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• Looking for a dynamic programming solution

  - by krammer

  Given a sequence of integers in range 1 to n. Each number can appear at most once. Let there be a symbol X in the sequence which means remove the minimum element from the list. There can be an arbitrarily number of X in the sequence. Example: 1,3,4,X,5,2,X The output is 1,2. We need to find the best way to perform this operation. The solution I have been thinking is: Scan the sequence from left to right and count number of X which takes O(n) time. Perform partial sorting and find the k smallest elements (k = number of X) which takes O(n+klogk) time using median of medians. Is there a better way to solve this problem using dynamic programming or any other way ?

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• Programming error in 'aptdaemon' [closed]

  - by Real

  Using Ubuntu 11.10 While performing updates through the update manager I get the following message: An unhandlable error occured There seems to be a programming error in aptdaemon, the software that allows you to install/remove software and to perform other package management related tasks. Details Traceback (most recent call last): File "/usr/lib/python2.7/dist-packages/aptdaemon/worker.py", line 968, in simulate trans.unauthenticated = self._simulate_helper(trans) File "/usr/lib/python2.7/dist-packages/aptdaemon/worker.py", line 1092, in _simulate_helper return depends, self._cache.required_download, \ File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 235, in required_download pm.get_archives(fetcher, self._list, self._records) SystemError: E:Method has died unexpectedly!, E:Sub-process returned an error code (100), E:Method /usr/lib/apt/methods/ did not start correctly Tried some of the fixes that were posted but did not work. What shall I do to fix this issue?

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• What programming language matches this description? [on hold]

  - by Benubird

  I am looking for a functional language that is basically dynamic programming - i.e. one where functions are first-class objects - but where all function calls are asynchronous by default; i.e. you define function X(a,b) = (Y(a)+Z(b)), and when X() is called, it sees it is waiting for the return from two functions, runs one in the current thread, and spawns a new thread to run the other. The future is very much parallel processing; multiple cores, multiple machines, the internet of things, etc. and I was wondering if there was a language specifically designed to make this kind of parallelization easy. I currently have only used imperative languages (c, php, java, ruby, etc), so I don't know anything about what kind of functional languages are available.

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• design a model for a system of dependent variables

  - by dbaseman

  I'm dealing with a modeling system (financial) that has dozens of variables. Some of the variables are independent, and function as inputs to the system; most of them are calculated from other variables (independent and calculated) in the system. What I'm looking for is a clean, elegant way to: define the function of each dependent variable in the system trigger a re-calculation, whenever a variable changes, of the variables that depend on it A naive way to do this would be to write a single class that implements INotifyPropertyChanged, and uses a massive case statement that lists out all the variable names x1, x2, ... xn on which others depend, and, whenever a variable xi changes, triggers a recalculation of each of that variable's dependencies. I feel that this naive approach is flawed, and that there must be a cleaner way. I started down the path of defining a CalculationManager<TModel> class, which would be used (in a simple example) something like as follows: public class Model : INotifyPropertyChanged { private CalculationManager<Model> _calculationManager = new CalculationManager<Model>(); // each setter triggers a "PropertyChanged" event public double? Height { get; set; } public double? Weight { get; set; } public double? BMI { get; set; } public Model() { _calculationManager.DefineDependency<double?>( forProperty: model => model.BMI, usingCalculation: (height, weight) => weight / Math.Pow(height, 2), withInputs: model => model.Height, model.Weight); } // INotifyPropertyChanged implementation here } I won't reproduce CalculationManager<TModel> here, but the basic idea is that it sets up a dependency map, listens for PropertyChanged events, and updates dependent properties as needed. I still feel that I'm missing something major here, and that this isn't the right approach: the (mis)use of INotifyPropertyChanged seems to me like a code smell the withInputs parameter is defined as params Expression<Func<TModel, T>>[] args, which means that the argument list of usingCalculation is not checked at compile time the argument list (weight, height) is redundantly defined in both usingCalculation and withInputs I am sure that this kind of system of dependent variables must be common in computational mathematics, physics, finance, and other fields. Does someone know of an established set of ideas that deal with what I'm grasping at here? Would this be a suitable application for a functional language like F#? Edit More context: The model currently exists in an Excel spreadsheet, and is being migrated to a C# application. It is run on-demand, and the variables can be modified by the user from the application's UI. Its purpose is to retrieve variables that the business is interested in, given current inputs from the markets, and model parameters set by the business.

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• Is copy paste programming bad ?

  - by ring bearer

  With plain google as well as google code search tools it is easy to find how to program using some resource or solve certain problems ( such as a Java class, or a ftp block in perl etc) and so developers are so tempted to just purely copy paste the code (in a way re-use) - is this an incompetency? I have done this myself though I think I am a better programmer than many others I have seen. Who has the time to RTFM? In this age of information abundance, I do not think that copy paste programming is bad. Isn't that what sites like stackoverflow do anyway? People ask - ok here is my problem - how to solve it? now someone will post complete code and the person who asked the question would simply copy paste the most voted answer. No matter how small the problem is. I am working with a bunch of young coders who heavily rely on internet to get their job done. I see convenience (for example, you may be quite good with algorithms and such but you may not know how to use a BufferedReader in Java - would you read complete Javadoc for BufferedReader or look up some example of using it somewhere??) in copy pasting and modifying code to get the job done. What are the real dangers of copy paste coding that can impact their competency?

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• Functional programming and stateful algorithms

  - by bigstones

  I'm learning functional programming with Haskell. In the meantime I'm studying Automata theory and as the two seem to fit well together I'm writing a small library to play with automata. Here's the problem that made me ask the question. While studying a way to evaluate a state's reachability I got the idea that a simple recursive algorithm would be quite inefficient, because some paths might share some states and I might end up evaluating them more than once. For example, here, evaluating reachability of g from a, I'd have to exclude f both while checking the path through d and c: So my idea is that an algorithm working in parallel on many paths and updating a shared record of excluded states might be great, but that's too much for me. I've seen that in some simple recursion cases one can pass state as an argument, and that's what I have to do here, because I pass forward the list of states I've gone through to avoid loops. But is there a way to pass that list also backwards, like returning it in a tuple together with the boolean result of my canReach function? (although this feels a bit forced) Besides the validity of my example case, what other techniques are available to solve this kind of problems? I feel like these must be common enough that there have to be solutions like what happens with fold* or map. So far, reading learnyouahaskell.com I didn't find any, but consider I haven't touched monads yet. (if interested, I posted my code on codereview)

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• Thread safe GUI programming

  - by James

  I have been programming Java with swing for a couple of years now, and always accepted that GUI interactions had to happen on the Event Dispatch Thread. I recently started to use GTK+ for C applications and was unsurprised to find that GUI interactions had to be called on gtk_main. Similarly, I looked at SWT to see in what ways it was different to Swing and to see if it was worth using, and again found the UI thread idea, and I am sure that these 3 are not the only toolkits to use this model. I was wondering if there is a reason for this design i.e. what is the reason for keeping UI modifications isolated to a single thread. I can see why some modifications may cause issues (like modifying a list while it is being drawn), but I do not see why these concerns pass on to the user of the API. Is there a limit imposed by an operating system? Is there a good reason these concerns are not 'hidden' (i.e. some form of synchronization that is invisible to the user)? Is there any (even purely conceptual) way of creating a thread safe graphics library, or is such a thing actually impossible? I found this http://blogs.operationaldynamics.com/andrew/software/gnome-desktop/gtk-thread-awareness which seems to describe GTK differently to how I understood it (although my understanding was the same as many people's) How does this differ to other toolkits? Is it possible to implement this in Swing (as the EDT model does not actually prevent access from other threads, it just often leads to Exceptions)

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• C# Threading Background Process - Programming - How to?

  - by Magic

  Hello...I have been given the horrible task of doing this. Launch the website Take a screenshot Fill in the form details, click on Next Take a screenshot ... ... ... Rinse. Repeat. Now, with various combinations, this comes up to 300 screenshots. And I have to do this for 4 different browsers. Chrome, Firefox, IE 6 and IE 7. I cannot use tools which will capture the screenshot and store them, such as, SnagIT. I need to take a screenshot, copy it to a Word Document and take the second screenshot and take it to a Word Document. I thought, I will write a tiny utility which will help me do this. Here is the requirement spec that I put up for it - An executable which once launched seats itself in the System Tray. While it is active, all instances of Key Press (Print Scrn), it should write the contents to a Word Document as defined (either a default path or a user defined one). Save the document periodically. Now, my question is - if I am going to develop this using C# (Winforms application), how do I go about doing this. I can do a fair bit of C# programming and I am willing to learn. But I am not able to locate the references for how to do a background process so that it runs in the background. And while it runs, it has to capture the Print Scrn command. Can you folks point me to the right material where I can learn this? Theoretical references should suffice. But if there are practical references, then nothing like it. Thanks!

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• Implementing features in an Entity System

  - by Bane

  After asking two questions on Entity Systems (1, 2), and reading some articles on them, I think that I understand them much better than before. But, I still have some uncertainties, and mainly they are about building a Particle Emitter, an Input system, and a Camera. I obviously still have some problems understanding Entity Systems, and they might apply to a whole other range of objects, but I chose these three because they are very different concepts and should cover a pretty big ground, and help me understand Entity Systems and how to handle problems like these myself, as they come along. I am building an engine in Javascript, and I've implemented most of the core features, which include: input handling, flexible animation system, particle emitter, math classes and functions, scene handling, a camera and a render, and a whole bunch of other things that engines usually support. Then, I read Byte56's answer that got me interested into making the engine into an Entity System one. It would still remain an HTML5 game engine with the basic Scene philosophy, but it should support dynamic creation of entities from components. These are some of the definitions from the previous questions, updated: An Entity is an identifier. It doesn't have any data, it's not an object, it's a simple id that represents an index in the Scene's list of all entities (which I actually plan to implement as a component matrix). A Component is a data holder, but with methods that can operate on that data. The best example is a Vector2D, or a "Position" component. It has data: x and y, but also some methods that make operating on the data a bit easier: add(), normalize(), and so on. A System is something that can operate on a set of entities that meet the certain requirements, usually they (the entities) need to have a specified (by the system itself) set of components to be operated upon. The system is the "logic" part, the "algorithm" part, all the functionality supplied by components is purely for easier data management. The problem that I have now is fitting my old engine concept into this new programming paradigm. Lets start with the simplest one, a Camera. The camera has a position property (Vector2D), a rotation property and some methods for centering it around a point. Each frame, it is fed to a renderer, along with a scene, and all the objects are translated according to it's position. Then the scene is rendered. How could I represent this kind of an object in an Entity System? Would the camera be an entity or simply a component? A combination (see my answer)? Another issues that is bothering me is implementing a Particle Emitter. For what exactly I mean by that, you can check out my video of it: http://youtu.be/BObargIMQsE. The problem I have with this is, again, what should be what. I'm pretty sure that particles themselves shouldn't be entities, as I want to support 10k+ of them, and creating that much entities would be a heavy blow on my performance, I believe. Or maybe not? Depends on the implementation, but anyone with experience: please, do answer. The last bit I wan't to talk about, which is also bugging me the most, is how input should be handled. In my current version of the engine, there is a class called Input. It's a handler that subscribes to browser's events, such as keypresses, and mouse position changes, and also it maintains an internal state. Then, the player class has a react() method, which accepts an input object as an argument. The advantage of this is that the input object could be serialized into JSON and then shared over the network, allowing for smooth multiplayer simulations. But how does this translate into an Entity System?

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• Build one to throw away vs Second-system effect

  - by m3th0dman

  One one hand there is an advice that says "Build one to throw away". Only after finishing a software system and seeing the end product we realize what went wrong in the design phase and understand how we should have really done it. On the other hand there is the "second-system effect" which says that the second system of the same kind that is designed is usually worse than the first one; there are many features that did not fit in the first project and were pushed into the second version usually leading to overly complex and overly engineered. Isn't here some contradiction between these principles? What is the correct view over the problems and where is the border between these two? I believe that these "good practices" are were firstly promoted in the seminal book The Mythical Man-Month by Fred Brooks. I know that some of these issues are solved by Agile methodologies, but deep down, the problem is still the principles still stand; for example we would not make important design changes 3 sprints before going live.

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• A programming language that does not allow IO. Haskell is not a pure language

  - by TheIronKnuckle

  (I asked this on Stack Overflow and it got closed as off-topic, I was a bit confused until I read the FAQ, which discouraged subjective theoratical debate style questions. The FAQ here doesn't seem to have a problem with it and it sounds like this is a more appropriate place to post. If this gets closed again, forgive me, I'm not trying to troll) Are there any 100% pure languages (as I describe in the Stack Overflow post) out there already and if so, could they feasibly be used to actually do stuff? i.e. do they have an implementation? I'm not looking for raw maths on paper/Pure lambda calculus. However Pure lambda calculus with a compiler or a runtime system attached is something I'd be interested in hearing about.

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• Learning by doing (and programming by trial and error)

  - by AlexBottoni

  How do you learn a new platform/toolkit while producing working code and keeping your codebase clean? When I know what I can do with the underlying platform and toolkit, I usually do this: I create a new branch (with GIT, in my case) I write a few unit tests (with JUnit, for example) I write my code until it passes my tests So far, so good. The problem is that very often I do not know what I can do with the toolkit because it is brand new to me. I work as a consulant so I cannot have my preferred language/platform/toolkit. I have to cope with whatever the customer uses for the task at hand. Most often, I have to deal (often in a hurry) with a large toolkit that I know very little so I'm forced to "learn by doing" (actually, programming by "trial and error") and this makes me anxious. Please note that, at some point in the learning process, usually I already have: read one or more five-stars books followed one or more web tutorials (writing working code a line at a time) created a couple of small experimental projects with my IDE (IntelliJ IDEA, at the moment. I use Eclipse, Netbeans and others, as well.) Despite all my efforts, at this point usually I can just have a coarse understanding of the platform/toolkit I have to use. I cannot yet grasp each and every detail. This means that each and every new feature that involves some data preparation and some non-trivial algorithm is a pain to implement and requires a lot of trial-and-error. Unfortunately, working by trial-and-error is neither safe nor easy. Actually, this is the phase that makes me most anxious: experimenting with a new toolkit while producing working code and keeping my codebase clean. Usually, at this stage I cannot use the Eclipse Scrapbook because the code I have to write is already too large and complex for this small tool. In the same way, I cannot use any more an indipendent small project for my experiments because I need to try the new code in place. I can just write my code in place and rely on GIT for a safe bail-out. This makes me anxious because this kind of intertwined, half-ripe code can rapidly become incredibly hard to manage. How do you face this phase of the development process? How do you learn-by-doing without making a mess of your codebase? Any tips&tricks, best practice or something like that?

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• How to get better at solving Dynamic programming problems

  - by newbie

  I recently came across this question: "You are given a boolean expression consisting of a string of the symbols 'true', 'false', 'and', 'or', and 'xor'. Count the number of ways to parenthesize the expression such that it will evaluate to true. For example, there is only 1 way to parenthesize 'true and false xor true' such that it evaluates to true." I knew it is a dynamic programming problem so i tried to come up with a solution on my own which is as follows. Suppose we have a expression as A.B.C.....D where '.' represents any of the operations and, or, xor and the capital letters represent true or false. Lets say the number of ways for this expression of size K to produce a true is N. when a new boolean value E is added to this expression there are 2 ways to parenthesize this new expression 1. ((A.B.C.....D).E) ie. with all possible parenthesizations of A.B.C.....D we add E at the end. 2. (A.B.C.(D.E)) ie. evaluate D.E first and then find the number of ways this expression of size K can produce true. suppose T[K] is the number of ways the expression with size K produces true then T[k]=val1+val2+val3 where val1,val2,val3 are calculated as follows. 1)when E is grouped with D. i)It does not change the value of D ii)it inverses the value of D in the first case val1=T[K]=N.( As this reduces to the initial A.B.C....D expression ). In the second case re-evaluate dp[K] with value of D reversed and that is val1. 2)when E is grouped with the whole expression. //val2 contains the number of 'true' E will produce with expressions which gave 'true' among all parenthesized instances of A.B.C.......D i) if true.E = true then val2 = N ii) if true.E = false then val2 = 0 //val3 contains the number of 'true' E will produce with expressions which gave 'false' among all parenthesized instances of A.B.C.......D iii) if false.E=true then val3=( 2^(K-2) - N ) = M ie. number of ways the expression with size K produces a false [ 2^(K-2) is the number of ways to parenthesize an expression of size K ]. iv) if false.E=false then val3 = 0 This is the basic idea i had in mind but when i checked for its solution http://people.csail.mit.edu/bdean/6.046/dp/dp_9.swf the approach there was completely different. Can someone tell me what am I doing wrong and how can i get better at solving DP so that I can come up with solutions like the one given above myself. Thanks in advance.

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• HTML5 game programming style

  - by fnx

  I am currently trying learn javascript in form of HTML5 games. Stuff that I've done so far isn't too fancy since I'm still a beginner. My biggest concern so far has been that I don't really know what is the best way to code since I don't know the pros and cons of different methods, nor I've found any good explanations about them. So far I've been using the worst (and propably easiest) method of all (I think) since I'm just starting out, for example like this: var canvas = document.getElementById("canvas"); var ctx = canvas.getContext("2d"); var width = 640; var height = 480; var player = new Player("pic.png", 100, 100, ...); also some other global vars... function Player(imgSrc, x, y, ...) { this.sprite = new Image(); this.sprite.src = imgSrc; this.x = x; this.y = y; ... } Player.prototype.update = function() { // blah blah... } Player.prototype.draw = function() { // yada yada... } function GameLoop() { player.update(); player.draw(); setTimeout(GameLoop, 1000/60); } However, I've seen a few examples on the internet that look interesting, but I don't know how to properly code in these styles, nor do I know if there are names for them. These might not be the best examples but hopefully you'll get the point: 1: Game = { variables: { width: 640, height: 480, stuff: value }, init: function(args) { // some stuff here }, update: function(args) { // some stuff here }, draw: function(args) { // some stuff here }, }; // from http://codeincomplete.com/posts/2011/5/14/javascript_pong/ 2: function Game() { this.Initialize = function () { } this.LoadContent = function () { this.GameLoop = setInterval(this.RunGameLoop, this.DrawInterval); } this.RunGameLoop = function (game) { this.Update(); this.Draw(); } this.Update = function () { // update } this.Draw = function () { // draw game frame } } // from http://www.felinesoft.com/blog/index.php/2010/09/accelerated-game-programming-with-html5-and-canvas/ 3: var engine = {}; engine.canvas = document.getElementById('canvas'); engine.ctx = engine.canvas.getContext('2d'); engine.map = {}; engine.map.draw = function() { // draw map } engine.player = {}; engine.player.draw = function() { // draw player } // from http://that-guy.net/articles/ So I guess my questions are: Which is most CPU efficient, is there any difference between these styles at runtime? Which one allows for easy expandability? Which one is the most safe, or at least harder to hack? Are there any good websites where stuff like this is explained? or... Does it all come to just personal preferance? :)

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• "cannot open file system. File system seems damaged "

  - by suresh kadiri

  I was using windows 7 till yesterday. I tried to install ubuntu 14. 04 Lts version yesterday with in windows 7. But it was not succeeded. Then I decided to install ubuntu only. By mistake I installed ubuntu in whole disk. After that to get deleted partitions I installed testdisk. I also used deeper search option. Now I'm getting "file system damaged". It shows The hard disk (320GB /298 GiB) seems to small! (<473 GB /441 GB) Check the Harddisk size: HD Jumpers setings, BIOS detection... The following partitions can't be recovered: Partition start end size in sectrors Linux 19077 177 45 57604 81 13 618930716 Linux 19080 192 57 57607 96 25 618930716 With ubcd also I used testdisk option. Same result comes."cannot open file system. File system seems damaged ". I have all my stuff in hard disk. Please help me to get recover my files in deleted partitions.

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• Functional Programming, JavaScript and UI - some neophyte questions

  - by jamesson

  This has been discussed in other threads, however I am hoping for some comments relevant to UI and an explanation of some vitriol I had flung my way in a Certain IRC Channel Which shall remain nameless. In the discussion here, the comments in the accepted answer suggest that I approach the given code from a functional perspective, which was new to me at the time. Wikipedia said, among other things, that FP "avoids state and mutable data", which includes according to the discussion global vars. Now, being that I am already pretty far along in my project I am not going to learn FP before I finish, but... How is it possible to avoid global vars if, for instance, I have a UI whose entire functionality changes if a mousebutton is down? I have a number of things like this. Why was there a strong negative reaction in the Certain IRC channel to implementing FP in JS? When I Brought up what seemed to me to be supportive comments by Crockford, people got even madder. Now, this being IRC there is no rep system, but they at least gave indication of having read TGP (which I haven't gotten to yet) so I'm assuming they're not idiots. Many thanks in advance Joe

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• STL algorithms and concurrent programming

  - by Andrew

  Hello everyone, Can any of STL algorithms/container operations like std::fill, std::transform be executed in parallel if I enable OpenMP for my compiler? I am working with MSVC 2008 at the moment. Or maybe there are other ways to make it concurrent? Thanks.

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• Languages and Tools for Web programming

  - by Mark Szymanski

  I am wanting to start Web Development and I was wondering what languages I would want to learn and what (if at all possible) free tools I would want to use.

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• Are we in a functional programming fad?

  - by TraumaPony

  I use both functional and imperative languages daily, and it's rather amusing to see the surge of adoption of functional languages from both sides of the fence. It strikes me, however, that it looks rather like a fad. Do you think that it's a fad? I know the reasons for using functional languages at times and imperative languages in others, but do you really think that this trend will continue due to the cliched "many-core" revolution that has been only "18 months from now" since 2004 (sort of like communism's Radiant Future), or do you think that it's only temporary; a fascination of the mainstream developer that will be quickly replaced by the next shiny idea, like Web 3.0 or GPGPU? Note, that I'm not trying to start a flamewar or anything (sorry if it sounds bitter), I'm just curious as to whether people will think functional or functional/imperative languages will become mainstream. Edit: By mainstream, I mean, equal number of programmers to say, Python, Java, C#, etc

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• Programming Language to manipulate an Access Database

  - by Wayne

  By quote, what is the appropiate language to manipulate an Access database? A Windows user interface to manipulate an existing Access Database. ... and why?

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• Sending mail with Gmail Account using System.Net.Mail in ASP.NET

  - by Jalpesh P. Vadgama

  Any web application is in complete without mail functionality you should have to write send mail functionality. Like if there is shopping cart application for example then when a order created on the shopping cart you need to send an email to administrator of website for Order notification and for customer you need to send an email of receipt of order. So any web application is not complete without sending email. This post is also all about sending email. In post I will explain that how we can send emails from our Gmail Account without purchasing any smtp server etc. There are some limitations for sending email from Gmail Account. Please note following things. Gmail will have fixed number of quota for sending emails per day. So you can not send more then that emails for the day. Your from email address always will be your account email address which you are using for sending email. You can not send an email to unlimited numbers of people. Gmail ant spamming policy will restrict this. Gmail provide both Popup and SMTP settings both should be active in your account where you testing. You can enable that via clicking on setting link in gmail account and go to Forwarding and POP/Imap. So if you are using mail functionality for limited emails then Gmail is Best option. But if you are sending thousand of email daily then it will not be Good Idea. Here is the code for sending mail from Gmail Account. using System.Net.Mail; namespace Experiement { public partial class WebForm1 : System.Web.UI.Page { protected void Page_Load(object sender,System.EventArgs e) { MailMessage mailMessage = new MailMessage(new MailAddress("[email protected]") ,new MailAddress("[email protected]")); mailMessage.Subject = "Sending mail through gmail account"; mailMessage.IsBodyHtml = true; mailMessage.Body = "<B>Sending mail thorugh gmail from asp.net</B>"; System.Net.NetworkCredential networkCredentials = new System.Net.NetworkCredential("[email protected]", "yourpassword"); SmtpClient smtpClient = new SmtpClient(); smtpClient.EnableSsl = true; smtpClient.UseDefaultCredentials = false; smtpClient.Credentials = networkCredentials; smtpClient.Host = "smtp.gmail.com"; smtpClient.Port = 587; smtpClient.Send(mailMessage); Response.Write("Mail Successfully sent"); } } } That’s run this application and you will get like below in your account. Technorati Tags: Gmail,System.NET.Mail,ASP.NET

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• Your thoughts on Best Practices for Scientific Computing?

  - by John Smith

  A recent paper by Wilson et al (2014) pointed out 24 Best Practices for scientific programming. It's worth to have a look. I would like to hear opinions about these points from experienced programmers in scientific data analysis. Do you think these advices are helpful and practical? Or are they good only in an ideal world? Wilson G, Aruliah DA, Brown CT, Chue Hong NP, Davis M, Guy RT, Haddock SHD, Huff KD, Mitchell IM, Plumbley MD, Waugh B, White EP, Wilson P (2014) Best Practices for Scientific Computing. PLoS Biol 12:e1001745. http://www.plosbiology.org/article/info%3Adoi%2F10.1371%2Fjournal.pbio.1001745 Box 1. Summary of Best Practices Write programs for people, not computers. (a) A program should not require its readers to hold more than a handful of facts in memory at once. (b) Make names consistent, distinctive, and meaningful. (c) Make code style and formatting consistent. Let the computer do the work. (a) Make the computer repeat tasks. (b) Save recent commands in a file for re-use. (c) Use a build tool to automate workflows. Make incremental changes. (a) Work in small steps with frequent feedback and course correction. (b) Use a version control system. (c) Put everything that has been created manually in version control. Don’t repeat yourself (or others). (a) Every piece of data must have a single authoritative representation in the system. (b) Modularize code rather than copying and pasting. (c) Re-use code instead of rewriting it. Plan for mistakes. (a) Add assertions to programs to check their operation. (b) Use an off-the-shelf unit testing library. (c) Turn bugs into test cases. (d) Use a symbolic debugger. Optimize software only after it works correctly. (a) Use a profiler to identify bottlenecks. (b) Write code in the highest-level language possible. Document design and purpose, not mechanics. (a) Document interfaces and reasons, not implementations. (b) Refactor code in preference to explaining how it works. (c) Embed the documentation for a piece of software in that software. Collaborate. (a) Use pre-merge code reviews. (b) Use pair programming when bringing someone new up to speed and when tackling particularly tricky problems. (c) Use an issue tracking tool. I'm relatively new to serious programming for scientific data analysis. When I tried to write code for pilot analyses of some of my data last year, I encountered tremendous amount of bugs both in my code and data. Bugs and errors had been around me all the time, but this time it was somewhat overwhelming. I managed to crunch the numbers at last, but I thought I couldn't put up with this mess any longer. Some actions must be taken. Without a sophisticated guide like the article above, I started to adopt "defensive style" of programming since then. A book titled "The Art of Readable Code" helped me a lot. I deployed meticulous input validations or assertions for every function, renamed a lot of variables and functions for better readability, and extracted many subroutines as reusable functions. Recently, I introduced Git and SourceTree for version control. At the moment, because my co-workers are much more reluctant about these issues, the collaboration practices (8a,b,c) have not been introduced. Actually, as the authors admitted, because all of these practices take some amount of time and effort to introduce, it may be generally hard to persuade your reluctant collaborators to comply them. I think I'm asking your opinions because I still suffer from many bugs despite all my effort on many of these practices. Bug fix may be, or should be, faster than before, but I couldn't really measure the improvement. Moreover, much of my time has been invested on defence, meaning that I haven't actually done much data analysis (offence) these days. Where is the point I should stop at in terms of productivity? I've already deployed: 1a,b,c, 2a, 3a,b,c, 4b,c, 5a,d, 6a,b, 7a,7b I'm about to have a go at: 5b,c Not yet: 2b,c, 4a, 7c, 8a,b,c (I could not really see the advantage of using GNU make (2c) for my purpose. Could anyone tell me how it helps my work with MATLAB?)

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• What Functional features are worth a little OOP confusion for the benefits they bring?

  - by bonomo

  After learning functional programming in Haskell and F#, the OOP paradigm seems ass-backwards with classes, interfaces, objects. Which aspects of FP can I bring to work that my co-workers can understand? Are any FP styles worth talking to my boss about retraining my team so that we can use them? Possible aspects of FP: Immutability Partial Application and Currying First Class Functions (function pointers / Functional Objects / Strategy Pattern) Lazy Evaluation (and Monads) Pure Functions (no side effects) Expressions (vs. Statements - each line of code produces a value instead of, or in addition to causing side effects) Recursion Pattern Matching Is it a free-for-all where we can do whatever the programming language supports to the limit that language supports it? Or is there a better guideline?

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• Entity System with C++

  - by Dono

  I'm working on a game engine using the Entity System and I have some questions. How I see Entity System : Components : A class with attributs, set and get. Sprite Physicbody SpaceShip ... System : A class with a list of components. (Component logic) EntityManager Renderer Input Camera ... Entity : Just a empty class with a list of components. What I've done : Currently, I've got a program who allow me to do that : // Create a new entity/ Entity* entity = game.createEntity(); // Add some components. entity->addComponent( new TransformableComponent() ) ->setPosition( 15, 50 ) ->setRotation( 90 ) ->addComponent( new PhysicComponent() ) ->setMass( 70 ) ->addComponent( new SpriteComponent() ) ->setTexture( "name.png" ) ->addToSystem( new RendererSystem() ); My questions Did the system stock a list of components or a list of entities ? In the case where I stock a list of entities, I need to get the component of this entities on each frame, that's probably heavy isn't it ? Did the system stock a list of components or a list of entities ? In the case where I stock a list of entities, I need to get the component of this entities on each frame, that's probably heavy isn't it ?

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• Advanced System Monitor/Task Manager?

  - by instanceofTom

  When using kubuntu I noticed that the standard task manager/system monitor was a bit more capable than gnome-system-monitor, is there a more advanced system/task monitor for ubuntu that is based on gnome opposed to KDE? Specifically the features from the Kubuntu task manager that I am looking for are the ability to control the I/O priority of individual processes (not just their nice), and the ability to control the I/O scheduling algorithm ( round-robin, FIFO, etc). What are my options?

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