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• PHP / C++ space calculations for parcel packing

  - by Andrew Willis

  I am working on a shopping cart project which requires a 'postage calculator' based on items that the person has in their cart. Obviously I will be storing the item's dimensions incl. weight and padding in a database and will also store the parcel (box) size and weight that the items will go in to, incl. box padding. Figuring the weight of the parcels will be easy but I was wondering how to go about figuring how to pack the box via PHP, that is, I would like the code to 'play tetris' with the items to make sure they get the best possible fit, giving accurate postage costs. Does anybody have any ideas on how best to achieve this or does anybody know of a PHP Class or function that can do this? EDIT: When I said 'best possible fit' maybe I was being optimistic! Having the script try every possible combination of package distribution within the parcel would be over the top, however I could improve the speed by writing the algoritm in C++ and running the program in PHP when the user 'checks out', the return value being an array with the parcel size and weight (which are all that are needed to calculate postage costs)

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• how can I save/keep-in-sync an in-memory graph of objects with the database?

  - by Greg

  Question - What is a good best practice approach for how can I save/keep-in-sync an jn-memory graph of objects with the database? Background: That is say I have the classes Node and Relationship, and the application is building up a graph of related objects using these classes. There might be 1000 nodes with various relationships between them. The application needs to query the structure hence an in-memory approach is good for performance no doubt (e.g. traverse the graph from Node X to find the root parents) The graph does need to be persisted however into a database with tables NODES and RELATIONSHIPS. Therefore what is a good best practice approach for how can I save/keep-in-sync an jn-memory graph of objects with the database? Ideal requirements would include: build up changes in-memory and then 'save' afterwards (mandatory) when saving, apply updates to database in correct order to avoid hitting any database constraints (mandatory) keep persistence mechanism separate from model, for ease in changing persistence layer if needed, e.g. don't just wrap an ADO.net DataRow in the Node and Relationship classes (desirable) mechanism for doing optimistic locking (desirable) Or is the overhead of all this for a smallish application just not worth it and I should just hit the database each time for everything? (assuming the response times were acceptable) [would still like to avoid if not too much extra overhead to remain somewhat scalable re performance]

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• Parameter cannot be null error after success save

  - by tigermain

  I am getting the following nhibernate error when saving an entity (via: NHibernateSession.Save(entity);) despite it being persisted to the database fine "Value cannot be null.\r\nParameter name: id" This is my hbm file <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" namespace="JeanieMaster.Domain.Entities" assembly="JeanieMaster.Domain"> <class name="ActionLog" table="ActionLog" schema="[DBSVR1].[mydatabase].[dbo]" select-before-update="false" optimistic-lock="none"> <id name="Id" column="ActionLogId" type="Int32"> <generator class="identity"/> </id> <property name="ActionId" type="Int32"/> <many-to-one name="User" class="JeanieUser" column="UserId" /> <many-to-one name="ApplicationProvider" class="ApplicationProvider" column="ApplicationProviderId" /> <many-to-one name="ContentProvider" class="ContentProvider" column="ContentProviderId" /> <many-to-one name="SearchLog" class="SearchLog" column="SearchLogId" /> <property name="Data" type="string"/> <property name="DateCreated" type="DateTime"/> <property name="ActionDuration" type="Double"/> </class> </hibernate-mapping>

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• How do you use FastInfoset with JAXWS?

  - by Chris Kessel

  I've got code that looks like it should be correct based on what I can find, but the spewed output doesn't indicate that it's using FastInfoset. My understanding is the Accept should indicate it can accept Fastinfoset and the response would actually use it, meaning it's not text/xml as the response type. Any idea what I'm doing wrong? I've scoured with Google and I'm having a hard time finding much detail on how to use FastInfoset at all. JaxWsProxyFactoryBean factory = new JaxWsProxyFactoryBean(); factory.getInInterceptors().add(new LoggingInInterceptor()); factory.getOutInterceptors().add(new LoggingOutInterceptor()); factory.setServiceClass( C360Server.class); factory.setAddress("http://localhost:8501/cxfcontroller/cl_v5"); C360Server client = (C360Server)factory.create(); ((BindingProvider)client).getRequestContext().put( "com.sun.xml.ws.client.ContentNegotiation", "optimistic"); C360Request requestTrans = new C360Request(); ... code to fill in the request ... C360Response response = client.findContacts( requestTrans ); The logging doesn't seem to indicate FastInfoset is even attempted though: INFO: Outbound Message --------------------------- ID: 1 Address: http://localhost:8501/cxfcontroller/cl_v5 Encoding: UTF-8 Content-Type: text/xml Headers: {SOAPAction=[""], Authorization=[Basic cWFfc3VwZXI6cWFfc3VwZXI=], Accept=[*/*]} Payload: <soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"><soap:Body><ns1:findContacts>...bunch of xml deleted for brevity...</ns1:findContacts></soap:Body></soap:Envelope> -------------------------------------- May 17, 2010 3:23:45 PM org.apache.cxf.interceptor.LoggingInInterceptor logging INFO: Inbound Message ---------------------------- ID: 1 Response-Code: 200 Encoding: UTF-8 Content-Type: text/xml; charset=utf-8 Headers: {content-type=[text/xml; charset=utf-8], Content-Length=[611], Server=[Jetty(6.1.x)]} Payload: <soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/"><soap:Body><ns1:findContactsResponse>...bunch of xml spew deleted for brevity...</ns1:findContactsResponse></soap:Body></soap:Envelope> -------------------------------------- Any ideas what I'm doing wrong? Even if the server wasn't supporting FastInfoset, I still should see the attempted negotiation in the request, right?

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• Core Data Errors vs Exceptions Part 3

  - by John Gallagher

  My question is similar to this one. Background I'm creating a large number of objects in a core data store using NSOperations to speed things up. I've followed all the Core Data multithreading rules - I've got a single persistent store coordinator and a managed object context per thread that on save is merging back to the main managed object context. The Problem When the number of threads running at once is more than 1, I get the exception logged on save of my core data store: NSExceptionHandler has recorded the following exception: NSInternalInconsistencyException -- optimistic locking failure What I've Tried My code that creates new entities is quite complex - it makes entities that have relationships with other entities that could be being created in a separate thread. If I replace my object creation routine with some very simple code just making non-related entries, everything works perfectly. Initially, as well as the exceptions, I was getting a save error saying core data couldn't save due to the merge failing. I read the docs and realised I needed a merge policy on the Managed Object Context I was saving to. I set this up and as this question states, the save error goes away, but the exception remains. My Question Do I need to worry about these exceptions? If I do need to get rid of the exceptions, any ideas on how I do it?

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• How to lock a transaction for reading a row and then inserting in Hibernate?

  - by at

  I have a table with a name and a name_count. So when I insert a new record, I first check what the maximum name_count is for that name. I then insert the record with that maximum + 1. Works great... except with mysql 5.1 and hibernate 3.5, by default the reads don't respect transaction boundaries. 2 of these inserts for the same name could happen at the same time and end up with the same name_count, which completely screws my application! Unfortunately, there are some specific situations where the above is actually fairly common. So what do I do? I assume I can do a pessimistic lock where any row I read is locked for further reading until I commit or roll-back my transaction. Or I can do an optimistic lock with a version column that automatically keeps trying until there are no conflicts? What's the best approach for my situation and how do I specify it in Hibernate 3.5 and mysql 5.1? The above table is massive and accessed frequently.

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• Java Spotlight Episode 139: Mark Heckler and José Pereda on JES based Energy Monitoring @MkHeck @JPeredaDnr

  - by Roger Brinkley

  Interview with Mark Heckler and José Pereda on using JavaSE Embedded with the Java Embedded Suite on a RaspberryPI along with a JavaFX client to monitor an energy production system and their JavaOne Tutorial- Java Embedded EXTREME MASHUPS: Building self-powering sensor nets for the IoT 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 Java Virtual Developer Day Session Videos Available JavaFX Maven Plugin 2.0 Released JavaFX Scene Builder 1.1 build b28 FXForm 2 release 0.2.2 OpenJDK8/Zero cross compile build for Foundation model HSAIL-based GPU offload: the Quest for Java Performance Begins Progress on Moving to Gradle Java EE 7 Launch Keynote Replay Java EE 7 Technical Breakouts Replay Java EE 7 support in NetBeans 7.3.1 Java EE 7 support in Eclipse 4.3 Java Magazine - May/June Events Jul 16-19, Uberconf, Denver, USA Jul 22-24, JavaOne Shanghai, China Jul 29-31, JVM Language Summit, Santa Clara Sep 11-12, JavaZone, Oslo, Norway Sep 19-20, Strange Loop, St. Louis Sep 22-26 JavaOne San Francisco 2013, USA Feature Interview Mark Heckler is an Oracle Corporation Java/Middleware/Core Tech Engineer with development experience in numerous environments. He has worked for and with key players in the manufacturing, emerging markets, retail, medical, telecom, and financial industries to develop and deliver critical capabilities on time and on budget. Currently, he works primarily with large government customers using Java throughout the stack and across the enterprise. He also participates in open-source development at every opportunity, being a JFXtras project committer and developer of DialogFX, MonologFX, and various other projects. When Mark isn't working with Java, he enjoys writing about his experiences at the Java Jungle website (https://blogs.oracle.com/javajungle/) and on Twitter (@MkHeck). José Pereda is a Structural Engineer working in the School of Engineers in the University of Valladolid in Spain for more than 15 years, and his passion is related to applying programming to solve real problems. Being involved with Java since 1999, José shares his time between JavaFX and the Embedded world, developing commercial applications and open source projects (https://github.com/jperedadnr), and blogging (http://jperedadnr.blogspot.com.es/) or tweeting (@JPeredaDnr) of both. What’s Cool AquaFX 0.1 - Mac OS X skin for JavaFX by Claudine Zillmann DromblerFX adds a docking framework Part 2 of Gerrit’s taming the Nashorn for writing JavaFX apps in Javascript Tool from mihosoft called JSelect for quickly switching JDKs Apache Maven Javadoc Plugin 2.9.1 Released Proposal: Java Concurrency Stress tests (jcstress) Slide-free Code-driven session at SV JUG JavaOne approvals/rejects gone out

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• Java Space on Parleys

  - by Yolande Poirier

  Now available! A great selection of JavaOne 2010 and JVM Language Summit 2010 sessions as well as Oracle Technology Network TechCasts on the new Java Space on Parleys website. Oracle partnered with Stephan Janssen, founder of Parleys to make this happen. Parleys website offers a user friendly experience to view online content. You can download some of the talks to your desktop or watch them on the go on mobile devices. The current selection is a well of expertise from top Java luminaries and Oracle experts. JavaOne 2010 sessions: ·        Best practices for signing code by Sean Mullan   ·        Building software using rich client platforms by Rickard Thulin ·        Developing beyond the component libraries by Ryan Cuprak ·        Java API for keyhole markup language by Florian Bachmann ·        Avoiding common user experience anti-patterns by Burk Hufnagel ·        Accelerating Java workloads via GPUs by Gary Frost JVM Languages Summit 2010 sessions: ·      Mixed language project compilation in Eclipse by Andy Clement  ·      Gathering the threads by John Rose  ·      LINQ: language features for concurrency by Neal Gafter  ·      Improvements in OpenJDK useful for JVM languages by Eric Caspole  ·      Symmetric Multilanguage - VM Architecture by Oleg Pliss  Special interviews with Oracle experts on product innovations: ·      Ludovic Champenois, Java EE architect on Glassfish 3.1 and Java EE. ·      John Jullion-Ceccarelli and Martin Ryzl on NetBeans IDE 6.9 You can chose to listen to a section of talks using the agenda view and search for related content while watching a presentation.  Enjoy the Java content and vote on it! 

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• JCP.Next - Early Adopters of JCP 2.8

  - by Heather VanCura

  JCP.Next is a series of three JSRs (JSR 348, JSR 355 and JSR 358), to be defined through the JCP process itself, with the JCP Executive Committee serving as the Expert Group. The proposed JSRs will modify the JCP's processes  - the Process Document and Java Specification Participation Agreement (JSPA) and will apply to all new JSRs for all Java platforms.   The first - JCP.next.1, or more formally JSR 348, Towards a new version of the Java Community Process - was completed and put into effect in October 2011 as JCP 2.8. This focused on a small number of simple but important changes to make our process more transparent and to enable broader participation. We're already seeing the benefits of these changes as new and existing JSRs adopt the new requirements. The second - JSR 355, Executive Committee Merge, is also Final. You can read the JCP 2.9 Process Document .  As part of the JSR 355 Final Release, the JCP Executive Committee published revisions to the JCP Process Document (version 2.9) and the EC Standing Rules (version 2.2).  The changes went into effect following the 2012 EC Elections in November. The third JSR 358, A major revision of the Java Community Process was submitted in June 2012.  This JSR will modify the Java Specification Participation Agreement (JSPA) as well as the Process Document, and will tackle a large number of complex issues, many of them postponed from JSR 348. For these reasons, the JCP EC (acting as the Expert Group for this JSR), expects to spend a considerable amount of time working on. The JSPA is defined by the JCP as "a one-year, renewable agreement between the Member and Oracle. The success of the Java community depends upon an open and transparent JCP program.  JSR 358, A major revision of the Java Community Process, is now in process and can be followed on java.net. The following JSRs and Spec Leads were the early adopters of JCP 2.8, who voluntarily migrated their JSRs from JCP 2.x to JCP 2.8 or above.  More candidates for 2012 JCP Star Spec Leads! JSR 236, Concurrency Utilities for Java EE (Anthony Lai/Oracle), migrated April 2012 JSR 308, Annotations on Java Types (Michael Ernst, Alex Buckley/Oracle), migrated September 2012 JSR 335, Lambda Expressions for the Java Programming Language (Brian Goetz/Oracle), migrated October 2012 JSR 337, Java SE 8 Release Contents (Mark Reinhold/Oracle) – EG Formation, migrated September 2012 JSR 338, Java Persistence 2.1 (Linda DeMichiel/Oracle), migrated January 2012 JSR 339, JAX-RS 2.0: The Java API for RESTful Web Services (Santiago Pericas-Geertsen, Marek Potociar/Oracle), migrated July 2012 JSR 340, Java Servlet 3.1 Specification (Shing Wai Chan, Rajiv Mordani/Oracle), migrated August 2012 JSR 341, Expression Language 3.0 (Kin-man Chung/Oracle), migrated August 2012 JSR 343, Java Message Service 2.0 (Nigel Deakin/Oracle), migrated March 2012 JSR 344, JavaServer Faces 2.2 (Ed Burns/Oracle), migrated September 2012 JSR 345, Enterprise JavaBeans 3.2 (Marina Vatkina/Oracle), migrated February 2012 JSR 346, Contexts and Dependency Injection for Java EE 1.1 (Pete Muir/RedHat) – migrated December 2011

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• JSR 360 and JSR 361: A Big Leap for Java ME 8

  - by terrencebarr

  It might have gone unnoticed to some, but Java ME took a big leap forward a couple of weeks ago with the filing of two new JSRs: JSR 360: “Connected Limited Device Configuration 8″ (aka CLDC 8) JSR 361: “Java ME Embedded Profile” (aka ME EP) Together, these two JSRs will significantly update, enhance, and modernize the Java ME platform, and specifically small embedded Java, with a host of new features and functionality. JSR 360 – Connected Limited Device Configuration 8 CLDC 8 is based on JSR 139 (CLDC 1.1) and updates the core Java ME VM, language support, libraries, and features to be aligned with Java SE 8. This will include: VM updated to comply with the JVM language specification version 2 Support for SE 7/8 language features like Generics, Assertions, Annotations, Try-with-Resources, and more New libraries such as Collections, NIO subset, Logging API subset A consolidated and enhanced Generic Connection Framework for multi-protocol I/O With CLDC 8, Java ME and Java SE are entering their next phase of alignment – making Java the only technology today that truly scales application development, code re-use, and tooling across the whole range of IT platforms, from small embedded to large enterprise. JSR 361 – Java ME Embedded Profile ME EP is based on JSR 228 (IMP-NG) and updates the specification in key areas to provide a powerful and flexible application environment for small embedded Java platforms, building on the features of CLDC 8:  A new, lightweight component and services model Shared libraries Multi-application concurrency, inter-application communication, and event system Application management API optionality, to address low-footprint use cases With ME EP, application developers will have a modern application environment which allows development and deployment of  modular, robust, sophisticated, and footprint-optimized solutions for a wide range of embedded use cases and devices. Summary While these JSRs are still under development, it’s clear that there are exciting new times ahead for Java ME – turning into a serious application platform while maintaining the focus on resource-constrained devices to address the expected explosion of small, smart, and connected embedded platforms. To learn more, click on the above links for JSR 360 and JSR 361. Or review the JavaOne 2012 online presentations on the topic: CON11300: Expanding the reach of the Java ME Platform CON5943: Java ME 8 Service Platform And stay tuned for more in this space! Cheers, – Terrence Filed under: Mobile & Embedded Tagged: "jsr 360", "jsr 361", "me 8", embedded, Embedded Java, JCP

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• JSR 360 and JSR 361: A Big Leap for Java ME 8

  - by terrencebarr

  It might have gone unnoticed to some, but Java ME took a big leap forward a couple of weeks ago with the filing of two new JSRs: JSR 360: “Connected Limited Device Configuration 8″ (aka CLDC 8) JSR 361: “Java ME Embedded Profile” (aka ME EP) Together, these two JSRs will significantly update, enhance, and modernize the Java ME platform, and specifically small embedded Java, with a host of new features and functionality. JSR 360 – Connected Limited Device Configuration 8 CLDC 8 is based on JSR 139 (CLDC 1.1) and updates the core Java ME VM, language support, libraries, and features to be aligned with Java SE 8. This will include: VM updated to comply with the JVM language specification version 2 Support for SE 7/8 language features like Generics, Assertions, Annotations, Try-with-Resources, and more New libraries such as Collections, NIO subset, Logging API subset A consolidated and enhanced Generic Connection Framework for multi-protocol I/O With CLDC 8, Java ME and Java SE are entering their next phase of alignment – making Java the only technology today that truly scales application development, code re-use, and tooling across the whole range of IT platforms, from small embedded to large enterprise. JSR 361 – Java ME Embedded Profile ME EP is based on JSR 228 (IMP-NG) and updates the specification in key areas to provide a powerful and flexible application environment for small embedded Java platforms, building on the features of CLDC 8:  A new, lightweight component and services model Shared libraries Multi-application concurrency, inter-application communication, and event system Application management API optionality, to address low-footprint use cases With ME EP, application developers will have a modern application environment which allows development and deployment of  modular, robust, sophisticated, and footprint-optimized solutions for a wide range of embedded use cases and devices. Summary While these JSRs are still under development, it’s clear that there are exciting new times ahead for Java ME – turning into a serious application platform while maintaining the focus on resource-constrained devices to address the expected explosion of small, smart, and connected embedded platforms. To learn more, click on the above links for JSR 360 and JSR 361. Or review the JavaOne 2012 online presentations on the topic: CON11300: Expanding the reach of the Java ME Platform CON5943: Java ME 8 Service Platform And stay tuned for more in this space! Cheers, – Terrence Filed under: Mobile & Embedded Tagged: "jsr 360", "jsr 361", "me 8", embedded, Embedded Java, JCP

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• Unification of TPL TaskScheduler and RX IScheduler

  - by JoshReuben

  using System; using System.Collections.Generic; using System.Reactive.Concurrency; using System.Security; using System.Threading; using System.Threading.Tasks; using System.Windows.Threading; namespace TPLRXSchedulerIntegration { public class MyScheduler :TaskScheduler, IScheduler     { private readonly Dispatcher _dispatcher; private readonly DispatcherScheduler _rxDispatcherScheduler; //private readonly TaskScheduler _tplDispatcherScheduler; private readonly SynchronizationContext _synchronizationContext; public MyScheduler(Dispatcher dispatcher)         {             _dispatcher = dispatcher;             _rxDispatcherScheduler = new DispatcherScheduler(dispatcher); //_tplDispatcherScheduler = FromCurrentSynchronizationContext();             _synchronizationContext = SynchronizationContext.Current;         }         #region RX public DateTimeOffset Now         { get { return _rxDispatcherScheduler.Now; }         } public IDisposable Schedule<TState>(TState state, DateTimeOffset dueTime, Func<IScheduler, TState, IDisposable> action)         { return _rxDispatcherScheduler.Schedule(state, dueTime, action);         } public IDisposable Schedule<TState>(TState state, TimeSpan dueTime, Func<IScheduler, TState, IDisposable> action)         { return _rxDispatcherScheduler.Schedule(state, dueTime, action);         } public IDisposable Schedule<TState>(TState state, Func<IScheduler, TState, IDisposable> action)         { return _rxDispatcherScheduler.Schedule(state, action);         }         #endregion         #region TPL /// Simply posts the tasks to be executed on the associated SynchronizationContext         [SecurityCritical] protected override void QueueTask(Task task)         {             _dispatcher.BeginInvoke((Action)(() => TryExecuteTask(task))); //TryExecuteTaskInline(task,false); //task.Start(_tplDispatcherScheduler); //m_synchronizationContext.Post(s_postCallback, (object)task);         } /// The task will be executed inline only if the call happens within the associated SynchronizationContext         [SecurityCritical] protected override bool TryExecuteTaskInline(Task task, bool taskWasPreviouslyQueued)         { if (SynchronizationContext.Current != _synchronizationContext)             { SynchronizationContext.SetSynchronizationContext(_synchronizationContext);             } return TryExecuteTask(task);         } // not implemented         [SecurityCritical] protected override IEnumerable<Task> GetScheduledTasks()         { return null;         } /// Implementes the MaximumConcurrencyLevel property for this scheduler class. /// By default it returns 1, because a <see cref="T:System.Threading.SynchronizationContext"/> based /// scheduler only supports execution on a single thread. public override Int32 MaximumConcurrencyLevel         { get             { return 1;             }         } //// preallocated SendOrPostCallback delegate //private static SendOrPostCallback s_postCallback = new SendOrPostCallback(PostCallback); //// this is where the actual task invocation occures //private static void PostCallback(object obj) //{ //    Task task = (Task) obj; //    // calling ExecuteEntry with double execute check enabled because a user implemented SynchronizationContext could be buggy //    task.ExecuteEntry(true); //}         #endregion     } }     What Design Pattern did I use here?

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• Back-sliding into Unmanaged Code

  - by Laila

  It is difficult to write about Microsoft's ambivalence to .NET without mentioning clichés about dog food.  In case you've been away a long time, you'll remember that Microsoft surprised everyone with the speed and energy with which it introduced and evangelised the .NET Framework for managed code. There was good reason for this. Once it became obvious to all that it had sleepwalked into third place as a provider of development languages, behind Borland and Sun, it reacted quickly to attract the best talent in the industry to produce a windows version of the Java runtime, with Bounds-checking, Automatic Garbage collection, structures exception handling and common data types. To develop applications for this managed runtime, it produced several excellent languages, and more are being provided. The only thing Microsoft ever got wrong was to give it a stupid name. The logical step for Microsoft would be to base the entire operating system on the .NET framework, and to re-engineer its own applications. In 2002, Bill Gates, then Microsoft Chairman and Chief Software Architect said about their plans for .NET, "This is a long-term approach. These things don't happen overnight." Now, eight years later, we're still waiting for signs of the 'long-term approach'. Microsoft's vision of an entirely managed operating system has subsided since the Vista fiasco, but stays alive yet dormant as Midori, still being developed by Microsoft Research. This is an Internet-centric fork of the singularity operating system, a research project started in 2003 to build a highly-dependable operating system in which the kernel, device drivers, and applications are all written in managed code. Midori is predicated on the prevalence of connected systems, with provisions for distributed concurrency where application components exist 'in the cloud', and supports a programming model that can tolerate cancellation, intermittent connectivity and latency. It features an entirely new security model that sandboxes applications for increased security. So have Microsoft converted its existing applications to the .NET framework? It seems not. What Windows applications can run on Mono? Very few, it seems. We all thought that .NET spelt the end of DLL Hell and the need for COM interop, but it looks as if Bill Gates' idea of 'not overnight' might stretch to a decade or more. The Operating System has shown only minimal signs of migrating to .NET. Even where the use of .NET has come to dominate, when used for server applications with IIS, IIS itself is still entirely developed in unmanaged code. This is an irritation to Microsoft's greatest supporters who committed themselves fully to the NET framework, only to find parts of the Ambivalent Microsoft Empire quietly backsliding into unmanaged code and the awful C++. It is a strategic mistake that the invigorated Apple didn't make with the Mac OS X Architecture. Cheers, Laila

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• Questions re: Eclipse Jobs API

  - by BenCole

  Similar to http://stackoverflow.com/questions/8738160/eclipse-jobs-api-for-a-stand-alone-swing-project This question mentions the Jobs API from the Eclipse IDE: ...The disadvantage of the pre-3.0 approach was that the user had to wait until an operation completed before the UI became responsive again. The UI still provided the user the ability to cancel the currently running operation but no other work could be done until the operation completed. Some operations were performed in the background (resource decoration and JDT file indexing are two such examples) but these operations were restricted in the sense that they could not modify the workspace. If a background operation did try to modify the workspace, the UI thread would be blocked if the user explicitly performed an operation that modified the workspace and, even worse, the user would not be able to cancel the operation. A further complication with concurrency was that the interaction between the independent locking mechanisms of different plug-ins often resulted in deadlock situations. Because of the independent nature of the locks, there was no way for Eclipse to recover from the deadlock, which forced users to kill the application... ...The functionality provided by the workspace locking mechanism can be broken down into the following three aspects: Resource locking to ensure multiple operations did not concurrently modify the same resource Resource change batching to ensure UI stability during an operation Identification of an appropriate time to perform incremental building With the introduction of the Jobs API, these areas have been divided into separate mechanisms and a few additional facilities have been added. The following list summarizes the facilities added. Job class: support for performing operations or other work in the background. ISchedulingRule interface: support for determining which jobs can run concurrently. WorkspaceJob and two IWorkspace#run() methods: support for batching of delta change notifications. Background auto-build: running of incremental build at a time when no other running operations are affecting resources. ILock interface: support for deadlock detection and recovery. Job properties for configuring user feedback for jobs run in the background. The rest of this article provides examples of how to use the above-mentioned facilities... In regards to above API, is this an implementation of a particular design pattern? Which one?

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• Design pattern for an ASP.NET project using Entity Framework

  - by MPelletier

  I'm building a website in ASP.NET (Web Forms) on top of an engine with business rules (which basically resides in a separate DLL), connected to a database mapped with Entity Framework (in a 3rd, separate project). I designed the Engine first, which has an Entity Framework context, and then went on to work on the website, which presents various reports. I believe I made a terrible design mistake in that the website has its own context (which sounded normal at first). I present this mockup of the engine and a report page's code behind: Engine (in separate DLL): public Engine { DatabaseEntities _engineContext; public Engine() { // Connection string and procedure managed in DB layer _engineContext = DatabaseEntities.Connect(); } public ChangeSomeEntity(SomeEntity someEntity, int newValue) { //Suppose there's some validation too, non trivial stuff SomeEntity.Value = newValue; _engineContext.SaveChanges(); } } And report: public partial class MyReport : Page { Engine _engine; DatabaseEntities _webpageContext; public MyReport() { _engine = new Engine(); _databaseContext = DatabaseEntities.Connect(); } public void ChangeSomeEntityButton_Clicked(object sender, EventArgs e) { SomeEntity someEntity; //Wrong way: //Get the entity from the webpage context someEntity = _webpageContext.SomeEntities.Single(s => s.Id == SomeEntityId); //Send the entity from _webpageContext to the engine _engine.ChangeSomeEntity(someEntity, SomeEntityNewValue); // <- oops, conflict of context //Right(?) way: //Get the entity from the engine context someEntity = _engine.GetSomeEntity(SomeEntityId); //undefined above //Send the entity from the engine's context to the engine _engine.ChangeSomeEntity(someEntity, SomeEntityNewValue); // <- oops, conflict of context } } Because the webpage has its own context, giving the Engine an entity from a different context will cause an error. I happen to know not to do that, to only give the Engine entities from its own context. But this is a very error-prone design. I see the error of my ways now. I just don't know the right path. I'm considering: Creating the connection in the Engine and passing it off to the webpage. Always instantiate an Engine, make its context accessible from a property, sharing it. Possible problems: other conflicts? Slow? Concurrency issues if I want to expand to AJAX? Creating the connection from the webpage and passing it off to the Engine (I believe that's dependency injection?) Only talking through ID's. Creates redundancy, not always practical, sounds archaic. But at the same time, I already recuperate stuff from the page as ID's that I need to fetch anyways. What would be best compromise here for safety, ease-of-use and understanding, stability, and speed?

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• JUDCon 2013 Trip Report

  - by reza_rahman

  JUDCon (JBoss Users and Developers Conference) 2013 was held in historic Boston on June 9-11 at the Hynes Convention Center. JUDCon is the largest get together for the JBoss community, has gone global in recent years but has it's roots in Boston. The JBoss folks graciously accepted a Java EE 7 talk from me and actually referenced my talk in their own sessions. I am proud to say this is my third time speaking at JUDCon/the Red Hat Summit over the years (this was the first time on behalf of Oracle). I had great company with many of the rock stars of the JBoss ecosystem speaking such as Lincoln Baxter, Jay Balunas, Gavin King, Mark Proctor, Andrew Lee Rubinger, Emmanuel Bernard and Pete Muir. Notably missing from JUDCon were Bill Burke, Burr Sutter, Aslak Knutsen and Dan Allen. Topics included Java EE, Forge, Arquillian, AeroGear, OpenShift, WildFly, Errai/GWT, NoSQL, Drools, jBPM, OpenJDK, Apache Camel and JBoss Tools/Eclipse. My session titled "JavaEE.Next(): Java EE 7, 8, and Beyond" went very well and it was a full house. This is our main talk covering the changes in JMS 2, the Java API for WebSocket (JSR 356), the Java API for JSON Processing (JSON-P), JAX-RS 2, JPA 2.1, JTA 1.2, JSF 2.2, Java Batch, Bean Validation 1.1, Java EE Concurrency and the rest of the APIs in Java EE 7. I also briefly talked about the possibilities for Java EE 8. The slides for the talk are here: JavaEE.Next(): Java EE 7, 8, and Beyond from reza_rahman Besides presenting my talk, it was great to catch up with the JBoss gang and attend a few interesting sessions. On Sunday night I went to one of my favorite hangouts in Boston - the exalted Middle East Club as Rolling Stone refers to it (other cool spots in an otherwise pretty boring town is "the Church"). As contradictory as it might sound to the uninitiated, the Middle East Club is possibly the best place in Boston to simultaneously get great Middle Eastern (primarily Lebanese) food and great underground metal. For folks with a bit more exposure, this is probably not contradictory at all given bands like Acrassicauda and documentaries like Heavy Metal in Baghdad. Luckily for me they were featuring a few local Thrash metal bands from the greater Boston area. It wasn't too bad considering it was primarily amateur twenty-something guys (although I'm not sure I'm a qualified critic any more since I all but stopped playing about at that age). It's great Boston has the Middle East as an incubator to keep the rock, metal, folk, jazz, blues and indie scene alive. I definitely enjoyed JUDCon/Boston and hope to be part of the conference next year again.

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• C++ Accelerated Massive Parallelism

  - by Daniel Moth

  At AMD's Fusion conference Herb Sutter announced in his keynote session a technology that our team has been working on that we call C++ Accelerated Massive Parallelism (C++ AMP) and during the keynote I showed a brief demo of an app built with our technology. After the keynote, I go deeper into the technology in my breakout session. If you read both those abstracts, you'll get some information about what C++ AMP is, without being too explicit since we published the abstracts before the technology was announced. You can find the official online announcement at Soma's blog post. Here, I just wanted to capture the key points about C++ AMP that can serve as an introduction and an FAQ. So, in no particular order… C++ AMP lowers the barrier to entry for heterogeneous hardware programmability and brings performance to the mainstream, without sacrificing developer productivity or solution portability. is designed not only to help you address today's massively parallel hardware (i.e. GPUs and APUs), but it also future proofs your code investments with a forward looking design. is part of Visual C++. You don't need to use a different compiler or learn different syntax. is modern C++. Not C or some other derivative. is integrated and supported fully in Visual Studio vNext. Editing, building, debugging, profiling and all the other goodness of Visual Studio work well with C++ AMP. provides an STL-like library as part of the existing concurrency namespace and delivered in the new amp.h header file. makes it extremely easy to work with large multi-dimensional data on heterogeneous hardware; in a manner that exposes parallelization. introduces only one core C++ language extension. builds on DirectX (and DirectCompute in particular) which offers a great hardware abstraction layer that is ubiquitous and reliable. The architecture is such, that this point can be thought of as an implementation detail that does not surface to the API layer. Stay tuned on my blog for more over the coming months where I will switch from just talking about C++ AMP to showing you how to use the API with code examples… Comments about this post welcome at the original blog.

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• Best Creational Pattern for loggers in a multi-threaded system?

  - by Dipan Mehta

  This is a follow up question on my past questions : Concurrency pattern of logger in multithreaded application As suggested by others, I am putting this question separately. As the learning from the last question. In a multi-threaded environment, the logger should be made thread safe and probably asynchronous (where in messages are queued while a background thread does writing releasing the requesting object thread). The logger could be signleton or it can be a per-group logger which is a generalization of the above. Now, the question that arise is how does logger should be assigned to the object? There are two options I can think of: 1. Object requesting for the logger: Should each of the object call some global API such as get_logger()? Such an API returns "the" singleton or the group logger. However, I feel this involves assumption about the Application environment to implement the logger -which I think is some kind of coupling. If the same object needs to be used by other application - this new application also need to implement such a method. 2. Assign logger through some known API The other alternative approach is to create a kind of virtual class which is implemented by application based on App's own structure and assign the object sometime in the constructor. This is more generalized method. Unfortunately, when there are so many objects - and rather a tree of objects passing on the logger objects to each level is quite messy. My question is there a better way to do this? If you need to pick any one of the above, which approach is would you pick and why? Other questions remain open about how to configure them: How do objects' names or ID are assigned so that will be used for printing on the log messages (as the module names) How do these objects find the appropriate properties (such as log levels, and other such parameters) In the first approach, the central API needs to deal with all this varieties. In the second approach - there needs to be additional work. Hence, I want to understand from the real experience of people, as to how to write logger effectively in such an environment.

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• Is there a pedagogical game engine?

  - by K.G.

  I'm looking for a book, website, or other resource that gives modern 3D game engines the same treatment as Operating Systems: Design and Implementation gave operating systems. I have read Jason Gregory's Game Engine Architecture, which I enjoyed. However, by intent the author treated components of the architecture as atomic units, whereas what I'm interested in is the plumbing between those units that makes a coherent whole out of ideally loosely coupled parts. In books such as these, one usually reads that "that's academic," but that's the point! I have also read Julian Gold's Object-oriented Game Development, which likewise was good, but I feel is beginning to show its age. Since even mobile platforms these days are multicore and have fast video memory, those kinds of things (concurrency, display item buffering) would ideally be covered. There are other resources, such as the Doom 3 source code, which is highly instructive for its being a shipped product. The problem with those is as follows: float Q_rsqrt( float number ) { long i; float x2, y; const float threehalfs = 1.5F; x2 = number * 0.5F; y = number; i = * ( long * ) &y; // evil floating point bit level hacking i = 0x5f3759df - ( i >> 1 ); // what the f***? y = * ( float * ) &i; y = y * ( threehalfs - ( x2 * y * y ) ); // 1st iteration // y = y * ( threehalfs - ( x2 * y * y ) ); // 2nd iteration, this can be removed return y; } To wit, while brilliant, this kind of source requires more enlightenment than I can usually muster upon first read. In summary, here's my white whale: For an adult reader with experience in programming. I wish I could save all the trees killed by every. Single. Game Programming book ever devoting the first two chapters to "Now just what is a variable anyway?" In C or C++, very preferably C++. Languages that are more concise are fantastic for teaching, except for when what you want to learn is how to cope with a verbose language. There is also the benefit of the guardrails that C++ doesn't provide, such as garbage collection. Platform agnostic. I'm sincerely afraid that this book is out there and it's Visual C++/DirectX oriented. I'm a Linux guy, and I'd do what it takes, but I would very much like to be able to use OpenGL. Thanks for everything! Before anyone gets on my case about it, Fast inverse square root was from Quake III Arena, not Doom 3!

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• How granular should a command be in a CQ[R]S model?

  - by Aaronaught

  I'm considering a project to migrate part of our WCF-based SOA over to a service bus model (probably nServiceBus) and using some basic pub-sub to achieve Command-Query Separation. I'm not new to SOA, or even to service bus models, but I confess that until recently my concept of "separation" was limited to run-of-the-mill database mirroring and replication. Still, I'm attracted to the idea because it seems to provide all the benefits of an eventually-consistent system while sidestepping many of the obvious drawbacks (most notably the lack of proper transactional support). I've read a lot on the subject from Udi Dahan who is basically the guru on ESB architectures (at least in the Microsoft world), but one thing he says really puzzles me: As we get larger entities with more fields on them, we also get more actors working with those same entities, and the higher the likelihood that something will touch some attribute of them at any given time, increasing the number of concurrency conflicts. [...] A core element of CQRS is rethinking the design of the user interface to enable us to capture our users’ intent such that making a customer preferred is a different unit of work for the user than indicating that the customer has moved or that they’ve gotten married. Using an Excel-like UI for data changes doesn’t capture intent, as we saw above. -- Udi Dahan, Clarified CQRS From the perspective described in the quotation, it's hard to argue with that logic. But it seems to go against the grain with respect to SOAs. An SOA (and really services in general) are supposed to deal with coarse-grained messages so as to minimize network chatter - among many other benefits. I realize that network chatter is less of an issue when you've got highly-distributed systems with good message queuing and none of the baggage of RPC, but it doesn't seem wise to dismiss the issue entirely. Udi almost seems to be saying that every attribute change (i.e. field update) ought to be its own command, which is hard to imagine in the context of one user potentially updating hundreds or thousands of combined entities and attributes as it often is with a traditional web service. One batch update in SQL Server may take a fraction of a second given a good highly-parameterized query, table-valued parameter or bulk insert to a staging table; processing all of these updates one at a time is slow, slow, slow, and OLTP database hardware is the most expensive of all to scale up/out. Is there some way to reconcile these competing concerns? Am I thinking about it the wrong way? Does this problem have a well-known solution in the CQS/ESB world? If not, then how does one decide what the "right level" of granularity in a Command should be? Is there some "standard" one can use as a starting point - sort of like 3NF in databases - and only deviate when careful profiling suggests a potentially significant performance benefit? Or is this possibly one of those things that, despite several strong opinions being expressed by various experts, is really just a matter of opinion?

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• "Hello World" in C++ AMP

  - by Daniel Moth

  Some say that the equivalent of "hello world" code in the data parallel world is matrix multiplication :) Below is the before C++ AMP and after C++ AMP code. For more on what it all means, watch the recording of my C++ AMP introduction (the example below is part of the session). void MatrixMultiply(vector<float>& vC, const vector<float>& vA, const vector<float>& vB, int M, int N, int W ) { for (int y = 0; y < M; y++) { for (int x = 0; x < N; x++) { float sum = 0; for(int i = 0; i < W; i++) { sum += vA[y * W + i] * vB[i * N + x]; } vC[y * N + x] = sum; } } } Change the function to use C++ AMP and hence offload the computation to the GPU, and now the calling code (which I am not showing) needs no changes and the overall operation gives you really nice speed up for large datasets…  #include <amp.h> using namespace concurrency; void MatrixMultiply(vector<float>& vC, const vector<float>& vA, const vector<float>& vB, int M, int N, int W ) { array_view<const float,2> a(M, W, vA); array_view<const float,2> b(W, N, vB); array_view<writeonly<float>,2> c(M, N, vC); parallel_for_each( c.grid, [=](index<2> idx) mutable restrict(direct3d) { float sum = 0; for(int i = 0; i < a.x; i++) { sum += a(idx.y, i) * b(i, idx.x); } c[idx] = sum; } ); } Again, you can understand the elements above, by using my C++ AMP presentation slides and recording… Stay tuned for more… Comments about this post welcome at the original blog.

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• Java @Contented annotation to help reduce false sharing

  - by Dave

  See this posting by Aleksey Shipilev for details -- @Contended is something we've wanted for a long time. The JVM provides automatic layout and placement of fields. Usually it'll (a) sort fields by descending size to improve footprint, and (b) pack reference fields so the garbage collector can process a contiguous run of reference fields when tracing. @Contended gives the program a way to provide more explicit guidance with respect to concurrency and false sharing. Using this facility we can sequester hot frequently written shared fields away from other mostly read-only or cold fields. The simple rule is that read-sharing is cheap, and write-sharing is very expensive. We can also pack fields together that tend to be written together by the same thread at about the same time. More generally, we're trying to influence relative field placement to minimize coherency misses. Fields that are accessed closely together in time should be placed proximally in space to promote cache locality. That is, temporal locality should condition spatial locality. Fields accessed together in time should be nearby in space. That having been said, we have to be careful to avoid false sharing and excessive invalidation from coherence traffic. As such, we try to cluster or otherwise sequester fields that tend to written at approximately the same time by the same thread onto the same cache line. Note that there's a tension at play: if we try too hard to minimize single-threaded capacity misses then we can end up with excessive coherency misses running in a parallel environment. Theres no single optimal layout for both single-thread and multithreaded environments. And the ideal layout problem itself is NP-hard. Ideally, a JVM would employ hardware monitoring facilities to detect sharing behavior and change the layout on the fly. That's a bit difficult as we don't yet have the right plumbing to provide efficient and expedient information to the JVM. Hint: we need to disintermediate the OS and hypervisor. Another challenge is that raw field offsets are used in the unsafe facility, so we'd need to address that issue, possibly with an extra level of indirection. Finally, I'd like to be able to pack final fields together as well, as those are known to be read-only.

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• Criteria for a programming language to be considered "mature"

  - by Giorgio

  I was recently reading an answer to this question, and I was struck by the statement "The language is mature". So I was wondering what we actually mean when we say that "A programming language is mature"? Normally, a programming language is initially developed out of a need, e.g. Try out / implement a new programming paradigm or a new combination of features that cannot be found in existing languages. Try to solve a problem or overcome a limitation of an existing language. Create a language for teaching programming. Create a language that solves a particular class of problems (e.g. concurrency). Create a language and an API for a special application field, e.g. the web (in this case the language might reuse a well-known paradigm, but the whole API must be new). Create a language to push your competitor out of the market (in this case the creator might want the new language to be very similar to an existing one, in order to attract developers to the new programming language and platform). Regardless of what the original motivation and scenario in which a language has been created, eventually some languages are considered mature. In my intuition, this means that the language has achieved (at least one of) its goals, e.g. "We can now use language X as a reliable tool for writing web applications." This is however a bit vague, so I wanted to ask what you consider the most important criteria (if any) that are applied when saying that a language is mature. IMPORTANT NOTE This question is (on purpose) language-agnostic because I am only interested in general criteria. Please write only language-agnostic answers and comments! I am not asking whether any specific "language X is mature" or "which programming languages can be considered mature", or whether "language X is more mature than language Y": please avoid posting any opinions or reference about any specific languages because these are out of the scope of this question. EDIT To make the question more precise, by criteria I mean such things as "tool support", "adoption by the industry", "stability", "rich API", "large user community", "successful application record", "standardization", "clean and uniform semantics", and so on.

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• Programming tourism

  - by Andrew_B

  I'm going on vacation to Paris, France for 10 days. Actually, it's my girlfriend's wish to go there but I'm not very interested in visiting, sightseeing, etc. Recently, I came up with an idea of trying to do something like programming tourism. :) I'd like to do something related to programming in a startup-like company. I do not want a salary or any kind of compensation. I want to overview process, social aspects, environment and "what it feels like" to development software in another country. I'm from Russia. I've been a software developer since 2003. I prefer C#4 but I'm ready to use anything Turing-complete. I have some MS certifications and am familiar with all .NETs since 1.1. Currently I'm finishing PhD in CS. I'm interested in multidimensional indexing and I can turn any piece of data and code to OLAP system. :) But it'd take too much time. What can I do? I have no more than one week. I want a totally complete project in a short amount of time. Implement some features in well-tested project Do a code review Debug memory, performance and concurrency issues Do unit testing So, about the questions: Is it legal? I'm ready to sign NDA if it's necessary. I'll have tourist visa. Is it possible? I'm really sure that bureaucratic companies with lots of HRs and PMs will not allow such experiments. But small companies can afford it. I'm ready to guarantee support on my code after leaving home :) P.S. I still havn't started learning French :) I hope it will not take too much time :) P.P.S. Yes, it's girlfriend-approved. What's in it for me? It's fun. It's fun to see new systems and people who created them. It's fun to complete meaningful things. Quickly. What's in it for them? Feature, debug, review or test. If my short-term colleagues will like this style of working I can invite them to make same trip into my company :) I think in Russia it's even more exciting :)

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• Occasional disk I/O errors in SQLite

  - by Alix Axel

  I have a very simple website running PHP and SQLite 3.7.9 (with PDO). After establishing the SQLite connection I immediately execute the following queries: PRAGMA busy_timeout=0; PRAGMA cache_size=8192; PRAGMA foreign_keys=ON; PRAGMA journal_size_limit=67110000; PRAGMA legacy_file_format=OFF; PRAGMA page_size=4096; PRAGMA recursive_triggers=ON; PRAGMA secure_delete=ON; PRAGMA synchronous=NORMAL; PRAGMA temp_store=MEMORY; PRAGMA journal_mode=WAL; PRAGMA wal_autocheckpoint=4096; This website only has one writer and a few occasional readers, so I don't expect any concurrency problems (and I'm even using WAL). Every couple of days, I've seen this error being reported by PHP: Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[HY000]: General error: 10 disk I/O error' in ... Stack trace: #0 ...: PDO-exec('PRAGMA cache_si...') There are several things that make this error very weird to me: it's not a transient problem - no matter how many times I refresh the page, it won't go away the database file is not corrupted - the sqlite3 executable can open the database without problems If the following pragmas are commented out, PHP stops throwing the disk I/O exception: PRAGMA cache_size=8192; PRAGMA synchronous=NORMAL; PRAGMA journal_mode=WAL; Then, after successfully reconnecting to the database, I'm able to reintroduce these pragmas and the code with run smoothly for days - until eventually, the same error will occur without any apparent reason. I wasn't able to reproduce this error so far, so I'm clueless about the origin of it. I'm really curious what may be causing this problem... Any ideas? Environment: Ubuntu Server 12.04 LTS PHP 5.4.15 SQLite 3.7.9 Database size: ? 10MiB Transaction (write) size: ? 1KiB EDIT: Might these symptoms have something to do with busy_timeout?

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