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  • When calling CRUD check if "parent" exists with read or join?

    - by Trick
    All my entities can not be deleted - only deactivated, so they don't appear in any read methods (SELECT ... WHERE active=TRUE). Now I have some 1:M tables on this entities on which all CRUD operations can be executed. What is more efficient or has better performance? My first solution: To add to all CRUD operations: UPDATE ... JOIN entity e ... WHERE e.active=TRUE My second solution: Before all CRUD operations check if entity is active: if (getEntity(someId) != null) { //do some CRUD } In getEntity there's just SELECT * FROM entity WHERE id=? AND active=TRUE. Or any other solution, recommendation,...?

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  • smallest perimiter rectangle with given integer area and integer sides

    - by remuladgryta
    Given an integer area A, how can one find integer sides w and h of a rectangle such that w*h = A and w+h is as small as possible? I'd rather the algorithm be simple than efficient (although within reasonable efficiency). What would be the best way to accomplish this? Finding out the prime factors of A, then combining them in some way that tries to balance w and h? Finding the two squares with integer sides with areas closest to A and then somehow interpolating between them? Any other method i'm not thinking of?

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  • Collision detection by sliding against a plane in XNA

    - by Bevin
    Hello, I am attempting to engineer a collision detection algorithm for a custom Minecraft client I'm making. Basically, the entire world is made up of cubes, and the player (or camera) needs to be able to stand on and move against these cubes. The result I want is illustrated in this image: The green line is the player's movement vector. When the player is brushing up against a plane of one of the cubes, I want the vector to change to one that is perpendicular with the plane. The vector should, however, keep all of it's velocity in the plane's direction, yet lose all velocity towards the plane. I hope I've made my question clear. What is the best and most efficient way to implement a collision detection system like this? Also, will a system like this allow for a simple gravity component?

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  • Choose item from a list with bias?

    - by ooboo
    Given a list of items x1 ... xn and associated probabilties p1 ... pn that sum up to 1 there's a well known procedure to select a random item with its associated proabability by sorting the list according to weight, choosing a random value between 1 and 0, and adding up to a culmination sum until it exceeds the value selected and return the item at this point. So if we have x1 - 0.5, x2 - 0.3, x3 - 0.2, if the randomly chosen value is less than 0.5 x1 will be chosen, if between 0.5 and 0.8, x2, and else x3. This requires sorting so it needs O(nlogn) time. Is there anything more efficient than that?

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  • Fastest way to check a List<T> for a date

    - by fishhead
    I have a list of dates that a machine has worked on, but it doesn't include a date that machine was down. I need to create a list of days worked and not worked. I am not sure of the best way to do this. I have started by incrementing through all the days of a range and checking to see if the date is in the list by iterating through the entire list each time. I am looking for a more efficient means of finding the dates. class machineday { datetime WorkingDay; } class machinedaycollection : List<machineday> { }

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  • C++ Thread Safe Integer

    - by Paul Ridgway
    Hello everyone, I have currently created a C++ class for a thread safe integer which simply stores an integer privately and has public get a set functions which use a boost::mutex to ensure that only one change at a time can be applied to the integer. Is this the most efficient way to do it, I have been informed that mutexes are quite resource intensive? The class is used a lot, very rapidly so it could well be a bottleneck... Googleing C++ Thread Safe Integer returns unclear views and oppinions on the thread safety of integer operations on different architectures. Some say that a 32bit int on a 32bit arch is safe, but 64 on 32 isn't due to 'alignment' Others say it is compiler/OS specific (which I don't doubt). I am using Ubuntu 9.10 on 32 bit machines, some have dual cores and so threads may be executed simultaneously on different cores in some cases and I am using GCC 4.4's g++ compiler. Thanks in advance...

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  • Time complexity O() of isPalindrome()

    - by Aran
    I have this method, isPalindrome(), and I am trying to find the time complexity of it, and also rewrite the code more efficiently. boolean isPalindrome(String s) { boolean bP = true; for(int i=0; i<s.length(); i++) { if(s.charAt(i) != s.charAt(s.length()-i-1)) { bP = false; } } return bP; } Now I know this code checks the string's characters to see whether it is the same as the one before it and if it is then it doesn't change bP. And I think I know that the operations are s.length(), s.charAt(i) and s.charAt(s.length()-i-!)). Making the time-complexity O(N + 3), I think? This correct, if not what is it and how is that figured out. Also to make this more efficient, would it be good to store the character in temporary strings?

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  • Opinions regarding C++ programming practice

    - by Sagar
    I have a program that I am writing, not too big. Apart from the main function, it has about 15 other functions that called for various tasks at various times. The code works just fine all in one file, and as it is right now. However, I was wondering if anyone had any advice on whether it is smarter/more efficient/better programming to put those functions in a separate file different from where main is, or whether it even matters at all. If yes, why? If no, why not? I am not new at C++, but definitely not an expert either, so if you think this question is stupid, feel free to tell me so. Thanks for your time!

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  • What's the fastest way to scrape a lot of pages in php?

    - by Yegor
    I have a data aggregator that relies on scraping several sites, and indexing their information in a way that is searchable to the user. I need to be able to scrape a vast number of pages, daily, and I have ran into problems using simple curl requests, that are fairly slow when executed in rapid sequence for a long time (the scraper runs 24/7 basically). Running a multi curl request in a simple while loop is fairly slow. I speeded it up by doing individual curl requests in a background process, which works faster, but sooner or later the slower requests start piling up, which ends up crashing the server. Are there more efficient ways of scraping data? perhaps command line curl?

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  • PHP/MySQL: Storing and retrieving UUIDS

    - by Greg
    I'm trying to add UUIDs to a couple of tables, but I'm not sure what the best way to store/retrieve these would be. I understand it's far more efficient to use BINARY(16) instead of VARCHAR(36). After doing a bit of research, I also found that you can convert a UUID string to binary with: UNHEX(REPLACE(UUID(),'-','')) Pardon my ignorance, but is there an easy way to this with PHP and then turn it back to a string, when needed, for readability? Also, would it make much difference if I used this as a primary key instead of auto_increment? EDIT: Found part of the answer: $bin = pack("h*", str_replace('-', '', $guid)); How would you unpack it?

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  • Python: Huge file reading by using linecache Vs normal file access open()

    - by user335223
    Hi, I am in a situation where multiple threads reading the same huge file with mutliple file pointers to same file. The file will have atleast 1 million lines. Eachline's length varies from 500 characters to 1500 characters. There won't "write" operations on the file. Each thread will start reading the same file from different lines. Which is the efficient way..? Using the Python's linecache or normal readline() or is there anyother effient way?

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  • Write data into .txt file created by CFileDialog, in C++

    - by younevertell
    I wanna Write data into .txt file created by CFileDialog, in C++. The problem I am facing is that below codes doesn't work, although there is no build error. The .txt file created by CFileDialog can not be found for some reason. What's wrong the code? what's the efficient way to Write data into .txt file created by CFileDialog, in C++? Thanks CFileDialog dlg(FALSE, NULL, NULL, OFN_OVERWRITEPROMPT, _T("My Data File (*.txt)|*.txt||")); if(dlg.DoModal() != IDOK) return; CString filename = dlg.GetPathName(); ofstream outfile (filename); int mydata = 10; outfile << "my data:" << mydata << endl; outfile.close();

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  • Get value from ajax-loaded form before submitting

    - by ldvldv
    Hi, I have an app that loads an ajax form when a button is clicked. I then want to check a value in that ajax loaded form called "comment_content" so that I don't send an ajax request if the comment_content is empty. I can capture the form submission using the live method, however, I can't capture the form element because it needs an element. I was looking at livequery but was wondering if there is a more efficient way by using live or if that I shouldn't even bother? Your help is very much appreciated. $("#comment_submit").live('click', function(){ var comment = $("#comment_content").html(); if(comment == ""){ $("#notice").html("").stop(true, true); $("#notice").append("<p>Are you going to write something in that comment?</p>"); $('#notice').slideDown().delay(2000).slideUp(); return false; } return true; });

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  • Determining whether a file is a duplicate

    - by Todd R
    Is there a reliable way to determine whether or not two files are the same? For example, two files with the same size and type may or may not be the same binarilly (yeah, I know it's not really a word). I assume that comparing one or two checksums of the files will help, but I wonder: How reliable are checksums at determining whether two files are different; what are the chances of two different files having the same checksum? Would reliability increase by applying additional checksum comparisons? Which checksum algorithm(s) would be the most efficient and/or reliable? Any ideas, suggestions or thoughts are appreciated! P.S. The code for this is being written in Java running on a nix system, but generic or platform agnostic input is most helpful.

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  • Facebook user_id as MongoDB BSON ObjectId?

    - by MattDiPasquale
    I'm rebuilding Lovers on Facebook with Sinatra & Redis. I like Redis because it doesn't have the long (12-byte) BSON ObjectIds and I am storing sets of Facebook user_ids for each user. The sets are requests_sent, requests_received, & relationships, and they all contain Facebook user ids. I'm thinking of switching to MongoDB because I want to use it's geospatial indexing. If I do, I'd want to use the FB user ids as the _id field because I want the sets to be small and I want the JSON responses to be small. But, is the BSON ObjectId better (more efficient for MongoDB) to use than just an integer (fb user_id)?

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  • C# - Inserting multiple rows using a stored procedure

    - by user177883
    I have a list of objects, this list contains about 4 million objects. there is a stored proc that takes objects attributes as params , make some lookups and insert them into tables. what s the most efficient way to insert this 4 million objects to db? How i do : -- connect to sql - SQLConnection ... foreach(var item in listofobjects) { SQLCommand sc = ... // assign params sc.ExecuteQuery(); } THis has been really slow. is there a better way to do this?

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  • Theory of Game Interface Design

    - by anon
    Anyone know of a good book on Game Interface Design (not game play mechanics; the actual UI). I'm particular interested in theories of cognition, and how game interfaces are designed to allow the enduser efficient communication with the game (whether it in FPS, RTS, or so on). In a modern game, the amount of information conveyed to the user, the amount of choices the user can make; and the support for the user to make said decisions is simply astounding (think UIs for Starcraft II / WoW). Any insights into this would be greatly appreciated.

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  • a completely decoupled OO system ?

    - by shrini1000
    To make an OO system as decoupled as possible, I'm thinking of the following approach: 1) we run an RMI/directory like service where objects can register and discover each other. They talk to this service through an interface 2) we run a messaging service to which objects can publish messages, and register subscription callbacks. Again, this happens through interfaces 3) when object A wants to invoke a method on object B, it discovers the target object's unique identity through #1 above, and publishes a message on the message service for object B 4) message services invokes B's callback to give it the message 5) B processes the request and sends the response for A on message service 6) A's callback is called and it gets the response. I feel this system is as decoupled as practically possible, but it has the following problems: 1) communication is typically asynchronous 2) hence it's non real time 3) the system as a whole is less efficient. Are there any other practical problems where this design obviously won't be applicable ? What are your thoughts on this design in general ?

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  • Writing a PHP web crawler using cron

    - by Horse
    Hi all I have written myself a web crawler using simplehtmldom, and have got the crawl process working quite nicely. It crawls the start page, adds all links into a database table, sets a session pointer, and meta refreshes the page to carry onto the next page. That keeps going until it runs out of links That works fine however obviously the crawl time for larger websites is pretty tedious. I wanted to be able to speed things up a bit though, and possibly make it a cron job. Any ideas on making it as quick and efficient as possible other than setting the memory limit / execution time higher?

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  • Database design for a Fantasy league

    - by Samidh T
    Here's the basic schema for my database Table user{ userid numeber primary key, count number } Table player{ pid number primary key, } Table user-player{ userid number primary key foreign key(user), pid number primary key foreign key(player) } Table temp{ pid number primary key, points number } Here's what I intend to do... After every match the temp table is updated which holds the id of players that played the last match and the points they earned. Next run a procedure that will match the pid from temp table with every uid of user-player table having the same pid. add the points from temp table to the count of user table for every matching uid. empty temp table. My questions is considering 200 players and 10000 users,Will this method be efficient? I am going to be using mysql for this.

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  • Prims vs Polys: what are the pros and cons of each?

    - by Richard Inglis
    I've noticed that most 3d gaming/rendering environments represent solids as a mesh of (usually triangular) 3d polygons. However some examples, such as Second Life, or PovRay use solids built from a set of 3d primitives (cube, sphere, cone, torus etc) on which various operations can be performed to create more complex shapes. So my question is: why choose one method over the other for representing 3d data? I can see there might be benefits for complex ray-tracing operations to be able to describe a surface as a single mathematical function (like PovRay does), but SL surely isn't attempting anything so ambitious with their rendering engine. Equally, I can imagine it might be more bandwidth-efficient to serve descriptions of generalised solids instead of arbitrary meshes, but is it really worth the downside that SL suffers from (ie modelling stuff is really hard, and usually the results are ugly) - was this just a bad decision made early in SL's development that they're now stuck with? Or is it an artefact of what's easiest to implement in OpenGL?

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  • JPA in distributed Java EE configuration

    - by sof
    Hello, I'm developing a JEE application to run on Glassfish: Database (javaDB, MS SQL, MySQL or Oracle) EJB layer with JPA (Toplink essentials - from Glassfish) for database access JSF/Icefaces based web UI accessing the EJB layer The application will have a lot of concurrent web client, so I want to run it on different physical servers and use a load-balancer. My problem is now how to keep the applications synchronized. I intend to set up multiple servers, each running Glassfish with my EAR app installed. Whenever on one of the servers data is added to or removed from the database (via JPA, no direct SQL queries), this change should be reflected in the JPA layer on the other servers. I've been looking around for solutions to this, but couldn't find anything I really like (the full Toplink from Oracle claims to have a solution, but don't know). Doing a refresh before every access to a JPA entity could work, but is far from efficient. Are there any patterns, libraries, ... that could help here? Thanks a lot!

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  • How do I create a point system in a Rails app that assigns points to users and non-authenticated-use

    - by codyvbrown
    I'm building a question and answer application on top of twitter and I'm hitting some snags because I'm inevitably dealing with two classes of users: authenticated and non-authenticated. The site enable users to give points to other users, who may or may not be authenticated, and I want to create a site-wide point system where the application stores and displays this information on their profile. I want to save this point data to the user because that would be faster and more efficient but non-authenticated users aren't in our system, we only have the twitter handle. So instead we display the points in our system like this: @points = point.all( :select => "tag, count(*) AS count", # Return tag and count :group => 'tag', # Group by the tag :order => "2 desc", :conditions => {:twitter_handle => params[:username]}) Is there a better way to do this? Is there a better way to associate data with non-authenticated users?

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  • High level programming logic, design, pattern

    - by Muhammad Shahzad
    I have been doing programming from last 7 years, getting better and better, but still i think that am lacking something. I have been doing work in JOOMLA, MAGENTO, WP, Custom PHP, Opencart, laravel, codeignitor. Sometimes i need to design logic for a huge database application, in the applications we need nesting loops and queries, although i follow OOPS standards, ORM etc, still i feel i need more robust coding designs. I need to know how can i improve these things, so that code remain neat, efficient and faster. Also how big webapps like facebook twitter tests there code speed? How high level programmers choose design patterns. If you can help me find something useful with examples?

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  • 2 Select or 1 Join query ?

    - by xRobot
    I have 2 tables: book ( id, title, age ) ---- 100 milions of rows author ( id, book_id, name, born ) ---- 10 millions of rows Now, supposing I have a generic id of a book. I need to print this page: Title: mybook authors: Tom, Graham, Luis, Clarke, George So... what is the best way to do this ? 1) Simple join like this: Select book.title, author.name From book, author WHERE ( author.book_id = book.id ) AND ( book.id = 342 ) 2) For avoid the join, I could make 2 simple query: Select title FROM book WHERE id = 342 Select name FROM author WHERE book_id = 342 What is the most efficient way ?

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