType = adLockPessimistic 'Check the locktype after opening; optimistic locking is worthless on a bound End With ' form, and ADO might open optimistically without firing an error! rstIn.Open cmd, , adOpenKeyset, adLockPessimistic 'This should run the query on the server and return an updatable recordset With cn If .Errors.Count <> 0 Then For Each errADO In .Errors Call HandleADOErrors(.Errors(I)) I = I + 1 Next errADO End If End With End Sub rstSource (the string containg the TSQL on which the recordset is based) is assembled by the calling routine, in this case from the Open event of the form being bound: Private Sub Form_Open(Cancel As Integer) Dim rst As ADODB.Recordset Dim strSource As String, DefaultSource as String Dim lngID As Long lngID = Forms!MyParent.CurrentID strSource = "SELECT TOP (100) PERCENT dbo.Customers.CustomerID, dbo.Customers.LegacyID, dbo.Customers.Active, dbo.Customers.TypeID, dbo.Customers.Category, " & _ "dbo.Customers.Source, dbo.Customers.CustomerName, dbo.Customers.CustAddrID, dbo.Customers.Email, dbo.Customers.TaxExempt, dbo.Customers.SalesTaxCode, " & _ "dbo.Customers.SalesTax2Code, dbo.Customers.CreditLimit, dbo.Customers.CreationDate, dbo.Customers.FirstOrder, dbo.Customers.LastOrder, " & _ "dbo.Customers.nOrders, dbo.Customers.Concurrency, dbo.Customers.LegacyLN, dbo.Addresses.AddrType, dbo.Addresses.AddrLine1, dbo.Addresses.AddrLine2, " & _ "dbo.Addresses.City, dbo.Addresses.State, dbo.Addresses.Country, dbo.Addresses.PostalCode, dbo.Addresses.PhoneLandline, dbo.Addresses.Concurrency " & _ "FROM dbo.Customers INNER JOIN " & _ "dbo.Addresses ON dbo.Customers.CustAddrID = dbo.Addresses.AddrID " strSource = strSource & "WHERE dbo.Customers.CustomerID= " & lngID With Me 'Default is Set up for editing one record If Not Nz(.RecordSource, vbNullString) = vbNullString Then If .Dirty Then .Dirty = False 'Save any changes on the form .RecordSource = vbNullString End If If rst Is Nothing Then 'Might not be first time through DefaultSource = .RecordSource Else rst.Close Set rst = Nothing End If End With Set rst = New ADODB.Recordset Call setupformrecordset(dbconn, rst, strSource) 'dbconn is a global variable With Me Set .Recordset = rst End With End Sub The recordset that is returned from setupformrecordset is fully updateable, and its .Supports property shows this. It can be edited and updated in code. The entire form, however, is read only, even though it's .AllowEdits and .AllowAdditions properties are both true. Even the fields from the right hand side (the 'many' side) cannot be edited. Removing the INNER JOIN clause from the TSQL (restricting strSource to one table) makes the form fully editable. I've verified that the TSQL includes priimary key fields from both tables, and each table includes a timestamp field for concurrency. I tried changing the .CursorType and .CursorLocation properties of the recordset to no avail. What am I doing wrong?

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• Trac FastCGI + Python on dreamhost leaves zombie python running

  - by Katsuke

  Hello there, Recently I installed trac in one of my dreamhost domains. I followed the instructions of http://trac.mlalonde.net/wiki/CreamyTrac and everything worked perfectly. At least i thought that was the case. After a few days, i started to notice that i was getting random 500 pages. I quickly checked the error log, and found a bunch of: [Fri Apr 16 14:35:34 2010] [error] [client *.*.*.*] Premature end of script headers: dispatch.fcgi [Fri Apr 16 14:35:54 2010] [error] [client *.*.*.*] Premature end of script headers: dispatch.fcgi, referer: http://www.trac.****.com/login [Fri Apr 16 16:05:58 2010] [error] [client *.*.*.*] Premature end of script headers: dispatch.fcgi, referer: http://www.trac.****.com/timeline The trac instance has very low traffic so it is possible that this might have been triggered faster if there was more use of it. So next step i went to look at top and am amazed by what i see: (this is NOT exactly what i saw, i just reproduced this from memory) 23730 rl_inst 20 0 44516 15m 4012 S 0.0 0.4 0:00.17 python2.4 23731 rl_inst 20 0 44616 15m 4012 S 0.0 0.4 0:03.17 python2.4 23732 rl_inst 20 0 44116 15m 4012 S 0.0 0.4 0:01.17 python2.4 23733 rl_inst 20 0 44826 15m 4012 S 0.0 0.4 0:04.17 python2.4 23734 rl_inst 20 0 44216 15m 4012 S 0.0 0.4 0:02.17 python2.4 23735 rl_inst 20 0 44416 15m 4012 S 0.0 0.4 0:01.17 python2.4 I opened the trac site again and that changed to this: 23730 rl_inst 20 0 44516 15m 4012 S 0.0 0.4 0:00.17 python2.4 23731 rl_inst 20 0 44616 15m 4012 S 0.0 0.4 0:03.17 python2.4 23732 rl_inst 20 0 44116 15m 4012 S 0.0 0.4 0:01.17 python2.4 23733 rl_inst 20 0 44826 15m 4012 S 0.0 0.4 0:04.17 python2.4 23734 rl_inst 20 0 44216 15m 4012 S 0.0 0.4 0:02.17 python2.4 23735 rl_inst 20 0 44416 15m 4012 S 0.0 0.4 0:01.17 python2.4 28378 rl_inst 20 0 2608 1208 1008 S 0.0 0.0 0:00.00 dispatch.fcgi 28382 rl_inst 20 0 44248 15m 4012 S 0.0 0.4 0:02.19 python2.4 So the dispatch.fcgi was being called correctly and was spawning correctly other python2.4 process. After the IDLE time passed this is the results: 23730 rl_inst 20 0 44516 15m 4012 S 0.0 0.4 0:00.17 python2.4 23731 rl_inst 20 0 44616 15m 4012 S 0.0 0.4 0:03.17 python2.4 23732 rl_inst 20 0 44116 15m 4012 S 0.0 0.4 0:01.17 python2.4 23733 rl_inst 20 0 44826 15m 4012 S 0.0 0.4 0:04.17 python2.4 23734 rl_inst 20 0 44216 15m 4012 S 0.0 0.4 0:02.17 python2.4 23735 rl_inst 20 0 44416 15m 4012 S 0.0 0.4 0:01.17 python2.4 28382 rl_inst 20 0 44248 15m 4012 S 0.0 0.4 0:02.19 python2.4 dispatch.fcgi was gone but the corresponding python2.4 was still there o_O. I had started with 5 sleeping processes of python and after idle time i ended up with 6. I repeated this and found that it kept spawning more and more python2.4, this was indeed what was causing my 500s indirectly. Let me explain my findings. Am on a shared hosting so my processes get killed if they are way too many. So everytime i opened trac 2 new processes spawned and one remained, to the point that dreamhost was killing a random process when i reached my limit. Sometimes killing the python2.4 that actually was rendering the current page. Hence header premature ending, python is gone the .fcgi doesnt know what to do and throws an 500. I found a dirty solution to this. I changed my dispatch.fcgi to contain a line that killed any currently running python2.4 process and then spawn a new one. Since then i dont get any rogues what so ever. But i dont think this is the best solution, calling killall in every fcgi just seems wrong. Anyone has run into this issue and found a cleaner solution? Is there anything that i have overlooked?

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• Sending changes from multiple tables in disconnected dataset to SQLServer...

  - by Stecy

  We have a third party application that accept calls using an XML RPC mechanism for calling stored procs. We send a ZIP-compressed dataset containing multiple tables with a bunch of update/delete/insert using this mechanism. On the other end, a CLR sproc decompress the data and gets the dataset. Then, the following code gets executed: using (var conn = new SqlConnection("context connection=true")) { if (conn.State == ConnectionState.Closed) conn.Open(); try { foreach (DataTable table in ds.Tables) { string columnList = ""; for (int i = 0; i < table.Columns.Count; i++) { if (i == 0) columnList = table.Columns[0].ColumnName; else columnList += "," + table.Columns[i].ColumnName; } var da = new SqlDataAdapter("SELECT " + columnList + " FROM " + table.TableName, conn); var builder = new SqlCommandBuilder(da); builder.ConflictOption = ConflictOption.OverwriteChanges; da.RowUpdating += onUpdatingRow; da.Update(ds, table.TableName); } } catch (....) { ..... } } Here's the event handler for the RowUpdating event: public static void onUpdatingRow(object sender, SqlRowUpdatingEventArgs e) { if ((e.StatementType == StatementType.Update) && (e.Command == null)) { e.Command = CreateUpdateCommand(e.Row, sender as SqlDataAdapter); e.Status = UpdateStatus.Continue; } } and the CreateUpdateCommand method: private static SqlCommand CreateUpdateCommand(DataRow row, SqlDataAdapter da) { string whereClause = ""; string setClause = ""; SqlConnection conn = da.SelectCommand.Connection; for (int i = 0; i < row.Table.Columns.Count; i++) { char quoted; if ((row.Table.Columns[i].DataType == Type.GetType("System.String")) || (row.Table.Columns[i].DataType == Type.GetType("System.DateTime"))) quoted = '\''; else quoted = ' '; string val = row[i].ToString(); if (row.Table.Columns[i].DataType == Type.GetType("System.Boolean")) val = (bool)row[i] ? "1" : "0"; bool isPrimaryKey = false; for (int j = 0; j < row.Table.PrimaryKey.Length; j++) { if (row.Table.PrimaryKey[j].ColumnName == row.Table.Columns[i].ColumnName) { if (whereClause != "") whereClause += " AND "; if (row[i] == DBNull.Value) whereClause += row.Table.Columns[i].ColumnName + "=NULL"; else whereClause += row.Table.Columns[i].ColumnName + "=" + quoted + val + quoted; isPrimaryKey = true; break; } } /* Only values for column that is not a primary key can be modified */ if (!isPrimaryKey) { if (setClause != "") setClause += ", "; if (row[i] == DBNull.Value) setClause += row.Table.Columns[i].ColumnName + "=NULL"; else setClause += row.Table.Columns[i].ColumnName + "=" + quoted + val + quoted; } } return new SqlCommand("UPDATE " + row.Table.TableName + " SET " + setClause + " WHERE " + whereClause, conn); } However, this is really slow when we have a lot of records. Is there a way to optimize this or an entirely different way to send lots of udpate/delete on several tables? I would really much like to use TSQL for this but can't figure a way to send a dataset to a regular sproc. Additional notes: We cannot directly access the SQLServer database. We tried without compression and it was slower.

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• Is it possible to call Javascript's onsubmit event programatically on a form?

  - by hoyhoy

  In Ruby on Rails, I'm attempting to update the innerHTML of a div tag using the form_remote_tag helper. This update happens whenever an associated select tag receives an onchange event. The problem is, <select onchange="this.form.submit();">; doesn't work. Nor does document.forms[0].submit(). The only way to get the onsubmit code generated in the form_remote_tag to execute is to create a hidden submit button, and invoke the click method on the button from the select tag. Here's a working ERb partial example. <% form_remote_tag :url => product_path, :update => 'content', :method => 'get' do -%> <% content_tag :div, :id => 'content' do -%> <%= select_tag :update, options_for_select([["foo", 1], ["bar", 2]]), :onchange => "this.form.commit.click" %> <%= submit_tag 'submit_button', :style => "display: none" %> <% end %> <% end %> What I want to do is something like this, but it doesn't work. <% form_remote_tag :url => product_path, :update => 'content', :method => 'get' do -%> <% content_tag :div, :id => 'content' do -%> # the following line does not work <%= select_tag :update, options_for_select([["foo", 1], ["bar", 2]]), :onchange => "this.form.onsubmit()" %> <% end %> <% end %> So, is there any way to remove the invisible submit button for this use case? There seems to be some confusion. So, let me explain. The basic problem is that submit() doesn't call the onsubmit() code rendered into the form. The actual HTML form that Rails renders from this ERb looks like this: <form action="/products/1" method="post" onsubmit="new Ajax.Updater('content', '/products/1', {asynchronous:true, evalScripts:true, method:'get', parameters:Form.serialize(this)}); return false;"> <div style="margin:0;padding:0"> <input name="authenticity_token" type="hidden" value="4eacf78eb87e9262a0b631a8a6e417e9a5957cab" /> </div> <div id="content"> <select id="update" name="update" onchange="this.form.commit.click"> <option value="1">foo</option> <option value="2">bar</option> </select> <input name="commit" style="display: none" type="submit" value="submit_button" /> </div> </form> I want to axe the invisible submit button, but using a straight form.submit appears to not work. So, I need some way to call the form's onsubmit event code. Update: Orion Edwards solution would work if there wasn't a return(false); generated by Rails. I'm not sure which is worse though, sending a phantom click to an invisible submit button or calling eval on the getAttribute('onsubmit') call after removing the return call with a javascript string replacement!

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• Why does virtual assignment behave differently than other virtual functions of the same signature?

  - by David Rodríguez - dribeas

  While playing with implementing a virtual assignment operator I have ended with a funny behavior. It is not a compiler glitch, since g++ 4.1, 4.3 and VS 2005 share the same behavior. Basically, the virtual operator= behaves differently than any other virtual function with respect to the code that is actually being executed. struct Base { virtual Base& f( Base const & ) { std::cout << "Base::f(Base const &)" << std::endl; return *this; } virtual Base& operator=( Base const & ) { std::cout << "Base::operator=(Base const &)" << std::endl; return *this; } }; struct Derived : public Base { virtual Base& f( Base const & ) { std::cout << "Derived::f(Base const &)" << std::endl; return *this; } virtual Base& operator=( Base const & ) { std::cout << "Derived::operator=( Base const & )" << std::endl; return *this; } }; int main() { Derived a, b; a.f( b ); // [0] outputs: Derived::f(Base const &) (expected result) a = b; // [1] outputs: Base::operator=(Base const &) Base & ba = a; Base & bb = b; ba = bb; // [2] outputs: Derived::operator=(Base const &) Derived & da = a; Derived & db = b; da = db; // [3] outputs: Base::operator=(Base const &) ba = da; // [4] outputs: Derived::operator=(Base const &) da = ba; // [5] outputs: Derived::operator=(Base const &) } The effect is that the virtual operator= has a different behavior than any other virtual function with the same signature ([0] compared to [1]), by calling the Base version of the operator when called through real Derived objects ([1]) or Derived references ([3]) while it does perform as a regular virtual function when called through Base references ([2]), or when either the lvalue or rvalue are Base references and the other a Derived reference ([4],[5]). Is there any sensible explanation to this odd behavior?

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• Help with this code.

  - by karthick6891

  Heading ##Hey guys i need help with this code.The short version is,i have to do match the follwing by using drag and drop in jquery and later i need to show a message whether it is right or wrong. var output = "Wrong"; var old_item ; var new_item ; var newObjArray=[]; $(function() { var $gallery = $('.gallery'), $trash = $('.trash'); $('div',$gallery).draggable({ revert: 'invalid', containment: 'document', helper: 'clone', cursor: 'move', }); // let the trash be droppable, accepting the gallery items $trash.droppable({ //accept: '#gallery div', //activeClass: 'ui-state-highlight', tolerance: 'touch', drop: function(ev, ui) { new_item = ui.draggable; $(this).droppable("option","activeClass",'.ui-state-highlight'); if(contains(newObjArray,ui.draggable)) { newObjArray.pop(ui.draggable); } newObjArray.push(ui.draggable); deleteImage(ui.draggable,$(this)); } }); // let the gallery be droppable as well, accepting items from the trash $gallery.droppable({ //accept: '#trash li', activeClass: 'custom-state-active', drop: function(ev, ui) { recycleImage(ui.draggable); } }); // image deletion function function deleteImage($item,element) { var $list; $item.fadeOut(10,function() { if($(".ui-widget-content", element).length <1){ old_item = $item; $list = $('<div class="gallery ui-helper-reset"/>').appendTo(element); //$('ul',$trash).length ? $('ul',$trash) : $('<ul class="gallery ui-helper-reset"/>').appendTo($trash); $item.appendTo($list).fadeIn(10); } else{ recycleImage($(".ui-widget-content",element)); $list = $('<div class="gallery ui-helper-reset"/>').appendTo(element); $item.appendTo($list).fadeIn(10); old_item = $item; } }); } //check for given answer // image recycle function function recycleImage($item) { $item.fadeOut(10,function() { $item.find("img").end().appendTo($gallery).fadeIn(10); }); } // image preview function, demonstrating the ui.dialog used as a modal window }); function checkOrder(){ if(newObjArray==null){ } else if(newObjArray!=null){ if(newObjArray[0].attr("id")=="5"&& newObjArray[1].attr("id")=="1" && newObjArray[2].attr("id")=="3" && newObjArray[3].attr("id")=="2" && newObjArray[4].attr("id")=="4"){ parent.parent.increaseCorrectA(); } else{ parent.parent.increaseWrongA(); } } } function contains(a, obj) { var i = a.length; while (i--) { if (a[i] === obj) { return true; } } return false; } I am calling the function checkOrder() from the html page after the matching of items is over.What happens here is i have just stored the user responses on the draggable over droppable in an array,based on it's position.It is a bad practice cause,i am saying whether it's right or wrong through its position in the array.The only thing i can do is get the draggable's id present in the droppable.But i dont know how to get that inside the function checkOrder().Any ideas please?

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• Nginx no longer servers uwsgi application behind HAProxy - Looks for static file instead

  - by Ralph

  We implemented our web application using web2py. It consists of several modules offering a REST API at various resources (e.g. /dids, /replicas, ...). The API is used by clients implementing requests.py. My problem is that our web app works fine if it's behind HAProxy and hosted by Apache using mod_wsgi. It also works fine if the clients interact with nginx directly. It doesn't work though when using HAProxy in front of nginx. My guess is that HAProxy somehow modifies the request and thus nginx behaves differently i.e. looking for a static file instead of calling the WSGI container. Unfortunately I can't figure out what's exactly going (wr)on(g). Here are the relevant config sections of these three component's config files. At least I guess they are interesting. If you miss anything, please let me know. 1) haproxy.conf frontend app-lb bind loadbalancer:443 ssl crt /etc/grid-security/hostcertkey.pem default_backend nginx-servers mode http backend nginx-servers balance leastconn option forwardfor server nginx-01 nginx-server-int-01.domain.com:80 check 2) nginx.conf: sendfile off; #tcp_nopush on; keepalive_timeout 65; include /etc/nginx/conf.d/*.conf; server { server_name nginx-server-int-01.domain.com; root /path/to/app/; location / { uwsgi_pass unix:///tmp/app.sock; include uwsgi_params; uwsgi_read_timeout 600; # Requests can run for a serious long time } 3) uwsgi.ini [uwsgi] chdir = /path/to/app/ chmod-socket = 777 no-default-app = True socket = /tmp/app.sock manage-script-name = True mount = /dids=did.py mount = /replicas=replica.py callable = application Now when I let my clients go against nginx-server-int-01.domain.com everything is fine. In the access.log of nginx lines like these are appearing: 128.142.XXX.XX0 - - [23/Aug/2014:01:29:20 +0200] "POST /dids/attachments HTTP/1.1" 201 17 "-" "python-requests/2.3.0 CPython/2.6.6 Linux/2.6.32-358.23.2.el6.x86_64" "-" 128.142.XXX.XX0 - - [23/Aug/2014:01:29:20 +0200] "POST /dids/attachments HTTP/1.1" 201 17 "-" "python-requests/2.3.0 CPython/2.6.6 Linux/2.6.32-358.23.2.el6.x86_64" "-" 128.142.XXX.XX0 - - [23/Aug/2014:01:29:20 +0200] "POST /dids/user.ogueta/cnt_mc12_8TeV.16304.stream_name_too_long.other.notype.004202218365415e990b9997ea859f20.user/dids HTTP/1.1" 201 17 "-" "python-requests/2.3.0 CPython/2.6.6 Linux/2.6.32-358.23.2.el6.x86_64" "-" 128.142.XXX.XX0 - - [23/Aug/2014:01:29:20 +0200] "POST /replicas/list HTTP/1.1" 200 5282 "-" "python-requests/2.3.0 CPython/2.6.6 Linux/2.6.32-358.23.2.el6.x86_64" "-" 128.142.XXX.XX0 - - [23/Aug/2014:01:29:20 +0200] "POST /replicas/list HTTP/1.1" 200 5094 "-" "python-requests/2.3.0 CPython/2.6.6 Linux/2.6.32-358.23.2.el6.x86_64" "-" 128.142.XXX.XX0 - - [23/Aug/2014:01:29:20 +0200] "POST /replicas/list HTTP/1.1" 200 528 "-" "python-requests/2.3.0 CPython/2.6.6 Linux/2.6.32-358.23.2.el6.x86_64" "-" 128.142.XXX.XX0 - - [23/Aug/2014:01:29:21 +0200] "GET /dids/mc13_14TeV/dids/search?project=mc13_14TeV&stream_name=%2Adummy&type=dataset&datatype=NTUP_SMDYMUMU HTTP/1.1" 401 73 "-" "python-requests/2.3.0 CPython/2.6.6 Linux/2.6.32-358.23.2.el6.x86_64" "-" 128.142.XXX.XX0 - - [23/Aug/2014:01:29:21 +0200] "POST /replicas/list HTTP/1.1" 200 713 "-" "python-requests/2.3.0 CPython/2.6.6 Linux/2.6.32-358.23.2.el6.x86_64" "-" 128.142.XXX.XX0 - - [23/Aug/2014:01:29:21 +0200] "POST /dids/attachments HTTP/1.1" 201 17 "-" "python-requests/2.3.0 CPython/2.6.6 Linux/2.6.32-358.23.2.el6.x86_64" "-" But when I switch the clients to go against HAProxy (loadbalancer.domain.com:443), the error.log of nginx shows lines like these: 2014/08/23 01:26:01 [error] 1705#0: *21231 open() "/usr/share/nginx/html/dids/attachments" failed (2: No such file or directory), client: 128.142.XXX.XX1, server: localhost, request: "POST /dids/attachments HTTP/1.1", host: "loadbalancer.domain.com" 2014/08/23 01:26:02 [error] 1705#0: *21232 open() "/usr/share/nginx/html/replicas/list" failed (2: No such file or directory), client: 128.142.XXX.XX1, server: localhost, request: "POST /replicas/list HTTP/1.1", host: "loadbalancer.domain.com" 2014/08/23 01:26:02 [error] 1705#0: *21233 open() "/usr/share/nginx/html/dids/attachments" failed (2: No such file or directory), client: 128.142.XXX.XX1, server: localhost, request: "POST /dids/attachments HTTP/1.1", host: "loadbalancer.domain.com" 2014/08/23 01:26:02 [error] 1705#0: *21234 open() "/usr/share/nginx/html/replicas/list" failed (2: No such file or directory), client: 128.142.XXX.XX1, server: localhost, request: "POST /replicas/list HTTP/1.1", host: "loadbalancer.domain.com" 2014/08/23 01:26:02 [error] 1705#0: *21235 open() "/usr/share/nginx/html/dids/attachments" failed (2: No such file or directory), client: 128.142.XXX.XXX, server: localhost, request: "POST /dids/attachments HTTP/1.1", host: "loadbalancer" 2014/08/23 01:26:02 [error] 1705#0: *21238 open() "/usr/share/nginx/html/replicas/list" failed (2: No such file or directory), client: 128.142.XXX.XXX, server: localhost, request: "POST /replicas/list HTTP/1.1", host: "loadbalancer.domain.com" 2014/08/23 01:26:02 [error] 1705#0: *21239 open() "/usr/share/nginx/html/dids/attachments" failed (2: No such file or directory), client: 128.142.XXX.XXX, server: localhost, request: "POST /dids/attachments HTTP/1.1", host: "loadbalancer.domain.com" 2014/08/23 01:26:02 [error] 1705#0: *21242 open() "/usr/share/nginx/html/replicas/list" failed (2: No such file or directory), client: 128.142.XXX.XXX, server: localhost, request: "POST /replicas/list HTTP/1.1", host: "loadbalancer.domain.com" 2014/08/23 01:26:02 [error] 1705#0: *21244 open() "/usr/share/nginx/html/dids/attachments" failed (2: No such file or directory), client: 128.142.XXX.XXX, server: localhost, request: "POST /dids/attachments HTTP/1.1", host: "loadbalancer.domain.com" As you can see, that request looks the same, only the client IP changed, from the client's host to the one from loadbalancer.domain.com. But due to what ever reasons ngxin seems to assume that it is a static file to be served which eventually results in the file not found message. I searched the web for multiple hours already, but without much luck so far. Any help is very much appreciated. Cheers, Ralph

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