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  • How to choose a integer linear programming solver ?

    - by Cassie
    Hi all, I am newbie for integer linear programming. I plan to use a integer linear programming solver to solve my combinational optimization problem. I am more familiar with C++/object oriented programming on an IDE. Now I am using NetBeans with Cygwin to write my applications most of time. May I ask if there is an easy use ILP solver for me? Or does it depend on the problem I want to solve ? I am trying to do some resources mapping optimization. please let me know if any further information is required. Thank you very much, Cassie.

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  • Sharing the model in MVP Winforms App

    - by Keith G
    I'm working on building up an MVP application (C# Winforms). My initial version is at http://stackoverflow.com/questions/1422343/ ... Now I'm increasing the complexity. I've broken out the code to handle two separate text fields into two view/presenter pairs. It's a trivial example, but it's to work out the details of multiple presenters sharing the same model. My questions are about the model: I am basically using a property changed event raised by the model for notifying views that something has changed. Is that a good approach? What if it gets to the point where I have 100 or 1000 properties? Is it still practical at that point? Is instantiating the model in each presenter with   NoteModel _model = NoteModel.Instance   the correct approach? Note that I do want to make sure all of the presenters are sharing the same data. If there is a better approach, I'm open to suggestions .... My code looks like this: NoteModel.cs public class NoteModel : INotifyPropertyChanged { private static NoteModel _instance = null; public static NoteModel Instance { get { return _instance; } } static NoteModel() { _instance = new NoteModel(); } private NoteModel() { Initialize(); } public string Filename { get; set; } public bool IsDirty { get; set; } public readonly string DefaultName = "Untitled.txt"; string _sText; public string TheText { get { return _sText; } set { _sText = value; PropertyHasChanged("TheText"); } } string _sMoreText; public string MoreText { get { return _sMoreText; } set { _sMoreText = value; PropertyHasChanged("MoreText"); } } public void Initialize() { Filename = DefaultName; TheText = String.Empty; MoreText = String.Empty; IsDirty = false; } private void PropertyHasChanged(string sPropName) { IsDirty = true; if (PropertyChanged != null) { PropertyChanged(this, new PropertyChangedEventArgs(sPropName)); } } public event PropertyChangedEventHandler PropertyChanged; } TextEditorPresenter.cs public class TextEditorPresenter { ITextEditorView _view; NoteModel _model = NoteModel.Instance; public TextEditorPresenter(ITextEditorView view)//, NoteModel model) { //_model = model; _view = view; _model.PropertyChanged += new PropertyChangedEventHandler(model_PropertyChanged); } void model_PropertyChanged(object sender, PropertyChangedEventArgs e) { if (e.PropertyName == "TheText") _view.TheText = _model.TheText; } public void TextModified() { _model.TheText = _view.TheText; } public void ClearView() { _view.TheText = String.Empty; } } TextEditor2Presenter.cs is essentially the same except it operates on _model.MoreText instead of _model.TheText. ITextEditorView.cs public interface ITextEditorView { string TheText { get; set; } } ITextEditor2View.cs public interface ITextEditor2View { string MoreText { get; set; } }

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  • how to generate dbml file from Sybase database?

    - by 5YrsLaterDBA
    I think we may have trouble with our existing project. For some reasons we have to switch from SQL Server to Sybase SQL Anywhere 11. now we trying to find a way continue use our existing LINQ code. We wish we can still use L2S? If cannot, we wish we can use L2E, then we have to change to ADO. how to generate dbml file from Sybase Anywhere 11? after that can we use sqlmetal to generate .cs files?

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  • Create Jinja2 macros that put content in separate places

    - by Brian M. Hunt
    I want to create a table of contents and endnotes in a Jinja2 template. How can one accomplish these tasks? For example, I want to have a template as follows: {% block toc %} {# ... the ToC goes here ... #} {% endblock %} {% include "some other file with content.jnj" %} {% block endnotes %} {# ... the endnotes go here ... #} {% endblock %} Where the some other file with content.jnj has content like this: {% section "One" %} Title information for Section One (may be quite long); goes in Table of Contents ... Content of section One {% section "Two" %} Title information of Section Two (also may be quite long) <a href="#" id="en1">EndNote 1</a> <script type="text/javsacript">...(may be reasonably long) </script> {# ... Everything up to here is included in the EndNote #} Where I say "may be quite/reasonably long" I mean to say that it can't reasonably be put into quotes as an argument to a macro or global function. I'm wondering if there's a pattern for this that may accommodate this, within the framework of Jinja2. My initial thought is to create an extension, so that one can have a block for sections and end-notes, like-so: {% section "One" %} Title information goes here. {% endsection %} {% endnote "one" %} <a href="#">...</a> <script> ... </script> {% endendnote %} Then have global functions (that pass in the Jinja2 Environment): {{ table_of_contents() }} {% include ... %} {{ endnotes() }} However, while this will work for endnotes, I'd presume it requires a second pass by something for the table of contents. Thank you for reading. I'd be much obliged for your thoughts and input. Brian

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  • Best Fit Scheduling Algorithm

    - by Teegijee
    I'm writing a scheduling program with a difficult programming problem. There are several events, each with multiple meeting times. I need to find an arrangement of meeting times such that each schedule contains any given event exactly once, using one of each event's multiple meeting times. Obviously I could use brute force, but that's rarely the best solution. I'm guessing this is a relatively basic computer science problem, which I'll learn about once I am able to start taking computer science classes. In the meantime, I'd prefer any links where I could read up on this, or even just a name I could Google.

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  • Any sample C# project that highlights separate data access layer (using EF) to business logic layer

    - by Greg
    Hi, I'm interested in having a look at a small sample project that would highlight a good technique to separate data access layer (using Entity Framework) to business logic layer. In C# would be good. That is, it would highlight how to pass data between the layer without coupling them. That is, the assumption here is not to use the EF classes in the Business Logic layer, and how to achieve this low coupling, but minimizing plumbing code.

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  • Database structure - To join or not to join

    - by Industrial
    Hi! We're drawing up the database structure with the help of mySQL Workbench for a new app and the number of joins required to make a listing of the data is increasing drastically as the many-to-many relationships increases. The application will be quite read-heavy and have a couple of hundred thousand rows per table. The questions: Is it really that bad to merge tables where needed and thereby reducing joins? Should we start looking at horizontal partitioning? (in conjunction with merging tables) Is there a better way then pivot tables to take care of many-to-many relationships? We discussed about instead storing all data in serialized text columns and having the application make the sorting instead of the database, but this seems like a very bad idea, even though that the database will be heavily cached. What do you think? Thanks!

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  • Ideas for web development practical jokes?

    - by Ellie P.
    I am a web developer for a Django-based site for a student organization, and I have the opportunity to make the website temporarily absurd for a day of general campus-wide debauchery and chaos (long story, doesn't matter.) What are your best ideas for web development practical jokes (that you could never use in the real world)? For example, one idea we had was to use a client-side script to convert each character to its upside down equivalent in Unicode, si?? ??i? ?ui????os. I'm not necessarily looking for Django-specific solutions. I imagine most of these things would happen on the front-end. I am also quite aware that usability will suffer considerably--the point is to be fun for a day, and there will always be a link to the normal version of the site. Also, everything must be relatively cosmetic and easily reversible--I'm happy to swap out static CSS/JS/HTML/templates/images, and even temporarily add a django view, but no messing with the data level!

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  • Create Class functions on the fly?

    - by JasonS
    Hi, i have a validation class which needs improving. If I require some custom validation I need to specify a custom function. It works a bit like this: The controller tells the validation that a custom validation function is required. The controller runs the validation. --- Gets iffy here --- Validation class creates a new instance of the controller class.... Validation class runs controller-custom_validation_function() Validation class returns true / false Is there someway that I can alter this to do something like this? $validation = new validation; // Insert rules here. $validation-function() = $this-function(); By doing this I could get rid of the step of creating an unneeded class instance.

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  • Modeling a Generic Relationship in a Database

    - by StevenH
    This is most likely one for all you sexy DBAs out there: How would I effieciently model a relational database whereby I have a field in an "Event" table which defines a "SportType". This "SportsType" field can hold a link to different sports tables E.g. "FootballEvent", "RubgyEvent", "CricketEvent" and "F1 Event". Each of these Sports tables have different fields specific to that sport. My goal is to be able to genericly add sports types in the future as required, yet hold sport specific event data (fields) as part of my Event Entity. Is it possible to use an ORM such as NHibernate / Entity framework which would reflect such a relationship? I have thrown together a quick C# example to express my intent at a higher level: public class Event<T> where T : new() { public T Fields { get; set; } public Event() { EventType = new T(); } } public class FootballEvent { public Team CompetitorA { get; set; } public Team CompetitorB { get; set; } } public class TennisEvent { public Player CompetitorA { get; set; } public Player CompetitorB { get; set; } } public class F1RacingEvent { public List<Player> Drivers { get; set; } public List<Team> Teams { get; set; } } public class Team { public IEnumerable<Player> Squad { get; set; } } public class Player { public string Name { get; set; } public DateTime DOB { get; set;} }

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  • WPF: Sort of inconsistence in the visual appearence of WPF controls derived by Selector class

    - by msfanboy
    Hello, focused items == selected items but selected items != focused items. Have you ever wondered about that? Do you specially style the backcolor of a focused/selected item ? I ask this question because a user has an enabled button because some customer items are selected. The user is wondering now "why the heck can I delete this customers (button is enabled...) when I have just clicked on the orders control selecting some orders ready to delete (button is enabled too). The thing is the selected customer items are nearly looking grayed out in the default style... Well its sort of inconsistence to the user NOT to the programmer because WE know the behavior. Do you cope with stuff like that?

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  • Stack and Hash joint

    - by Alexandru
    I'm trying to write a data structure which is a combination of Stack and HashSet with fast push/pop/membership (I'm looking for constant time operations). Think of Python's OrderedDict. I tried a few things and I came up with the following code: HashInt and SetInt. I need to add some documentation to the source, but basically I use a hash with linear probing to store indices in a vector of the keys. Since linear probing always puts the last element at the end of a continuous range of already filled cells, pop() can be implemented very easy without a sophisticated remove operation. I have the following problems: the data structure consumes a lot of memory (some improvement is obvious: stackKeys is larger than needed). some operations are slower than if I have used fastutil (eg: pop(), even push() in some scenarios). I tried rewriting the classes using fastutil and trove4j, but the overall speed of my application halved. What performance improvements would you suggest for my code? What open-source library/code do you know that I can try?

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  • Do fluent interfaces violate the Law of Demeter?

    - by Jakub Šturc
    The wikipedia article about Law of Demeter says: The law can be stated simply as "use only one dot". However a simple example of a fluent interface may look like this: static void Main(string[] args) { new ZRLabs.Yael.Pipeline("cat.jpg") .Rotate(90) .Watermark("Monkey") .RoundCorners(100, Color.Bisque) .Save("test.png"); } So does this goes together?

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  • One check constraint or multiple check constraints?

    - by RenderIn
    Any suggestions on whether fewer check constraints are better, or more? How should they be grouped if at all? Suppose I have 3 columns which are VARCHAR2(1 BYTE), each of which is a 'T'/'F' flag. I want to add a check constraint to each column specifying that only characters IN ('T', 'F') are allowed. Should I have 3 separate check constraints, one for each column: COL_1 IN ('T', 'F') COL_2 IN ('T', 'F') COL_3 IN ('T', 'F') Or a single check constraint: COL_1 IN ('T', 'F') AND COL_2 IN ('T', 'F') AND COL_3 IN ('T', 'F') My thoughts are it is best to keep these three separate, as the columns are logically unrelated to each other. The only case I would have a check constraint that examines more than one column is if there was some relationship between the value in one and the value in another, e.g.: (PARENT_CNT > 0 AND PRIMARY_PARENT IS NOT NULL) OR (PARENT_CNT = 0 AND PRIMARY_PARENT IS NULL)

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  • Best pattern for storing (product) attributes in SQL Server

    - by EdH
    We are starting a new project where we need to store product and many product attributes in a database. The technology stack is MS SQL 2008 and Entity Framework 4.0 / LINQ for data access. The products (and Products Table) are pretty straightforward (a SKU, manufacturer, price, etc..). However there are also many attributes to store with each product (think industrial widgets). These may range from color to certification(s) to pipe size. Every product may have different attributes, and some may have multiples of the same attribute (Ex: Certifications). The current proposal is that we will basically have a name/value pair table with a FK back to the product ID in each row. An example of the attributes Table may look like this: ProdID AttributeName AttributeValue 123 Color Blue 123 FittingSize 1.25 123 Certification AS1111 123 Certification EE2212 123 Certification FM.3 456 Pipe 11 678 Color Red 999 Certification AE1111 ... Note: Attribute name would likely come from a lookup table or enum. So the main question here is: Is this the best pattern for doing something like this? How will the performance be? Queries will be based on a JOIN of the product and attributes table, and generally need many WHEREs to filter on specific attributes - the most common search will be to find a product based on a set of known/desired attributes. If anyone has any suggestions or a better pattern for this type of data, please let me know. Thanks! -Ed

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  • What's missing in Cocoa?

    - by Bridgeyman
    If you could add anything to Cocoa, what would it be? Are there any features, major or minor, that you would say are missing in Cocoa. Perhaps there is a wheel you have had to invent over and over because of an omission in the frameworks?

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  • Reuse nib's across multiple UIViewControllers

    - by colm
    I've created some custom UITableViewCells in a nib file and would like to use that across multiple UIViewControllers. Can anyone tell me the best practice way to do that? My limited knowledge around loading nibs seems to suggest that you have to specify a single owner class in Interface Builder. Thanks.

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  • C# threading pattern that will let me flush

    - by Jeff Alexander
    I have a class that implements the Begin/End Invocation pattern where I initially used ThreadPool.QueueUserWorkItem() to do thread my work. I now have the side effect where someone using my class is calling the Begin (with callback) a ton of times to do a lot of processing so ThreadPool.QueueUserWorkItem is creating a ton of threads to do the processing. That in itself isn't bad but there are instances where they want to abandon the processing and start a new process but they are forced to wait for their first request to finish. Since ThreadPool.QueueUseWorkItem() doesn't allow me to cancel the threads I am trying to come up with a better way to queue up the work and maybe use an explicit FlushQueue() method in my class to allow the caller to abandon work in my queue. Anyone have any suggestion on a threading pattern that fits my needs?

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  • Suggest a Game Idea for my 3D World

    - by mrlinx
    Been creating a 3D complete world in OpenGL. For now, it features navigation like Google Earth, making possible the zooming from outter space to meter like level. My question is: How do you suggest I make this a fun and interesting game? My initial tought was to have a kind of moon lander where the user simply navigated the lander around the world. Anything better to suggest?

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  • 3rd party data - Store in Data Warehouse or Primary database?

    - by brydgesk
    This is mostly a data warehouse philosophy question. My project involves an Oracle forms application, and a Teradata Data Warehouse for reporting and ad-hoc purposes. In addition to the primary data created by the users of our application, we also require data from various other sources. Currently, this 3rd party data comes via FTPd flat files directly to our Data Warehouse. To access the data, our users must use a series of custom BusinessObjects reports. My question is, would it make more sense for this data to be sent to our source Oracle system instead? Is it ever appropriate for a Data Warehouse to be the point of origin for users to access raw data? In short, is it more important that the operational database contain only the data created by your project, or that the data warehouse remain dedicated solely to reporting and analysis?

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  • MVC pattern and (Game) State pattern

    - by topright
    Game States separate I/O processing, game logic and rendering into different classes: while (game_loop) { game->state->io_events(this); game->state->logic(this); game->state->rendering(); } You can easily change a game state in this approach. MVC separation works in more complex way: while (game_loop) { game->cotroller->io_events(this); game->model->logic(this); game->view->rendering(); } So changing Game States becomes error prone task (switch 3 classes, not 1). What are practical ways of combining these 2 concepts?

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