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  • Task vs. process, is there really any difference?

    - by DASKAjA
    Hi there, I'm studying for my final exams in my CS major on the subject distributed systems and operating systems. I'm in the need for a good definition for the terms task, process and threads. So far I'm confident that a process is the representation of running (or suspended, but initiated) program with its own memory, program counter, registers, stack, etc (process control block). Processes can run threads which share memory, so that communication via shared memory is possible in contrast to processes which have to communicate via IPC. But what's the difference between tasks and process. I often read that they're interchangable and that the term task isn't used anymore. Is that really true?

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  • Mutual Information / Entropy Calculation Help

    - by Fillip
    Hi, Hoping someone can give me some pointers with this entropy problem. Say X is chosen randomly from the uniform integer distribution 0-32 (inclusive). I calculate the entropy, H(X) = 32 bits, as each Xi has equal probability of occurring. Now, say the following pseudocode executes. int r = rand(0,1); // a random integer 0 or 1 r = r * 33 + X; How would I work out the mutual information between the two variables r and X? Mutual Information is defined as I(X; Y) = H(X) - H(X|Y) but I don't really understand how to apply the conditional entropy H(X|Y) to this problem. Thanks

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  • Is XSLT worth investing time in and are there any actual alternatives?

    - by Keeno
    I realize this has been a few other questions on this topic, and people are saying use your language of choice to manipulate the XML etc etc however, not quite fit my question exactly. Firstly, the scope of the project: We want to develop platform independent e-learning, currently, its a bunch of HTML pages but as they grow and develop they become hard to maintain. The idea: Generate up an XML file + Schema, then produce some XSLT files that process the XML into the eLearning modiles. XML to HTML via XSLT. Why: We would like the flexibilty to be able to easy reformat the content (I realize CSS is a viable alternative here) If we decide to alter the pages layout or functionality in anyway, im guessing altering the "shared" XSLT files would be easier than updating the HTML files. So far, we have about 30 modules, with up to 10-30 pages each Depending on some "parameters" we could output drastically different page layouts/structures, above and beyond what CSS can do Now, all this has to be platform independent, and to be able to run "offline" i.e. without a server powering the HTML Negatives I've read so far for XSLT: Overhead? Not exactly sure why...is it the compute power need to convert to HTML? Difficult to learn Better alternatives Now, what I would like to know exactly is: are there actually any viable alternatives for this "offline"? Am I going about it in the correct manner, do you guys have any advice or alternatives. Thanks!

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  • What is a 'better' approach to query/save from server: DTO or Wcf Data Services?

    - by bonefisher
    From my perspective, the Data Services and their query approach is useful when querying simple object graphs from your server-side domain model. But when you want to query complex dependencies I couldn't create anything good out of it. The classic DTO approach is fine-grained and can handle everything, but the downside is that you have to create Dto classes for every type of server-request which is time consuming and you have to synchronize the Dto type with your domain entity/business logic.

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  • Avoiding mass propagation of properties and events for exposure to ViewModels.

    - by firoso
    I have an MVVM application I am developing that is to the point where I'm ready to start putting together a user interface (my client code is largely functional) I'm now running into the issue that I'm trying to get my application data to where I need it so that it can be consumed by the view model and then bound to the view. Unfortunately, it seems that I've either got a few structural oversights, or I'm just going to have to face the reality that I need to be propogating events and raising excessive amounts of errors to notify view models that thier properties have changed. Let me go into some examples of my issue: I have a class "Unit" contained in a class "Test", contained in a class "Session" contained in a class "TestManager" which is contained in "TestDataModel" which is utilized by "TestViewModel" which is databound to by my "TestView" .... WHOA. Now, consider that Unit (the bottom of the heiarchy) has a property called "Results" that is updated periodically, I want to expose that to my viewmodel and then databind it to my view, trouble is, the only way I can really think to do this is to perpetuate events WAY up a chain that say "I've been updated!" and then request the new value... This seems like an aweful way to do this. Alternatively, I could register a static event and raise it, and have the appropriate "Unit view model" grab the event and request the update. This SEEMS better... but... static events? Is that a taboo idea? Also, having an expression like: TestDataModel.TestManager.Session.Test.Unit.Results[i] Seems REALLY gross to have on a View Model. I know this all reeks of a bad design issue, but I can't figure out what I did wrong? Should I be using more singleton/container controlled lifetimes type objects? Register object instances with static helper containers? Obviously these are hard questions to answer without being intimate with the existing structure, but if you've run into situations like this, what did you do to refactor? Should I just live with this, add mass events, and propogate them?

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  • Visual Studio 2010 UML Tools. How do they integrate with the code? For small/mid size products is t

    - by punkouter
    I just got a book that goes over all the VS2010 tools. Most I have never used like load testing/web testing, UML Tools, Layer Diagrams.... Has anyone had any real world experience with using these VS2010 tools like the UML diagramming? I am wondering if it is something that would really be useful starting a new project or is it just busy work that no one ever uses once they are made? How are the UML diagrams integrated with the rest of development in VS2010 ? The last project we just made some really basic Visio diagrams but maybe this is better. Alot of VS2010 Ultimate tools are over kill (layer diagram) for small/mid level projects it seems. UML seems to be one of those things I hear about past 10 years but never seem to use.

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  • What database strategy to choose for a large web application

    - by Snoopy
    I have to rewrite a large database application, running on 32 servers. The hardware is up to date, each machine has two quad core Xeon and 32 GByte RAM. The database is multi-tenant, each customer has his own file, around 5 to 10 GByte each. I run around 50 databases on this hardware. The app is open to the web, so I have no control on the load. There are no really complex queries, so SQL is not required if there is a better solution. The databases get updated via FTP every day at midnight. The database is read-only. C# is my favourite language and I want to use ASP.NET MVC. I thought about the following options: Use two big SQL servers running SQL Server 2012 to serve the 32 servers with data. On the 32 servers running IIS hosting providing REST services. Denormalize the database and use Redis on each webserver. Use booksleeve as a Redis client. Use a combination of SQL Server and Redis Use SQL Server 2012 together with Hadoop Use Hadoop without SQL Server What is the best way for a read-only database, to get the best performance without loosing maintainability? Does Map-Reduce make sense at all in such a scenario? The reason for the rewrite is, the old app written in C++ with ISAM technology is too slow, the interfaces are old fashioned and not nice to use from an website, especially when using ajax. The app uses a relational datamodel with many tables, but it is possible to write one accerlerator table where all queries can be performed on, and all other information from the other tables are possible by a simple key lookup.

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  • Thoughts on streamlining multiple .Net apps

    - by John Virgolino
    We have a series of ASP.Net applications that have been written over the course of 8 years. Mostly in the first 3-4 years. They have been running quite well with little maintenance, but new functionality is being requested and we are running into IDE and platform issues. The apps were written in .Net 1.x and 2.x and run in separate spaces but are presented as a single suite of applications which use a common navigation toolbar (implemented as a user control). Every time we want to add something to a menu in the nav we have to modify it in all the apps which is a pain. Also, the various versions of Crystal reports and that we used tables to organize the visual elements and we end up with a mess, especially with all the multi-platform .Net versions running. We need to streamline the suite of apps and make it easier to add on new apps without a hassle. We also need to bring all these apps under one .Net platform and IDE. In addition, there is a WordPress blog styled to match the style of the application suite "integrated" into the UI and a link to a MediaWiki Wiki application as well. My current thinking is to use an open source content management system (CMS) like Joomla (PHP based unfortunately, but it works well) as the user interface framework for style templating and menu management. Joomla's article management would allow us to migrate the Wiki content into articles which could be published without interfering with the .Net apps. Then essentially use an IFrame within an "article" to "host" the .Net application, then... Upgrade the .Net apps to VS2010, strip out all the common header/footer controls and migrate the styles to use the style sheets used in the CMS. As I write this, I certainly realize this is a lot of work and there are optimization issues which this may cause as well as using IFrames seems a bit like cheating and I've read about issues with IFrames. I know that we could use .Net application styling, but it seems like a lot more work (not sure really). Also, the use of a CMS to handle the blog and wiki also seems appealing, unless there is a .Net CMS out there that can handle all of these requirements. Given this information, I am looking to know if I am totally going in the wrong direction? We tried to use open source and integrate it over time, but not this has become hard to maintain. Am I not aware of some technology out there that will meet our requirements? Did we do this right and should we just focus on getting the .Net streamlined? I understand that no matter what we do, it's going to be a lot of work. The communities considerable experience would be helpful. Thanks!! PS - A complete rewrite is not an option.

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  • Architecting a generic search result web control

    - by Bartek Tatkowski
    In a project I'm currently working for we've stumbled upon the need for several kinds of search results presentation controls. The search result are similar, but not identical. For example, in the "office search" result we might want to present the office name and location, while in the "document search" could contain document name, author and publishing date. These fields should be sortable. My current strategy is to employ the Factory pattern and do something like this: ISearchResult officeResults = SearchResultFactory.CreateOfficeSearchResults(data); ISearchResult documentResults = SearchResultFactory.CreateDocumentSearchResults(data); The problem is: I don't know how to implement the markup code. Should I just do Controls.Add(officeResults); in the containing page? Or is there some ASPX trickery to create generic web controls? Or maybe I'm overthinking this and just should create five classes? ;)

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  • NHibernate 2nd level cache provider for NHibernate 2.1.1.4000

    - by Rippo
    I am using s#arp which is built against NHibernate 2.1.1.4000, However I would like to use NHibernate.Caches.SysCache as my second level cache. However the Nhibernate contrib caches are built against NHibernate 2.1.2.4000 which obviously gives me a problem. Can anyone point me to a URL that I can download NHibernate.Caches.SysCache.dll that is built against NHibernate 2.1.1.4000 Or is there another 2nd level cache provider that is easy to implement and is built against NHibernate 2.1.1.4000 Thanks

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  • Are .NET's regular expressions Turing complete?

    - by Robert
    Regular expressions are often pointed to as the classical example of a language that is not Turning complete. For example "regular expressions" is given in as the answer to this SO question looking for languages that are not Turing complete. In my, perhaps somewhat basic, understanding of the notion of Turning completeness, this means that regular expressions cannot be used check for patterns that are "balanced". Balanced meaning have an equal number of opening characters as closing characters. This is because to do this would require you to have some kind of state, to allow you to match the opening and closing characters. However the .NET implementation of regular expressions introduces the notion of a balanced group. This construct is designed to let you backtrack and see if a previous group was matched. This means that a .NET regular expressions: ^(?<p>a)*(?<-p>b)*(?(p)(?!))$ Could match a pattern that: ab aabb aaabbb aaaabbbb ... etc. ... Does this means .NET's regular expressions are Turing complete? Or are there other things that are missing that would be required for the language to be Turing complete?

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  • How practical to change MVC app from traditional authentication to cookieless?

    - by Phil.Wheeler
    I have an application written in MVC that uses your regular .Net Forms Authentication. There's nothing particularly new or exciting going on with it. My client has now asked that users be able to log in to the app on the same machine but in different browsers, or different tabs within the same browser. To my mind, he's asking for a scope change to have authentication moved to cookieless instead of its current design. Not having had any experience with doing this in MVC, I'm curious to know before I get started how much hurt I'm in for by trying this. Are there better ways to do it? What should I consider? Any advice appreciated.

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  • import csv file/excel into sql database asp.net

    - by kiev
    Hi everyone! I am starting a project with asp.net visual studio 2008 / SQL 2000 (2005 in future) using c#. The tricky part for me is that the existing DB schema changes often and the import files columns will all have to me matched up with the existing db schema since they may not be one to one match on column names. (There is a lookup table that provides the tables schema with column names I will use) I am exploring different ways to approach this, and need some expert advice. Is there any existing controls or frameworks that I can leverage to do any of this? So far I explored FileUpload .NET control, as well as some 3rd party upload controls to accomplish the upload such as SlickUpload but the files uploaded should be < 500mb Next part is reading of my csv /excel and parsing it for display to the user so they can match it with our db schema. I saw CSVReader and others but for excel its more difficult since I will need to support different versions. Essentially The user performing this import will insert and/or update several tables from this import file. There are other more advance requirements like record matching but and preview of the import records, but I wish to get through understanding how to do this first. Update: I ended up using csvReader with LumenWorks.Framework for uploading the csv files.

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  • Data Warehouse: One Database or many?

    - by drrollins
    At my new company, they keep all data associated with the data warehouse, including import, staging, audit, dimension and fact tables, together in the same physical database. I've been a database developer for a number of years now and this consolidation of function and form seems counter to everything I know. It seems to make security, backup/restore and performance management issues more manually intensive. Is this something that is done in the industry? Are there substantial reasons for doing or not doing it? The platform is Netezza. The size is in terabytes, hundreds of millions of rows. What I'm looking to get from answers to this question is a solid understanding of how right or wrong this path is. From your experience, what are the issues I should be focused on arguing if this is a path that will cause trouble for us down the road. If it is no big deal, then I'd like to know that as well.

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  • Good workflow for website design

    - by Olav
    I would like some idea about a good workflow for Website Design, with a high degree of "offshoring" (Elance, Odesk etc.). I would to do as much as possible "pre production", with client input, ideas etc. stored in IA diagrams, wireframe mockups etc. in something like a Wiki. Also a like the idea about having different people come up with different design proposals. Wouldlike to have some ideas of costs of different phases and tasks ($, %, hours). With Design I mean roughly the aspects of a site that can be done with client-side tools, especially XHTML and CSS. What other tools should I use than IA diagrams.

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  • SQLite not pluralizing Table Names

    - by weenet
    I am using SQLite as my db during development, and I want to postpone actually creating a final database until my domains are fully mapped. So I have this in my Global.asax.cs file: private void InitializeNHibernateSession() { Configuration cfg = NHibernateSession.Init( webSessionStorage, new [] { Server.MapPath("~/bin/MyNamespace.Data.dll") }, new AutoPersistenceModelGenerator().Generate(), Server.MapPath("~/NHibernate.config")); if (ConfigurationManager.AppSettings["DbGen"] == "true") { var export = new SchemaExport(cfg); export.Execute(true, true, false, NHibernateSession.Current.Connection, File.CreateText(@"DDL.sql")); } } The AutoPersistenceModelGenerator hooks up the various conventions, including a TableNameConvention like so: public void Apply(FluentNHibernate.Conventions.Instances.IClassInstance instance) { instance.Table(Inflector.Net.Inflector.Pluralize(instance.EntityType.Name)); } This is working nicely execpt that the sqlite db generated does not have pluralized table names. Any idea what I'm missing? Thanks.

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  • What is the best way to implement this composite GetHashCode()

    - by Frank Krueger
    I have a simple class: public class TileName { int Zoom, X, Y; public override bool Equals (object obj) { var o = obj as TileName; return (o != null) && (o.Zoom == Zoom) && (o.X == X) && (o.Y == Y); } public override int GetHashCode () { return (Zoom + X + Y).GetHashCode(); } } I was curious if I would get a better distribution of hash codes if I instead did something like: public override int GetHashCode () { return Zoom.GetHashCode() + X.GetHashCode() + Y.GetHashCode(); } This class is going to be used as a Dictionary key, so I do want to make sure there is a decent distribution.

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  • testing the controller in asp.net mvc

    - by csetzkorn
    Hi, I would like to test the validation of submitted DTO. This is the bare bone of a controller create action: [AcceptVerbs(HttpVerbs.Post)] public RedirectToRouteResult Create(SomeDTO SomeDTO) { SomeObject SomeObject = null; try { SomeObject = this.RepositoryService.getSomeObjectRepository().Create(SomeDTO, this.RepositoryService); } catch (BrokenRulesException ex) { ex.AddModelStateErrors(ModelState, "Model"); } catch (Exception e) { ModelState.AddModelError("Exception", e.Message); } TempData["ViewData"] = ViewData; TempData["SomeDTO "] = SomeDTO; return ModelState.IsValid ? RedirectToAction("SomeObjectDetail", new { Id = SomeObject.Id }) : RedirectToAction("Form"); } The mechanics , although not relevant, is as follows: I have a strongly typed view = form which submits a dto to this action which either returns the form or the details page of the created object. I would like to unit test whether the Model contains certain key/errorMessage combinations given some invalid dto. Did someone do similar stuff? Any pointers would be very much appreciated. Thanks. Best wishes, Christian

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  • Detecting Markers Using OpenCV

    - by Hamza Yerlikaya
    I am trying to detect various objects containing colored markers, so a red blue green marker identifies object A, and a red blue red marker identifies object B. My problem is I can't use template matching cause objects can be rotated, currently I am thinking about check for each color then find the object by checking the distance between colors but it seems inefficient, so my question is there a better way to do this?

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  • O(log N) == O(1) - Why not?

    - by phoku
    Whenever I consider algorithms/data structures I tend to replace the log(N) parts by constants. Oh, I know log(N) diverges - but does it matter in real world applications? log(infinity) < 100 for all practical purposes. I am really curious for real world examples where this doesn't hold. To clarify: I understand O(f(N)) I am curious about real world examples where the asymptotic behaviour matters more than the constants of the actual performance. If log(N) can be replaced by a constant it still can be replaced by a constant in O( N log N). This question is for the sake of (a) entertainment and (b) to gather arguments to use if I run (again) into a controversy about the performance of a design.

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