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  • PPR in tr:selectOneChoice does not work

    - by Nhut Le
    Hi, I have a simple testing page that test my PPR on a selectOneChoice component. when select a value from selectOnechoice 1, the selected value will display on a output label and also reset the selected value and the other selectOneChoice. However, it prints the selected values to the label correctly but it can't set the selected value for the other selectOneChoice. and Here are my page and my value change event method. <tr:form id="nhutForm"> <tr:selectOneChoice id="one" value="#{nhutTestBean.one}" autoSubmit="true" immediate="true" valueChangeListener="#{nhutTestBean.onMyValueChanged}"> <tr:selectItem label="0" value="0"/> <tr:selectItem label="1" value="1"/> <tr:selectItem label="2" value="2"/> <tr:selectItem label="3" value="3"/> </tr:selectOneChoice> <tr:selectOneChoice id="two" value="#{nhutTestBean.two}" partialTriggers="one"> <f:selectItems value="#{nhutTestBean.myList}"/> </tr:selectOneChoice> <tr:outputText id="nhutTextBox" value="hello: #{nhutTestBean.output}" partialTriggers="one"/></tr:form> and my valueChangeEvent method: public void onMyValueChanged(ValueChangeEvent event) { this.setOutput((String)event.getNewValue()); this.setTwo((String)event.getNewValue()); } One thing I realize is that it calls my setTwo twice, the first the set the correct values, but the second time set it to null so that nothing would be selected for the two drop down box. please help. thank you so much.

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  • How should I generate the partitions / pairs for the Chinese Postman problem?

    - by Simucal
    I'm working on a program for class that involves solving the Chinese Postman problem. Our assignment only requires us to write a program to solve it for a hard-coded graph but I'm attempting to solve it for the general case on my own. The part that is giving me trouble is generating the partitions of pairings for the odd vertices. For example, if I had the following labeled odd verticies in a graph: 1 2 3 4 5 6 I need to find all the possible pairings / partitions I can make with these vertices. I've figured out I'll have i paritions given: n = num of odd verticies k = n / 2 i = ((2k)(2k-1)(2k-2)...(k+1))/2 So, given the 6 odd verticies above, we will know that we need to generate i = 15 partitions. The 15 partions would look like: 1 2 3 4 5 6 1 2 3 5 4 6 1 2 3 6 4 5 ... 1 6 ... Then, for each partition, I take each pair and find the shortest distance between them and sum them for that partition. The partition with the total smallest distance between its pairs is selected, and I then double all the edges between the shortest path between the odd vertices (found in the selected partition). These represent the edges the postman will have to walk twice. At first I thought I had worked out an appropriate algorithm for generating these partitions / pairs but it is flawed. I found it wasn't a simple permutation/combination problem. Does anyone who has studied this problem before have any tips that can help point me in the right direction for generating these partitions?

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  • SoundChannel, removeEventHandler, AS3

    - by pixelGreaser
    Is there a better way to use the sound channel is AS3? This works, but I hate it when I tap the play button twice and it starts doubling. Please advise. var mySound:Sound = new Sound(); playButton.addEventListener (MouseEvent.CLICK, myPlayButtonHandler); var myChannel:SoundChannel = new SoundChannel(); function myPlayButtonHandler (e:MouseEvent):void { myChannel = mySound.play(); } stopButton.addEventListener(MouseEvent.CLICK, onClickStop); function onClickStop(e:MouseEvent):void{ myChannel.stop(); } /*-----------------------------------------------------------------*/ //global sound buttons, add instance of 'killswitch' and 'onswitch' to stage killswitch.addEventListener(MouseEvent.CLICK, clipKillSwitch); function clipKillSwitch(e:MouseEvent):void{ var transform1:SoundTransform=new SoundTransform(); transform1.volume=0; flash.media.SoundMixer.soundTransform=transform1; } onswitch.addEventListener(MouseEvent.CLICK, clipOnSwitch); function clipOnSwitch(e:MouseEvent):void{ var transform1_:SoundTransform=new SoundTransform(); transform1_.volume=1; flash.media.SoundMixer.soundTransform=transform1_; }

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  • Why does one of these statements compile in Scala but not the other?

    - by Jeff
    (Note: I'm using Scala 2.7.7 here, not 2.8). I'm doing something pretty simple -- creating a map based on the values in a simple, 2-column CSV file -- and I've completed it easily enough, but I'm perplexed at why my first attempt didn't compile. Here's the code: // Returns Iterator[String] private def getLines = Source.fromFile(csvFilePath).getLines // This doesn't compile: def mapping: Map[String,String] = { Map(getLines map { line: String => val pairArr = line.split(",") pairArr(0) -> pairArr(1).trim() }.toList:_*) } // This DOES compile def mapping: Map[String,String] = { def strPair(line: String): (String,String) = { val pairArr = line.split(",") pairArr(0) -> pairArr(1).trim() } Map(getLines.map( strPair(_) ).toList:_*) } The compiler error is CsvReader.scala:16: error: value toList is not a member of (St ring) = (java.lang.String, java.lang.String) [scalac] possible cause: maybe a semicolon is missing before `value toList'? [scalac] }.toList:_*) [scalac] ^ [scalac] one error found So what gives? They seem like they should be equivalent to me, apart from the explicit function definition (vs. anonymous in the nonworking example) and () vs. {}. If I replace the curly braces with parentheses in the nonworking example, the error is "';' expected, but 'val' found." But if I remove the local variable definition and split the string twice AND use parens instead of curly braces, it compiles. Can someone explain this difference to me, preferably with a link to Scala docs explaining the difference between parens and curly braces when used to surround method arguments?

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  • Core principles, rules, and habits for CS students

    - by Asad Butt
    No doubt there is a lot to read on blogs, in books, and on Stack Overflow, but can we identify some guidelines for CS students to use while studying? For me these are: Finish your course books early and read 4-5 times more material relative to your course work. Programming is the one of the fastest evolving professions. Follow the blogs on a daily basis for the latest updates, news, and technologies. Instead of relying on assignments and exams, do at least one extra, non-graded, small to medium-sized project for every programming course. Fight hard for internships or work placements even if they are unpaid, since 3 months of work 1 year at college. Practice everything, every possible and impossible way. Try doing every bit of your assignments project yourself; i.e. fight for every inch. Rely on documentation as the first source for help and samples, Google, and online forums as the last source. Participate often in online communities and forums to learn the best possible approach for every solution to your problem. (After doing your bit.) Make testing one of your habits as it is getting more important everyday in programming. Make writing one of your habits. Write something productive once or twice a week and publish it.

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  • Changing variables outside of Scope C#

    - by sam
    Hi, I'm a beginner C# programmer, and to improve my skills I decided to give Project Euler a try. The first problem on the site asks you to find the sum of all the multiples of 3 and 5 under 1000. Since I'm essentially doing the same thing twice, I made a method to multiply a base number incrementally, and add the sum of all the answers togethor. public static int SumOfMultiplication(int Base, int limit) { bool Escape = false; for (int mult = 1; Escape == true; mult++) { int Number = 0; int iSum = 0; Number = Base * mult; if (Number > limit) return iSum; else iSum = iSum + Number; } regardless of what I put in for both parameters, it ALWAYS returns zero. I'm 99% sure it has something to do with the scope of the variables, but I have no clue how to fix it. All help is appreciated. Thanks in advance, Sam

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  • How to handle pagination queries properly with mongodb and php?

    - by luckytaxi
    Am I doing this right? I went to look at some old PHP code w/ MySQL and I've managed to get it to work, however I'm wondering if there's a much "cleaner" and "faster" way of accomplishing this. First I would need to get the total number of "documents" $total_documents = $collection->find(array("tags" => $tag, "seeking" => $this->session->userdata('gender'), "gender" => $this->session->userdata('seeking')))->count(); $skip = (int)($docs_per_page * ($page - 1)); $limit = $docs_per_page; $total_pages = ceil($total_documents / $limit); // Query to populate array so I can display with pagination $data['result'] = $collection->find(array("tags" => $tag, "seeking" => $this->session->userdata('gender'), "gender" => $this->session->userdata('seeking')))->limit($limit)->skip($skip)->sort(array("_id" => -1)); My question is, can I run the query in one shot? I'm basically running the same query twice, except the second time I'm passing the value to skip between records.

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  • JBoss Clustered Service that sends emails from txt file

    - by michael lucas
    I need a little push in the right direction. Here's my problem: I have to create an ultra-reliable service that sends email messages to clients whose addresses are stored in txt file on FTP server. Single txt file may contain unlimited number of entries. Most often the file contains about 300,000 entries. Service exposes interface with just two simple methods: TaskHandle sendEmails(String ftpFilePath); ProcessStatus checkProcessStatus(TaskHandle taskHandle); Method sendEmails() returns TaskHandle by which we can ask for ProcessStatus. For such a service to be reliable clustering is necessary. Processing single txt file might take a long time. Restarting one node in a cluster should have no impact on sending emails. We use JBoss AS 4.2.0 which comes with a nice HASingletonController that ensure one instance of service is running at given time. But once a fail-over happens, the second service should continue work from where the first one stopped. How can I share state between nodes in a cluster in such a way that leaves no possibility of sending some emails twice?

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  • Dynamically created controls and the ASP.NET page lifecycle

    - by Dirk
    I'm working on an ASP.NET project in which the vast majority of the forms are generated dynamically at run time (form definitions are stored in a DB for customizability). Therefore, I have to dynamically create and add my controls to the Page every time OnLoad fires, regardless of IsPostBack. This has been working just fine and .NET takes care of managing ViewState for these controls. protected override void OnLoad(EventArgs e) { base.OnLoad(e); RenderDynamicControls() } private void RenderDynamicControls(){ //1. call service layer to retrieve form definition //2. create and add controls to page container } I have a new requirement in which if a user clicks on a given button (this button is created at design time) the page should be re-rendered in a slightly different way. So in addition to the code that executes in OnLoad (i.e. RenderDynamicControls()), I have this code: protected void MyButton_Click(object sender, EventArgs e) { RenderDynamicControlsALittleDifferently() } private void RenderDynamicControlsALittleDifferently() (){ //1. clear all controls from the page container added in RenderDynamicControls() //2. call service layer to retrieve form definition //3. create and add controls to page container } My question is, is this really the only way to accomplish what I'm after? It seems beyond hacky to effectively render the form twice simply to respond to a button click. I gather from my research that this is simply how the page-lifecycle works in ASP.NET: Namely, that OnLoad must fire on every Postback before child events are invoked. Still, it's worthwhile to check with the SO community before having to drink the kool-aid. On a related note, once I get this feature completed, I'm planning on throwing an UpdatePanel on the page to perform the page updates via Ajax. Any code/advice that make that transition easier would be much appreciated. Thanks

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  • Help with Assembly/SSE Multiplication

    - by Brett
    I've been trying to figure out how to gain some improvement in my code at a very crucial couple lines: float x = a*b; float y = c*d; float z = e*f; float w = g*h; all a, b, c... are floats. I decided to look into using SSE, but can't seem to find any improvement, in fact it turns out to be twice as slow. My SSE code is: Vector4 abcd, efgh, result; abcd = [float a, float b, float c, float d]; efgh = [float e, float f, float g, float h]; _asm { movups xmm1, abcd movups xmm2, efgh mulps xmm1, xmm2 movups result, xmm1 } I also attempted using standard inline assembly, but it doesn't appear that I can pack the register with the four floating points like I can with SSE. Any comments, or help would be greatly appreciated, I mainly need to understand why my calculations using SSE are slower than the serial C++ code? I'm compiling in Visual Studio 2005, on a Windows XP, using a Pentium 4 with HT if that provides any additional information to assit. Thanks in advance!

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  • SQL query for selecting the firsts in a series by cloumn

    - by SP
    I'm having some trouble coming up with a query for what I am trying to do. I've got a table we'll call 'Movements' with the following columns: RecID(Key), Element(f-key), Time(datetime), Room(int) The table is holding a history of Movements for the Elements. One record contains the element the record is for, the time of the recorded location, and the room it was in at that time. What I would like are all records that indicate that an Element entered a room. That would mean the first (by time) entry for any element in a series of movements for that element in the same room. The input is a room number and a time. IE, I would like all of the records indicating that any Element entered room X after time Y. The closest I came was this Select Element, min(Time) from Movements where Time > Y and Room = x group by Element This will only give me one room entry record per Element though (If the Element has entered the room X twice since time Y I'll only get the first one back) Any ideas? Let me know if I have not explained this clearly. I'm using MS SQLServer 2005.

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  • Looking for a web based, embeddable file manager

    - by Kristi H.
    I'm looking for a web based, embeddable file manager. I haven't found anything suitable through Google or the Stack Overflow archives. Does anyone know of a file manager that meets the following criteria? The file manager must… …be embeddable (e.g. Flash or a Java applet) …run from my server (no storing uploads in a remote location) …be licensed for business use (fees are okay) …let me disable uploads. Users shouldn't be able to upload files, only download them …allow me to tag files and/or place them in folders …let me disable authentication or handle it from the backend. My app already has a login system and I don't want to make users log in twice …allow users to select and download multiple files …have an attractive interface The file manager should… …have an external config file …display thumbnail previews for files …be skinnable …be actively developed or at least actively maintained Thanks for your help. I need a sophisticated file manager and I'd like to avoid writing it from scratch.

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  • Applications result affected by another running application.

    - by Jamie Keeling
    This is a follow on from my previous question although this is about something else. I've been having a problem where for some reason my message that I pass from one process to another only displays the first letter, in this case "M". My application is based on a MSDN sample so to make sure I hadn't missed something I create a separate solution, added the MSDN sample (without any changes for my needs) and unsurprisingly it works fine. Now for the weird bit, when I run the MSDN sample running (as in debugging) and have my own application running, the text prints out fine without any problems. The second I run my on its own without the original MSDN sample being open, and it fails to work and only shows an "M". I've looked in the debugger and don't seem to notice anything suspicious (it's a slightly dated picture, I've fixed the data type inconsistency). Can anyone provide a solution for this? I've never encountered anything like this before. To look at my source code it's easier to just look at the link I posted at the top of the question, there's no point in me posting it twice. Thank you for any help.

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  • The fastest way to iterate through a collection of objects

    - by Trev
    Hello all, First to give you some background: I have some research code which performs a Monte Carlo simulation, essential what happens is I iterate through a collection of objects, compute a number of vectors from their surface then for each vector I iterate through the collection of objects again to see if the vector hits another object (similar to ray tracing). The pseudo code would look something like this for each object { for a number of vectors { do some computations for each object { check if vector intersects } } } As the number of objects can be quite large and the amount of rays is even larger I thought it would be wise to optimise how I iterate through the collection of objects. I created some test code which tests arrays, lists and vectors and for my first test cases found that vectors iterators were around twice as fast as arrays however when I implemented a vector in my code in was somewhat slower than the array I was using before. So I went back to the test code and increased the complexity of the object function each loop was calling (a dummy function equivalent to 'check if vector intersects') and I found that when the complexity of the function increases the execution time gap between arrays and vectors reduces until eventually the array was quicker. Does anyone know why this occurs? It seems strange that execution time inside the loop should effect the outer loop run time.

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  • Singleton Pattern combine with a Decorator

    - by Mike
    Attached is a classic Decorator pattern. My question is how would you modify the below code so that you can wrap zero or one of each topping on to the Pizza Right now I can have a Pepporini - Sausage -- Pepporini -- Pizza class driving the total cost up to $10, charging twice for Pepporini. I don't think I want to use the Chain of Responsibility pattern as order does not matter and not all toppings are used? Thank you namespace PizzaDecorator { public interface IPizza { double CalculateCost(); } public class Pizza: IPizza { public Pizza() { } public double CalculateCost() { return 8.00; } } public abstract class Topping : IPizza { protected IPizza _pizzaItem; public Topping(IPizza pizzaItem) { this._pizzaItem = pizzaItem; } public abstract double CalculateCost(); } public class Pepporini : Topping { public Pepporini(IPizza pizzaItem) : base(pizzaItem) { } public override double CalculateCost() { return this._pizzaItem.CalculateCost() + 0.50; } } public class Sausage : Topping { public Sausage(IPizza pizzaItem) : base(pizzaItem) { } public override double CalculateCost() { return this._pizzaItem.CalculateCost() + 1.00; } } public class Onions : Topping { public Onions(IPizza pizzaItem) : base(pizzaItem) { } public override double CalculateCost() { return this._pizzaItem.CalculateCost() + .25; } } }

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  • Accelerometer gravity components

    - by Dvd
    Hi, I know this question is definitely solved somewhere many times already, please enlighten me if you know of their existence, thanks. Quick rundown: I want to compute from a 3 axis accelerometer the gravity component on each of these 3 axes. I have used 2 axes free body diagrams to work out the accelerometer's gravity component in the world X-Z, Y-Z and X-Y axes. But the solution seems slightly off, it's acceptable for extreme cases when only 1 accelerometer axis is exposed to gravity, but for a pitch and roll of both 45 degrees, the combined total magnitude is greater than gravity (obtained by Xa^2+Ya^2+Za^2=g^2; Xa, Ya and Za are accelerometer readings in its X, Y and Z axis). More detail: The device is a Nexus One, and have a magnetic field sensor for azimuth, pitch and roll in addition to the 3-axis accelerometer. In the world's axis (with Z in the same direction as gravity, and either X or Y points to the north pole, don't think this matters much?), I assumed my device has a pitch (P) on the Y-Z axis, and a roll (R) on the X-Z axis. With that I used simple trig to get: Sin(R)=Ax/Gxz Cos(R)=Az/Gxz Tan(R)=Ax/Az There is another set for pitch, P. Now I defined gravity to have 3 components in the world's axis, a Gxz that is measurable only in the X-Z axis, a Gyz for Y-Z, and a Gxy for X-Y axis. Gxz^2+Gyz^2+Gxy^2=2*G^2 the 2G is because gravity is effectively included twice in this definition. Oh and the X-Y axis produce something more exotic... I'll explain if required later. From these equations I obtained a formula for Az, and removed the tan operations because I don't know how to handle tan90 calculations (it's infinity?). So my question is, anyone know whether I did this right/wrong or able to point me to the right direction? Thanks! Dvd

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  • PHP: What is an efficient way to parse a text file containing very long lines?

    - by Shaun
    I'm working on a parser in php which is designed to extract MySQL records out of a text file. A particular line might begin with a string corresponding to which table the records (rows) need to be inserted into, followed by the records themselves. The records are delimited by a backslash and the fields (columns) are separated by commas. For the sake of simplicity, let's assume that we have a table representing people in our database, with fields being First Name, Last Name, and Occupation. Thus, one line of the file might be as follows [People] = "\Han,Solo,Smuggler\Luke,Skywalker,Jedi..." Where the ellipses (...) could be additional people. One straightforward approach might be to use fgets() to extract a line from the file, and use preg_match() to extract the table name, records, and fields from that line. However, let's suppose that we have an awful lot of Star Wars characters to track. So many, in fact, that this line ends up being 200,000+ characters/bytes long. In such a case, taking the above approach to extract the database information seems a bit inefficient. You have to first read hundreds of thousands of characters into memory, then read back over those same characters to find regex matches. Is there a way, similar to the Java String next(String pattern) method of the Scanner class constructed using a file, that allows you to match patterns in-line while scanning through the file? The idea is that you don't have to scan through the same text twice (to read it from the file into a string, and then to match patterns) or store the text redundantly in memory (in both the file line string and the matched patterns). Would this even yield a significant increase in performance? It's hard to tell exactly what PHP or Java are doing behind the scenes.

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  • Adding one subquery makes query a little slower, adding another makes it way slower

    - by Jason Swett
    This is fast: select ba.name, penamt.value penamt, #address_line4.value address_line4 from account a join customer c on a.customer_id = c.id join branch br on a.branch_id = br.id join bank ba on br.bank_id = ba.id join account_address aa on aa.account_id = a.id join address ad on aa.address_id = ad.id join state s on ad.state_id = s.id join import i on a.import_id = i.id join import_bundle ib on i.import_bundle_id = ib.id join (select * from unused where heading_label = 'PENAMT') penamt ON penamt.account_id = a.id #join (select * from unused where heading_label = 'Address Line 4') address_line4 ON address_line4.account_id = a.id where i.active=1 And this is fast: select ba.name, #penamt.value penamt, address_line4.value address_line4 from account a join customer c on a.customer_id = c.id join branch br on a.branch_id = br.id join bank ba on br.bank_id = ba.id join account_address aa on aa.account_id = a.id join address ad on aa.address_id = ad.id join state s on ad.state_id = s.id join import i on a.import_id = i.id join import_bundle ib on i.import_bundle_id = ib.id #join (select * from unused where heading_label = 'PENAMT') penamt ON penamt.account_id = a.id join (select * from unused where heading_label = 'Address Line 4') address_line4 ON address_line4.account_id = a.id where i.active=1 But this is slow: select ba.name, penamt.value penamt, address_line4.value address_line4 from account a join customer c on a.customer_id = c.id join branch br on a.branch_id = br.id join bank ba on br.bank_id = ba.id join account_address aa on aa.account_id = a.id join address ad on aa.address_id = ad.id join state s on ad.state_id = s.id join import i on a.import_id = i.id join import_bundle ib on i.import_bundle_id = ib.id join (select * from unused where heading_label = 'PENAMT') penamt ON penamt.account_id = a.id join (select * from unused where heading_label = 'Address Line 4') address_line4 ON address_line4.account_id = a.id where i.active=1 Why is it fast when I include just one of the two subqueries but slow when I include both? I would think it should be twice as slow when I include both, but it takes a really long time. On on MySQL.

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  • NUnit integration programmatically with spring

    - by harkon
    Hi! I have a component based architecture framework designed and I use NUnit for isolated testing - okay so far. Now I want to enable integration tests. Therefore the tests use real implementations of the existing components. Each element of the component has a life cycle (init, start and stop) and I created a NUnit component. In the start section the Console runner of the NUnit will be executed. Okay - now if I have a test fixture class in my dlls in the execution path the runner exectues them - fine! But: And this is crucial! Each to be tested implementation exists so far in the process and I want to use this instances for testing. If I use NUnit runner in the current way each instance will be created twice - and above all: I have a spring container and a implementation registry. Via this registry I can get access to all instances in the processes. But how do I give the test fixture access to the existing registry? Good: I can start the component architecture framework in the startup of the nunit runner - but this is not what I want. My guide is the apache Cactus framework (with JUnit and tomcat, JBoss etc.) Can someone help? Thanks a lot! Check: http://cone.codeplex.com

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  • jQuery e.target bubbling best practice ?

    - by olouv
    In my heavy-ajax code, i always bind "click" the body tag & act depending on $(e.target) & using $.fn.hasClass(). However when i click on an anchor that has a </span> tag inside, my $(e.target) equals this node, and not the parent anchor as i would like it to. From now on, i have used this trick (var $t = $(e.target);) : /** bubbling **/ if($t.get(0).tagName !== "A" && $t.get(0).tagName !== "AREA") { $t = $t.parent("a"); if(empty($t)) return true; //else console.log("$t.bubble()", $t); } It feels wrong somehow... Do you have any better implementation ? $.fn.live() does not solve my issue as it still returns the span as the target. Moreover i'm looking for speed (running on atom-based touch devices) & live appeared to be way slower (twice) : http://jsperf.com/bind-vs-click/3 In fact, as @Guffa pointed, using $.fn.live() solves the span bubbling issue as i don't need the event.target anymore. I guess there is no other "right" answer here (using bind).

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  • Strange behavior with complex Q object filter queries in Django

    - by HWM-Rocker
    Hi I am trying to write a tagging system for Django, but today I encountered a strange behavior in filter or the Q object (django.db.models.Q). I wrote a function, that converts a search string into a Q object. The next step would be to filter the TaggedObject with these query. But unfortunately I get a strange behavior. when I search (id=20) = Q: (AND: ('tags__tag__id', 20)) and it returns 2 Taged Objects with the ID 1127 and 132 when I search (id=4) = Q: (AND: ('tags__tag__id', 4)) and it returns also 2 Objects, but this time 1180 and 1127 until here is everything fine, but when i make a little bit more complex query like (id=4) or (id=20) = Q: (OR: ('tags__tag__id', 4), ('tags__tag__id', 20)) then it returns 4(!) Objects 1180, 1127, 1127, 132 But the object with the ID 1127 is returned twice, but thats not the behaviour I want. Do I have to live with it, and uniqify that list or can I do something different. The representation of the Q object looks fine for me. But the worst is now, when I search for (id=20) and (id=4) = Q: (AND: ('tags__tag__id', 20), ('tags__tag__id', 4)) then it returns no object at all. But why? The representation should be ok and the object with the id 1127 is tagged by both. What am I missing? Here are also the relevant parts of the classes, that are involved: class TaggedObject(models.Model): """ class that represent a tagged object """ tags = generic.GenericRelation('ObjectTagBridge', blank=True, null=True) class ObjectTagBridge(models.Model): """ Help to connect a generic object to a Tag. """ # pylint: disable-msg=W0232,R0903 content_type = models.ForeignKey(ContentType) object_id = models.PositiveIntegerField() content_object = generic.GenericForeignKey('content_type', 'object_id') tag = models.ForeignKey('Tag') class Tag(models.Model): ... Thanks for your help

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  • linq: SQL performance on high loaded web applications

    - by Alex
    I started working with linq to SQL several weeks ago. I got really tired of working with SQL server directly through the SQL queries (sqldatareader, sqlcommand and all this good stuff).  After hearing about linq to SQL and mvc I quickly moved all my projects to these technologies. I expected linq to SQL work slower but it suprisongly turned out to be pretty fast, primarily because I always forgot to close my connections when using datareaders. Now I don't have to worry about it. But there's one problem that really bothers me. There's one page that's requested thousands of times a day. The system gets data in the beginning, works with it and updates it. Primarily the updates are ++ @ -- (increase and decrease values). I used to do it like this UPDATE table SET value=value+1 WHERE ID=@I'd It worked with no problems obviously. But with linq to SQL the data is taken in the beginning, moved to the class, changed and then saved. Stats.registeredusers++; Db.submitchanges(); Let's say there were 100 000 users. Linq will say "let it be 100 001" instead of "let it be increased by 1". But if there value of users has already been increased (that happens in my site all the time) then linq will be like oops, this value is already 100 001. Whatever I'll throw an exception" You can change this behavior so that it won't throw an exception but it still will not set the value to 100 002. Like I said, it happened with me all the time. The stas value was increased twice a second on average. I simply had to rewrite this chunk of code with classic ado net. So my question is how can you solve the problem with linq

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  • C# Fun with Generics - Mutual Dependencies

    - by Kenneth Cochran
    As an experiment I'm trying to write a generic MVP framework. I started with: public interface IPresenter<TView> where TView: IView<IPresenter<... { TView View { get; set;} } public interface IView<TPresenter> where TPresenter:IPresenter<IView<... { TPresenter Presenter { get; set; } } Obviously this can't work because the types of TView and TPresenter can't be resolved. You'd be writing Type<Type<... forever. So my next attempt looked like this: public interface IView<T> where T:IPresenter { ... } public interface IView:IView<IPresenter> { } public interface IPresenter<TView> where TView: IView { ... } public interface IPresenter: IPresenter<IView> { ... } This actually compiles and you can even inherit from these interfaces like so: public class MyView : IView, IView<MyPresenter> { ... } public class MyPresenter : IPresenter, IPresenter<MyView> { ... } The problem is in the class definition you have to define any members declared in the generic type twice. Not ideal but it still compiles. The problem's start creeping up when you actually try to access the members of a Presenter from a View or vice versa. You get an Ambiguous reference when you try to compile. Is there any way to avoid this double implementation of a member when you inherit from both interfaces? Is it even possible to resolve two mutually dependent generic types at compile time?

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  • What can cause my code to run slower when the server JIT is activated?

    - by durandai
    I am doing some optimizations on an MPEG decoder. To ensure my optimizations aren't breaking anything I have a test suite that benchmarks the entire codebase (both optimized and original) as well as verifying that they both produce identical results (basically just feeding a couple of different streams through the decoder and crc32 the outputs). When using the "-server" option with the Sun 1.6.0_18, the test suite runs about 12% slower on the optimized version after warmup (in comparison to the default "-client" setting), while the original codebase gains a good boost running about twice as fast as in client mode. While at first this seemed to be simply a warmup issue to me, I added a loop to repeat the entire test suite multiple times. Then execution times become constant for each pass starting at the 3rd iteration of the test, still the optimized version stays 12% slower than in the client mode. I am also pretty sure its not a garbage collection issue, since the code involves absolutely no object allocations after startup. The code consists mainly of some bit manipulation operations (stream decoding) and lots of basic floating math (generating PCM audio). The only JDK classes involved are ByteArrayInputStream (feeds the stream to the test and excluding disk IO from the tests) and CRC32 (to verify the result). I also observed the same behaviour with Sun JDK 1.7.0_b98 (only that ist 15% instead of 12% there). Oh, and the tests were all done on the same machine (single core) with no other applications running (WinXP). While there is some inevitable variation on the measured execution times (using System.nanoTime btw), the variation between different test runs with the same settings never exceeded 2%, usually less than 1% (after warmup), so I conclude the effect is real and not purely induced by the measuring mechanism/machine. Are there any known coding patterns that perform worse on the server JIT? Failing that, what options are available to "peek" under the hood and observe what the JIT is doing there?

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  • Why are my events being called more than once?

    - by Arms
    In my Flash project I have a movieclip that has 2 keyframes. Both frames contain 1 movieclip each. frame 1 - Landing frame 2 - Game The flow of the application is simple: User arrives on landing page (frame 1) User clicks "start game" button User is brought to the game page (frame 2) When the game is over, the user can press a "play again" button which brings them back to step 1 Both Landing and Game movieclips are linked to separate classes that define event listeners. The problem is that when I end up back at step 1 after playing the game, the Game event listeners fire twice for their respective event. And if I go through the process a third time, the event listeners fire three times for every event. This keeps happening, so if I loop through the application flow 7 times, the event listeners fire seven times. I don't understand why this is happening because on frame 1, the Game movieclip (and I would assume its related class instance) does not exist - but I'm clearly missing something here. I've run into this problem in other projects too, and tried fixing it by first checking if the event listeners existed and only defining them if they didn't, but I ended up with unexpected results that didn't really solve the problem. I need to ensure that the event listeners only fire once. Any advice & insight would be greatly appreciated, thanks!

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