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• The speed of .NET in numerical computing

  - by Yin Zhu

  In my experience, .net is 2 to 3 times slower than native code. (I implemented L-BFGS for multivariate optimization). I have traced the ads on stackoverflow to http://www.centerspace.net/products/ the speed is really amazing, the speed is close to native code. How can they do that? They said that: Q. Is NMath "pure" .NET? A. The answer depends somewhat on your definition of "pure .NET". NMath is written in C#, plus a small Managed C++ layer. For better performance of basic linear algebra operations, however, NMath does rely on the native Intel Math Kernel Library (included with NMath). But there are no COM components, no DLLs--just .NET assemblies. Also, all memory allocated in the Managed C++ layer and used by native code is allocated from the managed heap. Can someone explain more to me? Thanks!

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• Mock Repository vs. Real Repository w/Mocked Data

  - by n8wrl

  I must be doing something fundamentally wrong. I am implmenting my repositories and then testing them with mocked data. All is well. Now I want to test my domain objects so I point them at mock repositories. But I'm finding that I have to re-implement logic from the 'real' repositories into the mocks, or, create 'helper classes' that encapsulate the logic and interact with the repositories (real or mock), and then I have to test those too. So what am I missing - why implement and test mock repositories when I could use the real ones with mocked data? EDIT: To clarify, by 'mocked data' I do not hit the actual database. I have a 'DB mock layer' I can insert under the real repositories that returns known-data.

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• Sharing output streams through a JNI interface

  - by Chris Conway

  I am writing a Java application that uses a C++ library through a JNI interface. The C++ library creates objects of type Foo, which are duly passed up through JNI to Java. Suppose the library has an output function void Foo::print(std::ostream &os) and I have a Java OutputStream out. How can I invoke Foo::print from Java so that the output appears on out? Is there any way to coerce the OutputStream to a std::ostream in the JNI layer? Can I capture the output in a buffer the JNI layer and then copy it into out?

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• Best Design for a Facebook clone on GAE Java

  - by charming30

  My current App is written in Python on GAE which can do Contacts management, Genealogy, Social Networking, Photo sharing, Telecom Integration (SMS, iVRS, URL Billing), CRON and performs business logic operations for our Mobile Apps. Current Architecture indlues python, django, jquery, memcache and few telecom APIs. Now, It feels that an SOA Architecture on GAE using Java would be really ideal and scalable for this kind of App where we want to build new features like widgets that users can turn on or off and third party developers can also develop and deploy features. Please correct me or improve the following design decision: UI (Current plan is GWT) Sessions, Security and ACL (Spring MVC 2.x) Reusable Business Logic components (?) Implementation of Web Services (?) Your advice would really help.

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• Play a beep that loop and change the frequency/speed

  - by Bono

  Hi all, I am creating an iphone application that use audio. I want to play a beep sound that loop indefinitely. I found an easy way to do that using the upper layer AVAudioPlayer and the numberOfLoops set to "-1". It works fine. But now I want to play this audio and be able to change the rate / speed. It may works like the sound played by a car when approaching an obstacle. At the beginning the beep has a low frequency and this frequency accelerate till reaching a continuous sound biiiiiiiiiiiip ... It seems this is not feasible using the high layer AVAudioPlayer, but even looking at AudioToolBox I found no solution. Does anybody have informations about how to do that? Thanks a lot for helping me!

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• CATransitionFade not working on newly added subviews

  - by David Liu

  For some reason, fading in new buttons using CATransition isn't working for me when it's a newly added button. The fade animation, however, is working on existing subviews. Code: // Add new button. CATransition *animation = [CATransition animation]; [animation setDuration:0.5]; [animation setType:kCATransitionFade]; [[button layer] addAnimation:animation forKey:@"fadeIn"]; [self.view addSubview:button]; // Enable previous button (Enabling fades in different type of background) if(toolbar.buttons.count != 0){ UIButton * prevButton = [toolbar.buttons objectAtIndex:(toolbar.buttons.count - 1)]; prevButton.enabled = YES; [[prevButton layer] addAnimation:animation forKey:@"fadeIn"]; }

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• How do I memoize expensive calculations on Django model objects?

  - by David Eyk

  I have several TextField columns on my UserProfile object which contain JSON objects. I've also defined a setter/getter property for each column which encapsulates the logic for serializing and deserializing the JSON into python datastructures. The nature of this data ensures that it will be accessed many times by view and template logic within a single Request. To save on deserialization costs, I would like to memoize the python datastructures on read, invalidating on direct write to the property or save signal from the model object. Where/How do I store the memo? I'm nervous about using instance variables, as I don't understand the magic behind how any particular UserProfile is instantiated by a query. Is __init__ safe to use, or do I need to check the existence of the memo attribute via hasattr() at each read? Here's an example of my current implementation: class UserProfile(Model): text_json = models.TextField(default=text_defaults) @property def text(self): if not hasattr(self, "text_memo"): self.text_memo = None self.text_memo = self.text_memo or simplejson.loads(self.text_json) return self.text_memo @text.setter def text(self, value=None): self.text_memo = None self.text_json = simplejson.dumps(value)

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• Exception design: Custom exceptions reading data from file?

  - by User

  I have a method that reads data from a comma separated text file and constructs a list of entity objects, let's say customers. So it reads for example, Name Age Weight Then I take these data objects and pass them to a business layer that saves them to a database. Now the data in this file might be invalid, so I'm trying to figure out the best error handling design. For example, the text file might have character data in the Age field. Now my question is, should I throw an exception such as InvalidAgeException from the method reading the file data? And suppose there is length restriction on the Name field, so if the length is greater than max characters do I throw a NameTooLongException or just an InvalidNameException, or do I just accept it and wait until the business layer gets a hold of it and throw exceptions from there? (If you can point me to a good resource that would be good too)

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• Debugging site written mainly in JScript with AJAX code injection

  - by blumidoo

  Hello, I have a legacy code to maintain and while trying to understand the logic behind the code, I have run into lots of annoying issues. The application is written mainly in Java Script, with extensive usage of jQuery + different plugins, especially Accordion. It creates a wizard-like flow, where client code for the next step is downloaded in the background by injecting a result of a remote AJAX request. It also uses callbacks a lot and pretty complicated "by convention" programming style (lots of events handlers are created on the fly based on certain object names - e.g. current page name, current step name). Adding to that, the code is very messy and there is no obvious inner structure - the functions are scattered in the code, file names do not reflect the business role of the code, lots of functions and code snippets are most likely not used at all etc. PROBLEM: How to approach this code base, so that the inner flow of the code can be sort-of "reverse engineered" using a suite of smart debugging tools. Ideally, I would like to be able to attach to the running application and step through the code, breaking on each new function call. Also, it would be nice to be able to create a "diagram of calls" in the application (i.e. in order to run a particular page logic, this particular flow of function calls was executed in a particular order). Not to mention to be able to run a coverage analysis, identifying potentially orphaned code fragments. I would like to stress out once more, that it is impossible to understand the inner logic of the application just by looking at the code itself, unless you have LOTS of spare time and beer crates, which I unfortunately do not have :/ (shame...) An IDE of some sort that would aid in extending that code would be also great, but I am currently looking into possibility to use Visual Studio 2010 to do the job, as the site itself is a mix of Classic ASP and ASP.NET (I'd say - 70% Java Script with jQuery, 30% ASP). I have obviously tried FireBug, but I was unable to find a way to define a breakpoint or step into the code, which is "injected" into the client JS using AJAX calls (i.e. the application retrieves the code by invoking an URL and injects it to the client local code). Venkman debugger had similar issues. Any hints would be welcome. Feel free to ask additional questions.

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• .Net opening and closing database connections

  - by Dan

  I designed the data access portion of our framework so that every time a business object needs to interact with the database it would have to open a connection, invoke the data access layer (to execute the query), and then close the connection. Then if it needed to run in a transaction it would open the connection, begin the transaction, invoke the data access layer (to execute the query) and then commit the transaction, close the transaction, and finally close the connection. I did it this way with the mindset of open late and close early... but what if I needed to call other BO's to submit data in a single transaction? Is there a better way to handle opening and closing connections as well as working with transactions? I'm a rookie in designing application architecture so I hope I'm not doing this wrongly... any help is appreciated.

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• groovy thread for urls

  - by Srinath

  I wrote logic for testing urls using threads. This works good for less number of urls and failing with more than 400 urls to check . class URL extends Thread{ def valid def url URL( url ) { this.url = url } void run() { try { def connection = url.toURL().openConnection() connection.setConnectTimeout(10000) if(connection.responseCode == 200 ){ valid = Boolean.TRUE }else{ valid = Boolean.FALSE } } catch ( Exception e ) { valid = Boolean.FALSE } } } def threads = []; urls.each { ur - def reader = new URL(ur) reader.start() threads.add(reader); } while (threads.size() 0) { for(int i =0; i < threads.size();i++) { def tr = threads.get(i); if (!tr.isAlive()) { if(tr.valid == true){ threads.remove(i); i--; }else{ threads.remove(i); i--; } } } Could any one please tell me how to optimize the logic and where i was going wrong . thanks in advance.

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• Swing code in sockets

  - by asb

  I am learning swings for making GUI. I was thinking which is the best possible way in case of socket with swings. 1. The whole swing code goes in the server file. All the handlers and logic in on server side. Client only create socket. 2. The server have logic part. The code for the swing to display interface goes on client side. Client Creates stream to send / rec. data from server. Whch is the good way out of 2 ?

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• Practices for Foreground/Background threads in .NET

  - by Andrei Taptunov

  I work with in-house legacy communication framework which exposes some high level abstractions. These abstractions are wrappers with some logic around .NET threads. When I looked at code I've noticed that some abstractions are wrappers around foreground threads while others are wrappers around background threads. The sad thing is that I don't see any logic why in some cases foreground threads are used and background in other cases. Are there any guidelines or patterns & practices when it's better to choose one over another on server side and client side (I believe there should be some difference)?

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• Dealing with missing messages in JavaScript when using BOSH

  - by JamieD

  We recently went into private beta on our flagship product and had a small launch event. Unfortunately the venue had a terrible wireless connection and packets were being dropped left right and centre causing havoc with out system, basically it wasn't able to work at all! Luckily we were able to switch to a different network and rescue the demo. This highlighted something that I knew was already an issue but hadn't appreciated quite how much of an issue it could be. Our system relies heavily on BOSH and has a rather large JavaScript code base which now works rather well under good network conditions. However we need to make it work well under bad network conditions as well. Due to the way that XMPP works, a fire and forget system, it's not easy to tell if a message you sent, or were supposed to receive, was actually sent or received. For instance, we have an offer system, one user will send an offer to another over BOSH. When this message is received by the server a message is published to the offering users offers_sent PEP node and a similar message to the receiving users offers_received PEP node. While the sending user is able to tell if their offer was send (relatively) easily, if the notification to the receiving user is never received that user will never know it missed a message. A little about out JavaScript setup, it has 4 main layers: StropheJS An MVC framework for dealing with low level tasks and to build on top of An application layer which contains the app logic routes, controllers models etc. as well as a browser cache of the model data A UI layer that receives events and publishes events to and from the application layer One way to solve the missing messages issue would be to periodically check the PEP nodes for new data that the browser doesn't know about. If a new message was discovered the browsers cache would be invalidated and all new data would be requested from the server. I'm not sure this is the best way to go and it also doesn't cover all situations. We certainly don't want to get into the situation where we are sending messages to confirm the previous message was received at it's destination as this would double the network traffic. With the number of real time websites growing daily this is an issue that must have been encountered by other developers, it would be interesting to see how it's been solved by others. As far as I can see there are two situations in which messages go missing: On poor connections messages are not sent or received due to the packets being dropped Involving navigating between pages, a message is received by the browser but is not fully processed and stored in the local cache before the page is unloaded. Or a message is added to the send queue but never sent before the page is unloaded I suspect the hardest issue to solve will be number 2. Any thoughts on the subject would be much appreciated.

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• Is it possible to build a JPA entity by extending a POJO?

  - by Freiheit

  Lets say I have the following POJO: public class MyThing { private int myNumber; private String myData; //assume getter/setter methods } Is it now possible to extend this POJO as a JPA entity? @Entity @Table(name = "my_thing") public class MyThingEntity extends MyThing implements Serializable { @Column(name = "my_number") //????????? @Column(name = "my_data") //???????? } I want to keep the POJO separate from the JPA entity. The POJO lives in a different project and is often used without a persistence layer, my project wants to persist it in a database and do so without the overhead of mapping from a POJO to an entity and back. I understand that JPA entities are POJOs, but in order to use it I would have to include a library that implements javax.persistence and the other projects using the same base object have no use for a persistence layer. Is this possible? Is this a good idea?

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• Books recommendation to learn about java networking

  - by elec

  In order to cover for my (glaring) lack of knowledge in the basics of networking, I'm looking for a book which would ideally cover: - 1 or 2 chapters on the transport layer: tcp, udp... - 1 or 2 chapters on the application layer: http, dns... - rest of the book would be devoted to pratical way of sending data across the wire using Java-related technologies. This would involve discussions about existing products (eg. hessian, protobuf, thrift, tibco...) , performances comparisons, case studies...etc.. Does such a book exist ?

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• Rails: Skinny Controller vs. Fat Model, or should I make my Controller Anorexic?

  - by Nick Gorbikoff

  I know similar questions have been answered before - such as: Where should logic go, where to do certain tasks, etc. But I have a more specific question - How far should I take this axiom: "keep your controller skinny, make your model fat!" Here is an example: For instance let's say I have multiple source of verification data. A good example would be a VIN number - I can verify it against, manufacturers data source, DMV's data source, also my local databases - to see what I have on record. So I have a model called Vin and vins_controller. Inside the model I have 5 methods: check_against_local_db, check_against_dmv, check_against_car_maker_1, check_against_car_maker_2, etc. In my controller keeping with the REST, in action show - I have a simple case statement which looks at the params[:source], and based on source specified - will call specific check method. Now here is the question: Should I leave the logic that governs which data source to call in controller or should I move it to model and then in controller just do something like check_vin(source, vin)? Should I make my controller anorexic?

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• Where should Nhibernate IPostInsertEventListener go in the 3 tier architecture

  - by Quintin Par

  I have a IPostInsertEventListener implementation like public class NHibernateEventListener : IPostInsertEventListener, IPostUpdateEventListener which catches some entity inserts and does an additional insert to another table for ETL. Essentially it requires references to the Nhibernate, Domain entity and Repository<> Now where do I go about adding this class? If I add it to ApplicationServices I’ll end up referencing Nhibernate at that layer. If I add this to the Data layer, I’ll have to reference Domain (circular). How do I go implementing this class with S#arp principles? Any thoughts?

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• Creating a drawable rectangle in xml with one gradient on the top half and another on the bottom hal

  - by synic

  I'm trying to create a drawable in xml, a rectangle with one gradient on the top half, and another on the bottom half. This is NOT the way to do it, apparently: <?xml version="1.0" encoding="utf-8"?> <layer-list xmlns:android="http://schemas.android.com/apk/res/android"> <item> <shape android:shape="rectangle"> <gradient android:startColor="#5a5a5a88" android:endColor="#14141488" android:angle="270" android:centerX="0.25"/> </shape> </item> <item> <shape android:shape="rectangle" android:top="80px"> <gradient android:startColor="#5aff5a88" android:endColor="#14ff1488" android:angle="270" android:centerX="0.25"/> </shape> </item> </layer-list> How can I do this, preferably in a way that makes it stretchable to any height?

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• Trying to get a json result back from method in another namespace, having issues

  - by Blankman

  I have a seperate .js file and namespace for json requests. I have another .js file and namespace for the actual logic. I can't seem to get the result back in my logic layer. var jsonResult = Blah.Data.LoadAggregates(); alert(jsonResult); alert(jsonResult.d.length); alert(jsonResult.length); all of the above calls are returning undefined. Blah.RegisterNamespace("Blah.Data"); (function(Data) { Data.LoadAggregates = function() { $.ajax({ type: "POST", url: "asdf.asmx/GetAggregates", data: "{}", contentType: "application/json; charset=utf-8", dataType: "json", success: function(data) { ??????? }, error: function(msg) { alert("error" + msg); } }); }; })(Blah.Data);

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• Windows Phone 7, MVVM, Silverlight and navigation best practice / patterns and strategies

  - by Matt F

  Whilst building a Windows Phone 7 app. using the MVVM pattern we've struggled to get to grips with a pattern or technique to centralise navigation logic that will fit with MVVM. To give an example, everytime the app. calls our web service we check that the logon token we've assigned the app. earlier hasn't expired. We always return some status to the phone from the web service and one of those might be Enum.AuthenticationExpired. If we receive that I'd imagine we'd alert the user and navigate back to the login screen. (this is one of many examples of status we might receive) Now, wanting to keep things DRY, that sort of logic feels like it should be in one place. Therein lies my question. How should I go about modelling navigation that relies on (essentially) switch or if statements to tell us where to navigate to next without repeating that in every view. Are there recognised patterns or techniques that someone could recommend? Thanks

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• Polling versus socket servers for online Flash games

  - by justin

  Hi, I want to make an online flash game, it will have social features but the gameplay will be primarily single-player. For example, no two players will appear on the screen at once, the social interaction will be through asynchronous messages, there won't be real-time chat or anything. Much of the logic would happen in the client, the server would validate the client logic, but it wouldn't need to be totally synchronous, which is why I'm thinking polling might be satisfactory. I have read in many places that socket servers can be more efficient than using polling for online games, but is that mainly a consideration for games that are more multi-player with more mult-player interactions than the game I have descriebed? If many users are playing online at the same time, but each playing a relatively isolated game, and not interacting to in real-time with each players, could polling be okay, or would using sockets be advisable no matter what if you have an online game that you envision many people playing at the same time? Thanks!

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• Is it possible to define a generic lambda?

  - by Mike OBrien

  I have some logic in a method that operates on a specified type and I'd like to create a generic lambda that encapsulates the logic. This is the spirit of what I'm trying to do: public void DoSomething() { // ... Func<T> GetTypeName = () => T.GetType().Name; GetTypeName<string>(); GetTypeName<DateTime>(); GetTypeName<int>(); // ... } I know I can pass the type as a parameter or create a generic method but I'm interested if it can just be a generic lambda (So I'm not looking for alternatives). From what I can tell C# 3.0 doesn't support this. TIA, m

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• ASP.Net MVC elegant UI and ModelBinder authorization

  - by SDReyes

  We know authorization stuff is a cross cutting concern, and we do anything we could to avoid merge business logic in our views. But I still not found an elegant way to filter UI components (e.g. widgets, form elements, tables, etc) using the current user roles without contaminate the view with business logic. same applies for model binding. Example Form: Product Creation Fields: Name Price Discount Roles: Role Administrator Is allowed to see and modify the Name field Is allowed to see and modify the Price field Is allowed to see and modify the Discount Role Administrator assistant Is allowed to see and modify the Name Is allowed to see and modify the Price Fields shown in each role are different, and model binding needs to ignore the discount field for 'Administrator assistant' role. How would you do it?

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• Custom spring interceptor

  - by Hari

  Hi, I want to convert some of our internal API into a spring bean spring interceptor that we can use in other projects. This API needs some instantiation and other logic which I want to encapsulate in this bean so that we can just put the bean into our app context with necessary propoerties alone, and this will then apply the logic. I remember having read an article on this somewhere in the past - but cant find it now. Any pointers to something similar will be helpful EDIT: Sorry, I meant a spring interceptor, not a bean - my bad - please see my edit. I want to apply this interceptor to another bean dealing in XML messages.

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