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  • Error "fixing recursive fault but reboot is needed"

    - by Gordon
    I am trying to install ubuntu for the first time. (long time windows user, first time linux!) Version = 11.04 Hardware = Acer Travelmate 4050 I can boot from USB or CD and it loads fine I have installed and reinstalled several times from both USB and CD and it completes correctly However, when I boot from the HDD I get the above error I don't see any errors like "kernel panic" mentioned elsewhere It happens whether I boot with AC adapter in or out and also with adapter in but battery out Not sure how to get further info to help with diagnosis Suggestions?

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  • Availability Best Practices on Oracle VM Server for SPARC

    - by jsavit
    This is the first of a series of blog posts on configuring Oracle VM Server for SPARC (also called Logical Domains) for availability. This series will show how to how to plan for availability, improve serviceability, avoid single points of failure, and provide resiliency against hardware and software failures. Availability is a broad topic that has filled entire books, so these posts will focus on aspects specifically related to Oracle VM Server for SPARC. The goal is to improve Reliability, Availability and Serviceability (RAS): An article defining RAS can be found here. Oracle VM Server for SPARC Principles for Availability Let's state some guiding principles for availability that apply to Oracle VM Server for SPARC: Avoid Single Points Of Failure (SPOFs). Systems should be configured so a component failure does not result in a loss of application service. The general method to avoid SPOFs is to provide redundancy so service can continue without interruption if a component fails. For a critical application there may be multiple levels of redundancy so multiple failures can be tolerated. Oracle VM Server for SPARC makes it possible to configure systems that avoid SPOFs. Configure for availability at a level of resource and effort consistent with business needs. Effort and resource should be consistent with business requirements. Production has different availability requirements than test/development, so it's worth expending resources to provide higher availability. Even within the category of production there may be different levels of criticality, outage tolerances, recovery and repair time requirements. Keep in mind that a simple design may be more understandable and effective than a complex design that attempts to "do everything". Design for availability at the appropriate tier or level of the platform stack. Availability can be provided in the application, in the database, or in the virtualization, hardware and network layers they depend on - or using a combination of all of them. It may not be necessary to engineer resilient virtualization for stateless web applications applications where availability is provided by a network load balancer, or for enterprise applications like Oracle Real Application Clusters (RAC) and WebLogic that provide their own resiliency. It's (often) the same architecture whether virtual or not: For example, providing resiliency against a lost device path or failing disk media is done for the same reasons and may use the same design whether in a domain or not. It's (often) the same technique whether using domains or not: Many configuration steps are the same. For example, configuring IPMP or creating a redundant ZFS pool is pretty much the same within the guest whether you're in a guest domain or not. There are configuration steps and choices for provisioning the guest with the virtual network and disk devices, which we will discuss. Sometimes it is different using domains: There are new resources to configure. Most notable is the use of alternate service domains, which provides resiliency in case of a domain failure, and also permits improved serviceability via "rolling upgrades". This is an important differentiator between Oracle VM Server for SPARC and traditional virtual machine environments where all virtual I/O is provided by a monolithic infrastructure that itself is a SPOF. Alternate service domains are widely used to provide resiliency in production logical domains environments. Some things are done via logical domains commands, and some are done in the guest: For example, with Oracle VM Server for SPARC we provide multiple network connections to the guest, and then configure network resiliency in the guest via IP Multi Pathing (IPMP) - essentially the same as for non-virtual systems. On the other hand, we configure virtual disk availability in the virtualization layer, and the guest sees an already-resilient disk without being aware of the details. These blogs will discuss configuration details like this. Live migration is not "high availability" in the sense of "continuous availability": If the server is down, then you don't live migrate from it! (A cluster or VM restart elsewhere would be used). However, live migration can be part of the RAS (Reliability, Availability, Serviceability) picture by improving Serviceability - you can move running domains off of a box before planned service or maintenance. The blog Best Practices - Live Migration on Oracle VM Server for SPARC discusses this. Topics Here are some of the topics that will be covered: Network availability using IP Multipathing and aggregates Disk path availability using virtual disks defined with multipath groups ("mpgroup") Disk media resiliency configuring for redundant disks that can tolerate media loss Multiple service domains - this is probably the most significant item and the one most specific to Oracle VM Server for SPARC. It is very widely deployed in production environments as the means to provide network and disk availability, but it can be confusing. Subsequent articles will describe why and how to configure multiple service domains. Note, for the sake of precision: an I/O domain is any domain that has a physical I/O resource (such as a PCIe bus root complex). A service domain is a domain providing virtual device services to other domains; it is almost always an I/O domain too (so it can have something to serve). Resources Here are some important links; we'll be drawing on their content in the next several articles: Oracle VM Server for SPARC Documentation Maximizing Application Reliability and Availability with SPARC T5 Servers whitepaper by Gary Combs Maximizing Application Reliability and Availability with the SPARC M5-32 Server whitepaper by Gary Combs Summary Oracle VM Server for SPARC offers features that can be used to provide highly-available environments. This and the following blog entries will describe how to plan and deploy them.

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  • Career Advice: finding challenging work in software and web development

    - by dianovich
    Having left my physics degree early, I started out in the realm of web design / front end web development and was able to get work quite quickly. I moved on to spend a chunk of my time on servers and gained experience with frameworks like Wordpress and Drupal, then the likes of Codeigniter and CakePHP and became comfortable in Debian-based and RHEL/CentOS environments. I ventured in to iOS development and published a couple of native apps to the app store too! I have started to spend a good deal of my time writing Python and have invested a little time in Django. The problem is, I still spend a fair chunk of my time doing more front end web development (writing markup and CSS for site themes, design-lead JavaScript, small applications for which application architecture and software engineering are relatively unimportant or too time consuming to invest in) in my job. What I want to do is really exercise the systematic/logical portion of my brain and tackle challenging problems on a daily basis. I want to have to care about big-oh running times, modularity in software, DRY, performance tuning and development methodologies. I want to work for a firm whose clients say: "Yes, these things are important to us and we'll pay you to get them right." But it is difficult: I have no formal training and am potentially becoming a jack of all trades. Not that being a jack of many trades is necessarily a bad thing, but the scope of work I find myself involved in is far too broad. And, there are only so many hours in a day outside of work! My question is: where do I go from here? I am starting to work on a few open source projects and have started to publish content to my blog. But this isn't likely to make it past the recruitment consultants and HR departments of many-a-firm. And I do not, for example, work in a team that practices agile methodologies, so how do I get work in such a team to gain experience? While I have been responsible for implementing version control and some solid working practices into our current environment, there is only so far I can go in this context. What would convince you that i'm worth taking a risk? What would convince you that i'll have caught up the other guys in your employ in next to no time?

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  • Customer Experience Management : A conversation with world experts RTD

    - by David lefranc
    A conversation with world experts in Customer Experience Management in Rome, Italy - Wed, June 20, 2012 It is our pleasure to share the registration link below for your chance to meet active members of the Oracle Real-Time Decisions Customer Advisory Board. Join us to hear how leading brands across the world have achieved tremendous return on investment through their Oracle Real-Time Decisions deployments and do not miss this unique opportunity to ask them specific questions directly during our customer roundtable. Please share this information with anyone interested in real-time decision management and cross-channel predictive process optimization.http://www.oracle.com/goto/RealTimeDecisions

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  • Customer Experience Management : A conversation with world experts RTD

    - by David lefranc
    A conversation with world experts in Customer Experience Management in Rome, Italy - Wed, June 20, 2012 It is our pleasure to share the registration link below for your chance to meet active members of the Oracle Real-Time Decisions Customer Advisory Board. Join us to hear how leading brands across the world have achieved tremendous return on investment through their Oracle Real-Time Decisions deployments and do not miss this unique opportunity to ask them specific questions directly during our customer roundtable. Please share this information with anyone interested in real-time decision management and cross-channel predictive process optimization.http://www.oracle.com/goto/RealTimeDecisions

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  • Google I/O 2010 - Next gen queries

    Google I/O 2010 - Next gen queries Google I/O 2010 - Next gen queries App Engine 301 Alfred Fuller This session will discuss the design and implications of improvements to the Datastore query engine including support for AND, OR and NOT query operators, the solution to exploding indexes and paging backwards with Cursors. Specific technologies discussed will be an improved zigzag merge join algorithm, a new extensible multiquery framework (with geo-query support) and a smaller more versatile Cursor design. For all I/O 2010 sessions, please go to code.google.com From: GoogleDevelopers Views: 16 1 ratings Time: 50:17 More in Science & Technology

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  • Approaching Java/JVM internals

    - by spinning_plate
    I've programmed in Java for about 8 years and I know the language quite well as a developer, but my goal is to deepen my knowledge of the internals. I've taken undergraduate courses in PL design, but they were very broad academic overviews (in Scheme, IIRC). Can someone suggest a route to start delving into the details? Specifically, are there particular topics (say, garbage collection) that might be more approachable or be a good starting point? Is there a decent high-level book on the internals of the JVM and the design of the Java programming language? My current approach is going to be to start with the JVM spec and research as needed.

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  • What naming anti-patterns exist?

    - by Billy ONeal
    There are some names, where if you find yourself reaching for those names, you know you've already messed something up. For example: XxxManager This is bad because a class should describe what the class does. If the most specific word you can come up with for what the class does is "manage," then the class is too big. What other naming anti-patterns exist? EDIT: To clarify, I'm not asking "what names are bad" -- that question is entirely subjective and there's no way to answer it. I'm asking, "what names indicate overall design problems with the system." That is, if you find yourself wanting to call a component Xyz, that probably indicates the component is ill concieved. Also note here that there are exceptions to every rule -- I'm just looking for warning flags for when I really need to stop and rethink a design.

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  • How important is knowing functionality before coding?

    - by minusSeven
    I work for a software development company where the development work have been off shored to us. The on shore team handle the support and talk directly to the clients. We never talk to the clients directly we just talk people from the on shore team who talk directly to the clients. When requirements come, on shore team talk to the clients and make requirement documents and informs us. We make design documents after studying the requirements (we follow traditional waterfall model ). But there is one problem in the whole process: nobody in the either off-shore or on-shore understand the functionality of the application completely. We just know its a big complex web app handling complex order processing, catalog management, campaign management and other activities. We struggle with the design document as the requirements would not be clear. It then goes into a series of questions/answers back and forth between the on shore team,off shore team and clients. We would often be told to understand functionality from the code. But that's usually not feasible as the code base is huge and even understanding a simple menu item take days if not weeks. We tried telling the clients to give us knowledge transfer about the application but to no avail. Our manager would often tell us to start coding even if the design document is not complete or requirements not clear. We would start by coding part of the requirement that seems clear and wait for the rest. This usually would delay the deployment by a month. In extreme cases we would have very low errors in the development and production but the clients would say that's not what they asked. That would start a blame game and a series of change requests and we would end up developing something very different. My question is how would you do development work if you don't know the functionality of the app fully? UPDATE About development methodology it isn't really my choice and I am not my team's lead It is the way it began. I tried to tell people about the advantages of agile but to no avail. Besides I don't think my team has the necessary mindset to work in AGILE environment.

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  • What is the best drink to drink when you have read nonsense questions on programmers?

    - by stefan
    I am having a hard time deciding what drink to drink after I have read a nonsense question on programmers.stackexchange. It's either Beer och Whisky; The beer is nice since you can down it some what relaxed but some times I feel the need for something "stronger" because the question is so utterly nonsense and stupid. Every time I have read a stupid / nonsense question on programmers.stackexchange.com I've questioned myself why I didnt write some code instead. I couldve probably written countless lines of codes, together probably building a new Facebook or Linux by now. But instead I sacrificed my precious time reading questions that shouldn't have been posted on the internet. It really makes me frustrating, I guess that is why I am so often considering the whisky part instead of beer. Since beer will maybe not calm me down enough and then I have to take the whisky too, together it's a) slightly more expensive and b) more time consuming. So, what is the best drink?

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  • Can't load some domain

    - by Grzegorz
    I can't load some domain on my ubuntu 13.04: youtube.com translate.google.com drive.google.com vk.com When I ping them they are responding: PING youtube.com (217.119.79.59) 56(84) bytes of data. 64 bytes from non-registered.plix.pl (217.119.79.59): icmp_req=1 ttl=59 time=21.9 ms 64 bytes from non-registered.plix.pl (217.119.79.59): icmp_req=2 ttl=59 time=20.5 ms 64 bytes from non-registered.plix.pl (217.119.79.59): icmp_req=3 ttl=59 time=21.3 ms --- youtube.com ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 2002ms rtt min/avg/max/mdev = 20.544/21.255/21.914/0.560 ms But they don't load in any browser like firefox, chrome, lynx. They load in my media centre on XBMCbuntu.

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  • Agile Development Requires Agile Support

    - by Matt Watson
    Agile developmentAgile development has become the standard methodology for application development. The days of long term planning with giant Gantt waterfall charts and detailed requirements is fading away. For years the product planning process frustrated product owners and businesses because no matter the plan, nothing ever went to plan. Agile development throws the detailed planning out the window and instead focuses on giving developers some basic requirements and pointing them in the right direction. Constant collaboration via quick iterations with the end users, product owners, and the development team helps ensure the project is done correctly.  The various agile development methodologies have helped greatly with creating products faster, but not without causing new problems. Complicated application deployments now occur weekly or monthly. Most of the products are web-based and deployed as a software service model. System performance and availability of these apps becomes mission critical. This is all much different from the old process of mailing new releases of client-server apps on CD once per quarter or year.The steady stream of new products and product enhancements puts a lot of pressure on IT operations to keep up with the software deployments and adding infrastructure capacity. The problem is most operations teams still move slowly thanks to change orders, documentation, procedures, testing and other processes. Operations can slow the process down and push back on the development team in some organizations. The DevOps movement is trying to solve some of these problems by integrating the development and operations teams more together. Rapid change introduces new problemsThe rapid product change ultimately creates some application problems along the way. Higher rates of change increase the likelihood of new application defects. Delivering applications as a software service also means that scalability of applications is critical. Development teams struggle to keep up with application defects and scalability concerns in their applications. Fixing application problems is a never ending job for agile development teams. Fixing problems before your customers do and fixing them quickly is critical. Most companies really struggle with this due to the divide between the development and operations groups. Fixing application problems typically requires querying databases, looking at log files, reviewing config files, reviewing error logs and other similar tasks. It becomes difficult to work on new features when your lead developers are working on defects from the last product version. Developers need more visibilityThe problem is most developers are not given access to see server and application information in the production environments. The operations team doesn’t trust giving all the developers the keys to the kingdom to log in to production and poke around the servers. The challenge is either give them no access, or potentially too much access. Those with access can still waste time figuring out the location of the application and how to connect to it over VPN. In addition, reproducing problems in test environments takes too much time and isn't always possible. System administrators spend a lot of time helping developers track down server information. Most companies give key developers access to all of the production resources so they can help resolve application defects. The problem is only those key people have access and they become a bottleneck. They end up spending 25-50% of their time on a daily basis trying to solve application issues because they are the only ones with access. These key employees’ time is best spent on strategic new projects, not addressing application defects. This job should fall to entry level developers, provided they have access to all the information they need to troubleshoot the problems.The solution to agile application support is giving all the developers limited access to the production environment and all the server information they need to see. Some companies create their own solutions internally to collect log files, centralize errors or other things to address the problem. Some developers even have access to server monitoring or other tools. But they key is giving them access to everything they need so they can see the full picture and giving access to the whole team. Giving access to everyone scales up the application support team and creates collaboration around providing improved application support.Stackify enables agile application supportStackify has created a solution that can give all developers a secure and read only view of the entire production server environment without console or remote desktop access.They provide a web application that provides real time visibility to the important information that developers need to see. An application centric view enables them to see all of their apps across multiple datacenters and environments. They don’t need to know where the application is deployed, just the name of the application to find it and dig in to see more. All your developers can see server health, application health, log files, config files, windows event viewer, deployment history, application notes, and much more. They can receive email and text alerts when problems arise and even safely query your production databases.Stackify enables companies that do agile development to scale up their application support team by getting more team members involved. The lead developers can spend more time on new projects. Application issues can be fixed quicker than ever. Operations can spend less time helping developers collect server information. Agile application support starts with Stackify. Visit Stackify.com to learn more.

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  • Why does flush dns often fail to work?

    - by Sharen Eayrs
    C:\Windows\system32>ipconfig /flushdns Windows IP Configuration Successfully flushed the DNS Resolver Cache. C:\Windows\system32>ping beautyadmired.com Pinging beautyadmired.com [xxx.45.62.2] with 32 bytes of data: Reply from xxx.45.62.2: bytes=32 time=253ms TTL=49 Reply from xxx.45.62.2: bytes=32 time=249ms TTL=49 Reply from xxx.45.62.2: bytes=32 time=242ms TTL=49 Reply from xxx.45.62.2: bytes=32 time=258ms TTL=49 Ping statistics for xxx.45.62.2: Packets: Sent = 4, Received = 4, Lost = 0 (0% loss), Approximate round trip times in milli-seconds: Minimum = 242ms, Maximum = 258ms, Average = 250ms My site should point to xx.73.42.27 I change the name server. It's been 3 hours. It still points to xxx.45.62.2 Actually what happen after we change name server anyway? Wait for what? I already flush dns. Why it still points to the wrong IP? Also most other people that do not have the DNS cache also still go to the wrong IP

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  • Experience vs. versatility

    - by Florin Bombeanu
    Let's say a .NET programmer works at a company which provides software on demand, not as a product. The programmer works in WPF for a period of time and he/she invests lots of time in it. He/she get very good at WPF and Windows Forms and desktop development in general. But the company has to provide a web application now, so the developer has to learn MVC or Web Forms. He/she is not experienced in web development so he/she starts investing time in this new technology and in time they get good at it. But this time the company has to provide a Sharepoint solution, and so on. What is more important: Being very very good at a certain technology, Or be as versatile as possible knowing less in each technology but covering a greater area of expertise? Should the programmer keep studying and working in WPF until he/she reaches a guru level or is it a good thing that they had to learn other technologies as well? I agree with those of you who will say that when learning different technologies you will also learn things which are useful no matter the technology you're programming in. But eventually, when the programmer will want to change jobs, will it matter more that he/she knows some WPF, MVC or Sharepoint than the fact that he/she is insanely good at one of them? I would think the second one is more important since most companies are looking for a developer for a certain technology. I don't think there are many companies looking for technical know-it-all people. What do you think?

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  • Passing additional parameters to JQuery bind event function

    - by kazim sardar mehdi
    To pass the additional parameter to the event function pass an array of key value, as the second parameter to the bind event bind('click', { message: time }, onClick); e.g { message: time } and access it in the function using event(function parameter).data.message(key)   <div id="div1" style="border: 1px solid black; width: 100px; height: 100px">click me</div> <script type="text/javascript"> function onClick(event) { alert(event.data.message); } var time = "loaded at:" + new Date().toString(); $("div.#div1").bind('click', { message: time }, onClick); </script>

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  • SP1 of RadControls for WinForms Q1 2010 released, featuring VS2010 and Client Profile support

    As always, Telerik's plans were closely aligned with Microsoft's release schedule, and we were dedicated to provide VS2010 support even before Visual Studio 2010 was officially launched. Now that the first VS2010 launch event is over, here comes the first of many Telerik Service Packs to support VS2010. This RadControls for WinForms release is the first to provide support for the Client Profile, introduced with .NET3.5, and now default when starting new windows forms projects with VS2010. The Client Profile is a smaller version of the.NET Framework that includes only the assemblies needed for deploying client-based applications, which in turn reduces the size of the application. Basically, the Design time classes are excluded from the Client Profile (CP), because they are only needed for designing and not for running an application. In Q1 2010 SP1 we have moved the designer classes from the run-time assemblies to a new dedicated assembly (Telerik.WinControls.UI.Design.dll), ...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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  • How do you go about training a replacement?

    - by SnOrfus
    I recently asked about leaving a position and got a lot of great answers. One of the common threads was that being around to train the new person would be expected and could go a long way. Now considering that (I think) most people don't stay at a company for a long time after they've given notice, and it will take time for the company to interview/hire one - that leaves for a short amount of time to get someone up to speed. I've also never trained anyone before. I did a bunch of tutoring in University and College, but teaching a language/technology is far different from training someone to replace you on your job. So the question is: how do you go about training someone to replace you in a, potentially, short amount of time?

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  • Unity 3d (Using Blender) - anime/manga/cel-shaded style characters

    - by David Archer
    Making a game using Blender for 3D models and Unity for the game engine. Just wondering if anyone knows any links to pages that give a tutorial on Japanese anime style 3D modelling, texturing and shading through blender. I'm actually looking to create a cel-shaded look eventually (read: Okami/Jet Set Radio style) and I'm kind of stuck with the design stuff. I'm not a Blender expert by any means, and still kind of new to the design side of things (I'm a programmer by trade), so please don't vote me down too hard. I've tried googling, but there doesn't seem to be much in the way of what I'm after. The only thing I've found really is a plugin for blender called freestyle, or using the ToonShader shading tool. If there are any good tutorials or anything, I'm really happy to sit through them - just want to learn :) Thanks for any help :)

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  • Subterranean IL: Generics and array covariance

    - by Simon Cooper
    Arrays in .NET are curious beasts. They are the only built-in collection types in the CLR, and SZ-arrays (single dimension, zero-indexed) have their own commands and IL syntax. One of their stranger properties is they have a kind of built-in covariance long before generic variance was added in .NET 4. However, this causes a subtle but important problem with generics. First of all, we need to briefly recap on array covariance. SZ-array covariance To demonstrate, I'll tweak the classes I introduced in my previous posts: public class IncrementableClass { public int Value; public virtual void Increment(int incrementBy) { Value += incrementBy; } } public class IncrementableClassx2 : IncrementableClass { public override void Increment(int incrementBy) { base.Increment(incrementBy); base.Increment(incrementBy); } } In the CLR, SZ-arrays of reference types are implicitly convertible to arrays of the element's supertypes, all the way up to object (note that this does not apply to value types). That is, an instance of IncrementableClassx2[] can be used wherever a IncrementableClass[] or object[] is required. When an SZ-array could be used in this fashion, a run-time type check is performed when you try to insert an object into the array to make sure you're not trying to insert an instance of IncrementableClass into an IncrementableClassx2[]. This check means that the following code will compile fine but will fail at run-time: IncrementableClass[] array = new IncrementableClassx2[1]; array[0] = new IncrementableClass(); // throws ArrayTypeMismatchException These checks are enforced by the various stelem* and ldelem* il instructions in such a way as to ensure you can't insert a IncrementableClass into a IncrementableClassx2[]. For the rest of this post, however, I'm going to concentrate on the ldelema instruction. ldelema This instruction pops the array index (int32) and array reference (O) off the stack, and pushes a pointer (&) to the corresponding array element. However, unlike the ldelem instruction, the instruction's type argument must match the run-time array type exactly. This is because, once you've got a managed pointer, you can use that pointer to both load and store values in that array element using the ldind* and stind* (load/store indirect) instructions. As the same pointer can be used for both input and output to the array, the type argument to ldelema must be invariant. At the time, this was a perfectly reasonable restriction, and maintained array type-safety within managed code. However, along came generics, and with it the constrained callvirt instruction. So, what happens when we combine array covariance and constrained callvirt? .method public static void CallIncrementArrayValue() { // IncrementableClassx2[] arr = new IncrementableClassx2[1] ldc.i4.1 newarr IncrementableClassx2 // arr[0] = new IncrementableClassx2(); dup newobj instance void IncrementableClassx2::.ctor() ldc.i4.0 stelem.ref // IncrementArrayValue<IncrementableClass>(arr, 0) // here, we're treating an IncrementableClassx2[] as IncrementableClass[] dup ldc.i4.0 call void IncrementArrayValue<class IncrementableClass>(!!0[],int32) // ... ret } .method public static void IncrementArrayValue<(IncrementableClass) T>( !!T[] arr, int32 index) { // arr[index].Increment(1) ldarg.0 ldarg.1 ldelema !!T ldc.i4.1 constrained. !!T callvirt instance void IIncrementable::Increment(int32) ret } And the result: Unhandled Exception: System.ArrayTypeMismatchException: Attempted to access an element as a type incompatible with the array. at IncrementArrayValue[T](T[] arr, Int32 index) at CallIncrementArrayValue() Hmm. We're instantiating the generic method as IncrementArrayValue<IncrementableClass>, but passing in an IncrementableClassx2[], hence the ldelema instruction is failing as it's expecting an IncrementableClass[]. On features and feature conflicts What we've got here is a conflict between existing behaviour (ldelema ensuring type safety on covariant arrays) and new behaviour (managed pointers to object references used for every constrained callvirt on generic type instances). And, although this is an edge case, there is no general workaround. The generic method could be hidden behind several layers of assemblies, wrappers and interfaces that make it a requirement to use array covariance when calling the generic method. Furthermore, this will only fail at runtime, whereas compile-time safety is what generics were designed for! The solution is the readonly. prefix instruction. This modifies the ldelema instruction to ignore the exact type check for arrays of reference types, and so it lets us take the address of array elements using a covariant type to the actual run-time type of the array: .method public static void IncrementArrayValue<(IncrementableClass) T>( !!T[] arr, int32 index) { // arr[index].Increment(1) ldarg.0 ldarg.1 readonly. ldelema !!T ldc.i4.1 constrained. !!T callvirt instance void IIncrementable::Increment(int32) ret } But what about type safety? In return for ignoring the type check, the resulting controlled mutability pointer can only be used in the following situations: As the object parameter to ldfld, ldflda, stfld, call and constrained callvirt instructions As the pointer parameter to ldobj or ldind* As the source parameter to cpobj In other words, the only operations allowed are those that read from the pointer; stind* and similar that alter the pointer itself are banned. This ensures that the array element we're pointing to won't be changed to anything untoward, and so type safety within the array is maintained. This is a typical example of the maxim that whenever you add a feature to a program, you have to consider how that feature interacts with every single one of the existing features. Although an edge case, the readonly. prefix instruction ensures that generics and array covariance work together and that compile-time type safety is maintained. Tune in next time for a look at the .ctor generic type constraint, and what it means.

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  • Project Euler 11: (Iron)Python

    - by Ben Griswold
    In my attempt to learn (Iron)Python out in the open, here’s my solution for Project Euler Problem 11.  As always, any feedback is welcome. # Euler 11 # http://projecteuler.net/index.php?section=problems&id=11 # What is the greatest product # of four adjacent numbers in any direction (up, down, left, # right, or diagonally) in the 20 x 20 grid? import time start = time.time() grid = [\ [8,02,22,97,38,15,00,40,00,75,04,05,07,78,52,12,50,77,91,8],\ [49,49,99,40,17,81,18,57,60,87,17,40,98,43,69,48,04,56,62,00],\ [81,49,31,73,55,79,14,29,93,71,40,67,53,88,30,03,49,13,36,65],\ [52,70,95,23,04,60,11,42,69,24,68,56,01,32,56,71,37,02,36,91],\ [22,31,16,71,51,67,63,89,41,92,36,54,22,40,40,28,66,33,13,80],\ [24,47,32,60,99,03,45,02,44,75,33,53,78,36,84,20,35,17,12,50],\ [32,98,81,28,64,23,67,10,26,38,40,67,59,54,70,66,18,38,64,70],\ [67,26,20,68,02,62,12,20,95,63,94,39,63,8,40,91,66,49,94,21],\ [24,55,58,05,66,73,99,26,97,17,78,78,96,83,14,88,34,89,63,72],\ [21,36,23,9,75,00,76,44,20,45,35,14,00,61,33,97,34,31,33,95],\ [78,17,53,28,22,75,31,67,15,94,03,80,04,62,16,14,9,53,56,92],\ [16,39,05,42,96,35,31,47,55,58,88,24,00,17,54,24,36,29,85,57],\ [86,56,00,48,35,71,89,07,05,44,44,37,44,60,21,58,51,54,17,58],\ [19,80,81,68,05,94,47,69,28,73,92,13,86,52,17,77,04,89,55,40],\ [04,52,8,83,97,35,99,16,07,97,57,32,16,26,26,79,33,27,98,66],\ [88,36,68,87,57,62,20,72,03,46,33,67,46,55,12,32,63,93,53,69],\ [04,42,16,73,38,25,39,11,24,94,72,18,8,46,29,32,40,62,76,36],\ [20,69,36,41,72,30,23,88,34,62,99,69,82,67,59,85,74,04,36,16],\ [20,73,35,29,78,31,90,01,74,31,49,71,48,86,81,16,23,57,05,54],\ [01,70,54,71,83,51,54,69,16,92,33,48,61,43,52,01,89,19,67,48]] # left and right max, product = 0, 0 for x in range(0,17): for y in xrange(0,20): product = grid[y][x] * grid[y][x+1] * \ grid[y][x+2] * grid[y][x+3] if product > max : max = product # up and down for x in range(0,20): for y in xrange(0,17): product = grid[y][x] * grid[y+1][x] * \ grid[y+2][x] * grid[y+3][x] if product > max : max = product # diagonal right for x in range(0,17): for y in xrange(0,17): product = grid[y][x] * grid[y+1][x+1] * \ grid[y+2][x+2] * grid[y+3][x+3] if product > max: max = product # diagonal left for x in range(0,17): for y in xrange(0,17): product = grid[y][x+3] * grid[y+1][x+2] * \ grid[y+2][x+1] * grid[y+3][x] if product > max : max = product print max print "Elapsed Time:", (time.time() - start) * 1000, "millisecs" a=raw_input('Press return to continue')

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  • Web services, Java EE, Spring, DB integration project ideas - maybe data mining related?

    - by saral jain
    I am a graduate Computer Science student (Data Mining and Machine Learning) and have good exposure to core Java (3 years). I have read up on a bunch of stuff on the following topics: Design patterns, Java EE Web services (SOAP and REST), Spring, and Hibernate Java Concurrency - advanced features like Task and Executors. I would now like to do a project combining this stuff -- over my free time of course -- to get a better understanding of these things and to kind of make an end to end software (to learn the best design principles etc + SVN, maven). Any good project ideas would be really appreciated. I just want to build this stuff to learn, so I don't really mind re-inventing the wheel. Also, anything related to data mining would be an added bonus as it fits with my research but is absolutely not necessary since this project is more to learn to do large scale software development.

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  • Object Oriented programming on 8-bit MCU Case Study

    - by Calvin Grier
    I see that there's a lot of questions related to OO Programming here. I'm actually trying to find a specific resource related to embedded OO approaches for an 8 bit MCU. Several years back (maybe 6) I was looking for material related to Object Oriented programming for resource constrained 8051 microprocessors. I found an article/website with a case history of a design group that used a very small RAM part, and implemented many Object based constructs during their C design and development. I believe it was an 8051. The project was a success, and managed to stay inside the very small ROM/RAM they had available. I'm attempting to find it again, but Google can't locate it. The article was well written, and recommended a "mixed" approach using C methods for inheritance and encapsulation - if I recall correctly. Can anyone help me locate this article?

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  • How do you balance documentation requirements with Agile developments

    - by Jeremy
    In our development group there is currently discussions around agile and waterfal methodology. No-one has any practical experience with agile, but we are doing some reading. The agile manifesto lists 4 values: Individuals and interactions over processes and tools Working software over comprehensive documentation Customer collaboration over contract negotiation Responding to change over following a plan We are an internal development group developing applications for the consumption of other units in our enterprise. A team of 10 developers builds and releases multiple projects simultanously, typically with 1 - maybe 2 (rarely) developer on each project. It seems to be that from a supportability perspective the organization needs to put some real value on documentation - as without it, there are serious risks with resourcing changes. With agile favouring interactions, and software deliverables over processes and documentation, how do you balance that with the requirements of supportable systems and maintaining knowledge and understanding of how those systems work? With a waterfall approach which favours documentation (requirements before design, design specs before construction) it is easy to build a process that meets some of the organizational requirements - how do we do this with an agile approach?

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  • Should integer divide by zero halt execution?

    - by Pyrolistical
    I know that modern languages handle integer divide by zero as an error just like the hardware does, but what if we could design a whole new language? Ignoring existing hardware, what should a programming language does when an integer divide by zero occurs? Should it return a NaN of type integer? Or should it mirror IEEE 754 float and return +/- Infinity? Or is the existing design choice correct, and an error should be thrown? Is there a language that handles integer divide by zero nicely? EDIT When I said ignore existing hardware, I mean don't assume integer is represented as 32 bits, it can be represented in anyway you can to imagine.

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