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  • solution for RPC_E_ATTEMPTED_MULTITHREAD error caused by SPRequestContext caching SPSites?

    - by kerray
    Hi, I'm developing a solution for SharePoint 2007, and I'm using SPSecurity.RunWithElevatedPrivileges a lot, passing in UserToken of the SystemAccount. After reading http://hristopavlov.wordpress.com/2009/01/19/understanding-sharepoint-sprequest/ I finally began to understand why I get these System.Runtime.InteropServices.COMException (0x80010102): Attempted to make calls on more than one thread in single threaded mode. (Exception from HRESULT: 0x80010102 (RPC_E_ATTEMPTED_MULTITHREAD)) errors, but there seems to be no solution - "known issue in the product" The article is more then a year old. I wasn't able to find anything more recent and helpful, but I was hoping maybe someone else has? My code goes like this SPSecurity.RunWithElevatedPrivileges(delegate() { using (SPSite elevatedSite = new SPSite(web.Site.ID, web.Site.SystemAccount.UserToken)) { using (SPWeb elevatedWeb = elevatedSite.OpenWeb(web.ID)) { // some operations on lists and items obtained through elevatedWeb } } } The errors come up wherever such an elevated code is used, and more often when there are more users who use these functionalities, so I guess perhaps the elevated SPSite is getting cached and reused. Is there any way to solve this? If my understanding is correct, how to make Sharepoint forget about the cached SPSites, and use a fresh one instead? Thanks

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  • Drawing custom graphics on the iPhone: CALayer vs. CGContext

    - by Henry Cooke
    Hi all, I have an application in which I'm doing some custom drawing, a bunch of lines on a gradient background, like so (ignore the text, they're just UILabels): At the moment, that's all done by starting a new CGContext, drawing stuff into it with CGContextDrawLinearGradient and CGContextStrokePath, then finally saving the resulting image with UIGraphicsGetImageFromCurrentImageContext. The positioning info is calculated while I'm laying out those labels, so it'd be a PITA (and duplication of effort) to calculate it all over again when the containing UIView is drawn with drawRect, so I'm drawing it ahead of time into a UIImage. All works fine, so far so good. However, I have a sneaking suspicion that it may be more efficient to use CALayers to do this drawing. My (cursory) understanding of the difference between the two approaches is that a CALayer is more like a bunch of instructions to draw stuff, and so takes up less memory until it's actually drawn onscreen, whereas drawing everything into a UIImage ahead of time means that you've got a sodding great bitmap kicking around in memory all the time, whether it's drawn or not. Is that a correct understanding? What is generally considered to be the best way of drawing custom images on the iPhone?

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  • Navigating between pages in a Facebook Platform iframe application

    - by Jimmy Cuadra
    I'm working on a Facebook Platform application that runs in iframe mode, and I'm having trouble understanding how to navigate between pages within the app. Let's say the first page that is loaded within the iframe at my canvas URL is one.html. Within that page, there is a link to two.html that just changes the source of the iframe and doesn't reload the Facebook chrome. When I do this, all the Facebook fb_sig_* query string parameters that Facebook passes to the original page aren't included, and so two.html has no awareness of the connection to Facebook and no ability to make API calls to generate the content for the page. One possible solution would be to manually extract all the Facebook parameters from one.html and append it to the link to two.html myself. This seems really ugly and I figured there had to be a cleaner way. For reference, my application is written in Perl and uses the WWW::Facebook::API module as a client library. I didn't see anything in it that I can use to easily reconstruct the Facebook parameters for use with links in iframe apps. Another possible solution would be to store all the Facebook parameters in a session on my server on the first page load, and just use the values in that session on subsequent page views. But what happens if the data I've stored no longer matches what Facebook would have sent if it were a completely new request (i.e. something in the user's Facebook session changed)? Is there something obvious I'm missing? What is the standard approach to navigating between pages within an iframe app? Facebook's documentation is atrocious and I haven't been able to find anything that clearly explains how this works. I also realize this wouldn't be an issue with an app using FBML instead of an iframe, but my understanding is that iframe apps are now encouraged over FBML apps, though again this seems ambiguous since so much of Facebook's documentation is outdated and contradictory.

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  • When should one use the following: Amazon EC2, Google App Engine, Microsoft Azure and Salesforce.com

    - by vicky21
    I am asking this in very general sense. Both from cloud provider and cloud consumer's perspective. Also the question is not for any specific kind of application (in fact the intention is to know which type of applications/domains can fit into which of the cloud slab -SaaS PaaS IaaS). My understanding so far is: IaaS: Raw Hardware (Processors, Networks, Storage). PaaS: OS, System Softwares, Development Framework, Virtual Machines. SaaS: Software Applications. It would be great if Stackoverflower's can share their understanding and experiences of cloud computing concept. EDIT: Ok, I will put it in more specific way - Amazon EC2: You don't have control over hardware layer. But you can take your choice of OS image, Dev Framework (.NET, J2EE, LAMP) and Application and put it on EC2 hardware. Can you deploy an applications built with Google App Engine or Azure on EC2? Google App Engine: You don't have control over hardware and OS and you get a specific Dev Framework to build your application. Can you take any existing Java or Python application and port it to GAE? Or vice versa, can applications that were built on GAE be taken out of GAE and ported to any Application Server like Websphere or Weblogic? Azure: You don't have control over hardware and OS and you get a specific Dev Framework to build your application. Can you take any existing .NET application and port it to Azure? Or vice versa, can applications that were built on Azure be taken out of Azure and ported to any Application Server like Biztalk?

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  • Getting started with character and text processing (encoding, regular expressions)

    - by TK
    I'd like to learn foundations of encodings, characters and text. Understanding these is important for dealing with a large set of text whether that are log files or text source for building algorithms for collective intelligence. My current knowledge is pretty basic: something like "As long as I use UTF-8, I'm okay." I don't say I need to learn about advanced topics right away. But I need to know: Bit and bytes level knowledge of encodings. Characters and alphabets not used in English. Multi-byte encodings. (I understand some Chinese and Japanese. And parsing them is important.) Regular expressions. Algorithm for text processing. Parsing natural languages. I also need an understanding of mathematics and corpus linguistics. The current and future web (semantic, intelligent, real-time web) needs processing, parsing and analyzing large text. I'm looking for some resources (maybe books?) that get me started with some of the bullets. (I find many helpful discussion on regular expressions here on Stack Overflow. So, you don't need to suggest resources on that topic.)

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  • how to better (inambiguaously) use the terms CAPTCHA and various types of interactions?

    - by vgv8
    I am working on survey of state-of-the-art and trends of spam prevention techniques. I observe that non-intrusive, transparent to visitor spam prevention techniques (like context-based filtering or honey traps) are frequently called non-captcha. Is it correct understanding of term CAPTCHA which is "type of challenge-response [ 2 ]test used in computing to ensure that the response is not generated by a compute" [ 1 ] and challenge-response does not seem to imply obligatory human involvement. So, which understanding (definition) of term and classification I'd better to stick with? How would I better call CAPTCHA without direct human interaction in order to avoid ambiguity and confusion of terms understnding? How would I better (succinctly and unambiguously) coin the term for captchas requiring human interaction but without typing into textbox? How would I better (succinctly and unambiguously) coin the terms to mark the difference between human interaction with images (playing, drag&dropping, rearranging, clicking with images) vs. just recognizing them (and then typing into a textbox the answer without interaction with images)? PS. The problem is that recognition of a wiggled word in an image or typing the answer to question is also interaction and when I start to use the terms "interaction", "interactive", "captcha", "protection", "non-captcha", "non-interactive", "static", "dynamic", "visible", "hidden" the terms overlap ambiguously with which another (especailly because the definitions or their actual practice of usage are vague or contradictive). [ 1 ] http://en.wikipedia.org/wiki/CAPTCHA

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  • USE case to Class Diagram - How do I?

    - by 01010011
    Hi, I would like your guidance on how to create classes and their relationships (generalization, association, aggregation and composition) accurately from my USE case diagram (please see below). I am trying to create this class diagram so I can use it to create a simple online PHP application that allows the user to register an account, login and logout, and store, search and retrieve data from a MySQL database. Are my classes correct? Or should I create more classes? And if so, what classes are missing? What relationships should I use when connecting the register, login, logout, search_database and add_to_database to the users? I'm new to design patterns and UML class diagrams but from my understanding, the association relationship relates one object with another object; the aggregation relationship is a special kind of association that allows "a part" to belong to more than one "whole" (e.g. a credit card and its PIN - the PIN class can also be used in a debit card class); and a composition relationship is a special form of aggregation that allows each part to belong to only one whole at a time. I feel like I have left out some classes or something because I just can't seem to find the relationships from my understanding of relationships. Any assistance will be really appreciated. Thanks in advance. USE CASE DIAGRAM CLASS DIAGRAM

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  • Explaining verity index and document search limits

    - by Ahmad
    As present, we currently have a CF8 standard edition server which have some limitations around verity indexing. According to Adobe Verity Server has the following document search limits (limits are for all collections registered to Verity Server): - 10,000 documents for ColdFusion Developer Edition - 125,000 documents for ColdFusion Standard Edition - 250,000 documents for ColdFusion Enterprise Edition We have now reached a stage where the server wide number of documents indexed exceed 125k. However, the largest verity collection consists of about 25k documents(and this is expected to grow). Only one collection is ever searched at a time. In my understanding, this means that I can still search an entire collection with no restrictions. Is this correct? Or does it mean that only documents that were indexed across all collection prior to reaching the limit are actually searchable? We are considering moving to CF9 standard as a solution to this and to use the Solr solution which has no restrictions. The coldfusionjedi highlights some differences between Verity and Solr. However, before we upgrade I am trying to gain a clearer understanding of this before we commit to an upgrade. Can someone provide me a clear explanation as to what this means and how it actually affects verity searching and indexing?

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  • Vertical-Align: A Full Explanation

    - by Livvy Jeffs
    I've been struggling with vertical alignments, a seemingly simple enough process that has a lot of idiosyncrasies throughout different languages and element types. I've done a lot of reading through stackexchange and can't seem to find a common thread of understanding. Here are the rules that I have been able to gather: 1) Vertical-align does not work in <\div>s, you have to set div {display: table-cell; vertical-align: middle} This seems like a big hassle, especially since table-cells override the height limitation even when overflow is set to hidden and expands to fit content, which means the vertical "center" is variable. I just read some source-code from Pinterest where button {vertical-align: middle}, but no other vertical-align commands seem to work. It seems as if button is by default aligned in the middle. Can someone provide a clear explanation for the vertical-align attribute? What html elements respond to vertical-align? Which html elements have default vertical-align attributes? Which html elements have non-overridable vertical-align attributes? And any clues as to understanding the idiosyncracies would help as well! Thanks in advance!

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  • How to print the address an ada access variable points to?

    - by georg
    I want to print the address of an access variable (pointer) for debugging purposes. type Node is private; type Node_Ptr is access Node; procedure foo(n: in out Node_Ptr) is package Address_Node is new System.Address_To_Access_Conversions(Node); use Address_Node; begin Put_Line("node at address " & System.Address_Image(To_Address(n))); end foo; Address_Image returns the string representation of an address. System.Address_To_Access_Conversions is a generic package to convert between addresses and access types (see ARM 13.7.2), defined as follows: generic type Object(<>) is limited private; package System.Address_To_Access_Conversions is -- [...] type Object_Pointer is access all Object; -- [...] function To_Address(Value : Object_Pointer) return Address; -- [...] end System.Address_To_Access_Conversions; gnat gives me the following errors for procedure foo defined above: expected type "System.Address_To_Access_Conversions.Object_Pointer" from instance at line... found type "Node_Ptr" defined at ... Object_Pointer ist definied as access all Object. From my understanding the type Object is Node, therefore Object_Ptr is access all Node. What is gnat complaining about? I guess my understanding of Ada generics is flawed and I am not using System.Address_To_Access_Conversions correctly. EDIT: I compiled my code with "gnatmake -gnatG" to see the generic instantiation: package address_node is subtype btree__clear__address_node__object__2 is btree__node; type btree__clear__address_node__object_pointer__2 is access all btree__clear__address_node__object__2; function to_address (value : btree__clear__address_node__object_pointer__2) return system__address; end address_node; btree__node is the mangled name of the type Node as defined above, so I really think the parameter type for to_address() is correct, yet gnat is complaining (see above).

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  • Controls added in the designer are null during Page_Load

    - by mwright
    All of the names below are generic and not the actual names used. I have a custom UserControl with a Panel that contains a a couple Labels, both .aspx controls. .aspx: <asp:Panel runat="server"> <asp:Label ID="label1" runat="server"> </asp:Label> </asp:Panel> <asp:Panel runat="server"> <asp:Label ID="label2" runat="server"> </asp:Label> </asp:Panel> Codebehind: private readonly Object object; protected void Page_Load(object sender, EventArgs e) { // These are the lines that are failing // label1 and label2 are null label1.Text = object.Value1; label2.Text = object.Value2; } public ObjectRow(Object objectToDisplay) { object = objectToDisplay; } On another page, in the code behind, I create a new instance of the custom user control. protected void Page_Load(object sender, EventArgs e) { CustomControl control = new CustomControl(object); } The user control takes the parameter and attempts to set the labels based off of the object passed in. The labels that it tries to assign the values to are however, null. Is this an ASP.net lifecycle issue that I'm not understanding? My understanding based on the Microsoft ASP.net lifecycle page was that page controls were available after the Page_Initialization. What is the proper way to do this? Is there a better way?

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  • Factory Method Pattern clarification

    - by nettguy
    My understanding of Factory Method Pattern is (Correct me if i am wrong) Factory Method Pattern "Factory Method allow the client to delegates the product creation (Instance Creation) to the subclass". There are two situation in which we can go for creating Factory Method pattern. (i) When the client is restricted to the product (Instance) creation. (ii) There are multiple products available.But a decision to be made which product instance need to be returned. If you want to create Abstract Method pattern You need to have abstract product Concrete Product Factory Method to return the appropriate product. Example : public enum ORMChoice { L2SQL, EFM, LS, Sonic } //Abstract Product public interface IProduct { void ProductTaken(); } //Concrete Product public class LinqtoSql : IProduct { public void ProductTaken() { Console.WriteLine("OR Mapping Taken:LinqtoSql"); } } //concrete product public class Subsonic : IProduct { public void ProductTaken() { Console.WriteLine("OR Mapping Taken:Subsonic"); } } //concrete product public class EntityFramework : IProduct { public void ProductTaken() { Console.WriteLine("OR Mapping Taken:EntityFramework"); } } //concrete product public class LightSpeed : IProduct { public void ProductTaken() { Console.WriteLine("OR Mapping Taken :LightSpeed"); } } public class Creator { //Factory Method public IProduct ReturnORTool(ORMChoice choice) { switch (choice) { case ORMChoice.EFM:return new EntityFramework(); break; case ORMChoice.L2SQL:return new LinqtoSql(); break; case ORMChoice.LS:return new LightSpeed(); break; case ORMChoice.Sonic:return new Subsonic(); break; default: return null; } } } **Client** Button_Click() { Creator c = new Creator(); IProduct p = c.ReturnORTool(ORMChoice.L2SQL); p.ProductTaken(); } Is my understanding of Factory Method is correct?

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  • Turing Machine & Modern Computer

    - by smwikipedia
    I heard a lot that modern computers are based on Turing machine. I'd like to share my understanding and hear your comments. I think the computer is a big general-purpose Turing machine. Each program we write is a small specific-purpose Turing machine. The classical Turing machine do its job based on the input and its current state inside and so do our programs. Let's take a running program (a process) as an example. We know that in the process's address space, there's areas for stack, heap, and code. A classical Turing machine doesn't have the ability to remember many things, so we borrow the concept of stack from the push-down automaton. The heap and stack areas contains the state of our specific-purpose Turing machine (our program). The code area represents the logic of this small Turing machine. And various I/O devices supply input to this Turing machine. The above is my naive understanding about the working paradigm of modern computer. I couln't wait to hear your comments. Thanks very much.

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  • mprotect - how aligning to multiple of pagesize works?

    - by user299988
    Hi, I am not understanding the 'aligning allocated memory' part from the mprotect usage. I am referring to the code example given on http://linux.die.net/man/2/mprotect char *p; char c; /* Allocate a buffer; it will have the default protection of PROT_READ|PROT_WRITE. */ p = malloc(1024+PAGESIZE-1); if (!p) { perror("Couldn't malloc(1024)"); exit(errno); } /* Align to a multiple of PAGESIZE, assumed to be a power of two */ p = (char *)(((int) p + PAGESIZE-1) & ~(PAGESIZE-1)); c = p[666]; /* Read; ok */ p[666] = 42; /* Write; ok */ /* Mark the buffer read-only. */ if (mprotect(p, 1024, PROT_READ)) { perror("Couldn't mprotect"); exit(errno); } For my understanding, I tried using a PAGESIZE of 16, and 0010 as address of p. I ended up getting 0001 as the result of (((int) p + PAGESIZE-1) & ~(PAGESIZE-1)). Could you please clarify how this whole 'alignment' works? Thanks,

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  • Re-tweets and replies with JTwitter

    - by Samuh
    I have not used Twitter enough to become familiar with its terminology or the way it works, so please help me in understanding the problem I have at hand. I am getting last 20 status updates posted by some Twitter user via RSS feed, the feed XML is parsed and the statuses are displayed in a ListView. Which means that I have the original tweet in a String variable(row of ListView). When I click a ListView item, I get the option of "Re-tweeting" and "post reply". As, I understand it, when re-tweeting I will have to just update my *status* as: RT @orig-poster <original tweet> and when posting a reply I will have to just update my status as: @orig-poster <my tweet> I skimmed through the JavaDocs of the Jwitter library(Twitter class) and found a setStatus(String) method. I dont think I will have to make use of retweet() or reply() functions of the Twitter class in JTwitter library. Is my understanding correct? Please correct me if I am wrong here or missing anything. Thanks!

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  • MongoDB - proper use of collections?

    - by zmg
    In Mongo my understanding is that you can have databases and collections. I'm working on a social-type app that will have blogs and comments (among other things) and had previously be using MySQL and pretty heavy partitioning in an attempt to limit possible concurrency issues. With MySQL I've stuffed all my user data into a _user database with several tables to further partition the data (blogs, pages, etc). My immediate reaction with Mongo would be to create a 'users' database with one collection per user. In this way user 'zach' blog entries would go into the 'zach' collection with associated comments and such becoming sub-objects in the same collection. Basically like dynamically creating one table per user in MySQL, but apparently without the complexity and limitations that might impose. Of course since I haven't really used Mongo before I'm having trouble gauging the (ahem..) quality of this idea and the potential problems it might cause down the road. I'd like user data to be treated a lot like a users directory in a *nix environment where user created/non-shared (mostly) gets put into one place (currently with MySQL that would be the appname_users as mentioned above). Most of the users data will be specific to the users page(s). Some of the user data which is queried across all site users (searchable user profiles) is currently kept in a separate database/table and I expect things like this could be put into a appname_system database and be broken up into collections and/or application specific databases (appname_profiles). Anyway, since the available documentation on this is currently a little thin and my experience is extremely limited I thought I might find a little guidance from someone with a better working understanding of the system. On the plus side I'd really already been attempting to treat MySQL as a schema-less document-store and doing this with Mongo seems much more intuitive/sane/rational so I'm really looking forward to getting started. Thanks, Zach

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  • Drawing half of a Bezier path in Raphael

    - by Fibericon
    Let's say I have a cubic Bezier path as follows (formatted for use with the Raphael path function): M55 246S55 247 55 248 Just an example. This was taken from my drawing application, where I use the cursor to draw a line when the user holds the mouse button down, kind of like a pencil or marker. I'm using jquery's mousemove event to draw the line between two points every time the user moves the mouse. There is another (the reference point) that is taken before the line is drawn, so that the Bezier curve can be created. Here's my question: is it possible to make Raphael only draw half of a given path? I'm aware of the getSubpath() function, but if my understanding of Bezier curves is correct, it would be rather difficult to calculate the second argument. The problem with the animate function is that it creates double lines (that is, it creates the curved line that I want, and the boxy line around it which should not be shown, possibly because the mouse is being moved faster than the animation can handle). Of course, if my approach itself is flawed in some way (or my understanding of the possible solutions), I'd like to hear it. Any help would be appreciated.

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  • How to create databinding over two xaml files?

    - by BionicGecko
    Hello, I am trying to come to a working understanding of how databinding works, but even after several tutorials I only have a basic understanding of how databinding works. Thus this question might seem fundamental to those more familiar with silverlight. Even if it is trivial, please point me to some tutorial that deals with this problem. All that I could find simply solved this via adding the data binding on a parent page.xaml (that i must not use in my case). For the sake of this example let us assume, that we have 5 files: starter.cs button1.xaml + codeBehind button2.xaml + codeBehind The two buttons are generated in code in the starter(.cs) file, and then added to some MapLayer button1 my_button1 = new button1(); button2 my_button1 = new button2(); someLayer.Children.Add(my_button1); someLayer.Children.Add(my_button2); My aim is to connect the two buttons, so that they always display the same "text" (i.e. my_button1.content==my_button2.content = true;). Thus when something changes my_button1.content this change should be propagated to the other button (two way binding). At the moment my button1.xaml looks like this: <Grid x:Name="LayoutRoot"> <Button x:Name="x_button1" Margin="0,0,0,0" Content="{Binding ElementName=x_button2, Path=Content}" ClickMode="Press" Click="button1_Click"/> </Grid> But everthing that i get out of that is a button with no content at all, it is just blank as the binding silently fails. How could I create the databinding in the context I described? Preferably in code and not XAML ;) Thanks in advance

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  • What's the difference between an option type and a nullable type?

    - by Peter Olson
    In F# mantra there seems to be a visceral avoidance of null, Nullable<T> and its ilk. In exchange, we are supposed to instead use option types. To be honest, I don't really see the difference. My understanding of the F# option type is that it allows you to specify a type which can contain any of its normal values, or None. For example, an Option<int> allows all of the values that an int can have, in addition to None. My understanding of the C# nullable types is that it allows you to specify a type which can contain any of its normal values, or null. For example, a Nullable<int> a.k.a int? allows all of the values that an int can have, in addition to null. What's the difference? Do some vocabulary replacement with Nullable and Option, null and None, and you basically have the same thing. What's all the fuss over null about?

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  • Volatile fields in C#

    - by Danny Chen
    From the specification 10.5.3 Volatile fields: The type of a volatile field must be one of the following: A reference-type. The type byte, sbyte, short, ushort, int, uint, char, float, bool, System.IntPtr, or System.UIntPtr. An enum-type having an enum base type of byte, sbyte, short, ushort, int, or uint. First I want to confirm my understanding is correct: I guess the above types can be volatile because they are stored as a 4-bytes unit in memory(for reference types because of its address), which guarantees the read/write operation is atomic. A double/long/etc type can't be volatile because they are not atomic reading/writing since they are more than 4 bytes in memory. Is my understanding correct? And the second, if the first guess is correct, why a user defined struct with only one int field in it(or something similar, 4 bytes is ok) can't be volatile? Theoretically it's atomic right? Or it's not allowed simply because that all user defined structs(which is possibly more than 4 bytes) are not allowed to volatile by design?

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  • Rails: Multi-Step New User Signup Form (FSM?)

    - by neezer
    I've read the "Create Multi-Step Wizard" in Advanced Rails Recipes. I've also read and re-read the documentation for the updated FSM I'm using called Workflow, and looked here and here. The Advanced Rails Recipe focuses on records (quizzes) that already exist, and doesn't cover creating new ones. The Workflow docs don't cover any code for controllers or views, so I've no idea what to do with all this model magic, and the last two links barely touch on implementation either. From the aforementioned resources, I have a good understanding of what a FSM in Rails is and how to play with it in the console or IRB, but I've got very little direction or understanding how to implement one into my Rails app. What I would like is this: a simple, multi-step user signup process. Step 1: User enters in their critical details (with validations). Step 2: User enters in their search criteria, for their profile (with validations). Step 3: User agrees to the Terms of Service (with validations). Step 4: User is greeted by a confirmation page, including a link that takes them to their newly created account. I'd also like full navigation between the steps and full capture (saves to the database) with each transition. Can someone please give me a clear implementation of something similar to this? I would LOVE an example app that includes a multi-step signup process where I can look at the code (FULL source code--models AND controllers and views) under the hood, but I've been unable to find anything like that. Any guidance would be appreciated! EDIT: Please help make this a Railscast! Ryan B. (a.k.a. Superman), if you're reading this, we need you! http://feedback.railscasts.com/forums/77-episode-suggestions/suggestions/35553-multi-step-forms-and-wizards

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  • Rails' page caching vs. HTTP reverse proxy caches

    - by John Topley
    I've been catching up with the Scaling Rails screencasts. In episode 11 which covers advanced HTTP caching (using reverse proxy caches such as Varnish and Squid etc.), they recommend only considering using a reverse proxy cache once you've already exhausted the possibilities of page, action and fragment caching within your Rails application (as well as memcached etc. but that's not relevant to this question). What I can't quite understand is how using an HTTP reverse proxy cache can provide a performance boost for an application that already uses page caching. To simplify matters, let's assume that I'm talking about a single host here. This is my understanding of how both techniques work (maybe I'm wrong): With page caching the Rails process is hit initially and then generates a static HTML file that is served directly by the Web server for subsequent requests, for as long as the cache for that request is valid. If the cache has expired then Rails is hit again and the static file is regenerated with the updated content ready for the next request With an HTTP reverse proxy cache the Rails process is hit when the proxy needs to determine whether the content is stale or not. This is done using various HTTP headers such as ETag, Last-Modified etc. If the content is fresh then Rails responds to the proxy with an HTTP 304 Not Modified and the proxy serves its cached content to the browser, or even better, responds with its own HTTP 304. If the content is stale then Rails serves the updated content to the proxy which caches it and then serves it to the browser If my understanding is correct, then doesn't page caching result in less hits to the Rails process? There isn't all that back and forth to determine if the content is stale, meaning better performance than reverse proxy caching. Why might you use both techniques in conjunction?

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  • Atomic swap in GNU C++

    - by Steve
    I want to verify that my understanding is correct. This kind of thing is tricky so I'm almost sure I am missing something. I have a program consisting of a real-time thread and a non-real-time thread. I want the non-RT thread to be able to swap a pointer to memory that is used by the RT thread. From the docs, my understanding is that this can be accomplished in g++ with: // global Data *rt_data; Data *swap_data(Data *new_data) { #ifdef __GNUC__ // Atomic pointer swap. Data *old_d = __sync_lock_test_and_set(&rt_data, new_data); #else // Non-atomic, cross your fingers. Data *old_d = rt_data; rt_data = new_data; #endif return old_d; } This is the only place in the program (other than initial setup) where rt_data is modified. When rt_data is used in the real-time context, it is copied to a local pointer. For old_d, later on when it is sure that the old memory is not used, it will be freed in the non-RT thread. Is this correct? Do I need volatile anywhere? Are there other synchronization primitives I should be calling? By the way I am doing this in C++, although I'm interested in whether the answer differs for C. Thanks ahead of time.

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  • Setting Class-Level Variable to Use Between Event Handlers

    - by lush
    I'm having a hard time understanding why the following code doesn't work. I'm sure it's something remedial that I'm missing or not understanding. I currently have a page that asks for user input. If, based on the input and logged in user, I find data from this page already in the database, I need to update the existing records rather than creating new ones, so I set a class-level bool to true. The problem is, when MyNextButton is clicked, PreviouslySubmitted is still false. So, I'm not sure how to make the value of this variable persist. Any advice is appreciated, thanks. public partial class MyForm : System.Web.UI.Page { private bool previouslySubmitted; protected void Page_Load(object sender, EventArgs e) { MyButton.Click += (o, i) => { q = from a in db.TableA where (a.SomeField == SomeValue) select a; if(q.Any()) { PreviouslySubmitted = true; //populate the form's fields with values from database for user to revise } } MyNextButton.Click += (o, i) => { if(PreviouslySubmitted) { //update database } else { //insert into database } }

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  • SQL Server full text query across multiple tables - why so slow?

    - by Mikey Cee
    Hi. I'm trying to understand the performance of an SQL Server 2008 full-text query I am constructing. The following query, using a full-text index, returns the correct results immediately: SELECT O.ID, O.Name FROM dbo.EventOccurrence O WHERE FREETEXT(O.Name, 'query') ie, all EventOccurrences with the word 'query' in their name. And the following query, using a full-text index from a different table, also returns straight away: SELECT V.ID, V.Name FROM dbo.Venue V WHERE FREETEXT(V.Name, 'query') ie. all Venues with the word 'query' in their name. But if I try to join the tables and do both full-text queries at once, it 12 seconds to return: SELECT O.ID, O.Name FROM dbo.EventOccurrence O INNER JOIN dbo.Event E ON O.EventID = E.ID INNER JOIN dbo.Venue V ON E.VenueID = V.ID WHERE FREETEXT(E.Name, 'search') OR FREETEXT(V.Name, 'search') Here is the execution plan: http://uploadpad.com/files/query.PNG From my reading, I didn't think it was even possible to make a free text query across multiple tables in this way, so I'm not sure I am understanding this correctly. Note that if I remove the WHERE clause from this last query then it returns all results within a second, so it's definitely the full-text that is causing the issue here. Can someone explain (i) why this is so slow and (ii) if this is even supported / if I am even understanding this correctly. Thanks in advance for your help.

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