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  • Dynamic Object Not Creating for Privately Inherited Class.

    - by mahesh
    Hi, What is the reason for the following code that does not let me to create object. class base { public: void foo() { cout << "base::foo()"; } }; class derived : private base { public: void foo() { cout << "deived::foo()"; } }; void main() { base *d = new derived(); d->foo(); } It Gives me error : " 'type cast' : conversion from 'derived *' to 'base *' exists, but is inaccessible" Thanks in advance :)

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  • Rails object inheritence with belongs_to

    - by Rabbott
    I have a simple has_many/belongs_to relationship between Report and Chart. The issue I'm having is that my Chart model is a parent that has children. So in my Report model I have class Report < ActiveRecord::Base has_many :charts end And my Chart model is a parent, where Pie, Line, Bar all inherit from Chart. I'm not sure where the belongs_to :report belongs within the chart model, or children of chart model. I get errors when I attempt to access chart.report because the object is of type "Class" undefined local variable or method `report' for #< Class:0x104974b90 The Chart model uses STI so its pulling say.. 'Pie' from the chart_type column in the charts table.. what am I missing?

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  • Should I put actors in the Domain-Model/Class-Diagram?

    - by devoured elysium
    When designing both the domain-model and class-diagrams I am having some trouble understanding what to put in them. I'll give an example of what I mean: I am doing a vacations scheduler program, that has an Administrator and End-Users. The Administrator does a couple of things like registering End-Users in the program, changing their previleges, etc. The End-User can choose his vacations days, etc. I initially defined an Administrator and End-User as concepts in the domain-model, and later as classes in the class-diagram. In the class-diagram, both classes ended up having a couple of methods like Administrator.RegisterNewUser(); Administrator.UnregisterUser(int id); etc. Only after some time I realised that actually both Administrator and End-User are actors, and maybe I got this design totally wrong. Instead of filling Administrator and End-User classes with methods to do what my Use-Cases request, I could define other classes from the domain to do them, and have controllers handle the Use-Cases(actually, I decided to do one for each Use-Case). I could have a UserDatabase.RegisterNewUser() and UserDatabase.UnregisterUser(int id);, for example, instead of having those methods on the Administrator class. The idea would be to try to think of the whole vacation-scheduler as a "closed-program" that has a set of features and doesn't bother with things such as authentication, that should be internal/protected, being that the only public things I'd let the outside world see would be its controllers. Is this the right approach? Or am I getting this totally wrong? Is it generally bad idea to put Actors in the domain-model/class-diagrams? What are good rules of thumb for this? My lecturer is following Applying UML and Patterns, which I find awful, so I'd like to know where I could look up more info on this described actor-models situation. I'm still a bit confused about all of this, as this new approach is radically different from anything I've done before.

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  • resort on a std::vector vs std::insert

    - by Abruzzo Forte e Gentile
    I have a sorted std::vector of relative small size ( from 5 to 20 elements ). I used std::vector since the data is continuous so I have speed because of cache. On a specific point I need to remove an element from this vector. I have now a doubt: which is the fastest way to remove this value between the 2 options below? setting that element to 0 and call sort to reorder: this has complexity but elements are on the same cache line. call erase that will copy ( or memcpy who knows?? ) all elements after it of 1 place ( I need to investigate the behind scense of erase ). Do you know which one is faster? I think that the same approach could be thought about inserting a new element without hitting the max capacity of the vector. Regards AFG

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  • When to define SDD(System Sequence Diagram) operations System->Actor?

    - by devoured elysium
    I am having some trouble understanding how to make System Sequence Diagrams, as I don't fully grasp why in some cases one should define operations for System - Actor and in others don't. Here is an example: Let's assume the System is a Cinema Ticket Store and the Actor is a client that wants to buy a ticket. 1) The User tells the System that wants to buy some tickets, stating his client number. 2) The System confirms that the given client number is valid. 3) The User tells the System the movie that wants to see. 4) The System shows the set of available sessions and seats for that movie. 5) The System asks the user which session/seat he wants. 6) The User tells the System the chosen session/seat. This would be converted to: a) -----> tellClientNumber(clientNumber) b) <----- validClientNumber c) -----> tellMovieToSee(movie) d) <----- showsAvailableSeatsHours e) -----> tellSystemChosenSessionSeat(session, seat) I know that when we are dealing with SDD's we are still far away from coding. But I can't help trying to imagine how it how it would have been had I to convert it right away to code: I can understand 1) and 2). It's like if it was a C#/Java method with the following signature: boolean tellClientNumber(clientNumber) so I put both on the SDD. Then, we have the pair 3) 4). I can imagine that as something as: SomeDataStructureThatHoldsAvailableSessionsSeats tellSystemMovieToSee(movie) Now, the problem: From what I've come to understand, my lecturer says that we shouldn't make an operation on the SDD for 5) as we should only show operations from the Actor to the System and when the System is either presenting us data (as in c)) or validating sent data (such as in b)). I find this odd, as if I try to imagine this like a DOS app where you have to put your input sequencially, it makes sense to make an arrow even for 5). Why is this wrong? How should I try to visualize this? Thanks

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  • What are the suggested alternatives for Class<T>.isAssignableFrom(Class<?> cls)?

    - by Wing C. Chen
    Currently I am doing the profiling to a piece of code. During the profiling, I discovered that this very method call, Class<T>.isAssignableFrom(Class<?> cls) takes up to quite amount of the entire time. Because this is a method from reflection, it takes a lot of time compared to normal keywords or method calls. I am wondering if there are some good alternatives for this method calls?

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  • SQL Profiles showing high activity

    - by Wong Chi
    I am running my application locally -- ie. No external traffic and very low number of queries, fully under my control. I see tons of 'Audit Login' and 'Audit Logout' events. What are these and where are they actually stored (ie. Where is this audit log)? Are these a hint of a problem with connections, because I have only a simple connection string within my app and thought that connections would remain active throughout the operation of my app (ie. a single login at launch, and then a single logout when terminating).

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  • High CPU - What to do.

    - by Udi Kantzuker
    I have a high CPU problem with MYSQL using "top" ( linux ) shows cpu peaks of 90%. I was trying to find the source of the problem, turned on general log and slow query log, The slow query log did not find anything. The Db contains a few small tables and one large table that contains almost 100k rows, Database Engine is MyIsam. strange thing i have noticed that on the large table, select, insert are very fast but update takes 0.2 - 0.5 secs. already used optimize and repair and no improvement. the table is being updated frequently, could this be the source of the high CPU% ? What can i do to improve this?

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  • Quickest way to compare a buch of array or list of values.

    - by zapping
    Can you please let me know on the quickest and efficient way to compare a large set of values. Its like there are a list of parent codes(string) and each code has a series of child values(string). The child lists have to be compared with each other and find out duplicates and count how many times they repeat. code1(code1_value1, code1_value2, code3_value3, ..., code1_valueN); code2(code2_value1, code1_value2, code2_value3, ..., code2_valueN); code3(code2_value1, code3_value2, code3_value3, ..., code3_valueN); . . . codeN(codeN_value1, codeN_value2, codeN_value3, ..., codeN_valueN); The lists are huge say like there are 100 parent codes and each has about 250 values in them. There will not be duplicates within a code list. Doing it in java and the solution i could figure out is. Store the values of first set of code in as codeMap.put(codeValue, duplicateCount). The count initialized to 0. Then compare the rest of the values with this. If its in the map then increment the count otherwise append it to the map. The downfall of this is to get the duplicates. Another iteration needs to be performed on a very large list. An alternative is to maintain another hashmap for duplicates like duplicateCodeMap.put(codeValue, duplicateCount) and change the initial hashmap to codeMap.put(codeValue, codeValue). Speed is what is requirement. Hope one of you can help me with it.

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  • Counting context switches per thread

    - by Sarmun
    Is there a way to see how many context switches each thread generates? (both in and out if possible) Either in X/s, or to let it run and give aggregated data after some time. (either on linux or on windows) I have found only tools that give aggregated context-switching number for whole os or per process. My program makes many context switches (50k/s), probably a lot not necessary, but I am not sure where to start optimizing, where do most of those happen.

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  • Slow first page load on asp.net site

    - by Tabloo Quijico
    Hi, Every now and then (always after a long period of idle-time, e.g. overnight) when I access a site built using asp.net - it takes around 15 seconds to load the page (15 seconds before I see any progress whatsoever, then the page comes up fast). Further pages on that site, or refreshes, are quick as usual - they are also fast on other machines, only the first one seems to take the 'hit'. Page tracing never through anything up (whole cycle was a fraction of a second) So my question is where else should I be looking? Perhaps IIS? Or could it still be my asp.net app and I'm just looking in the wrong place (the trace) for clues? As I don't have much control over the IIS server, anything I can check through asp.net would be more helpful, before I go ask that particular admin. cheers :D

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  • Class architecture, no friends allowed

    - by Captain Comic
    The question of why there are no friends in C# has been extensively discussed. I have the following design problems. I have a class that has only one public function AddOrder(Order ord). Clients are allowed to call only this function. All other logic must be hidden. Order class is listening to market events and must call other other function of TradingSystem ExecuteOrder, so I have to make it public as well. Doing that I will allow clients of Trading system to call this function and I don't want that. class TradingSystem { // Trading system stores list of orders List<Order> _orders; // this function is made public so that Order can call ir public ExecuteOrder(Order ord) { } // this function is made public for external clients public AddOrder(OrderRequest ordreq) { // create order and pass it this order.OnOrderAdded(this); } } class Order { TradingSystem _ts; public void OnOrderAdded(TradingSystem ts) { _ts = ts; } void OnMarketEvent() { _ts.ExecuteOrder() } }

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  • Fastest way for inserting very large number of records into a Table in SQL

    - by Irchi
    The problem is, we have a huge number of records (more than a million) to be inserted into a single table from a Java application. The records are created by the Java code, it's not a move from another table, so INSERT/SELECT won't help. Currently, my bottleneck is the INSERT statements. I'm using PreparedStatement to speed-up the process, but I can't get more than 50 recods per second on a normal server. The table is not complicated at all, and there are no indexes defined on it. The process takes too long, and the time it takes will make problems. What can I do to get the maximum speed (INSERT per second) possible? Database: MS SQL 2008. Application: Java-based, using Microsoft JDBC driver.

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  • How to find root cause for "too many connections" error in MySQL/PHP

    - by Nir
    I'm running a web service which runs algorithms that serve millions of calls daily and run some background processing as well. Every now and than I see "Too many connections" error in attempts to connect to the MySQL box" for a few seconds. However this is not necessarily attributed to high traffic times or anything I can put my finger on. I want to find the bottleneck causing it. Other than in the specific times this happens the server isn't too loaded in terms of CPU and Memory, and has 2-3 connections (threads) open and everything works smoothly. (I use Zabbix for monitoring) Any creative ideas on how to trace it?

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  • Persistance Queue Implementation

    - by Winter
    I was reading an article on Batch Processing in java over at JDJ http://java.sys-con.com/node/415321 . The article mentioned using a persistence queue as a Batch Updater instead of immediately sending an individual insert or update to the database. The author doesn't give a concrete example of this concept so I googled Persistence Queue but that didn't come up with much. Does anyone know of a good example of this?

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  • effective counter for unique number of visits in PHP & MySQL

    - by Adnan
    Hello, I am creating a counter for unique number of visits on a post, so what I have until now is a table for storing data like this; cvp_post_id | cvp_ip | cvp_user_id In cases a registered user visits a post, for the first time a record is inserted with cpv_post_id and cvp_user_id, so for his next visit I query the table and if the record is available I do not count him as a new visitor. In cases of an anonymous user the same happens but now the cvp_ip and cpv_post_id are used. My concerns is that I do a query every time anyone visits a post for checking if there has been a visit, what would be a more effective way for doing this?

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  • Long primitive or AtomicLong for a counter?

    - by Rich
    Hi I have a need for a counter of type long with the following requirements/facts: Incrementing the counter should take as little time as possible. The counter will only be written to by one thread. Reading from the counter will be done in another thread. The counter will be incremented regularly (as much as a few thousand times per second), but will only be read once every five seconds. Precise accuracy isn't essential, only a rough idea of the size of the counter is good enough. The counter is never cleared, decremented. Based upon these requirements, how would you choose to implement your counter? As a simple long, as a volatile long or using an AtomicLong? Why? At the moment I have a volatile long but was wondering whether another approach would be better. I am also incrementing my long by doing ++counter as opposed to counter++. Is this really any more efficient (as I have been led to believe elsewhere) because there is no assignment being done? Thanks in advance Rich

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  • ASP.NET problem - Firebug shows odd behaviour

    - by Brandi
    I have an ASP.NET application that does a large database read. It loads up a gridview inside an update panel. In VS2008, just running on my local machine, it runs fantastically. In production (identical code, just published and put on one of our network servers), it runs slow as dirt. Debug is set to false, so this is not the cause of the slow down. I'm not an experienced web developer, so besides that, feel free to suggest the obvious. I have been using Firebug to determine what's going on, and here is what that has turned up: On production, there are around 500 requests. The timeline bar is very short. The size column varies from run to run, but is always the same for the duration of the run. Locally, there are about 30 requests. The timeline bar takes up the entire space. Can anyone shed some light on why this is happening and what I can do to fix it? Also, I can't find much of anything on the web about this, so any references are helpful too.

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  • What would be a good starting point for development of a 3D application for representation of struct

    - by Lela Dax
    I was thinking QT on OpenGL. Multiplatform ability and being able to be closed (at no cost) at a later point would be important points. But I'm very interested in finding a way that is not only viable but also has the least amount of reinvention of the wheel. e.g. "Why not Ogre? A ready powerful 3D engine without reinventing that part". But I'm very uncertain in what is the optimal collection of tools for that job.

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  • Speed up :visible:input selector avoiding filter

    - by macca1
    I have a jQuery selector that is running way too slow on my unfortunately large page: $("#section").find(":visible:input").filter(":first").focus(); Is there a quicker way to select the first visible input without having to find ALL the visible inputs and then filtering THAT selection for the first? I want something like :visible:input:first but that doesn't seem to work.

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  • oracle index for string column - does format of data affects quality of index?

    - by Jayan
    We have following type of "Unique ID" column for many tables in the database (Oracle). It is a string with following format <randomnumber>-<ascendingnumber>-<machinename> So we have some thing like this U1234-12345-NBBJD U1234-12346-NBBJD U1234-12347-NBBJD U1234-12348-NBBJD U1234-12349-NBBJD The UID value is unique, we have unique index on them. Does the following format is more efficient than above for index scans? NBBJD-U1234-12345 NBBJD-U1234-12346 NBBJD-U1234-12347 NBBJD-U1234-12348 NBBJD-U1234-12349

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  • Exporting ActiveRecord objects into POROs

    - by Lucas d. Prim
    Hello, I'm developing a "script generator" to automatize some processes at work. It has a Rails application running on a server that stores all data needed to make the script and generates the script itself at the end of the process. The problem I am having is how to export the data from the ActiveRecord format to Plain Old Ruby Objects (POROs) so I can deal with them in my script with no database support and a pure-ruby implementation. I tought about YAML, CSV or something like this to export the data but it would be a painful process to update these structures if the process changes. Is there a simpler way? Ty!

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