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  • Controlling ASP.NET output cache memory usage

    - by Josh Einstein
    I would like to use output caching with WCF Data Services and although there's nothing specifically built in to support caching, there is an OnStartProcessingRequest method that allows me to hook in and set the cacheability of the request using normal ASP.NET mechanisms. But I am worried about the worker process getting recycled due to excessive memory consumption if large responses are cached. Is there a way to specify an upper limit for the ASP.NET output cache so that if this limit is exceeded, items in the cache will be discarded? I've seen the caching configuration settings but I get the impression from the documentation that this is for explicit caching via the Cache object since there is a separate outputCacheSettings which has no memory-related attributes. Here's a code snippet from Scott Hanselman's post that shows how I'm setting the cacheability of the request. protected override void OnStartProcessingRequest(ProcessRequestArgs args) { base.OnStartProcessingRequest(args); //Cache for a minute based on querystring HttpContext context = HttpContext.Current; HttpCachePolicy c = HttpContext.Current.Response.Cache; c.SetCacheability(HttpCacheability.ServerAndPrivate); c.SetExpires(HttpContext.Current.Timestamp.AddSeconds(60)); c.VaryByHeaders["Accept"] = true; c.VaryByHeaders["Accept-Charset"] = true; c.VaryByHeaders["Accept-Encoding"] = true; c.VaryByParams["*"] = true; }

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  • Anything speaking against the bitnami.org Ruby/Rails/Redmine Stack?

    - by Pekka
    I am looking to set up a Redmine server on a Windows virtual machine on my local workstation. (Background in this related question.) I have zero knowledge of Ruby nor Rails, and while Redmine may be the opportunity to dip into those platforms somewhat, my first goal is to get it running as quickly and easily as possible. For that, I am eyeing the Bitnami Redmine Package. It promises point-and-click install, and a self-contained environment with everything you need. Apart from the learning factor, are there any serious limitations this method implies? Any serious cutdowns in customizability? I will be wanting to customize the template right away, for example, and install plugins. The package looks o.k. to me but before I install it, I was curious to know whether anybody would advise against it and why. Edit: The first impression is great. From 0 to a working Redmine installation in twelve minutes! Wow.

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  • Registering custom webcontrol inside mvc view?

    - by kastermester
    I am in the middle of a project where I am migrating some code for a website from WebForms to MVC - unfortunatly there's not enough time to do it all at once, so I will have to do some... not so pretty solutions. I am though facing a problems with a custom control I have written that inherits from the standard GridView control namespace Controls { public class MyGridView : GridView { ... } } I have added to the web.config file as usual: <configuration> ... <system.web> ... <pages> ... <controls> ... <add tagPrefix="Xui" namespace="Controls"/> </controls> </pages> </system.web> </configuration> Then on the MVC View: <Xui:MyGridView ID="GridView1" runat="server" ...>...</Xui:MyGgridView> However I am getting a parser error stating that the control cannot be found. I am suspecting this has to do with the mix up of MVC and WebForms, however I am/was under the impression that such mixup should be possible, is there any kind of tweak for this? I realise this solution is far from ideal, however there's no time to "do the right thing". Thanks

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  • Why do the overloads of String.Format exist?

    - by GiddyUpHorsey
    I was using Reflector to look at the implementation of String.Format and had always been under the impression that the overloads of String.Format that took 1, 2 & 3 arguments were optimized versions of the method that takes an object array. However, what I found was that internally they create an object array and then call a method that takes an object array. 1 arg public static string Format(string format, object arg0) { if (format == null) { throw new ArgumentNullException("format"); } return Format(null, format, new object[] { arg0 }); } 2 args public static string Format(string format, object arg0, object arg1) { if (format == null) { throw new ArgumentNullException("format"); } return Format(null, format, new object[] { arg0, arg1 }); } 3 args public static string Format(string format, object arg0, object arg1, object arg2) { if (format == null) { throw new ArgumentNullException("format"); } return Format(null, format, new object[] { arg0, arg1, arg2 }); } Object array public static string Format(string format, params object[] args) { if ((format == null) || (args == null)) { throw new ArgumentNullException((format == null) ? "format" : "args"); } return Format(null, format, args); } Internally they all end up using the same code and so using the 1, 2 & 3 argument versions are no faster than the object array version. So my question is - why do they exist? When you use the object array version with a comma separated list of values, the compiler automatically converts the arguments into an object array because of the params/ParamArray keyword which is essentially what the 1, 2 & 3 versions do, so they seem redundant. Why did the BCL designers add these overloads?

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  • Telerik vs. Infragistics for Silverlight

    - by JeffN825
    Yes, this is certainly a duplicate question, but I wanted to get some fresh takes. My impression is that Telerik is a much more complete suite, but I'm really really turned off by the responsiveness of their controls. It just seems "clunky" in terms of responsiveness (I have a very fast computer and video card). Scrolling in a grid and transitions chunk, even in their latest demos where they claim to have good performance. I do like that their WPF suite matches their SL one in terms of API. Infragistics has fewer controls and less theming possibilities, but their controls are very responsive. Scrolling in a grid is fluid, as are their combo menus and all the other controls. I checked out ComponentOne and their controls seem analogous to Telerik's in terms of the points mentioned above but are a little less "pretty". Any thoughts from other users of these suites? Basically, what I'm looking for is a suite that will be highly performant and responsive, relatively customizable from a theming standpoint, and have enough functionality to develop a LOB SL application without having to use multiple suites to satisfy the majority of common requirements.

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  • What makes merging in DVCS easy?

    - by afriza
    I read at Joel on Software: With distributed version control, the distributed part is actually not the most interesting part. The interesting part is that these systems think in terms of changes, not in terms of versions. and at HgInit: When we have to merge, Subversion tries to look at both revisions—my modified code, and your modified code—and it tries to guess how to smash them together in one big unholy mess. It usually fails, producing pages and pages of “merge conflicts” that aren’t really conflicts, simply places where Subversion failed to figure out what we did. By contrast, while we were working separately in Mercurial, Mercurial was busy keeping a series of changesets. And so, when we want to merge our code together, Mercurial actually has a whole lot more information: it knows what each of us changed and can reapply those changes, rather than just looking at the final product and trying to guess how to put it together. By looking at the SVN's repository folder, I have the impression that Subversion is maintaining each revisions as changeset. And from what I know, Hg is using both changeset and snapshot while Git is purely using snapshot to store the data. If my assumption is correct, then there must be other ways that make merging in DVCS easy. What are those?

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  • Why can't I initialize a class through a setter?

    - by Rob emenaker
    If I have a custom class called Tires: #import <Foundation/Foundation.h> @interface Tires : NSObject { @private NSString *brand; int size; } @property (nonatomic,copy) NSString *brand; @property int size; - (id)init; - (void)dealloc; @end ============================================= #import "Tires.h" @implementation Tires @synthesize brand, size; - (id)init { if (self = [super init]) { [self setBrand:[[NSString alloc] initWithString:@""]]; [self setSize:0]; } return self; } - (void)dealloc { [super dealloc]; [brand release]; } @end And I synthesize a setter and getter in my View Controller: #import <UIKit/UIKit.h> #import "Tires.h" @interface testViewController : UIViewController { Tires *frontLeft, *frontRight, *backleft, *backRight; } @property (nonatomic,copy) Tires *frontLeft, *frontRight, *backleft, *backRight; @end ==================================== #import "testViewController.h" @implementation testViewController @synthesize frontLeft, frontRight, backleft, backRight; - (void)viewDidLoad { [super viewDidLoad]; [self setFrontLeft:[[Tires alloc] init]]; } - (void)dealloc { [super dealloc]; } @end It dies after [self setFrontLeft:[[Tires alloc] init]] comes back. It compiles just fine and when I run the debugger it actually gets all the way through the init method on Tires, but once it comes back it just dies and the view never appears. However if I change the viewDidLoad method to: - (void)viewDidLoad { [super viewDidLoad]; frontLeft = [[Tires alloc] init]; } It works just fine. I could just ditch the setter and access the frontLeft variable directly, but I was under the impression I should use setters and getters as much as possible and logically it seems like the setFrontLeft method should work. This brings up an additional question that my coworkers keep asking in these regards (we are all new to Objective-C); why use a setter and getter at all if you are in the same class as those setters and getters.

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  • How to delete duplicate vectors within a multidimensional vector?

    - by David
    I have a vector of vectors: vector< vector<int> > BigVec; It contains an arbitrary number of vectors, each of an arbitrary size. I want to delete not duplicate elements of each vector, but any vectors that are the exact same as another. I don't need to preserve the order of the vectors so I can sort etc.. It should be a really simple problem to solve but I'm new to this, my (not-working) best effort: for (int i = 0; i < BigVec.size(); i++) { for (int j = 1; j < BigVec.size() ; j++ ) { if (BigVec[i][0] == BigVec [j][i]); { BigVec.erase(BigVec.begin() + j); i = 0; // because i get the impression deleting a j = 1; // vector messes up a simple iteration through } } } I think there might be a solution using Unique(), but I can't get that to work either.

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  • Positioning problem in VIsta when Aero Theme is enabled

    - by Adeel Rehman
    Hi, I have a Windows form which has tab pages. On a Tab Page, I have a Combo Box. When I click the combobox a drop down opens up just below the combo box to give the impression of a drop down. The drop down is a windows form and this is how I set its position Popup.Location = control.PointToScreen(parentcontrol.PointToClient(new System.Drawing.Point(0, control.Height))); Popup = drop down that opens below the combo box (Windows Form) control = my combo box (Combo Box) parentcontrol = the windows form on which the control is present (Parent Form) Problem:- The X coordinate is not plotted correctly on the screen with Aero theme enabled. This works perfectly fine on XP (with some variance in y due to tablelayout panel i assume). But when i use the same code on Vista with Aero theme enabled the x-cordinate wanders away about 20-30 pixels. If I Turn Aero theme off on Vista, it works fine. I have found the X and Y coordiantes calculated in both cases are the same. But the way Vista draws these coordinates on the screen (when aero theme is enabled) is different. Is there any solution to this problem? Thanks, Adeel Rehman.

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  • Perform Grouping of Resultsets in Code, not on Database Level

    - by NinjaBomb
    Stackoverflowers, I have a resultset from a SQL query in the form of: Category Column2 Column3 A 2 3.50 A 3 2 B 3 2 B 1 5 ... I need to group the resultset based on the Category column and sum the values for Column2 and Column3. I have to do it in code because I cannot perform the grouping in the SQL query that gets the data due to the complexity of the query (long story). This grouped data will then be displayed in a table. I have it working for specific set of values in the Category column, but I would like a solution that would handle any possible values that appear in the Category column. I know there has to be a straightforward, efficient way to do it but I cannot wrap my head around it right now. How would you accomplish it? EDIT I have attempted to group the result in SQL using the exact same grouping query suggested by Thomas Levesque and both times our entire RDBMS crashed trying to process the query. I was under the impression that Linq was not available until .NET 3.5. This is a .NET 2.0 web application so I did not think it was an option. Am I wrong in thinking that? EDIT Starting a bounty because I believe this would be a good technique to have in the toolbox to use no matter where the different resultsets are coming from. I believe knowing the most concise way to group any 2 somewhat similar sets of data in code (without .NET LINQ) would be beneficial to more people than just me.

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  • Core Data - How to check if a managed object's properties have been deallocated?

    - by georryan
    I've created a program that uses core data and it works beautifully. I've since attempted to move all my core data methods calls and fetch routines into a class that is self contained. My main program then instantiates that class and makes some basic method calls into that class, and the class then does all the core data stuff behind the scenes. What I'm running into, is that sometimes I'll find that when I grab a managed object from the context, I'll have a valid object, but its properties have been deallocated, and I'll cause a crash. I've played with the zombies and looked for memory leaks, and what I have gathered is it seems that the run loop is probably responsible for deallocating the memory, but I'm not sure. Is there a way to determine if that memory has been deallocated and force the core data to get it back if I need to access it? My managedObjectContext never gets deallocated, and the fetchedResultsController never does, either. I thought maybe I needed to use the [managedObjectContext refreshObject:mergeData:] method, or the [managedObjectContext setRetainsRegisteredObjects:] method. Although, I'm under the impression that last one may not be the best bet since it will be more memory intensive (from what I understand). These errors only popped up when I moved the core data calls into another class file, and they are random when they show up. Any insight would be appreciated. -Ryan

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  • Extension Methods and Application Code

    - by Mystagogue
    I have seen plenty of online guidelines for authoring extension methods, usually along these lines: 1) Avoid authoring extension methods when practical - prefer other approaches first (e.g. regular static methods). 2) Don't author extension methods to extend code you own or currently develop. Instead, author them to extend 3rd party or BCL code. But I have the impression that a couple more guidelines are either implied or advisable. What does the community think of these two additional guidelines: A) Prefer to author extension methods to contain generic functionality rather than application-specific logic. (This seems to follow from guideline #2 above) B) An extension method should be sizeable enough to justify itself (preferably at least 5 lines of code in length). Item (B) is intended to discourage a develoer from writing dozens of extension methods (totalling X lines of code) to refactor or replace what originally was already about X lines of inline code. Perhaps item (B) is badly qualified, or even misinformed about how a one line extension method is actually powerful and justified. I'm curious to know. But if item (B) is somehow dismissed by the community, I must admist I'm still particularly interested in feedback on guideline (A).

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  • does anyone know of good delphi docking components?

    - by X-Ray
    we'd like to add movable panels to an application. presently we've used DevExpress docking library but have found them to be disappointingly quirky & difficult to work with. it also has some limitations that aren't so great. auto-hide, pinning, and moving of pages by drag-and-drop are all features we'd like to use. the built-in delphi docking doesn't seem to be full-featured enough to do the things we need (also see sample below). perhaps i should dig deeper into delphi's docking abilities...my initial impression is that they seem very toolbar-oriented rather than something i can drop a frame into. i'm not experienced at docking topics. my only experience has been with the DevExpress docking library where i needed to programmatically create & dock panels. is it my imagination or are DevExpress's products unduly difficult to use/learn? the DevExpress Ribbon Bar component compared to the d2009 Ribbon Bar was certainly a useful experience. i will migrate to the d2009 Ribbon Bar as soon as convenient to do so. it was refreshingly straight-forward to learn and use. a sharp contrast compared to the DevExpress equivalent. if it takes 4x as longer to make it using the DevExpress equivalent, it's time to change direction. what would you suggest in regard to the docking library? thank you for your suggestions/comments!

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  • Valueurl Binding On Large Arrays Causes Sluggish User Interface

    - by Hooligancat
    I have a large data set (some 3500 objects) that returns from a remote server via HTTP. Currently the data is being presented in an NSCollectionView. One aspect of the data is a path pack to the server for a small image that represents the data (think thumbnail for simplicity). Bindings works fantastically for the data that is already returned, and binding the image via a valueurl binding is easy to do. However, the user interface is very sluggish when scrolling through the data set - which makes me think that the NSCollectionView is retrieving all the image data instead of just the image data used to display the currently viewable images. I was under the impression that Cocoa controls were smart enough to only retrieve data for the information that is actually being output to the user interface through lazy loading. This certainly seems to be the case with NSTableView - but I could be misguided on this thought. Should valueurl binding act lazily and, moreover, should it act lazily in an NSCollectionView? I could create a caching mechanism (in fact I already have such a thing in place for another application - see my post here if you are interested http://stackoverflow.com/questions/1740209/populating-nsimage-with-data-from-an-asynchronous-nsurlconnection) but I really don't want to go this route if I don't have to for this specific implementation as the user could potentially change data sets often and may only want small sub-sets of the data. Any suggested approaches? Thanks!

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  • Rhino ServiceBus: Sagas with multiple messages

    - by illdev
    I have a saga that can handle multiple messages like so: public class OrderSaga : ISaga<Order> , InitiatedBy<StartOrderSaga> , Orchestrates<CancelOrder> , Orchestrates<PaymentForOrderReceived> , Orchestrates<CheckOrderWasPaid> , Orchestrates<OrderAbandoned> , Orchestrates<CheckOrderHasBeenShipped> , Orchestrates<OrderShipped> , Orchestrates<CheckOrderHasDelayDuringShipment> , Orchestrates<OrderArrivedAtDestination> , Orchestrates<OrderCompleted> {...} but only Orchestrates<CancelOrder seems to be picked up. So I suppose (I did not find the line, but am under a strong impression this is so), that only the first Orchestrates is registered. Probably this is by design. From what I imagined a saga to be, it seems only logical that it receives many different messages, but I might be wrong. I might be wrong with my whole assumption, too :) How am I supposed to handle this? Are Sagas supposed to only handle one (in my case) a ChangeStateMessage<State or should I wire the other ConsumerOfs/Orchestrates by hand?

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  • How to detect when video is buffering?

    - by Leon
    Hi guys, my question today deals with Flash AS3 video buffering. (Streaming or Progressive) I want to be able to detect when the video is being buffered, so I can display some sort of animation letting the user know to wait just a little longer. Currently my video will start up, hold on frame 1 for 3-4 secs then play. Kinda giving the impression that the video is paused or broken :( Update Thanks to iandisme I believe I'm faced in the right direction now. NetStatusEvent from livedocs. It seems to me that the key status to be working in is "NetStream.Buffer.Empty" so I added some code in there to see if this would trigger my animation or a trace statement. No luck yet, however when the Buffer is full it will trigger my code :/ Maybe my video is always somewhere between Buffer.Empty and Buffer.Full that's why it won't trigger any code when I test case for Buffer.Empty? Current Code public function netStatusHandler(event:NetStatusEvent):void { // handles net status events switch (event.info.code) { case "NetStream.Buffer.Empty": trace("¤¤¤ Buffering!"); //<- never traces addChild(bufferLoop); //<- doesn't execute break; case "NetStream.Buffer.Full": trace("¤¤¤ FULL!"); //<- trace works here removeChild(bufferLoop); //<- so does any other code break; case "NetStream.Buffer.Flush": trace("¤¤¤ FLUSH!"); //Not sure if this is important break } }

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  • Trouble using the ref keyword. Very newbie question!

    - by Sergio Tapia
    Here's my class: public class UserInformation { public string Username { get; set; } public string ComputerName { get; set; } public string Workgroup { get; set; } public string OperatingSystem { get; set; } public string Processor { get; set; } public string RAM { get; set; } public string IPAddress { get; set; } public UserInformation GetUserInformation() { var CompleteInformation = new UserInformation(); GetPersonalDetails(ref CompleteInformation); GetMachineDetails(ref CompleteInformation); return CompleteInformation; } private void GetPersonalDetails(ref UserInformation CompleteInformation) { } private void GetMachineDetails(ref UserInformation CompleteInformation) { } } I'm under the impression that the ref keyword tells the computer to use the same variable and not create a new one. Am I using it correctly? Do I have to use ref on both the calling code line and the actual method implementation?

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  • Anything speaking against the bitnami.org Ruby/Rails/Redmine Stack?

    - by Pekka
    I am looking to set up a Redmine server on a Windows virtual machine on my local workstation. (Background in this related question.) I have zero knowledge of Ruby nor Rails, and while Redmine may be the opportunity to dip into those platforms somewhat, my first goal is to get it running as quickly and easily as possible. For that, I am eyeing the Bitnami Redmine Package. It promises point-and-click install, and a self-contained environment with everything you need. Apart from the learning factor, are there any serious limitations this method implies? Any serious cutdowns in customizability? I will be wanting to customize the template right away, for example, and install plugins. The package looks o.k. to me but before I install it, I was curious to know whether anybody would advise against it and why. Edit: The first impression is great. From 0 to a working Redmine installation in twelve minutes! Wow.

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  • Changing save directory

    - by Nathan
    Disregard my previous pre-edit post. Rethought what I needed to do. This is what I'm currently doing: https://developer.mozilla.org/en/XPCOM_Interface_Reference/nsIScriptableIO downloadFile: function(httpLoc) { try { //new obj_URI object var obj_URI = Cc["@mozilla.org/network/io-service;1"].getService(Ci.nsIIOService). newURI(httpLoc, null, null); //new file object //set file with path obj_TargetFile.initWithPath("C:\\javascript\\cache\\test.pdf"); //if file doesn't exist, create if(!obj_TargetFile.exists()) { obj_TargetFile.create(0x00,0644); } //new persitence object var obj_Persist = Cc["@mozilla.org/embedding/browser/nsWebBrowserPersist;1"]. createInstance(Ci.nsIWebBrowserPersist); // with persist flags if desired const nsIWBP = Ci.nsIWebBrowserPersist; const flags = nsIWBP.PERSIST_FLAGS_REPLACE_EXISTING_FILES; obj_Persist.persistFlags = flags | nsIWBP.PERSIST_FLAGS_FROM_CACHE; //save file to target obj_Persist.saveURI(obj_URI,null,null,null,null,obj_TargetFile); return true; } catch (e) { alert(e); } },//end downloadFile As you can see the directory is hardcoded in there, I want to save the pdf file open in the active tab to a relative temporary directory, or anywhere that's out of the way enough that the user won't stumble along and delete it. I'm going to try that using File I/O, I was under the impression that what I was looking for was in scriptable file I/O and thus disabled.

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  • Intercepting hyperlinks in an embedded Word document

    - by Ryan
    Hello, I'm working on an app which uses embedded Word documents. We have a feature which allows them to insert a small clickable image into the doc - when the user clicks on it, we want the app to open another window based on some data specified by the user when the image was added. What the application does now is: When the image is inserted, the app creates a hyperlink for it and the data is used as the link destination The user ctrl+clicks on the image and the Word document the WindowSelectionChange event The app handles the WindowSelectionChange event and goes to open the specified window This approach worked fine with previous versions, when we had the 11.0 / Word 2003 interop dll's. We upgraded to 12.0/Word 2007 for the upcoming release, and in many cases the event is not firing when I click on the image - sometimes it does, sometimes it doesn't, and I'm descending into the cargo-cult world trying to figure out why - sometimes saving and re-opening the document works, sometimes killing the Word process and starting a new one fixes (or breaks) the feature. My guess is there's something going wrong with the WinSelChg event, but I'm not sure what. The usual process we have for applying the event handler is: try //remove the old one if any { ((Document)myAXFramerControl.ActiveDocument).Application.WindowSelectionChange -= new ApplicationEvents4_WindowSelectionChangeEventHandler(WSC_eventhandlerfunction); } catch{} ((Document)myAXFramerControl.ActiveDocument).Application.WindowSelectionChange += new ApplicationEvents4_WindowSelectionChangeEventHandler(WSC_eventhandlerfunction); Sometimes one or both of these will throw exceptions - usually a NullReferenceException when removing the handler. Adding the handler sometimes throws the "com object that has been separated from its underlying rcw cannot be used" exception, which I don't understand at all - my impression was that this only occurs when you, say, store a reference to the Word application or document and try to use it later. As it stands the WSC event handler is frequently never run; while I'm happy to fiddle with the app until it works once I can't really expect the same of the users who have been happily using this feature for a while now. Any ideas?

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  • Using Hidden Markov Model for designing AI mp3 player

    - by Casper Slynge
    Hey guys. Im working on an assignment, where I want to design an AI for a mp3 player. The AI must be trained and designed with the use of a HMM method. The mp3 player shall have the functionality of adapting to its user, by analyzing incoming biological sensor data, and from this data the mp3 player will choose a genre for the next song. Given in the assignment is 14 samples of data: One sample consist of Heart Rate, Respiration, Skin Conductivity, Activity and finally the output genre. Below is the 14 samples of data, just for you to get an impression of what im talking about. Sample HR RSP SC Activity Genre S1 Medium Low High Low Rock S2 High Low Medium High Rock S3 High High Medium Low Classic S4 High Medium Low Medium Classic S5 Medium Medium Low Low Classic S6 Medium Low High High Rock S7 Medium High Medium Low Classic S8 High Medium High Low Rock S9 High High Low Low Classic S10 Medium Medium Medium Low Classic S11 Medium Medium High High Rock S12 Low Medium Medium High Classic S13 Medium High Low Low Classic S14 High Low Medium High Rock My time of work regarding HMM is quite low, so my question to you is if I got the right angle on the assignment. I have three different states for each sensor: Low, Medium, High. Two observations/output symbols: Rock, Classic In my own opinion I see my start probabilities as the weightened factors for either a Low, Medium or High state in the Heart Rate. So the ideal solution for the AI is that it will learn these 14 sets of samples. And when a users sensor input is received, the AI will compare the combination of states for all four sensors, with the already memorized samples. If there exist a matching combination, the AI will choose the genre, and if not it will choose a genre according to the weightened transition probabilities, while simultaniously updating the transition probabilities with the new data. Is this a right approach to take, or am I missing something ? Is there another way to determine the output probability (read about Maximum likelihood estimation by EM, but dont understand the concept)? Best regards, Casper

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  • Why linking doesn't work in my Xtext-based DSL?

    - by reprogrammer
    The following is the Xtext grammar for my DSL. Model: variableTypes=VariableTypes predicateTypes=PredicateTypes variableDeclarations= VariableDeclarations rules=Rules; VariableType: name=ID; VariableTypes: 'var types' (variableTypes+=VariableType)+; PredicateTypes: 'predicate types' (predicateTypes+=PredicateType)+; PredicateType: name=ID '(' (variableTypes+=[VariableType|ID])+ ')'; VariableDeclarations: 'vars' (variableDeclarations+=VariableDeclaration)+; VariableDeclaration: name=ID ':' type=[VariableType|ID]; Rules: 'rules' (rules+=Rule)+; Rule: head=Head ':-' body=Body; Head: predicate=Predicate; Body: (predicates+=Predicate)+; Predicate: predicateType=[PredicateType|ID] '(' (terms+=Term)+ ')'; Term: variable=Variable; Variable: variableDeclaration=[VariableDeclaration|ID]; terminal WS: (' ' | '\t' | '\r' | '\n' | ',')+; And, the following is a program in the above DSL. var types Node predicate types Edge(Node, Node) Path(Node, Node) vars x : Node y : Node z : Node rules Path(x, y) :- Edge(x, y) Path(x, y) :- Path(x, z) Path(z, y) When I used the generated Switch class to traverse the EMF object model corresponding to the above program, I realized that the nodes are not linked together properly. For example, the getPredicateType() method on a Predicate node returns null. Having read the Xtext user's guide, my impression is that the Xtext default linking semantics should work for my DSL. But, for some reason, the AST nodes of my DSL don't get linked together properly. Can anyone help me in diagnosing this problem?

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  • Can parser combinators be made efficient?

    - by Jon Harrop
    Around 6 years ago, I benchmarked my own parser combinators in OCaml and found that they were ~5× slower than the parser generators on offer at the time. I recently revisited this subject and benchmarked Haskell's Parsec vs a simple hand-rolled precedence climbing parser written in F# and was surprised to find the F# to be 25× faster than the Haskell. Here's the Haskell code I used to read a large mathematical expression from file, parse and evaluate it: import Control.Applicative import Text.Parsec hiding ((<|>)) expr = chainl1 term ((+) <$ char '+' <|> (-) <$ char '-') term = chainl1 fact ((*) <$ char '*' <|> div <$ char '/') fact = read <$> many1 digit <|> char '(' *> expr <* char ')' eval :: String -> Int eval = either (error . show) id . parse expr "" . filter (/= ' ') main :: IO () main = do file <- readFile "expr" putStr $ show $ eval file putStr "\n" and here's my self-contained precedence climbing parser in F#: let rec (|Expr|) (P(f, xs)) = Expr(loop (' ', f, xs)) and loop = function | ' ' as oop, f, ('+' | '-' as op)::P(g, xs) | (' ' | '+' | '-' as oop), f, ('*' | '/' as op)::P(g, xs) -> let h, xs = loop (op, g, xs) let op = match op with | '+' -> (+) | '-' -> (-) | '*' -> (*) | '/' -> (/) loop (oop, op f h, xs) | _, f, xs -> f, xs and (|P|) = function | '('::Expr(f, ')'::xs) -> P(f, xs) | c::xs when '0' <= c && c <= '9' -> P(int(string c), xs) My impression is that even state-of-the-art parser combinators waste a lot of time back tracking. Is that correct? If so, is it possible to write parser combinators that generate state machines to obtain competitive performance or is it necessary to use code generation?

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  • Implementing Model-level caching

    - by Byron
    I was posting some comments in a related question about MVC caching and some questions about actual implementation came up. How does one implement a Model-level cache that works transparently without the developer needing to manually cache, yet still remains efficient? I would keep my caching responsibilities firmly within the model. It is none of the controller's or view's business where the model is getting data. All they care about is that when data is requested, data is provided - this is how the MVC paradigm is supposed to work. (Source: Post by Jarrod) The reason I am skeptical is because caching should usually not be done unless there is a real need, and shouldn't be done for things like search results. So somehow the Model itself has to know whether or not the SELECT statement being issued to it worthy of being cached. Wouldn't the Model have to be astronomically smart, and/or store statistics of what is being most often queried over a long period of time in order to accurately make a decision? And wouldn't the overhead of all this make the caching useless anyway? Also, how would you uniquely identify a query from another query (or more accurately, a resultset from another resultset)? What about if you're using prepared statements, with only the parameters changing according to user input? Another poster said this: I would suggest using the md5 hash of your query combined with a serialized version of your input arguments. This would require twice the number of serialization options. I was under the impression that serialization was quite expensive, and for large inputs this might be even worse than just re-querying. And is the minuscule chance of collision worth worrying about? Conceptually, caching in the Model seems like a good idea to me, but it seems in practicality the developer should have direct control over caching and write it into the controller. Thoughts/ideas? Edit: I'm using PHP and MySQL if that helps to narrow your focus.

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  • E-Commerce Security: Only Credit Card Fields Encrypted?!

    - by bizarreunprofessionalanddangerous
    I'd like your opinions on how a major bricks-and-mortar company is running the security for its shopping Web site. After a recent update, when you are logged into your shopping account, the session is now not secured. No 'https', no browser 'lock'. All the personal contact info, shopping history -- and if I'm not mistaken submit and change password -- are being sent unencrypted. There is a small frame around the credit card fields that is https. There's a little notice: "Our website is secure. Our website uses frames and because of this the secure icon will not appear in your browser" On top of this the most prominent login fields for the site are broken, and haven't gotten fixed for a week or longer (giving the distinct impression they have no clue what's going on and can't be trusted with anything). Now is it just me -- or is this simply incomprehensible for a billion dollar company, significant shopping site, in the year 2010. No lock. "We use frames" (maybe they forget "Best viewed in IE4"). Customers complaining, as you can see from their FAQ "explaining" why you aren't seeing https. I'm getting nowhere trying to convince customer service that they REALLY need to do something about this, and am about to head for the CEO. But I just want to make sure this is as BIZARRE and unprofessional and dangerous a situation as I think it is. (I'm trying to visualize what their Web technical team consists of. I'm getting A) some customer service reps who were given a 3 hour training course on Web site maintenance, B) a 14 year old boy in his bedroom masquerading as a major technical services company, C) a guy in a hut in a jungle with an e-commerce book from 1996.)

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