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  • Measuring the performance of classification algorithm

    - by Silver Dragon
    I've got a classification problem in my hand, which I'd like to address with a machine learning algorithm ( Bayes, or Markovian probably, the question is independent on the classifier to be used). Given a number of training instances, I'm looking for a way to measure the performance of an implemented classificator, with taking data overfitting problem into account. That is: given N[1..100] training samples, if I run the training algorithm on every one of the samples, and use this very same samples to measure fitness, it might stuck into a data overfitting problem -the classifier will know the exact answers for the training instances, without having much predictive power, rendering the fitness results useless. An obvious solution would be seperating the hand-tagged samples into training, and test samples; and I'd like to learn about methods selecting the statistically significant samples for training. White papers, book pointers, and PDFs much appreciated!

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  • Correct way to give users access to additional schemas in Oracle

    - by Jacob
    I have two users Bob and Alice in Oracle, both created by running the following commands as sysdba from sqlplus: create user $blah identified by $password; grant resource, connect, create view to $blah; I want Bob to have complete access to Alice's schema (that is, all tables), but I'm not sure what grant to run, and whether to run it as sysdba or as Alice. Happy to hear about any good pointers to reference material as well -- don't seem to be able to get a good answer to this from either the Internet or "Oracle Database 10g The Complete Reference", which is sitting on my desk.

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  • C 64-bit Pointer Alignment

    - by DuneBug
    Are pointers on a 64-bit system still 4 byte aligned (similar to a double on a 32 bit system)? Or are they note 8 byte aligned? For example, on a 64-bit system how big is the following data structure: struct a { void* ptr; char myChar; } Would the pointer by 8 byte aligned, causing 7 bytes of padding for the character (total = 8 + 8 = 16)? Or would the pointer be 4 byte aligned (4 bytes + 4 bytes) causing 3 bytes of padding (total = 4 + 4 + 4 = 12)? Thanks, Ryan

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  • multiple C++ deletion of a memory pointed by multiple objects

    - by elgcom
    Another c++ pointer deletion question is in the following example: class Foo { public: int *p; ~Foo() { delete p; p = NULL; } }; Foo *f1 = new Foo(); Foo *f2 = new Foo(); f1->p = new int(1); f2->p = f1->p; delete f2; // ok delete f1; // no error? Why I did not get error when calling "delete f1"? didn't I delete the same address (*p) twice? If I directly delete the pointers in the last 2 lines of code, I will get error. delete f2->p; // ok delete f1->p; // error!! *** glibc detected *** double free or corruption (fasttop) ***

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  • Windows Phone 7 and C++/CLI

    - by Fabio Ceconello
    Microsoft recently released tools and documentation for its new Phone 7 platform, which to the dismay of those who have a big C++ codebase (like me) doesn't support native development anymore. Although I've found speculation about this decision being reversed, I doubt it. So I was thinking how viable would be to make this codebase available to Phone 7 by adapting it to compile under C++/CLI. Of course the user interface parts couldn't be ported, but I'm not sure about the rest. Anyone had a similar experience? I'm not talking about code that does heavy low-level stuff - but there's a quite frequent use of templates and smart pointers.

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  • php $_REQUEST data is only half-decoded

    - by hackmaster.a
    I am retrieving a url via querystring. I need to pass it again to the next page. When I retrieve it the first time, using $_REQUEST['url'], only the slashes are decoded, e.g: http://example.com/search~S10?/Xllamas&searchscope=10&SORT=D/Xllamas&searchscope=10&SORT=D&SUBKEY=llamas/51%2C64%2C64%2CB/browse The php docs page for urldecode advises against decoding request data, and says that it will already be decoded. I need it either completely decoded, so I can encode it again without double-encoding some parts, or not decoded at all. I'm not sure why my experience of this data is incongruous with the php docs. Appreciate any help or pointers to same!!

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  • suggestions for someone studying for java certification

    - by newguy
    I have been working with java (J2EE) for about 4 years. I have been putting off the certification for a while now. I bought the exam last year and still have not taken the exam. it expires in june so I am going to give it a shot. I know certifications don't get jobs but interviews but where I work...certification will put a 'stamp' on my resume and I think it'll popout in the eyes of the management. Anyways, I am going for JAVA 6. Can someone suggest some good mock exams that are kind of new and relevant. I came across this link but most of these exams are fairly old. I am using kathy Sierra's book for studying. Any other resources/pointers?

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  • PHP - Concatenating objects and casting to string - bad idea?

    - by franko75
    Is it bad practice to concatenate objects when used in this context: $this->template->head .= new View('custom_javascript') This is the way i normally add extra css/js stuff to specific pages. I use an MVC structure where my basic html template has a $head variable which I set in my main Website_controller. I have used this approach for a while as it means I can just add bits and pieces of css/js stuff from whichever page/controller needs it. But having come across a problem in PHP 5.1.6 where the above code results in "Object ID #24", the result of toString() not being called i think, I am rethinking whether i should just fix this to work in PHP 5.1.6 or if i should rethink this approach in general. Any pointers appreciated!

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  • Can't append to array using string field name [$] when performing update on array fields

    - by Haraldo
    rowsI am attempting to perform a mongodb update on each field in an array of records. An example schema is below: { "_id" : ObjectId("508710f16dc636ec07000022"), "summary" : "", "uid" : "ABCDEF", "username" : "bigcheese", "name" : "Name of this document", "status_id" : 0, "rows" : [ { "score" : 12, "status_id" : 0, "uid" : 1 }, { "score" : 51, "status_id" : 0, "uid" : 2 } ] } So far I have been able to perform single updates like this: db.mycollection.update({"uid":"ABCDEF","rows.uid":1}, {$set:{"rows.$.status_id":1}},false,false) However, I am struggling as to how to perform an update that will update all array records to a status_id of 1 (for instance). Below is how I imagine it should work: db.mycollection.update({"uid":"ABCDEF"}, {$set:{"rows.$.status_id":1}},false,true) However I get the error: can't append to array using string field name [$] I have tried for quite a while with no luck. Any pointers?

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  • Most efficient way to download media files from a server from within an iPhone app.

    - by nikki
    Hi, I have an iPhone application which contains a lot of media files, so far we have been able to keep the size of the iPhone app to less than 20 MB. We add new content with new updates, it would be difficult to keep the app size within the 20 MB limit. The right thing to do here would be to fetch the files on demand from a media/web server. If you have any pointers on how to go about doing this, please suggest. What we would need is to fetch the media files (.jpg/.png images ) on demand when the user taps on a small thumbnail for the image. Are there existing frameworks/servers that provide such services to iPhone clients. Thanks.

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  • When to pass by value?

    - by Dervin Thunk
    Dear all. I was wondering if there are examples of situations where you would purposefully pass an argument by value in C. Let me rephrase. When do you purposefully use C's pass-by-value for large objects? Or, when do you care that the object argument is fully copied in a local variable? EDIT: Now that I think about it, if you can avoid pointers, then do. Nowadays, "deep" copying is possible for mostly everything in small apps, and shallow copying is more prone to pointer bugs. Maybe.

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  • Implementing implicitly shared classes outside of Qt

    - by Timothy Baldridge
    I'm familiar with the way Qt uses D-pointers for managing data. How do I do this in my code? I tried this method: 1) move all data into a struct 2) add a QAtomicInt to the struct 3) implement a = operator and change my constructor/deconstructor to check-up on the reference count. The issue is, when I go to do a shallow copy of the object, I get an error about QObject declaring = as private. How then do I accomplish this? Here's an example of my copy operator: HttpRequest & HttpRequest::operator=(const HttpRequest &other) { other.d->ref.ref(); if (!d->ref.deref()) delete d; d = other.d; return *this; } Am I going about this the wrong way?

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  • how to open many files simultaneously for reading in c

    - by monkeyking
    I'm trying to port some of my c++ code into c. I have the following construct class reader{ private: FILE *fp; alot_of_data data;//updated by read_until() method public: reader(const char*filename) read_until(some conditional dependent on the contents of the file, and the arg supplied) } Im then instantiating hundreds of these object and iterate over them using several 'read_until()' for each file until allfiles is at eof. I'm failing to see any clever way to do this in c, the only solution I can come up with is making an array of FILE pointers, and do the same with all the private member data from my class. But this seems very messy, can I implement the functionality of my class as a function pointer, or anything better, I think I'm missing a fundamental design pattern? The files are way to big to have all in memory, so reading everything from every file is not feasible Thanks

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  • How to accomplish covariant return types when returning a shared_ptr?

    - by Kyle
    using namespace boost; class A {}; class B : public A {}; class X { virtual shared_ptr<A> foo(); }; class Y : public X { virtual shared_ptr<B> foo(); }; The return types aren't covariant (nor are they, therefore, legal), but they would be if I was using raw pointers instead. What's the commonly accepted idiom to work around this, if there is one?

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  • Document Not Saved Error in Excel.

    - by Sowmya
    This is my code snippet for comparing 2 excel files. I call this function from my QTP scripts. I get this error quite often which causes my test script to fail. Any pointers will be appreciated. Set objExcel = CreateObject("Excel.Application") objExcel.Application.Visible = False objExcel.DisplayAlerts = False Set objWorkbook1= objExcel.Workbooks.Open(excelFile1) Set objWorkbook2= objExcel.Workbooks.Open(excelFile2) Set objWorksheet1= objWorkbook1.Worksheets(1) Set objWorksheet2= objWorkbook2.Worksheets(1) <Code that compares the 2 files & marks the cell in red where there is a mismatch) objWorkbook2.Save ERROR MESSAGE: Document not saved. Function file: C:\Program Files\Mercury Interactive\QuickTest Professional\Tests\ReusableFunctions.qfl Line (33): "objWorkbook2.Save".

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  • implementing type inference

    - by deepblue
    well I see some interesting discussions here about static vs. dynamic typing I generally prefer static typing, due to compile type checking, better documented code,etc. However I do agree that they do clutter up the code if done the way Java does it, for example. so Im about to start building a language of my own and type inference is one of the things that I want to implement, in a functional style language... I do understand that it is a big subject, and Im not trying to create something that has not been done before, just basic inferencing... any pointers on what to read up that will help me with this? preferably something more pragmatic/practical as oppose to more theoretical category theory/type theory texts. If there's a implementation discussion text out here, with data structures/algorithms, that would just be lovely much appreciated

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  • Render asp.net repeater as-and-when chunks of html is ready (streaming)

    - by sash
    The problem is to render huge reports. Basically we have lots of data that get rendered in html reports (mostly using repeater or gridview). As it so happens, the data started out small and now we have tons of it. There are lots of such reports already built so total rewrite is not an option. Heck, the business is not even letting us page the data. Now server memory is shooting up each time we try to render some reports. So the question is - is there some way we can bind data to repeater and have it stream html to browser as and when chunks are ready? That way we hope to not bring all that data into app server at once. I'm thinking we'll use a datareader or something to get parts of data and render it to browser. Any pointers, links, ideas?

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  • JUnit4 + Eclipse "An internal error occured during Launching"

    - by Mike
    Hello I'm trying to run JUnit4 test cases on Eclipse 3.4.2 but it's not even starting for me. I am sure that I properly have junit-4.7.jar in my build path and the test application. Here is a simple example that illustrates my problem package test; import org.junit.Before; import org.junit.Test; public class UTest { @Test public void test() { } @Before public void setUp() throws Exception { } } This compiles fine Then I do "Run JUnit Test case" from Eclipse and I get an error dialog with this message "Launching UTest' has encountered a problem An internal error occurred during: "Launching UTest". java.lang.NullPointerException I'm not sure how to figure out what exactly generating this NullPointerException. Some pointers would be appreciated

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  • Rails: Ajax-enabled form without a model object

    - by Caffeine Coma
    I'm new to Rails and having a hard time figuring out how to create a form that submits over Ajax without having a corresponding model object. My use case is a simple form that collects an email address and sends it an email; there's nothing to be persisted, so no model. In cases where I do have a model, I've had success with form_for(@model, remote: true). I can't seem to find the right helper for the case where there is no model. I tried form_tag(named_path, remote: true) and that works, but does not use Ajax. Pointers to an example with an example with a proper controller, .html.erb and routes.rb would be really appreciated.

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  • Using NSPredicate to filter on both Core attribute and entity

    - by Ben Thompson
    I have two entities in core data (call them entityOne and entityTwo). I have a entityOne<---entityTwo relationship between them. I am now trying to code an NSPredicate to fetch entityTwo objects on the following basis: Fetch entityTwo objects that have a relationship with a specified entityOne object. Filter out those entityTwo objects which have no value for one of their attributes. I am best doing both of these in an NSPredicate or is there a better way? I am trying the following: NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(attribute <> "") AND (relationship == entityOne"]; [request setPredicate:predicate]; Any pointers on coding great fully received.

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  • Developing browser plug-ins?

    - by JavaMan
    I have a project that I'd like to try that involves developing an internet browser plug-in. I have knowledge in Java and DHTML, but nothing in the world of browser plug-in development. I thought I would just ask here then what is the most efficient way to develop a browser plug-in? If possible, I'd like to streamline the process so that getting the plug-in to work in different browsers involves as little work as possible. Can this be done? I'm not asking for a tutorial like the trolls do, just a few pointers that's all. I don't waste mine or anyone else's time.

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  • Complex jquery selction that also involves custom xml tags

    - by thecoshman
    I want to write a select something like... #window_4 > content > p:eq(0) I think I have this correct, but I have a few selectors that are all similar but I can't test them all at once. Am I right in saying this is selecting an element, who is the fist p tag child of a content tag that is a child of a tag with id 'window_4' If I have gotten this wrong, can you give me some pointers. Would love to be able to simplify this code, I have more code selecting the tag I am after then actually doing stuff with them.

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  • How do I construct a request for a WCF http post call?

    - by James Hay
    I have a really simple service that I'm messing about with defined by: [OperationContract] [WebInvoke(UriTemplate = "Review/{val}", RequestFormat = WebMessageFormat.Xml, Method = "POST", BodyStyle=WebMessageBodyStyle.Bare)] void SubmitReview(string val, UserReview review); UserReview is, at the moment, a class with no properties. All very basic. When I try and test this in Fiddler I get a bad request status (400) message. I'm trying to call the service using the details: POST http://127.0.0.1:85/Service.svc/Review/hello Headers User-Agent: Fiddler Content-Type: application/xml Host: 127.0.0.1:85 Content-Length: 25 Body <UserReview></UserReview> I would think i'm missing something fairly obvious. Any pointers?

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  • Best way to perform authentication on every request

    - by Nik
    Hello. In my asp.net mvc 2 app, I'm wondering about the best way to implement this: For every incoming request I need to perform custom authorization before allowing the file to be served. (This is based on headers and contents of the querystring. If you're familiar with how Amazon S3 does rest authentication - exactly that). I'd like to do this in the most perfomant way possible, which probably means as light a touch as possible, with IIS doing as much of the actual work as possible. The service will need to handle GET requests, as well as writing new files coming in via POST/PUT requests. The requests are for an abitrary file, so it could be: GET http://storage.foo.com/bla/egg/foo18/something.bin POST http://storage.foo.com/else.txt Right now I've half implemented it using an IHttpHandler which handles all routes (with routes.RouteExistingFiles = true), but not sure if that's the best, or if I should be hooking into the lifecycle somewhere else? Many thanks for any pointers. (IIS7)

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  • testing the controller in asp.net mvc

    - by csetzkorn
    Hi, I would like to test the validation of submitted DTO. This is the bare bone of a controller create action: [AcceptVerbs(HttpVerbs.Post)] public RedirectToRouteResult Create(SomeDTO SomeDTO) { SomeObject SomeObject = null; try { SomeObject = this.RepositoryService.getSomeObjectRepository().Create(SomeDTO, this.RepositoryService); } catch (BrokenRulesException ex) { ex.AddModelStateErrors(ModelState, "Model"); } catch (Exception e) { ModelState.AddModelError("Exception", e.Message); } TempData["ViewData"] = ViewData; TempData["SomeDTO "] = SomeDTO; return ModelState.IsValid ? RedirectToAction("SomeObjectDetail", new { Id = SomeObject.Id }) : RedirectToAction("Form"); } The mechanics , although not relevant, is as follows: I have a strongly typed view = form which submits a dto to this action which either returns the form or the details page of the created object. I would like to unit test whether the Model contains certain key/errorMessage combinations given some invalid dto. Did someone do similar stuff? Any pointers would be very much appreciated. Thanks. Best wishes, Christian

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