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  • BSOD in nltdi.sys Vista x64

    - by W1N9Zr0
    BSOD caused by NetLimiter's nltdi.sys Error codes vary, but this is pretty constant: SYMBOL_NAME: tdx!TdxSendConnection+2a0 MODULE_NAME: tdx IMAGE_NAME: tdx.sys Stack trace includes: nltdi+0x1144 example

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  • 504 Gateway Timeout on server clusters

    - by Sixfoot Studio
    Hi All, Here's our scenario: We're running three websites on three web servers hosted on virtual machines running the following: IIS6 Win 2003 Standard Edition Oracle 10g Sitefinity 3.7 We do not have constant control over these servers and something's gone wrong in the interim in that we're getting constant 504 Gateway Timeouts. The other thing that's happening is that if you hit one of the sites, that site is trying to pull themes from one of the sites App_Themes folder in Sitefinity, which of course should not be happening at all. If someone has any ideas on why this should suddenly have started happening I would appreciate it. Many thanks

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  • Window 2003 is PHP Limiting my Download Speed?

    - by JohnScout
    Hello, I have window 2003 100mbps server, i have tried using php script such as php indexer, zina pancake.org and others. The php script use to serve download such as images and music songs. I personally have 20mbps internet speed. When i use the php script (download pass thru PHP headers) , it will download at constant speed of 30-40KBps. I have tried different webserver such as apache 1.3, apache 2.2, abyss webserver & lighttpd for windows. The speed while relying on php is same constant 30-40KBps however when i tried direct link/straight from apache, the speed is 1MB/s. Is there any settings in Window 2003 Registry or PHP should i change to make the download speed is more faster when going thru PHP?

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  • Anti-Forgery Request Recipes For ASP.NET MVC And AJAX

    - by Dixin
    Background To secure websites from cross-site request forgery (CSRF, or XSRF) attack, ASP.NET MVC provides an excellent mechanism: The server prints tokens to cookie and inside the form; When the form is submitted to server, token in cookie and token inside the form are sent in the HTTP request; Server validates the tokens. To print tokens to browser, just invoke HtmlHelper.AntiForgeryToken():<% using (Html.BeginForm()) { %> <%: this.Html.AntiForgeryToken(Constants.AntiForgeryTokenSalt)%> <%-- Other fields. --%> <input type="submit" value="Submit" /> <% } %> This invocation generates a token then writes inside the form:<form action="..." method="post"> <input name="__RequestVerificationToken" type="hidden" value="J56khgCvbE3bVcsCSZkNVuH9Cclm9SSIT/ywruFsXEgmV8CL2eW5C/gGsQUf/YuP" /> <!-- Other fields. --> <input type="submit" value="Submit" /> </form> and also writes into the cookie: __RequestVerificationToken_Lw__= J56khgCvbE3bVcsCSZkNVuH9Cclm9SSIT/ywruFsXEgmV8CL2eW5C/gGsQUf/YuP When the above form is submitted, they are both sent to server. In the server side, [ValidateAntiForgeryToken] attribute is used to specify the controllers or actions to validate them:[HttpPost] [ValidateAntiForgeryToken(Salt = Constants.AntiForgeryTokenSalt)] public ActionResult Action(/* ... */) { // ... } This is very productive for form scenarios. But recently, when resolving security vulnerabilities for Web products, some problems are encountered. Specify validation on controller (not on each action) The server side problem is, It is expected to declare [ValidateAntiForgeryToken] on controller, but actually it has be to declared on each POST actions. Because POST actions are usually much more then controllers, the work would be a little crazy. Problem Usually a controller contains actions for HTTP GET and actions for HTTP POST requests, and usually validations are expected for HTTP POST requests. So, if the [ValidateAntiForgeryToken] is declared on the controller, the HTTP GET requests become invalid:[ValidateAntiForgeryToken(Salt = Constants.AntiForgeryTokenSalt)] public class SomeController : Controller // One [ValidateAntiForgeryToken] attribute. { [HttpGet] public ActionResult Index() // Index() cannot work. { // ... } [HttpPost] public ActionResult PostAction1(/* ... */) { // ... } [HttpPost] public ActionResult PostAction2(/* ... */) { // ... } // ... } If browser sends an HTTP GET request by clicking a link: http://Site/Some/Index, validation definitely fails, because no token is provided. So the result is, [ValidateAntiForgeryToken] attribute must be distributed to each POST action:public class SomeController : Controller // Many [ValidateAntiForgeryToken] attributes. { [HttpGet] public ActionResult Index() // Works. { // ... } [HttpPost] [ValidateAntiForgeryToken(Salt = Constants.AntiForgeryTokenSalt)] public ActionResult PostAction1(/* ... */) { // ... } [HttpPost] [ValidateAntiForgeryToken(Salt = Constants.AntiForgeryTokenSalt)] public ActionResult PostAction2(/* ... */) { // ... } // ... } This is a little bit crazy, because one application can have a lot of POST actions. Solution To avoid a large number of [ValidateAntiForgeryToken] attributes (one for each POST action), the following ValidateAntiForgeryTokenWrapperAttribute wrapper class can be helpful, where HTTP verbs can be specified:[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)] public class ValidateAntiForgeryTokenWrapperAttribute : FilterAttribute, IAuthorizationFilter { private readonly ValidateAntiForgeryTokenAttribute _validator; private readonly AcceptVerbsAttribute _verbs; public ValidateAntiForgeryTokenWrapperAttribute(HttpVerbs verbs) : this(verbs, null) { } public ValidateAntiForgeryTokenWrapperAttribute(HttpVerbs verbs, string salt) { this._verbs = new AcceptVerbsAttribute(verbs); this._validator = new ValidateAntiForgeryTokenAttribute() { Salt = salt }; } public void OnAuthorization(AuthorizationContext filterContext) { string httpMethodOverride = filterContext.HttpContext.Request.GetHttpMethodOverride(); if (this._verbs.Verbs.Contains(httpMethodOverride, StringComparer.OrdinalIgnoreCase)) { this._validator.OnAuthorization(filterContext); } } } When this attribute is declared on controller, only HTTP requests with the specified verbs are validated:[ValidateAntiForgeryTokenWrapper(HttpVerbs.Post, Constants.AntiForgeryTokenSalt)] public class SomeController : Controller { // GET actions are not affected. // Only HTTP POST requests are validated. } Now one single attribute on controller turns on validation for all POST actions. Maybe it would be nice if HTTP verbs can be specified on the built-in [ValidateAntiForgeryToken] attribute, which is easy to implemented. Specify Non-constant salt in runtime By default, the salt should be a compile time constant, so it can be used for the [ValidateAntiForgeryToken] or [ValidateAntiForgeryTokenWrapper] attribute. Problem One Web product might be sold to many clients. If a constant salt is evaluated in compile time, after the product is built and deployed to many clients, they all have the same salt. Of course, clients do not like this. Even some clients might want to specify a custom salt in configuration. In these scenarios, salt is required to be a runtime value. Solution In the above [ValidateAntiForgeryToken] and [ValidateAntiForgeryTokenWrapper] attribute, the salt is passed through constructor. So one solution is to remove this parameter:public class ValidateAntiForgeryTokenWrapperAttribute : FilterAttribute, IAuthorizationFilter { public ValidateAntiForgeryTokenWrapperAttribute(HttpVerbs verbs) { this._verbs = new AcceptVerbsAttribute(verbs); this._validator = new ValidateAntiForgeryTokenAttribute() { Salt = AntiForgeryToken.Value }; } // Other members. } But here the injected dependency becomes a hard dependency. So the other solution is moving validation code into controller to work around the limitation of attributes:public abstract class AntiForgeryControllerBase : Controller { private readonly ValidateAntiForgeryTokenAttribute _validator; private readonly AcceptVerbsAttribute _verbs; protected AntiForgeryControllerBase(HttpVerbs verbs, string salt) { this._verbs = new AcceptVerbsAttribute(verbs); this._validator = new ValidateAntiForgeryTokenAttribute() { Salt = salt }; } protected override void OnAuthorization(AuthorizationContext filterContext) { base.OnAuthorization(filterContext); string httpMethodOverride = filterContext.HttpContext.Request.GetHttpMethodOverride(); if (this._verbs.Verbs.Contains(httpMethodOverride, StringComparer.OrdinalIgnoreCase)) { this._validator.OnAuthorization(filterContext); } } } Then make controller classes inheriting from this AntiForgeryControllerBase class. Now the salt is no long required to be a compile time constant. Submit token via AJAX For browser side, once server side turns on anti-forgery validation for HTTP POST, all AJAX POST requests will fail by default. Problem In AJAX scenarios, the HTTP POST request is not sent by form. Take jQuery as an example:$.post(url, { productName: "Tofu", categoryId: 1 // Token is not posted. }, callback); This kind of AJAX POST requests will always be invalid, because server side code cannot see the token in the posted data. Solution Basically, the tokens must be printed to browser then sent back to server. So first of all, HtmlHelper.AntiForgeryToken() need to be called somewhere. Now the browser has token in both HTML and cookie. Then jQuery must find the printed token in the HTML, and append token to the data before sending:$.post(url, { productName: "Tofu", categoryId: 1, __RequestVerificationToken: getToken() // Token is posted. }, callback); To be reusable, this can be encapsulated into a tiny jQuery plugin:/// <reference path="jquery-1.4.2.js" /> (function ($) { $.getAntiForgeryToken = function (tokenWindow, appPath) { // HtmlHelper.AntiForgeryToken() must be invoked to print the token. tokenWindow = tokenWindow && typeof tokenWindow === typeof window ? tokenWindow : window; appPath = appPath && typeof appPath === "string" ? "_" + appPath.toString() : ""; // The name attribute is either __RequestVerificationToken, // or __RequestVerificationToken_{appPath}. tokenName = "__RequestVerificationToken" + appPath; // Finds the <input type="hidden" name={tokenName} value="..." /> from the specified. // var inputElements = $("input[type='hidden'][name='__RequestVerificationToken" + appPath + "']"); var inputElements = tokenWindow.document.getElementsByTagName("input"); for (var i = 0; i < inputElements.length; i++) { var inputElement = inputElements[i]; if (inputElement.type === "hidden" && inputElement.name === tokenName) { return { name: tokenName, value: inputElement.value }; } } return null; }; $.appendAntiForgeryToken = function (data, token) { // Converts data if not already a string. if (data && typeof data !== "string") { data = $.param(data); } // Gets token from current window by default. token = token ? token : $.getAntiForgeryToken(); // $.getAntiForgeryToken(window). data = data ? data + "&" : ""; // If token exists, appends {token.name}={token.value} to data. return token ? data + encodeURIComponent(token.name) + "=" + encodeURIComponent(token.value) : data; }; // Wraps $.post(url, data, callback, type). $.postAntiForgery = function (url, data, callback, type) { return $.post(url, $.appendAntiForgeryToken(data), callback, type); }; // Wraps $.ajax(settings). $.ajaxAntiForgery = function (settings) { settings.data = $.appendAntiForgeryToken(settings.data); return $.ajax(settings); }; })(jQuery); In most of the scenarios, it is Ok to just replace $.post() invocation with $.postAntiForgery(), and replace $.ajax() with $.ajaxAntiForgery():$.postAntiForgery(url, { productName: "Tofu", categoryId: 1 }, callback); // Token is posted. There might be some scenarios of custom token, where $.appendAntiForgeryToken() is useful:data = $.appendAntiForgeryToken(data, token); // Token is already in data. No need to invoke $.postAntiForgery(). $.post(url, data, callback); And there are scenarios that the token is not in the current window. For example, an HTTP POST request can be sent by an iframe, while the token is in the parent window. Here, token's container window can be specified for $.getAntiForgeryToken():data = $.appendAntiForgeryToken(data, $.getAntiForgeryToken(window.parent)); // Token is already in data. No need to invoke $.postAntiForgery(). $.post(url, data, callback); If you have better solution, please do tell me.

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  • Need some advice regarding collision detection with the sprite changing its width and height

    - by Frank Scott
    So I'm messing around with collision detection in my tile-based game and everything works fine and dandy using this method. However, now I am trying to implement sprite sheets so my character can have a walking and jumping animation. For one, I'd like to to be able to have each frame of variable size, I think. I want collision detection to be accurate and during a jumping animation the sprite's height will be shorter (because of the calves meeting the hamstrings). Again, this also works fine at the moment. I can get the character to animate properly each frame and cycle through animations. The problems arise when the width and height of the character change. Often times its position will be corrected by the collision detection system and the character will be rubber-banded to random parts of the map or even go outside the map bounds. For some reason with the linked collision detection algorithm, when the width or height of the sprite is changed on the fly, the entire algorithm breaks down. The solution I found so far is to have a single width and height of the sprite that remains constant, and only adjust the source rectangle for drawing. However, I'm not sure exactly what to set as the sprite's constant bounding box because it varies so much with the different animations. So now I'm not sure what to do. I'm toying with the idea of pixel-perfect collision detection but I'm not sure if it would really be worth it. Does anyone know how Braid does their collision detection? My game is also a 2D sidescroller and I was quite impressed with how it was handled in that game. Thanks for reading.

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  • Daylight Saving Time Visualized

    - by Jason Fitzpatrick
    When you map out the Daylight Saving Time adjusted sunrise and sunset times over the course of the year, an interesting pattern emerges. Chart designer Germanium writes: I tried to come up with the reason for the daylight saving time change by just looking at the data for sunset and sunrise times. The figure represents sunset and sunrise times thought the year. It shows that the daylight saving time change marked by the lines (DLS) is keeping the sunrise time pretty much constant throughout the whole year, while making the sunset time change a lot. The spread of sunrise times as measured by the standard deviation is 42 minutes, which means that the sunrise time changes within that range the whole year, while the standard deviation for the sunset times is 1:30 hours. Whatever the argument for doing this is, it’s pretty clear that reason is to keep the sunrise time constant. You can read more about the controversial history of Daylight Saving Time here. Daylight Saving Time Explained [via Cool Infographics] 6 Ways Windows 8 Is More Secure Than Windows 7 HTG Explains: Why It’s Good That Your Computer’s RAM Is Full 10 Awesome Improvements For Desktop Users in Windows 8

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  • Unit testing statically typed functional code

    - by back2dos
    I wanted to ask you people, in which cases it makes sense to unit test statically typed functional code, as written in haskell, scala, ocaml, nemerle, f# or haXe (the last is what I am really interested in, but I wanted to tap into the knowledge of the bigger communities). I ask this because from my understanding: One aspect of unit tests is to have the specs in runnable form. However when employing a declarative style, that directly maps the formalized specs to language semantics, is it even actually possible to express the specs in runnable form in a separate way, that adds value? The more obvious aspect of unit tests is to track down errors that cannot be revealed through static analysis. Given that type safe functional code is a good tool to code extremely close to what your static analyzer understands. However a simple mistake like using x instead of y (both being coordinates) in your code cannot be covered. However such a mistake could also arise while writing the test code, so I am not sure whether its worth the effort. Unit tests do introduce redundancy, which means that when requirements change, the code implementing them and the tests covering this code must both be changed. This overhead of course is about constant, so one could argue, that it doesn't really matter. In fact, in languages like Ruby it really doesn't compared to the benefits, but given how statically typed functional programming covers a lot of the ground unit tests are intended for, it feels like it's a constant overhead one can simply reduce without penalty. From this I'd deduce that unit tests are somewhat obsolete in this programming style. Of course such a claim can only lead to religious wars, so let me boil this down to a simple question: When you use such a programming style, to which extents do you use unit tests and why (what quality is it you hope to gain for your code)? Or the other way round: do you have criteria by which you can qualify a unit of statically typed functional code as covered by the static analyzer and hence needs no unit test coverage?

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  • Knockout with ASP.Net MVC2 - HTML Extension Helpers for input controls

    - by Renso
    Goal: Defining Knockout-style input controls can be tedious and also may be something that you may find obtrusive, mixing your HTML with data bind syntax as well as binding your aspx, ascx files to Knockout. The goal is to make specifying Knockout specific HTML tags easy, seamless really, as well as being able to remove references to Knockout easily. Environment considerations: ASP.Net MVC2 or later Knockoutjs.js How to:     public static class HtmlExtensions     {         public static string DataBoundCheckBox(this HtmlHelper helper, string name, bool isChecked, object htmlAttributes)         {             var builder = new TagBuilder("input");             var dic = new RouteValueDictionary(htmlAttributes) { { "data-bind", String.Format("checked: {0}", name) } };             builder.MergeAttributes(dic);             builder.MergeAttribute("type", @"checkbox");             builder.MergeAttribute("name", name);             builder.MergeAttribute("value", @"true");             if (isChecked)             {                 builder.MergeAttribute("checked", @"checked");             }             return builder.ToString(TagRenderMode.SelfClosing);         }         public static MvcHtmlString DataBoundSelectList(this HtmlHelper helper, string name, IEnumerable<SelectListItem> selectList, String optionLabel)         {             var attrProperties = new StringBuilder();             attrProperties.Append(String.Format("optionsText: '{0}'", name));             if (!String.IsNullOrEmpty(optionLabel)) attrProperties.Append(String.Format(", optionsCaption: '{0}'", optionLabel));             attrProperties.Append(String.Format(", value: {0}", name));             var dic = new RouteValueDictionary { { "data-bind", attrProperties.ToString() } };             return helper.DropDownList(name, selectList, optionLabel, dic);         }         public static MvcHtmlString DataBoundSelectList(this HtmlHelper helper, string name, IEnumerable<SelectListItem> selectList, String optionLabel, object htmlAttributes)         {             var attrProperties = new StringBuilder();             attrProperties.Append(String.Format("optionsText: '{0}'", name));             if (!String.IsNullOrEmpty(optionLabel)) attrProperties.Append(String.Format(", optionsCaption: '{0}'", optionLabel));             attrProperties.Append(String.Format(", value: {0}", name));             var dic = new RouteValueDictionary(htmlAttributes) {{"data-bind", attrProperties}};             return helper.DropDownList(name, selectList, optionLabel, dic);         }         public static String DataBoundSelectList(this HtmlHelper helper, String options, String optionsText, String value)         {             return String.Format("<select data-bind=\"options: {0},optionsText: '{1}',value: {2}\"></select>", options, optionsText, value);         }         public static MvcHtmlString DataBoundTextBox(this HtmlHelper helper, string name, object value, object htmlAttributes)         {             var dic = new RouteValueDictionary(htmlAttributes);             dic.Add("data-bind", String.Format("value: {0}", name));             return helper.TextBox(name, value, dic);         }         public static MvcHtmlString DataBoundTextBox(this HtmlHelper helper, string name, string observable, object value, object htmlAttributes)         {             var dic = new RouteValueDictionary(htmlAttributes);             dic.Add("data-bind", String.Format("value: {0}", observable));             return helper.TextBox(name, value, dic);         }         public static MvcHtmlString DataBoundTextArea(this HtmlHelper helper, string name, string value, int rows, int columns, object htmlAttributes)         {             var dic = new RouteValueDictionary(htmlAttributes);             dic.Add("data-bind", String.Format("value: {0}", name));             return helper.TextArea(name, value, rows, columns, dic);         }         public static MvcHtmlString DataBoundTextArea(this HtmlHelper helper, string name, string observable, string value, int rows, int columns, object htmlAttributes)         {             var dic = new RouteValueDictionary(htmlAttributes);             dic.Add("data-bind", String.Format("value: {0}", observable));             return helper.TextArea(name, value, rows, columns, dic);         }         public static string BuildUrlFromExpression<T>(this HtmlHelper helper, Expression<Action<T>> action)         {             var values = CreateRouteValuesFromExpression(action);             var virtualPath = helper.RouteCollection.GetVirtualPath(helper.ViewContext.RequestContext, values);             if (virtualPath != null)             {                 return virtualPath.VirtualPath;             }             return null;         }         public static string ActionLink<T>(this HtmlHelper helper, Expression<Action<T>> action, string linkText)         {             return helper.ActionLink(action, linkText, null);         }         public static string ActionLink<T>(this HtmlHelper helper, Expression<Action<T>> action, string linkText, object htmlAttributes)         {             var values = CreateRouteValuesFromExpression(action);             var controllerName = (string)values["controller"];             var actionName = (string)values["action"];             values.Remove("controller");             values.Remove("action");             return helper.ActionLink(linkText, actionName, controllerName, values, new RouteValueDictionary(htmlAttributes)).ToHtmlString();         }         public static MvcForm Form<T>(this HtmlHelper helper, Expression<Action<T>> action)         {             return helper.Form(action, FormMethod.Post);         }         public static MvcForm Form<T>(this HtmlHelper helper, Expression<Action<T>> action, FormMethod method)         {             var values = CreateRouteValuesFromExpression(action);             string controllerName = (string)values["controller"];             string actionName = (string)values["action"];             values.Remove("controller");             values.Remove("action");             return helper.BeginForm(actionName, controllerName, values, method);         }         public static MvcForm Form<T>(this HtmlHelper helper, Expression<Action<T>> action, FormMethod method, object htmlAttributes)         {             var values = CreateRouteValuesFromExpression(action);             string controllerName = (string)values["controller"];             string actionName = (string)values["action"];             values.Remove("controller");             values.Remove("action");             return helper.BeginForm(actionName, controllerName, values, method, new RouteValueDictionary(htmlAttributes));         }         public static string VertCheckBox(this HtmlHelper helper, string name, bool isChecked)         {             return helper.CustomCheckBox(name, isChecked, null);         }          public static string CustomCheckBox(this HtmlHelper helper, string name, bool isChecked, object htmlAttributes)         {             TagBuilder builder = new TagBuilder("input");             builder.MergeAttributes(new RouteValueDictionary(htmlAttributes));             builder.MergeAttribute("type", "checkbox");             builder.MergeAttribute("name", name);             builder.MergeAttribute("value", "true");             if (isChecked)             {                 builder.MergeAttribute("checked", "checked");             }             return builder.ToString(TagRenderMode.SelfClosing);         }         public static string Script(this HtmlHelper helper, string script, object scriptAttributes)         {             var pathForCRMScripts = ScriptsController.GetPathForCRMScripts();             if (ScriptOptimizerConfig.EnableMinimizedFileLoad)             {                 string newPathForCRM = pathForCRMScripts + "Min/";                 ScriptsController.ServerPathMapper = new ServerPathMapper();                 string fullPath = ScriptsController.ServerMapPath(newPathForCRM);                 if (!File.Exists(fullPath + script))                     return null;                 if (!Directory.Exists(fullPath))                     return null;                 pathForCRMScripts = newPathForCRM;             }             var builder = new TagBuilder("script");             builder.MergeAttributes(new RouteValueDictionary(scriptAttributes));             builder.MergeAttribute("type", @"text/javascript");             builder.MergeAttribute("src", String.Format("{0}{1}", pathForCRMScripts.Replace("~", String.Empty), script));             return builder.ToString(TagRenderMode.SelfClosing);         }         private static RouteValueDictionary CreateRouteValuesFromExpression<T>(Expression<Action<T>> action)         {             if (action == null)                 throw new InvalidOperationException("Action must be provided");             var body = action.Body as MethodCallExpression;             if (body == null)             {                 throw new InvalidOperationException("Expression must be a method call");             }             if (body.Object != action.Parameters[0])             {                 throw new InvalidOperationException("Method call must target lambda argument");             }             // This will build up a RouteValueDictionary containing the controller name, action name, and any             // parameters passed as part of the "action" parameter.             string name = body.Method.Name;             string controllerName = typeof(T).Name;             if (controllerName.EndsWith("Controller", StringComparison.OrdinalIgnoreCase))             {                 controllerName = controllerName.Remove(controllerName.Length - 10, 10);             }             var values = BuildParameterValuesFromExpression(body) ?? new RouteValueDictionary();             values.Add("controller", controllerName);             values.Add("action", name);             return values;         }         private static RouteValueDictionary BuildParameterValuesFromExpression(MethodCallExpression call)         {             // Build up a RouteValueDictionary containing parameter names as keys and parameter values             // as values based on the MethodCallExpression passed in.             var values = new RouteValueDictionary();             ParameterInfo[] parameters = call.Method.GetParameters();             // If the passed in method has no parameters, just return an empty dictionary.             if (parameters.Length == 0)             {                 return values;             }             for (int i = 0; i < parameters.Length; i++)             {                 object parameterValue;                 Expression expression = call.Arguments[i];                 // If the current parameter is a constant, just use its value as the parameter value.                 var constant = expression as ConstantExpression;                 if (constant != null)                 {                     parameterValue = constant.Value;                 }                 else                 {                     // Otherwise, compile and execute the expression and use that as the parameter value.                     var function = Expression.Lambda<Func<object>>(Expression.Convert(expression, typeof(object)),                                                                    new ParameterExpression[0]);                     try                     {                         parameterValue = function.Compile()();                     }                     catch                     {                         parameterValue = null;                     }                 }                 values.Add(parameters[i].Name, parameterValue);             }             return values;         }     }   Some observations: The first two DataBoundSelectList overloaded methods are specifically built to load the data right into the drop down box as part of the HTML response stream rather than let Knockout's engine populate the options client-side. The third overloaded method does it client-side via the viewmodel. The first two overloads can be done when you have no requirement to add complex JSON objects to your lists. Furthermore, why render and parse the JSON object when you can have it all built and rendered server-side like any other list control.

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  • Duplication of code (backend and javascript - knockout)

    - by Michal B.
    We have a new developer in our team. He seems a smart guy (he just came in so I cannot really judge). He started with implementing some small enhancements in the project (MVC3 web application using javascript - jquery and knockout). Let's say we have two values: A - quite complex calculation C - constant B = A + C On the screen there is value B and user can change it (normal texbox). When B changes, A changes as well because C is constant. So there is linear dependency between A and B. Now, all the calculations are done in the backend, but we need to recalculate A as user changes B (in js, I would use knockout). I thought about storing old A and B and when B changes by 10 then we know that new A will be old A + 10. He says this is dirty, because it's duplication of code (we make use of the fact that they are dependent and according to him that should be only in one place in our app). I understand it's not ideal, but making AJAX request after every key press seems a bit too much. It's a really small thing and I would not post if we haven't had long discussion about it. How do you deal with such problems? Also I can imagine that using knockout implies lots of calculations on the client side, which very often leads to duplication of the same calculations from the backend. Does anyone have links to some articles/thoughts on this topic?

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  • Server outputs the sourcecode of PHP page

    - by Akhilesh B Chandran
    I have a Shared Hosting package with HostGator. In it, I'm hosting around 4 websites. They are just some simple sites that doesn't likely to attract more visitors. But a few days ago, when I accessed one of my sites(via a browser), it outputted the PHP code of index.php, instead of outputting it as HTML. I think, at that time, the server was a bit busy or something. I heard that, Facebook also have got a similar condition where the home page's code was made available. So, how do I take preventive measures for this ? I always use phpBB forum's style of coding. That is, each sub pages, common functions, etc. are separated into subfolders. And in PHP, I would just include_once() or require_once() it. Also, these subfolders have a .htaccess file in which I have set the deny permission to the files inside it from outside. Also, in the main page(index), I would define a constant. And the first line of the subpages(which is situated in separate folders) is to check whether this constant is set. If not, calls die(). I am looking forward for solutions to this problem of outputting raw code when the page is accessed. Thanks in advance :)

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  • How to implement child-parent aggregation link in C++?

    - by Giorgio
    Suppose that I have three classes P, C1, C2, composition (strong aggregation) relations between P <>- C1 and P <>- C2, i.e. every instance of P contains an instance of C1 and an instance of C2, which are destroyed when the parent P instance is destroyed. an association relation between instances of C1 and C2 (not necessarily between children of the same P). To implement this, in C++ I normally define three classes P, C1, C2, define two member variables of P of type boost::shared_ptr<C1>, boost::shared_ptr<C2>, and initialize them with newly created objects in P's constructor, implement the relation between C1 and C2 using a boost::weak_ptr<C2> member variable in C1 and a boost::weak_ptr<C1> member variable in C2 that can be set later via appropriate methods, when the relation is established. Now, I also would like to have a link from each C1 and C2 object to its P parent object. What is a good way to implement this? My current idea is to use a simple constant raw pointer (P * const) that is set from the constructor of P (which, in turn, calls the constructors of C1 and C2), i.e. something like: class C1 { public: C1(P * const p, ...) : paren(p) { ... } private: P * const parent; ... }; class P { public: P(...) : childC1(new C1(this, ...)) ... { ... } private: boost::shared_ptr<C1> childC1; ... }; Honestly I see no risk in using a private constant raw pointer in this way but I know that raw pointers are often frowned upon in C++ so I was wondering if there is an alternative solution.

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  • Implementing `fling` logic without pan gesture recognizers

    - by KDiTraglia
    So I am trying to port over a simple game that I originally wrote to iphone into cocos2d-x. I've hit a minor bump however in implementing simple 'fling' logic I had in the iphone version that is difficult to port over to the c++. In iOS I could get the velocity of a pan gesture very easily: CGPoint velocity = [recognizer velocityInView:recognizer.view]; However now I basically only know where the touch began, where the touch ended, and all the touches that are logged in between. For now I logged all the pts onto a stack then pulled the last point and the 6th to last point (seemed to work the best), find the difference between those pts multiply by a constant and use that as the velocity. It works relatively well, but I'm wondering if anyone else has any better algorithms, when given a bunch of touch pts, to figure out a new speed upon releasing an object that feels natural (Note speed in my game is just a constant x and y, there's no drag or spin or anything tricky like that). Bonus points if anyone has figured out how to get pan gestures into the newest version (3.0 alpha) of cocos2d-x without losing ability to build cross platform.

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  • Why does working processors harder use more electrical power?

    - by GazTheDestroyer
    Back in the mists of time when I started coding, at least as far as I'm aware, processors all used a fixed amount of power. There was no such thing as a processor being "idle". These days there are all sorts of technologies for reducing power usage when the processor is not very busy, mostly by dynamically reducing the clock rate. My question is why does running at a lower clock rate use less power? My mental picture of a processor is of a reference voltage (say 5V) representing a binary 1, and 0V representing 0. Therefore I tend to think of of a constant 5V being applied across the entire chip, with the various logic gates disconnecting this voltage when "off", meaning a constant amount of power is being used. The rate at which these gates are turned on and off seems to have no relation to the power used. I have no doubt this is a hopelessly naive picture, but I am no electrical engineer. Can someone explain what's really going on with frequency scaling, and how it saves power. Are there any other ways that a processor uses more or less power depending on state? eg Does it use more power if more gates are open? How are mobile / low power processors different from their desktop cousins? Are they just simpler (less transistors?), or is there some other fundamental design difference?

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  • Adjusting the rate of movement of different objects on the same timer

    - by theUg
    I have a series of objects moving along the straight lines. I want to implement slight changes of velocity of each of the object. Constraint is existing model of animation. I am new to this, and not sure if it is the best way to accommodate varying speeds, but what do I know? It is a Java application that repaints the panel every time the timer expires. Timer is set via swing.Timer object that is set by timer delay constant. Every time the game is stepped objects’ coordinates advanced by an increment constant. Most of the objects are of the same class. Is there fairly easy way to refactor existing system to allow changing velocity for an individual object? Is there some obvious common solution I am not aware about? Idea I am having right now is to set timer delay fairly small, and only move objects every so many cycles of animation so that the apparent speed can be adjusted by varying how often they get moved. But that seems fairly involved, and I do not think it is the most elegant solution in terms of performance what with repainting the whole frame every 3-5 milliseconds. Can it be done by advancing the objects so many (varying) times during the certain interval (let’s say 35ms for something like 28fps), and use repaint() method to redraw just individual object? Do I need to mess with pausing animation for smoothness at higher redraw rates? Is it common practise to check for collision at larger step interval, but draw animation a lot more frequently?

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  • How can I read a portion of one Minecraft world file and write it into another?

    - by RapierMother
    I'm looking to read block data from one Minecraft world and write the data into certain places in another. I have a Minecraft world, let's say "TemplateWorld", and a 2D list of Point objects. I'm developing an application that should use the x and y values of these Points as x and z reference coordinates from which to read constant-sized areas of blocks from the TemplateWorld. It should then write these blocks into another Minecraft world at constant y coordinates, with x & z coordinates determined based on each Point's index in the 2D list. The issue is that, while I've found a decent amount of information online regarding Minecraft world formats, I haven't found what I really need: more of a breakdown by hex address of where/what everything is. For example, I could have the TemplateWorld actually be a .schematic file rather than a world; I just need to be able to read the bytes of the file, know that the actual block data starts always at a certain address (or after a certain instance of FF, etc.), and how it's stored. Once I know that, it's easy as pie to just read the bytes and store them.

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  • FP for simulation and modelling

    - by heaptobesquare
    I'm about to start a simulation/modelling project. I already know that OOP is used for this kind of projects. However, studying Haskell made me consider using the FP paradigm for modelling a system of components. Let me elaborate: Let's say I have a component of type A, characterised by a set of data (a parameter like temperature or pressure,a PDE and some boundary conditions,etc.) and a component of type B, characterised by a different set of data(different or same parameter, different PDE and boundary conditions). Let's also assume that the functions/methods that are going to be applied on each component are the same (a Galerkin method for example). If I were to use an OOP approach, I would create two objects that would encapsulate each type's data, the methods for solving the PDE(inheritance would be used here for code reuse) and the solution to the PDE. On the other hand, if I were to use an FP approach, each component would be broken down to data parts and the functions that would act upon the data in order to get the solution for the PDE. This approach seems simpler to me assuming that linear operations on data would be trivial and that the parameters are constant. What if the parameters are not constant(for example, temperature increases suddenly and therefore cannot be immutable)? In OOP, the object's (mutable) state can be used. I know that Haskell has Monads for that. To conclude, would implementing the FP approach be actually simpler,less time consuming and easier to manage (add a different type of component or new method to solve the pde) compared to the OOP one? I come from a C++/Fortran background, plus I'm not a professional programmer, so correct me on anything that I've got wrong.

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  • I have an "amoeba" game mechanic. Any idea on how to implement it?

    - by Jason
    Outside of a tetris clone, a crappy 2D top-down shooter, and some messing around with stuff like Unity and Flixel, I realize that I have yet to complete a single, polished, bells-and-whistles game. I want to change this, and I have an idea for my next project. The idea is that you're an amoeba. Amoebas have these eye-like cores (or something like that, I don't know biology), and you have two of 'em. You control one with WASD and the other with IJKL. There has to be a constant radius of stuff around each of the cores: And the area of the amoeba has to stay constant. So if you move a core in one direction, you increase the amoeba's area, but that increase is compensated by a decrease somewhere else: Aaaaaand I'd like to implement a vagination mechanic. You absorb things by engulfing them, like a boss. Maybe even an extra core, or a needle that pops you and causes all your inner stuff to start gushing out: But here's the problem: I don't know how to make this. However, I would like some ideas on how to implement it. Should I explore physics libraries like Box2D? Or maybe something involving fluid physics? Any help would be much appreciated. P.S. Feel free to steal this idea. I have plenty of ideas. If you do, please tell me how you made it so I can try it myself.

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  • Boundary conditions for testing

    - by Loggie
    Ok so in a programming test I was given the following question. Question 1 (1 mark) Spot the potential bug in this section of code: void Class::Update( float dt ) { totalTime += dt; if( totalTime == 3.0f ) { // Do state change m_State++; } } The multiple choice answers for this question were. a) It has a constant floating point number where it should have a named constant variable b) It may not change state with only an equality test c) You don't know what state you are changing to d) The class is named poorly I wrongly answered this with answer C. I eventually received feedback on the answers and the feedback for this question was Correct answer is a. This is about understanding correct boundary conditions for tests. The other answers are arguably valid points, but do not indicate a potential bug in the code. My question here is, what does this have to do with boundary conditions? My understanding of boundary conditions is checking that a value is within a certain range, which isn't the case here. Upon looking over the question, in my opinion, B should be the correct answer when considering the accuracy issues of using floating point values.

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  • CLR Profiler Allocated Bytes and XNA ContentManager

    - by Vackup
    I've been fighting with XNA ContentManager and memory allocations for some weeks because I'm trying to port my game from XNA (Windows) to ExEn / Monotouch (iphone). The problem is that after playing a few levels, my game exits unexpectedly on a real iPhone device (not simulator). Profiling memory usage on Windows with CLRProfile, I found some useful stuff but I also found something I dont understand. If I use 2 ContentManagers (1 for shared assets and 1 for level assets), when profiling, "Allocated Bytes" grows and grows after level through level but Memory consumption measured by Windows Task Manager stays constant (down when I unload the content manager and up again when I load content). Obviously, I contentManager.Unload() when level ends. After a few levels my game exits unexpectedly on an iPhone device. If I use 1 content manager, "CRLProfiler Allocated Bytes" stays constant on Windows and on the iPhone; I can play the game normally and it doesnt exit unexpectedly. I use the same assets level through level. It seems like in ios (iPhone) when loading and unloading the same assets, it allocates memory and consumes all device memory, so the ios kill it. Can anybody explain me how this really works? I've read quite a bit, but I still don't understand what's going on.

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  • strlen returns incorrect value when called in gdb

    - by alesplin
    So I'm noticing some severely incorrect behavior from calls to standard library functions inside GDB. I have the following program to illustrate: #include <stdio.h> #include <stdlib.h> #include <string.h> int main(int argc, char *argv[]) { char *s1 = "test"; char *s2 = calloc(strlen("test")+1,sizeof(char)); snprintf(s2,strlen("test")+1,"test"); printf("string constant: %lu\n", strlen(s1)); printf("allocated string: %lu\n", strlen(s2)); free(s2); return 0; } When run from the command-line, this program outputs just what you'd expect: string constant: 4 allocated string: 4 However, in GDB, I get the following, incorrect output from calls to strlen(): (gdb) p strlen(s1) $1 = -938856896 (gdb) p strlen(s2) $2 = -938856896 I'm pretty sure this is a problem with glibc shipped with Ubuntu (I'm using 10.10), but this is a serious problem for those of us who spend lots of time in GDB. Is anyone else experiencing this kind of error? What's the best way to fix it? Build glibc from source? (I'm already running a version of GDB built from source)

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  • C# 4.0: Named And Optional Arguments

    - by Paulo Morgado
    As part of the co-evolution effort of C# and Visual Basic, C# 4.0 introduces Named and Optional Arguments. First of all, let’s clarify what are arguments and parameters: Method definition parameters are the input variables of the method. Method call arguments are the values provided to the method parameters. In fact, the C# Language Specification states the following on §7.5: The argument list (§7.5.1) of a function member invocation provides actual values or variable references for the parameters of the function member. Given the above definitions, we can state that: Parameters have always been named and still are. Parameters have never been optional and still aren’t. Named Arguments Until now, the way the C# compiler matched method call definition arguments with method parameters was by position. The first argument provides the value for the first parameter, the second argument provides the value for the second parameter, and so on and so on, regardless of the name of the parameters. If a parameter was missing a corresponding argument to provide its value, the compiler would emit a compilation error. For this call: Greeting("Mr.", "Morgado", 42); this method: public void Greeting(string title, string name, int age) will receive as parameters: title: “Mr.” name: “Morgado” age: 42 What this new feature allows is to use the names of the parameters to identify the corresponding arguments in the form: name:value Not all arguments in the argument list must be named. However, all named arguments must be at the end of the argument list. The matching between arguments (and the evaluation of its value) and parameters will be done first by name for the named arguments and than by position for the unnamed arguments. This means that, for this method definition: public static void Method(int first, int second, int third) this call declaration: int i = 0; Method(i, third: i++, second: ++i); will have this code generated by the compiler: int i = 0; int CS$0$0000 = i++; int CS$0$0001 = ++i; Method(i, CS$0$0001, CS$0$0000); which will give the method the following parameter values: first: 2 second: 2 third: 0 Notice the variable names. Although invalid being invalid C# identifiers, they are valid .NET identifiers and thus avoiding collision between user written and compiler generated code. Besides allowing to re-order of the argument list, this feature is very useful for auto-documenting the code, for example, when the argument list is very long or not clear, from the call site, what the arguments are. Optional Arguments Parameters can now have default values: public static void Method(int first, int second = 2, int third = 3) Parameters with default values must be the last in the parameter list and its value is used as the value of the parameter if the corresponding argument is missing from the method call declaration. For this call declaration: int i = 0; Method(i, third: ++i); will have this code generated by the compiler: int i = 0; int CS$0$0000 = ++i; Method(i, 2, CS$0$0000); which will give the method the following parameter values: first: 1 second: 2 third: 1 Because, when method parameters have default values, arguments can be omitted from the call declaration, this might seem like method overloading or a good replacement for it, but it isn’t. Although methods like this: public static StreamReader OpenTextFile( string path, Encoding encoding = null, bool detectEncoding = true, int bufferSize = 1024) allow to have its calls written like this: OpenTextFile("foo.txt", Encoding.UTF8); OpenTextFile("foo.txt", Encoding.UTF8, bufferSize: 4096); OpenTextFile( bufferSize: 4096, path: "foo.txt", detectEncoding: false); The complier handles default values like constant fields taking the value and useing it instead of a reference to the value. So, like with constant fields, methods with parameters with default values are exposed publicly (and remember that internal members might be publicly accessible – InternalsVisibleToAttribute). If such methods are publicly accessible and used by another assembly, those values will be hard coded in the calling code and, if the called assembly has its default values changed, they won’t be assumed by already compiled code. At the first glance, I though that using optional arguments for “bad” written code was great, but the ability to write code like that was just pure evil. But than I realized that, since I use private constant fields, it’s OK to use default parameter values on privately accessed methods.

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  • Why do we use Pythagoras in game physics?

    - by Starkers
    I've recently learned that we use Pythagoras a lot in our physics calculations and I'm afraid I don't really get the point. Here's an example from a book to make sure an object doesn't travel faster than a MAXIMUM_VELOCITY constant in the horizontal plane: MAXIMUM_VELOCITY = <any number>; SQUARED_MAXIMUM_VELOCITY = MAXIMUM_VELOCITY * MAXIMUM_VELOCITY; function animate(){ var squared_horizontal_velocity = (x_velocity * x_velocity) + (z_velocity * z_velocity); if( squared_horizontal_velocity <= SQUARED_MAXIMUM_VELOCITY ){ scalar = squared_horizontal_velocity / SQUARED_MAXIMUM_VELOCITY; x_velocity = x_velocity / scalar; z_velocity = x_velocity / scalar; } } Let's try this with some numbers: An object is attempting to move 5 units in x and 5 units in z. It should only be able to move 5 units horizontally in total! MAXIMUM_VELOCITY = 5; SQUARED_MAXIMUM_VELOCITY = 5 * 5; SQUARED_MAXIMUM_VELOCITY = 25; function animate(){ var x_velocity = 5; var z_velocity = 5; var squared_horizontal_velocity = (x_velocity * x_velocity) + (z_velocity * z_velocity); var squared_horizontal_velocity = 5 * 5 + 5 * 5; var squared_horizontal_velocity = 25 + 25; var squared_horizontal_velocity = 50; // if( squared_horizontal_velocity <= SQUARED_MAXIMUM_VELOCITY ){ if( 50 <= 25 ){ scalar = squared_horizontal_velocity / SQUARED_MAXIMUM_VELOCITY; scalar = 50 / 25; scalar = 2.0; x_velocity = x_velocity / scalar; x_velocity = 5 / 2.0; x_velocity = 2.5; z_velocity = z_velocity / scalar; z_velocity = 5 / 2.0; z_velocity = 2.5; // new_horizontal_velocity = x_velocity + z_velocity // new_horizontal_velocity = 2.5 + 2.5 // new_horizontal_velocity = 5 } } Now this works well, but we can do the same thing without Pythagoras: MAXIMUM_VELOCITY = 5; function animate(){ var x_velocity = 5; var z_velocity = 5; var horizontal_velocity = x_velocity + z_velocity; var horizontal_velocity = 5 + 5; var horizontal_velocity = 10; // if( horizontal_velocity >= MAXIMUM_VELOCITY ){ if( 10 >= 5 ){ scalar = horizontal_velocity / MAXIMUM_VELOCITY; scalar = 10 / 5; scalar = 2.0; x_velocity = x_velocity / scalar; x_velocity = 5 / 2.0; x_velocity = 2.5; z_velocity = z_velocity / scalar; z_velocity = 5 / 2.0; z_velocity = 2.5; // new_horizontal_velocity = x_velocity + z_velocity // new_horizontal_velocity = 2.5 + 2.5 // new_horizontal_velocity = 5 } } Benefits of doing it without Pythagoras: Less lines Within those lines, it's easier to read what's going on ...and it takes less time to compute, as there are less multiplications Seems to me like computers and humans get a better deal without Pythagoras! However, I'm sure I'm wrong as I've seen Pythagoras' theorem in a number of reputable places, so I'd like someone to explain me the benefit of using Pythagoras to a maths newbie. Does this have anything to do with unit vectors? To me a unit vector is when we normalize a vector and turn it into a fraction. We do this by dividing the vector by a larger constant. I'm not sure what constant it is. The total size of the graph? Anyway, because it's a fraction, I take it, a unit vector is basically a graph that can fit inside a 3D grid with the x-axis running from -1 to 1, z-axis running from -1 to 1, and the y-axis running from -1 to 1. That's literally everything I know about unit vectors... not much :P And I fail to see their usefulness. Also, we're not really creating a unit vector in the above examples. Should I be determining the scalar like this: // a mathematical work-around of my own invention. There may be a cleverer way to do this! I've also made up my own terms such as 'divisive_scalar' so don't bother googling var divisive_scalar = (squared_horizontal_velocity / SQUARED_MAXIMUM_VELOCITY); var divisive_scalar = ( 50 / 25 ); var divisive_scalar = 2; var multiplicative_scalar = (divisive_scalar / (2*divisive_scalar)); var multiplicative_scalar = (2 / (2*2)); var multiplicative_scalar = (2 / 4); var multiplicative_scalar = 0.5; x_velocity = x_velocity * multiplicative_scalar x_velocity = 5 * 0.5 x_velocity = 2.5 Again, I can't see why this is better, but it's more "unit-vector-y" because the multiplicative_scalar is a unit_vector? As you can see, I use words such as "unit-vector-y" so I'm really not a maths whiz! Also aware that unit vectors might have nothing to do with Pythagoras so ignore all of this if I'm barking up the wrong tree. I'm a very visual person (3D modeller and concept artist by trade!) and I find diagrams and graphs really, really helpful so as many as humanely possible please!

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  • Understanding the 'High Performance' meaning in Extreme Transaction Processing

    - by kyap
    Despite my previous blogs entries on SOA/BPM and Identity Management, the domain where I'm the most passionated is definitely the Extreme Transaction Processing, commonly called XTP.I came across XTP back to 2007 while I was still FMW Product Manager in EMEA. At that time Oracle acquired a company called Tangosol, which owned an unique product called Coherence that we renamed to Oracle Coherence. Beside this innovative renaming of the product, to be honest, I didn't know much about it, except being a "distributed in-memory cache for Extreme Transaction Processing"... not very helpful still.In general when people doesn't fully understand a technology or a concept, they tend to find some shortcuts, either correct or not, to justify their lack-of understanding... and of course I was part of this category of individuals. And the shortcut was "Oracle Coherence Cache helps to improve Performance". Excellent marketing slogan... but not very meaningful still. By chance I was able to get away quickly from that group in July 2007* at Thames Valley Park (UK), after I attended one of the most interesting workshops, in my 10 years career in Oracle, delivered by Brian Oliver. The biggest mistake I made was to assume that performance improvement with Coherence was related to the response time. Which can be considered as legitimus at that time, because after-all caches help to reduce latency on cached data access, hence reduce the response-time. But like all caches, you need to define caching and expiration policies, thinking about the cache-missed strategy, and most of the time you have to re-write partially your application in order to work with the cache. At a result, the expected benefit vanishes... so, not very useful then?The key mistake I made was my perception or obsession on how performance improvement should be driven, but I strongly believe this is still a common problem to most of the developers. In fact we all know the that the performance of a system is generally presented by the Capacity (or Throughput), with the 2 important dimensions Speed (response-time) and Volume (load) :Capacity (TPS) = Volume (T) / Speed (S)To increase the Capacity, we can either reduce the Speed(in terms of response-time), or to increase the Volume. However we tend to only focus on reducing the Speed dimension, perhaps it is more concrete and tangible to measure, and nicer to present to our management because there's a direct impact onto the end-users experience. On the other hand, we assume the Volume can be addressed by the underlying hardware or software stack, so if we need more capacity (scale out), we just add more hardware or software. Unfortunately, the reality proves that IT is never as ideal as we assume...The challenge with Speed improvement approach is that it is generally difficult and costly to make things already fast... faster. And by adding Coherence will not necessarily help either. Even though we manage to do so, the Capacity can not increase forever because... the Speed can be influenced by the Volume. For all system, we always have a performance illustration as follow: In all traditional system, the increase of Volume (Transaction) will also increase the Speed (Response-Time) as some point. The reason is simple: most of the time the Application logics were not designed to scale. As an example, if you have a while-loop in your application, it is natural to conceive that parsing 200 entries will require double execution-time compared to 100 entries. If you need to "Speed-up" the execution, you can only upgrade your hardware (scale-up) with faster CPU and/or network to reduce network latency. It is technically limited and economically inefficient. And this is exactly where XTP and Coherence kick in. The primary objective of XTP is about designing applications which can scale-out for increasing the Volume, by applying coding techniques to keep the execution-time as constant as possible, independently of the number of runtime data being manipulated. It is actually not just about having an application running as fast as possible, but about having a much more predictable system, with constant response-time and linearly scale, so we can easily increase throughput by adding more hardwares in parallel. It is in general combined with the Low Latency Programming model, where we tried to optimize the network usage as much as possible, either from the programmatic angle (less network-hoops to complete a task), and/or from a hardware angle (faster network equipments). In this picture, Oracle Coherence can be considered as software-level XTP enabler, via the Distributed-Cache because it can guarantee: - Constant Data Objects access time, independently from the number of Objects and the Coherence Cluster size - Data Objects Distribution by Affinity for in-memory data grouping - In-place Data Processing for parallel executionTo summarize, Oracle Coherence is indeed useful to improve your application performance, just not in the way we commonly think. It's not about the Speed itself, but about the overall Capacity with Extreme Load while keeping consistant Speed. In the future I will keep adding new blog entries around this topic, with some sample codes experiences sharing that I capture in the last few years. In the meanwhile if you want to know more how Oracle Coherence, I strongly suggest you to start with checking how our worldwide customers are using Oracle Coherence first, then you can start playing with the product through our tutorial.Have Fun !

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  • Why do we use the Pythagorean theorem in game physics?

    - by Starkers
    I've recently learned that we use Pythagorean theorem a lot in our physics calculations and I'm afraid I don't really get the point. Here's an example from a book to make sure an object doesn't travel faster than a MAXIMUM_VELOCITY constant in the horizontal plane: MAXIMUM_VELOCITY = <any number>; SQUARED_MAXIMUM_VELOCITY = MAXIMUM_VELOCITY * MAXIMUM_VELOCITY; function animate(){ var squared_horizontal_velocity = (x_velocity * x_velocity) + (z_velocity * z_velocity); if( squared_horizontal_velocity <= SQUARED_MAXIMUM_VELOCITY ){ scalar = squared_horizontal_velocity / SQUARED_MAXIMUM_VELOCITY; x_velocity = x_velocity / scalar; z_velocity = x_velocity / scalar; } } Let's try this with some numbers: An object is attempting to move 5 units in x and 5 units in z. It should only be able to move 5 units horizontally in total! MAXIMUM_VELOCITY = 5; SQUARED_MAXIMUM_VELOCITY = 5 * 5; SQUARED_MAXIMUM_VELOCITY = 25; function animate(){ var x_velocity = 5; var z_velocity = 5; var squared_horizontal_velocity = (x_velocity * x_velocity) + (z_velocity * z_velocity); var squared_horizontal_velocity = 5 * 5 + 5 * 5; var squared_horizontal_velocity = 25 + 25; var squared_horizontal_velocity = 50; // if( squared_horizontal_velocity <= SQUARED_MAXIMUM_VELOCITY ){ if( 50 <= 25 ){ scalar = squared_horizontal_velocity / SQUARED_MAXIMUM_VELOCITY; scalar = 50 / 25; scalar = 2.0; x_velocity = x_velocity / scalar; x_velocity = 5 / 2.0; x_velocity = 2.5; z_velocity = z_velocity / scalar; z_velocity = 5 / 2.0; z_velocity = 2.5; // new_horizontal_velocity = x_velocity + z_velocity // new_horizontal_velocity = 2.5 + 2.5 // new_horizontal_velocity = 5 } } Now this works well, but we can do the same thing without Pythagoras: MAXIMUM_VELOCITY = 5; function animate(){ var x_velocity = 5; var z_velocity = 5; var horizontal_velocity = x_velocity + z_velocity; var horizontal_velocity = 5 + 5; var horizontal_velocity = 10; // if( horizontal_velocity >= MAXIMUM_VELOCITY ){ if( 10 >= 5 ){ scalar = horizontal_velocity / MAXIMUM_VELOCITY; scalar = 10 / 5; scalar = 2.0; x_velocity = x_velocity / scalar; x_velocity = 5 / 2.0; x_velocity = 2.5; z_velocity = z_velocity / scalar; z_velocity = 5 / 2.0; z_velocity = 2.5; // new_horizontal_velocity = x_velocity + z_velocity // new_horizontal_velocity = 2.5 + 2.5 // new_horizontal_velocity = 5 } } Benefits of doing it without Pythagoras: Less lines Within those lines, it's easier to read what's going on ...and it takes less time to compute, as there are less multiplications Seems to me like computers and humans get a better deal without Pythagorean theorem! However, I'm sure I'm wrong as I've seen Pythagoras' theorem in a number of reputable places, so I'd like someone to explain me the benefit of using Pythagorean theorem to a maths newbie. Does this have anything to do with unit vectors? To me a unit vector is when we normalize a vector and turn it into a fraction. We do this by dividing the vector by a larger constant. I'm not sure what constant it is. The total size of the graph? Anyway, because it's a fraction, I take it, a unit vector is basically a graph that can fit inside a 3D grid with the x-axis running from -1 to 1, z-axis running from -1 to 1, and the y-axis running from -1 to 1. That's literally everything I know about unit vectors... not much :P And I fail to see their usefulness. Also, we're not really creating a unit vector in the above examples. Should I be determining the scalar like this: // a mathematical work-around of my own invention. There may be a cleverer way to do this! I've also made up my own terms such as 'divisive_scalar' so don't bother googling var divisive_scalar = (squared_horizontal_velocity / SQUARED_MAXIMUM_VELOCITY); var divisive_scalar = ( 50 / 25 ); var divisive_scalar = 2; var multiplicative_scalar = (divisive_scalar / (2*divisive_scalar)); var multiplicative_scalar = (2 / (2*2)); var multiplicative_scalar = (2 / 4); var multiplicative_scalar = 0.5; x_velocity = x_velocity * multiplicative_scalar x_velocity = 5 * 0.5 x_velocity = 2.5 Again, I can't see why this is better, but it's more "unit-vector-y" because the multiplicative_scalar is a unit_vector? As you can see, I use words such as "unit-vector-y" so I'm really not a maths whiz! Also aware that unit vectors might have nothing to do with Pythagorean theorem so ignore all of this if I'm barking up the wrong tree. I'm a very visual person (3D modeller and concept artist by trade!) and I find diagrams and graphs really, really helpful so as many as humanely possible please!

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  • Need additional help with binding multiple CommandParameters using MultiBinding

    - by Dave
    I need to have a command handler for a ToggleButton that can take multiple parameters, namely the IsChecked property of said ToggleButton, along with a constant value, which could be a string, byte, int... doesn't matter. I found this great question on SO and followed the answer's link and read up on MultiBinding and IMultiValueConverter. It went really smoothly until I had to write the MultiBinding, when I realized that I also need to pass a constant value and couldn't do something like <Binding Value="1" /> I then came across another similar question that Kent Boogaart answered, and then I started to think about ways that I could get around this. One possible way is to not use MVVM and simply add the Tag property to my ToggleButton, in which case my MultiBinding would look like this: <MultiBinding Converter="{StaticResource MyConverter}"> <MultiBinding.Bindings> <Binding Path="IsChecked" /> <Binding Path="Tag" /> </MultiBinding.Bindings> </MultiBinding> Kent had made a comment along the lines of, "if you're using MVVM you should be able to get around this issue". However, I'm not sure that's an option for me, even though I have adopted MVVM as my WPF pattern of necessity choice. The reason why I say this is that I have wayyyy more than one ToggleButton in the UserControl, and each of the ToggleButtons' Commands need to call the same function. But since they are ToggleButtons, I can't use the property bound to IsChecked in the ViewModel, because I don't know which one was last clicked. I suppose I could add another private property to keep track of this, but it seems a little silly. As far as the constant goes, I could probably get rid of this if I did the tracking idea, but not sure of any other way to get around it. Does anyone have good suggestions for me here? :) EDIT -- ok, so I need to update my bindings, which still don't work quite right: <ToggleButton Tag="1" Command="{Binding MyCommand}" Style="{StaticResource PassFailToggleButtonStyle}" HorizontalContentAlignment="Center" Background="Transparent" BorderBrush="Transparent" BorderThickness="0"> <ToggleButton.CommandParameter> <MultiBinding Converter="{StaticResource MyConverter}"> <MultiBinding.Bindings> <Binding Path="IsChecked" RelativeSource="{RelativeSource Mode=Self}" /> <Binding Path="Tag" RelativeSource="{RelativeSource Mode=Self}" /> </MultiBinding.Bindings> </MultiBinding> </ToggleButton.CommandParameter> </ToggleButton> IsChecked was working, but not Tag. I just realized that Tag is a string... duh. It's working now! The key was to use a RelativeSource of Self.

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