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• Cross-platform independent development

  - by Joe Wreschnig

  Some years ago, if you wrote in C and some subset of C++ and used a sufficient number of platform abstractions (via SDL or whatever), you could run on every platform an indie could get on - Linux, Windows, Mac OS of various versions, obscure stuff like BeOS, and the open consoles like the GP2X and post-death Dreamcast. If you got a contract for a closed platform at some point, you could port your game to that platform with "minimal" code changes as well. Today, indie developers must use XNA to get on the Xbox 360 (and upcoming Windows phone); must not use XNA to work anywhere else but Windows; until recently had to use Java on Android; Flash doesn't run on phones, HTML5 doesn't work on IE. Unlike e.g. DirectX vs. OpenGL or Windows vs. Unix, these are changes to the core language you write your code in and can't be papered over without, basically, writing a compiler. You can move some game logic into scripts and include an interpreter - except when you can't, because the iPhone SDK doesn't allow it, and performance suffers because no one allows JIT. So what can you do if you want a really cross-platform portable game, or even just a significant body of engine and logic code? Is this not a problem because the platforms have fundamentally diverged - it's just plain not worthwhile to try to target both an iPhone and the Xbox 360 with any shared code because such a game would be bad? (I find this very unlikely. I can easily see wanting to share a game between a Windows Mobile phone and an Android, or an Xbox 360 and an iPad.) Are interfaces so high-level now that porting time is negligible? (I might believe this for business applications, but not for games with strict performance requirements.) Is this going to become more pronounced in the future? Is the split going to be, somewhat scarily, still down vendor lines? Will we all rely on high-level middleware like Flash or Unity to get anything cross-platform done? tl;dr - Is porting a problem, is it going to be a bigger problem in the future, and if so how do we solve it?

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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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• Exciting product releases (and one disappointing thing) with Mix10

  - by Jeff

  Sadly, I'm not at Mix this year, for the first time in a few years. It's a little harder to go if you work for Microsoft, oddly enough. And then there's this little guy next to me, who at ten days old really needs his daddy to be around! But oh, the excitement of what Microsoft has in store! It's great to finally see all of these major releases coming together for Microsoft developer products. There is a great deal of excitement among people internally no matter where you work, because there is so much cool stuff in the pipe. In case you live under a rock...Visual Studio 2010 - Great to see all of the positive feedback on the Twitter and what not. I've been using it on one of my home products for awhile, and I really like it. The newer nightly builds of ReSharper also seem to be gaining speed in quality as well. I like the new debugging features, and the text readability is not imagined. Love it.Silverlight 4 - I've been running a couple of minor SL3 apps on my personal sites for awhile now, and I'm thrilled with the platform. With a couple of key concepts down, .NET folk like you and me can do some stellar things with this, and if you're a Mac nerd (like me), it's all kinds of awesome to be able to build stuff for it without the agony of Objective-C and X Code.Windows Phone 7 Series - A few weeks ago you got to see the shiny new UI that went beyond the icon grid, and now you've got the developer story as well. That I can adapt my existing Silverlight apps with minimal effort to work on the phone is pretty powerful. Millions of .NET devs just because phone developers, using the tools they already know. How great is that?ASP.NET MVC2 - The final bits shipped last week, and there was much rejoicing. I love this framework because of the testability and the real ability to get to the true mechanics of HTTP. The other cool thing is the speed at which the framework has evolved. v2 in less than a year is pretty "un-Microsoft" in a lot of eyes.The video of keynotes and sessions is starting to appear on the Mix site, but for reasons I can't understand, they're WMV downloads. For real? Not that helpful for Mac folk. Why wouldn't they be using a Silverlight player?In any case, the thing that continues to motivate me is that getting what you imagine on to the Internet gets easier every year. This is not a new revelation for me. I've only been at Microsoft for four months, but I've felt this way for years. I'm thrilled to be a part of it.

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• Best Platform/Engine for turn based Client/Server Android game

  - by Paradine

  I'm currently designing a turn based game for tablets. Initially for Android with porting to iOS later considered in design. I'm having trouble narrowing down the available technologies to even know where to spend my research time. I am hoping that if I explain what I am trying to achieve someone may be able to suggest a platform and/or engine. I've looked into some of the open source Engines ( http://www.cuteandroid.com/ten-open-source-android-2d-or-3d-game-engine-for-android-developers ) and some appear to handle much of what I might require - although with a higher focus on graphics than i need. Mages looks interesting although development appears to have ceased. If I could somehow leverage GoogleApps that would be excellent. Here is what I am trying to achieve: PvP turn based strategy game over internet - minimal animation and bandwidth required Players match up online using MetaGame system MatchID created on Resolution Server and Game starts Clients have 30 second countdown to select MoveString Clients sends small secure timestamped and MatchIDed MoveString to Resolution server Resolution server looks up Move String for each player, Resolves and Updates Players status in MatchID on Server Resolution server updates Client Views Repeat until victory conditions met - MatchID Closed, Rewards earned in MetaGame There will also need to be a full social and account system and metagame backend - but this could be running on separate system(s) Tablet in Offline mode would be catalog browsing and perhaps single player AI - bum I'm focusing on the Resolution Server at this point I'm not even certain if I would be looking at an Android App or a WebApp at this stage! I want a custom GUI so I guess an app - but maybe as I have little animation a WebApp might also work. Probably some combination of both. There will be very small overhead in data between client server - essentially a small text string every 30 seconds sent to the Resolution server which looks up the Effect and applies it to the Opponents string and determines some results to apply to the match. The client view is updated minimally with the results (only 5 in game Integers tracked) - perhaps triggering small animations/popups on the client to show the end result. e.g Explosion. If you have suggestions for a good technology or platform to best achieving the Resolution Server I'd love to hear. Also if you have experience with open source Engines - and could narrow down which (if any ) might be most suitable that would be a big help. Thanks in advance

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• How do I install a 32-bit Java runtime on an amd64 server with multiarch?

  - by kbyrd

  I'm a long time Ubuntu user, but I haven't been following the community for the last several versions. I just did fresh default minimal amd64 install of Oneiric and I need a 32-bit JRE for a particular application. I last did this on 10.10, so I am not familiar with the multiarch stuff. Instead of installing ia32-libs, I read a bit and tried: aptitude install default-jre-headless:i386 But that just got me: The following NEW packages will be installed: default-jre-headless{b} openjdk-6-jre-headless{ab} The following packages are RECOMMENDED but will NOT be installed: icedtea-6-jre-cacao icedtea-6-jre-jamvm 0 packages upgraded, 2 newly installed, 0 to remove and 0 not upgraded. Need to get 27.3 MB of archives. After unpacking 82.1 MB will be used. The following packages have unmet dependencies: default-jre-headless: Depends: java-common which is a virtual package. openjdk-6-jre-headless: Depends: openjdk-6-jre-lib (>= 6b23~pre10-0ubuntu5) which is a virtual package. Depends: ca-certificates-java which is a virtual package. Depends: tzdata-java which is a virtual package. Depends: java-common (>= 0.28) which is a virtual package. Depends: libcups2 but it is not going to be installed. Depends: liblcms1 but it is not going to be installed. Depends: libjpeg62 but it is not going to be installed. Depends: libnss3-1d (>= 3.12.9+ckbi-1.82-0ubuntu4) but it is not going to be installed. Depends: libc6 (>= 2.11) but it is not going to be installed. Depends: libfreetype6 (>= 2.2.1) but it is not going to be installed. Depends: libgcc1 (>= 1:4.1.1) but it is not going to be installed. Depends: libstdc++6 (>= 4.1.1) but it is not going to be installed. Depends: zlib1g (>= 1:1.1.4) but it is not going to be installed. The following actions will resolve these dependencies: Keep the following packages at their current version: 1) default-jre-headless [Not Installed] 2) openjdk-6-jre-headless [Not Installed] Accept this solution? [Y/n/q/?] q Is aptitude not installing the 32-bit versions of the dependencies? What is the right way to do this? I'll likely want both a 64-bit and a 32-bit JRE if that matters.

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• Subterranean IL: Fault exception handlers

  - by Simon Cooper

  Fault event handlers are one of the two handler types that aren't available in C#. It behaves exactly like a finally, except it is only run if control flow exits the block due to an exception being thrown. As an example, take the following method: .method public static void FaultExample(bool throwException) { .try { ldstr "Entering try block" call void [mscorlib]System.Console::WriteLine(string) ldarg.0 brfalse.s NormalReturn ThrowException: ldstr "Throwing exception" call void [mscorlib]System.Console::WriteLine(string) newobj void [mscorlib]System.Exception::.ctor() throw NormalReturn: ldstr "Leaving try block" call void [mscorlib]System.Console::WriteLine(string) leave.s Return } fault { ldstr "Fault handler" call void [mscorlib]System.Console::WriteLine(string) endfault } Return: ldstr "Returning from method" call void [mscorlib]System.Console::WriteLine(string) ret } If we pass true to this method the following gets printed: Entering try block Throwing exception Fault handler and the exception gets passed up the call stack. So, the exception gets thrown, the fault handler gets run, and the exception propagates up the stack afterwards in the normal way. If we pass false, we get the following: Entering try block Leaving try block Returning from method Because we are leaving the .try using a leave.s instruction, and not throwing an exception, the fault handler does not get called. Fault handlers and C# So why were these not included in C#? It seems a pretty simple feature; one extra keyword that compiles in exactly the same way, and with the same semantics, as a finally handler. If you think about it, the same behaviour can be replicated using a normal catch block: try { throw new Exception(); } catch { // fault code goes here throw; } The catch block only gets run if an exception is thrown, and the exception gets rethrown and propagates up the call stack afterwards; exactly like a fault block. The only complications that occur is when you want to add a fault handler to a try block with existing catch handlers. Then, you either have to wrap the try in another try: try { try { // ... } catch (DirectoryNotFoundException) { // ... // leave.s as normal... } catch (IOException) { // ... throw; } } catch { // fault logic throw; } or separate out the fault logic into another method and call that from the appropriate handlers: try { // ... } catch (DirectoryNotFoundException ) { // ... } catch (IOException ioe) { // ... HandleFaultLogic(); throw; } catch (Exception e) { HandleFaultLogic(); throw; } To be fair, the number of times that I would have found a fault handler useful is minimal. Still, it's quite annoying knowing such functionality exists, but you're not able to access it from C#. Fortunately, there are some easy workarounds one can use instead. Next time: filter handlers.

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• Virtual Box - How to open a .VDI Virtual Machine

  - by [email protected]

  TUESDAY, APRIL 27, 2010 How to open a .VDI Virtual MachineSometimes someone share with us one Virtual machine with extension .VDI, after that we can wonder how and what with?Well the answer is... It is a VirtualBox - Virtual Machine. If you have not downloaded it you can do this easily just follow this post.http://listeningoracle.blogspot.com/2010/04/que-es-virtualbox.htmlorhttp://oracleoforacle.wordpress.com/2010/04/14/ques-es-virtualbox/Ok, Now with VirtualBox Installed open it and proceed with the following:1. Open the Virtual File Manager.2. Click on Actions ? Add and select the .VDI fileClick "Ok"3. Now we can register the new Virtual Machine - Click New, and Click Next4. Write down a Name for the virtual Machine a proceed to select a Operating System and Version. (In this case it is a Linux (Oracle Enterprise Linux or RedHat)Click Next5. Select the memory amount base for the Virtual Machine(Minimal 1280 for our case) - Click Next6. Select the Disk 11GR2_OEL5_32GB.vdi it was added in the virtual media manager in the step 2.Dont forget let selected Boot hard Disk (Primary Master) . Given it is the only disk assigned to the virtual machine.Click Next7. Click Finish8. This step is important. Once you have click on the settings Button. 9. On General option click the advanced settings. Here you must change the default directory to save your Snapshots; my recommendation set it to the same directory where the .Vdi file is. Otherwise you can have the same Virtual Machine and its snapshots in different paths.10. Now Click on System, and proceed to assign the correct memory (If you did not before)Note: Enable "Enable IO APIC" if you are planning to assign more than one CPU to the Virtual Machine.Define the processors for the Virtual machine. If you processor is dual core choose 211. Select the video memory amount you want to assign to the Virtual Machine12. Associated more storage disk to the Virtual machine, if you have more VDI files.(Not our case)The disk must be selected as IDE Primary Master.13. Well you can verify the other options, but with these changes you will be able to start the VM.Note: Sometime the VM owner may share some instructions, if so follow his instructions.14. Finally Start the Virtual Machine (Click > Start)

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• 13.04 Logitech bluetooth speaker adapter pairing but no mixer output

  - by user1455622

  I had to change [General] Enable = Socket in /etc/bluetooth/audio.conf to get it to pair. But now that they are I don't get an output in pavucontrol. D: [pulseaudio] bluetooth-util.c: Registering /MediaEndpoint/HFPAG on adapter /org/bluez/3855/hci0. D: [pulseaudio] bluetooth-util.c: Registering /MediaEndpoint/HFPHS on adapter /org/bluez/3855/hci0. D: [pulseaudio] bluetooth-util.c: Registering /MediaEndpoint/A2DPSource on adapter /org/bluez/3855/hci0. D: [pulseaudio] bluetooth-util.c: Registering /MediaEndpoint/A2DPSink on adapter /org/bluez/3855/hci0. E: [pulseaudio] bluetooth-util.c: org.bluez.Media.RegisterEndpoint() failed: org.bluez.Error.AlreadyExists: Already Exists E: [pulseaudio] bluetooth-util.c: org.bluez.Media.RegisterEndpoint() failed: org.bluez.Error.AlreadyExists: Already Exists E: [pulseaudio] bluetooth-util.c: org.bluez.Media.RegisterEndpoint() failed: org.bluez.Error.AlreadyExists: Already Exists E: [pulseaudio] bluetooth-util.c: org.bluez.Media.RegisterEndpoint() failed: org.bluez.Error.AlreadyExists: Already Exists D: [pulseaudio] bluetooth-util.c: dbus: property 'State' changed to value 'disconnected' D: [pulseaudio] bluetooth-util.c: dbus: property 'State' changed to value 'disconnected' D: [pulseaudio] bluetooth-util.c: dbus: property 'State' changed to value 'disconnected' D: [pulseaudio] bluetooth-util.c: dbus: property 'State' changed to value 'disconnected' D: [pulseaudio] bluetooth-util.c: dbus: property 'State' changed to value 'connected' D: [pulseaudio] bluetooth-util.c: dbus: property 'State' changed to value 'connected' D: [pulseaudio] bluetooth-util.c: Unknown Bluetooth minor device class 0 D: [pulseaudio] module-card-restore.c: Not restoring profile for card bluez_card.C8_84_47_15_B7_34, because already set. I: [pulseaudio] module-card-restore.c: Restoring port latency offsets for card bluez_card.C8_84_47_15_B7_34. I: [pulseaudio] card.c: Created 2 "bluez_card.C8_84_47_15_B7_34" W: [pulseaudio] module-bluetooth-device.c: Profile has no transport D: [pulseaudio] core-subscribe.c: Dropped redundant event due to change event. I: [pulseaudio] card.c: Changed profile of card 2 "bluez_card.C8_84_47_15_B7_34" to off I: [pulseaudio] module.c: Loaded "module-bluetooth-device" (index: #22; argument: "address=C8:84:47:15:B7:34 profile=a2dp"). I: [alsa-source] alsa-source.c: Scheduling delay of 10,06ms, you might want to investigate this to improve latency... I: [alsa-source] ratelimit.c: 5 events suppressed I: [alsa-source] alsa-source.c: Overrun! I: [alsa-source] alsa-source.c: Increasing minimal latency to 2,00 ms D: [alsa-source] alsa-source.c: latency set to 20,00ms D: [alsa-source] alsa-source.c: hwbuf_unused=62008 D: [alsa-source] alsa-source.c: setting avail_min=442 What can I do to get it working? Regards,

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• Attunity Oracle CDC Solution for SSIS - Beta

  We in no way work for Attunity but we were asked to test drive a beta version of their Oracle CDC solution for SSIS.  Everybody should know that moving more data than you need to takes too much time and uses resources that may better be employed doing something else.  Change data Capture is a technology that is designed to help you identify only the data that has had something done to it and you can therefore move only what is needed.  Microsoft have implemented this exact functionality into SQL server 2008 and I really like it there.  Attunity though are doing it on Oracle. DISCLAIMER: This is a BETA release and some of the parts are a bit ugly/difficult to work with.  The idea though is definitely right and the product once working does exactly what it says on the tin.  They have always been helpful to me when I have had a problem with the product and if that continues then beta testing pain should be eased somewhat. In due course I am going to be doing some videos around me using the product.  If you use Oracle and SSIS then give it a go. Here is their product description.   Attunity is a Microsoft SQL Server technology partner and the creator of the Microsoft Connectors for Oracle and Teradata, currently available in SQL Server 2008 Enterprise Edition. Attunity released a beta version of the Attunity Oracle-CDC for SSIS, a product that integrates continually changing Oracle data into SSIS, efficiently and in real-time. Attunity designed the product and integrated it into SSIS to create the simple creation of change data capture (CDC) solutions, accelerate implementation time, and reduce resources and costs. They also utilize log-based CDC so the solution has minimal impact on the Oracle source system. You can use the product to implement enterprise-class data replication, synchronization, and real-time business intelligence (BI) and data warehousing projects, quickly and efficiently, leveraging their existing SQL Server investments and resource skills. Attunity architected the product specifically for the Microsoft SSIS developer community and the product is available for both SQL Server 2005 and SQL Server 2008. It offers the following key capabilities: · Log-based, non-intrusive Oracle CDC · Full integration into SSIS and the Business Intelligence Developer Studio · Automatic generation of SSIS packages for CDC as well as full-loads of Oracle data · Filtering of Oracle tables and columns at the source · Monitoring and control of CDC processing Click to learn more and download the beta.

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• What are the software design essentials? [closed]

  - by Craig Schwarze

  I've decided to create a 1 page "cheat sheet" of essential software design principles for my programmers. It doesn't explain the principles in any great depth, but is simply there as a reference and a reminder. Here's what I've come up with - I would welcome your comments. What have I left out? What have I explained poorly? What is there that shouldn't be? Basic Design Principles The Principle of Least Surprise – your solution should be obvious, predictable and consistent. Keep It Simple Stupid (KISS) - the simplest solution is usually the best one. You Ain’t Gonna Need It (YAGNI) - create a solution for the current problem rather than what might happen in the future. Don’t Repeat Yourself (DRY) - rigorously remove duplication from your design and code. Advanced Design Principles Program to an interface, not an implementation – Don’t declare variables to be of a particular concrete class. Rather, declare them to an interface, and instantiate them using a creational pattern. Favour composition over inheritance – Don’t overuse inheritance. In most cases, rich behaviour is best added by instantiating objects, rather than inheriting from classes. Strive for loosely coupled designs – Minimise the interdependencies between objects. They should be able to interact with minimal knowledge of each other via small, tightly defined interfaces. Principle of Least Knowledge – Also called the “Law of Demeter”, and is colloquially summarised as “Only talk to your friends”. Specifically, a method in an object should only invoke methods on the object itself, objects passed as a parameter to the method, any object the method creates, any components of the object. SOLID Design Principles Single Responsibility Principle – Each class should have one well defined purpose, and only one reason to change. This reduces the fragility of your code, and makes it much more maintainable. Open/Close Principle – A class should be open to extension, but closed to modification. In practice, this means extracting the code that is most likely to change to another class, and then injecting it as required via an appropriate pattern. Liskov Substitution Principle – Subtypes must be substitutable for their base types. Essentially, get your inheritance right. In the classic example, type square should not inherit from type rectangle, as they have different properties (you can independently set the sides of a rectangle). Instead, both should inherit from type shape. Interface Segregation Principle – Clients should not be forced to depend upon methods they do not use. Don’t have fat interfaces, rather split them up into smaller, behaviour centric interfaces. Dependency Inversion Principle – There are two parts to this principle: High-level modules should not depend on low-level modules. Both should depend on abstractions. Abstractions should not depend on details. Details should depend on abstractions. In modern development, this is often handled by an IoC (Inversion of Control) container.

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• Selectively Exposing Functionallity in .Net

  - by David V. Corbin

  Any developer should be aware of the principles of encapsulation, cross-tier isolation, and cross-functional separation of concerns. However, it seems the few take the time to consider the adage of "minimal yet complete"1 when developing the software. Consider the exposure of "business objects" to the user interface. Some common situations occur: Accessing a given element requires a compound set of calls that do not "make sense" to the User Interface. More information than absolutely required is exposed to the user interface It would be much cleaner if a custom interface was provided that exposed exactly (and only) the information that is required by the consumer. Achieving this using conventional techniques would require the creation (and maintenance!) of custom classes to filter and transpose the information into the ideal format. Determining the ROI on this approach can be very difficult to ascertain, and as a result it is often ignored completely. There is another approach, which is largely made practical by virtual of the Action and Func delegates. From a callers point of view, the following two samples can be used interchangeably:     interface ISomeInterface     {         void SampleMethod1(string param);         string SamepleMethod2(string param);     }       class ISomeInterface     {         public Action<string> SampleMethod1 {get; }         public Func<string,string> SamepleMethod2 {get; }     }   The capabilities this simple changes enable are significant (and remember it does not cange the syntax at the call site): The delegates can be initialized to directly call the proper method of any target class. The delegates can be dynamically updated based on the current state. The "interface" can NOT be cast to the concrete class (which often exposes more functionallity). This patterns By limiting the interface to the exact functionallity required, the reduced surface area will typically result in lower development, testing and maintenance costs. We are currently in the process of posting a project on CodePlex which illustrates this (and many other) techniques which have proven helpful in creating robust yet flexible solutions that are highly efficient2 and maintainable. This post will be updated as soon as the project is published. 1) Credit: Scott  Meyers, Effective C++, Addison-Wesley 1992 2) For those who read my previous post on performance it should be noted that the use of delegates is on the same order of magnitude (actually a tiny amount faster) as conventional interfaces.

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• Don Knuth and MMIXAL vs. Chuck Moore and Forth -- Algorithms and Ideal Machines -- was there cross-pollination / influence in their ideas / work?

  - by AKE

  Question: To what extent is it known (or believed) that Chuck Moore and Don Knuth had influence on each other's thoughts on ideal machines, or their work on algorithms? I'm interested in citations, interviews, articles, links, or any other sort of evidence. It could also be evidence of the form of A and B here suggest that Moore might have borrowed or influenced C and D from Knuth here, or vice versa. (Opinions are of course welcome, but references / links would be better!) Context: Until fairly recently, I have been primarily familiar with Knuth's work on algorithms and computing models, mostly through TAOCP but also through his interviews and other writings. However, the more I have been using Forth, the more I am struck by both the power of a stack-based machine model, and the way in which the spareness of the model makes fundamental algorithmic improvements more readily apparent. A lot of what Knuth has done in fundamental analysis of algorithms has, it seems to me, a very similar flavour, and I can easily imagine that in a parallel universe, Knuth might perhaps have chosen Forth as his computing model. That's the software / algorithms / programming side of things. When it comes to "ideal computing machines", Knuth in the 70s came up with the MIX computer model, and then, collaborating with designers of state-of-the-art RISC chips through the 90s, updated this with the modern MMIX model and its attendant assembly language MMIXAL. Meanwhile, Moore, having been using and refining Forth as a language, but using it on top of whatever processor happened to be in the computer he was programming, began to imagine a world in which the efficiency and value of stack-based programming were reflected in hardware. So he went on in the 80s to develop his own stack-based hardware chips, defining the term MISC (Minimal Instruction Set Computers) along the way, and ending up eventually with the first Forth chip, the MuP21. Both are brilliant men with keen insight into the art of programming and algorithms, and both work at the intersection between algorithms, programs, and bare metal hardware (i.e. hardware without the clutter of operating systems). Which leads me to the headlined question... Question:To what extent is it known (or believed) that Chuck Moore and Don Knuth had influence on each other's thoughts on ideal machines, or their work on algorithms?

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• Patterns for Handling Changing Property Sets in C++

  - by Bhargav Bhat

  I have a bunch "Property Sets" (which are simple structs containing POD members). I'd like to modify these property sets (eg: add a new member) at run time so that the definition of the property sets can be externalized and the code itself can be re-used with multiple versions/types of property sets with minimal/no changes. For example, a property set could look like this: struct PropSetA { bool activeFlag; int processingCount; /* snip few other such fields*/ }; But instead of setting its definition in stone at compile time, I'd like to create it dynamically at run time. Something like: class PropSet propSetA; propSetA("activeFlag",true); //overloading the function call operator propSetA("processingCount",0); And the code dependent on the property sets (possibly in some other library) will use the data like so: bool actvFlag = propSet["activeFlag"]; if(actvFlag == true) { //Do Stuff } The current implementation behind all of this is as follows: class PropValue { public: // Variant like class for holding multiple data-types // overloaded Conversion operator. Eg: operator bool() { return (baseType == BOOLEAN) ? this->ToBoolean() : false; } // And a method to create PropValues various base datatypes static FromBool(bool baseValue); }; class PropSet { public: // overloaded[] operator for adding properties void operator()(std::string propName, bool propVal) { propMap.insert(std::make_pair(propName, PropVal::FromBool(propVal))); } protected: // the property map std::map<std::string, PropValue> propMap; }; This problem at hand is similar to this question on SO and the current approach (described above) is based on this answer. But as noted over at SO this is more of a hack than a proper solution. The fundamental issues that I have with this approach are as follows: Extending this for supporting new types will require significant code change. At the bare minimum overloaded operators need to be extended to support the new type. Supporting complex properties (eg: struct containing struct) is tricky. Supporting a reference mechanism (needed for an optimization of not duplicating identical property sets) is tricky. This also applies to supporting pointers and multi-dimensional arrays in general. Are there any known patterns for dealing with this scenario? Essentially, I'm looking for the equivalent of the visitor pattern, but for extending class properties rather than methods. Edit: Modified problem statement for clarity and added some more code from current implementation.

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• New channels for Exadata 11.2.3.1.1

  - by Rene Kundersma

  With the release of Exadata 11.2.3.1.0 back in April 2012 Oracle has deprecated the minimal pack for the Exadata Database Servers (compute nodes). From that release the Linux Database Server updates will be done using ULN and YUM. For the 11.2.3.1.0 release the ULN exadata_dbserver_11.2.3.1.0_x86_64_base channel was made available and Exadata operators could subscribe their system to it via linux.oracle.com. With the new 11.2.3.1.1 release two additional channels are added: a 'latest' channel (exadata_dbserver_11.2_x86_64_latest) a 'patch' channel (exadata_dbserver_11.2_x86_64_patch) The patch channel has the new or updated packages updated in 11.2.3.1.1 from the base channel. The latest channel has all the packages from 11.2.3.1.0 base and patch channels combined.  From here there are three possible situations a Database Server can be in before it can be updated to 11.2.3.1.1: Database Server is on Exadata release < 11.2.3.1.0 Database Server is patched to 11.2.3.1.0 Database Server is freshly imaged to 11.2.3.1.0 In order to bring a Database Server to 11.2.3.1.1 for all three cases the same approach for updating can be used (using YUM), but there are some minor differences: For Database Servers on a release < 11.2.3.1.0 the following high-level steps need to be performed: Subscribe to el5_x86_64_addons, ol5_x86_64_latest and  exadata_dbserver_11.2_x86_64_latest Create local repository Point Database Server to the local repository* install the update * during this process a one-time action needs to be done (details in the README) For Database Servers patched to 11.2.3.1.0: Subscribe to patch channel  exadata_dbserver_11.2_x86_64_patch Create local repository Point Database Server to the local repository Update the system For Database Servers freshly imaged to 11.2.3.1.0: Subscribe to patch channel  exadata_dbserver_11.2_x86_64_patch Create local  repository Point Database Server to the local repository Update the system The difference between 'situation 2' (Database Server is patched to 11.2.3.1.0) and 'situation 3' (Database Server is freshly imaged to 11.2.3.1.0) is that in situation 2 the existing Exadata-computenode.repo file needs to be edited while in situation 3 this file is not existing  and needs to be created or copied. Another difference is that you will end up with more OFA packages installed in situation 2. This is because none are removed during the updating process.  The YUM update functionality with the new channels is a great enhancements to the Database Server update procedure. As usual, the updates can be done in a rolling fashion so no database service downtime is required.  For detailed and up-to-date instructions always see the patch README's 1466459.1 patch 13998727 888828.1 Rene Kundersma

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• Will polishing my current project be a better learning experience than starting a new one?

  - by Alejandro Cámara

  I started programming many years ago. Now I'm trying to make games. I have read many recommendations to start cloning some well known games like galaga, tetris, arkanoid, etc. I have also read that I should go for the whole game (including menus, sound, score, etc.). Yesterday I finished the first complete version of my arkanoid clone. But it is far from over. I can still work on it for months (I program as a hobby in my free time) implementing a screen resolution switcher, remap of the control keys, power-ups falling from broken bricks, and a huge etc. But I do not want to be forever learning how to clone ONE game. I have the urge to get to the next clone in order to apply some design ideas I have come upon while developing this arkanoid clone (at the same time I am reading the GoF book and much source code from Ludum Dare 21 game contest). So the question is: Should I keep improving the arkanoid clone until it has all the features the original game had? or should I move to the next clone (there are almost infinite games to clone) and start mending the things I did wrong with the previous clone? This can be a very subjective question, so please restrain the answers to the most effective way to learn how to make my own games (not cloning someone ideas). Thank you! CLARIFICATION In order to clarify what I have implemented I make this list: Features implemented: Bouncing capabilities (the ball bounces on walls, on bricks, and on the bar). Sounds when bouncing on bricks and the bar, and when the player wins or loses. Basic title menu (new game and exit only). Also in-game menu and win/lose menus. Only three levels, but the map system is so easy I do not think it will teach me much (am I wrong?). Features not-implemented: Power-ups when breaking the bricks. Complex bricks (with more than one "hit point" and invincible). Better graphics (I am not really good at it). Programming polishing (use more intensively the design patterns). Here's a link to its (minimal) webpage: http://blog.acamara.es/piperine/ I kind of feel ashamed to show it, so please do not hit me too hard :-) My question was related to the not-implemented features. I wondered what was the fastest (optimal) path to learn. 1) implement the not-implemented features in this project which is getting big, or 2) make a new game which probably will teach me those lessons and new ones. ANSWER I choose @ashes999 answer because, in my case, I think I should polish more and try to "ship" the game. I think all the other answers are also important to bear in mind, so if you came here having the same question, before taking a rush decision read all the discussion. Thank you all!

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• Cannot install packages. "Warning: untrusted versions..." plus "method driver /usr/lib/apt/methods/http could not be found"

  - by Steve Tjoa

  Judging from Internet forums, these errors appear to be popular when attempting to install packages: steve:~$ sudo aptitude install examplepackage The following NEW packages will be installed: examplepackage examplepackage-common{a} 0 packages upgraded, 2 newly installed, 0 to remove and 0 not upgraded. Need to get 1,834 kB of archives. After unpacking 7,631 kB will be used. Do you want to continue? [Y/n/?] WARNING: untrusted versions of the following packages will be installed! Untrusted packages could compromise your system's security. You should only proceed with the installation if you are certain that this is what you want to do. examplepackage examplepackage-common Do you want to ignore this warning and proceed anyway? To continue, enter "Yes"; to abort, enter "No": Yes E: The method driver /usr/lib/apt/methods/http could not be found. E: The method driver /usr/lib/apt/methods/http could not be found. E: Internal error: couldn't generate list of packages to download I followed this post by uninstalling ubuntu-keyring. But I cannot reinstall ubuntu-keyring or ubuntu-minimal -- the above errors reappear. In fact, I don't even seem to have apt (I must have caused this along the way by trying a bad solution, or maybe a clean): steve:~$ sudo apt-get update sudo: apt-get: command not found Aptitude works, but I can't install apt: steve:~$ sudo aptitude install apt The following NEW packages will be installed: apt 0 packages upgraded, 1 newly installed, 0 to remove and 0 not upgraded. Need to get 1,046 kB of archives. After unpacking 3,441 kB will be used. E: The method driver /usr/lib/apt/methods/http could not be found. E: The method driver /usr/lib/apt/methods/http could not be found. E: Internal error: couldn't generate list of packages to download ...or update steve:~$ sudo aptitude update E: The method driver /usr/lib/apt/methods/http could not be found. E: The method driver /usr/lib/apt/methods/http could not be found. E: The method driver /usr/lib/apt/methods/http could not be found. I tried this post. Didn't help. To summarize, the main problem is that I cannot install anything. While attempting to fix the problem, the other aforementioned errors occurred. Can you help me fix this error? Feel free to ask if you need more information. Stats: steve:~$ lsb_release -a No LSB modules are available. Distributor ID: Ubuntu Description: Ubuntu 11.10 Release: 11.10 Codename: oneiric

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• How do I import my first sprites?

  - by steven_desu

  Continuing from this question (new question - now unrelated) So I have a thorough background in programming already (algorithms, math, logic, graphing problems, etc.) however I've never attempted to code a game before. In fact, I've never had anything more than minimal input from a user during the execution of a program. Generally input was given from a file or passed through console, all necessary functions were performed, then the program terminated with an output. I decided to try and get in on the world of game development. From several posts I've seen around gamedev.stackexchange.com XNA seems to be a favorite, and it was recommended to me when I asked where to start. I've downloaded and installed Visual Studio 2010 along with the XNA Framework and now I can't seem to get moving in the right direction. I started out looking on Google for "xna game studio tutorial", "xna game development beginners", "my first xna game", etc. I found lots of crap. The official "Introduction to Game Studio 4.0" gave me this (plus my own train of thought happily pasted on top thanks to MSPaint): http://tinypic.com/r/2w1sgvq/7 The "Get Additional Help" link (my best guess, since there was no "Continue" or "Next" link) lead me to this page: http://tinypic.com/r/2qa0dgx/7 I tried every page. The forum was the only thing that seemed helpful, however searching for "beginner", "newbie", "getting started", "first project", and similar on the forums turned up many threads with specific questions that are a bit above my level ("beginner to collision detection", for instance) Disappointed I returned to the XNA Game Studio home page. Surely their own website would have some introduction, tutorial, or at least a useful link to a community. EVERYTHING on their website was about coding Windows Phone 7.... Everything. http://tinypic.com/r/10eit8i/7 http://tinypic.com/r/120m9gl/7 Giving up on any official documentation after a while, I went back to Google. I managed to locate www.xnadevelopment.com. The website is built around XNA Game Studio 3.0, but how different can 3.0 be from 4.0?.... Apparently different enough. http://tinypic.com/r/5d8mk9/7 http://tinypic.com/r/25hflli/7 Figuring that this was the correct folder, I right-clicked.... http://tinypic.com/r/24o94yu/7 Hmm... maybe by "Add Content Reference" they mean "Add a reference to an existing file (content)"? Let's try it (after all- it's my only option) http://tinypic.com/r/2417eqt/7 At this point I gave up. I'm back. My original goal in my last question was to create a keyboard-navigable 3D world (no physics necessary, no logic or real game necessary). After my recent failures my goal has been revised. I want to display an image on the screen. Hopefully in time I'll be able to move it with the keyboard.

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• Arrive steering behavior

  - by dbostream

  I bought a book called Programming game AI by example and I am trying to implement the arrive steering behavior. The problem I am having is that my objects oscillate around the target position; after oscillating less and less for awhile they finally come to a stop at the target position. Does anyone have any idea why this oscillating behavior occur? Since the examples accompanying the book are written in C++ I had to rewrite the code into C#. Below is the relevant parts of the steering behavior: private enum Deceleration { Fast = 1, Normal = 2, Slow = 3 } public MovingEntity Entity { get; private set; } public Vector2 SteeringForce { get; private set; } public Vector2 Target { get; set; } public Vector2 Calculate() { SteeringForce.Zero(); SteeringForce = SumForces(); SteeringForce.Truncate(Entity.MaxForce); return SteeringForce; } private Vector2 SumForces() { Vector2 force = new Vector2(); if (Activated(BehaviorTypes.Arrive)) { force += Arrive(Target, Deceleration.Slow); if (!AccumulateForce(force)) return SteeringForce; } return SteeringForce; } private Vector2 Arrive(Vector2 target, Deceleration deceleration) { Vector2 toTarget = target - Entity.Position; double distance = toTarget.Length(); if (distance > 0) { //because Deceleration is enumerated as an int, this value is required //to provide fine tweaking of the deceleration.. double decelerationTweaker = 0.3; double speed = distance / ((double)deceleration * decelerationTweaker); speed = Math.Min(speed, Entity.MaxSpeed); Vector2 desiredVelocity = toTarget * speed / distance; return desiredVelocity - Entity.Velocity; } return new Vector2(); } private bool AccumulateForce(Vector2 forceToAdd) { double magnitudeRemaining = Entity.MaxForce - SteeringForce.Length(); if (magnitudeRemaining <= 0) return false; double magnitudeToAdd = forceToAdd.Length(); if (magnitudeToAdd > magnitudeRemaining) magnitudeToAdd = magnitudeRemaining; SteeringForce += Vector2.NormalizeRet(forceToAdd) * magnitudeToAdd; return true; } This is the update method of my objects: public void Update(double deltaTime) { Vector2 steeringForce = Steering.Calculate(); Vector2 acceleration = steeringForce / Mass; Velocity = Velocity + acceleration * deltaTime; Velocity.Truncate(MaxSpeed); Position = Position + Velocity * deltaTime; } If you want to see the problem with your own eyes you can download a minimal example here. Thanks in advance.

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• Getting WLAN on my Laptop to work (Medion MD98300)

  - by Anand Böhmer

  Dear Ubuntu Community, I am having difficulties to get the WLAN Adapter on my Medion 98300 Laptop to work. The WLAN Card seems to be connected through an internal USB Interface and the Card itself had shown up as a wirelles Network while installing Ubuntu. I have tried a few things earlier, but none of my google reasearches have brought me to a working solution... I am quite new to the Linux System and only knoew a couple of terminal commands so far, so I probably have missed out on a few possible solutions. Maybe you can help me? Thank you very much in advance! A fre minimal technical Details: AMD Turion 64 X2 Dual-Core Mobile Technolgie TL-50 NVIDIA GeForce Go 6150 SanDisk 64GB SSD 2GB RAM DDR2 667 nForce Chipset (I forgt the Version, but deductable from the GPU I guess) WiFi: ZyDAS ZD1211B 802.11g Thank's a lot again! :) UPDATE: I tried around myself a little and found a guide on the Linux Mint forums that helped! I already had tried to install the linux backport modules etc. What I finally did was update the linux firmware and run the following command: echo "options acer_wmi wirelles=1" sudo tee /etc/modprobe.d/acer_wmi.conf and rebooted now I found and could connect to networks, but unfortunately I found, that the link quality was very bad, around 40 to 50. Eventhough my Router is running at high power and is only 6 Meters away! I then switched a few channels, but that did not improve much. Before, under Windows, I had a very good link quality and had the entire 16mbit/s internet connection at disposal, now I can only get about 3-5Mbit/s. better then nothing, but still pretty bad! The "TX power" is fixed on 20dBm and iwconfig says, that the "Power Management" is off... Maybe the power of the module is set too low?... UPDATE2: I figured that 20dBm is a normal power output. I even tried to change the power using iwconfig wlan0 txpower INTEGERHERE but, obviously my "Card" does not support more then 20. More would probably be illegal as well, so I won't even use more then 20. I guess that I will have to figure out a way, or maybe just switch cards. Are the Mailboard-USB-Connectors on a laptop of the same property as the standard external ones? If so, I could simply solder a micro Wirelless N Adapter onto the board :)

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• Memory read/write access efficiency

  - by wolfPack88

  I've heard conflicting information from different sources, and I'm not really sure which one to believe. As such, I'll post what I understand and ask for corrections. Let's say I want to use a 2D matrix. There are three ways that I can do this (at least that I know of). 1: int i; char **matrix; matrix = malloc(50 * sizeof(char *)); for(i = 0; i < 50; i++) matrix[i] = malloc(50); 2: int i; int rowSize = 50; int pointerSize = 50 * sizeof(char *); int dataSize = 50 * 50; char **matrix; matrix = malloc(dataSize + pointerSize); char *pData = matrix + pointerSize - rowSize; for(i = 0; i < 50; i++) { pData += rowSize; matrix[i] = pData; } 3: //instead of accessing matrix[i][j] here, we would access matrix[i * 50 + j] char *matrix = malloc(50 * 50); In terms of memory usage, my understanding is that 3 is the most efficient, 2 is next, and 1 is least efficient, for the reasons below: 3: There is only one pointer and one allocation, and therefore, minimal overhead. 2: Once again, there is only one allocation, but there are now 51 pointers. This means there is 50 * sizeof(char *) more overhead. 1: There are 51 allocations and 51 pointers, causing the most overhead of all options. In terms of performance, once again my understanding is that 3 is the most efficient, 2 is next, and 1 is least efficient. Reasons being: 3: Only one memory access is needed. We will have to do a multiplication and an addition as opposed to two additions (as in the case of a pointer to a pointer), but memory access is slow enough that this doesn't matter. 2: We need two memory accesses; once to get a char *, and then to the appropriate char. Only two additions are performed here (once to get to the correct char * pointer from the original memory location, and once to get to the correct char variable from wherever the char * points to), so multiplication (which is slower than addition) is not required. However, on modern CPUs, multiplication is faster than memory access, so this point is moot. 1: Same issues as 2, but now the memory isn't contiguous. This causes cache misses and extra page table lookups, making it the least efficient of the lot. First and foremost: Is this correct? Second: Is there an option 4 that I am missing that would be even more efficient?

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• Why would you dual-run an app on Azure and AWS?

  - by Elton Stoneman

  Originally posted on: http://geekswithblogs.net/EltonStoneman/archive/2013/11/10/why-would-you-dual-run-an-app-on-azure-and-aws.aspxI had this question from a viewer of my Pluralsight course, Implementing the Reactive Manifesto with Azure and AWS, and thought I’d publish the response. So why would you dual-run your cloud app by hosting it on Azure and AWS? Sounds like a lot of extra development and management overhead. Well the most compelling reasons are reliability and portability. In 2012 I was working for a client who was making a big investment in the cloud, and at the end of the year we published their first external API for business partners. It was hosted in Azure and used some really nice features to route back into existing on-premise services. We were able to publish a clean, simple API to partners, and hide away the underlying complexity of the internal services while still leveraging them to do all the work. Two days after we went live, we were hit by the Azure SSL certificate expiry outage, and our API was unavailable for the best part of 3 days. Fortunately we had planned a gradual roll-out to partners, so the impact was minimal, but we’d been intending to ramp up quickly, and if the outage had happened a week or two later we would have been in a very bad place. Not least because our app could only run on Azure, we couldn’t package it up for another service without going back and reworking the code. More recently AWS had an issue with a networking device in one of their data centres which caused an outage that took the best part of a day to resolve. In both scenarios the SLAs are worthless, as you’ll get back a small percentage of your cloud expenditure, which is going to be negligible compared to your costs in dealing with the outage. And if your app is built specifically for AWS or Azure then if there’s an extended outage you can’t just deploy it onto a new set of kit from a different supplier. And the chances are pretty good there will be another extended outage, both for Microsoft and for Amazon. But the chances are small that it will happen to both at the same time. So my basic guidance has been: ignore the SLAs, go for better uptime by using two clouds. As soon as you need to scale beyond a single instance, start by scaling out to another cloud. Then scale out to different data centres in both clouds. Then you’ve got dual-cloud, quadruple-datacentre redundancy, so any more scaling you need can be left to the clouds to auto-scale themselves. By running in both clouds, you’ve made your app portable, so in the highly unlikely event that both AWS and Azure go down in multiple regions, you’ll have a deployment package which will let you spin up a new stack on yet another cloud, without having to rework your solution.

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• Disk drive for / not ready on boot after upgrade from 10.04 to 12.04

  - by Mathieu M-Gosselin

  After upgrading (using the Upgrade button from the update manager) from 10.04.4 to 12.04.1, I cannot boot anymore. Upon booting, I am greeted with the Ubuntu logo and the error "The disk drive for / is not ready yet or not present". I have the option to wait, to skip and to access a basic shell. Waiting overnight did nothing, skipping just gives me the same error for /tmp, /home, then for a UUID and finally it just goes to a black screen with a white "_" in the top left corner. My setup is a dual boot one with XP on a single hard drive, I use separate partitions for / and /home. Back in the day I installed 8.04 directly from the CD while leaving a partition for XP, which I installed after. This setup had never caused any such issues, even when upgrading from 8.04 to 10.04. I have done plenty of research regarding this issue, as many others seem to have had similar issues after doing the same upgrade as me. However, while for most what fixed the problem was running: apt-get -f install after remounting / in read-write, it didn't do it for me. I got dependency errors (see here), which I also investigated. I found https://bugs.launchpad.net/ubuntu/+source/python-defaults/+bug/990740 where most people say the solution that worked is (prior to running the above command) running: apt-get install -o APT::Immediate-Configure=false -f apt python-minimal but that also got me a lot of dependencies errors as output (see here), similar to #34 in the above thread. I also read that running: dpkg --configure -a could help, at first it wouldn't run because it had trouble parsing /var/lib/dpkg/status since there was an extra blank line in a package description (see https://bugs.launchpad.net/ubuntu/+source/dpkg/+bug/916799) but I removed it using vim (and then reran the command). It still gives me output that looks like an error, though. Here it is: http://paste.ubuntu.com/1338074/. I also tried re-running the above apt-get commands after that, to no avail. I'm running out of things to try in the hope of getting this fixed, your help would be very much appreciated! Thank you in advance.

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• Use Expressions with LINQ to Entities

  - by EltonStoneman

  [Source: http://geekswithblogs.net/EltonStoneman] Recently I've been putting together a generic approach for paging the response from a WCF service. Paging changes the service signature, so it's not as simple as adding a behavior to an existing service in config, but the complexity of the paging is isolated in a generic base class. We're using the Entity Framework talking to SQL Server, so when we ask for a page using LINQ's .Take() method we get a nice efficient SQL query for just the rows we want, with minimal impact on SQL Server and network traffic. We use the maximum ID of the record returned as a high-water mark (rather than using .Skip() to go to the next record), so the approach caters for records being deleted between page requests. In the paged response we include a HasMorePages indicator, computed by comparing the max ID in the page of results to the max ID for the whole resultset - if the latter is bigger, then there are more pages. In some quick performance testing, the paged version of the service performed much more slowly than the unpaged version, which was unexpected. We narrowed it down to the code which gets the max ID for the full resultset - instead of building an efficient MAX() SQL query, EF was returning the whole resultset and then computing the max ID in the service layer. It's easy to reproduce - take this AdventureWorks query:             var context = new AdventureWorksEntities();             var query = from od in context.SalesOrderDetail                         where od.ModifiedDate >= modified                          && od.SalesOrderDetailID.CompareTo(id) > 0                         orderby od.SalesOrderDetailID                         select od;   We can find the maximum SalesOrderDetailID like this:             var maxIdEfficiently = query.Max(od => od.SalesOrderDetailID);   which produces our efficient MAX() SQL query. If we're doing this generically and we already have the ID function in a Func:             Func<SalesOrderDetail, int> idFunc = od => od.SalesOrderDetailID;             var maxIdInefficiently = query.Max(idFunc);   This fetches all the results from the query and then runs the Max() function in code. If you look at the difference in Reflector, the first call passes an Expression to the Max(), while the second call passes a Func. So it's an easy fix - wrap the Func in an Expression:             Expression<Func<SalesOrderDetail, int>> idExpression = od => od.SalesOrderDetailID;             var maxIdEfficientlyAgain = query.Max(idExpression);   - and we're back to running an efficient MAX() statement. Evidently the EF provider can dissect an Expression and build its equivalent in SQL, but it can't do that with Funcs.

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• Zenoss Setup for Windows Servers

  - by Jay Fox

  Recently I was saddled with standing up Zenoss for our enterprise.  We're running about 1200 servers, so manually touching each box was not an option.  We use LANDesk for a lot of automated installs and patching - more about that later.The steps below may not necessarily have to be completed in this order - it's just the way I did it.STEP ONE:Setup a standard AD user.  We want to do this so there's minimal security exposure.  Call the account what ever you want "domain/zenoss" for our examples.***********************************************************STEP TWO:Make the following local groups accessible by your zenoss account.Distributed COM UsersPerformance Monitor UsersEvent Log Readers (which doesn't exist on pre-2008 machines)Here's the Powershell script I used to setup access to these local groups:# Created to add Active Directory account to local groups# Must be run from elevated prompt, with permissions on the remote machine(s).# Create txt file should contain the names of the machines that need the account added, one per line.# Script will process machines line by line.foreach($i in (gc c:\tmp\computers.txt)){# Add the user to the first group$objUser=[ADSI]("WinNT://domain/zenoss")$objGroup=[ADSI]("WinNT://$i/Distributed COM Users")$objGroup.PSBase.Invoke("Add",$objUser.PSBase.Path)# Add the user to the second group$objUser=[ADSI]("WinNT://domain/zenoss")$objGroup=[ADSI]("WinNT://$i/Performance Monitor Users")$objGroup.PSBase.Invoke("Add",$objUser.PSBase.Path)# Add the user to the third group - Group doesn't exist on < Server 2008#$objUser=[ADSI]("WinNT://domain/zenoss")#$objGroup=[ADSI]("WinNT://$i/Event Log Readers")#$objGroup.PSBase.Invoke("Add",$objUser.PSBase.Path)}**********************************************************STEP THREE:Setup security on the machines namespace so our domain/zenoss account can access itThe default namespace for zenoss is:  root/cimv2Here's the Powershell script:#Grant account defined below (line 11) access to WMI Namespace#Has to be run as account with permissions on remote machinefunction get-sid{Param ($DSIdentity)$ID = new-object System.Security.Principal.NTAccount($DSIdentity)return $ID.Translate( [System.Security.Principal.SecurityIdentifier] ).toString()}$sid = get-sid "domain\zenoss"$SDDL = "A;;CCWP;;;$sid" $DCOMSDDL = "A;;CCDCRP;;;$sid"$computers = Get-Content "c:\tmp\computers.txt"foreach ($strcomputer in $computers){    $Reg = [WMIClass]"\\$strcomputer\root\default:StdRegProv"    $DCOM = $Reg.GetBinaryValue(2147483650,"software\microsoft\ole","MachineLaunchRestriction").uValue    $security = Get-WmiObject -ComputerName $strcomputer -Namespace root/cimv2 -Class __SystemSecurity    $converter = new-object system.management.ManagementClass Win32_SecurityDescriptorHelper    $binarySD = @($null)    $result = $security.PsBase.InvokeMethod("GetSD",$binarySD)    $outsddl = $converter.BinarySDToSDDL($binarySD[0])    $outDCOMSDDL = $converter.BinarySDToSDDL($DCOM)    $newSDDL = $outsddl.SDDL += "(" + $SDDL + ")"    $newDCOMSDDL = $outDCOMSDDL.SDDL += "(" + $DCOMSDDL + ")"    $WMIbinarySD = $converter.SDDLToBinarySD($newSDDL)    $WMIconvertedPermissions = ,$WMIbinarySD.BinarySD    $DCOMbinarySD = $converter.SDDLToBinarySD($newDCOMSDDL)    $DCOMconvertedPermissions = ,$DCOMbinarySD.BinarySD    $result = $security.PsBase.InvokeMethod("SetSD",$WMIconvertedPermissions)     $result = $Reg.SetBinaryValue(2147483650,"software\microsoft\ole","MachineLaunchRestriction", $DCOMbinarySD.binarySD)}***********************************************************STEP FOUR:Get the SID for our zenoss account.Powershell#Provide AD User get SID$objUser = New-Object System.Security.Principal.NTAccount("domain", "zenoss") $strSID = $objUser.Translate([System.Security.Principal.SecurityIdentifier]) $strSID.Value******************************************************************STEP FIVE:Modify the Service Control Manager to allow access to the zenoss AD account.This command can be run from an elevated command line, or through Powershellsc sdset scmanager "D:(A;;CC;;;AU)(A;;CCLCRPRC;;;IU)(A;;CCLCRPRC;;;SU)(A;;CCLCRPWPRC;;;SY)(A;;KA;;;BA)(A;;CCLCRPRC;;;PUT_YOUR_SID_HERE_FROM STEP_FOUR)S:(AU;FA;KA;;;WD)(AU;OIIOFA;GA;;;WD)"******************************************************************In step two the script plows through a txt file that processes each computer listed on each line.  For the other scripts I ran them on each machine using LANDesk.  You can probably edit those scripts to process a text file as well.That's what got me off the ground monitoring the machines using Zenoss.  Hopefully this is helpful for you.  Watch the line breaks when copy the scripts.

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• need some concrete examples on user stories, tasks and how they relate to functional and technical specifications

  - by gideon

  Little heads up, Im the only lonely dev building/planning/mocking my project as I go. Ive come up with a preview release that does only the core aspects of the system, with good business value and I've coded most of the UI as dirty throw-able mockups over nicely abstracted and very minimal base code. In the end I know quite well what my clients want on the whole. I can't take agile-ish cowboying anymore because Im completely dis-organized and have no paper plan and since my clients are happy, things are getting more complex with more features and ideas. So I started using and learning Agile & Scrum Here are my problems: I know what a functional spec is.(sample): Do all user stories and/or scenarios become part of the functional spec? I know what user stories and tasks are. Are these kinda user stories? I dont see any Business Value reason added to them. I made a mind map using freemind, I had problems like this: Actor : Finance Manager Can Add a Financial Plan into the system because well thats the point of it? What Business Value reason do I add for things like this? Example : A user needs to be able to add a blog article (in the blogger app) because..?? Its the point of a blogger app, it centers around that feature? How do I go into the finer details and system definitions: Actor: Finance Manager Action: Adds a finance plan. This adding is a complicated process with lots of steps. What User Story will describe what a finance plan in the system is ?? I can add it into the functional spec under definitions explaining what a finance plan is and how one needs to add it into the system, but how do I get to the backlog planning from there? Example: A Blog Article is mostly a textual document that can be written in rich text in the system. To add a blog article one must...... But how do you create backlog list/features out of this? Where are the user stories for what a blog article is and how one adds/removes it? Finally, I'm a little confused about the relations between functional specs and user stories. Will my spec contain user stories in them with UI mockups? Now will these user stories then branch out tasks which will make up something like a technical specification? Example : EditorUser Can add a blog article. Use XML to store blog article. Add a form to add blog. Add Windows Live Writer Support. That would be agile tasks but would that also be part of/or form the technical specs? Some concrete examples/answers of my questions would be nice!!

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