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• Psychology researcher wants to learn new language

  - by user273347

  I'm currently considering R, matlab, or python, but I'm open to other options. Could you help me pick the best language for my needs? Here are the criteria I have in mind (not in order): Simple to learn. I don't really have a lot of free time, so I'm looking for something that isn't extremely complicated and/or difficult to pick up. I know some C, FWIW. Good for statistics/psychometrics. I do a ton of statistics and psychometrics analysis. A lot of it is basic stuff that I can do with SPSS, but I'd like to play around with the more advanced stuff too (bootstrapping, genetic programming, data mining, neural nets, modeling, etc). I'm looking for a language/environment that can help me run my simpler analyses faster and give me more options than a canned stat package like SPSS. If it can even make tables for me, then it'll be perfect. I also do a fair bit of experimental psychology. I use a canned experiment "programming" software (SuperLab) to make most of my experiments, but I want to be able to program executable programs that I can run on any computer and that can compile the data from the experiments in a spreadsheet. I know python has psychopy and pyepl and matlab has psychtoolbox, but I don't know which one is best. If R had something like this, I'd probably be sold on R already. I'm looking for something regularly used in academe and industry. Everybody else here (including myself, so far) uses canned stat and experiment programming software. One of the reasons I'm trying to learn a programming language is so that I can keep up when I move to another lab. Looking forward to your comments and suggestions. Thank you all for your kind and informative replies. I appreciate it. It's still a tough choice because of so many strong arguments for each language. Python - Thinking about it, I've forgotten so much about C already (I don't even remember what to do with an array) that it might be better for me to start from scratch with a simple program that does what it's supposed to do. It looks like it can do most of the things I'll need it to do, though not as cleanly as R and MATLAB. R - I'm really liking what I'm reading about R. The packages are perfect for my statistical work now. Given the purpose of R, I don't think it's suited to building psychological experiments though. To clarify, what I mean is making a program that presents visual and auditory stimuli to my specifications (hundreds of them in a preset and/or randomized sequence) and records the response data gathered from participants. MATLAB - It's awesome that cognitive and neuro folk are recommending MATLAB, because I'm preparing for the big leap from social and personality psychology to cognitive neuro. The problem is the Uni where I work doesn't have MATLAB licenses (and 3750 GBP for a compiler license is not an option for me haha). Octave looks like a good alternative. PsychToolbox is compatible with Octave, thankfully. SQL - Thanks for the tip. I'll explore that option, too. Python will be the least backbreaking and most useful in the short term. R is well suited to my current work. MATLAB is well suited to my prospective work. It's a tough call, but I think I am now equipped to make a more well-informed decision about where to go next. Thanks again!

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• Update twitter profile image using OAuth

  - by sjobe

  I'm trying to get twitter update_profile_image to work using OAuth. I was using curl with regular authentication and everything was working fine, but I switched to OAuth using this library, and now everything except update_profile_image works. I read something about twitter OAuth having problems with multipart data, but that was a while ago and the plugin is supposed to have dealt with that issue. My working regular authentication with curl code $url = 'http://api.twitter.com/1/account/update_profile_image.xml'; $uname = $_POST['username']; $pword = $_POST['password']; $img_path = 'xxx'; $userpwd = $uname . ':' . $pword; $img_post = array('image' => '@' . $img_path . ';type=image/jpeg', 'tile' => 'true'); $format = 'xml'; //alternative: json $message = 'Test update with a random num'.rand(); $opts = array(CURLOPT_URL => $url, CURLOPT_FOLLOWLOCATION => true, CURLOPT_RETURNTRANSFER => true, CURLOPT_HEADER => true, CURLOPT_POST => true, CURLOPT_POSTFIELDS => $img_post, CURLOPT_HTTPAUTH => CURLAUTH_ANY, CURLOPT_USERPWD => $userpwd, CURLOPT_HTTPHEADER => array('Expect:'), CURLINFO_HEADER_OUT => true); $ch = curl_init(); curl_setopt_array($ch, $opts); $response = curl_exec($ch); $err = curl_error($ch); $info = curl_getinfo($ch); curl_close($ch); My current OAuth code [I had to cut it down, so do not minor look for syntax errors] include 'EpiCurl.php'; include 'EpiOAuth.php'; include 'EpiTwitter.php'; include 'secret.php'; $twitterObj = new EpiTwitter($consumer_key, $consumer_secret); $twitterObj->setToken($_GET['oauth_token']); $token = $twitterObj->getAccessToken(); $twitterObj->setToken($token->oauth_token, $token->oauth_token_secret); try{ $img_path = 'xxx'; //$twitterObj->post_accountUpdate_profile_image(array('@image' => "@".$img_path)); $twitterObj->post('/account/update_profile_image.json', array('@image' => "@".$img_path)); $twitterObj->post_statusesUpdate(array('status' => 'This is my new status:'.rand())); //This works $twitterInfo= $twitterObj->get_accountVerify_credentials(); echo $twitterInfo->responseText; }catch(Exception $e){ echo $e->getMessage(); } I've been trying to figure this out for a while, ANY help would be greatly appreciated. I'm not in any way tied to this library, so feel free to recommend others.

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• HTML: Place an image on top of another one

  - by Dimitris Baltas

  Inside a div, there is a picture that should have 10px margin in all directions from the DIV's border. On the left bottom corner of the picture there is an about-image. The picture is only displayed when its loaded in the DOM through jquery. The problem is that the existence of the about-image dislocates the picture downwards as many pixels as the height of the about-image. I am looking for the cleanest possible alternative to keep the picture inside the DIV and still display the about-image on top of it. Setting the picture as background will not work since i need the picture to load at once. Any improvement on the #about css would be greatly appreciated. Below is a full html page that reproduces the issue <html> <head> <title>Troubleshooting :: align the main picture inside the DIV</title> <style type="text/css"> html, body { background-color: #000000; } #about { z-index:2; position:relative; top:82%; left:3%; } #pic { width:100%; height:96%; } #main-content-image { height:100%; margin-right:10px; margin-left:10px; margin-top:10px; margin-bottom:10px; } #main-content { height:490px; border-width: 1px; border-style: solid; border-color: #777777; } #main-content-image.loading { background: url(http://farros.gr/images/ajax-loader2.gif) no-repeat center center; } a { text-decoration: none; text-decoration: none; color: #868686; outline:none; } .hide { display:none; } </style> <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"></script> <script type="text/javascript"> <!-- $(document).ready(function(){ $(function () { var img = new Image(); $(img).load(function () { $(this).hide(); $(this).width('100%'); $(this).height('96%'); $('#main-content-image').removeClass('loading').append(this); $(this).fadeIn(); }).error(function () { // notify the user that the image could not be loaded }).attr('src', 'http://farros.gr/images/bg.jpg'); }); }); </script> </head> <body> <div id="main-content"> <div id="main-content-image" class="loading"> <a href="#"><img id="about" src='http://farros.gr/images/about.png' alt='Haris Farros'/></a> </div> </div> </body> </html>

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• Recommended ASP.NET Shared Hosting (USA)

  - by coffeeaddict

  Ok, I have to admit I'm getting fed up with www.discountasp.net's pricing model and this annoyance has built up over the past 8 years or so. I've been with them for years and absolutely love them on the technical side, however it's getting ridiculously expensive for so little that you get. I mean here's my scenario: 1) I am running 2 SQL Server databases which costs me $10/ea per month so that's $20/month for 2 and I only get 500 mb disk space which is horrible 2) I am paying $10/mo just for the hosting itself which I only get 1 gig of disk space! I mean common! 3) I am simply running 2 small apps (Screwturn Wiki & Subtext Blog)...so I don't really care if it's up 99% or not, it's not worth paying a total of $300 just to keep these 2 apps running over discountasp.net Anyone else feel the same? Yes, I know they have great support, probably have great servers running behind this but in the end I really don't care as long as my site is up 95% or better. Yes, the hosting toolset rocks. But you know I bet you I can find a similar set somewhere else. I like how I can totally control IIS 7 at discountasp and I can control my own app pool etc. That's very powerful and essential. But anyone have any good alternatives to discountasp that gives me close to the same at a much more reasonable cost point? I mean http://www.m6.net/prices.aspx gives you 10 SQL Databases for $7 and 200 gigs disk space! I don't know about their tools or support but just looking at those numbers and some other hosts I've seen, I feel that discountasp.net is way out of line. They don't even offer any purchasing discounts such as it would be nice if my 2nd SQL Server is only $5/month not $10...stuff like this, to make it much more realistic and fair. Opinions (people who do have discountasp.net, people who have left them, or people who have another host they like)??? But geez $300 just to host a couple DBs and lightweight open source apps? Not worth the price they are charging. I'm almost at a price point that enables me to get a decent dedicated server! I really don't care about beta ASP.NET frameworks support. Not a big deal to me. If you have alternative suggestions rather than your experience with discountasp, I'd like to know how their toolset is. Do you have complete control over your DB in terms of adding users, and same goes for the web app pool, etc.? Discountasp.net's control panel rocks. I don't want to loose the ability to at least control and add virtual directories, recycle my dedicated app pool myself, backup my sql database myself, through tools which is what discountasp does give you. I'd also want to know that the hoster at least gets the latest and greatest in terms of non-beta ASP.NET related frameworks available to its shared hosters.

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• Mercurial "hg clone" on Windows via ssh with plink issue

  - by Kyle Tolle

  I have a Windows Server 2008 machine (iis7) that has CopSSH set up on it. To connect to it, I have a Windows 7 machine with Mercurial 1.5.1 (and TortoiseHg) installed. I can connect to the server using PuTTY with a non-standard ssh port and a .ppk file just fine. So I know the server can be SSH'd into. Next, I wanted to use the CLI to connect via hg clone to get a private repo. I've seen elsewhere that you need to have ssh configured in your mercurial.ini file, so my mercurial.ini has a line: ssh = plink.exe -ssh -C -l username -P #### -i "C:/Program Files/PuTTY/Key Files/KyleKey.ppk" Note: username is filled in with the username I set up via copSSH. #### is filled in with the non-standard ssh port I've defined for copSSH. I try to do the command hg clone ssh://inthom.com but I get this error: remote: bash: inthom.com: command not found abort: no suitable response from remote hg! It looks like hg or plink parses the hostname such that it thinks that inthom.com is a command instead of the server to ssh to. That's really odd. Next, I tried to just use plink to connect by plink -P #### ssh://inthom.com, and I am then prompted for my username, and next password. I enter them both and then I get this error: bash: ssh://inthom.com: No such file or directory So now it looks like plink doesn't parse the hostname correctly. I fiddled around for a while trying to figure out how to do call hg clone with an empty ssh:// field and eventually figured out that this command allows me to reach the server and clone a test repo on the inthom.com server: hg clone ssh://!/Repos/test ! is the character I've found that let's me leave the hostname blank, but specify the repo folder to clone. What I really don't understand is how plink knows what server to ssh to at all. neither my mercurial.ini nor the command specify a server. None of the hg clone examples I've seen have a ! character. They all use an address, which makes sense, so you can connect to any repo via ssh that you want to clone. My only guess is that it somehow defaults to the last server I used PuTTY to SSH to, but I SSH'd into another server, and then tried to use plink to get to it, but plink still defaults to inthom.com (verified with the -v arg to plink). So I am at a loss as to how plink gets this server value at all. For "fun", I tried using TortoiseHg and can only clone a repo when I use ssh://!/Repos/test as the Source. Now, you can see that, since plink doesn't parse the hostname correctly, I had to specify the port number and username in the mercurial.ini file, instead of in the hostname like [email protected]:#### like you'd expect to. Trying to figure this out at first drove me insane, because I would get errors that the host couldn't be reached, which I knew shouldn't be the case. My question is how can I configure my setup so that ssh://[email protected]:####/Repos/test is parsed correctly as the username, hostname, port number, and repo to copy? Is it something wrong with the version of plink that I'm using, or is there some setting I may have messed up? If it is plink's fault, is there an alternative tool I can use? I'm going to try to get my friend set up to connect to this same repo, so I'd like to have a clean solution instead of this ! business. Especially when I have no idea how plink gets this default server, so I'm not sure if he'd even be able to get to inthom.com correctly. PS. I've had to use a ton of different tutorials to even get to this stage. Therefore, I haven't tried pushing any changes to the server yet. Hopefully I'll get this figured out and then I can try pushing changes to the repo.

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• PHP mail send code not working

  - by acctman

  I'm trying to use this coding but its not processing, and its not outputing any errors. function send_email($subject='Activate Your Account', $html_content, $text_content, $headers) { $en['email'] = '[email protected]'; $to = $en['email']; $en['memb_id'] = '39'; $en['confcode'] = '69696969'; $en['user'] = 'couple'; $text_content = "Confirm Your domain.com Account\r\n"; $text_content.= "UserName: " . $en['user'] . "\r\n"; $text_content.= "Activate Your Account by visiting this link below:\r\n"; $text_content.= "http://www.domain.com/confirm/" . $en['memb_id'] . "/" . $en['confcode'] . "\r\n"; $text_content.= "\r\n"; $text_content.= "______________________\r\n"; $text_content.= "Thanks,\r\n"; $text_content.= "Staff"; $html_content = "<html><body><h1>Confirm Your domain.com Account</h1>"; $html_content.= "<p>UserName: " . $en['user'] . "<br>"; $html_content.= "Activate Your Account by visiting this link below:<br>"; $html_content.= "<a href=http://www.domain.com/confirm/" . $en['memb_id'] . "/" . $en['confcode'] . ">http://www.domain.com/confirm/" . $en['memb_id'] . "/" . $en['confcode'] . "</a>"; $html_content.= "</p>"; $html_content.= "______________________<br>"; $html_content.= "Thanks,<br>"; $html_content.= " Staff"; $html_content.= "</body></html>"; $mime_boundary = 'Multipart_Boundary_x'.md5(time()).'x'; $headers = "MIME-Version: 1.0\r\n"; $headers.= "Content-Type: multipart/alternative; boundary=\"$mime_boundary\"\r\n"; $headers.= "Content-Transfer-Encoding: 7bit\r\n"; $body = "This is a multi-part message in mime format.\n\n"; $body.= "--$mime_boundary\n"; $body.= "Content-Type: text/plain; charset=\"charset=us-ascii\"\n"; $body.= "Content-Transfer-Encoding: 7bit\n\n"; $body.= $text_content; $body.= "\n\n"; $body.= "--$mime_boundary\n"; $body.= "Content-Type: text/html; charset=\"UTF-8\"\n"; $body.= "Content-Transfer-Encoding: 7bit\n\n"; $body.= $html_content; $body.= "\n\n"; $body.= "--$mime_boundary--\n"; $headers.= 'From: <[email protected]>' . "\r\n"; $headers.= "X-Sender-IP: $_SERVER[SERVER_ADDR]\r\n"; $headers.= 'Date: '.date('n/d/Y g:i A')."\r\n"; $headers.= 'Reply-To: <[email protected]>' . "\r\n"; return mail($to, $subject, $body, $headers); echo $to; echo $subject; echo $body; echo $headers; }

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• Unable to launch onscreen keyboard (osk.exe) from a 32-bit process on Win7 x64

  - by Steven Robbins

  90% of the time I am unable to launch osk.exe from a 32bit process on Win7 x64. Originally the code was just using: Process.Launch("osk.exe"); Which won't work on x64 because of the directory virtualization. Not a problem I thought, I'll just disable virtualization, launch the app, and enable it again, which I thought was the correct way to do things. I also added some code to bring the keyboard back up if it has been minimized (which works fine) - the code (in a sample WPF app) now looks as follows: using System; using System.Collections.Generic; using System.Linq; using System.Text; using System.Windows; using System.Windows.Controls; using System.Windows.Data; using System.Windows.Documents; using System.Windows.Input; using System.Windows.Media; using System.Windows.Media.Imaging; using System.Windows.Navigation;using System.Diagnostics; using System.Runtime.InteropServices; namespace KeyboardTest { /// <summary> /// Interaction logic for MainWindow.xaml /// </summary> public partial class MainWindow : Window { [DllImport("kernel32.dll", SetLastError = true)] private static extern bool Wow64DisableWow64FsRedirection(ref IntPtr ptr); [DllImport("kernel32.dll", SetLastError = true)] public static extern bool Wow64RevertWow64FsRedirection(IntPtr ptr); private const UInt32 WM_SYSCOMMAND = 0x112; private const UInt32 SC_RESTORE = 0xf120; [DllImport("user32.dll", CharSet = CharSet.Auto)] static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam); private string OnScreenKeyboadApplication = "osk.exe"; public MainWindow() { InitializeComponent(); } private void KeyboardButton_Click(object sender, RoutedEventArgs e) { // Get the name of the On screen keyboard string processName = System.IO.Path.GetFileNameWithoutExtension(OnScreenKeyboadApplication); // Check whether the application is not running var query = from process in Process.GetProcesses() where process.ProcessName == processName select process; var keyboardProcess = query.FirstOrDefault(); // launch it if it doesn't exist if (keyboardProcess == null) { IntPtr ptr = new IntPtr(); ; bool sucessfullyDisabledWow64Redirect = false; // Disable x64 directory virtualization if we're on x64, // otherwise keyboard launch will fail. if (System.Environment.Is64BitOperatingSystem) { sucessfullyDisabledWow64Redirect = Wow64DisableWow64FsRedirection(ref ptr); } // osk.exe is in windows/system folder. So we can directky call it without path using (Process osk = new Process()) { osk.StartInfo.FileName = OnScreenKeyboadApplication; osk.Start(); osk.WaitForInputIdle(2000); } // Re-enable directory virtualisation if it was disabled. if (System.Environment.Is64BitOperatingSystem) if (sucessfullyDisabledWow64Redirect) Wow64RevertWow64FsRedirection(ptr); } else { // Bring keyboard to the front if it's already running var windowHandle = keyboardProcess.MainWindowHandle; SendMessage(windowHandle, WM_SYSCOMMAND, new IntPtr(SC_RESTORE), new IntPtr(0)); } } } } But this code, most of the time, throws the following exception on osk.Start(): The specified procedure could not be found at System.Diagnostics.Process.StartWithShellExecuteEx(ProcessStartInfo startInfo) I've tried putting long Thread.Sleep commands in around the osk.Start line, just to make sure it wasn't a race condition, but the same problem persists. Can anyone spot where I'm doing something wrong, or provide an alternative solution for this? It seems to work fine launching Notepad, it just won't play ball with the onscreen keyboard.

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• A methology that allows for a single Java code base covering many different versions?

  - by Thorbjørn Ravn Andersen

  I work in a small shop where we have a LOT of legacy Cobol code and where a methology has been adopted to allow us to minimize forking and branching as much as possible. For a given release we have three levels: CORE - bottom layer, this code is common to all releases GROUP - optional code common to several customers. CUSTOMER - optional code specific for a single customer. When a program is needed, it is first searched for in CUSTOMER, then in GROUP and finally in CORE. A given application for us invokes many programs which all are looked for in this sequence (think exe files and PATH under Windows). We also have Java programs interacting with this legacy code, and as the core-group-customer lookup mehchanism does not lend it self easily to Java it has tended to grow in a CVS branch for each customer, requiring much too much maintainance. The Java part and the backend part tend to be developed in parallel. I have been assigned to figure out a way to make the two worlds meet. Essentially we want a Java enviornment which allows us to have a single code base with sources for each release, where we easily can select a group and a customer and work with the application as it goes for that customer, and then easily switch to another codeset and THAT customer. I was thinking of perhaps a scenario with an Eclipse project for each core, customer, and group and then use Project Sets to select those we need for a given scenario. The problem I cannot get my head about, is how we would create robust code in the CORE projects which will work regardless of which group and customer is selected. A Factory class which knows which sub class of a passed Class object to invoke instead of each and every new? Others must have had similar code base management problems. Anybody with experiences to share? EDIT: The conclusion to this problem above has been that CVS needs to be replaced with a source code management system better suited for dealing with many branches concurrently and the migration of source from one component to the other while keeping history. Inspired by the recent migration by slf4j and logback we are currently looking at git as it handles branches very well. We've considered subversion and mercurial too but git appears to be better for single location, multibranched projects. I've asked about Perforce in another question, but my personal inclination is towards open source solutions for something as crucial as this. EDIT: After some more pondering, we've found that our actual pain point is that we use branches in CVS, and that branches in CVS are the easiest to work with if you branch ALL files! The revised conclusion is that we can do this with CVS alone, by switching to a forest of java projects, each corresponding to one of the levels above, and use the Eclipse build paths to tie them together so each CUSTOMER version pulls in the appropriate GROUP and CORE project. We still want to switch to a better versioning system but this is so important a decision so we want to delay it as much as possible. EDIT: I now have a proof-of-concept implementation of the CORE-GROUP-CUSTOMER concept using Google Guice 2.0 - the @ImplementedBy tag is just what we need. I wonder what everybody else does? Using if's all over the place? EDIT: Now I also need this functionality for web applications. Guice was until the JSR-330 is in place. Anybody with versioning experience? EDIT: JSR-330/299 is now in place with the JEE6 reference implementation Weld based on JBoss Seam and I have reimplemented the proof-of-concept with Weld and can see that if we use @Alternative along with ... in beans.xml we can get the behaviour we desire. I.e. provide a new implementation for a given functionality in CORE without changing a bit in the CORE jars. Initial reading up on the Servlet 3.0 specification indicates that it may support the same functionality for web application resources (not code). We will now do initial testing on the real application.

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• Extjs4: editable rowbody

  - by peter

  in my first ExtJs4 project i use a editable grid with the feature rowbody to have a big textfield displayed under each row. I want it to be editable on a dblclick. I succeeded in doing so by replacing the innerHTML of the rowbody by a textarea but the special keys don't do what they are supposed to do (move the cursor). If a use the textarea in a normal field i don't have this probem. Same problem in IE7 and FF4 gridInfo = Ext.create('Ext.ux.LiveSearchGridPanel', { id: 'gridInfo', height: '100%', width: '100%', store: storeInfo, columnLines: true, selType: 'cellmodel', columns: [ {text: "Titel", flex: 1, dataIndex: 'titel', field:{xtype:'textfield'}}, {text: "Tags", id: "tags", flex: 1, dataIndex: 'tags', field:{xtype:'textfield'}}, {text: "Hits", dataIndex: 'hits'}, {text: "Last Updated", renderer: Ext.util.Format.dateRenderer('d/m/Y'), dataIndex: 'lastChange'} ], plugins: [ Ext.create('Ext.grid.plugin.CellEditing', { clicksToEdit: 1 }) ], features: [ { ftype: 'rowbody', getAdditionalData: function(data, idx, record, orig) { var headerCt = this.view.headerCt, colspan = headerCt.getColumnCount(); return { rowBody: data.desc, //the big textfieldvalue, can't use a textarea here 8< rowBodyCls: this.rowBodyCls, rowBodyColspan: colspan }; } }, {ftype: 'rowwrap'} ] }); me.on('rowbodydblclick', function(gridView, el, event, o) { ... rb = td.down('.x-grid-rowbody').dom; var value = rb.innerText?rb.innerText:rb.textContent; rb.innerHTML = ''; Ext.create('Ext.form.field.TextArea', { id: 'textarea1', value : value, renderTo: rb, border: false, enterIsSpecial: true, enableKeyEvents: true, disableKeyFilter: true, listeners: { 'blur': function(el, o) { rb.innerHTML = el.value; }, 'specialkey': function(field, e){ console.log(e.keyCode); //captured but nothing happens } } }).show(); damn, can't publish my own solution, looks like somebody else has to answer, anyway, here is the function that works function editDesc(me, gridView, el, event, o) { var width = Ext.fly(el).up('table').getWidth(); var rb = event.target; var value = rb.innerText?rb.innerText:rb.textContent; rb.innerHTML = '' var txt = Ext.create('Ext.form.field.TextArea', { value : value, renderTo: rb, border: false, width: width, height: 300, enterIsSpecial: true, disableKeyFilter: true, listeners: { 'blur': function(el, o) { var value = el.value.replace('\n','<br>') rb.innerHTML = value; }, 'specialkey': function(field, e){ e.stopPropagation(); } } }); var txtTextarea = Ext.fly(rb).down('textarea'); txtTextarea.dom.style.color = 'blue'; txtTextarea.dom.style.fontSize = '11px'; } Hi Molecule Man, as an alternative to the approach above i tried the Ext.Editor. It works but i want it inline but when i render it to the rowbody, the field blanks and i have no editor, any ideas ? gridInfo = Ext.create('Ext.grid.Panel', { id: 'gridInfo', height: '100%', width: '100%', store: storeInfo, columnLines: true, selType: 'cellmodel', viewConfig: {stripeRows: false, trackOver: true}, columns: [ {text: "Titel", flex: 1, dataIndex: 'titel', field:{xtype:'textfield'}}, ... {text: "Last Updated", renderer: Ext.util.Format.dateRenderer('d/m/Y'), dataIndex: 'lastChange'} ], plugins: [ Ext.create('Ext.grid.plugin.CellEditing', { clicksToEdit: 1 }) ], features: [ { ftype: 'rowbody', getAdditionalData: function(data, idx, record, orig) { var headerCt = this.view.headerCt, colspan = headerCt.getColumnCount(); return { rowBody: data.desc, rowBodyCls: this.rowBodyCls, rowBodyColspan: colspan }; } } ], listeners:{ rowbodyclick: function(gridView, el, event) { //werkt editDesc(this, gridView, el, event); } } }); function editDesc(me, gridView, el, event, o) { var rb = event.target; me.txt = new Ext.Editor({ field: {xtype: 'textarea'}, updateEl: true, cancelOnEsc: true, floating: true, renderTo: rb //when i do this, the field becomes empty and i don't get the editor }); me.txt.startEdit(el); }

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• Weighted round robins via TTL - possible?

  - by Joe Hopfgartner

  I currently use DNS round robin for load balancing, which works great. The records look like this (I have a ttl of 120 seconds) ;; ANSWER SECTION: orion.2x.to. 116 IN A 80.237.201.41 orion.2x.to. 116 IN A 87.230.54.12 orion.2x.to. 116 IN A 87.230.100.10 orion.2x.to. 116 IN A 87.230.51.65 I learned that not every ISP / device treats such a response the same way. For example some DNS servers rotate the addresses randomly or always cycle them through. Some just propagate the first entry, others try to determine which is best (regionally near) by looking at the ip address. However if the userbase is big enough (spreads over multiple ISPs etc) it balances pretty well. The discrepancies from highest to lowest loaded server hardly every exceeds 15%. However now I have the problem that I am introducing more servers into the systems, that not all have the same capacities. I currently only have 1gbps servers, but I want to work with 100mbit and also 10gbps servers too. So what I want is I want to introduce a server with 10 GBps with a weight of 100, a 1 gbps server with a weight of 10 and a 100 mbit server with a weight of 1. I used to add servers twice to bring more traffic to them (which worked nice. the bandwidth doubled almost.) But adding a 10gbit server 100 times to DNS is a bit rediculous. So I thought about using the TTL. If I give server A 240 seconds ttl and server B only 120 seconds (which is about about the minimum to use for round robin, as a lot of dns servers set to 120 if a lower ttl is specified.. so i have heard) I think something like this should occour in an ideal scenario: first 120 seconds 50% of requests get server A -> keep it for 240 seconds. 50% of requests get server B -> keep it for 120 seconds second 120 seconds 50% of requests still have server A cached -> keep it for another 120 seconds. 25% of requests get server A -> keep it for 240 seconds 25% of requests get server B -> keep it for 120 seconds third 120 seconds 25% will get server A (from the 50% of Server A that now expired) -> cache 240 sec 25% will get server B (from the 50% of Server A that now expired) -> cache 120 sec 25% will have server A cached for another 120 seconds 12.5% will get server B (from the 25% of server B that now expired) -> cache 120sec 12.5% will get server A (from the 25% of server B that now expired) -> cache 240 sec fourth 120 seconds 25% will have server A cached -> cache for another 120 secs 12.5% will get server A (from the 25% of b that now expired) -> cache 240 secs 12.5% will get server B (from the 25% of b that now expired) -> cache 120 secs 12.5% will get server A (from the 25% of a that now expired) -> cache 240 secs 12.5% will get server B (from the 25% of a that now expired) -> cache 120 secs 6.25% will get server A (from the 12.5% of b that now expired) -> cache 240 secs 6.25% will get server B (from the 12.5% of b that now expired) -> cache 120 secs 12.5% will have server A cached -> cache another 120 secs ... i think i lost something at this point but i think you get the idea.... As you can see this gets pretty complicated to predict and it will for sure not work out like this in practice. But it should definitely have an effect on the distribution! I know that weighted round robin exists and is just controlled by the root server. It just cycles through dns records when responding and returns dns records with a set propability that corresponds to the weighting. My DNS server does not support this, and my requirements are not that precise. If it doesnt weight perfectly its okay, but it should go into the right direction. I think using the TTL field could be a more elegant and easier solution - and it deosnt require a dns server that controls this dynamically, which saves resources - which is in my opinion the whole point of dns load balancing vs hardware load balancers. My question now is... are there any best prectices / methos / rules of thumb to weight round robin distribution using the TTL attribute of DNS records? Edit: The system is a forward proxy server system. The amount of Bandwidth (not requests) exceeds what one single server with ethernet can handle. So I need a balancing solution that distributes the bandwidth to several servers. Are there any alternative methods than using DNS? Of course I can use a load balancer with fibre channel etc, but the costs are rediciulous and it also increases only the width of the bottleneck and does not eliminate it. The only thing i can think of are anycast (is it anycast or multicast?) ip addresses, but I don't have the means to set up such a system.

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• performing authorisation/authentication between webservices

  - by mary

  Hi, i am developing webservices.In that i want to maintain state information so that all WebMethods could be access only after Login. I have tried but getting problem. I am attaching my code. Any other alternative will also be welcomed. [ WebService(Namespace = "http://amSubfah.org/")] [ WebServiceBinding(ConformsTo = WsiProfiles.BasicProfile1_1)] // To allow this Web Service to be called from script, using ASP.NET AJAX, uncomment the following line. // [System.Web.Script.Services.ScriptService] public class Login : System.Web.Services.WebService { Message msgObj = new Message(); BaseClass b = new BaseClass(); PasswordEncryptionDecryption pedObj = new PasswordEncryptionDecryption(); public AuthHeader Authentication=new AuthHeader (); public Login () { //Uncomment the following line if using designed components //InitializeComponent(); } [ SoapHeader("Authentication", Required = true)] [System.Web.Services. WebMethod(EnableSession = true)] public string checkUserLogin(string user, string pwd) { DataSet dsLogin = new DataSet(); List sqlParams = new List(); SqlParameter sqlParam1 = new SqlParameter("@UserName", SqlDbType.NVarChar); sqlParam1.Value = user; sqlParams.Add(sqlParam1); SqlParameter sqlParam2 = new SqlParameter("@Password", SqlDbType.NVarChar); string pass = pedObj.encryptPassword(pwd); sqlParam2.Value = pass; sqlParams.Add(sqlParam2); try { b.initializeDBConnection(); dsLogin = b.execSelectLoginQuery( Query.strSelectLoginData, sqlParams); } catch (SqlException sqlEx) { string str = msgObj.msgErrorMessage + sqlEx.Message + sqlEx.StackTrace; } {if ((dsLogin != null) && (dsLogin.Tables[0].Rows.Count != 0)) { Session[ "username"] = user; string sessionId = System.Guid.NewGuid().ToString(); Authentication.sessionId = sessionId; Authentication.Username = user; return msgObj.msgLoginSuccess; } else return msgObj .msgLoginFail ; } //webmethod for registration [ SoapHeader("Authentication", Required = true)] [System .Web .Services . WebMethod (EnableSession =true )] public string insertRegistrationDetails(string fName,string lName,string email,string pwd) { //string u = Session["username"].ToString(); //if (u == "") //{ // //checkUserLogin(fName,pwd ); // return "Please login first"; //} if (Authentication.Username == null || Authentication.sessionId == null) { return "Please Login first"; } List sqlParams = new List(); int insert = 0; string msg = "" ; SqlParameter sqlParam = new SqlParameter("@FName", SqlDbType.NVarChar); sqlParam.Value = fName; sqlParam.Size = 50; sqlParams.Add(sqlParam); SqlParameter sqlParam1 = new SqlParameter("@LName", SqlDbType.NVarChar); sqlParam1.Value = lName; sqlParam1.Size = 50; sqlParams.Add(sqlParam1); SqlParameter sqlParam5 = new SqlParameter("@Email", SqlDbType.NVarChar); sqlParam5.Value = email; sqlParam5.Size = 50; sqlParams.Add(sqlParam5); SqlParameter sqlParam7 = new SqlParameter("@Password", SqlDbType.NVarChar); sqlParam7.Value = pedObj .encryptPassword (pwd); sqlParam7.Size = 50; sqlParams.Add(sqlParam7); try { b.initializeDBConnection(); insert = b.execByKeyParams( Query.strInsertIntoRegistrationTable1, sqlParams); if (insert !=0) { msg = msgObj .msgRecInsertedSuccess ; } } catch (SqlException sqlEx) { string str = msgObj.msgErrorMessage + sqlEx.Message + sqlEx.StackTrace; } return msg; } public class AuthHeader : SoapHeader { public string Username; public string sessionId; } }

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• help needed on deciphering the g++ vtable dumps

  - by Ganesh Kundapur

  Hi, for the fallow class hierarchy class W { public: virtual void f() { cout << "W::f()" << endl; } virtual void g() { cout << "W::g()" << endl; } }; class AW : public virtual W { public: void g() { cout << "AW::g()" << endl; } }; class BW : public virtual W { public: void f() { cout << "BW::f()" << endl; } }; class CW : public AW, public BW { }; g++ -fdump-class-hierarchy is Vtable for W W::_ZTV1W: 4u entries 0 (int ()(...))0 4 (int ()(...))(& _ZTI1W) 8 W::f 12 W::g Class W size=4 align=4 base size=4 base align=4 W (0xb6e3da50) 0 nearly-empty vptr=((& W::_ZTV1W) + 8u) Vtable for AW AW::_ZTV2AW: 7u entries 0 0u 4 0u 8 0u 12 (int ()(...))0 16 (int ()(...))(& _ZTI2AW) 20 W::f 24 AW::g VTT for AW AW::_ZTT2AW: 2u entries 0 ((& AW::_ZTV2AW) + 20u) 4 ((& AW::_ZTV2AW) + 20u) Class AW size=4 align=4 base size=4 base align=4 AW (0xb6dbf6c0) 0 nearly-empty vptridx=0u vptr=((& AW::_ZTV2AW) + 20u) W (0xb6e3da8c) 0 nearly-empty virtual primary-for AW (0xb6dbf6c0) vptridx=4u vbaseoffset=-0x00000000000000014 Vtable for BW BW::_ZTV2BW: 7u entries 0 0u 4 0u 8 0u 12 (int ()(...))0 16 (int ()(...))(& _ZTI2BW) 20 BW::f 24 W::g VTT for BW BW::_ZTT2BW: 2u entries 0 ((& BW::_ZTV2BW) + 20u) 4 ((& BW::_ZTV2BW) + 20u) Class BW size=4 align=4 base size=4 base align=4 BW (0xb6dbf7c0) 0 nearly-empty vptridx=0u vptr=((& BW::_ZTV2BW) + 20u) W (0xb6e3dac8) 0 nearly-empty virtual primary-for BW (0xb6dbf7c0) vptridx=4u vbaseoffset=-0x00000000000000014 Vtable for CW CW::_ZTV2CW: 14u entries 0 0u 4 0u 8 4u 12 (int ()(...))0 16 (int ()(...))(& _ZTI2CW) 20 BW::_ZTv0_n12_N2BW1fEv 24 AW::g 28 4294967292u 32 4294967292u 36 0u 40 (int ()(...))-0x00000000000000004 44 (int ()(...))(& _ZTI2CW) 48 BW::f 52 0u Construction vtable for AW (0xb6dbf8c0 instance) in CW CW::_ZTC2CW0_2AW: 7u entries 0 0u 4 0u 8 0u 12 (int ()(...))0 16 (int ()(...))(& _ZTI2AW) 20 W::f 24 AW::g Construction vtable for BW (0xb6dbf900 instance) in CW CW::_ZTC2CW4_2BW: 13u entries 0 4294967292u 4 4294967292u 8 0u 12 (int ()(...))0 16 (int ()(...))(& _ZTI2BW) 20 BW::f 24 0u 28 0u 32 4u 36 (int ()(...))4 40 (int ()(...))(& _ZTI2BW) 44 BW::_ZTv0_n12_N2BW1fEv 48 W::g VTT for CW CW::_ZTT2CW: 7u entries 0 ((& CW::_ZTV2CW) + 20u) 4 ((& CW::_ZTC2CW0_2AW) + 20u) 8 ((& CW::_ZTC2CW0_2AW) + 20u) 12 ((& CW::_ZTC2CW4_2BW) + 20u) 16 ((& CW::_ZTC2CW4_2BW) + 44u) 20 ((& CW::_ZTV2CW) + 20u) 24 ((& CW::_ZTV2CW) + 48u) Class CW size=8 align=4 base size=8 base align=4 CW (0xb6bea2d0) 0 vptridx=0u vptr=((& CW::_ZTV2CW) + 20u) AW (0xb6dbf8c0) 0 nearly-empty primary-for CW (0xb6bea2d0) subvttidx=4u W (0xb6e3db04) 0 nearly-empty virtual primary-for AW (0xb6dbf8c0) vptridx=20u vbaseoffset=-0x00000000000000014 BW (0xb6dbf900) 4 nearly-empty lost-primary subvttidx=12u vptridx=24u vptr=((& CW::_ZTV2CW) + 48u) W (0xb6e3db04) alternative-path what are each entries in Vtable for AW AW::_ZTV2AW: 7u entries 0 0u // ? 4 0u // ? 8 0u // ? Vtable for CW CW::_ZTV2CW: 14u entries 0 0u // ? 4 0u // ? 8 4u // ? 12 (int ()(...))0 16 (int ()(...))(& _ZTI2CW) 20 BW::_ZTv0_n12_N2BW1fEv // ? 24 AW::g 28 4294967292u // ? 32 4294967292u // ? 36 0u // ? 40 (int ()(...))-0x00000000000000004 // some delta 44 (int ()(...))(& _ZTI2CW) 48 BW::f 52 0u // ? Thanks, Ganesh

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• How do you stop scripters from slamming your website hundreds of times a second?

  - by davebug

  [update] I've accepted an answer, as lc deserves the bounty due to the well thought-out answer, but sadly, I believe we're stuck with our original worst case scenario: CAPTCHA everyone on purchase attempts of the crap. Short explanation: caching / web farms make it impossible for us to actually track hits, and any workaround (sending a non-cached web-beacon, writing to a unified table, etc.) slows the site down worse than the bots would. There is likely some pricey bit of hardware from Cisco or the like that can help at a high level, but it's hard to justify the cost if CAPTCHAing everyone is an alternative. I'll attempt to do a more full explanation in here later, as well as cleaning this up for future searchers (though others are welcome to try, as it's community wiki). I've added bounty to this question and attempted to explain why the current answers don't fit our needs. First, though, thanks to all of you who have thought about this, it's amazing to have this collective intelligence to help work through seemingly impossible problems. I'll be a little more clear than I was before: This is about the bag o' crap sales on woot.com. I'm the president of Woot Workshop, the subsidiary of Woot that does the design, writes the product descriptions, podcasts, blog posts, and moderates the forums. I work in the css/html world and am only barely familiar with the rest of the developer world. I work closely with the developers and have talked through all of the answers here (and many other ideas we've had). Usability of the site is a massive part of my job, and making the site exciting and fun is most of the rest of it. That's where the three goals below derive. CAPTCHA harms usability, and bots steal the fun and excitement out of our crap sales. To set up the scenario a little more, bots are slamming our front page tens of times a second screenscraping (and/or scanning our rss) for the Random Crap sale. The moment they see that, it triggers a second stage of the program that logs in, clicks I want One, fills out the form, and buys the crap. In current (2/6/2009) order of votes: lc: On stackoverflow and other sites that use this method, they're almost always dealing with authenticated (logged in) users, because the task being attempted requires that. On Woot, anonymous (non-logged) users can view our home page. In other words, the slamming bots can be non-authenticated (and essentially non-trackable except by IP address). So we're back to scanning for IPs, which a) is fairly useless in this age of cloud networking and spambot zombies and b) catches too many innocents given the number of businesses that come from one IP address (not to mention the issues with non-static IP ISPs and potential performance hits to trying to track this). Oh, and having people call us would be the worst possible scenario. Can we have them call you? BradC Ned Batchelder's methods look pretty cool, but they're pretty firmly designed to defeat bots built for a network of sites. Our problem is bots are built specifically to defeat our site. Some of these methods could likely work for a short time until the scripters evolved their bots to ignore the honeypot, screenscrape for nearby label names instead of form ids, and use a javascript-capable browser control. lc again "Unless, of course, the hype is part of you

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• drupal_get_form is not passing along node array

  - by ElectronicBlacksmith

  I have not been able to get drupal_get_form to pass on the node data. Code snippets are below. The drupal_get_form documentation (api.drupal.org) states that it will pass on the extra parameters. I am basing the node data not being passed because (apparently) $node['language'] is not defined in hook_form which causes $form['qqq'] not to be created and thus the preview button shows up. My goal here is that the preview button show up using path "node/add/author" but doesn't show up for "milan/author/add". Any alternative methods for achieving this goal would be helpful but the question I want answered is in the preceding paragraph. Everything I've read indicates that it should work. This menu item $items['milan/author/add'] = array( 'title' = 'Add Author', 'page callback' = 'get_author_form', 'access arguments' = array('access content'), 'file' = 'author.pages.inc', ); calls this code function get_author_form() { //return node_form(NULL,NULL); //return drupal_get_form('author_form'); return author_ajax_form('author'); } function author_ajax_form($type) { global $user; module_load_include('inc', 'node', 'node.pages'); $types = node_get_types(); $type = isset($type) ? str_replace('-', '_', $type) : NULL; // If a node type has been specified, validate its existence. if (isset($types[$type]) && node_access('create', $type)) { // Initialize settings: $node = array('uid' = $user-uid, 'name' = (isset($user-name) ? $user-name : ''), 'type' = $type, 'language' = 'bbb','bbb' = 'TRUE'); $output = drupal_get_form($type .'_node_form', $node); } return $output; } And here is the hook_form and hook_form_alter code function author_form_author_node_form_alter(&$form, &$form_state) { $form['author']=NULL; $form['taxonomy']=NULL; $form['options']=NULL; $form['menu']=NULL; $form['comment_settings']=NULL; $form['files']=NULL; $form['revision_information']=NULL; $form['attachments']=NULL; if($form["qqq"]) { $form['buttons']['preview']=NULL; } } function author_form(&$node) { return make_author_form(&$node); } function make_author_form(&$node) { global $user; $type = node_get_types('type', $node); $node = author_make_title($node); drupal_set_breadcrumb(array(l(t('Home'), NULL), l(t($node-title), 'node/' . $node-nid))); $form['authorset'] = array( '#type' = 'fieldset', '#title' = t('Author'), '#weight' = -50, '#collapsible' = FALSE, '#collapsed' = FALSE, ); $form['author_id'] = array( '#access' = user_access('create pd_recluse entries'), '#type' = 'hidden', '#default_value' = $node-author_id, '#weight' = -20 ); $form['authorset']['last_name'] = array( '#type' = 'textfield', '#title' = t('Last Name'), '#maxlength' = 60, '#default_value' = $node-last_name ); $form['authorset']['first_name'] = array( '#type' = 'textfield', '#title' = t('First Name'), '#maxlength' = 60, '#default_value' = $node-first_name ); $form['authorset']['middle_name'] = array( '#type' = 'textfield', '#title' = t('Middle Name'), '#maxlength' = 60, '#default_value' = $node-middle_name ); $form['authorset']['suffix_name'] = array( '#type' = 'textfield', '#title' = t('Suffix Name'), '#maxlength' = 14, '#default_value' = $node-suffix_name ); $form['authorset']['body_filter']['body'] = array( '#access' = user_access('create pd_recluse entries'), '#type' = 'textarea', '#title' = 'Describe Author', '#default_value' = $node-body, '#required' = FALSE, '#weight' = -19 ); $form['status'] = array( '#type' = 'hidden', '#default_value' = '1' ); $form['promote'] = array( '#type' = 'hidden', '#default_value' = '1' ); $form['name'] = array( '#type' = 'hidden', '#default_value' = $user-name ); $form['format'] = array( '#type' = 'hidden', '#default_value' = '1' ); // NOTE in node_example there is some addition code here not needed for this simple node-type $thepath='milan/author'; if($_REQUEST["theletter"]) { $thepath .= "/" . $_REQUEST["theletter"]; } if($node['language']) { $thepath='milan/authorajaxclose'; $form['qqq'] = array( '#type' = 'hidden', '#default_value' = '1' ); } $form['#redirect'] = $thepath; return $form; } That menu path coincides with this theme (PHPTemplate)

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• Paging, sorting and filtering in a stored procedure (SQL Server)

  - by Fruitbat

  I was looking at different ways of writing a stored procedure to return a "page" of data. This was for use with the asp ObjectDataSource, but it could be considered a more general problem. The requirement is to return a subset of the data based on the usual paging paremeters, startPageIndex and maximumRows, but also a sortBy parameter to allow the data to be sorted. Also there are some parameters passed in to filter the data on various conditions. One common way to do this seems to be something like this: [Method 1] ;WITH stuff AS ( SELECT CASE WHEN @SortBy = 'Name' THEN ROW_NUMBER() OVER (ORDER BY Name) WHEN @SortBy = 'Name DESC' THEN ROW_NUMBER() OVER (ORDER BY Name DESC) WHEN @SortBy = ... ELSE ROW_NUMBER() OVER (ORDER BY whatever) END AS Row, ., ., ., FROM Table1 INNER JOIN Table2 ... LEFT JOIN Table3 ... WHERE ... (lots of things to check) ) SELECT * FROM stuff WHERE (Row > @startRowIndex) AND (Row <= @startRowIndex + @maximumRows OR @maximumRows <= 0) ORDER BY Row One problem with this is that it doesn't give the total count and generally we need another stored procedure for that. This second stored procedure has to replicate the parameter list and the complex WHERE clause. Not nice. One solution is to append an extra column to the final select list, (SELECT COUNT(*) FROM stuff) AS TotalRows. This gives us the total but repeats it for every row in the result set, which is not ideal. [Method 2] An interesting alternative is given here (http://www.4guysfromrolla.com/articles/032206-1.aspx) using dynamic SQL. He reckons that the performance is better because the CASE statement in the first solution drags things down. Fair enough, and this solution makes it easy to get the totalRows and slap it into an output parameter. But I hate coding dynamic SQL. All that 'bit of SQL ' + STR(@parm1) +' bit more SQL' gubbins. [Method 3] The only way I can find to get what I want, without repeating code which would have to be synchronised, and keeping things reasonably readable is to go back to the "old way" of using a table variable: DECLARE @stuff TABLE (Row INT, ...) INSERT INTO @stuff SELECT CASE WHEN @SortBy = 'Name' THEN ROW_NUMBER() OVER (ORDER BY Name) WHEN @SortBy = 'Name DESC' THEN ROW_NUMBER() OVER (ORDER BY Name DESC) WHEN @SortBy = ... ELSE ROW_NUMBER() OVER (ORDER BY whatever) END AS Row, ., ., ., FROM Table1 INNER JOIN Table2 ... LEFT JOIN Table3 ... WHERE ... (lots of things to check) SELECT * FROM stuff WHERE (Row > @startRowIndex) AND (Row <= @startRowIndex + @maximumRows OR @maximumRows <= 0) ORDER BY Row (Or a similar method using an IDENTITY column on the table variable). Here I can just add a SELECT COUNT on the table variable to get the totalRows and put it into an output parameter. I did some tests and with a fairly simple version of the query (no sortBy and no filter), method 1 seems to come up on top (almost twice as quick as the other 2). Then I decided to test probably I needed the complexity and I needed the SQL to be in stored procedures. With this I get method 1 taking nearly twice as long as the other 2 methods. Which seems strange. Is there any good reason why I shouldn't spurn CTEs and stick with method 3? UPDATE - 15 March 2012 I tried adapting Method 1 to dump the page from the CTE into a temporary table so that I could extract the TotalRows and then select just the relevant columns for the resultset. This seemed to add significantly to the time (more than I expected). I should add that I'm running this on a laptop with SQL Server Express 2008 (all that I have available) but still the comparison should be valid. I looked again at the dynamic SQL method. It turns out I wasn't really doing it properly (just concatenating strings together). I set it up as in the documentation for sp_executesql (with a parameter description string and parameter list) and it's much more readable. Also this method runs fastest in my environment. Why that should be still baffles me, but I guess the answer is hinted at in Hogan's comment.

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• Faster method for Matrix vector product for large matrix in C or C++ for use in GMRES

  - by user35959

  I have a large, dense matrix A, and I aim to find the solution to the linear system Ax=b using an iterative method (in MATLAB was the plan using its built in GMRES). For more than 10,000 rows, this is too much for my computer to store in memory, but I know that the entries in A are constructed by two known vectors x and y of length N and the entries satisfy: A(i,j) = .5*(x[i]-x[j])^2+([y[i]-y[j])^2 * log(x[i]-x[j])^2+([y[i]-y[j]^2). MATLAB's GMRES command accepts as input a function call that can compute the matrix vector product A*x, which allows me to handle larger matrices than I can store in memory. To write the matrix-vecotr product function, I first tried this in matlab by going row by row and using some vectorization, but I avoid spawning the entire array A (since it would be too large). This was fairly slow unfortnately in my application for GMRES. My plan was to write a mex file for MATLAB to, which is in C, and ideally should be significantly faster than the matlab code. I'm rather new to C, so this went rather poorly and my naive attempt at writing the code in C was slower than my partially vectorized attempt in Matlab. #include <math.h> #include "mex.h" void Aproduct(double *x, double *ctrs_x, double *ctrs_y, double *b, mwSize n) { mwSize i; mwSize j; double val; for (i=0; i<n; i++) { for (j=0; j<i; j++) { val = pow(ctrs_x[i]-ctrs_x[j],2)+pow(ctrs_y[i]-ctrs_y[j],2); b[i] = b[i] + .5* val * log(val) * x[j]; } for (j=i+1; j<n; j++) { val = pow(ctrs_x[i]-ctrs_x[j],2)+pow(ctrs_y[i]-ctrs_y[j],2); b[i] = b[i] + .5* val * log(val) * x[j]; } } } The above is the computational portion of the code for the matlab mex file (which is slightly modified C, if I understand correctly). Please note that I skip the case i=j, since in that case the variable val will be a 0*log(0), which should be interpreted as 0 for me, so I just skip it. Is there a more efficient or faster way to write this? When I call this C function via the mex file in matlab, it is quite slow, slower even than the matlab method I used. This surprises me since I suspected that C code should be much faster than matlab. The alternative matlab method which is partially vectorized that I am comparing it with is function Ax = Aprod(x,ctrs) n = length(x); Ax = zeros(n,1); for j=1:(n-3) v = .5*((ctrs(j,1)-ctrs(:,1)).^2+(ctrs(j,2)-ctrs(:,2)).^2).*log((ctrs(j,1)-ctrs(:,1)).^2+(ctrs(j,2)-ctrs(:,2)).^2); v(j)=0; Ax(j) = dot(v,x(1:n-3); end (the n-3 is because there is actually 3 extra components, but they are dealt with separately,so I excluded that code). This is partly vectorized and only needs one for loop, so it makes some sense that it is faster. However, I was hoping I could go even faster with C+mex file. Any suggestions or help would be greatly appreciated! Thanks! EDIT: I should be more clear. I am open to any faster method that can help me use GMRES to invert this matrix that I am interested in, which requires a faster way of doing the matrix vector product without explicitly loading the array into memory. Thanks!

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• Multidimensional array problem in VHDL?

  - by Nektarios

  I'm trying to use a multidimensional array in VHDL and I'm having a lot of trouble getting it to work properly. My issue is that I've got an array of 17, of 16 vectors, of a given size. What I want to do is create 17 registers that are array of 16 * std_logic_vector of 32 bits (which = my b, 512). So, I'm trying to pass in something to input and output on the register instantiation that tells the compiler/synthesizer that I want to pass in something that is 512 bits worth... Similar to in C if I had: int var[COLS][ROWS][ELEMENTS]; memcpy(&var[3].. // I'm talking about 3rd COL here, passing in memory that is ROWS*ELEMENTS long (My actual declaration is here:) type partial_pipeline_registers_type is array (0 to 16, 0 to 15) of std_logic_vector(iw - 1 downto 0); signal h_blk_pipelined_input : partial_pipeline_registers_type; I tried simply using h_blk_pipelined_input(0) .. up to (16) but this doesn't work. I get the following error, which makes me see that I need to double index in to the array: ERROR:HDLParsers:821 - (at the register) Wrong index type for h_blk_pipelined_input. So then I tried what's below, and I get this error: ERROR:HDLParsers:164 - (at the register code). parse error, unexpected TO, expecting COMMA or CLOSEPAR instantiate_h_pipelined_reg : regn generic map ( N=> b, init => bzeros ) port map ( clk => clk , rst => '0', en => '1', input => h_blk_pipelined_input((i - 1), 0 to 15), output=> h_blk_pipelined_input((i), 0 to 15)); -- Changing 0 to 15 to (0 to 15) has no effect... I'm using XST, and from their documentation (http://www.xilinx.com/itp/xilinx6/books/data/docs/xst/xst0067_9.html), the above should have worked: ...declaration: subtype MATRIX15 is array(4 downto 0, 2 downto 0) of STD_LOGIC_VECTOR (7 downto 0); A multi-dimensional array signal or variable can be completely used: Just a slice of one row can be specified: MATRIX15 (4,4 downto 1) <= TAB_B (3 downto 0); One alternative is that I can create more registers that are 16 times smaller, and instead of trying to do all '0 to 15' at once, I would just do that 15 additional times. However, I think this may lead to inefficiency in synthesis and I don't feel like this is the right solution. EDIT: Tried what Ben said, instantiate_h_m_qa_pipeline_registers: for i in 1 to 16 generate instantiate_h_pipelined_reg : regn generic map ( N=> b, init => bzeros ) port map ( clk => clk , rst => '0', en => '1', input => h_blk_pipelined_input(i - 1), output=> h_blk_pipelined_input(i)); end generate instantiate_h_m_qa_pipeline_registers; The signals are now defined as: type std_logic_block is array (0 to 15) of std_logic_vector(iw - 1 downto 0) ; type partial_pipeline_registers_type is array (0 to 16) of std_logic_block; signal h_blk_pipelined_input : partial_pipeline_registers_type; And the error I get from XST is: ERROR:HDLParsers:800 - ((where the register part is)) Type of input is incompatible with type of h_blk_pipelined_input. I'm able to do everything I was able to do before, using ()() syntax instead of ( , ) so I haven't lost anything going this way, but it still doesn't resolve my problem.

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• surfaceDestroyed called out of turn

  - by Avasulthiris

  I'm currently developing on minimum sdk version 3 (Android 1.5 - cupcake) and I'm having a strange unexplained issue that I have not been able to solve on my own. It is now becoming a rather urgent issue as I've already missed 1 deadline... I'm writing a high-level library to make long term android development easier and quicker. The one specific module has to capture images for a application... I've gotten everything right so far over the last couple months, except this one little thing and I don't know what to do any more: When I use the Camera object and implement a SurfaceHolder.Callback, the methods surfaceCreated() and surfaceChanged() are called one after the other. Then when the activity finishes, surfaceDestroyed() is called. This is how it should be, but when I stick the exact same code in my library (plain Java library that references the Android API - not in an activity), surfaceDestroyed() is called directly after created and changed. As a result - the camera object is closed before I can use it and the application force closes. What a pain. I can't do anything! This method call is controlled by the device.. Why does the surface close for no reason? Even when I post it to run on the activity thread through my own invokeAndWait(Runnable) method, like I do for many other things. I have 5 different working examples of different ways and implementations of capturing images in android but I still get the same issue when I plug it into my library. I don't understand what the difference is. The code is pretty much the same - and I post all the related code to the UI thread so its not a thread handling issue or anything like that. I've rewritten it about 20 times in different ways - same issue every time.. The only other way to approach it that I know of is creating a new Camera and setting it to the VideoView. The android source (c++ native code) however provides no Camera constructor, only an open() method which automatically forwards the camera's state to 'prepared' but I can only set the camera to the VideoView from the 'initialized' state. Pretty silly, I know, but there is no way around it unless I modify the Android library source code haha. not an option! The API does not allow for this method - you are expected to use it like my first example. So essentially - i just need to understand exactly why surfaceDestroyed() is called out of turn and if there is anything I can do to avoid it closing? If i can just understand the exact logic behind it and how it works! The documentation isn't much help! Secondly, if someone knows of any alternative ways to do it, as my second example, but hopefully one which the API actually allows for? haha Thanks guys. I would post code, but its fairly complicated, a couple thousand lines for this specific class and it would probably take a couple days to explain with all the threading and event listeners and what not. I just need help with this 1 single thing. Please let me know if you have any questions.

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• How do I use constructor dependency injection to supply Models from a collection to their ViewModels

  - by GraemeF

  I'm using constructor dependency injection in my WPF application and I keep running into the following pattern, so would like to get other people's opinion on it and hear about alternative solutions. The goal is to wire up a hierarchy of ViewModels to a similar hierarchy of Models, so that the responsibility for presenting the information in each model lies with its own ViewModel implementation. (The pattern also crops up under other circumstances but MVVM should make for a good example.) Here's a simplified example. Given that I have a model that has a collection of further models: public interface IPerson { IEnumerable<IAddress> Addresses { get; } } public interface IAddress { } I would like to mirror this hierarchy in the ViewModels so that I can bind a ListBox (or whatever) to a collection in the Person ViewModel: public interface IPersonViewModel { ObservableCollection<IAddressViewModel> Addresses { get; } void Initialize(); } public interface IAddressViewModel { } The child ViewModel needs to present the information from the child Model, so it's injected via the constructor: public class AddressViewModel : IAddressViewModel { private readonly IAddress _address; public AddressViewModel(IAddress address) { _address = address; } } The question is, what is the best way to supply the child Model to the corresponding child ViewModel? The example is trivial, but in a typical real case the ViewModels have more dependencies - each of which has its own dependencies (and so on). I'm using Unity 1.2 (although I think the question is relevant across the other IoC containers), and I am using Caliburn's view strategies to automatically find and wire up the appropriate View to a ViewModel. Here is my current solution: The parent ViewModel needs to create a child ViewModel for each child Model, so it has a factory method added to its constructor which it uses during initialization: public class PersonViewModel : IPersonViewModel { private readonly Func<IAddress, IAddressViewModel> _addressViewModelFactory; private readonly IPerson _person; public PersonViewModel(IPerson person, Func<IAddress, IAddressViewModel> addressViewModelFactory) { _addressViewModelFactory = addressViewModelFactory; _person = person; Addresses = new ObservableCollection<IAddressViewModel>(); } public ObservableCollection<IAddressViewModel> Addresses { get; private set; } public void Initialize() { foreach (IAddress address in _person.Addresses) Addresses.Add(_addressViewModelFactory(address)); } } A factory method that satisfies the Func<IAddress, IAddressViewModel> interface is registered with the main UnityContainer. The factory method uses a child container to register the IAddress dependency that is required by the ViewModel and then resolves the child ViewModel: public class Factory { private readonly IUnityContainer _container; public Factory(IUnityContainer container) { _container = container; } public void RegisterStuff() { _container.RegisterInstance<Func<IAddress, IAddressViewModel>>(CreateAddressViewModel); } private IAddressViewModel CreateAddressViewModel(IAddress model) { IUnityContainer childContainer = _container.CreateChildContainer(); childContainer.RegisterInstance(model); return childContainer.Resolve<IAddressViewModel>(); } } Now, when the PersonViewModel is initialized, it loops through each Address in the Model and calls CreateAddressViewModel() (which was injected via the Func<IAddress, IAddressViewModel> argument). CreateAddressViewModel() creates a temporary child container and registers the IAddress model so that when it resolves the IAddressViewModel from the child container the AddressViewModel gets the correct instance injected via its constructor. This seems to be a good solution to me as the dependencies of the ViewModels are very clear and they are easily testable and unaware of the IoC container. On the other hand, performance is OK but not great as a lot of temporary child containers can be created. Also I end up with a lot of very similar factory methods. Is this the best way to inject the child Models into the child ViewModels with Unity? Is there a better (or faster) way to do it in other IoC containers, e.g. Autofac? How would this problem be tackled with MEF, given that it is not a traditional IoC container but is still used to compose objects?

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• Perl not closing TCP sockets if clients are no longer connected?

  - by LM

  The purpose of the application is to listen for a specific UDP multicast and then to forward the data to any TCP clients connected to the server. The code works fine, but I have a problem with the sockets not closing after the TCP clients disconnects. A socketsniffer utility shows the the sockets remain open and all the UDP data continues to be forwarded to the clients. The problem I believe is with the "if ($write-connected())" block as it always return true, even if the TCP client is no longer connected. I use standard Windows Telnet to connect to the server and to see the data. When I close telnet, the TCP socket is suppose to close on the server. Any reason why connected() show the connections as active even if they are not? Also, what alternative should I use then? Code: #!/usr/bin/perl use IO::Socket::Multicast; use IO::Socket; use IO::Select; my $tcp_port = "4550"; my $tcp_socket = IO::Socket::INET->new( Listen => SOMAXCONN, LocalAddr => '0.0.0.0', LocalPort => $tcp_port, Proto => 'tcp', ReuseAddr => 1, ); use Socket qw(IPPROTO_TCP TCP_NODELAY); setsockopt( $tcp_socket, IPPROTO_TCP, TCP_NODELAY, 1); use constant GROUP => '239.2.0.81'; use constant PORT => '6550'; my $udp_socket= IO::Socket::Multicast->new(Proto=>'udp',LocalPort=>PORT); $udp_socket->mcast_add(GROUP) || die "Couldn't set group: $!\n"; my $read_select = IO::Select->new(); my $write_select = IO::Select->new(); $read_select->add($tcp_socket); $read_select->add($udp_socket); ## Loop forever, reading data from the UDP socket and writing it to the ## TCP socket(s). while (1) { ## No timeout specified (see docs for IO::Select). This will block until a TCP ## client connects or we have data. my @read = $read_select->can_read(); foreach my $read (@read) { if ($read == $tcp_socket) { ## Handle connect from TCP client. Note that UDP connections are ## stateless (no accept necessary)... my $new_tcp = $read->accept(); $write_select->add($new_tcp); } elsif ($read == $udp_socket) { ## Handle data received from UDP socket... my $recv_buffer; $udp_socket->recv($recv_buffer, 1024, undef); ## Write the data read from UDP out to the TCP client(s). Again, no ## timeout. This will block until a TCP socket is writable. my @write = $write_select->can_write(); foreach my $write (@write) { ## Make sure the socket is still connected before writing. if ($write->connected()) { $write->send($recv_buffer); } else { $write_select->remove($write); close $write; } } } } }

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• Categorising a large mysql result with php while?

  - by Ryan

  I'm using the following to grab my large result set from a mysql db: $discresult = 'SELECT t.id, t.subject, t.topicimage, t.topictype, c.user_id, c.disc_id FROM topics AS t LEFT JOIN collections AS c ON t.id=c.disc_id WHERE c.user_id='.$user_id; $userdiscs = $db->query($discresult) or error('Error.', __FILE__, __LINE__, $db->error()); This returns a list of all items that the user owns. I'm then needing to categorise these items based on the value of the "topictype" column, which Im currently doing by using: <h2>Category 1</h2> <?php while ($cur_img = mysql_fetch_array($userdiscs)) { if ($cur_img['topictype']=="cat-1") { if ($cur_img['topicimage']!="") { echo "<div><a href=\"viewtopic.php?id=".$cur_img['id']."\" title=\"".$cur_img['subject']."\"><img src=\"".$cur_img['topicimage']."\" style=\"width:60px; height: 60px\" /></a><br /><a href=\"viewtopic.php?id=".$cur_img['id']."\" title=\"".$cur_img['subject']."\">".$cur_img['subject']."</a></div>"; } else { echo "<div><a href=\"viewtopic.php?id=".$cur_img['id']."\" title=\"".$cur_img['subject']."\"><img src=\"img/no-disc-art.jpg\" style=\"width:60px; height: 60px\" /></a><br /><a href=\"viewtopic.php?id=".$cur_img['id']."\" title=\"".$cur_img['subject']."\">".$cur_img['subject']."</a></div>"; } } } mysql_data_seek($userdiscs, 0); ?> <h2>Category 2</h2> <?php while ($cur_img = mysql_fetch_array($userdiscs)) { if ($cur_img['topictype']=="cat-2") { if ($cur_img['topicimage']!="") { echo "<div><a href=\"viewtopic.php?id=".$cur_img['id']."\" title=\"".$cur_img['subject']."\"><img src=\"".$cur_img['topicimage']."\" style=\"width:60px; height: 60px\" /></a><br /><a href=\"viewtopic.php?id=".$cur_img['id']."\" title=\"".$cur_img['subject']."\">".$cur_img['subject']."</a></div>"; } else { echo "<div><a href=\"viewtopic.php?id=".$cur_img['id']."\" title=\"".$cur_img['subject']."\"><img src=\"img/no-disc-art.jpg\" style=\"width:60px; height: 60px\" /></a><br /><a href=\"viewtopic.php?id=".$cur_img['id']."\" title=\"".$cur_img['subject']."\">".$cur_img['subject']."</a></div>"; } } } mysql_data_seek($userdiscs, 0); ?> This works fine when I rinse and repeat the code, but as the site grows I expect I'll run into problems as the number of "topictype" options increases (expecting around 30 categories). I dont want to have to make seperate queries for each categorised group of discs either, as Id eventually have 30 queries being run as categories increase, so hoping to hear some suggestions or alternative approaches :) Thanks

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• Modern alternatives to Java

  - by Ralph

  I have been a Java developer for 14 years and have written an enterprise-level (~500 kloc) Swing application that uses most of the standard library APIs. Recently, I have become disappointed with the progress that the language has made to "modernize" itself, and am looking for an alternative for ongoing development. I have considered moving to the .NET platform, but I have issues with using something the only runs well in Windows (I know about Mono, but that is still far behind Microsoft). I also plan on buying a new Macbook Pro as soon as Apple releases their new rumored Arrandale-based machines and want to develop in an environment that will feel "at home" in Unix/Linux. I have considered using Python or Ruby, but the standard Java library is arguably the largest of any modern language. In JVM-based languages, I looked at Groovy, but am disappointed with its performance. Rumor has it that with the soon-to-be released JDK7, with its InvokeDynamic instruction, this will improve, but I don't know how much. Groovy is also not truly a functional language, although it provides closures and some of the "functional" features on collections. It does not embrace immutability. I have narrowed my search down to two JVM-based alternatives: Scala and Clojure. Each has its strengths and weaknesses. I am looking for opinions. I am not an expert at either of these languages; I have read 2 1/2 books on Scala and am currently reading Stu Halloway's book on Clojure. Scala is strongly statically typed. I know the dynamic language folks claim that static typing is a crutch for not doing unit testing, but it does provide a mechanism for compile-time location of a whole class of errors. Scala is more concise than Java, but not as much as Clojure. Scala's inter-operation with Java seems to be better than Clojure's, in that most Java operations are easier to do in Scala than in Clojure. For example, I can find no way in Clojure to create a non-static initialization block in a class derived from a Java superclass. For example, I like the Apache commons CLI library for command line argument parsing. In Java and Scala, I can create a new Options object and add Option items to it in an initialization block as follows (Java code): final Options options = new Options() { { addOption(new Option("?", "help", false, "Show this usage information"); // other options } }; I can't figure out how to the same thing in Clojure (except by using (doit...)), although that may reflect my lack of knowledge of the language. Clojure's collections are optimized for immutability. They rarely require copy-on-write semantics. I don't know if Scala's immutable collections are implemented using similar algorithms, but Rich Hickey (Clojure's inventor) goes out of his way to explain how that language's data structures are efficient. Clojure was designed from the beginning for concurrency (as was Scala) and with modern multi-core processors, concurrency takes on more importance, but I occasionally need to write simple non-concurrent utilities, and Scala code probably runs a little faster for these applications since it discourages, but does not prohibit, "simple" mutability. One could argue that one-off utilities do not have to be super-fast, but sometimes they do tasks that take hours or days to complete. I know that there is no right answer to this "question", but I thought I would open it up for discussion. Are there other JVM-based languages that can be used for enterprise level development?

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• MySQL access classes in PHP

  - by Mike

  I have a connection class for MySQL that looks like this: class MySQLConnect { private $connection; private static $instances = 0; function __construct() { if(MySQLConnect::$instances == 0) { //Connect to MySQL server $this->connection = mysql_connect(MySQLConfig::HOST, MySQLConfig::USER, MySQLConfig::PASS) or die("Error: Unable to connect to the MySQL Server."); MySQLConnect::$instances = 1; } else { $msg = "Close the existing instance of the MySQLConnector class."; die($msg); } } public function singleQuery($query, $databasename) { mysql_select_db(MySQLConfig::DB, $this->connection) or die("Error: Could not select database " . MySQLConfig::DB . " from the server."); $result = mysql_query($query) or die('Query failed.'); return $result; } public function createResultSet($query, $databasename) { $rs = new MySQLResultSet($query, MySQLConfig::DB, $this->connection ) ; return $rs; } public function close() { MySQLConnect::$instances = 0; if(isset($this->connection) ) { mysql_close($this->connection) ; unset($this->connection) ; } } public function __destruct() { $this->close(); } } The MySQLResultSet class looks like this: class MySQLResultSet implements Iterator { private $query; private $databasename; private $connection; private $result; private $currentRow; private $key = 0; private $valid; public function __construct($query, $databasename, $connection) { $this->query = $query; //Select the database $selectedDatabase = mysql_select_db($databasename, $connection) or die("Error: Could not select database " . $this->dbname . " from the server."); $this->result = mysql_query($this->query) or die('Query failed.'); $this->rewind(); } public function getResult() { return $this->result; } // public function getRow() // { // return mysql_fetch_row($this->result); // } public function getNumberRows() { return mysql_num_rows($this->result); } //current() returns the current row public function current() { return $this->currentRow; } //key() returns the current index public function key() { return $this->key; } //next() moves forward one index public function next() { if($this->currentRow = mysql_fetch_array($this->result) ) { $this->valid = true; $this->key++; }else{ $this->valid = false; } } //rewind() moves to the starting index public function rewind() { $this->key = 0; if(mysql_num_rows($this->result) > 0) { if(mysql_data_seek($this->result, 0) ) { $this->valid = true; $this->key = 0; $this->currentRow = mysql_fetch_array($this->result); } } else { $this->valid = false; } } //valid returns 1 if the current position is a valid array index //and 0 if it is not valid public function valid() { return $this->valid; } } The following class is an example of how I am accessing the database: class ImageCount { public function getCount() { $mysqlConnector = new MySQLConnect(); $query = "SELECT * FROM images;"; $resultSet = $mysqlConnector->createResultSet($query, MySQLConfig::DB); $mysqlConnector->close(); return $resultSet->getNumberRows(); } } I use the ImageCount class like this: if(!ImageCount::getCount()) { //Do something } Question: Is this an okay way to access the database? Could anybody recommend an alternative method if it is bad? Thank-you.

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• Beginner question: ArrayList can't seem to get it right! Pls help

  - by elementz

  I have been staring at this code all day now, but just can't get it right. ATM I am just pushing codeblocks around without being able to concentrate anymore, with the due time being within almost an hour... So you guys are my last resort here. I am supposed to create a few random balls on a canvas, those balls being stored within an ArrayList (I hope an ArrayList is suitable here: the alternative options to choose from were HashSet and HashMap). Now, whatever I do, I get the differently colored balls at the top of my canvas, but they just get stuck there and refuse to move at all. Apart from that I now get a ConcurrentModificationException, when running the code: java.util.ConcurrentModificationException at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372) at java.util.AbstractList$Itr.next(AbstractList.java:343) at BallDemo.bounce(BallDemo.java:109) Reading up on that exception, I found out that one can make sure ArrayList is accessed in a threadsafe manner by somehow synchronizing access. But since I have remember fellow students doing without synchronizing, my guess is, that it would actually be the wrong path to go. Maybe you guys could help me get this to work, I at least need those stupid balls to move ;-) /** * Simulate random bouncing balls */ public void bounce(int count) { int ground = 400; // position of the ground line System.out.println(count); myCanvas.setVisible(true); // draw the ground myCanvas.drawLine(50, ground, 550, ground); // Create an ArrayList of type BouncingBalls ArrayList<BouncingBall>balls = new ArrayList<BouncingBall>(); for (int i = 0; i < count; i++){ Random numGen = new Random(); // Creating a random color. Color col = new Color(numGen.nextInt(256), numGen.nextInt(256), numGen.nextInt(256)); // creating a random x-coordinate for the balls int ballXpos = numGen.nextInt(550); BouncingBall bBall = new BouncingBall(ballXpos, 80, 20, col, ground, myCanvas); // adding balls to the ArrayList balls.add(bBall); bBall.draw(); boolean finished = false; } for (BouncingBall bBall : balls){ bBall.move(); } } This would be the original unmodified method we got from our teacher, which only creates two balls: /** * Simulate two bouncing balls */ public void bounce() { int ground = 400; // position of the ground line myCanvas.setVisible(true); myCanvas.drawLine(50, ground, 550, ground); // draw the ground // crate and show the balls BouncingBall ball = new BouncingBall(50, 50, 16, Color.blue, ground, myCanvas); ball.draw(); BouncingBall ball2 = new BouncingBall(70, 80, 20, Color.red, ground, myCanvas); ball2.draw(); // make them bounce boolean finished = false; while(!finished) { myCanvas.wait(50); // small delay ball.move(); ball2.move(); // stop once ball has travelled a certain distance on x axis if(ball.getXPosition() >= 550 && ball2.getXPosition() >= 550) { finished = true; } } ball.erase(); ball2.erase(); } }

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• Survey Data Model - How to avoid EAV and excessive denormalization?

  - by AlexDPC

  Hi everyone, My database skills are mediocre at best and I have to design a data model for survey data. I have spent some thoughts on this and right now I feel that I am stuck between some kind of EAV model and a design involving hundreds of tables, each with hundreds of columns (and thousands of records). There must be a better way to do this and I hope that the wise folks on this forum can help me. I have already searched various forums, but I couldn't really find a solution. If it has already been given elsewhere, please excuse me and provide me with a link so I can read it up. Some assumptions about the data I have to deal with: Each survey consists of 1 to n questionnaires Each questionnaire consists of 100-2,000 questions (please ignore that 2,000 questions really sound like a lot to answer...) Questions can be of various types: multiple-choice, free text, a number (like age, income, percentages, ...) Each survey involves 10-200 countries (These are not the respondents. The respondents are actually people in the countries.) Depending on the type of questionnaire, each questionnaire is answered by 100-20,000 respondents per country. A country can adapt the questionnaires for a survey, i.e. add, remove or edit questions The data for one country is gathered in a separate database in that country. There is no possibility for online integration from the start. The data for all countries has to be integrated later. This means for example, if a country has deleted a question, that data must somehow be derived from what they sent in order to achieve a uniform design across all countries I will have to write the integration and cleaning software, which will need to work with every country's data In the end the data needs to be exported to flat files, one rectangular grid per country and questionnaire. I have already discussed this topic with people from various backgrounds and have not come to a good solution yet. I mainly got two kinds of opinions. The domain experts, who are used to working with flat files (spreadsheet-style) for data processing and analysis vote for a denormalized structure with loads of tables and columns as I described above (1 table per country and questionnaire). This sounds terrible to me, because I learned that wide tables are to be avoided, it will be annoying to determine which columns are actually in a table when working with it, the database will become cluttered with hundreds of tables (or I even need to set up multiple databases, each with a similar yet a bit differetn design), etc. O-O-programmers vote for a strongly "normalized" design, which would effectively lead to a central table containing all the answers from all respondents to all questions. This table would either need to contain a column of type sql_variant type or multiple answer columns with different types to store answers of different types (multiple choice, free text, ..). The former would essentially be a EAV model. I tend to follow Joe Celko here, who strongly discourages its use (he calls it OTLT or "One True Lookup Table"). The latter would imply that each row would contain null cells for the not applicable types by design. Another alternative I could think of would be to create one table per answer type, i.e., one for multiple-choice questions, one for free text questions, etc.. That's not so generic, it would lead to a lot of union joins, I think and I would have to add a table if a new answer type is invented. Sorry for boring you with all this text and thank you for your input! Cheers, Alex PS: I asked the same question here: http://www.eggheadcafe.com/community/aspnet/13/10242616/survey-data-model--how-to-avoid-eav-and-excessive-denormalization.aspx

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