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• C++ volatile required when spinning on boost::shared_ptr operator bool()?

  - by JaredC

  I have two threads referencing the same boost::shared_ptr: boost::shared_ptr<Widget> shared; On thread is spinning, waiting for the other thread to reset the boost::shared_ptr: while(shared) boost::thread::yield(); And at some point the other thread will call: shared.reset(); My question is whether or not I need to declare the shared pointer as volatile to prevent the compiler from optimizing the call to shared.operator bool() out of the loop and never detecting the change? I know that if I were simply looping on a variable, waiting for it to reach 0 I would need volatile, but I'm not sure if boost::shared_ptr is implemented in such a way that it is not necessary here.

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• Finding the most similar numbers across multiple lists in Python

  - by new_sysadmin

  In Python, I have 3 lists of floating-point numbers (angles), in the range 0-360, and the lists are not the same length. I need to find the triplet (with 1 number from each list) in which the numbers are the closest. (It's highly unlikely that any of the numbers will be identical, since this is real-world data.) I was thinking of using a simple lowest-standard-deviation method to measure agreement, but I'm not sure of a good way to implement this. I could loop through each list, comparing the standard deviation of every possible combination using nested for loops, and have a temporary variable save the indices of the triplet that agrees the best, but I was wondering if anyone had a better or more elegant way to do something like this. Thanks!

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• How it is called when write or read return less that requested?

  - by Vi

  What term should I use to describe situations (or bugs in software) caused by read, write, send, recv doing less work than expected? For example, write(fd, "123456", 6); may return 3 and we need to write "456" to finish our work. I expect any good program should do all their reads and writes in a loop until without relying that write will write everything. Am I right? /* Implemented simple FUSE filesystem which only allows reading and writing with small buffers, very often returning that it is written less bytes that in a buffer. Some programs work, some not. Are them buggy? */

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• Write set of integers to std::ofstream and be able to read them back

  - by bndu

  Hello, I need to write a bunch of unsigned integers to std::ofstream in binary mode: std::ofstream f; f.open("some path", std::ios::out | std::ios::binary); // some loop { unsigned int k = get_k(); // may product numbers from 0 to 65535 f << k; } f.close(); They are written to the output file "as is" w/o any delimiter. So when I'm trying to read them back (expecting to get what I wrote) using std::ifstream I get very strange values. What I'm doing wrong? Or I should to put ' ' (space) to the stream after any added number to separate them? Thanks.

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• Passing a String from PHP to a JavaScript function

  - by user635614

  Hello. am trying to write a code to pass a php string when clicked on the table : <?php . . . echo("<td onclick = 'print_("$file[$i]->Name");' >". $files[$i]->Name."</td>"); ... ?> where files[] is an array, and each element is a class with Name as a String, and it is put in a ''for'' loop, Am trying to pass it to a JavaScript function where i need the name there,and it's not working,i tried passing the i variable and it was passed correctly so i thought there should be a special syntax for dealing with strings... function print_(var x) { alert(x);}

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• Can't seem to be able to set ListViewItem.imageIndex

  - by TKL

  I have been scratching my head with this error for at least an hour, what the heck is wrong here? In a loop: if (selectedItems[x].ImageIndex == 3) { List<ListViewItem> dupes = CP.listCache.FindAll(delegate(ListViewItem item) { return item.Text == selectedItems[x].Text; }); if (dupes != null && dupes.Count == 1) dupes[0].ImageIndex = 0; } I can access the imageIndex, but not set it. ArgumentOutOfRange exception occurs.

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• How to read arbitrary number of values using std::copy?

  - by Miro Kropacek

  Hi, I'm trying to code opposite action to this: std::ostream outs; // properly initialized of course std::set<int> my_set; // ditto outs << my_set.size(); std::copy( my_set.begin(), my_set.end(), std::ostream_iterator<int>( outs ) ); it should be something like this: std::istream ins; std::set<int>::size_type size; ins >> size; std::copy( std::istream_iterator<int>( ins ), std::istream_iterator<int>( ins ) ???, std::inserter( my_set, my_set.end() ) ); But I'm stuck with the 'end' iterator -- input interators can't use std::advance and neither I can use two streams with the same source... Is there any elegant way how to solve this? Of course I can use for loop, but maybe there's something nicer :)

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• Sql-server Database query help

  - by menacheb

  Hi, I have a problem that I didn't manage to solve for a very long time, and I quite desperate. I have a Database (SQL Server) with table named 'ProcessData' and columns named 'Process_Name' (Data Type: nvarchar(50)), 'Start_At' (DataType: DateTime) and 'End_At' (Data Type: DateTime). I need to know for each 'Time-Interval' (let's say 1 minute) how many processes (Process_Name = PN) was open (after or equal to the 'Start_at' column and before or equal to the 'End_At' column) during this time (It can be a few rows with the same data). Does anyone know how to make this query without a 'for' loop? (It ITSELF will promote the time), (The answer will be a table with two columns (1. The time the check took place. 2. the number of open processes at this time.) and a row for each 'Time-Interval' (1 minute in this example ) Many thanks,

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• Are there any well-known algorithms or computer models that computer scientists use to predict FIFA

  - by Khnle

  Occasionally I read news articles that mention about some computer models that computer scientists use to predict winners of some sporting events or the odds for betting which I think there must be a mathematical model behind it. I never bothered to think twice even though I am a "pseudo computer scientist" myself. With the 2010 FIFA World Cup just underway, and since I am also a "pseudo football/soccer player" myself, I just started to wonder about these calculations algorithms. For example, I know one factor is determining the strength of opponents, so that a win against a strong opponent can count more than a win against a weak opponent. But it now kind of gets in a circular loop, or at least how does one determine the strength of a team in the first place, before that team can be considered strong or weak? If it's based on a historical data then there's no way that could be accurate, because those players of the past are no longer on the fields so their impact is none (except maybe if they become coaches like Maradona) Anyway, long question short, if you're happen to be working in this field or have some knowledge, please shed some lights.

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• Converting keys of an array/object-tree to lowercase

  - by tstenner

  Im currently optimizing a PHP application and found one function being called around 10-20k times, so I'd thought I'd start optimization there. function keysToLower($obj) { if(!is_object($obj) && !is_array($obj)) return $obj; foreach($obj as $key=>$element) { $element=keysToLower($element); if(is_object($obj)) { $obj->{strtolower($key)}=$element; if(!ctype_lower($key)) unset($obj->{$key}); } else if(is_array($obj) && ctype_upper($key)) { $obj[strtolower($key)]=$element; unset($obj[$key]); } } return $obj; } Most of the time is spent in recursive calls (which are quite slow in PHP), but I don't see any way to convert it to a loop. What would you do?

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• how to set and access variable values from another classess

  - by BittenApple

  I am modifying QuartzDemo example app and want to do set and read values of integer type variables in other classes which are already included. For example, in MainViewController.m I want to set a numeric value (simple numbers from 1-100) to a variable which is then going to be called (read) in file QuartzImages.m. Question is how to define variable properly, set and access (read) the value. I am a beginner with Obj C and iPhone SDK in general and have some experience with Delphi and VB but this doesn't help at all :) Thank you, whoever and wherever you are, person who will take me out of this endless googling loop.

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• What is the '@(' doing in this Perl code?

  - by Anthony Veckey

  In this code snippet: use strict; use warnings; use Data::Dumper; my $r = [qw(testing this thing)]; print Dumper($r); foreach my $row (@({$r}) { print "$row\n"; $row .= 'mod'; } print Dumper($r); print Dumper(@({$r}); I figured out that the '(' after the '@' in the foreach is causing this not to loop correctly. I have no idea why this code even works as there is no ending parenthesis. What is this doing? It looks to be creating a new variable on the fly, but shouldn't 'use strict' have fired or something? Please help explain what that '@(' is doing and why it still runs without an ending parenthesis.

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• PHP+MYSQL Server Config

  - by Matias

  Hi guys, I am parsing an XML file with PHP and inserting the rows in a MYSQL database. I am using PHP simplexml_load_files to load the XML and a foreach to loop through the array and insert the rows into my database. It works perfectly fine with small files i am testing, but it comes to reality I need to parse a large 500mb XML file and nothing happens. I was wondering what was the right Php.ini config for this case ? I have a VPS Linux Cent OS, with 256 mb of dedicated Memory and MYSQL 5.0.5. I have also set php memory_limit = 256M (maximum of my server) Any suggestions, similar experiences will be greatly appreciated Thanks

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• How can I declare classes that refer to each other?

  - by Without me Its just Aweso

  It's been a long time since I've done C++ and I'm running into some trouble with classes referencing each other. Right now I have something like: a.h class a { public: a(); bool skeletonfunc(b temp); }; b.h class b { public: b(); bool skeletonfunc(a temp); }; Since each one needs a reference to the other, I've found I can't do a #include of each other at the top or I end up in a weird loop of sorts with the includes. So how can I make it so that a can use b and vice versa without making a cyclical #include problem? thanks!

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• How to optimize indexing of large number of DB records using Zend_Lucene and Zend_Paginator

  - by jdichev

  So I have this cron script that is deployed and ran using Cron on a host and indexes all the records in a database table - the index is later used both for the front end of the site and the backed operations as well. After the operation, the index is about 3-4 MB. The problem is it takes a lot of resources (CPU: 30+ and a good chunk of memory) and slows the machine down. My question is about how to optimize the operation described below: First there is a select query built using the Zend Framework API, this query is then passed to a Paginator factory that returns a paginator which I am using to balance the current number of items being indexed and not iterate over too much items. The script is iterating over the current items in the paginator object using a foreach loop until reaching the end and then it starts from the beginning after getting items for the next page. I am suspecting this overhead is caused by the Zend_Lucene but no idea how this could be improved.

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• Concatenating Strings in Obj C

  - by eco_bach

  Hi It seems that Objective C jumps thru hoops to make seemingly simple tasks extremely difficult. I simply need to create a sequence of strings, image1.jpg, image2.jpg, etc etc ie in a loop var imgString:String='image'+i+'.jpg; I assume a best practice is to use a NSMutableString with appendString method? What am I doing wrong?? NSMutableString *imgString; for(int i=1;i<=NUMIMAGES;i++){ imgString.appendString(@"image"+i+@".jpg"); } I get the following error error: request for member 'appendString' in something not a structure or union

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• PHP fetch all Twitter Followers and compare them to friends

  - by ArneRie

  Hi, iam looking for performant way to do the following: User login Fetch all Friends from Twitter Fetch all Followers from Twitter Display all Friends wich aren't Followers The Problem: How to do this in a performant way? An user can have up to 2 Million Friends or Followers. In the moment im Storing both inside an sqllite table an compare them through an loop. When the user comes back the table is cleared and process starts again. This works finde on 100 - 1000 Friends.. but will be tricky with 500000 Friends. I cant cache the lists because they can change every moment.. Does someone knows a good way to handle such big amount of data?

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• Adding anchors to h2 in text using python and regexp

  - by Oli

  I'm trying to add anchors to all h2's in my html, using python. This code will add those anchors, but I need to fill the name of the anchors too. Any idea if the name can be the number of the match in the loop or a slugified version of the text between the h2 tags? Here's the code so far: regex = '(?P<name><h2>.*?</h2>)' text = re.sub(regex, "<a name=''/>"+r"\g<name>", text)

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• Python: How to quit CLI when stuck in blocking raw_input?

  - by christianschluchter

  I have a GUI program which should also be controllable via CLI (for monitoring). The CLI is implemented in a while loop using raw_input. If I quit the program via a GUI close button, it hangs in raw_input and does not quit until it gets an input. How can I immediately abort raw_input without entering an input? I run it on WinXP but I want it to be platform independent, it should also work within Eclipse since it is a developer tool. Python version is 2.6. I searched stackoverflow for hours and I know there are many answers to that topic, but is there really no platform independent solution to have a non-blocking CLI reader? If not, what would be the best way to overcome this problem? Thanks

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• CodeIgniter - Returning multiple file upload details

  - by Chris

  Hey All, Im using the codeigniter upload library to upload multiple files, which works fine ... What im having problems with is returning the information about the files. Im using the following code to print the results for testing echo '<pre>'; print_r($this->upload->data()); echo '</pre>'; A cut down version of the results are as follows Array ( [file_name] => Array ( [0] => filename1.gif [1] => filename2.jpg ) ) The way my view is setup, is that i use jquery to insert multiple dynamic file input fields so the amount of files can be 1, it can be 50 and so on. Im wondering how i would loop through that array to send each filename to the database

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• Putting li's into rows

  - by panthro

  I have a long list of li's. <ul> <li> <img src="test.jpg"> </li> <li> <img src="test.jpg"> </li> //etc Each li has this styling: width: 10%; display: inline-block; vertical-align: middle; When I get to more than 10 li's in a row, they go on to the next row. Is this the correct way to do it? or should I wrap each 10 li's into something that breaks the line? What the best/correct method? i intialy chose this method as it would be easily to loop out data from a database.

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• an array of strings as a jQuery selector?

  - by dalbaeb

  I have an array of strings that are valid jQuery selectors (i.e. IDs of elements on the page): ["#p1", "#p2", "#p3", "#p4", "#p5"] I want to select elements with those IDs into a jQuery array. This is probably elementary, but I can't find anything online. I could have a for-loop which creates a string "#p1,#p2,#p3,#p4,#p5" which could then be passed to jQuery as a single selector, but isn't there another way? Isn't there a way to pass an array of strings as a selector? EDIT: Actually, there is an answer out there already.

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• Force freeing memory in PHP

  - by DBa

  Hi everybody, in a PHP program, I sequentially read a bunch of files (with file_get_contents), gzdecode them, json_decode the result, analyze the contents, throw the most of it away, and store about 1% in an array. Unfortunately, with each iteration (I traverse over an array containing the filenames), there seems to be some memory lost (according to memory_get_peak_usage, about 2-10 MB each time). I have double- and triplechecked my code, I am not storing unneded data in the loop (and the needed data hardly exceeds about 10MB overall), but I am frequently rewriting (actually, strings in an array). Apparently, PHP does not free the memory correctly, thus using more and more RAM until it hits the limit. Is there any way to do a forced garbage collection? Or, at least, to find out where the memory is used? Thanks in advance, Dmitri

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• How to import datarow from one dataset to another?

  - by Disciple

  Hi, I want to copy the row to the new dataset if the previous value in second column isn't the same as the current one (i.e this dataset should have rows with unique values): DataTable tbl = new DataTable(); DataTable tmpTable = ds.Tables[0]; for( var rowIndex = 0; rowIndex < ds.Tables[0].Rows.Count; rowIndex++ ) { object value = null; foreach (DataRow x in tbl.Rows) { if (ds.Tables[0].Rows[rowIndex][1] == x[1]) { value = ds.Tables[0].Rows[rowIndex][1]; break; } } // value already exists if (value == null) { tbl.ImportRow(ds.Tables[0].Rows[rowIndex]); } } How to do this correctly? Maybe one loop instead 2?

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• Are `return` and `break` useless inside a Ruby block when used as a callback?

  - by Skilldrick

  In Rails, blocks can be used as callbacks, e.g.: class User < ActiveRecord::Base validates_presence_of :login, :email before_create {|user| user.name = user.login.capitalize if user.name.blank?} end When a block is used like this, is there any use for break and return? I'm asking because normally in a block, break will break out of the loop, and return will return from the enclosing method. But in a callback context, I can't get my head round what that means. The Ruby Programming Language suggests that return could cause a LocalJumpError but I haven't been able to reproduce this in a Rails callback. Edit: with the following code I'd expect a LocalJumpError, but all the return does is stop the rest of the callback executing. class User < ActiveRecord::Base validates_presence_of :login, :email before_create do |user| return user.name = user.login.capitalize end

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