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Search found 243 results on 10 pages for 'yan cheng cheok'.

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  • Sql combine 2 rows to one

    - by Yan
    Hi , i have this table Testers employee name ------------ Sam Korch dan mano i want to combine tow rows to one, it will be "Sam Korch,Dan Mano" i have this query select @theString = COALESCE(@theString + ',', '') + EmployeeName from Testers join vw_EKDIR on Testers.TesterGlobalId = vw_EKDIR.GlobalID where TestId = 31 it working but i dont want to do select i want the result will be in @thestring so i try to do this query set @theString = ( select @theString = COALESCE(@theString + ',', '') + EmployeeName from Testers join vw_EKDIR on Testers.TesterGlobalId = vw_EKDIR.GlobalID where TestId = 31 ) it is not working ... i want @thestring will be the result. any idaes ? thanks

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  • Why Enumerable.Range is faster than a direct yield loop?

    - by Morgan Cheng
    Below code is checking performance of three different ways to do same solution. public static void Main(string[] args) { // for loop { Stopwatch sw = Stopwatch.StartNew(); int accumulator = 0; for (int i = 1; i <= 100000000; ++i) { accumulator += i; } sw.Stop(); Console.WriteLine("time = {0}; result = {1}", sw.ElapsedMilliseconds, accumulator); } //Enumerable.Range { Stopwatch sw = Stopwatch.StartNew(); var ret = Enumerable.Range(1, 100000000).Aggregate(0, (accumulator, n) => accumulator + n); sw.Stop(); Console.WriteLine("time = {0}; result = {1}", sw.ElapsedMilliseconds, ret); } //self-made IEnumerable<int> { Stopwatch sw = Stopwatch.StartNew(); var ret = GetIntRange(1, 100000000).Aggregate(0, (accumulator, n) => accumulator + n); sw.Stop(); Console.WriteLine("time = {0}; result = {1}", sw.ElapsedMilliseconds, ret); } } private static IEnumerable<int> GetIntRange(int start, int count) { int end = start + count; for (int i = start; i < end; ++i) { yield return i; } } } The result is like this: time = 306; result = 987459712 time = 1301; result = 987459712 time = 2860; result = 987459712 It is not surprising that "for loop" is faster than the other two solutions, because Enumerable.Aggregate takes more method invocations. However, it really surprises that "Enumerable.Range" is faster than the "self-made IEnumerable". I thought that Enumerable.Range will take more overhead than the simple GetIntRange method. What is the possible reason for this?

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  • How to make write operation idempotent?

    - by Morgan Cheng
    I'm reading article about recently release Gizzard sharding framework by twitter(http://engineering.twitter.com/2010/04/introducing-gizzard-framework-for.html). It mentions that all write operations must be idempotent to make sure high reliability. According to wikipedia, "Idempotent operations are operations that can be applied multiple times without changing the result." But, IMHO, in Gazzard case, idempotent write operation should be operations that sequence doesn't matter. Now, my question is: How to make write operation idempotent? The only thing I can image is to have a version number attached to each write. For example, in blog system. Each blog must have a $blog_id and $content. In application level, we always write a blog content like this write($blog_id, $content, $version). The $version is determined to be unique in application level. So, if application first try to set one blog to "Hello world" and second want it to be "Goodbye", the write is idempotent. We have such two write operations: write($blog_id, "Hello world", 1); write($blog_id, "Goodbye", 2); These two operations are supposed to changed two different records in DB. So, no matter how many times and what sequence these two operations executed, the results are same. This is just my understanding. Please correct me if I'm wrong.

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  • Is it safe to draw three separate QImages in three separate QThreads?

    - by yan bellavance
    I have a QMainWindow with three widgets inside that are promoted to a class containing a subclassed QThread. They each draw on a local QImage in their rexpective qthread which is sent with a signal once its drawn and then rendered by calling update (mandlebrot example) from the slot. Is this safe or dangerous? They do not share any data, at least none that I am generating and am wondering what data they could be sharing that is outside of my coding range ie that is generated by Qt automatically.

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  • How to check whether user is login in web application?

    - by Morgan Cheng
    I want to learn the whole details of web application authentication. So, I decided to write a CodeIgniter authentication library from scratch. Now, I have to make design decision about how to determine whether one user is login. Basically, after user input username & password pair. A cookie is set for this session, following navigations in the web application will not require username & password. The server side will check whether the session cookie is valid to determine whether current user is login. The question is: how to determine whether cookie is valid cookie issued from server side? I can image the most simple way is to have the cookie value stored in session status as well. For each HTTP request, compare the value from cookie and the value from server session. (Since CodeIgniter session library store session variables in cookies, it is not applicable without some tweak.) This method requires storage in server side. For huge web application that is deployed in multiple datacenters. It is possible that user input username & password when browsing in one datacenter, while he/she access the web application in another datacenter later. The expected behavior is that user just input username & password once. As a result, all datacenters should be able to access the session status. That is possible not applicable even the session status is stored in external storage such as database. I tried Google. I login Google with Asian proxy which is supposed to direct me to datacenters in Asian. Then I switch to North American proxy which should direct me to datacenters in North America. It recognize my login without asking username and password again. So, is there any way to determine whether user is login without server side session status?

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  • Output from OouraFFT correct sometimes but completely false other times. Why ?

    - by Yan
    Hi I am using Ooura FFT to compute the FFT of the accelerometer data in windows of 1024 samples. The code works fine, but then for some reason it produces very strange outputs, i.e. continuous spectrum with amplitudes of the order of 10^200. Here is the code: OouraFFT *myFFT=[[OouraFFT alloc] initForSignalsOfLength:1024 NumWindows:10]; // had to allocate it UIAcceleration *tempAccel = nil; double *input=(double *)malloc(1024 * sizeof(double)); double *frequency=(double *)malloc(1024*sizeof(double)); if (input) { //NSLog(@"%d",[array count]); for (int u=0; u<[array count]; u++) { tempAccel = (UIAcceleration *)[array objectAtIndex:u]; input[u]=tempAccel.z; //NSLog(@"%g",input[u]); } } myFFT.inputData=input; // specifies input data to myFFT [myFFT calculateWelchPeriodogramWithNewSignalSegment]; // calculates FFT for (int i=0;i<myFFT.dataLength;i++) // loop to copy output of myFFT, length of spectrumData is half of input data, so copy twice { if (i<myFFT.numFrequencies) { frequency[i]=myFFT.spectrumData[i]; // } else { frequency[i]=myFFT.spectrumData[myFFT.dataLength-i]; // copy twice } } for (int i=0;i<[array count];i++) { TransformedAcceleration *NewAcceleration=[[TransformedAcceleration alloc]init]; tempAccel=(UIAcceleration*)[array objectAtIndex:i]; NewAcceleration.timestamp=tempAccel.timestamp; NewAcceleration.x=tempAccel.x; NewAcceleration.y=tempAccel.z; NewAcceleration.z=frequency[i]; [newcurrentarray addObject:NewAcceleration]; // this does not work //[self replaceAcceleration:NewAcceleration]; //[NewAcceleration release]; [NewAcceleration release]; } TransformedAcceleration *a=nil;//[[TransformedAcceleration alloc]init]; // object containing fft of x,y,z accelerations for(int i=0; i<[newcurrentarray count]; i++) { a=(TransformedAcceleration *)[newcurrentarray objectAtIndex:i]; //NSLog(@"%d,%@",i,[a printAcceleration]); fprintf(fp,[[a printAcceleration] UTF8String]); //this is going wrong somewhow } fclose(fp); [array release]; [myFFT release]; //[array removeAllObjects]; [newcurrentarray release]; free(input); free(frequency);

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  • Segmentation fault in Qt application framework

    - by yan bellavance
    this generates a segmentation fault becuase of "QColor colorMap[9]";. If I remove colorMap the segmentation fault goes away. If I put it back. It comes back. If I do a clean all then build all, it goes away. If I increase its arraysize it comes back. On the other hand if I reduce it it doesnt come back. I tired adding this array to another project and What could be happening. I am really curious to know. I have removed everything else in that class. This widget subclassed is used to promote a widget in a QMainWindow. class LevelIndicator : public QWidget { public: LevelIndicator(QWidget * parent); void paintEvent(QPaintEvent * event ); float percent; QColor colorMap[9]; int NUM_GRADS; }; the error happens inside ui_mainwindow.h at one of these lines: hpaFwdPwrLvl->setObjectName(QString::fromUtf8("hpaFwdPwrLvl")); verticalLayout->addWidget(hpaFwdPwrLvl); I know i am not providing much but I will give alink to the app. Im trying to see if anyone has a quick answer for this.

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  • can I acces a struct inside of a struct without using the dot operator?

    - by yan bellavance
    I have 2 structures that have 90% of their fields the same. I want to group those fields in a structure but I do not want to use the dot operator to access them. The reason is I already coded with the first structure and have just created the second one. before: struct{ int a; int b; int c; object1 name; }str1; struct{ int a; int b; int c; object2 name; }str2; now I would create a third struct: struct{ int a; int b; int c; }str3; and would change the str1 and atr2 to this: struct{ str3 str; object1 name; }str1; struct { str3 str; object2 name; }str2; Finally I would like to be able to access a,b and c by doing: str1 myStruct; myStruct.a; myStruct.b; myStruct.c; and not: myStruct.str.a; myStruct.str.b; myStruct.str.c; Is there a way to do such a thing. The reason for doing this is I want keep the integrety of the data if chnges to the struct were to occur and to not repeat myself and not have to change my existing code and not have fields nested too deeply.

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  • What's the best way to store Logon User information for Web Application?

    - by Morgan Cheng
    I was once in a project of web application developed on ASP.NET. For each logon user, there is an object (let's call it UserSessionObject here) created and stored in RAM. For each HTTP request of given user, matching UserSessoinObject instance is used to visit user state information and connection to database. So, this UserSessionObject is pretty important. This design brings several problems found later: 1) Since this UserSessionObject is cached in ASP.NET memory space, we have to config load balancer to be sticky connection. That is, HTTP request in single session would always be sent to one web server behind. This limit scalability and maintainability. 2) This UserSessionObject is accessed in every HTTP request. To keep the consistency, there is a exclusive lock for the UserSessionObject. Only one HTTP request can be processed at any given time because it must to obtain the lock first. The performance and response time is affected. Now, I'm wondering whether there is better design to handle such logon user case. It seems Sharing-Nothing-Architecture helps. That means long user info is retrieved from database each time. I'm afraid that would hurt performance. Is there any design pattern for long user web app? Thanks.

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  • How to design data storage for partitioned tagging system?

    - by Morgan Cheng
    How to design data storage for huge tagging system (like digg or delicious)? There is already discussion about it, but it is about centralized database. Since the data is supposed to grow, we'll need to partition the data into multiple shards soon or later. So, the question turns to be: How to design data storage for partitioned tagging system? The tagging system basically has 3 tables: Item (item_id, item_content) Tag (tag_id, tag_title) TagMapping(map_id, tag_id, item_id) That works fine for finding all items for given tag and finding all tags for given item, if the table is stored in one database instance. If we need to partition the data into multiple database instances, it is not that easy. For table Item, we can partition its content with its key item_id. For table Tag, we can partition its content with its key tag_id. For example, we want to partition table Tag into K databases. We can simply choose number (tag_id % K) database to store given tag. But, how to partition table TagMapping? The TagMapping table represents the many-to-many relationship. I can only image to have duplication. That is, same content of TagMappping has two copies. One is partitioned with tag_id and the other is partitioned with item_id. In scenario to find tags for given item, we use partition with tag_id. If scenario to find items for given tag, we use partition with item_id. As a result, there is data redundancy. And, the application level should keep the consistency of all tables. It looks hard. Is there any better solution to solve this many-to-many partition problem?

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  • vagrant box add: where does .box file get downloaded to?

    - by Calvin Cheng
    What actually happens to the .box file (which according to the docs is simply a vbox image in tar form, in a particular format) after the first command vagrant box add lucid32 http://files.vagrantup.com/lucid32.box is executed? I can't seem to find the filesystem location of lucid32.box after the download has successfully completed... I am aware it doesn't really matter as vagrant init lucid32 vagrant up vagrant ssh will get me into the vm irregardless. But I am curious where .box is located.

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  • How can i handle mouse double click event on textbox?

    - by Kar Cheng
    Hello, I want to open one child window on mouse double click of textbox. I know the only event available in Silverlight is MouseLeftButtonDown and you have to simulate double click. However it still doesn't work when i click in the middle of the textbox. It only works when i double click on the border of the textbox. Anybody has any ideas of how can i do this? If any 3rd party library is available then also it's fine. Thanks in advance:)

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  • How to implement a collection (list, map?) of complicated strings in Java?

    - by Alex Cheng
    Hi all. I'm new here. Problem -- I have something like the following entries, 1000 of them: args1=msg args2=flow args3=content args4=depth args6=within ==> args5=content args1=msg args2=flow args3=content args4=depth args6=within args7=distance ==> args5=content args1=msg args2=flow args3=content args6=within ==> args5=content args1=msg args2=flow args3=content args6=within args7=distance ==> args5=content args1=msg args2=flow args3=flow ==> args4=flowbits args1=msg args2=flow args3=flow args5=content ==> args4=flowbits args1=msg args2=flow args3=flow args6=depth ==> args4=flowbits args1=msg args2=flow args3=flow args6=depth ==> args5=content args1=msg args2=flow args4=depth ==> args3=content args1=msg args2=flow args4=depth args5=content ==> args3=content args1=msg args2=flow args4=depth args5=content args6=within ==> args3=content args1=msg args2=flow args4=depth args5=content args6=within args7=distance ==> args3=content I'm doing some sort of suggestion method. Say, args1=msg args2=flow args3=flow == args4=flowbits If the sentence contains msg, flow, and another flow, then I should return the suggestion of flowbits. How can I go around doing it? I know I should scan (whenever a character is pressed on the textarea) a list or array for a match and return the result, but, 1000 entries, how should I implement it? I'm thinking of HashMap, but can I do something like this? <"msg,flow,flow","flowbits" Also, in a sentence the arguments might not be in order, so assuming that it's flow,flow,msg then I can't match anything in the HashMap as the key is "msg,flow,flow". What should I do in this case? Please help. Thanks a million!

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  • How can I set where a Qt app finds a Qt module?

    - by yan bellavance
    I would like to include libQtGui.so.4 libQtNetwork.so.4 and libQtCore.so.4 in the same directory as where my app resides. How would I make Qt understand this? y purpose is to have a standalone app that uses shared libraries update: im gonna try to first remove them with QT-=gui etc and seeif I can add mine back after

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  • qapps runs well but breakpoint sometimes generates segmentation fault

    - by yan bellavance
    I have a qApp that generates a segmentation fault only when a breakpoint is inserted in the code (I can put it at different places) and only after 4-5 breakpoint stops. Do I have a problem with my code or is this a DBG bug. the method is part of a QThread Class. Basically what I did is i took the mandlebrot example, and have 3 instances of it in my program. So the program would look like a mainwindow that has 3 mandlebrot widgets in it, one besides the other. Is it possible that GDB doesnt support debugging qthread subclasses that are instantiated multiple times or is it thread-unsafe to do so. I dont have any problems at run-time.

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  • How to set JComboBox not to select an element when created? (Java)

    - by Alex Cheng
    Hi all. Problem: I am using JComboBox, and tried using setSelectionIndex(-1) in my code (this code is placed in caretInvoke()) suggestionComboBox.removeAllItems(); for (int i = 0; i < suggestions.length; i++) { suggestionComboBox.addItem(suggestions[i]); } suggestionComboBox.setSelectedIndex(-1); suggestionComboBox.setEnabled(true); This is the initial setting when it was added to a pane: suggestionComboBox = new JComboBox(); suggestionComboBox.setEditable(false); suggestionComboBox.setPreferredSize(new Dimension(25, 25)); suggestionComboBox.addActionListener(new SuggestionComboBoxListener()); When the caretInvoke triggers the ComboBox initialisation, even before the user selects an element, the actionPerformed is already triggered (I tried a JOptionPane here): First popup (notice that "flow byte_jump" is selected): Second popup (I think the setSelectionIndex is executed) Then in the end: The problem is: My program autoinserts the selected text when the user selects an element from the ComboBox. So without the user selecting anything, it is automatically inserted already. How can I overcome the problem in this situation? Thanks.

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  • Why Windows Live Spaces Fetch Image Through HTTPS?

    - by Morgan Cheng
    I happens to find that, when a live space page is loaded, inline images are fetched by https protocol instead of http protocol. This doesn't make sense. The text part of live space is not fetched by https, why images are fetched with https? I bet the https way to fetch image just make the page loaded slower. Is there any special advantage to choose https over http in this case?

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  • why multipart/x-mixed-replace is needed for Comet?

    - by Morgan Cheng
    I'm reading this article about Comet http://en.wikipedia.org/wiki/Comet_(programming). It mentions that browser should support multipart/x-mixed-replace to make XmlHttpRequest Streaming possible. Why this multipart/x-mixed-replace is necessary? Without this header, HTTP response can still be chunked and sent piece by piece to browser, right?

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  • drupal display submenu when parent has been selected

    - by Steven Cheng
    I've have a menu structure that has a depth of 3 levels on a drupal 6 CMS. When I click on a level 1 that has children, the level 2 menu items display fine. If the level 2 has children, it is not showing the level 3. If I check the expanded box the level 3 is displayed however, it displays all the time irrespective of the level 2 that has been selected. It seems to display whenever it's parent level 1 is selected. For further information, the menu items are a mixture of custom links & content links. i.e. Links I've enetered manually when creating the menu and others generated by when creating a node or view display. All I want is to show the children if there are any for the selected parent. Am I missing something fundamental here? Thanks Steve

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  • How to Implement Dynamic Timestamp in Web Page?

    - by Morgan Cheng
    In Facebook and twitter, we can see that there is a timestamp like "23 seconds ago" or "1 hour ago" for each event & tweet. If we leave the page for some time, the timestamp changes accordingly. Since it is possible that user machine doesn't have same system time as server machine, how to make the dynamic timestamp accurate? My idea is: It is always based on server time. When request is sent to server for the web page, timestamp T1 (seconds to 1970/1/1) is rendered into inline javascript variable. The displayed timestamp ("23 seconds ago") is calculated by T1 instead of local time. I'm not sure whether this is how Facebook/Twitter do it. Is there any better idea?

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  • What requests do browsers' "F5" and "Ctrl + F5" refreshes generate?

    - by Morgan Cheng
    Is there a standard for what actions F5 and Ctrl+F5 trigger in web browsers? I once did experiment in IE6 and Firefox 2.x. The "F5" refresh would trigger a HTTP request sent to the server with an "If-Modified-Since" header, while "Ctrl+F5" would not have such a header. In my understanding, F5 will try to utilize cached content as much as possible, while "Ctrl+F5" is intended to abandon all cached content and just retrieve all content from the servers again. But today, I noticed that in some of the latest browsers (Chrome, IE8) it doesn't work in this way anymore. Both "F5" and "Ctrl+F5" send the "If-Modified-Since" header. So how is this supposed to work, or (if there is no standard) how do the major browsers differ in how they implement these refresh features?

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  • Is Form Tag Necessary in AJAX Web Application?

    - by Morgan Cheng
    I read some AJAX-Form tutorial like this. The tag form is used in HTML code. However, I believed that it is not necessary. Since we send HTTP request through XmlHttpRequest, the sent data can be anything, not necessary input in form. So, is there any reason to have form tag in HTML for AJAX application?

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