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• Resources to learn about engineering aspects of data analytics (OLAP, warehousing, ETL, etc.)

  - by JT

  I'm a math/stats guy, interested in learning more about the engineering aspects of "data analytics" (this may be an overly broad term, this is a case of "I don't know what I don't know", so I'm not sure how to be more specific). I'm fine with manipulating and analyzing the data once it's already stored somewhere and I can access it, and I'm fine with writing scripts and SQL queries (and have a general knowledge of things like normalization). What I don't know is the whole engineering process of capturing and storing the data. For example, terms I've heard thrown about that I only vaguely understand the meaning of include: - OLAP, OLTP - Data warehousing - ETL - ??? What's a good book (or any other resource) to learn about these kinds of things? What are things I should know about database design (normalization seems kinda "obvious" to me, something I would have done even before I knew the term -- is there anything else?)? In other words, for jobs falling under the umbrella term of "analytics engineer", what kinds of things should I know?

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• What is the best way for communication between cluster nodes

  - by Tom

  I have an application written in a combination of ASP/VB6/VBScript and ASP.NET/C# that consists of a website part, SOAP-like webservice part and a queue processing part processing incoming files in a hotfolder. We are used to running under load balancers (Microsoft or other make). Often we need to communicate between the different load balanced servers. Currently we do this through the SQL Server database that is common for all nodes, however, this comes with a performance penalty as each message requires a transaction and continual polling from the other nodes. What would be better ways to achieve this? Tom, Appelby

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• Out-Of-Memory while doing Core Data migration

  - by Kamchatka

  Hello, I'm migrating a CoreData model between two versions of an application. I was storing binary data as blobs in the previous version and I want to take them out of the blobs for performance. My issue is that during the migration it seems that Core Data loads everything into memory which leads to Low Memory Warnings and then to my app being killed. Apple documentation suggests the following : http://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/CoreDataVersioning/Articles/vmCustomizingTheProcess.html#//apple_ref/doc/uid/TP40005510-SW9 However, it seems to rely on the fact that the large objects are applied different mapping. In my case, all the objects are basically the same and the same mapping has to be applied to each of them. I don't see in this case how I could apply their technique. How should I handle a migration with very large objects ?

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• Android: Deciding between SurfaceView and OpenGL (GLSurfaceView)

  - by Rich

  Is there a way to decide up front based on the expected complexity of a game/app in the planning phase whether to use regular Canvas drawing in a SurfaceView or to go with OpenGL? I've been playing around with a Canvas and only need 2D movement, and on a fairly new phone I'm getting pretty decent performance with a bunch of primitive objects and a few bitmaps running around the screen on a solid background. Is it fair to say that if I'm going to be drawing background images and increasing the number of objects being moved and drawn on top of them that I should go straight to OpenGL?

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• C#: Check if administrator has write access to a file

  - by Bilal Aslam

  The Problem: I need to check if a user (local user or domain user, either one is possible) has write access to a file (if you're curious, %windir%\system32\inetsrv\applicationHost.config. This file is protected by Windows and you need to be an administrator to write to it.) My Solution: The general construct is: using (Impersonator impersonator = new Impersonator(domain, username, password)) { try { using (FileStream fs = File.OpenWrite(appHostConfigPath)) { return true; } catch { return false; } } As you can imagine, the Impersonator class is an IDisposible which uses native interop to call LogonUser. Nothing too creative, and it works. Where I am stuck: On Windows OSs with UAC enabled, this function always return false even if the user specified by username is an administrator. Even though my program is running elevated as an administrator, I suspect what's happening is that the impersonated code is running as a limited administrator. Hence, the method is returning false. I don't have any creative solutions to this. Can anyone help?

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• rewrite URLs in CSS files

  - by Don

  Hi, I'm writing a Maven plugin that merges CSS files together. So all the CSS files that match /foo/bar/*.css might get merged to /foo/merged.css. A concern is that in a file such as /foo/bar/baz.css there might be a property such as: background: url("images/pic.jpg") So when the file is merged into /foo/merged.css this will need to be changed to background: url("bar/images/pic.jpg") The recalculated URL obviously depends on 3 factors: original URL original CSS file location merged CSS file location Assuming that the original and merged CSS files are both on the same filesystem, is there a general formula (or Java library) that can be used to calculate the new url given these 3 inputs? Thanks, Don

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• Method hiding with interfaces

  - by fearofawhackplanet

  interface IFoo { int MyReadOnlyVar { get; } } class Foo : IFoo { int MyReadOnlyVar { get; set; } } public IFoo GetFoo() { return new Foo { MyReadOnlyVar = 1 }; } Is the above an acceptable way of implementing a readonly/immutable object? The immutability of IFoo can be broken with a temporary cast to Foo. In general (non-critical) cases, is hiding functionality through interfaces a common pattern? Or is it considered lazy coding? Or even an anti-pattern?

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• Reasons to learn MSIL

  - by mannu

  Hi, Learning MSIL is fun and all that. Understanding what is going on "under the hood" can in many ways improve how you write your code performance-wise. However, the IL that is produced by the compiler is quite verbose and does not tell the whole story since JIT will optimize away a lot of the code. I, personally, have had good use of my very basic IL understanding when I've had to make a small fix in an assembly I do not have the source code for. But, I could as well have used Reflector to generate C# code. I would like to know if you've ever had good use of MSIL understanding and/or why you think it is worth learning it (except for the fun in it, of course). I'd also like to know if you think one should not learn it and why.

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• What is the difference between MVC model 1 and model 2?

  - by Alex Ciminian

  I've recently discovered that MVC is supposed to have two different flavors, model one and model two. I'm supposed to give a presentation on MVC1 and I was instructed that "it's not the web based version, that is refered to as MVC2". As the presentations are about design patterns in general, I doubt that this separation is related to Java (I found some info on Sun's site, but it seemed far off) or ASP. I have a pretty good understanding of what MVC is and I've used several (web) frameworks that enforce it, but this terminology is new to me. How is the web-based version different from other MVC (I'm guessing GUI) implementations? Does it have something to do with the stateless nature of HTTP? Thanks, Alex

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• Using Large Lists

  - by cam

  In an Outlook AddIn I'm working on, I use a list to grab all the messages in the current folder, then process them, then save them. First, I create a list of all messages, then I create another list from the list of messages, then finally I create a third list of messages that need to be moved. Essentially, they are all copies of eachother, and I made it this way to organize it. Would it increase performance if I used only one list? I thought lists were just references to the actual item.

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• What messaging technologies in windows-ce for gauranteed msg delivery?

  - by Aidanapword

  All, We are building a windows-ce (6.0R3) based device that requires guaranteed and audit-ready message delivery (including store & forward) up to and down from the cloud. I have been looking for choices beyond: MSMQ a proprietary solution (what our prototype device is using) AMQP (research on using this in our context is now starting) ... are there any others? We will be transporting sensitive data (who isn't?!?!) over a public network, and large scale options are required. Anything running on an embedded device will be performance sensitive too. Thanks! Aidanapword

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• How can I prevent users from taking screenshots of my application window?

  - by Midday

  What are some methods to prevent screenshots from being taken, if any? I've considered setting the "Print Screen" button as a hotkey, which makes the window fuzzy. However, there would be the problem of other 3rd party screenshot tools. How can I prevent their use? Why would I want such a thing? The idea is to create a chat client which you can't share the chatted information with others, not by copy & paste nor by print screen... Looking for general ideas or suggestions rather than actual code.

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• Collection wrapping a array is read-only. Possible to make it writeable without casting?

  - by Brian Triplett

  I have a Collection<T> property that wraps a array like T[] array; public Collection<T> Items { get { return new Collection<T>(array); } } When I attempt to assign to the collection via: T variable; Items[i] = variable; I get a NotSupportedException because the colleciton's IsReadOnly property is true. Turns out that this is a design choice by Microsoft. Does anyone know a workaround that does NOT involve enumeration? It could be done if the underlying data is not an array but I enjoy the performance gains because the data is fixed length.

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• pros and cons of TryCatch versus TryParse

  - by Vijesh

  What are the pros and cons of using either of the following approaches to pulling out a double from an object? Beyond just personal preferences, issues I'm looking for feedback on include ease of debugging, performance, maintainability etc. public static double GetDouble(object input, double defaultVal) { try { return Convert.ToDouble(input); } catch { return defaultVal; } } public static double GetDouble(object input, double defaultVal) { double returnVal; if (double.TryParse(input.ToString(), out returnVal)) { return returnVal; } else { return defaultVal; } }

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• Send Keyboard Events from one Form to another Form

  - by thalm

  Hello, my question is quite simple: Our C# application has one MainForm with a menu and several keyboard shortcuts associated with the menu entries. Now we need to trigger the menu entries from some child forms too. But since the MainForm is inactive when one of the child forms is active, the shortcuts do not work. Is there a simple way to propagate all keyboard events from the child form to the 'Owner' form? Or just to another form in general? Ah, and we cannot use some low level windows stuff, because we need to run the application on Mono/Linux too.

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• LogCat acting patchy

  - by OceanBlue

  The LogCat output in eclipse suddenly started weird. It sometimes shows all the output as expected. Other times it just doesn't show anything - is completely blank. After some internet research, I thought Mylyn plugin might be responsible. So I tried de-selecting "Mylyn Tasks UI" & "Mylyn Team UI" on eclipse Window -- Preferences -- General -- Startup and Shutdown -- programs that are started at startup. No Luck. Has anyone else encountered & solved this problem?

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• How can open source projects obtain license for commercial software without spending a lot of money?

  - by Ikaso

  I just joined an open source project on codeplex. The project is based on the .NET compact framework. So the development tool is Visual Studio. Currently I am using some trial version of Visual Studio which is going to end and I wondered how can I obtain a valid license to work on the project without spending a lot of money. Please pay attention that the Express edition does not help me since my application is running on Windows Mobile 6.5 which is not supported on the Express edition (and the 2010 Express edition supports only Windows Mobile Phone 7 series development). In the general sense, are there some organizations that donate software licenses for open source projects?

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• Is it safe to catch an access violation in this scenario?

  - by Eloff

  I've read a lot, including here on SO that suggests this is a very bad idea in general and that the only thing you can do safely is exit the program. I'm not sure that this is true. This is for a pooling memory allocator that hands off large allocations to malloc. During pool_free() a pointer needs to be checked it it belongs to a pool or was allocated with malloc. By rounding the address down to the nearest 1MB boundary, I get a pointer to the beginning of a block of memory in the pool, or undefined if malloc was used. In the first case I can easily verify that the block of memory belongs to the pool, but, if it does not I will either fail this verification, or I will get an access violation (note that this is a read-only process). Could I not catch this with SEH (Windows) or handle the signal (POSIX) and simply treat it as a failed verification? (i.e. this is only possible if malloc was used, so pass the ptr to free())

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• What are the pros and cons to keeping SQL in Stored Procs versus Code

  - by Guy

  What are the advantages/disadvantages of keeping SQL in your C# source code or in Stored Procs? I've been discussing this with a friend on an open source project that we're working on (C# ASP.NET Forum). At the moment, most of the database access is done by building the SQL inline in C# and calling to the SQL Server DB. So I'm trying to establish which, for this particular project, would be best. So far I have: Advantages for in Code: Easier to maintain - don't need to run a SQL script to update queries Easier to port to another DB - no procs to port Advantages for Stored Procs: Performance Security

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• Candidate Elimination Question---Please help!

  - by leon

  Hi , I am doing a question on Candidate Elimination Algorithm. I am a little confused with the general boundary G. Here is an example, I got G and S to the fourth case, but I am not sure with the last case. Sunny,Warm,Normal,Strong,Warm,Same,EnjoySport=yes Sunny,Warm,High,Strong,Warm,Same,EnjoySport=yes Rainy,Cold,High,Strong,Warm,Change,EnjoySport=no Sunny,Warm,High,Strong,Cool,Change,EnjoySport=yes Sunny,Warm,Normal,Weak,Warm,Same,EnjoySport=no What I have here is : S 0 :{0,0,0,0,0,0} S 1 :{Sunny,Warm,Normal,Strong,Warm,Same} S 2 , S 3 : {Sunny,Warm,?,Strong,Warm,Same} S 4 :{Sunny,Warm,?,Strong,?,?} G 4 :{Sunny,?,?,?,?,?,?,Warm,?,?,?,?} G 3 :{Sunny,?,?,?,?,?,?,Warm,?,?,?,?,?,?,?,?,?,Same} G 0 , G 1 , G 2 : {?,?,?,?,?,?} What would be the result of G5? Is it G5 empty? {}? or {???Strong??) ? Thanks

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• code for find out nth larget number in an array by using perl

  - by user136104

  I have written following code in perl #!/usr/bin/perl @array =(3,6,8,1,2); my $second_largest =0; my $largest = 0; for (@array) { if($_ > $largest) { $second_largest = $largest; $largest = $_; } if($_ > $second_largest && $_ < $largest) { $second_largest = $_; } } print "Second largest::".$second_largest; print "largest::".$largest; But I need a general code to find out "Nth" largest and smallest number of an array Plz help me

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• Function Object in Java .

  - by Tony

  I wanna implement a javascript like method in java , is this possible ? Say , I have a Person class : public class Person { private String name ; private int age ; // constructor ,accessors are omitted } And a list with Person objects: Person p1 = new Person("Jenny",20); Person p2 = new Person("Kate",22); List<Person> pList = Arrays.asList(new Person[] {p1,p2}); I wanna implement a method like this: modList(pList,new Operation (Person p) { incrementAge(Person p) { p.setAge(p.getAge() + 1)}; }); modList receives two params , one is a list , the other is the "Function object", it loops the list ,and apply this function to every element in the list. In functional programming language,this is easy , I don't know how java do this? Maybe could be done through dynamic proxy, does that have a performance trade off?

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• Easy Way for Non-Nerd to Manage Simple Site?

  - by Mark Evans

  Hi I'm not sure if this is an appropriate question for StackOverflow. I have a friend show wants a simple "Brochure Ware" web site. I could make it for him but it would be better if he could manage it himself. Are there any services out there that allow a non-technical person to create and maintain a very simple site? I'm thinking just a few pages - contact, about, home with some photos and general info. He also wants to sell some stuff but I'm going to suggest he does this using EBay but the web site would be a handy reference for potential customers who want to know more about him and his services. Thanks a lot! Cheers Mark

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• Most Efficient Alternative Method of Storing Settings for iPhone Apps

  - by JPK

  I am not using the Settings bundle to store the settings for my app, as I prefer to allow the user to access the settings within the app (they may be changed fairly often). I do realize that there is the option to do both, but for now, I am trying to find the most optimal place to store the settings within the app. I have a good number of settings (from what I have read, probably too many for NSUserDefaults), and the two main options I am considering are: 1) storing the settings in a dictionary in the plist, loading the settings into a NSDictionary property in the app delegate and accessing them via the sharedDelegate 2) storing the settings in a Core Data entity (1 row on Settings entity), loading the settings into a Settings object in the app delegate and accessing them via the sharedDelegate Of these two, which would be the optimal method, performance wise?

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• How to deal with routing when developing a custom CMS in Codeigniter

  - by Ashley Ward

  Hi All - I’m a recent user of Codeigniter and am developing a simple backend CMS to manage pages. Based on a URL (in this example I have hidden “index.php”) : mysite.com/pagename I would like the system to detect if there is a value of “pagename” in my database, if there is, I need the system to re-route to a custom controller (eg: Pagemaker) and if there is no record called pagename, just do it’s normal thing (i.e. find a controller called pagename) Currently I have: $route['(:any)'] = "pagemaker/create/$1"; whereby all requests are forwarded to my custom function. However I want to change this structure so that if the page does NOT exist in the db, the traditional codeigniter request process is followed. Can anyone offer any advice about how to complete this? Or any advice about routing custom CMS’s in codeigniter in general?

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