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• Algorithms to trim leading zeroes from a SQL field?

  - by froadie

  I just came across the interesting problem of trying to trim the leading zeroes from a non-numeric field in SQL. (Since it can contain characters, it can't just be converted to a number and then back.) This is what we ended up using: SELECT REPLACE(LTRIM(REPLACE(fieldWithLeadingZeroes,'0',' ')),' ','0') It replaces the zeroes with spaces, left trims it, and then puts the zeroes back in. I thought this was a very clever and interesting way to do it, although not so readable if you've never come across it before. Are there any clearer ways to do this? Any more efficient ways to do this? Or any other ways to do this period? I was intrigued by this problem and would be interested to see any methods of getting around it.

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• How to combine elements of a list

  - by Addie

  I'm working in c#. I have a sorted List of structures. The structure has a DateTime object which stores month and year and an integer which stores a value. The list is sorted by date. I need to traverse the list and combine it so that I only have one instance of the structure per date. For example: My initial list would look like this: { (Apr10, 3), (Apr10, 2), (Apr10, -3), (May10, 1), (May10, 1), (May10, -3), (Jun10, 3) } The resulting list should look like this: { (Apr10, 2), (May10, -1), (Jun10, 3) } I'm looking for a simple / efficient solution. The struct is: class CurrentTrade { public DateTime date; public int dwBuy; } The list is: private List<CurrentTrade> FillList

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• Video learning for database design

  - by donpal

  I'm trying to learn good relational database design (using mysql and php if that makes any difference). I've already done some database work, so I'm not totally clueless, but I suspect that my solutions may not have adhered to best practices for efficient searching, optimization, etc. Can someone suggest a good set of videos on the topic? If you know something is superb or has really made a difference in your own learning, please post your suggestion. Prefer videos, but books (as long as they're not too huge) are ok too. But prefer videos. Thank you

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• Concurrent web requests with Ruby (Sinatra?)?

  - by cbmeeks

  I have a Sinatra app that basically takes some input values and then finds data matching those values from external services like Flickr, Twitter, etc. For example: input:"Chattanooga Choo Choo" Would go out and find images at Flickr on the Chattanooga Choo Choo and tweets from Twitter, etc. Right now I have something like: @images = Flickr::...find...images.. @tweets = Twitter::...find...tweets... @results << @images @results << @tweets So my question is, is there an efficient way in Ruby to run those requests concurrently? Instead of waiting for the images to finish before the tweets finish. Thanks.

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• Coordinate geometry operations in images/discrete space

  - by avd

  I have images which have line segments, rays etc. I am representing these line segments using Bresenham algorithm (means whatever coordinates I get using this algorithm between two points). Now I want to do operations such as finding intersection point between two line segments, finding the projection of one vector onto other etc... The problem is I am not working in continuous space. The line segments are being approximated using Bresenham algorithm. So I want suggestions on what are the best and most efficient ways to do this? A link to C++ library or implementation would also be good enough. Please suggest some books which deal with such problems.

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• Definitive best practice for injecting, manipulating AJAX data

  - by Nic

  Ever since my foray into AJAX, I've always used the "whatever works" method of manipulating AJAX data returns. I'd like to know what the definitive and modern best practice is for handling data. Is it best practice to generate the HTML via the server script and introduce the returned data on the onComplete function? Should XML/JSON be looked at first before anything? How about manipulating the returned data? Using .live() doesn't seem like it is the most efficient way. I've never seen a definitive answer to this question. Your expertise is much appreciated.

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• What do I use when a cron job isn't enough? (php)

  - by mike

  I'm trying to figure out the most efficient way to running a pretty hefty PHP task thousands of times a day. It needs to make an IMAP connection to Gmail, loop over the emails, save this info to the database and save images locally. Running this task every so often using a cron isn't that big of a deal, but I need to run it every minute and I know eventually the crons will start running on top of each other and cause memory issues. What is the next step up when you need to efficiently run a task multiple times a minute? I've been reading about beanstalk & pheanstalk and I'm not entirely sure if that will do what I need. Thoughts???

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• Handling inverse kinematics: animation blending or math?

  - by meds

  I've been working for the past four days on inverse kinematics for my game engine. I'm working on a game with a shoestring budget so when the idea of inverse kinematics came up I knew I had to make it such that the 3D models bones would be mathematically changed to appear to be stepping on objects. This is causing some serious problems with my animation, after it was technically implemented the animations started looking quite bad when the character was wlaking up inclines or steps even though mathematically the stepping was correct and was even smoothly interpolating. So I was wondering, is it actually possible to get a smooth efficient inverse kinematic system based exclusively on math where bones are changed or is this just a wild goose chase and I should either solve the inverse kinematics problem with animation blending or don't do it at all?

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• Scala - Enumeration vs. Case-Classes

  - by tzofia

  I've created akka actor called LogActor. The LogActors's receive method handling messages from other actors and logging them to the specified log level. I can distinguish between the different levels in 2 ways. The first one: import LogLevel._ object LogLevel extends Enumeration { type LogLevel = Value val Error, Warning, Info, Debug = Value } case class LogMessage(level : LogLevel, msg : String) The second: (EDIT) abstract class LogMessage(msg : String) case class LogMessageError(msg : String) extends LogMessage(msg) case class LogMessageWarning(msg : String) extends LogMessage(msg) case class LogMessageInfo(msg : String) extends LogMessage(msg) case class LogMessageDebug(msg : String) extends LogMessage(msg) Which way is more efficient? does it take less time to match case class or to match enum value? (I read this question but there isn't any answer referring to the runtime issue)

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• NoSQL: How to retrieve a 'house' based on lat & long?

  - by Tedk

  I have a NoSQL system for storing real estate houses. One piece of information I have in my key-value store for each house is the longitude and latitude. If I wanted to retrieve all houses within a geo-lat/long box, like the SQL below: SELECT * from houses WHERE latitude IS BETWEEN xxx AND yyy AND longitude IS BETWEEN www AND zzz Question: How would I do this type of retrival with NoSQL ... using just a key-value store system? Even if I could do this with NoSQL, would it even be efficient or would simply going back to using a tradition database retrieve this type of information faster?

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• How to save big "database-like" class in python

  - by Rafal

  Hi there, I'm doing a project with reasonalby big DataBase. It's not a probper DB file, but a class with format as follows: DataBase.Nodes.Data=[[] for i in range(1,1000)] f.e. this DataBase is all together something like few thousands rows. Fisrt question - is the way I'm doing efficient, or is it better to use SQL, or any other "proper" DB, which I've never used actually. And the main question - I'd like to save my DataBase class with all record, and then re-open it with Python in another session. Is that possible, what tool should I use? cPickle - it seems to be only for strings, any other? In matlab there's very useful functionality named save workspace - it saves all Your variables to a file that You can open at another session - this would be vary useful in python!

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• Are there any programs to aid in the mass-editing of Visual SourceSafe checkin comments?

  - by Schnapple

  I know that in Visual SourceSafe you can go in and drill down to the history of an individual file and then drill down to an individual check-in and apply a comment to the check-in that way but that's tedious and time consuming - if you have a lot of files that were checked in at the same time and you want the same comment to apply to all of them this will take forever. I use the tool VSSReporter to generate reports of checkins and other stuff from VSS, but it cannot edit anything, only report on them. Are there any tools which will let you go back and retroactively apply comments to check-ins in an efficient and easy manner?

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• Initializing "new users" in Rails

  - by mathee

  I'm creating a Ruby on Rails application, and I'm trying to create/login/logout users. This is the schema for Users: create_table "users", :force => true do |t| t.string "first_name" t.string "last_name" t.text "reputation" t.integer "questions_asked" t.integer "answers_given" t.string "request" t.datetime "created_at" t.datetime "updated_at" t.string "email_hash" t.string "username" t.string "hashed_password" t.string "salt" end The user's personal information (username, first/last names, email) is populated through a POST. Other things such as questions_asked, reputation, etc. are set by the application, so should be initialized when we create new users. Right now, I'm just setting each of those manually in the create method for UsersController: def create @user = User.new(params[:user]) @user.reputation = 0 @user.questions_asked = 0 @user.answers_given = 0 @user.request = nil ... end Is there a more elegant/efficient way of doing this?

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• SDK for writing DVD's

  - by Matt Warren

  I need to add DVD writing functionality to an application I'm working on. However it needs to be able to write out files that are being grabbed "live" from a camera, over a long period of time. I can't wait until all the files are captured before I start writing them to the DVD, I need to write them out in chunks as I go along. I've looked at IMAPI v2, but the main problems seems to be that you need to point it to all the files you plan to write out to disk before you start the burning process. I know it has to concept of "sessions", which means you can write to the DVD in several parts, before you finally "close" it. But I was wondering if there were any other DVD writing SDK's that allow you to be constantly writing files to a DVD and in particular files that are only in memory. It would be more efficient if I didn't have to write the captured images out to hard before they are burned to DVD. The solution needs to work under .NET on Windows XP and vista

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• Information Label

  - by caisenm

  I am trying to make an information label that should display the events the application doing. deleting data, reading data, writing data, connection to db. etc.. I've added a label to my form and I am changing its text property for each operation like: label1.Text = "stored procedure is being executed.."; But, in the run time the text of the label does not change. I've tried to add the method Application.DoEvents(); to every place I've changed the label's text property. It works fine. But it looks silly. So I've tried to add this method to my label's "TextChanged" event. But it does not work! Am I doing something wrong? Or, is there any efficient way to make an information label?

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• Drawing Rounded Rectangle in DirectX/3D for 2D

  - by Jengerer

  I'm using Direct3D to draw 2D elements in a C++ application of mine, and it'd be neat if I could create rounded-rectangle GUI elements that were varying in size, but I'm not sure how to do that in the most efficient manner possible. I thought of the "easy" way which would be to have images of the four corners and then just place them in the proper positions, and fill in the rest, but varying radii for the rectangle corners would be a definite plus, and this method doesn't accommodate that feature well. Through my searches I've come across the terms Pixel Shader, Stencil Buffering, and HLSL, but I'm not sure whether these terms are relevant and which one to jump into if so. Thanks in advance, Jengerer

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• Remove a certain value from string which keeps on changing

  - by user2971375

  I m trying to make a utility to generate a Insert script of sql tables along with relational table. I got all the values in c#. Now I want to remove the one column name and its value from the script.most probably the identity column. Eg. The string I have (which keeps on changing with table name and varies) INSERT Core.Customers ([customerId],[customername],[customeradress],[ordernumber]) Values(123,N'Rahul',N'244 LIZ MORN',2334) NOW I know I have to remove CustomerId. (sometimes need to be replaces with @somevariable) Please give me an efficient way how to retrieve customerId value and Deleting column name and value . Conditions: insert script length and columns names keep changing. Method should return the deleted value. At some point of time customer id can be same as order id. In that case my string.remove method fails.

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• Distributed datastore

  - by Julien Genestoux

  We're trying to add some kind of persistence in our app. The app generates about 250 entries per second. Each of these entries belong to one of 2M files. For each file, we want to keep the last 10 entries, so we can look them up later. The way our client application works : it gets a stream of all the data it fetches the right file (GET) it adds the new content it saves the file back (PUT) We're looking for an efficient way to store this data that can scale horizontally as the amount of data we're getting is doubling every few weeks. We initially looked at S3. It works fine, but becomes very expensive very fast ($1000 monthly just in PUT operations!) We then gave a shot at Riak. But it seems we can't get more than 60 write/sec on each node, which is very very slow. Any other solution out there?

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• Matrix Comparison algorithm

  - by SysAdmin

  If you have 2 Matrices of dimensions N*M. what is the best way to get the difference Rect? Example: 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 4 5 4 3 2 3 <---> 2 3 2 3 2 3 2 3 2 3 4 5 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 2 3 | | \ / Rect([2,2] , [3,4]) 4 5 4 4 5 2-> A (2 x 3 Matrix) The best I could think of is to scan from Top-Left hit the point where there is difference. Then scan from Bottom Right and hit the point where there is a difference. But In worst case, this is O(N*M). is there a better efficient algorithm?

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• How can I efficiently group a large list of URLs by their host name in Perl?

  - by jesper

  I have text file that contains over one million URLs. I have to process this file in order to assign URLs to groups, based on host address: { 'http://www.ex1.com' = ['http://www.ex1.com/...', 'http://www.ex1.com/...', ...], 'http://www.ex2.com' = ['http://www.ex2.com/...', 'http://www.ex2.com/...', ...] } My current basic solution takes about 600 MB of RAM to do this (size of file is about 300 MB). Could you provide some more efficient ways? My current solution simply reads line by line, extracts host address by regex and puts the url into a hash. EDIT Here is my implementation (I've cut off irrelevant things): while($line = <STDIN>) { chomp($line); $line =~ /(http:\/\/.+?)(\/|$)/i; $host = "$1"; push @{$urls{$host}}, $line; } store \%urls, 'out.hash';

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• Efficiency of checking for null varbinary(max) column ?

  - by Moe Sisko

  Using SQL Server 2008. Example table : CREATE table dbo.blobtest (id int primary key not null, name nvarchar(200) not null, data varbinary(max) null) Example query : select id, name, cast((case when data is null then 0 else 1 end) as bit) as DataExists from dbo.blobtest Now, the query needs to return a "DataExists" column, that returns 0 if the blob is null, else 1. This all works fine, but I'm wondering how efficient it is. i.e. does SQL server need to read in the whole blob to its memory, or is there some optimization so that it just does enough reads to figure out if the blob is null or not ? (FWIW, the sp_tableoption "large value types out of row" option is set to OFF for this example).

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• Position of least significant bit that is set

  - by peterchen

  I am looking for an efficient way to determine the position of the least significant bit that is set in an integer, e.g. for 0x0FF0 it would be 4. A trivial implementation is this: unsigned GetLowestBitPos(unsigned value) { assert(value != 0); // handled separately unsigned pos = 0; while (!(value & 1)) { value >>= 1; ++pos; } return pos; } Any ideas how to squeeze some cycles out of it? (Note: this question is for people that enjoy such things, not for people to tell me xyzoptimization is evil.) [edit] Thanks everyone for the ideas! I've learnt a few other things, too. Cool!

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• Web Page Opinions and Suggestions

  - by MrEnder

  Been working my * off on this for a few days trying to keep updating it to make it most efficient with everything I learn... I'm quite proud of it so far considering I'm not actually the best coder lol most JS and PHP confuses the crap outa me unless I do it from scratch. So anyways here is the link. Tell me what you think. Suggestions would be amazing. I'd love to know what I screwed up as long as you explain in detail as to why and how to fix it. I really hate when people hand me a huge snippet and expect me to understand it -_- Thanks Shelby LINK http://opentech.durhamcollege.ca/~in...rittains/labs/

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• Searching Techniques/Algorithms for Resources over a given area

  - by Raydon

  I have a flat area with nodes randomly placed on this flat surface. I need techniques which are able to take a starting point, move in a certain way (the algorithm), find nodes and continue searching. I do not have an overall view of the surface (i.e. I cannot see everything), only a limited view (i.e. 4 cells in any direction). Ideally, these methods would be efficient in the way that they work. Any points in the right direction would be greatly appreciated.

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• Polling versus socket servers for online Flash games

  - by justin

  Hi, I want to make an online flash game, it will have social features but the gameplay will be primarily single-player. For example, no two players will appear on the screen at once, the social interaction will be through asynchronous messages, there won't be real-time chat or anything. Much of the logic would happen in the client, the server would validate the client logic, but it wouldn't need to be totally synchronous, which is why I'm thinking polling might be satisfactory. I have read in many places that socket servers can be more efficient than using polling for online games, but is that mainly a consideration for games that are more multi-player with more mult-player interactions than the game I have descriebed? If many users are playing online at the same time, but each playing a relatively isolated game, and not interacting to in real-time with each players, could polling be okay, or would using sockets be advisable no matter what if you have an online game that you envision many people playing at the same time? Thanks!

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