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• Document ranking strategy for P2P file sharing system.

  - by ablmf

  Recently, I got a task of building a P2P file sharing system. There is one requirement : the system should have a document ranking algorithm so that it could be used help users find more valuable files. Several strategy might be useful : force user to give a score to a file before it was downloaded The documents containing certain key words would get higher rank Manager could modify file ranking manually the more a file was downloaded, it would get a higher rank. Do you know any other strategy or methods that also appropriate? Or is there any real world example?

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• Strange profiling results: definitely non-bottleneck method pops up

  - by jkff

  I'm profiling a program using sampling profiling in YourKit and JProfiler, and also "manually" (I launch it and press Ctrl-Break several times to get thread dumps). All three methods give me extremely strange results: some tens of percents of time spent in a 3-line method that does not even do any allocation or synchronization and doesn't have loops etc. Moreover, after I made this method into a NOP and even removed its invocation completely, the observable program performance didn't change at all (although it got a negligible memory leak, since it was a method for freeing a cheap resource). I'm thinking that this might be because of the constraints that JVM puts on the moments at which a thread's stacktrace may be taken, and it somehow turns out that in my program it is exactly the moments where this method is invoked, although there is absolutely nothing special about it or the context in which it is invoked. What can be the explanation for this phenomenon? What are the aforementioned constraints? What further measurements can I take to clarify the situation?

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• DDD: Trying to code sorting and filtering as it pertains to Poco, Repository, DTO, and DAO using C#?

  - by Dr. Zim

  I get a list of items from my Repository. Now I need to sort and filter them, which I believe would be done in the Repository for efficiency. I think there would be two ways of doing this in a DDD way: Send a filter and a sort object full of conditions to the Repository (What is this called)? Repository result would produce an object with .filter and .sort methods? (This wouldn't be a POJO/POCO because it contains more than one object?). So is the answer 1, 2, or other? Could you explain why? I am leaning toward #1 because the Repository would be able to only send the data I want (or will #2 be able to delay accessing data like a LazyList?) A code example (or website link) would be very helpful. Example: Product product = repo.GetProducts(mySortObject, myFilterObject); // List of Poco product.AddFilter("price", "lessThan", "3.99"); product.AddSort("price", "descending");

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• Modify action names for route collections in Symfony?

  - by James Skidmore

  When creating an sfPropelRouteCollection, how can I edit the action names that the collection will generate? For example: # Routing for "product" CRUD product: class: sfPropelRouteCollection options: model: Product module: product actions: [new, create, edit, update, delete] How can I change the actual action that is called for any of the new/create/edit/update/delete methods? I'd like for them to call "ajaxNew," "ajaxCreate," etc. so the URL would look something like "product/ajaxNew", or the action for "update" would be "ajaxUpdate". Let me know if I need to clarify further. Thanks.

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• How to set Chrome's user script version number.

  - by Atli

  Hey. I've been wondering how I might set the version number displayed for user-scripts in Chrome's extension tab So far the obvious methods have failed: // ==UserScript== // @version 1.1.5 // @uso:version 1.1.5 // ==/UserScript== I know Greasemonkey for Firefox doesn't use a version value, but since Chrome actually displays a version number, I thought it might. Perhaps this is a feature that has not been implemented? Or maybe it was never intended to be there, but it is there because extensions have version numbers, and user-scripts are currently installed as extensions? (I'm using the Linux beta, version: 4.0.249.43, by the way) Thanks. Edit: Seems this is listed as an unconfirmed bug in the Chromium bug database (Issue 30760)

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• What are good ways to guarantee business continuity with a SaaS product?

  - by tommyvdz

  For my Bachelor Thesis I am researching how SaaS providers can arrange some sort of business continuity guarantee. You probably know the Source Code Escrow arrangements for 'shrink-wrapped' software. They give customers access to the source code and all applicable documentation whenever the software supplier gets into (financial) trouble. This clearly does not work for SaaS, because customers have no use for just the source code, and customers probably can not afford not being able to login to their CRM system for a couple weeks because the SaaS provider went bankrupt. I am currently researching different methods to solve this problem. Do you know good and practical solutions to solve this continuity problem? Or companies that already offer a good solution? Thanks!

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• net c# lock statement in data access layer

  - by Pedro Rivera

  I saw a code where they have the data access layer like this: public class CustomerDA{ private static readonly object _sync = new object(); private static readonly CustomerDA _mutex = new CustomerDA(); private CustomerDA(){ } public CustomerDA GetInstance(){ lock(_sync){ return _mutex; } } public DataSet GetCustomers(){ //database SELECT //return a DataSet } public int UpdateCustomer(some parameters){ //update some user } } public class CustomerBO{ public DataSet GetCustomers(){ //some bussiness logic return CustomerDA.GetInstance().GetCustomers(); } } I was using it, but start thinking... "and what if had to build a facebook like application where there are hundreds of thousands of concurrent users? would I be blocking each user from doing his things until the previous user ends his database stuff? and for the Update method, is it useful to LOCK THREADS in the app when database engines already manage concurrency at database server level?" Then I started to think about moving the lock to the GetCustomers and UpdateCustomer methods, but think again: "is it useful at all?"

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• Evaluating Django Chained QuerySets Locally

  - by jnadro52

  Hello All: I am hoping someone can help me out with a quick question I have regarding chaining Django querysets. I am noticing a slow down because I am evaluating many data points in the database to create data trends. I was wondering if there was a way to have the chained filters evaluated locally instead of hitting the database. Here is a (crude) example: pastries = Bakery.objects.filter(productType='pastry') # <--- will obviously always hit DB, when evaluated cannoli = pastries.filter(specificType='cannoli') # <--- can this be evaluated locally instead of hitting the DB when evaluated, as long as pastries was evaluated? I have checked the docs and I do not see anything specifying this, so I guess it's not possible, but I wanted to check with the 'braintrust' first ;-). BTW - I know that I can do this myself by implementing some methods to loop through these datapoints and evaluate the criteria, but there are so many datapoints that my deadline does not permit me manually implementing this. Thanks in advance.

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• General zoom algorithm for drawing program

  - by Steven Sproat

  My GUI toolkit, wxPython provides some methods for implementing a user zoom factor, however the quality isn't too good. I'm looking for ideas on how to create a zooming feature, which I know is complicated. I have a bitmap representing my canvas which is drawn to. This is displayed inside a scrolled window. Problems I forsee: - performance when zoomed in and panning around the canvas - difficulties with "real" coordinates and zoomed in coordinates - image quality not degrading with the zoom Using wxPython's SetUserScale() on its device contexts presents image quality like this - this is with a 1px line, at 30% zoomed in. I'm just wondering the general steps I'll need to take and the challenges I'll encounter. Thanks for any suggestions

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• Creating many new instances vs reusing them?

  - by Hugo Riley

  I have multiple business entities in VB.NET Windows Forms application. Right now they are instanced on application startup and used when needed. They hold descriptions of business entities and methods for storing and retrieving data. To cut the long story short, they are somewhat heavy objects to construct (they have some internal dictionaries and references to other objects) created and held in one big global variable called "BLogic". Should I refactor this so that each object is created when needed and released when out of scope? Then every event on UI will probably create a few of this objects. Should I strive to minimize creation of new objects or to minimize number of static and global objects? Generally I am trying to minimize the scope of every variable but should I treat this business logic objects specially?

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• WCF Service method syncronous/async

  - by Rafal

  Hi I have a problem withi calling WCF Service methods vs Silverlight 3. ` private bool usr_OK = false; clientService.CheckUserMailAsync(this.mailTF.Text); if (usr_OK == true) { isValidationOK = true; } else { isValidationOK = false; MessageBox.Show("User already exists.", "User registered succes!", MessageBoxButton.OK); } ` CheckUserMail should change usr_OK parameter. However it runs in other thread and it does not change the usr_OK param before IF block begins. I've tried thread.join byt the application freezed and i do not know what to do else. Please help me...how can i wait for WCF method to return param usr_OK.

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• Best .NET Framework compression class?

  - by Jack

  Hi all Yes, I know GZipStream or DeflateStream is the common ones in .NET Framework which handle compression/decompression. I wish to have compress/decompress functions in my program, but I wish a .NET Framework C# one, not a 3rd party open source. I can't use because of those copyright restrictions in my program. GZipStream and DeflateStream are not so good. for e.g., GZipStream compress a file to 480KB while 7Zip compress the same file to the size of 57KB. Does Microsoft have other good compression methods??? Thanks

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• PHP APC - Why is loading cached array op codes slow?

  - by Aaron Kreider

  I'm using APC to reduce my loading time for my PHP files. My files load very fast, except for one file where I define more than 100 arrays. This 270 kb file takes 200 ms to load. The rest of the files are full of objects, methods, and functions. I'm wondering: does OP code caching not work as well for arrays? My APC cache should be big enough to handle all of my classes. Currently 40% of my cache is free. My hit rate is 99%. apc.shm_size=32 M apc.max_file_size = 1M apc.shm_segments= 1 APC 3.1.6 I'm using PHP 5.2, Apache 2, and Windows Vista.

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• show definition (browse) in *.pdb of *.dll file

  - by ala

  I have built a Library project (DLL) in .NET. And sometimes I use the DLL along with its PDB file as a reference in some other projects. Now in the new project, I cant browse through the code of the DLL to debug. I can only see the definitions of class/methods/variables. That's by using "show definition" by browsing through the "class view" However, only in case of an exception I the contents of the DLL opens and I could see the entire code of the DLL from the new project. How could I see the contents (code) of the DLL before an exception occur?

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• Catching constraint violations in JPA 2.0.

  - by Dennetik

  Consider the following entity class, used with, for example, EclipseLink 2.0.2 - where the link attribute is not the primary key, but unique nontheless. @Entity public class Profile { @Id private Long id; @Column(unique = true) private String link; // Some more attributes and getter and setter methods } When I insert records with a duplicate value for the link attribute, EclipseLink does not throw a EntityExistsException, but throws a DatabaseException, with the message explaining that the unique constraint was violated. This doesn't seem very usefull, as there would not be a simple, database independent, way to catch this exception. What would be the advised way to deal with this? A few things that I have considered are: Checking the error code on the DatabaseException - I fear that this error code, though, is the native error code for the database; Checking the existence of a Profile with the specific value for link beforehand - this obviously would result in an enormous amount of superfluous queries.

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• C# generics method invocation

  - by Firat KÜÇÜK

  Hi, i have some polymorphic methods and i want to call via using an intermediate method. Following class is the simplified version of my program. class Program { public class A { } public class B { } public class C { } public void SomeMethod(A value) { Console.WriteLine("A value"); } public void SomeMethod(B value) { Console.WriteLine("B value"); } public void SomeMethod(C value) { Console.WriteLine("C value"); } static void Main(string[] args) { Program p = new Program(); // code block p.IntermediateMethod<A>(new A()); p.IntermediateMethod<B>(new B()); p.IntermediateMethod<C>(new C()); } public void IntermediateMethod<T>(T value) { // code block SomeMethod(value); // code block } }

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• Determine Android phone's proximity to known point while conserving power

  - by ahsteele

  I am trying to determine if an Android user has had a close proximity to a list of predetermined locations. I'd like to do this with the least amount of drain on the phone's battery. The two mechanisms I see for accomplishing this are proximity alerts and requesting location updates. What are the pros and cons of the two methods? Will one have less affect on the battery than the other? In either case I would guess the specific location manager used would affect power usage (existing Stack Overflow answer).

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• can't see the result after i update a row in a table in a gridview

  - by aleo

  Peace! i created a gridview and ive bended the data using a ObjectDataSource, for some reasons i created the CRUD methods to do the work instead of using the CRUD method generated by the LINQDataSource; everything is just working fine but the update method, when i update a row in my gridview everything become as if there isnt any update! but when i check the database i can see that the rows is been updated! i can't find a solution (yet) to this issue. i'am using the updatepanel to have the autopostback without refreshing the page. thank you

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• LDAP in medium trust

  - by eych

  I've have a solution with one website and several projects. The projects all have the AllowPartiallyTrustedCallers attribute and are strongly-named. The site works in full trust. However, after set the trust to medium, I get the System.Security.SecurityException: Request failed. error as soon as I browse to the site. In my projects, I have calls to LogOnUser, as well as many calls to variousSystem.DirectoryServices.AccountManagement methods. Can this site run with medium trust or do I have to have full trust for all the LDAP calls? As I mentioned, I've set the AllowPartiallyTrustedCallers attribute on all projects. Not sure what else to do. Also, I have no idea what/where the error is being generated. The event logs on the server have nothing in regards to this SecurityException. Is there any way to find out what the error location is so maybe I can attempt to rewrite some code? [running .NET 4.0 on Win2k8R2]

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• How does struts 1.X ActionForm handle pure html checkbox list?

  - by BlueDolphin

  I am dealing with an old application which uses struts 1.2. And for some reason, we are using pure html form to submit to struts action. For example: for the content output of testAction.do, I try to submit to itself. item 1 item 2 Then I associate an form bean TestForm with testAction. I am not sure how to specify the properties in the form so that it take the value from myitem1 after user click "submit" I tried to add getMyitem1(), setMyitem1(String[] items), getSelectedMyitem1(), setSelectedMyitem1(String[] items) Those set methods are only called when page are loaded. I guess my understanding of ActionForm in struts 1.x must be wrong. Please advise, thanks.

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• What is "sentry object" in C++?

  - by Romain Hippeau

  I answered this question, and Potatoswatter answered too as The modern C++ equivalent would be a sentry object: construct it at the beginning of a function, with its constructor implementing call(), and upon return (or abnormal exit), its destructor implements I am not familiar with using sentry objects in C++. I thought they were limited to input and output streams. Could somebody explain to me about C++ sentry objects as well as how to use them as an around interceptor for one or more methods in a class ? i.e. How to do this ? Sentry objects are very similar indeed. On the one hand they require explicit instantiation (and being passed this) but on the other hand you can add to them so that they check not only the invariants of the class but some pre/post conditions for the function at hand.

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• Entity Aspect (in Spring)

  - by niklassaers

  Hi guys, I'm having a bit of a problem defining my aspects. I've got a bunch of entities that I'd like to profile the get-methods in, so I've written the following pointcut and method @Pointcut("execution(* tld.myproject.data.entities.*.get*()") public void getEntityProperty() {} @Around("getEntityProperty()") public Object profileGetEntityProperty(ProceedingJoinPoint pjp) throws Throwable { long start = System.currentTimeMillis(); String name = pjp.getSignature().getName(); Object output = pjp.proceed(); long elapsedTime = System.currentTimeMillis() - start; if(elapsedTime > 100) System.err.println("profileGetEntityProperty: Entity method " + name + " execution time: " + elapsedTime + " ms."); return output; } I've got weaving turned on in my configuration, and aspects weaving into the business layer work just fine. Is my pointcut correctly written? Or is there something about entities that make them non-weavable? (my entity is prefixed with @Entity before the class definition) Cheers Nik

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• UIWebView in multithread ViewController

  - by Tao

  I have a UIWebView in a viewcontroller, which has two methods as below. The question is if I pop out(tap back on navigation bar) this controller before the second thread is done, the app will crash after [super dealloc], because "Tried to obtain the web lock from a thread other than the main thread or the web thread. This may be a result of calling to UIKit from a secondary thread.". Any help would be really appreciated. -(void)viewDidAppear:(BOOL)animated { [super viewWillAppear:animated]; NSInvocationOperation *operation = [[NSInvocationOperation alloc] initWithTarget:self selector:@selector(load) object:nil]; [operationQueue addOperation:operation]; [operation release]; } -(void)load { [NSThread sleepForTimeInterval:5]; [self performSelectorOnMainThread:@selector(done) withObject:nil waitUntilDone:NO]; }

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• Is it hacky to manually construct JSON and manually handle GET, POST instead of using a proper RESTful API for AJAX functionality?

  - by kliao

  I started building a Django app, but this probably applies to other frameworks as well. In Backbone.js methods that call the server (fetch(), create(), destroy(), etc.), should you be using a proper RESTful API such as one provided by Tastypie or Django-Piston? I've founded it easier and more flexible to just construct the JSON in my Django Views, which are mapped to some URLs that Backbone.js can use. Then again, I'm probably not leveraging Tastypie/Django-Piston functionality to the fullest. I'm not ready to make a full-fledged RESTful API for my app yet. I simply would like to use some of the AJAXy functionality that Backbone.js supports. Pros/Cons of doing this?

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• Is there an IDE that provides code completion for Python

  - by Justin Walgran

  I am quite fond of the Intellisense code completion baked into Microsoft Visual Studio. I find that I only type 2 to 4 characters of any given keyword which drasticaly speeds up my coding. Now that I have been spending time writing some Python code I find myself reaching for ctrl+space. Are there any IDEs that support code completion in Python? I do my python development on a Mac so an OS x tool would be preferable. It seems like the doc string property of Python methods is a perfect match for inline API discovery.

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