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  • Javascript inheritance: call super-constructor or use prototype chain?

    - by Jeremy S.
    Hi folks, quite recently I read about javascript call usage in MDC https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Function/call one linke of the example shown below, I still don't understand. Why are they using inheritance here like this Prod_dept.prototype = new Product(); is this necessary? Because there is a call to the super-constructor in Prod_dept() anyway, like this Product.call is this just out of common behaviour? When is it better to use call for the super-constructor or use the prototype chain? function Product(name, value){ this.name = name; if(value >= 1000) this.value = 999; else this.value = value; } function Prod_dept(name, value, dept){ this.dept = dept; Product.call(this, name, value); } Prod_dept.prototype = new Product(); // since 5 is less than 1000, value is set cheese = new Prod_dept("feta", 5, "food"); // since 5000 is above 1000, value will be 999 car = new Prod_dept("honda", 5000, "auto"); Thanks for making things clearer

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  • mysql to excel genration using php

    - by pmms
    <?php // DB Connection here mysql_connect("localhost","root",""); mysql_select_db("hitnrunf_db"); $select = "SELECT * FROM jos_users "; $export = mysql_query ( $select ) or die ( "Sql error : " . mysql_error( ) ); $fields = mysql_num_fields ( $export ); for ( $i = 0; $i < $fields; $i++ ) { $header .= mysql_field_name( $export , $i ) . "\t"; } while( $row = mysql_fetch_row( $export ) ) { $line = ''; foreach( $row as $value ) { if ( ( !isset( $value ) ) || ( $value == "" ) ) { $value = "\t"; } else { $value = str_replace( '"' , '""' , $value ); $value = '"' . $value . '"' . "\t"; } $line .= $value; } $data .= trim( $line ) . "\n"; } $data = str_replace( "\r" , "" , $data ); if ( $data == "" ) { $data = "\n(0) Records Found!\n"; } header("Content-type: application/octet-stream"); header("Content-Disposition: attachment; filename=your_desired_name.xls"); header("Pragma: no-cache"); header("Expires: 0"); print "$header\n$data"; ? the above code is used for genrating mysql to excel sheet but we are getting following error the file youare trying to open, 'users.xls',is in a different format than specified by the file extension. verify that the file is not corrupted and is from a trusted source before opening the file. do you want to open the file now?

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  • Get type of the parameter from list of objects, templates, C++

    - by CrocodileDundee
    This question follows to my previous question Get type of the parameter, templates, C++ There is the following data structure: Object1.h template <class T> class Object1 { private: T a1; T a2; public: T getA1() {return a1;} typedef T type; }; Object2.h template <class T> class Object2: public Object1 <T> { private: T b1; T b2; public: T getB1() {return b1;} } List.h template <typename Item> struct TList { typedef std::vector <Item> Type; }; template <typename Item> class List { private: typename TList <Item>::Type items; }; Is there any way how to get type T of an object from the list of objects (i.e. Object is not a direct parameter of the function but a template parameter)? template <class Object> void process (List <Object> *objects) { typename Object::type a1 = objects[0].getA1(); // g++ error: 'Object1<double>*' is not a class, struct, or union type } But his construction works (i.e. Object represents a parameter of the function) template <class Object> void process (Object *o1) { typename Object::type a1 = o1.getA1(); // OK }

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  • Cordova polluted logs with persistent.js add()

    - by slaver113
    I am using the latest phonegap/cordova version 2.1. and my log in Eclipse logcat get polluted with code when i do var allItems = Item.all(); allItems.list(null, function (results) { results.forEach(function (r) { console.log(r.id+ " " + r.lat + " " + r.long + " " + r.state); }); }); I get a output like (for 100s of lines) 10-29 10:56:13.270: I/Web Console(5961): } function (value) { 10-29 10:56:13.270: I/Web Console(5961): if (value === undefined) { 10-29 10:56:13.270: I/Web Console(5961): return getterCallback(); 10-29 10:56:13.270: I/Web Console(5961): } else { 10-29 10:56:13.270: I/Web Console(5961): setterCallback(value); 10-29 10:56:13.270: I/Web Console(5961): return scope; 10-29 10:56:13.270: I/Web Console(5961): } 10-29 10:56:13.270: I/Web Console(5961): } function (value) { 10-29 10:56:13.270: I/Web Console(5961): if (value === undefined) { 10-29 10:56:13.270: I/Web Console(5961): return getterCallback(); 10-29 10:56:13.270: I/Web Console(5961): } else { 10-29 10:56:13.270: I/Web Console(5961): setterCallback(value); 10-29 10:56:13.270: I/Web Console(5961): return scope; 10-29 10:56:13.270: I/Web Console(5961): } 10-29 10:56:13.270: I/Web Console(5961): } function (value) { 10-29 10:56:13.270: I/Web Console(5961): if (value === undefined) { 10-29 10:56:13.270: I/Web Console(5961): return getterCallback(); 10-29 10:56:13.270: I/Web Console(5961): } else { 10-29 10:56:13.270: I/Web Console(5961): setterCallback(value); 10-29 10:56:13.270: I/Web Console(5961): return scope; 10-29 10:56:13.270: I/Web Console(5961): } 10-29 10:56:13.270: I/Web Console(5961): } at :1149822901

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  • html escape characters

    - by user1468537
    I have the following: <form name="input" method="get" action="http://site:8083/Default.aspx?DC=" target="foo" onSubmit="window.open('', 'foo', 'width=1100 height=500,status=no,resizable=yes,scrollbars=yes')"> <select name="DC"> <option value="1&Type=type1">1</option> <option value="2&Type=type2">2</option> <option value="3&Type=type3">3</option> <option value="4&Type=type4">4</option> <option value="5&Type=type5">5</option> <option value="6&Type=type6">6</option> <option value="7&Type=type7">7</option> </select> <input type="submit" value=">>"/>&nbsp;&nbsp; </form> Basically my querystring should be something like DC=1&Type=type1 the problem I have is that when I click the button above the html screws up the stirng by changing & to %26 and = to %3D How can I make the value stay as I have it in the code above?

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  • [Concept] How does unlink() find the file to delete?

    - by Prasad
    My app has a 'Photo' field to store URL. It uses sfWidgetFormInputFileEditable for the widget schema. To delete the old image when a new image is uploaded, I use unlink before setting the value in the over-ridden setter and it works!!! if (file_exists($this->_get('photo'))) unlink($this->_get('photo')); Photos are stored in uploads/photos and when saving 'Photo' only the file name xxx-yyy.zzz is saved (and not the full path). However, I wish to know how symfony/php knows the full path of the file to be deleted? Part 2: I am using sfThumbnailPlugin to generate thumbnails. So the actual code looks like this: public function setPhoto($value) { if(!empty($value)) { Contact::generateThumbnail($value); // delete current Photo & create thumbnail $this->_set('photo',$value); // setting new value after deleting old one } } public function generateThumbnail($value) { $uploadDir = sfConfig::get('app_photo_upload'); // path to upload folder if (file_exists($this->_get('photo'))) { unlink($this->_get('photo')); // delete full-size image // path to thumbnail $thumbpath = $uploadDir.'/thumbnails/'.$this->get('photo'); // read a blog, tried setting dir manually, doesn't work :( //chdir('/thumbnails/'); // tried closing the file too, doesn't work! :( //fclose($thumbpath) or die("can't close file"); //unlink($this->_get('photo')); // doesn't work; no error :( unlink($thumbpath); // doesn't work, no error :( } $thumbnail = new sfThumbnail(150, 150); $thumbnail->loadFile($uploadDir.'/'.$value); $thumbnail->save($uploadDir.'/thumbnails/'.$value, 'image/png'); } Why can't the thumbnail be deleted using unlink()? is the sequence of ops incorrect? Is it because the old thumbnail is displayed in the sfWidgetFormInputFileEditable widget? I've spent hours trying to figure this out, but unable to nail down the real cause. Thanks in advance.

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  • PHP Array to CSV

    - by JohnnyFaldo
    I'm trying to convert an array of products into a CSV file, but it doesn't seem to be going to plan. The CSV file is one long line, here is my code: for($i=0;$i<count($prods);$i++) { $sql = "SELECT * FROM products WHERE id = '".$prods[$i]."'"; $result = $mysqli->query($sql); $info = $result->fetch_array(); } $header = ''; for($i=0;$i<count($info);$i++) { $row = $info[$i]; $line = ''; for($b=0;$b<count($row);$b++) { $value = $row[$b]; if ( ( !isset( $value ) ) || ( $value == "" ) ) { $value = "\t"; } else { $value = str_replace( '"' , '""' , $value ); $value = '"' . $value . '"' . "\t"; } $line .= $value; } $data .= trim( $line ) . "\n"; } $data = str_replace( "\r" , "" , $data ); if ( $data == "" ) { $data = "\n(0) Records Found!\n"; } header("Content-type: application/octet-stream"); header("Content-Disposition: attachment; filename=your_desired_name.xls"); header("Pragma: no-cache"); header("Expires: 0"); print "$data"; Also, the header doesn't force a download. I've been copy and pasting the output and saving as .csv

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  • jquery problem in IE working fine in FF

    - by Bharanikumar
    function populate_customer_details(){ $.ajax({ type : 'POST', url : 'populate_customer_details.php', data: { email : $('#txt_email_id').val() }, success : function(data){ if(data=="NOROWSFOUND"){ alert("Sorry, Email ID not exist in our database"); document.getElementById("txt_email_id").focus(); }else{ var val = explode_all_into_arr(data,"|=|"); document.getElementById("FirstName").value = val[0]; document.getElementById("LastName").value = val[1]; document.getElementById("mobilecountrycode").value = parseInt(val[2]); document.getElementById("MobileNo").value = val[3]; document.getElementById("homecountrycode").value = parseInt(val[4]); document.getElementById("HomeNo").value = val[5]; document.getElementById("PaxEmail").value = val[6]; document.getElementById("PaxEmailConf").value = val[6]; } }, }); } This is my snippet purpose is getting the customer details and populate into textfield and combo box , That is Firstname will append into Firstname text field , Secondname will append into Secondname text field , Same like mobilecountrycode (but this is dropdown combo), Some time combo selectedindex work fine, but some time not selecting the value , I am not sure what s problem in that... Nothing works in IE , Also showing object expected error in IE , i have ajax_common.js : in this i added above script , in the page top first i included the jquery.js , Then i include ajax_common.js file, But no idea why this problem. Regards (NOTE i included the jquery.js ) ,

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  • Why does applying this gradient style break my silverlight app ?

    - by Robotsushi
    I am having some issues with applying a gradient to a RadButton. I have a gradient definition in my styles resource dictionairy like so : <LinearGradientBrush x:Key="GridView_HeaderBackground" EndPoint="0.5,1" StartPoint="0.5,0"> <GradientStop Color="#FF5B5B5B" Offset="1"/> <GradientStop Color="#FF868686"/> <GradientStop Color="#FF4F4F4F" Offset="0.42"/> <GradientStop Color="#FF0E0E0E" Offset="0.43"/> </LinearGradientBrush> When i apply this gradient directly to the background of a RadButton everything works. Here is the button and the template definition: Button <telerik:RadButton Margin="5,10,5,0" Click="RadButton_Click" Tag="30" Content="30 Days" Style="{StaticResource SliderButton}" Background="{StaticResource GridView_HeaderBackground}" /> Template: <!-- Style Template for Slider RadButton --> <Style x:Key="SliderButton" TargetType="telerik:RadButton"> <Setter Property="Height" Value="30" /> <Setter Property="Foreground" Value="#FFFFFF" /> <Setter Property="BorderThickness" Value="0" /> <Setter Property="Margin" Value="5,2" /> </Style> However when applying this gradient in the resource dictionary, my application will not load it simply gets to the silverlight loading screen and then never proceeds Here is the button and template which breaks my app. Button: <telerik:RadButton Margin="5,10,5,0" Click="RadButton_Click" Tag="30" Content="30 Days" Style="{StaticResource SliderButton}" /> Template: <!-- Style Template for Slider RadButton --> <Style x:Key="SliderButton" TargetType="telerik:RadButton"> <Setter Property="Background" Value="{StaticResource GridView_HeaderBackground}" /> <Setter Property="Height" Value="30" /> <Setter Property="Foreground" Value="#FFFFFF" /> <Setter Property="BorderThickness" Value="0" /> <Setter Property="Margin" Value="5,2" /> </Style> When i observe the js error console in google chrome i notice the following error is produced: "Cannot find a resource with the name/key ResourceWrapper"

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  • JQuery: Create n selects after choosing it in the select box

    - by Tom
    I have this select: <select name="main"> <option value="2">2s</option> <option value="3">3s</option> <option value="5">5s</option> </select> How do I make, that after choosing 2s, 2 selects would be created: <select name="select1"> <option value="0">0</option> <option value="1">1</option> <option value="2">2</option> </select> <select name="select2"> <option value="0">0</option> <option value="1">1</option> <option value="2">2</option> </select> After choosing 3s, it would create 3 selects and so on. Thanks Would appreciate jsfiddle example

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  • How to synchronize access to many objects

    - by vividos
    I have a thread pool with some threads (e.g. as many as number of cores) that work on many objects, say thousands of objects. Normally I would give each object a mutex to protect access to its internals, lock it when I'm doing work, then release it. When two threads would try to access the same object, one of the threads has to wait. Now I want to save some resources and be scalable, as there may be thousands of objects, and still only a hand full of threads. I'm thinking about a class design where the thread has some sort of mutex or lock object, and assigns the lock to the object when the object should be accessed. This would save resources, as I only have as much lock objects as I have threads. Now comes the programming part, where I want to transfer this design into code, but don't know quite where to start. I'm programming in C++ and want to use Boost classes where possible, but self written classes that handle these special requirements are ok. How would I implement this? My first idea was to have a boost::mutex object per thread, and each object has a boost::shared_ptr that initially is unset (or NULL). Now when I want to access the object, I lock it by creating a scoped_lock object and assign it to the shared_ptr. When the shared_ptr is already set, I wait on the present lock. This idea sounds like a heap full of race conditions, so I sort of abandoned it. Is there another way to accomplish this design? A completely different way?

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  • How do I extract specific data with preg_match?

    - by paulswansea
    I'm looking to extract values from a whole load of html (i've just trimmed down to the relevant data), there are multiple 'select' elements, and only want to extract those who's 'name' element matches the name 'aMembers'. So the resulting values I would like to retrieve are 5,10,25 and 30 (see below) how can I achieve this with preg_match? <DIV id="searchM" class="search"><select name="aMembers" id="aMembers" tabIndex="2"> <option selected="selected" value="">Data 3</option> <option value="5">A name</option> <option value="10">Another name</option> </select> </DIV> <DIV id="searchM" class="search"><select name="bMembers" id="bMembers" tabIndex="2"> <option selected="selected" value="">Data 2</option> <option value="15">A name</option> <option value="20">Another name</option> </select> </DIV> <DIV id="searchM" class="search"><select name="aMembers" id="Members" tabIndex="2"> <option selected="selected" value="">Data 1</option> <option value="25">A name</option> <option value="30">Another name</option> </select> </DIV>

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  • CheckBOX ASP MVC

    - by NewmanASPMVC
    Hi i am new to ASP.NET MVC. I am not sure how to deal with Check box or Radio Button to get values when they are clicked. Can any one help me? I am providing a simple code that might help you understand what i meant to be. Please share examples. <script type="text/javascript" > function check(browser) { document.getElementById("answer").value=browser; } </script> <form action=""> <input type="radio" name="browser" onclick="check(this.value)" value="Internet Explorer"/>Internet Explorer<br /> <input type="radio" name="browser" onclick="check(this.value)" value="Firefox"/>Firefox<br /> <input type="radio" name="browser" onclick="check(this.value)" value="Netscape"/>Netscape<br /> <input type="radio" name="browser" onclick="check(this.value)" value="Opera"/>Opera<br /> <br /> Your favorite browser is: <input type="text" id="answer" size="20"/> </form>

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  • Credit card validation with regexp using test()

    - by Matt
    I'm trying to complete some homework and it appears the book might have gotten it wrong. I have a simple html page that allows user to pick a credit card in our case american express. The user then enters a number and evalutes that number based on a regular expression. My question ends up being when test() evaluates the number it returns a boolean or a string? I should then compare that string or boolean? True == true should fire off the code in a nested if statement. Heres what the book gives me as valid code: if(document.forms[0].cardName.value == "American Express") { var cardProtocol = new RegExp("^3[47][0-9]{13}$"); //REGEX ENTRY HERE if(cardProtocol.test(document.forms[0].cardNumber.value)) document.forms[0].ccResult.value = "Valid credit card number"; } The above code doesn't work in firefox. I've tried modifying it with 2 alerts to make sure the number is good and the boolean is good...and still no luck: if(document.forms[0].cardName.value == "American Express") { var cardProtocol = new RegExp("^3[47][0-9]{13}$"); //REGEX ENTRY HERE <------ alert(document.forms[0].cardNumber.value) alert(cardProtocol.test(document.forms[0].cardNumber.value)) if((cardProtocol.test(document.forms[0].cardNumber.value)) == true ) // <--Problem { document.forms[0].ccResult.value = "Valid credit card number"; } else { document.forms[0].ccResult.value = "Invalid credit card number"; } } Any ideas? the if loop is the culprit but I'm not figuring out why it is not working. Please throw up the code for the if loop! Thanks for the help!

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  • Deserializing child elements as attributes of parent

    - by LloydPickering
    I have XML files which I need to deserialize. I used the XSD tool from Visual Studio to create c# object files. the generated classes do deserialize the files except not in the way which I need. I would appreciate any help figuring out how to solve this problem. The child elements named 'data' should be attributes of the parent element 'task'. A shortened example of the XML is below: <task type="Nothing" id="2" taskOnFail="false" > <data value="" name="prerequisiteTasks" /> <data value="" name="exclusionTasks" /> <data value="" name="allowRepeats" /> <task type="Wait for Tasks" id="10" taskOnFail="false" > <data value="" name="prerequisiteTasks" /> <data value="" name="exclusionTasks" /> <data value="" name="allowRepeats" /> </task> <task type="Wait for Tasks" id="10" taskOnFail="false" > <data value="" name="prerequisiteTasks" /> <data value="" name="exclusionTasks" /> <data value="" name="allowRepeats" /> </task> </task> The Class definition I am trying to deserialize to is in the form: public class task { public string prerequisiteTasks {get;set;} public string exclusionTasks {get;set;} public string allowRepeats {get;set;} [System.Xml.Serialization.XmlElementAttribute("task")] public List<task> ChildTasks {get;set;} } The child 'task's are fine, but the generated files put the 'data' elements into an array of data[] rather than as named members of the task class as I need.

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  • jquery - how to get number from a string with mixture of letters and number

    - by Alex
    How do I use JQuery to get number from the drop down select? <select aria-invalid="false" id="RatePercent" class="wpcf7-form-control wpcf7-select ratePercent" name="RatePercent"> <option value="">---</option> <option value="Floating-6.5%">Floating-6.5%</option> <option value="6 Months-5.65%">6 Months-5.65%</option> <option value="1 Year-5.85%">1 Year-5.85%</option> <option value="18 Months-5.99%">18 Months-5.99%</option> <option value="2 Years-6.19%">2 Years-6.19%</option> <option value="3 Years-6.85%">3 Years-6.85%</option> <option value="4 Years-7.19%">4 Years-7.19%</option> <option value="5 Years-7.40%">5 Years-7.40%</option> </select> If you choose 1 Year-5.85%, it returns '5.85', instead of '1 Year-5.85%'?

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  • jQuery Time Entry with Time Navigation Keys

    - by Rick Strahl
    So, how do you display time values in your Web applications? Displaying date AND time values in applications is lot less standardized than date display only. While date input has become fairly universal with various date picker controls available, time entry continues to be a bit of a non-standardized. In my own applications I tend to use the jQuery UI DatePicker control for date entries and it works well for that. Here's an example: The date entry portion is well defined and it makes perfect sense to have a calendar pop up so you can pick a date from a rich UI when necessary. However, time values are much less obvious when it comes to displaying a UI or even just making time entries more useful. There are a slew of time picker controls available but other than adding some visual glitz, they are not really making time entry any easier. Part of the reason for this is that time entry is usually pretty simple. Clicking on a dropdown of any sort and selecting a value from a long scrolling list tends to take more user interaction than just typing 5 characters (7 if am/pm is used). Keystrokes can make Time Entry easier Time entry maybe pretty simple, but I find that adding a few hotkeys to handle date navigation can make it much easier. Specifically it'd be nice to have keys to: Jump to the current time (Now) Increase/decrease minutes Increase/decrease hours The timeKeys jQuery PlugIn Some time ago I created a small plugin to handle this scenario. It's non-visual other than tooltip that pops up when you press ? to display the hotkeys that are available: Try it Online The keys loosely follow the ancient Quicken convention of using the first and last letters of what you're increasing decreasing (ie. H to decrease, R to increase hours and + and - for the base unit or minutes here). All navigation happens via the keystrokes shown above, so it's all non-visual, which I think is the most efficient way to deal with dates. To hook up the plug-in, start with the textbox:<input type="text" id="txtTime" name="txtTime" value="12:05 pm" title="press ? for time options" /> Note the title which might be useful to alert people using the field that additional functionality is available. To hook up the plugin code is as simple as:$("#txtTime").timeKeys(); You essentially tie the plugin to any text box control. OptionsThe syntax for timeKeys allows for an options map parameter:$(selector).timeKeys(options); Options are passed as a parameter map object which can have the following properties: timeFormatYou can pass in a format string that allows you to format the date. The default is "hh:mm t" which is US time format that shows a 12 hour clock with am/pm. Alternately you can pass in "HH:mm" which uses 24 hour time. HH, hh, mm and t are translated in the format string - you can arrange the format as you see fit. callbackYou can also specify a callback function that is called when the date value has been set. This allows you to either re-format the date or perform post processing (such as displaying highlight if it's after a certain hour for example). Here's another example that uses both options:$("#txtTime").timeKeys({ timeFormat: "HH:mm", callback: function (time) { showStatus("new time is: " + time.toString() + " " + $(this).val() ); } }); The plugin code itself is fairly simple. It hooks the keydown event and checks for the various keys that affect time navigation which is straight forward. The bulk of the code however deals with parsing the time value and formatting the output using a Time class that implements parsing, formatting and time navigation methods. Here's the code for the timeKeys jQuery plug-in:/// <reference path="jquery.js" /> /// <reference path="ww.jquery.js" /> (function ($) { $.fn.timeKeys = function (options) { /// <summary> /// Attaches a set of hotkeys to time fields /// + Add minute - subtract minute /// H Subtract Hour R Add houR /// ? Show keys /// </summary> /// <param name="options" type="object"> /// Options: /// timeFormat: "hh:mm t" by default HH:mm alternate /// callback: callback handler after time assignment /// </param> /// <example> /// var proxy = new ServiceProxy("JsonStockService.svc/"); /// proxy.invoke("GetStockQuote",{symbol:"msft"},function(quote) { alert(result.LastPrice); },onPageError); ///</example> if (this.length < 1) return this; var opt = { timeFormat: "hh:mm t", callback: null } $.extend(opt, options); return this.keydown(function (e) { var $el = $(this); var time = new Time($el.val()); //alert($(this).val() + " " + time.toString() + " " + time.date.toString()); switch (e.keyCode) { case 78: // [N]ow time = new Time(new Date()); break; case 109: case 189: // - time.addMinutes(-1); break; case 107: case 187: // + time.addMinutes(1); break; case 72: //H time.addHours(-1); break; case 82: //R time.addHours(1); break; case 191: // ? if (e.shiftKey) $(this).tooltip("<b>N</b> Now<br/><b>+</b> add minute<br /><b>-</b> subtract minute<br /><b>H</b> Subtract Hour<br /><b>R</b> add hour", 4000, { isHtml: true }); return false; default: return true; } $el.val(time.toString(opt.timeFormat)); if (opt.callback) { // call async and set context in this element setTimeout(function () { opt.callback.call($el.get(0), time) }, 1); } return false; }); } Time = function (time, format) { /// <summary> /// Time object that can parse and format /// a time values. /// </summary> /// <param name="time" type="object"> /// A time value as a string (12:15pm or 23:01), a Date object /// or time value. /// /// </param> /// <param name="format" type="string"> /// Time format string: /// HH:mm (23:01) /// hh:mm t (11:01 pm) /// </param> /// <example> /// var time = new Time( new Date()); /// time.addHours(5); /// time.addMinutes(10); /// var s = time.toString(); /// /// var time2 = new Time(s); // parse with constructor /// var t = time2.parse("10:15 pm"); // parse with .parse() method /// alert( t.hours + " " + t.mins + " " + t.ampm + " " + t.hours25) ///</example> var _I = this; this.date = new Date(); this.timeFormat = "hh:mm t"; if (format) this.timeFormat = format; this.parse = function (time) { /// <summary> /// Parses time value from a Date object, or string in format of: /// 12:12pm or 23:01 /// </summary> /// <param name="time" type="any"> /// A time value as a string (12:15pm or 23:01), a Date object /// or time value. /// /// </param> if (!time) return null; // Date if (time.getDate) { var t = {}; var d = time; t.hours24 = d.getHours(); t.mins = d.getMinutes(); t.ampm = "am"; if (t.hours24 > 11) { t.ampm = "pm"; if (t.hours24 > 12) t.hours = t.hours24 - 12; } time = t; } if (typeof (time) == "string") { var parts = time.split(":"); if (parts < 2) return null; var time = {}; time.hours = parts[0] * 1; time.hours24 = time.hours; time.mins = parts[1].toLowerCase(); if (time.mins.indexOf("am") > -1) { time.ampm = "am"; time.mins = time.mins.replace("am", ""); if (time.hours == 12) time.hours24 = 0; } else if (time.mins.indexOf("pm") > -1) { time.ampm = "pm"; time.mins = time.mins.replace("pm", ""); if (time.hours < 12) time.hours24 = time.hours + 12; } time.mins = time.mins * 1; } _I.date.setMinutes(time.mins); _I.date.setHours(time.hours24); return time; }; this.addMinutes = function (mins) { /// <summary> /// adds minutes to the internally stored time value. /// </summary> /// <param name="mins" type="number"> /// number of minutes to add to the date /// </param> _I.date.setMinutes(_I.date.getMinutes() + mins); } this.addHours = function (hours) { /// <summary> /// adds hours the internally stored time value. /// </summary> /// <param name="hours" type="number"> /// number of hours to add to the date /// </param> _I.date.setHours(_I.date.getHours() + hours); } this.getTime = function () { /// <summary> /// returns a time structure from the currently /// stored time value. /// Properties: hours, hours24, mins, ampm /// </summary> return new Time(new Date()); h } this.toString = function (format) { /// <summary> /// returns a short time string for the internal date /// formats: 12:12 pm or 23:12 /// </summary> /// <param name="format" type="string"> /// optional format string for date /// HH:mm, hh:mm t /// </param> if (!format) format = _I.timeFormat; var hours = _I.date.getHours(); if (format.indexOf("t") > -1) { if (hours > 11) format = format.replace("t", "pm") else format = format.replace("t", "am") } if (format.indexOf("HH") > -1) format = format.replace("HH", hours.toString().padL(2, "0")); if (format.indexOf("hh") > -1) { if (hours > 12) hours -= 12; if (hours == 0) hours = 12; format = format.replace("hh", hours.toString().padL(2, "0")); } if (format.indexOf("mm") > -1) format = format.replace("mm", _I.date.getMinutes().toString().padL(2, "0")); return format; } // construction if (time) this.time = this.parse(time); } String.prototype.padL = function (width, pad) { if (!width || width < 1) return this; if (!pad) pad = " "; var length = width - this.length if (length < 1) return this.substr(0, width); return (String.repeat(pad, length) + this).substr(0, width); } String.repeat = function (chr, count) { var str = ""; for (var x = 0; x < count; x++) { str += chr }; return str; } })(jQuery); The plugin consists of the actual plugin and the Time class which handles parsing and formatting of the time value via the .parse() and .toString() methods. Code like this always ends up taking up more effort than the actual logic unfortunately. There are libraries out there that can handle this like datejs or even ww.jquery.js (which is what I use) but to keep the code self contained for this post the plugin doesn't rely on external code. There's one optional exception: The code as is has one dependency on ww.jquery.js  for the tooltip plugin that provides the small popup for all the hotkeys available. You can replace that code with some other mechanism to display hotkeys or simply remove it since that behavior is optional. While we're at it: A jQuery dateKeys plugIn Although date entry tends to be much better served with drop down calendars to pick dates from, often it's also easier to pick dates using a few simple hotkeys. Navigation that uses + - for days and M and H for MontH navigation, Y and R for YeaR navigation are a quick way to enter dates without having to resort to using a mouse and clicking around to what you want to find. Note that this plugin does have a dependency on ww.jquery.js for the date formatting functionality.$.fn.dateKeys = function (options) { /// <summary> /// Attaches a set of hotkeys to date 'fields' /// + Add day - subtract day /// M Subtract Month H Add montH /// Y Subtract Year R Add yeaR /// ? Show keys /// </summary> /// <param name="options" type="object"> /// Options: /// dateFormat: "MM/dd/yyyy" by default "MMM dd, yyyy /// callback: callback handler after date assignment /// </param> /// <example> /// var proxy = new ServiceProxy("JsonStockService.svc/"); /// proxy.invoke("GetStockQuote",{symbol:"msft"},function(quote) { alert(result.LastPrice); },onPageError); ///</example> if (this.length < 1) return this; var opt = { dateFormat: "MM/dd/yyyy", callback: null }; $.extend(opt, options); return this.keydown(function (e) { var $el = $(this); var d = new Date($el.val()); if (!d) d = new Date(1900, 0, 1, 1, 1); var month = d.getMonth(); var year = d.getFullYear(); var day = d.getDate(); switch (e.keyCode) { case 84: // [T]oday d = new Date(); break; case 109: case 189: d = new Date(year, month, day - 1); break; case 107: case 187: d = new Date(year, month, day + 1); break; case 77: //M d = new Date(year, month - 1, day); break; case 72: //H d = new Date(year, month + 1, day); break; case 191: // ? if (e.shiftKey) $el.tooltip("<b>T</b> Today<br/><b>+</b> add day<br /><b>-</b> subtract day<br /><b>M</b> subtract Month<br /><b>H</b> add montH<br/><b>Y</b> subtract Year<br/><b>R</b> add yeaR", 5000, { isHtml: true }); return false; default: return true; } $el.val(d.formatDate(opt.dateFormat)); if (opt.callback) // call async setTimeout(function () { opt.callback.call($el.get(0),d); }, 10); return false; }); } The logic for this plugin is similar to the timeKeys plugin, but it's a little simpler as it tries to directly parse the date value from a string via new Date(inputString). As mentioned it also uses a helper function from ww.jquery.js to format dates which removes the logic to perform date formatting manually which again reduces the size of the code. And the Key is… I've been using both of these plugins in combination with the jQuery UI datepicker for datetime values and I've found that I rarely actually pop up the date picker any more. It's just so much more efficient to use the hotkeys to navigate dates. It's still nice to have the picker around though - it provides the expected behavior for date entry. For time values however I can't justify the UI overhead of a picker that doesn't make it any easier to pick a time. Most people know how to type in a time value and if they want shortcuts keystrokes easily beat out any pop up UI. Hopefully you'll find this as useful as I have found it for my code. Resources Online Sample Download Sample Project © Rick Strahl, West Wind Technologies, 2005-2011Posted in jQuery  HTML   Tweet (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • A Taxonomy of Numerical Methods v1

    - by JoshReuben
    Numerical Analysis – When, What, (but not how) Once you understand the Math & know C++, Numerical Methods are basically blocks of iterative & conditional math code. I found the real trick was seeing the forest for the trees – knowing which method to use for which situation. Its pretty easy to get lost in the details – so I’ve tried to organize these methods in a way that I can quickly look this up. I’ve included links to detailed explanations and to C++ code examples. I’ve tried to classify Numerical methods in the following broad categories: Solving Systems of Linear Equations Solving Non-Linear Equations Iteratively Interpolation Curve Fitting Optimization Numerical Differentiation & Integration Solving ODEs Boundary Problems Solving EigenValue problems Enjoy – I did ! Solving Systems of Linear Equations Overview Solve sets of algebraic equations with x unknowns The set is commonly in matrix form Gauss-Jordan Elimination http://en.wikipedia.org/wiki/Gauss%E2%80%93Jordan_elimination C++: http://www.codekeep.net/snippets/623f1923-e03c-4636-8c92-c9dc7aa0d3c0.aspx Produces solution of the equations & the coefficient matrix Efficient, stable 2 steps: · Forward Elimination – matrix decomposition: reduce set to triangular form (0s below the diagonal) or row echelon form. If degenerate, then there is no solution · Backward Elimination –write the original matrix as the product of ints inverse matrix & its reduced row-echelon matrix à reduce set to row canonical form & use back-substitution to find the solution to the set Elementary ops for matrix decomposition: · Row multiplication · Row switching · Add multiples of rows to other rows Use pivoting to ensure rows are ordered for achieving triangular form LU Decomposition http://en.wikipedia.org/wiki/LU_decomposition C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-lu-decomposition-for-solving.html Represent the matrix as a product of lower & upper triangular matrices A modified version of GJ Elimination Advantage – can easily apply forward & backward elimination to solve triangular matrices Techniques: · Doolittle Method – sets the L matrix diagonal to unity · Crout Method - sets the U matrix diagonal to unity Note: both the L & U matrices share the same unity diagonal & can be stored compactly in the same matrix Gauss-Seidel Iteration http://en.wikipedia.org/wiki/Gauss%E2%80%93Seidel_method C++: http://www.nr.com/forum/showthread.php?t=722 Transform the linear set of equations into a single equation & then use numerical integration (as integration formulas have Sums, it is implemented iteratively). an optimization of Gauss-Jacobi: 1.5 times faster, requires 0.25 iterations to achieve the same tolerance Solving Non-Linear Equations Iteratively find roots of polynomials – there may be 0, 1 or n solutions for an n order polynomial use iterative techniques Iterative methods · used when there are no known analytical techniques · Requires set functions to be continuous & differentiable · Requires an initial seed value – choice is critical to convergence à conduct multiple runs with different starting points & then select best result · Systematic - iterate until diminishing returns, tolerance or max iteration conditions are met · bracketing techniques will always yield convergent solutions, non-bracketing methods may fail to converge Incremental method if a nonlinear function has opposite signs at 2 ends of a small interval x1 & x2, then there is likely to be a solution in their interval – solutions are detected by evaluating a function over interval steps, for a change in sign, adjusting the step size dynamically. Limitations – can miss closely spaced solutions in large intervals, cannot detect degenerate (coinciding) solutions, limited to functions that cross the x-axis, gives false positives for singularities Fixed point method http://en.wikipedia.org/wiki/Fixed-point_iteration C++: http://books.google.co.il/books?id=weYj75E_t6MC&pg=PA79&lpg=PA79&dq=fixed+point+method++c%2B%2B&source=bl&ots=LQ-5P_taoC&sig=lENUUIYBK53tZtTwNfHLy5PEWDk&hl=en&sa=X&ei=wezDUPW1J5DptQaMsIHQCw&redir_esc=y#v=onepage&q=fixed%20point%20method%20%20c%2B%2B&f=false Algebraically rearrange a solution to isolate a variable then apply incremental method Bisection method http://en.wikipedia.org/wiki/Bisection_method C++: http://numericalcomputing.wordpress.com/category/algorithms/ Bracketed - Select an initial interval, keep bisecting it ad midpoint into sub-intervals and then apply incremental method on smaller & smaller intervals – zoom in Adv: unaffected by function gradient à reliable Disadv: slow convergence False Position Method http://en.wikipedia.org/wiki/False_position_method C++: http://www.dreamincode.net/forums/topic/126100-bisection-and-false-position-methods/ Bracketed - Select an initial interval , & use the relative value of function at interval end points to select next sub-intervals (estimate how far between the end points the solution might be & subdivide based on this) Newton-Raphson method http://en.wikipedia.org/wiki/Newton's_method C++: http://www-users.cselabs.umn.edu/classes/Summer-2012/csci1113/index.php?page=./newt3 Also known as Newton's method Convenient, efficient Not bracketed – only a single initial guess is required to start iteration – requires an analytical expression for the first derivative of the function as input. Evaluates the function & its derivative at each step. Can be extended to the Newton MutiRoot method for solving multiple roots Can be easily applied to an of n-coupled set of non-linear equations – conduct a Taylor Series expansion of a function, dropping terms of order n, rewrite as a Jacobian matrix of PDs & convert to simultaneous linear equations !!! Secant Method http://en.wikipedia.org/wiki/Secant_method C++: http://forum.vcoderz.com/showthread.php?p=205230 Unlike N-R, can estimate first derivative from an initial interval (does not require root to be bracketed) instead of inputting it Since derivative is approximated, may converge slower. Is fast in practice as it does not have to evaluate the derivative at each step. Similar implementation to False Positive method Birge-Vieta Method http://mat.iitm.ac.in/home/sryedida/public_html/caimna/transcendental/polynomial%20methods/bv%20method.html C++: http://books.google.co.il/books?id=cL1boM2uyQwC&pg=SA3-PA51&lpg=SA3-PA51&dq=Birge-Vieta+Method+c%2B%2B&source=bl&ots=QZmnDTK3rC&sig=BPNcHHbpR_DKVoZXrLi4nVXD-gg&hl=en&sa=X&ei=R-_DUK2iNIjzsgbE5ID4Dg&redir_esc=y#v=onepage&q=Birge-Vieta%20Method%20c%2B%2B&f=false combines Horner's method of polynomial evaluation (transforming into lesser degree polynomials that are more computationally efficient to process) with Newton-Raphson to provide a computational speed-up Interpolation Overview Construct new data points for as close as possible fit within range of a discrete set of known points (that were obtained via sampling, experimentation) Use Taylor Series Expansion of a function f(x) around a specific value for x Linear Interpolation http://en.wikipedia.org/wiki/Linear_interpolation C++: http://www.hamaluik.com/?p=289 Straight line between 2 points à concatenate interpolants between each pair of data points Bilinear Interpolation http://en.wikipedia.org/wiki/Bilinear_interpolation C++: http://supercomputingblog.com/graphics/coding-bilinear-interpolation/2/ Extension of the linear function for interpolating functions of 2 variables – perform linear interpolation first in 1 direction, then in another. Used in image processing – e.g. texture mapping filter. Uses 4 vertices to interpolate a value within a unit cell. Lagrange Interpolation http://en.wikipedia.org/wiki/Lagrange_polynomial C++: http://www.codecogs.com/code/maths/approximation/interpolation/lagrange.php For polynomials Requires recomputation for all terms for each distinct x value – can only be applied for small number of nodes Numerically unstable Barycentric Interpolation http://epubs.siam.org/doi/pdf/10.1137/S0036144502417715 C++: http://www.gamedev.net/topic/621445-barycentric-coordinates-c-code-check/ Rearrange the terms in the equation of the Legrange interpolation by defining weight functions that are independent of the interpolated value of x Newton Divided Difference Interpolation http://en.wikipedia.org/wiki/Newton_polynomial C++: http://jee-appy.blogspot.co.il/2011/12/newton-divided-difference-interpolation.html Hermite Divided Differences: Interpolation polynomial approximation for a given set of data points in the NR form - divided differences are used to approximately calculate the various differences. For a given set of 3 data points , fit a quadratic interpolant through the data Bracketed functions allow Newton divided differences to be calculated recursively Difference table Cubic Spline Interpolation http://en.wikipedia.org/wiki/Spline_interpolation C++: https://www.marcusbannerman.co.uk/index.php/home/latestarticles/42-articles/96-cubic-spline-class.html Spline is a piecewise polynomial Provides smoothness – for interpolations with significantly varying data Use weighted coefficients to bend the function to be smooth & its 1st & 2nd derivatives are continuous through the edge points in the interval Curve Fitting A generalization of interpolating whereby given data points may contain noise à the curve does not necessarily pass through all the points Least Squares Fit http://en.wikipedia.org/wiki/Least_squares C++: http://www.ccas.ru/mmes/educat/lab04k/02/least-squares.c Residual – difference between observed value & expected value Model function is often chosen as a linear combination of the specified functions Determines: A) The model instance in which the sum of squared residuals has the least value B) param values for which model best fits data Straight Line Fit Linear correlation between independent variable and dependent variable Linear Regression http://en.wikipedia.org/wiki/Linear_regression C++: http://www.oocities.org/david_swaim/cpp/linregc.htm Special case of statistically exact extrapolation Leverage least squares Given a basis function, the sum of the residuals is determined and the corresponding gradient equation is expressed as a set of normal linear equations in matrix form that can be solved (e.g. using LU Decomposition) Can be weighted - Drop the assumption that all errors have the same significance –-> confidence of accuracy is different for each data point. Fit the function closer to points with higher weights Polynomial Fit - use a polynomial basis function Moving Average http://en.wikipedia.org/wiki/Moving_average C++: http://www.codeproject.com/Articles/17860/A-Simple-Moving-Average-Algorithm Used for smoothing (cancel fluctuations to highlight longer-term trends & cycles), time series data analysis, signal processing filters Replace each data point with average of neighbors. Can be simple (SMA), weighted (WMA), exponential (EMA). Lags behind latest data points – extra weight can be given to more recent data points. Weights can decrease arithmetically or exponentially according to distance from point. Parameters: smoothing factor, period, weight basis Optimization Overview Given function with multiple variables, find Min (or max by minimizing –f(x)) Iterative approach Efficient, but not necessarily reliable Conditions: noisy data, constraints, non-linear models Detection via sign of first derivative - Derivative of saddle points will be 0 Local minima Bisection method Similar method for finding a root for a non-linear equation Start with an interval that contains a minimum Golden Search method http://en.wikipedia.org/wiki/Golden_section_search C++: http://www.codecogs.com/code/maths/optimization/golden.php Bisect intervals according to golden ratio 0.618.. Achieves reduction by evaluating a single function instead of 2 Newton-Raphson Method Brent method http://en.wikipedia.org/wiki/Brent's_method C++: http://people.sc.fsu.edu/~jburkardt/cpp_src/brent/brent.cpp Based on quadratic or parabolic interpolation – if the function is smooth & parabolic near to the minimum, then a parabola fitted through any 3 points should approximate the minima – fails when the 3 points are collinear , in which case the denominator is 0 Simplex Method http://en.wikipedia.org/wiki/Simplex_algorithm C++: http://www.codeguru.com/cpp/article.php/c17505/Simplex-Optimization-Algorithm-and-Implemetation-in-C-Programming.htm Find the global minima of any multi-variable function Direct search – no derivatives required At each step it maintains a non-degenerative simplex – a convex hull of n+1 vertices. Obtains the minimum for a function with n variables by evaluating the function at n-1 points, iteratively replacing the point of worst result with the point of best result, shrinking the multidimensional simplex around the best point. Point replacement involves expanding & contracting the simplex near the worst value point to determine a better replacement point Oscillation can be avoided by choosing the 2nd worst result Restart if it gets stuck Parameters: contraction & expansion factors Simulated Annealing http://en.wikipedia.org/wiki/Simulated_annealing C++: http://code.google.com/p/cppsimulatedannealing/ Analogy to heating & cooling metal to strengthen its structure Stochastic method – apply random permutation search for global minima - Avoid entrapment in local minima via hill climbing Heating schedule - Annealing schedule params: temperature, iterations at each temp, temperature delta Cooling schedule – can be linear, step-wise or exponential Differential Evolution http://en.wikipedia.org/wiki/Differential_evolution C++: http://www.amichel.com/de/doc/html/ More advanced stochastic methods analogous to biological processes: Genetic algorithms, evolution strategies Parallel direct search method against multiple discrete or continuous variables Initial population of variable vectors chosen randomly – if weighted difference vector of 2 vectors yields a lower objective function value then it replaces the comparison vector Many params: #parents, #variables, step size, crossover constant etc Convergence is slow – many more function evaluations than simulated annealing Numerical Differentiation Overview 2 approaches to finite difference methods: · A) approximate function via polynomial interpolation then differentiate · B) Taylor series approximation – additionally provides error estimate Finite Difference methods http://en.wikipedia.org/wiki/Finite_difference_method C++: http://www.wpi.edu/Pubs/ETD/Available/etd-051807-164436/unrestricted/EAMPADU.pdf Find differences between high order derivative values - Approximate differential equations by finite differences at evenly spaced data points Based on forward & backward Taylor series expansion of f(x) about x plus or minus multiples of delta h. Forward / backward difference - the sums of the series contains even derivatives and the difference of the series contains odd derivatives – coupled equations that can be solved. Provide an approximation of the derivative within a O(h^2) accuracy There is also central difference & extended central difference which has a O(h^4) accuracy Richardson Extrapolation http://en.wikipedia.org/wiki/Richardson_extrapolation C++: http://mathscoding.blogspot.co.il/2012/02/introduction-richardson-extrapolation.html A sequence acceleration method applied to finite differences Fast convergence, high accuracy O(h^4) Derivatives via Interpolation Cannot apply Finite Difference method to discrete data points at uneven intervals – so need to approximate the derivative of f(x) using the derivative of the interpolant via 3 point Lagrange Interpolation Note: the higher the order of the derivative, the lower the approximation precision Numerical Integration Estimate finite & infinite integrals of functions More accurate procedure than numerical differentiation Use when it is not possible to obtain an integral of a function analytically or when the function is not given, only the data points are Newton Cotes Methods http://en.wikipedia.org/wiki/Newton%E2%80%93Cotes_formulas C++: http://www.siafoo.net/snippet/324 For equally spaced data points Computationally easy – based on local interpolation of n rectangular strip areas that is piecewise fitted to a polynomial to get the sum total area Evaluate the integrand at n+1 evenly spaced points – approximate definite integral by Sum Weights are derived from Lagrange Basis polynomials Leverage Trapezoidal Rule for default 2nd formulas, Simpson 1/3 Rule for substituting 3 point formulas, Simpson 3/8 Rule for 4 point formulas. For 4 point formulas use Bodes Rule. Higher orders obtain more accurate results Trapezoidal Rule uses simple area, Simpsons Rule replaces the integrand f(x) with a quadratic polynomial p(x) that uses the same values as f(x) for its end points, but adds a midpoint Romberg Integration http://en.wikipedia.org/wiki/Romberg's_method C++: http://code.google.com/p/romberg-integration/downloads/detail?name=romberg.cpp&can=2&q= Combines trapezoidal rule with Richardson Extrapolation Evaluates the integrand at equally spaced points The integrand must have continuous derivatives Each R(n,m) extrapolation uses a higher order integrand polynomial replacement rule (zeroth starts with trapezoidal) à a lower triangular matrix set of equation coefficients where the bottom right term has the most accurate approximation. The process continues until the difference between 2 successive diagonal terms becomes sufficiently small. Gaussian Quadrature http://en.wikipedia.org/wiki/Gaussian_quadrature C++: http://www.alglib.net/integration/gaussianquadratures.php Data points are chosen to yield best possible accuracy – requires fewer evaluations Ability to handle singularities, functions that are difficult to evaluate The integrand can include a weighting function determined by a set of orthogonal polynomials. Points & weights are selected so that the integrand yields the exact integral if f(x) is a polynomial of degree <= 2n+1 Techniques (basically different weighting functions): · Gauss-Legendre Integration w(x)=1 · Gauss-Laguerre Integration w(x)=e^-x · Gauss-Hermite Integration w(x)=e^-x^2 · Gauss-Chebyshev Integration w(x)= 1 / Sqrt(1-x^2) Solving ODEs Use when high order differential equations cannot be solved analytically Evaluated under boundary conditions RK for systems – a high order differential equation can always be transformed into a coupled first order system of equations Euler method http://en.wikipedia.org/wiki/Euler_method C++: http://rosettacode.org/wiki/Euler_method First order Runge–Kutta method. Simple recursive method – given an initial value, calculate derivative deltas. Unstable & not very accurate (O(h) error) – not used in practice A first-order method - the local error (truncation error per step) is proportional to the square of the step size, and the global error (error at a given time) is proportional to the step size In evolving solution between data points xn & xn+1, only evaluates derivatives at beginning of interval xn à asymmetric at boundaries Higher order Runge Kutta http://en.wikipedia.org/wiki/Runge%E2%80%93Kutta_methods C++: http://www.dreamincode.net/code/snippet1441.htm 2nd & 4th order RK - Introduces parameterized midpoints for more symmetric solutions à accuracy at higher computational cost Adaptive RK – RK-Fehlberg – estimate the truncation at each integration step & automatically adjust the step size to keep error within prescribed limits. At each step 2 approximations are compared – if in disagreement to a specific accuracy, the step size is reduced Boundary Value Problems Where solution of differential equations are located at 2 different values of the independent variable x à more difficult, because cannot just start at point of initial value – there may not be enough starting conditions available at the end points to produce a unique solution An n-order equation will require n boundary conditions – need to determine the missing n-1 conditions which cause the given conditions at the other boundary to be satisfied Shooting Method http://en.wikipedia.org/wiki/Shooting_method C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-shooting-method-for-solving.html Iteratively guess the missing values for one end & integrate, then inspect the discrepancy with the boundary values of the other end to adjust the estimate Given the starting boundary values u1 & u2 which contain the root u, solve u given the false position method (solving the differential equation as an initial value problem via 4th order RK), then use u to solve the differential equations. Finite Difference Method For linear & non-linear systems Higher order derivatives require more computational steps – some combinations for boundary conditions may not work though Improve the accuracy by increasing the number of mesh points Solving EigenValue Problems An eigenvalue can substitute a matrix when doing matrix multiplication à convert matrix multiplication into a polynomial EigenValue For a given set of equations in matrix form, determine what are the solution eigenvalue & eigenvectors Similar Matrices - have same eigenvalues. Use orthogonal similarity transforms to reduce a matrix to diagonal form from which eigenvalue(s) & eigenvectors can be computed iteratively Jacobi method http://en.wikipedia.org/wiki/Jacobi_method C++: http://people.sc.fsu.edu/~jburkardt/classes/acs2_2008/openmp/jacobi/jacobi.html Robust but Computationally intense – use for small matrices < 10x10 Power Iteration http://en.wikipedia.org/wiki/Power_iteration For any given real symmetric matrix, generate the largest single eigenvalue & its eigenvectors Simplest method – does not compute matrix decomposition à suitable for large, sparse matrices Inverse Iteration Variation of power iteration method – generates the smallest eigenvalue from the inverse matrix Rayleigh Method http://en.wikipedia.org/wiki/Rayleigh's_method_of_dimensional_analysis Variation of power iteration method Rayleigh Quotient Method Variation of inverse iteration method Matrix Tri-diagonalization Method Use householder algorithm to reduce an NxN symmetric matrix to a tridiagonal real symmetric matrix vua N-2 orthogonal transforms     Whats Next Outside of Numerical Methods there are lots of different types of algorithms that I’ve learned over the decades: Data Mining – (I covered this briefly in a previous post: http://geekswithblogs.net/JoshReuben/archive/2007/12/31/ssas-dm-algorithms.aspx ) Search & Sort Routing Problem Solving Logical Theorem Proving Planning Probabilistic Reasoning Machine Learning Solvers (eg MIP) Bioinformatics (Sequence Alignment, Protein Folding) Quant Finance (I read Wilmott’s books – interesting) Sooner or later, I’ll cover the above topics as well.

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  • Static vs Singleton in C# (Difference between Singleton and Static)

    - by Jalpesh P. Vadgama
    Recently I have came across a question what is the difference between Static and Singleton classes. So I thought it will be a good idea to share blog post about it.Difference between Static and Singleton classes:A singleton classes allowed to create a only single instance or particular class. That instance can be treated as normal object. You can pass that object to a method as parameter or you can call the class method with that Singleton object. While static class can have only static methods and you can not pass static class as parameter.We can implement the interfaces with the Singleton class while we can not implement the interfaces with static classes.We can clone the object of Singleton classes we can not clone the object of static classes.Singleton objects stored on heap while static class stored in stack.more at my personal blog: dotnetjalps.com

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  • C# ?? null coalescing operator

    - by anirudha
    the null coalescing operator is used for set the value when object is null. if object have some value that nothing change and still have their default value they have.  string str = "i am string";            string message = str ?? "it is null";   the message have same value as str variable because str not null. if str is null that message have value “it is null”; as declared in statement. coalescing operator does not work on nullable operator such as int?

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  • ~/.xsession-errors is 2.7gb big (and growing), on fresh install, caused by gnome-settings-daemon errors

    - by Alex Black
    I've just installed Ubuntu 10.10 x64, activated the recommended Nvidia drivers, and I noticed my hard disk space is disappearing, I narrowed the culprit down to this: alex@alex-home:~$ ls -la .x* -rw------- 1 alex alex 4436076400 2010-11-19 22:35 .xsession-errors -rw------- 1 alex alex 10495 2010-11-19 21:46 .xsession-errors.old Any idea what this file is, why its so big, and why its growing? A few seconds later: alex@alex-home:~$ ls -la .x* -rw------- 1 alex alex 5143604317 2010-11-19 22:36 .xsession-errors -rw------- 1 alex alex 10495 2010-11-19 21:46 .xsession-errors.old tailing it: alex@alex-home:~$ tail .xsession-errors (gnome-settings-daemon:1514): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed (gnome-settings-daemon:1514): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed (gnome-settings-daemon:1514): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed (gnome-settings-daemon:1514): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed (gnome-settings-daemon:1514): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed Also, the process "gnome-settings" seems to be using 100% cpu: PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1514 alex 20 0 268m 10m 7044 R 100 0.1 7:06.10 gnome-settings-

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  • ASP.NET MVC 2 Model Binding for a Collection

    - by nmarun
    Yes, my yet another post on Model Binding (previous one is here), but this one uses features presented in MVC 2. How I got to writing this blog? Well, I’m on a project where we’re doing some MVC things for a shopping cart. Let me show you what I was working with. Below are my model classes: 1: public class Product 2: { 3: public int Id { get; set; } 4: public string Name { get; set; } 5: public int Quantity { get; set; } 6: public decimal UnitPrice { get; set; } 7: } 8:   9: public class Totals 10: { 11: public decimal SubTotal { get; set; } 12: public decimal Tax { get; set; } 13: public decimal Total { get; set; } 14: } 15:   16: public class Basket 17: { 18: public List<Product> Products { get; set; } 19: public Totals Totals { get; set;} 20: } The view looks as below:  1: <h2>Shopping Cart</h2> 2:   3: <% using(Html.BeginForm()) { %> 4: 5: <h3>Products</h3> 6: <% for (int i = 0; i < Model.Products.Count; i++) 7: { %> 8: <div style="width: 100px;float:left;">Id</div> 9: <div style="width: 100px;float:left;"> 10: <%= Html.TextBox("ID", Model.Products[i].Id) %> 11: </div> 12: <div style="clear:both;"></div> 13: <div style="width: 100px;float:left;">Name</div> 14: <div style="width: 100px;float:left;"> 15: <%= Html.TextBox("Name", Model.Products[i].Name) %> 16: </div> 17: <div style="clear:both;"></div> 18: <div style="width: 100px;float:left;">Quantity</div> 19: <div style="width: 100px;float:left;"> 20: <%= Html.TextBox("Quantity", Model.Products[i].Quantity)%> 21: </div> 22: <div style="clear:both;"></div> 23: <div style="width: 100px;float:left;">Unit Price</div> 24: <div style="width: 100px;float:left;"> 25: <%= Html.TextBox("UnitPrice", Model.Products[i].UnitPrice)%> 26: </div> 27: <div style="clear:both;"><hr /></div> 28: <% } %> 29: 30: <h3>Totals</h3> 31: <div style="width: 100px;float:left;">Sub Total</div> 32: <div style="width: 100px;float:left;"> 33: <%= Html.TextBox("SubTotal", Model.Totals.SubTotal)%> 34: </div> 35: <div style="clear:both;"></div> 36: <div style="width: 100px;float:left;">Tax</div> 37: <div style="width: 100px;float:left;"> 38: <%= Html.TextBox("Tax", Model.Totals.Tax)%> 39: </div> 40: <div style="clear:both;"></div> 41: <div style="width: 100px;float:left;">Total</div> 42: <div style="width: 100px;float:left;"> 43: <%= Html.TextBox("Total", Model.Totals.Total)%> 44: </div> 45: <div style="clear:both;"></div> 46: <p /> 47: <input type="submit" name="Submit" value="Submit" /> 48: <% } %> .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Nothing fancy, just a bunch of div’s containing textboxes and a submit button. Just make note that the textboxes have the same name as the property they are going to display. Yea, yea, I know. I’m displaying unit price as a textbox instead of a label, but that’s beside the point (and trust me, this will not be how it’ll look on the production site!!). The way my controller works is that initially two dummy products are added to the basked object and the Totals are calculated based on what products were added in what quantities and their respective unit price. So when the page loads in edit mode, where the user can change the quantity and hit the submit button. In the ‘post’ version of the action method, the Totals get recalculated and the new total will be displayed on the screen. Here’s the code: 1: public ActionResult Index() 2: { 3: Product product1 = new Product 4: { 5: Id = 1, 6: Name = "Product 1", 7: Quantity = 2, 8: UnitPrice = 200m 9: }; 10:   11: Product product2 = new Product 12: { 13: Id = 2, 14: Name = "Product 2", 15: Quantity = 1, 16: UnitPrice = 150m 17: }; 18:   19: List<Product> products = new List<Product> { product1, product2 }; 20:   21: Basket basket = new Basket 22: { 23: Products = products, 24: Totals = ComputeTotals(products) 25: }; 26: return View(basket); 27: } 28:   29: [HttpPost] 30: public ActionResult Index(Basket basket) 31: { 32: basket.Totals = ComputeTotals(basket.Products); 33: return View(basket); 34: } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } That’s that. Now I run the app, I see two products with the totals section below them. I look at the view source and I see that the input controls have the right ID, the right name and the right value as well. 1: <input id="ID" name="ID" type="text" value="1" /> 2: <input id="Name" name="Name" type="text" value="Product 1" /> 3: ... 4: <input id="ID" name="ID" type="text" value="2" /> 5: <input id="Name" name="Name" type="text" value="Product 2" /> .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } So just as a regular user would do, I change the quantity value of one of the products and hit the submit button. The ‘post’ version of the Index method gets called and I had put a break-point on line 32 in the above snippet. When I hovered my mouse on the ‘basked’ object, happily assuming that the object would be all bound and ready for use, I was surprised to see both basket.Products and basket.Totals were null. Huh? A little research and I found out that the reason the DefaultModelBinder could not do its job is because of a naming mismatch on the input controls. What I mean is that when you have to bind to a custom .net type, you need more than just the property name. You need to pass a qualified name to the name property of the input control. I modified my view and the emitted code looked as below: 1: <input id="Product_Name" name="Product.Name" type="text" value="Product 1" /> 2: ... 3: <input id="Product_Name" name="Product.Name" type="text" value="Product 2" /> 4: ... 5: <input id="Totals_SubTotal" name="Totals.SubTotal" type="text" value="550" /> .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Now, I update the quantity and hit the submit button and I see that the Totals object is populated, but the Products list is still null. Once again I went: ‘Hmm.. time for more research’. I found out that the way to do this is to provide the name as: 1: <%= Html.TextBox(string.Format("Products[{0}].ID", i), Model.Products[i].Id) %> 2: <!-- this will be rendered as --> 3: <input id="Products_0__ID" name="Products[0].ID" type="text" value="1" /> .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } It was only now that I was able to see both the products and the totals being properly bound in the ‘post’ action method. Somehow, I feel this is kinda ‘clunky’ way of doing things. Seems like people at MS felt in a similar way and offered us a much cleaner way to solve this issue. The simple solution is that instead of using a Textbox, we can either use a TextboxFor or an EditorFor helper method. This one directly spits out the name of the input property as ‘Products[0].ID and so on. Cool right? I totally fell for this and changed my UI to contain EditorFor helper method. At this point, I ran the application, changed the quantity field and pressed the submit button. Of course my basket object parameter in my action method was correctly bound after these changes. I let the app complete the rest of the lines in the action method. When the page finally rendered, I did see that the quantity was changed to what I entered before the post. But, wait a minute, the totals section did not reflect the changes and showed the old values. My status: COMPLETELY PUZZLED! Just to recap, this is what my ‘post’ Index method looked like: 1: [HttpPost] 2: public ActionResult Index(Basket basket) 3: { 4: basket.Totals = ComputeTotals(basket.Products); 5: return View(basket); 6: } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } A careful debug confirmed that the basked.Products[0].Quantity showed the updated value and the ComputeTotals() method also returns the correct totals. But still when I passed this basket object, it ended up showing the old totals values only. I began playing a bit with the code and my first guess was that the input controls got their values from the ModelState object. For those who don’t know, the ModelState is a temporary storage area that ASP.NET MVC uses to retain incoming attempted values plus binding and validation errors. Also, the fact that input controls populate the values using data taken from: Previously attempted values recorded in the ModelState["name"].Value.AttemptedValue Explicitly provided value (<%= Html.TextBox("name", "Some value") %>) ViewData, by calling ViewData.Eval("name") FYI: ViewData dictionary takes precedence over ViewData's Model properties – read more here. These two indicators led to my guess. It took me quite some time, but finally I hit this post where Brad brilliantly explains why this is the preferred behavior. My guess was right and I, accordingly modified my code to reflect the following way: 1: [HttpPost] 2: public ActionResult Index(Basket basket) 3: { 4: // read the following posts to see why the ModelState 5: // needs to be cleared before passing it the view 6: // http://forums.asp.net/t/1535846.aspx 7: // http://forums.asp.net/p/1527149/3687407.aspx 8: if (ModelState.IsValid) 9: { 10: ModelState.Clear(); 11: } 12:   13: basket.Totals = ComputeTotals(basket.Products); 14: return View(basket); 15: } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } What this does is that in the case where your ModelState IS valid, it clears the dictionary. This enables the values to be read from the model directly and not from the ModelState. So the verdict is this: If you need to pass other parameters (like html attributes and the like) to your input control, use 1: <%= Html.TextBox(string.Format("Products[{0}].ID", i), Model.Products[i].Id) %> .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Since, in EditorFor, there is no direct and simple way of passing this information to the input control. If you don’t have to pass any such ‘extra’ piece of information to the control, then go the EditorFor way. The code used in the post can be found here.

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  • Munin not creating HTML files in Ubuntu Server 14.04

    - by lepe
    I have used munin in several servers and this is the first time is taking me so much time to set it up. When I telnet munin directly, I can list the services, there is no error at the logs and munin its being updated every 5 minutes. However no html files are created. I'm using the default location (/var/cache/munin/www) and I can confirm the permissions of that directory are set to munin.munin (IP and domain has been changed) munin.conf: dbdir /var/lib/munin htmldir /var/cache/munin/www logdir /var/log/munin rundir /var/run/munin [example.com;] address 100.100.50.200 munin-node.conf: log_level 4 log_file /var/log/munin/munin-node.log pid_file /var/run/munin/munin-node.pid background 1 setsid 1 user root group root host_name example.com allow ^127\.0\.0\.1$ allow ^100\.100\.50\.200$ allow ^::1$ /etc/hosts : 100.100.50.200 example.com 127.0.0.1 localhost $ telnet example.com 4949 Trying 100.100.50.200... Connected to example.com. Escape character is '^]'. # munin node at example.com list apache_accesses apache_processes apache_volume cpu cpuspeed df df_inode entropy fail2ban forks fw_packets if_err_eth0 if_err_eth1 if_eth0 if_eth1 interrupts ipmi_fans ipmi_power ipmi_temp irqstats load memory munin_stats mysql_bin_relay_log mysql_commands mysql_connections mysql_files_tables mysql_innodb_bpool mysql_innodb_bpool_act mysql_innodb_insert_buf mysql_innodb_io mysql_innodb_io_pend mysql_innodb_log mysql_innodb_rows mysql_innodb_semaphores mysql_innodb_tnx mysql_myisam_indexes mysql_network_traffic mysql_qcache mysql_qcache_mem mysql_replication mysql_select_types mysql_slow mysql_sorts mysql_table_locks mysql_tmp_tables ntp_2001:e40:100:208::123 ntp_91.189.94.4 ntp_kernel_err ntp_kernel_pll_freq ntp_kernel_pll_off ntp_offset ntp_states open_files open_inodes postfix_mailqueue postfix_mailvolume proc_pri processes swap threads uptime users vmstat fetch df _dev_sda3.value 2.1762874086869 _sys_fs_cgroup.value 0 _run.value 0.0503536980635825 _run_lock.value 0 _run_shm.value 0 _run_user.value 0 _dev_sda5.value 0.0176986285727571 _dev_sda8.value 1.08464646179852 _dev_sda7.value 0.0346633563514803 _dev_sda9.value 6.81031810822797 _dev_sda6.value 9.0932802215469 . /var/log/munin/munin-node.log Process Backgrounded 2014/08/16-14:13:36 Munin::Node::Server (type Net::Server::Fork) starting! pid(19610) Binding to TCP port 4949 on host 100.100.50.200 with IPv4 2014/08/16-14:23:11 CONNECT TCP Peer: "[100.100.50.200]:55949" Local: "[100.100.50.200]:4949" 2014/08/16-14:36:16 CONNECT TCP Peer: "[100.100.50.200]:56209" Local: "[100.100.50.200]:4949" /var/log/munin/munin-update.log ... 2014/08/16 14:30:01 [INFO]: Starting munin-update 2014/08/16 14:30:01 [INFO]: Munin-update finished (0.00 sec) 2014/08/16 14:35:02 [INFO]: Starting munin-update 2014/08/16 14:35:02 [INFO]: Munin-update finished (0.00 sec) 2014/08/16 14:40:01 [INFO]: Starting munin-update 2014/08/16 14:40:01 [INFO]: Munin-update finished (0.00 sec) $ ls -la /var/cache/munin/www/ drwxr-xr-x 3 munin munin 19 Aug 16 13:55 . drwxr-xr-x 3 root root 16 Aug 16 13:54 .. drwxr-xr-x 2 munin munin 4096 Aug 16 13:55 static Any ideas on why it is not working? EDIT This is how /var/log/munin/ log looks like after some days: -rw-r----- 1 www-data 0 Aug 16 13:54 munin-cgi-graph.log -rw-r----- 1 www-data 0 Aug 16 13:54 munin-cgi-html.log -rw-rw-r-- 1 munin 0 Aug 16 13:55 munin-html.log -rw-r----- 1 munin 0 Aug 19 06:18 munin-limits.log -rw-r----- 1 munin 15K Aug 18 14:10 munin-limits.log.1 -rw-r----- 1 munin 1.8K Aug 18 06:15 munin-limits.log.2.gz -rw-rw-r-- 1 munin 1.3K Aug 17 06:15 munin-limits.log.3.gz -rw-r--r-- 1 root 6.5K Aug 16 13:55 munin-node-configure.log -rw-r--r-- 1 root 0 Aug 17 06:18 munin-node.log -rw-r--r-- 1 root 420 Aug 16 14:52 munin-node.log.1.gz -rw-r----- 1 munin 0 Aug 19 06:18 munin-update.log -rw-r----- 1 munin 11K Aug 18 14:10 munin-update.log.1 -rw-r----- 1 munin 1.6K Aug 18 06:15 munin-update.log.2.gz -rw-rw-r-- 1 munin 1.5K Aug 17 06:15 munin-update.log.3.gz

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  • Dynamically loading Assemblies to reduce Runtime Dependencies

    - by Rick Strahl
    I've been working on a request to the West Wind Application Configuration library to add JSON support. The config library is a very easy to use code-first approach to configuration: You create a class that holds the configuration data that inherits from a base configuration class, and then assign a persistence provider at runtime that determines where and how the configuration data is store. Currently the library supports .NET Configuration stores (web.config/app.config), XML files, SQL records and string storage.About once a week somebody asks me about JSON support and I've deflected this question for the longest time because frankly I think that JSON as a configuration store doesn't really buy a heck of a lot over XML. Both formats require the user to perform some fixup of the plain configuration data - in XML into XML tags, with JSON using JSON delimiters for properties and property formatting rules. Sure JSON is a little less verbose and maybe a little easier to read if you have hierarchical data, but overall the differences are pretty minor in my opinion. And yet - the requests keep rolling in.Hard Link Issues in a Component LibraryAnother reason I've been hesitant is that I really didn't want to pull in a dependency on an external JSON library - in this case JSON.NET - into the core library. If you're not using JSON.NET elsewhere I don't want a user to have to require a hard dependency on JSON.NET unless they want to use the JSON feature. JSON.NET is also sensitive to versions and doesn't play nice with multiple versions when hard linked. For example, when you have a reference to V4.4 in your project but the host application has a reference to version 4.5 you can run into assembly load problems. NuGet's Update-Package can solve some of this *if* you can recompile, but that's not ideal for a component that's supposed to be just plug and play. This is no criticism of JSON.NET - this really applies to any dependency that might change.  So hard linking the DLL can be problematic for a number reasons, but the primary reason is to not force loading of JSON.NET unless you actually need it when you use the JSON configuration features of the library.Enter Dynamic LoadingSo rather than adding an assembly reference to the project, I decided that it would be better to dynamically load the DLL at runtime and then use dynamic typing to access various classes. This allows me to run without a hard assembly reference and allows more flexibility with version number differences now and in the future.But there are also a couple of downsides:No assembly reference means only dynamic access - no compiler type checking or IntellisenseRequirement for the host application to have reference to JSON.NET or else get runtime errorsThe former is minor, but the latter can be problematic. Runtime errors are always painful, but in this case I'm willing to live with this. If you want to use JSON configuration settings JSON.NET needs to be loaded in the project. If this is a Web project, it'll likely be there already.So there are a few things that are needed to make this work:Dynamically create an instance and optionally attempt to load an Assembly (if not loaded)Load types into dynamic variablesUse Reflection for a few tasks like statics/enumsThe dynamic keyword in C# makes the formerly most difficult Reflection part - method calls and property assignments - fairly painless. But as cool as dynamic is it doesn't handle all aspects of Reflection. Specifically it doesn't deal with object activation, truly dynamic (string based) member activation or accessing of non instance members, so there's still a little bit of work left to do with Reflection.Dynamic Object InstantiationThe first step in getting the process rolling is to instantiate the type you need to work with. This might be a two step process - loading the instance from a string value, since we don't have a hard type reference and potentially having to load the assembly. Although the host project might have a reference to JSON.NET, that instance might have not been loaded yet since it hasn't been accessed yet. In ASP.NET this won't be a problem, since ASP.NET preloads all referenced assemblies on AppDomain startup, but in other executable project, assemblies are just in time loaded only when they are accessed.Instantiating a type is a two step process: Finding the type reference and then activating it. Here's the generic code out of my ReflectionUtils library I use for this:/// <summary> /// Creates an instance of a type based on a string. Assumes that the type's /// </summary> /// <param name="typeName">Common name of the type</param> /// <param name="args">Any constructor parameters</param> /// <returns></returns> public static object CreateInstanceFromString(string typeName, params object[] args) { object instance = null; Type type = null; try { type = GetTypeFromName(typeName); if (type == null) return null; instance = Activator.CreateInstance(type, args); } catch { return null; } return instance; } /// <summary> /// Helper routine that looks up a type name and tries to retrieve the /// full type reference in the actively executing assemblies. /// </summary> /// <param name="typeName"></param> /// <returns></returns> public static Type GetTypeFromName(string typeName) { Type type = null; // Let default name binding find it type = Type.GetType(typeName, false); if (type != null) return type; // look through assembly list var assemblies = AppDomain.CurrentDomain.GetAssemblies(); // try to find manually foreach (Assembly asm in assemblies) { type = asm.GetType(typeName, false); if (type != null) break; } return type; } To use this for loading JSON.NET I have a small factory function that instantiates JSON.NET and sets a bunch of configuration settings on the generated object. The startup code also looks for failure and tries loading up the assembly when it fails since that's the main reason the load would fail. Finally it also caches the loaded instance for reuse (according to James the JSON.NET instance is thread safe and quite a bit faster when cached). Here's what the factory function looks like in JsonSerializationUtils:/// <summary> /// Dynamically creates an instance of JSON.NET /// </summary> /// <param name="throwExceptions">If true throws exceptions otherwise returns null</param> /// <returns>Dynamic JsonSerializer instance</returns> public static dynamic CreateJsonNet(bool throwExceptions = true) { if (JsonNet != null) return JsonNet; lock (SyncLock) { if (JsonNet != null) return JsonNet; // Try to create instance dynamic json = ReflectionUtils.CreateInstanceFromString("Newtonsoft.Json.JsonSerializer"); if (json == null) { try { var ass = AppDomain.CurrentDomain.Load("Newtonsoft.Json"); json = ReflectionUtils.CreateInstanceFromString("Newtonsoft.Json.JsonSerializer"); } catch (Exception ex) { if (throwExceptions) throw; return null; } } if (json == null) return null; json.ReferenceLoopHandling = (dynamic) ReflectionUtils.GetStaticProperty("Newtonsoft.Json.ReferenceLoopHandling", "Ignore"); // Enums as strings in JSON dynamic enumConverter = ReflectionUtils.CreateInstanceFromString("Newtonsoft.Json.Converters.StringEnumConverter"); json.Converters.Add(enumConverter); JsonNet = json; } return JsonNet; }This code's purpose is to return a fully configured JsonSerializer instance. As you can see the code tries to create an instance and when it fails tries to load the assembly, and then re-tries loading.Once the instance is loaded some configuration occurs on it. Specifically I set the ReferenceLoopHandling option to not blow up immediately when circular references are encountered. There are a host of other small config setting that might be useful to set, but the default seem to be good enough in recent versions. Note that I'm setting ReferenceLoopHandling which requires an Enum value to be set. There's no real easy way (short of using the cardinal numeric value) to set a property or pass parameters from static values or enums. This means I still need to use Reflection to make this work. I'm using the same ReflectionUtils class I previously used to handle this for me. The function looks up the type and then uses Type.InvokeMember() to read the static property.Another feature I need is have Enum values serialized as strings rather than numeric values which is the default. To do this I can use the StringEnumConverter to convert enums to strings by adding it to the Converters collection.As you can see there's still a bit of Reflection to be done even in C# 4+ with dynamic, but with a few helpers this process is relatively painless.Doing the actual JSON ConversionFinally I need to actually do my JSON conversions. For the Utility class I need serialization that works for both strings and files so I created four methods that handle these tasks two each for serialization and deserialization for string and file.Here's what the File Serialization looks like:/// <summary> /// Serializes an object instance to a JSON file. /// </summary> /// <param name="value">the value to serialize</param> /// <param name="fileName">Full path to the file to write out with JSON.</param> /// <param name="throwExceptions">Determines whether exceptions are thrown or false is returned</param> /// <param name="formatJsonOutput">if true pretty-formats the JSON with line breaks</param> /// <returns>true or false</returns> public static bool SerializeToFile(object value, string fileName, bool throwExceptions = false, bool formatJsonOutput = false) { dynamic writer = null; FileStream fs = null; try { Type type = value.GetType(); var json = CreateJsonNet(throwExceptions); if (json == null) return false; fs = new FileStream(fileName, FileMode.Create); var sw = new StreamWriter(fs, Encoding.UTF8); writer = Activator.CreateInstance(JsonTextWriterType, sw); if (formatJsonOutput) writer.Formatting = (dynamic)Enum.Parse(FormattingType, "Indented"); writer.QuoteChar = '"'; json.Serialize(writer, value); } catch (Exception ex) { Debug.WriteLine("JsonSerializer Serialize error: " + ex.Message); if (throwExceptions) throw; return false; } finally { if (writer != null) writer.Close(); if (fs != null) fs.Close(); } return true; }You can see more of the dynamic invocation in this code. First I grab the dynamic JsonSerializer instance using the CreateJsonNet() method shown earlier which returns a dynamic. I then create a JsonTextWriter and configure a couple of enum settings on it, and then call Serialize() on the serializer instance with the JsonTextWriter that writes the output to disk. Although this code is dynamic it's still fairly short and readable.For full circle operation here's the DeserializeFromFile() version:/// <summary> /// Deserializes an object from file and returns a reference. /// </summary> /// <param name="fileName">name of the file to serialize to</param> /// <param name="objectType">The Type of the object. Use typeof(yourobject class)</param> /// <param name="binarySerialization">determines whether we use Xml or Binary serialization</param> /// <param name="throwExceptions">determines whether failure will throw rather than return null on failure</param> /// <returns>Instance of the deserialized object or null. Must be cast to your object type</returns> public static object DeserializeFromFile(string fileName, Type objectType, bool throwExceptions = false) { dynamic json = CreateJsonNet(throwExceptions); if (json == null) return null; object result = null; dynamic reader = null; FileStream fs = null; try { fs = new FileStream(fileName, FileMode.Open, FileAccess.Read); var sr = new StreamReader(fs, Encoding.UTF8); reader = Activator.CreateInstance(JsonTextReaderType, sr); result = json.Deserialize(reader, objectType); reader.Close(); } catch (Exception ex) { Debug.WriteLine("JsonNetSerialization Deserialization Error: " + ex.Message); if (throwExceptions) throw; return null; } finally { if (reader != null) reader.Close(); if (fs != null) fs.Close(); } return result; }This code is a little more compact since there are no prettifying options to set. Here JsonTextReader is created dynamically and it receives the output from the Deserialize() operation on the serializer.You can take a look at the full JsonSerializationUtils.cs file on GitHub to see the rest of the operations, but the string operations are very similar - the code is fairly repetitive.These generic serialization utilities isolate the dynamic serialization logic that has to deal with the dynamic nature of JSON.NET, and any code that uses these functions is none the wiser that JSON.NET is dynamically loaded.Using the JsonSerializationUtils WrapperThe final consumer of the SerializationUtils wrapper is an actual ConfigurationProvider, that is responsible for handling reading and writing JSON values to and from files. The provider is simple a small wrapper around the SerializationUtils component and there's very little code to make this work now:The whole provider looks like this:/// <summary> /// Reads and Writes configuration settings in .NET config files and /// sections. Allows reading and writing to default or external files /// and specification of the configuration section that settings are /// applied to. /// </summary> public class JsonFileConfigurationProvider<TAppConfiguration> : ConfigurationProviderBase<TAppConfiguration> where TAppConfiguration: AppConfiguration, new() { /// <summary> /// Optional - the Configuration file where configuration settings are /// stored in. If not specified uses the default Configuration Manager /// and its default store. /// </summary> public string JsonConfigurationFile { get { return _JsonConfigurationFile; } set { _JsonConfigurationFile = value; } } private string _JsonConfigurationFile = string.Empty; public override bool Read(AppConfiguration config) { var newConfig = JsonSerializationUtils.DeserializeFromFile(JsonConfigurationFile, typeof(TAppConfiguration)) as TAppConfiguration; if (newConfig == null) { if(Write(config)) return true; return false; } DecryptFields(newConfig); DataUtils.CopyObjectData(newConfig, config, "Provider,ErrorMessage"); return true; } /// <summary> /// Return /// </summary> /// <typeparam name="TAppConfig"></typeparam> /// <returns></returns> public override TAppConfig Read<TAppConfig>() { var result = JsonSerializationUtils.DeserializeFromFile(JsonConfigurationFile, typeof(TAppConfig)) as TAppConfig; if (result != null) DecryptFields(result); return result; } /// <summary> /// Write configuration to XmlConfigurationFile location /// </summary> /// <param name="config"></param> /// <returns></returns> public override bool Write(AppConfiguration config) { EncryptFields(config); bool result = JsonSerializationUtils.SerializeToFile(config, JsonConfigurationFile,false,true); // Have to decrypt again to make sure the properties are readable afterwards DecryptFields(config); return result; } }This incidentally demonstrates how easy it is to create a new provider for the West Wind Application Configuration component. Simply implementing 3 methods will do in most cases.Note this code doesn't have any dynamic dependencies - all that's abstracted away in the JsonSerializationUtils(). From here on, serializing JSON is just a matter of calling the static methods on the SerializationUtils class.Already, there are several other places in some other tools where I use JSON serialization this is coming in very handy. With a couple of lines of code I was able to add JSON.NET support to an older AJAX library that I use replacing quite a bit of code that was previously in use. And for any other manual JSON operations (in a couple of apps I use JSON Serialization for 'blob' like document storage) this is also going to be handy.Performance?Some of you might be thinking that using dynamic and Reflection can't be good for performance. And you'd be right… In performing some informal testing it looks like the performance of the native code is nearly twice as fast as the dynamic code. Most of the slowness is attributable to type lookups. To test I created a native class that uses an actual reference to JSON.NET and performance was consistently around 85-90% faster with the referenced code. This will change though depending on the size of objects serialized - the larger the object the more processing time is spent inside the actual dynamically activated components and the less difference there will be. Dynamic code is always slower, but how much it really affects your application primarily depends on how frequently the dynamic code is called in relation to the non-dynamic code executing. In most situations where dynamic code is used 'to get the process rolling' as I do here the overhead is small enough to not matter.All that being said though - I serialized 10,000 objects in 80ms vs. 45ms so this is hardly slouchy performance. For the configuration component speed is not that important because both read and write operations typically happen once on first access and then every once in a while. But for other operations - say a serializer trying to handle AJAX requests on a Web Server one would be well served to create a hard dependency.Dynamic Loading - Worth it?Dynamic loading is not something you need to worry about but on occasion dynamic loading makes sense. But there's a price to be paid in added code  and a performance hit which depends on how frequently the dynamic code is accessed. But for some operations that are not pivotal to a component or application and are only used under certain circumstances dynamic loading can be beneficial to avoid having to ship extra files adding dependencies and loading down distributions. These days when you create new projects in Visual Studio with 30 assemblies before you even add your own code, trying to keep file counts under control seems like a good idea. It's not the kind of thing you do on a regular basis, but when needed it can be a useful option in your toolset… © Rick Strahl, West Wind Technologies, 2005-2013Posted in .NET  C#   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • SOA Suite 11g Dynamic Payload Testing with soapUI Free Edition

    - by Greg Mally
    Overview Many web service developers use soapUI for various tests like: smoke test, unit test, and load testing because you can get a free edition that is fairly robust. However, if you need to venture into more complex testing that requires a dynamic payload, then the free edition doesn't necessarily make it easy. This feature does exist in soapUI, but for obvious reasons it is in the Pro version. In this blog I will show you how to use soapUI free edition for dynamic payloads in a simplified example. Hopefully this will open the doors for you to expand into more complex scenarios. The following assumes that you have a working knowledge of soapUI and will not go into concepts like setting up a project etc. For the basics, please review the documentation for soapUI: http://www.soapui.org/Getting-Started/. Additionally, we will be using asynchronous web services and you can review the setup for this in my blog: SOA Suite 11g Asynchronous Testing with soapUI. Features in soapUI Free Edition Relating to this Topic The soapUI test tool provides a very feature rich environment that can do many things provided you are willing to go beyond point and click. For this example, we will be leveraging just a couple features for our dynamic payload example: Test Case Properties Scripting with Groovy Basically, we will be using a property as a global variable and we will manipulate that property using a Groovy script. Setting Up Our Property Properties are available throughout soapUI and here is a snippet from the soapUI website defining the locations: Projects : for handling Project scope values, for example a subscription ID TestSuite : for handling TestSuite scoped values, can be seen as "arguments" to a TestSuite TestCases : for handling TestCase scoped values, can be seen as "arguments" to a TestCase Properties TestStep : for providing local values/state within a TestCase Local TestStep properties : several TestStep types maintain their own list of properties specific to their functionality : DataSource, DataSink, Run TestCase MockServices : for handling MockService scoped values/arguments MockResponses : for handling MockResponse scoped values Global Properties : for handling Global properties, optionally from an external source For our example, we will be defining a custom property in a TestCase called SimpleAsyncPayload. The property can be created in either the Custom Properties tab located at the bottom of the Navigator panel when the TestCase is selected in the Navigator or the Properties label in the TestCase editor: Navigator Panel TestCase Editor You will notice that I set a value of “0” for the custom property. For this simplified example, we will need to retrieve that value and manipulate it prior to making the web service request invocation. In order to accomplish this, we will need to get Groovy ;) Let's Get Groovy We will now add a new Groovy Script step to the TestCase called Manipulate Payload: TestCase Editor > Append Step > Groovy Script Once we have added the Groovy Script step to our TestCase, we can open the Groovy Script editor to add the code to: Get the current value of the property we created called SimpleAsyncPayload. Convert the value of the property to an integer. Increment the value. Store the incremented value back into the TestCase property called SimpleAsyncPayload. The script should look something like the following: Groovy Script Editor – Manipulate Payload At this point we can test the script to see if it is working by simply running the TestCase (left-click on the green triangle in the upper left-hand corner of the TestCase editor). To verify if it ran correctly, we can look at the value of the SimpleAsyncPayload property which should now be 1: TestCase Editor – Run Results All that is left to complete the TestCase is to append another step of type Test Request. The information required to append the request is a name and an operation to invoke. In this example we will use the default name and select the SimpleAsyncBPELProcessBingd -> process as the operation (any other information being requested, simply use the defaults unless you are calling an asynchronous operation then do not add any assertions). We are now in familiar ground with the Test Request editor. Depending upon the type of operation you are invoking (synchronous or asynchronous), please update the request with the necessary information (e.g., callback information for asynchronous operations). We will now tweak the Test Request payload to retrieve the value of the SimpleAsyncPayload property. The soapUI editor makes this very simple: right-click in the payload and navigate to the property (e.g., right-click > Get Data.. > TestCase: [Groovy TestCase] > Property [SimpleAsyncPayload]): Test Request Editor – Insert Property Value Your payload should now look something like the following: Test Request Editor – Inserted Property Value Just like before, we are now ready to run the TestCase. If everything goes as expected we should see a response like the following: Message Viewer – Results of TestCase Run We are now setup to be able to run a stress test where the payload will change for each request. This simple example can be expanded to include multiple payload values, complex calculations in the scripts, or whatever can be done via the soapUI scripting. Hopefully you have found this useful and happy testing to you :)

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