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  • Some web pages (especially Apple documentation) cause heavy CPU usage in Windows IE8

    - by Mark Lutton
    Maybe this belongs in Server Fault instead, but some of you may have noticed this issue (particularly those developing on Mac, using a Windows machine to read the reference material). I posted the same question on a Microsoft forum and got one answer from someone who reproduced the problem, so it's not just my machine. No solution yet. Ever since this month's security updates, I find that many web pages cause the CPU to run at maximum for as long as the web page is visible. This happens in both IE7 and IE8 on at least three different computers (two with Windows XP, one with Vista). Here is one of the pages, running on XP with IE 8: http://learning2code.blogspot.com/2007/11/update-using-subversion-with-xcode-3.html Here is one that does it in Vista with IE8: http://developer.apple.com/iphone/library/documentation/Cocoa/Reference/Foundation/Classes/NSString_Class/Reference/NSString.html You can leave the page open for hours and the CPU is still at high usage. This doesn't happen every time. It is not always reproduceable. Sometimes it is OK the second or third time it loads. In IE7 the high usage is in ieframe.dll, version 7.0.6000.16890. In IE8 the high usage is in iertutil.dll, version 8.0.6001.18806.

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  • In my cakephp project the save function is not working?

    - by Faheem
    My controller action is: function add() { if (!empty($this-data)) { $this-Customer-create(); if ($this-Customer-save($this-data)) { $this-Session-setFlash('A new Customer has been added'); $this-redirect(array('action'='index')); } else { $this-Session-setFlash('The customer cannot be added this time. Try again later.'); $this-redirect(array('action'='index')); } } } My model is: class Customer extends AppModel { var $name = 'Customer'; var $validate = array( 'name' = array( 'length'= array( 'rule' = array('between', 4,50), 'message' = 'Name must be minimum 4 and maximum 50 characters long.' ), 'checkUnique'= array( 'rule' = 'isUnique', 'message' = 'This Name is already registered' ) )); and this is my view: create('Customer',array('action'='add'));? input('Customer.name'); echo $form-input('Customer.balance',array('type'='hidden','default'=0)); ? end('Submit');? every time I submit the form it splashes: The customer cannot be added this time. Try again later.

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  • IBM Worklight v6.1.0.1 : Error when using Ionic Framework with Worklight and run on IOS environment

    - by NickNguyen
    I have created demo app using Ionic with Worklight and it worked on Android but got error on IOS, when i used mobile browser simulator and debugged on IOS environment, i got the folowing error message: Uncaught InvalidCharacterError: Failed to execute 'add' on 'DOMTokenList': The token provided ('platform-ios - iphone') contains HTML space characters, which are not valid in tokens. I just add Ionic files in index.html: <!DOCTYPE HTML> <html> <head> <meta charset="UTF-8"> <title>index</title> <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0, user-scalable=0"> <link rel="shortcut icon" href="images/favicon.png"> <link rel="apple-touch-icon" href="images/apple-touch-icon.png"> <link rel="stylesheet" href="css/main.css"> <link rel="stylesheet" href="ionic/css/ionic.css"> <script src="ionic/js/ionic.bundle.js"></script> </head> <body style="display: none;"> <!--application UI goes here--> <div class="bar bar-header bar-positive"> <h1 class="title">bar-positive</h1> </div> <script src="js/initOptions.js"></script> <script src="js/main.js"></script> <script src="js/messages.js"></script> </body> </html> I also tested on mobile device on both Android and IOS and only got error on IOS device. I don't know how to fix this. Can anyone help? Thanks.

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  • How to calculate the height of the text rectangle from an NSString?

    - by mystify
    I know there is this one: sizeWithFont:minFontSize:actualFontSize:forWidth:lineBreakMode: But since the CGSize always has the same height and doesn't adjust to any shrinked text or whatsoever, the CGSize is not telling how heigh the text is. Example: Make a UILabel with 320 x 55 points and put a loooooooooooooong text in there. Let the label shrink the text down. Surprise: CGSize.height remains the same height even if the text is so tiny that you need a microscope. Ok so after banging my head against my macbook pro which is half way broken now, the only think that can help is that nasty actualFontSize. But the font size is in pica I think, it's not really what you get on the screen, isn't it? When that font size is 10, is my text really 10 points heigh at maximum? Once in a while I tried exactly that, and as soon as the text had a y or some character that extends to below (like that tail of an y does), it is out of bounds and the whole text is bigger than 10 points. So how would you calculate the real text height for a single line uilabel without getting a long beard and some hospital experience?

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  • What is an elegant way to solve this max and min problem in Ruby or Python?

    - by ????
    The following can be done by step by step, somewhat clumsy way, but I wonder if there are elegant method to do it. There is a page: http://www.mariowiki.com/Mario_Kart_Wii, where there are 2 tables... there is Mario - 6 2 2 3 - - Luigi 2 6 - - - - - Diddy Kong - - 3 - 3 - 5 [...] The name "Mario", etc are the Mario Kart Wii character names. The numbers are for bonus points for: Speed Weight Acceleration Handling Drift Off-Road Mini-Turbo and then there is table 2 Standard Bike S 39 21 51 51 54 43 48 Out Bullet Bike 53 24 32 35 67 29 67 In Bubble Bike / Jet Bubble 48 27 40 40 45 35 37 In [...] These are also the characteristics for the Bike or Kart. I wonder what's the most elegant solution for finding all the maximum combinations of Speed, Weight, Acceleration, etc, and also for the minimum, either by directly using the HTML on that page or copy and pasting the numbers into a text file. Actually, in that character table, Mario to Bower Jr are all medium characters, Baby Mario to Dry Bones are small characters, and the rest are all big characters, except the small, medium, or large Mii are just as what the name says. Small characters can only ride small bike or small kart, and so forth for medium and large.

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  • VS 2008 C++ build output?

    - by STingRaySC
    Why when I watch the build output from a VC++ project in VS do I see: 1Compiling... 1a.cpp 1b.cpp 1c.cpp 1d.cpp 1e.cpp [etc...] 1Generating code... 1x.cpp 1y.cpp [etc...] The output looks as though several compilation units are being handled before any code is generated. Is this really going on? I'm trying to improve build times, and by using pre-compiled headers, I've gotten great speedups for each ".cpp" file, but there is a relatively long pause during the "Generating Code..." message. I do not have "Whole Program Optimization" nor "Link Time Code Generation" turned on. If this is the case, then why? Why doesn't VC++ compile each ".cpp" individually (which would include the code generation phase)? If this isn't just an illusion of the output, is there cross-compilation-unit optimization potentially going on here? There don't appear to be any compiler options to control that behavior (I know about WPO and LTCG, as mentioned above). EDIT: The build log just shows the ".obj" files in the output directory, one per line. There is no indication of "Compiling..." vs. "Generating code..." steps. EDIT: I have confirmed that this behavior has nothing to do with the "maximum number of parallel project builds" setting in Tools - Options - Projects and Solutions - Build and Run. Nor is it related to the MSBuild project build output verbosity setting. Indeed if I cancel the build before the "Generating code..." step, the ".obj" files will not exist for the most recent set of "compiled" files. E.g., if I cancel the build during "c.cpp" above, I will see only "a.obj" and "b.obj".

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  • Counting string length in javascript and Ruby on Rails

    - by williamjones
    I've got a text area on a web site that should be limited in length. I'm allowing users to enter 255 characters, and am enforcing that limit with a Rails validation: validates_length_of :body, :maximum => 255 At the same time, I added a javascript char counter like you see on Twitter, to give feedback to the user on how many characters he has already used, and to disable the submit button when over length, and am getting that length in Javascript with a call like this: element.length Lastly, to enforce data integrity, in my Postgres database, I have created this field as a varchar(255) as a last line of defense. Unfortunately, these methods of counting characters do not appear to be directly compatible. Javascript counts the best, in that it counts what users consider as number of characters where everything is a single character. Once the submission hits Rails, however, all of the carriage returns have been converted to \r\n, now taking up 2 characters worth of space, which makes a close call fail Rails validations. Even if I were to handcode a different length validation in Rails, it would still fail when it hits the database I think, though I haven't confirmed this yet. What's the best way for me to make all this work the way the user would want? Best Solution: an approach that would enable me to meet user expectations, where each character of any type is only one character. If this means increasing the length of the varchar database field, a user should not be able to sneakily send a hand-crafted post that creates a row with more than 255 letters. Somewhat Acceptable Solution: a javascript change that enables the user to see the real character count, such that hitting return increments the counter 2 characters at a time, while properly handling all symbols that might have these strange behaviors.

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  • How do you get the viewport scale after pinch/zoom on an iPhone web app?

    - by Loktar
    Does anyone know how to get the size in pixels or scale value of the viewport after a user has pinched or double tapped to zoom in/out on a page in JavaScript? I've tried using window.innerWidth but I've had mixed results. Sometimes it seems to accurately give the number of pixels the viewport is showing, however, if I zoom way in on a page and then do a large pinch to zoom back out, window.innerWidth will be around 600-700 even though it is only showing ~200px of the page. The page is only 400px wide and it didn't show the checkered "you've gone too far" background you see when you zoom out beyond the page size. If I do small pinches to zoom in and out, window.innerWidth appears to work just fine. Unfortunately I can't rely on a user only making small pinch gestures :) I've also tried to use the scale property on the gesture event object, but I've found that unreliable because you don't always know the initial scale when you reload the page or use back/forward buttons to navigate to it even when using the meta tag to specify it. Ultimately, I'm trying to make an app that is aware of when a user is trying to zoom out beyond the maximum zoom level so if there is another way to do this I'm interested in hearing about it :) Here's the code I'm using to get the innerWidth: document.body.addEventListener('gestureend', function (evt) { console.log(window.innerWidth); // inaccurate when doing large pinch gestures }, false); Thanks!

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  • ASP.NET RangeValidator can't do even the most basic math !?!?!?

    - by marc_s
    I'm having an issue with my ASP.NET RangeValidator controls. I want to allow users to enter a discount amount, and this amount must be negative (< $0.00). I want to verify that the amount entered in a textbox is a negative value, so I have this in my page markup: <asp:TextBox ID="tbxDiscount" runat="server" /> <asp:RangeValidator ID="rvDiscount" runat="server" ControlToValidate="tbxDiscount" MinimumValue="0.0" MaximumValue="0.0" EnableClientScript="true" ErrorMessage="Please enter a negative value for a discount" /> and I attempt to set the MinimumValue dynamically in my code before the page gets rendered - to the negative equivalent of my item price. So if the item is $69, I want to set the minimum value to - $69: rvDiscount.MinimumValue = (-1.0m * Price).ToString(); Trouble is: I keep getting this error message: The maximum value 0.0 cannot be less than the minimum value -69.00 for rvDiscount WTF?!?!??! Where I come from, -69 $ IS less than $0 ...... so what's the problem? And more importantly: what is the solution to the problem??

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  • Memory Profiling with DotTrace Questions

    - by cam
    I ran dotTrace on my application (which is having some issues). IntPtr System.Windows.Forms.UnsafeNativeMethods.CallWindowProc(IntPtr, IntPtr, Int32, IntPtr, IntPtr) Void System.Windows.Forms.UnsafeNativeMethods.WaitMessage() Are the two main functions that came up, taking about 94% of the application time. Since I didn't know what these two functions were, I ran through my code line by line. It runs smooth and efficiently until a point where it just hangs. "newFrm.Show()". The newFrm only contains a textbox. The larger the file I load into the text box (it's a notepad program), the longer it takes. Now normally this makes sense, but it takes about 30 seconds for a 167 kB file. Now I'm not sure what to do. It runs incredibly slow/stops functioning when you load a textfile and try to resize the window containing the text file too. Then I realized that it is only struggling to open text files with a long string of hex inside (ie) "XX-XX-XX-" etc. With other similarly sized files it struggles with resizing somewhat, but opens within a couple seconds. Does this have something to do with the textbox properties? I've set it to multiline and set maximum characters to 0 (so unlimited). How do I solve this issue? Is there some way I can see what is being called in those functions?

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  • advanced winform framework

    - by alfredo dobrekk
    Hi, i m starting a new project that would basically take input from user and save them to database among about 30 screens, and i would like to find a framework that will allow the maximum number of these features out of the box : .net c#. windows form. unit testing continuous integration screens with lists, combo boxes, text boxes, add, delete, save, cancel that are easy to update when you add a property to your classes or a field to your database. auto completion on controls to help user find its way use of an orm like nhibernate easy multithreading and display of wait screens for user easy undo redo tabbed child windows search forms ability to grant access to some functionnalities according to user profiles mvp/mvvm or whatever design patterns either some code generation from database to c# classe or generation of database schema from c# classes some kind of database versioning / upgrade to easily update database when i release patches to application once in production code metrics analysis some code generator i can use against my entities that would generate some rough form i can rearrange after code documentation generator ... Any ideas ? I know its lot but i really would like to use existing code to build upon so i can focus on business rules. Do u have any suggestion to add to the list before starting ? What open source tools would u use to achieve these ?

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  • HttpWebResonse hangs on multiple request

    - by Ehsan
    I've an application that create many web request to donwload the news pages of a web site (i've tested for many web sites) after a while I find out that the application slows down in fetching the html source then I found out that HttpWebResonse fails getting the response. I post only the function that do this job. public PageFetchResult Fetch() { PageFetchResult fetchResult = new PageFetchResult(); try { HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create(URLAddress); HttpWebResponse resp = (HttpWebResponse)req.GetResponse(); Uri requestedURI = new Uri(URLAddress); Uri responseURI = resp.ResponseUri; if (Uri.Equals(requestedURI, responseURI)) { string resultHTML = ""; byte[] reqHTML = ResponseAsBytes(resp); if (!string.IsNullOrEmpty(FetchingEncoding)) resultHTML = Encoding.GetEncoding(FetchingEncoding).GetString(reqHTML); else if (!string.IsNullOrEmpty(resp.CharacterSet)) resultHTML = Encoding.GetEncoding(resp.CharacterSet).GetString(reqHTML); resp.Close(); fetchResult.IsOK = true; fetchResult.ResultHTML = resultHTML; } else { URLAddress = responseURI.AbsoluteUri; relayPageCount++; if (relayPageCount > 5) { fetchResult.IsOK = false; fetchResult.ErrorMessage = "Maximum page redirection occured."; return fetchResult; } return Fetch(); } } catch (Exception ex) { fetchResult.IsOK = false; fetchResult.ErrorMessage = ex.Message; } return fetchResult; } any solution would greatly appreciate

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  • Handling user interface in a multi-threaded application (or being forced to have a UI-only main thre

    - by Patrick
    In my application, I have a 'logging' window, which shows all the logging, warnings, errors of the application. Last year my application was still single-threaded so this worked [quite] good. Now I am introducing multithreading. I quickly noticed that it's not a good idea to update the logging window from different threads. Reading some articles on keeping the UI in the main thread, I made a communication buffer, in which the other threads are adding their logging messages, and from which the main thread takes the messages and shows them in the logging window (this is done in the message loop). Now, in a part of my application, the memory usage increases dramatically, because the separate threads are generating lots of logging messages, and the main thread cannot empty the communication buffer quickly enough. After the while the memory decreases again (if the other threads have finished their work and the main thread gradually empties the communication buffer). I solved this problem by having a maximum size on the communication buffer, but then I run into a problem in the following situation: the main thread has to perform a complex action the main thread takes some parts of the action and let's separate threads execute this while the seperate threads are executing their logic, the main thread processes the results from the other threads and continues with its work if the other threads are finished Problem is that in this situation, if the other threads perform logging, there is no UI-message loop, and so the communication buffer is filled, but not emptied. I see two solutions in solving this problem: require the main thread to do regular polling of the communication buffer only performing user interface logic in the main thread (no other logic) I think the second solution seems the best, but this may not that easy to introduce in a big application (in my case it performs mathematical simulations). Are there any other solutions or tips? Or is one of the two proposed the best, easiest, most-pragmatic solution? Thanks, Patrick

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  • Apache ReWriteEngine throwing 500 Internal Server Error for too many internal redirects... why?!?!?!

    - by Stephen G
    I'm trying to implement a new ReWrite rule on my local dev machine. I have 13 rules set up already, and all work fine (even as of this writing). However, for some reason the newest one is throwing me 500 Internal Server Errors. The ReWrite rule is: RewriteRule stuff/public_html/vault/mystuff/view/(.*) /stuff/public_html/vault/mystuff/view/index.php?stuff=$1 RewriteRule stuff/public_html/vault/mystuff/view/(.*)/ /stuff/public_html/vault/mystuff/view/index.php?stuff=$1 Checked my apache logs and got this: [Thu Jan 13 22:07:43 2011] [error] [client ::1] mod_rewrite: maximum number of internal redirects reached. Assuming configuration error. Use 'RewriteOptions MaxRedirects' to increase the limit if neccessary., referer: http://localhost:8888/stuff/public_html/vault/mystuff/all/index.php?curr=7 On the script I am trying to redirect to view/index.php?stuff=$1, there is nothing that even remotely resembles a redirect of any kind. I do have a very, very basic session verifier being called at the top of the landing script, which is as follows: //Start session session_start(); //Check whether the session variable SESS_MEMBER_ID is present or not if(!isset($_SESSION['SESS_MEMBER_ID']) || (trim($_SESSION['SESS_MEMBER_ID']) == '')) { header("location: ".$root_http.""); exit(); } However, when I access the page directly, it acts as it should, and there is no redirect. All of my other ReWrite rules and their corresponding landing pages are set up the exact same way. This is blowing my mind. Any help, PLEASE!?

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  • Limit TCP requests per IP

    - by asmo
    Hello! I'm wondering how to limit the TCP requests per client (per specific IP) in Java. For example, I would like to allow a maximum of X requests per Y seconds for each client IP. I thought of using static Timer/TimerTask in combination with a HashSet of temporary restricted IPs. private static final Set<InetAddress> restrictedIPs = Collections.synchronizedSet(new HashSet<InetAddress>()); private static final Timer restrictTimer = new Timer(); So when a user connects to the server, I add his IP to the restricted list, and start a task to unrestrict him in X seconds. restrictedIPs.add(socket.getInetAddress()); restrictTimer.schedule(new TimerTask() { public void run() { restrictedIPs.remove(socket.getInetAddress()); } }, MIN_REQUEST_INTERVAL); My problem is that at the time the task will run, the socket object may be closed, and the remote IP address won't be accessible anymore... Any ideas welcomed! Also, if someone knows a Java-framework-built-in way to achieve this, I'd really like to hear it.

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  • Converting ntext to nvcharmax(max) - Getting around size limitation

    - by Overflew
    Hi all, I'm trying to change an existing SQL NText column to nvcharmax(max), and encountering an error on the size limit. There's a large amount of existing data, some of which is more than the 8k limit, I believe. We're looking to convert this, so that the field is searchable in LINQ. The 2x SQL statements I've tried are: update Table set dataNVarChar = convert(nvarchar(max), dataNtext) where dataNtext is not null update Table set dataNVarChar = cast(dataNtext as nvarchar(max)) where dataNtext is not null And the error I get is: Cannot create a row of size 8086 which is greater than the allowable maximum row size of 8060. This is using SQL Server 2008. Any help appreciated, Thanks. Update / Solution: The marked answer below is correct, and SQL 2008 can change the column to the correct data type in my situation, and there are no dramas with the LINQ-utilising application we use on top of it: alter table [TBL] alter column [COL] nvarchar(max) I've also been advised to follow it up with: update [TBL] set [COL] = [COL] Which completes the conversion by moving the data from the lob structure to the table (if the length in less than 8k), which improves performance / keeps things proper.

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  • amount of data returned by wcf 3.0 service contract method causes error

    - by ferrell carr
    CommuncationException was unhandled The maximum message size quota for incoming messages (65536) has been exceeded. To increase the quota, use the MaxReceivedMessageSize property on the appropriate binding element. here is my svc.map file <?xml version="1.0" encoding="utf-8"?> <ServiceReference> <ProxyGenerationParameters ServiceReferenceUri="http://d3w9501/SimpleWCF/SimpleWCF.svc" Name="svc" NotifyPropertyChange="False" UseObservableCollection="False"> </ProxyGenerationParameters> <EndPoints> <EndPoint Address="http://d3w9501.americas.hpqcorp.net/SimpleWCF/SimpleWCF.svc" BindingConfiguration="BasicHttpBinding_ISimpleWCF" Contract="TestSimpleWCF.svc.ISimpleWCF" > </EndPoint> <bindings> <basicHttpBinding> <binding name="BasicHttpBinding_ISimpleWCF" maxBufferSize="2147483647" maxReceivedMessageSize="2147483647" > <security mode="None" /> </binding> </basicHttpBinding> </bindings> </EndPoints> </ServiceReference>

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  • How do I view the full content of a text or varchar(MAX) column in SQL Server 2008 Management Studio

    - by adamjford
    In this live SQL Server 2008 (build 10.0.1600) database, there's an Events table, which contains a text column named Details. (Yes, I realize this should actually be a varchar(MAX) column, but whoever set this database up did not do it that way.) This column contains very large logs of exceptions and associated JSON data that I'm trying to access through SQL Server Management Studio, but whenever I copy the results from the grid to a text editor, it truncates it at 43679 characters. I've read on various locations on the Internet that you can set your Maximum Characters Retrieved for XML Data in Tools > Options > Query Results > SQL Server > Results To Grid to Unlimited, and then perform a query such as this: select Convert(xml, Details) from Events where EventID = 13920 (Note that the data is column is not XML at all. CONVERTing the column to XML is merely a workaround I found from Googling that someone else has used to get around the limit SSMS has from retrieving data from a text or varchar(MAX) column.) However, after setting the option above, running the query, and clicking on the link in the result, I still get the following error: Unable to show XML. The following error happened: Unexpected end of file has occurred. Line 5, position 220160. One solution is to increase the number of characters retrieved from the server for XML data. To change this setting, on the Tools menu, click Options. So, any idea on how to access this data? Would converting the column to varchar(MAX) fix my woes?

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  • How can I differentiate a manual scroll (via mousewheel/scrollbar) from a Javascript/jQuery scroll?

    - by David Murdoch
    UPDATE: Here is a jsbin example demonstrating the problem. Basically, I have the following javascript which scrolls the window to an anchor on the page: // get anchors with href's that start with "#" $("a[href^=#]").live("click", function(){ var target = $($(this).attr("href")); // if the target exists: scroll to it... if(target[0]){ // If the page isn't long enough to scroll to the target's position // we want to scroll as much as we can. This part prevents a sudden // stop when window.scrollTop reaches its maximum. var y = Math.min(target.offset().top, $(document).height() - $(window).height()); // also, don't try to scroll to a negative value... y=Math.max(y,0); // OK, you can scroll now... $("html,body").stop().animate({ "scrollTop": y }, 1000); } return false; }); It works perfectly......until I manually try to scroll the window. When the scrollbar or mousewheel is scrolled I need to stop the current scroll animation...but I'm not sure how to do this. This is probably my starting point... $(window).scroll(e){ if(IsManuallyScrolled(e)){ $("html,body").stop(); } } ...but I'm not sure how to code the IsManuallyScrolled function. I've checked out e (the event object) in Google Chrome's console and AFAIK there is not way to differentiate between a manual scroll and jQuery's animate() scroll. How can I differentiate between a manual scroll and one called via jQuery's $.fn.animate function?

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  • Ad distribution problem: an optimal solution?

    - by Mokuchan
    I'm asked to find a 2 approximate solution to this problem: You’re consulting for an e-commerce site that receives a large number of visitors each day. For each visitor i, where i € {1, 2 ..... n}, the site has assigned a value v[i], representing the expected revenue that can be obtained from this customer. Each visitor i is shown one of m possible ads A1, A2 ..... An as they enter the site. The site wants a selection of one ad for each customer so that each ad is seen, overall, by a set of customers of reasonably large total weight. Thus, given a selection of one ad for each customer, we will define the spread of this selection to be the minimum, over j = 1, 2 ..... m, of the total weight of all customers who were shown ad Aj. Example Suppose there are six customers with values 3, 4, 12, 2, 4, 6, and there are m = 3 ads. Then, in this instance, one could achieve a spread of 9 by showing ad A1 to customers 1, 2, 4, ad A2 to customer 3, and ad A3 to customers 5 and 6. The ultimate goal is to find a selection of an ad for each customer that maximizes the spread. Unfortunately, this optimization problem is NP-hard (you don’t have to prove this). So instead give a polynomial-time algorithm that approximates the maximum spread within a factor of 2. The solution I found is the following: Order visitors values in descending order Add the next visitor value (i.e. assign the visitor) to the Ad with the current lowest total value Repeat This solution actually seems to always find the optimal solution, or I simply can't find a counterexample. Can you find it? Is this a non-polinomial solution and I just can't see it?

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  • Using shared_ptr to implement RCU (read-copy-update)?

    - by yongsun
    I'm very interested in the user-space RCU (read-copy-update), and trying to simulate one via tr1::shared_ptr, here is the code, while I'm really a newbie in concurrent programming, would some experts help me to review? The basic idea is, reader calls get_reading_copy() to gain the pointer of current protected data (let's say it's generation one, or G1). writer calls get_updating_copy() to gain a copy of the G1 (let's say it's G2), and only one writer is allowed to enter the critical section. After the updating is done, writer calls update() to do a swap, and make the m_data_ptr pointing to data G2. The ongoing readers and the writer now hold the shared_ptr of G1, and either a reader or a writer will eventually deallocate the G1 data. Any new readers would get the pointer to G2, and a new writer would get the copy of G2 (let's say G3). It's possible the G1 is not released yet, so multiple generations of data my co-exists. template <typename T> class rcu_protected { public: typedef T type; typedef std::tr1::shared_ptr<type> rcu_pointer; rcu_protected() : m_data_ptr (new type()) {} rcu_pointer get_reading_copy () { spin_until_eq (m_is_swapping, 0); return m_data_ptr; } rcu_pointer get_updating_copy () { spin_until_eq (m_is_swapping, 0); while (!CAS (m_is_writing, 0, 1)) {/* do sleep for back-off when exceeding maximum retry times */} rcu_pointer new_data_ptr(new type(*m_data_ptr)); // as spin_until_eq does not have memory barrier protection, // we need to place a read barrier to protect the loading of // new_data_ptr not to be re-ordered before its construction _ReadBarrier(); return new_data_ptr; } void update (rcu_pointer new_data_ptr) { while (!CAS (m_is_swapping, 0, 1)) {} m_data_ptr.swap (new_data_ptr); // as spin_until_eq does not have memory barrier protection, // we need to place a write barrier to protect the assignments of // m_is_writing/m_is_swapping be re-ordered bofore the swapping _WriteBarrier(); m_is_writing = 0; m_is_swapping = 0; } private: volatile long m_is_writing; volatile long m_is_swapping; rcu_pointer m_data_ptr; };

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  • How to efficiently convert String, integer, double, datetime to binary and vica versa?

    - by Ben
    Hi, I'm quite new to C# (I'm using .NET 4.0) so please bear with me. I need to save some object properties (their properties are int, double, String, boolean, datetime) to a file. But I want to encrypt the files using my own encryption, so I can't use FileStream to convert to binary. Also I don't want to use object serialization, because of performance issues. The idea is simple, first I need to somehow convert objects (their properties) to binary (array), then encrypt (some sort of xor) the array and append it to the end of the file. When reading first decrypt the array and then somehow convert the binary array back to object properties (from which I'll generate objects). I know (roughly =) ) how to convert these things by hand and I could code it, but it would be useless (too slow). I think the best way would be just to get properties' representation in memory and save that. But I don't know how to do it using C# (maybe using pointers?). Also I though about using MemoryStream but again I think it would be inefficient. I am thinking about class Converter, but it does not support toByte(datetime) (documentation says it always throws exception). For converting back I think the only options is class Converter. Note: I know the structure of objects and they will not change, also the maximum String length is also known. Thank you for all your ideas and time. EDIT: I will be storing only parts of objects, in some cases also parts of different objects (a couple of properties from one object type and a couple from another), thus I think that serialization is not an option for me.

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  • Algorithm Question

    - by Ravi
    Hi, I am trying to find a O (n) algorithm for this problem but unable to do so even after spending 3 - 4 hours. The brute force method times out (O (n^2)). I am confused as to how to do it ? Does the solution requires dynamic programming solution ? http://acm.timus.ru/problem.aspx?space=1&num=1794 In short the problem is this: There are some students sitting in circle and each one of them has its own choice as to when he wants to be asked a question from a teacher. The teacher will ask the questions in clockwise order only. For example: 5 3 3 1 5 5 This means that there are 5 students and : 1st student wants to go third 2nd student wants to go third 3rd student wants to go first 4th student wants to go fifth 5th student wants to go fifth. The question is as to where should teacher start asking questions so that maximum number of students will get the turn as they want. For this particular example, the answer is 5 because 3 3 1 5 5 2 3 4 5 1 You can see that by starting at fifth student as 1st, 2 students (3 and 5) are getting the choices as they wanted. For this example the answer is 12th student : 12 5 1 2 3 6 3 8 4 10 3 12 7 because 5 1 2 3 6 3 8 4 10 3 12 7 2 3 4 5 6 7 8 9 10 11 12 1 four students get their choices fulfilled. Thanks Ravi

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  • How to store unlimited characters in Oracle 11g?

    - by vicky21
    We have a table in Oracle 11g with a varchar2 column. We use a proprietary programming language where this column is defined as string. Maximum we can store 2000 characters (4000 bytes) in this column. Now the requirement is such that the column needs to store more than 2000 characters (in fact unlimited characters). The DBAs don't like BLOB or LONG datatypes for maintenance reasons. The solution that I can think of is to remove this column from the original table and have a separate table for this column and then store each character in a row, in order to get unlimited characters. This tble will be joined with the original table for queries. Is there any better solution to this problem? UPDATE: The proprietary programming language allows to define variables of type string and blob, there is no option of CLOB. I understand the responses given, but I cannot take on the DBAs. I understand that deviating from BLOB or LONG will be developers' nightmare, but still cannot help it.

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  • "Subforms" associated with tree view in VB

    - by knomdeguerre
    I am using VB Express 2008 to demonstrate my ideas for an improved UI for an existing product for my colleagues at work. The current UI has a certain page with ten tabs, allowing the user to define up to ten "things". The available choices for each of the ten "things" are all the same. On each of the ten tabs, there is a checkbox to enable that definition. Generally, a user will never use more than 5 or 6 unique definitions, the rest will remain disabled. So far, my prototype has a tree view control with one branch to contain this list of definitions, Add and Delete buttons. My idea is: there is one sub-branch to start with (corresponding to the first tab in the current UI); if the user wants addtional definitions, they click Add and other branches are added to the tree view, up to maximum of ten. I think I should be able to create a "class" that has a sub-UI (like a sub-form in Access) along with behavior code, that can be instantiated with each press of the Add button; each instantiation's settings can be set independently and is displayed in the main UI form )in a panel or frame) when selected in the tree view. For example, suppose the user Adds to make a total of three definitions: the tree view now has three sub-branches, each of which presents the same sub-UI with settings that can be set specific to the selected sub-branch. I'm sure it's possible but not sure how to do it. I know a comprehensive "answer" might be complicated and long, but I may just need some quick hints to get underway - don't be shy! Thanks in advance!

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