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  • JavaOne Latin America Sessions

    - by Tori Wieldt
    The stars of Java are gathering in São Paulo next week. Here are just a few of the outstanding sessions you can attend at JavaOne Latin America: “Designing Java EE Applications in the Age of CDI” Michel Graciano, Michael Santos “Don’t Get Hacked! Tips and Tricks for Securing Your Java EE Web Application” Fabiane Nardon, Fernando Babadopulos “Java and Security Programming” Juan Carlos Herrera “Java Craftsmanship: Lessons Learned on How to Produce Truly Beautiful Java Code” Edson Yanaga “Internet of Things with Real Things: Java + Things – API + Raspberry PI + Toys!” Vinicius Senger “OAuth 101: How to Protect Your Resources in a Web-Connected Environment” Mauricio Leal “Approaching Pure REST in Java: HATEOAS and HTTP Tuning” Eder Ignatowicz “Open Data in Politics: Using Java to Follow Your Candidate” Bruno Gualda, Thiago Galbiatti Vespa "Java EE 7 Platform: More Productivity and Integrated HTML" Arun Gupta  Go to the JavaOne site for a complete list of sessions. JavaOne Latin America will in São Paulo, 4-6 December 2012 at the Transamerica Expo Center. Register by 3 December and Save R$ 300,00! Para mais informações ou inscrição ligue para (11) 2875-4163. 

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  • How to rotate a sprite using multi-touch with AndEngine?

    - by 786
    I am new to Android game development. I am using AndEngine GLES-2. I have created a box with a sprite. This box is now draggable by using the code below. It works fine. But I want multi-touch on this: I want to rotate the sprite with two fingers on that box, and to keep it draggable. I've no idea how do do that, which way should I go? final float centerX = (CAMERA_WIDTH - this.mBox.getWidth()) / 2; final float centerY = (CAMERA_HEIGHT - this.mBox.getHeight()) / 2; Box = new Sprite(centerX, centerY, this.mBox, this.getVertexBufferObjectManager()) { public boolean onAreaTouched(TouchEvent pSceneTouchEvent, float pTouchAreaLocalX, float pTouchAreaLocalY) { this.setPosition(pSceneTouchEvent.getX() - this.getWidth()/ 2, pSceneTouchEvent.getY() - this.getHeight() / 2); float pValueX = pSceneTouchEvent.getX(); float pValueY = CAMERA_HEIGHT-pSceneTouchEvent.getY(); float dx = pValueX - gun.getX(); float dy = pValueY - gun.getY(); double Radius = Math.atan2(dy,dx); double Angle = Radius * 360 ; Box.setRotation((float)Math.toDegrees(Angle)); return true; }

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  • NINE Great Reasons to Attend the GlassFish Community Event at JavaOne 2012

    - by Alexandra Huff
    Are you coming to the annual GlassFish Community Event at JavaOne this year? Here are nine great reasons not to miss it! Great company Meet and mingle with community leaders and luminaries, the GlassFish engineering team, and Oracle executives! Learn from others How are your peers using GlassFish in creative ways? A few community members will share their challenges and creative solutions. Ask tough questions Meet Oracle GlassFish and Middleware executives; the panel discussion will be moderated by one of our stellar community leaders! Shirts! Be sure to get this year's GlassFish T-shirt, designed by and voted on by YOU, our community members! Don't miss it - they go fast. Share your story Give us a two minute update on why you love GlassFish and how you are using it! We will immortalize you in a very brief video and post it to our GlassFish Stories page! Find out... about the new book, hot off the press, authored by our very own Arun Gupta: "Java EE 6 Pocket Guide: A Quick Reference for Simplified Enterprise Java Development" If you share... your story, you will win a copy of Arun's new book as our thank you gift! Suggest... some ideas on how to make GlassFish even better! Have fun Lively discussion, news and updates, excellent company -- this is THE place to be on Sunday at JavaOne! Convinced? Excellent! Then please register here! A JavaOne Pass is required to enter Moscone Center. All passes accepted, including Discover, Exhibitor, Press, Blogger, etc. Agenda 11:00 - 11:05: Introduction 11:05 - 11:30: Roadmap and Community Updates 11:30 - 12:15: Q&A with Executive Speaker Panel from Oracle and the GlassFish Team 12:15 - 01:00: Customer Testimonials Location: Moscone West, Room 2005 Add sessions UGF10359 and UGF10360 to Schedule Builder

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  • Desktop application, dependency injection

    - by liori
    I am thinking of applying a real dependency injection library to my toy C#/GTK# desktop application. I chose NInject, but I think this is irrelevant to my question. There is a database object, a main window and several utility window classes. It's clear that I can inject the database into every window object, so here DI is useful. But does it make sense to inject utility window classes into other window classes? Example: I have classes such as: class MainWindow {…} class AddItemWindow {…} class AddAttachmentWindow {…} class BrowseItemsWindow {…} class QueryBuilderWindow {…} class QueryBrowserWindow {…} class PreferencesWindow {…} … Each of the utility classes can be opened from MainWindow. Some utility windows can also be opened from other utility windows. Generally, there might be a really complex graph of who can open whom. So each of those classes might need quite a lot of other window classes injected. I'm worried that such usage will go against the suggestion not to inject too many classes at once and become a code smell. Should I use some kind of a service locator object here?

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  • Weekly Cloud Roundup 2012-15

    - by Alan Smith
    Filtering the informative, insightful and quirky from the fire hose of cloud-based hype. Irving Wladawsky-Berger provides some great insight into The Complex Transition to the Cloud, sharing his views on the slow adoption of cloud computing in organizations. “…a prediction by the research firm Gartner that while cloud computing will continue to grow at almost 20 percent a year, it will account for less than 5 percent of totally IT spending in 2015.” With a more positive mindset, Balaji Viswanathan highlights 7 Salient Trends and Directions in Cloud Computing that could be shaping the industry over the next few years. Cloud computing also looks to save energy “A small business with 100 users that moved the Microsoft applications to the cloud could cut energy use and carbon emissions by 90%. Large organizations with 10,000 users saw a 30% reduction.” More on that story here. The expansion of Windows Azure has been in the news with the announcement of “East US” and “West US” datacenters; this was covered by Visual Studio Magazine and Mary-Jo, and according to thenextweb.com Microsoft are also building $112 million data center in Wyoming. The cloud price war is still in full swing with Joe Panettieri discussing the pricing of Windows Azure and Office 365 and asking How Low Can It Go?

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  • Why The Athene Group Chose Fusion CRM

    - by Tony Berk
    A guest post by Vikas Bhambri, Managing Partner, The Athene Group This year, The Athene Group (www.theathenegroup.com) celebrated our tenth anniversary. The company has accomplished a lot in ten years overcoming a number of hurdles and challenges to have grown organically to a 150+ person global company with offices in the US, UK, and India and customers in the US, Canada, and Europe. Now more than ever with the current global landscape from an economic and competitive standpoint it was vital that we make some changes to remain successful for the next ten years. There were two key initiatives that we discussed internally that would enable us to successfully accomplish this – collaboration and the concept of “insight to action”. With our existing Oracle CRM On Demand platform we had components of this but not the full depth and breadth that we were looking for. When we started to discuss Fusion CRM we immediately saw several next generation tools that would embrace these two objectives. For a consulting and development organization the collaboration required between business development and consulting delivery is as important as the collaboration required during the projects between the project delivery and account management teams. The Activity Streams functionality in Fusion CRM immediately addressed the communication of key discussion topics and exchanges around our clients. Of course when we saw the Oracle Social Network (which is part of our Fusion CRM roadmap) we were blown away. The combination OSN and our CRM is going to make us more effective as we discuss and work cohesively on client engagements – ensuring mutual success for both Athene and our clients. When we looked at “insight to action” we saw that we had a great platform when folks were at their desks, unfortunately a lot of our business development and consulting folks are on the road. The Fusion Mobile Sales and Fusion Outlook Desktop provide information to our teams when they are on the go. So that they can provide real-time information and react to real-time information provided by their peers. We are in the early stages of our transformative experience with Fusion CRM but we believe the platform along with our people and processes are going to help us achieve our goals in the future.

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  • How is software used in critical life-or-death systems tested?

    - by waiwai933
    An airplane, as opposed to, for example, a website, is a system where any failure in certain systems is completely unacceptable, since errors in e.g. flight monitoring can cause the autopilot to malfunction and do a dive. Obviously, this doesn't happen since the brilliant engineers at Boeing and Airbus have checks in the autopilot to make sure it doesn't suddenly decide a dive is a perfectly acceptable and safe maneuver. Or perhaps the computer crashes, and the pilots in the newer fly-by-wire aircraft can no longer actually fly the plane. Of course, there are various safety procedures and redundancies built into these systems to prevent a crash (of both the software and the aircraft). However, on the other hand, it's quite obvious that software isn't perfect—both open source and closed source software do crash regularly, and only the simplest "Hello World" program doesn't fail. How can the engineers who design the software systems in the aeronautic, medical, and other life-or-death industries manage to test their software so that it doesn't fail (and if it does fail, at least fail gracefully)? I'm desperately hoping that you're not all going to go: "Oh, I work for Boeing/Airbus/(some other company) and it's not! Have fun on your next flight/hospital visit."

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  • What would be a good filter to create 'magnetic deformers' from a depth map?

    - by sebf
    In my project, I am creating a system for deforming a highly detailed mesh (clothing) so that it 'fits' a convex mesh. To do this I use depth maps of the item and the 'hull' to determine at what point in world space the deviation occurs and the extent. Simply transforming all occluded vertices to the depths as defined by the 'hull' is fairly effective, and has good performance, but it suffers the problem of not preserving the features of the mesh and requires extensive culling to avoid false-positives. I would like instead to generate from the depth deviation map a set of simple 'deformers' which will 'push'* all vertices of the deformed mesh outwards (in world space). This way, all features of the mesh are preserved and there is no need to have complex heuristics to cull inappropriate vertices. I am not sure how to go about generating this deformer set however. I am imagining something like an algorithm that attempts to match a spherical surface to each patch of contiguous deviations within a certain range, but do not know where to start doing this. Can anyone suggest a suitable filter or algorithm for generating deformers? Or to put it another way 'compressing' a depth map? (*Push because its fitting to a convex 'bulgy' humanoid so transforms are likely to be 'spherical' from the POV of the surface.)

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  • An ideal way to decode JSON documents in C?

    - by AzizAG
    Assuming I have an API to consume that uses JSON as a data transmission method, what is an ideal way to decode the JSON returned by each API resource? For example, in Java I'd create a class for each API resource then initiate an object of that class and consume data from it. for example: class UserJson extends JsonParser { public function UserJson(String document) { /*Initial document parsing goes here...*/ } //A bunch of getter methods . . . . } The probably do something like this: UserJson userJson = new UserJson(jsonString);//Initial parsing goes in the constructor String username = userJson.getName();//Parse JSON name property then return it as a String. Or when using a programming language with associative arrays(i.e., hash table) the decoding process doesn't require creating a class: (PHP) $userJson = json_decode($jsonString);//Decode JSON as key=>value $username = $userJson['name']; But, when I'm programming in procedural programming languages (C), I can't go with either method, since C is neither OOP nor supports associative arrays(by default, at least). What is the "correct" method of parsing pre-defined JSON strings(i.e., JSON documents specified by the API provider via examples or documentation)? The method I'm currently using is creating a file for each API resource to parse, the problem with this method is that it's basically a lousy version of the OOP method, as it looks exactly like the OOP method but doesn't provide any OOP benefits(e.g., can't pass an object of the parser, etc.). I've been thinking about encapsulating each API resource parser file in a publicly accessed structure(pointing all functions/publicly usable variables to the structure) then accessing the parser file code from within the structure(parser.parse(), parser.getName(), etc.). As this way looks a bit better than the my current method, it still just a rip off the OOP way, isn't it? Any suggestions for methods to parse JSON documents on procedural programming lanauges? Any comments on the methods I'm currently using(either 3 of them)?

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  • How to write your unit tests to switch between NUnit and MSTest

    - by Justin Jones
    On my current project I found it useful to use both NUnit and MsTest for unit testing. When using ReSharper for running unit tests, it just simply works better with NUnit, and on large scale projects NUnit tends to run faster. We would have just simply used NUnit for everything, but MSTest gave us a few bonuses out of the box that were hard to pass up. Namely code coverage (without having to shell out thousands of extra dollars for the privilege) and integrated tests into the build process. I’m one of those guys who wants the build to fail if the unit tests don’t pass. If they don’t pass, there’s no point in sending that build on to QA. So making the build work with MsTest is easiest if you just create a unit test project in your solution. This adds the right references and project type Guids in the project file so that everything just automagically just works. Then (using NuGet of course) you add in NUnit. At the top of your test file, remove the using statements that refer to MsTest and replace it with the following: #if NUNIT using NUnit.Framework; #else using TestFixture = Microsoft.VisualStudio.TestTools.UnitTesting.TestClassAttribute; using Test = Microsoft.VisualStudio.TestTools.UnitTesting.TestMethodAttribute; using TestFixtureSetUp = Microsoft.VisualStudio.TestTools.UnitTesting.TestInitializeAttribute; using SetUp = Microsoft.VisualStudio.TestTools.UnitTesting.TestInitializeAttribute; using Microsoft.VisualStudio.TestTools.UnitTesting; #endif Basically I’m taking the NUnit naming conventions, and redirecting them to MsTest. You can go the other way, of course. I only chose this direction because I had already written the tests as NUnit tests. NUnit and MsTest provide largely the same functionality with slightly differing class names. There’s few actual differences between then, and I have not run into them on this project so far. To run the tests as NUnit tests, simply open up the project properties tab and add the compiler directive NUNIT. Remove it, and you’re back in MsTest land.

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  • New Feature! Automatic Categories for Geekswithblogs.net

    - by Jeff Julian
    One of the features we have been working on is a way to categorize posts without the need of all our bloggers getting on the same page with what categories we have and making them select the categories.  Johnny Kauffman, one of our team members at AJI Software, developed what we call the Sherlock Project over the past few months.  Sherlock is a category suggestion engine based on the content within the posts.  Now, after a post is published, Sherlock will investigate the content and come up with the suggested categories that content fits in.  This will now allow you to go to the specific topics you are interested in and see all the related posts. This is just the beginning, so many more opportunities will arise now that we have our content organized.  One of the first features I will be adding is RSS feeds for each category and sub category.  If you are into ALM, we will have a feed for that! I hope you enjoy these and the engine will continue to get better as we start testing the data.  I hope you are as excited about this as I am :D.  Technorati Tags: Geekswithblogs.net,Categories,Sherlock

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  • Reading OpenDocument spreadsheets using C#

    - by DigiMortal
    Excel with its file formats is not the only spreadsheet application that is widely used. There are also users on Linux and Macs and often they are using OpenOffice and other open-source office packages that use ODF instead of OpenXML. In this post I will show you how to read Open Document spreadsheet in C#. Importer as example My previous post about importers showed you how to build flexible importers support to your web application. This post introduces you practical example of one of my importers. Of course, sensitive code is omitted. We start with ODS importer class and we add new methods as we go. public class OdsImporter : ImporterBase {     public OdsImporter()     {     }       public override string[] SupportedFileExtensions     {         get { return new[] { "ods" }; }     }       public override ImportResult Import(Stream fileStream, long companyId, short year)     {         string contentXml = GetContentXml(fileStream);           var result = new ImportResult();         var doc = XDocument.Parse(contentXml);           var rows = doc.Descendants("{urn:oasis:names:tc:opendocument:xmlns:table:1.0}table-row").Skip(1);           foreach (var row in rows)         {             ImportRow(row, companyId, year, result);         }           return result;     } } The class given here just extends base class for importers (previous post uses interface but as I already told there you move to abstract base class when writing code for real projects). Import method reads data from *.ods file, parses it (it is XML), finds all data rows and imports data. As you may see then first row is skipped. This is because the first row on my sheet is always headers row. Reading ODS file Our import method starts with getting XML from *.ods file. ODS files like OpenXml files are zipped containers that contain different files. We need content.xml as all data is kept there. To get the contents of file we use SharpZipLib library to read uploaded file as *.zip file. private static string GetContentXml(Stream fileStream) {     var contentXml = "";       using (var zipInputStream = new ZipInputStream(fileStream))     {         ZipEntry contentEntry = null;         while ((contentEntry = zipInputStream.GetNextEntry()) != null)         {             if (!contentEntry.IsFile)                 continue;             if (contentEntry.Name.ToLower() == "content.xml")                 break;         }           if (contentEntry.Name.ToLower() != "content.xml")         {             throw new Exception("Cannot find content.xml");         }           var bytesResult = new byte[] { };         var bytes = new byte[2000];         var i = 0;           while ((i = zipInputStream.Read(bytes, 0, bytes.Length)) != 0)         {             var arrayLength = bytesResult.Length;             Array.Resize<byte>(ref bytesResult, arrayLength + i);             Array.Copy(bytes, 0, bytesResult, arrayLength, i);         }         contentXml = Encoding.UTF8.GetString(bytesResult);     }     return contentXml; } If here is content.xml file then we stop browsing the file. We read this file to memory and return it as UTF-8 format string. Importing rows Our last task is to import rows. We use special method for this as we have to handle some tricks here. To keep files smaller the cell count on row is not always the same. If we have more than one empty cell one after another then ODS keeps only one cell for sequential empty cells. This cell has attribute called number-columns-repeated and it’s value is set to the number of sequential empty cells. This is why we use two indexers for cells collection. private void ImportRow(XElement row, ImportResult result) {     var cells = (from c in row.Descendants()                 where c.Name == "{urn:oasis:names:tc:opendocument:xmlns:table:1.0}table-cell"                 select c).ToList();       var dto = new DataDto();       var count = cells.Count;     var j = -1;       for (var i = 0; i < count; i++)     {         j++;         var cell = cells[i];         var attr = cell.Attribute("{urn:oasis:names:tc:opendocument:xmlns:table:1.0}number-columns-repeated");         if (attr != null)         {             var numToSkip = 0;             if (int.TryParse(attr.Value, out numToSkip))             {                 j += numToSkip - 1;             }         }           if (i > 30) break;         if (j == 0)         {             dto.SomeProperty = cells[i].Value;         }         if (j == 1)         {             dto.SomeOtherProperty = cells[i].Value;         }         // some more data reading     }       // save data } You can define your own class for import results and add there all problems found during data import. Your application gets the results and shows them to user. Conclusion Reading ODS files may seem to complex task but actually it is very easy if we need only data from those documents. We can use some zip-library to get the content file and then parse it to XML. It is not hard to go through the XML but there are some optimization tricks we have to know. The code here is safe to use in web applications as it is not using any API-s that may have special needs to server and infrastructure.

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  • Logistics of code reuse (OOP)

    - by Ominus
    One of the driving points behind OOP is code reuse. I am curious about the actual logistics of this and how others both in team or solo handle it. For example lets say you have 5 projects you have worked on and between them you have a ton of classes that you think would be useful in other projects. How do you store them? Are they just in the normal project repository or do you break out the relevant classes and have them (as now copies) in another unique source repository that only houses code pieces that are intended to be reused? How do you go about finding or even knowing that there is a good piece of code out there that you should reuse? It's easier if your solo because you remember that you have coded something similar but even then it becomes kind of a stretch. If there is some way that you are storing these pieces of code do you then also have them indexed and searchable by tag or something. I fear that it just boils down to some tribal knowledge that you just know that for situation A i need solution B and we have a good piece of code that already can help here. A bit verbose but I hope you get what I am aiming at. If you think of a better way to make the question clearer please have at it :) TIA!

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  • Keeping files that are often changed in sync between desktop and laptop

    - by N.N.
    I'm looking for a way to keep a desktop and a laptop in sync. What I want to keep in sync are some folders, mainly ~/Documents, that are changed often when working on them. If it matters I can connect to my desktop from anywhere via an URL but my laptop is harder to access since it might be behind NAT and such. I have been looking at Ubuntu One but it seems to not go well with working on documents written in LaTeX. If I work on a .tex file in the Ubuntu One directory and compile it (with pdflatex) every now and then (as often as every 10 sec when working) it will create several new files including a pdf which are uploaded to Ubuntu One and this seems stupid since it will create continuous upload when working on .tex files. I also usually keep .tex documents version controlled by git and then every commit (which also can happen frequently) will cause upload (by changes in ./.git) so that it happens continuously when working. Another example is editing images that are saved often. What I think would be best is for sync to happen every tenth minute or at the end of every working session (but there might be some other way to handle this?).

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  • cpu use goes to 100% when I lock the screen

    - by gianni
    Whenever I lock the screen, after a certain amount of time, the cpu and the cpu fan use go up near the limit, and it returns back to normal the moment I unlock the screen again (as shown by psensor). How can I find out what process is responsible for this? I've tried with "top -S", and the result is this... PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 2114 me 20 0 326m 104m 40m R 16 2.6 66:50.03 compiz 1234 root 20 0 396m 152m 98m R 6 3.8 20:23.88 Xorg 2204 me 20 0 160m 38m 30m S 4 1.0 0:33.35 yakuake 2446 me 20 0 206m 18m 12m S 4 0.5 6:32.18 psensor 2280 me 20 0 220m 18m 10m S 2 0.5 5:01.60 unity-panel 9138 me 20 0 154m 27m 15m S 2 0.7 0:03.63 plugin-cont 2282 me 20 0 65800 5272 3316 S 1 0.1 4:36.90 hud-service 2143 me 20 0 140m 11m 8352 S 1 0.3 2:50.16 indicator-m 9095 me 20 0 720m 253m 36m S 1 6.4 0:26.34 firefox 2076 me 20 0 7168 3484 828 S 1 0.1 1:46.53 dbus-daemon 2307 me 20 0 55000 5132 3632 S 1 0.1 2:01.55 indicator-a 2557 me 20 0 86328 6028 4576 S 0 0.1 1:44.71 conky 6290 me 20 0 2836 1296 964 R 0 0.0 0:29.64 top 6291 me 20 0 2836 1188 884 S 0 0.0 0:29.49 top 1 root 20 0 3644 1984 1284 S 0 0.0 60:57.76 init specs: ubuntu 12.04 fresh install intel core i5 4gB ram

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  • Of transactions and Mongo

    - by Nuri Halperin
    Originally posted on: http://geekswithblogs.net/nuri/archive/2014/05/20/of-transactions-and-mongo-again.aspxWhat's the first thing you hear about NoSQL databases? That they lose your data? That there's no transactions? No joins? No hope for "real" applications? Well, you *should* be wondering whether a certain of database is the right one for your job. But if you do so, you should be wondering that about "traditional" databases as well! In the spirit of exploration let's take a look at a common challenge: You are a bank. You have customers with accounts. Customer A wants to pay B. You want to allow that only if A can cover the amount being transferred. Let's looks at the problem without any context of any database engine in mind. What would you do? How would you ensure that the amount transfer is done "properly"? Would you prevent a "transaction" from taking place unless A can cover the amount? There are several options: Prevent any change to A's account while the transfer is taking place. That boils down to locking. Apply the change, and allow A's balance to go below zero. Charge person A some interest on the negative balance. Not friendly, but certainly a choice. Don't do either. Options 1 and 2 are difficult to attain in the NoSQL world. Mongo won't save you headaches here either. Option 3 looks a bit harsh. But here's where this can go: ledger. See, and account doesn't need to be represented by a single row in a table of all accounts with only the current balance on it. More often than not, accounting systems use ledgers. And entries in ledgers - as it turns out – don't actually get updated. Once a ledger entry is written, it is not removed or altered. A transaction is represented by an entry in the ledger stating and amount withdrawn from A's account and an entry in the ledger stating an addition of said amount to B's account. For sake of space-saving, that entry in the ledger can happen using one entry. Think {Timestamp, FromAccountId, ToAccountId, Amount}. The implication of the original question – "how do you enforce non-negative balance rule" then boils down to: Insert entry in ledger Run validation of recent entries Insert reverse entry to roll back transaction if validation failed. What is validation? Sum up the transactions that A's account has (all deposits and debits), and ensure the balance is positive. For sake of efficiency, one can roll up transactions and "close the book" on transactions with a pseudo entry stating balance as of midnight or something. This lets you avoid doing math on the fly on too many transactions. You simply run from the latest "approved balance" marker to date. But that's an optimization, and premature optimizations are the root of (some? most?) evil.. Back to some nagging questions though: "But mongo is only eventually consistent!" Well, yes, kind of. It's not actually true that Mongo has not transactions. It would be more descriptive to say that Mongo's transaction scope is a single document in a single collection. A write to a Mongo document happens completely or not at all. So although it is true that you can't update more than one documents "at the same time" under a "transaction" umbrella as an atomic update, it is NOT true that there' is no isolation. So a competition between two concurrent updates is completely coherent and the writes will be serialized. They will not scribble on the same document at the same time. In our case - in choosing a ledger approach - we're not even trying to "update" a document, we're simply adding a document to a collection. So there goes the "no transaction" issue. Now let's turn our attention to consistency. What you should know about mongo is that at any given moment, only on member of a replica set is writable. This means that the writable instance in a set of replicated instances always has "the truth". There could be a replication lag such that a reader going to one of the replicas still sees "old" state of a collection or document. But in our ledger case, things fall nicely into place: Run your validation against the writable instance. It is guaranteed to have a ledger either with (after) or without (before) the ledger entry got written. No funky states. Again, the ledger writing *adds* a document, so there's no inconsistent document state to be had either way. Next, we might worry about data loss. Here, mongo offers several write-concerns. Write-concern in Mongo is a mode that marshals how uptight you want the db engine to be about actually persisting a document write to disk before it reports to the application that it is "done". The most volatile, is to say you don't care. In that case, mongo would just accept your write command and say back "thanks" with no guarantee of persistence. If the server loses power at the wrong moment, it may have said "ok" but actually no written the data to disk. That's kind of bad. Don't do that with data you care about. It may be good for votes on a pole regarding how cute a furry animal is, but not so good for business. There are several other write-concerns varying from flushing the write to the disk of the writable instance, flushing to disk on several members of the replica set, a majority of the replica set or all of the members of a replica set. The former choice is the quickest, as no network coordination is required besides the main writable instance. The others impose extra network and time cost. Depending on your tolerance for latency and read-lag, you will face a choice of what works for you. It's really important to understand that no data loss occurs once a document is flushed to an instance. The record is on disk at that point. From that point on, backup strategies and disaster recovery are your worry, not loss of power to the writable machine. This scenario is not different from a relational database at that point. Where does this leave us? Oh, yes. Eventual consistency. By now, we ensured that the "source of truth" instance has the correct data, persisted and coherent. But because of lag, the app may have gone to the writable instance, performed the update and then gone to a replica and looked at the ledger there before the transaction replicated. Here are 2 options to deal with this. Similar to write concerns, mongo support read preferences. An app may choose to read only from the writable instance. This is not an awesome choice to make for every ready, because it just burdens the one instance, and doesn't make use of the other read-only servers. But this choice can be made on a query by query basis. So for the app that our person A is using, we can have person A issue the transfer command to B, and then if that same app is going to immediately as "are we there yet?" we'll query that same writable instance. But B and anyone else in the world can just chill and read from the read-only instance. They have no basis to expect that the ledger has just been written to. So as far as they know, the transaction hasn't happened until they see it appear later. We can further relax the demand by creating application UI that reacts to a write command with "thank you, we will post it shortly" instead of "thank you, we just did everything and here's the new balance". This is a very powerful thing. UI design for highly scalable systems can't insist that the all databases be locked just to paint an "all done" on screen. People understand. They were trained by many online businesses already that your placing of an order does not mean that your product is already outside your door waiting (yes, I know, large retailers are working on it... but were' not there yet). The second thing we can do, is add some artificial delay to a transaction's visibility on the ledger. The way that works is simply adding some logic such that the query against the ledger never nets a transaction for customers newer than say 15 minutes and who's validation flag is not set. This buys us time 2 ways: Replication can catch up to all instances by then, and validation rules can run and determine if this transaction should be "negated" with a compensating transaction. In case we do need to "roll back" the transaction, the backend system can place the timestamp of the compensating transaction at the exact same time or 1ms after the original one. Effectively, once A or B visits their ledger, both transactions would be visible and the overall balance "as of now" would reflect no change.  The 2 transactions (attempted/ reverted) would be visible , since we do actually account for the attempt. Hold on a second. There's a hole in the story: what if several transfers from A to some accounts are registered, and 2 independent validators attempt to compute the balance concurrently? Is there a chance that both would conclude non-sufficient-funds even though rolling back transaction 100 would free up enough for transaction 117 (some random later transaction)? Yes. there is that chance. But the integrity of the business rule is not compromised, since the prime rule is don't dispense money you don't have. To minimize or eliminate this scenario, we can also assign a single validation process per origin account. This may seem non-scalable, but it can easily be done as a "sharded" distribution. Say we have 11 validation threads (or processing nodes etc.). We divide the account number space such that each validator is exclusively responsible for a certain range of account numbers. Sounds cunningly similar to Mongo's sharding strategy, doesn't it? Each validator then works in isolation. More capacity needed? Chop the account space into more chunks. So where  are we now with the nagging questions? "No joins": Huh? What are those for? "No transactions": You mean no cross-collection and no cross-document transactions? Granted - but don't always need them either. "No hope for real applications": well... There are more issues and edge cases to slog through, I'm sure. But hopefully this gives you some ideas of how to solve common problems without distributed locking and relational databases. But then again, you can choose relational databases if they suit your problem.

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  • Assigning valid moves on board game

    - by Kunal4536
    I am making a board game in unity 4.3 2d similar to checkers. I have added an empty object to all the points where player can move and added a box collider to each empty object.I attached a click to move script to each player token. Now I want to assign valid moves. e.g. as shown in picture... Players can only move on vertex of each square.Player can only move to adjacent vertex.Thus it can only move from red spot to yellow and cannot move to blue spot.There is another condition which is : if there is the token of another player at the yellow spot then the player cannot move to that spot. Instead it will have to go from red to green spot. How can I find the valid moves of the player by scripting. I have another problem with click to move. When I click all the objects move to that position.But I only want to move a single token. So what can i add to script to select a specific object and then click to move the specific object.Here is my script for click to move. var obj:Transform; private var hitPoint : Vector3; private var move: boolean = false; private var startTime:float; var speed = 1; function Update () { if(Input.GetKeyDown(KeyCode.Mouse0)) { var hit : RaycastHit; // no point storing this really var ray = Camera.main.ScreenPointToRay (Input.mousePosition); if (Physics.Raycast (ray, hit, 10000)) { hitPoint = hit.point; move = true; startTime = Time.time; } } if(move) { obj.position = Vector3.Lerp(obj.position, hitPoint, Time.deltaTime * speed); if(obj.position == hitPoint) { move = false; } } }`

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  • rel="nofollow" SEO impact

    - by Torez
    I saw a technique used where there was a block with three parts: 1. Image (wrapped in an anchor tag) 2. Heading (anchor tag with heading text) 3. Paragraph (regular p tag with synopsis content) e.g. <li class="block"> <a rel="nofollow" class="thumb" href="#"><img src="images/placeholder_service_thumbnail.jpg" alt="" /></a> <a class="h3" href="#"Good SEO Heading</a> <pPellentesque habitant morbi tristique senectus et netus et malesuada fames ac turpis egestas. Vestibulum tortor quam, feugiat vitae, ultricies eget, tempor sit amet, ante. Donec eu...</p> </li> With the image tag there was a rel="nofollow" on the wrapped anchor tag. So the idea is that the users still has the ability to click the image and go to the details page, but the image link does not rank. When users click on the heading text, that is only what ranks for that specific page. Q: Is this the correct approach? Does this even do anything? What is the best practice?

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  • C# Cursor stuck on busy state

    - by Ben
    So I implemented a fixed time step loop for my C# game. All it does at the moment is make a square bounce around the screen. The problem I'm having is that when I execute the program, the window doesn't allow me to close the program and the cursor is stuck on the busy icon. I have to go into visual studio and stop the program manually. Here's the loop at the moment public void run() { int updates = 0; int frames = 0; double msPerTick = 1000.0 / 60.0; double threshhold = 0; long lastTime = getCurrentTime(); long lastTimer = getCurrentTime(); while (true) { long currTime = getCurrentTime(); threshhold += (currTime - lastTime) / msPerTick; lastTime = currTime; while (threshhold >= 1) { update(); updates++; threshhold -= 1; } this.Refresh(); frames++; if ((getCurrentTime() - lastTimer) >= 1000) { this.Text = updates + " updates and " + frames + " frames per second"; updates = 0; frames = 0; lastTimer += 1000; } } }

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  • How do I backup my customer's data?

    - by marcamillion
    If you run a SaaS app, or work on one, I would love to hear from you. Where the safety and security of your customer's data is paramount, how do you secure it and back it up? I would love to know your main host (e.g. Heroku, Engine Yard, Rackspace, MediaTemple, etc.) and who you use for your backup. Be as detailed as possible - e.g. a quick overview of your service and the data you store (images for instance), what happens with the images when the user uploads them (e.g. they go to your Linode VPS, and posted to the site for them to see - then they are automatically sent to AWS or wherever, then once a week they are backed up to tape by the managed hosting provider, and you also back them up to your house/office). If you could also give some idea as to what the unit cost (per GB/per user/per month) of storage is - on average, I would really appreciate that. Getting ready to launch my app, and I would love to get some more perspective on the nitty gritty details involved. Thanks!

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  • Augmenting functionality of subclasses without code duplication in C++

    - by Rob W
    I have to add common functionality to some classes that share the same superclass, preferably without bloating the superclass. The simplified inheritance chain looks like this: Element -> HTMLElement -> HTMLAnchorElement Element -> SVGElement -> SVGAlement The default doSomething() method on Element is no-op by default, but there are some subclasses that need an actual implementation that requires some extra overridden methods and instance members. I cannot put a full implementation of doSomething() in Element because 1) it is only relevant for some of the subclasses, 2) its implementation has a performance impact and 3) it depends on a method that could be overridden by a class in the inheritance chain between the superclass and a subclass, e.g. SVGElement in my example. Especially because of the third point, I wanted to solve the problem using a template class, as follows (it is a kind of decorator for classes): struct Element { virtual void doSomething() {} }; // T should be an instance of Element template<class T> struct AugmentedElement : public T { // doSomething is expensive and uses T virtual void doSomething() override {} // Used by doSomething virtual bool shouldDoSomething() = 0; }; class SVGElement : public Element { /* ... */ }; class SVGAElement : public AugmentedElement<SVGElement> { // some non-trivial check bool shouldDoSomething() { /* ... */ return true; } }; // Similarly for HTMLAElement and others I looked around (in the existing (huge) codebase and on the internet), but didn't find any similar code snippets, let alone an evaluation of the effectiveness and pitfalls of this approach. Is my design the right way to go, or is there a better way to add common functionality to some subclasses of a given superclass?

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  • Resolution stuck in 640x480 in grub, 11.04 and 12.04

    - by user89797
    I have three operating systems on my machine, Windows 7x64, Ubuntu 11.10 and 12.04 both x64 as well. All three were running at full resolution for my monitor, as well as in the Grub 1.99 boot screen. After booting into Windows, I rebooted my machine and found my Grub resolution was suddenly 640x480. Booting into both versions of Ubuntu, I find myself stuck at that resolution as well. I made no driver changes recently, and hadn't even booted into the 11.10 build in a month or more. I've gone through both proprietary Nvidia driver options for my card (GeForce 9800GT) as well as the open source drivers in 12.04 to no avail. I can't figure out what could have caused this change in both versions of Ubuntu and Grub simultaneously. Windows 7 is unaffected so I think that safely rules out hardware failure. EDIT Ok, so I couldn't boot an graphical live disks, I tried ubuntu 12.04 i386 and x64 as well as 12.10 beta x64 and all of them would flash the initial logo, go to a blank screen with a flashing cursor in the upper left and then my display would die. I managed to boot 12.04 server and get into recovery. I reinstalled grub and went into recovery mode for my 12.04 build. If I boot in safe graphics mode I can get 1280x768, but as soon as I reboot it's broken again. I've tried reinstalling the nvidia drivers and that leaves me with a system stuck at max 640x480. None of these changes have had any impact on the 11.10 build, which is still stuck at 640x480 Given that I can push a somewhat higher resolution in 12.04, and full resolution in windows 7 I'm pretty convinced it's not an issue of my monitor failing. It must be something to do with the graphics drivers. I can't figure out what could be the issue though. I'm especially perplexed that I can't boot any live images

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  • Repeat use of Schema / Rich Snippets Markup i.e LocalBusiness Data

    - by bybe
    I am unable to find official wording and I'm hoping that some Rich Snippets/Schema Guru can give me some insight into proper usage of repeated content when it comes to using markup. I'm building a site that wants to use Schema as the markup type and the owner would like as much usage as possible. The business name, telephone and address will appear on every page now is it valid or even useful to use Rich Snippets on every page where this information is displayed. For example this information appears in the header, and footer of every page of the site and too give you an example of my current markup see below: <body itemscope itemtype="http://schema.org/LocalBusiness"> <header> <a itemprop="url" href="http://www.domain.co.uk/"> <img itemprop="logo" src="image.png" alt="Company Name Logo" /> </a> <span itemprop="telephone">01202 000 000</span> </header> <div> This is where the content will go</div> <footer> <span itemprop="name">Company Name</span> <span itemprop="description"> A small little bit about this company</span> <div itemprop="address" itemscope itemtype="http://schema.org/PostalAddress"> <span itemprop="streetAddress">Address Goes here</span> <span itemprop="addressLocality">Area Here</span>, <span itemprop="addressRegion">Region Here</span> </div> </footer> </body> !-- Local Business Schema Now Closed --> So as you can see above this information will be displayed on every single page.... Is this valid or bad to repeat usage of this information in schema format...

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  • Create indefinitely oscillating pendulum in Farseer Physics 3.3.1/Box2d

    - by GONeale
    I am new to Farseer Physics and using version 3.3.1. I am after some help and would even be happy to receive Box2d answers just to ensure I get a response as I should then be able to convert it! -- Thanks ...After a lot of tinkering around I have managed to produce a thin vertical rectangle shape on the screen and I wish this to swing back and forth pinned at the top up to an angle I set (90 degrees would be fine for this sample). When it is approaching the top I wish it to slow down, then fall back the way it just came, increase speed then obviously slow to a stop at the top again. Almost how a swinging pirate ship would work at a theme park. This is the code I have so far which swings the shape, but it is seeming to lose speed on each swing eventually grinding to a halt: float playerWidth = ConvertUnits.ToSimUnits(5), playerHeight = ConvertUnits.ToSimUnits(68); playerPosition = ConvertUnits.ToSimUnits(-350, 0); playerBody = BodyFactory.CreateRectangle(World, playerWidth, playerHeight, 2f, playerPosition); playerBody.BodyType = BodyType.Dynamic; // create player sprite based on player body _rectangleSprite = new Sprite(ScreenManager.Assets.TextureFromShape(playerBody.FixtureList[0].Shape, MaterialType.Player, Color.Orange, 1f)); // Create swinging joint var joint = JointFactory.CreateFixedRevoluteJoint(World, playerBody, ConvertUnits.ToSimUnits(0, -34), playerBody.Position); If somebody could also provide the command I would need to pause the shape on a mouse click or keyboard command at it's current angle and then continue when I let go of the mouse click that would be super fantastic! (I actually posted this on StackOverflow as well before I realised there was a dedicated game development forum) Cheers

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  • PHP Battle System for RPG game

    - by Jay
    I posted this a while ago on stackoverflow, they thought it would be better place here, I agree. Essentially I know what I want to accomplish, and I have something to the effect of what I want but I am not satisfied with it. Here's the problem. Each user has some states: STR (how hard they hit), DEF (dodging/blocking attacks), SPD (when they can strike), and STAMINA (basically their endurance in game, if this runs out they can no longer fight and lose) What I need is something like this: UserA Stats: STR: 1,000 DEF: 2500 SPD: 2000 (HP: 1000/1000) UserB Stats: STR: 1,500 DEF: 500 SPD: 4000 (HP: 1000/1000) Because the second user has double the speed, he lands twice the amount of hits on the first user, before he gets hit. Because he has less strength than the first users defence, he will do no, to little damage. This is how the battle would theoretically go: UserB strikes UserA for 0 damage UserB strikes UserA for 0 damage UserA strikes UserB for 500 damage UserB strikes UserA for 0 damage UserB strikes UserA for 0 damage UserA strikes UserB for 500 damage, and sends him to the hospital! I was using this code, which is buggy, and not efficient, I just need a better way to do this: http://pastebin.com/15LiQQuJ Oh, and if anyone has some good ideas on how to improve the concept that would be cool too! It's not that elaborate so I'll be thinking of all sorts of things to make it more dynamic. Thanks.

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