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• Calculating rotation and translation matrices between two odometry positions for monocular linear triangulation

  - by user1298891

  Recently I've been trying to implement a system to identify and triangulate the 3D position of an object in a robotic system. The general outline of the process goes as follows: Identify the object using SURF matching, from a set of "training" images to the actual live feed from the camera Move/rotate the robot a certain amount Identify the object using SURF again in this new view Now I have: a set of corresponding 2D points (same object from the two different views), two odometry locations (position + orientation), and camera intrinsics (focal length, principal point, etc.) since it's been calibrated beforehand, so I should be able to create the 2 projection matrices and triangulate using a basic linear triangulation method as in Hartley & Zissermann's book Multiple View Geometry, pg. 312. Solve the AX = 0 equation for each of the corresponding 2D points, then take the average In practice, the triangulation only works when there's almost no change in rotation; if the robot even rotates a slight bit while moving (due to e.g. wheel slippage) then the estimate is way off. This also applies for simulation. Since I can only post two hyperlinks, here's a link to a page with images from the simulation (on the map, the red square is simulated robot position and orientation, and the yellow square is estimated position of the object using linear triangulation.) So you can see that the estimate is thrown way off even by a little rotation, as in Position 2 on that page (that was 15 degrees; if I rotate it any more then the estimate is completely off the map), even in a simulated environment where a perfect calibration matrix is known. In a real environment when I actually move around with the robot, it's worse. There aren't any problems with obtaining point correspondences, nor with actually solving the AX = 0 equation once I compute the A matrix, so I figure it probably has to do with how I'm setting up the two camera projection matrices, specifically how I'm calculating the translation and rotation matrices from the position/orientation info I have relative to the world frame. How I'm doing that right now is: Rotation matrix is composed by creating a 1x3 matrix [0, (change in orientation angle), 0] and then converting that to a 3x3 one using OpenCV's Rodrigues function Translation matrix is composed by rotating the two points (start angle) degrees and then subtracting the final position from the initial position, in order to get the robot's straight and lateral movement relative to its starting orientation Which results in the first projection matrix being K [I | 0] and the second being K [R | T], with R and T calculated as described above. Is there anything I'm doing really wrong here? Or could it possibly be some other problem? Any help would be greatly appreciated.

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• Please help with iPhone Memory & Images, memory usage crashing app

  - by Andrew Gray

  I have an issue with memory usage relating to images and I've searched the docs and watched the videos from cs193p and the iphone dev site on memory mgmt and performance. I've searched online and posted on forums, but I still can't figure it out. The app uses core data and simply lets the user associate text with a picture and stores the list of items in a table view that lets you add and delete items. Clicking on a row shows the image and related text. that's it. Everything runs fine on the simulator and on the device as well. I ran the analyzer and it looked good, so i then starting looking at performance. I ran leaks and everything looked good. My issue is when running Object Allocations as every time i select a row and the view with the image is shown, the live bytes jumps up a few MB and never goes down and my app eventually crashes due to memory usage. Sorting the live bytes column, i see 2 2.72MB mallocs (5.45Mb total), 14 CFDatas (3.58MB total), 1 2.74MB malloc and everything else is real small. the problem is all the related info in instruments is really technical and all the problem solving examples i've seen are just missing a release and nothing complicated. Instruments shows Core Data as the responsible library for all but one (libsqlite3.dylib the other) with [NSSQLCore _prepareResultsFromResultSet:usingFetchPlan:withMatchingRows:] as the caller for all but one (fetchResultSetReallocCurrentRow the other) and im just not sure how to track down what the problem is. i've looked at the stack traces and opened the last instance of my code and found 2 culprits (below). I havent been able to get any responses at all on this, so if anyone has any tips or pointers, I'd really appreciate it!!!! //this is from view controller that shows the title and image - (void)viewWillAppear:(BOOL)animated { [super viewWillAppear:animated]; self.title = item.title; self.itemTitleTextField.text = item.title; if ([item.notes length] == 0) { self.itemNotesTextView.hidden = YES; } else { self.itemNotesTextView.text = item.notes; } //this is the line instruments points to UIImage *image = item.photo.image; itemPhoto.image = image; } - (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath { if (editingStyle == UITableViewCellEditingStyleDelete) { // Delete the managed object for the given index path NSManagedObjectContext *context = [fetchedResultsController managedObjectContext]; [context deleteObject:[fetchedResultsController objectAtIndexPath:indexPath]]; // Save the context. NSError *error = nil; if (![context save:&error]) //this is the line instruments points to { NSLog(@"Unresolved error %@, %@", error, [error userInfo]); exit(-1); } } }

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• IP address numbers in MySQL subquery

  - by Iain Collins

  I have a problem with a subquery involving IPV4 addresses stored in MySQL (MySQL 5.0). The IP addresses are stored in two tables, both in network number format - e.g. the format output by MySQL's INET_ATON(). The first table ('events') contains lots of rows with IP addresses associated with them, the second table ('network_providers') contains a list of provider information for given netblocks. events table (~4,000,000 rows): event_id (int) event_name (varchar) ip_address (unsigned 4 byte int) network_providers table (~60,000 rows): ip_start (unsigned 4 byte int) ip_end (unsigned 4 byte int) provider_name (varchar) Simplified for the purposes of the problem I'm having, the goal is to create an export along the lines of: event_id,event_name,ip_address,provider_name If do a query along the lines of either of the following, I get the result I expect: SELECT provider_name FROM network_providers WHERE INET_ATON('192.168.0.1') >= network_providers.ip_start ORDER BY network_providers.ip_start DESC LIMIT 1 SELECT provider_name FROM network_providers WHERE 3232235521 >= network_providers.ip_start ORDER BY network_providers.ip_start DESC LIMIT 1 That is to say, it returns the correct provider_name for whatever IP I look up (of course I'm not really using 192.168.0.1 in my queries). However, when performing this same query as a subquery, in the following manner, it doesn't yield the result I would expect: SELECT event.id, event.event_name, (SELECT provider_name FROM network_providers WHERE event.ip_address >= network_providers.ip_start ORDER BY network_providers.ip_start DESC LIMIT 1) as provider FROM events Instead the a different (incorrect) value for network_provider is returned - over 90% (but curiously not all) values returned in the provider column contain the wrong provider information for that IP. Using event.ip_address in a subquery just to echo out the value confirms it contains the value I'd expect and that the subquery can parse it. Replacing event.ip_address with an actual network number also works, just using it dynamically in the subquery in this manner that doesn't work for me. I suspect the problem is there is something fundamental and important about subqueries in MySQL that I don't get. I've worked with IP addresses like this in MySQL quite a bit before, but haven't previously done lookups for them using a subquery. The question: I'd really appreciate an example of how I could get the output I want, and if someone here knows, some enlightenment as to why what I'm doing doesn't work so I can avoid making this mistake again. Notes: The actual real-world usage I'm trying to do is considerably more complicated (involving joining two or three tables). This is a simplified version, to avoid overly complicating the question. Additionally, I know I'm not using a between on ip_start & ip_end - that's intentional (the DB's can be out of date, and such cases the owner in the DB is almost always in the next specified range and 'best guess' is fine in this context) however I'm grateful for any suggestions for improvement that relate to the question. Efficiency is always nice, but in this case absolutely not essential - any help appreciated.

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• EXC_BAD_ACCESS when scrolling table after json data is imported

  - by Michael Robinson

  Hello, I'm having a bear of a time trying to figure out why I'm getting a EXC_BAD ACCESS error. The console is giving me this eror: " -[CFArray objectAtIndex:]: message sent to deallocated instance 0x3b14110", I Can't figure it out...Thanks in advance. // Customize the number of rows in the table view. - (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section { return [rows count]; } // Customize the appearance of table view cells. - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease]; } // Configure the cell. NSDictionary *dict = [rows objectAtIndex: indexPath.row]; cell.textLabel.text = [dict objectForKey:@"name"]; cell.detailTextLabel.text = [dict objectForKey:@"age"]; return cell; } // Implement viewDidLoad to do additional setup after loading the view, typically from a nib. - (void)viewDidLoad { [super viewDidLoad]; self.navigationController.navigationBar.tintColor = [UIColor colorWithRed:0.0/255.0 green:207.0/255.0 blue:255.0/255.0 alpha:1.0]; self.title = NSLocalizedString(@"How Big Now", @"How Big Now"); NSURL *url = [NSURL URLWithString:@"http://10.0.1.8/~imac/iphone/jsontest.php"]; NSString *jsonreturn = [[NSString alloc] initWithContentsOfURL:url]; // NSLog(jsonreturn); // Look at the console and you can see what the restults are NSData *jsonData = [jsonreturn dataUsingEncoding:NSUTF32BigEndianStringEncoding]; NSError *error = nil; // In "real" code you should surround this with try and catch NSDictionary * dict = [[CJSONDeserializer deserializer] deserializeAsDictionary:jsonData error:&error]; if (dict) { rows = [dict objectForKey:@"member"]; } NSLog(@"Array: %@",rows); [jsonreturn release]; } - (void)didReceiveMemoryWarning { // Releases the view if it doesn't have a superview. [super didReceiveMemoryWarning]; // Release any cached data, images, etc that aren't in use. } - (void)viewDidUnload { // Release any retained subviews of the main view. // e.g. self.myOutlet = nil; } - (void)dealloc { [super dealloc]; } @end

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• ASP.NET MVC 2 AJAX dilemma: Lose Models concept or create unmanageable JavaScript

  - by Slightly Frustrated

  Hi, Ok, let's assume we are working with ASP.NET MVC 2 (latest and greatest preview) and we want to create AJAX user interface with jQuery. So what are our real options here? Option 1 - Pass Json from the Controller to the view, and then the view submits Json back to the controller. This means (in the order given): User opens some View (let's say - /Invoices/January) which has to visualize a list of data (e.g. <IEnumerable<X.Y.Z.Models.Invoice>>) Controller retrieves the Model from the repository (assuming we are using repository pattern). Controller creates a new instance of a class which we will serialize to Json. The reasaon we do this, is because the model may not be serializable (circular reference ftl) Controller populates the soon-to-be-serialized class with data Controller serializes the class to Json and passes it the view. User does some change and submits the 'form' The View submits back Json to the controller The Controller now must 'manually' validate the input, because the Json passed does not bind to a Model See, if our View is communicating to the controller via Json, we lose the Model validation, which IMHO is incredible disadvantage. In this case, forget about data annotations and stuff. Option 2 - Ok, the alternative of the first approach is to pass the Models to the Views, which is the default behavior in the template when you start a new project. We pass a strong typed model to the view The view renders the appropriate html and javascript, sticking to the model property names. This is important! The user submits the form. If we stick to the model names, when we .serialize() the form and submit it to the controller it will map to a model. There is no Json mapping. The submitted form directly binds to a strongly typed model, hence, we can use the model validation. E.g. we keep the business logic where it should be. Problem with this approach is, if we refactor some of the Models (change property names, types, etc), the javascript we wrote would become invalid. We will have to manually refactor the scripting and hope we don't miss something. There is no way you can test it either. Ok, the question is - how to write an AJAX front end, which keeps the business logic validation in the model (e.g. controller passes and receives a Model type), but in the same time doesn't screw up the javascript and html when we refactor the model?

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• How do I create a Spring 3 + Tiles 2 webapp using REST-ful URLs?

  - by Ichiro Furusato

  I'm having a heck of a time resolving URLs with Spring 3.0 MVC. I'm just building a HelloWorld to try out how to build a RESTful webapp in Spring, nothing theoretically complicated. All of the examples I've been able to find are based on configurations that pay attention to file extensions ("*.htm" or "*.do"), include an artificial directory name prefix ("/foo") or even prefix paths with a dot (ugly), all approaches that use some artificial regex pattern as a signal to the resolver. For a REST approach I want to avoid all that muck and use only the natural URL patterns of my application. I would assume (perhaps incorrectly) that in web.xml I'd set a url-pattern of "/*" and pass everything to the DispatcherServlet for resolution, then just rely on URL patterns in my controller. I can't reliably get my resolver(s) to catch the URL patterns, and in all my trials this results in a resource not found error, a stack overflow (loop), or some kind of opaque Spring 3 ServletException stack trace — one of my ongoing frustrations with Spring generally is that the error messages are not often very helpful. I want to work with a Tiles 2 resolver. I've located my *.jsp files in WEB-INF/views/ and have a single line index.jsp file at the application root redirecting to the index file set by my layout.xml (the Tiles 2 Configurer). I do all the normal Spring 3 high-level configuration: <mvc:annotation-driven /> <mvc:view-controller path="/" view-name="index"/> <context:component-scan base-package="com.acme.web.controller" /> ...followed by all sorts of combinations and configurations of UrlBasedViewResolver, InternalResourceViewResolver, UrlFilenameViewController, etc. with all manner of variantions in my Tiles 2 configuration file. Then in my controller I've trying to pick up my URL patterns. Problem is, I can't reliably even get the resolver(s) to catch the patterns to send to my controller. This has now stretched to multiple days with no real progress on something I thought would be very simple to implement. I'm perhaps trying to do too much at once, though I would think this should be a simple (almost a default) configuration. I'm just trying to create a simple HelloWorld-type application, I wouldn't expect this is rocket science. Rather than me post my own configurations (which have ranged all over the map), does anyone know of an online example that: shows a simple Spring 3 MVC + Tiles 2 web application that uses REST-ful URLs (i.e., avoiding forced URL patterns such as file extensions, added directory names or dots) and relies solely on Spring 3 code/annotations (i.e., nothing outside of Spring MVC itself) to accomplish this? Is there an easy way to do this? Thanks very much for any help.

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• how get fully result from Asynchronism communication?

  - by rima

  Hi all refer to these post : here1 and here2 at last I solve my problem by build a asynchronous solution,and it work well!!! but there is a problem that i face with it,now my code is like this: class MyProcessStarter { private Process process; private StreamWriter myStreamWriter; private static StringBuilder shellOutput = null; public String GetShellOutput { get { return shellOutput.ToString(); }} public MyProcessStarter(){ shellOutput = new StringBuilder(""); process = new Process(); process.StartInfo.FileName = "sqlplus"; process.StartInfo.UseShellExecute = false; process.StartInfo.CreateNoWindow = true; process.OutputDataReceived += new DataReceivedEventHandler(ShellOutputHandler); process.StartInfo.RedirectStandardInput = true; process.StartInfo.RedirectStandardOutput = true; //process.StartInfo.RedirectStandardError = true; process.Start(); myStreamWriter = process.StandardInput; process.BeginOutputReadLine(); } private static void ShellOutputHandler(object sendingProcess,DataReceivedEventArgs outLine) { if (!String.IsNullOrEmpty(outLine.Data)) shellOutput.Append(Environment.NewLine + outLine.Data); } public void closeConnection() { myStreamWriter.Close(); process.WaitForExit(); process.Close(); } public void RunCommand(string arguments) { myStreamWriter.WriteLine(arguments); myStreamWriter.Flush(); process.WaitForExit(100); Console.WriteLine(shellOutput); Console.WriteLine("============="+Environment.NewLine); process.WaitForExit(2000); Console.WriteLine(shellOutput); } } and my input is like this: myProcesStarter.RunCommand("myusername/mypassword"); Console.writeline(myProcesStarter.GetShellOutput); but take a look at my out put: SQL*Plus: Release 11.1.0.6.0 - Production on Thu May 20 11:57:38 2010 Copyright (c) 1982, 2007, Oracle. All rights reserved. ============= SQL*Plus: Release 11.1.0.6.0 - Production on Thu May 20 11:57:38 2010 Copyright (c) 1982, 2007, Oracle. All rights reserved. Enter user-name: Connected to: Oracle Database 11g Enterprise Edition Release 11.1.0.6.0 - Production With the Partitioning, OLAP, Data Mining and Real Application Testing options as u see the output for run a function is not same in different time!So now would you do me a faver and help me that how I can wait until all the output done in other mean how I can customize my process to wait until output finishing ?? because I want to write a sqlcompiler so I need the exact output of shell. plz help me soon.thanxxxxxxxxxxxx :X

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• Why do some questions get closed for no reason? [closed]

  - by IVlad

  Recently there was a question asking about generating all subsets of a set using a stack and a queue, which was closed (and now deleted it seems) as not a real question for no good reason, since it didn't fit into any of these conditions: It's difficult to tell what is being asked here. No, it was clear what was being asked. This question is ambiguous, vague, incomplete, or rhetorical and cannot be reasonably answered in its current form. Not ambiguous, not vague, not incomplete, definitely not rhetorical and could easily be answered if one knew the solution. Now, the exact same thing has happened with this question: http://stackoverflow.com/questions/2791982/a-shortest-path-problem-with-superheroes-and-intergalactic-journeys/2793746#2793746 I am interested in hearing a logical argument for why that question is either ambiguous, vague, incomplete, rhetorical or cannot reasonably be answered in its current form. It seems that (the same bunch of) people like to close questions that they think are homework questions, especially when they think people want to be served the solution on a platter, which is also not the case: Any suggestions or ideas of how this problem might be solved would be most welcomed. Most of the time the people asking these questions are very reasonable and appreciate even the most vague idea, yet their question is closed. Let's go further and assume that it IS a homework problem. So what? When I registered here I didn't see any rule that said not to post homework problems, nor do I see such a rule now. What is wrong with posting homework problems that makes people hunt them down with a passion to close them without even reading the entire question body? This site is full of questions asked by people who get paid to know the things they are asking, yet their questions are considered fine. How is solving someone's homework problem worse? In some places (like where I live), computer science is a mandatory high school subject, and not everyone is interested in it. How is helping at least those people worse than doing someone's JOB? Not answering homework questions is fine and it's everyone's choice, but I consider closing them to be an act of power abuse, selfishness, and an insult to the fellow community members who are also interested in a solution or want feedback on their proposed solution. So my questions are: - Why do questions like the above get closed for reasons that do not apply? Why do you close them? Why don't you? - Why doesn't a vote to reopen a question reopen it automatically? Needing 5 votes for a reopen takes too long, and it's not fair because one reopen vote basically cancels out a close vote, making it 4 close votes (or 5 to 1, which is the same as only 4 people wanting to close the question), which isn't enough to close the question. I think a question should only be closed when CloseVotes - ReopenVotes >= 5. I'm hoping this will stay up, but I realize it probably won't. In either case, I think this is worth saying and discussing, since it IS community-related.

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• How to read XML parent node tag value

  - by kaibuki

  HI Guys, I have a java code to read XML nodes, I want to add in the addition and want to read the parent node value also. my XML file sample is below: <breakfast_menu><food id=1><name> Belgian Waffles </name><price> $5.95 </price><description> two of our famous Belgian Waffles with plenty of real maple syrup </description><calories> 650 </calories></food><food id=2><name>Strawberry Belgian waffles</name><price>$7.95</price><description>light Belgian waffles covered with strawberries and whipped cream</description><calories>900</calories></food></breakfast_menu> and my code for parsing xml is : public static String getProductItem(String pid, String item) { try { url = new URL(""); urlConnection = url.openConnection(); } catch (MalformedURLException e) { e.printStackTrace(); } catch (IOException e) { } try { dBuilder = dbFactory.newDocumentBuilder(); } catch (ParserConfigurationException e) { } try { doc = dBuilder.parse(urlConnection.getInputStream()); } catch (SAXException e) { } catch (IOException e) { } doc.getDocumentElement().normalize(); NodeList nList = doc.getElementsByTagName("food"); for (int temp = 0; temp < nList.getLength(); temp++) { Node nNode = nList.item(temp); if (nNode.getNodeType() == Node.ELEMENT_NODE) { Element eElement = (Element) nNode; data = getTagValue(item, eElement); } } doc = null; dBuilder = null; return data; } private static String getTagValue(String sTag, Element eElement) { NodeList nlList = eElement.getElementsByTagName(sTag).item(0) .getChildNodes(); Node nValue = (Node) nlList.item(0); return nValue.getNodeValue(); } What I want to do is to read the "id" value of food, so if if I am searching for a food, it only checks those food nodes, whose id matched the food node id. thanks in advance. cheers.. kai

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• How to do the processing and keep GUI refreshed using databinding?

  - by macias

  History of the problem This is continuation of my previous question How to start a thread to keep GUI refreshed? but since Jon shed new light on the problem, I would have to completely rewrite original question, which would make that topic unreadable. So, new, very specific question. The problem Two pieces: CPU hungry heavy-weight processing as a library (back-end) WPF GUI with databinding which serves as monitor for the processing (front-end) Current situation -- library sends so many notifications about data changes that despite it works within its own thread it completely jams WPF data binding mechanism, and in result not only monitoring the data does not work (it is not refreshed) but entire GUI is frozen while processing the data. The aim -- well-designed, polished way to keep GUI up to date -- I am not saying it should display the data immediately (it can skip some changes even), but it cannot freeze while doing computation. Example This is simplified example, but it shows the problem. XAML part: <StackPanel Orientation="Vertical"> <Button Click="Button_Click">Start</Button> <TextBlock Text="{Binding Path=Counter}"/> </StackPanel> C# part (please NOTE this is one piece code, but there are two sections of it): public partial class MainWindow : Window,INotifyPropertyChanged { // GUI part public MainWindow() { InitializeComponent(); DataContext = this; } private void Button_Click(object sender, RoutedEventArgs e) { var thread = new Thread(doProcessing); thread.IsBackground = true; thread.Start(); } // this is non-GUI part -- do not mess with GUI here public event PropertyChangedEventHandler PropertyChanged; public void OnPropertyChanged(string property_name) { if (PropertyChanged != null) PropertyChanged(this, new PropertyChangedEventArgs(property_name)); } long counter; public long Counter { get { return counter; } set { if (counter != value) { counter = value; OnPropertyChanged("Counter"); } } } void doProcessing() { var tmp = 10000.0; for (Counter = 0; Counter < 10000000; ++Counter) { if (Counter % 2 == 0) tmp = Math.Sqrt(tmp); else tmp = Math.Pow(tmp, 2.0); } } } Known workarounds (Please do not repost them as answers) Those two first are based on Jon ideas: pass GUI dispatcher to library and use it for sending notifications -- why it is ugly? because it could be no GUI at all give up with data binding COMPLETELY (one widget with databinding is enough for jamming), and instead check from time to time data and update the GUI manually -- well, I didn't learn WPF just to give up with it now ;-) and this is mine, it is ugly, but simplicity of it kills -- before sending notification freeze a thread -- Thread.Sleep(1) -- to let the potential receiver "breathe" -- it works, it is minimalistic, it is ugly though, and it ALWAYS slows down computation even if no GUI is there So... I am all ears for real solutions, not some tricks.

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• How could I send live video stream to remote server from my phone !!!

  - by poc

  Hello , I have a problem about streaming my video to server in real-time from my phone. that is , let my phone be a IP Camera , and server can watch the live video from my phone I have googled many many solutions, but there is no one can solve my problem. I use MediaRecorder to record . it can save video file in the SD card correctly. then , I refered this page and used some method as followings skt = new Socket(InetAddress.getByName(hostname),port); pfd =ParcelFileDescriptor.fromSocket(skt); mediaRecorder.setOutputFile(pfd.getFileDescriptor()); now it seems I can send the video stream while recording however, I wrote a receiver-side program to receive the video stream from Android , but it doesn't work . is there any error? I can receive file , but I can not open the video file . I guess the problem may caused by file format ? there are outline of my code. in android side Socket skt = new Socket(hostIP,port); ParcelFileDescriptor pfd =ParcelFileDescriptor.fromSocket(skt); .... .... mediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC); mediaRecorder.setVideoSource(MediaRecorder.VideoSource.DEFAULT); mediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4); mediaRecorder.setOutputFile(pfd.getFileDescriptor()); ..... mediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.DEFAULT); mediaRecorder.setVideoEncoder(MediaRecorder.VideoEncoder.MPEG_4_SP); ..... mediaRecorder.start(); in receiver side (my ACER notebook) // anyway , I don't think the file extentions will do any effect File video = new File (strDate+".3gpp"); FileOutputStream fos; try { fos = new FileOutputStream(video); byte[] data = new byte[1024]; int count =-1; while( (count = fin.read(data,0,1024) ) !=-1) { fos.write(data,0,count); fos.flush(); } fos.close(); fin.close(); I confused a long time.... thanks in advance

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• When I really need to use [NSThread sleepForTimeInterval:1];

  - by Timbo

  Hi there, I have a program that needs to use sleep. Like really needs to. In lieu of spending ages explaining why, suffice to say that it needs it. Now I'm told to split off my code into a separate thread if it requires sleep so I don't lose interface responsiveness, so I've started learning how to use NSThread. I've created a brand new program that is conceptual so to solve the issue for this example will help me in my real program. Short story is I have a class, it has instance variables and I need a loop with a sleep to be depended on the value of that instance variable. Here's what I've put together anyway, your help is very much appreciated :) Cheers Tim /// Start Test1ViewController.h /// #import <UIKit/UIKit.h> @interface Test1ViewController : UIViewController { UILabel* label; } @property (assign) IBOutlet UILabel *label; @end /// End Test1ViewController.h /// /// Start Test1ViewController.m /// #import "Test1ViewController.h" #import "MyClass.h" @implementation Test1ViewController @synthesize label; - (void)viewDidAppear:(BOOL)animated { [super viewDidAppear:animated]; label.text = @"1"; [NSThread detachNewThreadSelector:@selector(backgroundProcess) toTarget:self withObject:nil]; } - (void)backgroundProcess { NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; // Create an instance of a class that will eventually store a whole load of variables MyClass *aMyClassInstance = [MyClass new]; [aMyClassInstance createMyClassInstance:(@"Timbo")]; while (aMyClassInstance.myVariable--) { NSLog(@"blah = %i",aMyClassInstance.myVariable); label.text = [NSString stringWithFormat:@"blah = %d", aMyClassInstance.myVariable]; //how do I pass the new value out to the updateLabel method, or reference aMyClassInstance.myVariable? [self performSelectorOnMainThread:@selector(updateLabel) withObject:nil waitUntilDone:NO]; //the sleeping of the thread is absolutely mandatory and must be worked around. The whole point of using NSThread is so I can have sleeps [NSThread sleepForTimeInterval:1]; } [pool release]; } - (void)updateLabel {label.text = [NSString stringWithFormat:@"blah = %d", aMyClassInstance.myVariable]; // be nice if i could } - (void)didReceiveMemoryWarning {[super didReceiveMemoryWarning];} - (void)viewDidUnload {} - (void)dealloc {[super dealloc];} @end /// End Test1ViewController.m /// /// Start MyClass.h /// #import <Foundation/Foundation.h> @interface MyClass : NSObject { NSString* name; int myVariable; } @property int myVariable; @property (assign) NSString *name; - (void) createMyClassInstance: (NSString*)withName; - (int) changeVariable: (int)toAmount; @end /// End MyClass.h /// /// Start MyClass.h /// #import "MyClass.h" @implementation MyClass @synthesize name, myVariable; - (void) createMyClassInstance: (NSString*)withName{ name = withName; myVariable = 10; } - (int) changeVariable: (int)toAmount{ myVariable = toAmount; return toAmount; } @end /// End MyClass.h ///

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• user defined Copy ctor, and copy-ctors further down the chain - compiler bug ? programmers brainbug

  - by J.Colmsee

  Hi. i have a little problem, and I am not sure if it's a compiler bug, or stupidity on my side. I have this struct : struct BulletFXData { int time_next_fx_counter; int next_fx_steps; Particle particles[2];//this is the interesting one ParticleManager::ParticleId particle_id[2]; }; The member "Particle particles[2]" has a self-made kind of smart-ptr in it (resource-counted texture-class). this smart-pointer has a default constructor, that initializes to the ptr to 0 (but that is not important) I also have another struct, containing the BulletFXData struct : struct BulletFX { BulletFXData data; BulletFXRenderFunPtr render_fun_ptr; BulletFXUpdateFunPtr update_fun_ptr; BulletFXExplosionFunPtr explode_fun_ptr; BulletFXLifetimeOverFunPtr lifetime_over_fun_ptr; BulletFX( BulletFXData data, BulletFXRenderFunPtr render_fun_ptr, BulletFXUpdateFunPtr update_fun_ptr, BulletFXExplosionFunPtr explode_fun_ptr, BulletFXLifetimeOverFunPtr lifetime_over_fun_ptr) :data(data), render_fun_ptr(render_fun_ptr), update_fun_ptr(update_fun_ptr), explode_fun_ptr(explode_fun_ptr), lifetime_over_fun_ptr(lifetime_over_fun_ptr) { } /* //USER DEFINED copy-ctor. if it's defined things go crazy BulletFX(const BulletFX& rhs) :data(data),//this line of code seems to do a plain memory-copy without calling the right ctors render_fun_ptr(render_fun_ptr), update_fun_ptr(update_fun_ptr), explode_fun_ptr(explode_fun_ptr), lifetime_over_fun_ptr(lifetime_over_fun_ptr) { } */ }; If i use the user-defined copy-ctor my smart-pointer class goes crazy, and it seems that calling the CopyCtor / assignment operator aren't called as they should. So - does this all make sense ? it seems as if my own copy-ctor of struct BulletFX should do exactly what the compiler-generated would, but it seems to forget to call the right constructors down the chain. compiler bug ? me being stupid ? Sorry about the big code, some small example could have illustrated too. but often you guys ask for the real code, so well - here it is :D EDIT : more info : typedef ParticleId unsigned int; Particle has no user defined copyctor, but has a member of type : Particle { .... Resource<Texture> tex_res; ... } Resource is a smart-pointer class, and has all ctor's defined (also asignment operator) and it seems that Resource is copied bitwise. EDIT : henrik solved it... data(data) is stupid of course ! it should of course be rhs.data !!! sorry for huge amount of code, with a very little bug in it !!! (Guess you shouldn't code at 1 in the morning :D )

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• What does these FindBug messages show?

  - by Hans Klock

  Not every description from from http://findbugs.sourceforge.net/bugDescriptions.html is clear to me. Sure, I can study the implementation but if somebody is more experienced then me, some explanation and examples would be great. Do you have some examples for UI_INHERITANCE_UNSAFE_GETRESOURCE when this is getting a problem? In BX_UNBOXED_AND_COERCED_FOR_TERNARY_OPERATOR I don't see the problem either. If one type is "bigger" then the other, for example int and float, then the result is float. If its Integer and Float its the wrapper Float too. That's what I expect. Does the GC_UNRELATED_TYPES really help to find errors? Isn't it the job of the compiler to check, if--taking the given example--Foo can't go into a Collection<String>. Does HE_SIGNATURE_DECLARES_HASHING_OF_UNHASHABLE_CLASS mean something like bla(Foo f){hashtable.put(f);}, where ´Foo´ is not hashable? Does FingBugs "see" the subclasses too? NP_GUARANTEED_DEREF_ON_EXCEPTION_PATH is stronger "wrong" then NP_ALWAYS_NULL_EXCEPTION? Why two error cases and with NP_NULL_ON_SOME_PATH_EXCEPTION even one more? Sounds very similar to me. What is an example of SIO_SUPERFLUOUS_INSTANCEOF? Something like foo(String s){if (s intenceof String) .... This does a null check too, but this is not the test here... NN_NAKED_NOTIFY. I my opinion the description is not clear. A change of the state is not necessary. If I use new Object() to wait and notify on I don't change the object state. Or is state the lock-state? I don't get it. SP_SPIN_ON_FIELD. Can this really happen that a compiler will move this outside from a loop? This doesn't make sense to me because from outside a Thread can always change the values. And if the variable is volatile the JVM can't cache the value. So what's the meaning? That is the difference between STCAL_STATIC_CALENDAR_INSTANCE and STCAL_INVOKE_ON_STATIC_CALENDAR_INSTANCE or STCAL_INVOKE_ON_STATIC_DATE_FORMAT_INSTANCE/STCAL_STATIC_SIMPLE_DATE_FORMAT_INSTANCE? Why is XXXX.class in WL_USING_GETCLASS_RATHER_THAN_CLASS_LITERAL better then getClass()? A getClass() in a superclass called from the subclass will always return the Class object from the subclass which is good I think. What exactly does EQ_UNUSUAL do? It should check that the argument is of the same type of the class itself but it does't? Did you ever had problems with breaks? Is there real value with SF_SWITCH_FALLTHROUGH? Sounds to strong for me. No idea what TQ_EXPLICIT_UNKNOWN_SOURCE_VALUE_REACHES_ALWAYS_SINK and TQ_EXPLICIT_UNKNOWN_SOURCE_VALUE_REACHES_NEVER_SINK could be.

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• In a PHP project, how do you organize and access your helper objects?

  - by Pekka

  How do you organize and manage your helper objects like the database engine, user notification, error handling and so on in a PHP based, object oriented project? Say I have a large PHP CMS. The CMS is organized in various classes. A few examples: the database object user management an API to create/modify/delete items a messaging object to display messages to the end user a context handler that takes you to the right page a navigation bar class that shows buttons a logging object possibly, custom error handling etc. I am dealing with the eternal question, how to best make these objects accessible to each part of the system that needs it. my first apporach, many years ago was to have a $application global that contained initialized instances of these classes. global $application; $application->messageHandler->addMessage("Item successfully inserted"); I then changed over to the Singleton pattern and a factory function: $mh =&factory("messageHandler"); $mh->addMessage("Item successfully inserted"); but I'm not happy with that either. Unit tests and encapsulation become more and more important to me, and in my understanding the logic behind globals/singletons destroys the basic idea of OOP. Then there is of course the possibility of giving each object a number of pointers to the helper objects it needs, probably the very cleanest, resource-saving and testing-friendly way but I have doubts about the maintainability of this in the long run. Most PHP frameworks I have looked into use either the singleton pattern, or functions that access the initialized objects. Both fine approaches, but as I said I'm happy with neither. I would like to broaden my horizon on what is possible here and what others have done. I am looking for examples, additional ideas and pointers towards resources that discuss this from a long-term, real-world perspective. Also, I'm interested to hear about specialized, niche or plain weird approaches to the issue. Bounty I am following the popular vote in awarding the bounty, the answer which is probably also going to give me the most. Thank you for all your answers!

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• Issues accessing an object's array values - returns null or 0s

  - by PhatNinja

  The function below should return an array of objects with this structure: TopicFrequency = { name: "Chemistry", //This is dependent on topic data: [1,2,3,4,5,6,7,8,9,10,11,12] //This would be real data }; so when I do this: myData = this.getChartData("line"); it should return two objects: {name : "Chemistry", data : [1,2,3,4,51,12,0,0, 2,1,41, 31]} {name : "Math", data : [0,0,41,4,51,12,0,0, 2,1,41, 90]} so when I do console.log(myData); it's perfect, returns exactly this. However when I do console.log(myData[0].data) it returns all 0s, not the values. I'm not sure what this issues is known as, and my question is simple what is this problem known as? Here is the full function. Somethings were hardcoded and other variables (notable server and queryContent) removed. Those parts worked fine, it is only when manipulated/retreiving the returned array's values that I run into problems. Note this is async. so not sure if that is also part of the problem. getChartData: function (chartType) { var TopicsFrequencyArray = new Array(); timePairs = this.newIntervalSet("Month"); topicList = new Array("Chemistry", "Math");//Hard coded for now var queryCopy = { //sensitive information }; for (i = 0; i < topicList.length; i++) { var TopicFrequency = { name: null, data: this.newFilledArray(12, 0) }; j = 0; TopicFrequency.name = topicList[i]; while (j < timePairs.length) { queryCopy.filter = TopicFrequency.name; //additional queryCopy parameter changes made here var request = esri.request({ url: server, content: queryCopy, handleAs: "json", load: sucess, error: fail }); j = j + 1; function sucess(response, io) { var topicCountData = 0; query = esri.urlToObject(io.url); var dateString = query.query.fromDate.replace("%", " "); dateString = dateString.replace(/-/g, "/"); dateString = dateString.split("."); date = new Date(dateString[0]); dojo.forEach(response.features, function (feature) { if (feature.properties.count > 0) { topicCountData = feature.properties.count; } TopicFrequency.data[date.getMonth()] = topicCountData; }); } function fail(error) { j = j + 1; alert("There was an unspecified error with this request"); console.log(error); } } TopicsFrequencyArray.push(TopicFrequency); } },

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• Alternative to Page_Load in ASP.NET (and a good WTF story)

  - by Jason

  Woo, I have a doozy of a problem (might even be one for the Daily WTF) and I'm hoping there's a solution. (My apologies for the long post...) I have been working on a website that I inherited about a month ago. One of the parts I have been working on is fixing one of the controls (essentially a dynamic header bar) so that it displays additional information as requested by my users. As part of doing this project, I created a Site.master file so that I wouldn't have to recode the header bar into every single page. When I first started doing this, it seemingly worked very well. All the pages I had developed looked great and the bar updated as it should displaying the information as it should. Well, when I dropped the Site.master (and this control) into older site pages (ones I did not specifically develop) I noticed that it looked bad on some of them, but not all of them. When I say it looked bad, basically, the control would left-align itself to the page rather than center as it should. I spent a couple hours debugging to no avail - CSS looked correct, the HTML appeared to be okay, I didn't see anything in the Javascript (although, I did miss something as I'll point out in a second), and even the old code looked correct (to the best that it could - it's not very well written). Another coworker took a look at the site and couldn't find anything at first, either. It wasn't until I just thought to look at the rendered source code of the page (I had been working in the developer view up to this point in IE8) that it became clear what was wrong. The original developer performs searches on many of the pages. To accomplish this, he queries the database for ALL the data and then loads them into Javascript arrays within the page so he can get access to them. This in itself is a huge problem because we're talking about thousands of items, and it obviously isn't scalable (and, yes, the site is slow). However, it finally clicked what was screwing up the Site.master - when he loads the data into the Javascript arrays, he writes out the data to the HTML upon Page_Load using numerous Response.Write(string) calls. The WTF (and what was messing me up) is that he inserts the Javascript before the DOCTYPE causing IE to go into quirks mode! So, because I need to at least get this release out (I'll fix the real problem later), I was wondering: is there a way I can force this Javascript to be inserted elsewhere into the HTML—after the DOCTYPE at the very least? Right now, all the Response.Write() calls are being done in the Page_Load method. I just need them to be inserted later.

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• R: Plotting a graph with different colors of points based on advanced criteria

  - by balconydoor

  What I would like to do is a plot (using ggplot), where the x axis represent years which have a different colour for the last three years in the plot than the rest. The last three years should also meet a certain criteria and based on this the last three years can either be red or green. The criteria is that the mean of the last three years should be less (making it green) or more (making it red) than the 66%-percentile of the remaining years. So far I have made two different functions calculating the last three year mean: LYM3 <- function (x) { LYM3 <- tail(x,3) mean(LYM3$Data,na.rm=T) } And the 66%-percentile for the remaining: perc66 <- function(x) { percentile <- head(x,-3) quantile(percentile$Data, .66, names=F,na.rm=T) } Here are two sets of data that can be used in the calculations (plots), the first which is an example from my real data where LYM3(df1) < perc66(df1) and the second is just made up data where LYM3 perc66. df1<- data.frame(Year=c(1979:2010), Data=c(347261.87, 145071.29, 110181.93, 183016.71, 210995.67, 205207.33, 103291.78, 247182.10, 152894.45, 170771.50, 206534.55, 287770.86, 223832.43, 297542.86, 267343.54, 475485.47, 224575.08, 147607.81, 171732.38, 126818.10, 165801.08, 136921.58, 136947.63, 83428.05, 144295.87, 68566.23, 59943.05, 49909.08, 52149.11, 117627.75, 132127.79, 130463.80)) df2 <- data.frame(Year=c(1979:2010), Data=c(sample(50,29,replace=T),75,75,75)) Here’s my code for my plot so far: plot <- ggplot(df1, aes(x=Year, y=Data)) + theme_bw() + geom_point(size=3, aes(colour=ifelse(df1$Year<2008, "black",ifelse(LYM3(df1) < perc66(df1),"green","red")))) + geom_line() + scale_x_continuous(breaks=c(1980,1985,1990,1995,2000,2005,2010), limits=c(1978,2011)) plot As you notice it doesn’t really do what I want it to do. The only thing it does seem to do is that it turns the years before 2008 into one level and those after into another one and base the point colour off these two levels. Since I don’t want this year to be stationary either, I made another tiny function: fun3 <- function(x) { df <- subset(x, Year==(max(Year)-2)) df$Year } So the previous code would have the same effect as: geom_point(size=3, aes(colour=ifelse(df1$Year<fun3(df1), "black","red"))) But it still does not care about my colours. Why does it make the years into levels? And how come an ifelse function doesn’t work within another one in this case? How would it be possible to the arguments to do what I like? I realise this might be a bit messy, asking for a lot at the same time, but I hope my description is pretty clear. It would be helpful if someone could at least point me in the right direction. I tried to put the code for the plot into a function as well so I wouldn’t have to change the data frame at all functions within the plot, but I can’t get it to work. Thank you!

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• Hibernate3: Self-Referencing Objects

  - by monojohnny

  Need some help on understanding how to do this; I'm going to be running recursive 'find' on a file system and I want to keep the information in a single DB table - with a self-referencing hierarchial structure: This is my DB Table structure I want to populate. DirObject Table: id int NOT NULL, name varchar(255) NOT NULL, parentid int NOT NULL); Here is the proposed Java Class I want to map (Fields only shown): public DirObject { int id; String name; DirObject parent; ... For the 'root' directory was going to use parentid=0; real ids will start at 1, and ideally I want hibernate to autogenerate the ids. Can somebody provide a suggested mapping file for this please; as a secondary question I thought about doing the Java Class like this instead: public DirObject { int id; String name; List<DirObject> subdirs; Could I use the same data model for either of these two methods ? (With a different mapping file of course). --- UPDATE: so I tried the mapping file suggested below (thanks!), repeated here for reference: <hibernate-mapping> <class name="my.proj.DirObject" table="category"> ... <set name="subDirs" lazy="true" inverse="true"> <key column="parentId"/> <one-to-many class="my.proj.DirObject"/> </set> <many-to-one name="parent" class="my.proj.DirObject" column="parentId" cascade="all" /> </class> ...and altered my Java class to have BOTH 'parentid' and 'getSubDirs' [returning a 'HashSet']. This appears to work - thanks, but this is the test code I used to drive this - I think I'm not doing something right here, because I thought Hibernate would take care of saving the subordinate objects in the Set without me having to do this explicitly ? DirObject dirobject=new DirObject(); dirobject.setName("/files"); dirobject.setParent(dirobject); DirObject d1, d2; d1=new DirObject(); d1.setName("subdir1"); d1.setParent(dirobject); d2=new DirObject(); d2.setName("subdir2"); d2.setParent(dirobject); HashSet<DirObject> subdirs=new HashSet<DirObject>(); subdirs.add(d1); subdirs.add(d2); dirobject.setSubdirs(subdirs); session.save(dirobject); session.save(d1); session.save(d2);

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• Turning Floats into Their Closest (UTF-8 Character) Fraction.

  - by Mark Tomlin

  I want to take any real number, and return the closest number, with the closest fraction as available in the UTF-8 character set, appropriate. 0/4 = 0.00 = # < .125 1/4 = 0.25 = ¼ # > .125 & < .375 2/4 = 0.50 = ½ # > .375 & < .625 3/4 = 0.75 = ¾ # > .625 & < .875 4/4 = 1.00 = # > .875 I made this function to do that task: function displayFraction($realNumber) { if (!is_float($realNumber)) { return $realNumber; } list($number, $decimal) = explode('.', $realNumber); $decimal = '.' . $decimal; switch($decimal) { case $decimal < 0.125: return $number; case $decimal > 0.125 && $decimal < 0.375: return $number . '¼'; # 188 ¼ &#188; case $decimal > 0.375 && $decimal < 0.625: return $number . '½'; # 189 ½ &#189; case $decimal > 0.625 && $decimal < 0.875: return $number . '¾'; # 190 ¾ &#190; case $decimal < 0.875: return ++$number; } } What are the better / diffrent way to do this? echo displayFraction(3.1) . PHP_EOL; # Outputs: 3 echo displayFraction(3.141593) . PHP_EOL; # Outputs: 3¼ echo displayFraction(3.267432) . PHP_EOL; # Outputs: 3¼ echo displayFraction(3.38) . PHP_EOL; # Outputs: 3½ Expand my mind!

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• Java app makes screen display unresponsive after 10 minutes of user idle time

  - by Ross

  I've written a Java app that allows users to script mouse/keyboard input (JMacro, link not important, only for the curious). I personally use the application to automate character actions in an online game overnight while I sleep. Unfortunately, I keep coming back to the computer in the morning to find it unresponsive. Upon further testing, I'm finding that my application causes the computer to become unresponsive after about 10 minutes of user idle time (even if the application itself it simulating user activity). I can't seem to pin-point the issue, so I'm hoping somebody else might have a suggestion of where to look or what might be causing the issue. The relevant symptoms and characteristics: Unresponsiveness occurs after user is idle for 10 minutes User can still move the mouse pointer around the screen Everything but the mouse appears frozen... mouse clicks have no effect and no applications update their displays, including the Windows 7 desktop I left the task manager up along the with the app overnight so I could see the last task manager image before the screen freezes... the Java app is at normal CPU/Memory usage and total CPU usage is only ~1% After moving the mouse (in other words, the user comes back from being idle), the screen image starts updating again within 30 minutes (this is very hit and miss... sometimes 10 minutes, sometimes no results after two hours) User can CTRL-ALT-DEL to get to Windows 7's CTRL-ALT-DEL screen (after a 30 second pause). User is still able to move mouse pointer, but clicking any of the button options causes the screen to appear to freeze again On some very rare occasions, the system never freezes, and I come back to it in the morning with full responsiveness The Java app automatically stops input scripting in the middle of the night, so Windows 7 detects "real" idleness and turns the monitors into Standby mode... which they successfully come out of upon manually moving the mouse in the morning when I wake up, even though the desktop display still appears frozen Given the symptoms and characteristics of the issue, it's as if the Java app is causing the desktop display of the logged in user to stop updating, including any running applications. Programming concepts and Java packages used: Multi-threading Standard out and err are rerouted to a javax.swing.JTextArea The application uses a Swing GUI awt.Robot (very heavily used) awt.PointerInfo awt.MouseInfo System Specs: Windows 7 Professional Java 1.6.0 u17 In conclusion, I should stress that I'm not looking for any specific solutions, as I'm not asking a very specific question. I'm just wondering if anybody has run into a similar problem when using the Java libraries that I'm using. I would also gladly appreciate any suggestions for things to try to attempt to further pinpoint what is causing my problem. Thanks! Ross PS, I'll post an update/answer if I manage to stumble across anything else while I continue to debug this.

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• Estimating the boundary of arbitrarily distributed data

  - by Dave

  I have two dimensional discrete spatial data. I would like to make an approximation of the spatial boundaries of this data so that I can produce a plot with another dataset on top of it. Ideally, this would be an ordered set of (x,y) points that matplotlib can plot with the plt.Polygon() patch. My initial attempt is very inelegant: I place a fine grid over the data, and where data is found in a cell, a square matplotlib patch is created of that cell. The resolution of the boundary thus depends on the sampling frequency of the grid. Here is an example, where the grey region are the cells containing data, black where no data exists. OK, problem solved - why am I still here? Well.... I'd like a more "elegant" solution, or at least one that is faster (ie. I don't want to get on with "real" work, I'd like to have some fun with this!). The best way I can think of is a ray-tracing approach - eg: from xmin to xmax, at y=ymin, check if data boundary crossed in intervals dx y=ymin+dy, do 1 do 1-2, but now sample in y An alternative is defining a centre, and sampling in r-theta space - ie radial spokes in dtheta increments. Both would produce a set of (x,y) points, but then how do I order/link neighbouring points them to create the boundary? A nearest neighbour approach is not appropriate as, for example (to borrow from Geography), an isthmus (think of Panama connecting N&S America) could then close off and isolate regions. This also might not deal very well with the holes seen in the data, which I would like to represent as a different plt.Polygon. The solution perhaps comes from solving an area maximisation problem. For a set of points defining the data limits, what is the maximum contiguous area contained within those points To form the enclosed area, what are the neighbouring points for the nth point? How will the holes be treated in this scheme - is this erring into topology now? Apologies, much of this is me thinking out loud. I'd be grateful for some hints, suggestions or solutions. I suspect this is an oft-studied problem with many solution techniques, but I'm looking for something simple to code and quick to run... I guess everyone is, really! Cheers, David

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• Can this way of storing typed objects be improved?

  - by Pindatjuh

  This is an "can it be improved"-question. Topic: Storing typed objects in memory. Background information: I'm building a compiler for the x86-32 Windows platform for my language. My goal includes typed objects. Idea: Every primitive is a semi-class (it can be used as if it was a normal class, but it's stored more compact). Every class is represented by primitives and some meta-data (containing class-properties, inheritance stuff, etc.). The meta-data is complex: it doesn't use fields but instead context-switches. For primitives, the meta-data is very small, compared to a "real" class, which is alot bigger. This enables another idea that "primitives are objects", in my language, which I found nessecairy. Example: If I have an array of 32 booleans, then the pure content of this array is exactly 4 byte (32 bits of booleans). The meta-data will contain flags that the type is an array of booleans, which contains 32 entries. The meta-data is very compacted, on bit-level: using a sort of "packing" mechanism, which is read by a FSM at runtime, when doing inspection of the type (like when passing the object to methods for checking, etc.) For instance (read from left to right, top to bottom, remember vertical position when going to the right, and check nearest column header for meaning of switch): Primitive? Array? Type-Meta 1 Byte? || Size (1 byte) 1 1 [...] 1 [...] done 0 2 Bytes? || Size (2 bytes) 1 [...] done || Size (4 bytes) 0 [...] done Integer? 1 Byte? 2 Bytes? 0 1 0 1 done 1 done 0 done Boolean? Byte? 0 1 0 done 1 done More-Primitives 0 .... Class-Stuff (Huge) 0 ... (After reaching done the data is inserted. || = byte alignment. [...] is variable sized. ... is not described here, for simplicity. And let's call them cost-based-data-structures.) For an array of 32 booleans containing all true values, the memory for this type would be (read top-down): 1 Primitive 1 Array 1 ArrayType: Primitive 0 Not-Array 0 Not-Integer 1 Boolean 0 Not-Byte (thus bit) 1 Integer Size: 1 Byte 00100000 Array size 01010101 01010101 01010101 01010101 Data (user defined) Thus, 8 bytes represent 32 booleans in an array: 11100101 00100000 01010101 01010101 01010101 01010101 How can I improve this? (Both performance- and memory-consumption wise)

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• SQL Server 2008: If Multiple Values Set In Other Mutliple Values Set

  - by AJH

  In SQL, is there anyway to accomplish something like this? This is based off a report built in SQL Server Report Builder, where the user can specify multiple text values as a single report parameter. The query for the report grabs all of the values the user selected and stores them in a single variable. I need a way for the query to return only records that have associations to EVERY value the user specified. -- Assume there's a table of Elements with thousands of entries. -- Now we declare a list of properties for those Elements to be associated with. create table #masterTable ( ElementId int, Text varchar(10) ) insert into #masterTable (ElementId, Text) values (1, 'Red'); insert into #masterTable (ElementId, Text) values (1, 'Coarse'); insert into #masterTable (ElementId, Text) values (1, 'Dense'); insert into #masterTable (ElementId, Text) values (2, 'Red'); insert into #masterTable (ElementId, Text) values (2, 'Smooth'); insert into #masterTable (ElementId, Text) values (2, 'Hollow'); -- Element 1 is Red, Coarse, and Dense. Element 2 is Red, Smooth, and Hollow. -- The real table is actually much much larger than this; this is just an example. -- This is me trying to replicate how SQL Server Report Builder treats -- report parameters in its queries. The user selects one, some, all, -- or no properties from a list. The written query treats the user's -- selections as a single variable called @Properties. -- Example scenario 1: User only wants to see Elements that are BOTH Red and Dense. select e.* from Elements e where (@Properties) --ideally a set containing only Red and Dense in (select Text from #masterTable where ElementId = e.Id) --ideally a set containing only Red, Coarse, and Dense --Both Red and Dense are within Element 1's properties (Red, Coarse, Dense), so Element 1 gets returned, but not Element 2. -- Example scenario 2: User only wants to see Elements that are BOTH Red and Hollow. select e.* from Elements e where (@Properties) --ideally a set containing only Red and Hollow in (select Text from #masterTable where ElementId = e.Id) --Both Red and Hollow are within Element 2's properties (Red, Smooth, Hollow), so Element 2 gets returned, but not Element 1. --Example Scenario 3: User only picked the Red option. select e.* from Elements e where (@Properties) --ideally a set containing only Red in (select Text from #masterTable where ElementId = e.Id) --Red is within both Element 1 and Element 2's properties, so both Element 1 and Element 2 get returned. The above syntax doesn't actually work because SQL doesn't seem to allow multiple values on the left side of the "in" comparison. Error that returns: Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression. Am I even on the right track here? Sorry if the example looks long-winded or confusing.

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• .NET: Is there a way to finagle a default namespace in an XPath 1.0 query?

  - by Cheeso

  I'm building a tool that performs xpath 1.0 queries on XHTML documents. The requirement to use a namespace prefix in the query is killing me. The query looks like this: html/body/div[@class='contents']/div[@class='body']/ div[@class='pgdbbyauthor']/h2[a[@name][starts-with(.,'Quick')]]/ following-sibling::ul[1]/li/a (all on one line) ...which is bad enough, except because it's xpath 1.0, I need to use an explicit namespace prefix on each QName, so it looks like this: ns1:html/ns1:body/ns1:div[@class='contents']/ns1:div[@class='body']/ ns1:div[@class='pgdbbyauthor']/ns1:h2[ns1:a[@name][starts-with(.,'Quick')]]/ following-sibling::ns1:ul[1]/ns1:li/ns1:a To set up the query, I do something like this: var xpathDoc = new XPathDocument(new StringReader(theText)); var nav = xpathDoc.CreateNavigator(); var xmlns = new XmlNamespaceManager(nav.NameTable); foreach (string prefix in xmlNamespaces.Keys) xmlns.AddNamespace(prefix, xmlNamespaces[prefix]); XPathNodeIterator selection = nav.Select(xpathExpression, xmlns); But what I want is for the xpathExpression to use the implicit default namespace. Is there a way for me to transform the unadorned xpath expression, after it's been written, to inject a namespace prefix for each element name in the query? I'm thinking, anything between two slashes, I could inject a prefix there. Excepting of course axis names like "parent::" and "preceding-sibling::" . And wildcards. That's what I mean by "finagle a default namespace". Is this hack gonna work? Addendum Here's what I mean. suppose I have an xpath expression, and before passing it to nav.Select(), I transform it. Something like this: string FixupWithDefaultNamespace(string expr) { string s = expr; s = Regex.Replace(s, "^(?!::)([^/:]+)(?=/)", "ns1:$1"); // beginning s = Regex.Replace(s, "/([^/:]+)(?=/)", "/ns1:$1"); // stanza s = Regex.Replace(s, "::([A-Za-z][^/:*]*)(?=/)", "::ns1:$1"); // axis specifier s = Regex.Replace(s, "\\[([A-Za-z][^/:*\\(]*)(?=[\\[\\]])", "[ns1:$1"); // predicate s = Regex.Replace(s, "/([A-Za-z][^/:]*)(?!<::)$", "/ns1:$1"); // end s = Regex.Replace(s, "^([A-Za-z][^/:]*)$", "ns1:$1"); // edge case s = Regex.Replace(s, "([-A-Za-z]+)\\(([^/:\\.,\\)]+)(?=[,\\)])", "$1(ns1:$2"); // xpath functions return s; } This actually works for simple cases I tried. To use the example from above - if the input is the first xpath expression, the output I get is the 2nd one, with all the ns1 prefixes. The real question is, is it hopeless to expect this Regex.Replace approach to work, as the xpath expressions get more complicated?

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