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• kick off a map reduce job from my java/mysql webapp

  - by Brian

  Hi guys, I need a bit of archecture advice. I have a java based webapp, with a JPA based ORM backed onto a mysql relational database. Now, as part of the application I have a batch job that compares thousands of database records with each other. This job has become too time consuming and needs to be parallelized. I'm looking at using mapreduce and hadoop in order to do this. However, I'm not too sure about how to integrate this into my current architecture. I think the easiest initial solution is to find a way to push data from mysql into hadoop jobs. I have done some initial research on this and found the following relevant information and possibilities: 1) https://issues.apache.org/jira/browse/HADOOP-2536 this gives an interesting overview of some inbuilt JDBC support 2) This article http://architects.dzone.com/articles/tools-moving-sql-database describes some third party tools to move data from mysql to hadoop. To be honest I'm just starting out with learning about hbase and hadoop but I really don't know how to integrate this into my webapp. Any advice is greatly appreciated. cheers, Brian

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• Trouble with C# array

  - by Biosci3c

  Hi, I am writing a card playing program as a way of learning C#. I ran into an issue with an array going out of bounds. Here is my code: namespace Pcardconsole { class Deck { public Deck() { // Assign standard deck to new deck object int j; for (int i = 0; i != CurrentDeck.Length; i++) { CurrentDeck[i] = originalCards[i]; } // Fisher-Yates Shuffling Algorithim Random rnd = new Random(); for (int k = CurrentDeck.Length - 1; k >= 0; k++) { int r = rnd.Next(0, k + 1); int tmp = CurrentDeck[k]; CurrentDeck[k] = CurrentDeck[r]; CurrentDeck[r] = tmp; // Console.WriteLine(i); } } public void Shuffle() { // TODO } // public int[] ReturnCards() // { // TODO // } public int[] originalCards = new int[54] { 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18, 0x19, 0x1A, 0x1B, 0x1C, 0x1D, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28, 0x29, 0x2A, 0x2B, 0x2C, 0x2D, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x3A, 0x3B, 0x3C, 0x3D, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, 0x49, 0x4A, 0x4B, 0x4C, 0x4D, 0x50, 0x51 }; public int[] CurrentDeck = new int[54]; } class Program { static void Main(string[] args) { // Create a Deck object Deck mainDeck = new Deck(); Console.WriteLine("Here is the card array:"); for (int index = 0; index != mainDeck.CurrentDeck.Length; index++) { string card = mainDeck.CurrentDeck[index].ToString("x"); Console.WriteLine("0x" + card); } } } The hexidecimal numbers stand for different cards. When I compile it I get an array index out of bounds error, and a crash. I don't understand what is wrong. Any help would be much appreciated.

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• ASP.NET MVC and NHibernate coupling

  - by Ben

  I have just started learning NHibernate. Over the past few months I have been using IoC / DI (structuremap) and the repository pattern and it has made my applications much more loosely coupled and easier to test. When switching my persistence layer to NHibernate I decided to stick with my repositories. Currently I am creating a new session on each method call but of course this means that I can not benefit from lazy loading. Therefore I wish to implement session-per-request but in doing so this will make my web project dependent on NHibernate (perhaps this is not such a bad thing?). I was planning to inject ISession into my repositories and create and dispose sessions on beginrequest/endrequest events (see http://ayende.com/Blog/archive/2009/08/05/do-you-need-a-framework.aspx) Is this a good approach? Presumably I cannot use session-per-request without having a reference to NHibernate in my web project? Having the web project dependent on NHibernate prompts my next (few) questions - why even bother with the repository? Since my web app is calling services that talk to the repositories, why not ditch the repositories and just add my NHibernate persistance code inside the services? And finally, is there really any need to split out into so many projects. Is a web project and an infrastructure project sufficient? I realise that I have veered off a bit from my original question but it seems that everyone seems to have their own opinion on these topics. Some people use the repository pattern with NHibernate, some don't. Some people stick their mapping files with the related classes, others have a separate project for this. Many thanks, Ben

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• Flex through Flash Builder 4; Connecting to a dynamic XML feed: "The response is not a valid XML or

  - by jtromans

  I am learning how to use Flex with Adobe Flash Builder 4 standalone. I am working my through the Adobe Flash Build 4 Bible by David Gassner. This has led me to create my own micro problems to try and solve. I am trying to connect to a dynamix XML feed created by the following aspx page: generate_xml.aspx When I create the data connection through the Data/Service panel, I can pick between XML and HTTP. I figured because the generate_xml.aspx has to generate the XML file first, I should use the HTTP service as opposed to the XML. The HTTP service offers GET, which seems to be the kinda thing I want. However, I am really struggling to do this. I keep getting: "The response is not a valid XML or a JSON string" The actual STATIC generated XML file that is created by this page works perfectly when I save it and manually connect with the XML service. Therefore I know my XML code is properly formatted and contains no other HTML of JavaScript. I figure my problem occurs because the page itself is .aspx, but I cannot work out how to successfully ask Flex to request the output of this page, rather than the page itself.

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• How to I display results of phpcs in VIM?

  - by Matt

  I am presently trying to use PHP Codesniffer (PEAR) in vim for PHP Files. I have found 2 sites that give code to add into the $HOME/.vim/plugin/phpcs.vim file. I have added the code and I "think" it is working, but I cannot see the results, I only see one line at the very bottom of vim that says (1 of 32) but I cannot see any of the 32 errors. Here is my .vimrc file " Backup Options -> Some People may not want this... it generates extra files set backup " Enable Backups set backupext=.bak " Add .bak extention to modified files set patchmode=.orig " Copy original file to with .orig extention Before saving. " Set Tabs and spacing for PHP as recomended by PEAR and Zend set expandtab set shiftwidth=4 set softtabstop=4 set tabstop=4 " Set Auto-indent options set cindent set smartindent set autoindent " Show lines that exceed 80 characters match ErrorMsg '\%80v.\+' " Set Colors set background=dark " Show a status bar set ruler set laststatus=2 " Set Search options highlight, and wrap search set hls is set wrapscan " File Type detection filetype on filetype plugin on " Enable Spell Checking set spell " Enable Code Folding set foldenable set foldmethod=syntax " PHP Specific options let php_sql_query=1 " Highlight sql in php strings let php_htmlInStrings=1 " Highlight HTML in php strings let php_noShortTags=1 " Disable PHP Short Tags let php_folding=1 " Enable Ability to FOLD html Code I have tried 2 different versions of phpcs.vim, and I get the same results for both: Version 1 (found at: VIM an a PHP IDE) function! RunPhpcs() let l:filename=@% let l:phpcs_output=system('phpcs --report=csv --standard=YMC '.l:filename) " echo l:phpcs_output let l:phpcs_list=split(l:phpcs_output, "\n") unlet l:phpcs_list[0] cexpr l:phpcs_list cwindow endfunction set errorformat+=\"%f\"\\,%l\\,%c\\,%t%*[a-zA-Z]\\,\"%m\" command! Phpcs execute RunPhpcs() Version 2: (found at Integrated PHP Codesniffer in VIM ) function! RunPhpcs() let l:filename=@% let l:phpcs_output=system('phpcs --report=csv --standard=YMC '.l:filename) let l:phpcs_list=split(l:phpcs_output, "\n") unlet l:phpcs_list[0] cexpr l:phpcs_list cwindow endfunction set errorformat+="%f"\\,%l\\,%c\\,%t%*[a-zA-Z]\\,"%m" command! Phpcs execute RunPhpcs() Both of these produce identical results. phpcs is installed on my system, and I am able to generate results outside of vim. Any help would be appreciated I am just learning more about vim...

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• Need help with an AJAX workflow

  - by Anders

  Sorry I couldn't be more descriptive with the title, I will elaborate fully below: I have a web application that I want to implement some AJAX functionality into. Currently, it is running ASP.NET 3.5 with VB.NET codebehind. My current "problem" is I want to dynamically be able to populate a DIV when a user clicks an item on a list. The list item currently contains a HttpUtility.UrlEncode() (ASP.NET) string of the content that should appear in the DIV. Example: <li onclick="setFAQ('The+maximum+number+of+digits+a+patient+account+number+can+contain+is+ten+(10).');"> What is the maximum number of digits a patient account number can contain?</li> I can decode the string partially with the JavaScript function unescape() but it does not fully decode the string. I would much rather pass the JavaScript function the faq ID then somehow pull the information from the database where it originates. I am 99% sure it is impossible to call an ASP function from within a JavaScript function, so I am kind of stumped. I am kind of new to AJAX/ASP.NET so this is a learning experience for me.

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• Suggestions for a PHP programmer wanting to create a timer app for an internet cafe

  - by grokker

  Hi, I was asked by a friend to make a timer app for his small internet cafe. He wants to have timers on each client PCs. The timers indicate how much time has been spent by the customer. On the PC that he uses, there's another program that has the overview of all the timers and there's a button for each client PCs that allows him to blacken out the screen. It's not automatic hence the button. The problem is I haven't done any desktop apps before so that's why I'm asking you guys (the awesome people at SO) for suggestions/advice on what language/tool to use. A little info about me: I did Java but haven't tried Swing though. I know a bit about Python and Ruby too. I don't mind learning new languages as long as I get to finish or get a prototype up and running. He doesn't mind if I could show him a prototype, it's actually for me. It gives me satisfaction to see I'm progressing. I'm not planning on asking him to pay me for doing this. Whatever he gives me is fine. P.S. He's using Windows XP

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• Rotating an object in OpenGL ES for iPhone [translate to origin --> rotate --> translate back is not

  - by ayanonagon

  I recently started working with OpenGL ES for the iPhone, and I am having a bit of trouble with it. I want to be able to rotate an object with your fingers. My problem is that I have my object placed at (0, 0, -3), and I would like to rotate it about its center. I know that I need to translate back to the origin, rotate, and then bring it back to the original place. I think I am facing a problem because I am using a matrix to keep track (?) of all of my rotations/translation/scaling etc, and I think it may be combining the operations in a way that order is not even considered (so the two translations would cancel each other). I just started learning OpenGL a day ago and am a complete newbie, so my assumption may be wrong. Here is the part of the in drawView that I am having trouble with: GLfloat matrix[16]; glGetFloatv(GL_MODELVIEW_MATRIX, matrix); glLoadIdentity(); glTranslatef(0, 0, 3); // bring to origin glRotatef(self.angle, self.dy, self.dx, 0); // rotate glTranslatef(0, 0, -3); // put it back in place glMultMatrixf(matrix); // save the transformations performed Help would be much appreciated, thank you!

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• ASP.Net Forms authentication provider issue

  - by George2

  Hello everyone, I am using VSTS 2008 + .Net 3.5 + ASP.Net to develop a simple web application. And I am using Forms authentication for my web site (I use command aspnet_regsql.exe to create a new database in SQL Server 2008 Enterprise to host database for Forms Authentication. I am not using SQL Server Express.). I am learning Forms authentication from here, http://msdn.microsoft.com/en-us/library/ff648345.aspx#paght000022_usingthesqlmembershipprovider my question is for the name of membership defaultProvider, the value must be "SqlProvider"? Or I can use any arbitrary name, for example like this (I replace the value "SqlProvider" to "MyTestSqlProvider")? <connectionStrings> <add name="MySqlConnection" connectionString="Data Source=MySqlServer;Initial Catalog=aspnetdb;Integrated Security=SSPI;" /> </connectionStrings> <system.web> ... <membership defaultProvider="MyTestSqlProvider" userIsOnlineTimeWindow="15"> <providers> <clear /> <add name="MyTestSqlProvider" type="System.Web.Security.SqlMembershipProvider" connectionStringName="MySqlConnection" applicationName="MyApplication" enablePasswordRetrieval="false" enablePasswordReset="true" requiresQuestionAndAnswer="true" requiresUniqueEmail="true" passwordFormat="Hashed" /> </providers> </membership> thanks in advance, George

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• How to get the ui:param value in Javabean

  - by mihaela

  Hello, I am learning facelets and Seam and I'm facing the following problem: I'm have 2 xhtml files, one includes the other and each one has its own Seam component as backing bean. I want to send and object to the included facelet and obtain that object in the backing bean corresponding to the included facelet. I'll take an example to explain better the situation: registration.xhtml with Seam component as backing bean Registration.java. In this class I have an object of type Person address.html with Seam component as backing bean Address.java. In this class i want to obtain the Person object from the Registration component and set the address. registration.xhtml includes the address.xhtml and passes an object using How to obtain this object in Address bean? Will be the same reference of the object from the Registration bean? is the solution of passing this object or there is another solution for that? (maybe f:attribute, but even in this case how do I obtain the object in bean) This example is simple and not necessarily realistic but I have a similar problem and I don't know how to solve it. Thanks in advance.

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• Tool for braceless, whitespace sensitive C syntax

  - by Ollie Saunders

  I'm writing some C at the moment and because I like whitespace sensitive syntax, I'd like to write it like this: #include <stdio.h> int main(void) printf("Hello, world!") return 0 Instead of this: #include <stdio.h> int main(void) { printf("Hello, world!"); return 0; } Does anybody know of a tool that will convert the former into the latter? Edit: I've really no interest in arguing with those that think this is a bad idea. By all means continue to think that, you have your reasons. But at least know this: I'm aware Python is a whitespace sensitive language but I have not used it. Why would I? I know Ruby already. Also know: I am not just learning C for the first time and I have used PHP and JavaScript for more than four years, so I am not requesting this out of some personal difficulty, lack of familiarity with block syntax, or dogmatic affiliation. I am also aware of what would be involved in writing one of these and that's not beyond my ability but I don't want this enough to justify spending the time writing one.

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• autocommit and @Transactional and Cascading with spring, jpa and hibernate

  - by subes

  Hi, what I would like to accomplish is the following: have autocommit enabled so per default all queries get commited if there is a @Transactional on a method, it overrides the autocommit and encloses all queries into a single transaction, thus overriding the autocommit if there is a @Transactional method that calls other @Transactional annotated methods, the outer most annotation should override the inner annotaions and create a larger transaction, thus annotations also override eachother I am currently still learning about spring-orm and couldn't find documentation about this and don't have a test project for this yet. So my questions are: What is the default behaviour of transactions in spring? If the default differs from my requirement, is there a way to configure my desired behaviour? Or is there a totally different best practice for transactions? --EDIT-- I have the following test-setup: @javax.persistence.Entity public class Entity { @Id @GeneratedValue private Integer id; private String name; public Integer getId() { return id; } public void setId(Integer id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } } @Repository public class Dao { @PersistenceContext private EntityManager em; public void insert(Entity ent) { em.persist(ent); } @SuppressWarnings("unchecked") public List<Entity> selectAll() { List<Entity> ents = em.createQuery("select e from " + Entity.class.getName() + " e").getResultList(); return ents; } } If I have it like this, even with autocommit enabled in hibernate, the insert method does nothing. I have to add @Transactional to the insert or the method calling insert for it to work... Is there a way to make @Transactional completely optional?

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• OpenGL depth buffer on Android

  - by kayahr

  I'm currently learning OpenGL ES programming on Android (2.1). I started with the obligatory rotating cube. It's rotating fine but I can't get the depth buffer to work. The polygons are always displayed in the order the GL commands render them. I do this during initialization of GL: gl.glClearColor(.5f, .5f, .5f, 1); gl.glShadeModel(GL10.GL_SMOOTH); gl.glClearDepthf(1f); gl.glEnable(GL10.GL_DEPTH_TEST); gl.glDepthFunc(GL10.GL_LEQUAL); gl.glHint(GL10.GL_PERSPECTIVE_CORRECTION_HINT, GL10.GL_NICEST); On surface-change I do this: gl.glViewport(0, 0, width, height); gl.glMatrixMode(GL10.GL_PROJECTION); gl.glLoadIdentity(); GLU.gluPerspective(gl, 45.0f, (float) width / (float) height, 0.1f, 100f); When I enable backface culling then everything looks correct. But backface culling is only a speed-optimization so it should also work with only the depth buffer or not? So what is missing here?

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• TFS and Forms Authentication

  - by George

  I don't know squat about TFS, other than as a user who has performed simple check in/outs. I just installed it locally and would like to do joint development with a friend. I was having trouble making my TFS web site on port 8080 visible (the whole scoop is here if your interested) and I wonder if it could be related to the fact that TFS is probably using Windows Authentication to identify the user. Can TFS be set up to use forms authentication? We probably need to set up a VPN, though that's a learning curve too. To use TFS, do our machines have to belong to a domain? We're not admin types, though he is better than me, though I would be interested in any feedback or advice on which path is likely to pan out the best. I already got AxoSoft OneTime working in this type of an environment and it suits us well, but I am tempted at all the bells & whistles with TFS and the ability to tie tracked bug items to code changes. As far as finding a good way to share code, do sites like SourceForge allow one to keep code secure among members only?

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• Which JavaScript framework for me?

  - by LeonixSolutions

  This is not to be a subjective question; nor is it intended to start a religious war. Which JavaScript framework for me? Until now, I haven't coded any JS at all (no biggy, it's just another language). I have been set in my ways and eschewed any client-side code, lest the user have JS turned off, or try to "just change this a little, to see what happens" - and then expect me to support it. So, until now it has all been server-side, with PHP and an ODBC compliant database. However, I am beginning to see advantages to client-side input validation and improved graphical experience for users which would help me to produce more professional web-based applications. I am looking for a framework which : doesn't have a steep learning curve is full-featured, although that does not mean that the one with the most features wins (remember the 80/20 rule) is mature an stable (even if still in development) integrates well with common IDEs if possible. I use NetBeans for PHP (and occasionally MS visual studio for C# (I seem to have drifted away from Eclipse)) allows me to develop web sites/apps for mobile devices support for Goggle charts (or other charting) would be a bonus has good AJAX/JSON support, but I imagine that they all do Taking that into consideration, is there a "right" framework for me, or does it not really matter? I looked briefly at JQuery and JQueryGui and liked what I saw, but I really don't have time, owing to deadlines, to try them all out and see which one suits me, much as I know that I ought to.

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• Ruby on Rails ActiveRecord/Include/Associations can't get my query to work

  - by Cypher

  I just started learning Rails and I'm just trying to set up query via associations. All the queries I try to write seem to be doing bizzare things and end up trying to query two tables parsed together with an '_' as one table. I have no clue why this would ever happen My tables are as follows: schools: id name variables: id name type var_entries: id variable_id entry school_entries: id school_id var_entry_id my rails association tables are $local = { :adapter => "mysql", :host => "localhost", :port => "3306".to_i, :database => "spy_2", :username =>"root", :password => "vertrigo" } class School < ActiveRecord::Base establish_connection $local has_many :school_entries has_many :var_entries, :through => school_entries end class Variable < ActiveRecord::Base establish_connection $local has_many :var_entries has_many :school_entries, :through => :var_entries end class VarEntry < ActiveRecord::Base establish_connection $local has_many_and_belongs_to :school_entries belongs_to :variables end class SchoolEntry < ActiveRecord::Base establish_connection $local belongs_to :school has_many :var_entries end I want to do this sql query: SELECT school_id, variable_id,rank FROM school_entries, variables, var_entries, schools WHERE var_entries.variable_id = variables.id AND school_entries.var_entry_id = var_entries.id AND schools.id = school_entries.school_id AND variables.type = 'number'; and put it into Rails notation: here is one of my many failed attempts schools = VarEntry.all(:include => [:school_entries, :variables], :conditions => "variables.type = 'number'") the error: 'const_missing': uninitialized constant VarEntry::Variables (NameError) if i remove variables schools = VarEntry.all(:include => [:school_entries, :variables], :conditions => "type = 'number'") the error is: Mysql::Error: Unkown column 'type' in 'where clause': SELECT * FROM 'var_entries' WHERE (type=number) (ActiveRecord::StatementInvalid) Can anyone tell me where I'm going horribly wrong?

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• Binary search in a sorted (memory-mapped ?) file in Java

  - by sds

  I am struggling to port a Perl program to Java, and learning Java as I go. A central component of the original program is a Perl module that does string prefix lookups in a +500 GB sorted text file using binary search (essentially, "seek" to a byte offset in the middle of the file, backtrack to nearest newline, compare line prefix with the search string, "seek" to half/double that byte offset, repeat until found...) I have experimented with several database solutions but found that nothing beats this in sheer lookup speed with data sets of this size. Do you know of any existing Java library that implements such functionality? Failing that, could you point me to some idiomatic example code that does random access reads in text files? Alternatively, I am not familiar with the new (?) Java I/O libraries but would it be an option to memory-map the 500 GB text file (I'm on a 64-bit machine with memory to spare) and do binary search on the memory-mapped byte array? I would be very interested to hear any experiences you have to share about this and similar problems.

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• subtotals in columns usind reshape2 in R

  - by user1043144

  I have spent some time now learning RESHAPE2 and plyr but I still do not get it. This time I have a problem with (a) subtotals and (b) passing different aggregate functions . Here an example using data from the excellent tutorial on the blog of mrdwab http://news.mrdwab.com/ # libraries library(plyr) library(reshape2) # get data and add few more variables book.sales = read.csv("http://news.mrdwab.com/data-booksales") book.sales$Stock = book.sales$Quantity + 10 book.sales$SubjCat[(book.sales$Subject == 'Economics') | (book.sales$Subject == 'Management') ] <- '1_EconSciences' book.sales$SubjCat[book.sales$Subject %in% c('Anthropology', 'Politics', 'Sociology') ] <- '2_SocSciences' book.sales$SubjCat[book.sales$Subject %in% c('Communication', 'Fiction', 'History', 'Research', 'Statistics') ] <- '3_other' # to get to my starting dataframe (close to the project I am working on) book.sales1 <- ddply(book.sales, c('Region', 'Representative', 'SubjCat', 'Subject', 'Publisher'), summarize, Stock = sum(Stock), Sold = sum(Quantity), Ratio = round((100 * sum(Quantity)/ sum(Stock)), digits = 1)) #melt it m.book.sales = melt(data = book.sales1, id.vars = c('Region', 'Representative', 'SubjCat', 'Subject', 'Publisher'), measured.vars = c('Stock', 'Sold', 'Ratio')) # cast it Tab1 <- dcast(data = m.book.sales, formula = Region + Representative ~ Publisher + variable, fun.aggregate = sum, margins = c('Region', 'Representative')) Now my questions : I have been able to add the subtotals in rows. But is it possible also to add margins in the columns. Say for example, Totals of Stock for one Publisher ? Sorry I meant to say example total sold for all publishers There is a problem with the columns with “ratio”. How can I get “mean” instead of “sum” for this variable ? P.S: I have seen some examples using reshape. Will you recommend to use it instead of reshape2 (which seems not to include the functionalities of two functions).

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• How to build a ~500 page Flash site

  - by philwilks

  I am about to embark on building a Flash site with approximately 500 pages. The site is an interactive learning type of system, with about 10 "chapters" each containing around 50 "pages". Each page has some sort of animation and interactivity, for example the user might have to decide whether a statement is true or false by clicking on one of two buttons, and then an appropriate response is displayed. The user can jump backwards and forwards between pages as they wish. As far as I know, these are some of my options... A) Build the entire site as a single Flash file with no external content. B) Build each of the 10 chapters as a separate Flash file, and then have a master Flash file which loads in the chapters. Each page would then be a separate movie clip within the chapter file. C) Build each indevidual page as a separate Flash file, and then have master Flash file which loads these in. At the moment I'm thinking that option B would be best, and I'd be very grateful for your thoughts on this! Of course, there are probably other options that I haven't thought of.

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• Django Threaded Commenting System

  - by Yasin Ozel

  (and sorry for my english) I am learning Python and Django. Now, my challange is developing threaded generic comment system. There is two models, Post and Comment. -Post can be commented. -Comment can be commented. (endless/threaded) -Should not be a n+1 query problem in system. (No matter how many comments, should not increase the number of queries) My current models are like this: class Post(models.Model): title = models.CharField(max_length=100) content = models.TextField() child = generic.GenericRelation( 'Comment', content_type_field='parent_content_type', object_id_field='parent_object_id' ) class Comment(models.Model): content = models.TextField() child = generic.GenericRelation( 'self', content_type_field='parent_content_type', object_id_field='parent_object_id' ) parent_content_type = models.ForeignKey(ContentType) parent_object_id = models.PositiveIntegerField() parent = generic.GenericForeignKey( "parent_content_type", "parent_object_id") Are my models right? And how can i get all comment (with hierarchy) of post, without n+1 query problem? Note: I know mttp and other modules but I want to learn this system. Edit: I run "Post.objects.all().prefetch_related("child").get(pk=1)" command and this gave me post and its child comment. But when I wanna get child command of child command a new query is running. I can change command to ...prefetch_related("child__child__child...")... then still a new query running for every depth of child-parent relationship. Is there anyone who has idea about resolve this problem?

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• What is the best way to handle autorotation with multiple subview?

  - by thangnguyen

  I am learning and programing an application. I do this project based on what I learned from the book Beginning iphone 3 development. I have two main questions here: I would like to create a multi utility application so I need multiple-view. I have a main view controller which will control switching between views. In this example I have two views A and B. I have 2 view controller A and B which will handles all of events on these 2 views. I have 2 nib files viewA.xib and viewB.xib. One of the uitility is reading PDF. So I create another class which handle the PDF file which can load a PDF page call PDFview. From Interface Builder, I selected class identity for view of the viewB.xib as PDFView class. The result is I can switching between View A and view B. View B will display the content of the PDF page. I am not sure if my solution is right or wrong but now I don't know how to handle the autorotation. The rotation will active the view controller B. But the PDFView handle how to display the PDF on the View. Could you please tell me how I should handle this in a right way? Second question: Should I create the subview automatically? In case I need to do the swipe page animation, how can I do that? I think that I need to load another subview so I can do the animation when swap view. But I think this solution will waste the resource. I can just load another page of the PDF, but in this case I don't know how to use animation? Please tell me how I should solve this? I highly appreciate your time reading and answering my question. Thang Nguyen

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• Python: OSX Library for fast full screen jpg/png display

  - by Parand

  Frustrated by lack of a simple ACDSee equivalent for OS X, I'm looking to hack one up for myself. I'm looking for a gui library that accommodates: Full screen image display High quality image fit-to-screen (for display) Low memory usage Fast display Reasonable learning curve (the simpler the better) Looks like there are several choices, so which is the best? Here are some I've run across: PyOpenGL PyGame PyQT wxpython I don't have any particular experience with any of these, nor any strong desire to become an expert - I'm looking for the simplest solution. What do you recommend? [Update] For those not familiar with ACDSee, here's what it does that I care about: Simple list/thubmnail display of images in a directory Sort by name/size/type Ability to view images full screen Single-key delete while viewing full screen Move to next/previous image while viewing full screen Ability to select a group of images for: move to / copy to directory delete resize ACDSee has a bunch of niceties as well, such as remembering directories you've moved images to in the past, remembering your resize settings, displaying the total size of the images you've selected, etc. I've tried most of the options I could find (including Xee) and none of them quite get there. Please keep in mind that this is a programming/library question, not a criticism of any of the existing tools.

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• How to compile ocaml to native code

  - by Indra Ginanjar

  i'm really interested learning ocaml, it fast (they said it could be compiled to native code) and it's functional. So i tried to code something easy like enabling mysql event scheduler. #load "unix.cma";; #directory "+mysql";; #load "mysql.cma";; let db = Mysql.quick_connect ~user:"username" ~password:"userpassword" ~database:"databasename"();; let sql = Printf.sprintf "SET GLOBAL EVENT_SCHEDULER=1;" in (Mysql.exec db sql);; It work fine on ocaml interpreter, but when i was trying to compile it to native (i'm using ubuntu karmic), neither of these command worked ocamlopt -o mysqleventon mysqleventon.ml unix.cmxa mysql.cmxa ocamlopt -o mysqleventon mysqleventon.ml unix.cma mysql.cma i also tried ocamlc -c mysqleventon.ml unix.cma mysql.cma all of them resulting same message File "mysqleventon.ml", line 1, characters 0-1: Error: Syntax error Then i tried to remove the "# load", so the code goes like this let db = Mysql.quick_connect ~user:"username" ~password:"userpassword" ~database:"databasename"();; let sql = Printf.sprintf "SET GLOBAL EVENT_SCHEDULER=1;" in (Mysql.exec db sql);; The ocamlopt resulting message File "mysqleventon.ml", line 1, characters 9-28: Error: Unbound value Mysql.quick_connect I hope someone could tell me, where did i'm doing wrong.

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• How do I add a header with data to a QTableWidget in Qt?

  - by San Jacinto

  Hi, I'm still learning Qt and I am indebted to the SO community for providing me with great, very timely answers to my Qt questions. Thank you. I'm quite confused on the idea of adding a header to a QTableWidget. What I'd like to do is have a table that contains information about team members. Each row for a member should contain his first and last name, each in its own cell, an email address in one cell, and office in the other cell. I'd to have a header above these columns to name them as appropriate. I'm trying to start off easy and get just the header to display "Last" (as in last name). Here is my code. int column = m_ui-teamTableWidget-columnCount(); m_ui-teamTableWidget-setColumnCount(column+1); QString* qq = new QString("Last"); m_ui-teamTableWidget-horizontalHeader()-model()-setHeaderData(0, Qt::Horizontal, QVariant(QVariant::String, &qq)); My table gets rendered corretly, but the header doesn't contain what I would expect. It contains 1 cell that contains the text "1". I am obviously doing something very silly here that is wrong, but i am lost. I keep pouring over the documentation, finding nothing. Here are the documentation links to the function calls I am making for the very last line. http://doc.trolltech.com/4.5/qtableview.html#horizontalHeader http://doc.trolltech.com/4.5/qabstractitemview.html#model http://doc.trolltech.com/4.5/qabstractitemmodel.html#setHeaderData Thanks for any and all help. Edit: HOW I SOLVED THE PROBLEM Using some help from the accepted answer, I came up with the following code: m_ui-teamTableWidget-setColumnCount(m_ui-teamTableWidget-columnCount()+1); QTableWidgetItem* qtwi = new QTableWidgetItem(QString("Last"),QTableWidgetItem::Type); m_ui-teamTableWidget-setHorizontalHeaderItem(0,qtwi);

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• Most efficient way to check for DBNull and then assign to a variable?

  - by ilitirit

  This question comes up occasionally but I haven't seen a satisfactory answer. A typical pattern is (row is a DataRow): if (row["value"] != DBNull.Value) { someObject.Member = row["value"]; } My first question is which is more efficient (I've flipped the condition): row["value"] == DBNull.Value; // Or row["value"] is DBNull; // Or row["value"].GetType() == typeof(DBNull) // Or... any suggestions? This indicates that .GetType() should be faster, but maybe the compiler knows a few tricks I don't? Second question, is it worth caching the value of row["value"] or does the compiler optimize the indexer away anyway? eg. object valueHolder; if (DBNull.Value == (valueHolder = row["value"])) {} Disclaimers: row["value"] exists. I don't know the column index of the column (hence the column name lookup) I'm asking specifically about checking for DBNull and then assignment (not about premature optimization etc). Edit: I benchmarked a few scenarios (time in seconds, 10000000 trials): row["value"] == DBNull.Value: 00:00:01.5478995 row["value"] is DBNull: 00:00:01.6306578 row["value"].GetType() == typeof(DBNull): 00:00:02.0138757 Object.ReferenceEquals has the same performance as "==" The most interesting result? If you mismatch the name of the column by case (eg. "Value" instead of "value", it takes roughly ten times longer (for a string): row["Value"] == DBNull.Value: 00:00:12.2792374 The moral of the story seems to be that if you can't look up a column by it's index, then ensure that the column name you feed to the indexer matches the DataColumn's name exactly. Caching the value also appears to be nearly twice as fast: No Caching: 00:00:03.0996622 With Caching: 00:00:01.5659920 So the most efficient method seems to be: object temp; string variable; if (DBNull.Value != (temp = row["value"]) { variable = temp.ToString(); } This was a good learning experience.

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