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  • Limiting the maximum number of concurrent requests django/apache

    - by Johan
    Hi, I have a django site that demonstrates the usage of a tool. One of my views takes a file as input and runs some fairly heavy computation trough an external python script and returns some output to the user. The tool runs fast enough to return the output in the same request though. I would however want to limit how many concurrent requests to this URL/view to keep the server from getting congested. Any tips on how i would go about doing this? The page in itself is very simple and the usage will be low.

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  • ASP.NET - Exception logging approach for concurrent user scenario

    - by Whiskey-Tango-Foxtrot
    I am involved in designing a asp.net webforms application using .NET 3.5. I have a requirement where we need to log exceptions. What is the best approach for exception handling, given that there would be concurrent users for this application? Is there a need or possibility to log in exceptions at a user level? My support team in-charge wants to have a feature where the support team can get user specific log files. To give you a background, this application is currently on VB 6.0 and we are migrating it along with some enhancements. So, today the support personnel have a provision to get user specific log files.

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  • C++ socket concurrent server

    - by gregpi
    Hi all; Im writing a concurrent server that's supposed to have a communication channel and a data channel. The client initially connect to the communication channel to authenticate, upon successful authentication, the client is then connected to the data channel to access data. My program is already doing that, and im using threads.My only issue is that if I try to connect another client, I get a "cannot bind : address already in use" error. I have it this way: PART A Client connect to port 4567 (and enter his login info). A thread spawn to handle the client(repeated for each client that connects). In the thread created, I have a function(let's call it FUNC_A) that checks the client's login info(dont worry about how the check is done), if successful, the thread starts the data server(listening on 8976) then sends an OK to the client, once received the client attempts to connect to the data server. PART B Once a client connect to the data server, from inside FUNC_A the client is accepted and another thread is spawn to handle the client's connection to the data server.(hopefully everything is clear). Now, all that is working fine. However, if I try to connect with second client when it gets to PART B I get a "cannot bind error: address already in use". I've tried so many different ways, I've even tried spawning a thread to start the data server and accept the client and then start another thread to handle that connection. still no luck. Please give me a suggestion as to what I'm doing wrong, how do I go about doing this or what's the best way to implement it. Thank you

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  • Performance of concurrent software on multicore processors

    - by Giorgio
    Recently I have often read that, since the trend is to build processors with multiple cores, it will be increasingly important to have programming languages that support concurrent programming in order to better exploit the parallelism offered by these processors. In this respect, certain programming paradigms or models are considered well-suited for writing robust concurrent software: Functional programming languages, e.g. Haskell, Scala, etc. The actor model: Erlang, but also available for Scala / Java (Akka), C++ (Theron, Casablanca, ...), and other programming languages. My questions: What is the state of the art regarding the development of concurrent applications (e.g. using multi-threading) using the above languages / models? Is this area still being explored or are there well-established practices already? Will it be more complex to program applications with a higher level of concurrency, or is it just a matter of learning new paradigms and practices? How does the performance of highly concurrent software compare to the performance of more traditional software when executed on multiple core processors? For example, has anyone implemented a desktop application using C++ / Theron, or Java / Akka? Was there a boost in performance on a multiple core processor due to higher parallelism?

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  • ReadOnlyCollection or IEnumerable for exposing member collections?

    - by Erik Öjebo
    Is there any reason to expose an internal collection as a ReadOnlyCollection rather than an IEnumerable if the calling code only iterates over the collection? class Bar { private ICollection<Foo> foos; // Which one is to be preferred? public IEnumerable<Foo> Foos { ... } public ReadOnlyCollection<Foo> Foos { ... } } // Calling code: foreach (var f in bar.Foos) DoSomething(f); As I see it IEnumerable is a subset of the interface of ReadOnlyCollection and it does not allow the user to modify the collection. So if the IEnumberable interface is enough then that is the one to use. Is that a proper way of reasoning about it or am I missing something? Thanks /Erik

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  • How to load entities into private collections using the entity framework

    - by Anton P
    I have a POCO domain model which is wired up to the entity framework using the new ObjectContext class. public class Product { private ICollection<Photo> _photos; public Product() { _photos = new Collection<Photo>(); } public int Id { get; set; } public string Name { get; set; } public virtual IEnumerable<Photo> Photos { get { return _photos; } } public void AddPhoto(Photo photo) { //Some biz logic //... _photos.Add(photo); } } In the above example i have set the Photos collection type to IEnumerable as this will make it read only. The only way to add/remove photos is through the public methods. The problem with this is that the Entity Framework cannot load the Photo entities into the IEnumerable collection as it's not of type ICollection. By changing the type to ICollection will allow callers to call the Add mentod on the collection itself which is not good. What are my options? Edit: I could refactor the code so it does not expose a public property for Photos: public class Product { public Product() { Photos = new Collection<Photo>(); } public int Id { get; set; } public string Name { get; set; } private Collection<Photo> Photos {get; set; } public IEnumerable<Photo> GetPhotos() { return Photos; } public void AddPhoto(Photo photo) { //Some biz logic //... Photos.Add(photo); } } And use the GetPhotos() to return the collection. The other problem with the approach is that I will loose the change tracking abilities as I cannot mark the collection as Virtual - It is not possible to mark a property as private virtual. In NHibernate I believe it's possible to map the proxy class to the private collection via configuration. I hope that this will become a feature of EF4. Currently i don't like the inability to have any control over the collection!

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  • Generics & Collections!

    - by RayAllen
    I had a doubt. Why,generics (in java or any other lang), works with the objects and not with primitive types ? For e.g Gen< Integer inum=new Gen< Integer(100); works fine , but Gen< int inums=new Gen< int(100); is not allowed. Thanks !

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  • Nhibernate , collections and compositeid

    - by Ciaran
    Hi, banging my head here and thought that some one out there might be able to help. Have Tables below. Bucket( bucketId smallint (PK) name varchar(50) ) BucketUser( UserId varchar(10) (PK) bucketId smallint (PK) ) The composite key is not the problem thats ok I know how to get around this but I want my bucket class to contanin a IList of BucketUser. I read the online reference and thought that I had cracked it but havent. The two mappings are below -- bucket -- <id name="BucketId" column="BucketId" type="Int16" unsaved-value="0"> <generator class="native"/> </id> <property column="BucketName" type="String" name="BucketName"/> <bag name="Users" table="BucketUser" inverse="true" generic="true" lazy="true"> <key> <column name="BucketId" sql-type="smallint"/> <column name="UserId" sql-type="varchar"/> </key> <one-to-many class="Bucket,Impact.Dice.Core" not-found="ignore"/> </bag> -- bucketUser --

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  • Java Collections and Garbage Collector

    - by Anth0
    A little question regarding performance in a Java web app. Let's assume I have a List<Rubrique> listRubriques with ten Rubrique objects. A Rubrique contains one list of products (List<product> listProducts) and one list of clients (List<Client> listClients). What exactly happens in memory if I do this: listRubriques.clear(); listRubriques = null; My point of view would be that, since listRubriques is empty, all my objects previously referenced by this list (including listProducts and listClients) will be garbage collected pretty soon. But since Collection in Java are a little bit tricky and since I have quite performance issues with my app i'm asking the question :) edit : let's assume now that my Client object contains a List<Client>. Therefore, I have kind of a circular reference between my objects. What would happen then if my listRubrique is set to null? This time, my point of view would be that my Client objects will become "unreachable" and might create a memory leak?

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  • Autowiring collections with IoC

    - by Marcus
    Hi, Anyone know if there exists any IoC container that can handle this: Given: ISomeInterfce<T> where T : Entity Impl1 : ISomeInterfce<Entity1> Impl2 : ISomeInterfce<Entity1> Impl3 : ISomeInterfce<Entity2> Impl4 : ISomeInterfce<Entity2> I want to be able to auto wire my system and be able to resolve like this IoC.ResolveAll(typeof(ISomeInterfce<Entity1>)) and get a collection back of all implementations of ISomeInterfce<Entity1>

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  • Better type safety in Java collections

    - by Paul Tomblin
    In my java coding, I often end up with several Map<String,Map<String,foo>> or Map<String,List<String>> and then I have trouble remembering which String is which key. I comment the declaration with //Map<capabiltyId,Map<groupId,foo>> or //Map<groupId,List<capabilityId>, but it's not the greatest solution. If String wasn't final, I would make new classes CapabilityId extends String and GroupId extends String, but I can't. Is there a better way to keep track of which thing is the key and maybe have the compiler enforce it?

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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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  • Subsonic, child records, and collections

    - by Dane
    Hi, I've been working with subsonic for a few weeks now, and it is working really well. However, I've just run into an issue with child objects with additional partial properties. Some of it is probably me just not understanding the .Net object lifecycle. I have an object - search. This has a few properties like permissions and stuff, and it links to a child table called search_options. In my Asp.Net app, it loops through these search options and creates controls. Then on postback, it grabs the values and assigns it back to a "value" property on the search_option. This value property is a simple string that's defined in a partial class. I then want to create a method on the search object, called PerformSearch. This then loops through the child search_options, and performs a custom query based on the "value" property. However, even though I assign the "value" property to the child search_option, when I access it later via the search.search_options collection, it is null. I'm guessing that maybe because it's accessing it in two different places, it performs another lazy load from the DB and the value is lost? Is there a way to tell the class that it's already loaded or something? or a way to access it so it's not reloaded from the DB? Code is below (shitty pseudocode, not full version) : ASP.Net page, loading back the values from postback : dim obj_search as search = new subsonic.query.select().......' retrieves the search object for each opt as search_option in obj_search.search_options opt.Value = Ctype(FindControl("search_option_" + opt.search_option_id),Textbox).Text debug.print(opt.Value) ' value is correct next for each opt as search_option in obj_search.search_options debug.print(opt.Value) 'this is nothing next Now, the partial class : public partial class search_option private m_value as string public property Value() as string get return m_value end get set( byval value as string) m_value = value end set end property end class

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  • Why does C# not implement GetHashCode for Collections?

    - by Peterdk
    I am porting something from Java to C#. In Java the hashcode of a ArrayList depends on the items in it. In C# I always get the same hashcode from a List... Why is this? For some of my objects the hashcode needs to be different because the objects in their list property make the objects non-equal. I would expect that a hashcode is always unique for the object's state and only equals another hashcode when the object is equal. Am I wrong?

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  • Searching through Collections in Java

    - by Click Upvote
    I have a java properties file containing a key/value pair of country names and codes. I will load the contents of this file into a Collection like List or HashMap. Then, I want users to be able to search for a country, e.g if they type 'Aus' in a textbox and click submit, then I want to search through the collection I have, containing a key/value pair of country codes/names (e.g AUS=Australia), and return those countries which are found matching. Is there any more efficient way of doing this, other than looping through the elements of the collection and using charAt()?

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  • customising serialisation of java collections using xstream

    - by Will Goring
    I have an object that needs to be serialised as XML, which contains the following field: List<String> tags = new List<String>(); XStream serialises it just fine (after some aliases) like this: <tags> <string>tagOne</string> <string>tagTwo</string> <string>tagThree</string> <string>tagFour</string> </tags> That's OK as far as it goes, but I'd like to be able to rename the <string> elements to, say, <tag>. I can't see an obvious way to do that from the alias documentation on the XStream site. Am I missing something obvious?

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  • How to load entities into readonly collections using the entity framework

    - by Anton P
    I have a POCO domain model which is wired up to the entity framework using the new ObjectContext class. public class Product { private ICollection<Photo> _photos; public Product() { _photos = new Collection<Photo>(); } public int Id { get; set; } public string Name { get; set; } public virtual IEnumerable<Photo> Photos { get { return _photos; } } public void AddPhoto(Photo photo) { //Some biz logic //... _photos.Add(photo); } } In the above example i have set the Photos collection type to IEnumerable as this will make it read only. The only way to add/remove photos is through the public methods. The problem with this is that the Entity Framework cannot load the Photo entities into the IEnumerable collection as it's not of type ICollection. By changing the type to ICollection will allow callers to call the Add mentod on the collection itself which is not good. What are my options?

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  • Java: Finding objects in collections.

    - by Jake
    This problem occurs over and over. I have some complicated object, such as a Cat, which has many properties, such as age, favorite cat food, and so forth. A bunch of Cats are stored in a Java Collection, and I need to find all the Cats that are aged 3, or those whose favorite cat food is Whiskas. Surely, I can write a custom method that finds those Cats with a specific property, but this gets cumbersome with many properties; is there some generic way of doing this?

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  • Collections removeAll method

    - by srinannapa
    I would like to know if something like below is possible , list<**MyObject**>.**removeAll**(list<**String**>) I hope the context is understandable. The list<MyObject : is a ArrayList<MyObject The list<String : is a ArrayList<String I know this can be achieved by overriding equals method in MyObject class. I would like to know if any other choice is prsent. Thanks,Srinivas N

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  • google collections ordering on map values

    - by chris-gr
    I would like to order a map based on the values. Function<Map.Entry<A, Double>, Double> getSimFunction = new Function<Map.Entry<A, Double>, Double>() { public Double apply(Map.Entry<A, Double> entry) { return entry.getValue(); } }; final Ordering<Map.Entry<A, Double>> entryOrdering = Ordering.natural().onResultOf(getSimFunction); ImmutableSortedMap.orderedBy(entryOrdering).putAll(....).build(); How can I create a new sortedMap based on the ordering results or a sortedset based on the map.keyset()?

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  • AutoMapping Custom Collections with FluentNHibernate

    - by ScottBelchak
    I am retrofitting a very large application to use NHibernate as it's data access strategy. Everything is going well with AutoMapping. Luckily when the domain layer was built, we used a code generator. The main issue that I am running into now is that every collection is hidden behind a custom class that derives from List<. For example public class League { public OwnerList owners {get;set;} } public class OwnerList : AppList<Owner> { } public class AppList<T> : List<T> { } What kind of Convention do I have to write to get this done?

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  • C++ stl collections or linked lists

    - by Lucas
    I'm developing a OpenGL based simulation in C++. I'm optmizing my code now and i see throughout the code the frequently use of std:list and std:vector. What is the more performatic: to continue using C++ stl data structs or a pointer based linked list? The main operation that involve std::list and std::vector is open a iterator and loop through all items in the data structs and apply some processing

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  • scala 2.8 implict java collections conversions

    - by nablik
    I have problem with JavaConversions with 2.8 beta: import scala.collection.JavaConversions._ class Utils(dbFile : File, sep: String) extends IUtils { (...) def getFeatures() : java.util.List[String] = csv.attributes.toList } And then exception: [INFO] Utils.scala:20: error: type mismatch; [INFO] found : List[String] [INFO] required: java.util.List[String] [INFO] def getFeatures() : java.util.List[String] = csv.attributes.toList [INFO]

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