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  • How to implement a set ?

    - by nomemory
    I want to implement a Set in C. Is it OK to use a linked list, when creating the SET, or should I use another approach ? How do you usually implement your own set (if needed). NOTE: If I use the Linked List approach, I will probably have the following complexities for my operations: init : O(1); destroy: O(n); insert: O(n); remove: O(n); union: O(n*m); intersection: O(n*m); difference: O(n*m); ismember: O(n); issubset: O(n*m); setisequal: O(n*m); O(n*m) seems may be a little to big especially for huge data... Is there a way to implement my Set more efficient ?

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  • Memcached - how to deal with adding/deploying servers

    - by Industrial
    Hi everybody, How do you handle replacing/adding/removing memcached nodes in your production applications? I will have a number of applications that are cloned and customized due to each customers need running on one and same webserver, so i'll guess that there will be a day when some of the nodes will be changed. Here's how memcached is populated by normal: $m = new Memcached(); $servers = array( array('mem1.domain.com', 11211, 33), array('mem2.domain.com', 11211, 67) ); $m->addServers($servers); My initial idea, is to make the $servers array to be populated from the database, also cached, but file-based, done once a day or something, with the option to force an update on next run of the function that holds the $addservers call. However, I am guessing that this might add some additional overhead since disks are quite slow storage... What do you think?

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  • Generating Fibonacci series in F#

    - by photo_tom
    I'm just starting to learn F# using VS2010 and below is my first attempt at generating the Fibonacci series. What I'm trying to do is to build a list of all numbers less than 400. let fabList = let l = [1;2;] let mutable a = 1 let mutable b = 2 while l.Tail < 400 do let c = a + b l.Add(c) let a = b let b = c My first problem is that on the last statement, I'm getting an error message "Incomplete structured construct at or before this point in expression" on the last line. I don't understand what I'm doing wrong here. While this seems to be an obvious way to build the list in a fairly efficient way (from a c++/C# programmer), from what little I know of f#, this doesn't seem to feel to be the right way to do the program. Am I correct in this feeling?

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  • simple search in rails

    - by Adnan
    Hi, I'm making a simple search form in rails. In my search view I have two select boxes with fixed values like: SELECT BOX 1 SELECT BOX 2 ALL, ALL, FR, FR, US, US, DE DE And I have 2 fields in my DB with country_from and country_to. So for making a simple search like from FR to US I use: @search_result = Load.find(:all, :conditions => "country_from='#{params[:country_from]}' AND country_to='#{params[:country_to]}'" ) that is fine, but I need to implement the ALL option as well, so when I make a search like from DE to ALL I get a list with all countries in country_to I image I can do it with ifs...but what would be the most efficient way to do it?

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  • How to save an order (permutation) in an sql db

    - by Bendlas
    I have a tree structure in an sql table like so: CREATE TABLE containers ( container_id serial NOT NULL PRIMARY KEY, parent integer REFERENCES containers (container_id)) Now i want to define an ordering between nodes with the same parent. I Have thought of adding a node_index column, to ORDER BY, but that seem suboptimal, since that involves modifying the index of a lot of nodes when modifying the stucture. That could include adding, removing, reordering or moving nodes from some subtree to another. Is there a sql datatype for an ordered sequence, or an efficient way to emulate one? Doesn't need to be fully standard sql, I just need a solution for mssql and hopefully postgresql EDIT To make it clear, the ordering is arbitrary. Actually, the user will be able to drag'n'drop tree nodes in the GUI

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  • How can an SQL query return data from multiple tables

    - by Fluffeh
    I would like to know how to get data from multiple tables in my database, what types of methods are there to do this, what are joins and unions and how are they different from one another? When should I use each one compared to the others? I am planning to use this in my (for example - PHP) application, but don't want to run multiple queries against the database, what options do I have to get data from multiple tables in a single query? Note: I am writing this as I would like to be able to link to a well written guide on the numerous questions that I constantly come across in the PHP queue, so I can link to this for further detail when I post an answer. The answers cover off the following: Part 1 - Joins and Unions Part 2 - Subqueries Part 3 - Tricks and Efficient Code

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  • MySQL "IS IN" equivalent?

    - by nute
    A while ago I worked on a MS-SQL project and I remember a "IS IN" thing. I tried it on a MySQL project and it did not work. Is there an equivalent? Workaround? Here is the full query I am trying to run: SELECT * FROM product_product, product_viewhistory, product_xref WHERE ( (product_viewhistory.productId = product_xref.product_id_1 AND product_xref.product_id_2 = product_product.id) OR (product_viewhistory.productId = product_xref.product_id_2 AND product_xref.product_id_1 = product_product.id) ) AND product_product.id IS IN (SELECT DISTINCT pvh.productId FROM product_viewhistory AS pvh WHERE pvh.cookieId = :cookieId ORDER BY pvh.viewTime DESC LIMIT 10) AND product_viewhistory.cookieId = :cookieId AND product_product.outofstock='N' ORDER BY product_xref.hits DESC LIMIT 10 It's pretty big ... but the part I am interested in is: AND product_product.id IS IN (SELECT DISTINCT pvh.productId FROM product_viewhistory AS pvh WHERE pvh.cookieId = :cookieId ORDER BY pvh.viewTime DESC LIMIT 10) Which basically says I want the products to be in the "top 10" of that sub-query. How would you achieve that with MySQL (while trying to be efficient)?

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  • Database Optimization techniques for amateurs.

    - by Zombies
    Can we get a list of basic optimization techniques going (anything from modeling to querying, creating indexes, views to query optimization). It would be nice to have a list of these, one technique per answer. As a hobbyist I would find this to be very useful, thanks. And for the sake of not being too vague, let's say we are using a maintstream DB such as MySQL or Oracle, and that the DB will contain 500,000-1m or so records across ~10 tables, some with foreign key contraints, all using the most typical storage engines (eg: InnoDB for MySQL). And of course, the basics such as PKs are defined as well as FK contraints.

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  • Best way to have unique key over 500M varchar(255) records in mysql/innodb?

    - by taw
    I have url column with unique key over it - but its performance on updates is absolutely atrocious. I suspect that's because the index doesn't all fit in memory. So I was thinking, how about adding a column of md5(url) with 16 bytes of binary data and unique-keying that instead. What would be the best datatype for that? I'd love to be able to just see 32-character hex hash, while mysql would convert it to/from 16 binary bytes and index that, as programs using the database might have some troubles with arbitrary binary data that I'd rather avoid if possible (also I'm a bit afraid that mysql might get some strange ideas about character sets and for example overalocating storage for that by 3:1 because it thinks it might need utf8, how do I avoid that for cure?).

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  • Recommand a Perl module to persist a large object for re-use between runs?

    - by Alnitak
    I've got a large XML file, which takes 40+ seconds to parse with XML::Simple. I'd like to be able to cache the resulting parsed object so that on the next run I can just retrieve the parsed object and not reparse the whole file. I've looked at using Data::Dumper but the documentation is a bit lacking on how to store and retrieve its output from disk files. Other classes I've looked at (e.g. Cache::Cache) appear designed for storage of many small objects, not a single large one. Can anyone recommend a module designed for this?

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  • Prevent RegEx Hang on Large Matches...

    - by developerjay
    This is a great regular expression for dates... However it hangs indefinitely on this one page I tried... I wanted to try this page ( http://pleac.sourceforge.net/pleac%5Fpython/datesandtimes.html ) for the fact that it does have lots of dates on it and I want to grab all of them. I don't understand why it is hanging when it doesn't on other pages... Why is my regexp hanging and/or how could I clean it up to make it better/efficient ? Python Code: monthnames = "(?:Jan\w*|Feb\w*|Mar\w*|Apr\w*|May|Jun\w?|Jul\w?|Aug\w*|Sep\w*|Oct\w*|Nov(?:ember)?|Dec\w*)" pattern1 = re.compile(r"(\d{1,4}[\/\\\-]+\d{1,2}[\/\\\-]+\d{2,4})") pattern4 = re.compile(r"(?:[\d]*[\,\.\ \-]+)*%s(?:[\,\.\ \-]+[\d]+[stndrh]*)+[:\d]*[\ ]?(PM)?(AM)?([\ \-\+\d]{4,7}|[UTCESTGMT\ ]{2,4})*"%monthnames, re.I) patterns = [pattern4, pattern1] for pattern in patterns: print re.findall(pattern, s) btw... when i say im trying it against this site.. I'm trying it against the webpage source.

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  • Updating a database periodically with Java

    - by MSR
    I would like to perform updates to a MySQL database using two separate classes (that do different things) -- one doing so every 10 seconds, and the second every minute. I have a few gaps in my Java knowledge and I'm wondering what the best way to achieve it is. Importantly, if connectivity to the database is lost, I need reconnection attempts to occur indefinitely, and I'm guessing the use of Prepared Statements will make queries more efficient. Should the connection to the database be left open all the time or closed between the updates being run? Maybe I also need to think about clearing objects/resources out of memory if the class instances are going to be run indefinitely.

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  • Why the streams in C++?

    - by oh boy
    As you all know there are libraries using streams such as iostream and fstream. My question is: Why streams? Why didn't they stick with functions similar to print, fgets and so on (for example)? They require their own operators << and >> but all they do could be implemented in simple functions like above, also the function printf("Hello World!"); is a lot more readable and logical to me than cout << "Hello World"; I also think that all of those string abstractions in C++ all compile down to (less efficient) standard function calls in binary.

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  • Retrieving a single Guid in CRM 4.0

    - by user1746560
    I'm new to CRM (version 4.0) and i'm trying to return a 'yearid' guide based on a given year (which is also stored in the entity).So far i've got: public static Guid GetYearID(string yearName) { ICrmService service = CrmServiceFactory.GetCrmService(); // Create the query object. QueryExpression query = new QueryExpression("year"); ColumnSet columns = new ColumnSet(); columns.AddColumn("yearid"); query.ColumnSet = columns; FilterExpression filter = new FilterExpression(); filter.FilterOperator = LogicalOperator.And; filter.AddCondition(new ConditionExpression { AttributeName = "yearName", Operator = ConditionOperator.Equal, Values = new object[] { yearName} }); query.Criteria = filter; } But my questions are: A) What code do in addition to this to actually store the Guid? B) Is using a QueryExpression the most efficient way to do this?

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  • Correct way to take absolute value of INT_MIN

    - by aka.nice
    I want to perform some arithmetic in unsigned, and need to take absolute value of negative int, something like do_some_arithmetic_in_unsigned_mode(int some_signed_value) { unsigned int magnitude; int negative; if(some_signed_value<0) { magnitude = 0 - some_signed_value; negative = 1; } else { magnitude = some_signed_value; negative = 0; } ...snip... } But INT_MIN might be problematic, 0 - INT_MIN is UB if performed in signed arithmetic. What is a standard/robust/safe/efficient way to do this in C?

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  • Paperclip generating wrong URLs in Heroku

    - by Tony
    Paperclip is generating wrong URLs in Heroku. I have an Audio model which has a mp3 field as follows: class Audio < ActiveRecord::Base has_attached_file :mp3, :storage => :s3, :s3_credentials => S3_CREDENTIALS, :bucket => S3_CREDENTIALS[:bucket], :path => ":rails_root/public/system/:attachment/:id/:style/:filename", :url => "/system/:attachment/:id/:style/:filename" I am calling audio.mp3.url from a controller, and it returns http://s3.amazonaws.com/MyApp/audios/mp3s//original/96a9ae89302fdf8462ee05eb829f2e17578b144e20120908-2-11f61zr.mp3?1347135050 instead of http://s3.amazonaws.com/MyApp/audios/mp3s/000/000/004/original/96a9ae89302fdf8462ee05eb829f2e17578b144e20120908-2-11f61zr.mp3?1347135050 (which works) Why is it missing the '000/000/004' part of the route? The same model is generating the right URL when used in a view. Any help? I am using paperclip 3.2.0 and Rails 3.1.8. Any help?

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  • How to correctly migrate urls from custom asp.net solution to Wordpress?

    - by Marek
    I have a web site built using asp.net with ugly URLs like /DisplayContent.aspx?id=789564. I know how to migrate the database, but the Wordpress urls will be (naturally) different. Can I simply write some mapping or do I have to include a rewrite rule for each subpage (300 pages) in .htaccess? Should I provide a rewrite rule for each existing page that would transform a full old url to the known new url, like for example: /DisplayContent.aspx?id=789798 -> /2010-5-10/Title-Of-The-Post Even if I manage to migrate the URLs, the structure of the HTML for the new content will naturally be different. How does this affect SEO? Should I run asp.net and wordpress side by side and issue the redirects from the asp.net application? What is the most efficient solution to this kind of migration of URLs without doing PHP programming?

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  • Hyperlinks in VS2008 Test Result Details

    - by Red XIII
    In case when resulting string in "Test Result Details" (TRD) is very long, the Visual Studio 2008 crashes. I fixed this by sending the result data into a file. There is a problem, however, because there isn't a simple way to open such file. Of course, I can manually open folder and then the file, but it isn't very efficient. Now, to the questions part. Is there a possibility to include in the "Error Message" part of TRD a hyperlink to a file? (something similar to what we can already find in the stack trace part) If not, is there any way to add such functionality (easy opening of a file) to TRD? If not, are there any ways to expand the default reporting of VS? Thanks for any help.

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  • Which is better, save a website images on Amazon S3, Flickr or Picasa?

    - by Amr ElGarhy
    I have a website and going to extend it, so users will upload their images on this website, i want to save users images in another storage service. Users will save images and view them, and also share with others. I know that i can do that using Amazon S3, Flickr or Picasa. But i want to know which is better than which? which one should i use and why? Based on your experiences, can you recommend one, or advice me if you a better service than those 3?

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  • Awk or Sed: File Annotation

    - by lukmac
    Hallo, my SO friend, my question is: Specification: annotate the fields of FILE_2 to the corresponding position of FILE_1. A field is marked, and hence identified, by a delimiter pair. I did this job in python before I knew awk and sed, with a couple hundred lines of code. Now I want to see how powerful and efficient awk and sed can be. Show me some masterpiece of awk or sed, please! The delimiter pairs can be configured in FILE_3, but let's assume the first delimiter in a pair is 'Marker (number i) start', the other one is 'Marker (number i) done' Example: |-----------------FILE_1------------------| text text text text blabla Marker_1_start Marker_1_done any text in between blabla Marker_2_start Marker_2_done text text |-----------------FILE_2------------------| Marker_1_start 11 1111 Marker_1_done Marker_2_start 2222 22 Marker_2_done Expected Output: |-----------------FILE_Out------------------| text text text text blabla Marker_1_start 11 1111 Marker_1_done any text in between blabla Marker_2_start 2222 22 Marker_2_done text text

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  • is there a limit of merge tables with Mysql ?

    - by sysko
    I'm working on a database with mysql 5.0 for an open source project it's used to stored sentences in specific languages and their translations in other languages I used to have a big table "sentences" and "sentences_translations" (use to join sentences to sentences) table but has we have now near one million entries, this begin to be a bit slow, moreover, most of request are made using a "where lang =" so I've decided to create a table by language sentences_LANGUAGECODE and sentences_translation_LANGSOURCE_LANGTARGET and to create merge table like this sentences_ENG_OTHERS which merge sentences_ENG_ARA sentences_ENG_DEU etc... when we want to have the translations in all languages of an english sentence sentences_OTHERS_ENG when we want to have only the english translations of some sentences I've created a script to create all these tables (they're around 31 languages so more than 60 merge table), I've tested, that works really great a request which use to take 160ms now take only 30 :) but I discover that all my merge table after the 15th use to have "NULL" as type of storage engine instead of MRG_MYISAM, and if delete one, then I can create an others, using FLUSH table between each creation also allow me to create more merge tables so is this a limitation from mysql ? can we override it ? thanks for your answers

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  • C++ syntax of constructors " 'Object1 a (1, Object1(2))''

    - by osgx
    Hello I have a such syntax in program class Object1 : BaseClass { BaseClass *link; int i; public: Object1(int a){i=a;} Object1(int a, Object1 /*place1*/ o) {i=a; link= &o;} }; int main(){ Object1 a(1, /*place2*/ Object1(2)); ... } What do I need in place1? I want to save a link (pointer) to the second object in the first object. Should I use in place1 reference "&"? What type will have "Object1(2)" in place2? Is it a constructor of the anonymous object? Will it have a "auto" storage type?

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  • Enter custom file name to be read ?

    - by ZaZu
    Hello, I want to allow users to type the name of any .txt file to be read/written. This is my code : printf("Enter .txt file name\n"); scanf("%s",&fname); FILE *inputf; inputf=fopen(&fname,"w"); Problem is this method does not work (having &fname) as a parameter. I can imagine its because C needs "filename.txt" for it work ... even if I enter for example : "custom.txt", the program returns an error of "Storage block not big enough for this operation" What is the correct method to accomplish this ? Im using C and im pretty much using basic commands .. (not too advanced) Thanks alot !!!

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  • Ruby on Rails: Best way to save search queries in a database

    - by Adam Templeton
    For a RoR app I'm helping develop, I need to save all search queries in a database so I can analyze them later. My plan right now is to create a Result model and table, and just save each search query's text in that table, along with a user's ID, the time, etc. However, the app has about 15,000 users, so I'm afraid the single table approach won't be super efficient when it comes time to parse that data. (The database is setup via MySQL, if that factors in at all.) Am I just being paranoid? Is there a Ruby gem that handles this sort of thing, or a better approach I could take? Any input would be appreciated.

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  • Convert unusual string into date time

    - by BlueChippy
    I have a system that outputs dates in the format "1{yy}{MM}{dd}" and I am trying to find a good way to parse it back into a real date. At the moment I am using this: var value = "1110825"; var z = Enumerable.Range(1,3).Select(i => int.Parse(value.Substring(i, 2))).ToList(); var d = new DateTime(2000 + z[0], z[1], z[2]); but I'm sure there's a cleaner/more efficient way to do it? I've tried DT.ParseExact, but can't find a suitable format string to use.

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