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Articles indexed in November 2011

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  • In a binary search Tree

    - by user1044800
    In a binary search tree that takes a simple object.....when creating the getter and setter methods for the left, right, and parent. do I a do a null pointer? as in this=this or do I create the object in each method? Code bellow... This is my code: public void setParent(Person parent) { parent = new Person( parent.getName(), parent.getWeight()); //or is the parent supposed to be a null pointer ???? This is the code it came from: public void setParent(Node parent) { this.parent = parent; } Their code takes a node from the node class...my set parent is taking a person object from my person class.....

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  • PHP 5.3.8 startup warning

    - by David
    How do I solve my PHP startup warning: PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/extensions /no-debug-non-zts-20090626/imap.so' - /usr/lib/php/extensions/no-debug-non-zts-20090626 /imap.so: cannot open shared object file: No such file or directory in Unknown on line 0 PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/extensions /no-debug-non-zts-20090626/mcrypt.so' - /usr/lib/php/extensions/no-debug-non-zts- 20090626/mcrypt.so: cannot open shared object file: No such file or directory in Unknown on line 0 PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/extensions /no-debug-non-zts-20090626/memcache.so' - /usr/lib/php/extensions/no-debug-non-zts- 20090626/memcache.so: cannot open shared object file: No such file or directory in Unknown on line 0 PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/extensions /no-debug-non-zts-20090626/mysql.so' - /usr/lib/php/extensions/no-debug-non-zts- 20090626/mysql.so: cannot open shared object file: No such file or directory in Unknown on line 0 PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib /php/extensions/no-debug-non-zts-20090626/mysqli.so' - /usr/lib/php/extensions /no-debug-non-zts-20090626/mysqli.so: cannot open shared object file: No such file or directory in Unknown on line 0 PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/extensions /no-debug-non-zts-20090626/pdo.so' - /usr/lib/php/extensions/no-debug-non-zts-20090626 /pdo.so: cannot open shared object file: No such file or directory in Unknown on line 0 PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/extensions /no-debug-non-zts-20090626/pdo_mysql.so' - /usr/lib/php/extensions/no-debug-non-zts- 20090626/pdo_mysql.so: cannot open shared object file: No such file or directory in Unknown on line 0 PHP Warning: PHP Startup: Unable to load dynamic library '/usr/lib/php/extensions /no-debug-non-zts-20090626/suhosin.so' - /usr/lib/php/extensions/no-debug-non-zts- 20090626/suhosin.so: cannot open shared object file: No such file or directory in Unknown on line 0 I've many configuration files in my config folder, I don't know where they come from: PHP Deprecated: Comments starting with '#' are deprecated in /etc/php5/conf.d/gd.ini on line 1 in Unknown on line 0 PHP Deprecated: Comments starting with '#' are deprecated in /etc/php5/conf.d/gd.ini on line 2 in Unknown on line 0 PHP Deprecated: Comments starting with '#' are deprecated in /etc/php5/conf.d/imap.ini on line 1 in Unknown on line 0 PHP Deprecated: Comments starting with '#' are deprecated in /etc/php5/conf.d/mcrypt.ini on line 1 in Unknown on line 0 PHP Deprecated: Comments starting with '#' are deprecated in /etc/php5/conf.d /memcache.ini on line 1 in Unknown on line 0 PHP Deprecated: Comments starting with '#' are deprecated in /etc/php5/conf.d /mysql.ini on line 1 in Unknown on line 0 PHP Deprecated: Comments starting with '#' are deprecated in /etc/php5/conf.d /mysqli.ini on line 1 in Unknown on line 0 PHP Deprecated: Comments starting with '#' are deprecated in /etc/php5/conf.d/pdo.ini on line 1 in Unknown on line 0 PHP Deprecated: Comments starting with '#' are deprecated in /etc/php5/conf.d /pdo_mysql.ini on line 1 in Unknown on line 0 PHP Deprecated: Comments starting with '#' are deprecated in /etc/php5/conf.d/xcache.ini on line 1 in Unknown on line 0 PHP Deprecated: Comments starting with '#' are deprecated in /etc/php5/conf.d/xcache.ini on line 9 in Unknown on line 0 Because of the warning I think I don't need them?

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  • What's wrong with this jQuery? It isn't working as intended

    - by Doug Smith
    Using cookies, I want it to remember the colour layout of the page. (So, if they set the gallery one color and the body background another color, it will save that on refresh. But it doesn't seem to be working. jQuery: $(document).ready(function() { if (verifier == 1) { $('body').css('background', $.cookie('test_cookie')); } if (verifier == 2) { $('#gallery').css('background', $.cookie('test_cookie')); } if (verifier == 3) { $('body').css('background', $.cookie('test_cookie')); $('#gallery').css('background', $.cookie('test_cookie')); } $('#set_cookie').click(function() { var color = $('#set_cookie').val(); $.cookie('test_cookie', color); }); $('#set_page').click(function() { $('body').css('background', $.cookie('test_cookie')); var verifier = 1; }); $('#set_gallery').click(function() { $('#gallery').css('background', $.cookie('test_cookie')); var verifier = 2; }); $('#set_both').click(function() { $('body').css('background', $.cookie('test_cookie')); $('#gallery').css('background', $.cookie('test_cookie')); var verifier = 3; }); }); HTML: <p>Please select a background color for either the page's background, the gallery's background, or both.</p> <select id="set_cookie"> <option value="#1d375a" selected="selected">Default</option> <option value="black">Black</option> <option value="blue">Blue</option> <option value="brown">Brown</option> <option value="darkblue">Dark Blue</option> <option value="darkgreen">Dark Green</option> <option value="darkred">Dark Red</option> <option value="fuchsia">Fuchsia</option> <option value="green">Green</option> <option value="grey">Grey</option> <option value="#d3d3d3">Light Grey</option> <option value="#32cd32">Lime Green</option> <option value="#f8b040">Macaroni</option> <option value="#ff7300">Orange</option> <option value="pink">Pink</option> <option value="purple">Purple</option> <option value="red">Red</option> <option value="#0fcce0">Turquoise</option> <option value="white">White</option> <option value="yellow">Yellow</option> </select> <input type="button" id="set_page" value="Page's Background" /><input type="button" id="set_gallery" value="Gallery's Background" /><input type="button" id="set_both" value="Both" /> </div> </div> </body> </html> Thanks so much for the help, I appreciate it. jsFiddle: http://jsfiddle.net/hL6Ye/

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  • Is This a Valid Way to Use Blocks in Objective-C?

    - by Carter
    I've been building a HTTP client that uses web services to synchronize information between the client and server. I've been using Blocks and NSURLConnection to achieve this on the client side, but I'm getting frequent EXC_BAD_ACCESS crashes in objc_msgSend(). From what I understand, this usually means that a stored block that has fallen off the stack has been called. I think I've coded things correctly to avoid this, but I'm still stuck. Here is conceptually what my code is doing. It starts by calling "synchronizeWithWebServer". That method invokes "listRootObjectsOnServerWithBlock:" which takes in a block to be called when the method returns. "listRootObjectsOnServersWithBlock:" initiates a NSURLConnection to the web server asynchronously. It to expects a block to be called when it returns. Inside that block I want to be able to execute the original Block (so aptly named 'block'). This is only a simplified version of my code. The real synchronization process is more complex but it's mostly more of the same as what you see below. Sometimes the code works perfectly, but about 80% of the time it crashes very early on in the routine. It seems to be more vulnerable to crashing when my data set gets larger. - (void)synchronizeWithWebServer { [self listRootObjectsOnServerWithBlock:^(NSArray *results, NSError *error) { //Iterate over result objects and perform some other similar routines. }]; } - (void)listRootObjectsOnServerWithBlock:(void (^)(NSArray *results, NSError *error))block { //Create NSURLRequest Here //Create connection asynchronously. block = [block copy]; [NSURLConnection sendAsynchronousRequest:urlRequest queue:[NSOperationQueue currentQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *error){ //Parse response from web server (stored in NSData *data) NSArray *results = ..... //Call 'block' block(results, error); [block release]; }]; }

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  • Visual Studio 2010 "Not enough storage is available to process this command"

    - by Daniel Perez
    I'm fighting with VS 2010 and this error that seems to be very common in previous versions, but it looks like not everyone is having it in the latest version. I've got VS 2010 SP1 and I'm getting this error quite often. The problem is that it's not even enough to restart VS in order to make it go away, I usually have to restart my pc, and i'm losing a lot of time doing this (it's quite frequent) I've got Windows 7 32bits (can't upgrade to 64 bits, the company doesn't allow it), and I can't do things like creating another solution (please don't reply this :) ) I've used the command to make devenv.exe LARGEADDRESSAWARE, but the error keeps on happening My virtual memory size is set to automatic, and the weird thing is that VS doesn't even take 2gb of ram, so I don't know if the error is really because it's lacking memory, or if it's some bug in the program any ideas, things to try, something?

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  • Facebook FB.api post how to specify a target

    - by Laurent Luce
    I am using FB.api OpenGraph to post a message on the user's wall. I would like the link target to be equal to '_blank' so it opens in a new tab. Is it possible ? The Facebook documentation doesn't give much details. var params = {}; params['message'] = 'message'; params['name'] = 'name'; params['link'] = 'http://link'; params['picture'] = 'http://picture'; params['description'] = 'description'; FB.api('/me/feed', 'post', params, function(response) { if (!response || response.error) { alert('Error occured'); } else { alert('Post ID: ' + response); } });

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  • Reading HttpURLConnection InputStream - manual buffer or BufferedInputStream?

    - by stormin986
    When reading the InputStream of an HttpURLConnection, is there any reason to use one of the following over the other? I've seen both used in examples. Manual Buffer: while ((length = inputStream.read(buffer)) > 0) { os.write(buf, 0, ret); } BufferedInputStream is = http.getInputStream(); bis = new BufferedInputStream(is); ByteArrayBuffer baf = new ByteArrayBuffer(50); int current = 0; while ((current = bis.read()) != -1) { baf.append(current); } EDIT I'm still new to HTTP in general but one consideration that comes to mind is that if I am using a persistent HTTP connection, I can't just read until the input stream is empty right? In that case, wouldn't I need to read the message length and just read the input stream for that length? And similarly, if NOT using a persistent connection, is the code I included 100% good to go in terms of reading the stream properly?

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  • jQuery .ajax success function not rendering html with jQuery UI elements

    - by tylerpenney
    How do I have the html loaded into my div from the .ajax render with jquery? the success function loads the HTML, but those elements do not show up as jQuery UI elements, just the static HTML types. Any pointers? $(function() { $('input[type=image]').click(function(){ $.ajax({ url: '_includes/callinfo.php', data: 'id=' + $(this).attr('value'), dataType: "html", success: function(html){ $('#callwindow').html(html); } }); }); });

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  • Using Objective-C blocks with old compiler

    - by H2CO3
    I'm using the opensource iPhone toolchain on Linux for developing for jailbroken iPhones. I'd like to take advantage of the new (4.0, 5.0) iOS SDK features, but I can't as my old build of GCC doesn't understand the ^ block syntax. I noticed that blocks are just of type id (struct objc_object *). I know this from two resources: first, class-dump reports them as id, second, Apple docs clarify that "blocks can be retained". My quiestion is, how can I take advantage of blocks using this knowledge? I thought of something like: // this is in SDK 4.x/5.x - (void) doSomethingWithBlock:((int)(^block)(int)); // and I modify it like: - (void) doSomethingWithBlock(id)block; the question is: HOW TO ACTUALLY CALL IT? How do I create blocks? I can, of course, create function pointers (IMPs in particular), but how to achieve the object-like memory layout?

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  • Java: How to make this Serializable?

    - by Hasslarn
    I dont know that much about Serializable, but i need this class to be. How to achieve it? package helpers; public class XY implements Comparable<XY> { public int x; public int y; public XY (int x, int y) { this.x = x; this.y = y; } public int compareTo( XY other ) { String compare1 = this.x + "-" + this.y; String compare2 = other.x + "-" + other.y; return compare1.compareTo( compare2 ); } public String toString() { return this.x + "-" + this.y; } } As of now i cant send it as an object with outputstream..I´ve tried just to implement Serializable but it doesnt do the trick!

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  • Confused as to why my PHP include isn't working

    - by Sam
    I had a prototype of my website working correctly, meaning it connected to the database correctly. This was done with just one file called "connect.php" which had mysql_connect() and such inside it. I then separated the connect information into to separate files, one containing the account information (account.php) and one containing the connect function (connect.php), with correct information (I triple checked) and it isn't connecting properly. All I can think of is that I'm not including it the right way. This is what I have in a file: <?php include('account.php'); include('connect.php'); include('functions.php'); ..... ?>

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  • Working with a list, performing arithmetic logic in Python

    - by haea ohoh
    Suppose I have made a large list of numbers, and I want to make another one which I will add, pairwise, with the first list. Here's the first list, A: [109, 77, 57, 34, 94, 68, 96, 72, 39, 67, 49, 71, 121, 89, 61, 84, 45, 40, 104, 68, 54, 60, 68, 62, 91, 45, 41, 118, 44, 35, 53, 86, 41, 63, 111, 112, 54, 34, 52, 72, 111, 113, 47, 91, 107, 114, 105, 91, 57, 86, 32, 109, 84, 85, 114, 48, 105, 109, 68, 57, 78, 111, 64, 55, 97, 85, 40, 100, 74, 34, 94, 78, 57, 77, 94, 46, 95, 60, 42, 44, 68, 89, 113, 66, 112, 60, 40, 110, 89, 105, 113, 90, 73, 44, 39, 55, 108, 110, 64, 108] And here's B: [35, 106, 55, 61, 81, 109, 82, 85, 71, 55, 59, 38, 112, 92, 59, 37, 46, 55, 89, 63, 73, 119, 70, 76, 100, 49, 117, 77, 37, 62, 65, 115, 93, 34, 107, 102, 91, 58, 82, 119, 75, 117, 34, 112, 121, 58, 79, 69, 68, 72, 110, 43, 111, 51, 102, 39, 52, 62, 75, 118, 62, 46, 74, 77, 82, 81, 36, 87, 80, 56, 47, 41, 92, 102, 101, 66, 109, 108, 97, 49, 72, 74, 93, 114, 55, 116, 66, 93, 56, 56, 93, 99, 96, 115, 93, 111, 57, 105, 35, 99] How might I generate the arithmatic addition logic, processing each pairwise value one by one (A[0] and B[0], through A[99], B[99]) and producing the list C (A[0] + B[0] through A[99]+ B[99])?

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  • how to make a border area go around the content of a page where there is a footer fixed to the bottom of the page and an header fixed to the top

    - by user277498
    consider the following: http://jsfiddle.net/PxabT/10/ There are 3 divs hd, bd, ft. hd is fixed to the top. ft is fixed to the bottom. I want the lime colored border to go totally around the white central area without increasing the height of the ft or hd divs. How do I achieve that? Many thanks! edit: see http://jsfiddle.net/PxabT/15/ which is a step forward by changing the borders to padding.

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  • Database design: Using hundred of fields for little values

    - by user964260
    I'm planning to develop a PHP Web App, it will mainly be used by registered users(sessions) While thinking about the DB design, I was contemplating that in order to give the best user experience possible there would be lots of options for the user to activate, deactivate, specify, etc. For example: - Options for each layout elements, dialog boxes, dashboard, grid, etc. - color, size, stay visible, invisible, don't ask again, show everytime, advanced mode, simple mode, etc. This would get like 100s of fields ranging from simple Yes/No or 1 to N values..., for each user. So, is it having a field for each of these options the way to go? or how do those CRMs or CMS or other Web Apps do it to store lots of 1-2 char long values? Do they group them on Text fields separated by a special char and then "explode" them as an array for runtime usage? thank you

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  • How to set text above and below a JButton icon?

    - by mre
    I want to set text above and below a JButton's icon. At the moment, in order to achieve this, I override the layout manager and use three JLabel instances (i.e. 2 for text and 1 for the icon). But this seems like a dirty solution. Is there a more direct way of doing this? Note -I'm not looking for a multi-line solution, I'm looking for a multi-label solution. Although this article refers to it as a multi-line solution, it actually seems to refer to a multi-label solution. EXAMPLE import java.awt.Component; import java.awt.FlowLayout; import javax.swing.BoxLayout; import javax.swing.Icon; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JLabel; import javax.swing.SwingUtilities; import javax.swing.UIManager; public final class JButtonDemo { public static void main(String[] args) { SwingUtilities.invokeLater(new Runnable(){ @Override public void run() { createAndShowGUI(); } }); } private static void createAndShowGUI(){ final JFrame frame = new JFrame(); frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); frame.setLayout(new FlowLayout()); frame.add(new JMultiLabelButton()); frame.pack(); frame.setLocationRelativeTo(null); frame.setVisible(true); } private static final class JMultiLabelButton extends JButton { private static final long serialVersionUID = 7650993517602360268L; public JMultiLabelButton() { super(); setLayout(new BoxLayout(this, BoxLayout.Y_AXIS)); add(new JCenterLabel("Top Label")); add(new JCenterLabel(UIManager.getIcon("OptionPane.informationIcon"))); add(new JCenterLabel("Bottom Label")); } } private static final class JCenterLabel extends JLabel { private static final long serialVersionUID = 5502066664726732298L; public JCenterLabel(final String s) { super(s); setAlignmentX(Component.CENTER_ALIGNMENT); } public JCenterLabel(final Icon i) { super(i); setAlignmentX(Component.CENTER_ALIGNMENT); } } }

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  • Load a dll library on Java

    - by crimson_king
    I need to load a library written in C on java. I have only dlls and header files. Since I didn't understand how to translate pointers or other derivated types from JNI documentation I tried to use an automating tool for this, gluegen and SWIG, but I couldn't manage on how to use them. I tried to create an interface file for SWIG but it only gives errors. Is there an example on how to load a dll to a java program using ANY tool that works and can generate translated C function and types from .h files ?

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  • Incorrect usage of UPDATE and ORDER BY

    - by nico55555
    I have written some code to update certain rows of a table with a decreasing sequence of numbers. To select the correct rows I have to JOIN two tables. The last row in the table needs to have a value of 0, the second last -1 and so on. To achieve this I use ORDER BY DESC. Unfortunately my code brings up the following error: Incorrect usage of UPDATE and ORDER BY My reading suggests that I can't use UPDATE, JOIN and ORDER BY together. I've read that maybe subqueries might help? I don't really have any idea how to change my code to do this. Perhaps someone could post a modified version that will work? while($row = mysql_fetch_array( $result )) { $products_id = $row['products_id']; $products_stock_attributes = $row['products_stock_attributes']; mysql_query("SET @i = 0"); $result2 = mysql_query("UPDATE orders_products op, orders ord SET op.stock_when_purchased = (@i:=(@i - op.products_quantity)) WHERE op.orders_id = ord.orders_id AND op.products_id = '$products_id' AND op.products_stock_attributes = '$products_stock_attributes' AND op.stock_when_purchased < 0 AND ord.orders_status = 2 ORDER BY orders_products_id DESC") or die(mysql_error()); }

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  • WP: AesManaged encryption vs. mcrypt_encrypt

    - by invalidusername
    I'm trying to synchronize my encryption and decryption methods between C# and PHP but something seems to be going wrong. In the Windows Phone 7 SDK you can use AESManaged to encrypt your data I use the following method: public static string EncryptA(string dataToEncrypt, string password, string salt) { AesManaged aes = null; MemoryStream memoryStream = null; CryptoStream cryptoStream = null; try { //Generate a Key based on a Password, Salt and HMACSHA1 pseudo-random number generator Rfc2898DeriveBytes rfc2898 = new Rfc2898DeriveBytes(password, Encoding.UTF8.GetBytes(salt)); //Create AES algorithm with 256 bit key and 128-bit block size aes = new AesManaged(); aes.Key = rfc2898.GetBytes(aes.KeySize / 8); aes.IV = new byte[] { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 }; // rfc2898.GetBytes(aes.BlockSize / 8); // to check my results against those of PHP var blaat1 = Convert.ToBase64String(aes.Key); var blaat2 = Convert.ToBase64String(aes.IV); //Create Memory and Crypto Streams memoryStream = new MemoryStream(); cryptoStream = new CryptoStream(memoryStream, aes.CreateEncryptor(), CryptoStreamMode.Write); //Encrypt Data byte[] data = Encoding.Unicode.GetBytes(dataToEncrypt); cryptoStream.Write(data, 0, data.Length); cryptoStream.FlushFinalBlock(); //Return Base 64 String string result = Convert.ToBase64String(memoryStream.ToArray()); return result; } finally { if (cryptoStream != null) cryptoStream.Close(); if (memoryStream != null) memoryStream.Close(); if (aes != null) aes.Clear(); } } I solved the problem of generating the Key. The Key and IV are similar as those on the PHP end. But then the final step in the encryption is going wrong. here is my PHP code <?php function pbkdf2($p, $s, $c, $dk_len, $algo = 'sha1') { // experimentally determine h_len for the algorithm in question static $lengths; if (!isset($lengths[$algo])) { $lengths[$algo] = strlen(hash($algo, null, true)); } $h_len = $lengths[$algo]; if ($dk_len > (pow(2, 32) - 1) * $h_len) { return false; // derived key is too long } else { $l = ceil($dk_len / $h_len); // number of derived key blocks to compute $t = null; for ($i = 1; $i <= $l; $i++) { $f = $u = hash_hmac($algo, $s . pack('N', $i), $p, true); // first iterate for ($j = 1; $j < $c; $j++) { $f ^= ($u = hash_hmac($algo, $u, $p, true)); // xor each iterate } $t .= $f; // concatenate blocks of the derived key } return substr($t, 0, $dk_len); // return the derived key of correct length } } $password = 'test'; $salt = 'saltsalt'; $text = "texttoencrypt"; #$iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC); #echo $iv_size . '<br/>'; #$iv = mcrypt_create_iv($iv_size, MCRYPT_RAND); #print_r (mcrypt_list_algorithms()); $iv = "\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"; $key = pbkdf2($password, $salt, 1000, 32); echo 'key: ' . base64_encode($key) . '<br/>'; echo 'iv: ' . base64_encode($iv) . '<br/>'; echo '<br/><br/>'; function addpadding($string, $blocksize = 32){ $len = strlen($string); $pad = $blocksize - ($len % $blocksize); $string .= str_repeat(chr($pad), $pad); return $string; } echo 'text: ' . $text . '<br/>'; echo 'text: ' . addpadding($text) . '<br/>'; // -- works till here $crypttext = mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, $text, MCRYPT_MODE_CBC, $iv); echo '1.' . $crypttext . '<br/>'; $crypttext = base64_encode($crypttext); echo '2.' . $crypttext . '<br/>'; $crypttext = mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, addpadding($text), MCRYPT_MODE_CBC, $iv); echo '1.' . $crypttext . '<br/>'; $crypttext = base64_encode($crypttext); echo '2.' . $crypttext . '<br/>'; ?> So to point out, the Key and IV look similar on both .NET and PHP, but something seems to be going wrong in the final call when executing mcrypt_encrypt(). The end result, the encrypted string, differs from .NET. Can anybody tell me what i'm doing wrong. As far as i can see everything should be correct. Thank you! EDIT: Additional information on the AESManaged object in .NET Keysize = 256 Mode = CBC Padding = PKCS7

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  • Silverlight Training Montreal in November 2011

    - by pluginbaby
    Still a few seats available for the next Silverlight Tour stop in Montreal, come and learn top Silverlight content from local experts!!! What: Silverlight training When: November 21-24 (4 days) Where: Montreal, Qc Registration/info Also note that we offer a free license of Telerik's RadControls for Silverlight to every attendee ($999 value)!! For more information on RadControls, visit: http://www.telerik.com/products/silverlight.aspx.

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  • WebGrid Helper and Complex Types

    - by imran_ku07
        Introduction:           WebGrid helper makes it very easy to show tabular data. It was originally designed for ASP.NET Web Pages(WebMatrix) to display, edit, page and sort tabular data but you can also use this helper in ASP.NET Web Forms and ASP.NET MVC. When using this helper, sometimes you may run into a problem if you use complex types in this helper. In this article, I will show you how you can use complex types in WebGrid helper.       Description:             Let's say you need to show the employee data and you have the following classes,   public class Employee { public string Name { get; set; } public Address Address { get; set; } public List<string> ContactNumbers { get; set; } } public class Address { public string City { get; set; } }               The Employee class contain a Name, an Address and list of ContactNumbers. You may think that you can easily show City in WebGrid using Address.City, but no. The WebGrid helper will throw an exception at runtime if any Address property is null in the Employee list. Also, you cannot directly show ContactNumbers property. The easiest way to show these properties is to add some additional properties,   public Address NotNullableAddress { get { return Address ?? new Address(); } } public string Contacts { get { return string.Join("; ",ContactNumbers); } }               Now you can easily use these properties in WebGrid. Here is the complete code of this example,  @functions{ public class Employee { public Employee(){ ContactNumbers = new List<string>(); } public string Name { get; set; } public Address Address { get; set; } public List<string> ContactNumbers { get; set; } public Address NotNullableAddress { get { return Address ?? new Address(); } } public string Contacts { get { return string.Join("; ",ContactNumbers); } } } public class Address { public string City { get; set; } } } @{ var myClasses = new List<Employee>{ new Employee { Name="A" , Address = new Address{ City="AA" }, ContactNumbers = new List<string>{"021-216452","9231425651"}}, new Employee { Name="C" , Address = new Address{ City="CC" }}, new Employee { Name="D" , ContactNumbers = new List<string>{"045-14512125","21531212121"}} }; var grid = new WebGrid(source: myClasses); } @grid.GetHtml(columns: grid.Columns( grid.Column("NotNullableAddress.City", header: "City"), grid.Column("Name"), grid.Column("Contacts")))                    Summary:           You can use WebGrid helper to show tabular data in ASP.NET MVC, ASP.NET Web Forms and  ASP.NET Web Pages. Using this helper, you can also show complex types in the grid. In this article, I showed you how you use complex types with WebGrid helper. Hopefully you will enjoy this article too.  

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  • Load and Web Performance Testing using Visual Studio Ultimate 2010-Part 3

    - by Tarun Arora
    Welcome back once again, in Part 1 of Load and Web Performance Testing using Visual Studio 2010 I talked about why Performance Testing the application is important, the test tools available in Visual Studio Ultimate 2010 and various test rig topologies, in Part 2 of Load and Web Performance Testing using Visual Studio 2010 I discussed the details of web performance & load tests as well as why it’s important to follow a goal based pattern while performance testing your application. In part 3 I’ll be discussing Test Result Analysis, Test Result Drill through, Test Report Generation, Test Run Comparison, Asp.net Profiler and some closing thoughts. Test Results – I see some creepy worms! In Part 2 we put together a web performance test and a load test, lets run the test to see load test to see how the Web site responds to the load simulation. While the load test is running you will be able to see close to real time analysis in the Load Test Analyser window. You can use the Load Test Analyser to conduct load test analysis in three ways: Monitor a running load test - A condensed set of the performance counter data is maintained in memory. To prevent the results memory requirements from growing unbounded, up to 200 samples for each performance counter are maintained. This includes 100 evenly spaced samples that span the current elapsed time of the run and the most recent 100 samples.         After the load test run is completed - The test controller spools all collected performance counter data to a database while the test is running. Additional data, such as timing details and error details, is loaded into the database when the test completes. The performance data for a completed test is loaded from the database and analysed by the Load Test Analyser. Below you can see a screen shot of the summary view, this provides key results in a format that is compact and easy to read. You can also print the load test summary, this is generated after the test has completed or been stopped.         Analyse the load test results of a previously run load test – We’ll see this in the section where i discuss comparison between two test runs. The performance counters can be plotted on the graphs. You also have the option to highlight a selected part of the test and view details, drill down to the user activity chart where you can hover over to see more details of the test run.   Generate Report => Test Run Comparisons The level of reports you can generate using the Load Test Analyser is astonishing. You have the option to create excel reports and conduct side by side analysis of two test results or to track trend analysis. The tools also allows you to export the graph data either to MS Excel or to a CSV file. You can view the ASP.NET profiler report to conduct further analysis as well. View Data and Diagnostic Attachments opens the Choose Diagnostic Data Adapter Attachment dialog box to select an adapter to analyse the result type. For example, you can select an IntelliTrace adapter, click OK and open the IntelliTrace summary for the test agent that was used in the load test.   Compare results This creates a set of reports that compares the data from two load test results using tables and bar charts. I have taken these screen shots from the MSDN documentation, I would highly recommend exploring the wealth of knowledge available on MSDN. Leaving Thoughts While load testing the application with an excessive load for a longer duration of time, i managed to bring the IIS to its knees by piling up a huge queue of requests waiting to be processed. This clearly means that the IIS had run out of threads as all the threads were busy processing existing request, one easy way of fixing this is by increasing the default number of allocated threads, but this might escalate the problem. The better suggestion is to try and drill down to the actual root cause of the problem. When ever the garbage collection runs it stops processing any pages so all requests that come in during that period are queued up, but realistically the garbage collection completes in fraction of a a second. To understand this better lets look at the .net heap, it is divided into large heap and small heap, anything greater than 85kB in size will be allocated to the Large object heap, the Large object heap is non compacting and remember large objects are expensive to move around, so if you are allocating something in the large object heap, make sure that you really need it! The small object heap on the other hand is divided into generations, so all objects that are supposed to be short-lived are suppose to live in Gen-0 and the long living objects eventually move to Gen-2 as garbage collection goes through.  As you can see in the picture below all < 85 KB size objects are first assigned to Gen-0, when Gen-0 fills up and a new object comes in and finds Gen-0 full, the garbage collection process is started, the process checks for all the dead objects and assigns them as the valid candidate for deletion to free up memory and promotes all the remaining objects in Gen-0 to Gen-1. So in the future when ever you clean up Gen-1 you have to clean up Gen-0 as well. When you fill up Gen – 0 again, all of Gen – 1 dead objects are drenched and rest are moved to Gen-2 and Gen-0 objects are moved to Gen-1 to free up Gen-0, but by this time your Garbage collection process has started to take much more time than it usually takes. Now as I mentioned earlier when garbage collection is being run all page requests that come in during that period are queued up. Does this explain why possibly page requests are getting queued up, apart from this it could also be the case that you are waiting for a long running database process to complete.      Lets explore the heap a bit more… What is really a case of crisis is when the objects are living long enough to make it to Gen-2 and then dying, this is definitely a high cost operation. But sometimes you need objects in memory, for example when you cache data you hold on to the objects because you need to use them right across the user session, which is acceptable. But if you wanted to see what extreme caching can do to your server then write a simple application that chucks in a lot of data in cache, run a load test over it for about 10-15 minutes, forcing a lot of data in memory causing the heap to run out of memory. If you get to such a state where you start running out of memory the IIS as a mode of recovery restarts the worker process. It is great way to free up all your memory in the heap but this would clear the cache. The problem with this is if the customer had 10 items in their shopping basket and that data was stored in the application cache, the user basket will now be empty forcing them either to get frustrated and go to a competitor website or if the customer is really patient, give it another try! How can you address this, well two ways of addressing this; 1. Workaround – A x86 bit processor only allows a maximum of 4GB of RAM, this means the machine effectively has around 3.4 GB of RAM available, the OS needs about 1.5 GB of RAM to run efficiently, the IIS and .net framework also need their share of memory, leaving you a heap of around 800 MB to play with. Because Team builds by default build your application in ‘Compile as any mode’ it means the application is build such that it will run in x86 bit mode if run on a x86 bit processor and run in a x64 bit mode if run on a x64 but processor. The problem with this is not all applications are really x64 bit compatible specially if you are using com objects or external libraries. So, as a quick win if you compiled your application in x86 bit mode by changing the compile as any selection to compile as x86 in the team build, you will be able to run your application on a x64 bit machine in x86 bit mode (WOW – By running Windows on Windows) and what that means is, you could use 8GB+ worth of RAM, if you take away everything else your application will roughly get a heap size of at least 4 GB to play with, which is immense. If you need a heap size of more than 4 GB you have either build a software for NASA or there is something fundamentally wrong in your application. 2. Solution – Now that you have put a workaround in place the IIS will not restart the worker process that regularly, which means you can take a breather and start working to get to the root cause of this memory leak. But this begs a question “How do I Identify possible memory leaks in my application?” Well i won’t say that there is one single tool that can tell you where the memory leak is, but trust me, ‘Performance Profiling’ is a great start point, it definitely gets you started in the right direction, let’s have a look at how. Performance Wizard - Start the Performance Wizard and select Instrumentation, this lets you measure function call counts and timings. Before running the performance session right click the performance session settings and chose properties from the context menu to bring up the Performance session properties page and as shown in the screen shot below, check the check boxes in the group ‘.NET memory profiling collection’ namely ‘Collect .NET object allocation information’ and ‘Also collect the .NET Object lifetime information’.    Now if you fire off the profiling session on your pages you will notice that the results allows you to view ‘Object Lifetime’ which shows you the number of objects that made it to Gen-0, Gen-1, Gen-2, Large heap, etc. Another great feature about the profile is that if your application has > 5% cases where objects die right after making to the Gen-2 storage a threshold alert is generated to alert you. Since you have the option to also view the most expensive methods and by capturing the IntelliTrace data you can drill in to narrow down to the line of code that is the root cause of the problem. Well now that we have seen how crucial memory management is and how easy Visual Studio Ultimate 2010 makes it for us to identify and reproduce the problem with the best of breed tools in the product. Caching One of the main ways to improve performance is Caching. Which basically means you tell the web server that instead of going to the database for each request you keep the data in the webserver and when the user asks for it you serve it from the webserver itself. BUT that can have consequences! Let’s look at some code, trust me caching code is not very intuitive, I define a cache key for almost all searches made through the common search page and cache the results. The approach works fine, first time i get the data from the database and second time data is served from the cache, significant performance improvement, EXCEPT when two users try to do the same operation and run into each other. But it is easy to handle this by adding the lock as you can see in the snippet below. So, as long as a user comes in and finds that the cache is empty, the user locks and starts to get the cache no more concurrency issues. But lets say you are processing 10 requests per second, by the time i have locked the operation to get the results from the database, 9 other users came in and found that the cache key is null so after i have come out and populated the cache they will still go in to get the results again. The application will still be faster because the next set of 10 users and so on would continue to get data from the cache. BUT if we added another null check after locking to build the cache and before actual call to the db then the 9 users who follow me would not make the extra trip to the database at all and that would really increase the performance, but didn’t i say that the code won’t be very intuitive, may be you should leave a comment you don’t want another developer to come in and think what a fresher why is he checking for the cache key null twice !!! The downside of caching is, you are storing the data outside of the database and the data could be wrong because the updates applied to the database would make the data cached at the web server out of sync. So, how do you invalidate the cache? Well if you only had one way of updating the data lets say only one entry point to the data update you can write some logic to say that every time new data is entered set the cache object to null. But this approach will not work as soon as you have several ways of feeding data to the system or your system is scaled out across a farm of web servers. The perfect solution to this is Micro Caching which means you cache the query for a set time duration and invalidate the cache after that set duration. The advantage is every time the user queries for that data with in the time span for which you have cached the results there are no calls made to the database and the data is served right from the server which makes the response immensely quick. Now figuring out the appropriate time span for which you micro cache the query results really depends on the application. Lets say your website gets 10 requests per second, if you retain the cache results for even 1 minute you will have immense performance gains. You would reduce 90% hits to the database for searching. Ever wondered why when you go to e-bookers.com or xpedia.com or yatra.com to book a flight and you click on the book button because the fare seems too exciting and you get an error message telling you that the fare is not valid any more. Yes, exactly => That is a cache failure! These travel sites or price compare engines are not going to hit the database every time you hit the compare button instead the results will be served from the cache, because the query results are micro cached, its a perfect trade-off, by micro caching the results the site gains 100% performance benefits but every once in a while annoys a customer because the fare has expired. But the trade off works in the favour of these sites as they are still able to process up to 30+ page requests per second which means cater to the site traffic by may be losing 1 customer every once in a while to a competitor who is also using a similar caching technique what are the odds that the user will not come back to their site sooner or later? Recap   Resources Below are some Key resource you might like to review. I would highly recommend the documentation, walkthroughs and videos available on MSDN. You can always make use of Fiddler to debug Web Performance Tests. Some community test extensions and plug ins available on Codeplex might also be of interest to you. The Road Ahead Thank you for taking the time out and reading this blog post, you may also want to read Part I and Part II if you haven’t so far. If you enjoyed the post, remember to subscribe to http://feeds.feedburner.com/TarunArora. Questions/Feedback/Suggestions, etc please leave a comment. Next ‘Load Testing in the cloud’, I’ll be working on exploring the possibilities of running Test controller/Agents in the Cloud. See you on the other side! Thank You!   Share this post : CodeProject

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  • Load and Web Performance Testing using Visual Studio Ultimate 2010-Part 2

    - by Tarun Arora
    Welcome back, in part 1 of Load and Web Performance Testing using Visual Studio 2010 I talked about why Performance Testing the application is important, the test tools available in Visual Studio Ultimate 2010 and various test rig topologies. In this blog post I’ll get into the details of web performance & load tests as well as why it’s important to follow a goal based pattern while performance testing your application. Tools => Options => Test Tools Have you visited the treasures of Visual Studio Menu bar tools => Options => Test Tools lately? The options to enable disable prompts on creating, editing, deleting or running manual/automated tests can be controller from here. The default test project language and default test types created on a new test project creation could be selected/unselected from here. Ever wondered how you can change the default limit of 25 test results, this can again be changed from here. If you record a lot of Web Tests and wish for the web test recorder to start with “that” URL populated, well this again can be specified from here. If you haven’t so far, I would urge you to spend 2 minutes in the test tools options.   Test Menu => Ready Steady Test Action! The Test tools are under the Test Menu in Visual Studio, apart from being able to create a new Test and Test List you can also load an existing vsmdi file. You can also manage your test controllers from here. A solution can have one or more test setting files, but there can only be one active test settings file at any time. Again, this selection can be done from here.  You can open the various test windows from under the windows option from the test menu. If you open the Test view window you will see that you have the option to group the tests by work items, project, test type, etc. You can set these properties by right clicking a test in the test list and choosing properties from the context menu.    So, what is a vsmdi file? vsmdi stands for Visual Studio Test Metadata File. Placed under the Solution Items this file keeps track of the list of unit tests in your solution. If you open the vsmdi file as an xml file you will see a series of Test Links nested with in the list Test List tags along with the Run Configuration tag. When in visual studio you run tests, the IDE looks at the vsmdi file to see what tests need to be run. You also have the option of using the vsmdi file in your team builds to specify which tests need to run as part of the build. Refer here for a walkthrough from a fellow blogger on how to use the vsmdi file in the team builds. Web Performance Test – The Truth! In Visual Studio 2010 “Web Tests” have been renamed to “Web Performance Tests”. Apart from renaming this test type there have been several improvements to this test type in visual studio 2010. I am very active on the MSDN Visual Studio And Load Testing forum and a frequent question from many users is “Do Web Tests support Pages that run JavaScript?” I will start with a little bit of background before answering this question. Web Performance Tests operate at the HTTP Layer, but why? To enable you to generate high loads with a relatively low amount of hardware, Web performance tests are driven at the protocol layer rather than instantiating a browser.The most common source of confusion is that users do not realize Web Performance Tests work at the HTTP layer. The tool adds to that misconception. After all, you record in IE, and when running a Web test you can select which browser to use, and then the result viewer shows the results in a browser window. So that means the tests run through the browser, right? NO! The Web test engine works at the HTTP layer, and does not instantiate a browser. What does that mean? In the diagram below, you can see there are no browsers running when the engine is sending and receiving requests. Does that mean I can’t test pages that use Java script? The best example for java script generating HTTP traffic is AJAX calls. The most common example of browser plugins are Silverlight or Flash. The Web test recorder will record HTTP traffic from AJAX calls and from most (but not all) browser plugins. This means you will still be able to web performance test pages that use java script or plugin and play back the results but the playback engine will not show the java script or plug in results in the ‘browser control’. If you want to test the page behaviour as a result of the java script or plug in consider using Coded UI Tests. This page looks like it failed, when in fact it succeeded! Looking closely at the response, and subsequent requests, it is clear the operation succeeded. As stated above, the reason why the browser control is pasting this message is because java script has been disabled in this control. So, to reiterate, the web performance test recorder: - Sends and receives data at the HTTP layer. - Does NOT run a browser. - Does NOT run java script. - Does NOT host ActiveX controls or plugins. There is a great series of blog posts from Ed Glas, i would highly recommend his blog to any one performing Load/Performance testing through Visual Studio. Demo – Web Performance Test [Demo] - Visual Studio Ultimate 2010: Test Settings and Configuration   [Demo]–Visual Studio Ultimate 2010: Web Performance Test   In this short video I try and answer the following questions, Why is performance Testing important? How does Visual Studio Help you performance Test your applications? How do i record a web performance test? How do make a web performance test data driven, transaction driven, loop driven, convert to code, add validations? Best practices for recording Web Performance Tests. I have a web performance test, what next? Creating the Web Performance Test was the first step towards load testing your application. Now that we have the base test we can test the page behaviour when N-users access the page. Have you ever had the head of business call you and mention that the marketing team has done a fantastic job and are expecting increased traffic on the web site, can the website survive the weekend with that additional load? This is the perfect opportunity to capacity test your application to see how your website holds up under various levels of load, you can work the results backwards to see how much hardware you may need to scale up your application to survive the weekend. Apart from that it is always a good idea to have some benchmarks around how the application performs under light loads for short duration, under heavy load for long duration and soak test the application run a constant load for a very week or two to record the effects of constant load for really long durations, this is a great way of identifying how your application handles the default IIS application pool reset which by default is configured to once every 25 hours. These bench marks will act as the perfect yard stick to measure performance gains when you start making improvements. BUT there are some best practices! => Goal Based Load Testing Approach Since the subject is vast and there are a lot of things to measure and analyse, … it is very easy to get distracted from the real goal!  You can optimize your application once you know where the pain points are. There is no point performing a load test of 5000 users if your intranet application will only have a 100 simultaneous users, it is important to keep focussed on the real goals of the project. So the idea is to have a user story around your load testing scenarios and test realistically. So it is recommended that you follow the below outline, It is an Iterative process, refine your objectives, identify the key scenarios, what is the expected workload, key metrics you want to report, record the web performance tests, simulate load and analyse results. Is your application already deployed in Production? This is great! You can analyse the IIS Logs to understand the user behaviour… But what are IIS LOGS? The IIS logs allow you to record events for each application and Web site on the Web server. You can create separate logs for each of your applications and Web sites. Logging information in IIS goes beyond the scope of the event logging or performance monitoring features provided by Windows. The IIS logs can include information, such as who has visited your site, what the visitor viewed, and when the information was last viewed. You can use the IIS logs to identify any attempts to gain unauthorized access to your Web server. How to configure IIS LOGS? For those Ninjas who already have IIS Logs configured (by the way its on by default) and need a way to analyse the IIS Logs, can use the Windows IIS Utility – Log Parser. Log Parser is a very powerful tool that provides a generic SQL-like language on top of many types of data like IIS Logs, Event Viewer entries, XML files, CSV files, File System and others; and it allows you to export the result of the queries to many output formats such as CSV, XML, SQL Server, Charts and others; and it works well with IIS 5, 6, 7 and 7.5. Frequently used Log Parser queries. Demo – Load Test [Demo]–Visual Studio Ultimate 2010: Load Testing   In this short video I try and answer the following questions, - Types of Performance Testing? - Perform Goal driven Load Testing, analyse Test Run Result and Generate a report? Recap A quick recap of what we have covered so far,     Thank you for taking the time out and reading this blog post, in part III of this blog series I’ll be getting into the details of Test Result Analysis, Test Result Drill through, Test Report Generation, Test Run Comparison, and the Asp.net Profiler. If you enjoyed the post, remember to subscribe to http://feeds.feedburner.com/TarunArora. Questions/Feedback/Suggestions, etc please leave a comment. See you on in Part III   Share this post : CodeProject

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  • More Fun With Math

    - by PointsToShare
    More Fun with Math   The runaway student – three different ways of solving one problem Here is a problem I read in a Russian site: A student is running away. He is moving at 1 mph. Pursuing him are a lion, a tiger and his math teacher. The lion is 40 miles behind and moving at 6 mph. The tiger is 28 miles behind and moving at 4 mph. His math teacher is 30 miles behind and moving at 5 mph. Who will catch him first? Analysis Obviously we have a set of three problems. They are all basically the same, but the details are different. The problems are of the same class. Here is a little excursion into computer science. One of the things we strive to do is to create solutions for classes of problems rather than individual problems. In your daily routine, you call it re-usability. Not all classes of problems have such solutions. If a class has a general (re-usable) solution, it is called computable. Otherwise it is unsolvable. Within unsolvable classes, we may still solve individual (some but not all) problems, albeit with different approaches to each. Luckily the vast majority of our daily problems are computable, and the 3 problems of our runaway student belong to a computable class. So, let’s solve for the catch-up time by the math teacher, after all she is the most frightening. She might even make the poor runaway solve this very problem – perish the thought! Method 1 – numerical analysis. At 30 miles and 5 mph, it’ll take her 6 hours to come to where the student was to begin with. But by then the student has advanced by 6 miles. 6 miles require 6/5 hours, but by then the student advanced by another 6/5 of a mile as well. And so on and so forth. So what are we to do? One way is to write code and iterate it until we have solved it. But this is an infinite process so we’ll end up with an infinite loop. So what to do? We’ll use the principles of numerical analysis. Any calculator – your computer included – has a limited number of digits. A double floating point number is good for about 14 digits. Nothing can be computed at a greater accuracy than that. This means that we will not iterate ad infinidum, but rather to the point where 2 consecutive iterations yield the same result. When we do financial computations, we don’t even have to go that far. We stop at the 10th of a penny.  It behooves us here to stop at a 10th of a second (100 milliseconds) and this will how we will avoid an infinite loop. Interestingly this alludes to the Zeno paradoxes of motion – in particular “Achilles and the Tortoise”. Zeno says exactly the same. To catch the tortoise, Achilles must always first come to where the tortoise was, but the tortoise keeps moving – hence Achilles will never catch the tortoise and our math teacher (or lion, or tiger) will never catch the student, or the policeman the thief. Here is my resolution to the paradox. The distance and time in each step are smaller and smaller, so the student will be caught. The only thing that is infinite is the iterative solution. The race is a convergent geometric process so the steps are diminishing, but each step in the solution takes the same amount of effort and time so with an infinite number of steps, we’ll spend an eternity solving it.  This BTW is an original thought that I have never seen before. But I digress. Let’s simply write the code to solve the problem. To make sure that it runs everywhere, I’ll do it in JavaScript. function LongCatchUpTime(D, PV, FV) // D is Distance; PV is Pursuers Velocity; FV is Fugitive’ Velocity {     var t = 0;     var T = 0;     var d = parseFloat(D);     var pv = parseFloat (PV);     var fv = parseFloat (FV);     t = d / pv;     while (t > 0.000001) //a 10th of a second is 1/36,000 of an hour, I used 1/100,000     {         T = T + t;         d = t * fv;         t = d / pv;     }     return T;     } By and large, the higher the Pursuer’s velocity relative to the fugitive, the faster the calculation. Solving this with the 10th of a second limit yields: 7.499999232000001 Method 2 – Geometric Series. Each step in the iteration above is smaller than the next. As you saw, we stopped iterating when the last step was small enough, small enough not to really matter.  When we have a sequence of numbers in which the ratio of each number to its predecessor is fixed we call the sequence geometric. When we are looking at the sum of sequence, we call the sequence of sums series.  Now let’s look at our student and teacher. The teacher runs 5 times faster than the student, so with each iteration the distance between them shrinks to a fifth of what it was before. This is a fixed ratio so we deal with a geometric series.  We normally designate this ratio as q and when q is less than 1 (0 < q < 1) the sum of  + … +  is  – 1) / (q – 1). When q is less than 1, it is easier to use ) / (1 - q). Now, the steps are 6 hours then 6/5 hours then 6/5*5 and so on, so q = 1/5. And the whole series is multiplied by 6. Also because q is less than 1 , 1/  diminishes to 0. So the sum is just  / (1 - q). or 1/ (1 – 1/5) = 1 / (4/5) = 5/4. This times 6 yields 7.5 hours. We can now continue with some algebra and take it back to a simpler formula. This is arduous and I am not going to do it here. Instead let’s do some simpler algebra. Method 3 – Simple Algebra. If the time to capture the fugitive is T and the fugitive travels at 1 mph, then by the time the pursuer catches him he travelled additional T miles. Time is distance divided by speed, so…. (D + T)/V = T  thus D + T = VT  and D = VT – T = (V – 1)T  and T = D/(V – 1) This “strangely” coincides with the solution we just got from the geometric sequence. This is simpler ad faster. Here is the corresponding code. function ShortCatchUpTime(D, PV, FV) {     var d = parseFloat(D);     var pv = parseFloat (PV);     var fv = parseFloat (FV);     return d / (pv - fv); } The code above, for both the iterative solution and the algebraic solution are actually for a larger class of problems.  In our original problem the student’s velocity (speed) is 1 mph. In the code it may be anything as long as it is less than the pursuer’s velocity. As long as PV > FV, the pursuer will catch up. Here is the really general formula: T = D / (PV – FV) Finally, let’s run the program for each of the pursuers.  It could not be worse. I know he’d rather be eaten alive than suffering through yet another math lesson. See the code run? Select  “Catch Up Time” in www.mgsltns.com/games.htm The host is running on Unix, so the link is case sensitive. That’s All Folks

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  • JavaScript in different browsers

    - by PointsToShare
    Adventures with JavaScript rendered in IE 8, Chrome 15, and Firefox 8.0 I have written a little monogram about the advantages of Math and wrote a few JavaScript applications to demonstrate them. I was a bit careless and used elements on the page in my JavaScript without using any of the GetElementsByXXXX methods to identify them.  Say I had a text box named tbSeqNum into which I entered a number to be used in a computation. In my code I simply referred to its value by using it directly. Like here: Function Blah() {                 return tbSeqNum.value; } This ran fine in IE8. In IE, the elements are available as global variables. This is not the case in either Firefox or Chrome. In there one has to create the variable and only then use it. Assuming I also used tbSeqNum as the element’s ID, this works: Function Blah() {                 return GetElementById(“tbSeqNum”).value; } Naturally this corrected function also works in IE, so be warned. Also, coming from windows programming (I am long in the tooth and programmed long before the internet), I have a habit of putting an “Exit” button on my pages and setting their onclick to: onclick=”window.close()”. Again, this works fine in IE. In Firefox and chrome, it does not! There you can only close a window that you opened in the code. A window that was opened by navigation to a URL will not close.  Before I deployed mu code to my website, I painfully removed all my Exit buttons. But my greatest surprise came when I tested my pages in the various browsers. In my code I do a comparison on the performance of two algorithms used to solve the same problem. One is brute force, the other uses a mathematical formula. The compare functions runs each many times and displays the time it took for each and also the ratio. Chrome runs JavaScript between 5 and 10 times faster than Firefox and between 50 and 100 times faster that IE. Wow!!! This difference is especially remarkable when the code uses iteration. I suspect that the JS engines in Chrome and Firefox simply cache the result of a function and if it is called again with the same parameters, it returns the cached result. To see it in action play run the “How Many Squares” page in www.mgsltns.com/games.htm The host is running on Unix, so the link is case sensitive. Last Note: IE9 runs JS a bit faster, but still lags behind almost as badly. That’s All Folks!

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  • Mounting a Microsoft Azure CloudDrive in a VMRole

    - by SeanBarlow
    Mounting a Drive in a VMRole is a little more complicated then a web or worker.  The Web and Worker roles offer OnStart and OnStop events, which you can use to mount or unmount your drives. The VMRole does not have these same events so you have to provide another way for the drives to be mounted or unmounted. The problem I have run into is what if you have multiple drives and you only want to mount certain drives. How do you let your user mount the drive. I am not going to go into details on what kind of GUI to present to the user. I have done this in a simple WPF application as well as a console application. We are going to need to get the storage account details. One thing to note when you are mounting cloud drives you cannot use https and have to use http. We force the use of http by using false when we create the CloudStorageAccount.   StorageCredentialsAccountAndKey credentials = new StorageCredentialsAccountAndKey("AccountName", "AccountKey"); CloudStorageAccount storageAccount = new CloudStorageAccount(credentials, false);   Next we need to get a reference to the container.   var blobClient = storageAccount.CreateCloudBlobClient(); var container = blobClient.GetContainerReference("ContainerName");   Now we need to get a list of the drives in the container   var drives = container.ListBlobs();   Now that we have a list of the drives in the container we can let the user choose which drive they want to mount. I am just selecting the 1st drive in the list for the example and getting the Uri of the drive.   var driveUri = drives.First().Uri;   Now that we have the Uri we need to get the reference to the drive. var drive = new CloudDrive(driveUri, storageAccount.Credentials);   Now all that is left is to mount the drive.   var driveLetter = drive.Mount(0, DriveMountOptions.None);   To unmount the drive all you have to do is call unmount on the drive. drive.Unmount();   You do need to make sure you unount the drives when you are done with them. I have run into issues with the drives being locked until the VMRole is rebooted. I have also managed to have a drive be permanently locked and I was forced to delete it and upload it again. I have been unable to reproduce the permanent lock but I am still trying. The CloudDrive class provides a handy method to retrieve all the mounted drives in the Role. foreach (var drive in CloudDrive.GetMountedDrives()) {          var mountedDrive = Account.CreateCloudDrive(drive.Value.PathAndQuery);          mountedDrive.Unmount(); }

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