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• gpgpu vs. physX for physics simulation

  - by notabene

  Hello First theoretical question. What is better (faster)? Develop your own gpgpu techniques for physics simulation (cloth, fluids, colisions...) or to use PhysX? (If i say develop i mean implement existing algorithms like navier-strokes...) I don't care about what will take more time to develop. What will be faster for end user? As i understand that physx are accelerated through PPU units in gpu, does it mean that physical simulation can run in paralel with rastarization? Are PPUs different units than unified shader units used as vertex/geometry/pixel/gpgpu shader units? And little non-theoretical question: Is physx able to do sofisticated simulation equal to lets say Autodesk's Maya fluid solver? Are there any c++ gpu accelerated physics frameworks to try? (I am interested in both physx and gpgpu, commercial engines are ok too).

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• Google présente le Nexus S fabriqué par Samsung, tournant sous Android 2.3 et équipé du NFC

  Google présente le Nexus S fabriqué par Samsung, au design épuré et équipé du NFC Mise à jour du 07.12.2010 par Katleen Cette fois-ci, c'est officiel. Le Nexus One aura un successeur, et c'est bel et bien cet appareil qu'Eric Schmidt avait furtivement montré il y a quelques semaines lors d'une conférence. Le second smartphone estampillé Google a été fabriqué par Samsung, qui a du le fabriquer en respectant scrupuleusement un cahier des charges très précis, en matière de hardware et de design. Son exclusivité ? Etre le premier à tourner sous Android 2.3 (Gingerbread) en version "pure" (non remodelée par les opérateurs, ni par Samsung). Autre grand pas en avant : l'inclusion d...

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• How do I share files with someone who does not have a ubuntu one account

  - by Bob

  I tried to search for an answer, except that, uhhh there is no search. I want to share a Ubuntu One folder with people who do not have a Ubuntu One account. Is that possible? I found this answer in the faq, "Yes! Since Ubuntu 10.04 LTS, Ubuntu One supports sharing files publicly. Right click on a file already synchronized by Ubuntu One and select "Publish via Ubuntu One". Right-click on the file again and select "Copy Ubuntu One public URL". You can now paste the URL and share it with whoever you want." That doesn't seem to help me with 11.04. There is no 'Publish via Ubuntu One' button in 11.04. Does anyone know if there is a way to share files with non-ubuntu users? If so, how? Thanks In Advance, Bob

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• ASP.NET Web API and Simple Value Parameters from POSTed data

  - by Rick Strahl

  In testing out various features of Web API I've found a few oddities in the way that the serialization is handled. These are probably not super common but they may throw you for a loop. Here's what I found. Simple Parameters from Xml or JSON Content Web API makes it very easy to create action methods that accept parameters that are automatically parsed from XML or JSON request bodies. For example, you can send a JavaScript JSON object to the server and Web API happily deserializes it for you. This works just fine:public string ReturnAlbumInfo(Album album) { return album.AlbumName + " (" + album.YearReleased.ToString() + ")"; } However, if you have methods that accept simple parameter types like strings, dates, number etc., those methods don't receive their parameters from XML or JSON body by default and you may end up with failures. Take the following two very simple methods:public string ReturnString(string message) { return message; } public HttpResponseMessage ReturnDateTime(DateTime time) { return Request.CreateResponse<DateTime>(HttpStatusCode.OK, time); } The first one accepts a string and if called with a JSON string from the client like this:var client = new HttpClient(); var result = client.PostAsJsonAsync<string>(http://rasxps/AspNetWebApi/albums/rpc/ReturnString, "Hello World").Result; which results in a trace like this: POST http://rasxps/AspNetWebApi/albums/rpc/ReturnString HTTP/1.1Content-Type: application/json; charset=utf-8Host: rasxpsContent-Length: 13Expect: 100-continueConnection: Keep-Alive "Hello World" produces… wait for it: null. Sending a date in the same fashion:var client = new HttpClient(); var result = client.PostAsJsonAsync<DateTime>(http://rasxps/AspNetWebApi/albums/rpc/ReturnDateTime, new DateTime(2012, 1, 1)).Result; results in this trace: POST http://rasxps/AspNetWebApi/albums/rpc/ReturnDateTime HTTP/1.1Content-Type: application/json; charset=utf-8Host: rasxpsContent-Length: 30Expect: 100-continueConnection: Keep-Alive "\/Date(1325412000000-1000)\/" (yes still the ugly MS AJAX date, yuk! This will supposedly change by RTM with Json.net used for client serialization) produces an error response: The parameters dictionary contains a null entry for parameter 'time' of non-nullable type 'System.DateTime' for method 'System.Net.Http.HttpResponseMessage ReturnDateTime(System.DateTime)' in 'AspNetWebApi.Controllers.AlbumApiController'. An optional parameter must be a reference type, a nullable type, or be declared as an optional parameter. Basically any simple parameters are not parsed properly resulting in null being sent to the method. For the string the call doesn't fail, but for the non-nullable date it produces an error because the method can't handle a null value. This behavior is a bit unexpected to say the least, but there's a simple solution to make this work using an explicit [FromBody] attribute:public string ReturnString([FromBody] string message) andpublic HttpResponseMessage ReturnDateTime([FromBody] DateTime time) which explicitly instructs Web API to read the value from the body. UrlEncoded Form Variable Parsing Another similar issue I ran into is with POST Form Variable binding. Web API can retrieve parameters from the QueryString and Route Values but it doesn't explicitly map parameters from POST values either. Taking our same ReturnString function from earlier and posting a message POST variable like this:var formVars = new Dictionary<string,string>(); formVars.Add("message", "Some Value"); var content = new FormUrlEncodedContent(formVars); var client = new HttpClient(); var result = client.PostAsync(http://rasxps/AspNetWebApi/albums/rpc/ReturnString, content).Result; which produces this trace: POST http://rasxps/AspNetWebApi/albums/rpc/ReturnString HTTP/1.1Content-Type: application/x-www-form-urlencodedHost: rasxpsContent-Length: 18Expect: 100-continue message=Some+Value When calling ReturnString:public string ReturnString(string message) { return message; } unfortunately it does not map the message value to the message parameter. This sort of mapping unfortunately is not available in Web API. Web API does support binding to form variables but only as part of model binding, which binds object properties to the POST variables. Sending the same message as in the previous example you can use the following code to pick up POST variable data:public string ReturnMessageModel(MessageModel model) { return model.Message; } public class MessageModel { public string Message { get; set; }} Note that the model is bound and the message form variable is mapped to the Message property as would other variables to properties if there were more. This works but it's not very dynamic. There's no real easy way to retrieve form variables (or query string values for that matter) in Web API's Request object as far as I can discern. Well only if you consider this easy:public string ReturnString() { var formData = Request.Content.ReadAsAsync<FormDataCollection>().Result; return formData.Get("message"); } Oddly FormDataCollection does not allow for indexers to work so you have to use the .Get() method which is rather odd. If you're running under IIS/Cassini you can always resort to the old and trusty HttpContext access for request data:public string ReturnString() { return HttpContext.Current.Request.Form["message"]; } which works fine and is easier. It's kind of a bummer that HttpRequestMessage doesn't expose some sort of raw Request object that has access to dynamic data - given that it's meant to serve as a generic REST/HTTP API that seems like a crucial missing piece. I don't see any way to read query string values either. To me personally HttpContext works, since I don't see myself using self-hosted code much.© Rick Strahl, West Wind Technologies, 2005-2012Posted in Web Api   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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• Why It Is So Important to Know Your Customer

  - by Christie Flanagan

  Over the years, I endured enough delayed flights, air turbulence and misadventures in airport security clearance to watch my expectations for the air travel experience fall to abysmally low levels. The extent of my loyalty to any one carrier had more to do with the proximity of the airport parking garage to their particular gate than to any effort on the airline’s part to actually earn and retain my business. That all changed one day when I found myself at the airport hoping to catch a return flight home a few hours earlier than expected, using an airline I had flown with for the first time just that week.  When you travel regularly for business, being able to catch a return flight home that’s even an hour or two earlier than originally scheduled is a big deal. It can mean the difference between having a normal evening with your family and having to sneak in like a cat burglar after everyone is fast asleep. And so I found myself on this particular day hoping to catch an earlier flight home. I approached the gate agent and was told that I could go on standby for their next flight out. Then I asked how much it was going to cost to change the flight, knowing full well that I wouldn’t get reimbursed by my company for any change fees. “Oh, there’s no charge to fly on standby,” the gate agent told me. I made a funny look. I couldn’t believe what I was hearing. This airline was going to let my fly on standby, at no additional charge, even though I was a new customer with no status or points. It had been years since I’d seen an airline pass up a short term revenue generating opportunity in favor of a long term loyalty generating one.  At that moment, this particular airline gained my loyal business. Since then, this airline has had the opportunity to learn a lot about me. They know where I live, where I fly from, where I usually fly to, and where I like to sit on the plane. In general, I’ve found their customer service to be quite good whether at the airport, via call center and even through social channels. They email me occasionally, and when they do, they demonstrate that they know me by promoting deals for flights from where I live to places that I’d be interested in visiting. And that’s part of why I’m always so puzzled when I visit their website.Does this company with the great service, customer friendly policies, and clean planes demonstrate that they know me at all when I visit their website? The answer is no. Even when I log in using my loyalty program credentials, it’s pretty obvious that they’re presenting the same old home page and same old offers to every single one of their site visitors. I mean, those promotional offers that they’re featuring so prominently  -- they’re for flights that originate thousands of miles from where I live! There’s no way I’d ever book one of those flights and I’m sure I’m not the only one of their customers to feel that way.My reason for recounting this story is not to pick on the one customer experience flaw I've noticed with this particular airline, in fact, they do so many things right that I’ll continue to fly with them. But I did want to illustrate just how glaringly obvious it is to customers today when a touch point they have with a brand is impersonal, unconnected and out of sync. As someone who’s spent a number of years in the web experience management and online marketing space, it particularly peeves me when that out of sync touch point is a brand’s website, perhaps because I know how important it is to make a customer’s online experience relevant and how many powerful tools are available for making a relevant experience a reality. The fact is, delivering a one-size-fits-all online customer experience is no longer acceptable or particularly effective in today’s world. Today’s savvy customers expect you to know who they are and to understand their preferences, behavior and relationship with your brand. Not only do they expect you to know about them, but they also expect you to demonstrate this knowledge across all of their touch points with your brand in a consistent and compelling fashion, whether it be on your traditional website, your mobile web presence or through various social channels.Delivering the kind of personalized online experiences that customers want can have tremendous business benefits. This is not just about generating feelings of goodwill and higher customer satisfaction ratings either. More relevant and personalized online experiences boost the effectiveness of online marketing initiatives and the statistics prove this out. Personalized web experiences can help increase online conversion rates by 70% -- that’s a huge number.1  And more than three quarters of consumers indicate that they’ve made additional online purchases based on personalized product recommendations.2Now if only this airline would get on board with delivering a more personalized online customer experience. I’d certainly be happier and more likely to spring for one of their promotional offers. And by targeting relevant offers on their home page to appropriate segments of their site visitors, I bet they’d be happier and generating additional revenue too. 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-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-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-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;}  ***** If you're interested in hearing more perspectives on the benefits of demonstrating that you know your customers by delivering a more personalized experience, check out this white paper on creating a successful and meaningful customer experience on the web.  Also catch the video below on the business value of CX in attracting new customers featuring Oracle's VP of Customer Experience Strategy, Brian Curran. 1 Search Engine Watch 2 Marketing Charts

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• Incorrect colour blending when using a pixel shader with XNA

  - by MazK

  I'm using XNA 4.0 to create a 2D game and while implementing a layer tinting pixel shader I noticed that when the texture's alpha value is anything between 1 or 0 the end result is different than expected. The tinting works from selecting a colour and setting the amount of tint. This is achieved via the shader which works out first the starting colour (for each r, g, b and a) : float red = texCoord.r * vertexColour.r; and then the final tinted colour : output.r = red + (tintColour.r - red) * tintAmount; The alpha value isn't tinted and is left as : output.a = texCoord.a * vertexColour.a; The picture in the link below shows different backdrops against an energy ball object where it's outer glow hasn't blended as I would like it to. The middle two are incorrect as the second non tinted one should not show a glow against a white BG and the third should be entirely invisible. The blending function is NonPremultiplied. Why the alpha value is interfering with the final colour?

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• Oracle SOA and the Sun acquisition

  - by Demed L'Her

  I just presented the SOA product strategy at the Oracle + Sun Welcome Event this morning in Redwood Shores, after 2 earlier sessions on that same topic in Atlanta and Reston. That made me realize that I still haven’t blogged about the Sun acquisition – you might wonder how I managed to ignore the elephant in the room! Reality is that we have been very busy lately working with our new colleagues from Sun on a joint strategy and the resulting engineering plans. Let me help you navigate the Oracle website by giving you the links you really need if your main focus of area is integration and SOA technologies: Entry point into all material relating to the Sun acquisition (and since you are there you might want to check the non-SOA content, such as the hardware story that is quite interesting) Hasan Rizvi’s webcast on the combined SOA strategy Schedule and registration for the live Welcome Events taking place around the world – a great opportunity to ask questions that are not answered in the material we have posted on the web So with this welcome to the Sun customers and Java CAPS users!   Technorati Tags: jcaps,java caps,sun,soa,oracle,glassfish esb,seebeyond,acquisition

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• Best way of storing voxels

  - by opiop65

  This should be a pretty easy question to answer, and I'm not looking for how to store the voxels data wise, I'm looking for the theory. Currently, my voxel engine has no global list of tiles. Each chunk has it's own list, and its hard to do things like collision detection or anything that may use tiles that are outside of its own chunk. I recently worked on procedural terrain with a non voxel engine. Now, I want to start using heightmaps in my voxel engine. But, I have a problem. If each chunk has its own list, then it will be pretty difficult to implement the heightmaps. My real question is, is should I store a global list of voxels independent of the chunks? And then I can just easily perform collision detection and terrain generation. However, it would probably be harder to do things such as frustum culling. So how should I store them?

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• Optimizing collision engine bottleneck

  - by Vittorio Romeo

  Foreword: I'm aware that optimizing this bottleneck is not a necessity - the engine is already very fast. I, however, for fun and educational purposes, would love to find a way to make the engine even faster. I'm creating a general-purpose C++ 2D collision detection/response engine, with an emphasis on flexibility and speed. Here's a very basic diagram of its architecture: Basically, the main class is World, which owns (manages memory) of a ResolverBase*, a SpatialBase* and a vector<Body*>. SpatialBase is a pure virtual class which deals with broad-phase collision detection. ResolverBase is a pure virtual class which deals with collision resolution. The bodies communicate to the World::SpatialBase* with SpatialInfo objects, owned by the bodies themselves. There currenly is one spatial class: Grid : SpatialBase, which is a basic fixed 2D grid. It has it's own info class, GridInfo : SpatialInfo. Here's how its architecture looks: The Grid class owns a 2D array of Cell*. The Cell class contains two collection of (not owned) Body*: a vector<Body*> which contains all the bodies that are in the cell, and a map<int, vector<Body*>> which contains all the bodies that are in the cell, divided in groups. Bodies, in fact, have a groupId int that is used for collision groups. GridInfo objects also contain non-owning pointers to the cells the body is in. As I previously said, the engine is based on groups. Body::getGroups() returns a vector<int> of all the groups the body is part of. Body::getGroupsToCheck() returns a vector<int> of all the groups the body has to check collision against. Bodies can occupy more than a single cell. GridInfo always stores non-owning pointers to the occupied cells. After the bodies move, collision detection happens. We assume that all bodies are axis-aligned bounding boxes. How broad-phase collision detection works: Part 1: spatial info update For each Body body: Top-leftmost occupied cell and bottom-rightmost occupied cells are calculated. If they differ from the previous cells, body.gridInfo.cells is cleared, and filled with all the cells the body occupies (2D for loop from the top-leftmost cell to the bottom-rightmost cell). body is now guaranteed to know what cells it occupies. For a performance boost, it stores a pointer to every map<int, vector<Body*>> of every cell it occupies where the int is a group of body->getGroupsToCheck(). These pointers get stored in gridInfo->queries, which is simply a vector<map<int, vector<Body*>>*>. body is now guaranteed to have a pointer to every vector<Body*> of bodies of groups it needs to check collision against. These pointers are stored in gridInfo->queries. Part 2: actual collision checks For each Body body: body clears and fills a vector<Body*> bodiesToCheck, which contains all the bodies it needs to check against. Duplicates are avoided (bodies can belong to more than one group) by checking if bodiesToCheck already contains the body we're trying to add. const vector<Body*>& GridInfo::getBodiesToCheck() { bodiesToCheck.clear(); for(const auto& q : queries) for(const auto& b : *q) if(!contains(bodiesToCheck, b)) bodiesToCheck.push_back(b); return bodiesToCheck; } The GridInfo::getBodiesToCheck() method IS THE BOTTLENECK. The bodiesToCheck vector must be filled for every body update because bodies could have moved meanwhile. It also needs to prevent duplicate collision checks. The contains function simply checks if the vector already contains a body with std::find. Collision is checked and resolved for every body in bodiesToCheck. That's it. So, I've been trying to optimize this broad-phase collision detection for quite a while now. Every time I try something else than the current architecture/setup, something doesn't go as planned or I make assumption about the simulation that later are proven to be false. My question is: how can I optimize the broad-phase of my collision engine maintaining the grouped bodies approach? Is there some kind of magic C++ optimization that can be applied here? Can the architecture be redesigned in order to allow for more performance? Actual implementation: SSVSCollsion Body.h, Body.cpp World.h, World.cpp Grid.h, Grid.cpp Cell.h, Cell.cpp GridInfo.h, GridInfo.cpp

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• Visualize flowchart diagram with multiple end symbols

  - by platzhirsch

  I am looking for a standardize way to visualize the following hierarchical logic: The state of the thread is represented by the answers to the hierarchical set of question You can read this listing like a flowchart, you iterate over the questions decide, go one step deeper and so on. Therefore I thought the best way to visualize it, using a flowchart. The problem is, in this hierarchical set it is possible to end in more than one state and its totally valid. I have never seen a flowchart where you can enter more than one state. Is it still possible and I am missing the right symbol to present this logic or are flowchart not fitting anyway? What other graphical representation could I use, is there something fitting in UML? A non-deterministic state machine seems not to be intuitive enough, transfering it into a deterministic state machine would result in to many states, and so on.

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• CUDA 4.0 : sortie de la Release Candidate de l'architecture de calcul parallèle de NVIDIA

  CUDA 4.0 : sortie de la Release Candidate De l'architecture de calcul parallèle de NVIDIA La sortie cette semaine aux développeurs enregistrés de CUDA est l'accomplissement de milliers d'heures dédiées à ce projet. Cette technologie peut sembler jeune, sa première version, la 1.0, n'a été sortie qu'en 2007. L'effet de cette sortie sur le monde entier n'a, sans nul doute possible, pas été nul. Elle n'est pas non plus le seul terrain d'avance pour les technologies massivement parallèles sur matériel NVIDIA : les API comme OpenCL et DirectCompute sont elles aussi supportées et améliorées, en plus d'un accès direct au GPU en C, C++ et Fortran. Comme toujours, NVIDIA est à la recherch...

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• New Exadata Book Available Soon

  - by Rob Reynolds

  Oracle Press is set to released the first book on data warehouse performance and Exadata on March 14th. Achieving Extreme Performance with Oracle Exadata , by my colleagues Rick Greenwald, Robert Stackowiak, Maqsood Alam, and Mans Bhuller will be available at your favorite booksellers next week. I've seen a sneak peak of the content in this book and its a great way to fully grasp the power of Exadata and how to best apply it to achieve extreme data warehouse performance. From the publisher's description: Achieving Extreme Performance with Oracle Exadata and the Sun Oracle Database Machine is filled with best practices for deployments, hardware sizing, architecting the database machine environments for maximum availability, and backup and recovery. Oracle Database 11gR2 features used within these offerings, as well as migration options and paths for Oracle and non-Oracle databases to Oracle Exadata are covered. This Oracle Press guide also discusses architecture, administration, maintenance, monitoring, and tuning of Oracle Exadata Storage Servers and the Sun Oracle Database Machine. If your company is considering Exadata, or if you need more horsepower out of your data warehouse, I highly recommend grabbing a copy of this book next week.

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• Do Not Optimize Without Measuring

  - by Alois Kraus

  Recently I had to do some performance work which included reading a lot of code. It is fascinating with what ideas people come up to solve a problem. Especially when there is no problem. When you look at other peoples code you will not be able to tell if it is well performing or not by reading it. You need to execute it with some sort of tracing or even better under a profiler. The first rule of the performance club is not to think and then to optimize but to measure, think and then optimize. The second rule is to do this do this in a loop to prevent slipping in bad things for too long into your code base. If you skip for some reason the measure step and optimize directly it is like changing the wave function in quantum mechanics. This has no observable effect in our world since it does represent only a probability distribution of all possible values. In quantum mechanics you need to let the wave function collapse to a single value. A collapsed wave function has therefore not many but one distinct value. This is what we physicists call a measurement. If you optimize your application without measuring it you are just changing the probability distribution of your potential performance values. Which performance your application actually has is still unknown. You only know that it will be within a specific range with a certain probability. As usual there are unlikely values within your distribution like a startup time of 20 minutes which should only happen once in 100 000 years. 100 000 years are a very short time when the first customer tries your heavily distributed networking application to run over a slow WIFI network… What is the point of this? Every programmer/architect has a mental performance model in his head. A model has always a set of explicit preconditions and a lot more implicit assumptions baked into it. When the model is good it will help you to think of good designs but it can also be the source of problems. In real world systems not all assumptions of your performance model (implicit or explicit) hold true any longer. The only way to connect your performance model and the real world is to measure it. In the WIFI example the model did assume a low latency high bandwidth LAN connection. If this assumption becomes wrong the system did have a drastic change in startup time. Lets look at a example. Lets assume we want to cache some expensive UI resource like fonts objects. For this undertaking we do create a Cache class with the UI themes we want to support. Since Fonts are expensive objects we do create it on demand the first time the theme is requested. A simple example of a Theme cache might look like this: using System; using System.Collections.Generic; using System.Drawing; struct Theme { public Color Color; public Font Font; } static class ThemeCache { static Dictionary<string, Theme> _Cache = new Dictionary<string, Theme> { {"Default", new Theme { Color = Color.AliceBlue }}, {"Theme12", new Theme { Color = Color.Aqua }}, }; public static Theme Get(string theme) { Theme cached = _Cache[theme]; if (cached.Font == null) { Console.WriteLine("Creating new font"); cached.Font = new Font("Arial", 8); } return cached; } } class Program { static void Main(string[] args) { Theme item = ThemeCache.Get("Theme12"); item = ThemeCache.Get("Theme12"); } } This cache does create font objects only once since on first retrieve of the Theme object the font is added to the Theme object. When we let the application run it should print “Creating new font” only once. Right? Wrong! The vigilant readers have spotted the issue already. The creator of this cache class wanted to get maximum performance. So he decided that the Theme object should be a value type (struct) to not put too much pressure on the garbage collector. The code Theme cached = _Cache[theme]; if (cached.Font == null) { Console.WriteLine("Creating new font"); cached.Font = new Font("Arial", 8); } does work with a copy of the value stored in the dictionary. This means we do mutate a copy of the Theme object and return it to our caller. But the original Theme object in the dictionary will have always null for the Font field! The solution is to change the declaration of struct Theme to class Theme or to update the theme object in the dictionary. Our cache as it is currently is actually a non caching cache. The funny thing was that I found out with a profiler by looking at which objects where finalized. I found way too many font objects to be finalized. After a bit debugging I found the allocation source for Font objects was this cache. Since this cache was there for years it means that the cache was never needed since I found no perf issue due to the creation of font objects. the cache was never profiled if it did bring any performance gain. to make the cache beneficial it needs to be accessed much more often. That was the story of the non caching cache. Next time I will write something something about measuring.

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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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• How to setup Thinkpad features on Thinkpad T500

  - by gijoemike

  I have a IBM-Lenovo Thinkpad T500. I was previously a exclusive windows user, but recently installed ubuntu and loving it because of speed and interface. The only thing is that I don't get some features that I came to enjoy in windows. I need help setting these up: Hard-drive protection - active protection software that pauses drive when there is movement My printer doesn't work (can't find the driver for this one): canon Ip2600 A way to change which graphics chip to use while in OS. I have both the integrated and non integrated (dual-graphics). (If not easy to setup, I know there's a way to do it before it boots, but don't know how). CPU performance level - in windows you can pick "high performance", "power saver", etc.. to save batteries. My integrated camera w/light - it works but need an app where I can record videos, take snapshots, etc. can't find one that works. Thanks!

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• Will Ubuntu break my RAID 0 array?

  - by Chad

  I am upgrading an older machine today with new Motherboard, RAM, and CPU. Then I am going to do a fresh install of Ubuntu 64bit. Currently the old machine has an 80gb system drive, and a 4TB RAID 0 array. The old Motherboard has no SATA ports, so I used a SATA card. Ubuntu set up the old RAID array, will it still recognize the array on a newer machine? Are there any steps I should take to ensure the array isn't damaged? It's non-crucial data, but I would rather not start over if it can be avoided. Thanks.

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• SQL SERVER – Replace a Column Name in Multiple Stored Procedure all together

  - by pinaldave

  I receive a lot of emails every day. I try to answer each and every email and comments on Facebook and Twitter. I prefer communication on social media as this gives opportunities to others to read the questions and participate along with me. There is always some question which everyone likes to read and remember. Here is one of the questions which I received in email. I believe the same question will be there any many developers who are beginning with SQL Server. I decided to blog about it so everyone can read it and participate. “I am beginner in SQL Server. I have a very interesting situation and need your help. I am beginner to SQL Server and that is why I do not have access to the production server and I work entirely on the development server. The project I am working on is also in the infant stage as well. In product I had to create a multiple tables and every table had few columns. Later on I have written Stored Procedures using those tables. During a code review my manager has requested to change one of the column which I have used in the table. As per him the naming convention was not accurate. Now changing the columname in the table is not a big issue. I figured out that I can do it very quickly either using T-SQL script or SQL Server Management Studio. The real problem is that I have used this column in nearly 50+ stored procedure. This looks like a very mechanical task. I believe I can go and change it in nearly 50+ stored procedure but is there a better solution I can use. Someone suggested that I should just go ahead and find the text in system table and update it there. Is that safe solution? If not, what is your solution. In simple words, How to replace a column name in multiple stored procedure efficiently and quickly? Please help me here with keeping my experience and non-production server in mind.” Well, I found this question very interesting. Honestly I would have preferred if this question was asked on my social media handles (Facebook and Twitter) as I am very active there and quite often before I reach there other experts have already answered this question. Anyway I am now answering the same question on the blog so all of us can participate here and come up with an appropriate answer. Here is my answer - “My Friend, I do not advice to touch system table. Please do not go that route. It can be dangerous and not appropriate. The issue which you faced today is what I used to face in early career as well I still face it often. There are two sets of argument I have observed – there are people who see no value in the name of the object and name objects like obj1, obj2 etc. There are sets of people who carefully chose the name of the object where object name is self-explanatory and almost tells a story. I am not here to take any side in this blog post – so let me go to a quick solution for your problem. Note: Following should not be directly practiced on Production Server. It should be properly tested on development server and once it is validated they should be pushed to your production server with your existing deployment practice. The answer is here assuming you have regular stored procedures and you are working on the Development NON Production Server. Go to Server Note >> Databases >> DatabaseName >> Programmability >> Stored Procedure Now make sure that Object Explorer Details are open (if not open it by clicking F7). You will see the list of all the stored procedures there. Now you will see a list of all the stored procedures on the right side list. Select either all of them or the one which you believe are relevant to your query. Now… Right click on the stored procedures >> SELECT DROP and CREATE to >> Now select New Query Editor Window or Clipboard. Paste the complete script to a new window if you have selected Clipboard option. Now press Control+H which will bring up the Find and Replace Screen. In this screen insert the column to be replaced in the “Find What”box and new column name into “Replace With” box. Now execute the whole script. As we have selected DROP and CREATE to, it will created drop the old procedure and create the new one. Another method would do all the same procedure but instead of DROP and CREATE manually replace the CREATE word with ALTER world. There is a small advantage in doing this is that if due to any reason the error comes up which prevents the new stored procedure to be created you will have your old stored procedure in the system as it is. “ Well, this was my answer to the question which I have received. Do you see any other workaround or solution? Reference : Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Server Management Studio, SQL Stored Procedure, SQL Tips and Tricks, T SQL, Technology

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• What functionality does dynamic typing allow?

  - by Justin984

  I've been using python for a few days now and I think I understand the difference between dynamic and static typing. What I don't understand is under what circumstances it would be preferred. It is flexible and readable, but at the expense of more runtime checks and additional required unit testing. Aside from non-functional criteria like flexibility and readability, what reasons are there to choose dynamic typing? What can I do with dynamic typing that isn't possible otherwise? What specific code example can you think of that illustrates a concrete advantage of dynamic typing?

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• SpringSource rachète Rabbit Technologies, société à l'origine de la solution AMQP Rabbit MQ

  Et une acquisition de plus pour SpringSource ! Non content d'avoir déjà une bonne assise dans le domaine de messaging en employant plusieurs commiter sur ActiveMQ, SpringSource rachète aquiert Rabbit Technologies. Rabbit Technologies est la société derrière RabbitMQ, qui est une implémentation d'un serveur AMQP. Ce protocol, contraitement à JMS qui n'a pour objectif de fournir une API d'accès, à pour but de standardiser tout le système de messaging allant des différents mode de transmission au format de messages. Grâce à cela, tout serveurs compatibles AMQP peuvent commiquer entre eux, indépendamment du langage dans lequel ils sont implémenté ou le système sur lequel il tourne.

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• How to change System default language on GNOME3?

  - by Vor

  I just installed GNOME3 on my Ubuntu. Everything worked fine till I restarted computer. Then I received a message if I want to change folders name to some other (different language, don't know what is this, but looks like Chinese). I pressed, 'keep old names' but it still changed all my folder names! And also the rest of the names. (like settings, and all that staff). So if you can give me the direction on where to click (cause all English names changed to non-English) and I simply don't know what does any of them means!

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• How do I report a missing package dependency during an upgrade?

  - by crasic

  A friend of mine (somewhat new to linux) recently upgraded from 10.10 to 11.04 and his OS broke from the upgrade. A few minutes of troubleshooting showed that the culprit was the PAE kernel that the upgrade decided to install since it determined he had 4GB of phyisical RAM. More specifically the upgrade forgot to install the linux-headers-generic-pae required by the closed source nvidia drivers. I'm not entirely sure how to report this bug to the devs. Its an easy fix (after booting into the non-pae kernel and installing the package everything worked), but they are encouraging users to use the built-in bug reporting system and I'm not entirely certain how to report update bugs.

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• Why not Green Threads?

  - by redjamjar

  Whilst I know questions on this have been covered already (e.g. http://stackoverflow.com/questions/5713142/green-threads-vs-non-green-threads), I don't feel like I've got a satisfactory answer. The question is: why don't JVM's support green threads anymore? It says this on the code-style Java FAQ: A green thread refers to a mode of operation for the Java Virtual Machine (JVM) in which all code is executed in a single operating system thread. And this over on java.sun.com: The downside is that using green threads means system threads on Linux are not taken advantage of and so the Java virtual machine is not scalable when additional CPUs are added. It seems to me that the JVM could have a pool of system processes equal to the number of cores, and then run green threads on top of that. This could offer some big advantages when you have a very number large of threads which block often (mostly because current JVM's cap the number of threads). Thoughts?

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• Ubuntu 13.10 AdobeAIR application: Failed to load module "unity-gtk-module"

  - by nobuzz

  I have installed AdobeAIR on 13.10, but am getting the following error messages when using: Gtk-Message: Failed to load module "overlay-scrollbar" Gtk-Message: Failed to load module "unity-gtk-module" Has someone faced this issue. I looked at comment giving a possible resolution here , but that didn't help, as I already have those packages installed. Basically to install AdobeAIR, being a 32-bit, I had to install various i386 packages: libgtk2.0-0:i386 libnss3-1d:i386 libnspr4-0d:i386 lib32nss-mdns libxml2:i386 libxslt1.1:i386 When I run the program as root, it opens up properly without errors. But that is not an option. Could it be a problem that necessary modules are not getting loaded on non-root user's environment.

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• R2 and Idera Idera SQL Safe (Freeware Edition)

  - by DavidWimbush

  Good news: the Freeware edition of Idera SQL Safe works on R2. You might not care but I certainly do. Here's why:  In September last year I started using Idera SQL Safe (the Freeware Edition) to get backup compression on my SQL 2005 servers. It seemed like a good idea at the time - it was free and my backups ran much faster and took up much less disk space. I really thought I'd actually scored a free lunch. Until they discontinued the product. I was thinking about what to do when I heard that R2 Standard would include native backup compression so I've just been keeping my fingers crossed since then. So I installed R2 Developer on my laptop, installed SQL Safe and kicked off a restore with it. No problem. Phew! Now I won't have to do a special, non-compressed backup and restore when we migrate.

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• Happy 3rd Birthday SilverlightCream!

  - by Dave Campbell

  Happy 3rd Birthday!     Yesterday (May 16) was the 'Birthday' of SilverlightCream, which started just after MIX in 2007 with a post "Interesting Silverlight posts today: Silverlight Control & Silverlight Pad". Too many good posts flying around led me to want to archive them, particularly since I was being aggregated at a new site Silverlight.net, and I could give some of that 'reach' to the community. Saturday's post was number 862, and as of that post, there were 5697 blog posts archived in the database all tagged up and searchable at SilverlightCream.com using the search page. The search needs to be better, and that's another discussion, but it does work. The blog didn't begin life as the SilverlightCream blog, as is obvious from the name, but once I realized people were following it closely, I've tried to keep the signal-to-noise ratio very high. I even secured another blog for when I just want to rant about something to keep that stuff out of this one :) If you've been around since MIX07 days you've heard all this, but after talking to some people at MIX10 I realized not everyone knows all the ways the information is presented, so I figured doing a post like this once a year probably isn't a bad idea :) I scrounge through an ever-growing list of blogs (right now sitting at 505) looking for good stuff. I try to spin through the list every day, but with the list growing that large, it's getting tough. I usually use it as a background task while working or watching TV. If I just sit and go through the blogs it takes about an hour. The list is long enough now that from time to time, I'll only get partway through it and have 10 to 13 entries, so I'll just stop there and go on the next day... I don't like to have more than 15 in any single post. It's all pattern recognition as in "seen that", "seen that", "that's new", etc... so if you're a blogger, look at a heading below for some comments about blogging from my perspective. When I see something new, I make sure you're not pulling a 'Mike Taulty' on me and dumping 6 or 8 new posts in one day :), and I tag the ones I want to review. If there's not a lot going on, I may just push the posts as I come across them. Some days there may be 60 posts in that 'to review' list! Some are non-Silverlight, some are essentially duplicates of others, some are demos, ads, new releases of something, session materials, etc. I push lots of material into a database at WynApse.com, and the "Tagged Posts" menu on the left sidebar there takes you to a tag cloud of (at this very moment) "9224 articles tagged 13915 different ways using 459 unique tags". There are links in there on Gibson guitars, Jazz Guitar instructional stuff, Ford F-250 links, and tons of technical and non-technical stuff I've been aggregating for about 5 years now. So when I decide to blog (or shoutout) something, I first push it into the database at WynApse.com. Then I tag it all up and push it into the database at SilverlightCream.com. Then it gets pushed to @SilverlightNews. For a little over a year now, we're tracking unique IP hits on posts launched from either the blog post or from one of the SilverlightCream.com pages, and the posts with top hits from unique IP addresses in the last 7 days are displayed in a 'Skim' page at SilverlightCream... and that page needs work as well. The Skim page and tracking was the brainchild of my buddy Michael Washington. What I blog/shoutout After some time doing posts, I decided there were things that probably have no need to be searchable, but are good information, so I post those as 'Shoutouts'. Eventually I also decided the Shoutouts should get posted to @SilverlightNews, and that's now taking place. Notes to bloggers Remember I said spinning throught the Big List-o-BlogsTM is pattern recognition... that means I don't spend a lot of time on any individual blog deciding if it has new content. If you're familiar with the term 'Above the Fold', then you're probably ok. If I have to scroll the page to see if there's something new, or wade through some maze of menus, I'm probably going to miss new stuff. Likewise if you only show the latest on the front page and make it a puzzle to find the rest of them, or if you make the titles and initial graphics almost identical to the previous article, I'll miss it. Another thing is name/brand-recognition. Far be it for me (WynApse) to comment on someone blogging with a pseudonym, but if you want to get get some recognition, you are going to want your name to be available somewhere. I can think right off the top of my head of a couple good blogs that I have no idea of the individuals' real names. I can pull that off a bit because I've been around so long almost everyone knows who I am, but if you're new to the blog-o-sphere, being able to be name-recognized is as important as getting your brand out there. Kick my tires Finally, stuff happens... I may hit the wrong key and delete your blog, or a post might slip past me and I not realize it's new because of the naming, and never blog it. If you think I missed something, send me an email or use the submit page at SilverlightCream.com. Some bloggers have figured out that if they submit (one way or another) to me, their posts will go out next. I try to honor anyone that takes the time to submit with a quicker 'Cream posting. Thanks! Finally, thanks to everyone that contributes to the community as a whole... the blogs, the videos, and the presentations. A special thanks to everyone that reads SilverlightCream, or follows @WynApse or @SilverlightNews. Keep it all coming, and... Stay in the 'Light

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