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  • Getting Custom NSCell with NSButtonCell instance to handle mouse click/mouse events

    - by sidha
    OK I'm really stumped on this one. I want to make a checkbox with a NSTextFieldCell combined together. It's important that the checkbox goes ON if the mouse hits the box, NOT the text. I've accomplished this, more or less, but the issue is receiving the mouse event because I click one checkbox in a row, but ALL of them turn to NSOnState. I will show what I've done and my various failed attempts in order to get this to work. So this is how I've done it so far: header: @interface MyCheckboxCellToo : NSTextFieldCell { NSButtonCell *_checkboxCell; } implementation: - (NSUInteger)hitTestForEvent:(NSEvent *)event inRect:(NSRect)cellFrame ofView:(NSView *)controlView { NSPoint point = [controlView convertPoint:[event locationInWindow] fromView:nil]; NSLog(@"%@", NSStringFromPoint(point)); NSRect checkFrame; NSDivideRect(cellFrame, &checkFrame, &cellFrame, cellFrame.size.height/*3 + [[_checkboxCell image] size].width*/, NSMinXEdge); if (NSMouseInRect(point, checkFrame, [controlView isFlipped])) { // the checkbox, or the small region around it, was hit. so let's flip the state NSCellStateValue checkState = ([_checkboxCell state] == NSOnState) ? NSOffState:NSOnState; [self setState:checkState]; [_checkboxCell setState:checkState]; [controlView setNeedsDisplay:YES]; return NSCellHitTrackableArea; } return [super hitTestForEvent:event inRect:cellFrame ofView:controlView]; } I know I probably shouldn't be doing: [self setState:checkState]; [_checkboxCell setState:checkState]; [controlView setNeedsDisplay:YES]; in there... because the result is that EVERY checkbox in every goes to NSOnState. Is this because cells are re-used? How come the ImageAndTextCell can have different images in the same tableview? How do I handle the mouse event? I have tried: - (BOOL)trackMouse:(NSEvent *)theEvent inRect:(NSRect)cellFrame ofView:(NSView *)controlView untilMouseUp:(BOOL)untilMouseUp { NSLog(@"%s %@", _cmd, theEvent); return [_checkboxCell trackMouse:theEvent inRect:cellFrame ofView:controlView untilMouseUp:untilMouseUp]; // return YES; // return [super trackMouse:theEvent inRect:cellFrame ofView:controlView untilMouseUp:untilMouseUp]; } - (BOOL)startTrackingAt:(NSPoint)startPoint inView:(NSView *)controlView { NSLog(@"%s %@", _cmd, NSStringFromPoint(startPoint)); return [super startTrackingAt:startPoint inView:controlView]; } - (BOOL)continueTracking:(NSPoint)lastPoint at:(NSPoint)currentPoint inView:(NSView *)controlView { NSLog(@"%s %@", _cmd, NSStringFromPoint(currentPoint)); return [super continueTracking:lastPoint at:currentPoint inView:controlView]; } - (void)stopTracking:(NSPoint)lastPoint at:(NSPoint)stopPoint inView:(NSView *)controlView mouseIsUp:(BOOL)flag { NSLog(@"%s %d %@", _cmd, flag, NSStringFromPoint(stopPoint)); } trackMouse: ... DOES gets called but startTrackingAt:..., continueTracking:..., and stopTracking:.... DO NOT get called when I click on the checkbox "hit area" in trackMouse:... I have tried return [_checkboxCell trackMouse:theEvent inRect:cellFrame ofView:controlView untilMouseUp:untilMouseUp]; and return [super trackMouse:theEvent inRect:cellFrame ofView:controlView untilMouseUp:untilMouseUp]; and neither seems to result in the mouse event being handled by the checkbox. How do I get that single checkbox to go NSOnState? I know I'm pretty close but after a lot of doc reading and google searching I haven't been successful at solving this. suggestions and comments welcome.. OK here is a bit more to show creation and destruction of the object.. - (id)init { if ((self = [super init])) { _checkboxCell = [[NSButtonCell alloc] init]; [_checkboxCell setButtonType:NSSwitchButton]; [_checkboxCell setTitle:@""]; [_checkboxCell setTarget:self]; [_checkboxCell setImagePosition:NSImageLeft]; [_checkboxCell setControlSize:NSRegularControlSize]; } return self; } - copyWithZone:(NSZone *)zone { MyCheckboxCellToo *cell = (MyCheckboxCellToo *)[super copyWithZone:zone]; cell->_checkboxCell = [_checkboxCell copyWithZone:zone]; return cell; } - (void)dealloc { [_checkboxCell release]; [super dealloc]; }

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  • Is SQL Server DRI (ON DELETE CASCADE) slow?

    - by Aaronaught
    I've been analyzing a recurring "bug report" (perf issue) in one of our systems related to a particularly slow delete operation. Long story short: It seems that the CASCADE DELETE keys were largely responsible, and I'd like to know (a) if this makes sense, and (b) why it's the case. We have a schema of, let's say, widgets, those being at the root of a large graph of related tables and related-to-related tables and so on. To be perfectly clear, deleting from this table is actively discouraged; it is the "nuclear option" and users are under no illusions to the contrary. Nevertheless, it sometimes just has to be done. The schema looks something like this: Widgets | +--- Anvils (1:1) | | | +--- AnvilTestData (1:N) | +--- WidgetHistory (1:N) | +--- WidgetHistoryDetails (1:N) Nothing too scary, really. A Widget can be different types, an Anvil is a special type, so that relationship is 1:1 (or more accurately 1:0..1). Then there's a large amount of data - perhaps thousands of rows of AnvilTestData per Anvil collected over time, dealing with hardness, corrosion, exact weight, hammer compatibility, usability issues, and impact tests with cartoon heads. Then every Widget has a long, boring history of various types of transactions - production, inventory moves, sales, defect investigations, RMAs, repairs, customer complaints, etc. There might be 10-20k details for a single widget, or none at all, depending on its age. So, unsurprisingly, there's a CASCADE DELETE relationship at every level here. If a Widget needs to be deleted, it means something's gone terribly wrong and we need to erase any records of that widget ever existing, including its history, test data, etc. Again, nuclear option. Relations are all indexed, statistics are up to date. Normal queries are fast. The system tends to hum along pretty smoothly for everything except deletes. Getting to the point here, finally, for various reasons we only allow deleting one widget at a time, so a delete statement would look like this: DELETE FROM Widgets WHERE WidgetID = @WidgetID Pretty simple, innocuous looking delete... that takes over 2 minutes to run, for a widget with no data! After slogging through execution plans I was finally able to pick out the AnvilTestData and WidgetHistoryDetails deletes as the sub-operations with the highest cost. So I experimented with turning off the CASCADE (but keeping the actual FK, just setting it to NO ACTION) and rewriting the script as something very much like the following: DECLARE @AnvilID int SELECT @AnvilID = AnvilID FROM Anvils WHERE WidgetID = @WidgetID DELETE FROM AnvilTestData WHERE AnvilID = @AnvilID DELETE FROM WidgetHistory WHERE HistoryID IN ( SELECT HistoryID FROM WidgetHistory WHERE WidgetID = @WidgetID) DELETE FROM Widgets WHERE WidgetID = @WidgetID Both of these "optimizations" resulted in significant speedups, each one shaving nearly a full minute off the execution time, so that the original 2-minute deletion now takes about 5-10 seconds - at least for new widgets, without much history or test data. Just to be absolutely clear, there is still a CASCADE from WidgetHistory to WidgetHistoryDetails, where the fanout is highest, I only removed the one originating from Widgets. Further "flattening" of the cascade relationships resulted in progressively less dramatic but still noticeable speedups, to the point where deleting a new widget was almost instantaneous once all of the cascade deletes to larger tables were removed and replaced with explicit deletes. I'm using DBCC DROPCLEANBUFFERS and DBCC FREEPROCCACHE before each test. I've disabled all triggers that might be causing further slowdowns (although those would show up in the execution plan anyway). And I'm testing against older widgets, too, and noticing a significant speedup there as well; deletes that used to take 5 minutes now take 20-40 seconds. Now I'm an ardent supporter of the "SELECT ain't broken" philosophy, but there just doesn't seem to be any logical explanation for this behaviour other than crushing, mind-boggling inefficiency of the CASCADE DELETE relationships. So, my questions are: Is this a known issue with DRI in SQL Server? (I couldn't seem to find any references to this sort of thing on Google or here in SO; I suspect the answer is no.) If not, is there another explanation for the behaviour I'm seeing? If it is a known issue, why is it an issue, and are there better workarounds I could be using?

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  • Python/numpy tricky slicing problem

    - by daver
    Hi stack overflow, I have a problem with some numpy stuff. I need a numpy array to behave in an unusual manner by returning a slice as a view of the data I have sliced, not a copy. So heres an example of what I want to do: Say we have a simple array like this: a = array([1, 0, 0, 0]) I would like to update consecutive entries in the array (moving left to right) with the previous entry from the array, using syntax like this: a[1:] = a[0:3] This would get the following result: a = array([1, 1, 1, 1]) Or something like this: a[1:] = 2*a[:3] # a = [1,2,4,8] To illustrate further I want the following kind of behaviour: for i in range(len(a)): if i == 0 or i+1 == len(a): continue a[i+1] = a[i] Except I want the speed of numpy. The default behavior of numpy is to take a copy of the slice, so what I actually get is this: a = array([1, 1, 0, 0]) I already have this array as a subclass of the ndarray, so I can make further changes to it if need be, I just need the slice on the right hand side to be continually updated as it updates the slice on the left hand side. Am I dreaming or is this magic possible? Update: This is all because I am trying to use Gauss-Seidel iteration to solve a linear algebra problem, more or less. It is a special case involving harmonic functions, I was trying to avoid going into this because its really not necessary and likely to confuse things further, but here goes. The algorithm is this: while not converged: for i in range(len(u[:,0])): for j in range(len(u[0,:])): # skip over boundary entries, i,j == 0 or len(u) u[i,j] = 0.25*(u[i-1,j] + u[i+1,j] + u[i, j-1] + u[i,j+1]) Right? But you can do this two ways, Jacobi involves updating each element with its neighbours without considering updates you have already made until the while loop cycles, to do it in loops you would copy the array then update one array from the copied array. However Gauss-Seidel uses information you have already updated for each of the i-1 and j-1 entries, thus no need for a copy, the loop should essentially 'know' since the array has been re-evaluated after each single element update. That is to say, every time we call up an entry like u[i-1,j] or u[i,j-1] the information calculated in the previous loop will be there. I want to replace this slow and ugly nested loop situation with one nice clean line of code using numpy slicing: u[1:-1,1:-1] = 0.25(u[:-2,1:-1] + u[2:,1:-1] + u[1:-1,:-2] + u[1:-1,2:]) But the result is Jacobi iteration because when you take a slice: u[:,-2,1:-1] you copy the data, thus the slice is not aware of any updates made. Now numpy still loops right? Its not parallel its just a faster way to loop that looks like a parallel operation in python. I want to exploit this behaviour by sort of hacking numpy to return a pointer instead of a copy when I take a slice. Right? Then every time numpy loops, that slice will 'update' or really just replicate whatever happened in the update. To do this I need slices on both sides of the array to be pointers. Anyway if there is some really really clever person out there that awesome, but I've pretty much resigned myself to believing the only answer is to loop in C.

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  • Fonts, goes back to default size

    - by Bladimir Ruiz
    Every time I change the font, it goes back to the default size, which is 12, even if I change it before with the "Tamano" menu, it only goes back to 12 every time, my guess would be the way I change the size with deriveFont(), but don't I now any other way to change it. public static class cambiar extends JFrame { public cambiar() { final Font aryal = new Font("Comic Sans MS", Font.PLAIN, 12); JFrame ventana = new JFrame("Cambios en el Texto!"); JPanel adentro = new JPanel(); final JLabel texto = new JLabel("Texto a Cambiar!"); texto.setFont(aryal); JMenuBar menu = new JMenuBar(); JMenu fuentes = new JMenu("Fuentes"); /* Elementos de Fuentes */ JMenuItem arial = new JMenuItem("Arial"); arial.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { Font arrrial = new Font("Arial", Font.PLAIN, 12); float tam = (float) texto.getFont().getSize(); String hola = String.valueOf(tam); texto.setFont(arrrial); texto.setFont(texto.getFont().deriveFont(tam)); } }); fuentes.add(arial); /* FIN Fuentes */ JMenu tamano = new JMenu("Tamano"); /* Elementos de Tamano */ JMenuItem font13 = new JMenuItem("13"); font13.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { texto.setFont(texto.getFont().deriveFont(23.0f)); } }); JMenuItem font14 = new JMenuItem("14"); arial.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { texto.setFont(aryal); } }); JMenuItem font15 = new JMenuItem("15"); arial.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { texto.setFont(aryal); } }); JMenuItem font16 = new JMenuItem("16"); arial.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { texto.setFont(aryal); } }); JMenuItem font17 = new JMenuItem("17"); arial.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { texto.setFont(aryal); } }); JMenuItem font18 = new JMenuItem("18"); arial.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { texto.setFont(aryal); } }); JMenuItem font19 = new JMenuItem("19"); arial.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { texto.setFont(aryal); } }); JMenuItem font20 = new JMenuItem("20"); arial.addActionListener(new ActionListener() { public void actionPerformed(ActionEvent e) { texto.setFont(aryal); } }); tamano.add(font13); /* FIN tanano */ JMenu tipo = new JMenu("Tipo"); /* Elementos de tipo */ /* FIN tipo */ /* Elementos del JMENU */ menu.add(fuentes); menu.add(tamano); menu.add(tipo); /* FIN JMENU */ /* Elementos del JPanel */ adentro.add(menu); adentro.add(texto); /* FIN JPanel */ /* Elementos del JFRAME */ ventana.add(adentro); ventana.setVisible(true); ventana.setSize(250, 250); /* FIN JFRAME */ } } Thanks in Advance!

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  • Writing more efficient xquery code (avoiding redundant iteration)

    - by Coquelicot
    Here's a simplified version of a problem I'm working on: I have a bunch of xml data that encodes information about people. Each person is uniquely identified by an 'id' attribute, but they may go by many names. For example, in one document, I might find <person id=1>Paul Mcartney</person> <person id=2>Ringo Starr</person> And in another I might find: <person id=1>Sir Paul McCartney</person> <person id=2>Richard Starkey</person> I want to use xquery to produce a new document that lists every name associated with a given id. i.e.: <person id=1> <name>Paul McCartney</name> <name>Sir Paul McCartney</name> <name>James Paul McCartney</name> </person> <person id=2> ... </person> The way I'm doing this now in xquery is something like this (pseudocode-esque): let $ids := distinct-terms( [all the id attributes on people] ) for $id in $ids return <person id={$id}> { for $unique-name in distinct-values ( for $name in ( [all names] ) where $name/@id=$id return $name ) return <name>{$unique-name}</name> } </person> The problem is that this is really slow. I imagine the bottleneck is the innermost loop, which executes once for every id (of which there are about 1200). I'm dealing with a fair bit of data (300 MB, spread over about 800 xml files), so even a single execution of the query in the inner loop takes about 12 seconds, which means that repeating it 1200 times will take about 4 hours (which might be optimistic - the process has been running for 3 hours so far). Not only is it slow, it's using a whole lot of virtual memory. I'm using Saxon, and I had to set java's maximum heap size to 10 GB (!) to avoid getting out of memory errors, and it's currently using 6 GB of physical memory. So here's how I'd really like to do this (in Pythonic pseudocode): persons = {} for id in ids: person[id] = set() for person in all_the_people_in_my_xml_document: persons[person.id].add(person.name) There, I just did it in linear time, with only one sweep of the xml document. Now, is there some way to do something similar in xquery? Surely if I can imagine it, a reasonable programming language should be able to do it (he said quixotically). The problem, I suppose, is that unlike Python, xquery doesn't (as far as I know) have anything like an associative array. Is there some clever way around this? Failing that, is there something better than xquery that I might use to accomplish my goal? Because really, the computational resources I'm throwing at this relatively simple problem are kind of ridiculous.

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  • Can I constrain a template parameter class to implement the interfaces that are supported by other?

    - by K. Georgiev
    The name is a little blurry, so here's the situation: I'm writing code to use some 'trajectories'. The trajectories are an abstract thing, so I describe them with different interfaces. So I have a code as this: namespace Trajectories { public interface IInitial < Atom > { Atom Initial { get; set; } } public interface ICurrent < Atom > { Atom Current { get; set; } } public interface IPrevious < Atom > { Atom Previous { get; set; } } public interface ICount < Atom > { int Count { get; } } public interface IManualCount < Atom > : ICount < Atom > { int Count { get; set; } } ... } Every concrete implementation of a trajectory will implement some of the above interfaces. Here's a concrete implementation of a trajectory: public class SimpleTrajectory < Atom > : IInitial < Atom >, ICurrent < Atom >, ICount < Atom > { // ICount public int Count { get; private set; } // IInitial private Atom initial; public Atom Initial { get { return initial; } set { initial = current = value; Count = 1; } } // ICurrent private Atom current; public Atom Current { get { return current; } set { current = value; Count++; } } } Now, I want to be able to deduce things about the trajectories, so, for example I want to support predicates about different properties of some trajectory: namespace Conditions { public interface ICondition &lt Atom, Trajectory &gt { bool Test(ref Trajectory t); } public class CountLessThan &lt Atom, Trajectory &gt : ICondition &lt Atom, Trajectory &gt where Trajectory : Trajectories.ICount &lt Atom &gt { public int Value { get; set; } public CountLessThan() { } public bool Test(ref Trajectory t) { return t.Count &lt Value; } } public class CurrentNormLessThan &lt Trajectory &gt : ICondition &lt Complex, Trajectory &gt where Trajectory : Trajectories.ICurrent &lt Complex &gt { public double Value { get; set; } public CurrentNormLessThan() { } public bool Test(ref Trajectory t) { return t.Current.Norm() &lt Value; } } } Now, here's the question: What if I wanted to implement AND predicate? It would be something like this: public class And &lt Atom, CondA, TrajectoryA, CondB, TrajectoryB, Trajectory &gt : ICondition &lt Atom, Trajectory &gt where CondA : ICondition &lt Atom, TrajectoryA &gt where TrajectoryA : // Some interfaces where CondB : ICondition &lt Atom, TrajectoryB &gt where TrajectoryB : // Some interfaces where Trajectory : // MUST IMPLEMENT THE INTERFACES FOR TrajectoryA AND THE INTERFACES FOR TrajectoryB { public CondA A { get; set; } public CondB B { get; set; } public bool Test(ref Trajectory t){ return A.Test(t) && B.Test(t); } } How can I say: support only these trajectories, for which the arguments of AND are ok? So I can be able to write: var vand = new CountLessThan(32) & new CurrentNormLessThan(4.0); I think if I create an orevall interface for every subset of interfaces, I could be able to do it, but it will become quite ugly.

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  • IE / Facebook Issue : Why Facebook Like box not display in Internet Explorer 6 - IE8 ?

    - by Vaibhav Bhalke
    IE / Facebook Issue : Why Facebook Like box not display in Internet Explorer6 - IE8 ? Facebook like box display throgh my web application on every browser excluding IE-IE8 Now final Application.html file contains are < !DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/DTD/strict.dtd"><BR> < html xmlns="http://www.w3.org/1999/xhtml" xmlns:fb="http://www.facebook.com/2008/fbml"> <BR>< head> < meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" /> < /head><BR> < body> < script type="text/javascript" language="javascript" src="http://static.ak.connect.facebook.com/js/api_lib/v0.4/FeatureLoader.js.php"> < /script> <BR> < script type="text/javascript"> FB_RequireFeatures(["Connect"], function(){ var x=1; } ); < /script> <BR> < script src="http://static.ak.connect.facebook.com/connect.php/en_US" type="text/javascript"> < /script> < /body> < /html> My Java code for LIke Box is as follows FBPageFanWidget.java class FBPageFanWidget extends Composite { public FBPageFanWidget() { VerticalPanel mainPanel = new VerticalPanel(); mainPanel .getElement() .setInnerHTML( "< script type='text/javascript' src='http://static.ak.connect.facebook.com/js/api_lib/v0.4/FeatureLoader.js.php/en_US'>< /script>< script type='text/javascript'>FB.init('');< /script>< fb:fan profile_id=\"113106068709539\" stream=\"0\" connections=\"10\" logobar=\"0\" width=\"244\" height=\"240\" css='http://127.0.01:8080/webapplicationname/facebook.css?1'>< /fb:fan>"); initWidget(mainPanel); } } We used proper facebook API_KEY & PAGE_ID It's very important for us to Show Facebook like Box in Our web application Because we have more IE users. If we add FBPageFanWidget.java in our web applicaton then Our Home page is not display in IE because we add Facebook LikeBox so we made changes in Our FBPageFanWidget.java class FBPageFanWidget extends Composite { public FBPageFanWidget() { VerticalPanel mainPanel = new VerticalPanel(); if (!isIE()) { mainPanel.getElement() .setInnerHTML("<script type='text/javascript' src='http://static.ak.connect.facebook.com/js/api_lib/v0.4/FeatureLoader.js.php/en_US'></script><script type='text/javascript'>FB.init('');</script><fb:fan profile_id=\"113106068709539\" stream=\"0\" connections=\"10\" logobar=\"0\" width=\"244\" height=\"240\" css='http://127.0.01:8080/webapplicationname/facebook.css?1'></fb:fan>"); } initWidget(mainPanel); } public native String getUserAgent() /*-{ return navigator.userAgent; }-*/; private boolean isIE() { return (getUserAgent().indexOf("MSIE") > -1); } } when we did this changes Then Facebook Like Box display in every browser excluding IE6 - IE8 :( and also display Our Home page in IE8 excludeing Facebook Like Box. It means There is probelm in IE ? or what changes i need to do in my html file or java file to show facebook like Box properly with displaying our home page It's very important for us to Show Facebook like Box in Our web application Because we have more IE users. Please Reply ASAP. Hope-for Best Co-operation from your side !!!!

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  • Problem with a blocking network task

    - by user326967
    Hello everyone. I'm new in Java so please forgive any obscene errors that I may make :) I'm developing a program in Java that among other things it should also handle clients that will connect to a server. The server has 3 threads running, and I have created them in the following way : DaemonForUI du; DaemonForPort da; DaemonForCheck dc; da = new DaemonForPort(3); dc = new DaemonForCheck(5); du = new DaemonForUI(7); Thread t_port = new Thread(da); Thread t_check = new Thread(dc); Thread t_ui = new Thread(du); t_port.setName("v1.9--PORTd"); t_check.setName("v1.9-CHECKd"); t_ui.setName("v1.9----UId"); t_port.start(); t_check.start(); t_ui.start(); Each thread handles a different aspect of the complete program. The thread t_ui is responsible to accept asynchronous incoming connections from clients, process the sent data and send other data back to the client. When I remove all the commands from the previous piece of code that has to with the t_ui thread, everything runs ok which in my case means that the other threads are printing their debug messages. If I set the t_ui thread to run too, then the whole program blocks at the "accept" of the t_ui thread. After reading at online manuals I saw that the accepted connections should be non-blocking, therefore use something like that : public ServerSocketChannel ssc = null; ssc = ServerSocketChannel.open(); ssc.socket().bind(new InetSocketAddress(port)); ssc.configureBlocking(false); SocketChannel sc = ssc.accept(); if (sc == null) { ; } else { System.out.println("The server and client are connected!"); System.out.println("Incoming connection from: " + sc.socket().getRemoteSocketAddress()); in = new DataInputStream(new BufferedInputStream(sc.socket().getInputStream())); out = new DataOutputStream(new BufferedOutputStream(sc.socket().getOutputStream())); //other magic things take place after that point... The thread for t_ui is created as follows : class DaemonForUI implements Runnable{ private int cnt; private int rr; public ListenerForUI serverListener; public DaemonForUI(int rr){ cnt = 0; this.rr = rr; serverListener = new ListenerForUI(); } public static String getCurrentTime() { final String DATE_FORMAT_NOW = "yyyy-MM-dd HH:mm:ss"; Calendar cal = Calendar.getInstance(); SimpleDateFormat sdf = new SimpleDateFormat(DATE_FORMAT_NOW); return (sdf.format(cal.getTime())); } public void run() { while(true) { System.out.println(Thread.currentThread().getName() + "\t (" + cnt + ")\t (every " + rr + " sec) @ " + getCurrentTime()); try{ Thread.sleep(rr * 1000); cnt++; } catch (InterruptedException e){ e.printStackTrace(); } } } } Obviously, I'm doing something wrong at the creation of the socket or at the use of the thread. Do you know what is causing the problem? Every help would be greatly appreciated.

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  • Error data: line 2 column 1 when using pycurl with gzip stream

    - by Sagar Hatekar
    Thanks for reading. Background: I am trying to read a streaming API feed that returns data in JSON format, and then storing this data to a pymongo collection. The streaming API requires a "Accept-Encoding" : "Gzip" header. What's happening: Code fails on json.loads and outputs - Extra data: line 2 column 1 - line 4 column 1 (char 1891 - 5597) (Refer Error Log below) This does NOT happen while parsing every JSON object - it happens at random. My guess is I am encountering some weird JSON object after every "x" proper JSON objects. I did reference how to use pycurl if requested data is sometimes gzipped, sometimes not? and Encoding error while deserializing a json object from Google but so far have been unsuccessful at resolving this error. Could someone please help me out here? Error Log: Note: The raw dump of the JSON object below is basically using the repr() method. '{"id":"tag:search.twitter.com,2005:207958320747782146","objectType":"activity","actor":{"objectType":"person","id":"id:twitter.com:493653150","link":"http://www.twitter.com/Deathnews_7_24","displayName":"Death News 7/24","postedTime":"2012-02-16T01:30:12.000Z","image":"http://a0.twimg.com/profile_images/1834408513/deathnewstwittersquare_normal.jpg","summary":"Crashes, Murders, Suicides, Accidents, Crime and Naturals Death News From All Around World","links":[{"href":"http://www.facebook.com/DeathNews724","rel":"me"}],"friendsCount":56,"followersCount":14,"listedCount":1,"statusesCount":1029,"twitterTimeZone":null,"utcOffset":null,"preferredUsername":"Deathnews_7_24","languages":["tr"]},"verb":"post","postedTime":"2012-05-30T22:15:02.000Z","generator":{"displayName":"web","link":"http://twitter.com"},"provider":{"objectType":"service","displayName":"Twitter","link":"http://www.twitter.com"},"link":"http://twitter.com/Deathnews_7_24/statuses/207958320747782146","body":"Kathi Kamen Goldmark, Writers\xe2\x80\x99 Catalyst, Dies at 63 http://t.co/WBsNlNtA","object":{"objectType":"note","id":"object:search.twitter.com,2005:207958320747782146","summary":"Kathi Kamen Goldmark, Writers\xe2\x80\x99 Catalyst, Dies at 63 http://t.co/WBsNlNtA","link":"http://twitter.com/Deathnews_7_24/statuses/207958320747782146","postedTime":"2012-05-30T22:15:02.000Z"},"twitter_entities":{"urls":[{"display_url":"nytimes.com/2012/05/30/boo\xe2\x80\xa6","indices":[52,72],"expanded_url":"http://www.nytimes.com/2012/05/30/books/kathi-kamen-goldmark-writers-catalyst-dies-at-63.html","url":"http://t.co/WBsNlNtA"}],"hashtags":[],"user_mentions":[]},"gnip":{"language":{"value":"en"},"matching_rules":[{"value":"url_contains: nytimes.com","tag":null}],"klout_score":11,"urls":[{"url":"http://t.co/WBsNlNtA","expanded_url":"http://www.nytimes.com/2012/05/30/books/kathi-kamen-goldmark-writers-catalyst-dies-at-63.html?_r=1"}]}}\r\n{"id":"tag:search.twitter.com,2005:207958321003638785","objectType":"activity","actor":{"objectType":"person","id":"id:twitter.com:178760897","link":"http://www.twitter.com/Mobanu","displayName":"Donald Ochs","postedTime":"2010-08-15T16:33:56.000Z","image":"http://a0.twimg.com/profile_images/1493224811/small_mobany_Logo_normal.jpg","summary":"","links":[{"href":"http://www.mobanuweightloss.com","rel":"me"}],"friendsCount":10272,"followersCount":9698,"listedCount":30,"statusesCount":725,"twitterTimeZone":"Mountain Time (US & Canada)","utcOffset":"-25200","preferredUsername":"Mobanu","languages":["en"],"location":{"objectType":"place","displayName":"Crested Butte, Colorado"}},"verb":"post","postedTime":"2012-05-30T22:15:02.000Z","generator":{"displayName":"twitterfeed","link":"http://twitterfeed.com"},"provider":{"objectType":"service","displayName":"Twitter","link":"http://www.twitter.com"},"link":"http://twitter.com/Mobanu/statuses/207958321003638785","body":"Mobanu: Can Exercise Be Bad for You?: Researchers have found evidence that some people who exercise do worse on ... http://t.co/mTsQlNQO","object":{"objectType":"note","id":"object:search.twitter.com,2005:207958321003638785","summary":"Mobanu: Can Exercise Be Bad for You?: Researchers have found evidence that some people who exercise do worse on ... http://t.co/mTsQlNQO","link":"http://twitter.com/Mobanu/statuses/207958321003638785","postedTime":"2012-05-30T22:15:02.000Z"},"twitter_entities":{"urls":[{"display_url":"nyti.ms/KUmmMa","indices":[116,136],"expanded_url":"http://nyti.ms/KUmmMa","url":"http://t.co/mTsQlNQO"}],"hashtags":[],"user_mentions":[]},"gnip":{"language":{"value":"en"},"matching_rules":[{"value":"url_contains: nytimes.com","tag":null}],"klout_score":12,"urls":[{"url":"http://t.co/mTsQlNQO","expanded_url":"http://well.blogs.nytimes.com/2012/05/30/can-exercise-be-bad-for-you/?utm_medium=twitter&utm_source=twitterfeed"}]}}\r\n' json exception: Extra data: line 2 column 1 - line 4 column 1 (char 1891 - 5597) Header Output: HTTP/1.1 200 OK Content-Type: application/json; charset=UTF-8 Vary: Accept-Encoding Date: Wed, 30 May 2012 22:14:48 UTC Connection: close Transfer-Encoding: chunked Content-Encoding: gzip get_stream.py: #!/usr/bin/env python import sys import pycurl import json import pymongo STREAM_URL = "https://stream.test.com:443/accounts/publishers/twitter/streams/track/Dev.json" AUTH = "userid:passwd" DB_HOST = "127.0.0.1" DB_NAME = "stream_test" class StreamReader: def __init__(self): try: self.count = 0 self.buff = "" self.mongo = pymongo.Connection(DB_HOST) self.db = self.mongo[DB_NAME] self.raw_tweets = self.db["raw_tweets_gnip"] self.conn = pycurl.Curl() self.conn.setopt(pycurl.ENCODING, 'gzip') self.conn.setopt(pycurl.URL, STREAM_URL) self.conn.setopt(pycurl.USERPWD, AUTH) self.conn.setopt(pycurl.WRITEFUNCTION, self.on_receive) self.conn.setopt(pycurl.HEADERFUNCTION, self.header_rcvd) while True: self.conn.perform() except Exception as ex: print "error ocurred : %s" % str(ex) def header_rcvd(self, header_data): print header_data def on_receive(self, data): temp_data = data self.buff += data if data.endswith("\r\n") and self.buff.strip(): try: tweet = json.loads(self.buff, encoding = 'UTF-8') self.buff = "" if tweet: try: self.raw_tweets.insert(tweet) except Exception as insert_ex: print "Error inserting tweet: %s" % str(insert_ex) self.count += 1 if self.count % 10 == 0: print "inserted "+str(self.count)+" tweets" except Exception as json_ex: print "json exception: %s" % str(json_ex) print repr(temp_data) stream = StreamReader()

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  • Design Question - how do you break the dependency between classes using an interface?

    - by Seth Spearman
    Hello, I apologize in advance but this will be a long question. I'm stuck. I am trying to learn unit testing, C#, and design patterns - all at once. (Maybe that's my problem.) As such I am reading the Art of Unit Testing (Osherove), and Clean Code (Martin), and Head First Design Patterns (O'Reilly). I am just now beginning to understand delegates and events (which you would see if you were to troll my SO questions of recent). I still don't quite get lambdas. To contextualize all of this I have given myself a learning project I am calling goAlarms. I have an Alarm class with members you'd expect (NextAlarmTime, Name, AlarmGroup, Event Trigger etc.) I wanted the "Timer" of the alarm to be extensible so I created an IAlarmScheduler interface as follows... public interface AlarmScheduler { Dictionary<string,Alarm> AlarmList { get; } void Startup(); void Shutdown(); void AddTrigger(string triggerName, string groupName, Alarm alarm); void RemoveTrigger(string triggerName); void PauseTrigger(string triggerName); void ResumeTrigger(string triggerName); void PauseTriggerGroup(string groupName); void ResumeTriggerGroup(string groupName); void SetSnoozeTrigger(string triggerName, int duration); void SetNextOccurrence (string triggerName, DateTime nextOccurrence); } This IAlarmScheduler interface define a component that will RAISE an alarm (Trigger) which will bubble up to my Alarm class and raise the Trigger Event of the alarm itself. It is essentially the "Timer" component. I have found that the Quartz.net component is perfectly suited for this so I have created a QuartzAlarmScheduler class which implements IAlarmScheduler. All that is fine. My problem is that the Alarm class is abstract and I want to create a lot of different KINDS of alarm. For example, I already have a Heartbeat alarm (triggered every (int) interval of minutes), AppointmentAlarm (triggered on set date and time), Daily Alarm (triggered every day at X) and perhaps others. And Quartz.NET is perfectly suited to handle this. My problem is a design problem. I want to be able to instantiate an alarm of any kind without my Alarm class (or any derived classes) knowing anything about Quartz. The problem is that Quartz has awesome factories that return just the right setup for the Triggers that will be needed by my Alarm classes. So, for example, I can get a Quartz trigger by using TriggerUtils.MakeMinutelyTrigger to create a trigger for the heartbeat alarm described above. Or TriggerUtils.MakeDailyTrigger for the daily alarm. I guess I could sum it up this way. Indirectly or directly I want my alarm classes to be able to consume the TriggerUtils.Make* classes without knowing anything about them. I know that is a contradiction, but that is why I am asking the question. I thought about putting a delegate field into the alarm which would be assigned one of these Make method but by doing that I am creating a hard dependency between alarm and Quartz which I want to avoid for both unit testing purposes and design purposes. I thought of using a switch for the type in QuartzAlarmScheduler per here but I know it is bad design and I am trying to learn good design. If I may editorialize a bit. I've decided that coding (predefined) classes is easy. Design is HARD...in fact, really hard and I am really fighting feeling stupid right now. I guess I want to know if you really smart people took a while to really understand and master this stuff or should I feel stupid (as I do) because I haven't grasped it better in the couple of weeks/months I have been studying. You guys are awesome and thanks in advance for your answers. Seth

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  • Duplication of menu items with ViewPager and Fragments

    - by Julian
    I'm building an Android Application (minimum SDK Level 10, Gingerbread 2.3.3) with some Fragments in a ViewPager. I'm using ActionBarSherlock to create an ActionBar and android-viewpagertabs to add tabs to the ViewPager just like in the Market client. I have one global menu item that I want to be shown on every tab/fragment. On the first of the three tabs I want to have two additional menu items. But now two strange things happen: First if I start the app, everything seems to be fine, I can see all three menu items on the first page and only one item if i swipe to the second and third tab. But if I swipe back to the second tab from the third one, I can see all three items again which shouldn't happen. If I swipe back to the first and then again to the second tab, everything is fine again. The other strange thing is that every time I rotate the device, the menu items from the fragment are added again, even though they are already in the menu. Code of the FragmentActivity that displays the ViewPager and its tabs: public class MainActivity extends FragmentActivity { public static final String TAG = "MainActivity"; private ActionBar actionBar; private Adapter adapter; private ViewPager viewPager; private ViewPagerTabs tabs; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.volksempfaenger); actionBar = getSupportActionBar(); adapter = new Adapter(getSupportFragmentManager()); adapter.addFragment(getString(R.string.title_tab_subscriptions), SubscriptionGridFragment.class); // adding more fragments here viewPager = (ViewPager) findViewById(R.id.viewpager); viewPager.setAdapter(adapter); tabs = (ViewPagerTabs) findViewById(R.id.tabs); tabs.setViewPager(viewPager); } public static class Adapter extends FragmentPagerAdapter implements ViewPagerTabProvider { private FragmentManager fragmentManager; private ArrayList<Class<? extends Fragment>> fragments; private ArrayList<String> titles; public Adapter(FragmentManager fm) { super(fm); fragmentManager = fm; fragments = new ArrayList<Class<? extends Fragment>>(); titles = new ArrayList<String>(); } public void addFragment(String title, Class<? extends Fragment> fragment) { titles.add(title); fragments.add(fragment); } @Override public int getCount() { return fragments.size(); } public String getTitle(int position) { return titles.get(position); } @Override public Fragment getItem(int position) { try { return fragments.get(position).newInstance(); } catch (InstantiationException e) { Log.wtf(TAG, e); } catch (IllegalAccessException e) { Log.wtf(TAG, e); } return null; } @Override public Object instantiateItem(View container, int position) { FragmentTransaction fragmentTransaction = fragmentManager .beginTransaction(); Fragment f = getItem(position); fragmentTransaction.add(container.getId(), f); fragmentTransaction.commit(); return f; } } @Override public boolean onCreateOptionsMenu(Menu menu) { BaseActivity.addGlobalMenu(this, menu); return true; } @Override public boolean onOptionsItemSelected(MenuItem item) { return BaseActivity.handleGlobalMenu(this, item); } } Code of the fragment that shall have its own menu items: public class SubscriptionGridFragment extends Fragment { private GridView subscriptionList; private SubscriptionListAdapter adapter; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setHasOptionsMenu(true); } // ... @Override public void onCreateOptionsMenu(Menu menu, MenuInflater inflater) { inflater.inflate(R.menu.subscription_list, menu); } @Override public boolean onOptionsItemSelected(MenuItem item) { // ... } }

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  • Input not cleared.

    - by SoulBeaver
    As the question says, for some reason my program is not flushing the input or using my variables in ways that I cannot identify at the moment. This is for a homework project that I've gone beyond what I had to do for it, now I just want the program to actually work :P Details to make the finding easier: The program executes flawlessly on the first run through. All throws work, only the proper values( n 0 ) are accepted and turned into binary. As soon as I enter my terminate input, the program goes into a loop and only asks for the termiante again like so: When I run this program on Netbeans on my Linux Laptop, the program crashes after I input the terminate value. On Visual C++ on Windows it goes into the loop like just described. In the code I have tried to clear every stream and initialze every variable new as the program restarts, but to no avail. I just can't see my mistake. I believe the error to lie in either the main function: int main( void ) { vector<int> store; int terminate = 1; do { int num = 0; string input = ""; if( cin.fail() ) { cin.clear(); cin.ignore( numeric_limits<streamsize>::max(), '\n' ); } cout << "Please enter a natural number." << endl; readLine( input, num ); cout << "\nThank you. Number is being processed..." << endl; workNum( num, store ); line; cout << "Go again? 0 to terminate." << endl; cin >> terminate // No checking yet, just want it to work! cin.clear(); }while( terminate ); cin.get(); return 0; } or in the function that reads the number: void readLine( string &input, int &num ) { int buf = 1; stringstream ss; vec_sz size; if( ss.fail() ) { ss.clear(); ss.ignore( numeric_limits<streamsize>::max(), '\n' ); } if( getline( cin, input ) ) { size = input.size(); for( int loop = 0; loop < size; ++loop ) if( isalpha( input[loop] ) ) throw domain_error( "Invalid Input." ); ss << input; ss >> buf; if( buf <= 0 ) throw domain_error( "Invalid Input." ); num = buf; ss.clear(); } }

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  • One letter game problem?

    - by Alex K
    Recently at a job interview I was given the following problem: Write a script capable of running on the command line as python It should take in two words on the command line (or optionally if you'd prefer it can query the user to supply the two words via the console). Given those two words: a. Ensure they are of equal length b. Ensure they are both words present in the dictionary of valid words in the English language that you downloaded. If so compute whether you can reach the second word from the first by a series of steps as follows a. You can change one letter at a time b. Each time you change a letter the resulting word must also exist in the dictionary c. You cannot add or remove letters If the two words are reachable, the script should print out the path which leads as a single, shortest path from one word to the other. You can /usr/share/dict/words for your dictionary of words. My solution consisted of using breadth first search to find a shortest path between two words. But apparently that wasn't good enough to get the job :( Would you guys know what I could have done wrong? Thank you so much. import collections import functools import re def time_func(func): import time def wrapper(*args, **kwargs): start = time.time() res = func(*args, **kwargs) timed = time.time() - start setattr(wrapper, 'time_taken', timed) return res functools.update_wrapper(wrapper, func) return wrapper class OneLetterGame: def __init__(self, dict_path): self.dict_path = dict_path self.words = set() def run(self, start_word, end_word): '''Runs the one letter game with the given start and end words. ''' assert len(start_word) == len(end_word), \ 'Start word and end word must of the same length.' self.read_dict(len(start_word)) path = self.shortest_path(start_word, end_word) if not path: print 'There is no path between %s and %s (took %.2f sec.)' % ( start_word, end_word, find_shortest_path.time_taken) else: print 'The shortest path (found in %.2f sec.) is:\n=> %s' % ( self.shortest_path.time_taken, ' -- '.join(path)) def _bfs(self, start): '''Implementation of breadth first search as a generator. The portion of the graph to explore is given on demand using get_neighboors. Care was taken so that a vertex / node is explored only once. ''' queue = collections.deque([(None, start)]) inqueue = set([start]) while queue: parent, node = queue.popleft() yield parent, node new = set(self.get_neighbours(node)) - inqueue inqueue = inqueue | new queue.extend([(node, child) for child in new]) @time_func def shortest_path(self, start, end): '''Returns the shortest path from start to end using bfs. ''' assert start in self.words, 'Start word not in dictionnary.' assert end in self.words, 'End word not in dictionnary.' paths = {None: []} for parent, child in self._bfs(start): paths[child] = paths[parent] + [child] if child == end: return paths[child] return None def get_neighbours(self, word): '''Gets every word one letter away from the a given word. We do not keep these words in memory because bfs accesses a given vertex only once. ''' neighbours = [] p_word = ['^' + word[0:i] + '\w' + word[i+1:] + '$' for i, w in enumerate(word)] p_word = '|'.join(p_word) for w in self.words: if w != word and re.match(p_word, w, re.I|re.U): neighbours += [w] return neighbours def read_dict(self, size): '''Loads every word of a specific size from the dictionnary into memory. ''' for l in open(self.dict_path): l = l.decode('latin-1').strip().lower() if len(l) == size: self.words.add(l) if __name__ == '__main__': import sys if len(sys.argv) not in [3, 4]: print 'Usage: python one_letter_game.py start_word end_word' else: g = OneLetterGame(dict_path = '/usr/share/dict/words') try: g.run(*sys.argv[1:]) except AssertionError, e: print e

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  • Java Applet Deployment, ClassNotFoundException (primary class)

    - by Matt
    This is driving me up the wall. I have checked and rechecked spelling and paths. I have tried just about every combination of paths, including relative, absolute, and full http paths. I continue to get the following error when trying to load a Java applet: java.lang.ClassNotFoundException: AppletClient.class at sun.plugin2.applet.Applet2ClassLoader.findClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at java.lang.ClassLoader.loadClass(Unknown Source) at sun.plugin2.applet.Plugin2ClassLoader.loadCode(Unknown Source) at sun.plugin2.applet.Plugin2Manager.createApplet(Unknown Source) at sun.plugin2.applet.Plugin2Manager$AppletExecutionRunnable.run(Unknown Source) at java.lang.Thread.run(Unknown Source) Exception: java.lang.ClassNotFoundException: AppletClient.class The HTML used to load the applet: <applet width="100" height="100" archive="applet/myapplet.jar, applet/applet_dependency.jar" code="AppletClient.class"> <param value="blahblah" name="username"> <param value="false" name="codebase_lookup"> </applet> The applet is in a relative directory, "applet", from the path of the current page. I have unzipped the jar file and can see AppletClient.class. Also, in the source of the project, it is spelled that way (casing and all). I have tried with/without the parameters. I have changed the names of the archive jars in the applet include tag just to see if I get a different error for bad file names (same error). I have manually done GETs on the jars to make sure the server is responding to the requests (it is). I have tried with and without the codebase tag, with all different varieties of paths (start getting bad "magic number" errors on those). I know that this error sometimes pops up when a dependency fails to load, so it can be misleading, but all dependencies are present, accounted for, and are fetchable via manual GETs. Between each and every attempt I always clear my cache in FireFox. These problems are reproduced in IE8 and Chrome as well. Per my Java Console from the browser, I am running Java Plug-in 1.6.0_20. This is from the same machine that I develop the applet on, which runs fine via Eclipse. Finally, I kicked on Fiddler2, and I don't see a single request for the jar files anywhere The host site is running from my Visual Studio debugger, so it's running on localhost. But I see the requests for all the other resources on Fiddler. Just... no Jars. ANYWHERE. I clear the log, cleared my browser cache, and did a ctrl-R refresh. And still, not a single Jar request on the Fiddler log. I even did a delayed write (with JS) of the applet tag after the page loaded, once all the Fiddler activity slowed down. The element gets written to the document (and I can see the 100x100 Java error window), but not a single request shows up on Fiddler. Any suggestions, before I go crawl into the corner and cry myself to sleep? EDIT: From the Java console, if I hit "l" (el) to "dump classloader list", I see something that looks like this: Live entry: key=http://localhost:55446/BaseWebSite/,http://localhost:55446/BaseWebSite/applet/myappliet.jar, http://localhost:55446/BaseWebSite/applet/applet_dependency.jar, refCount=1, threadGroup=sun.plugin2.applet.Applet2ThreadGroup[name=http://localhost:55446/BaseWebSite/-threadGroup,maxpri=4]

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  • Best way to get back to using the power of lxml after having to use a regex to find something in an

    - by PyNEwbie
    I am trying to rip some text out of a large number of html documents (numbers in the hundreds of thousands). The documents are really forms but they are prepared by a very large group of different organizations so there is significant variation in how they create the document. For example, the documents are divided into chapters. I might want to extract the contents of Chapter 5 from every document so I can analyze the content of the chapter. Initially I thought this would be easy but it turns out that the authors might use a set of non-nested tables throughout the document to hold the content so that Chapter n could be displayed using td tags inside a table. Or they might use other elements such as p tags H tags, div tags or any other block level element. After trying repeatedly to use lxml to help me identify the beginning and end of each chapter I have determined that it is a lot cleaner to use a regular expression because in every case, no matter what the enclosing html element is the chapter label is always in the form of >Chapter # It is a little more complicated in that there might be some white space or non-breaking space represented in different ways (  or   or just spaces). Nonetheless it was trivial to write a regular expression to identify the beginning of each section. (The beginning of one section is the end of the previous section.) But now I want to use lxml to get the text out. My thought is that I have really no choice but to walk along my string to find the close tag for the element that encloses the text I am using to find the relevant section. That is here is one example where the element holding the Chapter name is a div <div style="DISPLAY: block; MARGIN-LEFT: 0pt; TEXT-INDENT: 0pt; MARGIN-RIGHT: 0pt" align="left"><font style="DISPLAY: inline; FONT-WEIGHT: bold; FONT-SIZE: 10pt; FONT-FAMILY: Times New Roman">Chapter 1.&#160;&#160;&#160;Our Beginnings.</font></div> So I am imagining that I would begin at the location where I found the match for chapter 1 and set up a regular expressions to find the next </div|</td|</p|</h1 . . . So at this point I have identified the type of element holding my chapter heading I can use the same logic to find all of the text that is within that element that is set up a regular expression to help me mark from >Chapter 1.&#160;&#160;&#160;Our Beginnings.< So I have identified where my Chapter 1 begins I can do the same for chapter 2 (which is where Chapter 1 ends) Now I am imagining that I am going to snip the document beginning at the opening of the element that I identified as the element the indicates where chapter 1 begins and ending just before the opening of the element that I identified as the element that indicates where Chapter 2 begins. The string that I have identified will then be fed to lxml to use its power to get the content. I am going to all of this trouble because I have read over and over - never use a regular expression to extract content from html documents and I have not hit on a way to be as accurate with lxml to identify the starting and ending locations for the text I want to extract. For example, I can never be certain that the subtitle of Chapter 1 is Our Beginnings it could be Our Red Canary. Let me say that I spent two solid days trying with lxml to be confident that I had the beginning and ending elements and I could only be accurate <60% of the time but a very short regular expression has given me better than 95% success. I have a tendency to make things more complicated than necessary so I am wondering if anyone has seen or solved a similar problems and if they had an approach (not the details mind you) that they would like to offer.

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  • what's wrong with my producer-consumer queue design?

    - by toasteroven
    I'm starting with the C# code example here. I'm trying to adapt it for a couple reasons: 1) in my scenario, all tasks will be put in the queue up-front before consumers will start, and 2) I wanted to abstract the worker into a separate class instead of having raw Thread members within the WorkerQueue class. My queue doesn't seem to dispose of itself though, it just hangs, and when I break in Visual Studio it's stuck on the _th.Join() line for WorkerThread #1. Also, is there a better way to organize this? Something about exposing the WaitOne() and Join() methods seems wrong, but I couldn't think of an appropriate way to let the WorkerThread interact with the queue. Also, an aside - if I call q.Start(#) at the top of the using block, only some of the threads every kick in (e.g. threads 1, 2, and 8 process every task). Why is this? Is it a race condition of some sort, or am I doing something wrong? using System; using System.Collections.Generic; using System.Text; using System.Messaging; using System.Threading; using System.Linq; namespace QueueTest { class Program { static void Main(string[] args) { using (WorkQueue q = new WorkQueue()) { q.Finished += new Action(delegate { Console.WriteLine("All jobs finished"); }); Random r = new Random(); foreach (int i in Enumerable.Range(1, 10)) q.Enqueue(r.Next(100, 500)); Console.WriteLine("All jobs queued"); q.Start(8); } } } class WorkQueue : IDisposable { private Queue _jobs = new Queue(); private int _job_count; private EventWaitHandle _wh = new AutoResetEvent(false); private object _lock = new object(); private List _th; public event Action Finished; public WorkQueue() { } public void Start(int num_threads) { _job_count = _jobs.Count; _th = new List(num_threads); foreach (int i in Enumerable.Range(1, num_threads)) { _th.Add(new WorkerThread(i, this)); _th[_th.Count - 1].JobFinished += new Action(WorkQueue_JobFinished); } } void WorkQueue_JobFinished(int obj) { lock (_lock) { _job_count--; if (_job_count == 0 && Finished != null) Finished(); } } public void Enqueue(int job) { lock (_lock) _jobs.Enqueue(job); _wh.Set(); } public void Dispose() { Enqueue(Int32.MinValue); _th.ForEach(th = th.Join()); _wh.Close(); } public int GetNextJob() { lock (_lock) { if (_jobs.Count 0) return _jobs.Dequeue(); else return Int32.MinValue; } } public void WaitOne() { _wh.WaitOne(); } } class WorkerThread { private Thread _th; private WorkQueue _q; private int _i; public event Action JobFinished; public WorkerThread(int i, WorkQueue q) { _i = i; _q = q; _th = new Thread(DoWork); _th.Start(); } public void Join() { _th.Join(); } private void DoWork() { while (true) { int job = _q.GetNextJob(); if (job != Int32.MinValue) { Console.WriteLine("Thread {0} Got job {1}", _i, job); Thread.Sleep(job * 10); // in reality would to actual work here if (JobFinished != null) JobFinished(job); } else { Console.WriteLine("Thread {0} no job available", _i); _q.WaitOne(); } } } } }

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  • easiest and best way to make a server queue java

    - by houlahan
    i have a server at the moment which makes a new thread for every user connected but after about 6 people are on the server for more than 15 mins it tends to flop and give me java heap out of memory error i have 1 thread that checks with a mysql database every 30 seconds to see if any of the users currently logged on have any new messages. what would be the easiest way to implement a server queue? this is the my main method for my server: public class Server { public static int MaxUsers = 1000; //public static PrintStream[] sessions = new PrintStream[MaxUsers]; public static ObjectOutputStream[] sessions = new ObjectOutputStream[MaxUsers]; public static ObjectInputStream[] ois = new ObjectInputStream[MaxUsers]; private static int port = 6283; public static Connection conn; static Toolkit toolkit; static Timer timer; public static void main(String[] args) { try { conn = (Connection) Mysql.getConnection(); } catch (Exception ex) { Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex); } System.out.println("****************************************************"); System.out.println("* *"); System.out.println("* Cloud Server *"); System.out.println("* ©2010 *"); System.out.println("* *"); System.out.println("* Luke Houlahan *"); System.out.println("* *"); System.out.println("* Server Online *"); System.out.println("* Listening On Port " + port + " *"); System.out.println("* *"); System.out.println("****************************************************"); System.out.println(""); mailChecker(); try { int i; ServerSocket s = new ServerSocket(port); for (i = 0; i < MaxUsers; ++i) { sessions[i] = null; } while (true) { try { Socket incoming = s.accept(); boolean found = false; int numusers = 0; int usernum = -1; synchronized (sessions) { for (i = 0; i < MaxUsers; ++i) { if (sessions[i] == null) { if (!found) { sessions[i] = new ObjectOutputStream(incoming.getOutputStream()); ois[i]= new ObjectInputStream(incoming.getInputStream()); new SocketHandler(incoming, i).start(); found = true; usernum = i; } } else { numusers++; } } if (!found) { ObjectOutputStream temp = new ObjectOutputStream(incoming.getOutputStream()); Person tempperson = new Person(); tempperson.setFlagField(100); temp.writeObject(tempperson); temp.flush(); temp = null; tempperson = null; incoming.close(); } else { } } } catch (IOException ex) { System.out.println(1); Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex); } } } catch (IOException ex) { System.out.println(2); Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex); } } public static void mailChecker() { toolkit = Toolkit.getDefaultToolkit(); timer = new Timer(); timer.schedule(new mailCheck(), 0, 10 * 1000); } }

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  • Trouble with datasource not being called from viewWillAppear

    - by user278859
    A little background. I have taken GCCalendar which only works in portrait orientation and extended it to work in landscape similar to how the iPhone's Calendar app works. I did this by duplicating the main view class and modifying it to work in landscape. So when the phone is in portrait orientation the CGCalendar is instantiated from the apps main view controller using the original portrait view class and when in landscape orientation using the new modified landscape view class. Most of the other classes in GCCalendar are shared without modification. A few had to be duplicated as well. I got it all working great except for an issue with the datasource. The datasource is called when the calendar is first loaded and each time the user changes the dates being viewed. Problem is I can't get the datasource call to work on the first call. I am stumped as it works fine in portrait orientation and I cannot find any difference between the 2 versions. Following is some of the code that shows how it gets to the datasource call the first time. Subsequent calls removes all the calendar subviews and instantiates them again with the new dates. The duplicated landscape class names end in LS. Otherwise as you can see they are identical. Does anyone has any idea of where else I might look to resolve this issue? Thanks, John -------------------------------- //App main view controller - (void)showLandscapeCalendar { GCCalendarLandscapeView *calendar = [[[GCCalendarLandscapeView alloc] init] autorelease]; calendar.dataSource = self; calendar.delegate = self; navigationController = [[UINavigationController alloc] initWithRootViewController:calendar]; [self presentModalViewController:navigationController animated:YES]; } - (void)showPortraitCalendar { GCCalendarPortraitView *calendar = [[[GCCalendarPortraitView alloc] init] autorelease]; calendar.dataSource = self; calendar.delegate = self; navigationController = [[UINavigationController alloc] initWithRootViewController:calendar]; [self presentModalViewController:navigationController animated:YES]; } - (NSArray *)calendarEventsForDate:(NSDate *)date{ //build and return the events array //this is the protocol datasource method //It is supposed to run every time the date changes in the calendar } ------------------------------- // GCCalendarLandscapeView... - (void)viewWillAppear:(BOOL)animated { [super viewWillAppear:animated]; if (viewDirty) { [self reloadDayAnimated:NO context:NULL]; viewDirty = NO; } viewVisible = YES; } - (void)reloadDayAnimated:(BOOL)animated context:(void *)context { GCCalendarDayViewLS *nextDayView = [[GCCalendarDayViewLS alloc] initWithCalendarView:self]; } ------------------------------- //GCCalendarDayViewLS - (id)initWithCalendarView:(GCCalendarView *)view { if (self = [super init]) { dataSource = view.dataSource; } return self; } - (void)reloadData { //** first time through the dataSource method does not run events = [dataSource calendarEventsForDate:date]; } ------------------------------- // GCCalendarPortraitView... - (void)viewWillAppear:(BOOL)animated { [super viewWillAppear:animated]; if (viewDirty) { [self reloadDayAnimated:NO context:NULL]; viewDirty = NO; } viewVisible = YES; } - (void)reloadDayAnimated:(BOOL)animated context:(void *)context { GCCalendarDayView *nextDayView = [[GCCalendarDayView alloc] initWithCalendarView:self]; } ------------------------------- //GCCalendarDayView - (id)initWithCalendarView:(GCCalendarView *)view { if (self = [super init]) { dataSource = view.dataSource; } return self; } - (void)reloadData { **//this one works every time events = [dataSource calendarEventsForDate:date]; }

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  • Php template caching design

    - by Thomas
    Hello to all, I want to include caching in my app design. Caching templates for starters. The design I have used so far is very modular. I have created an ORM implementation for all my tables and each table is represented by the corresponding class. All the requests are handled by one controller which routes them to the appropriate webmethod functions. I am using a template class for handling UI parts. What I have in mind for caching includes the implementation of a separate Cache class for handling caching with the flexibility to either store in files, apc or memcache. Right now I am testing with file caching. Some thoughts Should I include the logic of checking for cached versions in the Template class or in the webmethods which handle the incoming requests and which eventually call the Template class. In the first case, things are pretty simple as I will not have to change anything more than pass the template class an extra argument (whether to load from cache or not). In the second case however, I am thinking of checking for a cached version immediately in the webmethod and if found return it. This will save all the processing done until the logic reaches the template (first case senario). Both senarios however, rely on an accurate mechanism of invalidating caches, which brings as to Invalidating caches As I see it (and you can add your input freely) a template cached file, becomes invalidate if: a. the expiration set, is reached. b. the template file itself is updated (ie by the developer when adding a new line) c. the webmethod that handles the request changes (ie the developer adds/deletes something in the code) d. content coming from the db and ending in the template file is modified I am thinking of storing a json encoded array inside the cached file. The first value will be the expiration timestamp of the cache. The second value will be the modification time of the php file with the code handling the request (to cope with option c above) The third will be the content itself The validation process I am considering, according to the above senarios, is: a. If the expiration of the cached file (stored in the array) is reached, delete the cache file b. if the cached file's mod time is smaller than the template's skeleton file mod time, delete the cached file c. if the mod time of the php file is greated than the one stored in the cache, delete the cached file. d. This is tricky. In the ORM implementation I ahve added event handlers (which fire when adding, updating, deleting objects). I could delete the cache file every time an object thatprovides content to the template, is modified. The problem is how to keep track which cached files correpond to each schema object. Take this example, a user has his shortprofile page and a full profile page (2 templates) These templates can be cached. Now, every time the user modifies his profile, the event handler would need to know which templates or cached files correspond to the User, so that these files can be deleted. I could store them in the db but I am looking for a beter approach

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  • Yet another bug of JSF?

    - by Nitesh Panchal
    Hello, Again i see that the @PostConstruct is firing every time even though no binding attribute is used. See this code :- <?xml version='1.0' encoding='UTF-8' ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:h="http://java.sun.com/jsf/html" xmlns:ui="http://java.sun.com/jsf/facelets" xmlns:c="http://java.sun.com/jsp/jstl/core"> <h:head> <title>Facelet Title</title> </h:head> <h:body> <h:form> <c:forEach var="item" items="#{TestBean.listItems}"> <h:outputText value="#{item}"/> </c:forEach> <h:commandButton value="Click" actionListener="#{TestBean.actionListener}"/> </h:form> </h:body> </html> And this is the simplest possible bean in JSF :- package managedBeans; import java.io.Serializable; import java.util.ArrayList; import java.util.List; import javax.annotation.PostConstruct; import javax.faces.bean.ManagedBean; import javax.faces.bean.ViewScoped; @ManagedBean(name="TestBean") @ViewScoped public class TestBean implements Serializable { private List<String> listItems; public List<String> getListItems() { return listItems; } public void setListItems(List<String> listItems) { this.listItems = listItems; } public TestBean() { } @PostConstruct public void init(){ System.out.println("Post Construct fired!"); listItems = new ArrayList<String>(); listItems.add("Mango"); listItems.add("Apple"); listItems.add("Banana"); } public void actionListener(){ System.out.println("Action Listener fired!"); } } Do you see any behaviour that should cause postconstruct callback to fire each time? I think JSF 2.0 is highly unstable. If it has to fire PostConstruct each and every time what purpose does @ViewScoped serve. Why not to use @RequestScoped only? I thought i have made some mistake in my application. But when i created this simplest possible in JSF, i still get this error. Am i not understanding the scopes of JSF? or are they not testing it properly? Further, if you remove c:forEach and replace it with ui:repeat, then it works fine. Waiting for replies to confirm whether it is bug or it is intentional to stop the programmers from using jstl?

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  • Decentralized synchronized secure data storage

    - by Alberich
    Introduction Hi, I am going to ask a question which seems utopic for me, but I need to know if there is a way to achieve what I need. And if not, I need to know why not. The idea Suppose I have a database structure, in MySql. I want to create some solution to allow anyone (no matter who, no matter where) to have a synchronized copy (updated clone) of this database (with its content) Well, and it is not going to be just one synchronized copy, it could (and should) be a multiple replication (supposing the basic, this means, for example, ten copies all over the world) And, the most important thing: It must be secure. By secure I mean only real-accepted transactions will be synchronized with all the others (no matter how many) database copies/clones. Note: Since it would be quite difficult to make the synchronization in real-time, I will design everything to make this feature dispensable. So it is not required. My auto-suggestion This is how I am thinking to manage it: Time identifiers and Updates checking: Every action (insert, update, delete...) will be stored as the action instruction itself, associated to the time identifier. [I think better than a DATETIME field, it'll be an INT one, with the number of miliseconds passed from 1st january 2013 on, for example]. So each copy is going to ask to the "neighbour copy" for new actions done since last update, and execute them after checking they are allowed. Problem 1: the "neighbour copy" could be outdated too. Solution 1: do not ask just one neighbour, create a random list with some of the copies/clones and ask them for news (I could avoid the list and ask ALL the clones for updates, but this will be inefficient if clones number ascends too much). Problem 2: Real-time global synchronization is not active. What if... Someone at CLONE_ENTERPRISING inserts a row into TABLE. ... this row goes to every clone ... Someone at CLONE_FIXEMALL deletes this row. ... and at the same time, somewhere in an outdated clone ... Someone at CLONE_DROPOUT edits this row (now inexistent at the other clones) Solution 2: easy stuff, force a GLOBAL synchronization before doing any new "depending-on-third-data action" (edit, for example). This global synch. will be unnecessary when making an INSERT, for instance. Note: Well, someone could have some fun, and make the same insert in two clones... since they're not getting updated in real-time, this row will exist twice. But, it's the same as when we have one single database, in some needed cases we check if there is an existing same-row before doing the final action. Not a problem. Problem 3: It is possible to edit the code and do not filter actions, so someone could spread instructions to delete everything, or just make some trolling activity. This is not a problem, since good clones will always be somewhere. Those who got bad won't interest anymore. I really appreciate if you read. I know this is not the perfect solution, it has possibly hundred of holes, but it is my basic start. I will now appreciate anything you can teach me now. Thanks a lot. PS.: It could be that all this I am trying already exists and has its own name. Sorry for asking then (I'd anyway thank this name, if it exists)

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  • Internet Explorer background-color hover problem

    - by danilo
    I have a strange Problem with table formating using IE 7. My table looks like this: In IE, when using border-collapse, the borders don't get displayed correctly. That's why I used this fix: .table-vmlist td { border-top: 1px solid black; } td.col-vm-status, tr.row-details td { border-left: 1px solid black; } td.col-vm-rdp, tr.row-details td { border-right: 1px solid black; } .table-vmlist { border-bottom: 1px solid black;} When hovering over the row, it gets highlighted with CSS: .table-vmlist tr.row-vm { background-color: #A4C3EF; } .table-vmlist tr.row-vm:hover { background-color: #91BAEF; } Now, in IE 7, when moving the mouse from the top to the bottom of the list, every row gets highlighted correctly and no problems happen. But if I move my mouse pointer from the bottom of the list to the top, every second row seems to loose the border. Can someone explain what the problem is, and how to solve it? This is my markup: <tr class="row-vm"> <td class="col-vm-status status-1"><img title="Host Down" alt="Down" src="/Technik/vm-management/img/hoststatus_1.png"></td> <td class="col-vm-name">V1-VM-1</td> <td class="col-vm-stati"> <img title="Ping" alt="Ping status" src="/Technik/vm-management/img/servicestatus_3.png"> <img title="CPU" alt="CPU status" src="/Technik/vm-management/img/servicestatus_3.png"> <img title="RAM" alt="RAM status" src="/Technik/vm-management/img/servicestatus_3.png"> <img title="C:\ Diskspace" alt="Disk space status" src="/Technik/vm-management/img/servicestatus_3.png"> </td> <td class="col-vm-owner">kus</td> <td class="col-vm-purpose">Citrix Testserver</td> <td class="col-vm-ip">-</td> <td class="col-vm-uptime">-</td> <td class="col-vm-rdp">&nbsp;</td> </tr> And the CSS: /* VM-Tabelle formatieren */ .table-vmlist { border-collapse: collapse; } .table-vmlist tr { border: 1px solid black; } .table-vmlist tr.row-header { border: none; } .table-vmlist tr.row-vm { background-color: #A4C3EF; } .table-vmlist tr.row-vm:hover { background-color: #91BAEF; } .table-vmlist th { text-align: left; } .table-vmlist td { } .table-vmlist th, table td { padding: 2px 0px; } /* Spaltenbreite der VM-Tabelle festlegen */ .table-vmlist #col-status { width: 25px; } .table-vmlist #col-stati { width: 90px; } .table-vmlist #col-owner { width: 90px; } .table-vmlist #col-ip { width: 100px; } .table-vmlist #col-uptime { width: 70px; } .table-vmlist #col-rdp { width: 25px; } .table-vmlist tr.row-details td { padding: 0px 10px; } /* Kein Rahmen um verlinkte Bilder */ a img { border-width: 0px; } /* Für Einschaltknopf Hand-Cursor anstatt normalen Pfeil anzeigen */ td.status-1 img { cursor: pointer; } img.ajax-loader { margin-left: 2px; } IE fix: .table-vmlist td { border-top: 1px solid black; } td.col-vm-status, tr.row-details td { border-left: 1px solid black; } td.col-vm-rdp, tr.row-details td { border-right: 1px solid black; } .table-vmlist { border-bottom: 1px solid black;}

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  • Where should I create my DbCommand instances?

    - by Domenic
    I seemingly have two choices: Make my class implement IDisposable. Create my DbCommand instances as private readonly fields, and in the constructor, add the parameters that they use. Whenever I want to write to the database, bind to these parameters (reusing the same command instances), set the Connection and Transaction properties, then call ExecuteNonQuery. In the Dispose method, call Dispose on each of these fields. Each time I want to write to the database, write using(var cmd = new DbCommand("...", connection, transaction)) around the usage of the command, and add parameters and bind to them every time as well, before calling ExecuteNonQuery. I assume I don't need a new command for each query, just a new command for each time I open the database (right?). Both of these seem somewhat inelegant and possibly incorrect. For #1, it is annoying for my users that I this class is now IDisposable just because I have used a few DbCommands (which should be an implementation detail that they don't care about). I also am somewhat suspicious that keeping a DbCommand instance around might inadvertently lock the database or something? For #2, it feels like I'm doing a lot of work (in terms of .NET objects) each time I want to write to the database, especially with the parameter-adding. It seems like I create the same object every time, which just feels like bad practice. For reference, here is my current code, using #1: using System; using System.Net; using System.Data.SQLite; public class Class1 : IDisposable { private readonly SQLiteCommand updateCookie = new SQLiteCommand("UPDATE moz_cookies SET value = @value, expiry = @expiry, isSecure = @isSecure, isHttpOnly = @isHttpOnly WHERE name = @name AND host = @host AND path = @path"); public Class1() { this.updateCookie.Parameters.AddRange(new[] { new SQLiteParameter("@name"), new SQLiteParameter("@value"), new SQLiteParameter("@host"), new SQLiteParameter("@path"), new SQLiteParameter("@expiry"), new SQLiteParameter("@isSecure"), new SQLiteParameter("@isHttpOnly") }); } private static void BindDbCommandToMozillaCookie(DbCommand command, Cookie cookie) { long expiresSeconds = (long)cookie.Expires.TotalSeconds; command.Parameters["@name"].Value = cookie.Name; command.Parameters["@value"].Value = cookie.Value; command.Parameters["@host"].Value = cookie.Domain; command.Parameters["@path"].Value = cookie.Path; command.Parameters["@expiry"].Value = expiresSeconds; command.Parameters["@isSecure"].Value = cookie.Secure; command.Parameters["@isHttpOnly"].Value = cookie.HttpOnly; } public void WriteCurrentCookiesToMozillaBasedBrowserSqlite(string databaseFilename) { using (SQLiteConnection connection = new SQLiteConnection("Data Source=" + databaseFilename)) { connection.Open(); using (SQLiteTransaction transaction = connection.BeginTransaction()) { this.updateCookie.Connection = connection; this.updateCookie.Transaction = transaction; foreach (Cookie cookie in SomeOtherClass.GetCookieArray()) { Class1.BindDbCommandToMozillaCookie(this.updateCookie, cookie); this.updateCookie.ExecuteNonQuery(); } transaction.Commit(); } } } #region IDisposable implementation protected virtual void Dispose(bool disposing) { if (!this.disposed && disposing) { this.updateCookie.Dispose(); } this.disposed = true; } public void Dispose() { this.Dispose(true); GC.SuppressFinalize(this); } ~Class1() { this.Dispose(false); } private bool disposed; #endregion }

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  • MySQL and INT auto_increment fields

    - by PHPguy
    Hello folks, I'm developing in LAMP (Linux+Apache+MySQL+PHP) since I remember myself. But one question was bugging me for years now. I hope you can help me to find an answer and point me into the right direction. Here is my challenge: Say, we are creating a community website, where we allow our users to register. The MySQL table where we store all users would look then like this: CREATE TABLE `users` ( `uid` int(2) unsigned NOT NULL auto_increment COMMENT 'User ID', `name` varchar(20) NOT NULL, `password` varchar(32) NOT NULL COMMENT 'Password is saved as a 32-bytes hash, never in plain text', `email` varchar(64) NOT NULL, `created` int(11) unsigned NOT NULL default '0' COMMENT 'Timestamp of registration', `updated` int(11) unsigned NOT NULL default '0' COMMENT 'Timestamp of profile update, e.g. change of email', PRIMARY KEY (`uid`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8; So, from this snippet you can see that we have a unique and automatically incrementing for every new user 'uid' field. As on every good and loyal community website we need to provide users with possibility to completely delete their profile if they want to cancel their participation in our community. Here comes my problem. Let's say we have 3 registered users: Alice (uid = 1), Bob (uid = 2) and Chris (uid = 3). Now Bob want to delete his profile and stop using our community. If we delete Bob's profile from the 'users' table then his missing 'uid' will create a gap which will be never filled again. In my opinion it's a huge waste of uid's. I see 3 possible solutions here: 1) Increase the capacity of the 'uid' field in our table from SMALLINT (int(2)) to, for example, BIGINT (int(8)) and ignore the fact that some of the uid's will be wasted. 2) introduce the new field 'is_deleted', which will be used to mark deleted profiles (but keep them in the table, instead of deleting them) to re-utilize their uid's for newly registered users. The table will look then like this: CREATE TABLE `users` ( `uid` int(2) unsigned NOT NULL auto_increment COMMENT 'User ID', `name` varchar(20) NOT NULL, `password` varchar(32) NOT NULL COMMENT 'Password is saved as a 32-bytes hash, never in plain text', `email` varchar(64) NOT NULL, `is_deleted` int(1) unsigned NOT NULL default '0' COMMENT 'If equal to "1" then the profile has been deleted and will be re-used for new registrations', `created` int(11) unsigned NOT NULL default '0' COMMENT 'Timestamp of registration', `updated` int(11) unsigned NOT NULL default '0' COMMENT 'Timestamp of profile update, e.g. change of email', PRIMARY KEY (`uid`) ) ENGINE=MyISAM DEFAULT CHARSET=utf8; 3) Write a script to shift all following user records once a previous record has been deleted. E.g. in our case when Bob (uid = 2) decides to remove his profile, we would replace his record with the record of Chris (uid = 3), so that uid of Chris becomes qual to 2 and mark (is_deleted = '1') the old record of Chris as vacant for the new users. In this case we keep the chronological order of uid's according to the registration time, so that the older users have lower uid's. Please, advice me now which way is the right way to handle the gaps in the auto_increment fields. This is just one example with users, but such cases occur very often in my programming experience. Thanks in advance!

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  • More localized, efficient Lowest Common Ancestor algorithm given multiple binary trees?

    - by mstksg
    I have multiple binary trees stored as an array. In each slot is either nil (or null; pick your language) or a fixed tuple storing two numbers: the indices of the two "children". No node will have only one child -- it's either none or two. Think of each slot as a binary node that only stores pointers to its children, and no inherent value. Take this system of binary trees: 0 1 / \ / \ 2 3 4 5 / \ / \ 6 7 8 9 / \ 10 11 The associated array would be: 0 1 2 3 4 5 6 7 8 9 10 11 [ [2,3] , [4,5] , [6,7] , nil , nil , [8,9] , nil , [10,11] , nil , nil , nil , nil ] I've already written simple functions to find direct parents of nodes (simply by searching from the front until there is a node that contains the child) Furthermore, let us say that at relevant times, both all trees are anywhere between a few to a few thousand levels deep. I'd like to find a function P(m,n) to find the lowest common ancestor of m and n -- to put more formally, the LCA is defined as the "lowest", or deepest node in which have m and n as descendants (children, or children of children, etc.). If there is none, a nil would be a valid return. Some examples, given our given tree: P( 6,11) # => 2 P( 3,10) # => 0 P( 8, 6) # => nil P( 2,11) # => 2 The main method I've been able to find is one that uses an Euler trace, which turns the given tree, with a node A to be the invisible parent of 0 and 1 with a depth of -1, into: A-0-2-6-2-7-10-7-11-7-2-0-3-0-A-1-4-1-5-8-5-9-5-1-A And from that, simply find the node between your given m and n that has the lowest number; For example, to find P(6,11), look for a 6 and an 11 on the trace. The number between them that is the lowest is 2, and that's your answer. If A is in between them, return nil. -- Calculating P(6,11) -- A-0-2-6-2-7-10-7-11-7-2-0-3-0-A-1-4-1-5-8-5-9-5-1-A ^ ^ ^ | | | m lowest n Unfortunately, I do believe that finding the Euler trace of a tree that can be several thousands of levels deep is a bit machine-taxing...and because my tree is constantly being changed throughout the course of the programming, every time I wanted to find the LCA, I'd have to re-calculate the Euler trace and hold it in memory every time. Is there a more memory efficient way, given the framework I'm using? One that maybe iterates upwards? One way I could think of would be the "count" the generation/depth of both nodes, and climb the lowest node until it matched the depth of the highest, and increment both until they find someone similar. But that'd involve climbing up from level, say, 3025, back to 0, twice, to count the generation, and using a terribly inefficient climbing-up algorithm in the first place, and then re-climbing back up. Are there any other better ways?

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