Search Results

Search found 12902 results on 517 pages for 'hobby programming'.

Page 290/517 | < Previous Page | 286 287 288 289 290 291 292 293 294 295 296 297  | Next Page >

• What is your workflow when designing HTML/CSS layouts?

  - by DMin

  I have been working with PHP/MySQL as a hobby for close to a couple of years now, I have been working with photoshop for a very long time, I know CSS & HTML well enough to write without any reference, so, I would not consider myself someone who's very new at this. I have recently started developing websites professionally - (only person working on the project). I have seen the power of Joomla and how you can make a website ready for your customer in a matter of hours(if not minutes). I find it very hard to make layouts that remotely look like the themes on joomla. I find making even simple layouts a very cumbersome process and takes a lot of time to get a good enough output. I have a feeling I may not be using the right tools or workflow for the job. What I wanted to findout was, as part of the industry : How do, you, make your website when you do it from scratch? What are the tools that you use? What is your workflow? Just noted a few things I know already, for your reference(You can skip this if you like) I have seen the export for web for Photoshop that exports CSS - but (as far as I know) exports only absolutely positioned webpages so they need to be beaten and fixed if you want to use them for example for joomla. I have used the SiteGrinder plugin for Photoshop that exports HTML/CSS. It looks promising but haven't tried it extensively. One of the tools that save loads of time is FireBug. This makes it easy to edit html and css on the fly and get the page looking exactly as you want it. Recently stumbled upon fireworks. But haven't explored it much. Thanks! :)

  Read the article

• Java application design question

  - by ring bearer

  I have a hobby project, which is basically to maintain 'todo' tasks in the way I like. One task can be described as: public class TodoItem { private String subject; private Date dueBy; private Date startBy; private Priority priority; private String category; private Status status; private String notes; } As you can imagine I would have 1000s of todo items at a given time. What is the best strategy to store a todo item? (currently on an XML file) such that all the items are loaded quickly up on app start up(the application shows kind of a dashboard of all the items at start up)? What is the best way to design its back-end so that it can be ported to Android/or a J2ME based phone? Currently this is done using Java Swing. What should I concentrate on so that it works efficiently on a device where memory is limited? The application throws open a form to enter new todo task. For now, I would like to save the newly added task to my-todos.xml once the user presses "save" button. What are the common ways to append such a change to an existing XML file?(note that I don't want to read the whole file again and then persist)

  Read the article

• Calculate the digital root of a number

  - by Gregory Higley

  A digital root, according to Wikipedia, is "the number obtained by adding all the digits, then adding the digits of that number, and then continuing until a single-digit number is reached." For instance, the digital root of 99 is 9, because 9 + 9 = 18 and 1 + 8 = 9. My Haskell solution -- and I'm no expert -- is as follows. digitalRoot n | n < 10 = n | otherwise = digitalRoot . sum . map (\c -> read [c]) . show $ n As a language junky, I'm interested in seeing solutions in as many languages as possible, both to learn about those languages and possibly to learn new ways of using languages I already know. (And I know at least a bit of quite a few.) I'm particularly interested in the tightest, most elegant solutions in Haskell and REBOL, my two principal "hobby" languages, but any ol' language will do. (I pay the bills with unrelated projects in Objective C and C#.) Here's my (verbose) REBOL solution: digital-root: func [n [integer!] /local added expanded] [ either n < 10 [ n ][ expanded: copy [] foreach c to-string n [ append expanded to-integer to-string c ] added: 0 foreach e expanded [ added: added + e ] digital-root added ] ] EDIT: As some have pointed out either directly or indirectly, there's a quick one-line expression that can calculate this. You can find it in several of the answers below and in the linked Wikipedia page. (I've awarded Varun the answer, as the first to point it out.) Wish I'd known about that before, but we can still bend our brains with this question by avoiding solutions that involve that expression, if you're so inclined. If not, Crackoverflow has no shortage of questions to answer. :)

  Read the article

• LGPL library with plugins of varied licenses

  - by Chris

  Note: "Plugins" here refers to shared objects that are accessed via dlopen() and friends. I'm writing a library that I'm planning on releasing under the LGPL. Its functionality can be extended (supporting new audio file formats, specifically) through plugins. I'm planning on creating an exception to the LGPL for this library so that plugins can be released under any license. So far so good. I've written a number of plugins already, some of which use LGPL and some of which use GPL libraries. I'm wary of releasing them with the main library, however, due to licensing issues. The LGPL-based ones would generally be fine, but for my "any license" clause. Would distributing these LGPL-based plugins with the library require the consent of the other license holders to create this exception? Along the same lines, would the inclusion of GPL-based plugins with my library force the whole thing to go GPL? I could also release the plugins separately. The advantage, I presume, is that the plugins an d library will now not be distributed together, creating more separation. But this seems to be no different, really, in the end. Boiled down: Can I include, with my LGPL library, plugins of varied licenses? If not, is it really any different releasing them separately? And if so, there's no real need to create an exception for non-LGPL plugins, is there? It's LGPL or nothing. I'd prefer asking a lawyer, of course, but this is just a hobby and I can't afford to hire a lawyer when I don't expect or want monetary compensation. I'm just hoping others have been in similar situations and have insight.

  Read the article

• How do I get into a career as a programmer/development DBA?

  - by markle976

  About 8-9 years ago I started getting into programming as a hobby. I started with my TI-86 calculator, and then moved into using Visual Basic. After about a year I started playing around with HTML and JavaScript. Then I discovered Flash; I programmed with Actionscript 2.0 for about 2 years which lead me to start using Coldfusion. After a while I realized that A) I am not a designer, and B) with the way that things were going with AJAX, .NET, and PHP there wasn’t much future in Coldfusion/Actionscript. I had been working mostly as an administrative assistant, but about 3-4 years ago I got a position where I would be doing some web development, and assisting the system admin with supporting windows desktop PCs. I have gotten some decent experience over the past few years, but it has been spread out in somewhat disparate areas: I spend about 40% of my time writing PHP/MySQL and HTML/CSS, etc. I spend about 20% of my time helping users with PC questions. I spend about 20% of my time doing administrative things (mail-merges, excel, etc). I spend about 20% of my time managing / creating reports from our Access Database. I have also taught myself many things on my own, and now have a beginner’s level understanding of things like: Windows Server, Java, Linux, Objective-C, SQL Server, C#, C++, Ruby, Mac OSX, VBA, VBScript, and basic IP networks. I feel like I am in a bit of a rut – I want to get my career moving, but I am not sure what I need to do. If I practice with C# and SQL Server Express for a year will that be enough to get me in the door somewhere? Would it be easier to get a position if I teach myself Linux/Apache since I have more experience with PHP/MySQL?

  Read the article

• Determining polygon intersection and containment

  - by Victor Liu

  I have a set of simple (no holes, no self-intersections) polygons, and I need to check that they don't intersect each other (one can be entirely contained in another; that is okay). I can check this by simply checking the per-vertex inside-ness of one polygon versus other polygons. I also need to determine the containment tree, which is the set of relationships that say which polygon contains any given polygon. Since no polygon can intersect any other, then any contained polygon has a unique container; the "next-bigger" one. In other words, if A contains B contains C, then A is the parent of B, and B is the parent of C, and we don't consider A the parent of C. The question: How do I efficiently determine the containment relationships and check the non-intersection criterion? I ask this as one question because maybe a combined algorithm is more efficient than solving each problem separately. The algorithm should take as input a list of polygons, given by a list of their vertices. It should produce a boolean B indicating if none of the polygons intersect any other polygon, and also if B = true, a list of pairs (P, C) where polygon P is the parent of child C. This is not homework. This is for a hobby project I am working on.

  Read the article

• URL protocol handler shell execute problem

  - by Chuck

  Hi, I'm working on a small hobby web site where I'm able to launch a local app with certain arguments based on links. Setting up a protocol wasn't difficult, as described in http://msdn.microsoft.com/en-us/library/aa767914(VS.85).aspx, but I have one dilemma: Let's say the protocol is: foo:127.0.0.1:1111, so a link like href="foo:127.0.0.1:1111" would launch an app like: bar.exe "%1". Since I don't have any control over bar.exe (if I had, then it would be no problem to just parse it, obviously), I need some help parsing %1. bar.exe will launch correctly if it's run as bar.exe 127.0.0.1:1111, but not if it's run as bar.exe foo:127.0.0.1:1111. So I guess my question is... is there ANY way to tell the registry to pass on not %1, but a trimmed %1? (Thinking in terms of regexp where you have match[0] = all of the matched, match[1] = first capture in the matched text). I can solve it by having a .bat instead of .exe, but as I would like to make it as easy as possible for the user to use, I would LOVE it if I could handle it all stricly in registry. Any help is greatly appreciated! Chuck

  Read the article

• Clarification of atomic memory access for different OSs

  - by murrekatt

  I'm currently porting a Windows C++ library to MacOS as a hobby project as a learning experience. I stumbled across some code using the Win Interlocked* functions and thus I've been trying to read up on the subject in general. Reading related questions here in SO, I understand there are different ways to do these operations depending on the OS. Interlocked* in Windows, OSAtomic* in MacOS and I also found that compilers have builtin (intrinsic) operations for this. After reading gcc builtin atomic memory access, I'm left wondering what is the difference between intrinsic and the OSAtomic* or Interlocked* ones? I mean, can I not choose between OSAtomic* or gcc builtin if I'm on MacOS when I use gcc? The same if I'd be on Windows using gcc. I also read that on Windows Interlocked* come as both inline and intrinsic versions. What to consider when choosing between intrinsic or inline? In general, are there multiple options on OSs what to use? Or is this again "it depends"? If so, what does it depend on? Thanks!

  Read the article

• Decimal problem in Java

  - by Jerome

  I am experimenting with writing a java class for financial engineering (hobby of mine). The algorithm that I desire to implement is: 100 / 0.05 = 2000 Instead I get: 100 / 0.05 = 2000.9999999999998 I understand the problem to be one with converting from binary numbers to decimals (float -- int). I have looked at the BigDecimal class on the web but have not quite found what I am looking for. Attached is the program and a class that I wrote: // DCF class public class DCF { double rate; double principle; int period; public DCF(double $rate, double $principle, int $period) { rate = $rate; principle = $principle; period = $period; } // returns the console value public double consol() { return principle/rate; } // to string Method public String toString() { return "(" + rate + "," + principle + "," + period + ")"; } } Now the actual program: // consol program public class DCFmain { public static void main(String[] args) { // create new DCF DCF abacus = new DCF(0.05, 100.05, 5); System.out.println(abacus); System.out.println("Console value= " + abacus.consol() ); } } Output: (0.05,100.05,5) Console value= 2000.9999999999998 Thanks!

  Read the article

• Is there an equivalent for ActiveRecord#find_by equivalent for C#?

  - by Benjamin Manns

  I'm originally a C# developer (as a hobby), but as of late I have been digging into Ruby on Rails and I am really enjoying it. Right now I am building an application in C# and I was wondering if there is any collection implementation for C# that could match (or "semi-match") the find_by method of ActiveRecord. What I am essentially looking for is a list that would hold Rectangles: class Rectangle { public int Width { get; set; } public int Height { get; set; } public String Name { get; set; } } Where I could query this list and find all entries with Height = 10, Width = 20, or name = "Block". This was done with ActiveRecord by doing a call similar to Rectangle.find_by_name('Block'). The only way I can think of doing this in C# is to create my own list implementation and iterate through each item manually checking each item against the criteria. I fear I would be reinventing the wheel (and one of poorer quality). Any input or suggestions is much appreciated.

  Read the article

• Partial class or "chained inheritance"

  - by Charlie boy

  Hi From my understanding partial classes are a bit frowned upon by professional developers, but I've come over a bit of an issue; I have made an implementation of the RichTextBox control that uses user32.dll calls for faster editing of large texts. That results in quite a bit of code. Then I added spellchecking capabilities to the control, this was made in another class inheriting RichTextBox control as well. That also makes up a bit of code. These two functionalities are quite separate but I would like them to be merged so that I can drop one control on my form that has both fast editing capabilities and spellchecking built in. I feel that simply adding the code form one class to the other would result in a too large code file, especially since there are two very distinct areas of functionality, so I seem to need another approach. Now to my question; To merge these two classes should I make the spellchecking RichTextBox inherit from the fast edit one, that in turn inherits RichTextBox? Or should I make the two classes partials of a single class and thus making them more “equal” so to speak? This is more of a question of OO principles and exercise on my part than me trying to reinvent the wheel, I know there are plenty of good text editing controls out there. But this is just a hobby for me and I just want to know how this kind of solution would be managed by a professional. Thanks!

  Read the article

• Developing a 2D Game for Windows Phone 8

  - by Vaccano

  I would like to develop a 2D game for Windows Phone 8. I am a professional Application Developer by day and this seems like a fun hobby. But I have been disapointed trying to get going. It seems that 2D games (far and away the majority of games) do not have any real support. It seems the Windows Phone makers did not include support for Direct2D. So unless you are planning to make a fully 3D app, you are out of luck. So, if you just wanted to make a nice 2D app, these are your choices: Write your game using Xaml and C# (Performance Issues?) Write your game using Direct3D and but only draw on one plane. Use the DirectX Took Kit found on codeplex. It allows you to use the dying XNA framework's API for development. Number 3 seems the best for my game. But I hate to waste my time learning the XNA api when Microsoft has clearly stated that it is not going to be supported going forward. Number 2 would work, but 3D development is really hard. I would rather not have to do all that to get the 2D effect. (Assuming Direct2D is easier. I have yet to look into that.) Number 1 seems the easiest, but I worry that my app will not run well if it is based off of xaml rendering rather than DirectX. What is the suggested method from Microsoft? And who decided that 2D games were going to get shortchanged?

  Read the article

• return ArrayList from spring controller for ajax call and render in second dropdown

  - by user1708125

  I've a spring bean with 3 Maps all of which are to be populated incrementally. First map is an item category list, second map is a product list and third map is a hobby for item type list All the maps are mapped to and on the JSP. When the page is loaded only the first map is populated on the onchange event of first map, I need to populate the second map in the bean and similarly on the onchange event of second map, I need to populate the third map in the bean. Is there a way to do this using Ajax?? I need some code samples to how to render JSON response in second and third dropdown. Clarification: @Donal: I have a simple JSP page with 3 dropdowns corresponding to 3 maps stored in my commandBean. So when the page loads for the first time only the first map and hence the first dropdown is populated. Now whenever the user selects anything out of the first dropdown, I need to send the same commandbean back with the values of the first dropdown and get the values for the second map and hence the second dropdown and so forth for the 3rd dropdown as well. For each dropdown I 've got 3 maps and 3 variables for storing the selected values. Now I want to understand if this is possible using Ajax. I hope this clarifies whatever you need to know. Thanx

  Read the article

• How do I become better in math, after being a programmer for several years.

  - by loxs

  I've had quite a weird career till now. First I graduated from a medical school. Then I went into marketing (pharmaceuticals). And then umm, after some time, I decided to go for my (till then) hobby and became a "professional" programmer. I've been quite successful at this ever since. I have quite some languages "under my belt". I earn not bad and I have been involved in the opensource community quite heavily. The thing is that I suck at math :). Well, not totally of course, as I get my work done. But I don't know how much I suck. And I don't know how to find out. Math has never really been of any priority during my middle/high school years. I only picked as little as I could afford, because I was always getting ready to go for Medicine. Of course I know the basics of algebra. Things like "normal" and square equations. Also the basics of geometry. But well, there are things that I have missed. And lately I am being fascinated by things like probability theory, infinity, chaos/order etc. But every time I try to learn something about these topics, I hit a wall of terminology, special symbols, and some special kind of thinking, that is quite like mine (a programmer), but also a lot different (and appears weird to me). So, what kinds of books would you recommend me? It's very hard to find something suitable. All that I find are either too easy (and boring) or totally impenetrable.

  Read the article

• File IO with Streams - Best Memory Buffer Size

  - by AJ

  I am writing a small IO library to assist with a larger (hobby) project. A part of this library performs various functions on a file, which is read / written via the FileStream object. On each StreamReader.Read(...) pass, I fire off an event which will be used in the main app to display progress information. The processing that goes on in the loop is vaired, but is not too time consuming (it could just be a simple file copy, for example, or may involve encryption...). My main question is: What is the best memory buffer size to use? Thinking about physical disk layouts, I could pick 2k, which would cover a CD sector size and is a nice multiple of a 512 byte hard disk sector. Higher up the abstraction tree, you could go for a larger buffer which could read an entire FAT cluster at a time. I realise with today's PC's, I could go for a more memory hungry option (a couple of MiB, for example), but then I increase the time between UI updates and the user perceives a less responsive app. As an aside, I'm eventually hoping to provide a similar interface to files hosted on FTP / HTTP servers (over a local network / fastish DSL). What would be the best memory buffer size for those (again, a "best-case" tradeoff between perceived responsiveness vs. performance).

  Read the article

• so i got an econ degree...computing science or software systems (software engineering) degree ?

  - by sofreakinghigh

  okay so here's the story. i want to work in developing software (not QA or writing tests), so although I am currently starting computing science this summer, i came across Software Systems (aka s.e.) program which is "applied" but under computing science.... so what is the difference between the 2 disciplines ? if i choose software engineering, would it require more in depth expertise with calculus (i fail at it), and more coding time ? i am looking for a way to write better and more efficient code. I want to go to school, so i wont get lazy. i want to pick a program that would directly aid me in writing and developing software. graduating with an Econ degree in last year doesn't really help in landing jobs requiring comp sci/software engineering degrees....i should've studied harder in Economics (and maybe land a job) but i was obsessed with learning how to program with various languages since day 1 at University, but i didn't think i was smart enough to pass comp sci courses (so i just relied on books + irc...) and my parents said software jobs are being outsourced to India so i thought this obsession was just a "phase" and i should keep it as a hobby. but yes, it's quite funny why i hadn't pursued this field much earlier. as Joelonsoftware.com says economics degree starts with a bang (microeconomics the only course you only need really)....predicting stock prices (ridiculous!) + realizing China's potential power to meltdown US economy and vice versa + interest rate is inversely related to bond premium which is inversely related to stock market it would absolutely awesome if there was a program that combined finance + programming.

  Read the article

• Pass variable to Info Window in FusionTableLayer

  - by user1030205

  I am building a web application that includes a Google Map layered with data from a Google Fusion Table. I have defined the info window for the markers in the Fusion Table and all is rendering as expected, but I have one issue. I need to pass a session variable from my web application to be included in the links that are defined in the info window, but can't seem to find a way to do this. Below is the javascript I am currently using to render the map: var myOptions = { zoom: 10, mapTypeId: google.maps.MapTypeId.ROADMAP, center: new google.maps.LatLng( 40.4230,-98.7372) } map = new google.maps.Map(document.getElementById("map_canvas"), myOptions); // Weather weatherLayer = new google.maps.weather.WeatherLayer({ temperatureUnits: google.maps.weather.TemperatureUnit.FAHRENHEIT }); weatherLayer.setMap(map); //Hobby Stores var storeLayer = new google.maps.FusionTablesLayer({ query: { select: "col2", from: "3991553" }, map: map, supressInfoWindows: true }); //Club Sites var siteLayer = new google.maps.FusionTablesLayer({ query: { select: "col13", from: "3855088" }, styles: [{ markerOptions: { iconName: "airports" }}], map: map, supressInfoWindows: true }); I'd like to be able to pass some type of parameter in the call to google.maps.FusionTableLayer that passes a value to be include in the info window, but can't find a way to do this. To view the actual page, visit www.dualrates.com. Enter your zipcode and select one of the airport markers to see the info window. You may have to zoom the map out to see an airfield.

  Read the article

• iPhone: Same Rows Repeated in Each Section of Grouped UITableview

  - by Rank Beginner

  I have an app that is a list of tasks, like a to do list. The user configures the tasks and that goes to the SQLite db. The list is displayed in a tableview. The SQL table in question consists of a taskid int, groupname varchar, taskname varchar, lastcompleted datetime, nextdue datetime, weighting integer. I currently have it working by creating an array from each column in the SQL table. In the tableView:cellForRowAtIndexPath: method, I create the controls for each task by binding their values to the array for each column. I want to add configurable task groups that should display as the section titles. I got the task groups to display as the section headers. My problem is that all the task rows are repeated in each group under each header. How do I get the correct rows to show up only under the correct section? I'm really new to development period and took on a hobby of trying to teach myself how to develop iphone apps. So, pretty please, be a little more detailed than you normally would with a professional developer. :)

  Read the article

• Peculiar JRE behaviour running RMI server under load, should I worry?

  - by darri

  I've been developing a minimalistic Java rich client CRUD application framework for the past few years, mostly as a hobby but also actively using it to write applications for my current employer. The framework provides database access to clients either via a local JDBC based connection or a lightweight RMI server. Last night I started a load testing application, which ran 100 headless clients, bombarding the server with requests, each client waiting only 1 - 2 seconds between running simple use cases, consisting of selecting records along with associated detail records from a simple e-store database (Chinook). This morning when I looked at the telemetry results from the server profiling session I noticed something which to me seemed strange (and made me keep the setup running for the remainder of the day), I don't really know what conclusions to draw from it. Here are the results: Memory GC activity Threads CPU load Interesting, right? So the question is, is this normal or erratic? Is this simply the JRE (1.6.0_03 on Windows XP) doing it's thing (perhaps related to the JRE configuration) or is my framework design somehow causing this? Running the server against MySQL as opposed to an embedded H2 database does not affect the pattern. I am leaving out the details of my server design, but I'll be happy to elaborate if this behaviour is deemed erratic.

  Read the article

• Space between 2 vertices on a heightmap

  - by Sietse

  First off, I am sorry for the crazy title. I couldn't really think of something else. I am working on a hobby project, it's a infinite world generated with Perlin Noise, Java and LWJGL. But I am having a problem, it is kinda hard to explain, so I made a video: http://youtu.be/D_NUBJZ_5Kw Obviously the problem is the black spaces in between all the pieces of ground. I have no idea what is causing it. I already tried making all the values doubles instead of floats, but that didn't fix it. Here is a piece of code I am using: float height2, height = (float)getHeight(x, y); height2 = (float) ((getHeight(x-1, y+1) + height) / 2); vertexhelper.addVertexColorAndTexture(x, height2, y+1, r, g, b, a, 0f, 1f); height2 = (float) ((getHeight(x+1, y+1) + height) / 2); vertexhelper.addVertexColorAndTexture(x+1, height2, y+1, r, g, b, a, 1f, 1f); height2 = (float) ((getHeight(x+1, y-1) + height) / 2); vertexhelper.addVertexColorAndTexture(x+1, height2, y, r, g, b, a, 1f, 0f); height2 = (float) ((getHeight(x-1, y-1) + height) / 2); vertexhelper.addVertexColorAndTexture(x, height2, y, r, g, b, a, 0f, 0f); I loop through this at the initialization of a chunk with x-16 and y-16. vertexhelper is a class I made that just puts everything in a array. (I am using floats here, but that's after doing the maths, so that shouldn't be a problem) I highly appreciate you reading this.

  Read the article

• how to reverse an angle

  - by MissHalberd

  I am no mathematician, but I somehow got into game development as a hobby. Having never studied anything beyond basic math, I have a lot of trouble figuring out how to reverse the angle of something, facing to the opposite direction, among the X axis. One image says more than 1000 words though (specially uneducated words): http://img156.imageshack.us/i/wihwin.png/ I basically want to reverse the direction of cannon objects adhered to a robot. When the robot changes from facing right to facing left, I do (180 - angle) as everyone suggested me, but it reverses the angle...literally, making the cannons aim up when they are aiming down. So, I need to do something else, but it escapes my knowledge. Anyone would be so kind to help me with this? Oh, I use regular C by the way, in case there's something built-in specific to it. To put it in other words, I work in 2D, so I want an angle that is facing right to face left. 0 being "totally to the right", 180 "left", 90 "up" and 270 "down". I want something that is aiming with an angle of 91 to turn into 89 when reversed, literally. There's no Z axis present. EDIT: Thanks for the answers! Trying them out now. I'll post which one worked in a minute!

  Read the article

• Cutting objects and applying texture to cut. Unity3d/C#

  - by Timothy Williams

  Basically what I'm trying to do is figure out how to calculate realtime cutting of objects, and apply a texture to the cut. I found some good scripts, but most of them have been abandoned and aren't really fully working yet. Applying textures: http://forum.unity3d.com/threads/75949-Mesh-Real-Cutting?highlight=mesh+real+cutting Cutting: http://forum.unity3d.com/threads/78594-Object-Cutter Another (Free) Cutter (Also, I'm not entirely sure how this one will handle cutting complex meshes): http://forum.unity3d.com/threads/69992-fake-slicer?p=449114&viewfull=1#post449114 My plan as of right now is to combine links 1 & 2 or 1 & 3 programming wise. What I'm asking here for is any advice on how to advance (links to asset store packages, or other codes to show how to accomplish something complex like this.)

  Read the article

• Parallelism in .NET – Part 13, Introducing the Task class

  - by Reed

  Once we’ve used a task-based decomposition to decompose a problem, we need a clean abstraction usable to implement the resulting decomposition.  Given that task decomposition is founded upon defining discrete tasks, .NET 4 has introduced a new API for dealing with task related issues, the aptly named Task class. The Task class is a wrapper for a delegate representing a single, discrete task within your decomposition.  We will go into various methods of construction for tasks later, but, when reduced to its fundamentals, an instance of a Task is nothing more than a wrapper around a delegate with some utility functionality added.  In order to fully understand the Task class within the new Task Parallel Library, it is important to realize that a task really is just a delegate – nothing more.  In particular, note that I never mentioned threading or parallelism in my description of a Task.  Although the Task class exists in the new System.Threading.Tasks namespace: Tasks are not directly related to threads or multithreading. Of course, Task instances will typically be used in our implementation of concurrency within an application, but the Task class itself does not provide the concurrency used.  The Task API supports using Tasks in an entirely single threaded, synchronous manner. Tasks are very much like standard delegates.  You can execute a task synchronously via Task.RunSynchronously(), or you can use Task.Start() to schedule a task to run, typically asynchronously.  This is very similar to using delegate.Invoke to execute a delegate synchronously, or using delegate.BeginInvoke to execute it asynchronously. The Task class adds some nice functionality on top of a standard delegate which improves usability in both synchronous and multithreaded environments. The first addition provided by Task is a means of handling cancellation via the new unified cancellation mechanism of .NET 4.  If the wrapped delegate within a Task raises an OperationCanceledException during it’s operation, which is typically generated via calling ThrowIfCancellationRequested on a CancellationToken, or if the CancellationToken used to construct a Task instance is flagged as canceled, the Task’s IsCanceled property will be set to true automatically.  This provides a clean way to determine whether a Task has been canceled, often without requiring specific exception handling. Tasks also provide a clean API which can be used for waiting on a task.  Although the Task class explicitly implements IAsyncResult, Tasks provide a nicer usage model than the traditional .NET Asynchronous Programming Model.  Instead of needing to track an IAsyncResult handle, you can just directly call Task.Wait() to block until a Task has completed.  Overloads exist for providing a timeout, a CancellationToken, or both to prevent waiting indefinitely.  In addition, the Task class provides static methods for waiting on multiple tasks – Task.WaitAll and Task.WaitAny, again with overloads providing time out options.  This provides a very simple, clean API for waiting on single or multiple tasks. Finally, Tasks provide a much nicer model for Exception handling.  If the delegate wrapped within a Task raises an exception, the exception will automatically get wrapped into an AggregateException and exposed via the Task.Exception property.  This exception is stored with the Task directly, and does not tear down the application.  Later, when Task.Wait() (or Task.WaitAll or Task.WaitAny) is called on this task, an AggregateException will be raised at that point if any of the tasks raised an exception.  For example, suppose we have the following code: Task taskOne = new Task( () => { throw new ApplicationException("Random Exception!"); }); Task taskTwo = new Task( () => { throw new ArgumentException("Different exception here"); }); // Start the tasks taskOne.Start(); taskTwo.Start(); try { Task.WaitAll(new[] { taskOne, taskTwo }); } catch (AggregateException e) { Console.WriteLine(e.InnerExceptions.Count); foreach (var inner in e.InnerExceptions) Console.WriteLine(inner.Message); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Here, our routine will print: 2 Different exception here Random Exception! Note that we had two separate tasks, each of which raised two distinctly different types of exceptions.  We can handle this cleanly, with very little code, in a much nicer manner than the Asynchronous Programming API.  We no longer need to handle TargetInvocationException or worry about implementing the Event-based Asynchronous Pattern properly by setting the AsyncCompletedEventArgs.Error property.  Instead, we just raise our exception as normal, and handle AggregateException in a single location in our calling code.

  Read the article

• A Case for Women in Technology

  - by Denise McInerney

  Pragmatic Works and the PASS Women in Tech chapter are co-sponsoring a webinar series featuring women speakers. I presented a session on “A Case for Women in Technology” explaining why we are all affected by the lack of women studying and working in tech. The recording is available here. And here are the slides from that presentation: The presentation includes a link to a trailer for an upcoming documentary. This short video makes a good case for why we need more women creating technology. There are many organizations doing good and important work on this issue. Here are some of them: National Center for Women & Information Technology Catalyst Anita Borg Institute Girls Inc Girls Who Code Code.org Black Girls Code Teaching Kids Programming Digigirlz IGNITE She++ The Ada Initiative PASS WIT Here are the publications I referenced in my slides: Women in IT: The Facts Why Diversity Matters Women in IT: By the Numbers NCWIT Scorecard

  Read the article

• Are high powered 3D game engines better at 2D games than engines made for 2D

  - by Adam

  I'm a software engineer that's new to game programming so forgive me if this is a dumb question as I don't know that much about game engines. If I was building a 2D game am I better off going with an engine like Torque that looks like it's built for 2D, or would higher powered engines like Unreal, Source and Unity work better? I'm mainly asking if 2D vs 3D is a large factor in choosing an engine. For the purpose of comparison, let's eliminate variables by saying price isn't a factor (even though it probably is). EDIT: I should probably also mention that the game we're developing has a lot of RTS and RPG elements regarding leveling up

  Read the article

< Previous Page | 286 287 288 289 290 291 292 293 294 295 296 297  | Next Page >