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  • why i cant read my webservice with jquery???

    - by rima
    what's my function problem?I wana read from my webservice but I just receive error :( the browser message is: "undefined- status:error" when I press button just I see the error function of my Jqueary calling but I dont know why??plz help me. function SetupCompanyInfo(companyID) { //alert('aaa'); companyID = '1'; $.ajax({ type: "POST", url: '../../../Services/CompanyServices.asmx/GetCompanyInfo', data: "{}", contentType: "application/json; charset=utf-8", dataType: "json", success: OnSuccess, error: OnError }); } function OnSuccess(data, status) { SetMainBody(data); } function OnError(request, status, error) { SetMainBody(error + '- ' + request + ' status:' + status); } my webservice: using System; using System.Web.Services; using System.Web.Script.Services; /// <summary> /// Summary description for CompanyServices /// </summary> [WebService(Namespace = "http://tempuri.org/")] [WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)] [ScriptService] //[System.ComponentModel.ToolboxItem(false)] public class CompanyServices : System.Web.Services.WebService { [WebMethod] public string GetCompanyInfo() { string response = "aaa"; Console.WriteLine("here"); return response.ToString(); } [WebMethod] public string GetCompanyInfo(string id) { string response = "aaa"; Console.WriteLine("here2"+id); return response.ToString(); } } my aspx file,part of head and my button code: <script src="../../Scripts/InnerFunctions.js" type="text/javascript"></script> <script src="../../Scripts/jquery-1.3.2.min.js" type="text/javascript"></script> <script src="../../Scripts/TabMenu.js" type="text/javascript"></script> <script src="Scripts/InternalFunctions.js" type="text/javascript"></script> <div dir="rtl" style="border: 1px solid #CCCCCC"> <asp:Image ID="Image1" runat="server" ImageUrl="../../generalImg/Icons/64X64/settings_Icon_64.gif" style="width: 27px; height: 26px" onclick="SetupCompanyInfo(1)" /></div>

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  • Why doesn't String's hashCode() cache 0?

    - by polygenelubricants
    I noticed in the Java 6 source code for String that hashCode only caches values other than 0. The difference in performance is exhibited by the following snippet: public class Main{ static void test(String s) { long start = System.currentTimeMillis(); for (int i = 0; i < 10000000; i++) { s.hashCode(); } System.out.format("Took %d ms.%n", System.currentTimeMillis() - start); } public static void main(String[] args) { String z = "Allocator redistricts; strict allocator redistricts strictly."; test(z); test(z.toUpperCase()); } } Running this in ideone.com gives the following output: Took 1470 ms. Took 58 ms. So my questions are: Why doesn't String's hashCode() cache 0? What is the probability that a Java string hashes to 0? What's the best way to avoid the performance penalty of recomputing the hash value every time for strings that hash to 0? Is this the best-practice way of caching values? (i.e. cache all except one?) For your amusement, each line here is a string that hash to 0: pollinating sandboxes amusement & hemophilias schoolworks = perversive electrolysissweeteners.net constitutionalunstableness.net grinnerslaphappier.org BLEACHINGFEMININELY.NET WWW.BUMRACEGOERS.ORG WWW.RACCOONPRUDENTIALS.NET Microcomputers: the unredeemed lollipop... Incentively, my dear, I don't tessellate a derangement. A person who never yodelled an apology, never preened vocalizing transsexuals.

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  • Why C++ is (one of) the best language to learn at first [closed]

    - by AlexV
    C++ is one of the most used programming language in the world since like 25+ years. My first job as programmer was in C++ and I coded in C++ everyday for nearly 4 years. Now I do mostly PHP, but I will forever cherish this C++ background. C++ has helped me understand many "under the hood" features/behaviors/restrictions of many other (and different) programming languages like PHP and Delphi. I'm a full time programmer for 6+ years now and since I have a quite varied programming background I often get questions by "newbies" as where to start to become a "good" programmer. I think C++ is one of the best language to start with because it gives you a real usefull experience that will last and will teach you how things work under the hood. It's not the easier one to learn for a newbie, but in my opinion it's the one who will reward the most in long term. I would like to know your opinion on this matter to add to my arguments when I guide "newbies". After this introduction, here's my question : Why C++ is for you (one of) the best language to learn at first. Since it's subjective, I've marked this question as community wiki.

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  • Scala always returning true....WHY?

    - by jhamm
    I am trying to learn Scala and am a newbie. I know that this is not optimal functional code and welcome any advice that anyone can give me, but I want to understand why I keep getting true for this function. def balance(chars: List[Char]): Boolean = { val newList = chars.filter(x => x.equals('(') || x.equals(')')); return countParams(newList, 0) } def countParams(xs: List[Char], y: Int): Boolean = { println(y + " right Here") if (y < 0) { println(y + " Here") return false } else { println(y + " Greater than 0") if (xs.size > 0) { println(xs.size + " this is the size") xs match { case xs if (xs.head.equals('(')) => countParams(xs.tail, y + 1) case xs if (xs.head.equals(')')) => countParams(xs.tail, y - 1) case xs => 0 } } } return true; } balance("()())))".toList) I know that I am hitting the false branch of my if statement, but it still returns true at the end of my function. Please help me understand. Thanks.

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  • Python: why can't descriptors be instance variables?

    - by Continuation
    Say I define this descriptor: class MyDescriptor(object): def __get__(self, instance, owner): return self._value def __set__(self, instance, value): self._value = value def __delete__(self, instance): del(self._value) And I use it in this: class MyClass1(object): value = MyDescriptor() >>> m1 = MyClass1() >>> m1.value = 1 >>> m2 = MyClass1() >>> m2.value = 2 >>> m1.value 2 So value is a class attribute and is shared by all instances. Now if I define this: class MyClass2(object) value = 1 >>> y1 = MyClass2() >>> y1.value=1 >>> y2 = MyClass2() >>> y2.value=2 >>> y1.value 1 In this case value is an instance attribute and is not shared by the instances. Why is it that when value is a descriptor it can only be a class attribute, but when value is a simple integer it becomes an instance attribute?

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  • Why doesn't this CompiledQuery give a performance improvement?

    - by Grammarian
    I am trying to speed up an often used query. Using a CompiledQuery seemed to be the answer. But when I tried the compiled version, there was no difference in performance between the compiled and non-compiled versions. Can someone please tell me why using Queries.FindTradeByTradeTagCompiled is not faster than using Queries.FindTradeByTradeTag? static class Queries { // Pre-compiled query, as per http://msdn.microsoft.com/en-us/library/bb896297 private static readonly Func<MyEntities, int, IQueryable<Trade>> mCompiledFindTradeQuery = CompiledQuery.Compile<MyEntities, int, IQueryable<Trade>>( (entities, tag) => from trade in entities.TradeSet where trade.trade_tag == tag select trade); public static Trade FindTradeByTradeTagCompiled(MyEntities entities, int tag) { IQueryable<Trade> tradeQuery = mCompiledFindTradeQuery(entities, tag); return tradeQuery.FirstOrDefault(); } public static Trade FindTradeByTradeTag(MyEntities entities, int tag) { IQueryable<Trade> tradeQuery = from trade in entities.TradeSet where trade.trade_tag == tag select trade; return tradeQuery.FirstOrDefault(); } }

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  • Why is T() = T() allowed?

    - by Rimo
    I believe the expression T() creates an rvalue (by the Standard). However, the following code compiles (at least on gcc4.0): class T {}; int main() { T() = T(); } I know technically this is possible because member functions can be invoked on temporaries and the above is just invoking the operator= on the rvalue temporary created from the first T(). But conceptually this is like assigning a new value to an rvalue. Is there a good reason why this is allowed? Edit: The reason I find this odd is it's strictly forbidden on built-in types yet allowed on user-defined types. For example, int(2) = int(3) won't compile because that is an "invalid lvalue in assignment". So I guess the real question is, was this somewhat inconsistent behavior built into the language for a reason? Or is it there for some historical reason? (E.g it would be conceptually more sound to allow only const member functions to be invoked on rvalue expressions, but that cannot be done because that might break some existing code.)

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  • Why use Intent.URI_INTENT_SCHEME

    - by hks
    while reading Android docs about Widgets I stumbled upon this piece of code whose purpose is to launch a service for retrieving a factory for StackView items. // Set up the intent that starts the StackViewService, which will // provide the views for this collection. Intent intent = new Intent(context, StackWidgetService.class); // Add the app widget ID to the intent extras. intent.putExtra(AppWidgetManager.EXTRA_APPWIDGET_ID, appWidgetIds[i]); intent.setData(Uri.parse(intent.toUri(Intent.URI_INTENT_SCHEME))); // Instantiate the RemoteViews object for the App Widget layout. RemoteViews rv = new RemoteViews(context.getPackageName(), R.layout.widget_layout); // Set up the RemoteViews object to use a RemoteViews adapter. // This adapter connects // to a RemoteViewsService through the specified intent. // This is how you populate the data. rv.setRemoteAdapter(appWidgetIds[i], R.id.stack_view, intent); You can find it here I have a problem understanding why do you need to call intent.setData(Uri.parse(intent.toUri(Intent.URI_INTENT_SCHEME))); I understand that it gives URI a prefix intent://, but is it necessary here?

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  • C# why unit test has this strange behaviour?

    - by 5YrsLaterDBA
    I have a class to encrypt the connectionString. public class SKM { private string connStrName = "AndeDBEntities"; internal void encryptConnStr() { if(isConnStrEncrypted()) return; ... } private bool isConnStrEncrypted() { bool status = false; // Open app.config of executable. System.Configuration.Configuration config = ConfigurationManager.OpenExeConfiguration(ConfigurationUserLevel.None); // Get the connection string from the app.config file. string connStr = config.ConnectionStrings.ConnectionStrings[connStrName].ConnectionString; status = !(connStr.Contains("provider")); Log.logItem(LogType.DebugDevelopment, "isConnStrEncrypted", "SKM::isConnStrEncrypted()", "isConnStrEncrypted=" + status); return status; } } Above code works fine in my application. But not in my unit test project. In my unit test project, I test the encryptConnStr() method. it will call isConnStrEncrypted() method. Then exception (null pointer) will be thrown at this line: string connStr = config.ConnectionStrings.ConnectionStrings[connStrName].ConnectionString; I have to use index like this to pass the unit test: string connStr = config.ConnectionStrings.ConnectionStrings[0].ConnectionString; I remember it worked several days ago at the time I added above unit test. But now it give me an error. The unit test is not integrated with our daily auto build yet. We only have ONE connectionStr. It works with product but not in unit test. Don't know why. Anybody can explain to me?

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  • Why my jquery function is not firing on Firefox

    - by Cristian Boariu
    I have some trouble with some jquery method (for some checkboxes I want them to fire on checked/unchecked so I can do something then). This method works perfectly on Chrome and IE but not on latest FF. jQuery(function () { jQuery(':checkbox').change(function () { var counter = jQuery('.count').text(); var thisCheck = jQuery(this); if (thisCheck.is(':checked')) { counter++; //apply green color to the selected row jQuery(this).closest('tr').addClass('checked'); } else { counter--; //remove green color to the selected row jQuery(this).closest('tr').removeClass('checked'); } jQuery('.count').html(counter); //enable export button when there are selected emails to be exported if (counter > 0) { jQuery(".exportButton").removeAttr("disabled", ""); } else { jQuery(".exportButton").attr("disabled", "disabled"); } }); }); Basically it's simply not firing...Even with Debug is not catching the first line (function declare nor other lines too). If I move this javascript(without function declare) inside jQuery(document).ready(function ($) { all works nice on Firefox too... Yes, I do use jQuery.noConflict(); before jQuery(document).ready(function ($) { Do you know why this happens?

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  • Why is my view controllers view not quadratic?

    - by mystify
    I created an UIViewController subclass, and figured out that the default implementation of -loadView in UIViewController will ignore my frame size settings in a strange way. To simplify it and to make sure it's really not the fault of my code, I did a clean test with a plain instance of UIViewController directly, rather than making a subclass. The result is the same. I try to make an exactly quadratic view of 320 x 320, but the view appears like 320 x 200. iPhone OS 3.0, please check this out: UIViewController *ts = [[UIViewController alloc] initWithNibName:nil bundle:nil]; ts.view.frame = CGRectMake(0.0f, 0.0f, 320.0f, 320.0f); ts.view.backgroundColor = [UIColor cyanColor]; [self.view addSubview:ts.view]; like you can see, I do this: 1) Create a UIViewController instance 2) Set the frame of the view to a quadratic dimension of 320 x 320 3) Give it a color, so I can see it 4) Added it as a subview. Now the part, that's even more strange: When I make my own implementation of -loadView, i.e. if I put this code in there like this: - (void)loadView { UIView *v = [[UIView alloc] initWithFrame:CGRectMake(0.0f, 0.0f, 320.0f, 320.0f)]; v.backgroundColor = [UIColor cyanColor]; self.view = v; [v release]; } then it looks right. Now lets think about that: In the first example, I do pretty much exactly the same, just that I let UIViewController create the view on it's own, and then take it over in order to change it's frame. Right? So why do I get this strange error? Right now I see no other way of messing around like that to correct this wrong behavior. I did not activate anything like clipsToBounds and there's no other code touching this.

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  • (Android) Why won't invalidate() update my buttons immediately?

    - by frustrated user
    I have read several forums and examples on using invalidate() in order to update views immediately but I still do not understand why what I am doing will not work. The code below uses image buttons defined by "red", "blue", "green", and "yellow". I set a 1 second delay between each time I try and change a button's appearance. Please someone tell me what i'm doing wrong. private void showPattern() { if (correct == true) { for (int k = 0; k < temp_basket.length; k++) { if (temp_basket[k] == 0) { red.setPressed(true); red.invalidate(); final Handler handler = new Handler(); Timer t = new Timer(); t.schedule(new TimerTask() { public void run() { handler.post(new Runnable() { public void run() { red.setPressed(false); red.invalidate(); } }); } }, 1000); There are 3 more or these blocks after this one that are blue, green, and yellow.

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  • why this code not works?

    - by badgirl
    Hello. I want to create new node of BeanTreeView, and when I add some node in constructor, then run the app, and then I try to view the window with tree, it throws this error java.lang.AssertionError: Component cannot be created for {component=null, displayName=Exploirer, instanceCreate=AlwaysEnabledAction[Exploirer]} at org.openide.windows.OpenComponentAction.getTopComponent(OpenComponentAction.java:71) Why? And how to add node there? See the code. private ProjectsChildren projectsChildren; private ProjectNode projectNode = new ProjectNode(new MainProject("ggg"), projectsChildren); public ExploirerTopComponent() { initComponents(); setName(NbBundle.getMessage(ExploirerTopComponent.class, "CTL_ExploirerTopComponent")); setToolTipText(NbBundle.getMessage(ExploirerTopComponent.class, "HINT_ExploirerTopComponent")); // setIcon(ImageUtilities.loadImage(ICON_PATH, true)); //map.put("delete", ExplorerUtils.actionDelete(mgr, true)); associateLookup (ExplorerUtils.createLookup(mgr, getActionMap())); //projectsChildren.createProject("demence"); /* somewhere here is the problem*/ mgr.setRootContext(projectNode); ProjectNode[] pr = null; pr[0] = projectNode; mgr.getRootContext().getChildren().add(pr); }

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  • VB6 Game Development : Don't ask me why :-)

    - by CVS-2600Hertz-wordpress-com
    Hi All, I am developing a game in VB6 (plz don't ask me why :) ). The storyboard is ready and a rough implementation is underway. I am following a "pure-software-rendering" approach. (i.e. no DirectX, no openGL etc.) Amongst many others, the following "serious" problems exist: 2D alpha transparency reqd. to implement overlays. Parallax implementation to give depth-of-field illusion. Capturing mouse-scroll events globally (as in FPS-es; mapping them to changing weapon). Async sound play with absolute "zero-lag". Any ideas anyone. Please suggest any well documented library/ocx or sample-code. Plz do provide solutions with max performance and with as little overhead as possible. Also, anyone who has developed any games, and would be open to sharing her/his code would be highly appreciated. (any well-acknowledged VB games whose source-code i can study??) Thank You

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  • why the exception is not caught?

    - by Álvaro García
    I have the following code: List<MyEntity> lstAllMyRecords = miDbContext.MyEntity.ToList<MyEntity>(); foreach MyEntity iterator in lstMainRecord) { tasks.Add( TaskEx.Run(() => { try { checkData(lstAllMyRecords.Where(n => n.IDReference == iterator.IDReference).ToList<MyEntity>()); } catch CustomRepository ex) { //handle my custom repository } catch (Exception) { throw; } }) ); }//foreach Task.WaitAll(tasks.ToArray()); I get all the records from my data base and in the foreach loop, I group all the records that have the same IDReference. Thenk I check if the data is correct with the method chekData. The checkData method throw a custom exception if something is wrong. I would like to catch this exception to handle it. But the problem is that with this code the exceptions are not caught and all seem to work without errors, but I know that this is not true. I try to check only one group of records that I know that has problems. If I check only one group of registrers, the loop is execute once and then only task is created. In this case the exception is caught, but if I have many groups, then any exception s thrwon. Why when I only have one task the exception is caught and with many groups are not? Thanks.

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  • Playing FLV unexpectedly stops, but why?

    - by Josamoto
    I am trying to play an FLV video that is about 90Mb big, using the following snippet: private function playVideo(url:String):void { var customClient:Object = new Object(); customClient.onMetaData = metaDataHandler; var nc:NetConnection = new NetConnection(); nc.connect(null); var ns:NetStream = new NetStream(nc); ns.client = customClient; ns.play(url); var myVideo:Video = new Video(); myVideo.attachNetStream(ns); addChild(myVideo); function metaDataHandler(infoObject:Object):void { myVideo.width = 640; myVideo.x = stage.stageWidth / 2 - 640 / 2; myVideo.height = 400; myVideo.y = 230; } } The video is not going to be streamed across the internet, in fact, the application will run locally and videos will also be loaded locally from disc. When starting my application, the video starts, but at random locations, playback completely freezes up, without any errors being thrown at all. Does anybody have any idea as to why this might happen?

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  • Why does C++ behave this way?

    - by eSKay
    #include<stdio.h> int b = 0; class A { public: int a;}; class B: public A { int c; int d; public: B(){ b++; a = b; printf("B:%d\n",b); } }; int main() { A* a = new B[10]; B* b = new B[10]; printf("\n%d", a->a); a++; printf("\n%d", a->a); // prints junk value printf("\n\n%d", b->a); b++; printf("\n%d", b->a); return 0; } The second printf prints a junk value. It should figure that it is pointing to an object of type B and increment by the sizof(B). Why does that not happen?

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  • Why is this giving me an infinite loop?

    - by Chase Yuan
    I was going through a code used to calculate investments until it has doubled and I received an infinite loop that I can't seem to solve. Can anyone figure out why this is giving me an infinite loop? I've gone through myself but I can't seem to find the problem. The "period" referred is how many times per year the interest is compounded. double account = 0; //declares the variables to be used double base = 0; double interest = 0; double rate = 0; double result = 0; double times = 0; int years = 0; int j; System.out.println("This is a program that calculates interest."); Scanner kbReader = new Scanner(System.in); //enters in all data System.out.print("Enter account balance: "); account = kbReader.nextDouble(); System.out.print("Enter interest rate (as decimal): "); rate = kbReader.nextDouble(); System.out.println(" " + "Years to double" + " " + "Ending balance"); base = account; result = account; for (j=0; j<3; j++){ System.out.print("Enter period: "); times = kbReader.nextDouble(); while (account < base*2){ interest = account * rate / times; account = interest + base; years++; } account = (((int)(account * 100))/100.0); //results System.out.print(" " + i + " " + account + "\n"); account = result; } The code should ask for three "periods", or three different times the entered data is compounded per year (ex annually, monthly, daily etc.) Thanks a lot!

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  • Why would this query cause a Merge Cartesian Join in Oracle

    - by decompiled
    I have a query that was recently required to be modified. Here's the original SELECT RTRIM (position) AS "POSITION", . // Other fields . . FROM schema.table x WHERE hours > 0 AND pay = 'RGW' AND NOT EXISTS( SELECT position FROM schema.table2 y where y.position = x.position ) Here's the new version SELECT RTRIM (position) AS "POSITION", . // Other fields . . FROM schema.table x WHERE hours > 0 AND pay = 'RGW' AND NOT EXISTS( SELECT position FROM schema.table2 y where y.date = get_fiscal_year_start_date (SYSDATE) AND y.position = x.position ) The UDF get_fiscal_year_start_date() returns the fiscal year start date of the date parameter. The first query runs fine, but the second creates a merge Cartesian join. I looked at the indexes on the tables and found that position and date were both indexed. My question for you stackoverflow is why would the addition of 'y.date = get_fiscal_year_start_date (SYSDATE)' cause a merge cartesian join in Oracle 10g.

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  • Why is the operation address incremented by two?

    - by Gavin Jones
    I am looking at a Javascript emulator of a NES to try and understand how it works. On this line: addr = this.load(opaddr+2); The opcode is incremented by two. However, the documentation (see appendix E) I'm reading says: Zero page addressing uses a single operand which serves as a pointer to an address in zero page ($0000-$00FF) where the data to be operated on can be found. By using zero page addressing, only one byte is needed for the operand, so the instruction is shorter and, therefore, faster to execute than with addressing modes which take two operands. An example of a zero page instruction is AND $12. So if the operand's argument is only one byte, shouldn't it appear directly after it, and be + 1 instead of + 2? Why +2? This is how I think it works, which may be incorrect. Suppose our memory looks like: ------------------------- | 0 | 1 | 2 | 3 | 4 | 5 | <- index ------------------------- | a | b | c | d | e | f | <- memory ------------------------- ^ \ PC and our PC is 0, pointing to a. For this cycle, we say that the opcode: var pc= 0; //for example's sake var opcode= memory[pc]; //a So shouldn't the first operand be the next slot, i.e. b? var first_operand = memory[pc + 1]; //b

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  • Why isn't my leak detected by Xcode Intrumensts?

    - by Arlaharen
    I am trying to analyze some code of mine, looking for memory leaks. My problem is that some of my objects are leaking (at least as far as I can see), but the Leaks tool doesn't detect the leaks. My guess is that some iPhone OS object still holds pointers to my leaked objects. The objects I am talking about are subclasses of UIViewController that I use like this: MyController *controller = [[MyController alloc] initWithNibName:@"MyController" bundle:nil]; [self.navigationController pushViewController:controller animated:YES]; When these objects are no longer needed I do: [self.navigationController popViewControllerAnimated:YES]; Without a [controller release] call right now. Now when I look at what objects that gets created I see a lot of MyController instances that never gets destroyed. To me these are memory leaks, but to the Leaks tool they are not. Can someone here tell me if there is some way Instruments can tell me what objects are pointing to my MyController instances and thereby making them not count as memory leaks? Or better yet, tell me why these leaks are not detecetd.

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  • why Floating point exception?

    - by livio8495
    I have a floating point exception, and I don't know why. the code is this: void calcola_fitness(){ vector<double> fitness; int n=nodes.size(); int e=edges.size(); int dim=feasibility.size(); int feas=(feasibility[dim-1])*100; int narchi=numarchicoll[dim-1]/e; int numero_nodi=freePathNode.size()/n; double dist_start_goal=node_dist(0,1); int i,f,t; double pathlenght=0; int siize=freePathNode.size(); for(i=0;i!=siize-1; i++){ f=freePathNode[i].getIndex(); i++; t=freePathNode[i].getIndex(); i--; pathlenght=pathlenght+node_dist(f,t); } double pathlenghtnorm=pathlenght/10*dist_start_goal; double fit=((double)numero_nodi+pathlenghtnorm+(double)narchi)*((double)feas); fitness.push_back(fit); } Could anybody help me? What's the problem? I could I solve this? thank you very much

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  • Script dies, I'm not sure why

    - by Webnet
    I'm trying to parse a 6,000 line 500 KB file into an array so I can import the data into our system. The problem is that the script stops executing somewhere between lines 3000-4000. There are no breaks in the code, we use it on other imports. Any ideas on why this might be happening and what I can do to prevent it? /** * Takes a seperated value string and makes it an array * @param $delimiter string The delimiter to be seperated by, usually a comma or tab * @param $string string The string to seperate * @return array The resulting array */ public function svToArray ($delimiter, $string) { $x = 0; $rowList = array(); $splitContent = preg_split("#\n+#", trim($string)); foreach ($splitContent as $key => $value) { $newData = preg_split("#".$delimiter."#", $value); if ($x == 0) { $headerValues = array_values($newData); } else { $tempRow = array(); foreach ($newData as $rowColumnKey => $rowColumnValue) { $tempRow[$headerValues[$rowColumnKey]] = $rowColumnValue; } $rowList[] = $tempRow; } $x++; } return $rowList; }

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  • Languages and VMs: Features that are hard to optimize and why

    - by mrjoltcola
    I'm doing a survey of features in preparation for a research project. Name a mainstream language or language feature that is hard to optimize, and why the feature is or isn't worth the price paid, or instead, just debunk my theories below with anecdotal evidence. Before anyone flags this as subjective, I am asking for specific examples of languages or features, and ideas for optimization of these features, or important features that I haven't considered. Also, any references to implementations that prove my theories right or wrong. Top on my list of hard to optimize features and my theories (some of my theories are untested and are based on thought experiments): 1) Runtime method overloading (aka multi-method dispatch or signature based dispatch). Is it hard to optimize when combined with features that allow runtime recompilation or method addition. Or is it just hard, anyway? Call site caching is a common optimization for many runtime systems, but multi-methods add additional complexity as well as making it less practical to inline methods. 2) Type morphing / variants (aka value based typing as opposed to variable based) Traditional optimizations simply cannot be applied when you don't know if the type of someting can change in a basic block. Combined with multi-methods, inlining must be done carefully if at all, and probably only for a given threshold of size of the callee. ie. it is easy to consider inlining simple property fetches (getters / setters) but inlining complex methods may result in code bloat. The other issue is I cannot just assign a variant to a register and JIT it to the native instructions because I have to carry around the type info, or every variable needs 2 registers instead of 1. On IA-32 this is inconvenient, even if improved with x64's extra registers. This is probably my favorite feature of dynamic languages, as it simplifies so many things from the programmer's perspective. 3) First class continuations - There are multiple ways to implement them, and I have done so in both of the most common approaches, one being stack copying and the other as implementing the runtime to use continuation passing style, cactus stacks, copy-on-write stack frames, and garbage collection. First class continuations have resource management issues, ie. we must save everything, in case the continuation is resumed, and I'm not aware if any languages support leaving a continuation with "intent" (ie. "I am not coming back here, so you may discard this copy of the world"). Having programmed in the threading model and the contination model, I know both can accomplish the same thing, but continuations' elegance imposes considerable complexity on the runtime and also may affect cache efficienty (locality of stack changes more with use of continuations and co-routines). The other issue is they just don't map to hardware. Optimizing continuations is optimizing for the less-common case, and as we know, the common case should be fast, and the less-common cases should be correct. 4) Pointer arithmetic and ability to mask pointers (storing in integers, etc.) Had to throw this in, but I could actually live without this quite easily. My feelings are that many of the high-level features, particularly in dynamic languages just don't map to hardware. Microprocessor implementations have billions of dollars of research behind the optimizations on the chip, yet the choice of language feature(s) may marginalize many of these features (features like caching, aliasing top of stack to register, instruction parallelism, return address buffers, loop buffers and branch prediction). Macro-applications of micro-features don't necessarily pan out like some developers like to think, and implementing many languages in a VM ends up mapping native ops into function calls (ie. the more dynamic a language is the more we must lookup/cache at runtime, nothing can be assumed, so our instruction mix is made up of a higher percentage of non-local branching than traditional, statically compiled code) and the only thing we can really JIT well is expression evaluation of non-dynamic types and operations on constant or immediate types. It is my gut feeling that bytecode virtual machines and JIT cores are perhaps not always justified for certain languages because of this. I welcome your answers.

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  • Why is my program getting slower and slower ?

    - by RedWolf
    I'm using the program to send data from database to the Excel file . It works fine at the beginning and then becomes more and more slowly,finally it run out of the memory and the following error ocurrs: "java.lang.OutOfMemoryError: Java heap space...". The problem can be resolved by adding the jvm heap sapce.But the question is that it spends too much time to run out the program. After several minutes,it finished a loop with 4 seconds which can be finished with 0.5 seconds at the beginning . I can't found a solution to make it always run in a certain speed. Is it my code problem? Any clues on this? Here is the code: public void addAnswerRow(List<FinalUsers> finalUsersList,WritableWorkbook book){ if (finalUsersList.size() >0 ) { try { WritableSheet sheet = book.createSheet("Answer", 0); int colCount = 0; sheet.addCell(new Label(colCount++,0,"Number")); sheet.addCell(new Label(colCount++,0,"SchoolNumber")); sheet.addCell(new Label(colCount++,0,"District")); sheet.addCell(new Label(colCount++,0,"SchoolName")); sheet.setColumnView(1, 15); sheet.setColumnView(3, 25); List<Elements> elementsList = this.elementsManager.getObjectElementsByEduTypeAndQuestionnaireType(finalUsersList.get(0).getEducationType().getId(), this.getQuestionnaireByFinalUsersType(finalUsersList.get(0).getFinalUsersType().getId())); Collections.sort(elementsList, new Comparator<Elements>(){ public int compare(Elements o1, Elements o2) { for(int i=0; i< ( o1.getItemNO().length()>o2.getItemNO().length()? o2.getItemNO().length(): o1.getItemNO().length());i++){ if (CommonFun.isNumberic(o1.getItemNO().substring(0, o1.getItemNO().length()>3? 4: o1.getItemNO().length()-1)) && !CommonFun.isNumberic(o2.getItemNO().substring(0, o2.getItemNO().length()>3? 4: o2.getItemNO().length()-1))){ return 1; } if (!CommonFun.isNumberic(o1.getItemNO().substring(0, o1.getItemNO().length()>3? 4: o1.getItemNO().length()-1)) && CommonFun.isNumberic(o2.getItemNO().substring(0,o2.getItemNO().length()>3? 4:o2.getItemNO().length()-1))){ return -1; } if ( o1.getItemNO().charAt(i)!=o2.getItemNO().charAt(i) ){ return o1.getItemNO().charAt(i)-o2.getItemNO().charAt(i); } } return o1.getItemNO().length()> o2.getItemNO().length()? 1:-1; }}); for (Elements elements : elementsList){ sheet.addCell(new Label(colCount++,0,this.getTitlePre(finalUsersList.get(0).getFinalUsersType().getId(), finalUsersList.get(0).getEducationType().getId())+elements.getItemNO()+elements.getItem().getStem())); } int sheetRowCount =1; int sheetColCount =0; for(FinalUsers finalUsers : finalUsersList){ sheetColCount =0; sheet.addCell(new Label(sheetColCount++,sheetRowCount,String.valueOf(sheetRowCount))); sheet.addCell(new Label(sheetColCount++,sheetRowCount,finalUsers.getSchool().getSchoolNumber())); sheet.addCell(new Label(sheetColCount++,sheetRowCount,finalUsers.getSchool().getDistrict().getDistrictNumber().toString().trim())); sheet.addCell(new Label(sheetColCount++,sheetRowCount,finalUsers.getSchool().getName())); List<AnswerLog> answerLogList = this.answerLogManager.getAnswerLogByFinalUsers(finalUsers.getId()); Map<String,String> answerMap = new HashMap<String,String>(); for(AnswerLog answerLog :answerLogList ){ if (answerLog.getOptionsId() != null) { answerMap.put(answerLog.getElement().getItemNO(), this.getOptionsAnswer(answerLog.getOptionsId())); }else if (answerLog.getBlanks()!= null){ answerMap.put(answerLog.getElement().getItemNO(), answerLog.getBlanks()); }else{ answerMap.put(answerLog.getElement().getItemNO(), answerLog.getSubjectiveItemContent()); } } for (Elements elements : elementsList){ sheet.addCell(new Label(sheetColCount++,sheetRowCount,null==answerMap.get(elements.getItemNO())?"0":answerMap.get(elements.getItemNO()))); } sheetRowCount++; } book.write(); book.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (RowsExceededException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (WriteException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }

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