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• Authenticate native mobile app using a REST API

  - by Supercell

  I'm starting a new project soon, which is targeting mobile application for all major mobile platforms (iOS, Android, Windows). It will be a client-server architecture. The app is both informational and transactional. For the transactional part, they're required to have an account and log in before a transaction can be made. I'm new to mobile development, so I don't know how the authentication part is done on these platforms. The clients will communicate with the server through a REST API. Will be using HTTPS ofcourse. I haven't yet decided if I want the user to log in when they open the app, or only when they perform a transaction. I got the following questions: 1) Like the Facebook application, you only enter your credentials when you open the application for the first time. After that, you're automatically signed in every time you open the app. How does one accomplish this? Just simply by encrypting and storing the credentials on the device and sending them every time the app starts? 2) Do I need to authenticate the user for each (transactional) request made to the REST API or use a token based approach? Please feel free to suggest other ways for authentication. Thanks!

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• Mechanics of reasoning during programming interviews

  - by user129506

  This is not the usual "I don't want to write code during an interview", in this question the assumption is that I need to write code during an interview (think about the level of rewriting the quicksort or mergesort from scratch) I know how the algorithm work or I have a basic idea of how I should start working from there, i.e. I don't remember the algorithm by heart I noticed that even on a whiteboard, I always end up writing bugged code or code that doesn't compile. If there's a typo, whatever I usually live with that.. but when there's a crash due to some uncaught particular case I end up losing confidence in my skills. I realize that perhaps interviewers might want to look at how I write code and/or how I solve problems rather than proof-compiling my whiteboard code, but I'd like to ask how should I approach the above problem in mental terms, i.e. what mental steps should I follow when writing code for an interview with the two bullet points above. There must be a unique and agreed series of steps I should follow to avoid getting stuck/caught into particular exception cases (limit cases) that might end up wasting my time and my energies rather than focusing on the overall algorithm for the general case. I hope I made my point clear

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• What is the disadvantage of using abstract class as a database connectivity in zend framework 2 instead of service locator

  - by arslaan ejaz

  If I use database by creating adapter with drivers, initialize it in some abstract class and extend that abstract class to required model. Then use simple query statement. Like this: namespace My-Model\Model\DB; abstract class MysqliDB { protected $adapter; public function __construct(){ $this->adapter = new \Zend\Db\Adapter\Adapter(array( 'driver' => 'Mysqli', 'database' => 'my-database', 'username' => 'root', 'password' => '' )); } } And use abstract class of database like this in my models: class States extends DB\MysqliDB{ public function __construct(){ parent::__construct(); } protected $states = array(); public function select_all_states(){ $data = $this->adapter->query('select * from states'); foreach ($data->execute() as $row){ $this->states[] = $row; } return $this->states; } } I am new to zend framework, before i have experience of working in YII and Codeigniter. I like the object oriented in zend so i want to use it like this. And don't want to use it through service locater something like this: public function getServiceConfig(){ return array( 'factories' => array( 'addserver-mysqli' => new Model\MyAdapterFactory('addserver-mysqli'), 'loginDB' => function ($sm){ $adapter = $sm->get('addserver-mysqli'); return new LoginDB($adapter); } ) ); } In module. Am i Ok with this approach?

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• Alternative to NV Occlusion Query - getting the number of fragments which passed the depth test

  - by Etan

  In "modern" environments, the "NV Occlusion Query" extension provide a method to get the number of fragments which passed the depth test. However, on the iPad / iPhone using OpenGL ES, the extension is not available. What is the most performant approach to implement a similar behaviour in the fragment shader? Some of my ideas: Render the object completely in white, then count all the colors together using a two-pass shader where first a vertical line is rendered and for each fragment the shader computes the sum over the whole row. Then, a single vertex is rendered whose fragment sums all the partial sums of the first pass. Doesn't seem to be very efficient. Render the object completely in white over a black background. Downsample recursively, abusing the hardware linear interpolation between textures until being at a reasonably small resolution. This leads to fragments which have a greyscale level depending on the number of white pixels where in their corresponding region. Is this even accurate enough? ... ?

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• Ranking players depending on decision making during a game

  - by tabchas

  How would I go about a ranking system for players that play a game? Basically, looking at video games, players throughout the game make critical decisions that ultimately impact the end game result. Is there a way or how would I go about a way to translate some of those factors (leveling up certain skills, purchasing certain items, etc.) into something like a curve that can be plotted on a graph? This game that I would like to implement this is League of Legends. Example: Player is Level 1 in the beginning. Gets a kill very early in the game (he gets gold because of the kill and it increases his "power curve"), and purchases attack damage (gives him more damage which also increases his "power curve". However, the player that he killed (Player 2), buys armor (counters attack damage). This slightly increases Player 2's own power curve, and reduces Player 1's power curve. There's many factors I would like to take into account. These relative factors (example: BECAUSE Player 2 built armor, and I am mainly attack damage, it lowers my OWN power curve) seem the hardest to implement. My question is this: Is there a certain way to approach this task? Are there similar theoretical concepts behind ranking systems that I should read up on? I've seen the ELO system, but it doesn't seem what I want since it simply takes into account wins and losses.

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• ArchBeat Link-o-Rama for October 23, 2013

  - by OTN ArchBeat

  Virtual Dev Day: Oracle ADF Development - Web, Mobile, and Beyond This free virtual event includes technical sessions that range from introductory to deep dive, covering Oracle ADF and Oracle ADF Mobile. Multiple tracks cover every interest and every level and include live online Q&A for answers to your technical questions. Register now! Americas: Tuesday, November 19, 9am-1pm PT / 12pm-4pm ET / 1pm-5pm BRT APAC: Thursday, November 21, 10am–1:30pm IST (India) / 12:30pm–4pm SGT (Singapore) / 3:30pm–7pm AESDT EMEA: Tuesday, November 26, 9am-1pm GMT / 1pm-5pm GST/ 2:30pm-6:30pm IST A Roadmap for SOA Development and Delivery | Mark Nelson Do you know the way to S-O-A? Mark Nelson does. His latest blog post, part of an ongoing series, will help to keep you from getting lost along the way. Updated ODI Statement of Direction | Robert Schweighardt Heads up Oracle Data Integrator fans! A new product statement of direction document is available, offering "an overview of the strategic product plans for Oracle’s data integration products for bulk data movement and transformation, specifically Oracle Data Integrator (ODI) and Oracle Warehouse Builder (OWB)." Java-Powered Robot Named NAO Wows Crowds | Tori Wieldt Java community manager Tori Wieldt interviews a robot and human. Nordic OTN Tour 2013 | Lonneke Dikmans Oracle ACE Director Lonneke Dikmans checks in from the Stockholm leg of the Nordic OTN Tour for 2013, sponsored by the Danish Oracle User Group and featuring fellow ACE Directors Tim Hall and Sten Vesterli, plus local speakers at various stops. Lonneke's post include the slides from three of the presentations. Thought for the Day "Some people approach every problem with an open mouth." — Adlai E. Stevenson23rd Vice President of the United States (October 23, 1835 – June 14, 1914) Source: brainyquote.com

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• Team Software Development using Ruby on Rails

  - by Panoy

  I used to work alone on small to medium sized programming projects before and have no experience working in a team environment. Currently, there will be 3 of us in an in-house software development team that is tasked to develop a number of software for an academic institution. We have decided to use the web for the majority of the projects and are planning to choose Ruby on Rails for this and I would like to ask for your inputs, advices and approaches with regards to software development as a team using the RoR web framework. One thing that has really confounded me is how you divide the programming tasks of a project if there are 3 of you that are really doing the coding. It’s obvious that we as developers approach a problem in a modular way and finish it one after another. If the project consists of 3 modules, should each one of us focus on each of those modules? Would it be faster that way? How about if the 3 of us would focus on one module first (that’s what I really prefer). Is using a distributed version control system such as Git the answer to this type of problem? Please don’t forget to put your tips and experiences with regards to team software development. Cheers!

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• Building Enterprise Smartphone App &ndash; Part 4: Application Development Considerations

  - by Tim Murphy

  This is the final part in a series of posts based on a talk I gave recently at the Chicago Information Technology Architects Group.  Feel free to leave feedback. Application Development Considerations Now we get to the actual building of your solutions.  What are the skills and resources that will be needed in order to develop a smartphone application in the enterprise? Language Knowledge One of the first things you need to consider when you are deciding which platform language do you either have the most in house skill base or can you easily acquire.  If you already have developers who know Java or C# you may want to use either Android or Windows Phone.  You should also take into consideration the market availability of developers.  If your key developer leaves how easy is it to find a knowledgeable replacement? A second consideration when it comes to programming languages is the qualities exposed by the languages of a particular platform.  How well does that development language and its associated frameworks support things like security and access to the features of the smartphone hardware?  This will play into your overall cost of ownership if you have to create this infrastructure on your own. Manage Limited Resources Everything is limited on a smartphone: battery, memory, processing power, network bandwidth.  When developing your applications you will have to keep your footprint as small as possible in every way.  This means not running unnecessary processes in the background that will drain the battery or pulling more data over the airwaves than you have to.  You also want to keep your on device in as compact a format as possible. Mobile Design Patterns There are a number of design patterns that have either come to life because of smartphone development or have been adapted for this use.  The main pattern in the Windows Phone environment is the MVVM (Model-View-View-Model).  This is great for overall application structure and separation of concerns.  The fun part is trying to keep that separation as pure as possible.  Many of the other patterns may or may not have strict definitions, but some that you need to be concerned with are push notification, asynchronous communication and offline data storage. Real estate is limited on smartphones and even tablets. You are also limited in the type of controls that can be represented in the UI. This means rethinking how you modularize your application. Typing is also much harder to do so you want to reduce this as much as possible.  This leads to UI patterns.  While not what we would traditionally think of as design patterns the guidance each platform has for UI design is critical to the success of your application.  If user find the application difficult navigate they will not use it. Development Process Because of the differences in development tools required, test devices and certification and deployment processes your teams will need to learn new way of working together.  This will include the need to integrate service contracts of back-end systems with mobile applications.  You will also want to make sure that you present consistency across different access points to corporate data.  Your web site may have more functionality than your smartphone application, but it should have a consistent core set of functionality.  This all requires greater communication between sub-teams of your developers. Testing Process Testing of smartphone apps has a lot more to do with what happens when you lose connectivity or if the user navigates away from your application. There are a lot more opportunities for the user or the device to perform disruptive acts.  This should be your main testing concentration aside from the main business requirements.  You will need to do things like setting the phone to airplane mode and seeing what the application does in order to weed out any gaps in your handling communication interruptions. Need For Outside Experts Since this is a development area that is new to most companies the need for experts is a lot greater. Whether these are consultants, vendor representatives or just development community forums you will need to establish expert contacts. Nothing is more dangerous for your project timelines than a lack of knowledge.  Make sure you know who to call to avoid lengthy delays in your project because of knowledge gaps. Security Security has to be a major concern for enterprise applications. You aren't dealing with just someone's game standings. You are dealing with a companies intellectual property and competitive advantage. As such you need to start by limiting access to the application itself.  Once the user is in the app you need to ensure that the data is secure at all times.  This includes both local storage and across the wire.  This means if a platform doesn’t natively support encryption for these functions you will need to find alternatives to secure your data.  You also need to keep secret (encryption) keys obfuscated or locked away outside of the application. People can disassemble the code otherwise and break your encryption. Offline Capabilities As we discussed earlier one your biggest concerns is not having connectivity.  Because of this a good portion of your code may be dedicated to handling loss of connection and reconnection situations.  What do you do if you lose the network?  Back up all your transactions and store of any supporting data so that operations can continue off line. In order to support this you will need to determine the available flat file or local data base capabilities of the platform.  Any failed transactions will need to support a retry mechanism whether it is automatic or user initiated.  This also includes your services since they will need to be able to roll back partially completed transactions.  What ever you do, don’t ignore this area when you are designing your system. Deployment Each platform has different deployment capabilities. Some are more suited to enterprise situations than others. Apple's approach is probably the most mature at the moment. Prior to the current generation of smartphone platforms it would have been Windows CE. Windows Phone 7 has the limitation that the app has to be distributed through the same network as public facing applications. You mark them as private which means that they are only accessible by a direct URL. Unfortunately this does not make them undiscoverable (although it is very difficult). This will change with Windows Phone 8 where companies will be able to certify their own applications and distribute them.  Given this Windows Phone applications need to be more diligent with application access in order to keep them restricted to the company's employees. My understanding of the Android deployment schemes is that it is much less standardized then either iOS or Windows Phone. Someone would have to confirm or deny that for me though since I have not yet put the time into researching this platform further. Given my limited exposure to the iOS and Android platforms I have not been able to confirm this, but there are varying degrees of user involvement to install and keep applications updated. At one extreme the user just goes to a website to do the install and in other case they may need to download files and perform steps to install them. Future Bluetooth Today we use Bluetooth for keyboards, mice and headsets.  In the future it could be used to interrogate car computers or manufacturing systems or possibly retail machines by service techs.  This would open smartphones to greater use as a almost a Star Trek Tricorder.  You would get you all your data as well as being able to use it as a universal remote for just about any device or machine. Better corporation controlled deployment At least in the Windows Phone world the upcoming release of Windows Phone 8 will include a private certification and deployment option that is currently not available with Windows Phone 7 (Mango). We currently have to run the apps through the Marketplace certification process and use a targeted distribution method. Platform independent approaches HTML5 and JavaScript with Web Service has become a popular topic lately for not only creating flexible web site, but also creating cross platform mobile applications.  I’m not yet convinced that this lowest common denominator approach is viable in most cases, but it does have it’s place and seems to be growing.  Be sure to keep an eye on it. Summary From my perspective enterprise smartphone applications can offer a great competitive advantage to many companies.  They are not cheap to build and should be approached cautiously.  Understand the factors I have outlined in this series, do you due diligence and see if there is a portion of your business that can benefit from the mobile experience. del.icio.us Tags: Architecture,Smartphones,Windows Phone,iOS,Android

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• Estimate angle to launch missile, maths question

  - by Jonathan

  I've been working on this for an hour or two now and my maths really isn't my strong suit which is definitely not a good thing for a game programmer but that shouldn't stop me enjoying a hobby surely? After a few failed attempts I was hoping someone else out there could help so here's the situation. I'm trying to implement a bit of faked intelligence when the A.I fires it's missiles at a target in a 2D game world. By predicting the likely position the target will be in given it's current velocity and the time it will take the missile to reach it's target. I created an image to demonstrate my thinking: http://i.imgur.com/SFmU3.png which also contains the logic I use for accelerating the missile after launch. The ship that fires the missile can fire within a total of 40 degree angle, 20 either side of itself, but this could likely become variable. My current attempt was to break the space between the two lines into segments which match the targets width. Then calculate the time it would take the missile to get to that location using the formula. So for each iteration of this we total up the values and that tells us the distance travelled, ad it would then just need compared to distance to the segment. startVelocity * ((startVelocity * acceleration)^(currentframe-1) So for example. If we start at a velocity of 1f/frame with an acceleration of 0.1f the formula, at frame 4, would be 1 * (1.1^3) = 1.331 But I quickly realized I was getting lost when trying to put this into practice. Does this seem like a correct starting point or am I going completely the wrong way about it? Any pointers would help me greatly. Maths really isn't my strong suit so I get easily lost in these matters and don't even really know a good phrase to search for with this. So I guess in summary my question is more about the correct way to approach this problem and any additional code samples on top of that would be great but I'm not averse to working out the complete code from helpful pointers.

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• ArchBeat Link-o-Rama for 2012-04-12

  - by Bob Rhubart

  2012 Real World Performance Tour Dates |Performance Tuning | Performance Engineering www.ioug.org Coming to your town: a full day of real world database performance with Tom Kyte, Andrew Holdsworth, and Graham Wood. Rochester, NY - March 8 Los Angeles, CA - April 30 Orange County, CA - May 1 Redwood Shores, CA - May 3 Oracle Technology Network Developer Day: MySQL - New York www.oracle.com Wednesday, May 02, 2012 8:00 AM – 4:30 PM Grand Hyatt New York 109 East 42nd Street, Grand Central Terminal New York, NY 10017 Webcast Series: Data Warehousing Best Practices event.on24.com April 19, 2012 - Best Practices for Workload Management of a Data Warehouse on Oracle Exadata May 10, 2012 - Best Practices for Extreme Data Warehouse Performance on Oracle Exadata Webcast: Untangle Your Business with Oracle Unified SOA and Data Integration event.on24.com Date: Tuesday, April 24, 2012 Time: 10:00 AM PT / 1:00 PM ET Speakers: Mala Narasimharajan - Senior Product Marketing Manager, Oracle Data Integration, Oracle Bruce Tierney - Director of Product Marketing, Oracle SOA Suite, Oracle The Increasing Focus on Architecture (ArchBeat) blogs.oracle.com As a "third wave" of computing, Cloud computing is changing how IT organizations and individuals within those organizations approach the creation of solutions. Updated SOA Documents now available in ITSO Reference Library blogs.oracle.com Nine updated documents have just been added to the IT Strategies from Oracle library, including SOA Practitioner Guides, SOA Reference Architectures, and SOA White Papers and Data Sheets. Access to all documents within the ITSO library is free to those with a free Oracle.com membership. WebLogic JMS Clustering and Spring | Rene van Wijk middlewaremagic.com Oracle ACE Rene van Wijk sets up a WebLogic cluster that includes a JMS environment, which will be used by Spring. Running Built-In Test Simulator with SOA Suite Healthcare 11g in PS4 and PS5 | Shub Lahiri blogs.oracle.com Shub Lahiri shows how the pre-installed simulator that comes with the SOA Suite for Healthcare Integration pack can be used as an external endpoint to generate inbound and outbound HL7 traffic on specified MLLP ports. In the cloud era, let's start calling IT what it is: 'Innovation Team' | Joe McKendrick www.zdnet.com Cloud, the third great shift in 50 years of computing, presents a golden opportunity for IT to get out in front and lead. Thought for the Day "Why do we never have time to do it right, but always have time to do it over?" — Anonymous

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• Is it possible to use 3G internet for a TCP/IP game server?

  - by Amit Ofer

  I'm working on a turned based multiplayer android game with a friend. I started working on the game server and client using socket programming. I found a few tutorials on how to implement a basic chat on android and I started extending that example to suit my needs. Basically the game is really simple and the communication only include sending a few string from the client to the server every turn and sending the calculated scores back to all the clients after each turn. the idea is that one of the players creates the game and thus initialize the server, and each player connects to this client using ip. I tried this solution and it seems to work great when all the players are using the same wifi connection or by using router port forwarding. The problem is when trying to use 3G internet for the server, I guess the problem is that 3G ip address isn't global and you can't use port forwarding there, correct me if I'm wrong here. Is there a way to overcome this issue? or the only solution is to limit my game to wifi only or think of a different solution than the standard socket programming solution? I.E web server etc. what do you think would be the best approach here? Thanks.

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• 3D physics engine for accurate collision handling on desktop/laptop computers (non-console)

  - by Georges Oates Larsen

  What are your suggestions for a physics engine that satisfies the following criteria? Capable of calculating collisions between multiple concave mesh-based colliders Handles many collisions going on at once (for instance one mesh being wedged between two others, which themselves may be wedged between two meshes) Does not allow for collider passthrough, even at high speeds. For instance, if I am applying force to a programmatically hinged object that makes it spin, I do not want it to pass through another rigidbody that it collides with while spinning. I have this problem using PhysX As implied before, reacts well to hinged objects, preferably has its own implementation of a hinge, but I am willing to program my own. The important part is that it has some sort of interface that guarantees accurate collision tracking even when dealing with these things Platform independent -- runs on mac as well as PC, also not tied down to specific graphics cards I think that's the best way to explain what I am looking for. Basically, I need SUPER reliable collisions. Something that can't be accomplished with a simple ray casting approach that sends a ray from the last position of the object to the current position (as this object may be potentially large and colliding with small objects via rotation) Bonus points for also including an OPEN SOURCE engine.

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• Caching by in-memory dictionaries. Are we doing it all wrong?

  - by user73983

  This approach is pretty much the accepted way to do anything in our company. A simple example : when a piece of data for a customer is requested from a service, we fetch all the data for that customer(relevant part to the service) and save it in a in-memory dictionary then serve it from there on following requests(we run singleton services). Any update goes to DB, then updates the in memory dictionary. It seems all simple and harmless but as we implement more complicated business rules the cache gets out of sync and we have to deal with hard to find bugs. Sometimes we defer writing to database, keeping new data in cache till then. There are cases when we store millions of rows in memory because the table has many relations to other tables and we need to show aggregate data quickly. All this cache handling is a big part of our codebase and I sense this is not the right way to do it. All of this juggling adds too much noise to the code and it makes it hard to understand the actual business logic. However I don't think we can serve data in a reasonable amount of time if we have to hit the database every time. I am unhappy about the current situation but I don't have a better alternative. My only solution would be to use NHibernate 2nd level cache but I have nearly no experience with it. I know many campanies use Redis or MemCached heavily to gain performance but I have no idea how I would integrate them into our system. I also don't know if they can perform better than in-memory data structures and queries. Are there any alternative approaches that I should look into?

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• OpenGL - Rendering from part of an index and vertex array depending on an element count

  - by user1423893

  I'm currently drawing my shapes as lines by using a VAO and then assigning the dynamic vertices and indices each frame. // Bind VAO glBindVertexArray(m_vao); // Update the vertex buffer with the new data (Copy data into the vertex buffer object) glBufferData(GL_ARRAY_BUFFER, numVertices * sizeof(VertexPosition), m_vertices.data(), GL_DYNAMIC_DRAW); // Update the index buffer with the new data (Copy data into the index buffer object) glBufferData(GL_ELEMENT_ARRAY_BUFFER, numIndices * sizeof(unsigned short), indices.data(), GL_DYNAMIC_DRAW); glDrawElements(GL_LINES, numIndices, GL_UNSIGNED_SHORT, BUFFER_OFFSET(0)); // Unbind VAO glBindVertexArray(0); What I would like to do is draw the lines using only part of the data stored in the index and vertex buffer objects. The vertex buffer has its vertices set from an array of defined maximum size: std::array<VertexPosition, maxVertices> m_vertices; The index buffer has its elements set from an array of defined maximum size: std::array<unsigned short, maxIndices> indices = { 0 }; A running total is kept of the number of vertices and indices needed for each draw call numVertices numIndices Can I not specify that the buffer data contain the entire array and only read from part of it when drawing? For example using the vertex buffer object glBufferData(GL_ARRAY_BUFFER, numVertices * sizeof(VertexPosition), m_vertices.data(), GL_DYNAMIC_DRAW); m_vertices.data() = Entire array is stored numVertices * sizeof(VertexPosition) = Amount of data to read from the entire array Is this not the correct way to approach this? I do not wish to use std::vector if possible.

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• Basic is Best

  - by Eric A. Stephens

  Fellow foodies will recognize the recent movement towards "farm-to-table" restaurants. These venues attempt to simplify their menus and source ingredients as close to the source as possible. I had the opportunity to dine at such a restaurant the other evening. I was gushing about the appetizer to my server when she described the preparation for the item and then punctuated her comments with "basic is best". I reminded my fellow enterprise architect diners there was an architecture lesson in that statement. They rolled their eyes and chuckled. But they also knew I was right. I'm reminded of Frederick Brooks' book The Mythical Man Month and his latest The Design of Design. The former must read book talks about complexity. But he refrains from damning all complexity. The world we live in and enterprises we strive to transform with enterprise architecture are complicated organisms, much like the human body. But sometimes a simple solution is the best approach. Fewer applications (think: portfolio rationalization). Fewer components. Fewer lines of code. Whatever level of abstraction you are working at, less is more. I'm reminded of the enterprise architecture principle "Control Technical Diversity". At one firm I created pithy catch phrases for each principles. I named this one "Less is More". But perhaps another variation is what my server said the other night, "Basic is Best".

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• Why is the use of abstractions (such as LINQ) so taboo?

  - by Matthew Patrick Cashatt

  I am an independent contractor and, as such, I interview 3-4 times a year for new gigs. I am in the midst of that cycle now and got turned down for an opportunity even though I felt like the interview went well. The same thing has happened to me a couple of times this year. Now, I am not a perfect guy and I don't expect to be a good fit for every organization. That said, my batting average is lower than usual so I politely asked my last interviewer for some constructive feedback, and he delivered! The main thing, according to the interviewer, was that I seemed to lean too much towards the use of abstractions (such as LINQ) rather than towards lower-level, organically grown algorithms. On the surface, this makes sense--in fact, it made the other rejections make sense too because I blabbed about LINQ in those interviews as well and it didn't seem that the interviewers knew much about LINQ (even though they were .NET guys). So now I am left with this question: If we are supposed to be "standing on the shoulders of giants" and using abstractions that are available to us (like LINQ), then why do some folks consider it so taboo? Doesn't it make sense to pull code "off the shelf" if it accomplishes the same goals without extra cost? It would seem to me that LINQ, even if it is an abstraction, is simply an abstraction of all the same algorithms one would write to accomplish exactly the same end. Only a performance test could tell you if your custom approach was better, but if something like LINQ met the requirements, why bother writing your own classes in the first place? I don't mean to focus on LINQ here. I am sure that the JAVA world has something comparable, I just would like to know why some folks get so uncomfortable with the idea of using an abstraction that they themselves did not write. UPDATE As Euphoric pointed out, there isn't anything comparable to LINQ in the Java world. So, if you are developing on the .NET stack, why not always try and make use of it? Is it possible that people just don't fully understand what it does?

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• Defining formula through user interface in user form

  - by BriskLabs Pakistan

  I am a student and developing a simple assignment - windows form application in visual studio 2010. The application is suppose to construct formulas as per user requirement. The process: It has to pick data from columns of Microsoft Access database and the user should be able to pick the data by column name like we do in a drop down menu. and create reusable formulas in it ( configure it once and can change it again). followings are column titles from database that can be picked for example. e.g Col -1 : Marks in Maths Col -2 : Total Marks in Maths Col -3 : Marks in science Col -4 : Total marks in science Finally we should be able to construct any formula in the UI like (Col 1 + Col 3 ) / ( col 2 + col 4) = Formula 1 once this is formula is set saved and a name is assigned to it by user. he/she can use the formula and results shall appear in a window below. i.e He would be able to calculate his desired figures (formula) by only manipulating underlying data on the UI layer....choose the data for a period and apply the formula and get the answer Problem: It looks like I have to create an app where rules are set through UI....... this means no stored procedures are required in SQL.... please suggest the right approach.

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• 12c - Invisible Columns...

  - by noreply(at)blogger.com (Thomas Kyte)

  Remember when 11g first came out and we had "invisible indexes"?  It seemed like a confusing feature - indexes that would be maintained by modifications (hence slowing them down), but would not be used by queries (hence never speeding them up).  But - after you looked at them a while, you could see how they can be useful.  For example - to add an index in a running production system, an index used by the next version of the code to be introduced later that week - but not tested against the queries in version one of the application in place now.  We all know that when you add an index - one of three things can happen - a given query will go much faster, it won't affect a given query at all, or... It will make some untested query go much much slower than it used to.  So - invisible indexes allowed us to modify the schema in a 'safe' manner - hiding the change until we were ready for it.Invisible columns accomplish the same thing - the ability to introduce a change while minimizing any negative side effects of that change.  Normally when you add a column to a table - any program with a SELECT * would start seeing that column, and programs with an INSERT INTO T VALUES (...) would pretty much immediately break (an INSERT without a list of columns in it).  Now we can add a column to a table in an invisible fashion, the column will not show up in a DESCRIBE command in SQL*Plus, it will not be returned with a SELECT *, it will not be considered in an INSERT INTO T VALUES statement.  It can be accessed by any query that asks for it, it can be populated by an INSERT statement that references it, but you won't see it otherwise.For example, let's start with a simple two column table:ops$tkyte%ORA12CR1> create table t  2  ( x int,  3    y int  4  )  5  /Table created.ops$tkyte%ORA12CR1> insert into t values ( 1, 2 );1 row created.Now, we will add an invisible column to it:ops$tkyte%ORA12CR1> alter table t add                     ( z int INVISIBLE );Table altered.Notice that a DESCRIBE will not show us this column:ops$tkyte%ORA12CR1> desc t Name              Null?    Type ----------------- -------- ------------ X                          NUMBER(38) Y                          NUMBER(38)and existing inserts are unaffected by it:ops$tkyte%ORA12CR1> insert into t values ( 3, 4 );1 row created.A SELECT * won't see it either:ops$tkyte%ORA12CR1> select * from t;         X          Y---------- ----------         1          2         3          4But we have full access to it (in well written programs! The ones that use a column list in the insert and select - never relying on "defaults":ops$tkyte%ORA12CR1> insert into t (x,y,z)                         values ( 5,6,7 );1 row created.ops$tkyte%ORA12CR1> select x, y, z from t;         X          Y          Z---------- ---------- ----------         1          2         3          4         5          6          7and when we are sure that we are ready to go with this column, we can just modify it:ops$tkyte%ORA12CR1> alter table t modify z visible;Table altered.ops$tkyte%ORA12CR1> select * from t;         X          Y          Z---------- ---------- ----------         1          2         3          4         5          6          7I will say that a better approach to this - one that is available in 11gR2 and above - would be to use editioning views (part of Edition Based Redefinition - EBR ).  I would rather use EBR over this approach, but in an environment where EBR is not being used, or the editioning views are not in place, this will achieve much the same.Read these for information on EBR:http://www.oracle.com/technetwork/issue-archive/2010/10-jan/o10asktom-172777.htmlhttp://www.oracle.com/technetwork/issue-archive/2010/10-mar/o20asktom-098897.htmlhttp://www.oracle.com/technetwork/issue-archive/2010/10-may/o30asktom-082672.html

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• How to store prices that have effective dates?

  - by lal00

  I have a list of products. Each of them is offered by N providers. Each providers quotes us a price for a specific date. That price is effective until that provider decides to set a new price. In that case, the provider will give the new price with a new date. The MySQL table header currently looks like: provider_id, product_id, price, date_price_effective Every other day, we compile a list of products/prices that are effective for the current day. For each product, the list contains a sorted list of the providers that have that particular product. In that way, we can order certain products from whoever happens to offer the best price. To get the effective prices, I have a SQL statement that returns all rows that have date_price_effective >= NOW(). That result set is processed with a ruby script that does the sorting and filtering necessary to obtain a file that looks like this: product_id_1,provider_1,provider_3,provider8,provider_10... product_id_2,provider_3,provider_2,provider1,provider_10... This works fine for our purposes, but I still have an itch that a SQL table is probably not the best way to store this kind of information. I have that feeling that this kind of problema has been solved previously in other more creative ways. Is there a better way to store this information other than in SQL? or, if using SQL, is there a better approach than the one I'm using?

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• c# scripting execution with xna (actions take more than 1 frame)

  - by user658091

  I'm trying to figure out how to implement c# scripting into my game (XNA with C#). I will be using C# as the scripting language. My question is, how to call functions that take more than 1 frame to finish? For example: class UserScript : Script { public override void execute(Game game) { //script must wait for dialog to be closed game.openDialog("This is a dialog"); //script should'nt wait for this int goldToGive = 100; goldToGive += 100; game.addGold(goldToGive); // //script should wait for cinematic to end game.startCinematic("name_of_cinematic"); //doesn't wait game.addGold(100); } } I found that you can do that with yield, but I'm not sure if it's the correct way (It's from 2010, the article mentioned no longer exists). http://stackoverflow.com/questions/3540231/implementing-a-simple-xml-based-scripting-language-for-an-xna-game Is yield the answer? If so, can anyone point me any examples/tutorials/books? I haven't found any regarding my situation. If not, what approach should I take? or am I better off with multi-threading?

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• Best Usage of Multiple Computers For a Developer

  - by whaley

  I have two Macbook Pros - both are comparable in hardware. One is a 17" and the other a 15". The 17" has a slightly swifter CPU clock speed, but beyond that the differences are completely negligible. I tried a setup a while back where I had the 17" hooked up to an external monitor in the middle of my desk with the 15" laptop immediately to the right of it, and was using teleport to control the 15" from my 17". All development, terminal usage, etc. etc. was being done on the 17" and the 15" was primarily used for email / IM / IRC... or anything secondary to what I was working on. I have a MobileMe account so preferences were synced, but otherwise I didn't really use anything else to keep the computers in sync (I use dropbox/git but probably not optimally). For reasons I can't put my finger on, this setup never felt quite right. A few things that irked me was the 15" was way under-utlized and the 17" was overutilized having 2 laptops and a 21" monitor all on one desk actually took up lots of desk space and it felt like I had too much to look at. I reverted back to just using the 17" and the external monitor and keeping the 15" around the house (and using it very sparingly). For those of you who are using multiple laptops (or just multiple machines for that matter), I'd like to see setups that work for you for when you have 2 or more machines that gives you optimal productivity and why. I'd like to give this one more shot but with a different approach than my previous - which was using the 15" as a machine for secondary things (communication, reading documentation, etc. etc).

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• How to represent a graph with multiple edges allowed between nodes and edges that can selectively disappear

  - by Pops

  I'm trying to figure out what sort of data structure to use for modeling some hypothetical, idealized network usage. In my scenario, a number of users who are hostile to each other are all trying to form networks of computers where all potential connections are known. The computers that one user needs to connect may not be the same as the ones another user needs to connect, though; user 1 might need to connect computers A, B and D while user 2 might need to connect computers B, C and E. Image generated with the help of NCTM Graph Creator I think the core of this is going to be an undirected cyclic graph, with nodes representing computers and edges representing Ethernet cables. However, due to the nature of the scenario, there are a few uncommon features that rule out adjacency lists and adjacency matrices (at least, without non-trivial modifications): edges can become restricted-use; that is, if one user acquires a given network connection, no other user may use that connection in the example, the green user cannot possibly connect to computer A, but the red user has connected B to E despite not having a direct link between them in some cases, a given pair of nodes will be connected by more than one edge in the example, there are two independent cables running from D to E, so the green and blue users were both able to connect those machines directly; however, red can no longer make such a connection if two computers are connected by more than one cable, each user may own no more than one of those cables I'll need to do several operations on this graph, such as: determining whether any particular pair of computers is connected for a given user identifying the optimal path for a given user to connect target computers identifying the highest-latency computer connection for a given user (i.e. longest path without branching) My first thought was to simply create a collection of all of the edges, but that's terrible for searching. The best thing I can think to do now is to modify an adjacency list so that each item in the list contains not only the edge length but also its cost and current owner. Is this a sensible approach? Assuming space is not a concern, would it be reasonable to create multiple copies of the graph (one for each user) rather than a single graph?

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• How do you avoid name similarities between your classes and the native ones?

  - by Oscar

  I just ran into an "interesting problem", which I would like your opinion about: I am developing a system and for many reasons (meaning: abstraction, technology independence, etc) we create our own types for exchanging information. For instance: if there is a method which is called SendEmail and is invoked by the business logic, it way have a parameter of type OurCompany.EMailMessage, which is an object which is completely technology independent and contains only "business relevant data" (for instance, no information abut head encoding). Inside the SendEmail function, we get this information from our EMailMEssage object and create a MailMessage (this one is technolgy specific) object so it can be sent over the network. As you can already notice, our class has a very similar name to the "native" language class. The problem is: this is exactly what they are, email messages, so it is hard to find another meaningful name for them. Do you have this problem often? How do you manage it? Edit: @mgkrebbs just commented about using fully qualified names. This is our current approach, but a little bit too verbose, IMHO. I would like something cleaner, if possible.

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• How do I improve terrain rendering batch counts using DirectX?

  - by gamer747

  We have determined that our terrain rendering system needs some work to minimize the number of batches being transferred to the GPU in order to improve performance. I'm looking for suggestions on how best to improve what we're trying to accomplish. We logically split our terrain mesh into smaller grid cells which are 32x32 world units. Each cell has meta data that dictates the four 256x256 textures that are used for spatting along with the alpha blend data, shadow, and light mappings. Each cell contains 81 vertices in a 9x9 grid. Presently, we examine each cell and determine the four textures that are being used to spat the cell. We combine that geometry with any other cell that perhaps uses the same four textures regardless of spat order. If the spat order for a cell differs, the blend map is adjusted so that the spat order is maintained the same as other like cells and blending happens in the right order too. But even with this batching approach, it isn't uncommon when looking out across an area of open terrain to have between 1200-1700 batch count depending upon how frequently textures differ or have different texture blends are between cells. We are only doing frustum culling presently. So using texture spatting, are there other alternatives that can reduce the batch count and allow rendering to be extremely performance-friendly even under DirectX9c? We considered using texture atlases since we're targeting DirectX 9c & older OpenGL platforms but trying to repeat textures using atlases and shaders result in seam artifacts which we haven't been able to eliminate with the exception of disabling mipmapping. Disabling mipmapping results in poor quality textures from a distance. How have others batched together terrain geometry such that one could spat terrain using various textures, minimizing batch count and texture state switches so that rendering performance isn't negatively impacted?

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• CoffeeScript - inability to support progressive adoption

  - by Renso

  First if, what is CoffeeScript?Web definitionsCoffeeScript is a programming language that compiles statement-by-statement to JavaScript. The language adds syntactic sugar inspired by Ruby and Python to enhance JavaScript's brevity and readability, as well as adding more sophisticated features like array comprehension and pattern matching.The issue with CoffeeScript is that it eliminates any progressive adoption. It is a purist approach, kind of like the Amish, if you're not borne Amish, tough luck. So for folks with thousands of lines of JavaScript code will have a tough time to convert it to CoffeeScript. You can use the js2coffee API to convert the JavaScript file to CoffeeScript but in my experience that had trouble converting the files. It would convert the file to CoffeeScript without any complaints, but then when trying to generate the CoffeeScript file got errors with guess what: INDENTATION!Tried to convince the CoffeeScript community on github but got lots of push-back to progressive adoption with comments like "stupid", "crap", "child's comportment", "it's like Ruby, Python", "legacy code" etc. As a matter of interest one of the first comments were that the code needs to be re-designed before converted to CoffeeScript. Well I rest my case then :-)So far the community on github has been very reluctant to even consider introducing some way to define code-blocks, obviously curly braces is not an option as they use it for json object definitions. They also have no consideration for a progressive adoption where some, if not all, JavaScript syntax will be allowed which means all of us in the real world that have thousands of lines of JavaScript will have a real issue converting it over. Worst, I for one lack the confidence that tools like js2coffee will provide the correct indentation that will determine the flow of control in your code!!! Actually it is hard for me to find enough justification for using spaces or tabs to control the flow of code. It is no wonder that C#, C, C++, Java, all enterprise-scale frameworks still use curly braces. Have never seen an enterprise app built with Ruby or PhP.Let me know what your concerns are with CoffeeScript and how you dealt with large scale JavaScript conversions to CoffeeScript.

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