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• Map Reduce Frameworks/Infrastructure

  - by Johannes Rudolph

  Map Reduce is a pattern that seems to get a lot of traction lately and I start to see it manifest in one of my projects that is focused on an event processing pipeline (iPhone Accelerometer and GPS data). I needed to built a lot of infrastructure for this project, in fact it overweighs the logic code interacting with it by 2x. Some of the components I built where EventProcessors (with in- and output plus buffering, timing etc.), multiplexers and aggregators. This leads me to my question what the "common" required infrastrucutre for map reduce is. Since I am working with .Net a lot I can see map reduce infrastructure built into the Framework and language constructs. Functional languages support this paradigm per se. It seems every language can be used with map reduce, some have better support than others, others again are built around that concept (e.g. Go). And there are Frameworks like Apache Hadoop to support map reduce.

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• Delete or comment out non-working JUnit tests?

  - by Chris Knight

  I'm currently building a CI build script for a legacy application. There are sporadic JUnit tests available and I will be integrating a JUnit execution of all tests into the CI build. However, I'm wondering what to do with the 100'ish failures I'm encountering in the non-maintained JUnit tests. Do I: 1) Comment them out as they appear to have reasonable, if unmaintained, business logic in them in the hopes that someone eventually uncomments them and fixes them 2) Delete them as its unlikely that anyone will fix them and the commented out code will only be ignored or be clutter for evermore 3) Track down those who have left this mess in my hands and whack them over the heads with the printouts of the code (which due to long-method smell will be sufficently suited to the task) while preaching the benefits of a well maintained and unit tested code base

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• Matrix multiplication in java (RE-POST)

  - by Chapax

  Apologies for the re-post; the earlier time I'd posted I did not have all the details. My colleague, who quit the firm was a C# programmer, was forced to write Java code that involved (large, dense) matrix multiplication. He's coded his own DataTable class in Java, in order to be able to a) create indexes to sort and join with other DataTables b) do matrix multiplication. The code in its current form is NOT maintainable/extensible. I want to clean up the code, and thought using something like R within Java will help me focus on business logic rather than sorting, joining, matrix multiplication, etc. Plus, I'm very new to the concept of DataTable; I just want to replace the DataTable with 2D arrays, and let R handle the rest. (I currently do not know how to join 2 large datasets in java very efficiently Please let me know what you think. Also, are there any simple examples that I can take a look at?

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• Can't set default value of string property to "" in the Xcode CoreData model designer

  - by glenc

  I have an entity in my datamodel with a string property that is currently optional, and I'd like to convert this property to a required property with a default value of the empty string. As others have discovered, leaving the default value blank results in validation errors (since the designer interprets this as NULL), but trying '', "", or @"" as the default value results in those literal characters being interpreted as the default, rather than the empty zero-length string, as desired. I did find this thread on Google, however, apart from the solution being really ugly (model definition split between the .xcdatamodel and objc source), it also doesn't work for lightweight migrations because those migrations are done solely based on the .xcdatamodel files and the objc logic from your entity implementations isn't loaded. Is there any way to achieve this in the data model designer?

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• Open Source Contribution for a newbie programmer.

  - by sasayins

  Hi, I am teaching programming to my nephews and I want them to improve their skills by contributing to open source projects. Now my question is, do you know any open source project that suit for a newbie programmer. What I mean is, the project does not have a large codebase, the project is very interesting and the project is written in C because I chose C language as their starting language but you can suggest other project made in other language. My goal here are to improve their logic by reading other source codes, familiarize to the available development tools like bug tracker, version control system, etc. and open their interest in open source community. Thanks. =)

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• How to fake Azure Table Storage in .NET for Unit Testing?

  - by Erick T

  I am working on a system that uses Azure Table Storage. In other systems (e.g., SQL, File based, etc), I can write a fake that allows me to test my data persistence logic. However, I can't see an easy way to create a fake for the Azure Table Service. I could create a new IIS project that behaves the same way, but that isn't a good way to write a unit test, it is more of an integration test. Any thoughts on how to unit test data access code that uses the Azure Table Storage client? Thanks, Erick

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• How do I make a universal iPhone / iPad application that programmatically uses UISplitViewController

  - by arash13

  I couldn't find a good answer anywhere to this. I am using a UINavigationController for my iPhone app, with everything is generated programmatically, nothing in Interface Builder. I am trying to port my app to iPad, using a UISplitViewController and my existing UINavigationController, but I am not sure where I should have the logic of my program separating the view controllers for iPhone or iPad. Do I set up my main file to use a different app delegate or do I use the same app delegate and have the user interface conditionally set up within it? Besides this, whenever I try to compile my app on the simulator it does not recognize the UISplitViewController or even the condition in which I check if the class exists. Can please someone put me in the right direction, remembering that I am not using any xibs?

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• Multiple port asynchronous I/O over serialport in C#

  - by firoso

  I'm trying to write a test application for serial I/O (RS-232) with multiple units in C# and I'm running into an issue with my lack of threading experience so I'm soliciting feedback for a best known method. I've got a pool of COM ports COM1-16 each of which can read/write at any time and I need to be able to manage them simultaneously. Is this a situation for a thread pool? What is some guidance on structuring this applet? Edit: Upon review I was wondering is I really even need to do asynchronous threads here, I could just maintain states for each COM-port and do flow logic (i.e., statemachine) for each COM-port individually.

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• Are there any tools to help the user to design a State Machine to be consumed by my application?

  - by kolrie

  When reading this question I remembered there was something I have been researching for a while now and I though Stackoverflow could be of help. I have created a framework that handles applications as state machines. Currently all the state business logic and transactions are handled via Java code. I was looking for some UI implementation that would allow the user to draw the state machines and transactions and generate a file that can later on be consumed by my framework to "run" the workflow according to one or more defined state machines. Ideally I would like to use an open standard like SCXML. The goal as the UI would be to have something like this plugin IBM have for Rational Software Architect: Do you know any editor, plugin or library that would have something similar or at least serve as a good starting point?

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• How to keep the session of user login?

  - by YaW

  Hi, I have an app that requires user to register. I've got the app conected to PHP in my server to do the logic of register/login and so, this is not problem at all. But, I want to keep a session of the user in local, so the user doesn't have to login again every time he runs the app. So, I want something like this: First time user, he opens the app, register and login. Do some stuff with the app and closes it. Open the app again, the user is recognized so he doesn't need to login again. I only need to store an ID and a Username (both fetched from the DB in the login php method). What's the best way to do this?? I've thought about doing a custom preference, store the data in files or even a local DB (sqlite). Any suggestions?

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• Equality Comparison with Multiple Instances/IEqualityComparer problems in LINQ

  - by Stacey

  This is similar to my last question; but from a different angle. http://stackoverflow.com/questions/2792393/see-if-item-exists-once-in-enumerable-linq Given the following set of items, and lists containing them... Item 1 Item 2 Item 3 Item 4 Item 5 class Item { string Name { get; set; } } List<Item> available = new List<Item>() { Item 1 Item 1 Item 2 Item 3 Item 5 } List<Item> selected = new List<Item>() { Item 1 Item 2 Item 3 } I need to make a third List that has everything from "available", except what is in "selected". However 'Item 1' is in 'available' twice, but only in 'selected' once. Since they are instances of the same item, I am having trouble figuring out the appropriate logic to accomodate this. The final array should look like... List<Item> selectable = new List<Item>() { Item 1 Item5 }

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• LINQ to SQL Web Application Best Practices

  - by derek

  In my experience building web applications, I've always used a n-tier approach. A DAL that gets data from the db and populates the objects, and BLL that gets objects from the DAL and performs any business logic required on them, and the website that gets it's display data from the BLL. I've recently started learning LINQ, and most of the examples show the queries occurring right from the Web Application code-behinds(it's possible that I've only seen overly simplified examples). In the n-tier architectures, this was always seen as a big no-no. I'm a bit unsure of how to architect a new Web Application. I've been using the Server Explorer and dbml designer in VS2008 to create the dbml and object relationships. It seems a little unclear to me if the dbml would be considered the DAL layer, if the website should call methods within a BLL, which then would do the LINQ queries, etc. What are some general architecture best practices, or approaches to creating a Web Application solution using LINQ to SQL?

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• ASP.Net Cross Page Posting

  - by John

  Currently I have two pages: The first page contains an input form, and the 2nd page generates an excel document. The input form's button posts to this 2nd page. What I'd like to do is add a second button which also posts to the 2nd page; however, I'll need requests created from this new button to act differently, which brings me to my question: Is there a way I can tell, from the 2nd page, which button was pressed to submit the request? The main reason I'm asking is I'd like to re-use the 2nd page's logic in parsing the information from the first page if possible; I'd rather not have to copy it to a new page and have the new button post to that. Thanks!

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• BLL returning the right Type of an instance

  - by Younes

  I have a class "Artikel" and there i write some Business Logic. I also have a class "tArtikel" which is a type. In my class "Artikel" I work with "tArtikel" and returns are of that type. Now when i instantiate an "Artikel" i want it to be of type "tArtikel", so what i tried in my code is: public tArtikel Artikel() { tArtikel artikel = new tArtikel(); } Which results in: "'Artikel' member names cannot be the same as their enclosing type". How would i set this up correctly?

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• XSD file, where to get xmlns argument?

  - by Daok

  <?xml version="1.0" encoding="utf-8"?> <xs:schema id="abc" targetNamespace="http://schemas.businessNameHere.com/SoftwareNameHere" elementFormDefault="qualified" xmlns="http://schemas.businessNameHere.com/SoftwareNameHere" xmlns:mstns="http://schemas.businessNameHere.com/SoftwareNameHere" xmlns:xs="http://www.w3.org/2001/XMLSchema"> <xs:element name="..." type="..." /> <xs:complexType name="..."> I am working on a project using XSD to generate .cs file. My question is concerning the string "http://schemas.businessNameHere.com/SoftwareNameHere" If I change it, it doesn't work. But the http:// is not a valid one... what is the logic behind and where can I can information about what to put there or how to change it?

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• Web service reference location?

  - by Damien Dennehy

  I have a Visual Studio 2008 solution that's currently consisting of three projects: A DataFactory project for Business Logic/Data Access. A Web project consisting of the actual user interface, pages, controls, etc. A Web.Core project consisting of utility classes, etc. The application requires consuming a web service. Normally I'd add the service reference to the Web project, but I'm not sure if this is best practice or not. The following options are open to me: Add the reference to the Web project. Add the reference to the Web.Core project, and create a wrapper method that Web will call to consume the web service. Add a new project called Web.Services, and copy step 2. This project is expected to increase in size so I'm open to any suggestions.

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• Does DB2 have an "insert or update" statement?

  - by Mikael Eriksson

  From my code (Java) I want to ensure that a row exists in the database (DB2) after my code is executed. My code now does a select and if no result is returned it does an insert. I really don't like this code since it exposes me to concurrency issuses when running in a multi-threaded environment. What I would like to do is to put this logic in DB2 instead of in my Java code. Does DB2 have an "insert-or-update" statement? Or anything like it that I can use? For example: insertupdate into mytable values ('myid') Another way of doing it would probably be to allways do the insert and catch "SQL-code -803 primary key already exists", but I would like to avoid that if possible.

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• onchange force page submit

  - by cometta

  <form jwcid="@Form" listener="listener:updateStaff"> <select jwcid="staffselect@Select" multiple="ognl:false" validators="validators:required" onchange="this.form.submit()" listener="listener:updateStaff"> <span jwcid="@For" source="ognl:hrStaff" value="ognl:currentHrStaff" index="ognl:currentHrStaffIndex"> <option class="text11" jwcid="@Option" selected="ognl:hrStaffSelection[currentHrStaffIndex]" label="ognl:currentHrStaff"/> </span> </select> </form> when onchange on selectbox, this form will be submitted and my pageValidate() will be called follow by upadteStaff() listener method. I wonder, when such submission is fired, can onchange='' pass a flag ('selectboxisfired' string) that i able to capture inside pagevalidate() 'selectboxisfired'? this will allow my logic inside pagevalidate to indicate is triggered by selectbox.

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• How to check if a variable is defined in a Master file in ASP.NET MVC

  - by Mortanis

  I've got a Site.Master file I've created to be my template for the majority of the site, with a navigation. This navigation is dynamically created, based on a recursive Entity (called Page) - Pages with a parentID of 0 are top level, and naturally each child carries it's parent's Id in that field. I've created a quick little HTML Helper that accepts the ID of an Page and generates the nav by doing a foreach on the children that have a parentId matching the passed Id. On the majority of the site, I want the Site.Master to use a parentId of 0, but if I'm on a strongly typed View displaying a Page, I naturally want to use the Id of the page. Is there a way to do such conditional logic in a Site.Master (and, does that violate MVC rules)? "If I'm on a strongly typed Page of /Page/{Id}, use the Id render nav, else use 0"

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• How do I mock memory allocation failures ?

  - by Andrei Ciobanu

  I want to extensively test some pieces of C code for memory leaks. On my machine I have 4 Gb of RAM, so it's very unlikely for a dynamic memory allocation to fail. Still I want to see the comportment of the code if memory allocation fails, and see if the recover mechanism is "strong" enough. What do you suggest ? How do I emulate an environment with lower memory specs ? How do i mock my tests ? EDIT: I want my tests to be code independent. I only have "access" to return values for different functions in the library I am testing. I am not supposed to write "test logic" inside the code I am testing.

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• Best practices for using memcached in Rails?

  - by Matt

  Hello everybody, as database transcations in our app are getting more and more time consuming, we have started to use memcached to reduce the amount of queries passed to MySQL. All in all, it works fine and really saves a lot of time. But as caching was "silently appearing" as a workaround to give the app more juice, a lot of our models now contain code like this: def self.all_cached Rails.cache.fetch('object_name') { find( :all, :include => [associations]) } end This is getting more and more a pain as filling and flushing the cache happens in several classes accross the application. Now, I was wondering if there was a better way to abstract memcached logic to make it more powerful and easy to use across all needed models? I was thinking about having some kind of memcached-module which is included in all needed modules. But before playing around, I thought: Let's ask experts first :-) Thanks Matt

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• How do I use theme preprocessor functions for my own templates?

  - by Jergason

  I have several .tpl.php files for nodes, CCK fields, and Views theming. These template files have a lot of logic in them to move things around, strip links, create new links, etc. I understand that this is bad development and not "The Drupal Way". If I understand correctly, "The Drupal Way" is to use preprocessor functions in your template.php file to manipulate variables and add new variables. A few questions about that: Is there a naming convention for creating a preprocessor function for a specific theme? For example, if I have a CCK field template called content-field-field_transmission_make_model.tpl, how would I name the preprocessor function? Can I use template preprocessor functions for node templates, CCK field templates, and Views templates? Do they have different methods of modifying template variables or adding new ones?

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• Language Agnositc Basic Programming Question

  - by Rachel

  This is very basic question from programming point of view but as I am in learning phase, I thought I would better ask this question rather than having an misunderstanding or narrow knowledge about the topic. So do excuse me if somehow I mess it up. Question: Let say I have class A,B,C and D now class A has some piece of code which I need to have in class B,C and D so I am extending class A in class B, class C, and class D Now how can I access the function of class A in other classes, do I need to create an object of class A and than access the function of class A or as am extending A in other classes than I can internally call the function using this parameter. If possible I would really appreciate if someone can explain this concept with code sample explaining how the logic flows.

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• Watching a variable for changes without polling.

  - by milkfilk

  I'm using a framework called Processing which is basically a Java applet. It has the ability to do key events because Applet can. You can also roll your own callbacks of sorts into the parent. I'm not doing that right now and maybe that's the solution. For now, I'm looking for a more POJO solution. So I wrote some examples to illustrate my question. Please ignore using key events on the command line (console). Certainly this would be a very clean solution but it's not possible on the command line and my actual app isn't a command line app. In fact, a key event would be a good solution for me but I'm trying to understand events and polling beyond just keyboard specific problems. Both these examples flip a boolean. When the boolean flips, I want to fire something once. I could wrap the boolean in an Object so if the Object changes, I could fire an event too. I just don't want to poll with an if() statement unnecessarily. import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; /* * Example of checking a variable for changes. * Uses dumb if() and polls continuously. */ public class NotAvoidingPolling { public static void main(String[] args) { boolean typedA = false; String input = ""; System.out.println("Type 'a' please."); while (true) { InputStreamReader isr = new InputStreamReader(System.in); BufferedReader br = new BufferedReader(isr); try { input = br.readLine(); } catch (IOException ioException) { System.out.println("IO Error."); System.exit(1); } // contrived state change logic if (input.equals("a")) { typedA = true; } else { typedA = false; } // problem: this is polling. if (typedA) System.out.println("Typed 'a'."); } } } Running this outputs: Type 'a' please. a Typed 'a'. On some forums people suggested using an Observer. And although this decouples the event handler from class being observed, I still have an if() on a forever loop. import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; import java.util.Observable; import java.util.Observer; /* * Example of checking a variable for changes. * This uses an observer to decouple the handler feedback * out of the main() but still is polling. */ public class ObserverStillPolling { boolean typedA = false; public static void main(String[] args) { // this ObserverStillPolling o = new ObserverStillPolling(); final MyEvent myEvent = new MyEvent(o); final MyHandler myHandler = new MyHandler(); myEvent.addObserver(myHandler); // subscribe // watch for event forever Thread thread = new Thread(myEvent); thread.start(); System.out.println("Type 'a' please."); String input = ""; while (true) { InputStreamReader isr = new InputStreamReader(System.in); BufferedReader br = new BufferedReader(isr); try { input = br.readLine(); } catch (IOException ioException) { System.out.println("IO Error."); System.exit(1); } // contrived state change logic // but it's decoupled now because there's no handler here. if (input.equals("a")) { o.typedA = true; } } } } class MyEvent extends Observable implements Runnable { // boolean typedA; ObserverStillPolling o; public MyEvent(ObserverStillPolling o) { this.o = o; } public void run() { // watch the main forever while (true) { // event fire if (this.o.typedA) { setChanged(); // in reality, you'd pass something more useful notifyObservers("You just typed 'a'."); // reset this.o.typedA = false; } } } } class MyHandler implements Observer { public void update(Observable obj, Object arg) { // handle event if (arg instanceof String) { System.out.println("We received:" + (String) arg); } } } Running this outputs: Type 'a' please. a We received:You just typed 'a'. I'd be ok if the if() was a NOOP on the CPU. But it's really comparing every pass. I see real CPU load. This is as bad as polling. I can maybe throttle it back with a sleep or compare the elapsed time since last update but this is not event driven. It's just less polling. So how can I do this smarter? How can I watch a POJO for changes without polling? In C# there seems to be something interesting called properties. I'm not a C# guy so maybe this isn't as magical as I think. private void SendPropertyChanging(string property) { if (this.PropertyChanging != null) { this.PropertyChanging(this, new PropertyChangingEventArgs(property)); } }

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• How do views reduce code duplication?

  - by Debuger

  Hi! I read something like this about db views: Views are incredibly powerful and useful for one reason that stands out above all the other very good reasons. They reduce code duplication. That is, in most cases, the bottom line. If a query will be used in three or more places, then a view will drastically simplify your changes if the schema or query parameters change. I once had to edit 22 stored procedures to change some query logic. If the original architecture had utilized views, then I would have had only three changes. Can anyone explain to me how it works, and maybe give me some examples? Best regards!

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