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• MVVM Light V4 preview 2 (BL0015) #mvvmlight

  - by Laurent Bugnion

  Over the past few weeks, I have worked hard on a few new features for MVVM Light V4. Here is a second early preview (consider this pre-alpha if you wish). The features are unit-tested, but I am now looking for feedback and there might be bugs! Bug correction: Messenger.CleanupList is now thread safe This was an annoying bug that is now corrected: In some circumstances, an exception could be thrown when the Messenger’s recipients list was cleaned up (i.e. the “dead” instances were removed). The method is called now and then and the exception was thrown apparently at random. In fact it was really a multi-threading issue, which is now corrected. Bug correction: AllowPartiallyTrustedCallers prevents EventToCommand to work This is a particularly annoying regression bug that was introduced in BL0014. In order to allow MVVM Light to work in XBAPs too, I added the AllowPartiallyTrustedCallers attribute to the assemblies. However, we just found out that this causes issues when using EventToCommand. In order to allow EventToCommand to continue working, I reverted to the previous state by removing the AllowPartiallyTrustedCallers attribute for now. I will work with my friends at Microsoft to try and find a solution. Stay tuned. Bug correction: XML documentation file is now generated in Release configuration The XML documentation file was not generated for the Release configuration. This was a simple flag in the project file that I had forgotten to set. This is corrected now. Applying EventToCommand to non-FrameworkElements This feature has been requested in order to be able to execute a command when a Storyboard is completed. I implemented this, but unfortunately found out that EventToCommand can only be added to Storyboards in Silverlight 3 and Silverlight 4, but not in WPF or in Windows Phone 7. This obviously limits the usefulness of this change, but I decided to publish it anyway, because it is pretty damn useful in Silverlight… Why not in WPF? In WPF, Storyboards added to a resource dictionary are frozen. This is a feature of WPF which allows to optimize certain objects for performance: By freezing them, it is a contract where we say “this object will not be modified anymore, so do your perf optimization on them without worrying too much”. Unfortunately, adding a Trigger (such as EventTrigger) to an object in resources does not work if this object is frozen… and unfortunately, there is no way to tell WPF not to freeze the Storyboard in the resources… so there is no way around that (at least none I can see. In Silverlight, objects are not frozen, so an EventTrigger can be added without problems. Why not in WP7? In Windows Phone 7, there is a totally different issue: Adding a Trigger can only be done to a FrameworkElement, which Storyboard is not. Here I think that we might see a change in a future version of the framework, so maybe this small trick will work in the future. Workaround? Since you cannot use the EventToCommand on a Storyboard in WPF and in WP7, the workaround is pretty obvious: Handle the Completed event in the code behind, and call the Command from there on the ViewModel. This object can be obtained by casting the DataContext to the ViewModel type. This means that the View needs to know about the ViewModel, but I never had issues with that anyway. New class: NotifyPropertyChanged Sometimes when you implement a model object (for example Customer), you would like to have it implement INotifyPropertyChanged, but without having all the frills of a ViewModelBase. A new class named NotifyPropertyChanged allows you to do that. This class is a simple implementation of INotifyPropertyChaned (with all the overloads of RaisePropertyChanged that were implemented in BL0014). In fact, ViewModelBase inherits NotifyPropertyChanged. ViewModelBase does not implement IDisposable anymore The IDisposable interface and the Dispose method had been marked obsolete in the ViewModelBase class already in V3. Now they have been removed. Note: By this, I do not mean that IDisposable is a bad interface, or that it shouldn’t be used on viewmodels. In the contrary, I know that this interface is very useful in certain circumstances. However, I think that having it by default on every instance of ViewModelBase was sending a wrong message. This interface has a strong meaning in .NET: After Dispose has been executed, the instance should not be used anymore, and should be ready for garbage collection. What I really wanted to have on ViewModelBase was rather a simple cleanup method, something that can be executed now and then during runtime. This is fulfilled by the ICleanup interface and its Cleanup method. If your ViewModels need IDisposable, you can still use it! You will just have to implement the interface on the class itself, because it is not available on ViewModelBase anymore. What’s next? I have a couple exciting new features implemented already but that need more testing before they go live… Just stay tuned and by MIX11 (12-14 April 2011), we should see at least a major addition to MVVM Light Toolkit, as well as another smaller feature which is pretty cool nonetheless More about this later! Happy Coding Laurent   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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• Aggregating cache data from OCEP in CQL

  - by Manju James

  There are several use cases where OCEP applications need to join stream data with external data, such as data available in a Coherence cache. OCEP’s streaming language, CQL, supports simple cache-key based joins of stream data with data in Coherence (more complex queries will be supported in a future release). However, there are instances where you may need to aggregate the data in Coherence based on input data from a stream. This blog describes a sample that does just that. For our sample, we will use a simplified credit card fraud detection use case. The input to this sample application is a stream of credit card transaction data. The input stream contains information like the credit card ID, transaction time and transaction amount. The purpose of this application is to detect suspicious transactions and send out a warning event. For the sake of simplicity, we will assume that all transactions with amounts greater than $1000 are suspicious. The transaction history is available in a Coherence distributed cache. For every suspicious transaction detected, a warning event must be sent with maximum amount, total amount and total number of transactions over the past 30 days, as shown in the diagram below. Application Input Stream input to the EPN contains events of type CCTransactionEvent. This input has to be joined with the cache with all credit card transactions. The cache is configured in the EPN as shown below: <wlevs:caching-system id="CohCacheSystem" provider="coherence"/> <wlevs:cache id="CCTransactionsCache" value-type="CCTransactionEvent" key-properties="cardID, transactionTime" caching-system="CohCacheSystem"> </wlevs:cache> Application Output The output that must be produced by the application is a fraud warning event. This event is configured in the spring file as shown below. Source for cardHistory property can be seen here. <wlevs:event-type type-name="FraudWarningEvent"> <wlevs:properties type="tuple"> <wlevs:property name="cardID" type="CHAR"/> <wlevs:property name="transactionTime" type="BIGINT"/> <wlevs:property name="transactionAmount" type="DOUBLE"/> <wlevs:property name="cardHistory" type="OBJECT"/> </wlevs:properties </wlevs:event-type> Cache Data Aggregation using Java Cartridge In the output warning event, cardHistory property contains data from the cache aggregated over the past 30 days. To get this information, we use a java cartridge method. This method uses Coherence’s query API on credit card transactions cache to get the required information. Therefore, the java cartridge method requires a reference to the cache. This may be set up by configuring it in the spring context file as shown below: <bean class="com.oracle.cep.ccfraud.CCTransactionsAggregator"> <property name="cache" ref="CCTransactionsCache"/> </bean> This is used by the java class to set a static property: public void setCache(Map cache) { s_cache = (NamedCache) cache; } The code snippet below shows how the total of all the transaction amounts in the past 30 days is computed. Rest of the information required by CardHistory object is calculated in a similar manner. Complete source of this class can be found here. To find out more information about using Coherence's API to query a cache, please refer Coherence Developer’s Guide. public static CreditHistoryData(String cardID) { … Filter filter = QueryHelper.createFilter("cardID = :cardID and transactionTime :transactionTime", map); CardHistoryData history = new CardHistoryData(); Double sum = (Double) s_cache.aggregate(filter, new DoubleSum("getTransactionAmount")); history.setTotalAmount(sum); … return history; } The java cartridge method is used from CQL as seen below: select cardID, transactionTime, transactionAmount, CCTransactionsAggregator.execute(cardID) as cardHistory from inputChannel where transactionAmount1000 This produces a warning event, with history data, for every credit card transaction over $1000. That is all there is to it. The complete source for the sample application, along with the configuration files, is available here. In the sample, I use a simple java bean to load the cache with initial transaction history data. An input adapter is used to create and send transaction events for the input stream.

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• Do private static methods in C# hurt anything?

  - by fish

  I created a private validation method for a certain validation that happens multiple times in my class (I can't store the validated data for various reasons). Now, ReSharper suggests that the function could be made static. I'm a little reluctant to do so due known problems with static methods. It would be a private static method. My question is, can private static methods cause similar coupling and testing problems like public static methods? Is it a bad practice? I would guess not, but I'm not sure if there is a pitfall here.

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• Database Documentation - Lands of Trolls: Why and How?

  When database documentation is mentioned in an IT Department, everybody nods wisely, yet everyone does their best to avoid doing it. Attention to the database documentation can be the best invertment in time a development group can make. It is essential, and no system can be properly maintained without it. Feodor gives a sensible explanation and guideline for the unloved task of creating database documentation.

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• Customer Support Spotlight: Clemson University

  - by cwarticki

  I've begun a Customer Support Spotlight series that highlights our wonderful customers and Oracle loyalists.  A week ago I visited Clemson University.  As I travel to visit and educate our customers, I provide many useful tips/tricks and support best practices (as found on my blog and twitter). Most of all, I always discover an Oracle gem who deserves recognition for their hard work and advocacy. Meet George Manley.  George is a Storage Engineer who has worked in Clemson's Data Center all through college, partially in the Hardware Architecture group and partially in the Storage group. George and the rest of the Storage Team work with most all of the storage technologies that they have here at Clemson. This includes a wide array of different vendors' disk arrays, with the most of them being Oracle/Sun 2540's.  He also works with SAM/QFS, ACSLS, and our SL8500 Tape Libraries (all three Oracle/Sun products). (pictured L to R, Matt Schoger (Oracle), Mark Flores (Oracle) and George Manley) George was kind enough to take us for a data center tour.  It was amazing.  I rarely get to see the inside of data centers, and this one was massive. Clemson Computing and Information Technology’s physical resources include the main data center located in the Information Technology Center at the Innovation Campus and Technology Park. The core of Clemson’s computing infrastructure, the data center has 21,000 sq ft of raised floor and is powered by a 14MW substation. The ITC power capacity is 4.5MW.  The data center is the home of both enterprise and HPC systems, and is staffed by CCIT staff on a 24 hour basis from a state of the art network operations center within the ITC. A smaller business continuance data center is located on the main campus.  The data center serves a wide variety of purposes including HPC (supercomputing) resources which are shared with other Universities throughout the state, the state's medicaid processing system, and nearly all other needs for Clemson University. Yes, that's no typo (14,256 cores and 37TB of memory!!! Thanks for the tour George and thank you very much for your time.  The tour was fantastic. I enjoyed getting to know your team and I look forward to many successes from Clemson using Oracle products. -Chris WartickiGlobal Customer Management

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• JD Edwards Delivers Once Again with Significant Announcements

  Listen to Lenley Hensarling, JD Edwards Group Vice President,talk about the significant JD Edwards announcements made during Oracle OpenWorld 2008.Lenley will highlight how JD Edwards’ customers can benefit from the latest product releases from EnterpriseOne and World,discuss the wave of companies who are upgrading to the most recent JD Edwards releases to take advantage of an array of industry specific enhancements,and elaborate on JD Edwards’ strategy about integrating to other Oracle solutions,bringing continuous value to customers.

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• LINQ and the use of Repeat and Range operator

  - by vik20000in

  LINQ is also very useful when it comes to generation of range or repetition of data.  We can generate a range of data with the help of the range method.     var numbers =         from n in Enumerable.Range(100, 50)         select new {Number = n, OddEven = n % 2 == 1 ? "odd" : "even"}; The above query will generate 50 records where the record will start from 100 till 149. The query also determines if the number is odd or even. But if we want to generate the same number for multiple times then we can use the Repeat method.     var numbers = Enumerable.Repeat(7, 10); The above query will produce a list with 10 items having the value 7. Vikram

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• Silverlight Cream for March 13, 2011 -- #1059

  - by Dave Campbell

  In this Issue: András Velvárt, WIndowsPhoneGeek(-2-), Jesse Liberty(-2-), Victor Gaudioso, Kunal Chowdhury, Jeremy Likness, Michael Crump, and Dhananjay Kumar. Above the Fold: Silverlight: "Application Library Caching in Silverlight 4" Kunal Chowdhury WP7: "Handling WP7 orientation changes via Visual States" András Velvárt Shoutouts: Joe McBride gave a MEF Head User Group presentation and has posted How to Become a MEF Head – Slides & Code From SilverlightCream.com: Handling WP7 orientation changes via Visual States András Velvárt has an Expression Blend/WP7 post up discussing WP7 orientation changes and handling them via Visual States ... see an example from his SurfCube app, and a behavior to handle the control... with source. WP7 PerformanceProgressBar in depth WIndowsPhoneGeek has a post up discussing the WP7 Performance bar from the Windows Phone Toolkit. This is an update on the Toolkit based on the Feb 2011 release. Great explanation of the PerformanceProgressBar, external links, and sample code. Getting data out of WP7 WMAppManifest is easy with Coding4Fun PhoneHelper Next WindowsPhoneGeek has a post up about the PhoneHelper in the Coding4Fun TOolkit, and using it to get data out of the WMAppManifest easily. Good discussion, Links, and code as always Silverlight Unit Test For Phone In Jesse Liberty's "Windows Phone From Scratch" number 41, he's discussing Unit Testing for WP7... he gives some good external links and some good examples. Yet Another Podcast #27–Paul Betts Jesse Liberty's next post is his "Yet Another Podcast" number 27, and an interview with Paul Betts, the creator of Reactive UI... check out the podcast and also the good links listed. New Silverlight Video Tutorial: How to use the Fluid Move Behavior Victor Gaudioso has a new video tutorial up on using the Fluid Move Behavior... making a selected item animate from a ListBox to a Master Details Grid. Application Library Caching in Silverlight 4 Kunal Chowdhury takes a break from SilverlightZone long enough to write a post about Application Library Caching... for example on-demand loading of a 3rd-party XAP. Jounce Part 13: Navigation Parameters Jeremy Likness has his 13th post of a series in understanding his Jounce MVVM framework up. This episode surrounds a new release and what it contains, the primary focus being navigation parameters... that is you can raise a navigation event with a payload. Profiling Silverlight Applications after installing Visual Studio 2010 Service Pack 1 Michael Crump digs into the performance wizard for Silverlight that we get with VS2010 SP1. He shows how to get and read a profile... great intro to a new tool. Binding XML File to Data Grid in Silverlight Dhananjay Kumar demonstrates reading an XML file using LINQ to XML and binding the result to a Silverlight DataGrid Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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• Andengine put bullet to pull, when it leaves screen

  - by Ashot

  i'm creating a bullet with physics body. Bullet class (extends Sprite class) has die() method, which unregister physics connector, hide sprite and put it in pull public void die() { Log.d("bulletDie", "See you in hell!"); if (this.isVisible()) { this.setVisible(false); mPhysicsWorld.unregisterPhysicsConnector(physicsConnector); physicsConnector.setUpdatePosition(false); body.setActive(false); this.setIgnoreUpdate(true); bulletsPool.recyclePoolItem(this); } } in onUpdate method of PhysicsConnector i executes die method, when sprite leaves screen physicsConnector = new PhysicsConnector(this,body,true,false) { @Override public void onUpdate(final float pSecondsElapsed) { super.onUpdate(pSecondsElapsed); if (!camera.isRectangularShapeVisible(_bullet)) { Log.d("bulletDie","Dead?"); _bullet.die(); } } }; it works as i expected, but _bullet.die() executes TWICE. what i`m doing wrong and is it right way to hide sprites? here is full code of Bullet class (it is inner class of class that represents player) private class Bullet extends Sprite implements PhysicsConstants { private final Body body; private final PhysicsConnector physicsConnector; private final Bullet _bullet; private int id; public Bullet(float x, float y, ITextureRegion texture, VertexBufferObjectManager vertexBufferObjectManager) { super(x,y,texture,vertexBufferObjectManager); _bullet = this; id = bulletId++; body = PhysicsFactory.createCircleBody(mPhysicsWorld, this, BodyDef.BodyType.DynamicBody, bulletFixture); physicsConnector = new PhysicsConnector(this,body,true,false) { @Override public void onUpdate(final float pSecondsElapsed) { super.onUpdate(pSecondsElapsed); if (!camera.isRectangularShapeVisible(_bullet)) { Log.d("bulletDie","Dead?"); Log.d("bulletDie",id+""); _bullet.die(); } } }; mPhysicsWorld.registerPhysicsConnector(physicsConnector); $this.getParent().attachChild(this); } public void reset() { final float angle = canon.getRotation(); final float x = (float) ((Math.cos(MathUtils.degToRad(angle))*radius) + centerX) / PIXEL_TO_METER_RATIO_DEFAULT; final float y = (float) ((Math.sin(MathUtils.degToRad(angle))*radius) + centerY) / PIXEL_TO_METER_RATIO_DEFAULT; this.setVisible(true); this.setIgnoreUpdate(false); body.setActive(true); mPhysicsWorld.registerPhysicsConnector(physicsConnector); body.setTransform(new Vector2(x,y),0); } public Body getBody() { return body; } public void setLinearVelocity(Vector2 velocity) { body.setLinearVelocity(velocity); } public void die() { Log.d("bulletDie", "See you in hell!"); if (this.isVisible()) { this.setVisible(false); mPhysicsWorld.unregisterPhysicsConnector(physicsConnector); physicsConnector.setUpdatePosition(false); body.setActive(false); this.setIgnoreUpdate(true); bulletsPool.recyclePoolItem(this); } } }

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• SQL Relay - G is for GO

  - by fatherjack

  At the SQL Relay event last week all the UK user group leaders did a combined session - The A to Z of SQL - where we all took two letters of the alphabet and gave a 2 minute (it was strictly timed) talk on something SQL related beginning with those letters. It was quite a riot working through 26 different talks in an hour with 25 speaker handovers and the associated switches between SSMS and the slide deck. As a speaker I thoroughly enjoyed it and i hoe we informed as much as  we entertained the...(read more)

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• Implementing a "state-machine" logic for methods required by an object in C++

  - by user827992

  What I have: 1 hypothetical object/class + other classes and related methods that gives me functionality. What I want: linking this object to 0 to N methods in realtime on request when an event is triggered Each event is related to a single method or a class, so a single event does not necessarily mean "connect this 1 method only" but can also mean "connect all the methods from that class or a group of methods" Avoiding linked lists because I have to browse the entire list to know what methods are linked, because this does not ensure me that the linked methods are kept in a particular order (let's say an alphabetic order by their names or classes), and also because this involve a massive amount of pointers usage. Example: I have an object Employee Jon, Jon acquires knowledge and forgets things pretty easily, so his skills may vary during a period of time, I'm responsible for what Jon can add or remove from his CV, how can I implement this logic?

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• Code refactoring with Visual Studio 2010-Part 3

  - by Jalpesh P. Vadgama

  I have been writing few post about Code refactoring features of visual studio 2010 and This blog post is also one of them. In this post I am going to show you reorder parameters features in visual studio 2010. As a developer you might need to reorder parameter of a method or procedure in code for better readability of the the code and if you do this task manually then it is tedious job to do. But Visual Studio Reorder Parameter code refactoring feature can do this stuff within a minute. So let’s see how its works. For this I have created a simple console application which I have used earlier posts . Following is a code for that. using System; namespace CodeRefractoring { class Program { static void Main(string[] args) { string firstName = "Jalpesh"; string lastName = "Vadgama"; PrintMyName(firstName, lastName); } private static void PrintMyName(string firstName, string lastName) { Console.WriteLine(string.Format("FirstName:{0}", firstName)); Console.WriteLine(string.Format("LastName:{0}", lastName)); Console.ReadLine(); } } } Above code is very simple. It just print a firstname and lastname via PrintMyName method. Now I want to reorder the firstname and lastname parameter of PrintMyName. So for that first I have to select method and then click Refactor Menu-> Reorder parameters like following. Once you click a dialog box appears like following where it will give options to move parameter with arrow navigation like following. Now I am moving lastname parameter as first parameter like following. Once you click OK it will show a preview option where I can see the effects of changes like following. Once I clicked Apply my code will be changed like following. using System; namespace CodeRefractoring { class Program { static void Main(string[] args) { string firstName = "Jalpesh"; string lastName = "Vadgama"; PrintMyName(lastName, firstName); } private static void PrintMyName(string lastName, string firstName) { Console.WriteLine(string.Format("FirstName:{0}", firstName)); Console.WriteLine(string.Format("LastName:{0}", lastName)); Console.ReadLine(); } } } As you can see its very easy to use this feature. Hoped you liked it.. Stay tuned for more.. Till that happy programming.

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• Task Flow Design Paper Revised

  - by Duncan Mills

  Thanks to some discussion over at the ADF Methodology Group and contributions from Simon Lessard and Jan Vervecken I have been able to make some refinements to the Task Flow Design Fundamentals paper on OTN.As a bonus, whilst I was making some edits anyway I've included some of Frank Nimphius's memory scope diagrams which are a really useful tool for understanding how request, view, backingBean and pageFlow scopes all fit together.

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• WebCenter Spaces 11g PS2 Template Customization

  - by javier.ductor(at)oracle.com

  Recently, we have been involved in a WebCenter Spaces customization project. Customer sent us a prototype website in HTML, and we had to transform Spaces to set the same look&feel as in the prototype.Protoype:First of all, we downloaded a Virtual Machine with WebCenter Spaces 11g PS2, same version as customer's. The next step was to download ExtendWebCenterSpaces application. This is a webcenter application that customizes several elements of WebCenter Spaces: templates, skins, landing page, etc. jDeveloper configuration is needed, we followed steps described in Extended Guide, this blog was helpful too. . After that, we deployed the application using WebLogic console, we created a new group space and assigned the ExtendedWebCenterSpaces template (portalCentricSiteTemplate) to it. The result was this:As you may see there is a big difference with the prototype, which meant a lot of work to do from our side.So we needed to create a new Spaces template with its skin.Using jDeveloper, we created a new template based on the default template. We removed all menus we did not need and inserted 'include'  tags for header, breadcrumb and footers. Each of these elements was defined in an isolated jspx file.In the beginning, we faced a problem: we had to add code from prototype (in plain HTML) to jspx templates (JSF language). We managed to workaround this issue using 'verbatim' tags with 'CDATA' surrounding HTML code in header, breadcrumb and footers.Once the template was modified, we added css styles to the default skin. So we had some styles from portalCentricSiteTemplate plus styles from customer's prototype.Then, we re-deployed the application, assigned this template to a new group space and checked the result. After testing, we usually found issues, so we had to do some modifications in the application, then it was necessary to re-deploy the application and restart Spaces server. Due to this fact, the testing process takes quite a bit of time.Added to the template and skin customization, we also customized the Landing Page using this application and Members task flow using another application: SpacesTaskflowCustomizationApplication. I will talk about this task flow customization in a future entry.After some issues and workarounds, eventually we managed to get this look&feel in Spaces:P.S. In this customization I was working with Francisco Vega and Jose Antonio Labrada, consultants from Oracle Malaga International Consulting Centre.

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• JRockit Virtual Edition Debug Key

  - by changjae.lee

  There are a few keys that can help the debugging of the JRVE env in console. you can type in each keys in JRVE console to see what's happening under the hood. key '0' : System information key '5' : Enable shutdown key '7' : Start JRockit Management Server (port 7091) key '8' : Statistics Counters key '9' : Full Thread Dump key '0' : Status of Debug-key Below is the sample out from each keys. Debug-key '1' pressed ============ JRockitVE System Information ============ JRockitVE version : 11.1.1.3.0-67-131044 Kernel version : 6.1.0.0-97-131024 JVM version : R27.6.6-28_o-125824-1.6.0_17-20091214-2104-linux-ia32 Hypervisor version : Xen 3.4.0 Boot state : 0x007effff Uptime : 0 days 02:04:31 CPU : uniprocessor @2327 Mhz CPU usage : 0% ctx/s: 285 preempt/s: 0 migrations/s: 0 Physical pages : 82379/261121 (321/1020 MB) Network info : 10.179.97.64 (10.179.97.64/255.255.254.0) GateWay : 10.179.96.1 MAC address : 00:16:3e:7e:dc:78 Boot options : vfsCwd : /application/user_projects/domains/wlsve_domain mainArgs : java -javaagent:/jrockitve/services/sshd/sshd.jar -cp /jrockitve/jrockit/lib/tools.jar:/jrockitve/lib/common.jar:/application/patch_wls1032/profiles/default/sys_manifest_classpath/weblogic_patch.jar:/application/wlserver_10.3/server/lib/weblogic.jar -Dweblogic.Name=WlsveAdmin -Dweblogic.Domain=wlsve_domain -Dweblogic.management.username=weblogic -Dweblogic.management.password=welcome1 -Dweblogic.management.GenerateDefaultConfig=true weblogic.Server consLog : /jrockitve/log/jrockitve.log mounts : ext2 / dev0; posixLocale : en_US posixTimezone : Asia/Seoul posixEncoding : ISO-8859-1 Local disk : Size: 1024M, Used: 728M, Free: 295M ======================================================== Debug-key '5' pressed Shutdown enabled. Debug-key '7' pressed [JRockit] Management server already started. Ignoring request. Debug-key '8' pressed Starting stat recording Debug-key '8' pressed ========= Statistics Counters for the last second ========= dev.eth0_rx.cnt : 22 packets dev.eth0_rx_bytes.cnt : 2704 bytes dev.net_interrupts.cnt : 22 interrupts evt.timer_ticks.cnt : 123 ticks hyper.priv_entries.cnt : 144 entries schedule.context_switches.cnt : 271 switches schedule.idle_cpu_time.cnt : 997318849 nanoseconds schedule.idle_cpu_time_0.cnt : 997318849 nanoseconds schedule.total_cpu_time.cnt : 1000031757 nanoseconds time.system_time.cnt : 1000 ns time.timer_updates.cnt : 123 updates time.wallclock_time.cnt : 1000 ns ======================================= Debug-key '9' pressed ===== FULL THREAD DUMP =============== Fri Jun 4 08:22:12 2010 BEA JRockit(R) R27.6.6-28_o-125824-1.6.0_17-20091214-2104-linux-ia32 "Main Thread" id=1 idx=0x4 tid=1 prio=5 alive, in native, waiting -- Waiting for notification on: weblogic/t3/srvr/T3Srvr@0x646ede8[fat lock] at jrockit/vm/Threads.waitForNotifySignal(JLjava/lang/Object;)Z(Native Method) at java/lang/Object.wait(J)V(Native Method) at java/lang/Object.wait(Object.java:485) at weblogic/t3/srvr/T3Srvr.waitForDeath(T3Srvr.java:919) ^-- Lock released while waiting: weblogic/t3/srvr/T3Srvr@0x646ede8[fat lock] at weblogic/t3/srvr/T3Srvr.run(T3Srvr.java:479) at weblogic/Server.main(Server.java:67) at jrockit/vm/RNI.c2java(IIIII)V(Native Method) -- end of trace "(Signal Handler)" id=2 idx=0x8 tid=2 prio=5 alive, in native, daemon Open lock chains ================ Chain 1: "ExecuteThread: '0' for queue: 'weblogic.socket.Muxer'" id=23 idx=0x50 tid=20 waiting for java/lang/String@0x630c588 held by: "ExecuteThread: '1' for queue: 'weblogic.socket.Muxer'" id=24 idx=0x54 tid=21 (active) ===== END OF THREAD DUMP =============== Debug-key '0' pressed Debug-keys enabled Happy Cloud Walking :)

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• Asynchronous connectToServer

  - by Pavel Bucek

  Users of JSR-356 – Java API for WebSocket are probably familiar with WebSocketContainer#connectToServer method. This article will be about its usage and improvement which was introduce in recent Tyrus release. WebSocketContainer#connectToServer does what is says, it connects to WebSocketServerEndpoint deployed on some compliant container. It has two or three parameters (depends on which representation of client endpoint are you providing) and returns aSession. Returned Session represents WebSocket connection and you are instantly able to send messages, register MessageHandlers, etc. An issue might appear when you are trying to create responsive user interface and use this method – its execution blocks until Session is created which usually means some container needs to be started, DNS queried, connection created (it’s even more complicated when there is some proxy on the way), etc., so nothing which might be really considered as responsive. Trivial and correct solution is to do this in another thread and monitor the result, but.. why should users do that? :-) Tyrus now provides async* versions of all connectToServer methods, which performs only simple (=fast) check in the same thread and then fires a new one and performs all other tasks there. Return type of these methods is Future<Session>. List of added methods: public Future<Session> asyncConnectToServer(Class<?> annotatedEndpointClass, URI path) public Future<Session> asyncConnectToServer(Class<? extends Endpoint>  endpointClass, ClientEndpointConfig cec, URI path) public Future<Session> asyncConnectToServer(Endpoint endpointInstance, ClientEndpointConfig cec, URI path) public Future<Session> asyncConnectToServer(Object obj, URI path) As you can see, all connectToServer variants have its async* alternative. All these methods do throw DeploymentException, same as synchronous variants, but some of these errors cannot be thrown as a result of the first method call, so you might get it as the cause ofExecutionException thrown when Future<Session>.get() is called. Please let us know if you find these newly added methods useful or if you would like to change something (signature, functionality, …) – you can send us a comment to [email protected] or ping me personally. Related links: https://tyrus.java.net https://java.net/jira/browse/TYRUS/ https://github.com/tyrus-project/tyrus

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• Making your WCF Web Apis to speak in multiple languages

  - by cibrax

  One of the key aspects of how the web works today is content negotiation. The idea of content negotiation is based on the fact that a single resource can have multiple representations, so user agents (or clients) and servers can work together to chose one of them. The http specification defines several “Accept” headers that a client can use to negotiate content with a server, and among all those, there is one for restricting the set of natural languages that are preferred as a response to a request, “Accept-Language”. For example, a client can specify “es” in this header for specifying that he prefers to receive the content in spanish or “en” in english. However, there are certain scenarios where the “Accept-Language” header is just not enough, and you might want to have a way to pass the “accepted” language as part of the resource url as an extension. For example, http://localhost/ProductCatalog/Products/1.es” returns all the descriptions for the product with id “1” in spanish. This is useful for scenarios in which you want to embed the link somewhere, such a document, an email or a page.  Supporting both scenarios, the header and the url extension, is really simple in the new WCF programming model. You only need to provide a processor implementation for any of them. Let’s say I have a resource implementation as part of a product catalog I want to expose with the WCF web apis. [ServiceContract][Export]public class ProductResource{ IProductRepository repository;  [ImportingConstructor] public ProductResource(IProductRepository repository) { this.repository = repository; }  [WebGet(UriTemplate = "{id}")] public Product Get(string id, HttpResponseMessage response) { var product = repository.GetById(int.Parse(id)); if (product == null) { response.StatusCode = HttpStatusCode.NotFound; response.Content = new StringContent(Messages.OrderNotFound); }  return product; }} The Get method implementation in this resource assumes the desired culture will be attached to the current thread (Thread.CurrentThread.Culture). Another option is to pass the desired culture as an additional argument in the method, so my processor implementation will handle both options. This method is also using an auto-generated class for handling string resources, Messages, which is available in the different cultures that the service implementation supports. For example, Messages.resx contains “OrderNotFound”: “Order Not Found” Messages.es.resx contains “OrderNotFound”: “No se encontro orden” The processor implementation bellow tackles the first scenario, in which the desired language is passed as part of the “Accept-Language” header. public class CultureProcessor : Processor<HttpRequestMessage, CultureInfo>{ string defaultLanguage = null;  public CultureProcessor(string defaultLanguage = "en") { this.defaultLanguage = defaultLanguage; this.InArguments[0].Name = HttpPipelineFormatter.ArgumentHttpRequestMessage; this.OutArguments[0].Name = "culture"; }  public override ProcessorResult<CultureInfo> OnExecute(HttpRequestMessage request) { CultureInfo culture = null; if (request.Headers.AcceptLanguage.Count > 0) { var language = request.Headers.AcceptLanguage.First().Value; culture = new CultureInfo(language); } else { culture = new CultureInfo(defaultLanguage); }  Thread.CurrentThread.CurrentCulture = culture; Messages.Culture = culture;  return new ProcessorResult<CultureInfo> { Output = culture }; }}   As you can see, the processor initializes a new CultureInfo instance with the value provided in the “Accept-Language” header, and set that instance to the current thread and the auto-generated resource class with all the messages. In addition, the CultureInfo instance is returned as an output argument called “culture”, making possible to receive that argument in any method implementation   The following code shows the implementation of the processor for handling languages as url extensions.   public class CultureExtensionProcessor : Processor<HttpRequestMessage, Uri>{ public CultureExtensionProcessor() { this.OutArguments[0].Name = HttpPipelineFormatter.ArgumentUri; }  public override ProcessorResult<Uri> OnExecute(HttpRequestMessage httpRequestMessage) { var requestUri = httpRequestMessage.RequestUri.OriginalString;  var extensionPosition = requestUri.LastIndexOf(".");  if (extensionPosition > -1) { var extension = requestUri.Substring(extensionPosition + 1);  var query = httpRequestMessage.RequestUri.Query;  requestUri = string.Format("{0}?{1}", requestUri.Substring(0, extensionPosition), query); ;  var uri = new Uri(requestUri);  httpRequestMessage.Headers.AcceptLanguage.Clear();  httpRequestMessage.Headers.AcceptLanguage.Add(new StringWithQualityHeaderValue(extension));  var result = new ProcessorResult<Uri>();  result.Output = uri;  return result; }  return new ProcessorResult<Uri>(); }} The last step is to inject both processors as part of the service configuration as it is shown bellow, public void RegisterRequestProcessorsForOperation(HttpOperationDescription operation, IList<Processor> processors, MediaTypeProcessorMode mode){ processors.Insert(0, new CultureExtensionProcessor()); processors.Add(new CultureProcessor());} Once you configured the two processors in the pipeline, your service will start speaking different languages :). Note: Url extensions don’t seem to be working in the current bits when you are using Url extensions in a base address. As far as I could see, ASP.NET intercepts the request first and tries to route the request to a registered ASP.NET Http Handler with that extension. For example, “http://localhost/ProductCatalog/products.es” does not work, but “http://localhost/ProductCatalog/products/1.es” does.

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• Slick and Timers?

  - by user3491043

  I'm making a game where I need events to happen in a precise amount of time. Explanation : I want that event A happens at 12000ms, and event B happens every 10000ms. So "if"s should looks like this. //event A if(Ticks == 12000) //do things //even B if(Ticks % 10000 == 0) //do stuff But now how can I have this "Ticks" value ? I tried to declare an int and then increasing it in the update method, I tried 2 ways of increasing it : Ticks++; It doesn't works because the update method is not always called every microseconds. Ticks += delta; It's kinda good but the delta is not always equals to 1, so I can miss the precise values I need in the if statements So if you know how can I do events in a precise amount of time please tell me how can I do this

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• XML Workshop 25 - Inserting elements and attributes to an XML document

  This article from MVP Jacob Sebastian looks at the modify method for changing an XML document.

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• SQLAuthority News – Presented Soft Skill Session on Presentation Skills at SQL Bangalore on May 3, 2014

  - by Pinal Dave

  I have presented on various database technologies for almost 10 years now. SQL, Database and NoSQL have been part of my life. Earlier this month, I had the opportunity to present on the topic Performing an Effective Presentation. I must say it was blast to prepare as well as present this session. This event was part of the SQL Bangalore community. If you are in Bangalore, you must be part of this group. SQL Bangalore is a wonderful community and we always have a great response when we present on technology. It is SQL User Group and we discuss everything SQL there. This month we had SQL Server 2014 theme and we had a community launch of SQL Server. We have the best of the best speakers presenting on SQL Server 2014 technology. The event had amazing speakers and each of them did justice to the subject. You can read about this over here. In this session I told a story from my life. I talked about who inspired me and how I learned to speak in public. I told stories about two legends  who have inspired me. There is no video recording of this session. If you want to get resources from this session, please sign up my newsletter at http://bit.ly/sqllearn. Well, I had a great time at this event. We had over 250 people showed up at this event and had a grand  time together. I personally enjoyed a session of Amit Benerjee, Balmukund Lakhani and Vinod Kumar. Ken and Surabh also entertained the audience. Overall, this was a grand event and if you were in Bangalore and did not make it to this event. You did miss out on a few things. Here are a few photos of this event. SQL Bangalore UG Nupur, Chandra, Shaivi, Balmukund, Amit, Vinod [captions This] SQL Bangalore UG Audience Pinal Dave presenting at SQL UG in Bangalore Here are few of the slides from this presentation: Reference: Pinal Dave (http://blog.sqlauthority.com)Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, SQLAuthority Author Visit, SQLAuthority News, T SQL

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• Java Spotlight Episode 85: Migrating from Spring to JavaEE 6

  - by Roger Brinkley

  Interview with Bert Ertman and Paul Bakker on migrating from Spring to JavaEE 6. Joining us this week on the Java All Star Developer Panel is Arun Gupta, Java EE Guy. Right-click or Control-click to download this MP3 file. You can also subscribe to the Java Spotlight Podcast Feed to get the latest podcast automatically. If you use iTunes you can open iTunes and subscribe with this link:  Java Spotlight Podcast in iTunes. Show Notes News Transactional Interceptors in Java EE 7 Larry Ellison and Mark Hurd on Oracle Cloud Duke’s Choice Award submissions open until June 15 Registration for the 2012 JVM Lanugage Summit now open Events June 11-14, Cloud Computing Expo, New York City June 12, Boulder JUG June 13, Denver JUG June 13, Eclipse Juno DemoCamp, Redwoood Shore June 13, JUG Münster June 14, Java Klassentreffen, Vienna, Austria June 18-20, QCon, New York City June 20, 1871, Chicago June 26-28, Jazoon, Zurich, Switzerland July 5, Java Forum, Stuttgart, Germany July 30-August 1, JVM Language Summit, Santa Clara Feature InterviewBert Ertman is a Fellow at Luminis in the Netherlands. Next to his customer assignments he is responsible for stimulating innovation, knowledge sharing, coaching, technology choices and presales activities. Besides his day job he is a Java User Group leader for NLJUG, the Dutch Java User Group. A frequent speaker on Enterprise Java and Software Architecture related topics at international conferences (e.g. Devoxx, JavaOne, etc) as well as an author and member of the editorial advisory board for Dutch software development magazine: Java Magazine. In 2008, Bert was honored by being awarded the coveted title of Java Champion by an international panel of Java leaders and luminaries. Paul Bakker is senior software engineer at Luminis Technologies where he works on the Amdatu platform, an open source, service-oriented application platform for web applications. He has a background as trainer where he teached various Java related subjects. Paul is also a regular speaker on conferences and author for the Dutch Java Magazine.TutorialsPart 1: http://howtojboss.com/2012/04/17/article-series-migrating-spring-applications-to-java-ee-6-part-1/Part 2: http://howtojboss.com/2012/04/17/article-series-migrating-spring-applications-to-java-ee-6-part-2/Part 3: http://howtojboss.com/2012/05/10/article-series-migrating-from-spring-to-java-ee-6-part-3/   Mail Bag What’s Cool Sang Shin in EE team @larryellison JavaOne content selection is almost complete-Notifications coming soon

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• Mobile Linux Gets Support From Chip Vendors

  <b>Hardware Central:</b> "The development of Linux on mobile devices may be poised to get a boost thanks to the formation of a new industry group called Linaro, backed by a consortium of chip vendors including ARM, Freescale, Texas Instruments, Samsung and ST-Ericsson."

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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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• How should I log time spent on multiple tasks?

  - by xenoterracide

  In Joel's blog on evidence based scheduling he suggests making estimates based on the smallest unit of work and logging extra work back to the original task. The problem I'm now experiencing is that I'll have create object A with subtask method A which creates object B and test all of the above. I create tasks for each of these that seems to be resulting in ok-ish estimates (need practice), but when I go to log work I find that I worked on 4 tasks at once because I tweak method A and find a bug in the test and refactor object B all while coding it. How should I go about logging this work? should I say I spent, for example, 2 hours on each of the 4 tasks I worked on in the 8 hour day?

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• 2d libgdx: runtime level generation

  - by lxknvlk

  I have encountered a problem during my first game development: I thought of a Array<Ground> groundArray that does groundArray.add when a new ground will appear on the screen, and removes oldest ground when it will no longer be seen, if player only moves to the right, like in flappy bird. The perfect structure would be a queue for such a mechanic, but libgdx doesnt have one. Using libgdx's Array is not intuitive too - i have to reverse the order of elements. It has a method pop() that removes the last element, but no such method to use on the first element. What are my options here? extend Array class and add something? writing my own queue-like class?

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