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  • Tips on Migrating from AquaLogic .NET Accelerator to WebCenter WSRP Producer for .NET

    - by user647124
    This year I embarked on a journey to migrate a group of ASP.NET web applications developed to integrate with WebLogic Portal 9.2 via the AquaLogic® Interaction .NET Application Accelerator 1.0 to instead use the Oracle WebCenter WSRP Producer for .NET and integrated with WebLogic Portal 10.3.4. It has been a very winding path and this blog entry is intended to share both the lessons learned and relevant approaches that led to those learnings. Like most journeys of discovery, it was not a direct path, and there are notes to let you know when it is practical to skip a section if you are in a hurry to get from here to there. For the Curious From the perspective of necessity, this section would be better at the end. If it were there, though, it would probably be read by far fewer people, including those that are actually interested in these types of sections. Those in a hurry may skip past and be none the worst for it in dealing with the hands-on bits of performing a migration from .NET Accelerator to WSRP Producer. For others who want to talk about why they did what they did after they did it, or just want to know for themselves, enjoy. A Brief (and edited) History of the WSRP for .NET Technologies (as Relevant to the this Post) Note: This section is for those who are curious about why the migration path is not as simple as many other Oracle technologies. You can skip this section in its entirety and still be just as competent in performing a migration as if you had read it. The currently deployed architecture that was to be migrated and upgraded achieved initial integration between .NET and J2EE over the WSRP protocol through the use of The AquaLogic Interaction .NET Application Accelerator. The .NET Accelerator allowed the applications that were written in ASP.NET and deployed on a Microsoft Internet Information Server (IIS) to interact with a WebLogic Portal application deployed on a WebLogic (J2EE application) Server (both version 9.2, the state of the art at the time of its creation). At the time this architectural decision for the application was made, both the AquaLogic and WebLogic brands were owned by BEA Systems. The AquaLogic brand included products acquired by BEA through the acquisition of Plumtree, whose flagship product was a portal platform available in both J2EE and .NET versions. As part of this dual technology support an adaptor was created to facilitate the use of WSRP as a communication protocol where customers wished to integrate components from both versions of the Plumtree portal. The adapter evolved over several product generations to include a broad array of both standard and proprietary WSRP integration capabilities. Later, BEA Systems was acquired by Oracle. Over the course of several years Oracle has acquired a large number of portal applications and has taken the strategic direction to migrate users of these myriad (and formerly competitive) products to the Oracle WebCenter technology stack. As part of Oracle’s strategic technology roadmap, older portal products are being schedule for end of life, including the portal products that were part of the BEA acquisition. The .NET Accelerator has been modified over a very long period of time with features driven by users of that product and developed under three different vendors (each a direct competitor in the same solution space prior to merger). The Oracle WebCenter WSRP Producer for .NET was introduced much more recently with the key objective to specifically address the needs of the WebCenter customers developing solutions accessible through both J2EE and .NET platforms utilizing the WSRP specifications. The Oracle Product Development Team also provides these insights on the drivers for developing the WSRP Producer: ***************************************** Support for ASP.NET AJAX. Controls using the ASP.NET AJAX script manager do not function properly in the Application Accelerator for .NET. Support 2 way SSL in WLP. This was not possible with the proxy/bridge set up in the existing Application Accelerator for .NET. Allow developers to code portlets (Web Parts) using the .NET framework rather than a proprietary framework. Developers had to use the Application Accelerator for .NET plug-ins to Visual Studio to manage preferences and profile data. This is now replaced with the .NET Framework Personalization (for preferences) and Profile providers. The WSRP Producer for .NET was created as a new way of developing .NET portlets. It was never designed to be an upgrade path for the Application Accelerator for .NET. .NET developers would create new .NET portlets with the WSRP Producer for .NET and leave any existing .NET portlets running in the Application Accelerator for .NET. ***************************************** The advantage to creating a new solution for WSRP is a product that is far easier for Oracle to maintain and support which in turn improves quality, reliability and maintainability for their customers. No changes to J2EE applications consuming the WSRP portlets previously rendered by the.NET Accelerator is required to migrate from the Aqualogic WSRP solution. For some customers using the .NET Accelerator the challenge is adapting their current .NET applications to work with the WSRP Producer (or any other WSRP adapter as they are proprietary by nature). Part of this adaptation is the need to deploy the .NET applications as a child to the WSRP producer web application as root. Differences between .NET Accelerator and WSRP Producer Note: This section is for those who are curious about why the migration is not as pluggable as something such as changing security providers in WebLogic Server. You can skip this section in its entirety and still be just as competent in performing a migration as if you had read it. The basic terminology used to describe the participating applications in a WSRP environment are the same when applied to either the .NET Accelerator or the WSRP Producer: Producer and Consumer. In both cases the .NET application serves as what is referred to as a WSRP environment as the Producer. The difference lies in how the two adapters create the WSRP translation of the .NET application. The .NET Accelerator, as the name implies, is meant to serve as a quick way of adding WSRP capability to a .NET application. As such, at a high level, the .NET Accelerator behaves as a proxy for requests between the .NET application and the WSRP Consumer. A WSRP request is sent from the consumer to the .NET Accelerator, the.NET Accelerator transforms this request into an ASP.NET request, receives the response, then transforms the response into a WSRP response. The .NET Accelerator is deployed as a stand-alone application on IIS. The WSRP Producer is deployed as a parent application on IIS and all ASP.NET modules that will be made available over WSRP are deployed as children of the WSRP Producer application. In this manner, the WSRP Producer acts more as a Request Filter than a proxy in the WSRP transactions between Producer and Consumer. Highly Recommended Enabling Logging Note: You can skip this section now, but you will most likely want to come back to it later, so why not just read it now? Logging is very helpful in tracking down the causes of any anomalies during testing of migrated portlets. To enable the WSRP Producer logging, update the Application_Start method in the Global.asax.cs for your .NET application by adding log4net.Config.XmlConfigurator.Configure(); IIS logs will usually (in a standard configuration) be in a sub folder under C:\WINDOWS\system32\LogFiles\W3SVC. WSRP Producer logs will be found at C:\Oracle\Middleware\WSRPProducerForDotNet\wsrpdefault\Logs\WSRPProducer.log InputTrace.webinfo and OutputTrace.webinfo are located under C:\Oracle\Middleware\WSRPProducerForDotNet\wsrpdefault and can be useful in debugging issues related to markup transformations. Things You Must Do Merge Web.Config Note: If you have been skipping all the sections that you can, now is the time to stop and pay attention J Because the existing .NET application will become a sub-application to the WSRP Producer, you will want to merge required settings from the existing Web.Config to the one in the WSRP Producer. Use the WSRP Producer Master Page The Master Page installed for the WSRP Producer provides common, hiddenform fields and JavaScripts to facilitate portlet instance management and display configuration when the child page is being rendered over WSRP. You add the Master Page by including it in the <@ Page declaration with MasterPageFile="~/portlets/Resources/MasterPages/WSRP.Master" . You then replace: <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" > <HTML> <HEAD> With <asp:Content ID="ContentHead1" ContentPlaceHolderID="wsrphead" Runat="Server"> And </HEAD> <body> <form id="theForm" method="post" runat="server"> With </asp:Content> <asp:Content ID="ContentBody1" ContentPlaceHolderID="Main" Runat="Server"> And finally </form> </body> </HTML> With </asp:Content> In the event you already use Master Pages, adapt your existing Master Pages to be sub masters. See Nested ASP.NET Master Pages for a detailed reference of how to do this. It Happened to Me, It Might Happen to You…Or Not Watch for Use of Session or Request in OnInit In the event the .NET application being modified has pages developed to assume the user has been authenticated in an earlier page request there may be direct or indirect references in the OnInit method to request or session objects that may not have been created yet. This will vary from application to application, so the recommended approach is to test first. If there is an issue with a page running as a WSRP portlet then check for potential references in the OnInit method (including references by methods called within OnInit) to session or request objects. If there are, the simplest solution is to create a new method and then call that method once the necessary object(s) is fully available. I find doing this at the start of the Page_Load method to be the simplest solution. Case Sensitivity .NET languages are not case sensitive, but Java is. This means it is possible to have many variations of SRC= and src= or .JPG and .jpg. The preferred solution is to make these mark up instances all lower case in your .NET application. This will allow the default Rewriter rules in wsrp-producer.xml to work as is. If this is not practical, then make duplicates of any rules where an issue is occurring due to upper or mixed case usage in the .NET application markup and match the case in use with the duplicate rule. For example: <RewriterRule> <LookFor>(href=\"([^\"]+)</LookFor> <ChangeToAbsolute>true</ChangeToAbsolute> <ApplyTo>.axd,.css</ApplyTo> <MakeResource>true</MakeResource> </RewriterRule> May need to be duplicated as: <RewriterRule> <LookFor>(HREF=\"([^\"]+)</LookFor> <ChangeToAbsolute>true</ChangeToAbsolute> <ApplyTo>.axd,.css</ApplyTo> <MakeResource>true</MakeResource> </RewriterRule> While it is possible to write a regular expression that will handle mixed case usage, it would be long and strenous to test and maintain, so the recommendation is to use duplicate rules. Is it Still Relative? Some .NET applications base relative paths with a fixed root location. With the introduction of the WSRP Producer, the root has moved up one level. References to ~/ will need to be updated to ~/portlets and many ../ paths will need another ../ in front. I Can See You But I Can’t Find You This issue was first discovered while debugging modules with code that referenced the form on a page from the code-behind by name and/or id. The initial error presented itself as run-time error that was difficult to interpret over WSRP but seemed clear when run as straight ASP.NET as it indicated that the object with the form name did not exist. Since the form name was no longer valid after implementing the WSRP Master Page, the likely fix seemed to simply update the references in the code. However, as the WSRP Master Page is external to the code, a compile time error resulted: Error      155         The name 'form1' does not exist in the current context                C:\Oracle\Middleware\WSRPProducerForDotNet\wsrpdefault\portlets\legacywebsite\module\Screens \Reporting.aspx.cs                51           52           legacywebsite.module Much hair-pulling research later it was discovered that it was the use of the FindControl method causing the issue. FindControl doesn’t work quite as expected once a Master Page has been introduced as the controls become embedded in controls, require a recursion to find them that is not part of the FindControl method. In code where the page form is referenced by name, there are two steps to the solution. First, the form needs to be referenced in code generically with Page.Form. For example, this: ToggleControl ctrl = new ToggleControl(frmManualEntry, FunctionLibrary.ParseArrayLst(userObj.Roles)); Becomes this: ToggleControl ctrl = new ToggleControl(Page.Form, FunctionLibrary.ParseArrayLst(userObj.Roles)); Generally the form id is referenced in most ASP.NET applications as a path to a control on the form. To reach the control once a MasterPage has been added requires an additional method to recurse through the controls collections within the form and find the control ID. The following method (found at Rick Strahl's Web Log) corrects this very nicely: public static Control FindControlRecursive(Control Root, string Id) { if (Root.ID == Id) return Root; foreach (Control Ctl in Root.Controls) { Control FoundCtl = FindControlRecursive(Ctl, Id); if (FoundCtl != null) return FoundCtl; } return null; } Where the form name is not referenced, simply using the FindControlRecursive method in place of FindControl will be all that is necessary. Following the second part of the example referenced earlier, the method called with Page.Form changes its value extraction code block from this: Label lblErrMsg = (Label)frmRef.FindControl("lblBRMsg" To this: Label lblErrMsg = (Label) FunctionLibrary.FindControlRecursive(frmRef, "lblBRMsg" The Master That Won’t Step Aside In most migrations it is preferable to make as few changes as possible. In one case I ran across an existing Master Page that would not function as a sub-Master Page. While it would probably have been educational to trace down why, the expedient process of updating it to take the place of the WSRP Master Page is the route I took. The changes are highlighted below: … <asp:ContentPlaceHolder ID="wsrphead" runat="server"></asp:ContentPlaceHolder> </head> <body leftMargin="0" topMargin="0"> <form id="TheForm" runat="server"> <input type="hidden" name="key" id="key" value="" /> <input type="hidden" name="formactionurl" id="formactionurl" value="" /> <input type="hidden" name="handle" id="handle" value="" /> <asp:ScriptManager ID="ScriptManager1" runat="server" EnablePartialRendering="true" > </asp:ScriptManager> This approach did not work for all existing Master Pages, but fortunately all of the other existing Master Pages I have run across worked fine as a sub-Master to the WSRP Master Page. Moving On In Enterprise Portals, even after you get everything working, the work is not finished. Next you need to get it where everyone will work with it. Migration Planning Providing that the server where IIS is running is adequately sized, it is possible to run both the .NET Accelerator and the WSRP Producer on the same server during the upgrade process. The upgrade can be performed incrementally, i.e., one portlet at a time, if server administration processes support it. Those processes would include the ability to manage a second producer in the consuming portal and to change over individual portlet instances from one provider to the other. If processes or requirements demand that all portlets be cut over at the same time, it needs to be determined if this cut over should include a new producer, updating all of the portlets in the consumer, or if the WSRP Producer portlet configuration must maintain the naming conventions used by the .NET Accelerator and simply change the WSRP end point configured in the consumer. In some enterprises it may even be necessary to maintain the same WSDL end point, at which point the IIS configuration will be where the updates occur. The downside to such a requirement is that it makes rolling back very difficult, should the need arise. Location, Location, Location Not everyone wants the web application to have the descriptively obvious wsrpdefault location, or needs to create a second WSRP site on the same server. The instructions below are from the product team and, while targeted towards making a second site, will work for creating a site with a different name and then remove the old site. You can also change just the name in IIS. Manually Creating a WSRP Producer Site Instructions (NOTE: all executables used are the same ones used by the installer and “wsrpdev” will be the name of the new instance): 1. Copy C:\Oracle\Middleware\WSRPProducerForDotNet\wsrpdefault to C:\Oracle\Middleware\WSRPProducerForDotNet\wsrpdev. 2. Bring up a command window as an administrator 3. Run C:\Oracle\Middleware\WSRPProducerForDotNet\uninstall_resources\IISAppAccelSiteCreator.exe install WSRPProducers wsrpdev "C:\Oracle\Middleware\WSRPProducerForDotNet\wsrpdev" 8678 2.0.50727 4. Run C:\Oracle\Middleware\WSRPProducerForDotNet\uninstall_resources\PermManage.exe add FileSystem C:\Oracle\Middleware\WSRPProducerForDotNet\wsrpdev "NETWORK SERVICE" 3 1 5. Run C:\Oracle\Middleware\WSRPProducerForDotNet\uninstall_resources\PermManage.exe add FileSystem C:\Oracle\Middleware\WSRPProducerForDotNet\wsrpdev EVERYONE 1 1 6. Open up C:\Oracle\Middleware\WSRPProducerForDotNet\wsdl\1.0\WSRPService.wsdl and replace wsrpdefault with wsrpdev 7. Open up C:\Oracle\Middleware\WSRPProducerForDotNet\wsdl\2.0\WSRPService.wsdl and replace wsrpdefault with wsrpdev Tests: 1. Bring up a browser on the host itself and go to http://localhost:8678/wsrpdev/wsdl/1.0/WSRPService.wsdl and make sure that the URLs in the XML returned include the wsrpdev changes you made in step 6. 2. Bring up a browser on the host itself and see if the default sample comes up: http://localhost:8678/wsrpdev/portlets/ASPNET_AJAX_sample/default.aspx 3. Register the producer in WLP and test the portlet. Changing the Port used by WSRP Producer The pre-configured port for the WSRP Producer is 8678. You can change this port by updating both the IIS configuration and C:\Oracle\Middleware\WSRPProducerForDotNet\[WSRP_APP_NAME]\wsdl\1.0\WSRPService.wsdl. Do You Need to Migrate? Oracle Premier Support ended in November of 2010 for AquaLogic Interaction .NET Application Accelerator 1.x and Extended Support ends in November 2012 (see http://www.oracle.com/us/support/lifetime-support/lifetime-support-software-342730.html for other related dates). This means that integration with products released after November of 2010 is not supported. If having such support is the policy within your enterprise, you do indeed need to migrate. If changes in your enterprise cause your current solution with the .NET Accelerator to no longer function properly, you may need to migrate. Migration is a choice, and if the goals of your enterprise are to take full advantage of newer technologies then migration is certainly one activity you should be planning for.

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  • LinqToXML removing empty xmlns attributes &amp; adding attributes like xmlns:xsi, xsi:schemaLocation

    - by Rohit Gupta
    Suppose you need to generate the following XML: 1: <GenevaLoader xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 2: xsi:schemaLocation="http://www.advent.com/SchemaRevLevel401/Geneva masterschema.xsd" 3: xmlns="http://www.advent.com/SchemaRevLevel401/Geneva"> 4: <PriceRecords> 5: <PriceRecord> 6: </PriceRecord> 7: </PriceRecords> 8: </GenevaLoader> Normally you would write the following C# code to accomplish this: 1: const string ns = "http://www.advent.com/SchemaRevLevel401/Geneva"; 2: XNamespace xnsp = ns; 3: XNamespace xsi = XNamespace.Get("http://www.w3.org/2001/XMLSchema-instance"); 4:  5: XElement root = new XElement( xnsp + "GenevaLoader", 6: new XAttribute(XNamespace.Xmlns + "xsi", xsi.NamespaceName), 7: new XAttribute( xsi + "schemaLocation", "http://www.advent.com/SchemaRevLevel401/Geneva masterschema.xsd")); 8:  9: XElement priceRecords = new XElement("PriceRecords"); 10: root.Add(priceRecords); 11:  12: for(int i = 0; i < 3; i++) 13: { 14: XElement price = new XElement("PriceRecord"); 15: priceRecords.Add(price); 16: } 17:  18: doc.Save("geneva.xml"); The problem with this approach is that it adds a additional empty xmlns arrtribute on the “PriceRecords” element, like so : 1: <GenevaLoader xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.advent.com/SchemaRevLevel401/Geneva masterschema.xsd" xmlns="http://www.advent.com/SchemaRevLevel401/Geneva"> 2: <PriceRecords xmlns=""> 3: <PriceRecord> 4: </PriceRecord> 5: </PriceRecords> 6: </GenevaLoader> The solution is to add the xmlns NameSpace in code to each child and grandchild elements of the root element like so : 1: XElement priceRecords = new XElement( xnsp + "PriceRecords"); 2: root.Add(priceRecords); 3:  4: for(int i = 0; i < 3; i++) 5: { 6: XElement price = new XElement(xnsp + "PriceRecord"); 7: priceRecords.Add(price); 8: }

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  • SQLAuthority News – Social Media Series – Facebook and Google+

    - by pinaldave
    Pinal on Facebook and Google+ Unless you have been living under a rock for the last few years, you know that Facebook is the first and last word in social networking.  Everyone has a Facebook account – from your local store to the 10-year old school child.  Because of this ability to be completely connected to everyone in your entire life, keeping a Facebook page for a professional business can be tricky. For the most part, I use Facebook strictly for personal matters.  I am friends only with friends I know in the “real” world (as opposed to my “virtual” online friends) and with family, of course.  I chat with friends on Facebook and upload personal photos to share with family who are far away.  I hope this doesn’t make readers from my professional life feel left out.  You can follow me on Facebook at www.facebook.com/SQLAuth, but you should know that Twitter is probably the better place to find updates about SQL Server and my blog (you can follow me on Twitter at www.twitter.com/pinaldave). There are definitely businesses who keep in touch with their clients using Facebook, but I felt the need to keep my personal and professional life separate.  That’s why I was so excited to find out Google was coming out with their own social media site, Google+.  On Google+ I post some personal things as well, and there is a lot of overlap between what I put on Facebook and what I put on Google+.  But since Google+ has become so popular amongst the “techie” crowd, I have found that it’s a good place to follow some of the stars of the Microsoft world, like Scott Hanselman and Buck Woody. If you are also a member of Google+, I am looking to expand my circle there.  You can find me at https://plus.google.com/104990425207662620918/posts.  Google+ is the newest face in the social media world, and it still hasn’t found a good footing between personal and professional yet.  That’s why I felt it would be a good idea to jump on the site early and help them determine which way to go.  Maybe someday it will be a place where business and personal can mix. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Social Media

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  • Database design and performance impact

    - by Craige
    I have a database design issue that I'm not quite sure how to approach, nor if the benefits out weigh the costs. I'm hoping some P.SE members can give some feedback on my suggested design, as well as any similar experiences they may have came across. As it goes, I am building an application that has large reporting demands. Speed is an important issue, as there will be peak usages throughout the year. This application/database has a multiple-level, many-to-many relationship. eg object a object b object c object d object b has relationship to object a object c has relationship to object b, a object d has relationship to object c, b, a Theoretically, this could go on for unlimited levels, though logic dictates it could only go so far. My idea here, to speed up reporting, would be to create a syndicate table that acts as a global many-to-many join table. In this table (with the given example), one might see: +----------+-----------+---------+ | child_id | parent_id | type_id | +----------+-----------+---------+ | b | a | 1 | | c | b | 2 | | c | a | 3 | | d | c | 4 | | d | b | 5 | | d | a | 6 | +----------+-----------+---------+ Where a, b, c and d would translate to their respective ID's in their respective tables. So, for ease of reporting all of a which exist on object d, one could query SELECT * FROM `syndicates` ... JOINS TO child and parent tables ... WHERE parent_id=a and type_id=6; rather than having a query with a join to each level up the chain. The Problem This table grows exponentially, and in a given year, could easily grow past 20,000 records for one client. Given multiple clients over multiple years, this table will VERY quickly explode to millions of records and beyond. Now, the database will, in time, be partitioned across multiple servers, but I would like (as most would) to keep the number of servers as low as possible while still offering flexibility. Also writes and updates would be exponentially longer (though possibly not noticeable to the end user) as there would be multiple inserts/updates/scans on this table to keep it in sync. Am I going in the right direction here, or am I way off track. What would you do in a similar situation? This solution seems overly complex, but allows the greatest flexibility and fastest read-operations. Sidenote 1 - This structure allows me to add new levels to the tree easily. Sidenote 2 - The database querying for this database is done through an ORM framework.

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  • PTLQueue : a scalable bounded-capacity MPMC queue

    - by Dave
    Title: Fast concurrent MPMC queue -- I've used the following concurrent queue algorithm enough that it warrants a blog entry. I'll sketch out the design of a fast and scalable multiple-producer multiple-consumer (MPSC) concurrent queue called PTLQueue. The queue has bounded capacity and is implemented via a circular array. Bounded capacity can be a useful property if there's a mismatch between producer rates and consumer rates where an unbounded queue might otherwise result in excessive memory consumption by virtue of the container nodes that -- in some queue implementations -- are used to hold values. A bounded-capacity queue can provide flow control between components. Beware, however, that bounded collections can also result in resource deadlock if abused. The put() and take() operators are partial and wait for the collection to become non-full or non-empty, respectively. Put() and take() do not allocate memory, and are not vulnerable to the ABA pathologies. The PTLQueue algorithm can be implemented equally well in C/C++ and Java. Partial operators are often more convenient than total methods. In many use cases if the preconditions aren't met, there's nothing else useful the thread can do, so it may as well wait via a partial method. An exception is in the case of work-stealing queues where a thief might scan a set of queues from which it could potentially steal. Total methods return ASAP with a success-failure indication. (It's tempting to describe a queue or API as blocking or non-blocking instead of partial or total, but non-blocking is already an overloaded concurrency term. Perhaps waiting/non-waiting or patient/impatient might be better terms). It's also trivial to construct partial operators by busy-waiting via total operators, but such constructs may be less efficient than an operator explicitly and intentionally designed to wait. A PTLQueue instance contains an array of slots, where each slot has volatile Turn and MailBox fields. The array has power-of-two length allowing mod/div operations to be replaced by masking. We assume sensible padding and alignment to reduce the impact of false sharing. (On x86 I recommend 128-byte alignment and padding because of the adjacent-sector prefetch facility). Each queue also has PutCursor and TakeCursor cursor variables, each of which should be sequestered as the sole occupant of a cache line or sector. You can opt to use 64-bit integers if concerned about wrap-around aliasing in the cursor variables. Put(null) is considered illegal, but the caller or implementation can easily check for and convert null to a distinguished non-null proxy value if null happens to be a value you'd like to pass. Take() will accordingly convert the proxy value back to null. An advantage of PTLQueue is that you can use atomic fetch-and-increment for the partial methods. We initialize each slot at index I with (Turn=I, MailBox=null). Both cursors are initially 0. All shared variables are considered "volatile" and atomics such as CAS and AtomicFetchAndIncrement are presumed to have bidirectional fence semantics. Finally T is the templated type. I've sketched out a total tryTake() method below that allows the caller to poll the queue. tryPut() has an analogous construction. Zebra stripping : alternating row colors for nice-looking code listings. See also google code "prettify" : https://code.google.com/p/google-code-prettify/ Prettify is a javascript module that yields the HTML/CSS/JS equivalent of pretty-print. -- pre:nth-child(odd) { background-color:#ff0000; } pre:nth-child(even) { background-color:#0000ff; } border-left: 11px solid #ccc; margin: 1.7em 0 1.7em 0.3em; background-color:#BFB; font-size:12px; line-height:65%; " // PTLQueue : Put(v) : // producer : partial method - waits as necessary assert v != null assert Mask = 1 && (Mask & (Mask+1)) == 0 // Document invariants // doorway step // Obtain a sequence number -- ticket // As a practical concern the ticket value is temporally unique // The ticket also identifies and selects a slot auto tkt = AtomicFetchIncrement (&PutCursor, 1) slot * s = &Slots[tkt & Mask] // waiting phase : // wait for slot's generation to match the tkt value assigned to this put() invocation. // The "generation" is implicitly encoded as the upper bits in the cursor // above those used to specify the index : tkt div (Mask+1) // The generation serves as an epoch number to identify a cohort of threads // accessing disjoint slots while s-Turn != tkt : Pause assert s-MailBox == null s-MailBox = v // deposit and pass message Take() : // consumer : partial method - waits as necessary auto tkt = AtomicFetchIncrement (&TakeCursor,1) slot * s = &Slots[tkt & Mask] // 2-stage waiting : // First wait for turn for our generation // Acquire exclusive "take" access to slot's MailBox field // Then wait for the slot to become occupied while s-Turn != tkt : Pause // Concurrency in this section of code is now reduced to just 1 producer thread // vs 1 consumer thread. // For a given queue and slot, there will be most one Take() operation running // in this section. // Consumer waits for producer to arrive and make slot non-empty // Extract message; clear mailbox; advance Turn indicator // We have an obvious happens-before relation : // Put(m) happens-before corresponding Take() that returns that same "m" for T v = s-MailBox if v != null : s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 // unlock slot to admit next producer and consumer return v Pause tryTake() : // total method - returns ASAP with failure indication for auto tkt = TakeCursor slot * s = &Slots[tkt & Mask] if s-Turn != tkt : return null T v = s-MailBox // presumptive return value if v == null : return null // ratify tkt and v values and commit by advancing cursor if CAS (&TakeCursor, tkt, tkt+1) != tkt : continue s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 return v The basic idea derives from the Partitioned Ticket Lock "PTL" (US20120240126-A1) and the MultiLane Concurrent Bag (US8689237). The latter is essentially a circular ring-buffer where the elements themselves are queues or concurrent collections. You can think of the PTLQueue as a partitioned ticket lock "PTL" augmented to pass values from lock to unlock via the slots. Alternatively, you could conceptualize of PTLQueue as a degenerate MultiLane bag where each slot or "lane" consists of a simple single-word MailBox instead of a general queue. Each lane in PTLQueue also has a private Turn field which acts like the Turn (Grant) variables found in PTL. Turn enforces strict FIFO ordering and restricts concurrency on the slot mailbox field to at most one simultaneous put() and take() operation. PTL uses a single "ticket" variable and per-slot Turn (grant) fields while MultiLane has distinct PutCursor and TakeCursor cursors and abstract per-slot sub-queues. Both PTL and MultiLane advance their cursor and ticket variables with atomic fetch-and-increment. PTLQueue borrows from both PTL and MultiLane and has distinct put and take cursors and per-slot Turn fields. Instead of a per-slot queues, PTLQueue uses a simple single-word MailBox field. PutCursor and TakeCursor act like a pair of ticket locks, conferring "put" and "take" access to a given slot. PutCursor, for instance, assigns an incoming put() request to a slot and serves as a PTL "Ticket" to acquire "put" permission to that slot's MailBox field. To better explain the operation of PTLQueue we deconstruct the operation of put() and take() as follows. Put() first increments PutCursor obtaining a new unique ticket. That ticket value also identifies a slot. Put() next waits for that slot's Turn field to match that ticket value. This is tantamount to using a PTL to acquire "put" permission on the slot's MailBox field. Finally, having obtained exclusive "put" permission on the slot, put() stores the message value into the slot's MailBox. Take() similarly advances TakeCursor, identifying a slot, and then acquires and secures "take" permission on a slot by waiting for Turn. Take() then waits for the slot's MailBox to become non-empty, extracts the message, and clears MailBox. Finally, take() advances the slot's Turn field, which releases both "put" and "take" access to the slot's MailBox. Note the asymmetry : put() acquires "put" access to the slot, but take() releases that lock. At any given time, for a given slot in a PTLQueue, at most one thread has "put" access and at most one thread has "take" access. This restricts concurrency from general MPMC to 1-vs-1. We have 2 ticket locks -- one for put() and one for take() -- each with its own "ticket" variable in the form of the corresponding cursor, but they share a single "Grant" egress variable in the form of the slot's Turn variable. Advancing the PutCursor, for instance, serves two purposes. First, we obtain a unique ticket which identifies a slot. Second, incrementing the cursor is the doorway protocol step to acquire the per-slot mutual exclusion "put" lock. The cursors and operations to increment those cursors serve double-duty : slot-selection and ticket assignment for locking the slot's MailBox field. At any given time a slot MailBox field can be in one of the following states: empty with no pending operations -- neutral state; empty with one or more waiting take() operations pending -- deficit; occupied with no pending operations; occupied with one or more waiting put() operations -- surplus; empty with a pending put() or pending put() and take() operations -- transitional; or occupied with a pending take() or pending put() and take() operations -- transitional. The partial put() and take() operators can be implemented with an atomic fetch-and-increment operation, which may confer a performance advantage over a CAS-based loop. In addition we have independent PutCursor and TakeCursor cursors. Critically, a put() operation modifies PutCursor but does not access the TakeCursor and a take() operation modifies the TakeCursor cursor but does not access the PutCursor. This acts to reduce coherence traffic relative to some other queue designs. It's worth noting that slow threads or obstruction in one slot (or "lane") does not impede or obstruct operations in other slots -- this gives us some degree of obstruction isolation. PTLQueue is not lock-free, however. The implementation above is expressed with polite busy-waiting (Pause) but it's trivial to implement per-slot parking and unparking to deschedule waiting threads. It's also easy to convert the queue to a more general deque by replacing the PutCursor and TakeCursor cursors with Left/Front and Right/Back cursors that can move either direction. Specifically, to push and pop from the "left" side of the deque we would decrement and increment the Left cursor, respectively, and to push and pop from the "right" side of the deque we would increment and decrement the Right cursor, respectively. We used a variation of PTLQueue for message passing in our recent OPODIS 2013 paper. ul { list-style:none; padding-left:0; padding:0; margin:0; margin-left:0; } ul#myTagID { padding: 0px; margin: 0px; list-style:none; margin-left:0;} -- -- There's quite a bit of related literature in this area. I'll call out a few relevant references: Wilson's NYU Courant Institute UltraComputer dissertation from 1988 is classic and the canonical starting point : Operating System Data Structures for Shared-Memory MIMD Machines with Fetch-and-Add. Regarding provenance and priority, I think PTLQueue or queues effectively equivalent to PTLQueue have been independently rediscovered a number of times. See CB-Queue and BNPBV, below, for instance. But Wilson's dissertation anticipates the basic idea and seems to predate all the others. Gottlieb et al : Basic Techniques for the Efficient Coordination of Very Large Numbers of Cooperating Sequential Processors Orozco et al : CB-Queue in Toward high-throughput algorithms on many-core architectures which appeared in TACO 2012. Meneghin et al : BNPVB family in Performance evaluation of inter-thread communication mechanisms on multicore/multithreaded architecture Dmitry Vyukov : bounded MPMC queue (highly recommended) Alex Otenko : US8607249 (highly related). John Mellor-Crummey : Concurrent queues: Practical fetch-and-phi algorithms. Technical Report 229, Department of Computer Science, University of Rochester Thomasson : FIFO Distributed Bakery Algorithm (very similar to PTLQueue). Scott and Scherer : Dual Data Structures I'll propose an optimization left as an exercise for the reader. Say we wanted to reduce memory usage by eliminating inter-slot padding. Such padding is usually "dark" memory and otherwise unused and wasted. But eliminating the padding leaves us at risk of increased false sharing. Furthermore lets say it was usually the case that the PutCursor and TakeCursor were numerically close to each other. (That's true in some use cases). We might still reduce false sharing by incrementing the cursors by some value other than 1 that is not trivially small and is coprime with the number of slots. Alternatively, we might increment the cursor by one and mask as usual, resulting in a logical index. We then use that logical index value to index into a permutation table, yielding an effective index for use in the slot array. The permutation table would be constructed so that nearby logical indices would map to more distant effective indices. (Open question: what should that permutation look like? Possibly some perversion of a Gray code or De Bruijn sequence might be suitable). As an aside, say we need to busy-wait for some condition as follows : "while C == 0 : Pause". Lets say that C is usually non-zero, so we typically don't wait. But when C happens to be 0 we'll have to spin for some period, possibly brief. We can arrange for the code to be more machine-friendly with respect to the branch predictors by transforming the loop into : "if C == 0 : for { Pause; if C != 0 : break; }". Critically, we want to restructure the loop so there's one branch that controls entry and another that controls loop exit. A concern is that your compiler or JIT might be clever enough to transform this back to "while C == 0 : Pause". You can sometimes avoid this by inserting a call to a some type of very cheap "opaque" method that the compiler can't elide or reorder. On Solaris, for instance, you could use :"if C == 0 : { gethrtime(); for { Pause; if C != 0 : break; }}". It's worth noting the obvious duality between locks and queues. If you have strict FIFO lock implementation with local spinning and succession by direct handoff such as MCS or CLH,then you can usually transform that lock into a queue. Hidden commentary and annotations - invisible : * And of course there's a well-known duality between queues and locks, but I'll leave that topic for another blog post. * Compare and contrast : PTLQ vs PTL and MultiLane * Equivalent : Turn; seq; sequence; pos; position; ticket * Put = Lock; Deposit Take = identify and reserve slot; wait; extract & clear; unlock * conceptualize : Distinct PutLock and TakeLock implemented as ticket lock or PTL Distinct arrival cursors but share per-slot "Turn" variable provides exclusive role-based access to slot's mailbox field put() acquires exclusive access to a slot for purposes of "deposit" assigns slot round-robin and then acquires deposit access rights/perms to that slot take() acquires exclusive access to slot for purposes of "withdrawal" assigns slot round-robin and then acquires withdrawal access rights/perms to that slot At any given time, only one thread can have withdrawal access to a slot at any given time, only one thread can have deposit access to a slot Permissible for T1 to have deposit access and T2 to simultaneously have withdrawal access * round-robin for the purposes of; role-based; access mode; access role mailslot; mailbox; allocate/assign/identify slot rights; permission; license; access permission; * PTL/Ticket hybrid Asymmetric usage ; owner oblivious lock-unlock pairing K-exclusion add Grant cursor pass message m from lock to unlock via Slots[] array Cursor performs 2 functions : + PTL ticket + Assigns request to slot in round-robin fashion Deconstruct protocol : explication put() : allocate slot in round-robin fashion acquire PTL for "put" access store message into slot associated with PTL index take() : Acquire PTL for "take" access // doorway step seq = fetchAdd (&Grant, 1) s = &Slots[seq & Mask] // waiting phase while s-Turn != seq : pause Extract : wait for s-mailbox to be full v = s-mailbox s-mailbox = null Release PTL for both "put" and "take" access s-Turn = seq + Mask + 1 * Slot round-robin assignment and lock "doorway" protocol leverage the same cursor and FetchAdd operation on that cursor FetchAdd (&Cursor,1) + round-robin slot assignment and dispersal + PTL/ticket lock "doorway" step waiting phase is via "Turn" field in slot * PTLQueue uses 2 cursors -- put and take. Acquire "put" access to slot via PTL-like lock Acquire "take" access to slot via PTL-like lock 2 locks : put and take -- at most one thread can access slot's mailbox Both locks use same "turn" field Like multilane : 2 cursors : put and take slot is simple 1-capacity mailbox instead of queue Borrow per-slot turn/grant from PTL Provides strict FIFO Lock slot : put-vs-put take-vs-take at most one put accesses slot at any one time at most one put accesses take at any one time reduction to 1-vs-1 instead of N-vs-M concurrency Per slot locks for put/take Release put/take by advancing turn * is instrumental in ... * P-V Semaphore vs lock vs K-exclusion * See also : FastQueues-excerpt.java dice-etc/queue-mpmc-bounded-blocking-circular-xadd/ * PTLQueue is the same as PTLQB - identical * Expedient return; ASAP; prompt; immediately * Lamport's Bakery algorithm : doorway step then waiting phase Threads arriving at doorway obtain a unique ticket number Threads enter in ticket order * In the terminology of Reed and Kanodia a ticket lock corresponds to the busy-wait implementation of a semaphore using an eventcount and a sequencer It can also be thought of as an optimization of Lamport's bakery lock was designed for fault-tolerance rather than performance Instead of spinning on the release counter, processors using a bakery lock repeatedly examine the tickets of their peers --

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  • ArchBeat Link-o-Rama for 2012-07-10

    - by Bob Rhubart
    Free Event Today: Virtual Developer Day: Oracle Fusion Development This free event—another in the ongoing series of OTN Virtual Developer Days—focuses on Oracle Fusion development, and features three session tracks plus hands-on labs. Agenda and session abstracts are available now so you can be ready for the live event when it kicks off today, July 10, 9am to 1pm PST / 12pm to 4pm EST / 1pm to 5pm BRT. Podcast: The Role of the Cloud Architect - Part 1/3 In part one of this three-part conversation, cloud architects Ron Batra (AT&T) and James Baty (Oracle) talk about how cloud computing is driving the supply-chaining of IT and the "democratization of the activity of architecture." Middleware and Cloud Computing Book | Tom Laszewski Cloud migration expert Tom Laszewski describes Middleware and Cloud Computing by Frank Munz as "one of only a couple books that really discuss AWS and Oracle in depth." Cloud computing moves from fad to foundation | David Linthicum "When enterprises make cloud computing work, they view the application of the technology as a trade secret of sorts, so there are no press releases or white papers," says David Linthicum. "Indeed, if you see one presentation around a successful cloud computing case study, you can bet you're not hearing about 100 more." Oracle Real-Time Decisions: Combined Likelihood Models | Lukas Vermeer Lukas Vermeer concludes his extensive series of posts on decision models with a look "an advanced approach to amalgamate models, taking us to a whole new level of predictive modeling and analytical insights; combination models predicting likelihoods using multiple child models." Running Oracle BPM 11g PS5 Worklist Task Flow and Human Task Form on Non-SOA Domain | Andrejus Baranovskis "With a standard setup, both the BPM worklist application and the Human task form run on the same SOA domain, where the BPM process is running," says Oracle ACE Director Andrejus Baranovskis. "While this work fine, this is not what we want in the development, test and production environment." BAM design pointers | Kavitha Srinivasan "When using EMS (Enterprise Message Source) as a BAM feed, the best practice is to use one EMS to write to one Data Object," says Oracle Fusion Middleware A-Team blogger Kavitha Srinivasan. "There is a possibility of collisions and duplicates when multiple EMS write to the same row of a DO at the same time." Changes in SOA Human Task Flow (Run-Time) for Fusion Applications | Jack Desai Oracle Fusion Middleware A-Team blogger Jack Desai shares a troubleshooting tip. Thought for the Day "A program which perfectly meets a lousy specification is a lousy program." — Cem Kaner Source: SoftwareQuotes.com

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  • How do I draw a scene with 2 nested frames

    - by Guido Granobles
    I have been trying for long time to figure out this: I have loaded a model from a directx file (I am using opengl and Java) the model have a hierarchical system of nested reference frames (there are not bones). There are just 2 frames, one of them is called x3ds_Torso and it has a child frame called x3ds_Arm_01. Each one of them has a mesh. The thing is that I can't draw the arm connected to the body. Sometimes the body is in the center of the screen and the arm is at the top. Sometimes they are both in the center. I know that I have to multiply the matrix transformation of every frame by its parent frame starting from the top to the bottom and after that I have to multiply every vertex of every mesh by its final transformation matrix. So I have this: public void calculeFinalMatrixPosition(Bone boneParent, Bone bone) { System.out.println("-->" + bone.name); if (boneParent != null) { bone.matrixCombined = bone.matrixTransform.multiply(boneParent.matrixCombined); } else { bone.matrixCombined = bone.matrixTransform; } bone.matrixFinal = bone.matrixCombined; for (Bone childBone : bone.boneChilds) { calculeFinalMatrixPosition(bone, childBone); } } Then I have to multiply every vertex of the mesh: public void transformVertex(Bone bone) { for (Iterator<Mesh> iterator = meshes.iterator(); iterator.hasNext();) { Mesh mesh = iterator.next(); if (mesh.boneName.equals(bone.name)) { float[] vertex = new float[4]; double[] newVertex = new double[3]; if (mesh.skinnedVertexBuffer == null) { mesh.skinnedVertexBuffer = new FloatDataBuffer( mesh.numVertices, 3); } mesh.vertexBuffer.buffer.rewind(); while (mesh.vertexBuffer.buffer.hasRemaining()) { vertex[0] = mesh.vertexBuffer.buffer.get(); vertex[1] = mesh.vertexBuffer.buffer.get(); vertex[2] = mesh.vertexBuffer.buffer.get(); vertex[3] = 1; newVertex = bone.matrixFinal.transpose().multiply(vertex); mesh.skinnedVertexBuffer.buffer.put(((float) newVertex[0])); mesh.skinnedVertexBuffer.buffer.put(((float) newVertex[1])); mesh.skinnedVertexBuffer.buffer.put(((float) newVertex[2])); } mesh.vertexBuffer = new FloatDataBuffer( mesh.numVertices, 3); mesh.skinnedVertexBuffer.buffer.rewind(); mesh.vertexBuffer.buffer.put(mesh.skinnedVertexBuffer.buffer); } } for (Bone childBone : bone.boneChilds) { transformVertex(childBone); } } I know this is not the more efficient code but by now I just want to understand exactly how a hierarchical model is organized and how I can draw it on the screen. Thanks in advance for your help.

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  • Aptronyms: fitting the profession to the name

    - by Tony Davis
    Writing a recent piece on the pains of index fragmentation, I found myself wondering why, in SQL Server, you can’t set the equivalent of a fill factor, on a heap table. I scratched my head…who might know? Phil Factor, of course! I approached him with a due sense of optimism only to find that not only did he not know, he also didn’t seem to care much either. I skulked off thinking how this may be the final nail in the coffin of nominative determinism. I’ve always wondered if there was anything in it, though. If your surname is Plumb or Leeks, is there even a tiny, extra percentage chance that you’ll end up fitting bathrooms? Some examples are quite common. I’m sure we’ve all met teachers called English or French, or lawyers called Judge or Laws. I’ve also known a Doctor called Coffin, a Urologist called Waterfall, and a Dentist called Dentith. Two personal favorites are Wolfgang Wolf who ended up managing the German Soccer team, Wolfsburg, and Edmund Akenhead, a Crossword Editor for The Times newspaper. Having forgiven Phil his earlier offhandedness, I asked him for if he knew of any notable examples. He had met the famous Dr. Batty and Dr. Nutter, both Psychiatrists, knew undertakers called Death and Stiff, had read a book by Frederick Page-Turner, and suppressed a giggle at the idea of a feminist called Gurley-Brown. He even managed to better my Urologist example, citing the article on incontinence in the British Journal of Urology (vol.49, pp.173-176, 1977) by A. J. Splatt and D. Weedon. What, however, if you were keen to gently nudge your child down the path to a career in IT? What name would you choose? Subtlety probably doesn’t really work, although in a recent interview, Rodney Landrum did congratulate PowerShell MVP Max Trinidad on being named after a SQL function. Grant “The Memory” Fritchey (OK, I made up that nickname) doesn’t do badly either. Some surnames, seem to offer a natural head start, although I know of no members of the Page-Reid clan in the profession. There are certainly families with the Table surname, although sadly, Little Bobby Tables was merely a legend by xkcd. A member of the well-known Key family would need to name their son Primary, or maybe live abroad, to make their mark. Nominate your examples of people seemingly destined, by name, for their chosen profession (extra points for IT). The best three will receive a prize. Cheers, Tony.

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  • Virtual Lab part 2&ndash;Templates, Patterns, Baselines

    - by Geoff N. Hiten
    Once you have a good virtualization platform chosen, whether it is a desktop, server or laptop environment, the temptation is to build “X”.  “X” may be a SharePoint lab, a Virtual Cluster, an AD test environment or some other cool project that you really need RIGHT NOW.  That would be doing it wrong. My grandfather taught woodworking and cabinetmaking for twenty-seven years at a trade school in Alabama.  He was the first instructor hired at that school and the only teacher for the first two years.  His students built tables, chairs, and workbenches so the school could start its HVAC courses.   Visiting as a child, I also noticed many extra “helper” stands, benches, holders, and gadgets all built from wood.  What does that have to do with a virtual lab, you ask?  Well, that is the same approach you should take.  Build stuff that you will use.  Not for solving a particular problem, but to let the Virtual Lab be part of your normal troubleshooting toolkit. Start with basic copies of various Operating Systems.  Load and patch server and desktop OS environments.  This also helps build your collection of ISO files, another essential element of a virtual Lab.  Once you have these “baseline” images, you can use your Virtualization software’s snapshot capability to freeze the image.  Clone the snapshot and you have a brand new fully patched machine in mere moments.  You may have to sysprep some of the Microsoft OS environments if you are going to create a domain environment or experiment with clustering.  That is still much faster than loading and patching from scratch. So once you have a stock of raw materials (baseline images in this case) where should you start.  Again, my grandfather’s workshop gives us the answer.  In the shop it was workbenches and tables to hold large workpieces that made the equipment more useful.  In a Windows environment the same role falls to the fundamental network services:  DHCP, DNS, Active Directory, Routing, File Services, and Storage services.  Plan your internal network setup.  Build out an AD controller with all the features listed.  Make the actual domain an isolated domain so it will not care about where you take it.  Add the Microsoft iSCSI target.  Once you have this single system, you can leverage it for almost any network environment beyond a simple stand-alone system. Having these templates and fundamental infrastructure elements ready to run means I can build a quick lab in minutes instead of hours.  My solutions are well-tested, my processes fully documented with screenshots, and my plans validated well before I have to make any changes to client systems.  the work I put in is easily returned in increased value and client satisfaction.

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  • Deserialize inherited classes into the same list in XNA

    - by M0rgenstern
    I am writing a Gui for a game (for what else ...). Therefor I wrote a class GuiElement which has some serializeable fields. From this class I deflect a Class "Button" which has one serializeable field more. Furthermore, I have a Class GuiWindow, which is as well deflected from "GuiElement". An Object of this Class has a Field "HandledElements" of the type "List". To know the layout of the Menues, I use XML-Files, which look like that (for example): <?xml version="1.0" encoding="utf-8" ?> <XnaContent xmlns:Generic="System.Collections.Generic"> <Asset Type="System.Collections.Generic.List[GUI.GuiWindow]"> <Item> <Position>0 0</Position> <AlternativeImagePath></AlternativeImagePath> <IsActive>true</IsActive> <Name>MainMenu</Name> <HandledElements> <Item> <Position>100 100</Position> <AlternativeImagePath></AlternativeImagePath> <IsActive>true</IsActive> <Name>Optionen</Name> <Caption>Optionen</Caption> </Item> </HandledElements> </Item> <Item> <Position>0 0</Position> <AlternativeImagePath></AlternativeImagePath> <IsActive>false</IsActive> <Name>Options</Name> <HandledElements> </HandledElements> </Item> </Asset> </XnaContent> As you can see, the first window has in its "HandledElements" List an Item with the Field . This is a field which only a Button has. The Problem is now: I can't deserialize this XML file, because GuiElement does not have this Field, it only has the few fields above. I thought it would know automatically which Class to use,but it doesn't. Do I really have to give my windows a list for each child class of GuiElement? Or can I do another workaround?

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  • How to correctly track the analytics when using iframe

    - by Sherry Ann Hernandez
    In our main aspx page we have this analytics code <script type="text/javascript"> var _gaq = _gaq || []; _gaq.push(['_setAccount', 'UA-1301114-2']); _gaq.push(['_setDomainName', 'florahospitality.com']); _gaq.push(['_setAllowLinker', true]); _gaq.push(['_trackPageview']); _gaq.push(function() { var pageTracker = _gat._getTrackerByName(); var iframe = document.getElementById('reservationFrame'); iframe.src = pageTracker._getLinkerUrl('https://reservations.synxis.com/xbe/rez.aspx?Hotel=15159&template=flex&shell=flex&Chain=5375&locale=en&arrive=11/12/2012&depart=11/13/2012&adult=2&child=0&rooms=1&start=availresults&iata=&promo=&group='); }); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); </script> Then inside this aspx page is an iframe. Inside the iframe we setup this analytics code <script type="text/javascript"> var _gaq = _gaq || []; _gaq.push(['_setAccount', 'UA-1301114-2']); _gaq.push(['_setDomainName', 'reservations.synxis.com']); _gaq.push(['_setAllowLinker', true]); _gaq.push(['_trackPageview', 'AvailabilityResults']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); </script> The problem is I see to pageview when I go to find the AvailabilityResults page. The first one is a direct traffic and the other one is a cpc. How come that they have different source? I was expecting that both of them is using a direct traffic.

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  • Make Browsing Safer for Children in Google Chrome

    - by Asian Angel
    If you are worried about the websites that your children could accidentally visit while browsing, then you may want to have a look at the Kid Safe – LinkExtend extension for Google Chrome. Kid Safe – LinkExtend in Action Before going any further you may want to have a quick look at the options. Everything is enabled by default but it is recommended that you disable the “Allow entering unsafe sites Option”. For our first example we visited “chatroulette.com”. As you can see in the screenshot WOT and McAfee SiteAdvisor gave the website a “green rating” but when it came specifically to its’ level of appropriateness for children LinkExtend gave it a “yellow rating”. Our second example was “hotbabes.com”…obviously not a good website for any child to visit. You can see that the entire window area has been totally “blacked out” and the available information for this site from each of the six ratings sources. The “Toolbar Button” is also displaying a “red rating”… Notice the two links at the bottom of the ratings screen…both will be visible if the “Allow entering unsafe sites Option” is not disabled (see Options above). You can see the difference for the links at the bottom of the ratings screen if you have the “Allow entering unsafe sites Option” disabled. Definitely much much better… Clicking on the “Find Kids Sites Link” will navigate the tab to the Yahoo! Kids website. The extension will also place “ratings buttons” beside search results at Google. As you can see in the screenshot below not all of the results had information available for them at this time. But it is certainly a lot better than nothing at all when it comes to keeping your children safe. A close-up look at the ratings for one of the search results. Conclusion While no browser add-in makes for a perfect solution the Kid Safe – LinkExtend extension will definitely be a helpful addition to your family’s Chrome browser. Links Download the Kid Safe – LinkExtend extension (Google Chrome Extensions) Similar Articles Productive Geek Tips How to Make Google Chrome Your Default BrowserAccess Browsing History in Google Chrome the Easy WayFocused New Tabs Quick-Fix for Google ChromeVisually Browse Through Your Open Tabs in Google ChromeSubscribe to RSS Feeds in Chrome with a Single Click TouchFreeze Alternative in AutoHotkey The Icy Undertow Desktop Windows Home Server – Backup to LAN The Clear & Clean Desktop Use This Bookmarklet to Easily Get Albums Use AutoHotkey to Assign a Hotkey to a Specific Window Latest Software Reviews Tinyhacker Random Tips DVDFab 6 Revo Uninstaller Pro Registry Mechanic 9 for Windows PC Tools Internet Security Suite 2010 Awe inspiring, inter-galactic theme (Win 7) Case Study – How to Optimize Popular Wordpress Sites Restore Hidden Updates in Windows 7 & Vista Iceland an Insurance Job? Find Downloads and Add-ins for Outlook Recycle !

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  • Multiple country-specific domains or one global domain [closed]

    - by CJM
    Possible Duplicate: How should I structure my urls for both SEO and localization? My company currently has its main (English) site on a .com domain with a .co.uk alias. In addition, we have separate sites for certain other countries - these are also hosted in the UK but are distinct sites with a country-specific domain names (.de, .fr, .se, .es), and the sites have differing amounts of distinct but overlapping content, For example, the .es site is entirely in Spanish and has a page for every section of the UK site but little else. Whereas the .de site has much more content (but still less than the UK site), in German, and geared towards our business focus in that country. The main point is that the content in the additional sites is a subset of the UK, is translated into the local language, and although sometimes is simply only a translated version of UK content, it is usually 'tweaked' for the local market, and in certain areas, contains unique content. The other sites get a fraction of the traffic of the UK site. This is perfectly understandable since the biggest chunk of work comes from the UK, and we've been established here for over 30 years. However, we are wanting to build up our overseas business and part of that is building up our websites to support this. The Question: I posed a suggestion to the business that we might consider consolidating all our websites onto the .com domain but with /en/de/fr/se/etc sections, as plenty of other companies seem to do. The theory was that the non-english sites would benefit from the greater reputation of the parent .com domain, and that all the content would be mutually supporting - my fear is that the child domains on their own are too small to compete on their own compared to competitors who are established in these countries. Speaking to an SEO consultant from my hosting company, he feels that this move would have some benefit (for the reasons mentioned), but they would likely be significantly outweighed by the loss of the benefits of localised domains. Specifically, he said that since the Panda update, and particularly the two sets of changes this year, that we would lose more than we would gain. Having done some Panda research since, I've had my eyes opened on many issues, but curiously I haven't come across much that mentions localised domain names, though I do question whether Google would see it as duplicated content. It's not that I disagree with the consultant, I just want to know more before I make recommendations to my company. What is the prevailing opinion in this case? Would I gain anything from consolidating country-specific content onto one domain? Would Google see this as duplicate content? Would there be an even greater penalty from the loss of country-specific domains? And is there anything else I can do to help support the smaller, country-specific domains?

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  • Parenting Opengl with Groups in LibGDX

    - by Rudy_TM
    I am trying to make an object child of a Group, but this object has a draw method that calls opengl to draw in the screen. Its class its this public class OpenGLSquare extends Actor { private static final ImmediateModeRenderer renderer = new ImmediateModeRenderer10(); private static Matrix4 matrix = null; private static Vector2 temp = new Vector2(); public static void setMatrix4(Matrix4 mat) { matrix = mat; } @Override public void draw(SpriteBatch batch, float arg1) { // TODO Auto-generated method stub renderer.begin(matrix, GL10.GL_TRIANGLES); renderer.color(color.r, color.g, color.b, color.a); renderer.vertex(x0, y0, 0f); renderer.color(color.r, color.g, color.b, color.a); renderer.vertex(x0, y1, 0f); renderer.color(color.r, color.g, color.b, color.a); renderer.vertex(x1, y1, 0f); renderer.color(color.r, color.g, color.b, color.a); renderer.vertex(x1, y1, 0f); renderer.color(color.r, color.g, color.b, color.a); renderer.vertex(x1, y0, 0f); renderer.color(color.r, color.g, color.b, color.a); renderer.vertex(x0, y0, 0f); renderer.end(); } } In my screen class I have this, i call it in the constructor MyGroupClass spriteLab = new MyGroupClass(spriteSheetLab); OpenGLSquare square = new OpenGLSquare(); square.setX0(100); square.setY0(200); square.setX1(400); square.setY1(280); square.color.set(Color.BLUE); square.setSize(); //spriteLab.addActorAt(0, clock); spriteLab.addActor(square); stage.addActor(spriteLab); And the render in the screen I have @Override public void render(float arg0) { this.gl.glClear(GL10.GL_COLOR_BUFFER_BIT |GL10.GL_DEPTH_BUFFER_BIT); stage.draw(); stage.act(Gdx.graphics.getDeltaTime()); } The problem its that when i use opengl with parent, it resets all the other chldren to position 0,0 and the opengl renderer paints the square in the exact position of the screen and not relative to the parent. I tried using batch.enableBlending() and batch.disableBlending() that fixes the position problem of the other children, but not the relative position of the opengl drawing and it also puts alpha to the glDrawing. What am i doing wrong?:/

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  • Making a Camera look at a target Vector

    - by Peteyslatts
    I have a camera that works as long as its stationary. Now I'm trying to create a child class of that camera class that will look at its target. The new addition to the class is a method called SetTarget(). The method takes in a Vector3 target. The camera wont move but I need it to rotate to look at the target. If I just set the target, and then call CreateLookAt() (which takes in position, target, and up), when the object gets far enough away and underneath the camera, it suddenly flips right side up. So I need to transform the up vector, which currently always stays at Vector3.Up. I feel like this has something to do with taking the angle between the old direction vector and the new one (which I know can be expressed by target - position). I feel like this is all really vague, so here's the code for my base camera class: public class BasicCamera : Microsoft.Xna.Framework.GameComponent { public Matrix view { get; protected set; } public Matrix projection { get; protected set; } public Vector3 position { get; protected set; } public Vector3 direction { get; protected set; } public Vector3 up { get; protected set; } public Vector3 side { get { return Vector3.Cross(up, direction); } protected set { } } public BasicCamera(Game game, Vector3 position, Vector3 target, Vector3 up) : base(game) { this.position = position; this.direction = target - position; this.up = up; CreateLookAt(); projection = Matrix.CreatePerspectiveFieldOfView( MathHelper.PiOver4, (float)Game.Window.ClientBounds.Width / (float)Game.Window.ClientBounds.Height, 1, 500); } public override void Update(GameTime gameTime) { // TODO: Add your update code here CreateLookAt(); base.Update(gameTime); } } And this is the code for the class that extends the above class to look at its target. class TargetedCamera : BasicCamera { public Vector3 target { get; protected set; } public TargetedCamera(Game game, Vector3 position, Vector3 target, Vector3 up) : base(game, position, target, up) { this.target = target; } public void SetTarget(Vector3 target) { direction = target - position; } protected override void CreateLookAt() { view = Matrix.CreateLookAt(position, target, up); } }

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  • Confusion about inheritance

    - by Samuel Adam
    I know I might get downvoted for this, but I'm really curious. I was taught that inheritance is a very powerful polymorphism tool, but I can't seem to use it well in real cases. So far, I can only use inheritance when the base class is an abstract class. Examples : If we're talking about Product and Inventory, I quickly assumed that a Product is an Inventory because a Product must be inventorized as well. But a problem occured when user wanted to sell their Inventory item. It just doesn't seem to be right to change an Inventory object to it's subtype (Product), it's almost like trying to convert a parent to it's child. Another case is Customer and Member. It is logical (at least for me) to think that a Member is a Customer with some more privileges. Same problem occurred when user wanted to upgrade an existing Customer to become a Member. A very trivial case is the Employee case. Where Manager, Clerk, etc can be derived from Employee. Still, the same upgrading issue. I tried to use composition instead for some cases, but I really wanted to know if I'm missing something for inheritance solution here. My composition solution for those cases : Create a reference of Inventory inside a Product. Here I'm making an assumption about that Product and Inventory is talking in a different context. While Product is in the context of sales (price, volume, discount, etc), Inventory is in the context of physical management (stock, movement, etc). Make a reference of Membership instead inside Customer class instead of previous inheritance solution. Therefor upgrading a Customer is only about instantiating the Customer's Membership property. This example is keep being taught in basic programming classes, but I think it's more proper to have those Manager, Clerk, etc derived from an abstract Role class and make it a property in Employee. I found it difficult to find an example of a concrete class deriving from another concrete class. Is there any inheritance solution in which I can solve those cases? Being new in this OOP thing, I really really need a guidance. Thanks!

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  • How to avoid the exception “Substitution controls cannot be used in cached User Controls or cached M

    - by DigiMortal
    Recently I wrote example about using user controls with donut caching. Because cache substitutions are not allowed inside partially cached controls you may get the error Substitution controls cannot be used in cached User Controls or cached Master Pages when breaking this rule. In this posting I will introduce some strategies that help to avoid this error. How Substitution control checks its location? Substitution control uses the following check in its OnPreRender method. protected internal override void OnPreRender(EventArgs e) {     base.OnPreRender(e);     for (Control control = this.Parent; control != null;          control = control.Parent)     {         if (control is BasePartialCachingControl)         {             throw new HttpException(SR.GetString("Substitution_CannotBeInCachedControl"));         }     } } It traverses all the control tree up to top from its parent to find at least one control that is partially cached. If such control is found then exception is thrown. Reusing the functionality If you want to do something by yourself if your control may cause exception mentioned before you can use the same code. I modified the previously shown code to be method that can be easily moved to user controls base class if you have some. If you don’t you can use it in controls where you need this check. protected bool IsInsidePartialCachingControl() {     for (Control control = Parent; control != null;         control = control.Parent)         if (control is BasePartialCachingControl)             return true;       return false; } Now it is up to you how to handle the situation where your control with substitutions is child of some partially cache control. You can add here also some debug level output so you can see exactly what controls in control hierarchy are cached and cause problems.

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  • Lookup Viewer

    - by Geertjan
    The Maven integrated view that I showed yesterday I was able to create because I happened to know that an implementation of SubprojectProvider and LogicalViewProvider are in the Lookup of Maven projects. With that knowledge, I was able to use and even delegate to those implementations. But what if you don't know that those implementations are in the Lookup of the Project object? In the case of the Maven Project implementation, you could look in the source code of the Maven Project implementation, at the "getLookup" method. However, any other module could be putting its own objects into that Lookup, dynamically, i.e., at runtime. So there's no way of knowing what's in the Lookup of any Project object or any other object with a Lookup. But now imagine that you have a Lookup Viewer, as a tool during development, which you would exclude when distributing the application. Whenever new objects are found in the Lookup, the viewer displays them. You could install the Lookup Viewer into NetBeans IDE, or any other NetBeans Platform application, and then get a quick impression of what's actually in the Lookup when you select a different item in the application during development. Here it is (though I vaguely remember someone else writing something similar): Above, a Maven Project is selected. The Lookup Window shows that, among many other classes, an implementation of SubprojectProvider and LogicalViewProvider are found in the Lookup when the Maven Project is selected. If an item in the Lookup Window has its own Lookup, the content of that Lookup is displayed as child nodes of the Lookup, etc, i.e., you can explore all the way down the Lookup of each item found within objects found within the current selection. (What's especially fun is seeing the SaveCookieImpl being added and removed from the Lookup Window when you make/save a change in a document.) Another example is below, showing the Lookup Window installed in a custom application created during a course at MIT in Boston: A small trick I had to apply is that I always show the previous Lookup, since the current Lookup, when you select one of the Nodes in the Lookup Window, would be the Lookup of the Lookup Window itself! If anyone is interested in this, I can publish the NetBeans module providing the above window to the NetBeans update center. 

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  • algorithm for project euler problem no 18

    - by Valentino Ru
    Problem number 18 from Project Euler's site is as follows: By starting at the top of the triangle below and moving to adjacent numbers on the row below, the maximum total from top to bottom is 23. 3 7 4 2 4 6 8 5 9 3 That is, 3 + 7 + 4 + 9 = 23. Find the maximum total from top to bottom of the triangle below: 75 95 64 17 47 82 18 35 87 10 20 04 82 47 65 19 01 23 75 03 34 88 02 77 73 07 63 67 99 65 04 28 06 16 70 92 41 41 26 56 83 40 80 70 33 41 48 72 33 47 32 37 16 94 29 53 71 44 65 25 43 91 52 97 51 14 70 11 33 28 77 73 17 78 39 68 17 57 91 71 52 38 17 14 91 43 58 50 27 29 48 63 66 04 68 89 53 67 30 73 16 69 87 40 31 04 62 98 27 23 09 70 98 73 93 38 53 60 04 23 NOTE: As there are only 16384 routes, it is possible to solve this problem by trying every route. However, Problem 67, is the same challenge with a triangle containing one-hundred rows; it cannot be solved by brute force, and requires a clever method! ;o) The formulation of this problems does not make clear if the "Traversor" is greedy, meaning that he always choosed the child with be higher value the maximum of every single walkthrough is asked The NOTE says, that it is possible to solve this problem by trying every route. This means to me, that is is also possible without! This leads to my actual question: Assumed that not the greedy one is the max, is there any algorithm that finds the max walkthrough value without trying every route and that doesn't act like the greedy algorithm? I implemented an algorithm in Java, putting the values first in a node structure, then applying the greedy algorithm. The result, however, is cosidered as wrong by Project Euler. sum = 0; void findWay(Node node){ sum += node.value; if(node.nodeLeft != null && node.nodeRight != null){ if(node.nodeLeft.value > node.nodeRight.value){ findWay(node.nodeLeft); }else{ findWay(node.nodeRight); } } }

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  • Small script to look for Project Replication actions that have failed

    - by Trond Strømme
    Today when looking at a couple of projects on a ZFS 7320 Storage Appliance I noticed on one project that one of its replication actions had failed, as I hadn't checked the Recent Alerts log yet I was not aware of this. I decided to write a small script to check if there were others that had failed. Nothing fancy, just a loop through all projects, look at the project's replication child and compare the values of the last_sync and last_try properties and print the result if they're not equal. (There are probably more sensible ways of doing this, but at least it involves me getting the chance to put on my headphones and doing just a little bit of coding.) script // this script will locate failed project level replication // it will look at the sync times for 'last_sync' and 'last_try' // and compare these, if they deviate you should investigate. // NOTE! this code is offered 'as is' Run at your own risk, // it will probably work as intended, but in now way can I // (or Oracle) be held responsible if your server starts behaving // like a three year old kid in a candy store.. (not that mine do, // they are very well behaved boys...) run('configuration'); run('storage'); printf('Host: %s, pool: %s\n', get('owner'),get('pool')); run('cd /'); run('shares'); proj=list(); printf("total projects: %d\n",proj.length +'\n'); // just for project level replication for(i=0;i<proj.length;i++){ run('select '+proj[i]); run('replication'); //get all replication actions preps = list(); for(j=0;j<preps.length;j++){ run('select ' + preps[j]); last_sync = get('last_sync'); last_try = get('last_try'); // printf("target %s\n", get('target')); //why the flip does this not get the proper name? if(!( last_sync.valueOf() === last_try.valueOf())){ printf("sync has failed for %s %s\n", proj[i], get('target')); }else{ // printf("OK %s %s\n", proj[i], get('target')); } run('done'); //done with the replica action } run('done'); run('done'); } printf("finished\n"); For a more on how to run the script, or testing it please look at my previous post. Sample output: Host: elb1sn01, pool: exalogic total projects: 45 sync has failed for ACSExalogicSystem cb3a24fe-ad60-c90f-d15d-adaafd595639 finished

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  • Rotate camera around player and set new forward directions

    - by Samurai Fox
    I have a 3rd person camera which can rotate around the player. When I look at the back of the player and press forward, player goes forward. Then I rotate 360 around the player and "forward direction" is tilted for 90 degrees. So every 360 turn there is 90 degrees of direction change. For example when camera is facing the right side of the player, when I press button to move forward, I want player to turn to the left and make that the "new forward". I have Player object with Camera as child object. Camera object has Camera script. Inside Camera script there are Player and Camera classes. Player object itself, has Input Controller. Also I'm making this script for joystick/ controller primarily. My camera script so far: using UnityEngine; using System.Collections; public class CameraScript : MonoBehaviour { public GameObject Target; public float RotateSpeed = 10, FollowDistance = 20, FollowHeight = 10; float RotateSpeedPerTime, DesiredRotationAngle, DesiredHeight, CurrentRotationAngle, CurrentHeight, Yaw, Pitch; Quaternion CurrentRotation; void LateUpdate() { RotateSpeedPerTime = RotateSpeed * Time.deltaTime; DesiredRotationAngle = Target.transform.eulerAngles.y; DesiredHeight = Target.transform.position.y + FollowHeight; CurrentRotationAngle = transform.eulerAngles.y; CurrentHeight = transform.position.y; CurrentRotationAngle = Mathf.LerpAngle(CurrentRotationAngle, DesiredRotationAngle, 0); CurrentHeight = Mathf.Lerp(CurrentHeight, DesiredHeight, 0); CurrentRotation = Quaternion.Euler(0, CurrentRotationAngle, 0); transform.position = Target.transform.position; transform.position -= CurrentRotation * Vector3.forward * FollowDistance; transform.position = new Vector3(transform.position.x, CurrentHeight, transform.position.z); Yaw = Input.GetAxis("Right Horizontal") * RotateSpeedPerTime; Pitch = Input.GetAxis("Right Vertical") * RotateSpeedPerTime; transform.Translate(new Vector3(Yaw, -Pitch, 0)); transform.position = new Vector3(transform.position.x, transform.position.y, transform.position.z); transform.LookAt(Target.transform); } }

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  • How far should an entity take care of its properties values by itself?

    - by Kharlos Dominguez
    Let's consider the following example of a class, which is an entity that I'm using through Entity Framework. - InvoiceHeader - BilledAmount (property, decimal) - PaidAmount (property, decimal) - Balance (property, decimal) I'm trying to find the best approach to keep Balance updated, based on the values of the two other properties (BilledAmount and PaidAmount). I'm torn between two practices here: Updating the balance amount every time BilledAmount and PaidAmount are updated (through their setters) Having a UpdateBalance() method that the callers would run on the object when appropriate. I am aware that I can just calculate the Balance in its getter. However, it isn't really possible because this is an entity field that needs to be saved back to the database, where it has an actual column, and where the calculated amount should be persisted to. My other worry about the automatically updating approach is that the calculated values might be a little bit different from what was originally saved to the database, due to rounding values (an older version of the software, was using floats, but now decimals). So, loading, let's say 2000 entities from the database could change their status and make the ORM believe that they have changed and be persisted back to the database the next time the SaveChanges() method is called on the context. It would trigger a mass of updates that I am not really interested in, or could cause problems, if the calculation methods changed (the entities fetched would lose their old values to be replaced by freshly recalculated ones, simply by being loaded). Then, let's take the example even further. Each invoice has some related invoice details, which also have BilledAmount, PaidAmount and Balance (I'm simplifying my actual business case for the sake of the example, so let's assume the customer can pay each item of the invoice separately rather than as a whole). If we consider the entity should take care of itself, any change of the child details should cause the Invoice totals to change as well. In a fully automated approach, a simple implementation would be looping through each detail of the invoice to recalculate the header totals, every time one the property changes. It probably would be fine for just a record, but if a lot of entities were fetched at once, it could create a significant overhead, as it would perform this process every time a new invoice detail record is fetched. Possibly worse, if the details are not already loaded, it could cause the ORM to lazy-load them, just to recalculate the balances. So far, I went with the Update() method-way, mainly for the reasons I explained above, but I wonder if it was right. I'm noticing I have to keep calling these methods quite often and at different places in my code and it is potential source of bugs. It also has a detrimental effect on data-binding because when the properties of the detail or header changes, the other properties are left out of date and the method has no way to be called. What is the recommended approach in this case?

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  • Separating logic and data in browser game

    - by Tesserex
    I've been thinking this over for days and I'm still not sure what to do. I'm trying to refactor a combat system in PHP (...sorry.) Here's what exists so far: There are two (so far) types of entities that can participate in combat. Let's just call them players and NPCs. Their data is already written pretty well. When involved in combat, these entities are wrapped with another object in the DB called a Combatant, which gives them information about the particular fight. They can be involved in multiple combats at once. I'm trying to write the logic engine for combat by having combatants injected into it. I want to be able to mock everything for testing. In order to separate logic and data, I want to have two interfaces / base classes, one being ICombatantData and the other ICombatantLogic. The two implementers of data will be one for the real objects stored in the database, and the other for my mock objects. I'm now running into uncertainties with designing the logic side of things. I can have one implementer for each of players and NPCs, but then I have an issue. A combatant needs to be able to return the entity that it wraps. Should this getter method be part of logic or data? I feel strongly that it should be in data, because the logic part is used for executing combat, and won't be available if someone is just looking up information about an upcoming fight. But the data classes only separate mock from DB, not player from NPC. If I try having two child classes of the DB data implementer, one for each entity type, then how do I architect that while keeping my mocks in the loop? Do I need some third interface like IEntityProvider that I inject into the data classes? Also with some of the ideas I've been considering, I feel like I'll have to put checks in place to make sure you don't mismatch things, like making the logic for an NPC accidentally wrap the data for a player. Does that make any sense? Is that a situation that would even be possible if the architecture is correct, or would the right design prohibit that completely so I don't need to check for it? If someone could help me just layout a class diagram or something for this it would help me a lot. Thanks. edit Also useful to note, the mock data class doesn't really need the Entity, since I'll just be specifying all the parameters like combat stats directly instead. So maybe that will affect the correct design.

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  • Are there any good Java/JVM libraries for my Expression Tree architecture?

    - by Snuggy
    My team and I are developing an enterprise-level application and I have devised an architecture for it that's best described as an "Expression Tree". The basic idea is that the leaf nodes of the tree are very simple expressions (perhaps simple values or strings). Nodes closer to the trunk will get more and more complex, taking the simpler nodes as their inputs and returning more complex results for their parents. Looking at it the other way, the application performs some task, and for this it creates a root expression. The root expression divides its input into smaller units and creates child expressions, which when evaluated it can use to build it's own result. The subdividing process continues until the simplest leaf nodes. There are two very important aspects of this architecture: It must be possible to manipulate nodes of the tree after it is built. The nodes may be given new input values to work with and any change in result for that node needs to be propagated back up the tree to the root node. The application must make best use of available processors and ultimately be scalable to other computers in a grid or in the cloud. Nodes in the tree will often be updating concurrently and notifying other interested nodes in the tree when they get a new value. Unfortunately, I'm not at liberty to discuss my actual application, but to aid understanding a little bit, you might imagine a kind of spreadsheet application being implemented with a similar architecture, where changes to cells in the table are propagated all over the place to other cells that need the result. The spreadsheet could get so massive that applying multi-core multi-computer distributed system to solve it would be of benefit. I've got my prototype "Expression Engine" working nicely on a single multi-core PC but I've started to run into a few concurrency issues (as expected because I haven't been taking too much care so far) so it's now time to start thinking about migrating the Engine to a more robust library, and that leads to a number of related questions: Is there any precedent for my "Expression Tree" architecture that I could research? What programming concepts should I consider. I realise this approach has many similarities to a functional programming style, and I'm already aware of the concepts of using futures and actors. Are there any others? Are there any languages or libraries that I should study? This question is inspired by my accidental discovery of Scala and the Akka library (which has good support for Actors, Futures, Distributed workloads etc.) and I'm wondering if there is anything else I should be looking at as well?

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  • Event-Driven Debugging

    - by Brian Donahue
    Most application troubleshooting involves getting an error, analyzing the error message, and at worst, attaching a debugger to work out the real cause. What is not really covered is how to troubleshoot an applicaiton that is not errant, but is having a performance issue, and more than likely, in the middle of the night when you are snug in your bed, sawing logs. What you need is an ever-vigilant cyborg who never sleeps to sit in front of your server all night, but as SkyNet is not live yet, you can settle for the next-best thing. Windows provides performance counters and alerts that can tell you when an applicaiton reaches an unacceptable threshold of naughty behavior, but although it can tattle on your brainchild, it won't be the child psychiatrist that you need to tell you why he's pulling your server's pigtails and pulling faces at the teacher. What you need is to plug a debugger into performance monitor and have it tell you what's going on with your applicaiton at the time. For this purpose, I'd used Microsoft's MDbgEngine as the basis for an applicaiton that will dump a program's stacks, I call it Application Slicer Dicer Wonder Dumper Super Cyborg, or StackOMatic for short. StackOMatic can look at a program's behavior and tell you if the stacks are not moving, but it can also work on the command-line to dump all managed methods on the stack at will. Now that there is a command you can use to dump the stacks, all you need to do is politely tell Windows to run it when you're displeased with your creation as it's trashing the CPU of your server at 3 AM. The first step is to create a scheduled task to tell StackOMatic to dump your applicaiton. Start Task Scheduler and right-click Task Scheduler Library and then Create Task. For this exercise I'm creating a task that will dump the Red Gate SQL Monitor Base Monitor Service. In the Actions tab, I enter the path to StackOMatic and use the arguments to log the stack dump to a file: /PN:RedGate.Response.Engine.Alerting.Base.Service /OUT:c:\users\administrator\MonitorLog.txt Next, I go into Windows Server 2008's Reliability and Performance Monitor and add a new Data Collector Set. This set will produce an alert on the %Processor Time for the service. When the processor time breaches 50%, it will run the StackDumpBaseService task I created. Whenever the service misbehaves, it will append to the log file. Now when I go to work in the morning, I can see what the service was doing when it overloaded the processor and take action.

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