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  • Optimal strategy to make a C++ hash table, thread safe

    - by Ajeet
    (I am interested in design of implementation NOT a readymade construct that will do it all.) Suppose we have a class HashTable (not hash-map implemented as a tree but hash-table) and say there are eight threads. Suppose read to write ratio is about 100:1 or even better 1000:1. Case A) Only one thread is a writer and others including writer can read from HashTable(they may simply iterate over entire hash table) Case B) All threads are identical and all could read/write. Can someone suggest best strategy to make the class thread safe with following consideration 1. Top priority to least lock contention 2. Second priority to least number of locks My understanding so far is thus : One BIG reader-writer lock(semaphore). Specialize the semaphore so that there could be eight instances writer-resource for case B, where each each writer resource locks one row(or range for that matter). (so i guess 1+8 mutexes) Please let me know if I am thinking on the correct line, and how could we improve on this solution.

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  • Grouped table with image in first row (and section), the remaining ones having text with different l

    - by Structurer
    Hi I have a grouped table with two sections where I display text with different length and therefore cell height. I have solved the problem with the different length/height with constrainedToSize in cellForRowAtIndexPath. Now I want to add a section with one single row in which I want to show a picture. How should I best implement that? (still a bit of a beginner with the Objective C) I would guess that I would have to create an UIImageView and somehow link that to the cell, but my biggest concern is how do I do with the dequeueReusableCellWithIdentifier now that I will have two different type of cells? Appreciate any advice that will help me save time from trial and error!

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  • Why delete and recreate a querydef object when you can just change the .SQL property?

    - by dblE
    Do you remember the venerable old Microsoft Query by Form (QBF) VBA example from back in the day link that recommended that you delete an existing query and then recreate it dynamically?: On Error Resume Next db.QueryDefs.Delete ("qryResults") On Error GoTo 0 Set qdf = db.CreateQueryDef("qryResults", "SELECT p.*... Why not just change the SQL property of the querydef object? qdf.SQL = "SELECT p.*... I am wondering if anyone knows why the MS engineers wrote an example that suggests that you delete and then recreate a query instead of simply changing the SQL property? I would guess that the act of deleting and recreating objects over time could contribute to corruption and bloating in your front end, not to mention changing the SQL property is so much simpler. Does anyone have more insight into this?

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  • SQL most popular

    - by Brae
    I have a mysql table with items in relation to their order. CREATE DATABASE IF NOT EXISTS `sqltest`; USE `sqltest`; DROP TABLE IF EXISTS `testdata`; CREATE TABLE `testdata` ( `orderID` varchar(10) DEFAULT NULL, `itemID` varchar(10) DEFAULT NULL, `qtyOrdered` int(10) DEFAULT NULL, `sellingPrice` decimal(10,2) DEFAULT NULL ) INSERT INTO `testdata`(`orderID`,`itemID`,`qtyOrdered`,`sellingPrice`) values ('1','a',1,'7.00'),('1','b',2,'8.00'),('1','c',3,'3.00'),('2','a',1,'7.00'),('2','c',4,'3.00'); Intended Result: A = (1+1)2 B = 2 C = (2+4)6 <- most popular How do I add up all the qty's for each item and result the highest one? It should be fairly strait forward but I'm new to SQL and I can't work this one out :S Solution needs to be mysql and or php. I guess there needs to be some sort of temporary tally variable for each item ID, but that seems like it could get messy with too many items.

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  • How to place a symbol (path) relative to the far end of svg text?

    - by dugeen
    I'm working on a program which generates SVG maps. Some of the map items have captions which need a symbol after them (like a plane symbol for an airport caption). If I have a text element thus <text x="30" y="30">Pericles</text> I can place another bit of text at the next character position by saying <text x="30" y="30">Pericles <tspan>!</tspan></text> but I'd like to draw my own symbol at that position with a <path> element. What I'm doing at the moment is having the generating program guess the extent of the text from tables of font metrics etc, but this isn't accurate enough to place the symbol consistently. Is there any way round this - like specifying a <marker> to be used when drawing the text, and using a tspan with an invisible dash in it or something to get the marker placed?

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  • Is it possible to auto generate Getter/Setter from Array Values in PHP?

    - by Phill Pafford
    So I have a couple of arrays $array_1 = Array('one','two','three'); $array_2 = Array('red','blue','green'); Is there a dynamic way to create the Setters and Getters for an array with single value entries? So the class would be something like: class xFromArray() { } So the above if I passed $array_1 it would generate something like this: private $one; setOne($x) { $one = $x; } getOne() { return $one; } if I passed $array_2 it would generate something like this: private $red; setRed($x) { $red = $x; } getRed() { return $red; } So I would call it somehow like this? (My best guess but doesn't seem that this would work) $xFromArray = new xFromArray; foreach($array_1 as $key=>$data) { $xFromArray->create_function(set.ucfirst($data)($data)); echo $xFromArray->create_function(get.ucfirst($data)); }

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  • How do you get the email using facebook api?

    - by Marwelln
    I'm using this code but I can't figure out how to get the email from the user. I know you must get special permission from the user but I don't know how. I can get the public data from the user but that's not what I even need. The only thing I need is the email. I guess it's something with this line: $me = $facebook->api('/me'); I have read the documentation but I still don't know how I can get the email. How do I get the email from the user loggin in on my website with the facebook api?

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  • [CakePHP] How to add some action after login (and before redirection)?

    - by user198003
    hello, trying to develop some sort of login tracker for my cakephp application. i know that i need code like: $this->data['LoginSession']['username'] = $_SERVER['REMOTE_ADDR']; $this->data['LoginSession']['ipAddress'] = $_SERVER['REMOTE_ADDR']; $this->LoginSession->save($this->data); ... in (i guess) users_controller, but don't know exactly where. also i would like to track successful, but also unsuccessful logins. can you help me with this please? thank you in advance!

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  • MySQL GROUP BY with three tables

    - by Psaniko
    I have the following tables: posts (post_id, content, etc) comments (comment_id, post_id, content, etc) posts_categories (post_category_id, post_id, category_id) and this query: SELECT `p`.*, COUNT(comments.comment_id) AS cmts, posts_categories.*,comments.* FROM `posts` AS `p` LEFT JOIN `posts_categories` ON `p`.post_id = `posts_categories`.post_id LEFT JOIN `comments` ON `p`.post_id = `comments`.post_id GROUP BY `p`.`post_id` There are three comments on post_id=1 and four in total. In posts_categories there are two rows, both assigned to post_id=1. I have four rows in posts. But if I query the statement above I get a result of 6 for COUNT(comments.comment_id) at post_id=1. How is this possible? I guess the mistake is somewhere in the GROUP BY clause but I can't figure out where. Any suggestions?

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  • Converting a macro to an inline function

    - by Rob
    I am using some Qt code that adds a VERIFY macro that looks something like this: #define VERIFY(cond) \ { \ bool ok = cond; \ Q_ASSERT(ok); \ } The code can then use it whilst being certain the condition is actually evaluated, e.g.: Q_ASSERT(callSomeFunction()); // callSomeFunction not evaluated in release builds! VERIFY(callSomeFunction()); // callSomeFunction is always evaluated Disliking macros, I would instead like to turn this into an inline function: inline VERIFY(bool condition) { Q_ASSERT(condition); } However, in release builds I am worried that the compiler would optimise out all calls to this function (as Q_ASSERT wouldn't actually do anything.) I am I worrying unnecessarily or is this likely depending on the optimisation flags/compiler/etc.? I guess I could change it to: inline VERIFY(bool condition) { condition; Q_ASSERT(condition); } But, again, the compiler may be clever enough to ignore the call. Is this inline alternative safe for both debug and release builds?

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  • Parallel.For(): Update variable outside of loop

    - by TSS
    I'm just looking in to the new .NET 4.0 features. With that, I'm attempting a simple calculation using Parallel.For and a normal for(x;x;x) loop. However, I'm getting different results about 50% of the time. long sum = 0; Parallel.For(1, 10000, y => { sum += y; } ); Console.WriteLine(sum.ToString()); sum = 0; for (int y = 1; y < 10000; y++) { sum += y; } Console.WriteLine(sum.ToString()); My guess is that the threads are trying to update "sum" at the same time. Is there an obvious way around it?

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  • Is it possible to disable auto formatting only for Html pages (not c#) on VS2010?

    - by ensecoz
    During the design html pages or aspx pages, I like to do the pure coding without Html Designer. The problem is that I like to have the following format on html page for better readability. <div> <% if (1 == 1) { %> Hello <% } else { %> World <% } %> </div> As you can guess, whenever you type '}' or ';' or etc, visual studio try to do the auto format and change to the following format <div> <% if (1 == 1) { %> Hello <% } else { %> World <% } %> </div> The question is "Is it possible to disable auto formatting just only for HTML pages on VS2010? (NOT for C# code, I still like to have auto formatting for C# pages)"

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  • Jquery, ajax() and each(), how to wait untill all info is really loaded?

    - by Moustard
    Hello, I have a function using $.ajax() to get values from an XML file, when the info is loaded and success event is fired, I use $(xml).find('').each(function(){}); to populate some vars... function getData() { $.ajax({ type: 'GET', url : 'info.xml', dataType: 'xml', success: function(xml) { $(xml).find('DATAS').each(function() { date = new Date($(this).attr('DATE')); alert(date); }) //Here I have a bigger find/each that should take more time }, error: function() { return false; } }); } In this case, when I trigger the function from the document ready function, the alert shows the right data, but If I remove the alert from the function and try this instead, date wont be defined yet: $(document).ready(function() { if(getData() != false) { alert(date); } }); I guess in this case the data is not ready yet? Is there a way to keep control on when the whole each() traversing is finished and ready?

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  • How can I write my code to attempt a database action but continue executing code on failure?

    - by Chris
    Simple question I guess, I want to use PHP to write an update to an existing row in my database, if it doesn't happen I want to log the failure but continue executing the code. While it would be nice to have records of failures to track down issues, that the update failed isn't that important to my user, nor will it affect the running of any other code; the query is simply for a 'cosmetic' but entirely unnecessary piece of information. My database class's query function is set to die on failure, could I modify that or is there another way of doing it without altering my standard query code?

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  • When open-sourcing a live Rails app, is it dangerous to leave the session key secret in source contr

    - by rspeicher
    I've got a Rails app that's been running live for some time, and I'm planning to open source it in the near future. I'm wondering how dangerous it is to leave the session key store secret in source control while the app is live. If it's dangerous, how do people usually handle this problem? I'd guess that it's easiest to just move the string to a text file that's ignored by the SCM, and read it in later. Just for clarity, I'm talking about this: # Your secret key for verifying cookie session data integrity. # If you change this key, all old sessions will become invalid! # Make sure the secret is at least 30 characters and all random, # no regular words or you'll be exposed to dictionary attacks. ActionController::Base.session = { :key => '_application_session', :secret => '(long, unique string)' } And while we're on the subject, is there anything else in a default Rails app that should be protected when open sourcing a live app?

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  • unable to start program problem in VS2008_C++

    - by epsilon_G
    Hi .. I was trying to code some projects .. but the I could't compile it , first I guess the code .. I change the code to the simplest code at all hello ... The same think , I can't compile it ... some one code with my VS and when he had compiled the program he had pressed of dialog box with "No" .. The prob is in the configuration of the IDE .. The system cannot find the file specified unfortunately , I uploaded the prob pics from my PC but I can't post them here

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  • Eclipse C++ on WinXP - Type `::iterator' has not been declared

    - by redwolfe
    I'm new to C++/Eclipse. I'm trying to get it working to get a new perspective on a problem with a program I wrote in DevCPP. The program is simple and builds fine in DevCPP. In Eclipse, I get hundreds of errors like the one above. I assume the compiler can't see my include files. I've checked that the project settings - GCC C++ compiler - directories contains the location for my include files (D:\MinGW\include\c++\3.4.5). I've prowled around and tried to change 'Discovery Options' to 'GCC C++ Compiler' from 'GCC C Compiler' but it keeps changing back. I guess this is not the problem. Any help would be very welcome. I'm on a tight deadline with many interruptions and this is cracking me up.

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  • How to change the name of an iPhone app?

    - by Robert Gould
    I began an iPhone project the other day with a silly development code name, and now I want to change the name of the project since its nearly finished. But I'm not sure how to do this with XCode, trying the obvious of changing the application's name in the pinfo, causes the signing process to go wrong (I think...) and my app won't launch giving me a Launcher error. I guess I could make a new project and copy paste everything over, but it seems so primitive, that I'm hoping for a more civilized solution. Thanks!

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  • How to achieve Bottom Align floated div that sizes to it's container.

    - by Davy8
    How can I achieve the following layout? Specifically the positioning of Image and DIV I've found that unless I set a specific width for the Div, it will just go on to the next line and take up the full width of the container. Additionally aligning it relative to the bottom of the image is giving me trouble. Currently they're both float:left Edit: The two solutions so far work if the image is a constant width which I guess I could work with, but it's going in a Wordpress theme for an author's profile page and it's possible that images would have slightly variable widths. Is there a solution that would have the Div right next to the image (minus padding) regardless of how wide or narrow the image is? Basically having the div adjust its width to accommodate the image width.

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  • What is the best practise for relational database tables in mysql?

    - by George
    Hi, I know, there is a lot of info on mysql out there. But I was not really able to find an answer to this specific and actually simple question: Let's say I have two tables: USERS (with many fields, e.g. name, street, email, etc.) and GROUPS (also with many fields) The relation is (I guess?) 1:n, that is ONE user can be a member of MANY groups. What I dis, is create another table, named USERS_GROUPS_REL. This table has only two fields: us_id (unique key of table USERS) and gr_id (unique key of table GROUPS) In PHP I do a query with join. Is this "best practice" or is there a better way? Thankful for any hint!

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  • Makefile: couple syntax questions

    - by Michael
    package_version := $(version)x0d$(date) what is the x0d part between version and date vars? is it just string? What $(dotin_files:.in=) does below code dotin_files := $(shell find . -type f -name \*.in) dotin_files := $(dotin_files:.in=) what this means $(dotin_files:=.in) code $(dotin_files): $(dotin_files:=.in) $(substitute) [email protected] > $@ can target contain multiple files? what is the meaning of declaring target variable as PHONY? code .PHONY: $(dotin_files) In the regex replacement code below code substitute := perl -p -e 's/@([^@]+)@/defined $$ENV{$$1} ? $$ENV{$$1} : $$&/ge' what are $$ENV{$$1} and $$&? I guess it's Perl scope... thanks for your time

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  • Possible to add hook as android fetches XML-strings?

    - by user247245
    I'm on my first week with android and would appreciate any insight if it's possible to hook or override the default behaviour when an android application reads their values from the resource-files to the shown layouts. What I want is to over time be able to add new/updated strings OTA and store locally and then on launch of application load new values instead of the ones in the default /res. Ideally i guess, would be an override of setContentView. Files holding updates will be in same xml-format as those in /res. (Please, no advices in other ways to do this. Just need to know if it's at all possible, without hacking the SDK) regards, /t

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  • function declaration

    - by robUK
    Hello, gcc 4.1.2 c89 I am reviewing some code and I have come across the following function. I have never seen a function declared like this before. There are no data types for the paraemeters. My best guess is that the function is using a list of data types separated by semi-colons. The return type seems to be returning a function with those parameters. However, the read function is not defined anywhere. What is the advantage and purpose of declaring a function like this? Many thanks for any advice, int my_read(fd, ptr, cnt) int fd; char *ptr; unsigned cnt; { printf("Read\n"); return(read(fd, ptr, cnt)); }

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  • Navigating sharepoint with a treeview

    - by linqmonkey
    I'm trying to replace the navigation on our sharepoint site with a treeview. It's a large site with up to 4 subsite leves in places. All I need it to do is show a consistent structure from page to page show only sites and pages The default sharepoint treeview seems to do neither of these things (doesn't display items from the parent site, includes document libraries but not pages). Does anyone have any idea how to achieve this? We're using the publishing site template throughout if that makes a difference. I've tried binding the tree to the datasource the quick launch uses but I guess from the error message they expect differently named properties.

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  • get text from running application window (osx)

    - by tensai
    Hi, I'm very very new to OSX/UNIX and i was wondering how i would go about getting a certain text from a application window. Explanation: App1 is running, it has a textfield with changing data. I start app2 and i want the data in the textfield from app1 available in app2. (i did not write app1 its a commercial app) I guess it should probably be done in c++ but any other solutions are welcome. If someone could help me in the right direction it would be much appreciated! Thx!

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