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• Reading from a file not line-by-line

  - by MadH

  Assigning a QTextStream to a QFile and reading it line-by-line is easy and works fine, but I wonder if the performance can be inreased by first storing the file in memory and then processing it line-by-line. Using FileMon from sysinternals, I've encountered that the file is read in chunks of 16KB and since the files I've to process are not that big (~2MB, but many!), loading them into memory would be a nice thing to try. Any ideas how can I do so? QFile is inhereted from QIODevice, which allows me to ReadAll() it into QByteArray, but how to proceed then and divide it into lines?

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• who wrote 250k tests for webkit?

  - by amwinter

  assuming a yield of 3 per hour, that's 83000 hours. 8 hours a day makes 10,500 days, divide by thirty to get 342 mythical man months. I call them mythical because writing 125 tests per person per week is unreal. can any wise soul out there on SO shed some light on what sort of mythical men write unreal quantities of tests for large software projects? thank you. update chrisw thinks there are only 20k tests (check out his explanation below). PS I'd really like to hear from folks who have worked on projects with large test bases

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• Splitting a double vector into equal parts

  - by Cosmin

  Greetings, Any input on a way to divide a std::vector into two equal parts ? I need to find the smallest possible difference between |part1 - part2|. This is how I'm doing it now, but from what you can probably tell it will yield a non-optimal split in some cases. auto mid = std::find_if(prim, ultim, [&](double temp) -> bool { if(tempsum >= sum) return true; tempsum += temp; sum -= temp; return false; }); The vector is sorted, highest to lowest, values can indeed appear twice. I'm not expecting part1 and part2 to have the same numbers of elements, but sum(part1) should be as close as possible to sum(part2) For example if we would have { 2.4, 0.12, 1.26, 0.51, 0.70 }, the best split would be { 2.4, 0.12 } and { 1.26, 0.51, 0.70 }. If it helps, I'm trying to achieve the splitting algorithm for the Shannon Fano encoding. Any input is appreciated, thanks!

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• How would MVVM be for games?

  - by Benny Jobigan

  Particularly for 2d games, and particularly silverlight/wpf games. If you think about it, you can divide a game object into its view (the graphic on the screen) and a view-model/model (the state, ai, and other data for the object). In silverlight, it seems common to make each object a user control, putting the model and view into a single object. I suppose the advantage of this is simplicity. But, perhaps it's less clean or has some disadvantages in terms of the underlying "game engine". What are your thoughts on this matter? What are some advantages and disadvantages of using the MVVM pattern for game development? How about performance? All thoughts are welcome.

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• Averaging corrupted images to eliminate the noise in Matlab

  - by Mertie Pertie

  Hi all As you can get it from the title, I want to average some .jpg images which are corrupted by zero-mean Gaussian additive. After searching over internet, I figured out to add image matrices and divide the sum by the # of matrices. However the resultant image is totally black. Normally when the number of image increases then the resultant image gets better. But When I use more images it gets darker. I am using 800x600 black and white images with .jpg ext Here is the script I used; image1 = imread ('PIC1.jpg'); image2 = imread ('PIC2.jpg'); image3 = imread ('PIC3.jpg'); image4 = imread ('PIC4.jpg'); sum = image1 + image2 + image3 + image4; av = sum / 4; imshow(av); Thanks in advance

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• Optimizing tiled maps in cocos2d-iphone

  - by Omega

  My cocos2d-iphone game has tiled maps. The tilesets textures are rather big. I got around 5 tilesets and each one is 2048x2048 (retina). My maps are around 80x80. They have around 8 layers and each one is obviously using one tileset. The frame rate falls (it goes around 30 sometimes. I know 30 is rather aceptable, but still, I want 50+). So given that textures are huge I can't afford to make many layers (since each one loads a texture of these). So how about I divide my tileset textures into much smaller tilesets (like 1024x1024 each)? That will allow me to use many more layers for my maps, right? Are there any other tips for huge retina display tile maps?

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• cutting a text file into multiple parts in emacs

  - by Gaurish Telang

  Hi I am using the GNU-Emacs-23 editor. I have this huge text file containing about 10,000 lines which I want to chop into multiple files. Using the mouse to select the required text to paste in another file is the really painful. Also this is prone to errors too. If I want to divide the text file according to the line numbers into say 4 file where first file:lines 1-2500 second file:lines 2500-5000 third file :lines 5000-7500 fourth file: lines: 7500-10000 how do I do this? At the very least, is there any efficient way to copy large regions of the file just by specifying line numbers

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• Is it hard problem?

  - by Lukasz Lew

  I can't solve it: You are given 8 integers: A, B, C representing a line on a plane with equation A*x + B*y = C a, b, c representing another line x, y representing a point on a plane The two lines are not parallel therefore divide plane into 4 pieces. Point (x, y) lies inside of one these pieces. Problem: Write a fast algorithm that will find a point with integer coordinates in the same piece as (x,y) that is closest to the cross point of the two given lines. Note: This is not a homework, this is old Euler-type task that I have absolutely no idea how to approach.

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• getting number of hours until the next event

  - by Andrew Heath

  I've got a table with this data: [ID] [event_name] [last_event] 1 stats 2011-01-01 01:47:32 last_event is a timestamp. The event occurs every 48 hours (it's a cron job). I'd like to show my users the number of hours until the event executes again. So far I've got: SELECT (lastFinish + INTERVAL 48 HOUR) FROM `cron_status` which gives me the exact time and date of the next occurence: 2011-01-03 01:47:32. So I figured if I subtracted the current datetime... SELECT ((lastFinish + INTERVAL 48 HOUR) - SYSDATE()) FROM `cron_status` which (I think?) gives me the difference in unix time: 1980015. But if I divide that by 3600 to convert the seconds to hours... SELECT (((lastFinish + INTERVAL 48 HOUR) - SYSDATE())/3600) FROM `cron_status` I get numbers an order of magnitude too high: 549.99. Where am I going wrong? The target is returning the number of hours until the next execution. Thank you!

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• How to send mail with large size attachment using System.Net.Mail to Google Apps ?

  - by Preeti

  Hi, I am trying to send mail with large size attachment upto (1MB,2MB). But sending mail fails.(Sending to Google Apps) as: MailItemEntry[] entries = new MailItemEntry[1]; String EmlPath = "C:\\testemail.eml"; String msg = File.ReadAllText(EmlPath); entries[0] = new MailItemEntry(); entries[0].Rfc822Msg = new Rfc822MsgElement(msg); How can i divide attachments into multi part? Exception I am getting while migrating this EML to Google apps is: {"The request was aborted: The request was canceled."}

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• SQL Server / T-SQL : How to update equal percentages of a resultset?

  - by Kent Comeaux

  I need a way to take a resultset of KeyIDs and divide it up as equally as possible and update records differently for each division based on the KeyIDs. In other words, there is SELECT KeyID FROM TableA WHERE (some criteria exists) I want to update TableA 3 different ways by 3 equal portions of KeyIDs. UPDATE TableA SET FieldA = Value1 WHERE KeyID IN (the first 1/3 of the SELECT resultset above) UPDATE TableA SET FieldA = Value2 WHERE KeyID IN (the second 1/3 of the SELECT resultset above) UPDATE TableA SET FieldA = Value3 WHERE KeyID IN (the third 1/3 of the SELECT resultset above) or something to that effect. Thanks for any and all of your responses.

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• Finding the centroid of a polygon?

  - by user146780

  I have tried: for each vertex, add to total, divide by number of verities to get center. I'v also tried: Find the topmost, bottommost - get midpoint... find leftmost, rightmost, find midpoint. Both of these did not return the perfect center because I'm relying on the center to scale a polygon. I want to scale my polygons so I may put a border around them. What is the best way to find the centroid of a polygon given that the polygon may be concave, convex and have many many sides of various lengths. Thanks

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• PHP: Iterate through folders and display HTML contents

  - by Mestika

  Hi, I’m currently trying to develop a method to get a overview of all my different web templates I’ve created and (legally) downloaded over the years. I thought about a displaying them like Wordpress is previewing it’s templates view a small preview windows, displaying the concrete file with styles and everything. How to divide them into rows and columns and create AJAX modal window open on preview and pagination and so on I believe I can manage, but it is the concept itself about iterate over several folders then find all index.htm / index.html pages and displaying them. I’ve not worked very much with directories in PHP and the only references and code stumps I’ve found so far is just to list all the files in a certain directory like, what it contains. I would be really grateful if someone knew about a script, a function, snippet or just could get me a nudge in the right direction to create such a (probably simple) preview function. Sincere Mestika

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• Searching a 2D array for a range of values in java

  - by Paige O

  I have a 2^n size int array and I want to check if an element exists that is greater than 0. If the element exists, I want to divide the array by 4 and check if the coordinates of the found element are in the 1st, 2nd, 3rd or 4th quadrant of the array. For example, logically if the element exists in the first quadrant it would look something like this: If array[][] 0 && the row of that coordinate is in the range 0-(grid.length/2-1) && the column of that coordinate is in the range 0-(grid.length/2-1) then do something. I'm really not sure how to check the row and column index of the found element and store those coordinates to use in my if statement. Help!

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• Algorithm design: can you provide a solution to the multiple knapsack problem?

  - by MalcomTucker

  I am looking for a pseudo-code solution to what is effectively the Multiple Knapsack Problem (optimisation statement is halfway down the page). I think this problem is NP Complete so the solution doesn't need to be optimal, rather if it is fairly efficient and easily implemented that would be good. The problem is this: I have many work items, with each taking a different (but fixed and known) amount of time to complete. I need to divide these work items into groups so as to have the smallest number of groups (ideally), with each group of work items taking no longer than a given total threshold - say 1 hour. I am flexible about the threshold - it doesnt need to be rigidly applied, though should be close. My idea was to allocate work items into bins where each bin represents 90% of the threshold, 80%, 70% and so on. I could then match items that take 90% to those that take 10%, and so on. Any better ideas?

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• Is it a good idea to use only a key to encrypt an entire (small) filesystem?

  - by Fernando Miguélez

  This question comes as part of my doubts presented on a broader question about ideas implementing a small encrypted filesystem on Java Mobile phones (J2ME, BlackBerry, Android). Provided the litte feedback received, considering the density of the question, I decided to divide those doubts into small questions. So to sum up I plan to "create" an encrypted filesystem for for mobile phones (with the help of BoucyCastle or a subset of JCE), providing an API that let access to them in a transparent way. Encryption would be carried out on a file basis (not blocks). My question is this: Is it a good idea to use only a simmetric key (maybe AES-256) to encrypt all the files (they wouldn't be that many, maybe tens of them) and store this key in a keystore (protected by a pin) or would you rather encrypt each file with an on-the-fly generated key stored alongside each file, encrypting that key with the "master" key stored on the keystore? What are the benefits/drawbacks of each approach?

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• Sprint to the finish: how to keep all team-members busy in the final days of a Scrum sprint?

  - by sdg

  Given that the tasks in a specific sprint will not divide perfectly into the team, and all finish on the same date, what do you do to keep everyone working as the sprint moves into its final stages? Inevitably it seems like there will be one or two people freed-up. If all the other tasks are done-done, and the remaining tasks are already underway, then what? Do those team-members pick up items from the top of the product backlog, as they are likely to be needed in the next sprint anyways to get a head start? What do you or your teams do?

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• How do I hook all http get requests and distinguish downloaded (by standard download manager) files

  - by Ivan

  I want to write a Firefox add-on for advanced history tracking and bookmarking which will send URLs the browser meets during usage (and all the metadata available about the context) to a web service which will keep track of them storing in an SQL database for further access and analysis. I'd like to divide URLs tracked into 5 groups: those I explicitly click to bookmark, those I download by Firefox standard built-in download manager, all other URLs accessed, all URLs met on all viewed pages as hrefs, all other URLs mentioned in HTML sources of all viewed pages. Any ideas of how to get those in an extension?

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• Flexible Data source for Multi-Section Table View Controller

  - by TuanCM

  I have a TableViewController which display a list of NewsItem objects: @interface NewsItem : NSObject { NSString *feedID; NSString *title; NSDate *published; } I'm trying to implement a Table View Controller (multiple sections) that can display the list in two ways: One divide News Items into sections which based on Published Date The other would be based on FeedID (News source). And I don't know how to structure the data source so that the code is easy to maintain. I tried to put the list of News Items into a 2 dimension Array in this case is a NSMutableArray of NSArray objects. However I got some objc_exception_throw and I don't think this is flexible enough. Could you guys give me some ideas?

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• What is the need for normalizing a vector?

  - by Rashed Hassan

  Trying to understand vectors a bit more. What is the need for normalizing a vector? If I have a vector, N = (x, y, z) What do you actually get when you normalize it - I get the idea you have to divide x/|N| y/|N| & z/|N|. My question is, why do we do this thing, I mean what do we get out of this equation? What is the meaning or 'inside' purpose of doing this. A bit of a maths question, I apologize, but I am really not clear in this topic.

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• Enums With Default Throw Clause?

  - by Tom Tresansky

  I noticed the following in the Java Language spec in the section on enumerations here: link switch(this) { case PLUS: return x + y; case MINUS: return x - y; case TIMES: return x * y; case DIVIDE: return x / y; } throw new AssertionError("Unknown op: " + this); However, looking at the switch statement definition section, I didn't notice this particular syntax (the associated throw statement) anywhere. Can I use this sort of "default case is throw an exception" syntactic sugar outside of enum definitions? Does it have any special name? Is this considered a good/bad practice for short-cutting this behavior of "anything not in the list throws an exception"?

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• Given two lines on a plane, how to find integer points closest to their intersection?

  - by Lukasz Lew

  I can't solve it: You are given 8 integers: A, B, C representing a line on a plane with equation A*x + B*y = C a, b, c representing another line x, y representing a point on a plane The two lines are not parallel therefore divide plane into 4 pieces. Point (x, y) lies inside of one these pieces. Problem: Write a fast algorithm that will find a point with integer coordinates in the same piece as (x,y) that is closest to the cross point of the two given lines. Note: This is not a homework, this is old Euler-type task that I have absolutely no idea how to approach. Update: You can assume that the 8 numbers on input are 32-bit signed integers. But you cannot assume that the solution will be 32 bit.

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• maximum of given function

  - by davit-datuashvili

  first of all i am doing programs in java language this code is merely taken from web site i have not question about divide and conqurer but about function and it's argument here is code of ternary search def ternarySearch(f, left, right, absolutePrecision): #left and right are the current bounds; the maximum is between them if (right - left) < absolutePrecision: return (left + right)/2 leftThird = (2*left + right)/3 rightThird = (left + 2*right)/3 if f(leftThird) < f(rightThird): return ternarySearch(f, leftThird, right, absolutePrecision) return ternarySearch(f, left, rightThird, absolutePrecision) i am not asking once again how implement it in java i am asking for example how define function?for example let y=x^+3 yes we can determine it as public static int y(int x){ return x*x+3; } but here return ternarySearch(f, leftThird, right, absolutePrecision) function f does not have argument and how do such?please help me

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• Code Golf: All +-*/ Combinations for 3 integers

  - by Flash84x

  Write a program that takes 3 integers separated by spaces and perform every single combination of addition, subtraction, multiplication and division operations possible and display the result with the operation combination used. Example: $./solution 1 2 3 Results in the following output 1+2+3 = 6 1-2-3 = -4 1*2*3 = 6 1/2/3 = 0 (integer answers only, round up at .5) 1*2-3 = -1 3*1+2 = 5 etc... Order of operation rules apply, assume there will be no parenthesis used i.e. (3-1)*2 = 4 is not a combination, although you could implement this for "extra credit" For results where a divide by 0 occurs simply return NaN

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• Haskell map function with predicate

  - by Paul

  I feel like this should be fairly obvious, or easy, but I just can't get it. What I want to do is apply a function to a list (using map) but only if a condition is held. Imagine you only wanted to divide the numbers which were even: map (`div` 2) (even) [1,2,3,4] And that would give out [1,1,3,2] since only the even numbers would have the function applied to them. Obviously this doesn't work, but is there a way to make this work without having to write a seperate function that you can give to map? Filter is almost there, except I also want to keep the elements which the condition doesn't hold for, and just not apply the function to them. Thanks

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