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• How do I learn algorithms?

  - by Panthe

  Brief History: Just graduated high school, learned a bit of python and C++, have no friends with any helpful computer knowledge at all. Out of anyone i met in my school years I was probably the biggest nerd, but no one really knew. I consider my self to have a vast amount of knowledge on computers and tech then the average person. built/fixed tons of computers, and ability to troubleshoot pretty much any problem I came across. Now that high school is over, Ive really been thinking about my career. Loving, living computers for the past 15 years of my life I decided to take my ability's and try to learn computer programming, why I didn't start earlier I don't know, seems to be big mistake on my part... Doing some research I concluded that Python was the first programming language I should learn, since it was high level and easier to understand then C++ and Java. I also knew that to become good at what I did I needed to know more then just 2 or 3 languages, which didn't seem like a big problem considering once I learned the way Python worked, mainly syntax changed, and the rest would come naturally. I watched a couple of youtube videos, downloaded some book pdf's and snooped around from some tutorials here and there to get the hang of what to do. A two solid weeks had passed of trying to understand the syntax, create small programs that used the basic functions and understanding how it worked, I think i have got the hang of it. It breaks down into what ive been dealing with all this time (although i kinda knew) is that, input,output, loops, functions and other things derived from 0's and 1's storing data and recalling it, ect. (A VERY BASIC IDEA). Ive been able to create small programs, Hangman, file storing, temperature conversion, Caeser Cipher decode/encoding, Fibonacci Sequence and more, which i can create and understand how each work. Being 2 weeks into this, I have learned alot. Nothing at all compared to what i should be lear ning in the years to come if i get a grip on what I'm doing. While doing these programs I wont stop untill I've done doing a practice problem on a book, which embarresing enough will take me a couple hour depending on the complexity of it. I absolutly will not put aside the challenge until its complete, WHICH CAN BE EXTREMELY DRAINING, ive tried most problems without cheating and reached success, which makes me feel extremely proud of my self after completing something after much trial and error. After all this I have met the demon, alogrithm's which seem to be key to effiecent code. I cant seem to rap my head around some of the computer codes people put out there using numbers, and sometimes even basic functions, I have been able to understand them after a while but i know there are alot more complex things to come, considering my self smart, functions that require complex codes, actually hurt my brain. NOTHING EVER IN LIFE HURT MY BRAIN....... not even math classes in highschool, trying to understand some of the stuff people put out there makes me feel like i have a mental disadvantage lol... i still walk forward though, crossing my fingers that the understanding will come with time. Sorry if is this is long i just wish someone takes all these things into consideration when answering my question. even through all these downsides im still pushing through and continuing to try and get good at this, i know reading these tutorials wont make me any good unless i can become creative and make my own, understand other peoples programs, so this leads me to the simple question i could have asked in the beginning..... WHERE IN THE WORLD DO I START ? Ive been trying to find out how to understand some of the open source projects, how i can work with experianced coders to learn from them and help them, but i dont think thats even possible by the way how far people's knowledge is compared to me, i have no freinds who i can learn from, can someone help me and guide me into the right direction.. i have a huge motivation to get good at coding, anything information would be extremely helpful

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• C#: The input stream is not a valid binary format.

  - by Mcoroklo

  I have a problem with deserializing in C#/ASP.NET, which gives the exact error: The input stream is not a valid binary format. The starting contents (in bytes) are: 41-41-45-41-41-41-44-2F-2F-2F-2F-2F-41-51-41-41-41 ... What I am trying to do I have a structure with 3 classes. I have a class A which is a base class, and then class B and C which are derived from A. I am trying to store random types of B and C in the database using LINQ to SQL, in a column with the type VARCHAR(MAX). I cannot use BINARY as the length is around 15.000. My code... Error is in the LAST codeblock C# Code in Business layer- Storing a record private void AddTraceToDatabase(FightTrace trace) { MemoryStream recieverStream = new MemoryStream(); MemoryStream firedStream = new MemoryStream(); MemoryStream moveStream = new MemoryStream(); BinaryFormatter binaryFormatter = new BinaryFormatter(); binaryFormatter.Serialize(recieverStream,trace.Reciever); binaryFormatter.Serialize(firedStream,trace.FiredBy); binaryFormatter.Serialize(moveStream,trace.Move); string reciever = Convert.ToBase64String(recieverStream.ToArray()); string fired = Convert.ToBase64String(firedStream.ToArray()); string move = Convert.ToBase64String(moveStream.ToArray()); this.dataAccess.AddFightTrace(trace.TraceType.ToString(),reciever,move,fired,trace.DateTime,this.FightId); } C# Code in Data access layer - Storing a record public void AddFightTrace(string type, string reciever, string Move, string firedBy, DateTime firedAt, int fightid) { GameDataContext db = new GameDataContext(); dbFightTrace trace = new dbFightTrace(); trace.TraceType = type; trace.Reciever = reciever; trace.Move = Move; trace.FiredBy = firedBy; trace.FiredAt = firedAt; trace.FightId = fightid; db.dbFightTraces.InsertOnSubmit(trace); db.SubmitChanges(); } C# Code getting the entry in the database public List<dbFightTrace> GetNewTraces(int fightid, DateTime lastUpdate) { GameDataContext db = new GameDataContext(); var data = from d in db.dbFightTraces where d.FightId==fightid && d.FiredAt > lastUpdate select d; return data.ToList(); } C# Factory, converting from LINQ to SQL class to my objects THIS IS HERE THE ERROR COMES public FightTrace CreateTrace(dbFightTrace trace) { TraceType traceType = (TraceType) Enum.Parse(typeof(TraceType), trace.TraceType); BinaryFormatter formatter = new BinaryFormatter(); System.Text.UTF8Encoding enc = new System.Text.UTF8Encoding(); MemoryStream recieverStream = new MemoryStream(enc.GetBytes(trace.Reciever)); recieverStream.Position = 0; MemoryStream firedStream = new MemoryStream(enc.GetBytes(trace.FiredBy)); firedStream.Position = 0; MemoryStream movedStream = new MemoryStream(enc.GetBytes(trace.Move)); movedStream.Position = 0; // THE NEXT LINE HERE CAUSES THE ERROR NPC reciever = formatter.Deserialize(recieverStream) as NPC; Player fired = formatter.Deserialize(firedStream) as Player; BaseAttack attack = formatter.Deserialize(movedStream) as BaseAttack; FightTrace t = new FightTrace(traceType,reciever,attack,fired); t.TraceId = trace.FightTraceId; t.DateTime = trace.FiredAt; return t; } So the error happends when the first Deserialize method is run, with the above error. I have tried several things but I am quite lost on this one.. Thanks! :-)

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• MVC multi page form losing session

  - by Bryan

  I have a multi-page form that's used to collect leads. There are multiple versions of the same form that we call campaigns. Some campaigns are 3 page forms, others are 2 pages, some are 1 page. They all share the same lead model and campaign controller, etc. There is 1 action for controlling the flow of the campaigns, and a separate action for submitting all the lead information into the database. I cannot reproduce this locally, and there are checks in place to ensure users can't skip pages. Session mode is InProc. This runs after every POST action which stores the values in session: protected override void OnActionExecuted(ActionExecutedContext filterContext) { base.OnActionExecuted(filterContext); if (this.Request.RequestType == System.Net.WebRequestMethods.Http.Post && this._Lead != null) ParentStore.Lead = this._Lead; } This is the Lead property within the controller: private Lead _Lead; /// <summary> /// Gets the session stored Lead model. /// </summary> /// <value>The Lead model stored in session.</value> protected Lead Lead { get { if (this._Lead == null) this._Lead = ParentStore.Lead; return this._Lead; } } ParentStore class: public static class ParentStore { internal static Lead Lead { get { return SessionStore.Get<Lead>(Constants.Session.Lead, new Lead()); } set { SessionStore.Set(Constants.Session.Lead, value); } } Campaign POST action: [HttpPost] public virtual ActionResult Campaign(Lead lead, string campaign, int page) { if (this.Session.IsNewSession) return RedirectToAction("Campaign", new { campaign = campaign, page = 0 }); if (ModelState.IsValid == false) return View(GetCampaignView(campaign, page), this.Lead); TrackLead(this.Lead, campaign, page, LeadType.Shared); return RedirectToAction("Campaign", new { campaign = campaign, page = ++page }); } The problem is occuring between the above action, and before the following Submit action executes: [HttpPost] public virtual ActionResult Submit(Lead lead, string campaign, int page) { if (this.Session.IsNewSession || this.Lead.Submitted || !this.LeadExists) return RedirectToAction("Campaign", new { campaign = campaign, page = 0 }); lead.AddCustomQuestions(); MergeLead(campaign, lead, this.AdditionalQuestionsType, false); if (ModelState.IsValid == false) return View(GetCampaignView(campaign, page), this.Lead); var sharedLead = this.Lead.ToSharedLead(Request.Form.ToQueryString(false)); //Error occurs here and sends me an email with whatever values are in the form collection. EAUtility.ProcessLeadProxy.SubmitSharedLead(sharedLead); this.Lead.Submitted = true; VisitorTracker.DisplayConfirmationPixel = true; TrackLead(this.Lead, campaign, page, LeadType.Shared); return RedirectToAction(this.ConfirmationView); } Every visitor to our site gets a unique GUID visitorID. But when these error occurs there is a different visitorID between the Campaign POST and the Submit POST. Because we track each form submission via the TrackLead() method during campaign and submit actions I can see session is being lost between calls, despite the OnActionExecuted firing after every POST and storing the form in session. So when there are errors, we get half the form under one visitorID and the remainder of the form under a different visitorID. Luckily we use a third party service which sends an API call every time a form value changes which uses it's own ID. These IDs are consistent between the first half of the form, and the remainder of the form, and the only way I can save the leads from the lost session issues. I should also note that this works fine 99% of the time. EDIT: I've modified my code to explicitly store my lead object in TempData and used the TempData.Keep() method to persist the object between subsequent requests. I've only deployed this behavior to 1 of my 3 sites but so far so good. I had also tried storing my lead objects in Session directly in the controller action i.e., Session.Add("lead", this._Lead); which uses HTTPSessionStateBase, attempting to circumvent the wrapper class, instead of HttpContext.Current.Session which uses HTTPSessionState. This modification made no difference on the issue, as expected.

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• Need a solution to store images (1 billion, 1000,000,000) which users will upload to a website via php or javascript upload [on hold]

  - by wish_you_all_peace

  I need a solution to store images (1 billion) which users will upload to a website via PHP or Javascript upload (website will have 1 billion page views a month using Linux Debian distros) assuming 20 photos per user maximum (10 thumbnails of size 90px by 90px and 10 large, script resized images of having maximum width 500px or maximum height 500px depending on shape of image, meaning square, rectangle, horizontal, vertical etc). Assume this to be a LEMP-stack (Linux Nginx MySQL PHP) social-media or social-matchmaking type application whose content will be text and images. Since everyone knows storing tons of images (website users uploaded images in this case) are bad inside a single directory or NFS etc, please explain all the details about the architecture and configuration of the entire setup of storage solution, to store 1 billion images on any method you recommend (no third-party cloud storage like S3 etc. It has to be within the private data center using our own hardware and resources.). The solution has to include both the storage solution and organizing the images uploaded by users. How will we organize the users images if a single user will not have more than 20 images (10 thumbs and 10 large of having either width or height 500px)? Please consider that this has to be organized in a structural way so we can fetch a single user's images via PHP/Javascript or API programmatically through some type of user's unique identifier(s).

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• What approaches exist to setting up continent/country/city drop down menus?

  - by Dave

  How easy (or difficult) is it to have a Continent/Country/City drop down menu? Where one select from Drop Down Menus (for example): 1 - Europe 2 - UK 3 - London and then writes the Province/Area (for example: Essex). Realistically, how long should it take an experienced web developer to write the code of the above, as well as to link this selection to a Browse function and database storing? I do not have a geographical database yet and I am wondering what the fastest and cheapest way to add it to the drop down menu is. Is there any way to get that geographical database for free? I can see this type of geographical drop down menu in thousands of websites, but I am struggling as to how to implement it ASAP. Follow Up: Tks All x your answers and comments so far. I hear what you are saying. I understand that there are rare occasions of Countries with multiple (same) name Cities and that it might be disputable whether a Country belongs to a certain Continent/Region or not (see Russia x example, Europe or Asia?). Anyway, please take a look, for instance, at this website Sign UP screen http://www.couchsurfing.org/register.html My question then is: Where do I get that list (Country/Cities) and how do I create that _array? Manually copying it somewhere else (which would take me ages) or are there ready made lists that can be downloaded from somewhere for free?

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• Pinterest and Social Commerce: The Social Networking Site Retailers Shouldn’t Ignore

  - by Jeri Kelley

  If you are in the midst of remodeling your home, researching the latest spring fashion trends, or simply trying to figure out what to cook for dinner you’ve probably been on Pinterest, and like me, find it extremely useful for generating new ideas and storing them all in one place. Gone are the days of folding over corners of magazines or bookmarking the URL of a Web page – Pinterest makes it easy for you to “pin” ideas, photos, links, and more to virtual bulletin boards where your “followers” can repin, like, and share. As a consumer, Pinterest has gained my attention and I’m definitely not the only one. According to a Monetate infographic, Pinterest’s unique visitors increased 329% from September to December 2011. With this explosion of users, what does it mean for social commerce? Also according to Monetate, Pinterest is one of the top traffic drivers for retailers – driving even more traffic than popular social networking sites like Google+.  For businesses, creating a presence on Pinterest is a great way to extend the reach of your brand, increase inbound links, and drive more traffic to your site. Socialnomics has a great post on how some of the biggest retail brands are using Pinterest to connect with consumers, offer cool content, and engage on a more personal level. When evaluating your social commerce program, while Facebook still delivers the most referrals, Pinterest shouldn’t be ignored as a way to help reach and connect with as many consumers as possible.

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• Z axis in isometric tilemap

  - by gyhgowvi

  I'm experimenting with isometric tile maps in JavaScript and HTML5 Canvas. I'm storing tile map data in JavaScript 2D array. // 0 - Grass // 1 - Dirt // ... var mapData = [ [0, 0, 0, 0, 0], [0, 0, 1, 0, 0, ... ] and draw for(var i = 0; i < mapData.length; i++) { for(var j = 0; j < mapData[i].length; j++) { var p = iso2screen(i, j, 0); // X, Y, Z context.drawImage(tileArray[mapData[i][j]], p.x, p.y); } } but this function mean's all tile Z axis is equal to zero. var p = iso2screen(i, j, 0); Maybe anyone have idea and how to do something like mapData[0][0] Z axis equal to 3 mapData[5][5] Z axis equal to 5? I have idea: Write function for grass, dirt and store this function to 2D array and draw and later mapData[0][0].setZ(3); But it is good idea to write functions for each tiles?

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• BAD ARCHIVE MIRROR using PXE BOOT method

  - by omkar

  i m trying to automatically install UBUNTU on a client PC by using the method of PXE BOOT method....my Objectives are below:- i m following the steps given in this link installation using PXE BOOT 1:-the server will have a KICKSTART config file which contains the parameters for the OS installation and the files which are required for the OS installations. 2:-the client will have to detect this configuration along with the setup files and complete the installation without any input from the user. In my server i have installed DHCP3-server,Apache2 and TFTP for helping me with the installation. i have nearly achieved my first objective,i m able to boot my client using the files stored in the server,but during the installation stage it is asking me to "CHOOSE A MIRROR of UBUNTU ARCHIVE".i gave the server's IP address and the path in the server where the files are located but then too its giving me error "BAD ARCHIVE MIRROR". so is it possible that instead of downloading all the files from the internet and storing them on my disk , can i use the files which comes with the UBUNTU-CD, and how to store this files in what format (should i zip them ) on the disk. secondly i am also generating the ks.cfg which i wanted to give to the client for automatic installation of the OS ,so how should the configuration file be given to the installation process.

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• .NET Weak Event Handlers – Part II

  - by João Angelo

  On the first part of this article I showed two possible ways to create weak event handlers. One using reflection and the other using a delegate. For this performance analysis we will further differentiate between creating a delegate by providing the type of the listener at compile time (Explicit Delegate) vs creating the delegate with the type of the listener being only obtained at runtime (Implicit Delegate). As expected, the performance between reflection/delegate differ significantly. With the reflection based approach, creating a weak event handler is just storing a MethodInfo reference while with the delegate based approach there is the need to create the delegate which will be invoked later. So, at creating the weak event handler reflection clearly wins, but what about when the handler is invoked. No surprises there, performing a call through reflection every time a handler is invoked is costly. In conclusion, if you want good performance when creating handlers that only sporadically get triggered use reflection, otherwise use the delegate based approach. The explicit delegate approach always wins against the implicit delegate, but I find the syntax for the latter much more intuitive. // Implicit delegate - The listener type is inferred at runtime from the handler parameter public static EventHandler WrapInDelegateCall(EventHandler handler); public static EventHandler<TArgs> WrapInDelegateCall<TArgs>(EventHandler<TArgs> handler) where TArgs : EventArgs; // Explicite delegate - TListener is the type that defines the handler public static EventHandler WrapInDelegateCall<TListener>(EventHandler handler); public static EventHandler<TArgs> WrapInDelegateCall<TArgs, TListener>(EventHandler<TArgs> handler) where TArgs : EventArgs;

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• Inside Amazon’s Warehouses

  - by Jason Fitzpatrick

  If you’re expecting the inside of Amazon’s warehouses to be some sort of rigidly organized robot-filled warehouse of tomorrow, you’ll be quite surprised to find that storage technique they employ is called “chaotic storage”. International Business Times paid a visit to a major Amazon warehouse and took a tour. Rather than finding robots they found: Amazon must rely on barcodes and human hands to find the ordered items and drop them into the proper bins — without robots, Amazon utilizes a system known as “chaotic storage,” where products are essentially shelved at random. By storing items randomly instead of categorically, the warehouse has a much better flow of material. Even without robots or automation, Amazon can compile a “picking list” where each item needs to be taken off the shelf and scanned again before it can be shipped. The real advantage to chaotic storage is that it’s significantly more flexible than conventional storage systems. If there are big changes in a product range, the company doesn’t need to plan for more space, because the products or their sales volumes don’t need to be known or planned in advance if they’re simply being stored at random. HTG Explains: Does Your Android Phone Need an Antivirus? How To Use USB Drives With the Nexus 7 and Other Android Devices Why Does 64-Bit Windows Need a Separate “Program Files (x86)” Folder?

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• Thread Synchronization and Synchronization Primitives

  When considering synchronization in an application, the decision truly depends on what the application and its worker threads are going to do. I would use synchronization if two or more threads could possibly manipulate the same instance of an object at the same time. An example of this in C# can be demonstrated through the use of storing data in a static object. A static object is initialized once per application and the data within the object can be accessed by all threads. I would use the synchronization primitives to prevent any data from being manipulated by multiple threads simultaneously. This would reduce any data corruption from occurring within the object. On the other hand if all the threads used non static objects and were independent of the other tasks there would be no need to use synchronization. Synchronization Primitives in C#: Basic Blocking Locking Signaling Non-Blocking Synchronization Constructs The Basic Blocking methods include Sleep, Join, and Task.Wait.  These methods force threads to wait until other threads have completed. In addition, these methods can also force a thread to wait a set amount of time before continuing to work.   The Locking primitive prevents a thread from entering a critical section of code while another thread is in the same critical section.  If another thread attempts to enter a locked code, it will wait, until the code block is released. The Signaling primitive allows a thread to temporarily pause work until receiving a notification from another thread that it is ok to continue working. The Signaling primitive removes the need for polling.The Non-Blocking Synchronization Constructs protect access to a common field by calling upon processor primitives.

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• REST: How to store and reuse REST call queries

  - by Jason Holland

  I'm learning C# by programming a real monstrosity of an application for personal use. Part of my application uses several SPARQL queries like so: const string ArtistByRdfsLabel = @" PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#> SELECT DISTINCT ?artist WHERE {{ {{ ?artist rdf:type <http://dbpedia.org/ontology/MusicalArtist> . ?artist rdfs:label ?rdfsLabel . }} UNION {{ ?artist rdf:type <http://dbpedia.org/ontology/Band> . ?artist rdfs:label ?rdfsLabel . }} FILTER ( str(?rdfsLabel) = '{0}' ) }}"; string Query = String.Format(ArtistByRdfsLabel, Artist); I don't like the idea of keeping all these queries in the same class that I'm using them in so I thought I would just move them into their own dedicated class to remove clutter in my RestClient class. I'm used to working with SQL Server and just wrapping every query in a stored procedure but since this is not SQL Server I'm scratching my head on what would be the best for these SPARQL queries. Are there any better approaches to storing these queries using any special C# language features (or general, non C# specific, approaches) that I may not already know about? EDIT: Really, these SPARQL queries aren't anything special. Just blobs of text that I later want to grab, insert some parameters into via String.Format and send in a REST call. I suppose you could think of them the same as any SQL query that is kept in the application layer, I just never practiced keeping SQL queries in the application layer so I'm wondering if there are any "standard" practices with this type of thing.

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• Allen for Umbraco with location EXIF meta data

  - by Vizioz Limited

  The latest version of Allen for Umbraco has now hit the Apple App store, we have managed to add some nice improvements to this version that include:Storing location and direction information when photos are taken within the AppEmbedding EXIF data into the images when they are uploadBackground UploadingPull to refresh the media tree Location and DirectionBy default when the camera is used within an application the location and direction that the camera is pointing is not stored within the image meta data. We have now added full support so that this data is now added. We have added a setting which allows you to prevent this data from being uploaded to your website if you do not want the location data to be sent you can turn it off within Allen, Note: Please don't forget that location services do need to be turned on to allow the app to access the images in the phone's asset library.We have had quite a few ideas from users already for using this location data, including logging free parking in Denmark to geo-tagging holiday photos and linking the photos to Google street view. Embedding EXIF dataWe now embed all the meta data available on the iPhone into the image when it is uploaded to your server, this allows you to pull the data out and use it within your site. Have a look at Cultiv's Photo Meta Data package for great example code that allows you to automatically pull this data out and populate properties on your Umbraco media item.We slightly modified the source code of this package to allow the package to always extract the image data, as the default package requires a property to allow the data to be extracted, it's an easy change, if you get stuck add a comment to this post. Background UploadingIf you try to upload multiple images and need to start doing something else on your phone, you can now click the home button and the application will continue to upload your images in the background. As soon as it has finished you will receive a standard Apple notification. Pull to RefreshOur final enhancement has been to add "Pull to refresh" to the media trees, just pull the tree downwards with your finger and it will refresh, this is useful if you are adding items to your media tree while testing your site with Allen for Umbraco. Future enhancements.. your ideas?If you have any ideas for future enhancement feel free to add a comment below!

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• The C++ Standard Template Library as a BDB Database (part 1)

  - by Gregory Burd

  If you've used C++ you undoubtedly have used the Standard Template Libraries. Designed for in-memory management of data and collections of data this is a core aspect of all C++ programs. Berkeley DB is a database library with a variety of APIs designed to ease development, one of those APIs extends and makes use of the STL for persistent, transactional data storage. dbstl is an STL standard compatible API for Berkeley DB. You can make use of Berkeley DB via this API as if you are using C++ STL classes, and still make full use of Berkeley DB features. Being an STL library backed by a database, there are some important and useful features that dbstl can provide, while the C++ STL library can't. The following are a few typical use cases to use the dbstl extensions to the C++ STL for data storage. When data exceeds available physical memory.Berkeley DB dbstl can vastly improve performance when managing a dataset which is larger than available memory. Performance suffers when the data can't reside in memory because the OS is forced to use virtual memory and swap pages of memory to disk. Switching to BDB's dbstl improves performance while allowing you to keep using STL containers. When you need concurrent access to C++ STL containers.Few existing C++ STL implementations support concurrent access (create/read/update/delete) within a container, at best you'll find support for accessing different containers of the same type concurrently. With the Berkeley DB dbstl implementation you can concurrently access your data from multiple threads or processes with confidence in the outcome. When your objects are your database.You want to have object persistence in your application, and store objects in a database, and use the objects across different runs of your application without having to translate them to/from SQL. The dbstl is capable of storing complicated objects, even those not located on a continous chunk of memory space, directly to disk without any unnecessary overhead. These are a few reasons why you should consider using Berkeley DB's C++ STL support for your embedded database application. In the next few blog posts I'll show you a few examples of this approach, it's easy to use and easy to learn.

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• Keep basic game physics separate from basic game object? [on hold]

  - by metamorphosis

  If anybody has dealt with a similar situation I'd be interested in your experience/wisdom, I'm developing a 2D game library in C++, I have game objects which have very basic physics, they also have movement classes attached to differing states, for example, a different movement type based on whether the character is jumping, on ice, whatever. In terms of storing velocity and acceleration impulses, are they best held by the object? Or by the associated movement class? The reason I ask is that I can see advantages to both approaches- if you store physics data in the movement class, you have to pass physics information between class instances when a state change occurs (ie. impulses, gravity etc) but the class has total control over whether those physics are updated or not. An obvious example of how this would be useful was if an object was affected by something which caused it to ignore gravity, or something like that. on the other hand if you store the physics data in the object class, it feels more logical, you don't have to go around passing physics impulses and gravity etc, however the control that the movement class has over the object's physics becomes more convoluted. Basically the difference is between: object->physics stacks (acceleration impulses etc) ->physics functions ->movement type <-movement type makes physics function calls through object and object->movement type->physics stacks ->physics functions ->object forwards external physics calls onto movement type ->object transfers physics stacks between movement types when state change occurs Are there best practices here?

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• SQL SERVER – Cleaning Up SQL Server Indexes – Defragmentation, Fillfactor – Video

  - by pinaldave

  Storing data non-contiguously on disk is known as fragmentation. Before learning to eliminate fragmentation, you should have a clear understanding of the types of fragmentation. When records are stored non-contiguously inside the page, then it is called internal fragmentation. When on disk, the physical storage of pages and extents is not contiguous. We can get both types of fragmentation using the DMV: sys.dm_db_index_physical_stats. Here is the generic advice for reducing the fragmentation. If avg_fragmentation_in_percent > 5% and < 30%, then use ALTER INDEX REORGANIZE: This statement is replacement for DBCC INDEXDEFRAG to reorder the leaf level pages of the index in a logical order. As this is an online operation, the index is available while the statement is running. If avg_fragmentation_in_percent > 30%, then use ALTER INDEX REBUILD: This is replacement for DBCC DBREINDEX to rebuild the index online or offline. In such case, we can also use the drop and re-create index method.(Ref: MSDN) Here is quick video which covers many of the above mentioned topics. While Vinod and I were planning about Indexing course, we had plenty of fun and learning. We often recording few of our statement and just left it aside. Afterwords we thought it will be really funny Here is funny video shot by Vinod and Myself on the same subject: Here is the link to the SQL Server Performance:  Indexing Basics. Here is the additional reading material on the same subject: SQL SERVER – Fragmentation – Detect Fragmentation and Eliminate Fragmentation SQL SERVER – 2005 – Display Fragmentation Information of Data and Indexes of Database Table SQL SERVER – De-fragmentation of Database at Operating System to Improve Performance Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Index, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology, Video

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• Overriding GetHashCode in a mutable struct - What NOT to do?

  - by Kyle Baran

  I am using the XNA Framework to make a learning project. It has a Point struct which exposes an X and Y value; for the purpose of optimization, it breaks the rules for proper struct design, since its a mutable struct. As Marc Gravell, John Skeet, and Eric Lippert point out in their respective posts about GetHashCode() (which Point overrides), this is a rather bad thing, since if an object's values change while its contained in a hashmap (ie, LINQ queries), it can become "lost". However, I am making my own Point3D struct, following the design of Point as a guideline. Thus, it too is a mutable struct which overrides GetHashCode(). The only difference is that mine exposes and int for X, Y, and Z values, but is fundamentally the same. The signatures are below: public struct Point3D : IEquatable<Point3D> { public int X; public int Y; public int Z; public static bool operator !=(Point3D a, Point3D b) { } public static bool operator ==(Point3D a, Point3D b) { } public Point3D Zero { get; } public override int GetHashCode() { } public override bool Equals(object obj) { } public bool Equals(Point3D other) { } public override string ToString() { } } I have tried to break my struct in the way they describe, namely by storing it in a List<Point3D>, as well as changing the value via a method using ref, but I did not encounter they behavior they warn about (maybe a pointer might allow me to break it?). Am I being too cautious in my approach, or should I be okay to use it as is?

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• Making a full-screen animation on Android? Should I use OPENGL?

  - by Roger Travis

  Say I need to make several full-screen animation that would consist of about 500+ frames each, similar to the TalkingTom app ( https://play.google.com/store/apps/details?id=com.outfit7.talkingtom2free ). Animation should be playing at a reasonable speed - supposedly not less, then 20fps - and pictures should be of a reasonable quality, not overly compressed. What method do you think should I use? So far I tried: storing each frame as a compressed JPEG before animation starts, loading each frame into a byteArray as the animation plays, decode corresponding byteArray into a bitmap and draw it on a surface view. Problem - speed is too low, usually about 5-10 FPS. I have thought of two other options. turning all animations into one movie file... but I guess there might be problems with starting, pausing and seeking to the exactly right frame... what do you think? another option I thought about was using OPENGL ( while I never worked with it before ), to play animation frame by frame. What do you think, would opengl be able to handle it? Thanks!

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• Silverlight Cream for June 09, 2010 -- #878

  - by Dave Campbell

  In this Issue: Andrea Boschin, Emiel Jongerius, Anton Polimenov, Andrew Veresov, SilverLaw, RoboBlob, Brandon Watson, and Charlie Kindel. From SilverlightCream.com: Implementing network protocol easily with a generic SocketClient Andrea Boschin has a post up at SilverlightShow about the SocketClient class and how to use it to implement a POP3 client ... source project included Passing parameters to a Silverlight XAP application Emiel Jongerius describes the two ways to pass parameters to your Silverlight app, with detailed code examples. WP7: What is Windows Phone 7 Anton Polimenov is beginning a WP7 series at SilvelightShow with this backgrounder article. I'm not sure where all of the info came from, but it's an interesting starter. Initialization State Manager Andrew Veresov has a post up discussing storing and managing state in your Silverlight app. The code isn't ready for prime time but it's available. How To Rotate A Regular Silverlight 3 and 4 ChildWindow SilverLaw responds to a forum post about rotating a child window. He's got a Silverlight 3 version on Expression Gallery, and describes the same in Silverlight 4 in this post. Silverlight MergedDictionaries – using styles and resources from Class Libraries RoboBlob has a very clearly-written post up about merged dictionaries, all the things possible with them, and all the code for the project. New Policies for Next Gen Windows Phone Marketplace Brandon Watson has an article up discussing the WP7 phone Marketplace. Lots of specifics and links out to more info... a definite read. Hey, You, Get Off of My Cloud Charlie Kindel has a post up describing the concept of a beta distribution channel through the WP7 Marketplace... another definite read. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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• Lucene and .NET Part I

  - by javarg

  I’ve playing around with Lucene.NET and trying to get a feeling of what was required to develop and implement a full business application using it. As you would imagine, many things are required for you to implement a robust solution for indexing content and searching it afterwards. Lucene is a great and robust solution for indexing content. It offers fast and performance enhanced search engine library available in Java and .NET. You will want to use this library in many particular scenarios: In Windows Azure, to support Full Text Search (a functionality not currently supported by SQL Azure) When storing files outside or not managed by your database (like in large document storage solutions that uses File System) When Full Text Search is not really what you need Lucene is more than a Full Text Search solution. It has several analyzers that let you process and search content in different ways (decomposing sentences, deriving words, removing articles, etc.). When deciding to implement indexing using Lucene, you will need to take into account the following: How content is to be indexed by Lucene and when. Using a service that runs after a specific interval Immediately when content changes When content is to available for searching / Availability of indexed content (as in real time content search) Immediately when content changes = near real time searching After a few minutes.. Ease of maintainability and development Some Technical Concerns.. When indexing content, indexes are locked for writing operations by the Index Writer. This means that Lucene is best designed to index content using single writer approach. When searching, Index Readers take a snapshot of indexes. This has the following implications: Setting up an index reader is a costly task. Your are not supposed to create one for each query or search. A good practice is to create readers and reuse them for several searches. The latter means that even when the content gets updated, you wont be able to see the changes. You will need to recycle the reader. In the second part of this post we will review some alternatives and design considerations.

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• /planes and /clubs or /wiki/planes and /wiki/clubs

  - by Jelmer

  I am currently working on a nice application about which I can't share all the details, but it will have some sort of a wiki part. In this wiki, you will be able to change the planes as well as the clubs, maybe in the future it will be possible to change the countries and manufacturers as well. But I have to think about this and I have to check how good this is. But, you will understand that it has to be expendable! That is really important. Use the planes controller with a edit page and the same for the clubs Route the planes and clubs controller to the wiki controller, so we have 1 nice "path" to edit this stuff. I want to have it called wiki that is for sure. Because that is what it is, but I am storing the planes and clubs data in its down table in my database. I think that is kinda obvious since it has to be maintainable. Right now you could edit a plane via the url: example.com/wiki/planes/edit/Duo_Discus.html Do you think that is better than example.com/planes/edit/Duo_Discus.html since it is easy to understand for the user, that he is working in the wiki instead of in the planes ? Or do you think this will break the user experience?

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• SkyDrive and Consumer Cloud Services

  - by Tim Murphy

  Paul Thurrrott recently posted an article on the future of SkyDrive and I was asked what I thought about its future by @UserCommunity.  So let’s take a look. The breakdown from Microsoft that Paul described I believe is an accurate representation of users and usages. While I can’t say that I leverage SkyDrive to the extent that it was meant to be I do enjoy having OneNote hosted their and being able to consult and edit it from the desktop, web and Windows Phone. Taking that one step further is the Midwest Geeks group which started as the community of Microsoft related user groups in our region uses SkyDrive groups and shares calendars and documents.  This collaboration aspect isn’t new in itself, but having it connected with the rest of your cloud assets makes life easier. Another recent usage of this type of cloud service is storing your personal music files in order to get that same universal access.  This is a scenario that has some arguments for and against.  On the one hand own once and listen anywhere is great, but the on the other hand the bandwidth cost becomes a giant downside.  This is especially the case since most carriers are now doing away with unlimited data packages. Ultimately I see this type of resource growing an evolving at a phenomenal rate over the next few years as we continue to become more mobile.  Having multiple players such as SkyDrive and iCloud will only help to give us more options.  Only time will tell where we end up next. del.icio.us Tags: SkyDrive,Cloud Services,Paul Thurrott,UserCommunity

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• when to introduce an application services tier in an n-tier application

  - by user20358

  I am developing a web based application whose primary objective is to fetch data from the database, display it on the UI, take in user inputs and write them back to the database. The application is not going to be doing any industrial strength algorithm crunching, but will be receiving a very high number of hits at peak times (described below) which will be changing thru the day. The layers are your typical Presentation, Business, Data. The data layer is taken care of by the database server. The business layer will contain the DAL component to access the database server over tcp. The choices I have to separate these layers into tiers are: The presentation and business layers can be either kept on the same tier. The presentation layer on a separate tier by itself and the business layer on a separate tier by itself. In the case of choice 2, the business layer will be accessed by the presentation layer using a WCF service either over http or tcp. I don't see any heavy processing being done on the Business layer, so I am leaning towards option 1 above. I also feel for the same reason, adding a new tier will only introduce the network latency. However, in terms of scalability in case I need to scale up or scale out, which is a better way to go? This application will need to be able to support up to 6 million users an hour. There will be a reasonable amount of data in each user session, storing user's preferences and other details. I will be using page level caching as well.

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• The UIManager Pattern

  - by Duncan Mills

  One of the most common mistakes that I see when reviewing ADF application code, is the sin of storing UI component references, most commonly things like table or tree components in Session or PageFlow scope. The reasons why this is bad are simple; firstly, these UI object references are not serializable so would not survive a session migration between servers and secondly there is no guarantee that the framework will re-use the same component tree from request to request, although in practice it generally does do so. So there danger here is, that at best you end up with an NPE after you session has migrated, and at worse, you end up pinning old generations of the component tree happily eating up your precious memory. So that's clear, we should never. ever, be storing references to components anywhere other than request scope (or maybe backing bean scope). So double check the scope of those binding attributes that map component references into a managed bean in your applications.  Why is it Such a Common Mistake?  At this point I want to examine why there is this urge to hold onto these references anyway? After all, JSF will obligingly populate your backing beans with the fresh and correct reference when needed.   In most cases, it seems that the rational is down to a lack of distinction within the application between what is data and what is presentation. I think perhaps, a cause of this is the logical separation between business data behind the ADF data binding (#{bindings}) façade and the UI components themselves. Developers tend to think, OK this is my data layer behind the bindings object and everything else is just UI.  Of course that's not the case.  The UI layer itself will have state which is intrinsically linked to the UI presentation rather than the business model, but at the same time should not be tighly bound to a specific instance of any single UI component. So here's the problem.  I think developers try and use the UI components as state-holders for this kind of data, rather than using them to represent that state. An example of this might be something like the selection state of a tabset (panelTabbed), you might be interested in knowing what the currently disclosed tab is. The temptation that leads to the component reference sin is to go and ask the tabset what the selection is.  That of course is fine in context - e.g. a handler within the same request scoped bean that's got the binding to the tabset. However, it leads to problems when you subsequently want the same information outside of the immediate scope.  The simple solution seems to be to chuck that component reference into session scope and then you can simply re-check in the same way, leading of course to this mistake. Turn it on its Head  So the correct solution to this is to turn the problem on its head. If you are going to be interested in the value or state of some component outside of the immediate request context then it becomes persistent state (persistent in the sense that it extends beyond the lifespan of a single request). So you need to externalize that state outside of the component and have the component reference and manipulate that state as needed rather than owning it. This is what I call the UIManager pattern.  Defining the Pattern The  UIManager pattern really is very simple. The premise is that every application should define a session scoped managed bean, appropriately named UIManger, which is specifically responsible for holding this persistent UI component related state.  The actual makeup of the UIManger class varies depending on a needs of the application and the amount of state that needs to be stored. Generally I'll start off with a Map in which individual flags can be created as required, although you could opt for a more formal set of typed member variables with getters and setters, or indeed a mix. This UIManager class is defined as a session scoped managed bean (#{uiManager}) in the faces-config.xml.  The pattern is to then inject this instance of the class into any other managed bean (usually request scope) that needs it using a managed property.  So typically you'll have something like this:   <managed-bean>     <managed-bean-name>uiManager</managed-bean-name>     <managed-bean-class>oracle.demo.view.state.UIManager</managed-bean-class>     <managed-bean-scope>session</managed-bean-scope>   </managed-bean>  When is then injected into any backing bean that needs it:    <managed-bean>     <managed-bean-name>mainPageBB</managed-bean-name>     <managed-bean-class>oracle.demo.view.MainBacking</managed-bean-class>     <managed-bean-scope>request</managed-bean-scope>     <managed-property>       <property-name>uiManager</property-name>       <property-class>oracle.demo.view.state.UIManager</property-class>       <value>#{uiManager}</value>     </managed-property>   </managed-bean> In this case the backing bean in question needs a member variable to hold and reference the UIManager: private UIManager _uiManager;  Which should be exposed via a getter and setter pair with names that match the managed property name (e.g. setUiManager(UIManager _uiManager), getUiManager()).  This will then give your code within the backing bean full access to the UI state. UI components in the page can, of course, directly reference the uiManager bean in their properties, for example, going back to the tab-set example you might have something like this: <af:paneltabbed>   <af:showDetailItem text="First"                disclosed="#{uiManager.settings['MAIN_TABSET_STATE'].['FIRST']}"> ...   </af:showDetailItem>   <af:showDetailItem text="Second"                      disclosed="#{uiManager.settings['MAIN_TABSET_STATE'].['SECOND']}">     ...   </af:showDetailItem>   ... </af:panelTabbed> Where in this case the settings member within the UI Manger is a Map which contains a Map of Booleans for each tab under the MAIN_TABSET_STATE key. (Just an example you could choose to store just an identifier for the selected tab or whatever, how you choose to store the state within UI Manger is up to you.) Get into the Habit So we can see that the UIManager pattern is not great strain to implement for an application and can even be retrofitted to an existing application with ease. The point is, however, that you should always take this approach rather than committing the sin of persistent component references which will bite you in the future or shotgun scattered UI flags on the session which are hard to maintain.  If you take the approach of always accessing all UI state via the uiManager, or perhaps a pageScope focused variant of it, you'll find your applications much easier to understand and maintain. Do it today!

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• Dapper and object validation/business rules enforcement

  - by Eugene

  This isn't really Dapper-specific, actually, as it relates to any XML-serializeable object.. but it came up when I was storing an object using Dapper. Anyways, say I have a user class. Normally, I'd do something like this: class User { public string SIN {get; private set;} public string DisplayName {get;set;} public User(string sin) { if (string.IsNullOrWhiteSpace(sin)) throw new ArgumentException("SIN must be specified"); this.SIN = sin; } } Since a SIN is required, I'd just create a constructor with a sin parameter, and make it read-only. However, with a Dapper (and probably any other ORM), I need to provide a parameterless constructor, and make all properties writeable. So now I have this: class User: IValidatableObject { public int Id { get; set; } public string SIN { get; set; } public string DisplayName { get; set; } public IEnumerable<ValidationResult> Validate(ValidationContext validationContext) { // implementation } } This seems.. can't really pick the word, a bad smell? A) I'm allowing to change properties that should not be changed ever after an object has been created (SIN, userid) B) Now I have to implement IValidatableObject or something like that to test those properties before updating them to db. So how do you go about it ?

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