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• In a multidisciplicary team, how much should each member's skills overlap?

  - by spade78

  I've been working in embedded software development for this small startup and our team is pretty small: about 3-4 people. We're responsible for all engineering which involves an RF device controlled by an embedded microcontroller that connects to a PC host which runs some sort of data collection and analysis software. I have come to develop these two guidelines when I work with my colleagues: Define a clear separation of responsibilities and make sure each person's contribution to the final product doesn't overlap. Don't assume your colleagues know everything about their responsibilities. I assume there is some sort of technology that I will need to be competent at to properly interface with the work of my colleagues. The first point is pretty easy for us. I do firmware, one guy does the RF, another does the PC software, and the last does the DSP work. Nothing overlaps in terms of two people's work being mixed into the final product. For that to happen, one guy has to hand off work to another guy who will vet it and integrate it himself. The second point is the heart of my question. I've learned the hard way not to trust the knowledge of my colleagues absolutley no matter how many years experience they claim to have. At least not until they've demonstrated it to me a couple of times. So given that whenever I develop a piece of firmware, if it interfaces with some technology that I don't know then I'll try to learn it and develop a piece of test code that helps me understand what they're doing. That way if my piece of the product comes into conflict with another piece then I have some knowledge about possible causes. For example, the PC guy has started implementing his GUI's in .NET WPF (C#) and using LibUSBdotNET for USB access. So I've been learning C# and the .NET USB library that he uses and I build a little console app to help me understand how that USB library works. Now all this takes extra time and energy but I feel it's justified as it gives me a foothold to confront integration problems. Also I like learning this new stuff so I don't mind. On the other hand I can see how this can turn into a time synch for work that won't make it into the final product and may never turn into a problem. So how much experience/skills overlap do you expect in your teammates relative to your own skills? Does this issue go away as the teams get bigger and more diverse?

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• How to leverage the internal HTTP endpoint available on Azure web roles?

  - by Alfredo Delsors

  Imagine you have a Web application using an in-memory collection that changes occasionally but is used very often. The collection gets loaded from storage on the Application_Start global.asax event and is updated whenever its content changes. If you want to deploy this application on Azure you need to keep in mind that more than one instance of the application can be running at any time and therefore you need to provide some mechanism to keep all instances informed with the latest changes. Because the communication through internal endpoints between Azure role instances is at no cost, a good solution can be maintaining the information on Azure Storage Tables, reading its contents on the Application_Start event and populating its changes to all other instances using the internal HTTP port available on Azure Web Roles. You need to follow these steps to leverage the internal HTTP endpoint available on Azure web roles to maintain all instances up to date. 1.   Define an internal HTTP endpoint in the Web Role properties, for example InternalHttpEndpoint   2.   Add a new WCF service to the Web Role, for example NotificationService.svc 3.   Disable multiple site bindings in web.config: <serviceHostingEnvironment multipleSiteBindingsEnabled="false"> 4.   Add a method on the new service to receive notifications from other role instances. namespace Service { [ServiceContract] public interface INotificationService { [OperationContract(IsOneWay = true)] void Notify(Information info); } } 5.   Declare a class that inherits from System.ServiceModel.Activation.ServiceHostFactory and override the method CreateServiceHost to host the internal endpoint. public class InternalServiceFactory : ServiceHostFactory { protected override ServiceHost CreateServiceHost(Type serviceType, Uri[] baseAddresses) { var internalEndpointAddress = string.Format( "http://{0}/NotificationService.svc", RoleEnvironment.CurrentRoleInstance.InstanceEndpoints["InternalHttpEndpoint"].IPEndpoint); ServiceHost host = new ServiceHost( typeof(NotificationService), new Uri(internalEndpointAddress)); BasicHttpBinding binding = new BasicHttpBinding(SecurityMode.None); host.AddServiceEndpoint( typeof(INotificationService), binding, internalEndpointAddress); return host; } } Note that you can use SecurityMode.None because the internal endpoint is private to the instances of the service. 6.   Edit the markup of the service right clicking the svc file and selecting "View markup" to add the new factory as the factory to be used to create the service <%@ ServiceHost Language="C#" Debug="true" Factory="Service.InternalServiceFactory" Service="Service.NotificationService" CodeBehind="NotificationService.svc.cs" %> 7.   Now you can notify changes to other instances using this code: var current = RoleEnvironment.CurrentRoleInstance; var endPoints = current.Role.Instances .Where(instance => instance != current) .Select(instance => instance.InstanceEndpoints["InternalHttpEndpoint"]); foreach (var ep in endPoints) { EndpointAddress address = new EndpointAddress( String.Format("http://{0}/NotificationService.svc", ep.IPEndpoint)); BasicHttpBinding binding = new BasicHttpBinding(SecurityMode.None); var factory = new ChannelFactory<INotificationService>(binding); INotificationService instance = factory.CreateChannel(address); instance.Notify(changedinfo); }

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• Revenue Recognition: Performance Obligation Pass a Hurdle

  - by Theresa Hickman

  I met up with Seamus Moran, our resident accounting expert, to get his thoughts about the latest happenings with IFRS. Last week, on March 13,  the comment period on the FASB and IASB exposure draft “Revenue From Contracts with Customers” closed.  FASB and IASB have just over 20 comment letters – a very small number.  The implication is that that the exposure draft does reflect general acceptance, and therefore will be published as both a US and Internationally Generally Accepted Accounting Standard. At a recent conference call, FASB and IASB expected to complete their report to both Boards on the comments by early summer, complete their deliberation of the comments by the fall and draft the final standard text by late this year. It is assumed the concept of Performance Obligations would become US GAAP and IFRS in place of the existing standards.  They confirmed that all existing US GAAP and IFRS guidelines would be withdrawn, and that they were in dialogue with the SEC on withdrawing the SEC guidelines on the revenue issue as well.The open question is when will Performance Obligations become effective?  The Boards have said that they would like this Revenue Recognition standard and the the Lease Accounting standard to be effective at the same time because what isn’t either insurance, interest, or a lease is a revenue arrangement.  However, ascertaining what is generally acceptable in respect of Leases is proving a little elusive, and the Boards have recently diverged a little on the P&L side of the accounting (although both are in agreement that there will be no off-balance sheet leases).  It is therefore likely that the Lease standard might be delayed. One wonders if the Boards will  define effectivity of the Revenue standard independently of the Lease standard or if they will stick with their resolve to make them co-effective.  The Boards have also said that neither standard will be effective before June 2015.Here is the gist of the new Revenue Recognition principle and the steps to apply it:Recognize revenue to depict the transfer of goods or services in an amount that reflects the consideration expected to be entitled in exchange for those goods and services.Steps to apply the core principles: Identify the contract with the customer Identify the separate performance obligations Determine the transaction price Allocate the the transaction price Recognize Revenue when a performance obligation is satisfied  

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• Exalogic 2.0.1 Tea Break Snippets - Creating and using Distribution Groups

  - by The Old Toxophilist

  By default running your Exalogic in a Virtual provides you with, what to Cloud Users, is a single large resource and they can just create vServers and not care about how they are laid down on the the underlying infrastructure. All the Cloud Users will know is that they can create vServers. For example if we have a Quarter Rack (8 Nodes) and our Cloud User creates 8 vServers those 8 vServers may run on 8 distinct nodes or may all run on the same node. Although in many cases we, as Cloud Users, may not be to worried how the Virtualisation Algorithm decides where to place our vServers there are cases where it is extremely important that vServers run on distinct physical compute nodes. For example if we have a Weblogic Cluster we will want the Servers with in the cluster to run on distinct physical node to cover for the situation where one physical node is lost. To achieve this the Exalogic Virtualised implementation provides Distribution Groups that define and anti-aliasing policy that the underlying Virtualisation Algorithm will take into account when placing vServers. It should be noted that Distribution Groups must be created before you create vServers because a vServer can only be added to a Distribution Group at creation time. Creating A Distribution Group To create a Distribution Groups we will first need to select the Account in which we want the Distribution Group to be created. Once we have selected the account we will see the Interface update and Account specific Actions will be displayed within the Action Panes. From the Action pane (or Right-Click on the Account) select the "Create Distribution Group" action. This will initiate the create wizard as follows. Distribution Group Details Within the first Step of the Wizard we can specify the name of the distribution group and this should be unique. In addition we can provide a detailed description of the group. Distribution Group Configuration The second step of the configuration wizard allows you to specify the number of elements that are required within this group and will specify a maximum of the number of nodes within you Exalogic. At this point it is always better to specify a group with spare capacity allowing for future expansion. As vServers are added to group the available slots decrease. Summary Finally the last step of the wizard display a summary of the information entered.

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• design a model for a system of dependent variables

  - by dbaseman

  I'm dealing with a modeling system (financial) that has dozens of variables. Some of the variables are independent, and function as inputs to the system; most of them are calculated from other variables (independent and calculated) in the system. What I'm looking for is a clean, elegant way to: define the function of each dependent variable in the system trigger a re-calculation, whenever a variable changes, of the variables that depend on it A naive way to do this would be to write a single class that implements INotifyPropertyChanged, and uses a massive case statement that lists out all the variable names x1, x2, ... xn on which others depend, and, whenever a variable xi changes, triggers a recalculation of each of that variable's dependencies. I feel that this naive approach is flawed, and that there must be a cleaner way. I started down the path of defining a CalculationManager<TModel> class, which would be used (in a simple example) something like as follows: public class Model : INotifyPropertyChanged { private CalculationManager<Model> _calculationManager = new CalculationManager<Model>(); // each setter triggers a "PropertyChanged" event public double? Height { get; set; } public double? Weight { get; set; } public double? BMI { get; set; } public Model() { _calculationManager.DefineDependency<double?>( forProperty: model => model.BMI, usingCalculation: (height, weight) => weight / Math.Pow(height, 2), withInputs: model => model.Height, model.Weight); } // INotifyPropertyChanged implementation here } I won't reproduce CalculationManager<TModel> here, but the basic idea is that it sets up a dependency map, listens for PropertyChanged events, and updates dependent properties as needed. I still feel that I'm missing something major here, and that this isn't the right approach: the (mis)use of INotifyPropertyChanged seems to me like a code smell the withInputs parameter is defined as params Expression<Func<TModel, T>>[] args, which means that the argument list of usingCalculation is not checked at compile time the argument list (weight, height) is redundantly defined in both usingCalculation and withInputs I am sure that this kind of system of dependent variables must be common in computational mathematics, physics, finance, and other fields. Does someone know of an established set of ideas that deal with what I'm grasping at here? Would this be a suitable application for a functional language like F#? Edit More context: The model currently exists in an Excel spreadsheet, and is being migrated to a C# application. It is run on-demand, and the variables can be modified by the user from the application's UI. Its purpose is to retrieve variables that the business is interested in, given current inputs from the markets, and model parameters set by the business.

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• Design pattern to handle queries using multiple models

  - by coderkane

  I am presented with a dilemma while trying to re-designing the class structure for my PHP/MySQL application to make it more elegant and conform it to the SOLID principle. The problem goes like this: Let as assume, there is an abstract class called person which has certain properties to define a generic person, such as name, age, date of birth etc. There are two classes, student, and teacher, that implements this abstract class. They add their own unique properties to it. I have designed all the three classes to include all the operational logic (details of which are not relevant in context of the question). Now, I need to create views/reports/data grids which contain details from multiple classes, for example, say, a list of all students doing projects in Chemistry mentored by a teacher whose name is the parameter to the query. This is just one example of a view, there are many different views in the application, which uses data from 3-4 tables, and each of them have multiple input parameters to generate them. Considering this particular example, I have written the relevant query using JOIN and the results are as expected and proper, now here is the dilemma: Keeping in mind the single responsibility principle, where should I keep this query? It does not belong to either Student class, or Teacher class or any other classes currently present. a) Should I create a new class, say dataView class, and design it as a MVC pattern and keep the query there? What about the other views? how do they fit in this architecture? b) Should I not keep the query in code at all, and make it DB View ? c) Am I completely wrong in the approach? If so what is the right approach? My considerations are as follows: a) should be easy to add new views later on if requirement comes, without having to copy-paste-modify code b) would like to make it as loosely coupled as possible so that if minor db structure changes happen, it does not break I did google searches on report design and OOP report generators, but all the result seem to focus on the visual design of the report rather than fetching the data. I have already taken care of the visual aspect of the report using MVC with html templates. I am sure this is a very fundamental problem with known solution, but I am somehow not able to find it (maybe searching with wrong keyword). Edit1: Modified the title to make it more relevant Edit2: The accepted answer got me thinking in the right direction and identify my design flaws, which eventually led me to find this question and the solution in Stack Overflow which gave me the detailed answer to clear the confusion.

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• Incorrect results for frustum cull

  - by DeadMG

  Previously, I had a problem with my frustum culling producing too optimistic results- that is, including many objects that were not in the view volume. Now I have refactored that code and produced a cull that should be accurate to the actual frustum, instead of an axis-aligned box approximation. The problem is that now it never returns anything to be in the view volume. As the mathematical support library I'm using does not provide plane support functions, I had to code much of this functionality myself, and I'm not really the mathematical type, so it's likely that I've made some silly error somewhere. As follows is the relevant code: class Plane { public: Plane() { r0 = Math::Vector(0,0,0); normal = Math::Vector(0,1,0); } Plane(Math::Vector p1, Math::Vector p2, Math::Vector p3) { r0 = p1; normal = Math::Cross((p2 - p1), (p3 - p1)); } Math::Vector r0; Math::Vector normal; }; This class represents one plane as a point and a normal vector. class Frustum { public: Frustum( const std::array<Math::Vector, 8>& points ) { planes[0] = Plane(points[0], points[1], points[2]); planes[1] = Plane(points[4], points[5], points[6]); planes[2] = Plane(points[0], points[1], points[4]); planes[3] = Plane(points[2], points[3], points[6]); planes[4] = Plane(points[0], points[2], points[4]); planes[5] = Plane(points[1], points[3], points[5]); } Plane planes[6]; }; The points are passed in order where (the inverse of) each bit of the index of each point indicates whether it's the left, top, and back of the frustum, respectively. As such, I just picked any three points where they all shared one bit in common to define the planes. My intersection test is as follows (based on this): bool Intersects(Math::AABB lhs, const Frustum& rhs) const { for(int i = 0; i < 6; i++) { Math::Vector pvertex = lhs.TopRightFurthest; Math::Vector nvertex = lhs.BottomLeftClosest; if (rhs.planes[i].normal.x <= -0.0f) { std::swap(pvertex.x, nvertex.x); } if (rhs.planes[i].normal.y <= -0.0f) { std::swap(pvertex.y, nvertex.y); } if (rhs.planes[i].normal.z <= -0.0f) { std::swap(pvertex.z, nvertex.z); } if (Math::Dot(rhs.planes[i].r0, nvertex) < 0.0f) { return false; } } return true; } Also of note is that because I'm using a left-handed co-ordinate system, I wrote my Cross function to return the negative of the formula given on Wikipedia. Any suggestions as to where I've made a mistake?

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• Cron job running successfully suddenly reports script is not found

  - by Ted B

  What might cause cron to suddenly report a file it is supposed to run is "not found," when the file hasn't been touched, and in fact, the entire system hasn't been touched since it last ran successfully? I have a cronjob schedule I define by doing sudo crontab -e In it, I have dozens of cron jobs that run successfully.. I do not have a PATH specified, and I use absolute paths to call all my scheduled scripts, setting the PATH in them as needed. I do not specify a SHELL in the crontab. All scripts identify the shell as their first line. Without me touching the system, a particular job defined in the middle of other jobs will suddenly stop running. To debug this, I added an output redirection to a log file. In that, the output clearly shows the output of the script successfully running time after time for weeks, and then suddenly the following appears: /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found /bin/sh: /home/iupress/bin/sync-email_images: not found If I do the ls command, copying and pasting that exact path from the error message, it clearly reports the file is still there (no surprise). Yet the log continues to report that file is "not found" until I take action. I can run the script manually and it runs just fine. If I do sudo crontab -e and save the file, the job runs on the next scheduled time, putting its output in the log, no longer reporting the script is "not found". It seems to me the contents of the script trying to be run are irrelevant since cron doesn't even process the file because it is "not found". I have a job scheduled below the one that is encountering this problem that I know is continuing to run, because I have its output mailed to me. So I know cron is running and continues to run at least one other job, even after it suddenly reports this job's script is "not found". All my lines end with a newline. I had no periods in the crontab until I added the redirection to a log file. I have now added a PATH specification, but left the absolute paths in the jobs. Unfortunately, I have no idea if and when this problem will occur. It will likely be weeks from now. By the way, I am running a script to syncronize the clock, and I see the time is exactly what it should be.

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• Another Custom Property Locator: a Library of Books

  - by Cindy McMullen

  Introduction The previous post gave an introduction to custom property locators and showed how create one using JDeveloper.  This post continues on the custom locator theme, with a slightly more complex locator: a library of books.  It demonstrates using the DAO pattern to delegate data access from the Locator, which is likely how many actual backing stores will integrate with the Locator.  You can imagine, rather than a library of books, the data store might be a user database of sorts.  The same sort of pattern would apply. This post uses the BookLocator example originally shown in the WebCenter documentation, but has: updated the source code to reflect the final Property APIs includes the steps for generating the namespace and property definition files via JDeveloper detailed usage of the PropertyService APIs Getting Started If you're new to JDeveloper, you might want to check out this tutorial.  There is also the "Jump-Start to using Personalization" blog post that you might find useful.  Otherwise, if you're already familiar with both, you can skip those tutorials and jump right in to using JDeveloper. Download the BookLocator.zip file (which has been updated from the original post) and unzip it to a new directory.  Start JDeveloper, navigate to the BookLocator.jws file, and open it.   It should look something like this: The Properties Namespace file contains the property definitions and property set definitions you define.  It is explained more in detail in the Namespace documentation.  Although this example doesn't show it, the property set definitions have the ability to reference multiple locators per property.   This can be done by right-clicking on the 'Locator Info' box.  Configure the contents of the Locator Map  by editing locators and mapping them to available property names in the property set definition. Compiling, deploying, and running your locator The rest of the steps in this tutorial basically follow those in the previous blog on custom locators, and won't be repeated here.   A scenario to invoke your locator is included with the sample app: see BookProperties.scenarios_diagram above.  Summary This post demonstrates a simple library of books accessed by the BookPropertyLocator via the DAO layer.  This is a useful pattern for more realistic property retrievals, such as a backing user store.  It also points out the possibility of retrieving properties from multiple locators, which would be quite handy to retrieve user attributes from multiple sources.

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• Best Frameworks/libraries/engines for 2D multiplayer C# Webbased RPG

  - by Thirlan

  Title is a mouthful but important because I'm looking to meet a specific criteria and it's complex enough that I need a lot of help in finding what I'm looking for. I really want people's suggestions because I trust it a lot more than anything else, so I just need to clearly define what it is I want heh : P Game is a 2D RPG. Think of Secret of Mana. Game is online multiplayer, but not MMO sized. Game must be webbased! I'm looking to the future and want to hit as many platforms as possible. I'm leaning to Webgl because of this, but still looking around. Since the users are seeing the game through the webbrowser the front-end should be mainly responsible for drawing, taking input and some basic checking such as preliminary collision detection. This is important because it means the game engine is NOT on the client's machine. The server should be responsible for the game engine and all the calculations. This means the server is doing all the work and the client is mostly a dumb terminal. Server language is c# I'm looking for fast project execution so I want to use as many pre-existing tools as possible. This would make sense because I'm making a game here, not an engine. I'm not creating some new revolutionary graphics or pushing the physics engines to the next level. Preference for commercially supported tools. For game mechanics reasons and for reasons 4 and 5, don't think I can use existing 2D rpg engines. I've seen them out there and I fear that if I try and use them they will have too many restrictions, but will be happy to hear out suggestions. So all this means I need a game engine on the server, or maybe just a physics engine, and then I need another engine/library to draw everything that the server is sending to the client on the webbrowser. Maybe this is how 50% of games work on the web and there are plenty of frameworks that support this! I wouldn't actually don't know : ( but my gut is telling me that most webgames are single player and 90% of the game is running on the client. So... any suggestions?

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• Maximizing the Value of Software

  - by David Dorf

  A few years ago we decided to increase our investments in documenting retail processes and architectures.  There were several goals but the main two were to help retailers maximize the value they derive from our software and help system integrators implement our software faster.  The sale is only part of our success metric -- its actually more important that the customer realize the benefits of the software.  That's when we actually celebrate. This week many of our customers are gathered in Chicago to discuss their successes during our annual Crosstalk conference.  That provides the perfect forum to announce the release of the Oracle Retail Reference Library.  The RRL is available for free to Oracle Retail customers and partners.  It contains 1000s of hours of work and represents years of experience in the retail industry.  The Retail Reference Library is composed of three offerings: Retail Reference Model We've been sharing the RRM for several years now, with lots of accolades.  The RRM is a set of business process diagrams at varying levels of granularity. This release marks the debut of Visio documents, which should make it easier for retailers to adopt and edit the diagrams.  The processes represent an approximation of the Oracle Retail software, but at higher levels they are pretty generic and therefore usable with other software as well.  Using these processes, the business and IT are better able to communicate the expectations of the software.  They can be used to guide customization when necessary, and help identify areas for optimization in the organization. Retail Reference Architecture When embarking on a software implementation project, it can be daunting to start from a blank sheet of paper.  So we offer the RRA, a comprehensive set of documents that describe the retail enterprise in terms of logical architecture, physical deployments, and systems integration.  These documents and diagrams describe how all the systems typically found in a retailer enterprise work together.  They serve as a way to jump-start implementations using best practices we've captured over the years. Retail Semantic Glossary Have you ever seen two people argue over something because they're using misaligned terminology?  Its a huge waste and happens all the time.  The Retail Semantic Glossary is a simple application that allows retailers to define terms and metrics in a centralized database.  This initial version comes with limited content with the goal of adding more over subsequent releases.  This is the single source for defining key performance indicators, metrics, algorithms, and terms so that the retail organization speaks in a consistent language. These three offerings are downloaded from MyOracleSupport separately and linked together using the start page above.  Everything is navigated using a Web browser.  See the Oracle Retail Documentation blog for more details.

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• Creating Asynchronous Methods in EJB 3.1

  - by cindo

  Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} OBE of the Month: Creating Asynchronous Methods in EJB 3.1 This OBE covers creating an EJB 3.1 application that demonstrates the use of the @Asynchronous annotation in an Enterprise Java Bean (EJB) class or specific method. In this tutorial, you will create a Java EE 6 Web Application and add the following components to it - a Stateless Session Bean with two asynchronous methods. You define a Servlet to call the asynchronous methods and to keep track of the invocation and completion times to demonstrate the asynchronous nature of the method calls. The index.jsp will contain a form with a submit button, Run allowing you to execute the application. The form will submit to the Servlet which invokes the asynchronous methods defined in the session bean and the response is re-directed to response.jsp. Information about the asynchronous handling procedure is displayed to users. From this information, users will notice that the invoker thread and the called asynchronous thread are working concurrently. Check out this new OBE on the Oracle Learning Library: Creating Asynchronous Methods in EJB 3.1. This OBE is part of the new EJB 3.1 New Features Series. Related OBE’s that might interest you: Creating a No-Interface View Session Bean and Packaging in a WAR File Creating and Accessing a Session Bean in a  Web Application

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• Write and fprintf for file I/O

  - by Darryl Gove

  fprintf() does buffered I/O, where as write() does unbuffered I/O. So once the write() completes, the data is in the file, whereas, for fprintf() it may take a while for the file to get updated to reflect the output. This results in a significant performance difference - the write works at disk speed. The following is a program to test this: #include <fcntl.h #include <unistd.h #include <stdio.h #include <stdlib.h #include <errno.h #include <stdio.h #include <sys/time.h #include <sys/types.h #include <sys/stat.h static double s_time; void starttime() { s_time=1.0*gethrtime(); } void endtime(long its) { double e_time=1.0*gethrtime(); printf("Time per iteration %5.2f MB/s\n", (1.0*its)/(e_time-s_time*1.0)*1000); s_time=1.0*gethrtime(); } #define SIZE 10*1024*1024 void test_write() { starttime(); int file = open("./test.dat",O_WRONLY|O_CREAT,S_IWGRP|S_IWOTH|S_IWUSR); for (int i=0; i<SIZE; i++) { write(file,"a",1); } close(file); endtime(SIZE); } void test_fprintf() { starttime(); FILE* file = fopen("./test.dat","w"); for (int i=0; i<SIZE; i++) { fprintf(file,"a"); } fclose(file); endtime(SIZE); } void test_flush() { starttime(); FILE* file = fopen("./test.dat","w"); for (int i=0; i<SIZE; i++) { fprintf(file,"a"); fflush(file); } fclose(file); endtime(SIZE); } int main() { test_write(); test_fprintf(); test_flush(); } Compiling and running I get 0.2MB/s for write() and 6MB/s for fprintf(). A large difference. There's three tests in this example, the third test uses fprintf() and fflush(). This is equivalent to write() both in performance and in functionality. Which leads to the suggestion that fprintf() (and other buffering I/O functions) are the fastest way of writing to files, and that fflush() should be used to enforce synchronisation of the file contents.

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• How to set the initial component focus

  - by frank.nimphius

  Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} In ADF Faces, you use the af:document tag's initialFocusId to define the initial component focus. For this, specify the id property value of the component that you want to put the initial focus on. Identifiers are relative to the component, and must account for NamingContainers. You can use a single colon to start the search from the root, or multiple colons to move up through the NamingContainers - "::" will pop out of the component's naming container and begin the search from there, ":::" will pop out of two naming containers and begin the search from there. Alternatively you can add the naming container IDs as a prefix to the component Id, e.g. nc1:nc2:comp1. http://download.oracle.com/docs/cd/E17904_01/apirefs.1111/e12419/tagdoc/af_document.html To set the initial focus to a component located in a page fragment that is exposed through an ADF region, keep in mind that ADF Faces regions - af:region - is a naming container too. To address an input text field with the id "it1" in an ADF region exposed by an af:region tag with the id r1, you use the following reference in af:document: <af:document id="d1" initialFocusId="r1:0:it1"> Note the "0" index in the client Id. Also, make sure the input text component has its clientComponent property set to true as otherwise no client component exist to put focus on.

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• Ubuntu Linux won't display netbook's native resolution

  - by Daniel

  FYI: My Netbook model is HP Mini 210-1004sa, which comes with Intel Graphics Media Accelerator 3150, and has a display 10.1" Active Matrix Colour TFT 1024 x 600. I recently removed Windows 7 Starter from my netbook, and replaced it with Ubuntu 12.10. The problem is the OS doesn't seem to recognise the native display resolution of 1024x600 i.e. the bottom bits of Ubuntu is hidden beneath the screen & the only 2 available resolutions are: the default 1024x768 and 800x600. I've also thought about replacing Ubuntu with Lubuntu or Puppy Linux, as the system does run a bit slow, but I can't, as then I won't be able to access the taskbar and application menu which will be hidden beneath the screen. Only Ubuntu with Unity is currently usable, as the Unity Launcher is visible enough. I was able to define a custom resolution 1024x600 using the Q&A: How set my monitor resolution? but when I set that resolution, there appears a black band at the top of the screen and the desktop area is lowered, with bits of it hidden beneath the screen. I tried leaving it at this new resolution and restarting the system to see if the black band would disappear & the display will fit correctly, but it gets reset to 1024x768 at startup and displays following error: Could not apply the stored configuration for monitors none of the selected modes were compatible with the possible modes: Trying modes for CRTC 63 CRTC 63: trying mode 800x600@60Hz with output at 1024x600@60Hz (pass 0) CRTC 63: trying mode 800x600@56Hz with output at 1024x600@60Hz (pass 0) CRTC 63: trying mode 640x480@60Hz with output at 1024x600@60Hz (pass 0) CRTC 63: trying mode 1024x768@60Hz with output at 1024x600@60Hz (pass 1) CRTC 63: trying mode 800x600@60Hz with output at 1024x600@60Hz (pass 1) CRTC 63: trying mode 800x600@56Hz with output at 1024x600@60Hz (pass 1) CRTC 63: trying mode 640x480@60Hz with output at 1024x600@60Hz (pass 1) Trying modes for CRTC 64 CRTC 64: trying mode 1024x768@60Hz with output at 1024x600@60Hz (pass 0) CRTC 64: trying mode 800x600@60Hz with output at 1024x600@60Hz (pass 0) CRTC 64: trying mode 800x600@56Hz with output at 1024x600@60Hz (pass 0) CRTC 64: trying mode 640x480@60Hz with output at 1024x600@60Hz (pass 0) CRTC 64: trying mode 1024x768@60Hz with output at 1024x600@60Hz (pass 1) CRTC 64: trying mode 800x600@60Hz with output at 1024x600@60Hz (pass 1) CRTC 64: trying mode 800x600@56Hz with output at 1024x600@60Hz (pass 1) CRTC 64: trying mode 640x480@60Hz with output at 1024x600@60Hz (pass 1)

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• Pixels - A cry for some insight

  - by CarrotFile

  I'm pretty new to web developing and I'd love some clarification. Although reading more than one book on the topic, I cannot seem to wrap my head around the pixel concept. I encounter problems with this issue when trying to use CSS and pixel units for design that fits different screen sizes. To my understanding a pixel is the most basic unit used by a monitor in order to compose an image on the screen. So if me resolution is 800 by 600, everything on my screen is rendered using those 800*600 basic building blocks. If I were to enlarge my screen resolution, 3 things would accrue: A. The basic image building block(the pixel) would shrink in size B. The pixels would move close together C. Well, more pixels would now be available All these combined lead to a sharper(depending on the viewing distance) and more detail enabling image. Well so far so good. Here is were I start getting lost: To my knowledge a pixel is not a physical, real object. Monitors are not embedded with a few thousand pixels. I am drawn to this conclusion because anyone can change his screen's resolution, making a pixel on his screen bigger or smaller, and adding or subtracting the amount of total pixels on screen. Adding to that, I have herd that different monitors have different pixel densities. For example Apple's retina monitors. Taking all of the above as my knowledge base, These are my questions: If a pixel has no real world constant size, what does comparing different pixel densities matter? Each screen company can define it's own pixel concept and declare the higher density. What does a bigger pixel density mean? Say we take two screens with the same physical dimensions, but with a different pixel density, am I to assert that the main difference would be the larger density screen being able to display a higher max resolution? Or am I to assert that given the same resolution on both monitors, the higher density one would display a sharper, smaller image? If a pixel is not a fixed size within one monitor, is it a fixed size between the same resolution on two different monitors? For example, would two different monitors, set to the same resolution, be comprised of same size, same quantity pixels? I'd love some help (:

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• How to perform Cross Join with Linq

  - by berthin

  Cross join consists to perform a Cartesian product of two sets or sequences. The following example shows a simple Cartesian product of the sets A and B: A (a1, a2) B (b1, b2) => C (a1 b1,            a1 b2,            a2 b1,            a2, b2 ) is the Cartesian product's result. Linq to Sql allows using Cross join operations. Cross join is not equijoin, means that no predicate expression of equality in the Join clause of the query. To define a cross join query, you can use multiple from clauses. Note that there's no explicit operator for the cross join. In the following example, the query must join a sequence of Product with a sequence of Pricing Rules: 1: //Fill the data source 2: var products = new List<Product> 3: { 4: new Product{ProductID="P01",ProductName="Amaryl"}, 5: new Product {ProductID="P02", ProductName="acetaminophen"} 6: }; 7:  8: var pricingRules = new List<PricingRule> 9: { 10: new PricingRule {RuleID="R_1", RuleType="Free goods"}, 11: new PricingRule {RuleID="R_2", RuleType="Discount"}, 12: new PricingRule {RuleID="R_3", RuleType="Discount"} 13: }; 14: 15: //cross join query 16: var crossJoin = from p in products 17: from r in pricingRules 18: select new { ProductID = p.ProductID, RuleID = r.RuleID };   Below the definition of the two entities using in the above example.   1: public class Product 2: { 3: public string ProductID { get; set; } 4: public string ProductName { get; set; } 5: } 1: public class PricingRule 2: { 3: public string RuleID { get; set; } 4: public string RuleType { get; set; } 5: }   Doing this: 1: foreach (var result in crossJoin) 2: { 3: Console.WriteLine("({0} , {1})", result.ProductID, result.RuleID); 4: }   The output should be similar on this:   ( P01   -    R_1 )   ( P01   -    R_2 )   ( P01   -    R_3 )   ( P02   -    R_1 )   ( P02   -    R_2 )   ( P02   -    R_3) Conclusion Cross join operation is useful when performing a Cartesian product of two sequences object. However, it can produce very large result sets that may caused a problem of performance. So use with precautions :)

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• Yet another frustum culling question

  - by Christian Frantz

  This one is kinda specific. If I'm to implement frustum culling in my game, that means each one of my cubes would need a bounding sphere. My first question is can I make the sphere so close to the edge of the cube that its still easily clickable for destroying and building? Frustum culling is easily done in XNA as I've recently learned, I just need to figure out where to place the code for the culling. I'm guessing in my method that draws all my cubes but I could be wrong. My camera class currently implements a bounding frustum which is in the update method like so frustum.Matrix = (view * proj); Simple enough, as I can call that when I have a camera object in my class. This works for now, as I only have a camera in my main game class. The problem comes when I decide to move my camera to my player class, but I can worry about that later. ContainmentType CurrentContainmentType = ContainmentType.Disjoint; CurrentContainmentType = CamerasFrustrum.Contains(cubes.CollisionSphere); Can it really be as easy as adding those two lines to my foreach loop in my draw method? Or am I missing something bigger here? UPDATE: I have added the lines to my draw methods and it works great!! So great infact that just moving a little bit removes the whole map. Many factors could of caused this, so I'll try to break it down. cubeBoundingSphere = new BoundingSphere(cubePosition, 0.5f); This is in my cube constructor. cubePosition is stored in an array, The vertices that define my cube are factors of 1 ie: (1,0,1) so the radius should be .5. I least I think it should. The spheres are created every time a cube is created of course. ContainmentType CurrentContainmentType = ContainmentType.Disjoint; foreach (Cube block in cube.cubes) { CurrentContainmentType = cam.frustum.Contains(cube.cubeBoundingSphere); ///more code here if (CurrentContainmentType != ContainmentType.Disjoint) { cube.Draw(effect); } Within my draw method. Now I know this works because the map disappears, its just working wrong. Any idea on what I'm doing wrong?

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• Interaction of a GUI-based App and Windows Service

  - by psubsee2003

  I am working on personal project that will be designed to help manage my media library, specifically recordings created by Windows Media Center. So I am going to have the following parts to this application: A Windows Service that monitors the recording folder. Once a new recording is completed that meets specific criteria, it will call several 3rd party CLI Applications to remove the commercials and re-encode the video into a more hard-drive friendly format. A controller GUI to be able to modify settings of the service, specifically add new shows to watch for, and to modify parameters for the CLI Applications A standalone (GUI-based) desktop application that can perform many of the same functions as the windows service, expect manually on specific files instead of automatically based on specific criteria. (It should be mentioned that I have limited experience with an application of this complexity, and I have absolutely zero experience with Windows Services) Since the 1st and 3rd bullet share similar functionality, my design plan is to pull the common functionality into a separate library shared by both parts applications, but these 2 components do not need to interact otherwise. The 2nd and 3rd bullets seem to share some common functionality, both will have a GUI, both will have to help define similar parameters (one to send to the service and the other to send directly to the CLI applications), so I can see some advantage to combining them into the same application. On the other hand, the standalone application (bullet #3) really does not need to interact with the service at all, except for possibly sharing a few common default parameters that can easily be put into an XML in a common location, so it seems to make more sense to just keep everything separate. The controller GUI (2nd bullet) is where I am stuck at the moment. Do I just roll this functionality (allow for user interaction with the service to update settings and criteria) into the standalone application? Or would it be a better design decision to keep them separate? Specifically, I'm worried about adding the complexity of communicating with the Windows Service to the standalone application when it doesn't need it. Is WCF the right approach to allow the controller GUI to interact with the Windows Service? Or is there a better alternative? At the moment, I don't envision a need for a significant amount of interaction, maybe just adding a new task once in a while and occasionally tweaking a parameter, but when something is changed, I do expect the windows service to immediately use the new settings.

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• Help writing server script to ban IP's from a list

  - by Chev_603

  I have a VPS that I use as an openvpn and web server. For some reason, my apache log files are filled with thousands of these hack attempts: "POST /xmlrpc.php HTTP/1.0" 404 395 These attack attempts fill up 90% of my logs. I think it's a WordPress vulnerability they're looking for. Obviously they are not successful (I don't even have Wordpress on my server), but it's annoying and probably resource consuming as well. I am trying to write a bash script that will do the following: Search the apache logs and grab the offending IP's (even if they try it once), Sort them into a list with each unique IP on a seperate line, And then block them using the IP table rules. I am a bash newb, and so far my script does everything except Step 3. I can manually block the IP's, but that's tedious and besides, this is Linux and it's perfectly capable of doing it for me. I also want the script to be customizable so that I (or anyone else who wants to use it) can change the variables to suit whatever situation I/they may deal with in the future. Here is the script so far: #!/bin/bash ##IP LIST GENERATOR ##Author Chev Young ##Script to search Apache logs and list IP's based on custom filters ## ##Define our variables: DIRECT=~/Script ##Location of script&where to put results/temp files LOGFILE=/var/log/apache2/access.log ## Logfile to search for offenders TEMPLIST=xml_temp ## Temporary file name IP_LIST=ipstoban ## Name of results file FILTER1=xmlrpc ## What are we looking for? (Requests we want to ban) cd $DIRECT if [ ! -f $TEMPLIST ];then touch $TEMPLIST ##Create temp file fi cat $LOGFILE | grep $FILTER1 >> $DIRECT/$TEMPLIST ## Only interested in the IP's, so: sed -e 's/\([0-9]\+\.[0-9]\+\.[0-9]\+\.[0-9]\+\).*$/\1/' -e t -e d $DIRECT/$TEMPLIST | sort | uniq > $DIRECT/$IP_LIST rm $TEMPLIST ## Clean temp file echo "Done. Results located at $DIRECT/$IP_LIST" So I need help with the next part of the script, which should ban the IP's (incoming and perhaps outgoing too) from the resulting $IP_LIST file. I don't care if it utilizes UFW or IPTables directly, as long as it bans the IP's. I'd probably run it as a cron task. What I'm having trouble with is understanding how to use line of the result file as a seperate variable to do something like: ufw deny $IP1 $IP2 $IP3, ect Any ideas? Thanks.

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• Hierachies....from the Top Down

  - by Joe G

  I've been struggling with how to write on the topic of the importance of hierarchy design.  It's not so much that hierarchies haven't always been important, it's more of that with Fusion, the timing of when the hierarchies are designed should take a higher priority.    I will attempt to explain..... When I was implementing applications, back in the day, we had the list of detailed account values to enter with the obvious parent accounts. Then, after the setup was complete and things were functioning, the reporting phase started.  Users explained the elements that they want on the reports, what totals should be included, and how things should be compared.  Frequently, there was at least one calculation that became a nightmare either because it was based on very specific things that didn't relate to anything else or because it was "hardcoded" so that when something changed, someone need to "fix" the report. With Fusion, the process changes slightly.  You still want to enter all of the detailed accounts, but before you start adding parent values, you should investigate the reporting requirements from the top-down.  It's better to build hierarchies based on the reporting requirements than it is to build reports based on random hierarchies. Build reports based on hierarchies that resemble the reports themselves, and maintain the hierarchies without rework of the reports. For example, if you look at an income statement, you may have line items for Material Costs, Employee Costs, Travel & Entertainment, and Total Operating Expenses.  In your hierarchy, you have detail values that roll up to Material Costs, Employee Costs, and Travel & Entertainment which roll up to Total Operating Expenses. Balances are stored automatically in the cube for each of these.  When you define the report, you pick each of these members - no calculations required.  If a new detail value is added, you simply add it to the hierarchy, and there is no need to modify the report. I realize that there are always exceptions that require special handling, but I am confident that you will end up with much fewer exceptions if you make reporting a priority and design your hierarchies from the top-down.

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• How to implement a component based system for items in a web game.

  - by Landstander

  Reading several other questions and answers on using a component based system to define items I want to use one for the items and spells in a web game written in PHP. I'm just stuck on the implementation. I'm going to use a DB schema suggested in this series (part 5 describes the schema); http://t-machine.org/index.php/2007/09/03/entity-systems-are-the-future-of-mmog-development-part-1/ This means I'll have an items table with generic item properties, a table listing all of the components for an item and finally records in each component table used to make up the item. Assuming I can select the first two together in a single query, I'm still going to do N queries for each component type. I'm kind of fine with this because I can cache the data into memcache and check there first before doing any queries. I'll need to build up the items on every request they are used in so the implementation needs to be on the lean side even if they're pulled from memcache. But right there is where I feel confident about implementing a component system for my items ends. I figure I'd need to bring attributes and behaviors into the container from each component it uses. I'm just not sure how to do that effectively and not end up writing a lot of specialized code to deal with each component. For example an AttackComponent might need to know how to filter targets inside of a battle context and also maybe provide an attack behavior. That same item might also have a UsableComponent which allows the item to be used and apply some effect onto a different set of targets filtered differently from the same battle context. Then not every part of an item is an active part, an AttributeBonusComponent might need to only kick in when the item is in an equipped state or when displaying the item details page. Ultimately, how should I bring all of the components together into the container so when I use an item as a weapon I get the correct list of targets? Know when a weapon can also be used as an item? Or to apply the bonuses the item provides to a character object? I feel like I've gone too far down the rabbit hole and I can't grasp onto the simple solution in front of me. (If that makes any sense at all.) Likewise if I were to implement the best answer from here I feel like I'd have a lot of the same questions. How to model multiple "uses" (e.g. weapon) for usable-inventory/object/items (e.g. katana) within a relational database.

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• How should game objects be aware of each other?

  - by Jefffrey

  I find it hard to find a way to organize game objects so that they are polymorphic but at the same time not polymorphic. Here's an example: assuming that we want all our objects to update() and draw(). In order to do that we need to define a base class GameObject which have those two virtual pure methods and let polymorphism kicks in: class World { private: std::vector<GameObject*> objects; public: // ... update() { for (auto& o : objects) o->update(); for (auto& o : objects) o->draw(window); } }; The update method is supposed to take care of whatever state the specific class object needs to update. The fact is that each objects needs to know about the world around them. For example: A mine needs to know if someone is colliding with it A soldier should know if another team's soldier is in proximity A zombie should know where the closest brain, within a radius, is For passive interactions (like the first one) I was thinking that the collision detection could delegate what to do in specific cases of collisions to the object itself with a on_collide(GameObject*). Most of the the other informations (like the other two examples) could just be queried by the game world passed to the update method. Now the world does not distinguish objects based on their type (it stores all object in a single polymorphic container), so what in fact it will return with an ideal world.entities_in(center, radius) is a container of GameObject*. But of course the soldier does not want to attack other soldiers from his team and a zombie doesn't case about other zombies. So we need to distinguish the behavior. A solution could be the following: void TeamASoldier::update(const World& world) { auto list = world.entities_in(position, eye_sight); for (const auto& e : list) if (auto enemy = dynamic_cast<TeamBSoldier*>(e)) // shoot towards enemy } void Zombie::update(const World& world) { auto list = world.entities_in(position, eye_sight); for (const auto& e : list) if (auto enemy = dynamic_cast<Human*>(e)) // go and eat brain } but of course the number of dynamic_cast<> per frame could be horribly high, and we all know how slow dynamic_cast can be. The same problem also applies to the on_collide(GameObject*) delegate that we discussed earlier. So what it the ideal way to organize the code so that objects can be aware of other objects and be able to ignore them or take actions based on their type?

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• ETPM Forms Accelerator

  - by MHundal

  The ETPM Forms Accelerator provides a template that can be used to enter data related to Registration and Tax Forms.  The Forms Accelerator includes a worksheet for each portion related to forms development (Form Type, Form Section, Form Lines and Form Rules).  The Forms Accelerator provides the details that must be defined in ETPM.  This allows for taking an existing form and translating the details of that form into the spreadsheet.  The spreadsheet can then be used to define the details in the system.  In addition, each of the items to be defined is explained it detail - what the field expects and based on the input, how it impacts the field and form definition.   This is a living document - as there is feedback provided, the document will be updated.  The goal of this accelerator is to be an aide in the Forms Development process.  We encourage feedback to help improve the document.  The document is for ETPM 2.3.1.  Implementations using older version of ETPM will find that some of the field definition options may not exist their current system.   The spreadsheet attached contains the following Worksheets: Instructions:  High-level overview for the different worksheets provided. Form Type:  The fields to be populated when defining the Form Type for a Registration or Tax Form Form Section:  The fields to be populated when creating a Form Section.  The number of sections will differ based on the the form being implemented. Form Lines:  The fields to be populated when creating different Form Lines. The number of lines per section will differ based on the form being implemented. Form Rules:  Based on the form, allows for documenting the Form Rules to be configured based on form instructions and Form Lines. Right click on the link and select the "Save Link As" option.  ETPM Forms Accelerator.xls Please provide feedback to [email protected]. You feedback is encouraged and appreciated.  

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• Lazy Processing of Streams

  - by Giorgio

  I have the following problem scenario: I have a text file and I have to read it and split it into lines. Some lines might need to be dropped (according to criteria that are not fixed). The lines that are not dropped must be parsed into some predefined records. Records that are not valid must be dropped. Duplicate records may exist and, in such a case, they are consecutive. If duplicate / multiple records exist, only one item should be kept. The remaining records should be grouped according to the value contained in one field; all records belonging to the same group appear one after another (e.g. AAAABBBBCCDEEEFF and so on). The records of each group should be numbered (1, 2, 3, 4, ...). For each group the numbering starts from 1. The records must then be saved somewhere / consumed in the same order as they were produced. I have to implement this in Java or C++. My first idea was to define functions / methods like: One method to get all the lines from the file. One method to filter out the unwanted lines. One method to parse the filtered lines into valid records. One method to remove duplicate records. One method to group records and number them. The problem is that the data I am going to read can be too big and might not fit into main memory: so I cannot just construct all these lists and apply my functions one after the other. On the other hand, I think I do not need to fit all the data in main memory at once because once a record has been consumed all its underlying data (basically the lines of text between the previous record and the current record, and the record itself) can be disposed of. With the little knowledge I have of Haskell I have immediately thought about some kind of lazy evaluation, in which instead of applying functions to lists that have been completely computed, I have different streams of data that are built on top of each other and, at each moment, only the needed portion of each stream is materialized in main memory. But I have to implement this in Java or C++. So my question is which design pattern or other technique can allow me to implement this lazy processing of streams in one of these languages.

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