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• Handling inverted pixels in bitmapData and bitmap class in as3

  - by intoTHEwild

  I am using bitmapData and bitmap classes to render a mouse cursor on the display screen. The bitmapData consists of an area whose colors should be inverted according to the background color. This is a very basic thing which could be observed with text cursor(the vertical line with two small horizontals on top and bottom), when moved over the text area. I want to be able to do the same with the pixels in my bitmapData, is there a way to find out the background color effectively and invert the color values? In this process i will be redrawing the whole pixels, is there any other efficient way to do that ?

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• How to prevent multiple browser windows from sharing the same session in asp.net.

  - by Barry

  I have ASP.net application that is basically a data entry screen for a physical inspection process. The users want to be able to have multiple browser windows open and enter data from multiple inspections concurrently. At first I was using cookie based sessions, and obviously this blew up. I switched to using cookie-less sessions, which stores the session in the URL and in testing this seemed to resolve the problem. Each browser window/tab had a different session ID, and data entered in one did not clobber data entered in the other. However my users are more efficient at breaking things than I expected and it seems that they're still managing to get the same session between browsers sometimes. I think that they're copying/pasting the address from one tab to the other in order to open the application, but I haven't been able to verify this yet (they're at another location so I can't easily ask them). Other than telling them don't copy and paste, or convince them to only enter one at a time, how can I prevent this situation from occurring?

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• Is writing to a socket an arbitrary limitation of the sendfile() syscall?

  - by Sufian

  Prelude sendfile() is an extremely useful syscall for two reasons: First, it's less code than a read()/write() (or recv()/send() if you prefer that jive) loop. Second, it's faster (less syscalls, implementation may copy between devices without buffer, etc...) than the aforementioned methods. Less code. More efficient. Awesome. In UNIX, everything is (mostly) a file. This is the ugly territory from the collision of platonic theory and real-world practice. I understand that sockets are fundamentally different than files residing on some device. I haven't dug through the sources of Linux/*BSD/Darwin/whatever OS implements sendfile() to know why this specific syscall is restricted to writing to sockets (specifically, streaming sockets). I just want to know... Question What is limiting sendfile() from allowing the destination file descriptor to be something besides a socket (like a disk file, or a pipe)?

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• Remove first 'n' elements from list without itterating

  - by Eldhose M Babu

  I need an efficient way of removing items from list. If some condition happens, I need to remove first 'n' elements from a list. Can some one suggest the best way to do this? Please keep in mind: performance is a factor for me, so I need a faster way than itterating. Thanks. I'm thinking of a way through which the 'n'th item can be made as the starting of the list so that the 0-n items will get garbage collected. Is it possible?

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• getting window screenshot windows API

  - by Oliver

  Hi, I am trying to make a program to work on top of an existing GUI to annotate it and provide extra calculations and statistical information. I want to do this using image recognition, as I have learned a fair amount about this in University using Matlab and similar things. I can get a handle to the window I want to perform image recognition on, but I don't know how to turn that handle into an image of that window, and all its visible child windows. I suppose I am looking for something like the screenshot function, but restricted to a single window. How would I go about doing this? I suppose I'd need something like a .bmp to mess about with. Also, it would have to be efficient enough that I could call it several times a second without my PC grinding to a halt. Hopefully this isn't an obvious question, I typed some things into google but didn't get anything related.

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• I do not write tests. Am I stupid?

  - by Josh Stodola

  I've done a little bit of reading on unit testing and TDD, and I've never seriously considered writing tests to such a precise extent. Granted, I am not working on any projects that are ridiculously huge. If all I build are small apps, am I stupid for not writing tests? Edit: To clarify, when I say "small apps", I mean apps that are not going to control a persons life and/or their belongings. I generally build things that are supposed to make peoples lives easier and to make them more efficient.

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• Php using unserialize() and serialize() changing values in a saved file

  - by Doodle

  I have a serialized array of values saved to a file and need to change the value of one of the variables. In the example I change the value of $two and then save the whole array back into the file with the new value. Is there a more efficient way of altering just the single value with out having to read and write the entire file/array. $data = file_get_contents('./userInfo'); $data = unserialize($data); extract($data); $two="this is a altered value"; $userData = array( 'one' => $one, 'two' => $two, 'three' => $three ); $file=fopen("../userInfo",'w'); fwrite($file, $userData); fclose($file);

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• Effective Android Programming Techniques

  - by kunjaan

  Please Help me compile a list of Effective Android Programming techniques Don't forget to free resources after use. Lot of resources like Cursors are overlooked. Free them too. Don't Use magic Numbers. values[0] is meaningless. The framework provides very useful accessors like values[SensorManager.DATA_X] "Make use of onPause()/onResume to save or close what does not need to be opened the whole time." protected void onResume() { mSensorManager.registerListener(...); } protected void onStop() { mSensorManager.unregisterListener(...); super.onStop(); } Make your Android UI Fast and Efficient from the Google I/O has a lot of useful UI Performance tips.

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• The fastest way to do a collection subtraction

  - by Tony

  I have two Sets. Set<B> b is the subset of Set<A> a. they're both very huge Sets. I want to subtract b from a , what's the best practice to do this common operation ? I've written to many codes like this , and I don't think it's efficient. what's your idea ? for(int i = 0 ; i < a.size(); i++) { for (int j=0 ; j < b.size() ;j++) { // do comparison , if found equals ,remove from a break; } } And I want to find an algorithm , not only applies to Sets, also works for Array.

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• Memory Issues When DOM Parsing A Large XML File on Android Devices

  - by tonyc

  Hey awesome SO users, I have an Android application that parses an XML file for users and displays results in a much more mobile friendly format. The app works great for most users, but some users have lots and lots of data and the app crashes on them because it runs out of memory. Is there any way I have a DOM style XML parser quit parsing data after a certain amount of parsing? I only need the first 30 or so elements so it would make the application much more efficient. I'd like to use a SAX or pull parser instead, but the XML I'm parsing is not valid and I have no control over it. Unless anyone has some good SAX solutions that let me parse messy, invalid XML, I think DOM is the only way to go. Thanks for reading!

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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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• 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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• 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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• bi-directional o2m/m2o beats uni-directional o2m in SQL efficiency?

  - by Henry

  Use these 2 persistent CFCs for example: // Cat.cfc component persistent="true" { property name="id" fieldtype="id" generator="native"; property name="name"; } // Owner.cfc component persistent="true" { property name="id" fieldtype="id" generator="native"; property name="cats" type="array" fieldtype="one-to-many" cfc="cat" cascade="all"; } When one-to-many (unidirectional) Note: inverse=true on unidirectional will yield undesired result: insert into cat (name) values (?) insert into Owner default values update cat set Owner_id=? where id=? When one-to-many/many-to-one (bi-directional, inverse=true on Owner.cats): insert into Owner default values insert into cat (name, ownerId) values (?, ?) Does that mean setting up bi-directional o2m/m2o relationship is preferred 'cause the SQL for inserting the entities is more efficient?

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• How to use Haar wavelet to detect LINES on an image?

  - by Ole Jak

  So I have Image like this I want to get something like this (I hevent drawn all lines I want but I hope you can get my idea) I want to use SURF ( (Speeded Up Robust Features) is a robust image descriptor, first presented by Herbert Bay et al. in 2006 ) or something that is based on sums of 2D Haar wavelet responses and makes an efficient use of integral images for finding all straight lines on image. I want to get relative to picture pixel coords start and end points of lines. So on this picture to find all lines between tiles and thouse 2 black lines on top. Is there any such Code Example (with lines search capability) to start from? I love C and C++ but any other readable code will probably work for me=)

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• Check if BigDecimal is integer value

  - by Adamski

  Can anyone recommend an efficient way of determining whether a BigDecimal is an integer value in the mathematical sense? At present I have the following code: private boolean isIntegerValue(BigDecimal bd) { boolean ret; try { bd.toBigIntegerExact(); ret = true; } catch (ArithmeticException ex) { ret = false; } return ret; } ... but would like to avoid the object creation overhead if necessary. Previously I was using bd.longValueExact() which would avoid creating an object if the BigDecimal was using its compact representation internally, but obviously would fail if the value was too big to fit into a long. Any help appreciated.

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• Optimization of running total calculation in SQL for multiple values per join condition

  - by Kiril

  I have the following table (test_table): date value --------------- d1 10.0 d1 20.0 d2 60.0 d2 10.0 d2 -20.0 d3 40.0 I calculate the running total as follows. I use the same query twice, because first I need to calculate the values for a specifi date, and afterwards I can calculate the running total. Otherwise, joining the two tables where date is not unique, I would get too many results from the join: SELECT t1.date, SUM(t2.value) AS total FROM (SELECT date, SUM(value) AS value FROM test_table GROUP BY date) AS t1 JOIN (SELECT date, SUM(value) AS value FROM test_table GROUP BY date) AS t2 ON t1.date >= t2.date GROUP BY t1.date ORDER BY t1.date This gives me (which is fine): date total ------------- d1 30.0 d2 80.0 d3 120.0 BUT, this query isn't very efficient, because I need to change conditions in two places, if necessary. In production, the test_table is a lot bigger ( 4 Mio. rows), and the query takes too much time to complete. Question: How can I avoid using the same query twice?

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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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• How to achieve a palette effect on iPhone using OpenGL

  - by Joe

  I'm porting a 2d retro game to iPhone that has the following properties: targets OpenGL ES 1.1 entire screen is filled with tiles (textured triangle strip tile textured using a single 256x256 RGBA texture image the texture is passed to OpenGL once at the start of the game only 4 displayed colours are used one of the displayed colours is black The original game flashed the screen when time starts to run out by toggling the black pixels to white using an indexed palette. What is the best (i.e. most efficient) way to achieve this in OpenGL ES 1.1? My thoughts so far: Generate an alternative texture with white instead of black pixels, and pass to OpenGL when the screen is flashing Render a white poly underneath the background and render the texture with alpha on to display it Try and render a poly on top with some blending that achieves the effect (not sure this is possible) I'm fairly new to OpenGL so I'm not sure what the performance drawbacks of each of these are, or if there's a better way of doing this.

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• Remove Duplicates from List of HashMap Entries

  - by HonorGod

  I have a List<HashMap<String,Object>> which represents a database where each list record is a database row. I have 10 columns in my database. There are several rows where the values of 2 particular columns are equals. I need to remove the duplicates from the list after the list is updated with all the rows from database. What is the efficient way? FYI - I am not able to do distinct while querying the database, because the GroupName is added at a later stage to the Map after the database is loaded. And since Id column is not primary key, once you add GroupName to the Map. You will have duplicates based on Id + GroupName combination! Hope my question makes sense. Let me know if we need more clarification.

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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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• Re-using jQuery widgets

  - by Micor

  I am looking for a most efficient way to re-use widgets with different selectors... For example if I have: $("#selector1").datepicker({ beforeShow: function(var1,var2) { // do stuff }, onClose: function(var1,var2) { // do stuff }, onSelect: function(var1,var2) { // do stuff } }) And later I am looking to assign this same widget with same functions inside to other selectors which are not known at load time. Since its not about choosing a better selector and I want to avoid: $("#new-selector2").datepicker({ beforeShow: function(var1,var2) { // do stuff }, onClose: function(var1,var2) { // do stuff }, onSelect: function(var1,var2) { // do stuff } }) $("#new-selector3").datepicker({ beforeShow: function(var1,var2) { // do stuff }, onClose: function(var1,var2) { // do stuff }, onSelect: function(var1,var2) { // do stuff } }) What would be the best way of doing something like: var reusableDatepicker = datepicker({ beforeShow: function(var1,var2) { // do stuff }, onClose: function(var1,var2) { // do stuff }, onSelect: function(var1,var2) { // do stuff } }) $("#selector1").attach(reusableDatepicker); $("#new-selector2").attach(reusableDatepicker); $("#new-selector3").attach(reusableDatepicker); I know it has to be obvious to all jQuery devs out there, so obvious I cannot find it in docs :) Thank you!

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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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• Detecting syllables in a word

  - by user50705

  I need to find a fairly efficient way to detect syllables in a word. E.g., invisible - in-vi-sib-le There are some syllabification rules that could be used: V CV VC CVC CCV CCCV CVCC *where V is a vowel and C is a consonant. e.g., pronunciation (5 Pro-nun-ci-a-tion; CV-CVC-CV-V-CVC) I've tried few methods, among which were using regex (which helps only if you want to count syllables) or hard coded rule definition (a brute force approach which proves to be very inefficient) and finally using a finite state automata (which did not result with anything useful). The purpose of my application is to create a dictionary of all syllables in a given language. This dictionary will later be used for spell checking applications (using Bayesian classifiers) and text to speech synthesis. I would appreciate if one could give me tips on an alternate way to solve this problem besides my previous approaches. I work in Java, but any tip in C/C++, C#, Python, Perl... would work for me.

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• Doing a "Diff" on an Associative Array in javascript / jQuery?

  - by Matrym

  If I have two associative arrays, what would be the most efficient way of doing a diff against their values? For example, given: array1 = { foreground: 'red', shape: 'circle', background: 'yellow' }; array2 = { foreground: 'red', shape: 'square', angle: '90', background: 'yellow' }; How would I check one against the other, such that the items missing or additional are the resulting array. In this case, if I wanted to compare array1 within array2, it would return: array3 = {shape: 'circle'} Whilst if I compared array2 within array1, it would return: array3 = {shape: 'square', angle: '90'} Thanks in advance for your help!

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