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• Parallel.For Inconsistency results

  - by ni Gue ???

  I am using VB.net to write a parallel based code. I use Parallel.For to generate pairs of 500 objects or in combination C(500,2) such as the following code; but I found that it didn't always generate all combinations which should be 124750 (shown from variable Counter). No other thread was runing when this code was run. I am using a Win-7 32 Bit desktop with Intel Core i5 CPU [email protected], 3.33 GHz and RAM 2GB. What's wrong with the code and how to solve this problem? Thank You. Dim Counter As Integer = 0 Parallel.For(0, 499, Sub(i) For j As Integer = i + 1 To 499 Counter += 1 Console.Write(i & ":" & j) Next End Sub) Console.Writeline("Iteration number: " & Counter)

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• At $20/month Windows Azure host my website with 99.97% uptime

  - by Gopinath

  Couple of years ago a reliable and decent performing Windows hosting was not affordable to many enthusiastic developers who want to try a startup idea or build a hobby site. I tried to start an ASP.NET website few years ago to provide services like – Mobile Tracing, Vehicle Tracing. But due to high cost of Windows hosting I developed those services using PHP (not an easy task for .NET developer) and hosted on them Linux servers.  But with recent evolution of Windows Azure, hosting ASP.NET websites on highly reliable servers is affordable. Today anyone can host a high responsive and available ASP.NET website for just $20/month using Windows Azure. My website coziie.com is running on Windows Azure and serves close to quarter millions visitors a month with 99.97% of uptime and most of the page load times are less than 3 seconds. All I spend to run this website is just around $20, if you translate it to India rupees its roughly Rs.1000. The web sever of coziie.com is powered by a single Extra Small Web role instance and the backend is powered by a SQL Azure instance. Azure is quite impressive to provide 99.97% of uptime. Response times during peak are around 3 seconds and on nomarl loads it is around 1.5 seconds. Here is the report of uptime provided by Royal Pingdom over last one year For just $20/month Windows Azure takes care of the following apart from hosting Patches up Windows OS to the latest version Upgrades ASP.NET to the latest version – coziie.com is running on ASP.NET MVC 3 and soon I’ll upgrade it to ASP.NET MVC 4 Hosts data on latest and best version Sql Server database SQL Azure maintains 3 copies of database and automatically recovers in case of server failures and disasters. I never worry about database backups/restore. Provides staging environment for deploying applications for testing purpose and move them to production – I upgrade  twice a month on average With Windows Azure I no longer focus on server maintenance or data backups. They are taken up by Microsoft team and I just focus on building my website. Wish there is a low cost Linux version of Windows Azure so that I can stop worrying about server maintenance of this blog!! If you are looking for a Windows hosting, look no further than Windows Azure. If you find $20/month is a bit expensive to start with you may explore Azure Website (sort of shared hosted environment) which is free to start with and as your traffic grows you can move to paid hosting.

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• What's a good starting point to learn about JIT compilers?

  - by davidk01

  I've spent the past few months learning about stack based virtual machines, parsers, compilers, and some elementary things about hardware architecture. I've also written a few parsers and compilers for C like languages to understand the generic parser/compiler pipeline. Now I'd like to take my understanding further by learning about optimizing compilers and JIT compilers but I'm having a hard time finding material at the right level. I don't yet understand enough to dive into a code base like PyPy or LuaJIT but I also know more than what most introductory compiler books have to offer. So what are some good books for an intermediate beginner like to me to look into?

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• OpenGL setup on Windows

  - by kevin james

  I have been trying to use OpenGL for two days now. First on Mac, then on Windows. The problem with Mac is that it doesn't support the newer versions of OpenGL. I ran a tutorial that actually did get some things working, but it only works in XCode (i.e., I can't create a new file, paste in the same code, and get it to work). Because of these issues, I moved to Windows. My Windows 7 has OpenGL 4.3, which is the same that is used in alot of other tutorials. However, not one of these tutorials gives any instruction on how to set it up for the first time. I have come across some vague posts saying that some libraries need to be linked. But WHAT libraries, and HOW do I link them? Please help. I am pretty desperate to set this up as this project is due for work soon. I have actually used OpenGL before at my university, but the computers already had everything set up. The project itself is very easy, but setting up OpenGL is not something I know how to do.

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• How necessary is it to learn JavaScript before jQuery?

  - by benhowdle89

  In my opinion, when I looked at JavaScript, it looked like not my cup of tea. When I came across jQuery, I loved it. I sat and watched Nettuts+ 15 days of jQuery screencasts, 1 year later and now I'm fairly confident I wouldn't develop a website without including jQuery's library. I have never felt this has held me back but my question is, will this come back and bite me in the ass one day, the fact that I didn't have a solid JavaScript foundation before jumping feet first into one of its best (if not the best) frameworks? Did anyone else take this approach?

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• "Imprinting" as a language feature?

  - by MKO

  Idea I had this idea for a language feature that I think would be useful, does anyone know of a language that implements something like this? The idea is that besides inheritance a class can also use something called "imprinting" (for lack of better term). A class can imprint one or several (non-abstract) classes. When a class imprints another class it gets all it's properties and all it's methods. It's like the class storing an instance of the imprinted class and redirecting it's methods/properties to it. A class that imprints another class therefore by definition also implements all it's interfaces and it's abstract class. So what's the point? Well, inheritance and polymorphism is hard to get right. Often composition gives far more flexibility. Multiple inheritance offers a slew of different problems without much benefits (IMO). I often write adapter classes (in C#) by implementing some interface and passing along the actual methods/properties to an encapsulated object. The downside to that approach is that if the interface changes the class breaks. You also you have to put in a lot of code that does nothing but pass things along to the encapsulated object. A classic example is that you have some class that implements IEnumerable or IList and contains an internal class it uses. With this technique things would be much easier Example (c#) [imprint List<Person> as peopleList] public class People : PersonBase { public void SomeMethod() { DoSomething(this.Count); //Count is from List } } //Now People can be treated as an List<Person> People people = new People(); foreach(Person person in people) { ... } peopleList is an alias/variablename (of your choice)used internally to alias the instance but can be skipped if not needed. One thing that's useful is to override an imprinted method, that could be achieved with the ordinary override syntax public override void Add(Person person) { DoSomething(); personList.Add(person); } note that the above is functional equivalent (and could be rewritten by the compiler) to: public class People : PersonBase , IList<Person> { private List<Person> personList = new List<Person>(); public override void Add(object obj) { this.personList.Add(obj) } public override int IndexOf(object obj) { return personList.IndexOf(obj) } //etc etc for each signature in the interface } only if IList changes your class will break. IList won't change but an interface that you, someone in your team, or a thirdparty has designed might just change. Also this saves you writing a whole lot of code for some interfaces/abstract classes. Caveats There's a couple of gotchas. First we, syntax must be added to call the imprinted classes's constructors from the imprinting class constructor. Also, what happends if a class imprints two classes which have the same method? In that case the compiler would detect it and force the class to define an override of that method (where you could chose if you wanted to call either imprinted class or both) So what do you think, would it be useful, any caveats? It seems it would be pretty straightforward to implement something like that in the C# language but I might be missing something :) Sidenote - Why is this different from multiple inheritance Ok, so some people have asked about this. Why is this different from multiple inheritance and why not multiple inheritance. In C# methods are either virtual or not. Say that we have ClassB who inherits from ClassA. ClassA has the methods MethodA and MethodB. ClassB overrides MethodA but not MethodB. Now say that MethodB has a call to MethodA. if MethodA is virtual it will call the implementation that ClassB has, if not it will use the base class, ClassA's MethodA and you'll end up wondering why your class doesn't work as it should. By the terminology sofar you might already confused. So what happens if ClassB inherits both from ClassA and another ClassC. I bet both programmers and compilers will be scratching their heads. The benefit of this approach IMO is that the imprinting classes are totally encapsulated and need not be designed with multiple inheritance in mind. You can basically imprint anything.

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• Which is preferable? To know jQuery well, or to know JavaScript well? [closed]

  - by Marwan

  I'm quite familiar with using jQuery, but I've come to feel like a bit of a dummy using it, as my knowledge of JavaScript itself is rather poor. So I'm considering abandoning jQuery and spending time working in straight JS... perhaps even creating my own framework as a learning experience. Does this make sense though? Is there any real point to obtaining more than a passing knowledge of JavaScript when jQuery allows me to accomplish so much, so quickly?

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• Make an object slide around an obstacle

  - by Isaiah

  I have path areas set up in a game I'm making for canvas/html5 and have got it working to keep the player within these areas. I have a function isOut(boundary, x, y) that returns true if the point is outside the boundary. What I do is check only the new position x/y separately with the corresponding old position x/y. Then if each one is out I assign them the past value from the frame before. The old positions are kept in a variable from a closure I made. like this: opos = [x,y];//old position npos = [x,y];//new position if(isOut(bound, npos[0], opos[1])){ npos[0] = opos[0]; //assign it the old x position } if(isOut(bound, opos[0], npos[1])){ npos[1] = opos[1]; //assign it the old y position } It looks nice and works good at certain angles, but if your boundary has diagonal regions it results in jittery motion. What's happening is the y pos exits the area while x doesn't and continues pushing the player to the side, once it has moved the player to the side a bit the player can move forward and then the y exits again and the whole process repeats. Anyone know how I may be able to achieve a smoother slide? I have access to the player's velocity vector, the angle, and the speed(when used with the angle). I can move the play with either angle/speed or x/yvelocities as I've built in backups to translate one to the other if either have been altered manually.

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• How is intermediate data organized in MapReduce?

  - by Pedro Cattori

  From what I understand, each mapper outputs an intermediate file. The intermediate data (data contained in each intermediate file) is then sorted by key. Then, a reducer is assigned a key by the master. The reducer reads from the intermediate file containing the key and then calls reduce using the data it has read. But in detail, how is the intermediate data organized? Can a data corresponding to a key be held in multiple intermediate files? What happens when there is too much data corresponding to one key to be held by a single file? In short, how do intermediate partitions differ from intermediate files and how are these differences dealt with in the implementation?

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• Languages like Tcl that have configurable syntax?

  - by boost

  I'm looking for a language that will let me do what I could do with Clipper years ago, and which I can do with Tcl, namely add functionality in a way other than just adding functions. For example in Clipper/(x)Harbour there are commands #command, #translate, #xcommand and #xtranslate that allow things like this: #xcommand REPEAT; => DO WHILE .T. #xcommand UNTIL <cond>; => IF (<cond>); ;EXIT; ;ENDIF; ;ENDDO LOCAL n := 1 REPEAT n := n + 1 UNTIL n > 100 Similarly, in Tcl I'm doing proc process_range {_for_ project _from_ dat1 _to_ dat2 _by_ slice} { set fromDate [clock scan $dat1] set toDate [clock scan $dat2] if {$slice eq "day"} then {set incrementor [expr 24 * 60]} if {$slice eq "hour"} then {set incrementor 60} set method DateRange puts "Scanning from [clock format $fromDate -format "%c"] to [clock format $toDate -format "%c"] by $slice" for {set dateCursor $fromDate} {$dateCursor <= $toDate} {set dateCursor [clock add $dateCursor $incrementor minutes]} { # ... } } process_range for "client" from "2013-10-18 00:00" to "2013-10-20 23:59" by day Are there any other languages that permit this kind of, almost COBOL-esque, syntax modification? If you're wondering why I'm asking, it's for setting up stuff so that others with a not-as-geeky-as-I-am skillset can declare processing tasks.

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• What is the philosophy/reasoning behind C#'s Pascal-casing method names?

  - by Nocturne

  I'm just starting to learn C#. Coming from a background in Java, C++ and Objective-C, I find C#'s Pascal-casing its method-names rather unique, and a tad difficult to get used to at first. What is the reasoning and philosophy behind this? I'm guessing it is because of C# properties. Unlike in Objective-C, where method names can be exactly the same as an instance variables, this is not the case with C#. I would guess one of the goals with properties (as it is with most of the languages that support it) is to make properties truly indistinguishable from variables and methods. So, one can have an "int x" in C#, and the corresponding property becomes X. To ensure that properties and methods are indistinguishable, all method names I'm guessing are also therefore expected to start with an uppercase letter. (This is just my hypothesis based on what I know of C# so far—I'm still learning). I'm very curious to know how this curious guideline came into being (given that it's not something one sees in most other languages where method names are expected to start with a lowercase letter) (EDIT: By Pascal-casing, I mean PascalCase (which is basically camelCase but starting with a capital letter). Method names typically start with a lowercase letter in most languages)

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• Techniques for separating game model from presentation

  - by liortal

  I am creating a simple 2D game using XNA. The elements that make up the game world are what i refer to as the "model". For instance, in a board game, i would have a GameBoard class that stores information about the board. This information could be things such as: Location Size Details about cells on the board (occupied/not occupied) etc This object should either know how to draw itself, or describe how to draw itself to some other entity (renderer) in order to be displayed. I believe that since the board only contains the data+logic for things regarding it or cells on it, it should not provide the logic of how to draw things (separation of concerns). How can i achieve a good partitioning and easily allow some other entity to draw it properly? My motivations for doing so are: Allow multiple "implementations" of presentation for a single game entity Easier porting to other environments where the presentation code is not available (for example - porting my code to Unity or other game technology that does not rely on XNA).

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• Java Applet Tower Defence Game needs tweeking

  - by Ephiras

  Hello :) i have made a tower defence Game for my computer science class as one of my major projects, but have encountered some rather fatal roadblocks. here they are creating a menu screen (class Menu) that can set the total number of enimies, the max number of towers, starting money and the map. i tried creating a constructor in my Main class that sets all the values to whatever the Menu class passes in. I want the Menu screen to close after a difficulty has been selected and the main class to begin. Another problem i would really like some help with is instead of having to write entire arrays i would like to create a small segment of code that runs through an entire picture and sets up an array based on that pixels color.this way i can have multiple levels just dragged into a level folder and have the program read through them. users can even create their own. so a 1 if its yellow, a two if blue and a 3 if purple, then everything else = 0; you can download all the classes and code uif you'd like here sorry about having to redirect you but i wasn't sure how to efficently add a code spoiler. help is greatly appreciated

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• How do I print values of an array in Three Rows?

  - by Ramkumar

  I need this output.. 1 3 5 2 4 6 I want to use array function like array(1,2,3,4,5,6). If I edit this array like array(1,2,3), it means the output need to show like 1 2 3 The concept is maximum 3 column only. If we give array(1,2,3,4,5), it means the output should be 1 3 5 2 4 Suppose we will give array(1,2,3,4,5,6,7,8,9), then it means output is 1 4 7 2 5 8 3 6 9 that is, maximum 3 column only. Depends upon the the given input, the rows will be created with 3 columns. Is this possible with PHP? I am doing small Research & Development in array functions. I think this is possible. Will you help me? For more info: * input: array(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15) * output: 1 6 11 2 7 12 3 8 13 4 9 14 5 10 15

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• I am afraid that my University is not going to teach me enough information [closed]

  - by Muhklayne

  I attend a University and am a Computer Science major. I have barely entered into the major, as I am a sophomore. However, the coursework I am doing is extremely easy already and I feel as though this degree is going to lead me to a path of knowledge without knowing how to bring it all together. Therefore, I am coming to you to ask where I should begin learning on my own! I am willing to dedicate hours upon hours of learning to code outside of class, as it is truly my passion. I will begin by completing all work on http://www.codecademy.com, however I feel this will not be enough either. I would love to learn to integrate visual languages for video games such as NXA and C# combining it with C++ (as I understand video games can be created in this manner). I would also like to look into LUA and Python scripting. I am asking for advice as to where I should begin my personal studies of learning to program, as with my research it has become quite apparent that simply attaining a degree in Computer Science is quite frankly not enough. Thank you for your time!

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• What is So Unique About Node.js?

  - by Adrian Shum

  Recently there has been a lot of praise for Node.js. I am not a developer that has had much exposure to network application. From my bare understanding of Nodes.js, its strength is: we have only one thread handling multiple connections, providing an event-based architecture. However, for example in Java, I can create only one thread using NIO/AIO (which is non-blocking APIs from my bare understanding), and handle multiple connections using that thread, and I provide an event-based architecture to implement the data handling logic (shouldn't be that difficult by providing some callback etc) ? Given JVM being a even more mature VM than V8 (I expect it to run faster too), and event-based handling architecture seems to be something not difficult to create, I am not sure why Node.js is attracting so much attention. Did I miss some important points?

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• Are two database trips reasonable for a login system?

  - by Randolph Potter

  I am designing a login system for a project, and have an issue about it requiring two trips to the database when a user logs in. User types in username and password Database is polled and password hash is retrieved for comparative purposes (first trip) Code tests hash against entered password (and salt), and if verified, resets the session ID New session ID and username are sent back to the database to write a row to the login table, and generate a login ID for that session. EDIT: I am using a random salt. Does this design make sense? Am I missing something? Is my concern about two trips unfounded? Comments and suggestions are welcome.

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• Sorting objects before rendering

  - by dreta

  I'm trying to implement a scene graph and in all the articles i've come across there is talk about object sorting. So you'd sort your objects by "material" for example. Now untill i sat down and started implementing it, i kind of took this for granted, because it made sense. But now i'm wondering what does sorting actually change? In my engine, i have a manager for UBOs, i use those to store data that'll be shared between programs, at the moment that only involves time, camera and projection matrices and lights (i'm not worrying about managing which lights affect which objects ATM). Now for each model i have to change the model to world matrix uniform, no sorting is going to change that. So is the jump from changing this matrix to also setting a material for each object that bad? I vaguely remember reading somewhere that each time you change something in the pipeline, it has to get flushed and that can cause performance issues. But for each drawing call i'm setting up a model to world matrix anyway, so what sense does it make to ever be concerned about this? BTW is there any information about whether changing a uniform and calling glBufferSubData is more (or less) expensive.

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• Single or multiple return statements in a function [on hold]

  - by Juan Carlos Coto

  When writing a function that can have several different return values, particularly when different branches of code return different values, what is the cleanest or sanest way of returning? Please note the following are really contrived examples meant only to illustrate different styles. Example 1: Single return def my_function(): if some_condition: return_value = 1 elif another_condition: return_value = 2 else: return_value = 3 return return_value Example 2: Multiple returns def my_function(): if some_condition: return 1 elif another_condition: return 2 else: return 3 The second example seems simpler and is perhaps more readable. The first one, however, might describe the overall logic a bit better (the conditions affect the assignment of the value, not whether it's returned or not). Is the second way preferable to the first? Why?

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• Where can I find game postmortems with a programmer perspective [on hold]

  - by Ken

  There are a number of interesting game post-mortems in places like GDC vault or gamastura.com. The post-mortems are generally give with a CEO/manager perspective or a designer perspective, or, more often a combination of both e.g DOOM postmortem But I have not been able to find many post-mortems which are primarily from the programmers perspective. I'm looking for discussions and rational for technical choices and tradeoffs and how technical problems were overcome. The motivation here is to learn what kind of problems real game programmers encounter and how they go about solving them. A perfect example of what I'm looking for is Renaud Bédard's excellent GDC talk on the development of Fez, "Cubes all the way down". Where can I find more like that?

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• Should I use AND or should I use OR

  - by BDotA

  An order can be in the "status" of Completed, Corrected or some other stratus. I saw some code that is checking it like this, the purpose is to disable some stuff when the status is in Completed or Corrected status. if (model.CurrentStatus != DSRHelper.OrderStatusEnum.Complete && model.CurrentStatus != DSRHelper.OrderStatusEnum.Corrected) I can't get it why the engineer has used "AND" for this, shouldn't it be an "OR"?

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• Maximum Length Of IP Address: 15 (IPv4) & 39(IPv6)

  - by Gopinath

  Problem You are designing a database table for a web application that requires to store IP address of users who visits the site. The IP address is required to be stored a character data in the table. To define size of the character column you need to know maximum length of IP address. So, what is the maximum length of an IP address? Solution The IPv4 version of IP address is in the following format 255.255.255.255 To store IPv4 address we require 15 characters. The IPv6 version of IP address is grouped into sets of 4 hex digits separated by colons, like the below 2001:0db8:85a3:0000:0000:8a2e:0370:7334 To store IPv6 address you require a 39 characters long column. Conclusion As IPv4 and IPv6 are the commonly use protocols, you better define a column with 39 characters length so that both the format address are saved in to the table without any issues. This article titled,Maximum Length Of IP Address: 15 (IPv4) & 39(IPv6), was originally published at Tech Dreams. Grab our rss feed or fan us on Facebook to get updates from us.

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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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• How to process large files in NetLogo? [closed]

  - by user65597

  I am running into problems in NetLogo with large *.csv / *.txt files. The documents can consist of about 1 million data sets and I need to read them (to eventually create a diagram based on the data). With the most straightforward source code, my program needs about 2 minutes to process these files. How should I approach reading such large data files faster in NetLogo? Is NetLogo even suitable for such tasks (as it seems to be designed more for teaching and learning)?

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• Why Nodes.js being that "unique"?

  - by Adrian Shum

  Recently years there are lots of praise to Nodes.js. I am not a developer that have much exposure on network application. From my bare understanding of Nodes.js, its strength is: We are having only on thread handling multiple connections, providing a event-based architecture. However, for example in Java, what if I am having only one thread, using NIO/AIO (which is non-blocking APIs from my bare understanding), and handle multiple connections using that thread, and I provide an event-based architecture to implement the data handling logic (shouldn't be that difficult by providing some callback etc) ? Given JVM being a even more mature VM than V8 (I expect it run faster too), and event-based handling architecture seems not something difficult to create. I am not sure why Nodes.js is attracting so much attention. Did I miss some important points?

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