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  • Weekend With #iPad

    - by andrewbrust
    Saturday morning, I got up, got dressed and took a 7-minute walk up to the Apple Store in New York’s Meatpacking District to pick up my reserved iPad.  This precinct, which borders Greenwich Village (where I live and grew up) was, when I was a kid, a very industrial and smelly neighborhood during the day  and a rough neighborhood at night.  So imagine my sense of irony as I walked up Hudson Street towards 14th Street, to go wait in line with a bunch of hipsters to buy an iPad on launch day. Numerous blue T-shirt-clad Apple store workers were on hand to check people in to the line specifically identified for people who had reserved an iPad.  Others workers passed out water and all of them, I kid you not, applauded people as they got their chance to go into the store and buy their devices.  They also cheered people and yelled “congratulations” as they left.  The event had all the charm of a mass wedding officiated by Reverend Sung Myung Moon.  Once inside, a nice dude named Trey, with lots of tattoos on his calves, helped me and I acquired my device in short order.  Another guy helped me activate the device, which was comical, because that has to be done through iTunes, which I hadn’t logged into in a while. Turns out my user id was my email address from the company I sold 5 1/2 years ago.  Who knew?  Regardless, I go the device working, packed up and left the store, shuddering as I was cheered and congratulated.  By this time (about 10:30am) the line for reserved units and even walk-ins, was gone.  The iPhone launch this was not. As much as I detested the Apple Store experience, I must say the device is really nice.  the screen is bright, the colors are bold, and the experience is ultra-smooth.  I quickly tested Safari, YouTube, Google Maps, and then installed a few apps, including the New York Times Editors’ Choice and a couple of Twitter clients. Some initial raves: Google Maps and Street View on the iPad is just amazing.  The screen is full-size like a PC or Mac, but it’s right in front of you and responding to taps and flicks and pinches and it’s really engulfing.  Video and photos are really nice on this device, despite the fact that 16:9 and anamorphic aspect ration content is letter boxed.  It still looks amazing.  And apps that are designed especially for the iPad, including The Weather Channel and Gilt and Kayak just look stunning.  The richness, the friendly layout, the finger-friendly UIs, and the satisfaction of not having a keyboard between you and the information you’re managing, while you sit on a couch or an easy chair, is just really a beautiful thing.  The mere experience of seeing these apps’ splash screens causes a shiver and Goosebumps.  Truly.  The iPad is not a desktop machine, and it’s not pocket device.  That doesn’t mean it’s useless though.  It’s the perfect “couchtop” computer. Now some downsides: the WiFi radio seems a bit flakey.  More than a few times, I have had to toggle the WiFi off and back on to get it to connect properly.  Worse yet, the iPad is totally bamboozled by the fact that I have four WiFi access points in my house, each with the same SSID.  My laptops are smart enough to roam from one to the other, but the iPad seems to maintain an affinity for the downstairs access point, even if I’m turning it on two flights up.  Telling the iPad to “forget” my WiFi network and then re-associate with it doesn’t help. More downers: as you might expect, there are far more applications developed for the iPhone than the iPad.  And although iPhone apps run on the iPad, that provides about the same experience as watching standard def on a big HD flat panel, complete with the lousy choice of thick black borders or zooming the picture in to fill the screen.  And speaking of iPhone Apps, I can’t get the Sonos one to work.  Ideally, they’d have a dedicated iPad app and it would work on the first try.  And the iPad is just as bad as any netbook when it comes to being a magnet for fingerprints.  The lack of multi-tasking is quite painful too – truly, I don’t mind if only one app can be active at once, but the lack of ability to switch between apps, and the requirement to return to the home screen and re-launch a previous app to switch back, is already old and I’ve had the thing less than 48 hours. These are just initial impressions.  I’ll have a fuller analysis soon, after I’ve had some more break-in time with my new toy.  I’ll be thinking not just about the iPad and iPhone but also about Android, the 2.1 update for which was pushed to my Droid today, and Windows Phone 7, whose “hub” concept I now understand the value of.  This has been a great year for alternative computing devices, and I see no net downside for Apple, Google or Microsoft.  Exciting times.

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  • What am I (a beginner) losing, by choosing Cherokee over Apache for serving dynamic content?

    - by Bad Learner
    I am a complete beginner and am planning to setup a photo sharing site. This is the setup I am planning, basically for a start - - Cherokee (instead of Apache) for serving dynamic content (python-based application), and Nginx for serving static files. Since, I am a beginner, what have I, to lose? So, can someone, from your experience, please tell me, what I'd lose by choosing Cherokee over Apache for serving dynamic content in PHP/Python/whatever? Anything other than the fact that there's lot of documentation, many people who can help when there's an issue etc as Apache is well established and the most popular web server? Again, my intention is not to spurt a flame war here. Just wanted to know if Cherokee would be better than Apache in terms of performance, reliability, and speed, when it matters (peak load times). Also, I heard it's a lot faster than Apache in serving dynamic content, is it true?

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  • Are there any font rendering libraries for games development that support hinting?

    - by Richard Fabian
    I've used angel code's bitmap font generator quite a bit and though it's very good, I wondered if there would be a way of using the hinting information to provide a better readable result by using hinting to provide differing thickness based on size/pixel coverage. I imagine any solution would have to use the distance field tech presented in the valve paper on smoothing fonts while maintaining or reducing asset size. (http://www.gamedev.net/community/forums/topic.asp?topic_id=494612) but I haven't found any demos of it being used with hinting information turned on or included in the field gradients in any way. Another way of looking at this is whether there are any font bitmap generators that will output mipmaps that still maintain their readability in the face of pixel size. I think the lower mip levels would try to guarantee fill and space where it is necessary to maintain readability/topology over maintaining style/form (the point of hinting). In response to "Is there a reason you can't just render the size you want", the problem lies in the fact that font rasterisers currently don't render in 3D, and hinting information would be important in different amounts due to the pixel density being different along different axes, even differing in importance along the length of a string due to the size reducing over distance. For example, I only want horizontal hinting in a texture that is viewed from the side, and only really want vertical hinting in a font that is viewed from below or above. This isn't meant to be a renderer that tries to render a perfect outline as accurately as possible, as hinting distorts the reality of the font, instead this is meant to be a rendering solution for quite static scenes, but scenes that have 3D transformed and warped text layout. In this case the legibility is important, more important than the accuracy of representation of the polygon shape.

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  • Custom/personal dyndns solution?

    - by Eddie Parker
    Hey: I can't think of how to make this work, but it seems like something that should be doable.. I currently own my own domain, and have been using dyndns.com's "custom DNS" to allow me to redirect 'example.com' to my website at home, which is on a dynamic IP. I've now switched over to a VPS solution which hosts my website and allows me root access to a box (me likey), which will now host "example.com" on a static IP. My question is, is it possible for me to somehow make "home.example.com" route to my box at home? Is there any software available that could automate updates to the DNS for this? Ideally I'd like not to pay a service if possible, but if that's the only way then I suppose I'll have to go that way. Thanks!

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  • Integrating Code Metrics in TFS 2010 Build

    - by Jakob Ehn
    The build process template and custom activity described in this post is available here: http://cid-ee034c9f620cd58d.office.live.com/self.aspx/BlogSamples/CodeMetricsSample.zip Running code metrics has been available since VS 2008, but only from inside the IDE. Yesterday Microsoft finally releases a Visual Studio Code Metrics Power Tool 10.0, a command line tool that lets you run code metrics on your applications.  This means that it is now possible to perform code metrics analysis on the build server as part of your nightly/QA builds (for example). In this post I will show how you can run the metrics command line tool, and also a custom activity that reads the output and appends the results to the build log, and also fails he build if the metric values exceeds certain (configurable) treshold values. The code metrics tool analyzes all the methods in the assemblies, measuring cyclomatic complexity, class coupling, depth of inheritance and lines of code. Then it calculates a Maintainability Index from these values that is a measure f how maintanable this method is, between 0 (worst) and 100 (best). For information on hwo this value is calculated, see http://blogs.msdn.com/b/codeanalysis/archive/2007/11/20/maintainability-index-range-and-meaning.aspx. After this it aggregates the information and present it at the class, namespace and module level as well. Running Metrics.exe in a build definition Running the actual tool is easy, just use a InvokeProcess activity last in the Compile the Project sequence, reference the metrics.exe file and pass the correct arguments and you will end up with a result XML file in the drop directory. Here is how it is done in the attached build process template: In the above sequence I first assign the path to the code metrics result file ([BinariesDirectory]\result.xml) to a variable called MetricsResultFile, which is then sent to the InvokeProcess activity in the Arguments property. Here are the arguments for the InvokeProcess activity: Note that we tell metrics.exe to analyze all assemblies located in the Binaries folder. You might want to do some more intelligent filtering here, you probably don’t want to analyze all 3rd party assemblies for example. Note also the path to the metrics.exe, this is the default location when you install the Code Metrics power tool. You must of course install the power tool on all build servers. Using the standard output logging (in the Handle Standard Output/Handle Error Output sections), we get the following output when running the build: Integrating Code Metrics into the build Having the results available next to the build result is nice, but we want to have results integrated in the build result itself, and also to affect the outcome of the build. The point of having QA builds that measure, for example, code metrics is to make it very clear how the code being built measures up to the standards of the project/company. Just having a XML file available in the drop location will not cause the developers to improve their code, but a (partially) failing build will! To do this, we need to write a custom activity that parses the metrics result file, logs it to the build log and fails the build if the values frfom the metrics is below/above some predefined treshold values. The custom activity performs the following steps Parses the XML. I’m using Linq 2 XSD for this, since the XML schema for the result file is available, it is vey easy to generate code that lets you query the structure using standard Linq operators. Runs through the metric result hierarchy and logs the metrics for each level and also verifies maintainability index and the cyclomatic complexity with the treshold values. The treshold values are defined in the build process template are are sent in as arguments to the custom activity If the treshold values are exceeded, the activity either fails or partially fails the current build. For more information about the structure of the code metrics result file, read Cameron Skinner's post about it. It is very simpe and easy to understand. I won’t go through the code of the custom activity here, since there is nothing special about it and it is available for download so you can look at it and play with it yourself. The treshold values for Maintainability Index and Cyclomatic Complexity is defined in the build process template, and can be modified per build definition: I have taken the default value for these settings from my colleague Terje Sandström post on Code Metrics - suggestions for approriate limits. You’ll notice that this is quite an improvement compared to using code metrics inside the IDE, where Red/Yellow/Green limits are fixed (and the default values are somewaht strange, see Terjes post for a discussion on this) This is the first version of the code metrics integration with TFS 2010 Build, I will proabably enhance the functionality and the logging (the “tree view” structure in the log becomes quite hard to read) soon. I will also consider adding it to the Community TFS Build Extensions site when it becomes a bit more mature. Another obvious improvement is to extend the data warehouse of TFS and push the metric results back to the warehouse and make it visible in the reports.

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  • How to configure Apache2 to host Django and PHP on multiple domains simultaneously?

    - by Bert B.
    I have a VPS (Ubuntu 10.04) that hosts multiple domains, one of them being a CodeIgniter (PHP) web app. The others are just static websites, no fancy backend languages required. Well I am starting a new project and want to use Django. I have Django installed, mod_wsgi enabled in Apache2, but when I did the first steps on the documentation (https://docs.djangoproject.com/en/dev/howto/deployment/wsgi/modwsgi/) it seemingly overwrote my existing Apache2 configuration and served up the Django welcome page to all my domains. What should my httpd.conf file should look like so that it doesn't overtake all my domains.

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  • A Closable jQuery Plug-in

    - by Rick Strahl
    In my client side development I deal a lot with content that pops over the main page. Be it data entry ‘windows’ or dialogs or simple pop up notes. In most cases this behavior goes with draggable windows, but sometimes it’s also useful to have closable behavior on static page content that the user can choose to hide or otherwise make invisible or fade out. Here’s a small jQuery plug-in that provides .closable() behavior to most elements by using either an image that is provided or – more appropriately by using a CSS class to define the picture box layout. /* * * Closable * * Makes selected DOM elements closable by making them * invisible when close icon is clicked * * Version 1.01 * @requires jQuery v1.3 or later * * Copyright (c) 2007-2010 Rick Strahl * http://www.west-wind.com/ * * Licensed under the MIT license: * http://www.opensource.org/licenses/mit-license.php Support CSS: .closebox { position: absolute; right: 4px; top: 4px; background-image: url(images/close.gif); background-repeat: no-repeat; width: 14px; height: 14px; cursor: pointer; opacity: 0.60; filter: alpha(opacity="80"); } .closebox:hover { opacity: 0.95; filter: alpha(opacity="100"); } Options: * handle Element to place closebox into (like say a header). Use if main element and closebox container are two different elements. * closeHandler Function called when the close box is clicked. Return true to close the box return false to keep it visible. * cssClass The CSS class to apply to the close box DIV or IMG tag. * imageUrl Allows you to specify an explicit IMG url that displays the close icon. If used bypasses CSS image styling. * fadeOut Optional provide fadeOut speed. Default no fade out occurs */ (function ($) { $.fn.closable = function (options) { var opt = { handle: null, closeHandler: null, cssClass: "closebox", imageUrl: null, fadeOut: null }; $.extend(opt, options); return this.each(function (i) { var el = $(this); var pos = el.css("position"); if (!pos || pos == "static") el.css("position", "relative"); var h = opt.handle ? $(opt.handle).css({ position: "relative" }) : el; var div = opt.imageUrl ? $("<img>").attr("src", opt.imageUrl).css("cursor", "pointer") : $("<div>"); div.addClass(opt.cssClass) .click(function (e) { if (opt.closeHandler) if (!opt.closeHandler.call(this, e)) return; if (opt.fadeOut) $(el).fadeOut(opt.fadeOut); else $(el).hide(); }); if (opt.imageUrl) div.css("background-image", "none"); h.append(div); }); } })(jQuery); The plugin can be applied against any selector that is a container (typically a div tag). The close image or close box is provided typically by way of a CssClass - .closebox by default – which supplies the image as part of the CSS styling. The default styling for the box looks something like this: .closebox { position: absolute; right: 4px; top: 4px; background-image: url(images/close.gif); background-repeat: no-repeat; width: 14px; height: 14px; cursor: pointer; opacity: 0.60; filter: alpha(opacity="80"); } .closebox:hover { opacity: 0.95; filter: alpha(opacity="100"); } Alternately you can also supply an image URL which overrides the background image in the style sheet. I use this plug-in mostly on pop up windows that can be closed, but it’s also quite handy for remove/delete behavior in list displays like this: you can find this sample here to look to play along: http://www.west-wind.com/WestwindWebToolkit/Samples/Ajax/AmazonBooks/BooksAdmin.aspx For closable windows it’s nice to have something reusable because in my client framework there are lots of different kinds of windows that can be created: Draggables, Modal Dialogs, HoverPanels etc. and they all use the client .closable plug-in to provide the closable operation in the same way with a few options. Plug-ins are great for this sort of thing because they can also be aggregated and so different components can pick and choose the behavior they want. The window here is a draggable, that’s closable and has shadow behavior and the server control can simply generate the appropriate plug-ins to apply to the main <div> tag: $().ready(function() { $('#ctl00_MainContent_panEditBook') .closable({ handle: $('#divEditBook_Header') }) .draggable({ dragDelay: 100, handle: '#divEditBook_Header' }) .shadow({ opacity: 0.25, offset: 6 }); }) The window is using the default .closebox style and has its handle set to the header bar (Book Information). The window is just closable to go away so no event handler is applied. Actually I cheated – the actual page’s .closable is a bit more ugly in the sample as it uses an image from a resources file: .closable({ imageUrl: '/WestWindWebToolkit/Samples/WebResource.axd?d=TooLongAndNastyToPrint', handle: $('#divEditBook_Header')}) so you can see how to apply a custom image, which in this case is generated by the server control wrapping the client DragPanel. More interesting maybe is to apply the .closable behavior to list scenarios. For example, each of the individual items in the list display also are .closable using this plug-in. Rather than having to define each item with Html for an image, event handler and link, when the client template is rendered the closable behavior is attached to the list. Here I’m using client-templating and the code that this is done with looks like this: function loadBooks() { showProgress(); // Clear the content $("#divBookListWrapper").empty(); var filter = $("#" + scriptVars.lstFiltersId).val(); Proxy.GetBooks(filter, function(books) { $(books).each(function(i) { updateBook(this); showProgress(true); }); }, onPageError); } function updateBook(book,highlight) { // try to retrieve the single item in the list by tag attribute id var item = $(".bookitem[tag=" +book.Pk +"]"); // grab and evaluate the template var html = parseTemplate(template, book); var newItem = $(html) .attr("tag", book.Pk.toString()) .click(function() { var pk = $(this).attr("tag"); editBook(this, parseInt(pk)); }) .closable({ closeHandler: function(e) { removeBook(this, e); }, imageUrl: "../../images/remove.gif" }); if (item.length > 0) item.after(newItem).remove(); else newItem.appendTo($("#divBookListWrapper")); if (highlight) { newItem .addClass("pulse") .effect("bounce", { distance: 15, times: 3 }, 400); setTimeout(function() { newItem.removeClass("pulse"); }, 1200); } } Here the closable behavior is applied to each of the items along with an event handler, which is nice and easy compared to having to embed the right HTML and click handling into each item in the list individually via markup. Ideally though (and these posts make me realize this often a little late) I probably should set up a custom cssClass to handle the rendering – maybe a CSS class called .removebox that only changes the image from the default box image. This example also hooks up an event handler that is fired in response to the close. In the list I need to know when the remove button is clicked so I can fire of a service call to the server to actually remove the item from the database. The handler code can also return false; to indicate that the window should not be closed optionally. Returning true will close the window. You can find more information about the .closable class behavior and options here: .closable Documentation Plug-ins make Server Control JavaScript much easier I find this plug-in immensely useful especial as part of server control code, because it simplifies the code that has to be generated server side tremendously. This is true of plug-ins in general which make it so much easier to create simple server code that only generates plug-in options, rather than full blocks of JavaScript code.  For example, here’s the relevant code from the DragPanel server control which generates the .closable() behavior: if (this.Closable && !string.IsNullOrEmpty(DragHandleID) ) { string imageUrl = this.CloseBoxImage; if (imageUrl == "WebResource" ) imageUrl = ScriptProxy.GetWebResourceUrl(this, this.GetType(), ControlResources.CLOSE_ICON_RESOURCE); StringBuilder closableOptions = new StringBuilder("imageUrl: '" + imageUrl + "'"); if (!string.IsNullOrEmpty(this.DragHandleID)) closableOptions.Append(",handle: $('#" + this.DragHandleID + "')"); if (!string.IsNullOrEmpty(this.ClientDialogHandler)) closableOptions.Append(",handler: " + this.ClientDialogHandler); if (this.FadeOnClose) closableOptions.Append(",fadeOut: 'slow'"); startupScript.Append(@" .closable({ " + closableOptions + "})"); } The same sort of block is then used for .draggable and .shadow which simply sets options. Compared to the code I used to have in pre-jQuery versions of my JavaScript toolkit this is a walk in the park. In those days there was a bunch of JS generation which was ugly to say the least. I know a lot of folks frown on using server controls, especially the UI is client centric as the example is. However, I do feel that server controls can greatly simplify the process of getting the right behavior attached more easily and with the help of IntelliSense. Often the script markup is easier is especially if you are dealing with complex, multiple plug-in associations that often express more easily with property values on a control. Regardless of whether server controls are your thing or not this plug-in can be useful in many scenarios. Even in simple client-only scenarios using a plug-in with a few simple parameters is nicer and more consistent than creating the HTML markup over and over again. I hope some of you find this even a small bit as useful as I have. Related Links Download jquery.closable West Wind Web Toolkit jQuery Plug-ins © Rick Strahl, West Wind Technologies, 2005-2010Posted in jQuery   ASP.NET  JavaScript  

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  • Serving a file with nginx

    - by jmetz
    I have a webapp built in angular.js and angular. Since angular takes care of most urls by itself, i want to serve the file indexAng.html (along with any arguments) in response to a request for /search/?arg1=x&arg2=y I've tried to do this with location blocks like this: location /search/ { alias /home/dotcloud/current/static/public/; index indexAng.html; } This seems to work, but i don't know how to serve the arguments with it. How do I serve arguments with indexAng.html, and is there a better or more appropriate way to go about this?

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  • moving dynamic disk from Windows to another Windows computer when original Windows is not available

    - by Andrei
    How do I mount dynamic disk on new system without access to the old OS ? I need to move Dynamic data disk from old Windows XP (Pro, SP3) system, where disk crashed, to new Windows system without having access to the old OS. On new system, Dynamic disk shows as "Dynamic - Foreign". Microfoft has instructions for moving Dynamic Disk [1]. But Microsoft assumes having access to the old system. But I do not have acess to the old system. I am struck with "Dynamic - Foreign" static of the disk on new system. Thanks WinXP Pro SP3 [1] http://technet.microsoft.com/en-us/library/cc779854(WS.10).aspx Move Disk to another computer.

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  • Object oriented design importance

    - by user5507
    I started studying Object Oriented Design and Modelling using the this book by James Rumbaugh. It uses a tool called Object Modeling Technique (OMT). I have certain newbie questions. I searched the net, but couldn't get answers The book is pretty old. Don't know why the school told me to learn this. I know OMT is a predecessor of the Unified Modeling Language (UML). So its a waste? Whether the concepts change very much when we move from OMT to UML? I know OMT has Object, Dynamic and Functional Model. Wikipedia says UML is compatible with OMT and UML is a model too. As per wikipedia the UML models are Static and Dynamic and they are represented by different diagrams like class, object, activity, sequence..... I couldn't find the equivalence of this in OMT. I read that there are many object oriented development methods like OMT, Booch,.... Which one is used by Industry ? Where could I get a comparison of different Object oriented development methods?

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  • Lucky Kid Gets Playable Angry Birds Cake [Video]

    - by ETC
    If you’re a six-year-old that loves Angry Birds we’re not sure you could get a better cake than a playable Angry Birds mock-up. It’s one thing to make a static Angry Birds cake, that takes a certain level of cake baking skill. It’s another thing altogether to make a cake that is a playable mock-up of the game, complete with slingshot and avian projectiles. It’s become a family tradition that I make increasingly ridiculous birthday cakes for my kids each year. So with my little boy Ben turning 6-years-old over the weekend, and appreciating his love of Angry Birds, I thought I’d have a shot a making him a playable Angry Birds birthday cake with working catapult and iced birds as ammunition. [...] It took 10 hours to make and 2 minutes to destroy. Angry Birds Cake [Electric Pig via Mashable] Latest Features How-To Geek ETC How To Make Hundreds of Complex Photo Edits in Seconds With Photoshop Actions How to Enable User-Specific Wireless Networks in Windows 7 How to Use Google Chrome as Your Default PDF Reader (the Easy Way) How To Remove People and Objects From Photographs In Photoshop Ask How-To Geek: How Can I Monitor My Bandwidth Usage? Internet Explorer 9 RC Now Available: Here’s the Most Interesting New Stuff Lucky Kid Gets Playable Angry Birds Cake [Video] See the Lord of the Rings Epic from the Perspective of Mordor [eBook] Smart Taskbar Is a Thumb Friendly Android Task Launcher Comix is an Awesome Comics Archive Viewer for Linux Get the MakeUseOf eBook Guide to Speeding Up Windows for Free Need Tech Support? Call the Star Wars Help Desk! [Video Classic]

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  • OpenVPN vs. IPSec - Pros and Cons, what to use?

    - by jens
    interestingly I have not found any good searchresults when searching for "OpenVPN vs IPSec": I need to setup a private LAN over an untrusted network. And as far as I know, both approaces seem to be valid. But I do not know which one is better. I would be very thankfull If you can list the pro's and con's of both approaches and maybe your suggestions and experiences what to use. Update (Regarding the comment/question): In my concrete case the goal is to have any number of Servers (with static IPs) be connected transparently with each other. But a small portion of "dynamic clients like road warriors" (with dynamic IPs) should also be able to connect. The main goal is however having a "transparent secure network" run top of untrusted network. I am quite a newbie so I do not know how to correctly interprete "1:1 Point to Point Connections" = The solution should support Broadcasts and all that stuff so it is a fully functional network... Thank you very much!! Jens

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  • C# 4.0: Covariance And Contravariance In Generics

    - by Paulo Morgado
    C# 4.0 (and .NET 4.0) introduced covariance and contravariance to generic interfaces and delegates. But what is this variance thing? According to Wikipedia, in multilinear algebra and tensor analysis, covariance and contravariance describe how the quantitative description of certain geometrical or physical entities changes when passing from one coordinate system to another.(*) But what does this have to do with C# or .NET? In type theory, a the type T is greater (>) than type S if S is a subtype (derives from) T, which means that there is a quantitative description for types in a type hierarchy. So, how does covariance and contravariance apply to C# (and .NET) generic types? In C# (and .NET), variance applies to generic type parameters and not to the resulting generic type. A generic type parameter is: covariant if the ordering of the generic types follows the ordering of the generic type parameters: Generic<T> = Generic<S> for T = S. contravariant if the ordering of the generic types is reversed from the ordering of the generic type parameters: Generic<T> = Generic<S> for T = S. invariant if neither of the above apply. If this definition is applied to arrays, we can see that arrays have always been covariant because this is valid code: object[] objectArray = new string[] { "string 1", "string 2" }; objectArray[0] = "string 3"; objectArray[1] = new object(); However, when we try to run this code, the second assignment will throw an ArrayTypeMismatchException. Although the compiler was fooled into thinking this was valid code because an object is being assigned to an element of an array of object, at run time, there is always a type check to guarantee that the runtime type of the definition of the elements of the array is greater or equal to the instance being assigned to the element. In the above example, because the runtime type of the array is array of string, the first assignment of array elements is valid because string = string and the second is invalid because string = object. This leads to the conclusion that, although arrays have always been covariant, they are not safely covariant – code that compiles is not guaranteed to run without errors. In C#, the way to define that a generic type parameter as covariant is using the out generic modifier: public interface IEnumerable<out T> { IEnumerator<T> GetEnumerator(); } public interface IEnumerator<out T> { T Current { get; } bool MoveNext(); } Notice the convenient use the pre-existing out keyword. Besides the benefit of not having to remember a new hypothetic covariant keyword, out is easier to remember because it defines that the generic type parameter can only appear in output positions — read-only properties and method return values. In a similar way, the way to define a type parameter as contravariant is using the in generic modifier: public interface IComparer<in T> { int Compare(T x, T y); } Once again, the use of the pre-existing in keyword makes it easier to remember that the generic type parameter can only be used in input positions — write-only properties and method non ref and non out parameters. Because covariance and contravariance apply only to the generic type parameters, a generic type definition can have both covariant and contravariant generic type parameters in its definition: public delegate TResult Func<in T, out TResult>(T arg); A generic type parameter that is not marked covariant (out) or contravariant (in) is invariant. All the types in the .NET Framework where variance could be applied to its generic type parameters have been modified to take advantage of this new feature. In summary, the rules for variance in C# (and .NET) are: Variance in type parameters are restricted to generic interface and generic delegate types. A generic interface or generic delegate type can have both covariant and contravariant type parameters. Variance applies only to reference types; if you specify a value type for a variant type parameter, that type parameter is invariant for the resulting constructed type. Variance does not apply to delegate combination. That is, given two delegates of types Action<Derived> and Action<Base>, you cannot combine the second delegate with the first although the result would be type safe. Variance allows the second delegate to be assigned to a variable of type Action<Derived>, but delegates can combine only if their types match exactly. If you want to learn more about variance in C# (and .NET), you can always read: Covariance and Contravariance in Generics — MSDN Library Exact rules for variance validity — Eric Lippert Events get a little overhaul in C# 4, Afterward: Effective Events — Chris Burrows Note: Because variance is a feature of .NET 4.0 and not only of C# 4.0, all this also applies to Visual Basic 10.

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  • Apache hanging with MaxClients is reached

    - by Ash White
    My Apache 2.2 (preform MPM) is hanging when MaxClients is reached, rather than queueing up requests and serving them when child processes become free. When this happens, the web server is totally unresponsive until it is manually restarted. The server stack is Ubuntu 8, MySQL 5, PHP 5. Hardware is Dual Xeons (2.8) with 2GB of RAM. It serves 30,000 - 50,000 pageviews per day. Static images, CSS, and JS are offloaded to a separate server and PHP is cached using eAccelerator. The HTML output of many pages is cached to the filesystem. Relevant Apache directives: KeepAlive On MaxKeepAliveRequests 50 KeepAliveTimeout 2 StartServers 2 MaxClients 150 MinSpareThreads 25 MaxSpareThreads 75 ThreadsPerChild 25 MaxRequestsPerChild 2000

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  • Spotlight on Claims: Serving Customers Under Extreme Conditions

    - by [email protected]
    Oracle Insurance's director of marketing for EMEA, John Sinclair, recently attended the CII Spotlight on Claims event in London. Bad weather and its implications for the insurance industry have become very topical as the frequency and diversity of natural disasters - including rains, wind and snow - has surged across Europe this winter. On England's wettest day on record, the county of Cumbria was flooded with 12 inches of rain within 24 hours. Freezing temperatures wreaked havoc on European travel, causing high speed TVG trains to break down and stranding hundreds of passengers under the English Chanel in a tunnel all night long without heat or electricity. A storm named Xynthia thrashed France and surrounding countries with hurricane force, flooding ports and killing 51 people. After the Spring Equinox, insurers may have thought the worst had past. Then came along Eyjafjallajökull, spewing out vast quantities of volcanic ash in what is turning out to be one of most costly natural disasters in history. Such extreme events challenge insurance companies' ability to service their customers just when customers need their help most. When you add economic downturn and competitive pressures to the mix, insurers are further stretched and required to continually learn and innovate to meet high customer expectations with reduced budgets. These and other issues were hot topics of discussion at the recent "Spotlight on Claims" seminar in London, focused on how weather is affecting claims and the insurance industry. The event was organized by the CII (Chartered Insurance Institute), a group with 90,000 members. CII has been at the forefront in setting professional standards for the insurance industry for over a century. Insurers came to the conference to hear how they could better serve their customers under extreme weather conditions, learn from the experience of their peers, and hear about technological breakthroughs in climate modeling, geographic intelligence and IT. Customer case studies at the conference highlighted the importance of effective and constant communication in handling the overflow of catastrophe related claims. First and foremost is the need to rapidly establish initial communication with claimants to build their confidence in a positive outcome. Ongoing communication then needs to be continued throughout the claims cycle to mange expectations and maintain ownership of the process from start to finish. Strong internal communication to support frontline staff was also deemed critical to successful crisis management, as was communication with the broader insurance ecosystem to tap into extended resources and business intelligence. Advances in technology - such web based systems to access policies and enter first notice of loss in the field - as well as customer-focused self-service portals and multichannel alerts, are instrumental in improving customer satisfaction and helping insurers to deal with the claims surge, which often can reach four or more times normal workloads. Dynamic models of the global climate system can now be used to better understand weather-related risks, and as these models mature it is hoped that they will soon become more accurate in predicting the timing of catastrophic events. Geographic intelligence is also being used within a claims environment to better assess loss reserves and detect fraud. Despite these advances in dealing with catastrophes and predicting their occurrence, there will never be a substitute for qualified front line staff to deal with customers. In light of pressures to streamline efficiency, there was debate as to whether outsourcing was the solution, or whether it was better to build on the people you have. In the final analysis, nearly everybody agreed that in the future insurance companies would have to work better and smarter to keep on top. An appeal was also made for greater collaboration amongst industry participants in dealing with the extreme conditions and systematic stress brought on by natural disasters. It was pointed out that the public oftentimes judged the industry as a whole rather than the individual carriers when it comes to freakish events, and that all would benefit at such times from the pooling of limited resources and professional skills rather than competing in silos for competitive advantage - especially the end customer. One case study that stood out was on how The Motorists Insurance Group was able to power through one of the most devastating catastrophes in recent years - Hurricane Ike. The keys to Motorists' success were superior people, processes and technology. They did a lot of upfront planning and invested in their people, creating a healthy team environment that delivered "max service" even when they were experiencing the same level of devastation as the rest of the population. Processes were rapidly adapted to meet the challenge of the catastrophe and continually adapted to Ike's specific conditions as they evolved. Technology was fundamental to the execution of their strategy, enabling them anywhere access, on the fly reassigning of resources and rapid training to augment the work force. You can learn more about the Motorists experience by watching this video. John Sinclair is marketing director for Oracle Insurance in EMEA. He has more than 20 years of experience in insurance and financial services.

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  • Setup VLAN agnostic ports on HP ProCurve 1810G (Ingress Filter, Trunking)

    - by Thomas
    I am wondering if it is possible to configure some ports of the web managed ProCurve Switch 1810G to participate in all VLAN traffic. Even if no VLAN with that ID has been set up inside the switch. The issue is that I have two virtualization servers that will use yet unknown VLANs of a certain range to communicate with each other. But the range is much larger than the 64 supported VLANs this switch can manage. The switch also offers static and LACP Link Trunks. But I guess there will also apply the Ingress Filter that drops packets with unconfigured VLAN IDs? A separate unmanaged switch that connects the two hosts and one ProCurve Port would work, but maybe I do not have to? Thanks

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  • Analysing and measuring the performance of a .NET application (survey results)

    - by Laila
    Back in December last year, I asked myself: could it be that .NET developers think that you need three days and a PhD to do performance profiling on their code? What if developers are shunning profilers because they perceive them as too complex to use? If so, then what method do they use to measure and analyse the performance of their .NET applications? Do they even care about performance? So, a few weeks ago, I decided to get a 1-minute survey up and running in the hopes that some good, hard data would clear the matter up once and for all. I posted the survey on Simple Talk and got help from a few people to promote it. The survey consisted of 3 simple questions: Amazingly, 533 developers took the time to respond - which means I had enough data to get representative results! So before I go any further, I would like to thank all of you who contributed, because I now have some pretty good answers to the troubling questions I was asking myself. To thank you properly, I thought I would share some of the results with you. First of all, application performance is indeed important to most of you. In fact, performance is an intrinsic part of the development cycle for a good 40% of you, which is much higher than I had anticipated, I have to admit. (I know, "Have a little faith Laila!") When asked what tool you use to measure and analyse application performance, I found that nearly half of the respondents use logging statements, a third use performance counters, and 70% of respondents use a profiler of some sort (a 3rd party performance profilers, the CLR profiler or the Visual Studio profiler). The importance attributed to logging statements did surprise me a little. I am still not sure why somebody would go to the trouble of manually instrumenting code in order to measure its performance, instead of just using a profiler. I personally find the process of annotating code, calculating times from log files, and relating it all back to your source terrifyingly laborious. Not to mention that you then need to remember to turn it all off later! Even when you have logging in place throughout all your code anyway, you still have a fair amount of potentially error-prone calculation to sift through the results; in addition, you'll only get method-level rather than line-level timings, and you won't get timings from any framework or library methods you don't have source for. To top it all, we all know that bottlenecks are rarely where you would expect them to be, so you could be wasting time looking for a performance problem in the wrong place. On the other hand, profilers do all the work for you: they automatically collect the CPU and wall-clock timings, and present the results from method timing all the way down to individual lines of code. Maybe I'm missing a trick. I would love to know about the types of scenarios where you actively prefer to use logging statements. Finally, while a third of the respondents didn't have a strong opinion about code performance profilers, those who had an opinion thought that they were mainly complex to use and time consuming. Three respondents in particular summarised this perfectly: "sometimes, they are rather complex to use, adding an additional time-sink to the process of trying to resolve the existing problem". "they are simple to use, but the results are hard to understand" "Complex to find the more advanced things, easy to find some low hanging fruit". These results confirmed my suspicions: Profilers are seen to be designed for more advanced users who can use them effectively and make sense of the results. I found yet more interesting information when I started comparing samples of "developers for whom performance is an important part of the dev cycle", with those "to whom performance is only looked at in times of crisis", and "developers to whom performance is not important, as long as the app works". See the three graphs below. Sample of developers to whom performance is an important part of the dev cycle: Sample of developers to whom performance is important only in times of crisis: Sample of developers to whom performance is not important, as long as the app works: As you can see, there is a strong correlation between the usage of a profiler and the importance attributed to performance: indeed, the more important performance is to a development team, the more likely they are to use a profiler. In addition, developers to whom performance is an important part of the dev cycle have a higher tendency to use a much wider range of methods for performance measurement and analysis. And, unsurprisingly, the less important performance is, the less varied the methods of measurement are. So all in all, to come back to my random questions: .NET developers do care about performance. Those who care the most use a wider range of performance measurement methods than those who care less. But overall, logging statements, performance counters and third party performance profilers are the performance measurement methods of choice for most developers. Finally, although most of you find code profilers complex to use, those of you who care the most about performance tend to use profilers more than those of you to whom performance is not so important.

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  • Server IP Address['s]

    - by Abdul
    hi there i am running server 2003, and seem to have this problem where the server starts kicking out users after a while, especially when they log off, they cant log back in, or the printers on the metwork stop connecting and they cant print to it. when i check the server, i notice that the server has 2 IP addresses, even though it has a static IP, it seems to pick up another IP address as well, but when you go into teh IPV set up, its not there, but of you run the IP scan utility tool, it picks it up. to correct this, i either can log off the server, then log back in, and the IP disappears, or sometimes this doesnt work, and i need to restart the server, but thsi happens like every 2 days or so.....can anyone out there help?

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  • Why is my Tiled map distorted when rendered with LibGDX?

    - by Sean
    I have a Tiled map that looks like this in the editor: But when I load it using an AssetManager (full static source available on GitHub) it appears completely askew. I believe the relevant portion of the code is below. This is the entire method; the others are either empty or might as well be. private OrthographicCamera camera; private AssetManager assetManager; private BitmapFont font; private SpriteBatch batch; private TiledMap map; private TiledMapRenderer renderer; @Override public void create() { float w = Gdx.graphics.getWidth(); float h = Gdx.graphics.getHeight(); camera = new OrthographicCamera(); assetManager = new AssetManager(); batch = new SpriteBatch(); font = new BitmapFont(); camera.setToOrtho(false, (w / h) * 10, 10); camera.update(); assetManager.setLoader(TiledMap.class, new TmxMapLoader( new InternalFileHandleResolver())); assetManager.load(AssetInfo.ICE_CAVE.assetPath, TiledMap.class); assetManager.finishLoading(); map = assetManager.get(AssetInfo.ICE_CAVE.assetPath); renderer = new IsometricTiledMapRenderer(map, 1f/64f); }

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  • LINQ: Enhancing Distinct With The PredicateEqualityComparer

    - by Paulo Morgado
    Today I was writing a LINQ query and I needed to select distinct values based on a comparison criteria. Fortunately, LINQ’s Distinct method allows an equality comparer to be supplied, but, unfortunately, sometimes, this means having to write custom equality comparer. Because I was going to need more than one equality comparer for this set of tools I was building, I decided to build a generic equality comparer that would just take a custom predicate. Something like this: public class PredicateEqualityComparer<T> : EqualityComparer<T> { private Func<T, T, bool> predicate; public PredicateEqualityComparer(Func<T, T, bool> predicate) : base() { this.predicate = predicate; } public override bool Equals(T x, T y) { if (x != null) { return ((y != null) && this.predicate(x, y)); } if (y != null) { return false; } return true; } public override int GetHashCode(T obj) { if (obj == null) { return 0; } return obj.GetHashCode(); } } Now I can write code like this: .Distinct(new PredicateEqualityComparer<Item>((x, y) => x.Field == y.Field)) But I felt that I’d lost all conciseness and expressiveness of LINQ and it doesn’t support anonymous types. So I came up with another Distinct extension method: public static IEnumerable<TSource> Distinct<TSource>(this IEnumerable<TSource> source, Func<TSource, TSource, bool> predicate) { return source.Distinct(new PredicateEqualityComparer<TSource>(predicate)); } And the query is now written like this: .Distinct((x, y) => x.Field == y.Field) Looks a lot better, doesn’t it?

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  • VPN networking issue

    - by DuncanDavies
    I have 2 servers hosted in the cloud. One an application server, one a VPN server, both running Win2008. Both have a local IP address assigned by DHCP in different network subnets, 10.227.55.0 (VPN) and 10.231.5.0 (App Server). These servers can ping each other. My VPN client connects in to the VPN server (using a L2TP connection on a Win7 client). It is assigned an IP Address from the VPN server's static pool (the VPN server takes 192.168.100.1, the client is given 192.168.100.2). The client can ping both the 192.168.100.1 address of the VPN server, and its 'local' IP address (10.227.55.X). What the client can't do is ping the App Server. How can I configure routing so that my client can access the App Server, without hard-coding any of the DHCP IP addresses anywhere? thanks Duncan

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  • Linksys WRT54G2 not showing connected PC's in DHCP table

    - by Moose
    For some reason all of a sudden my linksys WRT54G2 no longer shows PC's connected in the DHCP table. It was being touchy then all of a sudden they all just disappeared. It showed 2 of the 4 connected then it showed the other 2 then it only showed 1 and then it was showing none. I seem to be having a connection reset every 30-60 minutes also not sure if that is related to the router going bad or if it is just comcast being it's typical crappy self. I have tried to reset my router and my cable modem and both problems still seem to keep happening(no PC's in table and connection reset every 30-60 mins). Now I know the router doesn't store clients after a router reboot but they normally show up within a matter of minutes for me in the past. Before anyone asks yes all devices on the network are using DHCP and not static. Could this be a sign of the router starting to go bad?

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  • Disable ProxyPass rules within a virtual host on apache 2

    - by chinto
    I have a global proxypass rule in httpd.conf rules at global level ProxyPass /test/css http://myserver:7788/test/css ProxyPassReverse /test/css http://myserver:7788/test/css and I have a virtual host Listen localhost:7788 NameVirtualHost localhost:7788 <VirtualHost localhost:7788> Alias /test/css/ "C:/jboss/server/default/deploy/test.ear/test-web-app.war/css/" </VirtualHost> I would like to disable all global proxypass rules applying in this virtual host? NoProxy doesn't seem to work. (The reason I would like to do this is I have below global rules which create a 502 proxy loop if applied within this virtual host #pass all requests to application server ProxyPass /test http://localhost:8080/test ProxyPassReverse /test http://localhost:8080/test ) What I'm trying to do is, serve all static content (like css) using apache, while still proxying all the rest of requests to the application server.

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  • Share laptop Wi-Fi with router set up as access point via ethernet cables

    - by obie
    I have an ADSL modem which serves as a wireless router. There's a laptop connected to it through cable. On the other room I have a laptop which is connected through the router wirelessly. Since I have other appliances that need to get connected but are not Wi-Fi capable I have another Wi-Fi router. How can I share the second laptop's Wi-Fi with the second router so that the router can then serve as an access point to give internet to my other appliances through ethernet cables? I want something like this: INTERNETMODEM (WIFI)LAPTOP 1 (WIFI)LAPTOP 2 (WIFI)Router 2 (ETHERNET)DREAMBOX & WDTV What I've tried so far is opened the admin interface of router 2 then set static IP 192.168.100.13 and disabled the DHCP. The DHCP of the main router starts with 192.168.100.1 then I hooked up router 2 with the laptop 2 through Cat5 cable but for some reason it's not working.

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  • Accessing IPv6 router interface from a minimal Fedora installation?

    - by Zack
    I've recently installed Fedora 16 and am trying to set up a simple apache server. The only problem I've run into so far is that I'm unable to access my router's web interface from any box on my network. It assigns addresses via dhcp, and the router always responds to a ping. The server is also picking up an IP from the router on the proper subnet. Now, all I really need to do is forward a port, however I am receiving "Unable to connect" through the web interfaces and "connection refused" via telnet. What are my options, and how might I go about troubleshooting this? Will I need the server's ip to be static in order to change these settings? The router is a "Netopia" model, if that helps.

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