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  • Out of Core Implementation of a Quadtree

    - by Nima
    Hi, I am trying to build a Quadtree data structure(or let's just say a tree) on the secondary memory(Hard Disk). I have a C++ program to do so and I use fopen to create the files. Also, I am using tesseral coding to store each cell in a file named with its corresponding code to store it on the disk in one directory. The problem is that after creating about 1,100 files, fopen just returns NULL and stops creating new files. I can create further files manually in that directory, but using C++ it can not create any further files. I know about max limit of inode on ext3 filesystem which is (from Wikipedia) 32,000 but mine is way less than that, also note that I can create files manually on the disk; just not through fopen. Also, I really appreciate any idea regarding the best way to store a very dynamic quadtree on disk(I need the nodes to be in separate files and the quadtree might have a depth of 50). Using nested directories is one idea, but I think it will slow down the performance because of following the links on the filesystem to access the file. Thanks, Nima

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  • C#: IComparable implementation private

    - by Anonymous Coward
    Hello I'm new to C# so this might be a really dump question: I implemented IComparable in my class and want to test it with NUnit. But the CompareTo-Method is marked as private and thus not accessible from the test. What's the reason for this and how can I fix this? The IComparable: public class PersonHistoryItem : DateEntity,IComparable { ... int IComparable.CompareTo(object obj) { PersonHistoryItem phi = (PersonHistoryItem)obj; return this.StartDate.CompareTo(phi.StartDate); } } The test: [TestMethod] public void TestPersonHistoryItem() { DateTime startDate = new DateTime(2001, 2, 2); DateTime endDate = new DateTime(2010, 2, 2); PersonHistoryItem phi1 = new PersonHistoryItem(startDate,endDate); PersonHistoryItem phi2 = new PersonHistoryItem(startDate, endDate); Assert.IsTrue(phi1.CompareTo(phi2)==0); }

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  • Python Locking Implementation (with threading module)

    - by Matty
    This is probably a rudimentary question, but I'm new to threaded programming in Python and am not entirely sure what the correct practice is. Should I be creating a single lock object (either globally or being passed around) and using that everywhere that I need to do locking? Or, should I be creating multiple lock instances in each of the classes where I will be employing them. Take these 2 rudimentary code samples, which direction is best to go? The main difference being that a single lock instance is used in both class A and B in the second, while multiple instances are used in the first. Sample 1 class A(): def __init__(self, theList): self.theList = theList self.lock = threading.Lock() def poll(self): while True: # do some stuff that eventually needs to work with theList self.lock.acquire() try: self.theList.append(something) finally: self.lock.release() class B(threading.Thread): def __init__(self,theList): self.theList = theList self.lock = threading.Lock() self.start() def run(self): while True: # do some stuff that eventually needs to work with theList self.lock.acquire() try: self.theList.remove(something) finally: self.lock.release() if __name__ == "__main__": aList = [] for x in range(10): B(aList) A(aList).poll() Sample 2 class A(): def __init__(self, theList,lock): self.theList = theList self.lock = lock def poll(self): while True: # do some stuff that eventually needs to work with theList self.lock.acquire() try: self.theList.append(something) finally: self.lock.release() class B(threading.Thread): def __init__(self,theList,lock): self.theList = theList self.lock = lock self.start() def run(self): while True: # do some stuff that eventually needs to work with theList self.lock.acquire() try: self.theList.remove(something) finally: self.lock.release() if __name__ == "__main__": lock = threading.Lock() aList = [] for x in range(10): B(aList,lock) A(aList,lock).poll()

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  • Concrete Implementation of Generic Form Not Working in Designer

    - by Dov
    I have a base class, defined as below (I'm also using DevExpress components): public abstract partial class BaseFormClass<R> : XtraForm where R : DataRow { ... } Contrary to what I've read from elsewhere, I'm still able to design this class. I didn't have to create a concrete class from it to do so. But, when I create a concrete class descended from it (as below), that class won't work in the designer. public partial class ConcreteFormClass : BaseFormClass<StronglyTypedRow> { ... } I get this message: The designer could not be shown for this file because none of the classes within it can be designed. The designer inspected the following classes in the file: ConcreteFormClass --- The base class 'BaseFormClass' could not be loaded. Ensure the assembly has been referenced and that all projects have been built. Has anyone seen this before? Any sort of known workaround?

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  • C#/Java: Proper Implementation of CompareTo when Equals tests reference identity

    - by Paul A Jungwirth
    I believe this question applies equally well to C# as to Java, because both require that {c,C}ompareTo be consistent with {e,E}quals: Suppose I want my equals() method to be the same as a reference check, i.e.: public bool equals(Object o) { return this == o; } In that case, how do I implement compareTo(Object o) (or its generic equivalent)? Part of it is easy, but I'm not sure about the other part: public int compareTo(Object o) { if (! (o instanceof MyClass)) return false; MyClass other = (MyClass)o; if (this == other) { return 0; } else { int c = foo.CompareTo(other.foo) if (c == 0) { // what here? } else { return c; } } } I can't just blindly return 1 or -1, because the solution should adhere to the normal requirements of compareTo. I can check all the instance fields, but if they are all equal, I'd still like compareTo to return a value other than 0. It should be true that a.compareTo(b) == -(b.compareTo(a)), and the ordering should stay consistent as long as the objects' state doesn't change. I don't care about ordering across invocations of the virtual machine, however. This makes me think that I could use something like memory address, if I could get at it. Then again, maybe that won't work, because the Garbage Collector could decide to move my objects around. hashCode is another idea, but I'd like something that will be always unique, not just mostly unique. Any ideas?

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  • Generics and collections ... struggling with an implementation

    - by mattruma
    I am trying to figure out a way to leverage generics so I can make the property Value be an actual type that initialized (not sure if this is the correct way of saying it) when my collection class is created. I would like to have the syntax be something like: var list = new ListItemCollection<Guid>(parameters would go here); I have the following class: [Serializable] public class ListItem { public object Value { get; set; } public string Text { get; set; } public object DataContext { get; set; } public Nullable<bool> Checked { get; set; } public ListItem() { this.Checked = false; } } I have the following collection: [Serializable] public class ListItemCollection : List<ListItem> { public ListItem this[object value] { get { foreach (var child in this) { if (child.Value.Equals(value)) return child; } return null; } } public bool Contains(object value) { foreach (var child in this) { if (child.Value.Equals(value)) return true; } return false; } public void Add(object value, string text) { this.Add(value, text, null); } public void Add(object value, string text, object dataContext) { var child = new ListItem(); child.Value = value; child.Text = text; child.DataContext = dataContext; this.Add(child); } public ListItemCollection() { } public ListItemCollection(IEnumerable items, string displayMember, string valueMember, bool showEmptyItem, string emptyItemText, object emptyItemValue) { if (showEmptyItem) { this.Add(emptyItemValue, emptyItemText); } foreach (object item in items) { object text = null; object value = null; text = item.GetType().GetProperty(displayMember).GetValue(item, null); value = item.GetType().GetProperty(valueMember).GetValue(item, null); // Add the item this.Add(value, text.ToString(), item); } } }

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  • Mixin or Trait implementation in AS3?

    - by Brian Heylin
    I'm looking for ideas on how to implement a Mixin/Trait style system in AS3. I want to be able to compose a number of classes together into a single object. Of course this is not a language level feature of AS3, but I'm hoping that there is maybe some way to do this using prototype based techniques or maybe some bytecode hacking that I believe AsMock uses to implement it's functionality. An existing Java example is Qi4J where the user define interfaces that the Qi4j framework implements based on metadata tags and coding by convention. Has anyone any ideas on how to get the Mixin/Trait concept working within AS3?

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  • Is generic Money<TAmount> a good implementation idea?

    - by jdk
    I have a Money Type that allows math operations and is sensitive to exchange rates so it will reduce one currency to another if rate is available to calculate in a given currency, rounds by various methods. It has other features that are sensitive to money, but I need to ask if the basic data type used should be made generic in nature. I've realized that the basic data type to hold an amount may differ for financial situations, for example: retail money might be expressed as all cents using int or long where fractions of cents do not matter, decimal is commonly used for its fixed behaviour, sometimes double seems to be used for big finance and large values sometimes a special BigInteger or 3rd-party type is used. I want to know if it would be considered good form to turn Money into Money<T_amount> so it can be used in any one of the above chosen scenarios?

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  • Netlogo Programming question - Chemical Equilibrium temperature and pressure implementation

    - by user286190
    Hi I am trying to code something in Netlogo..I am using an existing model Chemical Equilibrium and am trying to implement the following: turtles-own [speed ] ask turtles [ ;; set velocity ( ambient-temperature = 30 ) ;; fd velocity if temp > 40 [ "speed" increases of turtles ] ifelse temperature < 30 [ speed of turtles decreases] ] ;; to temp but it does not seem to work (it temperature is more than 40 the speed of the turtles increases if the temperature is less than 30 the speed of the turtles decreases) temperature is a slider on the model the same for pressure ask turtles [ ;; if pressure > 50 then speed increases of turtles ;; if pressure < 50 then speed decreases of turtles ] ;; to pressure thanks

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  • Limited IList<> implementation ?

    - by Wam
    Hello people, I'm doing some work with stats, and want to refactor the following method : public static blah(float[] array) { //Do something over array, sum it for example. } However, instead of using float[] I'd like to be using some kind of indexed enumerable (to use dynamic loading from disk for very large arrays for example). I had created a simple interface, and wanted to use it. public interface IArray<T> : IEnumerable<T> { T this[int j] { get; set; } int Length { get; } } My problem is : float[] only inherits IList, not IArray, and AFAIK there's no way to change that. I'd like to ditch IArray and only use IList, but my classes would need to implement many methods like Add, RemoveAt although they are fixed size And then my question : how can float[] implement IList whereas it doesn't have these methods ? Any help is welcome. Cheers

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  • Asp.Net MVC 2 Client validation implementation for Enterprise Library Validation Block

    - by er-v
    Hello to everybody. I've found a very good article about how to use EntLib Validation Block for server validation in MVC 2. But as there pointed out The current design of EntLib’s Validation Application Block uses the Composite pattern; that is, when we ask for validation for an object, it returns back a single validator object that contains a list of all the validation work to be done. While this is very convenient from a normal usage scenario, the unfortunate side-effect is that we can’t “peek inside” to see what the individual validations are that it’s doing, and therefore can’t generate the appropriate client-side validation hints. So how is it possible to implement client side validation for EntLib? Is there work around?

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  • [C++] Producer/Consumer Implementation -- Feedback Wanted

    - by bobber205
    I'm preparing for an interview in a few weeks and I thougth I would give threads in boost a go, as well as do the simple producer/consumer problem I learned in school. Haven't done it quite awhile so I was curious what you guys think of this? What should I add to make it a better example etc. Thanks for the feedback! :) ////////////////////////////////////////////////////////////////////////// boost::mutex bufferMutex; deque<int> buffer; const int maxBufferSize = 5; ////////////////////////////////////////////////////////////////////////// bool AddToBuffer(int i) { if (buffer.size() < maxBufferSize) { buffer.push_back(i); return true; } else { return false; } } bool GetFromBuffer(int& toReturn) { if (buffer.size() == 0) { return false; } else { toReturn = buffer[buffer.size()-1]; buffer.pop_back(); return true; } } struct Producer { int ID; void operator()() { while (true) { boost::mutex::scoped_lock lock(bufferMutex); int num = dice(); bool result = AddToBuffer(num); lock.unlock(); //safe area done if (result) { cout << "Producer " << this->ID << " Added " << num << endl; } else { cout << "!!Buffer was Full!!" << endl; } //Added //Now wait boost::xtime xt; xtime_get( &xt, boost::TIME_UTC); xt.nsec += 1000000 + 100000 * (rand() % 1000); boost::thread::sleep(xt); } } }; struct Consumer { int ID; void operator()() { while (true) { int returnedInt = 0; boost::mutex::scoped_lock lock(bufferMutex); bool result = GetFromBuffer(returnedInt); lock.unlock(); //safe area done if (result) { cout << "\tConsumer " << this->ID << " Took Out " << returnedInt << endl; } else { cout << "!!Buffer was Empty!!" << endl; } //Added //Now wait boost::xtime xt; xtime_get( &xt, boost::TIME_UTC); xt.nsec += 1000000 + 100000 * (rand() % 1000); boost::thread::sleep(xt); } } }; void main() { Producer p, p2; Consumer c, c2; p.ID = 1; p2.ID = 2; c.ID = 1; c2.ID = 2; boost::thread thread1(boost::ref(p)); boost::thread thread2(boost::ref(c)); boost::thread thread3(boost::ref(p2)); boost::thread thread4(boost::ref(c2)); int x; cin >> x; }

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  • Open-source PHP Accounting/General Ledger Implementation

    - by Prasad
    Hi, I'm looking for any open-source accounting module that I can include in my Symfony project. I was thinking of writing my own & releasing a plugin, but then I came across 2 solutions: http://arias.sourceforge.net/ http://frontaccounting.net/ Please answer on the lines of... Choosing one of the above, your experience, community support Other alternatives Thanks a lot!

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  • Problem with interface implementation in partial classes.

    - by Bas
    I have a question regarding a problem with L2S, Autogenerated DataContext and the use of Partial Classes. I have abstracted my datacontext and for every table I use, I'm implementing a class with an interface. In the code below you can see I have the Interface and two partial classes. The first class is just there to make sure the class in the auto-generated datacontext inherets Interface. The other autogenerated class makes sure the method from Interface is implemented. namespace PartialProject.objects { public interface Interface { Interface Instance { get; } } //To make sure the autogenerated code inherits Interface public partial class Class : Interface { } //This is autogenerated public partial class Class { public Class Instance { get { return this.Instance; } } } } Now my problem is that the method implemented in the autogenerated class gives the following error: - Property 'Instance' cannot implement property from interface 'PartialProject.objects.Interface'. Type should be 'PartialProjects.objects.Interface'. <- Any idea how this error can be resolved? Keep in mind that I can't edit anything in the autogenerated code. Thanks in advance!

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  • Recursion in Unity and Dispose pattern implementation

    - by Budda
    My class is inherited from UnityContainer (from Unity 2.0), here is source code: public class UnityManager : UnityContainer { private UnityManager() { _context = new MyDataClassesDataContext(); // ... } protected override void Dispose(bool disposing) { if ( disposing ) { _context.Dispose(); } base.Dispose(disposing); } private readonly CMCoreDataClassesDataContext _context; } When Dispose method is called for the instance of UnityManager class it drop into recursion... Why? As far as I know base.Dispose should call the Dispose method of base class only... isn't it? Who call back the Dispose(bool) of UnityManager? How to prevent that? Thanks.

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  • C# Login Dialog Implementation

    - by arc1880
    I have implemented a LoginAccess class that prompts the user to enter their active directory username and password. Then I save the login data as an encrypted file. Every subsequent start of the application, the LoginAccess class will read the encrypted file and check against the active directory to see if the login information is still valid. If it is not, then it will prompt the user again. I have made it so that the reading of the encrypted file and displaying of the login dialog is done on a separate thread. A delegate is fired when the login process is complete. The issue that I'm having is that I have a class that is used in multiple places. This class contains the call to the LoginAccess object. Every time I instantiate a new object there are multiple calls to the LoginAccess object and I get multiple dialogs appearing when it tries to prompt for a username and password. Any suggestions on how to have only one dialog appear would be greatly appreciated.

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  • Pipe implementation

    - by nunos
    I am trying to implement a linux shell that supports piping. I have already done simple commands, commands running in background, redirections, but piping is still missing. I have already read about it and seen some snippets of code, but still haven't been able to sort out a working solution. What I have so far: int fd[2]; pid_t pid = fork(); if (pid == -1) return -1; if (pid == 0) { dup2(0, fd[0]); execlp("sort", "sort", NULL); } I am a novice programmer, as you can probably tell, and when I am programming something I don't know much about, this being obviously the case, I like to start with something really easy and concrete and then build from there. So, before being able to implement three and more different commands in pipeline, I would like to be able to compute "ls names.txt | sort" or something similiar, in which names.txt is a file of names alfabetically unordered. Thanks.

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  • Linux's thread local storage implementation

    - by anon
    __thread Foo foo; How is "foo" actually resolved? Does the compiler silently replace every instance of "foo" with a function call? Is "foo" stored somewhere relative to the bottom of the stack, and the compiler stores this as "hey, for each thread, have this space near the bottom of the stack, and foo is stored as 'offset x from bottom of stack'"?

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  • Up to date, JPA compliant GenericDAO Implementation

    - by HDave
    I read this article: http://www.ibm.com/developerworks/java/library/j-genericdao.html several times and believe I understand what it is saying. However, it is 4 years old and I have a JPA compliant Java application to contend with. In addition, I see that there is a JPATemplate in Spring that has some good functionality, but the Spring documentation says it is already deprecated! Can anybody point me to a solid, modern, JPA compliant, Spring based, working example of a GenericDAOImpl that proxies an Interface to provide generic finder execution?

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  • SpringMvc Annotations for DAO interface and DAO implementation

    - by dev_darin
    I would like to know if I am annotating these classes correctly, since I am new to the annotations: Country.java @Component public class Country { private int countryId; private String countryName; private String countryCode; /** * No args constructor */ public Country() { } /** * @param countryId * @param countryName * @param countryCode */ public Country(int countryId, String countryName, String countryCode) { this.countryId = countryId; this.countryName = countryName; this.countryCode = countryCode; } //getters and setters } CountryDAO.java @Repository public interface CountryDAO { public List<Country> getCountryList(); public void saveCountry(Country country); public void updateCountry(Country country); } JdbcCountryDAO.java @Component public class JdbcCountryDAO extends JdbcDaoSupport implements CountryDAO{ private final Logger logger = Logger.getLogger(getClass()); @Autowired public List<Country> getCountryList() { int countryId = 6; String countryCode = "AI"; logger.debug("In getCountryList()"); String sql = "SELECT * FROM TBLCOUNTRY WHERE countryId = ? AND countryCode = ?"; logger.debug("Executing getCountryList String "+sql); Object[] parameters = new Object[] {countryId, countryCode}; logger.info(sql); //List<Country> countryList = getJdbcTemplate().query(sql,new CountryMapper()); List<Country> countryList = getJdbcTemplate().query(sql, parameters,new CountryMapper()); return countryList; } CountryManagerIFace.java @Repository public interface CountryManagerIFace extends Serializable{ public void saveCountry(Country country); public List<Country> getCountries(); } CountryManager.java @Component public class CountryManager implements CountryManagerIFace{ @Autowired private CountryDAO countryDao; public void saveCountry(Country country) { countryDao.saveCountry(country); } public List<Country> getCountries() { return countryDao.getCountryList(); } public void setCountryDao(CountryDAO countryDao){ this.countryDao = countryDao; } }

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  • New to AVL tree implementation.

    - by nn
    I am writing a sliding window compression algorithm (LZ77) that searches for phrases in a "moving" dictionary. So far I have written a BST where each node is stored in an array and it's index in the array is also the value of the starting position in the window itself. I am now looking at transforming the BST to an AVL tree. I am a little confused at the sample implementations I have seen. Some only appear to store the balance factors whereas others store the height of each tree. Are there any performance advantage/disadvantages of storing the height and/or balance factor for each node? Apologies if this is a very simple question, but I'm still not visualizing how I want to restructure my BST to implement height balancing. Thanks.

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  • Ideas for a rudimentary software licensing implementation

    - by Ross
    I'm trying to decide how to implement a very basic licensing solution for some software I wrote. The software will run on my (hypothetical) clients' machines, with the idea being that the software will immediately quit (with a friendly message) if the client is running it on greater-than-n machines (n being the number of licenses they have purchased). Additionally, the clients are non-tech-savvy to the point where "basic" is good enough. Here is my current design, but given that I have little to no experience in the topic, I wanted to ask SO before I started any development on it: A remote server hosts a MySQL database with a table containing two columns: client-key and license quantity The client-side application connects to the MySQL database on startup, offering it's client-key that I've put into a properties file packaged into the distribution (I would create a new distribution for each new client) Chances are, I'll need a second table to store validation history, so that with some short logic, the software can decide if it can be run on a given machine (maybe a sliding window of n machines using the software per 24 hours) If the software cannot establish a connection to the MySQL database, or decides that it's over the n allowed machines per day, it closes The connection info for the remote server hosting the MySQL database should be hard-coded into the app? (That sounds like a bad idea, but otherwise they could point it to some other always-validates-to-success server) I think that about covers my initial design. The intent being that while it certainly isn't full-proof, I think I've made it at least somewhat difficult to create an easily-sharable cracking solution. Also, I can easily adjust the license amount for a given client/key pair. I gotta figure this has been done a million times before, so tell me about a better solution that's just as simple to implement and provides the same (low) amount of security. In the event that external libraries are used, I prefer Java, as that's what the software has been written in.

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