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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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  • Antenna Aligner Part 5: Devil is in the detail

    - by Chris George
    "The first 90% of a project takes 90% of the time and the last 10% takes the another 200%"  (excerpt from onista) Now that I have a working app (more or less), it's time to make it pretty and slick. I can't stress enough how useful it is to get other people using your software, and my simple app is no exception. I handed my iPhone to a couple of my colleagues at Red Gate and asked them to use it and give me feedback. Immediately it became apparent that the delay between the list page being shown and the list being drawn was too long, and everyone who tried the app clicked on the "Recalculate" button before it had finished. Similarly, selecting a transmitter heralded a delay before the compass page appeared with similar consequences. All users expected there to be some sort of feedback/spinny etc. to show them it is actually doing something. In a similar vein although for opposite reasons, clicking the Recalculate button did indeed recalculate the available transmitters and redraw them, but it did this too fast! One or two users commented that they didn't know if it had done anything. All of these issues resulted in similar solutions; implement a waiting spinny. Thankfully, jquery mobile has one built in, primarily used for ajax operations. Not wishing to bore you with the many many iterations I went through trying to get this to work, I'll just give you my solution! (Seriously, I was working on this most evenings for at least a week!) The final solution for the recalculate problem came in the form of the code below. $(document).on("click", ".show-page-loading-msg", function () {            var $this = $(this),                theme = $this.jqmData("theme") ||                        $.mobile.loadingMessageTheme;            $.mobile.showPageLoadingMsg(theme, "recalculating", false);            setTimeout(function ()                           { $.mobile.hidePageLoadingMsg(); }, 2000);            getLocationData();        })        .on("click", ".hide-page-loading-msg", function () {              $.mobile.hidePageLoadingMsg();        }); The spinny is activated by setting the class of a button (for example) to the 'show-page-loading-msg' class. &lt;a data-role="button" class="show-page-loading-msg"Recalculate This means the code above is fired, calling the showPageLoadingMsg on the document.mobile object. Then, after a 2 second timeout, it calls the hidePageLoadingMsg() function. Supposedly, it should show "recalculating" underneath the spinny, but I've not got that to work. I'm wondering if there is a problem with the jquery mobile implementation. Anyway, it doesn't really matter, it's the principle I'm after, and I now have spinnys!

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  • Block-level deduplicating filesystem

    - by James Haigh
    I'm looking for a deduplicating copy-on-write filesystem solution for general user data such as /home and backups of it. It should use online/inline/synchronous deduplication at the block-level using secure hashing (for negligible chance of collisions) such as SHA256 or TTH. Duplicate blocks need not even touch the disk. The idea is that I should be able to just copy /home/<user> to an external HDD with the same such filesystem to do a backup. Simple. No messing around with incremental backups where corruption to any of the snapshots will nearly always break all later snapshots, and no need to use a specific tool to delete or 'checkout' a snapshot. Everything should simply be done from the file browser without worry. Can you imagine how easy this would be? I'd never have to think twice about backing-up again! I don't mind a performance hit, reliability is the main concern. Although, with specific implementations of cp, mv and scp, and a file browser plugin, these operations would be very fast, especially when there is a lot of duplication as they would only need to transfer the absent blocks. Accidentally using conventional copy tools that do not integrate with the FS would merely take longer, waste some bandwidth when copying remotely and waste some CPU, as the duplicate data would be re-read, re-transferred and re-hashed (although nothing would be re-written), but would absolutely not corrupt anything. (Some filesharing software may also be able to benefit by integrating with the FS.) So what's the best way of doing this? I've looked at some options: lessfs - Looks unmaintained. Any good? [Opendedup/SDFS][3] - Java? Could I use this on Android?! What does [SDFS][4] stand for? [Btrfs][5] - Some patches floating around on mailing list archives, but no real support. [ZFS][6] - Hopefully they'll one day relicense under a true Free/Opensource GPL-compatible licence. Also, 2 years ago I had a go at an attempt in Python using Fuse at the file-level to be used over the top of a typical solid FS such as EXT4, but I found Fuse for Python underdocumented and didn't manage to implement all of the system calls. My first post here, so I can't post more than 2 links until I get over 10 rep: [3]: http://www.opendedup.org/ [4]: https://en.wikipedia.org/w/index.php?title=SDFS&action=edit&redlink=1 [5]: https://en.wikipedia.org/wiki/Btrfs#Features [6]: https://en.wikipedia.org/wiki/ZFS#Linux

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  • Loose Coupling and UX Patterns for Applications Integrations

    - by ultan o'broin
    I love that software architecture phrase loose coupling. There’s even a whole book about it. And, if you’re involved in enterprise methodology you’ll know just know important loose coupling is to the smart development of applications integrations too. Whether you are integrating offerings from the Oracle partner ecosystem with Fusion apps or applications coexistence scenarios, loose coupling enables the development of scalable, reliable, flexible solutions, with no second-guessing of technology. Another great book Enterprise Integration Patterns: Designing, Building, and Deploying Messaging Solutions tells us about loose coupling benefits of reducing the assumptions that integration parties (components, applications, services, programs, users) make about each other when they exchange information. Eliminating assumptions applies to UI development too. The days of assuming it’s enough to hard code a UI with linking libraries called code on a desktop PC for an office worker are over. The book predates PaaS development and SaaS deployments, and was written when web services and APIs were emerging. Yet it calls out how using middleware as an assumptions-dissolving technology “glue" is central to applications integration. Realizing integration design through a set of middleware messaging patterns (messaging in the sense of asynchronously communicating data) that enable developers to meet the typical business requirements of enterprises requiring integrated functionality is very Fusion-like. User experience developers can benefit from the loose coupling approach too. User expectations and work styles change all the time, and development is now about integrating SaaS through PaaS. Cloud computing offers a virtual pivot where a single source of truth (customer or employee data, for example) can be experienced through different UIs (desktop, simplified, or mobile), each optimized for the context of the user’s world of work and task completion. Smart enterprise applications developers, partners, and customers use design patterns for user experience integration benefits too. The Oracle Applications UX design patterns (and supporting guidelines) enable loose coupling of the optimized UI requirements from code. Developers can get on with the job of creating integrations through web services, APIs and SOA without having to figure out design problems about how UIs should work. Adding the already user proven UX design patterns (and supporting guidelines to your toolkit means ADF and other developers can easily offer much more than just functionality and be super productive too. Great looking application integration touchpoints can be built with our design patterns and guidelines too for a seamless applications UX. One of Oracle’s partners, Innowave Technologies used loose coupling architecture and our UX design patterns to create an integration for a customer that was scalable, cost effective, fast to develop and kept users productive while paving a roadmap for customers to keep pace with the latest UX designs over time. Innowave CEO Basheer Khan, a Fusion User Experience Advocate explains how to do it on the Usable Apps blog.

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  • How to end a relationship with a client without pissing them off?

    - by thesam18888
    Here's my situation: I'm a freelancing student and I was working on a software project for a client over the summer holidays of 2010. At the time I completed the application, tested it on my machine, delivered it to the client and went back to University. However the client is not completely satisfied with the product and apparently has found a couple of bugs with it. Ever since I went back to Uni, they have been chasing me up and asking me to spend some time to fix the bugs. I have explained that this is simply not possible as I am extremely busy with my Uni work and cannot afford to spare my time for anything else. The client is getting increasingly pissed off and have been chasing me by calling during lectures at evenings and even asking me if I could go over to their place over the weekend to talk about this. This is in turn pissing me off as well because they're essentially asking me to give up my education so that I could help them out by fixing bugs. I go to Uni 5 days a week, 9-6 and feel it is unreasonable for them to call me during evenings and to ask me to work over weekends etc. I would like to end my relationship with this client but would like to do it amicably without pissing them off. How can I do this? I really wish they would just find someone else but I was charging them piss-poor rates so I think they don't want to go to anyone else because they would have to pay more. EDIT The application does not seem to work perfectly on their machine. I had tested it extensively on my machine and it seemed to work fine. I am not sure what exactly is causing it to not work. I was paid a very low amount and it was on an hourly basis. e.g. I would send an invoice saying I worked on this for x amount of hours and they would pay me for it. Apart from the work itself, I have not charged them for all the time spent sending e-mails back and forth, phone calls, visits to their place etc. I would really like to end all my dealings with this client right away.

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  • Partners - Steer Clear of the Unknown with Oracle Enterprise Manager12c and Plug-in Extensibility

    - by Get_Specialized!
    Imagine if you just purchased a new car and as you entered the vehicle to drive it home and you found there was no steering wheel. And upon asking the dealer you were told that it was an option and you had a choice now or later of a variety of aftermarket steering wheels that fit a wide variety of automobiles. If you expected the car to already have a steering wheel designed to manage your transportation solution, you might wonder why someone would offer an application solution where its management is not offered as an option or come as part of the solution... Using management designed to support the underlying technology and that can provide management and support  for your own Oracle technology based solution can benefit your business  a variety of ways: increased customer satisfaction, reduction of support calls, margin and revenue growth. Sometimes when something is not included or recommended , customers take their own path which may not be optimal when using your solution and has later impact on the customers satisfaction or worse a negative impact on their business. As an Oracle Partner, you can reduce your research, certification, and time to market by selecting and offering management designed, developed, and supported for Oracle product technology by Oracle with Oracle Enterprise Manager 12c. For partners with solution specific management needs or seeking to differentiate themselves in the market, Enterprise Manager 12c is extensible and provides partners the opportunity to create their own plug-ins as well as a validation program for them.  Today a number of examples by partners are available and Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 /* 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-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-family:"Calibri","sans-serif"; mso-ascii- mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi- mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} more on the way from such partners as NetApp for NetApp storage and Blue Medora for VMware vSphere. To review and consider further for applicability to your solution, visit  the Oracle PartnerNetwork KnowledgeZone for Enterprise Manager under the Develop Tab http://www.oracle.com/partners/goto/enterprisemanager

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  • Powerful Lessons in Data from the Presidential Election

    - by Christina McKeon
    Now that we’ve had a few days to recover from the U.S. presidential election, it’s a good time to take a step back from politics and look for the customer experience lessons that we can take away. The most powerful lesson is that when you know more about your base, you will have an advantage over your competition. That advantage will translate into you winning and your competition losing. Michael Scherer of TIME was given access to Obama’s data analysts two days before the election. His account is documented in Inside the Secret World of the Data Crunchers Who Helped Obama Win. What we learned from Scherer’s inside view is how well Obama’s team did in getting the right data, analyzing it, and acting on it. This data team recognized how critical it was to break down data silos within the campaign. As Scherer noted, they created “a single system that merged information from pollsters, fundraisers, field workers, consumer databases, and social-media and mobile contacts with the main Democratic voter files in the swing states.” The Obama analysis was so meticulous that they knew which celebrity and which type of celebrity event would help them maximize campaign contributions. With a single system, their data models became more precise. They determined which messages were more successful with specific demographic groups and that who made the calls mattered. Data analysis also led to many other changes in Obama’s campaign including a new ad buying strategy, using social media and applications to tap into supporters’ friends, and using new social news sites. While we did not have that same inside view into Romney’s campaign, much of the post-mortem coverage indicates that Romney’s team did not have the right analysis. As Peter Hamby of CNN wrote in Analysis: Why Romney Lost, “Romney officials had modeled an electorate that looked something like a mix of 2004 and 2008….” That historical data did not account for the changing demographics in the U.S. Does your organization approach data like the Obama or Romney team? Do you really know your base? How well can you predict what is going to happen in your business? If you haven’t already put together a strategy and plan to know more, this week’s civics lesson is a powerful reason to do it sooner rather than later. Your competitors are probably thinking the same thing that you are!

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  • Oracle Brings Java to iOS Devices (and Android too)

    - by Shay Shmeltzer
    Java developer, did you ever wish that you can take your Java skills and apply them to building applications for iOS mobile devices? Well, now you can! With the new Oracle ADF Mobile solution, Oracle has created a unique technology that allows developers to use the Java language and develop applications that install and run on both iOS and Android mobile devices. The solution is based on a thin native container that installs as part of your application. The container is able to run the same application you develop unchanged on both Android and iOS devices. One part of the container is a headless lightweight JVM based on the Java ME CDC technology. This allows the execution of Java code on your mobile device. Java is used for building business logic, accessing local SQLite encrypted database, and invoking and interacting with remote services. Java concept on the UI too To further help transition Java developers to mobile developers, ADF Mobile borrows familiar concepts from the world of JSF to make the UI development experience simpler. The user interface layer of Oracle ADF Mobile is rendered with HTML5 which delivers native user experience on the devices, including animations and gesture support. Using a set of rich components, developers can create mobile pages without needing to write low level HTML5 and JavaScript code. The components cover everything from simple controls such as text fields, date pickers, buttons and links, to advanced data visualization components such as graphs, gauges and maps, and including unique mobile UI patterns such as lists, and toggle selectors. Want to see the components in action? Access this demo instance from your mobile device. Need to further customize the look and feel? You can use CSS3 to achieve this. A controller layer - similar in functionality to the JSF controller - allows developer to simplify the way they build navigation between pages. The logic behind the pages is written in managed beans with various scopes – again similar to the JSF approach. Need to interact with device features like camera, SMS, Contacts etc? Oracle conveniently packaged access to these services in a set of services that you can just drag and drop into your pages as buttons and links, or code into your managed beans Java calls to activate. Underneath the covers this layer is implemented using the open source phonegap solution. With the new Oracle ADF Mobile solution, transferring your Java skills into the Mobile world has become much easier. Check out this development experience demo. And then go and download JDeveloper and the ADF Mobile extension and try it out on your own. For more on ADF Mobile, see the ADF Mobile OTN page.

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  • Delay command execution over sockets

    - by David
    I've been trying to fix the game loop in a real time (tick delay) MUD. I realized using Thread.Sleep would seem clunky when the user spammed commands through their choice of client (Zmud, etc) e.g. east;south;southwest would wait three move ticks and then output everything from the past couple rooms. The game loop basically calls a Flush and Fill method for each socket during each tick (50ms) private void DoLoop() { Stopwatch stopWatch = new Stopwatch(); stopWatch.Start(); while (running) { // for each socket, flush and fill ConnectionMonitor.Update(); stopWatch.Stop(); WaitIfNeeded(stopWatch.ElapsedMilliseconds); stopWatch.Reset(); } } The Fill method fires the command events, but as mentioned before, they currently block using Thread.Sleep. I tried adding a "ready" flag to the state object that attempts to execute the command along with a queue of spammed commands, but it ends up executing one command and queuing up the rest i.e. each subsequent command executes something that got queued up that should've been executed before. I must be missing something about the timer. private readonly Queue<SpammedCommand> queuedCommands = new Queue<SpammedCommand>(); private bool ready = true; private void TryExecuteCommand(string input) { var commandContext = CommandContext.Create(input); var player = Server.Current.Database.Get<Player>(Session.Player.Key); var commandInfo = Server.Current.CommandLookup .FindCommand(commandContext.CommandName, player.IsAdmin); if (commandInfo != null) { if (!ready) { // queue command queuedCommands.Enqueue(new SpammedCommand() { Context = commandContext, Info = commandInfo }); return; } if (queuedCommands.Count > 0) { // queue the incoming command queuedCommands.Enqueue(new SpammedCommand() { Context = commandContext, Info = commandInfo, }); // dequeue and execute var command = queuedCommands.Dequeue(); command.Info.Command.Execute(Session, command.Context); setTimeout(command.Info.TickLength); return; } commandInfo.Command.Execute(Session, commandContext); setTimeout(commandInfo.TickLength); } else { Session.WriteLine("Command not recognized"); } } Finally, setTimeout was supposed to set the execution delay (TickLength) for that command, and makeReady just sets the ready flag on the state object to true. private void setTimeout(TickDelay tickDelay) { ready = false; var t = new System.Timers.Timer() { Interval = (long) tickDelay, AutoReset = false, }; t.Elapsed += makeReady; t.Start(); // fire this in tickDelay ms } // MAKE READYYYYY!!!! private void makeReady(object sender, System.Timers.ElapsedEventArgs e) { ready = true; } Am I missing something about the System.Timers.Timer created in setTimeout? How can I execute (and output) spammed commands per TickLength without using Thread.Sleep?

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  • Upgrades from Beta or CTP SQL Server Software is NOT Supported

    - by BuckWoody
    As of this writing, SQL Server 2008 R2 has released, and just like every release, I get e-mails and calls from folks with this question: “Can I upgrade from Customer Technical Preview (CTP) x or Beta #x or Release Candidate (RC) to the “Released to Manufacturing” (RTM) version?” No. Right up until the last minute, things are changing in the code – and you want that to happen. Our internal testing runs right up until the second we lock down for release, and we watch the CTP/RC/Beta reports to make sure there are no show-stoppers, and fix what we find. And it’s not just “big” changes you need to worry about – a simple change in one line of code can have a massive effect. I know, I know – you’ve possibly upgraded an RC or CTP to the RTM version and it worked “just fine”. But hear this tale: I’ve dealt with someone who faced this exact situation in SQL Server 2008. They upgraded (which is clearly prohibited in the documentation) from a CTP to the RTM version over a year ago. Everything was working fine. But then…one day they had an issue. Couldn’t fix it themselves, we took a look, days went by, and we finally had to call in the big guns for support. Turns out, the upgrade was the problem. So we had to come up with some elaborate schemes to get the system migrated over while they were in production. This was painful for everyone involved. So the answer is still no. Just don’t do it. There is one caveat to this story – if you are a “TAP” customer (you’ll know if you are), we help you move from the CTP products to RTM, but that’s a special case that we track carefully and send along special instructions and tools to help you along. That level of effort isn’t possible on a large scale, so it’s not just a magic tool that we run to upgrade from CTP to RTM. So again, unless you’re a TAP customer, it’s a no-no. Share this post: email it! | bookmark it! | digg it! | reddit! | kick it! | live it!

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  • A solution for a PHP website without a framework

    - by lortabac
    One of our customers asked us to add some dynamic functionality to an existent website, made of several static HTML pages. We normally work with an MVC framework (mostly CodeIgniter), but in this case moving everything to a framework would require too much time. Since it is not a big project, not having the full functionality of a framework is not a problem. But the question is how to keep code clean. The solution I came up with is to divide code in libraries (the application's API) and models. So inside HTML there will only be API calls, and readability will not be sacrificed. I implemented this with a sort of static Registry (sorry if I'm wrong, I am not a design pattern expert): <?php class Custom_framework { //Global database instance private static $db; //Registered models private static $models = array(); //Registered libraries private static $libraries = array(); //Returns a database class instance static public function get_db(){ if(isset(self::$db)){ //If instance exists, returns it return self::$db; } else { //If instance doesn't exists, creates it self::$db = new DB; return self::$db; } } //Returns a model instance static public function get_model($model_name){ if(isset(self::$models[$model_name])){ //If instance exists, returns it return self::$models[$model_name]; } else { //If instance doesn't exists, creates it if(is_file(ROOT_DIR . 'application/models/' . $model_name . '.php')){ include_once ROOT_DIR . 'application/models/' . $model_name . '.php'; self::$models[$model_name] = new $model_name; return self::$models[$model_name]; } else { return FALSE; } } } //Returns a library instance static public function get_library($library_name){ if(isset(self::$libraries[$library_name])){ //If instance exists, returns it return self::$libraries[$library_name]; } else { //If instance doesn't exists, creates it if(is_file(ROOT_DIR . 'application/libraries/' . $library_name . '.php')){ include_once ROOT_DIR . 'application/libraries/' . $library_name . '.php'; self::$libraries[$library_name] = new $library_name; return self::$libraries[$library_name]; } else { return FALSE; } } } } Inside HTML, API methods are accessed like this: <?php echo Custom_framework::get_library('My_library')->my_method(); ?> It looks to me as a practical solution. But I wonder what its drawbacks are, and what the possible alternatives.

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  • Code Design question, circular reference across classes?

    - by dsollen
    I have no code here, as this is more of a design question (I assume this is still the best place to ask it). I have a very simple server in java which stores a mapping between certain values and UUID which are to be used by many systems across multiple platforms. It accepts a connection from a client and creates a clientSocket which stores the socket and all the other relevant data unique to that connection. Each clientSocket will run in their own thread and will block on the socket waiting for a read. I expect very little strain on this system, it will rarely get called, but when it does get a call it will need to respond quickly and due to the risk of it having a peak time with multiple calls coming in at once threaded is still better. Each thread has a reference to a Mapper class which stores the mapping of UUID which it's reporting to others (with proper synchronization of course). This all works until I have to add a new UUID to the list. When this happens I want to report to all clients that care about that particular UUID that a new one was added. I can't multicast (limitation of the system I'm running on) so I'm having each socket send the message to the client through the established socket. However, since each thread only knows about the socket it's waiting on I didn't have a clear method of looking up every thread/socket that cares about the data to inform them of the new UUID. Polling is out mostly because it seems a little too convoluted to try to maintain a list of newly added UUID. My solution as of now is to have the 'parent' class which creates the mapper class and spawns all the threads pass itself as an argument to the mapper. Then when the mapper creates a new UUID it can make a call to the parent class telling it to send out updates to all the other sockets that care about the change. I'm concerned that this may be a bad design due to the use of a circular reference; parent has a reference to mapper (to pass it to new ClientSocket threads) and mapper points to parent. It doesn't really feel like a bad design to me but I wanted to check since circular references are suppose to be bad. Note: I realize this means that the thread associated with whatever socket originally received the request that spawned the creation of a UUID is going to pay the 'cost' of outputting to all the other clients that care about the new UUID. I don't care about this; as I said I suspect the client to receive only intermittent messages. It's unlikely for one socket to receive multiple messages at one time, and there won't be that many sockets so it shouldn't take too long to send messages to each of them. Perhaps later I'll fix the fact that I'm saddling higher work load on whatever unfortunate thread gets the first request; but for now I think it's fine.

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  • How do you make a bullet ricochet off a vertical wall?

    - by Bagofsheep
    First things first. I am using C# with XNA. My game is top-down and the player can shoot bullets. I've managed to get the bullets to ricochet correctly off horizontal walls. Yet, despite using similar methods (e.g. http://stackoverflow.com/questions/3203952/mirroring-an-angle) and reading other answered questions about this subject I have not been able to get the bullets to ricochet off a vertical wall correctly. Any method I've tried has failed and sometimes made ricocheting off a horizontal wall buggy. Here is the collision code that calls the ricochet method: //Loop through returned tile rectangles from quad tree to test for wall collision. If a collision occurs perform collision logic. for (int r = 0; r < returnObjects.Count; r++) if (Bullets[i].BoundingRectangle.Intersects(returnObjects[r])) Bullets[i].doCollision(returnObjects[r]); Now here is the code for the doCollision method. public void doCollision(Rectangle surface) { if (Ricochet) doRicochet(surface); else Trash = true; } Finally, here is the code for the doRicochet method. public void doRicochet(Rectangle surface) { if (Position.X > surface.Left && Position.X < surface.Right) { //Mirror the bullet's angle. Rotation = -1 * Rotation; //Moves the bullet in the direction of its rotation by given amount. moveFaceDirection(Sprite.Width * BulletScale.X); } else if (Position.Y > surface.Top && Position.Y < surface.Bottom) { } } Since I am only dealing with vertical and horizontal walls at the moment, the if statements simply determine if the object is colliding from the right or left, or from the top or bottom. If the object's X position is within the boundaries of the tile's X boundaries (left and right sides), it must be colliding from the top, and vice verse. As you can see, the else if statement is empty and is where the correct code needs to go.

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  • Tricky situation with EF and Include while projecting (Select / SelectMany)

    - by Vincent Grondin
    Originally posted on: http://geekswithblogs.net/vincentgrondin/archive/2014/06/07/tricky-situation-with-ef-and-include-while-projecting-select.aspxHello, the other day I stumbled on a problem I had a while back with EF and Include method calls and decided this was it and I was going to blog about it…  This would sort of to pin it inside my head and maybe help others too !  So I was using DBContext and wanted to query a DBSet and include some of it’s associations and in the end, do a projection to get a list of Ids…   At first it seems easy…  Query your DBSet, call Include right afterward, then code the rest of your statement with the appropriate where clause and then, do the projection…   Well it wasn’t that easy as my query required I code my where on some entities a few degree further in the association chain and most of these links where “Many”…  I had to do my projection right away with the SelectMany method.  So I did my stuff and tested the query….  no association where loaded…  My Include statement was simply ignored !  Then I remembered this behavior and how to get it to work…  You need to move the Include AFTER your first projection (Select or SelectMany).  So my sequence became:   Query the DBSet, do the projection with SelectMany, Include the associations, code the where clause and do the final projection…. but it wouldn’t compile…   It kept saying that it could not find an “Include” method on an IQueryable… which is perfectly true!  I knew this should work so I went to the definition of the DBset and saw it inherited DBQuery and sure enough the include method was there…  So I had to cast my statement from start until the end of the first projection in a DBQuery then do the Includes and then the rest of my query….   Bottom line is, whenever your Include statement seem to be ignored, then maybe you will need to move them further down in your query and cast your statement in whatever class gives you access to the Include…   Happy coding all !

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  • How can I cleanly and elegantly handle data and dependancies between classes

    - by Neophyte
    I'm working on 2d topdown game in SFML 2, and need to find an elegant way in which everything will work and fit together. Allow me to explain. I have a number of classes that inherit from an abstract base that provides a draw method and an update method to all the classes. In the game loop, I call update and then draw on each class, I imagine this is a pretty common approach. I have classes for tiles, collisions, the player and a resource manager that contains all the tiles/images/textures. Due to the way input works in SFML I decided to have each class handle input (if required) in its update call. Up until now I have been passing in dependencies as needed, for example, in the player class when a movement key is pressed, I call a method on the collision class to check if the position the player wants to move to will be a collision, and only move the player if there is no collision. This works fine for the most part, but I believe it can be done better, I'm just not sure how. I now have more complex things I need to implement, eg: a player is able to walk up to an object on the ground, press a key to pick it up/loot it and it will then show up in inventory. This means that a few things need to happen: Check if the player is in range of a lootable item on keypress, else do not proceed. Find the item. Update the sprite texture on the item from its default texture to a "looted" texture. Update the collision for the item: it might have changed shape or been removed completely. Inventory needs to be updated with the added item. How do I make everything communicate? With my current system I will end up with my classes going out of scope, and method calls to each other all over the place. I could tie up all the classes in one big manager and give each one a reference to the parent manager class, but this seems only slightly better. Any help/advice would be greatly appreciated! If anything is unclear, I'm happy to expand on things.

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  • Organization &amp; Architecture UNISA Studies &ndash; Chap 13

    - by MarkPearl
    Learning Outcomes Explain the advantages of using a large number of registers Discuss the way in which compilers optimize register usage Discuss the evolution of CISC machines Describe the characteristics of RISC architecture Discuss the RISC vs. CISC controversy Describe the way in which RISC and CISC design principles can be combined Instruction Execution Characteristics To understand the the line of reasoning of RISC advocates, we need a brief overview of instruction execution characteristics. These include… Operations Operands Procedure Calls These three sections can be studied in depth in the textbook at pages 503 - 505 A number of groups have come up with the conclusion that the attempt to make the instruction set architecture closer to HLLs (High Level Languages) is not the most effective design strategy. Rather HLL’s can be best supported by optimizing performance of the most time-consuming features of typical HLL programs. Generally 3 main characteristics came up to improve performance… Use a large number of registers or use a compiler to optimize register usage Careful attention needs to be paid to the design of instruction pipelines A simplified (reduced) instruction set is indicated The use of a large register optimization One of the most important design principles of RISC machines is the use of a large number of registers. The concept of register windows and the use of a large register file versus the use of cache memory are discussed. On the face of it, the use of a large set of registers should decrease the need to access memory. The design task is to organize the registers in such a fashion that this goal is realized. Read page 507 – 510 for a detailed explanation. Compiler-based register optimization   Reduced Instructions Set Architecture There are two advantages to smaller programs… Because the program takes up less memory, there is a savings in that resource (this was more compelling when memory was more expensive) Smaller programs should improve performance, and this will happen in two ways – fewer instructions means fewer instruction bytes to be fetched and in a paging environment smaller programs occupy fewer pages, reducing page faults. Certain characteristics are common to RISC processors… One instruction per cycle Register-to-register operations Simple addressing modes Simple instruction formats RISC vs. CISC After initial enthusiasm for RISC machines, there has been a growing realization that RISC designs may benefit from the inclusion of some CISC features CISC designs may benefit from the inclusion of some RISC features

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  • Setting uniform value of a vertex shader for different sprites in a SpriteBatch

    - by midasmax
    I'm using libGDX and currently have a simple shader that does a passthrough, except for randomly shifting the vertex positions. This shift is a vec2 uniform that I set within my code's render() loop. It's declared in my vertex shader as uniform vec2 u_random. I have two different kind of Sprites -- let's called them SpriteA and SpriteB. Both are drawn within the same SpriteBatch's begin()/end() calls. Prior to drawing each sprite in my scene, I check the type of the sprite. If sprite instance of SpriteA: I set the uniform u_random value to Vector2.Zero, meaning that I don't want any vertex changes for it. If sprite instance of SpriteB, I set the uniform u_random to Vector2(MathUtils.random(), MathUtils.random(). The expected behavior was that all the SpriteA objects in my scene won't experience any jittering, while all SpriteB objects would be jittering about their positions. However, what I'm experiencing is that both SpriteA and SpriteB are jittering, leading me to believe that the u_random uniform is not actually being set per Sprite, and being applied to all sprites. What is the reason for this? And how can I fix this such that the vertex shader correctly accepts the uniform value set to affect each sprite individually? passthrough.vsh attribute vec4 a_color; attribute vec3 a_position; attribute vec2 a_texCoord0; uniform mat4 u_projTrans; uniform vec2 u_random; varying vec4 v_color; varying vec2 v_texCoord; void main() { v_color = a_color; v_texCoord = a_texCoord0; vec3 temp_position = vec3( a_position.x + u_random.x, a_position.y + u_random.y, a_position.z); gl_Position = u_projTrans * vec4(temp_position, 1.0); } Java Code this.batch.begin(); this.batch.setShader(shader); for (Sprite sprite : sprites) { Vector2 v = Vector2.Zero; if (sprite instanceof SpriteB) { v.x = MathUtils.random(-1, 1); v.y = MathUtils.random(-1, 1); } shader.setUniformf("u_random", v); sprite.draw(this.batch); } this.batch.end();

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  • PHP - Internal APIs/Libraries - What makes sense?

    - by Mark Locker
    I've been having a discussion lately with some colleagues about the best way to approach a new project, and thought it'd be interesting to get some external thoughts thrown into the mix. Basically, we're redeveloping a fairly large site (written in PHP) and have differing opinions on how the platform should be setup. Requirements: The platform will need to support multiple internal websites, as well as external (non-PHP) projects which at the moment consist of a mobile app and a toolbar. We have no plans/need in the foreseeable future to open up an API externally (for use in products other than our own). My opinion: We should have a library of well documented native model classes which can be shared between projects. These models will represent everything in our database and can take advantage of object orientated features such as inheritance, traits, magic methods, etc. etc. As well as employing ORM. We can then add an API layer on top of these models which can basically accept requests and route them to the appropriate methods, translating the response so that it can be used platform independently. This routing for each method can be setup as and when it's required. Their opinion: We should have a single HTTP API which is used by all projects (internal PHP ones or otherwise). My thoughts: To me, there are a number of issues with using the sole HTTP API approach: It will be very expensive performance wise. One page request will result in several additional http requests (which although local, are still ones that Apache will need to handle). You'll lose all of the best features PHP has for OO development. From simple inheritance, to employing the likes of ORM which can save you writing a lot of code. For internal projects, the actual process makes me cringe. To get a users name, for example, a request would go out of our box, over the LAN, back in, then run through a script which calls a method, JSON encodes the output and feeds that back. That would then need to be JSON decoded, and be presented as an array ready to use. Working with arrays, as appose to objects, makes me sad in a modern PHP framework. Their thoughts (and my responses): Having one method of doing thing keeps things simple. - You'd only do things differently if you were using a different language anyway. It will become robust. - Seeing as the API will run off the library of models, I think my option would be just as robust. What do you think? I'd be really interested to hear the thoughts of others on this, especially as opinions on both sides are not founded on any past experience.

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  • Rebuilding a Mac Mini (early 2009)

    - by Kelly Jones
    This weekend I decided to rebuild the family’s Mac Mini.  It’s the early 2009 model and I hadn’t done it since we got it in March of 2009.  Even worse, I had done the import data step (or whatever Apple calls it) which brought over all of the data files and apps from our previous Mac.  AND that install goes back to before 2005, as far as I can remember.  SO, to say that “cruft” had built up in the operating system, is probably a bit of an understatement. The rebuild went pretty smoothly, especially since I had a couple of spare hard drives.  I hooked up a spare USB drive and formatted it for use with the Mac.  I then used Carbon Copy to clone the internal hard drive onto the USB drive.  (Carbon Copy is a great little app that I used several years ago and I was happy to see it was not only still around, but updated as well.) Once I had my backup, I shut down the Mac and replaced the internal hard drive.  I had purchased the hard drive last fall to use with my work laptop, but I got a new work laptop (with awesome dual SSDs) so I wasn’t using it anymore.  The replacement drive (Seagate Momentus 7200.4 ST9500420AS 500GB 7200 RPM 2.5" SATA 3.0Gb/s Internal Notebook Hard Drive) has more than double the original’s capacity and is also faster.  I’ll have to keep an eye on the temperature, since that 7200 drive will run hotter. Opening the Mac Mini is not for the easily intimidated!  That cool little case is quite the pain to open.  Luckily, OWC put a video together here.  After replacing the drive, I then installed a clean copy of OS 10.5 using the DVDs that came with the Mac.  After the OS, it was time to reinstall the apps.  I downloaded some of the freeware, just to make sure I had the latest versions.  For the rest, I just copied from the backup cloned drive to the new drive.  (I love the way most Mac apps are written – with almost everything contained within a “package” that I can just copy from one drive to another.  MUCH better than the Windows way of using shared DLLs and the registry to store critical pieces that the app needs in order to run!) The whole process took longer than I would have preferred, but it was long overdue.  It definitely “feels” faster, especially boot time and application launches.

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

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

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  • Encapsulating code in F# (Part 1)

    - by MarkPearl
    I have been looking at F# for a while now and seem a few really interesting samples and snippets on howto’s. This has been great to see the basic outline of the language and the possibilities, however a nagging question in the back of my mind has been what does an F# project look like? How do I code group code in F# so that it can be modularized and brought in and out of a project easily? My Expert F# book has an entire chapter (7) dedicated to this and after browsing the other chapters of the book I decided that this topic was something I really wanted to know more about now! Because of my C# background I keep trying to think in F# of objects. So to try and get a clearer idea of how to do things the F# way I am first going to take a very simplified C# example and try to “translate” it. using System; namespace ConsoleApplication1 { namespace ExampleOfEncapsulationInCSharp { class Program { static void EncapsulatedVariableInAMethod() { int count = 10; Console.WriteLine(count); } static void Main(string[] args) { EncapsulatedVariableInAMethod(); Console.ReadLine(); } } } } From the above example the count integer is encapsulated within EncapsulatedVariableInAMethod method. You couldn’t access the count variable from outside the scope of its parent method but have full access to it within the method. Lets look at my F# equivalent… open System let EncapsulatedVariableInAMethod = let count = 10 Console.WriteLine(count) () EncapsulatedVariableInAMethod Console.ReadLine()   Now, when I first attempted to write the F# code I got stuck… I didn’t have the Console.WriteLine calls but had the following… open System let EncapsulatedVariableInAMethod = let count = 10 EncapsulatedVariableInAMethod Console.ReadLine()   The compiler didn’t like the let before the count = 10. This is because every F# expression must evaluate to a value. If I did not want to make the Console call, I would still need to evaluate the expression to something – and for this reason the Unit Type is provided. I could have done something like…. open System let EncapsulatedVariableInAMethod = let count = 10 () EncapsulatedVariableInAMethod Console.ReadLine()   Which the compiler would be happy with…

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  • Does OO, TDD, and Refactoring to Smaller Functions affect Speed of Code?

    - by Dennis
    In Computer Science field, I have noticed a notable shift in thinking when it comes to programming. The advice as it stands now is write smaller, more testable code refactor existing code into smaller and smaller chunks of code until most of your methods/functions are just a few lines long write functions that only do one thing (which makes them smaller again) This is a change compared to the "old" or "bad" code practices where you have methods spanning 2500 lines, and big classes doing everything. My question is this: when it call comes down to machine code, to 1s and 0s, to assembly instructions, should I be at all concerned that my class-separated code with variety of small-to-tiny functions generates too much extra overhead? While I am not exactly familiar with how OO code and function calls are handled in ASM in the end, I do have some idea. I assume that each extra function call, object call, or include call (in some languages), generate an extra set of instructions, thereby increasing code's volume and adding various overhead, without adding actual "useful" code. I also imagine that good optimizations can be done to ASM before it is actually ran on the hardware, but that optimization can only do so much too. Hence, my question -- how much overhead (in space and speed) does well-separated code (split up across hundreds of files, classes, and methods) actually introduce compared to having "one big method that contains everything", due to this overhead? UPDATE for clarity: I am assuming that adding more and more functions and more and more objects and classes in a code will result in more and more parameter passing between smaller code pieces. It was said somewhere (quote TBD) that up to 70% of all code is made up of ASM's MOV instruction - loading CPU registers with proper variables, not the actual computation being done. In my case, you load up CPU's time with PUSH/POP instructions to provide linkage and parameter passing between various pieces of code. The smaller you make your pieces of code, the more overhead "linkage" is required. I am concerned that this linkage adds to software bloat and slow-down and I am wondering if I should be concerned about this, and how much, if any at all, because current and future generations of programmers who are building software for the next century, will have to live with and consume software built using these practices. UPDATE: Multiple files I am writing new code now that is slowly replacing old code. In particular I've noted that one of the old classes was a ~3000 line file (as mentioned earlier). Now it is becoming a set of 15-20 files located across various directories, including test files and not including PHP framework I am using to bind some things together. More files are coming as well. When it comes to disk I/O, loading multiple files is slower than loading one large file. Of course not all files are loaded, they are loaded as needed, and disk caching and memory caching options exist, and yet still I believe that loading multiple files takes more processing than loading a single file into memory. I am adding that to my concern.

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  • "Whole-team" C++ features?

    - by Blaisorblade
    In C++, features like exceptions impact your whole program: you can either disable them in your whole program, or you need to deal with them throughout your code. As a famous article on C++ Report puts it: Counter-intuitively, the hard part of coding exceptions is not the explicit throws and catches. The really hard part of using exceptions is to write all the intervening code in such a way that an arbitrary exception can propagate from its throw site to its handler, arriving safely and without damaging other parts of the program along the way. Since even new throws exceptions, every function needs to provide basic exception safety — unless it only calls functions which guarantee throwing no exception — unless you disable exceptions altogether in your whole project. Hence, exceptions are a "whole-program" or "whole-team" feature, since they must be understood by everybody in a team using them. But not all C++ features are like that, as far as I know. A possible example is that if I don't get templates but I do not use them, I will still be able to write correct C++ — or will I not?. I can even call sort on an array of integers and enjoy its amazing speed advantage wrt. C's qsort (because no function pointer is called), without risking bugs — or not? It seems templates are not "whole-team". Are there other C++ features which impact code not directly using them, and are hence "whole-team"? I am especially interested in features not present in C. Update: I'm especially looking for features where there's no language-enforced sign you need to be aware of them. The first answer I got mentioned const-correctness, which is also whole-team, hence everybody needs to learn about it; however, AFAICS it will impact you only if you call a function which is marked const, and the compiler will prevent you from calling it on non-const objects, so you get something to google for. With exceptions, you don't even get that; moreover, they're always used as soon as you use new, hence exceptions are more "insidious". Since I can't phrase this as objectively, though, I will appreciate any whole-team feature. Appendix: Why this question is objective (if you wonder) C++ is a complex language, so many projects or coding guides try to select "simple" C++ features, and many people try to include or exclude some ones according to mostly subjective criteria. Questions about that get rightfully closed regularly here on SO. Above, instead, I defined (as precisely as possible) what a "whole-team" language feature is, provide an example (exceptions), together with extensive supporting evidence in the literature about C++, and ask for whole-team features in C++ beyond exceptions. Whether you should use "whole-team" features, or whether that's a relevant concept, might be subjective — but that only means the importance of this question is subjective, like always.

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  • Threads slowing down application and not working properly

    - by Belgin
    I'm making a software renderer which does per-polygon rasterization using a floating point digital differential analyzer algorithm. My idea was to create two threads for rasterization and have them work like so: one thread draws each even scanline in a polygon and the other thread draws each odd scanline, and they both start working at the same time, but the main application waits for both of them to finish and then pauses them before continuing with other computations. As this is the first time I'm making a threaded application, I'm not sure if the following method for thread synchronization is correct: First of all, I use two global variables to control the two threads, if a global variable is set to 1, that means the thread can start working, otherwise it must not work. This is checked by the thread running an infinite loop and if it detects that the global variable has changed its value, it does its job and then sets the variable back to 0 again. The main program also uses an empty while to check when both variables become 0 after setting them to 1. Second, each thread is assigned a global structure which contains information about the triangle that is about to be rasterized. The structures are filled in by the main program before setting the global variables to 1. My dilemma is that, while this process works under some conditions, it slows down the program considerably, and also it fails to run properly when compiled for Release in Visual Studio, or when compiled with any sort of -O optimization with gcc (i.e. nothing on screen, even SEGFAULTs). The program isn't much faster by default without threads, which you can see for yourself by commenting out the #define THREADS directive, but if I apply optimizations, it becomes much faster (especially with gcc -Ofast -march=native). N.B. It might not compile with gcc because of fscanf_s calls, but you can replace those with the usual fscanf, if you wish to use gcc. Because there is a lot of code, too much for here or pastebin, I created a git repository where you can view it. My questions are: Why does adding these two threads slow down my application? Why doesn't it work when compiling for Release or with optimizations? Can I speed up the application with threads? If so, how? Thanks in advance.

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  • I have a performance problem

    - by Alan
    (copied from my wordpress blog). So start 95% of the performance calls that I receive. They usually continue something like: I have gathered some *stat data for you (eg the guds tool from Document 1285485.1), can you please root cause our problem? So, do you think you could? Neither can I, based on this my answer inevitably has to be "No". Given this kind of problem statement, I have no idea about the expectations, the boundary conditions, or even the application. The answer may as well be "Performance problems? Consult your local Doctor for Viagra". It's really not a lot to go on. So, What kind of problem description is going to allow me to start work on the issue that is being seen? I don't doubt that there really is an issue, it just needs to be pinned down somewhat. What behavior exactly are you expecting to see? Be specific and use business metrics. For example "run-time", "response-time" and "throughput". This helps us define exit criterea. Now, let's look at the system that is having problems. How is what you are seeing different? Use the same type of metrics. The answers to these two questions take us a long way towards being able to work a call. Even more helpful are answers to questions like Has this system ever worked to expectation? If so, when did it start exhibiting this behavior? Is the problem always present, or does it sometimes work to expectation? If it sometimes works to expectation, when are you seeing the problem? Is there any discernible pattern? Is the impact of the problem getting better, worse, or remaining constant? What kind of differences are there between when the system was performing to expectation and when it is not? Are there other machines where we could expect to see the same issue (eg similar usage and load), but are not? Again, differences? Once we start to gather information like this we start to build up a much clearer picture of exactly what we need to investigate, and what we need to achieve so that both you and me agree that the problem has been solved. Please help get that figure of poorly defined problem statements down from it's current 95% value.

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