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  • Delivering the Integrated Portal Experience!

    - by Michael Snow
    v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} Guest post by Richard Maldonado, Principal Product Manager, Oracle WebCenter Portal Organizations are still struggling to standardize on a user interaction platform which can meet the needs of all their target audiences.  This has not only resulted in inefficient and inconsistent experiences for their users, but it also creates inefficiencies (productivity and costs) for the departments that manage the applications and information systems.  Portals have historically been the unifying platform that provide IT with a common interface which can securely surface the most relevant interactions for a given user and/or group of users.  However, organizations have found that the technologies available have either not provided the flexibility necessary to address all of their use cases, or they rely too much on IT resources to manage, maintain, and evolve.  Empowering  the Business Groups The core issue that IT departments face with delivering portal experiences is having enough resources to respond and address the influx of requirements which come in from the business.  Commonly, when a business group wants a new portal site established for their group, they will submit a request to the IT dept, the IT dept then assigns a resource to an administrator and/or developer to build.  Unfortunately, this approach is not scalable, it can be a time consuming activity which requires significant interaction between the business owner and the IT resource.  A modern user interaction platforms should empower the business groups by providing them tools which they can use to build and manage the portal experiences without the need for IT's involvement.  And because business groups rarely have technical resources (developers) on staff, the tools must be easy enough that virtually any business user could use.  In addition, the tool must be powerful enough to allow them to build the experience that they need, things such as creating a whole new portal, add/manage page and page hierarchy, manage user/group access, add/modify components within the page, etc.  This balance between ease-of-use and flexibility is key to the successful adoption of tools which will ultimately reduce the burden on IT, respond to the needs of the business, and deliver high-value experiences for the users.  Ready or Not, Here They Come: Smartphones and Tablets Recently, several studies have highlighted that smartphone and tablet-style devices have overtaken PC's in both sales and usage.  This shift is further driving organizations to revaluate how they're delivering data, information, and applications to their users.  Users are expecting to get the same level of access and interaction, but in a ways which are optimized for the capabilities of the device that they are using.  Expect More With the ever growing number of new IT projects and flat/shrinking budgets, organizations are looking for comprehensive solutions which can deliver integrated web experiences that are tailored for the users and optimized for mobile devices.  Piecing together a number of point solutions is no longer an option.  A modern portal technology should not only address the traditional needs of integrating and surfacing back-end applications/information, but it should enable the business through easy-to-use tools and accelerate the delivery of mobile optimized experiences.   v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} 12.00 Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-family:"Calibri","sans-serif"; mso-bidi-font-family:"Times New Roman";} 12.00 Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-family:"Calibri","sans-serif"; mso-ascii- mso-ascii-theme-font:minor-latin; mso-hansi- mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} WebCenter in Action Series: Qualcomm Provides a Seamless Experience for Customers with Oracle WebCenter Featuring Qualcomm & Keste 12.00 Normal 0 false false false EN-US X-NONE X-NONE MicrosoftInternetExplorer4 -"/ /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:Calibri; mso-fareast-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} 12.00 Normal 0 false false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-family:"Calibri","sans-serif"; mso-fareast- mso-bidi-font-family:"Times New Roman";}

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  • How does this ruby error handling module code work

    - by Michael Durrant
    Trying to get a better handle on ruby exception handling. I have this code (from a book): def err_with_msg(pattern) m = Module.new (class << m; self; end).instance_eval do define_method(:===) do |e| pattern === e.msg end end m end So ok this is a method. We're creating a new Module. I think of module as mix-ins. Not sure what it's doing here. Not we add the module to the class. Fair enough. Then we have self on its own. What that for? I guess we have a little anonymouse method this is just about self. hmmm ok, now for each of the above, check the pattern match. but for each, I thought the above for for a new Module, did the module get to use instance's by being included? A better explanation of what's going on here would be most helpful.

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  • Getting My Head Around Immutability

    - by Michael Mangold
    I'm new to object-oriented programming, and one concept that has been taking me a while to grasp is immutability. I think the light bulb went off last night but I want to verify: When I come across statements that an immutable object cannot be changed, I'm puzzled because I can, for instance, do the following: NSString *myName = @"Bob"; myName = @"Mike"; There, I just changed myName, of immutable type NSString. My problem is that the word, "object" can refer to the physical object in memory, or the abstraction, "myName." The former definition applies to the concept of immutability. As for the variable, a more clear (to me) definition of immutability is that the value of an immutable object can only be changed by also changing its location in memory, i.e. its reference (also known as its pointer). Is this correct, or am I still lost in the woods?

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  • What is the cost of custom made 2D game sprites? [closed]

    - by Michael Harroun
    Possible Duplicate: How much to pay for artwork in an indie game? I am looking for sprites similar in style to those of Final fantasy Tactics, but with a much higher resolution that will work well for both a browser and an iPhone. In terms of animations: Walking in 4 directions Swinging with 1 hand Some sort of "casting animation" (depending on cost I may use the 1 hand swing with a wand). Taking a hit Kneeling Fallen How much would something like that cost per sprite?

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  • Adding PostSharp to new projects, when it's installed for some projects in solution.

    - by Michael Freidgeim
    Recently I've posted my experience with installation of PostSharp Once PostSharp  is installed in  solution's packages folder for some project(s), I often need to add PostSharp to another project in the same solutionSection "Adding PostSharp to your project using PostSharp HQ" of documentation described the process quite well.I only want to add that the  actual location of  PostSharp HQ ( if it was installed from NuGet) is[solution root ]packages\PostSharp.2.1.7.15\tools\Release\PostSharp.HQ.exe.Also you need to ensure that the project is checked out,i.e. not readOnly.

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  • How do I get Windows 7 wallpaper to display the company logo properly?

    - by David Silva Smith
    Windows 7 is not displaying our company background properly. Curves show pixelation and straight lines are jagged. I'm working with a scalable vector graphics (SVG) image that I've exported to the same resolution (pixel dimensions, to be technical) as the desktop, which is 1440x900. I have tried exporting the image as a .png, .jpg, and .bmp. All of these look correct in an image viewing program, such as Windows Photo Viewer and Paint, but when I set the Windows background to these images, curves show pixelation and straight lines are jagged. Reading online, it seems that behind the scenes, Windows is converting the image to a .jpg with low quality compression, which is causing the issue. I've tried setting the image as a background through Internet Explorer, saving it as a .jpg, and putting the file in the Windows photo directory as suggested in some online forums, but none of those solutions have fixed my issue.

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  • A Trio of Presentations: Little Wonders, StyleCop, and LINQ/Lambdas

    - by James Michael Hare
    This week is a busy week for me.  First of all I’m giving another presentation on a LINQ/Lambda primer for the rest of the developers in my company.  Of Lambdas and LINQ View more presentations from BlackRabbitCoder Then this Saturday the 25th of June I’ll be reprising my Little Wonders presentation for the Kansas City Developers Camp.  If you are in the area I highly recommend attending and seeing the other great presentations as well.  Their link is here. Little Wonders View more presentations from BlackRabbitCoder Finally, this Monday the 27th I’ll be speaking at the Saint Louis .NET Users group, giving my Automating Code Standards Using StyleCop and FxCop presentation.  If you are in the Saint Louis area stop by!  There’s two other simultaneous presentations as well if they’re more suited to your interests.  The link for the SLDNUG is here. Automating C# Coding Standards using StyleCop and FxCop View more presentations from BlackRabbitCoder Tweet Technorati Tags: C#,.NET,LINQ,Lambda,StyleCop,FxCop,Little Wonders

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  • IsNullOrDefault generic helper function for nullable types

    - by Michael Freidgeim
    I've wrote  IsNullOrDefault generic helper function       public  static bool IsNullOrDefault<T>(this Nullable<T> param) where T : struct     {         T deflt = default(T);         if (!param.HasValue)             return true;         else if (param.Value.Equals(deflt))             return true;         return false;     }   , but then realized that there is more short implementation on stackoverflow submitted by Josh

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  • Install a different version of a package

    - by Michael Wiles
    I'm running lucid server and have installed tomcat. The version it installed is 6.0.24-2ubuntu1.6. Is this the version I'm tied to? Is it possible to install a more recent version? The one available from maverick is 6.0.28. Maybe I can add a source to provide my lucid install with this version? In the package manager user interface I can "force version". Is it possible to force version from command line alternative as well?

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  • Oracle Commerce Best Practices for the Communications Industry

    - by Michael Seback
      In today’s volatile economy, Communications Service Providers are challenged to offer a complete, cross-channel commerce experience. With Oracle Commerce solutions, CSPs can get closer to customers and gain valuable insight to maximize ROI across all commerce activities. Join us for a  live webcast on September 26th with featured speakers Raghavendra Ademane, Omni-Channel Commerce Consultant at Professional Access and Brenna Johnson, Product Manager, Oracle and learn how you can manage and deliver commerce experiences for Communications that engage customers and promote loyalty. The panelists will guide you through a number of topics including: Current Communications market trends, opportunities and challenges Introduction to the Oracle Commerce solution with case studies Demonstration of the solution for Communications with live Q&A Register today and learn how Oracle's latest innovations for Communications can help you increase online sales and enhance cross-channel commerce interactions.

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  • Ubuntu Lenove OCZ Agility3 - No Grub after install

    - by Michael
    I've tried a dualboot (Win7 + Ubuntu) installation it on a Lenovo E330 with Agility3 240 Gigs... Conclusions: Ubuntu:: Ubuntu 12.04 x86_64 ( 21.06.2012 ) is not able to install grub in a bootable way. Grub will be installed and does update-grub during Installation, recognizes also the Win OS. But after a restart it boots directly to Windows.This is directly connected to the OCZ Agility3. On a good old fashion harddisk (those with the moving parts) Ubuntu is capable to install grub with no problem in a bootable manner. PinguyOS:: PinguyOS 12.04 LTS x86_64 (which is a Ubuntu based distro) is able to handle the Grub installation on OCZ Agility3. However they both use Grub 1.99... What i did:: Installed Windows. Installed Ubuntu. Installed PinguyOS. Grub Updates:: Grub updates are only through Pinguy OS possible, this means you have to edit the Ubuntu Grub entries manually after Kernelupdates on Ubuntu, in the PiguyOS sytem.. What i've already tried: Firmwareupgrade OCZ (livestick, successfull) Install Ubuntu Grub to sda Install Ubuntu Grub to sdc (Ubuntu Partion) Install Ubuntu Grub to /boot update-grub manually after install restore grub any ideas appreciated..

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  • From Pocket to Instapaper

    - by Michael Freidgeim
    Some time ago I’ve described the issues that I’ve had since a new version of Read It Later, named Pocket, was introduced.I’ve waited with hope for a new upgrade, but I had a huge disappointment with the latest version 16 June 2012. It didn’t fixed any of the two major problems, that I  experienced since new Pocket was introduced-  1. iPad app still didn’t show many of the saved links. 2. ability to rename articles on iPad still wasn’t restored.I’ve posted the message into their forum. They did not show my comment on their forum( I would name it censorship, not moderation), but a few days ago I’ve received an email, recommending “try logging out of the app on your iPad, and back in again.” Their suggestion helped,  but I don’t understand, why it is not posted as a recommendation on their support site.So I decided to try InstAPaper on my iPad, Previously I’ve used it for Kindle. I never considered it before on iPad, because there were no free demo and I was very satisfied with RIL free and then RIL Pro. Currently InstAPaper cost $3, so the price is not an issue.I’ve checked that it has most of features that I am using(e.g. renaming, folders) and I am quite happy with it now. Actually I am using Pocket (or RIL free) for old bookmarks( I have 1000+ stored on my iPad) and for new bookmarks I am using InstAPaper.Having a solid experience with RIL/Pocket I’ve created a list of suggestions to Marco Arment to implement.1. Some pages stored in InstAPaper have removed essential sections of the text. E.g in many blogs comments are not stored in  InstAPaper. Some pages lost almost all of important links (e.g. http://www.lib.rus.ec/a/32416 -sorry, in Russian). RIL/Pocket has 2 modes to store offline- Web view and Article view. Web View includes all links/images of the original page, but it’s very reliable. Article view suppose to strip unrelated information, but often corrupts the content. I prefer to use offline Web view.InstAPaper should also support offline Web view, in case if stripped view removes important part of content.2.  Black full screen Saving on iPad Safari is very annoying. After user pressed a bookmark, the saving has some delay and then for a few seconds prevents from reading the text.Would be better to show as message on the top part(as in Pocket ). I am surprised, that  a full screen popup was  implemented recently as a desired feature. 3.There are no comments allowed on http://blog.instapaper.com/. I would prefer to post some of these notes as comments on http://blog.instapaper.com/ rather than write them in my blog and then send link to Marco.(I found recommendation how to add support of comments on tumblr at http://www.tumblr.com/help, but then realized that Marko was the lead developer ofTumblr.)4. Also there is no support forum. I understand that maintenance of the forum ican be a hassle, but stackexchange fSome time ago I’ve described the issues that I’ve had since a new version of Read It Later, named Pocket, was introduced.I’ve waited with hope for a new upgrade, but I had a huge disappointment with the latest version 16 June 2012. It didn’t fixed any of the two major problems, that I  experienced since new Pocket was introduced- orums can be referred on  http://www.instapaper.com/main/support page, i.e.http://webapps.stackexchange.com/search?q=Instapaper  or http://apple.stackexchange.com/search?q=Instapaper 5. Tags are more convenient than folders. i.e. an ability for the same article to have more than one tag. Also creating of new folders is not supported offline, which is an annoying limitation.6. I would like to have a narrow list - additionally to existing list modes have a subject only list or subject+site list to show more list items on a screen.7. Limit of 500 offline articles sounds quite big, but my RIL list exceeded 1000, so it could be a issue in the future.8. Search button on iPad version is visible, but doesn’t work- it forces to buy Premium subscription. I think, that it’s not correct. If the button in a paid version is visible and enabled, it should  provide  a working functionality, e.g. search in article names only. And leave full-text search for the premium support.9..Copy URL is an important operation and deserves to be in a first level of Action menu, rather than in Share sub-menu.I’ve also have comment re post http://www.marco.org/2011/04/28/removed-instapaper-free. Marco Arment  explained, why he doesn’t provide free version of Instapaper.  I believe that he is loosing essential part of his customers. When I decided which of iPad application to choose, I’ve selected RIL, because I was able to play with free version, and I liked it. I didn’t have a chance to compare RIL and InstAPaper on iPad, so I’ve bought  RIL pro. For a user there is no point to pay even $3 , if there are similar free product, that user can try and see, is it suitable for him/her.I’ve also played with Readability. It doesn’t have folders or tags(which is very important for me), but nicely supports full text search

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  • Failed install 12.04 on Intel Hardware Raid with Large Partition (> 2TB)

    - by Michael Wiles
    I have Intel Hardware Raid on the motherboard. I have 10 2 TB HDD that I've configured as RAID 1+0 to be one big 8 TB HDD. Now I'm trying to install ubuntu 12.04 on it. After installing with default desktop installation disk I get a blank screen with a cursor flashing. If I try the alternate guided partitioning option I get error: out of disk. and the grub prompt. If I boot with the rescue disk or such like I can drop into a shell and view the disk. Everything also installs without an issue. Don't know what to do...

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  • Zero bytes on home partition

    - by Michael Z
    I decided to replace the hard drive on my machine running Ubuntu 12.04 LTS . After using the new hard drive for a few days, I noticed that the new hard drive has bad sectors. So I decided to plug my old hard drive back in. First, I plugged both hard drives in and copied some data files from the new hard drive to the old one. After unplugging the new hard drive, I booted the computer with the old hard drive, and here I got a surprise: I can see 0 bytes available on my /home partition! The df utility shows that the /home partition has 0 available bytes. I have tried to move some files. But I still has 0 bytes on /home! However, GParted correctly shows that the available size is near 2Gb. UPDATE 1: To my surprise, System Monitor shows me that approximately 2 Gb are free and 0 bytes are available on the /home partition. It's slightly shocked me! Are "free" and "available" not the same? Any help is really appreciated!

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  • C# Toolbox: Debug-able, Self-Installable Windows Service Template Redux

    - by James Michael Hare
    I had written a pair of posts before about creating a debug-able and self-installing windows service template in C#.  This is a template I began creating to ease creating windows services and to take some of the mundane tasks out of the coding effort.  The original posts were here: C# Windows Services (1 of 2) - Debug-able Windows Services C# Windows Services (2 of 2) - Self-Installing Windows Services But at the time, though I gave the code samples I didn't have a downloadable for of the template on the blog.  After getting many requests for the actual source, I zipped it up and am posting it with this blog entry.  Click on the link below to download the archive.  The password on the archive is, imaginatively enough, password.  Hope you enjoy and please feel free to comment and suggest changes! Debug-able, Self-Installing Windows Service Template download Enjoy! Tweet Technorati Tags: C#,Windows Service,Toolbox

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  • Testing Reference Data Mappings

    - by Michael Stephenson
    Background Mapping reference data is one of the common scenarios in BizTalk development and its usually a bit of a pain when you need to manage a lot of reference data whether it be through the BizTalk Cross Referencing features or some kind of custom solution. I have seen many cases where only a couple of the mapping conditions are ever tested. Approach As usual I like to see these things tested in isolation before you start using them in your BizTalk maps so you know your mapping functions are working as expected. This approach can be used for almost all of your reference data type mapping functions where you can take advantage of MSTests data driven tests to test lots of conditions without having to write millions of tests. Walk Through Rather than go into the details of this here, I'm going to call out to one of my colleagues who wrote a nice little walk through about using data driven tests a while back. Check out Callum's blog: http://callumhibbert.blogspot.com/2009/07/data-driven-tests-with-mstest.html

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  • Combining javascript files

    - by Michael Freidgeim
    I’ve read Combining Client Scripts into a Composite Script and wanted to use it. Then I’ve read Julian Jelfs concerns ScriptManager.CompositeScript issues However the article Combining javascript files with Ajax toolkit library describes workarounds, that make the solution workable. You also can use Script reference profiler: http://aspnet.codeplex.com/releases/view/13356 Related posts: Using ScriptManager with other frameworks MSDN documentation: CompositeScriptReference he older implementations, that has been superseded by CompositeScript class: ToolkitScriptManager Combining, Compressing, Minifying ASP.NET ScriptResource and HTML Markups

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  • What technologies are used for Game development now days?

    - by Monika Michael
    Whenever I ask a question about game development in an online forum I always get suggestions like learning line drawing algorithms, bit level image manipulation and video decompression etc. However looking at games like God of War 3, I find it hard to believe that these games could be developed using such low level techniques. The sheer awesomeness of such games defy any comprehensible(for me) programming methodology. Besides the gaming hardware is really a monster now days. So it stands to reason that the developers would work at a higher level of abstraction. What is the latest development methodology in the gaming industry? How is it that a team of 30-35 developers (of which most is management and marketing fluff) able to make such mind boggling games?

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  • C#/.NET Little Wonders: Interlocked CompareExchange()

    - by James Michael Hare
    Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. Two posts ago, I discussed the Interlocked Add(), Increment(), and Decrement() methods (here) for adding and subtracting values in a thread-safe, lightweight manner.  Then, last post I talked about the Interlocked Read() and Exchange() methods (here) for safely and efficiently reading and setting 32 or 64 bit values (or references).  This week, we’ll round out the discussion by talking about the Interlocked CompareExchange() method and how it can be put to use to exchange a value if the current value is what you expected it to be. Dirty reads can lead to bad results Many of the uses of Interlocked that we’ve explored so far have centered around either reading, setting, or adding values.  But what happens if you want to do something more complex such as setting a value based on the previous value in some manner? Perhaps you were creating an application that reads a current balance, applies a deposit, and then saves the new modified balance, where of course you’d want that to happen atomically.  If you read the balance, then go to save the new balance and between that time the previous balance has already changed, you’ll have an issue!  Think about it, if we read the current balance as $400, and we are applying a new deposit of $50.75, but meanwhile someone else deposits $200 and sets the total to $600, but then we write a total of $450.75 we’ve lost $200! Now, certainly for int and long values we can use Interlocked.Add() to handles these cases, and it works well for that.  But what if we want to work with doubles, for example?  Let’s say we wanted to add the numbers from 0 to 99,999 in parallel.  We could do this by spawning several parallel tasks to continuously add to a total: 1: double total = 0; 2:  3: Parallel.For(0, 10000, next => 4: { 5: total += next; 6: }); Were this run on one thread using a standard for loop, we’d expect an answer of 4,999,950,000 (the sum of all numbers from 0 to 99,999).  But when we run this in parallel as written above, we’ll likely get something far off.  The result of one of my runs, for example, was 1,281,880,740.  That is way off!  If this were banking software we’d be in big trouble with our clients.  So what happened?  The += operator is not atomic, it will read in the current value, add the result, then store it back into the total.  At any point in all of this another thread could read a “dirty” current total and accidentally “skip” our add.   So, to clean this up, we could use a lock to guarantee concurrency: 1: double total = 0.0; 2: object locker = new object(); 3:  4: Parallel.For(0, count, next => 5: { 6: lock (locker) 7: { 8: total += next; 9: } 10: }); Which will give us the correct result of 4,999,950,000.  One thing to note is that locking can be heavy, especially if the operation being locked over is trivial, or the life of the lock is a high percentage of the work being performed concurrently.  In the case above, the lock consumes pretty much all of the time of each parallel task – and the task being locked on is relatively trivial. Now, let me put in a disclaimer here before we go further: For most uses, lock is more than sufficient for your needs, and is often the simplest solution!    So, if lock is sufficient for most needs, why would we ever consider another solution?  The problem with locking is that it can suspend execution of your thread while it waits for the signal that the lock is free.  Moreover, if the operation being locked over is trivial, the lock can add a very high level of overhead.  This is why things like Interlocked.Increment() perform so well, instead of locking just to perform an increment, we perform the increment with an atomic, lockless method. As with all things performance related, it’s important to profile before jumping to the conclusion that you should optimize everything in your path.  If your profiling shows that locking is causing a high level of waiting in your application, then it’s time to consider lighter alternatives such as Interlocked. CompareExchange() – Exchange existing value if equal some value So let’s look at how we could use CompareExchange() to solve our problem above.  The general syntax of CompareExchange() is: T CompareExchange<T>(ref T location, T newValue, T expectedValue) If the value in location == expectedValue, then newValue is exchanged.  Either way, the value in location (before exchange) is returned. Actually, CompareExchange() is not one method, but a family of overloaded methods that can take int, long, float, double, pointers, or references.  It cannot take other value types (that is, can’t CompareExchange() two DateTime instances directly).  Also keep in mind that the version that takes any reference type (the generic overload) only checks for reference equality, it does not call any overridden Equals(). So how does this help us?  Well, we can grab the current total, and exchange the new value if total hasn’t changed.  This would look like this: 1: // grab the snapshot 2: double current = total; 3:  4: // if the total hasn’t changed since I grabbed the snapshot, then 5: // set it to the new total 6: Interlocked.CompareExchange(ref total, current + next, current); So what the code above says is: if the amount in total (1st arg) is the same as the amount in current (3rd arg), then set total to current + next (2nd arg).  This check and exchange pair is atomic (and thus thread-safe). This works if total is the same as our snapshot in current, but the problem, is what happens if they aren’t the same?  Well, we know that in either case we will get the previous value of total (before the exchange), back as a result.  Thus, we can test this against our snapshot to see if it was the value we expected: 1: // if the value returned is != current, then our snapshot must be out of date 2: // which means we didn't (and shouldn't) apply current + next 3: if (Interlocked.CompareExchange(ref total, current + next, current) != current) 4: { 5: // ooops, total was not equal to our snapshot in current, what should we do??? 6: } So what do we do if we fail?  That’s up to you and the problem you are trying to solve.  It’s possible you would decide to abort the whole transaction, or perhaps do a lightweight spin and try again.  Let’s try that: 1: double current = total; 2:  3: // make first attempt... 4: if (Interlocked.CompareExchange(ref total, current + i, current) != current) 5: { 6: // if we fail, go into a spin wait, spin, and try again until succeed 7: var spinner = new SpinWait(); 8:  9: do 10: { 11: spinner.SpinOnce(); 12: current = total; 13: } 14: while (Interlocked.CompareExchange(ref total, current + i, current) != current); 15: } 16:  This is not trivial code, but it illustrates a possible use of CompareExchange().  What we are doing is first checking to see if we succeed on the first try, and if so great!  If not, we create a SpinWait and then repeat the process of SpinOnce(), grab a fresh snapshot, and repeat until CompareExchnage() succeeds.  You may wonder why not a simple do-while here, and the reason it’s more efficient to only create the SpinWait until we absolutely know we need one, for optimal efficiency. Though not as simple (or maintainable) as a simple lock, this will perform better in many situations.  Comparing an unlocked (and wrong) version, a version using lock, and the Interlocked of the code, we get the following average times for multiple iterations of adding the sum of 100,000 numbers: 1: Unlocked money average time: 2.1 ms 2: Locked money average time: 5.1 ms 3: Interlocked money average time: 3 ms So the Interlocked.CompareExchange(), while heavier to code, came in lighter than the lock, offering a good compromise of safety and performance when we need to reduce contention. CompareExchange() - it’s not just for adding stuff… So that was one simple use of CompareExchange() in the context of adding double values -- which meant we couldn’t have used the simpler Interlocked.Add() -- but it has other uses as well. If you think about it, this really works anytime you want to create something new based on a current value without using a full lock.  For example, you could use it to create a simple lazy instantiation implementation.  In this case, we want to set the lazy instance only if the previous value was null: 1: public static class Lazy<T> where T : class, new() 2: { 3: private static T _instance; 4:  5: public static T Instance 6: { 7: get 8: { 9: // if current is null, we need to create new instance 10: if (_instance == null) 11: { 12: // attempt create, it will only set if previous was null 13: Interlocked.CompareExchange(ref _instance, new T(), (T)null); 14: } 15:  16: return _instance; 17: } 18: } 19: } So, if _instance == null, this will create a new T() and attempt to exchange it with _instance.  If _instance is not null, then it does nothing and we discard the new T() we created. This is a way to create lazy instances of a type where we are more concerned about locking overhead than creating an accidental duplicate which is not used.  In fact, the BCL implementation of Lazy<T> offers a similar thread-safety choice for Publication thread safety, where it will not guarantee only one instance was created, but it will guarantee that all readers get the same instance.  Another possible use would be in concurrent collections.  Let’s say, for example, that you are creating your own brand new super stack that uses a linked list paradigm and is “lock free”.  We could use Interlocked.CompareExchange() to be able to do a lockless Push() which could be more efficient in multi-threaded applications where several threads are pushing and popping on the stack concurrently. Yes, there are already concurrent collections in the BCL (in .NET 4.0 as part of the TPL), but it’s a fun exercise!  So let’s assume we have a node like this: 1: public sealed class Node<T> 2: { 3: // the data for this node 4: public T Data { get; set; } 5:  6: // the link to the next instance 7: internal Node<T> Next { get; set; } 8: } Then, perhaps, our stack’s Push() operation might look something like: 1: public sealed class SuperStack<T> 2: { 3: private volatile T _head; 4:  5: public void Push(T value) 6: { 7: var newNode = new Node<int> { Data = value, Next = _head }; 8:  9: if (Interlocked.CompareExchange(ref _head, newNode, newNode.Next) != newNode.Next) 10: { 11: var spinner = new SpinWait(); 12:  13: do 14: { 15: spinner.SpinOnce(); 16: newNode.Next = _head; 17: } 18: while (Interlocked.CompareExchange(ref _head, newNode, newNode.Next) != newNode.Next); 19: } 20: } 21:  22: // ... 23: } Notice a similar paradigm here as with adding our doubles before.  What we are doing is creating the new Node with the data to push, and with a Next value being the original node referenced by _head.  This will create our stack behavior (LIFO – Last In, First Out).  Now, we have to set _head to now refer to the newNode, but we must first make sure it hasn’t changed! So we check to see if _head has the same value we saved in our snapshot as newNode.Next, and if so, we set _head to newNode.  This is all done atomically, and the result is _head’s original value, as long as the original value was what we assumed it was with newNode.Next, then we are good and we set it without a lock!  If not, we SpinWait and try again. Once again, this is much lighter than locking in highly parallelized code with lots of contention.  If I compare the method above with a similar class using lock, I get the following results for pushing 100,000 items: 1: Locked SuperStack average time: 6 ms 2: Interlocked SuperStack average time: 4.5 ms So, once again, we can get more efficient than a lock, though there is the cost of added code complexity.  Fortunately for you, most of the concurrent collection you’d ever need are already created for you in the System.Collections.Concurrent (here) namespace – for more information, see my Little Wonders – The Concurent Collections Part 1 (here), Part 2 (here), and Part 3 (here). Summary We’ve seen before how the Interlocked class can be used to safely and efficiently add, increment, decrement, read, and exchange values in a multi-threaded environment.  In addition to these, Interlocked CompareExchange() can be used to perform more complex logic without the need of a lock when lock contention is a concern. The added efficiency, though, comes at the cost of more complex code.  As such, the standard lock is often sufficient for most thread-safety needs.  But if profiling indicates you spend a lot of time waiting for locks, or if you just need a lock for something simple such as an increment, decrement, read, exchange, etc., then consider using the Interlocked class’s methods to reduce wait. Technorati Tags: C#,CSharp,.NET,Little Wonders,Interlocked,CompareExchange,threading,concurrency

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  • What is good usage scenario for Rackspace Cloud Files CDN (powered by AKAMAI) [closed]

    - by Andrew Smith
    I have just setup my website as static page via Rackspace CDN / Akamai. www.example.co.uk is an alias for d9771e6f24423091aebc-345678991111238fabcdef6114258d0e1.r61.cf3.rackcdn.com. d9771e6f24423091aebc-345678991111238fabcdef6114258d0e1.r61.cf3.rackcdn.com is an alias for a61.rackcdn.com. a61.rackcdn.com is an alias for a61.rackcdn.com.mdc.edgesuite.net. a61.rackcdn.com.mdc.edgesuite.net is an alias for a63.dscg10.akamai.net. a63.dscg10.akamai.net has address 63.166.98.41 a63.dscg10.akamai.net has address 63.166.98.40 a63.dscg10.akamai.net has IPv6 address 2001:428:4c02::cda8:ecb9 a63.dscg10.akamai.net has IPv6 address 2001:428:4c02::cda8:ed09 The HTTP header: HTTP/1.0 200 OK Last-Modified: Fri, 19 Oct 2012 23:27:41 GMT ETag: fdf9e14b77def799e09e8ce815a521da X-Timestamp: 1350689261.23382 Content-Type: text/html X-Trans-Id: tx457979be3bd746c2b4e5403a1189cdbc Cache-Control: public, max-age=900 Expires: Sat, 27 Oct 2012 22:18:56 GMT Date: Sat, 27 Oct 2012 22:03:56 GMT Content-Length: 7124 Connection: keep-alive I am wondering, if it's really the fastest solution to power the website? By investigating it thru http://www.just-ping.com/ it seems, that from many places the ping is very high, and during quick investigation I found that they use GeoIP to resolve addresses based on WHOIS, which is not accurate and because of that from many places the ping is above 300ms (for example, if ISP is in balgladore and request is routed to bangladore even if it's 300ms, for period of 1 month), while by just using Amazon Web Services and Route 53 Anycast DNS servers and only 4 EC2 instances it seems that for example India is always below 100ms, while using Akamai it goes above 300ms in some cases, and this is because Route 53 is using BGP. By quickly checking the Akamai, it seems that they are not getting feedback from the traffic - the high ping stays constant even if I keep downloading large files and videos, which is opposite to what they say on their website. They state, that they optimize the performance by taking feedback from the requests, while it seems they just use GeoIP with per City resolution (which are mostly big cities). Because of this, AWS with Route 53 / Anycast DNS seems to be much more reliable, as well EdgeCast which is using BGP, but I dont know how much does it cost to deploy static website. Actually, I dont know if EdgeCast is not a lie, because from isolated places there are many errors - so their performance is at the cost of quality of delivery, because of BGP switching the routes during transfer of large files. So I was wondering, what is really Akamai good for, because they dont seem to pose any strength in any field in what I do understand now, except they offer some software based WAF on their website, but what I really care about is the core distribiution, so the question is? Is really Akamai good for Videos? For static websites? ??? I found so far AWS most usable with most consistent ping and stable transfers.

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  • ejabberd starts slow and fails

    - by Michael Tanner
    I installed ejabberd and tried to set it up. On my server there are strict rules which allow only several services and denies everything else. I experienced starting problems with my iptables rules and found out that ejabberd works when I allow everything in the iptables and restore my rules afterwards. Then it also works for connecting, registering and else. What could be the problem in my rules? Attached here: http://fixee.org/paste/s5s744j/ Would be nice to get a correction straight on fixee if I made a mistake. Thanks in advance. Edit 1: In the log files there are no specific error messages during startup.

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  • Ubuntu server loses exactly 5 minutes once in a while

    - by Harold Smith
    I noticed that my server, an Ubuntu server 12.04, was losing time. I figured the hardware clock was off or maybe dying due to a faulty CMOS battery. I installed NTP to ensure the drift would be corrected, but to no avail. During a day it would lose 20 minutes or so. To debug, I created a small cron job to check against a remote servers time, which I knew to be correct. The script calculates the difference in seconds between local and remote time. The result was interesting. It seems to be losing exactly 5 minutes several times during the day. Look at this log (difference from remote server noted in seconds): Tue Oct 23 03:30:02 CEST 2012: 284 Tue Oct 23 03:35:02 CEST 2012: 284 Tue Oct 23 03:40:01 CEST 2012: 285 Tue Oct 23 03:45:02 CEST 2012: 285 Tue Oct 23 03:50:02 CEST 2012: 285 Tue Oct 23 03:55:02 CEST 2012: 284 Tue Oct 23 04:00:02 CEST 2012: 284 Tue Oct 23 04:05:01 CEST 2012: 285 Tue Oct 23 04:10:01 CEST 2012: 285 Tue Oct 23 04:15:02 CEST 2012: 585 Tue Oct 23 04:20:02 CEST 2012: 584 Tue Oct 23 04:25:02 CEST 2012: 584 Tue Oct 23 04:30:02 CEST 2012: 584 Tue Oct 23 04:35:01 CEST 2012: 585 Tue Oct 23 04:40:01 CEST 2012: 585 Tue Oct 23 04:45:02 CEST 2012: 585 Tue Oct 23 04:50:02 CEST 2012: 584 Tue Oct 23 04:55:02 CEST 2012: 584 Tue Oct 23 05:00:02 CEST 2012: 584 Tue Oct 23 05:05:01 CEST 2012: 585 Tue Oct 23 05:10:01 CEST 2012: 585 Tue Oct 23 05:15:02 CEST 2012: 585 Tue Oct 23 05:20:02 CEST 2012: 584 Tue Oct 23 05:25:02 CEST 2012: 584 Tue Oct 23 05:30:02 CEST 2012: 584 Tue Oct 23 05:35:01 CEST 2012: 585 Tue Oct 23 05:40:01 CEST 2012: 585 Tue Oct 23 05:45:02 CEST 2012: 584 Tue Oct 23 05:50:02 CEST 2012: 584 Tue Oct 23 05:55:02 CEST 2012: 584 Tue Oct 23 06:00:02 CEST 2012: 584 Tue Oct 23 06:05:03 CEST 2012: 584 Tue Oct 23 06:10:02 CEST 2012: 584 Tue Oct 23 06:15:01 CEST 2012: 585 Tue Oct 23 06:20:02 CEST 2012: 584 Tue Oct 23 06:25:02 CEST 2012: 584 Tue Oct 23 06:30:02 CEST 2012: 584 Tue Oct 23 06:35:02 CEST 2012: 584 Tue Oct 23 06:40:02 CEST 2012: 584 Tue Oct 23 06:45:01 CEST 2012: 585 Tue Oct 23 06:50:02 CEST 2012: 584 Tue Oct 23 06:55:01 CEST 2012: 585 Tue Oct 23 07:00:02 CEST 2012: 584 Tue Oct 23 07:05:02 CEST 2012: 584 Tue Oct 23 07:10:02 CEST 2012: 584 Tue Oct 23 07:15:02 CEST 2012: 584 Tue Oct 23 07:20:02 CEST 2012: 584 Tue Oct 23 07:25:02 CEST 2012: 584 Tue Oct 23 07:30:01 CEST 2012: 585 Tue Oct 23 07:35:02 CEST 2012: 584 Tue Oct 23 07:40:02 CEST 2012: 584 Tue Oct 23 07:45:02 CEST 2012: 584 Tue Oct 23 07:50:02 CEST 2012: 584 Tue Oct 23 07:55:02 CEST 2012: 584 Tue Oct 23 08:00:01 CEST 2012: 585 Tue Oct 23 08:05:02 CEST 2012: 584 Tue Oct 23 08:10:02 CEST 2012: 584 Tue Oct 23 08:15:02 CEST 2012: 584 Tue Oct 23 08:20:02 CEST 2012: 584 Tue Oct 23 08:25:02 CEST 2012: 584 Tue Oct 23 08:30:01 CEST 2012: 585 Tue Oct 23 08:35:02 CEST 2012: 584 Tue Oct 23 08:40:02 CEST 2012: 584 Tue Oct 23 08:45:02 CEST 2012: 584 Tue Oct 23 08:50:02 CEST 2012: 584 Tue Oct 23 08:55:02 CEST 2012: 584 Tue Oct 23 09:00:02 CEST 2012: 584 Tue Oct 23 09:05:03 CEST 2012: 584 Tue Oct 23 09:10:02 CEST 2012: 584 Tue Oct 23 09:15:02 CEST 2012: 584 Tue Oct 23 09:20:02 CEST 2012: 584 Tue Oct 23 09:25:02 CEST 2012: 584 Tue Oct 23 09:30:01 CEST 2012: 584 Tue Oct 23 09:35:02 CEST 2012: 584 Tue Oct 23 09:40:02 CEST 2012: 584 Tue Oct 23 09:45:02 CEST 2012: 584 Tue Oct 23 09:50:02 CEST 2012: 584 Tue Oct 23 09:55:02 CEST 2012: 584 Tue Oct 23 10:00:01 CEST 2012: 584 Tue Oct 23 10:05:02 CEST 2012: 584 Tue Oct 23 10:10:07 CEST 2012: 584 Tue Oct 23 10:15:02 CEST 2012: 584 Tue Oct 23 10:20:02 CEST 2012: 884 Tue Oct 23 10:25:02 CEST 2012: 884 Tue Oct 23 10:30:02 CEST 2012: 883 Tue Oct 23 10:35:01 CEST 2012: 884 Tue Oct 23 10:40:02 CEST 2012: 884 Tue Oct 23 10:45:02 CEST 2012: 884 Tue Oct 23 10:50:02 CEST 2012: 884 Tue Oct 23 10:55:02 CEST 2012: 1184 Tue Oct 23 11:00:02 CEST 2012: 1183 Tue Oct 23 11:05:01 CEST 2012: 1184 Tue Oct 23 11:10:02 CEST 2012: 1184 Tue Oct 23 11:15:02 CEST 2012: 1184 Tue Oct 23 11:20:02 CEST 2012: 1184 This does not seem to be faulty CMOS battery in my opinion. But what do you think?

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  • PS/2 vs USB keyboards: performance and energy consumption

    - by Mister Smith
    As far as I know, PS/2 keyboards are interrupt driven, while USB are polled. Typically a PS/2 keyboard was assigned IRQ_1 on Windows. I'm no hardware expert, but at a first glance seems like the PS/2 keyboards are more efficient. So here are my questions: On modern day computers, are PS/2 keyboard better (or faster), and if so, would it be noticeable at all? (e.g.: in gaming) Since they don't need polling, do PS/2 keyboards save energy compared to USB? (notice I'm not talking only about the peripheral here, but about the overall computer energy consumption). In case PS/2 had any advantage over USB, would adding a PS/2 adapter to my USB keyboard make the device as good as an actual PS/2 keyboard? Conversely, would adding a USB adapter to a PS/2 make it as bad as a USB KB? Thanks in advance.

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  • The next step for a graduate?

    - by Michael Hobbs
    I will complete my degree in Computer Science in July of 2013 however I will have two years of military service left. I would like to get some hands on C#/C++ programming experience in the mean time. I have been looking around the web at all the open source project that are out there. There are literally 10's of thousands. How would you go about picking one that is: A) good for a graduate level programmer B) will probably go somewhere, and C) are willing to take a novice under their wing. I would even be happy to work for a company for free, remotely as a debugger, tester, or what have you. As a side note would prefer to stick in the C# realm but understand I need to branch out at the same time.

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