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• Using different numeric variable types

  - by DataPimp

  Im still pretty new so bear with me on this one, my question(s) are not meant to be argumentative or petty but during some reading something struck me as odd. Im under the assumption that when computers were slow and memory was expensive using the correct variable type was much more of a necessity than it is today. Now that memory is a bit easier to come by people seem to have relaxed a bit. For example, you see this sample code everywhere: for (int i = 0; i < length; i++) int? (-2,147,483,648 to 2,147,483,648) for length? Isnt byte (0-255) a better choice? So Im curious of your opinion and what you believe to be best practice, I hate to think this would be used only because the acronym "int" is more intuitive for a beginner...or has memory just become so cheap that we really dont need to concern ourselves with such petty things and therefore we should just use long so we can be sure any other numbers/types(within reason) used can be cast automagically? ...or am Im just being silly by concerning myself with such things?

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• Specify Columntype in nhibernate

  - by Bipul

  I have a class CaptionItem public class CaptionItem { public virtual int SystemId { get; set; } public virtual int Version { get; set; } protected internal virtual IDictionary<string, string> CaptionValues {get; private set;} } I am using following code for nHibernate mapping Id(x => x.SystemId); Version(x => x.Version); Cache.ReadWrite().IncludeAll(); HasMany(x => x.CaptionValues) .KeyColumn("CaptionItem_Id") .AsMap<string>(idx => idx.Column("CaptionSet_Name"), elem => elem.Column("Text")) .Not.LazyLoad() .Cascade.Delete() .Table("CaptionValue") .Cache.ReadWrite().IncludeAll(); So in database two tables get created. One CaptionValue and other CaptionItem. In CaptionItem table has three columns 1. CaptionItem_Id int 2. Text nvarchar(255) 3. CaptionSet_Name nvarchar(255) Now, my question is how can I make the columnt type of Text to nvarchar(max)? Thanks in advance.

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• Nhibernate Fluent domain Object with Id(x => x.id).GeneratedBy.Assigned not saveable

  - by urpcor

  Hi there, I am using for some legacy db the corresponding domainclasses with mappings. Now the Ids of the entities are calculated by some stored Procedure in the DB which gives back the Id for the new row.(Its legacy, I cant change this) Now I create the new entity , set the Id and Call Save. But nothing happens. no exeption. Even NH Profiler does not say a bit. its as the Save call does nothing. I expect that NH thinks that the record is already in the db because its got an Id already. But I am using Id(x = x.id).GeneratedBy.Assigned() and intetionally the Session.Save(object) method. I am confused. I saw so many samples there it worked. does any body have any ideas about it? public class Appendix { public virtual int id { get; set; } public virtual AppendixHierarchy AppendixHierachy { get; set; } public virtual byte[] appendix { get; set; } } public class AppendixMap : ClassMap<Appendix> { public AppendixMap () { WithTable("appendix"); Id(x => x.id).GeneratedBy.Assigned(); References(x => x.AppendixHierachy).ColumnName("appendixHierarchyId"); Map(x => x.appendix); } }

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• C++ destructor problem with boost::scoped_ptr

  - by bb-generation

  I have a question about the following code: #include <iostream> #include <boost/scoped_ptr.hpp> class Interface { }; class A : public Interface { public: A() { std::cout << "A()" << std::endl; } virtual ~A() { std::cout << "~A()" << std::endl; } }; Interface* get_a() { A* a = new A; return a; } int main() { { std::cout << "1" << std::endl; boost::scoped_ptr<Interface> x(get_a()); std::cout << "2" << std::endl; } std::cout << "3" << std::endl; } It creates the following output: 1 A() 2 3 As you can see, it doesn't call the destructor of A. The only way I see to get the destructor of A being called, is to add a destructor for the Interface class like this: virtual ~Interface() { } But I really want to avoid any Implementation in my Interface class and virtual ~Interface() = 0; doesn't work (produces some linker errors complaining about a non existing implementation of ~Interface(). So my question is: What do I have to change in order to make the destructor being called, but (if possible) leave the Interface as an Interface (only abstract methods).

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• Drools - Doing Complex Stuff inside a Rule Condition or Consequence

  - by mfcabrera

  Hello, In my company we are planning to use Drools a BRE for couple of projects. Now we trying to define some best-practices. My question is what should be and shouldn't be done inside a Rule Condition/Consequence. Given that we can write Java directly or call methods (for example From a Global object in the Working Memory). Example. Given a Rule that evaluates a generic Object (e.g. Person) have property set to true. Now, that specific propertie can only be defined for that Object going to the database and fetching that info. So we have two ways of implementing that: Alternative A: Go to the database and fetch the object property (true/false, a code) Insert the Object in the working memory Evaluate the rule Alternative B: Insert a Global Object that has a method that connects to the database and check for the property for the given object. Insert the Object to eval in Working Memory In the rule, call the Global Object and perform the access to the database Which of those is considered better? I really like A, but sometimes B is more straightforward, however what would happen if something like a Exception from the Database is raised? I have seen the alternative B implemented in the Drools 5.0 Book from Packt Publishing,however they are doing a mocking and they don't talk about the actual implications of going to the database at all. Thank you,

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• How to "wrap" implementation in C#

  - by igor

  Hello, I have these classes in C# (.NET Framework 3.5) described below: public class Base { public int State {get; set;} public virtual int Method1(){} public virtual string Method2(){} ... public virtual void Method10(){} } public class B: Base { // some implementation } public class Proxy: Base { private B _b; public class Proxy(B b) { _b = b; } public override int Method1() { if (State == Running) return _b.Method1(); else return base.Method1(); } public override string Method2() { if (State == Running) return _b.Method2(); else return base.Method2(); } public override void Method10() { if (State == Running) _b.Method10(); else base.Method10(); } } I want to get something this: public Base GetStateDependentImplementation() { if (State == Running) // may be some other rule return _b; else return base; // compile error } and my Proxy's implementation will be: public class Proxy: Base { ... public override int Method1() { return GetStateDependentImplementation().Method1(); } public override string Method2() { return GetStateDependentImplementation().Method2(); } ... } Of course, I can do this (aggregation of base implementation): public RepeaterOfBase: Base // no any overrides, just inheritance { } public class Proxy: Base { private B _b; private RepeaterOfBase _Base; public class Proxy(B b, RepeaterOfBase aBase) { _b = b; _base = aBase; } } ... public Base GetStateDependentImplementation() { if (State == Running) return _b; else return _Base; } ... But instance of Base class is very huge and I have to avoid to have other additional copy in memory. So I have to simplify my code have to "wrap" implementation have to avoid a code duplication have to avoid aggregation of any additional instance of Base class (duplication) Is it possible to reach these goals?

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• Entity Framework 1:1 Relationship Identity Colums

  - by Hupperware

  I cannot for the life of me get two separate tables to save with a relationship and two identity columns. I keep getting errors like A dependent property in a ReferentialConstraint is mapped to a store-generated column. Column: 'OlsTerminalId'. I can't imagine that this setup is abnormal. [DataContract] public class OlsData { private static readonly DateTime theUnixEpoch = new DateTime(1970, 1, 1, 0, 0, 0, 0, DateTimeKind.Utc); [DatabaseGenerated(DatabaseGeneratedOption.Identity)] public int OlsDataId { get; set; } [DataMember(Name = "id")] public int Id { get; set; } public DateTime Timestamp { get; set; } [DataMember(Name = "created")] [NotMapped] public double Created { get { return (Timestamp - theUnixEpoch).TotalMilliseconds; } set { Timestamp = theUnixEpoch.AddMilliseconds(value); } } [InverseProperty("OlsData")] [DataMember(Name = "terminal")] public virtual OlsTerminal OlsTerminal { get; set; } } [DataContract] public class OlsTerminal { [DatabaseGenerated(DatabaseGeneratedOption.Identity)] public int OlsTerminalId { get; set; } public int OlsDataId { get; set; } [DataMember(Name = "account")] [NotMapped] public virtual OlsAccount OlsAccount { get; set; } [DataMember(Name = "terminalId")] public string TerminalId { get; set; } [DataMember(Name = "merchantId")] public string MerchantId { get; set; } public virtual OlsData OlsData { get; set; } } public class OlsDataContext : DbContext { protected override void OnModelCreating(DbModelBuilder aModelBuilder) { aModelBuilder.Conventions.Remove<PluralizingTableNameConvention>(); } public OlsDataContext(string aConnectionString) : base(aConnectionString) {} public DbSet<OlsData> OlsData { get; set; } public DbSet<OlsTerminal> OlsTerminal { get; set; } public DbSet<OlsAccount> OlsAccount { get; set; } }

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• c++ specialized overload?

  - by acidzombie24

  -edit- i am trying to close the question. i solved the problem with boost::is_base_and_derived In my class i want to do two things. 1) Copy int, floats and other normal values 2) Copy structs that supply a special copy function (template T copyAs(); } the struct MUST NOT return int's unless i explicitly say ints. I do not want the programmer mistaking the mistake by doing int a = thatClass; -edit- someone mention classes dont return anything, i mean using the operator Type() overload. How do i create my copy operator in such a way i can copy both 1) ints, floats etc and the the struct restricted in the way i mention in 2). i tried doing template <class T2> T operator = (const T2& v); which would cover my ints, floats etc. But how would it differentiate from structs? so i wrote T operator = (const SomeGenericBase& v); The idea was the GenericBase would be unsed instead then i can do v.Whatever. But that backfires bc the functions i want wouldnt exist, unless i use virtual, but virtual templates dont exist. Also i would hate to use virtual I think the solution is to get rid of ints and have it convert to something that can do .as(). So i wrote something up but now i have the same problem, how does that differentiate ints and structs that have the .as() function template?

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• Split UInt32 (audio frame) into two SInt16s (left and right)?

  - by morgancodes

  Total noob to anything lower-level than Java, diving into iPhone audio, and realing from all of the casting/pointers/raw memory access. I'm working with some example code wich reads a WAV file from disc and returns stereo samples as single UInt32 values. If I understand correctly, this is just a convenient way to return the 32 bits of memory required to create two 16 bit samples. Eventually this data gets written to a buffer, and an audio unit picks it up down the road. Even though the data is written in UInt32-sized chunks, it eventually is interpreted as pairs of 16-bit samples. What I need help with is splitting these UInt32 frames into left and right samples. I'm assuming I'll want to convert each UInt32 into an SInt16, since an audio sample is a signed value. It seems to me that for efficiency's sake, I ought to be able to simply point to the same blocks in memory, and avoid any copying. So, in pseudo-code, it would be something like this: UInt32 myStereoFrame = getFramefromFilePlayer; SInt16* leftChannel = getFirst16Bits(myStereoFrame); SInt16* rightChannel = getSecond16Bits(myStereoFrame); Can anyone help me turn my pseudo into real code?

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• JAR files, don't they just bloat and slow Java down?

  - by Josamoto

  Okay, the question might seem dumb, but I'm asking it anyways. After struggling for hours to get a Spring + BlazeDS project up and running, I discovered that I was having problems with my project as a result of not including the right dependencies for Spring etc. There were .jars missing from my WEB-INF/lib folder, yes, silly me. After a while, I managed to get all the .jar files where they belong, and it comes at a whopping 12.5MB at that, and there's more than 30 of them! Which concerns me, but it probably and hopefully shouldn't be concerned. How does Java operate in terms of these JAR files, they do take up quite a bit of hard drive space, taking into account that it's compressed and compiled source code. So that can really quickly populate a lot of RAM and in an instant. My questions are: Does Java load an entire .jar file into memory when say for instance a class in that .jar is instantiated? What about stuff that's in the .jar that never gets used. Do .jars get cached somehow, for optimized application performance? When a single .jar is loaded, I understand that the thing sits in memory and is available across multiple HTTP requests (i.e. for the lifetime of the server instance running), unlike PHP where objects are created on the fly with each request, is this assumption correct? When using Spring, I'm thinking, I had to include all those fiddly .jars, wouldn't I just be better off just using native Java, with say at least and ORM solution like Hibernate? So far, Spring just took extra time configuring, extra hard drive space, extra memory, cpu consumption, so I'm concerned that the framework is going to cost too much application performance just to get for example, IoC implemented with my BlazeDS server. There still has to come ORM, a unit testing framework and bits and pieces here and there. It's just so easy to bloat up a project quickly and irresponsibly easily. Where do I draw the line?

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• How do I organize C# classes that inherit from one another, but also have properties that inherit from one another?

  - by Chris

  I have an application that has a concept of a Venue, a place where events happen. A Venue is owned by a Company and has many VenueParts. So, it looks like this: public abstract class Venue { public int Id { get; set; } public string Name { get; set; } public virtual Company Company { get; set; } public virtual ICollection<VenuePart> VenueParts { get; set; } } A Venue can be a GolfCourseVenue, which is a Venue that has a Slope and a specific kind of VenuePart called a HoleVenuePart: public class GolfCourseVenue { public string Slope { get; set; } public virtual ICollection<HoleVenuePart> Holes { get; set; } } In the future, there may also be other kinds of Venues that all inherit from Venue. They might add their own fields, and will always have VenueParts of their own specific type. My declarations above seem wrong, because now I have a GolfCourseVenue with two collections, when really it should just have the one. I can't override it, because the type is different, right? When I run reports, I would like to refer to the classes generically, where I just spit out Venues and VenueParts. But, when I render forms and such, I would like to be specific. I have a lot of relationships like this and am wondering what I am doing wrong. For example, I have an Order that has OrderItems, but also specific kinds of Orders that have specific kinds of OrderItems.

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• [c++] - Help about class and error: C3861

  - by Chelsea_cole

  Can someone help me in this error? in "cDef.h" : #pragma once class cDef { public: static int STATE_LOGO; static int STATE_MENU; static int MESSAGE_ENTER; static int MESSAGE_UPDATE; static int MESSAGE_PAINT; static int MESSAGE_EXIT; }; in "GameState.h": #pragma once #ifndef _GameState_ #define _GameState_ #include "cDef.h" class MainGame; class GameState; class GameState { public: MainGame *mg; int GAME_STATE_DEF; virtual void MessengeEnter(int message) = 0; virtual void MessengeUpdate(int message,int keys) = 0; virtual void MessengePaint(int message,CDC *pDc) = 0; void StateHandler(int message,CDC *pDc,int keys); public: GameState(void); public: ~GameState(void); }; #endif in "GameState.cpp": #include "StdAfx.h" #include "GameState.h" GameState::GameState(void) { GAME_STATE_DEF = -1; } GameState::~GameState(void) { } void GameState::StateHandler(int message,CDC *pDc,int keys) { if(message == cDef.MESSAGE_ENTER) { MessageEnter(message); } if(message == cDef.MESSAGE_UPDATE) { MessageUpdate(message,keys); } if(message == cDef.MESSAGE_PAINT) { MessagePaint(message,pDC); } } error: warning C4832: token '.' is illegal after UDT 'cDef' see declaration of 'cDef' error C3861: 'MessageUpdate': identifier not found error C3861: 'MessageEnter': identifier not found error C3861: 'MessagePaint': identifier not found ..... Thanks in advance!

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• FluentNHibernate error -- "Invalid object name"

  - by goober

  I'm attempting to do the most simple of mappings with FluentNHibernate & Sql2005. Basically, I have a database table called "sv_Categories". I'd like to add a category, setting the ID automatically, and adding the userid and title supplied. Database table layout: CategoryID -- int -- not-null, primary key, auto-incrementing UserID -- uniqueidentifier -- not null Title -- varchar(50) -- not null Simple. My SessionFactory code (which works, as far as I can tell): _SessionFactory = Fluently.Configure().Database( MsSqlConfiguration.MsSql2005 .ConnectionString(c => c.FromConnectionStringWithKey("SVTest"))) .Mappings(x => x.FluentMappings.AddFromAssemblyOf<CategoryMap>()) .BuildSessionFactory(); My ClassMap code: public class CategoryMap : ClassMap<Category> { public CategoryMap() { Id(x => x.ID).Column("CategoryID").Unique(); Map(x => x.Title).Column("Title").Not.Nullable(); Map(x => x.UserID).Column("UserID").Not.Nullable(); } } My Class code: public class Category { public virtual int ID { get; private set; } public virtual string Title { get; set; } public virtual Guid UserID { get; set; } public Category() { // do nothing } } And the page where I save the object: public void Add(Category catToAdd) { using (ISession session = SessionProvider.GetSession()) { using (ITransaction Transaction = session.BeginTransaction()) { session.Save(catToAdd); Transaction.Commit(); } } } I receive the error Invalid object name 'Category'. Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code. Exception Details: System.Data.SqlClient.SqlException: Invalid object name 'Category'. I think it might be that I haven't told the CategoryMap class to use the "sv_Categories" table, but I'm not sure how to do that. Any help would be appreciated. Thanks!

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• How to limit TCP writes to particular size and then block untlil the data is read

  - by ustulation

  {Qt 4.7.0 , VS 2010} I have a Server written in Qt and a 3rd party client executable. Qt based server uses QTcpServer and QTcpSocket facilities (non-blocking). Going through the articles on TCP I understand the following: the original implementation of TCP mentioned the negotiable window size to be a 16-bit value, thus maximum being 65535 bytes. But implementations often used the RFC window-scale-extension that allows the sliding window size to be scalable by bit-shifting to yield a maximum of 1 gigabyte. This is implementation defined. This could have resulted in majorly different window sizes on receiver and sender end as the server uses Qt facilities without hardcoding any window size limit. Client 1st asks for all information it can based on the previous messages from the server before handling the new (accumulating) incoming messages. So at some point Server receives a lot of messages each asking for data of several MB's. This the server processes and puts it into the sender buffer. Client however is unable to handle the messages at the same pace and it seems that client’s receiver buffer is far smaller (65535 bytes maybe) than sender’s transmit window size. The messages thus get accumulated at sender’s end until the sender’s buffer is full too after which the TCP writes on sender would block. This however does not happen as sender buffer is much larger. Hence this manifests as increase in memory consumption on the sender’s end. To prevent this from happening, I used Qt’s socket’s waitForBytesWritten() with timeout set to -1 for infinite waiting period. This as I see from the behaviour blocks the thread writing TCP data until the data has actually been sensed by the receiver’s window (which will happen when earlier messages have been processed by the client at application level). This has caused memory consumption at Server end to be almost negligible. is there a better alternative to this (in Qt) if i want to restrict the memory consumption at server end to say x MB's? Also please point out if any of my understandings is incorrect.

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• Loading more than 10 images on iPhone??

  - by SeniorLee

  I'm trying to add more than 10 pictures on ScrollView. NSUInteger i; for (i = 1; i <= numberOfImage; i++) { NSString *imageName = [NSString stringWithFormat:@"d%dimage%d.png", imageSection, i]; UIImage *image = [UIImage imageNamed:imageName]; UIImageView *imageView = [[UIImageView alloc] initWithImage:image]; // setup each frame to a default height and width, it will be properly placed when we call "updateScrollList" CGRect rect = imageView.frame; rect.size.height = kScrollObjHeight; rect.size.width = kScrollObjWidth; imageView.frame = rect; imageView.tag = i; // tag our images for later use when we place them in serial fashion [scrollView addSubview:imageView]; [imageView release]; } This code is from Apple example and it works fine. But if the variable 'i' is bigger than 10, 'UIImage *image' is empty. The imageName seems to correct. But I don't know why it does not load image. Does anybody sees the problem?? And one more thing. If I do like that, does iOS controls memory automatically? I mean it's kind of wasting memory if all (more than 10) images are loaded on memory even they are not displayed. I've heard that iOS loads images only displayed on screen and free images those are not displayed. Is that right? Thanks for reading.

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• Android opengl releasing textures

  - by user1642418

  I have a bit of a problem. I am developing a game for android + engine and I got stuck. I am getting OpenGL out of memory error and either app crashes or phone hangs after loading a scene multiple times. For example: app launches, shows main menu, 1st level/scene is loaded. Then I go back to main menu, and repeat. It doesnt matter which scene I load, after 4-6 times the error occurs. Some background: Each time when scene is loaded all the resources are released and upon first frame render - needed stuff gets loaded. The performance is more or less ok. Note that I am calling glDeleteTexture method, but I think its not doing its job and releasing memory. Thing is that -when I minimize and open it again - problem doesn't occur, but almost the same things are executed. Problem doesn't occur. This way android releases memory. How do I release/get rid of unused textures properly? This happens on HTC Desire HD ( ice cream sandwich 4.0.4) . Other games works fine, so I bet this is not the problem in ROM.

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• Asp.Net MVC3 - How create Dynamic DropDownList

  - by Bibo

  I found many articles on this but still I don´t know how exactly to do this. I am trying to create my own blog engine, I have View for create article (I am using EF and Code first) and now I must fill number of category in which article should be add but I want to change it to dropdownlist with names of categories. My model looks this: public class Article { public int ArticleID { get; set; } [Required] public string Title { get; set; } [Required] public int CategoryID { get; set; } public DateTime Date { get; set; } [Required()] [DataType(DataType.MultilineText)] [AllowHtml] public string Text { get; set; } public virtual Category Category { get; set; } public IEnumerable<SelectListItem> Categories { get; set; } public virtual ICollection<Comment> Comments { get; set; } } public class Category { public int CategoryID { get; set; } [Required] public string Name { get; set; } public virtual ICollection<Article> Articles { get; set; } } I know I must use Enum (or I think) but I am not exactly sure how. I don´t know which tutorial from that I found is best for me.

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• Testing paginated UIScrollView on iPad

  - by Piotr Czapla

  I'm creating a magazine reader (something like iGizmo on iPad). I have two scrollviews one that paginate over articles and second to paginate inside of an article through pages. I'd like to check memory usage of my app after scrolling through 20 pages. To do so I decided to create an automated ui test that scrolls 20 times right and the check the memory foot print at the end of the test. I need that info to have some metrics before I start optimizing the memory usage And Here is the thing: I can't make the ui automation to pass to the second page. My automation code looks like that: var window = UIATarget.localTarget().frontMostApp().mainWindow(); var articleScrollView = window.scrollViews()[0]; articleScrollView.scrollRight(); // do you know any command to wait until first scrolls ends? articleScrollView.scrollRight(); // this one doesn't work I guess that I need to wait for the first scorlling to end before I can run another one, but I don't know how to do that as each page is just an image. (I don't have anything else on pages yet) Any idea?

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• parse a special xml in python

  - by zhaojing

  I have s special xml file like below: <alarm-dictionary source="DDD" type="ProxyComponent"> <alarm code="402" severity="Alarm" name="DDM_Alarm_402"> <message>Database memory usage low threshold crossed</message> <description>dnKinds = database type = quality_of_service perceived_severity = minor probable_cause = thresholdCrossed additional_text = Database memory usage low threshold crossed </description> </alarm> ... </alarm-dictionary> I know in python, I can get the "alarm code", "severity" in tag alarm by: for alarm_tag in dom.getElementsByTagName('alarm'): if alarm_tag.hasAttribute('code'): alarmcode = str(alarm_tag.getAttribute('code')) And I can get the text in tag message like below: for messages_tag in dom.getElementsByTagName('message'): messages = "" for message_tag in messages_tag.childNodes: if message_tag.nodeType in (message_tag.TEXT_NODE, message_tag.CDATA_SECTION_NODE): messages += message_tag.data But I also want to get the value like dnkind(database), type(quality_of_service), perceived_severity(thresholdCrossed) and probable_cause(Database memory usage low threshold crossed ) in tag description. That is, I also want to parse the content in the tag in xml. Could anyone help me with this? Thanks a lot!

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• Help Me With This MS-Access Query

  - by yae

  I have 2 tables: "products" and "pieces" PRODUCTS idProd product price PIECES id idProdMain idProdChild quant idProdMain and idProdChild are related with the table: "products". Other considerations is that 1 product can have some pieces and 1 product can be a piece. Price product equal a sum of quantity * price of all their pieces. "Products" table contains all products (p EXAMPLE: TABLE PRODUCTS (idProd - product - price) 1 - Computer - 300€ 2 - Hard Disk - 100€ 3 - Memory - 50€ 4 - Main Board - 100€ 5 - Software - 50€ 6 - CDroms 100 un. - 30€ TABLE PIECES (id - idProdMain - idProdChild - Quant.) 1 - 1 - 2 - 1 2 - 1 - 3 - 2 3 - 1 - 4 - 1 WHAT I NEED? I need update the price of the main product when the price of the product child (piece) is changed. Following the previous example, if I change the price of this product "memory" (is a piece too) to 60€, then product "Computer" will must change his price to 320€ How I can do it using queries? Already I have tried this to obtain the price of the main product, but not runs. This query not returns any value: SELECT Sum(products.price*pieces.quant) AS Expr1 FROM products LEFT JOIN pieces ON (products.idProd = pieces.idProdChild) AND (products.idProd = pieces.idProdChild) AND (products.idProd = pieces.idProdMain) WHERE (((pieces.idProdMain)=5)); MORE INFO The table "products" contains all the products to sell that it is in the shop. The table "pieces" is to take a control of the compound products. To know those who are the products children. For example of compound product: computers. This product is composed by other products (motherboard, hard disk, memory, cpu, etc.)

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• Best tree/heap data structure for fixed set of nodes with changing values + need top 20 values?

  - by user350139

  I'm writing something like a game in C++ where I have a database table containing the current score for each user. I want to read that table into memory at the start of the game, quickly change each user's score while the game is being played in response to what each user does, and then when the game ends write the current scores back to the database. I also want to be able to find the 20 or so users with the highest scores. No users will be added or deleted during the short period when the game is being played. I haven't tried it yet, but updating the database might take too much time during the period when the game is being played. Fixed set of users (might be 10,000 to 50,000 users) Will map user IDs to their score and other user-specific information. User IDs will be auto_increment values. If the structure has a high memory overhead that's probably not an issue. If the program crashes during gameplay it can just be re-started. Quickly get a user's current score. Quickly add to a user's current score (and return their current score) Quickly get 20 users with highest score. No deletes. No inserts except when the structure is first created, and how long that takes isn't critical. Getting the top 20 users will only happen every five or ten seconds, but getting/adding will happen much more frequently. If not for the last, I could just create a memory block equal to sizeof(user) * max(user id) and put each user at user id * sizeof(user) for fast access. Should I do that plus some other structure for the Top 20 feature, or is there one structure that will handle all of this together?

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• Quickly accessing files in a 'project'

  - by bbbscarter

  Hi all. I'm looking for a way to quickly open files in my project's source tree. What I've been doing so far is adding files to the file-name-cache like so: (file-cache-add-directory-recursively (concat project-root "some/sub/folder") ".*\\.\\(py\\)$") after which I can use anything-for-files to access any file in the source tree with about 4 keystrokes. Unfortunately, this solution started falling over today. I've added another folder to the cache and emacs has started running out of memory. What's weird is that this folder contains less than 25% of files I'm adding, and yet emacs memory use goes up from 20mb to 400mb on adding just this folder. The total number of files is around 2000, so this memory use seems very high. Presumably I'm abusing the file cache. Anyway, what do other people do for this? I like this solution for its simplicity and speed; I've looked at some of the many, many project management packages for emacs and none of them really grabbed me... Thanks in advance! Simon

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• Storing large numbers of varying size objects on disk

  - by Foredecker

  I need to develop a system for storing large numbers (10's to 100's of thousands) of objects. Each object is email-like - there is a main text body, and several ancillary text fields of limited size. A body will be from a few bytes, to several KB in size. Each item will have a single unique ID (probably a GUID) that identifies it. The store will only be written to when an object is added to it. It will be read often. Deletions will be rare. The data is almost all human readable text so it will be readily compressible. A system that lets me issue the I/Os and mange the memory and caching would be ideal. I'm going to keep the indexes in memory, using it to map indexes to the single (and primary) key for the objects. Once I have the key, then I'll load it from disk, or the cache. The data management system needs to be part of my application - I do not want to depend on OS services. Or separately installed packages. Native (C++) would be best, but a manged (C#) thing would be ok. I believe that a database is an obvious choice, but this needs to be super-fast for look up and loading into memory of an object. I am not experienced with data base tech and I'm concerned that general relational systems will not handle all this variable sized data efficiently. (Note, this has nothing to do with my job - its a personal project.) In your experience, what are the viable alternatives to a traditional relational DB? Or would a DB work well for this?

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• Criteria for triggering garbage collection in .Net

  - by Kennet Belenky

  I've come across some curious behavior with regard to garbage collection in .Net. The following program will throw an OutOfMemoryException very quickly (after less than a second on a 32-bit, 2GB machine). The Foo finalizer is never called. class Foo { static Dictionary<Guid, WeakReference> allFoos = new Dictionary<Guid, WeakReference>(); Guid guid = Guid.NewGuid(); byte[] buffer = new byte[1000000]; static Random rand = new Random(); public Foo() { // Uncomment the following line and the program will run forever. // rand.NextBytes(buffer); allFoos[guid] = new WeakReference(this); } ~Foo() { allFoos.Remove(guid); } static public void Main(string args[]) { for (; ; ) { new Foo(); } } } If the rand.nextBytes line is uncommented, it will run ad infinitum, and the Foo finalizer is regularly invoked. Why is that? My best guess is that in the former case, either the CLR or the Windows VMM is lazy about allocating physical memory. The buffer never gets written to, so the physical memory is never used. When the address space runs out, the system crashes. In the latter case, the system runs out of physical memory before it runs out of address space, the GC is triggered and the objects are collected. However, here's the part I don't get. Assuming my theory is correct, why doesn't the GC trigger when the address space runs low? If my theory is incorrect, then what's the real explanation?

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• How to find unmapped properties in a NHibernate mapped class?

  - by haarrrgh

  I just had a NHibernate related problem where I forgot to map one property of a class. A very simplified example: public class MyClass { public virtual int ID { get; set; } public virtual string SomeText { get; set; } public virtual int SomeNumber { get; set; } } ...and the mapping file: <?xml version="1.0" encoding="utf-8" ?> <hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="MyAssembly" namespace="MyAssembly.MyNamespace"> <class name="MyClass" table="SomeTable"> <property name="ID" /> <property name="SomeText" /> </class> </hibernate-mapping> In this simple example, you can see the problem at once: there is a property named "SomeNumber" in the class, but not in the mapping file. So NHibernate will not map it and it will always be zero. The real class had a lot more properties, so the problem was not as easy to see and it took me quite some time to figure out why SomeNumber always returned zero even though I was 100% sure that the value in the database was != zero. So, here is my question: Is there some simple way to find this out via NHibernate? Like a compiler warning when a class is mapped, but some of its properties are not. Or some query that I can run that shows me unmapped properties in mapped classes...you get the idea. (Plus, it would be nice if I could exclude some legacy columns that I really don't want mapped.)

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