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"Work stealing" vs. "Work shrugging"?

- by John

Why is it that I can find lots of information on "work stealing" and nothing on "work shrugging" as a dynamic load-balancing strategy? By "work-shrugging" I mean busy processors pushing excessive work towards less loaded neighbours rather than idle processors pulling work from busy neighbours ("work-stealing"). I think the general scalability should be the same for both strategies. However I believe that it is much more efficient for busy processors to wake idle processors if and when there is definitely work for them to do than having idle processors spinning or waking periodically to speculatively poll all neighbours for possible work. Anyway a quick google didn't show up anything under the heading of "Work Shrugging" or similar so any pointers to prior-art and the jargon for this strategy would be welcome. Clarification/Confession In more detail:- By "Work Shrugging" I actually envisage the work submitting processor (which may or may not be the target processor) being responsible for looking around the immediate locality of the preferred target processor (based on data/code locality) to decide if a near neighbour should be given the new work instead because they don't have as much work to do. I am talking about an atomic read of the immediate (typically 2 to 4) neighbours' estimated q length here. I do not think this is any more coupling than implied by the thieves polling & stealing from their neighbours - just much less often - or rather - only when it makes economic sense to do so. (I am assuming "lock-free, almost wait-free" queue structures in both strategies). Thanks.

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NSPredicate as a constraint solver?

- by Felixyz

I'm working on a project which includes some slightly more complex dynamic layout of interface elements than what I'm used to. I always feel stupid writing complex code that checks if so-and-so is close to such-and-such and in that case move it x% in some direction, etc. That's just not how programming should be done. Programming should be as declarative as possible! Precisely because what I'm going to do is fairly simple, I thought it would be a good opportunity to try something new, and I thought of using NSPredicate as a simple constraints solver. I've only used NSPredicate for very simple tasks so far, but I know that it capable of much more. Are there any ideas, experiences, examples, warnings, insights that could be useful here? I'll give a very simple example so there will be something concrete to answer. How could I use NSPredicate to solve the following constraints: viewB.xmid = (viewB.leftEdge + viewB.width) / 2 viewB.xmid = max(300, viewA.rightEdge + 20 + viewB.width/2) ("viewB should be horizontally centered on coordinate 300, unless its left edge gets within 20 pixels of viewB's right edge, in which case viewA's left edge should stay fixed at 20 pixels to the right of viewB's right edge and viewA's horizontal center get pushed to the right.") viewA.rightEdge and viewB.width can vary, and those are the 'input variables'. EDIT: Any solution would probably have to use the NSExpression method -(id)expressionValueWithObject:(id)object context:(NSMutableDictionary *)context. This answer is relevant.

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Android Multiple Handlers Design Question

- by Soumya Simanta

This question is related to an existing question I asked. I though I'll ask a new question instead of replying back to the other question. Cannot "comment" on my previous question because of a word limit. Marc wrote - I've more than one Handlers in an Activity." Why? If you do not want a complicated handleMessage() method, then use post() (on Handler or View) to break the logic up into individual Runnables. Multiple Handlers makes me nervous. I'm new to Android. Is having multiple handlers in a single activity a bad design ? I'm new to Android. My question is - is having multiple handlers in a single activity a bad design ? Here is the sketch of my current implementation. I've a mapActivity that creates a data thread (a UDP socket that listens for data). My first handler is responsible for sending data from the data thread to the activity. On the map I've a bunch of "dynamic" markers that are refreshed frequently. Some of these markers are video markers i.e., if the user clicks a video marker, I add a ViewView that extends a android.opengl.GLSurfaceView to my map activity and display video on this new vide. I use my second handler to send information about the marker that the user tapped on ItemizedOverlay onTap(int index) method. The user can close the video view by tapping on the video view. I use my third handler for this. I would appreciate if people can tell me what's wrong with this approach and suggest better ways to implement this. Thanks.

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Microsoft JScript runtime error: '(function name)' is undefined

- by Velika2

Microsoft JScript runtime error: 'txtGivenName_OnFocus' is undefined After adding what I thought was unrelated javascript code to a web page, I am suddenly getting errors that suggest that the browser cannot locate a javascript function that, to me, appears plain as day in design mode. I'm thinking that this is a load sequence order problem of some sort. Originally, my script was at the bottom of the page. I did this with the intent of helping my site's SEO ranking. When I moved the function to the top of the web page, the error went away. Now it is back. I have a feeling someone is going to suggest a jQuery solution to execute some code only when the page is fully loaded. I'm I ignorant of jQuery. IfjQuery is given in the answer, please explain what I need to do (references, placement of script files) for VS 2010 RTM. I am trying to set the focus to the first textbox on the webpage and preselect all of the text in the textbox More info: If I disable this Validator, the problem goes away: <asp:CustomValidator ID="valSpecifyOccupation" runat="server" ErrorMessage="Required" ClientValidationFunction="txtSpecifyOccupation_ClientValidate" Display="Dynamic" Enabled="False"></asp:CustomValidator> function txtSpecifyOccupation_ClientValidate(source, args) { var optOccupationRetired = document.getElementById("<%=optOccupationRetired.ClientID %>"); if (optOccupationRetired.checked) { args.IsValid = true; } else { var txtSpecifyOccupation = document.getElementById("<%=txtSpecifyOccupation.ClientID %>"); args.IsValid = ValidatorTrim(txtSpecifyOccupation.value) != ""; } }

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Flash As3.0 PHP Variables?

- by user311421

Is it possible to make php variables public and accessible anywhere on the timeline? The script I included works fine if I set it as the document class only (it won't work if I try importing it). The variables pass the text to dynamic text fields on the main timeline. The problem: It will pull the information and display it when the SWF first loads but if I move to my second frame and then back it erases the information. It also will not pass any variables to the second frame. The only way to see the variables after going back to the first frame is to reload the whole SWF. I'm pretty much stuck at this point trying to make the variables persistent through all frames. this is my code: package { import flash.display.MovieClip; import flash.events.*; import flash.net.*; import flash.display.Stage; public class Main extends MovieClip { public function Main() { var request:URLRequest = new URLRequest("http://localhost/mytest2/dataLayer.php"); request.method = URLRequestMethod.GET; var loader:URLLoader = new URLLoader(); loader.dataFormat = URLLoaderDataFormat.VARIABLES; loader.addEventListener(Event.COMPLETE, completeHandler); loader.load(request); function completeHandler(evt:Event) { var username = evt.target.data.username; var pclass = evt.target.data.pclass; var hpoints = evt.target.data.hpoints; var spoints = evt.target.data.spoints; username_txt.text = username; class_txt.text = pclass; hpoints_txt.text = hpoints; spoints_txt.text = spoints; } } } }

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sending HTML email with a variable in the URL

- by Rob Crouch

I am using the following script to send a dynamic page (php) as a html email... the page being emailed uses a variable in the URL to determine what record is shown from a database <? $evid = $_GET['evid']; $to = '[email protected]'; $subject = 'A test email!'; // To send HTML mail, the Content-type header must be set $headers = 'MIME-Version: 1.0' . "\r\n"; $headers .= 'Content-type: text/html; charset=iso-8859-1' . "\r\n"; // Put your HTML here $message = file_get_contents('http://www.url.co.uk/diary/i.php?evid=2'); // Mail it mail($to, $subject, $message, $headers); ?> as you can see the html file being emailed has a evid variable... if i set this to $evid and try to send the variable when running the current script I get an error... does anyone know of a way round this? hope i explained that clear enough Rob

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Placement/Positioning/Alignment of UIScrollView w.r.t. length of Title NSString

- by Shoaibi

I have a scenario where i show stuff like: ----------------------------------- titleview (UITextView) ______________ tArea (UIScrollView) ttextview (UITextView) ----------------------------------- Now here is the condition: Length of titleview's text is dynamic, varies based on user input. Because of the condition I have trouble placing tArea e.g. UIScrollView on the screen, it either appears way too below than the titleview, or overlaps it. Previously what i did: Count the number of characters in titleview.text.length and divide them by 27 (e.g. characters in one line when using boldSystemFontOfSize:20) and multiply by 10 to get the starting X of tArea e.g. UIScrollView. But that sucked. Because i had to duplicate code for rotation to landscape. What do i have now? : CGSize titlesize = [title sizeWithFont:[UIFont systemFontOfSize:20] constrainedToSize:CGSizeMake(5, 90) lineBreakMode:UILineBreakModeWordWrap]; ttitleview = [[UITextView alloc] initWithFrame:CGRectMake(5, 5, 310,titlesize.height)]; ttitleview.text = title; ttitleview.font = [UIFont boldSystemFontOfSize:20]; ttitleview.backgroundColor = [UIColor clearColor]; ttitleview.editable = NO; [self.view addSubview:ttitleview]; CGSize textsize = [ttext sizeWithFont:[UIFont systemFontOfSize:20] constrainedToSize:CGSizeMake(5, 350) lineBreakMode:UILineBreakModeWordWrap]; tArea = [[UIScrollView alloc] initWithFrame:CGRectMake(5, titlesize.height, 310, 230)]; tArea.contentSize = CGSizeMake(310, textsize.height+20); tArea.pagingEnabled = FALSE; tArea.scrollEnabled = TRUE; tArea.backgroundColor = [UIColor clearColor]; [self.view addSubview:tArea]; ttextview = [[UITextView alloc] initWithFrame:CGRectMake(0, 0, 310, textsize.height + 20)]; ttextview.text = ttext; ttextview.font = [UIFont systemFontOfSize:20]; ttextview.backgroundColor = [UIColor clearColor]; ttextview.editable = NO; [tArea addSubview:ttextview]; But its no use. Looking for an elegant solution than this.

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how to write css for nth child in css

- by steven spielberg

<div id="boxcontent"> <div>some content this div may be missing [dynamic genrated]</div> <div class="elem"></div> <div class="elem"></div> <div class="elem"></div> </div> <div id="boxcontent"> <div class="elem"></div> <div class="elem"></div> <div class="elem"></div> </div> <div id="boxcontent"> <div class="elem"></div> <div class="elem"></div> <div class="elem"></div> </div> i want to write some css on every 3rd div who have class .elem if i try nth-child to select them then sometime they select other. How i can select 3rd .elem class div when parent div have some other div as child or not. any way to select 3rd div who have class .elem

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Need a code snippet for backward paging...

- by Ali

Hi guys I'm in a bit on a fix here. I know how easy it is to build simple pagination links for dynamic pages whereby you can navigate between partial sets of records from sql queries. However the situation I have is as below: COnsider that I wish to paginate between records listed in a flat file - I have no problem with the retrieval and even the pagination assuming that the flat file is a csv file with the first field as an id and new reocrds on new lines. However I need to make a pagination system which paginates backwards i.e I want the LAST entry in the file to appear as the first as so forth. Since I don't have the power of sql to help me here I'm kinda stuck - all I have is a fixed sequence which needs to be paginated, also note that the id mentioned as first field is not necessarily numeric so forget about sorting by numerics here. I basically need a way to loop through the file but backwards and paginate it as such. How can I do that - I'm working in php - I just need the code to loop through and paginate i.e how to tell which is the offset and which is the current page etc.

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Simple ASP.NET MVC views without writing a controller

- by Jake Stevenson

We're building a site that will have very minimal code, it's mostly just going to be a bunch of static pages served up. I know over time that will change and we'll want to swap in more dynamic information, so I've decided to go ahead and build a web application using ASP.NET MVC2 and the Spark view engine. There will be a couple of controllers that will have to do actual work (like in the /products area), but most of it will be static. I want my designer to be able to build and modify the site without having to ask me to write a new controller or route every time they decide to add or move a page. So if he wants to add a "http://mysite.com/News" page he can just create a "News" folder under Views and put an index.spark page within it. Then later if he decides he wants a /News/Community page, he can drop a community.spark file within that folder and have it work. I'm able to have a view without a specific action by making my controllers override HandleUnknownAction, but I still have to create a controller for each of these folders. It seems silly to have to add an empty controller and recompile every time they decide to add an area to the site. Is there any way to make this easier, so I only have to write a controller and recompile if there's actual logic to be done? Some sort of "master" controller that will handle any requests where there was no specific controller defined?

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Value is not changing in the javascript variable on the onClick event

- by Chetan sharma

I am trying to implement a dynamic search jquery and php, but I am not able to change the value of a javascript variable on my onclick event. <script type="text/javascript"> var main_category = '<?php echo $main_category?>'; var main_url = '<?php echo $url?>get/' + encodeURIComponent(main_category) + '/'; var container_id = '<?php echo $unique_id?>content_area'; //name $('#<?php echo $unique_id?>search_by_name').autocomplete('<?php echo $url?>get_autocomplete_data/' + encodeURIComponent(main_category) + '/names/', { matchContains: "word", autoFill: true, width: 310 });$('#<?php echo $unique_id?>search_by_name').result(function (event, data){ var url = main_url + 'search/title/' + encodeURIComponent(data); load_div(container_id, url); }); //on click of displayed categories $('[rel="<?php echo $unique_id?>sub_category"]').click(function (){ window['main_category'] = this.title; $('#<?php echo $unique_id?>category').html('' +main_category+ ''); return false; }); }); </script> It changes the value when on click is fired //on click of displayed categories $('[rel="<?php echo $unique_id?>sub_category"]').click(function (){ window['main_category'] = this.title; $('#<?php echo $unique_id?>category').html('' +main_category+ ''); return false; }); but when after that i add data for the search it still searches for the old category $('#<?php echo $unique_id?>search_by_name').result(function (event, data){ var url = main_url + 'search/title/' + encodeURIComponent(data); load_div(container_id, url); }); "main_category" value is not changing in the "main_url"

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DatagGridViewColumn.DataPropertyName to an array element?

- by unknown

Hi there, I'm using a DataGridView binding its datasource to a List, and specifying the properties for each column. An example would be: DataGridViewTextBoxColumn colConcept = new DataGridViewTextBoxColumn(); DataGridViewCell cell4 = new DataGridViewTextBoxCell(); colConcept.CellTemplate = cell4; colConcept.Name = "concept"; colConcept.HeaderText = "Concept"; colConcept.DataPropertyName = "Concept"; colConcept.Width = 200; this.dataGridViewBills.Columns.Add(colConcept); {... assign other colums...} And finally this.dataGridViewBills.DataSource=billslist; //billslist is List<Bill> Obviously Class Bill has a Property called Concept, as well as one Property for each column. Well, now my problem, is that Bill should have and Array/List/whateverdynamicsizecontainer of strings called Years. Let's assume that every Bill will have the same Years.Count, but this only known at runtime.Thus, I can't specify properties like Bill.FirstYear to obtain Bill.Years[0], Bill.SecondYear to obtain Bills.Years[1]... etc... and bind it to each column. The idea, is that now I want to have a grid with dynamic number of colums (known at runtime), and each column filled with a string from the Bill.Years List. I can make a loop to add columns to the grid at runtime depending of Bill.Years.Count, but is possible to bind them to each of the strings that the Bill.Years List contains??? I'm not sure if I'm clear enough. The result ideally would be something like this, for 2 bills on the list, and 3 years for each bill: --------------------------------------GRID HEADER------------------------------- NAME CONCEPT YEAR1 YEAR2 YEAR3 --------------------------------------GRID VALUES------------------------------- Bill1 Bill1.Concept Bill1.Years[0] Bill1.Years[1] Bill1.Years[2] Bill2 Bill2.Concept Bill2.Years[0] Bill2.Years[1] Bill2.Years[2] I can always forget the datasource, and write each cell manually, as the MSFlexGrid used to like, but if possible, I would like to use the binding capabilities of the DataGridView. Any ideas? Thanks a lot.

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Will rel=canonical break site: queries ?

- by Justin Grant

Our company publishes our software product's documentation using a custom-built content management system using a dynamic URL namespace like this: http://ourproduct.com/documentation/version/pageid Where "version" is the version number to which the documentation applies, and "pageid" is a unique string which identifies that page in our back-end content management system. For example, if content (e.g. a page about configuration best practices) is unchanged from version 3.0 and 4.0 of our product, it'd be reachable by two different URLs: http://ourproduct.com/documentation/3.0/configuration-best-practices http://ourproduct.com/documentation/4.0/configuration-best-practices This URL scheme allows us to scope Google search results to see only documentaiton for a particular product version, like this: configuration site:ourproduct.com/documentation/4.0 But when the user is searching across all versions, we don't want Google to arbitrarily choose one of the URLs to show in results. Instead, we always want the latest version to show up. Hence our planned use of rel=canonical so we can proscriptively tell Google which URL we want to show up if multiple versions are being searched. (Users who do oddball things like searching 2 versions but not all of them are a corner case, so we don't care which version(s) show up in that case-- the primary use-cases we care about is searching one version or searching all versions) But what will happen to scoped searches if we do this? If my rel=canonical URL points to version 4.0, but my search is scoped to 3.0, will Google return a result? Even if you don't know the answer offhand, do you know a site which uses rel=canonical to redirect across folders in a URL namespace. If so, I could run a few Google searches and figure out the answer.

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Managing/Storing complex application form

- by mickyjtwin

I am developing an online application form, which can be of two categories, either domestic/international. Each different type has commong questions, and also specific questions. They are approx 6 pages/steps of questions. The application form can also be saved at the end of each step, and can be completed at a later date. Some questions will vary depending on answers to previous questions, so there are some complex business rules. In terms of storage of results, would it be best to store the answers in and XML field in SQL? What would be the best way to reference a question to an answer. There is no need for the form to be dynamic in rendering questions etc. e.g. <Application id="123" type="Domestic"> <Answers> <EmailAddress>[email protected]</EmailAddress> <HomePhone>555-5555</HomePhone> <Suburb>MySuburb</Suburb> <Guardians> <Guardian type="Mother"> <FirstName>Mom</FirstName> </Guardian> </Guardians> <Answers> </Application>

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asp.net mvc ajax form helper/post additional data

- by Jopache

I would like to use the ajax helper to create ajax requests that send additional, dynamic data with the post (for example, get the last element with class = blogCommentDateTime and send the value of that last one to the controller which will return only blog comments after it). I have successfully done so with the help of jQuery Form plugin like so: $(document).ready(function () { $("#addCommentForm").submit(function () { var lastCommentDate = $(".CommentDateHidden:last").val(); var lastCommentData = { lastCommentDateTicks: lastCommentDate }; var formSubmitParams = { data: lastCommentData, success: AddCommentResponseHandler } $("#addCommentForm").ajaxSubmit(formSubmitParams); return false; }); This form was created with html.beginform() method. I am wondering if there is an easy way to do this using the ajax.beginform() helper? When I try to use the same code but replace html.beginform() with ajax.beginform(), when i try to submit the form, I am issuing 2 posts (which is understandable, one being taken care of by the helper, the other one by me with the JS above. I can't create 2 requests, so this option is out) I tried getting rid of the return false and changing ajaxSubmit() to ajaxForm() so that it would only "prepare" the form, and this leads in only one post, but it does not include the extra parameter that I defined, so this is worthless as well. I then tried keeping the ajaxForm() but calling that whenever the submit button on the form gets clicked rather than when the form gets submitted (I guess this is almost the same thing) and that results in 2 posts also. The biggest reason I am asking this question is that I have run in to some issues with the javascript above and using mvc validation provided by the mvc framework (which i will set up another question for) and would like to know this so I can dive further in to my validation issue.

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Tool for generating flat files from SQL objects dynamically

- by Fabio Gouw

Hello! I'm looking for a tool or component that generates flat files given a SQL Server's query result (from a stored procedure or a SELECT * over a table or view). This will be a batch process which runs every day, and every day a new file is created. I could use SQL Server Integration Services (DTS), but I have a mandatory requirement: the output of the file need to be dynamic. If a new column is added in my query result, the file must have this new column too, without having to modify my SSIS package. If a column is removed, then the flat file no longer will have it. I’ve tried to do this with SSIS, but when I create a new package I need to specify the number of columns. Another requirement is configuring the format of the output, depending on the data type of the column. If it’s a datetime, the format needs to be YYYY-MM-DD. If it’s a float, then I need to use 2 decimal digits, and so on. Does anyone know a tool that does this job? Thanks

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How should a one-man development shop document their code?

- by CKoenig

Hi, please let me first describe my situation. I work in an IT department for a small-to-medium sized industrial-company and basically I'm the only real developer (sometimes a second guy joins in for his own projects). I programm mostly in C#/.net. Of course I only programm for internal need (Intranet, reporting, data-driven apps, some mobile apps, ...). My question is how should I document my work? It's a highly dynamic environment (the features and bug fixes I implement are tested by me during production, and go live, often within a day. If I technical documentation like MSDN or even overview diagramms those would take me more time to sync than the whole programming process. Also I feel it's a waste of time because I would be the only one who ever read it. I do understand that if I get sick, leave, or forget this documentation would be valuable. PS:well of course you are right - the quesion is how much and how/where. I try using the XML-docu comments for the public exposed parts but as I'm a believer in self-documenting code the comments mostly restates in plain text what you can read from the method-head itself :(Maybe using the remarks section is the key but if you have 30 lines of code with a 15 line xml-comment in front it just looks dirty (sorry for posting it here but our firewall rejects JSON :( )

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how do i execute a stored procedure with vici coolstorage?

- by lincolnk

I'm building an app around Vici Coolstorage (asp.net version). I have my classes created and mapped to my database tables and can pull a list of all records fine. I've written a stored procedure where the query jumps across databases that aren't mapped with Coolstorage, however, the fields in the query result map directly to one of my classes. The procedure takes 1 parameter. so 2 questions here: how do i execute the stored procedure? i'm doing this CSParameterCollection collection = new CSParameterCollection(); collection.Add("@id", id); var result = Vici.CoolStorage.CSDatabase.RunQuery("procedurename", collection); and getting the exception "Incorrect syntax near 'procedurename'." (i'm guessing this is because it's trying to execute it as text rather than a procedure?) and also, since the class representing my table is defined as abstract, how do i specify that result should create a list of MyTable objects instead of generic or dynamic or whatever objects? if i try Vici.CoolStorage.CSDatabase.RunQuery<MyTable>(...) the compiler yells at me for it being an abstract class.

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How to reliably replace a library-defined error handler with my own?

- by sharptooth

On certain error cases ATL invokes AtlThrow() which is implemented as ATL::AtlThrowImpl() which in turn throws CAtlException. The latter is not very good - CAtlException is not even derived from std::exception and also we use our own exceptions hierarchy and now we will have to catch CAtlException separately here and there which is lots of extra code and error-prone. Looks like it is possible to replace ATL::AtlThrowImpl() with my own handler - define _ATL_CUSTOM_THROW and define AtlThrow() to be the custom handler before including atlbase.h - and ATL will call the custom handler. Not so easy. Some of ATL code is not in sources - it comes compiled as a library - either static or dynamic. We use the static - atls.lib. And... it is compiled in such way that it has ATL::ThrowImpl() inside and some code calling it. I used a static analysis tool - it clearly shows that there're paths on which the old default handler is called. To ensure I even tried to "reimplement" ATL::AtlThrowImpl() in my code. Now the linker says it sees two declarations of ATL::AtlThrowImpl() which I suppose confirms that there's another implementation that can be called by some code. How can I handle this? How do I replace the default handler completely and ensure that the default handler is never called?

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Getting Started with Ruby & Ruby on Rails

- by JakeTheSnake

Some background: I'm a jack-of-all traits, one of which is programming. I learned VB6 through Excel and PHP for creating websites and so far it's worked out just fine for me. I'm not CS major or even mathematically inclined - logic is what interests me. Current status: I'm willing to learn new and more powerful languages; my first foray into such a route is learning Ruby. I went to the main Ruby website and did the interactive intro. (by the way, I'm currently getting redirected to google.com when I try the link...it's happening to other websites as well...is my computer infected?) I liked what I learned and wanted to get started using Ruby to create websites. I downloaded InstantRails and installed it; everything so far has been fine - the program starts up just fine, and I can test some Ruby code in the console. However my troubles begin when I try and view a web page with Ruby code present. Lastly, my problem: As in PHP, I can browse to the .php file directly and through using PHP tags and some simple 'echo' statements I can be on my way in making dynamic web pages. However with the InstantRails app working, accessing a .rb or .rhtml page doesn't produce similar results. I made a simple text file named 'test.rb' and put basic HTML tags in there (html, head, body) and the Ruby tags <%= and % with some ruby code inside. The web page actually shows the tags and the code - as if it's all just plain HTML. I take it Ruby isn't parsing the page before it is displayed to the user, but this is where my lack of understanding of the Ruby environment stops me short. Where do I go from here?

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LinqKit stack overflow exception using predicate builder

- by MLynn

I am writing an application in C# using LINQ and LINQKit. I have a very large database table with company registration numbers in it. I want to do a LINQ query which will produce the equivalent SQL: select * from table1 where regno in('123','456') The 'in' clause may have thousands of terms. First I get the company registration numbers from a field such as Country. I then add all the company registration numbers to a predicate: var predicate = PredicateExtensions.False<table2>(); if (RegNos != null) { foreach (int searchTerm in RegNos) { int temp = searchTerm; predicate = predicate.Or(ec => ec.regno.Equals(temp)); } } On Windows Vista Professional a stack overflow exception occured after 4063 terms were added. On Windows Server 2003 a stack overflow exception occured after about 1000 terms were added. I had to solve this problem quickly for a demo. To solve the problem I used this notation: var predicate = PredicateExtensions.False<table2>(); if (RegNosDistinct != null) { predicate = predicate.Or(ec => RegNos.Contains(ec.regno)); } My questions are: Why does a stack overflow occur using the foreach loop? I take it Windows Server 2003 has a much smaller stack per process\thread than NT\2000\XP\Vista\Windows 7 workstation versions of Windows. Which is the fastest and most correct way to achieve this using LINQ and LINQKit? It was suggested I stop using LINQ and go back to dynamic SQL or ADO.NET but I think using LINQ and LINQKit is far better for maintainability.

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I'm trying to install psycopg2 onto Mac OS 10.6.3; it claims it can't find "stdarg.h" but I can see

- by cojadate

I'm desperately trying to successfully install psycopg2 but keep running into errors. The latest one seems to involve it not being to find "stdarg.h" (see code below). However I can see with my own eyes that a file called stdarg.h exists at /Developer/SDKs/MacOSX10.4u.sdk/usr/include/stdarg.h (where it claims it can't find anything) so I've no idea what to do about it. I'm running Mac OS 10.6.3 and within the last few days I've made sure I have all the latest OS developer tools. I have Python 2.6.2 and PostgreSQL 8.4 if that makes any difference. python setup.py install running install running build running build_py running build_ext building 'psycopg2._psycopg' extension creating build/temp.macosx-10.3-fat-2.6 creating build/temp.macosx-10.3-fat-2.6/psycopg gcc -arch ppc -arch i386 -isysroot /Developer/SDKs/MacOSX10.4u.sdk -fno-strict-aliasing -fno-common -dynamic -DNDEBUG -g -O3 -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.2.1 (dt dec ext pq3)" -DPG_VERSION_HEX=0x080404 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -DHAVE_PQPROTOCOL3=1 -I/Library/Frameworks/Python.framework/Versions/2.6/include/python2.6 -I. -I/opt/local/include/postgresql84 -I/opt/local/include/postgresql84/server -c psycopg/psycopgmodule.c -o build/temp.macosx-10.3-fat-2.6/psycopg/psycopgmodule.o In file included from /Library/Frameworks/Python.framework/Versions/2.6/include/python2.6/unicodeobject.h:4, from /Library/Frameworks/Python.framework/Versions/2.6/include/python2.6/Python.h:85, from psycopg/psycopgmodule.c:27: /Developer/SDKs/MacOSX10.4u.sdk/usr/include/stdarg.h:4:25: error: stdarg.h: No such file or directory In file included from /Library/Frameworks/Python.framework/Versions/2.6/include/python2.6/unicodeobject.h:4, from /Library/Frameworks/Python.framework/Versions/2.6/include/python2.6/Python.h:85, from psycopg/psycopgmodule.c:27: /Developer/SDKs/MacOSX10.4u.sdk/usr/include/stdarg.h:4:25: error: stdarg.h: No such file or directory lipo: can't figure out the architecture type of: /var/folders/MQ/MQ-tWOWWG+izzuZCrAJpzk+++TI/-Tmp-//ccakFhRS.out error: command 'gcc' failed with exit status

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Why is setting HTML5's CanvasPixelArray values is ridiculously slow and how can I do it faster?

- by Nixuz

I am trying to do some dynamic visual effects using the HTML 5 canvas' pixel manipulation, but I am running into a problem where setting pixels in the CanvasPixelArray is ridiculously slow. For example if I have code like: imageData = ctx.getImageData(0, 0, 500, 500); for (var i = 0; i < imageData.length; i += 4){ imageData.data[index] = buffer[i]; imageData.data[index + 1] = buffer[i]; imageData.data[index + 2] = buffer[i]; } ctx.putImageData(imageData, 0, 0); Profiling with Chrome reveals, it runs 44% slower than the following code where CanvasPixelArray is not used. tempArray = new Array(500 * 500 * 4); imageData = ctx.getImageData(0, 0, 500, 500); for (var i = 0; i < imageData.length; i += 4){ tempArray[index] = buffer[i]; tempArray[index + 1] = buffer[i]; tempArray[index + 2] = buffer[i]; } ctx.putImageData(imageData, 0, 0); My guess is that the reason for this slowdown is due to the conversion between the Javascript doubles and the internal unsigned 8bit integers, used by the CanvasPixelArray. Is this guess correct? Is there anyway to reduce the time spent setting values in the CanvasPixelArray?

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How best to implement "favourites" feature? (like favourite products on a data driven website)

- by ClarkeyBoy

Hi, I have written a dynamic database driven, object oriented website with an administration frontend etc etc. I would like to add a feature where customers can save items as "favourites", without having to create an account and login, to come back to them later, but I dont know how exactly to go about doing this... I see three options: Log favourites based on IP address and then change these to be logged against an account if the customer then creates an account; Force customers to create an account to be able to use this functionality; Log favourites based on IP address but give users the option to save their favourites under a name they specify. The problem with option 1 is that I dont know much about IP addresses - my Dad thinks they are unique, but I know people have had problems with systems like this. The problem with 1 and 2 is that accounts have not been opened up to customers yet - only administrators can log in at the moment. It should be easy to alter this (no more than a morning or afternoons work) but I would also have to implement usergroups too. The problem with option 3 is that if user A saves a favourites list called "My Favourites", and then user B tries to save a list under this name and it is refused, user B will then be able to access the list saved by user A because they now know it already exists. A solution to this is to password protect lists, but to go to all this effort I may as well implement option 2. Of course I could always use option 4; use an alternative if anyone can suggest a better solution than any of the above options. So has anyone ever done something like this before? If so how did you go about it? What do you recommend (or not recommend)? Many thanks in advance, Regards, Richard

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Thread safe lazy contruction of a singleton in C++

- by pauldoo

Is there a way to implement a singleton object in C++ that is: Lazily constructed in a thread safe manner (two threads might simultaneously be the first user of the singleton - it should still only be constructed once). Doesn't rely on static variables being constructed beforehand (so the singleton object is itself safe to use during the construction of static variables). (I don't know my C++ well enough, but is it the case that integral and constant static variables are initialized before any code is executed (ie, even before static constructors are executed - their values may already be "initialized" in the program image)? If so - perhaps this can be exploited to implement a singleton mutex - which can in turn be used to guard the creation of the real singleton..) Excellent, it seems that I have a couple of good answers now (shame I can't mark 2 or 3 as being the answer). There appears to be two broad solutions: Use static initialisation (as opposed to dynamic initialisation) of a POD static varible, and implementing my own mutex with that using the builtin atomic instructions. This was the type of solution I was hinting at in my question, and I believe I knew already. Use some other library function like pthread_once or boost::call_once. These I certainly didn't know about - and am very grateful for the answers posted.

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