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• Materials from Parallel Programming Pattern Presentation at Charlottesville .NET User Group Meeting

  - by John Blumenauer

  On Thursday, May 27, I had the privilege of presenting “A Look at Parallel Programming Patterns” at the Charlottesville .NET User Group’s monthly meeting.  Those folks in attendance had many great questions and were obviously very interested in what the Parallel Task Library has to offer.  The code and slides can be found HERE.  Thanks again to CHODOTNET for having me in town to speak.  If you experience any problems downloading the slides or code, please let me know.

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• Is there a way to avoid type-checking in this scenario?

  - by Prog

  I have a class SuperClass with two subclasses SubClassA and SubClassB. I have a method in a different class which takes a SuperClass parameter. The method should do different things depending on the type of the object it receives. To illustrate: public void doStuff(SuperClass object){ // if the object is of type SubClassA, do something. // if it's of type SubClassB, do something else. } I want to avoid type-checking (i.e. instanceof) because it doesn't feel like proper OO design. But I can't figure out how to employ Polymorphism to elegantly solve this problem. How can I solve this problem elegantly?

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• Which parallel pattern to use?

  - by Wim Van Houts

  I need to write a server application that fetches mails from different mail servers/mailboxes and then needs to process/analyze these mails. Traditionally, I would do this multi-threaded, launching a thread for fetching mails (or maybe one per mailbox) and then process the mails. We are moving more and more to servers where we have 8+ cores, so I would like to make use of these cores as much as possible (and not use 1 at 100% and leave the seven others untouched). So conceptually, as an example, it would be nice that I could write the application in such a way that two cores are "continuously" fetching emails and four cores are "continuously" processing/analyzing the emails (since processing and analyzing mails is more CPU intensive than fetching mails). This seems like a good concept, but after studying some parallel patterns, I'm not really sure how this is best implemented. None of the patterns really fit. I'm working in VS2012, native C++, but I guess from a design point of view this does not really matter and just some pointers on how to organize this would be great!

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• Tech Article: Tired of Null Pointer Exceptions? Use Java SE 8's Optional!

  - by Tori Wieldt

  A wise man once said you are not a real Java programmer until you've dealt with a null pointer exception. The null reference is the source of many problems because it is often used to denote the absence of a value. Java SE 8 introduces a new class called java.util.Optional that can alleviate some of these problems. In the tech article "Tired of Null Pointer Exceptions? Use Java SE 8's Optional!" Java expert Raoul-Gabriel Urma shows you how to make your code more readable and protect it against null pointer exceptions. Urma explains "The purpose of Optional is not to replace every single null reference in your codebase but rather to help design better APIs in which—just by reading the signature of a method—users can tell whether to expect an optional value. In addition, Optional forces you to actively unwrap an Optional to deal with the absence of a value; as a result, you protect your code against unintended null pointer exceptions." Learn how to go from writing painful nested null checks to writing declarative code that is composable, readable, and better protected from null pointer exceptions. Read "Tired of Null Pointer Exceptions? Use Java SE 8's Optional!"

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• Draw contour around object in Opengl

  - by Maciekp

  I need to draw contour around 2d objects in 3d space. I tried drawing lines around object(+points to fill the gap), but due to line width, some part of it(~50%) was covering object. I tried to use stencil buffer, to eliminate this problem, but I got sth like this(contour is green): http://goo.gl/OI5uc (sorry I can't post images, due to my reputation) You can see(where arrow points), that some parts of line are behind object, and some are above. This changes when I move camera, but always there is some part, that is covering it. Here is code, that I use for drawing object: glColorMask(1,1,1,1); std::list<CObjectOnScene*>::iterator objIter=ptr->objects.begin(),objEnd=ptr->objects.end(); int countStencilBit=1; while(objIter!=objEnd) { glColorMask(1,1,1,1); glStencilFunc(GL_ALWAYS,countStencilBit,countStencilBit); glStencilOp(GL_REPLACE,GL_KEEP,GL_REPLACE ); (*objIter)->DrawYourVertices(); glStencilFunc(GL_NOTEQUAL,countStencilBit,countStencilBit); glStencilOp(GL_KEEP,GL_KEEP,GL_REPLACE); (*objIter)->DrawYourBorder(); ++objIter; ++countStencilBit; } I've tried different settings of stencil buffer, but always I was getting sth like that. Here is question: 1.Am I setting stencil buffer wrong? 2. Are there any other simple ways to create contour on such objects? Thanks in advance. EDIT: 1. I don't have normals of objects. 2. Object can be concave. 3. I can't use shaders(see below why).

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• How to loop through a javascript object and check each key exists in a separate multidimensional object

  - by Paul Atkins

  I have 2 javascript objects and I am trying to loop through one object and check whether the key exists in a second multidimensional object going one level deeper each time. Here are the two objects var check = {'scope':'instance', 'item':'body', 'property': 'background'}; var values = {'instance': {'body' : {'background': '000000'}}}; b.map(check, function(key){ console.log(values[key]); }); How am I able to check 1 level deeper in the values object each time? What I am trying to do is check the values object as follows: 1st values['instance'] 2nd values['instance']['body'] 3rd values['instance']['body']['background'] Thanks

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• MySQL Unions/Subselects not utilizing keys from associated tables

  - by Brett

  I've noticed by doing EXPLAINs that when a MySQL union between two tables is used, mysql creates a temporary table, but the temp table does not use keys, so queries are slowed considerably. Here is an example: SELECT * FROM ( SELECT `part_number`, `part_manufacturer_clean`, `part_number_clean`, `part_heci`, `part_manufacturer`, `part_description` FROM `new_products` AS `a` UNION SELECT `part` as `part_number`, `manulower` as `part_manufacturer_clean`, `partdeluxe` as `part_number_clean`, `heci` as `part_heci`, `manu` as `part_manufacturer`, `description` as `part_description` FROM `warehouse` AS `b` ) AS `c` WHERE `part_manufacturer_clean` = 'adc' EXPLAIN yields this: id select_type table type possible_keys key key_len ref rows Extra 1 PRIMARY <derived2> ALL (NULL) (NULL) (NULL) (NULL) 17206 Using where 2 DERIVED a ALL (NULL) (NULL) (NULL) (NULL) 17743 3 UNION b ALL (NULL) (NULL) (NULL) (NULL) 5757 (NULL) UNION RESULT <union2,3> ALL (NULL) (NULL) (NULL) (NULL) (NULL) In this case, part_manufacturer_clean and manulower are keys in both tables. When I don't use the subselects and union, and just use one table, everything works fine. I'm not sure if the issue is with the union or with the subselects. Is there any way to union two tables and still use keys/indexes for performance?

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• MVC pattern synchronisation

  - by Hariprasad

  I am facing a problem in synchronizing my model and view threads I have a view which is table. In it, user can select a few rows. I update the view as soon as the user clicks on any row since I don't want the UI to be slow. This updating is done by a logic which runs in the controller thread below. At the same time, the controller will update the model data too, which takes place in a different thread. i.e., controller puts the query in a queue, which is then executed by the model thread - which is a single-threaded interface. As soon as the query executes, controller will get a signal. Now, In order to keep the view and model synchronized, I will update the view again based on the return value of the query (the data returned by model) - even though I updated the view already for that user action. But, I am facing issues because, its taking a lot of time for the model to return the result, by that time user would have performed multiple clicks. So, as a result of updating the view again based on the information from model, the view sometimes goes back to the state in which the previous clicks were made (Suppose user clicks thrice on different rows. I update the view as soon as the click happens. Also, I update the view when I get data back from the model - which is supposed to be same as the already updated state of the view. Now, when the user clicks third time, I get data for the first click from model. As a result, view goes back to a state which is generated by the first click) Is there any way to handle such a synchronization issue?

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• Extension objects pattern

  - by voroninp

  In this MSDN Magazine article Peter Vogel describes Extension Objects partten. What is not clear is whether extensions can be later implemented by client code residing in a separate assembly. And if so how in this case can extension get acces to private members of the objet being extended? I quite often need to set different access levels for different classes. Sometimes I really need that descendants does not have access to the mebmer but separate class does. (good old friend classes) Now I solve this in C# by exposing callback properties in interface of the external class and setting them with private methods. This also alows to adjust access: read only or read|write depending on the desired interface. class Parent { private int foo; public void AcceptExternal(IFoo external) { external.GetFooCallback = () => this.foo; } } interface IFoo { Func<int> GetFooCallback {get;set;} } Other way is to explicitly implement particular interface. But I suspect more aspproaches exist.

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• Determining Object Access Using SQL Server Profiler

  Deanna Dicken examines an SQL Server Profiler event to determine object access...who is using the object, when, and how. This gives the SQL developer or database administrator much needed information for impact analysis prior to a change or the decommissioning of a SQL Server object.

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• Creating Objects

  - by user1424667

  I have a general coding standard question. Is it bad practice to initialize and create an object in multiple methods depending on the outcome of a users choice. So for example if the user quits a poker game, create the poker hand with the cards the user has received, even if < 5, and if the user played till the end create object to show completed hand to show outcome of the game. The key is that the object will only be created once in actuality, there are just different paths and parameters is will receive depending on if the user folded, or played on to the showdown.

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• Visitor-pattern vs inheritance for rendering

  - by akaltar

  I have a game engine that currently uses inheritance to provide a generic interface to do rendering: class renderable { public: void render(); }; Each class calls the gl_* functions itself, this makes the code hard to optimize and hard to implement something like setting the quality of rendering: class sphere : public renderable { public: void render() { glDrawElements(...); } }; I was thinking about implementing a system where I would create a Renderer class that would render my objects: class sphere { void render( renderer* r ) { r->renderme( *this ); } }; class renderer { renderme( sphere& sphere ) { // magically get render resources here // magically render a sphere here } }; My main problem is where should I store the VBOs and where should I Create them when using this method? Should I even use this approach or stick to the current one, perhaps something else? PS: I already asked this question on SO but got no proper answers.

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• while(true) and loop-breaking - anti-pattern?

  - by KeithS

  Consider the following code: public void doSomething(int input) { while(true) { TransformInSomeWay(input); if(ProcessingComplete(input)) break; DoSomethingElseTo(input); } } Assume that this process involves a finite but input-dependent number of steps; the loop is designed to terminate on its own as a result of the algorithm, and is not designed to run indefinitely (until cancelled by an outside event). Because the test to see if the loop should end is in the middle of a logical set of steps, the while loop itself currently doesn't check anything meaningful; the check is instead performed at the "proper" place within the conceptual algorithm. I was told that this is bad code, because it is more bug-prone due to the ending condition not being checked by the loop structure. It's more difficult to figure out how you'd exit the loop, and could invite bugs as the breaking condition might be bypassed or omitted accidentally given future changes. Now, the code could be structured as follows: public void doSomething(int input) { TransformInSomeWay(input); while(!ProcessingComplete(input)) { DoSomethingElseTo(input); TransformInSomeWay(input); } } However, this duplicates a call to a method in code, violating DRY; if TransformInSomeWay were later replaced with some other method, both calls would have to be found and changed (and the fact that there are two may be less obvious in a more complex piece of code). You could also write it like: public void doSomething(int input) { var complete = false; while(!complete) { TransformInSomeWay(input); complete = ProcessingComplete(input); if(!complete) { DoSomethingElseTo(input); } } } ... but you now have a variable whose only purpose is to shift the condition-checking to the loop structure, and also has to be checked multiple times to provide the same behavior as the original logic. For my part, I say that given the algorithm this code implements in the real world, the original code is the most readable. If you were going through it yourself, this is the way you'd think about it, and so it would be intuitive to people familiar with the algorithm. So, which is "better"? is it better to give the responsibility of condition checking to the while loop by structuring the logic around the loop? Or is it better to structure the logic in a "natural" way as indicated by requirements or a conceptual description of the algorithm, even though that may mean bypassing the loop's built-in capabilities?

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• Passing class names or objects?

  - by nischayn22

  I have a switch statement switch ( $id ) { case 'abc': return 'Animal'; case 'xyz': return 'Human'; //many more } I am returning class names,and use them to call some of their static functions using call_user_func(). Instead I can also create a object of that class, return that and then call the static function from that object as $object::method($param) switch ( $id ) { case 'abc': return new Animal; case 'xyz': return new Human; //many more } Which way is efficient? To make this question broader : I have classes that have mostly all static methods right now, putting them into classes is kind of a grouping idea here (for example the DB table structure of Animal is given by class Animal and so for Human class). I need to access many functions from these classes so the switch needs to give me access to the class

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• Master-Detail-MoreDetail Functional Pattern

  How to develop synchronized three part pages (PDF)

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• How to Do htaccess 301 Redirect from Old Filename Pattern to New Filename Pattern?

  - by user249493

  I have a bunch of old files prefixed with "old-" (e.g. "old-abcde.php"). I need an htaccess rule to set up a 301 redirect so that any request for a file starting with "old-" goes to its corresponding new version (e.g. "abcde.php"). To be clear, I have many files, not just one, so I can't do a literal filename match. I basically just need to strip off the "old-" from request and redirect to the version without it. I know I probably just need a simple regular expression, but I'm not good at writing them. Can anyone provide assistance?

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• Dynamic Strategy Pattern [migrated]

  - by Karl Barker

  So I'm writing a web service architecture which includes FunctionProvider classes which do the actual processing of requests, and a main Endpoint class which receives and delegates requests to the proper FunctionProvider. I don't know exactly the FunctionProviders available at runtime, so I need to be able to 'register' (if that's the right word) them with my main Endpoint class, and query them to see if they match an incoming request. public class MyFunc implements FunctionProvider{ static { MyEndpoint.register(MyFunc); } public Boolean matchesRequest(Request req){...} public void processRequest(Request req){...} } public class MyEndpoint{ private static ArrayList<FunctionProvider> functions = new ArrayList<FunctionProvider>(); public void register(Class clz){ functions.add(clz); } public void doPost(Request request){ //find the FunctionProvider in functions //matching the request } } I've really not done much reflective Java like this (and the above is likely wrong, but hopefully demonstrates my intentions). What's the nicest way to implement this without getting hacky?

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• Layering Design Pattern in Java clean code style

  - by zeraDev

  As a Java developer, I am developing trying to use the clean code rules. But in my team we are facing a concrete problem: We have a business layer offering a service called "createObject", this service makes a lot of operation which can result to problem. E.g: parentObjectDontExist, objectAlreadyExist, dontHaveAuthorizationToCreate, operationFailed... and we want the UI using this service to display different information messages depending which error occurred. In old java dev, we should have create all signed exception type and throw it in createObject. As Clean code says, it is forbidden to use Exception for business logic AND signed exceptions are evil... Why not...But i don't know how to solved this problem and i don't want to use return code. How do you do? Thanks for youre experience return.

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• Pattern for loading and handling resources

  - by Enoon

  Many times there is the need to load external resources into the program, may they be graphics, audio samples or text strings. Is there a patten for handling the loading and the handling of such resources? For example: should I have a class that loads all the data and then call it everytime I need the data? As in: GraphicsHandler.instance().loadAllData() ...//and then later: draw(x,y, GraphicsHandler.instance().getData(WATER_IMAGE)) //or maybe draw(x,y, GraphicsHandler.instance().WATER_IMAGE) Or should I assign each resource to the class where it belongs? As in (for example, in a game): Graphics g = GraphicsLoader.load(CHAR01); Character c = new Character(..., g); ... c.draw(); Generally speaking which of these two is the more robust solution? GraphicsHandler.instance().getData(WATER_IMAGE) //or GraphicsHandler.instance().WATER_IMAGE //a constant reference

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• Entity and pattern validation vs DB constraint

  - by Joerg

  When it comes to performance: What is the better way to validate the user input? If you think about a phone number and you only want numbers in the database, but it could begin with a 0, so you will use varchar: Is it better to check it via the entity model like this: @Size(min = 10, max = 12) @Digits(fraction = 0, integer = 12) @Column(name = "phone_number") private String phoneNumber; Or is it better to use on the database side a CHECK (and no checking in the entity model) for the same feature?

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• ADF Faces RC : Enable/Disable Pattern

  How to dynamically enable/disable items

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• MVC Design Pattern to Combine Multiple Models for use

  - by roverred

  In my design, I have multiple models and each model has a controller. I need to use all the models to process some operation. Most examples I see are pretty simple with 1 view, 1 controller, and 1 model. How would you get all these models together? Only ways I can think of are 1) Have a top-level controller which has a reference to every controller. Those controllers will have a getter/setter function for their model. Does this violate MVC because every controller should have a model? 2) Have an Intermediate class to combine every model into a one model. Then you create a controller for that new super model. Do you know of any better ideas? Thanks.

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• ADF Design Pattern Documentation Available As an Extension

  Includes updated UI Shell - get it with check for updates

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• Refactoring to the Template Method Design Pattern

  By Refactoring to established Design Patterns your maintenance efforts will improve rather than degrade the quality of the code.

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• How to create an object oriented Win32 Console application

  How to create an object oriented Win32 Console application

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