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• Ubuntu Preseed set Norwegian Keyboard?

  - by Vangelis Tasoulas

  It's been a couple of days now that I am trying to make a fully automated unattended installation. I managed to make it work with Ubuntu/Cobbler and a preseed file, but I cannot set the correct keyboard layout which is Norwegian in this case. I am doing the tests on a virtual machine and when I am going with a normal manual installation (no preseed) everything is working fine. When I am using the preseed file, I always end up with an "English (US)" keyboard no matter the many different options I have tried. I can change it manually with the "dpkg-reconfigure keyboard-configuration" command, but that's not the case. It should be handled automatically using the preseed file. I am using DEBCONF_DEBUG=5 when the grub is loading, and as I see in "/var/log/installer/syslog" file after the installation has finished, the preseeding commands are accepted. Can anyone help on this? The preseed file I am using is following: d-i debian-installer/country string NO d-i debian-installer/language string en_US:en d-i debian-installer/locale string en_US.UTF-8 d-i console-setup/ask_detect boolean false d-i keyboard-configuration/layout select Norwegian d-i keyboard-configuration/variant select Norwegian d-i keyboard-configuration/modelcode string pc105 d-i keyboard-configuration/layoutcode string no d-i keyboard-configuration/xkb-keymap select no d-i netcfg/choose_interface select auto d-i netcfg/get_hostname string myhostname d-i netcfg/get_domain string simula.no d-i hw-detect/load_firmware boolean true d-i mirror/country string manual d-i mirror/http/hostname string ftp.uninett.no d-i mirror/http/directory string /ubuntu d-i mirror/http/proxy string http://10.0.1.253:3142/ d-i mirror/codename string precise d-i mirror/suite string precise d-i clock-setup/utc boolean true d-i time/zone string Europe/Oslo d-i clock-setup/ntp boolean true d-i clock-setup/ntp-server string 10.0.1.254 d-i partman-auto/method string lvm partman-auto-lvm partman-auto-lvm/new_vg_name string vg0 d-i partman-auto/purge_lvm_from_device boolean true d-i partman-lvm/device_remove_lvm boolean true d-i partman-md/device_remove_md boolean true d-i partman-lvm/confirm boolean true d-i partman-lvm/confirm_nooverwrite boolean true d-i partman-auto-lvm/guided_size string max d-i partman-auto/choose_recipe select 30atomic d-i partman/default_filesystem string ext4 d-i partman-partitioning/confirm_write_new_label boolean true d-i partman/choose_partition select finish d-i partman/confirm boolean true d-i partman/confirm_nooverwrite boolean true d-i partman/mount_style select uuid d-i passwd/root-login boolean false d-i passwd/make-user boolean true d-i passwd/user-fullname string vangelis d-i passwd/username string vangelis d-i passwd/user-password-crypted password $6$asdafdsdfasdfasdf d-i passwd/user-uid string d-i user-setup/allow-password-weak boolean false d-i passwd/user-default-groups string adm cdrom dialout lpadmin plugdev sambashare d-i user-setup/encrypt-home boolean false d-i apt-setup/restricted boolean true d-i apt-setup/universe boolean true d-i apt-setup/backports boolean true d-i apt-setup/services-select multiselect security d-i apt-setup/security_host string security.ubuntu.com d-i apt-setup/security_path string /ubuntu tasksel tasksel/first multiselect Basic Ubuntu server, OpenSSH server d-i pkgsel/include string build-essential htop vim nmap ntp d-i pkgsel/upgrade select safe-upgrade d-i pkgsel/update-policy select none d-i pkgsel/updatedb boolean true d-i grub-installer/only_debian boolean true d-i grub-installer/with_other_os boolean true d-i finish-install/keep-consoles boolean false d-i finish-install/reboot_in_progress note d-i cdrom-detect/eject boolean true d-i debian-installer/exit/halt boolean false d-i debian-installer/exit/poweroff boolean false

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• org.apache.sling.scripting.jsp.jasper.JasperException: Unable to load tag handler class [migrated]

  - by Babak Behzadi

  I'm developing an Apache Sling WCMS and using java tag libs to rendering some data. I defined a jsp tag lib with following descriptor and handler class: TLD file contains: <?xml version="1.0" encoding="UTF-8"?> <taglib version="2.1" xmlns="http://java.sun.com/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-jsptaglibrary_2_1.xsd"> <tlib-version>1.0</tlib-version> <short-name>taglibdescriptor</short-name> <uri>http://bob/taglibs</uri> <tag> <name>testTag</name> <body-content>tagdependent</body-content> <tag-class>org.bob.taglibs.test.TestTagHandler</tag-class> </tag> </taglib> Tag handler class: package org.bob.taglibs.test; import javax.servlet.jsp.tagext.TagSupport; public class TestTagHandler extends TagSupport{ @Override public int doStartTag(){ try { pageContext.getOut().print("<h1>Helloooooooo</h1>"); } catch(Exception e) { return SKIP_BODY; } return EVAL_BODY_INCLUDE; } } I packaged the tag lib as BobTagLib.jar and deployed it as a bundle using Sling Web Console. I used this tag lib in a jsp page deployed in my Sling repository: index.jsp: <%@ page contentType="text/html;charset=UTF-8" language="java" %> <%@ taglib prefix="bob" uri="http://bob/taglibs" %> <html> <head><title>Simple jsp page</title></head> <body> <bob:testTag/> </body> </html> Calling the page cause the following exception: org.apache.sling.scripting.jsp.jasper.JasperException: /apps/TagTest/index.jsp(7,5) Unable to load tag handler class "org.bob.taglibs.test.TestTagHandler" for tag "bob:testTag" ... Can any one get me a solution? In advance, any help is apreciated.

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• ArchBeat Link-o-Rama for August 1, 2013

  - by OTN ArchBeat

  Performance Tuning – Systems Running BPEL Processes | Ravi Saraswathi and Jaswant Sing Ravi Saraswathi and Jaswant Singh, the authors of "Oracle SOA BPEL Process Manager 11gR1 - A Hands-on Tutorial" explain performance tuning of SOA composite applications for optimal performance and scalability. Steps to configure SAML 2.0 with Weblogic Server | Puneeth The blogger known only as Punteeth shares an illustrated technical post that will be of interest to those working with Oracle WebLogic and the Security Assertion Markup Language (SAML). Video: Planning and Getting Started - Developer PCs | Chris Muir Tune in to the latest episode of ADF Architecture TV to see Chris Muir explain why you don't have to buy the most expensive PCs in order to run JDeveloper. Key User Experience Design Principles for working with Big Data | John Fuller User Experience Designer John Fuller shares 6 core design principles for working with big data that focus on "helping people bring together a variety of data types in a fast and flexible way." Event: OTN Developer Day: ADF Mobile - Burlington, MA - Aug 28 Through six sessions, including a hands-on workshop, you'll learn a simpler way to leverage your existing skills to develop enterprise mobile applications using Oracle ADF Mobile. Registration is free, but seating is limited. Optimizing WebCenter Portal Mobile Delivery | Jeevan Joseph FMW solution architect Jeevan Joseph "walks you through identifying and analyzing some common WebCenter Portal performance bottlenecks related to page weight and describes a generic approach that can streamline your portal while improving the performance and response times." Customizing specific instances of a WebCenter task flow | Jeevan Joseph Fusion Middleware A-Team solution architect Jeevan Joseph strikes again with this article that explains "how to set up parameters on MDS customization so that it is applied only under certain conditions...making it possible to customize individual instances of task flows." Exalogic Virtual Tea Break Snippets – Modifying Memory, CPU and Storage on a vServer | Andrew Hopkinson FMW solution architect Andrew Hopkinson walks you through "the simple process of resizing the resources associated with an already existing Exalogic vServer." Oracle ADF Mobile Virtual Developer Day - Next Week | Shay Shmeltzer JDeveloper product team lead Shay Schmeltzer shares agenda information for the OTN Virtual Developer Day event covering Mobile Application Development for iOS and Android, coming up one week from today, on August 7, 2013, 9am PT/Noon ET/1pm BRT. What's New In Oracle Enterprise Pack for Eclipse 12.1.2.1.0? New features and updates on the newly-released Oracle Enterprise Pack for Eclipse 12.1.2.1.0, now available for download from OTN. IOUG Cloud Builders Unite | Jeff Erickson Check out this great Oracle Magazine article by Jeff Erickson about IOUG members organizing around their common interest in building private clouds. Thought for the Day "Stuff that's hidden and murky and ambiguous is scary because you don't know what it does." — Jerry Garcia (August 1, 1942 – August 9, 1995) Source: brainyquote.com

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• SQL SERVER – Preserve Leading Zero While Coping to Excel from SSMS

  - by pinaldave

  Earlier I wrote two articles about how to efficiently copy data from SSMS to Excel. Since I wrote that post there are plenty of interest generated on this subject. There are a few questions I keep on getting over this subject. One of the question is how to get the leading zero preserved while copying the data from SSMS to Excel. Well it is almost the same way as my earlier post SQL SERVER – Excel Losing Decimal Values When Value Pasted from SSMS ResultSet. The key here is in EXCEL and not in SQL Server. The step here is to change the format of Excel Cell to Text from Numbers and that will preserve the value of the with leading or trailing Zeros in Excel. However, I assume this is done for display purpose only because once you convert column to Text you may find it difficult to do numeric operations over the column for example Aggregation, Average etc. If you need to do the same you should either convert the columns back to Numeric in Excel or do the process in Database and export the same value as along with it as well. However, I have seen in requirement in the real world where the user has to have a numeric value with leading Zero values in it for display purpose. Here is my suggestion, instead of manipulating numeric value in the database and converting it to character value the ideal thing to do is to store it as a numeric value only in the database. Whatever changes you want to do for display purpose should be handled at the time of the display using the format function of SQL or Application Language. Honestly, database is data layer and presentation is presentation layer – they are two different things and if possible they should not be mixed. If due to any reason you cannot follow above advise and you need is to have append leading zeros in the database only here are two of my previous articles I suggest you to refer them. I am open to learn new tricks as these articles are almost three years old. Please share your opinion and suggestions in the comments area. SQL SERVER – Pad Ride Side of Number with 0 – Fixed Width Number Display SQL SERVER – UDF – Pad Ride Side of Number with 0 – Fixed Width Number Display Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Function, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Excel

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• “Play Now” via website vs. download & install

  - by Inside

  I've spent some time looking over the various threads here on GDSE and also on the regular Stackoverflow site, and while I saw a lot of posts and threads regarding various engines that could be used in game development, I haven't seen very much discussion regarding the various platforms that they can be used on. In particular, I'm talking about browser games vs. desktop games. I want to develop a simple 3D networked multiplayer game - roughly on the graphics level of Paper Mario and gameplay with roughly the same level of interaction as a hack & slash action/adventure game - and I'm having a hard time deciding what platform I want to target with it. I have some experience with using C++/Ogre3D and Python/Panda3D (and also some synchronized/networked programming), but I'm wondering if it's worth it to spend the extra time to learn another language and another engine/toolkit just so that the game can be played in a browser window (I'm looking at jMonkeyEngine right now). Is it worth it to go with engines that are less-mature, have less documentation, have fewer features, and smaller communities* just so that a (possibly?) larger audience can be reached? Does it make sense to even go with a web-environment for the kind of game that I want to make? Does anyone have any experiences with decisions like this? (* With the exception of Flash-based engines it seems like most of the other approaches have downsides when compared to what is available for desktop-based environments. I'd go with Flash, but I'm worried that Flash's 3D capabilities aren't mature enough right now to do what I want easily. There's also Unity3D, but I'm not sure how I feel about that at all. It seems highly polished, but requires a plugin to be downloaded for the game to be played -- at that rate I might as well have players download my game.) For simple & short games the Newgrounds approach (go to the site, click "play now", instant gratification) seems to work well. What about for more complex games? Is there a point where the complexity of a game is enough for people to say "OK, I'm going to download and play that"?

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• Harness MySQL's Continued Performance Tuning Improvements

  - by Antoinette O'Sullivan

  To fully harness the continued improvements in performance tuning you get with MySQL, take the MySQL Performance Tuning course. This 4 day class teaches you practical, safe, highly efficient ways to optimize performance for the MySQL Server. You will learn the skills needed to use tools for monitoring, evaluating and tuning.  You can take this course in the following three ways: Training-on-Demand: Follow this course at your own pace and from your own desk with streaming video of instructor delivery and booking time to follow hands-on exercises at your own convenience. Live-Virtual: Attend a live instructor-led event from your own desk. Choose from the numerous events on the schedule. In-Class:  Travel to an education center to follow this class. A sample of events on the schedule is shown below:  Location  Date  Delivery Language  Tokyo, Japan  19 November 2012  Japanese  Mechelen, Belgium  4 February 2013  English  London, England  19 November 2012  English  Budapest, Hungary  21 May 2013  Hungarian  Milan, Italy  14 January 2013  Italian  Rome, Italy  3 December 2012  Italian  Riga, Latvia  10 December 2012  Latvian  Amsterdam, Netherlands  7 January 2013  Dutch  Nieuwegein, Netherlands  26 November 2012  Dutch  Warsaw, Poland  3 December 2012  Polish  Lisbon, Portugal  4 February 2013  European Portugese  Porto, Portugal  4 February 2013  European Portugese  Barcelona, Spain  25 March 2013  Spanish  Madrid, Spain  17 December 2012  Spanish  Sydney, Australia  26 November 2012  English  Edmonton, Canada  10 December 2012  English  Montreal, Canada  26 November 2012  English  Ottawa, Canada  26 November 2012  English  Toronto, Canada  26 November 2012  English  Vancouver, Canada  10 December 2012  English  Sao Paolo, Brazil  26 November 2012  Brazilan Portugese For more information on this class or to know more about other courses on the authentic MySQL curriculum. see http://oracle.com/education/mysql. Note, many organizations deploy both Oracle Database and MySQL side by side to serve different needs, and as a database professional you can find training courses on both topics at Oracle University! Check out the upcoming Oracle Database training courses and MySQL training courses. Even if you're only managing Oracle Databases at this point of time, getting familiar with MySQL will broaden your career path with growing job demand.

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• Victor Grazi, Java Champion!

  - by Tori Wieldt

  Congratulations to Victor Grazi, who has been made a Java Champion! He was nominated by his peers and selected as a Java Champion for his experience as a developer, and his work in the Java and Open Source communities. Grazi is a Java evangelist and serves on the Executive Committee of the Java Community Process, representing Credit Suisse - the first non-technology vendor on the JCP. He also arranges the NY Java SIG meetings at Credit Suisse's New York campus each month, and he says it has been a valuable networking opportunity. He also is the spec lead for JSR 354, the Java Money and Currency API. Grazi has been building real time financial systems in Java since JDK version 1.02! In 1996, the internet was just starting to happen, Grazi started a dot com called Supermarkets to Go, that provided an on-line shopping presence to supermarkets and grocers. Grazi wrote most of the code, which was a great opportunity for him to learn Java and UI development, as well as database management. Next, he went to work at Bank of NY building a trading system. He studied for Java certification, and he noted that getting his certification was a game changer because it helped him started to learn the nuances of the Java language. He has held other development positions, "You may have noticed that you don't get as much junk mail from Citibank as you used to - that is thanks to one of my projects!" he told us. Grazi joined Credit Suisse in 2005 and is currently Vice President on the central architecture team. Grazi is proud of his open source project, Java Concurrent Animated, a series of animations that visualize the functionality of the components in the java.util.concurrent library. "It has afforded me the opportunity to speak around the globe" and because of it, has discovered that he really enjoys doing public presentations. He is a fine addition to the Java Champions program. The Java Champions are an exclusive group of passionate Java technology and community leaders who are community-nominated and selected under a project sponsored by Oracle. Nominees are named and selected through a peer review process. Java Champions get the opportunity to provide feedback, ideas, and direction that will help Oracle grow the Java Platform. This interchange may be in the form of technical discussions and/or community-building activities with Oracle's Java Development and Developer Program teams.

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• WebCenter Spaces 11g PS2 Template Customization

  - by javier.ductor(at)oracle.com

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

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• Visual Studio 2010 RC &ndash; Silverlight 4 and WCF RIA Services Development - Updates from MIX Anno

  - by Harish Ranganathan

  MIX is happening and there is a lot of excitement around the various releases such as the Windows Phone 7 Developer Preview, IE9 Platform Preview and few other announcements that have been made.  Clearly, the Windows Phone 7 Developer Preview has generated the maximum interest and opened a plethora of opportunities for .NET Developers.  It also takes the mobile development to a new generation and doesn’t force developers to learn different programming language. Along with this, few other releases have been out.  The most anticipated Silverlight 4 RC is out and its corresponding templates are also out there for you to download.  Once VS 2010 RC was released, it was much of a disappointment that it doesn’t support SL4 development as well as the SL4 Business Application Development (a.k.a. WCF RIA Services).   There were few workarounds though nothing concrete.  Earlier I had written about how the WCF RIA Services Preview does work with ASP.NET Development using VS 2010 RC. However, with the release of SL4 RC and the corresponding tooling updates, one can develop for both SL4 as well as SL4 + WCF RIA Services using VS 2010 RC.  This is kind of important and keeps the continuum going until VS 2010 RTMs.  So, the purpose of this post is to quickly give the updates and links to install the relevant tools. Silverlight 4 RC Runtime Windows Runtime or the Mac Runtime Silverlight 4 RC Developer Tools for Visual Studio 2010 RC Silverlight 4 Tools for Visual Studio 2010 (this would install the Runtime as well automatically) Expression Blend 4 Beta Expression Blend 4 Beta If you install the SL4 RC Developer Tools, it also installs the WCF RIA Services Preview automatically.  You just need to install the WCF RIA Services Toolkit that can be downloaded from Install the WCF RIA Services Toolkit Of course you can also just install the WCF RIA Services for VS 2010 RC separately (without SL4 Tools) from here Kindly note, all the above mentioned links are with respect to Visual Studio 2010 RC edition.  If you are developing with VS 2008, then you can just target SL3 (as I write this, there seems to be no official support for developing SL4 with VS 2008) and the related tools can be downloaded from http://www.silverlight.net/getstarted/ Basically you need to download SL 3 Runtime, SDK, Expression Blend 3 and the Silverlight Toolkit.  All the links for the download are available in the above mentioned page. Also, a version of WCF RIA Services that is supported in VS 2008 is available for download at WCF RIA Services Beta for VS 2008 I know there are far too many things to keep in mind.  So, I put a flowchart that could help with depicting it pictorial.  Note that this is just my own imagination and doesn’t cover all scenarios.  for example, if you are neither developing for Webform, Silverlight, you end up nowhere whereas in actual scenario you may want to develop Desktop, Services, Console, Game and what not.  So, keep in mind this is just Web. Cheers !!!

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• Implement Negascout Algorithm with stack

  - by Dan

  I'm not familiar with how these stack exchange accounts work so if this is double posting I apologize. I asked the same thing on stackoverflow. I have added an AI routine to a game I am working on using the Negascout algorithm. It works great, but when I set a higher maximum depth it can take a few seconds to complete. The problem is it blocks the main thread, and the framework I am using does not have a way to deal with multi-threading properly across platforms. So I am trying to change this routine from recursively calling itself, to just managing a stack (vector) so that I can progress through the routine at a controlled pace and not lock up the application while the AI is thinking. I am getting hung up on the second recursive call in the loop. It relies on a returned value from the first call, so I don't know how to add these to a stack. My Working c++ Recursive Code: MoveScore abNegascout(vector<vector<char> > &board, int ply, int alpha, int beta, char piece) { if (ply==mMaxPly) { return MoveScore(evaluation.evaluateBoard(board, piece, oppPiece)); } int currentScore; int bestScore = -INFINITY; MoveCoord bestMove; int adaptiveBeta = beta; vector<MoveCoord> moveList = evaluation.genPriorityMoves(board, piece, findValidMove(board, piece, false)); if (moveList.empty()) { return MoveScore(bestScore); } bestMove = moveList[0]; for(int i=0;i<moveList.size();i++) { MoveCoord move = moveList[i]; vector<vector<char> > newBoard; newBoard.insert( newBoard.end(), board.begin(), board.end() ); effectMove(newBoard, piece, move.getRow(), move.getCol()); // First Call ****** MoveScore current = abNegascout(newBoard, ply+1, -adaptiveBeta, -max(alpha,bestScore), oppPiece); currentScore = - current.getScore(); if (currentScore>bestScore){ if (adaptiveBeta == beta || ply>=(mMaxPly-2)){ bestScore = currentScore; bestMove = move; }else { // Second Call ****** current = abNegascout(newBoard, ply+1, -beta, -currentScore, oppPiece); bestScore = - current.getScore(); bestMove = move; } if(bestScore>=beta){ return MoveScore(bestMove,bestScore); } adaptiveBeta = max(alpha, bestScore) + 1; } } return MoveScore(bestMove,bestScore); } If someone can please help by explaining how to get this to work with a simple stack. Example code would be much appreciated. While c++ would be perfect, any language that demonstrates how would be great. Thank You.

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

  - by Roger Brinkley

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

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• Is inline SQL still classed as bad practice now that we have Micro ORMs?

  - by Grofit

  This is a bit of an open ended question but I wanted some opinions, as I grew up in a world where inline SQL scripts were the norm, then we were all made very aware of SQL injection based issues, and how fragile the sql was when doing string manipulations all over the place. Then came the dawn of the ORM where you were explaining the query to the ORM and letting it generate its own SQL, which in a lot of cases was not optimal but was safe and easy. Another good thing about ORMs or database abstraction layers were that the SQL was generated with its database engine in mind, so I could use Hibernate/Nhibernate with MSSQL, MYSQL and my code never changed it was just a configuration detail. Now fast forward to current day, where Micro ORMs seem to be winning over more developers I was wondering why we have seemingly taken a U-Turn on the whole in-line sql subject. I must admit I do like the idea of no ORM config files and being able to write my query in a more optimal manner but it feels like I am opening myself back up to the old vulnerabilities such as SQL injection and I am also tying myself to one database engine so if I want my software to support multiple database engines I would need to do some more string hackery which seems to then start to make code unreadable and more fragile. (Just before someone mentions it I know you can use parameter based arguments with most micro orms which offers protection in most cases from sql injection) So what are peoples opinions on this sort of thing? I am using Dapper as my Micro ORM in this instance and NHibernate as my regular ORM in this scenario, however most in each field are quite similar. What I term as inline sql is SQL strings within source code. There used to be design debates over SQL strings in source code detracting from the fundamental intent of the logic, which is why statically typed linq style queries became so popular its still just 1 language, but with lets say C# and Sql in one page you have 2 languages intermingled in your raw source code now. Just to clarify, the SQL injection is just one of the known issues with using sql strings, I already mention you can stop this from happening with parameter based queries, however I highlight other issues with having SQL queries ingrained in your source code, such as the lack of DB Vendor abstraction as well as losing any level of compile time error capturing on string based queries, these are all issues which we managed to side step with the dawn of ORMs with their higher level querying functionality, such as HQL or LINQ etc (not all of the issues but most of them). So I am less focused on the individual highlighted issues and more the bigger picture of is it now becoming more acceptable to have SQL strings directly in your source code again, as most Micro ORMs use this mechanism. Here is a similar question which has a few different view points, although is more about the inline sql without the micro orm context: http://stackoverflow.com/questions/5303746/is-inline-sql-hard-coding

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• Game development: “Play Now” via website vs. download & install

  - by Inside

  Heyo, I've spent some time looking over the various threads here on gamedev and also on the regular stackoverflow and while I saw a lot of posts and threads regarding various engines that could be used in game development, I haven't seen very much discussion regarding the various platforms that they can be used on. In particular, I'm talking about browser games vs. desktop games. I want to develop a simple 3D networked multiplayer game - roughly on the graphics level of Paper Mario and gameplay with roughly the same level of interaction as a hack & slash action/adventure game - and I'm having a hard time deciding what platform I want to target with it. I have some experience with using C++/Ogre3D and Python/Panda3D (and also some synchronized/networked programming), but I'm wondering if it's worth it to spend the extra time to learn another language and another engine/toolkit just so that the game can be played in a browser window (I'm looking at jMonkeyEngine right now). For simple & short games the newgrounds approach (go to the site, click "play now", instant gratification) seems to work well. What about for more complex games? Is there a point where the complexity of a game is enough for people to say "ok, I'm going to download and play that"? Is it worth it to go with engines that are less-mature, have less documentation, have fewer features, and smaller communities* just so that a (possibly?) larger audience can be reached? Does it make sense to even go with a web-environment for the kind of game that I want to make? Does anyone have any experiences with decisions like this? Thanks! (* With the exception of flash-based engines it seems like most of the other approaches have these downsides when compared to what is available for desktop-based environments. I'd go with flash, but I'm worried that flash's 3D capabilities aren't mature enough right now to do what I want easily. There's also Unity3D, but I'm not sure how I feel about that at all. It seems highly polished, but requires a plugin to be downloaded for the game to be played -- at that rate I might as well have players download my game.)

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• Fixing the #mvvmlight code snippets in Visual Studio 11

  - by Laurent Bugnion

  If you installed the latest MVVM Light version for Windows 8, you may encounter an issue where code snippets are not displayed correctly in the Intellisense popup. I am working on a fix, but for now here is how you can solve the issue manually. The code snippets MVVM Light, when installed correctly, will install a set of code snippets that are very useful to allow you to type less code. As I use to say, code is where bugs are, so you want to type as little of that as possible ;) With code snippets, you can easily auto-insert segments of code and easily replace the keywords where needed. For instance, every coder who uses MVVM as his favorite UI pattern for XAML based development is used to the INotifyPropertyChanged implementation, and how boring it can be to type these “observable properties”. Obviously a good fix would be something like an “Observable” attribute, but that is not supported in the language or the framework for the moment. Another fix involves “IL weaving”, which is a post-build operation modifying the generate IL code and inserting the “RaisePropertyChanged” instruction. I admire the invention of those who developed that, but it feels a bit too much like magic to me. I prefer more “down to earth” solutions, and thus I use the code snippets. Fixing the issue Normally, you should see the code snippets in Intellisense when you position your cursor in a C# file and type mvvm. All MVVM Light snippets start with these 4 letters. Normal MVVM Light code snippets However, in Windows 8 CP, there is an issue that prevents them to appear correctly, so you won’t see them in the Intellisense windows. To restore that, follow the steps: In Visual Studio 11, open the menu Tools, Code Snippets Manager. In the combobox, select Visual C#. Press Add… Navigate to C:\Program Files (x86)\Laurent Bugnion (GalaSoft)\Mvvm Light Toolkit\SnippetsWin8 and select the CSharp folder. Press Select Folder. Press OK to close the Code Snippets Manager. Now if you type mvvm in a C# file, you should see the snippets in your Intellisense window. Cheers Laurent   Laurent Bugnion (GalaSoft) Subscribe | Twitter | Facebook | Flickr | LinkedIn

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• Am I experienced enough to learn and develop immediately using Ruby on Rails?

  - by acheong87

  General Question I understand that discussions revolving around questions of this form run the risk of becoming too specific to help others. So, perhaps a better, general question would be: What kind of experience, if any, translates easily to Ruby on Rails; and if none, then what's the learning curve like, in comparison to other popular languages? Background I have the opportunity to build a website using whatever technologies I wish to use. It's a fairly simple website, for listing products, taking payments, managing customer data, providing a back-end portal for employees to manage data, possibly hooking in flight information (the products are travel related), possibly integrating a blog and all the social-networking goodies. Specific Problem I have to let the client know by tonight whether I'm interested in taking up this project, before he talks to other potential developers, but I'm on the fence. I already work a full-time C++ development job, so the money doesn't do it for me. It's the opportunity to (be paid to) learn some new technologies and to have a real, running product in the end. I've heard and read great things about Ruby, and am really intrigued. I zipped through some introductory Ruby tutorials, no sweat. However I found the Rails tutorials a little overwhelming, especially not being able to try it out anywhere. And researching Rails hosts like Heroku and EngineYard makes me think that maybe I don't know what I'm getting myself into. The ship's leaving port! I wish I had more time to learn, better yet play with the language, but I have to decide soon! Should I venture or pass? Additional Details My experiences are in C/C++/Tcl/Perl/PHP/jQuery, and basic knowledge of Java/C#. I didn't study C.S. formally so I wasn't exposed to design principles, programming paradigms, etc., which is my greatest concern. Will my lack of understanding in this realm make RoR frustrating to learn? Will it be so incompatible with a C++ "way" of thinking that I'll wish I never started? Am I putting my client at risk by attempting this? If it helps, I'm quick to learn new things (self-taught so far) and care a great deal about correctness, using things for their intended purposes, and so on. I've read numerous recommendations of Agile Development with Rails and would love to read it (though perhaps, while developing in parallel, for shortness of time). Worse comes to worst, I'd give up and do the standard LAMP gig, of course, not charging the client for wasted time. But I'm hoping to avoid the project altogether if it's gonna come down to that! Thanks in advance for any tips, insights, votes of confidence, votes of discouragement (for the better), and such.

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• Should I be put off a junior role that uses an online development test?

  - by Ninefingers

  I've applied for a junior development role, or rather been found by a recruiter looking for a developer. In order to get to a telephone interview stage I've been asked to sit one of those online coding assessments. This wasn't quite what I expected. I consider myself a fairly good developer for my age and experience, but I've no illusions about being Don Knuth or anything. The test was a series of incredibly obtuse questions asking about the results of various obscure evaluations. About 30 minutes in I was thinking to myself I hadn't intended to enter an obfuscated code contest/code golf exercise. After my last telephone interview I was asked to build something. I did. That seemed fair. Go away and work this out is more my in office experience of programming than "please evaluate this combination of lambdas, filters, maps, lists, tuples etc". So I'm a little put off, to be honest. I never claimed to know the language inside out or all the little corner cases. My questions, then: Should I be put off? Why? Why not? Are these kinds of tests what I should be expecting for junior roles? Should I learn stuff exam style? That seems to be the objective of these tests, for which you are timed and not supposed to use references or books? Normally, in the course of development I have a fairly good idea of basic types, rules, flow control and whatever. Occasionally I'll come up on something I need to use a regex for and have to go and remind myself of the exact piece of syntax I need if trying what I think should work doesn't. Or I'll come up against a module I've not used before and go and look it up. For example, if I wanted to write a server using sockets in C right now, I'd probably check the last piece of code I wrote doing that (and or the various books I have) and work from there. Chances are I probably couldn't do it exactly from scratch and from memory, although I can tell you you'd need a socket(), bind(), listen() and accept() call and you might also want select() depending on whether you intend to pthread_create or not. So I know what the calls are, but not their specific parameter list. What are your experiences if you are a recruiting manager? Are you after programmers who can quote you the API or do you not mind if your programmers have a few books on their desk and google function calls every so often?

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• Securing User Account Details with MySQL

  - by Antoinette O'Sullivan

  Keeping user account details secure is always at the forefront of a Database Administrator's mind. However, users want to get up and running as soon as possible without complex login procedures. You can learn more about this and many other topics in the MySQL for Database Administrator course. For example, MySQL 5.6.6 introduced a new utility: mysql_config_editor, which makes secure access via MySQL client applications much easier to establish, while still providing a good measure of security. The mysql_config_editor stores a user's authentication details in an encrypted login file called mylogin.cnf. This login file is readable and writable for the user who invokes the utility, and invisible to everyone else. You can use it to collect all your hard-to-remember server locations and paswords safe in the knowledge that your passwords are never invoked using clear text. The MySQL for Database Administrators course is a 5-day instructor-led course which is available as a: Training-on-Demand: Start training within 24 hours of registration, following lecture material at your own pace through streaming video and booking time on a lab environment to suit your schedule. Live-Virtual Event: Attend a live event from your own desk, choosing from a selection of events on the schedule to suit different timezones. In-Class Event: Travel to an education center to attend this course. Below is a selection of the events already on the schedule. Location  Date  Delivery Language  Brisbane, Australia  18 August 2014  English  Brussels, Belgium  25 August 2014  English  Sao Paulo, Brazil  2 June 2014  Brazilian Portuguese  Cairo, Egypt  28 September 2014  Arabic  London, England  14 July 2014  English  Belfast, Ireland  15 September 2014  English  Dublin, Ireland  29 September 2014  English  Rome, Italy  16 June 2014  Italian  Seoul, Korea  9 June 2014  Korean  Petaling Jaya, Malaysia  16 June 2014  English  Utrecht, Netherlands  25 August 2014  English  Edinburgh, Scotland  26 June 2014  English  Madrid, Spain  6 October 2014  Spanish  Tunis, Tunisia  27 October 2014  French  Istanbul, Turkey  14 July 2014  Turkish To register for an event, request an additional event or learn more about the authentic MySQL curriculum, go to http://education.oracle.com/mysql. To read more about MySQL security, consult the MySQL Reference Manual - http://dev.mysql.com/doc/refman/5.6/en/security.html.

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• Array Multiplication and Division

  - by Narfanator

  I came across a question that (eventually) landed me wondering about array arithmetic. I'm thinking specifically in Ruby, but I think the concepts are language independent. So, addition and subtraction are defined, in Ruby, as such: [1,6,8,3,6] + [5,6,7] == [1,6,8,3,6,5,6,7] # All the elements of the first, then all the elements of the second [1,6,8,3,6] - [5,6,7] == [1,8,3] # From the first, remove anything found in the second and array * scalar is defined: [1,2,3] * 2 == [1,2,3,1,2,3] But What, conceptually, should the following be? None of these are (as far as I can find) defined: Array x Array: [1,2,3] * [1,2,3] #=> ? Array / Scalar: [1,2,3,4,5] / 2 #=> ? Array / Scalar: [1,2,3,4,5] % 2 #=> ? Array / Array: [1,2,3,4,5] / [1,2] #=> ? Array / Array: [1,2,3,4,5] % [1,2] #=> ? I've found some mathematical descriptions of these operations for set theory, but I couldn't really follow them, and sets don't have duplicates (arrays do). Edit: Note, I do not mean vector (matrix) arithmetic, which is completely defined. Edit2: If this is the wrong stack exchange, tell me which is the right one and I'll move it. Edit 3: Add mod operators to the list. Edit 4: I figure array / scalar is derivable from array * scalar: a * b = c => a = b / c [1,2,3] * 3 = [1,2,3]+[1,2,3]+[1,2,3] = [1,2,3,1,2,3,1,2,3] => [1,2,3] = [1,2,3,1,2,3,1,2,3] / 3 Which, given that programmer's division ignore the remained and has modulus: [1,2,3,4,5] / 2 = [[1,2], [3,4]] [1,2,3,4,5] % 2 = [5] Except that these are pretty clearly non-reversible operations (not that modulus ever is), which is non-ideal. Edit: I asked a question over on Math that led me to Multisets. I think maybe extensible arrays are "multisets", but I'm not sure yet.

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• The SmartAssembly Rearchitecture

  - by Simon Cooper

  You may have noticed that not a lot has happened to SmartAssembly in the past few months. However, the team has been very busy behind the scenes working on an entirely new version of SmartAssembly. SmartAssembly 6.5 Over the past few releases of SmartAssembly, the team had come to the realisation that the current 'architecture' - grown organically, way before RedGate bought it, from a simple name obfuscator over the years into a full-featured obfuscator and assembly instrumentation tool - was simply not up to the task. Not for what we wanted to do with it at the time, and not what we have planned for the future. Not only was it not up to what we wanted it to do, but it was severely limiting our development capabilities; long-standing bugs in the root architecture that couldn't be fixed, some rather...interesting...design decisions, and convoluted logic that increased the complexity of any bugfix or new feature tenfold. So, we set out to fix this. Earlier this year, a new engine was written on which SmartAssembly would be based. Over the following few months, each feature was ported over to the new engine and extensively tested by our existing unit and integration tests. The engine was linked into the existing UI (no easy task, due to the tight coupling between the UI and old engine), and existing RedGate products were tested on the new SmartAssembly to ensure the new engine acted in the same way. The result is SmartAssembly 6.5. The risks of a rearchitecture Are there risks to rearchitecting a product like SmartAssembly? Of course. There was a lot of undocumented behaviour in the old engine, and as part of the rearchitecture we had to find this behaviour, define it, and document it. In the process we found some behaviour of the old engine that simply did not make sense; hence the changes in pruning & obfuscation behaviour in the release notes. All the special edge cases we had to find, document, and re-implement. There was a chance that these special cases would not be found until near the end of the project, when everything is functionally complete and interacting together. By that stage, it would be hard to go back and change anything without a whole lot of extra work, delaying the release by months. We always knew this was a possibility; our initial estimate of the time required was '4 months, ± 4 months'. And that was including various mitigation strategies to reduce the likelihood of these issues being found right at the end. Fortunately, this worst-case did not happen. However, the rearchitecture did produce some benefits. As well as numerous bug fixes that we could not fix any other way, we've also added logging that lets you find out exactly why a particular field or property wasn't pruned or obfuscated. There's a new command line interface, we've tested it with WP7.1 and Silverlight 5, and we've added a new option to error reporting to improve the performance of instrumented apps by ~10%, at the cost of inaccurate line numbers in reports. So? What differences will I see? Largely none. SmartAssembly 6.5 produces the same output as SmartAssembly 6.2. The performance of 6.5 will be much faster for some users, and generally the same as 6.2 for the remaining. If you've encountered a bug with previous versions of SmartAssembly, I encourage you to try 6.5, as it has most likely been fixed in the rearchitecture. If you encounter a bug with 6.5, please do tell us; we'll be doing another release quite soon, so we'll aim to fix any issues caused by 6.5 in that release. Most importantly, the new architecture finally allows us to implement some Big Things with SmartAssembly we've been planning for many months; these will fundamentally change how you build, release and monitor your application. Stay tuned for further updates!

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• Game of Phones

  - by Carlos Chang

  Game  of  Phones There’s an excellent DZone article titled: 2014 Guide to Mobile Development. It’s loaded with excellent information including some results from a mobile related survey to more than 1000 IT professionals. Without giving away too much, these highlights should convince you to read the entire article.  Web and Hybrid apps are gaining tons of traction particularly in the enterprise. If you want to better understand the differences between Web, Native and Hybrid, this article has you covered. Enterprise developers are increasingly more interested in cross platform tools. Makes sense right?  I mean, unless you have infinite resources (e.g. Facebook) and can afford to write native apps to every platform, finding something that can meet your needs for iOS and Android makes sense.  And toss in the possibility of Windows Phone …and oh, just to be current, the addition of Apple’s new mobile language, Swift, to add to Objective C.. and oh boy.  Why not check out cross platform tools? BTW, don’t  forget testing on each platform, and maintenance and the next versions of the app. It’s not one and done. If you’re successful, you’re never done. Various mobile vendors are represented and many provide some great information.  Oracle's own Suhas Uliyar, VP of Mobile Strategy, represented with some great insights into the challenges of mobile back end integration (SOA, mBaaS, etc.) and moving from "mobile first" to a mobile plus world. BTW, Suhas was recently named Top 100 Wireless Technology Experts for 2014 by Today's Wireless World magazine.  And if your not yet convinced, DZone did a very nice job with their mobile infographic stylized after the insanely popular series, Game of Thrones.  Even though there were no dragons illustrated, worth the price of admission just for that.   Check it out here.

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• Subterranean IL: Custom modifiers

  - by Simon Cooper

  In IL, volatile is an instruction prefix used to set a memory barrier at that instruction. However, in C#, volatile is applied to a field to indicate that all accesses on that field should be prefixed with volatile. As I mentioned in my previous post, this means that the field definition needs to store this information somehow, as such a field could be accessed from another assembly. However, IL does not have a concept of a 'volatile field'. How is this information stored? Attributes The standard way of solving this is to apply a VolatileAttribute or similar to the field; this extra metadata notifies the C# compiler that all loads and stores to that field should use the volatile prefix. However, there is a problem with this approach, namely, the .NET C++ compiler. C++ allows methods to be overloaded using properties, like volatile or const, on the parameters; this is perfectly legal C++: public ref class VolatileMethods { void Method(int *i) {} void Method(volatile int *i) {} } If volatile was specified using a custom attribute, then the VolatileMethods class wouldn't be compilable to IL, as there is nothing to differentiate the two methods from each other. This is where custom modifiers come in. Custom modifiers Custom modifiers are similar to custom attributes, but instead of being applied to an IL element separately to its declaration, they are embedded within the field or parameter's type signature itself. The VolatileMethods class would be compiled to the following IL: .class public VolatileMethods { .method public instance void Method(int32* i) {} .method public instance void Method( int32 modreq( [mscorlib]System.Runtime.CompilerServices.IsVolatile)* i) {} } The modreq([mscorlib]System.Runtime.CompilerServices.IsVolatile) is the custom modifier. This adds a TypeDef or TypeRef token to the signature of the field or parameter, and even though they are mostly ignored by the CLR when it's executing the program, this allows methods and fields to be overloaded in ways that wouldn't be allowed using attributes. Because the modifiers are part of the signature, they need to be fully specified when calling such a method in IL: call instance void Method( int32 modreq([mscorlib]System.Runtime.CompilerServices.IsVolatile)*) There are two ways of applying modifiers; modreq specifies required modifiers (like IsVolatile), and modopt specifies optional modifiers that can be ignored by compilers (like IsLong or IsConst). The type specified as the modifier argument are simple placeholders; if you have a look at the definitions of IsVolatile and IsLong they are completely empty. They exist solely to be referenced by a modifier. Custom modifiers are used extensively by the C++ compiler to specify concepts that aren't expressible in IL, but still need to be taken into account when calling method overloads. C++ and C# That's all very well and good, but how does this affect C#? Well, the C++ compiler uses modreq(IsVolatile) to specify volatility on both method parameters and fields, as it would be slightly odd to have the same concept represented using a modifier or attribute depending on what it was applied to. Once you've compiled your C++ project, it can then be referenced and used from C#, so the C# compiler has to recognise the modreq(IsVolatile) custom modifier applied to fields, and vice versa. So, even though you can't overload fields or parameters with volatile using C#, volatile needs to be expressed using a custom modifier rather than an attribute to guarentee correct interoperability and behaviour with any C++ dlls that happen to come along. Next up: a closer look at attributes, and how certain attributes compile in unexpected ways.

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• I'm creating my own scalable, rapid prototyping web server. How should I design it?

  - by Mike Willliams

  I'm going to create my own web server that focuses on scalability, rapid prototyping and the use of JavaScript as the server's scripting language, much like node.js. It will use a Model-View-Controller design pattern so a web application can support more concurrent users just by adding hardware -- and not having to redesign the software. Basically, I'm aiming to produce a framework that allows for fast and easy development of cloud applications without the need to write lots of boiler plate code. I've got some questions about this... How hard will it be to put MySQL in the cloud? How could I go about implementing this and make the resulting product free? Will I have to write my own engine or modify an existing one, if I do what should I watch out for? To make this scalable I need to adjust from one server to hundreds of servers this creates the requirement for the servers to be load balancing, how should I do this? If I balance based on the work load per server I would need gateway to handle all the incoming requests. Is it the right idea to have all the servers check into the gateway and update there status. By having the servers run through a gateway if the gateway dies all the incoming requests are ignored. I'm thinking that having all the servers maintain a list of each other, or at least a few I could rebuild the list of servers and establish a new gateway. Is it worth it? Or should I have a backup gateway that could switch out? Should I let the user choose? How should I pick which server handles the database and which handles the page serving? Should I spread the database so that queries are preformed on multiple servers? Which would theoretically improve performance. The servers would need to mirror the database at least once so that if a server goes down the database isn't corrupted. So this brings up writing another question, should I broadcast SQL queries so that all the servers can take a bit of the work load? If I do it that way wouldn't a query clog up the network so that other queries couldn't be preformed? What are my alternatives? Finally, is there a free solution already out there that might need a little modification that suits my needs?

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• Subterranean IL: Exception handler semantics

  - by Simon Cooper

  In my blog posts on fault and filter exception handlers, I said that the same behaviour could be replicated using normal catch blocks. Well, that isn't entirely true... Changing the handler semantics Consider the following: .try { .try { .try { newobj instance void [mscorlib]System.Exception::.ctor() // IL for: // e.Data.Add("DictKey", true) throw } fault { ldstr "1: Fault handler" call void [mscorlib]System.Console::WriteLine(string) endfault } } filter { ldstr "2a: Filter logic" call void [mscorlib]System.Console::WriteLine(string) // IL for: // (bool)((Exception)e).Data["DictKey"] endfilter }{ ldstr "2b: Filter handler" call void [mscorlib]System.Console::WriteLine(string) leave.s Return } } catch object { ldstr "3: Catch handler" call void [mscorlib]System.Console::WriteLine(string) leave.s Return } Return: // rest of method If the filter handler is engaged (true is inserted into the exception dictionary) then the filter handler gets engaged, and the following gets printed to the console: 2a: Filter logic 1: Fault handler 2b: Filter handler and if the filter handler isn't engaged, then the following is printed: 2a:Filter logic 1: Fault handler 3: Catch handler Filter handler execution The filter handler is executed first. Hmm, ok. Well, what happens if we replaced the fault block with the C# equivalent (with the exception dictionary value set to false)? .try { // throw exception } catch object { ldstr "1: Fault handler" call void [mscorlib]System.Console::WriteLine(string) rethrow } we get this: 1: Fault handler 2a: Filter logic 3: Catch handler The fault handler is executed first, instead of the filter block. Eh? This change in behaviour is due to the way the CLR searches for exception handlers. When an exception is thrown, the CLR stops execution of the thread, and searches up the stack for an exception handler that can handle the exception and stop it propagating further - catch or filter handlers. It checks the type clause of catch clauses, and executes the code in filter blocks to see if the filter can handle the exception. When the CLR finds a valid handler, it saves the handler's location, then goes back to where the exception was thrown and executes fault and finally blocks between there and the handler location, discarding stack frames in the process, until it reaches the handler. So? By replacing a fault with a catch, we have changed the semantics of when the filter code is executed; by using a rethrow instruction, we've split up the exception handler search into two - one search to find the first catch, then a second when the rethrow instruction is encountered. This is only really obvious when mixing C# exception handlers with fault or filter handlers, so this doesn't affect code written only in C#. However it could cause some subtle and hard-to-debug effects with object initialization and ordering when using and calling code written in a language that can compile fault and filter handlers.

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• How does I/O work for large graph databases?

  - by tjb1982

  I should preface this by saying that I'm mostly a front end web developer, trained as a musician, but over the past few years I've been getting more and more into computer science. So one idea I have as a fun toy project to learn about data structures and C programming was to design and implement my own very simple database that would manage an adjacency list of posts. I don't want SQL (maybe I'll do my own query language? I'm just having fun). It should support ACID. It should be capable of storing 1TB let's say. So with that, I was trying to think of how a database even stores data, without regard to data structures necessarily. I'm working on linux, and I've read that in that world "everything is a file," including hardware (like /dev/*), so I think that that obviously has to apply to a database, too, and it clearly does--whether it's MySQL or PostgreSQL or Neo4j, the database itself is a collection of files you can see in the filesystem. That said, there would come a point in scale where loading the entire database into primary memory just wouldn't work, so it doesn't make sense to design it with that mindset (I assume). However, reading from secondary memory would be much slower and regardless some portion of the database has to be in primary memory in order for you to be able to do anything with it. I read this post: Why use a database instead of just saving your data to disk? And I found it difficult to understand how other databases, like SQLite or Neo4j, read and write from secondary memory and are still very fast (faster, it would seem, than simply writing files to the filesystem as the above question suggests). It seems the key is indexing. But even indexes need to be stored in secondary memory. They are inherently smaller than the database itself, but indexes in a very large database might be prohibitively large, too. So my question is how is I/O generally done with large databases like the one I described above that would be at least 1TB storing a big adjacency list? If indexing is more or less the answer, how exactly does indexing work--what data structures should be involved?

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