Search Results

Search found 8258 results on 331 pages for 'sequence points'.

Page 307/331 | < Previous Page | 303 304 305 306 307 308 309 310 311 312 313 314  | Next Page >

  • function which given a point and a value of the area of a square as input parameter returns four squ

    - by osabri
    in this code i don't understand why teacher used sometimes +value, - value; /******************************************/ // function void returnSquares(POINT point, int value) void returnSquares(POINT point, int value) { SQUARE tabSquares[4]; // table of squares that we are creating int i; // getting points of 4 squares // for first square input point is point C tabSquares[0].pointA.dimX = point.dimX - value; tabSquares[0].pointA.dimY = point.dimY + value; tabSquares[0].pointB.dimX = point.dimX; tabSquares[0].pointB.dimY = point.dimY + value; tabSquares[0].pointC.dimX = point.dimX; tabSquares[0].pointC.dimY = point.dimY; tabSquares[0].pointD.dimX = point.dimX - value; tabSquares[0].pointD.dimY = point.dimY; // for 2nd square input point is point D tabSquares[1].pointA.dimX = point.dimX; tabSquares[1].pointA.dimY = point.dimY + value; tabSquares[1].pointB.dimX = point.dimX + value; tabSquares[1].pointB.dimY = point.dimY + value; tabSquares[1].pointC.dimX = point.dimX + value; tabSquares[1].pointC.dimY = point.dimY; tabSquares[1].pointD.dimX = point.dimX; tabSquares[1].pointD.dimY = point.dimY; // for 3rd square input point is point A tabSquares[2].pointA.dimX = point.dimX; tabSquares[2].pointA.dimY = point.dimY; tabSquares[2].pointB.dimX = point.dimX + value; tabSquares[2].pointB.dimY = point.dimY; tabSquares[2].pointC.dimX = point.dimX + value; tabSquares[2].pointC.dimY = point.dimY - value; tabSquares[2].pointD.dimX = point.dimX; tabSquares[2].pointD.dimY = point.dimY - value; // for 4th square input point is point B tabSquares[3].pointA.dimX = point.dimX - value; tabSquares[3].pointA.dimY = point.dimY; tabSquares[3].pointB.dimX = point.dimX; tabSquares[3].pointB.dimY = point.dimY; tabSquares[3].pointC.dimX = point.dimX; tabSquares[3].pointC.dimY = point.dimY - value; tabSquares[3].pointD.dimX = point.dimX - value; tabSquares[3].pointD.dimY = point.dimY - value; for (i=0; i<4; i++) { printf("Square number %d\n",i); // now we print parameters of each point in current Square printf("point A x= %0.2f y= %0.2f\n",tabSquares[i].pointA.dimX,tabSquares[i].pointA.dimY); printf("point B x= %0.2f y= %0.2f\n",tabSquares[i].pointB.dimX,tabSquares[i].pointB.dimY); printf("point C x= %0.2f y= %0.2f\n",tabSquares[i].pointC.dimX,tabSquares[i].pointC.dimY); printf("point D x= %0.2f y= %0.2f\n",tabSquares[i].pointD.dimX,tabSquares[i].pointD.dimY); } }

    Read the article

  • Silverlight? WPF? or Windows Form?

    - by Amit
    After Silverlight 4.0 has been released with new WPF, I am kind of confused with these technologies: Silverlight? WPF? Windows Form? The main motive that we want to achieve for BIG business project is following: Performance Security And platform independent** If I consider all above three points then only Silverlight is the option as I don’t want people buying emulator on MacOS for WPF or Windows Form. Now how good the Silverlight is for Business applications, I was completely against when Silverlight 2.0 was in the market but now it is Silverlight 4.0 and they have provided many new features (but still basics) that is required in any challenging business applications. Comparing Silverlight and WPF -* Silverlight and WPF are very new technology and if I'd to compare from these two then I'd prefer WPF because it can be considered stable and mature. But it is not same as Windows Form. -* If I go with Silverlight then I am sure about keep updating to the latest version of Silverlight. I remembered when we were developing software for version 2.0 then we'd to create our own framework with dynamic loading DLL, and then Navigation concept. But everything was got changed once Silverlight 3.0 came. I don't want this to be happening with this new product. -* If we go with WPF then we don't get the platform independence. Now, why not we just focus on making WPF and then move to Silverlght. As someone (Tim?) from Microsoft has said that the idea is to make Silverlight as close as WPF. But if that is the case then why XAML structure is different; I will not be convinced with by saying that .Net framework for SL is too small.. well the difference is coming from the namespace ? I was searching on this subject and found "Microsoft WPF-Silverlight Comparison Whitepaper v1.1.pdf". This guide is very good that gives you ins-outs about how can we build common apps that runs on both. But again, it is comparing Silverlight 2 and not 4. I am sure many architect/ developers/ project managers must be facing similar kind of questions in their premises and wants to initiate this discussion, if it has not been :). We've still got 2 weeks to make this decision, so I'm expecting everyone to participate, gurus?

    Read the article

  • Given a trace of packets, how would you group them into flows?

    - by zxcvbnm
    I've tried it these ways so far: 1) Make a hash with the source IP/port and destination IP/port as keys. Each position in the hash is a list of packets. The hash is then saved in a file, with each flow separated by some special characters/line. Problem: Not enough memory for large traces. 2) Make a hash with the same key as above, but only keep in memory the file handles. Each packet is then put into the hash[key] that points to the right file. Problems: Too many flows/files (~200k) and it might run out of memory as well. 3) Hash the source IP/port and destination IP/port, then put the info inside a file. The difference between 2 and 3 is that here the files are opened and closed for each operation, so I don't have to worry about running out of memory because I opened too many at the same time. Problems: WAY too slow, same number of files as 2 so also impractical. 4) Make a hash of the source IP/port pairs and then iterate over the whole trace for each flow. Take the packets that are part of that flow and place them into the output file. Problem: Suppose I have a 60 MB trace that has 200k flows. This way, I would process, say, a 60 MB file 200k times. Maybe removing the packets as I iterate would make it not so painful, but so far I'm not sure this would be a good solution. 5) Split them by IP source/destination and then create a single file for each one, separating the flows by special characters. Still too many files (+50k). Right now I'm using Ruby to do it, which might've been a bad idea, I guess. Currently I've filtered the traces with tshark so that they only have relevant info, so I can't really make them any smaller. I thought about loading everything in memory as described in 1) using C#/Java/C++, but I was wondering if there wouldn't be a better approach here, especially since I might also run out of memory later on even with a more efficient language if I have to use larger traces. In summary, the problem I'm facing is that I either have too many files or that I run out of memory. I've also tried searching for some tool to filter the info, but I don't think there is one. The ones I've found only return some statistics and wouldn't scan for every flow as I need.

    Read the article

  • question about book example - Java Concurrency in Practice, Listing 4.12

    - by mike
    Hi, I am working through an example in Java Concurrency in Practice and am not understanding why a concurrent-safe container is necessary in the following code. I'm not seeing how the container "locations" 's state could be modified after construction; so since it is published through an 'unmodifiableMap' wrapper, it appears to me that an ordinary HashMap would suffice. EG, it is accessed concurrently, but the state of the map is only accessed by readers, no writers. The value fields in the map are syncronized via delegation to the 'SafePoint' class, so while the points are mutable, the keys for the hash, and their associated values (references to SafePoint instances) in the map never change. I think my confusion is based on what precisely the state of the collection is in the problem. Thanks!! -Mike Listing 4.12, Java Concurrency in Practice, (this listing available as .java here, and also in chapter form via google) /////////////begin code @ThreadSafe public class PublishingVehicleTracker { private final Map<String, SafePoint> locations; private final Map<String, SafePoint> unmodifiableMap; public PublishingVehicleTracker( Map<String, SafePoint> locations) { this.locations = new ConcurrentHashMap<String, SafePoint>(locations); this.unmodifiableMap = Collections.unmodifiableMap(this.locations); } public Map<String, SafePoint> getLocations() { return unmodifiableMap; } public SafePoint getLocation(String id) { return locations.get(id); } public void setLocation(String id, int x, int y) { if (!locations.containsKey(id)) throw new IllegalArgumentException( "invalid vehicle name: " + id); locations.get(id).set(x, y); } } // monitor protected helper-class @ThreadSafe public class SafePoint { @GuardedBy("this") private int x, y; private SafePoint(int[] a) { this(a[0], a[1]); } public SafePoint(SafePoint p) { this(p.get()); } public SafePoint(int x, int y) { this.x = x; this.y = y; } public synchronized int[] get() { return new int[] { x, y }; } public synchronized void set(int x, int y) { this.x = x; this.y = y; } } ///////////end code

    Read the article

  • How do I set libavcodec to use 4:2:2 chroma when encoding MPEG-2 4:2:2 profile?

    - by Mike Pollitt
    I have a project using libavcodec (ffmpeg). I'm using it to encode MPEG-2 video at 4:2:2 Profile, Main Level. I have the pixel format PIX_FMT_YUV422P selected in the AVCodecContext, however the video output I'm getting has all the colours wrong, and looks to me like the encoder is incorrectly reading the buffers as though it thinks it is 4:2:0 chroma rather than 4:2:2. Here's my codec setup: // // AVFormatContext* _avFormatContext previously defined as mpeg2video // // // Set up the video stream for output // AVVideoStream* _avVideoStream = av_new_stream(_avFormatContext, 0); if (!_avVideoStream) { err = ccErrWFFFmpegUnableToAllocateStream; goto bail; } _avCodecContext = _avVideoStream->codec; _avCodecContext->codec_id = CODEC_ID_MPEG2VIDEO; _avCodecContext->codec_type = CODEC_TYPE_VIDEO; // // Set up required parameters // _avCodecContext->rc_max_rate = _avCodecContext->rc_min_rate = _avCodecContext->bit_rate = src->_avCodecContext->bit_rate; _avCodecContext->flags = CODEC_FLAG_INTERLACED_DCT; _avCodecContext->flags2 = CODEC_FLAG2_INTRA_VLC | CODEC_FLAG2_NON_LINEAR_QUANT; _avCodecContext->qmin = 1; _avCodecContext->qmax = 1; _avCodecContext->rc_buffer_size = _avCodecContext->rc_initial_buffer_occupancy = 2000000; _avCodecContext->rc_buffer_aggressivity = 0.25; _avCodecContext->profile = 0; _avCodecContext->level = 5; _avCodecContext->width = f->GetWidth(); // f is a private Frame class with width, height properties etc. _avCodecContext->height = f->GetHeight(); _avCodecContext->time_base.den = 25; _avCodecContext->time_base.num = 1; _avCodecContext->gop_size = 12; _avCodecContext->max_b_frames = 2; _avCodecContext->pix_fmt = PIX_FMT_YUV422P; if (_avFormatContext->oformat->flags & AVFMT_GLOBALHEADER) { _avCodecContext->flags |= CODEC_FLAG_GLOBAL_HEADER; } if (av_set_parameters(_avFormatContext, NULL) < 0) { err = ccErrWFFFmpegUnableToSetParameters; goto bail; } // // Set up video codec for encoding // AVCodec* _avCodec = avcodec_find_encoder(_avCodecContext->codec_id); if (!_avCodec) { err = ccErrWFFFmpegUnableToFindCodecForOutput; goto bail; } if (avcodec_open(_avCodecContext, _avCodec) < 0) { err = ccErrWFFFmpegUnableToOpenCodecForOutput; goto bail; } A screengrab of the resulting video frame can be seen at http://ftp.limeboy.com/images/screen_grab.png (the input was standard colour bars). I've checked by outputting debug frames to TGA format at various points in the process, and I can confirm that it is all fine and dandy up until the point that libavcodec encodes the frame. Any assistance most appreciated! Cheers, Mike.

    Read the article

  • Coroutines in Java

    - by JUST MY correct OPINION
    I would like to do some stuff in Java that would be clearer if written using concurrent routines, but for which full-on threads are serious overkill. The answer, of course, is the use of coroutines, but there doesn't appear to be any coroutine support in the standard Java libraries and a quick Google on it brings up tantalising hints here or there, but nothing substantial. Here's what I've found so far: JSIM has a coroutine class, but it looks pretty heavyweight and conflates, seemingly, with threads at points. The point of this is to reduce the complexity of full-on threading, not to add to it. Further I'm not sure that the class can be extracted from the library and used independently. Xalan has a coroutine set class that does coroutine-like stuff, but again it's dubious if this can be meaningfully extracted from the overall library. It also looks like it's implemented as a tightly-controlled form of thread pool, not as actual coroutines. There's a Google Code project which looks like what I'm after, but if anything it looks more heavyweight than using threads would be. I'm basically nervous of something that requires software to dynamically change the JVM bytecode at runtime to do its work. This looks like overkill and like something that will cause more problems than coroutines would solve. Further it looks like it doesn't implement the whole coroutine concept. By my glance-over it gives a yield feature that just returns to the invoker. Proper coroutines allow yields to transfer control to any known coroutine directly. Basically this library, heavyweight and scary as it is, only gives you support for iterators, not fully-general coroutines. The promisingly-named Coroutine for Java fails because it's a platform-specific (obviously using JNI) solution. And that's about all I've found. I know about the native JVM support for coroutines in the Da Vinci Machine and I also know about the JNI continuations trick for doing this. These are not really good solutions for me, however, as I would not necessarily have control over which VM or platform my code would run on. (Indeed any bytecode manipulation system would suffer similar problems -- it would be best were this pure Java if possible. Runtime bytecode manipulation would restrict me from using this on Android, for example.) So does anybody have any pointers? Is this even possible? If not, will it be possible in Java 7?

    Read the article

  • How do I recover from an unchecked exception?

    - by erickson
    Unchecked exceptions are alright if you want to handle every failure the same way, for example by logging it and skipping to the next request, displaying a message to the user and handling the next event, etc. If this is my use case, all I have to do is catch some general exception type at a high level in my system, and handle everything the same way. But I want to recover from specific problems, and I'm not sure the best way to approach it with unchecked exceptions. Here is a concrete example. Suppose I have a web application, built using Struts2 and Hibernate. If an exception bubbles up to my "action", I log it, and display a pretty apology to the user. But one of the functions of my web application is creating new user accounts, that require a unique user name. If a user picks a name that already exists, Hibernate throws an org.hibernate.exception.ConstraintViolationException (an unchecked exception) down in the guts of my system. I'd really like to recover from this particular problem by asking the user to choose another user name, rather than giving them the same "we logged your problem but for now you're hosed" message. Here are a few points to consider: There a lot of people creating accounts simultaneously. I don't want to lock the whole user table between a "SELECT" to see if the name exists and an "INSERT" if it doesn't. In the case of relational databases, there might be some tricks to work around this, but what I'm really interested in is the general case where pre-checking for an exception won't work because of a fundamental race condition. Same thing could apply to looking for a file on the file system, etc. Given my CTO's propensity for drive-by management induced by reading technology columns in "Inc.", I need a layer of indirection around the persistence mechanism so that I can throw out Hibernate and use Kodo, or whatever, without changing anything except the lowest layer of persistence code. As a matter of fact, there are several such layers of abstraction in my system. How can I prevent them from leaking in spite of unchecked exceptions? One of the declaimed weaknesses of checked exceptions is having to "handle" them in every call on the stack—either by declaring that a calling method throws them, or by catching them and handling them. Handling them often means wrapping them in another checked exception of a type appropriate to the level of abstraction. So, for example, in checked-exception land, a file-system–based implementation of my UserRegistry might catch IOException, while a database implementation would catch SQLException, but both would throw a UserNotFoundException that hides the underlying implementation. How do I take advantage of unchecked exceptions, sparing myself of the burden of this wrapping at each layer, without leaking implementation details?

    Read the article

  • Internationalization of static pages with Rails

    - by Gavin
    I feel like I'm missing something really simple and I keep spinning my wheels on this problem. I currently have internationalization working throughout my app. The translations work and the routes work perfectly. At least, most of the site works with the exception of the routes to my two static pages, my "About" and "FAQ" pages. Every other link throughout the app points to the proper localized route. For example if I select "french" as my language, links point to the appropriate "(/:locale)/controller(.:format)." However, despite the changes I make throughout the app my links for the "About" and "FAQ" refuse to point to "../fr/static/about" and always point to "/static/about." To make matters stranger, when I run rake routes I see: "GET (/:locale)/static/:permalink(.:format) pages#show {:locale=/en|fr/}" and when I manually type in "../fr/static/about" the page translates perfectly. My Routes file: devise_for :users scope "(:locale)", :locale => /en|fr/ do get 'static/:permalink', :controller => 'pages', :action => 'show' resources :places, only: [:index, :show, :destroy] resources :homes, only: [:index, :show] match '/:locale' => 'places#index' get '/'=>'places#index',:as=>"root" end My ApplicationController: before_filter :set_locale def set_locale I18n.locale=params[:locale]||I18n.default_locale end def default_url_options(options={}) logger.debug "default_url_options is passed options: #{options.inspect}\n" { :locale => I18n.locale } end and My Pages Controller: class PagesController < ApplicationController before_filter :validate_page PAGES = ['about_us', 'faq'] def show render params[:permalink] end def validate_page redirect_to :status => 404 unless PAGES.include?(params[:permalink]) end end I'd be very grateful for any help ... it's just been one of those days. Edit: Thanks to Terry for jogging me to include views. <div class="container-fluid nav-collapse"> <ul class="nav"> <li class="dropdown"> <a href="#" class="dropdown-toggle" data-toggle="dropdown"><%= t(:'navbar.about') %><b class="caret"></b></a> <ul class="dropdown-menu"> <li><%=link_to t(:'navbar.about_us'), "/static/about_us"%></li> <li><%=link_to t(:'navbar.faq'), "/static/faq"%></li> <li><%=link_to t(:'navbar.blog'), '#' %></li> </ul> </li>

    Read the article

  • Get latlng and draw a polyline between that two latlng

    - by anup sharma
    I have some issue in my code in that first I want to get latlng of my given address/city name from two text boxes after that i converts it to from position's latlng and to position's latlng and at last i want to draw a polyline between these point and markers on both point also, But now i am trying to draw a line between these points. But still not working this code also no any error in console also. code is here for your help. function getRoute(){ var from_text = document.getElementById("travelFrom").value; var to_text = document.getElementById("travelTo").value; if(from_text == ""){ alert("Enter travel from field") document.getElementById("travelFrom").focus(); } else if(to_text == ""){ alert("Enter travel to field"); document.getElementById("travelTo").focus(); } else{ //google.maps.event.addListener(map, "", function (e) { var myLatLng = new google.maps.LatLng(28.6667, 77.2167); var mapOptions = { zoom: 3, center: myLatLng, mapTypeId: google.maps.MapTypeId.TERRAIN }; var map = new google.maps.Map(document.getElementById('map-canvas'), mapOptions); var geocoder = new google.maps.Geocoder(); var address1 = from_text; var address2 = to_text; var from_latlng,to_latlng; //var prepath = path; //if(prepath){ // prepath.setMap(null); //} geocoder.geocode( { 'address': address1}, function(results, status) { if (status == google.maps.GeocoderStatus.OK) { // do something with the geocoded result // alert(results[0].geometry.location); from_latlng = results[0].geometry.location; // from_lat = results[0].geometry.location.latitude; // from_lng = results[0].geometry.location.longitude; // alert(from_latlng); } }); geocoder.geocode( { 'address': address2}, function(results, status) { if (status == google.maps.GeocoderStatus.OK) { // do something with the geocoded result to_latlng = results[0].geometry.location; // to_lat = results[0].geometry.location.latitude; // to_lng = results[0].geometry.location.longitude; // results[0].geometry.location.longitude // alert(to_latlng) } }); setTimeout(function(){ var flightPlanCoordinates = [ new google.maps.LatLng(from_latlng), new google.maps.LatLng(to_latlng) ]; //alert("123") var polyline; polyline = new google.maps.Polyline({ path: flightPlanCoordinates, strokeColor: "#FF0000", strokeOpacity: 1.0, strokeWeight: 2 }); polyline.setMap(map); // assign to global var path // path = polyline; },4000); // }); } }

    Read the article

  • Issues adding search to iPhone app

    - by Graeme
    Hi, Basically I'm trying to add a search function to my iPhone app, but I'm not having much luck at the moment. I've downloaded the Apple provided Table Search app, and have copied across the code to mine. It builds OK, but here's the problem. Unlike the Apple example, all my data is stored in an array, that is accessed by calling [ciParser.currentArray]. Any ideas on how to change the code to suit my needs? I'm getting an error "Terminating app due to uncaught exception 'NSRangeException', reason: '* -[NSCFArray objectAtIndex:]: index (0) beyond bounds (0)'" whenever I click on the search bar and the app exits. Below is the code in particular that the debugger highlights as being troublesome. Apparently this error means the database trying to be searched is empty, but I could be wrong. FYI my app downloads and parsers an RSS feed using a class which is referenced by ciParser - which in turn stores the downloaded content in an array that I need to search. // Customize the appearance of table view cells. - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleDefault reuseIdentifier:CellIdentifier] autorelease]; } /* If the requesting table view is the search display controller's table view, configure the cell using the filtered content, otherwise use the main list. */ CurrentItem * nextCurrentItem=[ciParser.currentArray objectAtIndex:indexPath.row]; if (tableView == self.searchDisplayController.searchResultsTableView) { (Code which debugger points to as being wrong) nextCurrentItem = [self.filteredListContent objectAtIndex:indexPath.row]; } else { nextCurrentItem = [ciParser.currentArray objectAtIndex:indexPath.row]; } NSString*settingValue = [[NSUserDefaults standardUserDefaults]stringForKey:@"state"]; if ([settingValue isEqualToString:@"New South Wales"]) { cell.textLabel.text=nextCurrentItem.title; } else if ([settingValue isEqualToString:@"Western Australia"]) { cell.textLabel.text=@"The FESA does not provide any Current Incident reports."; } else if ([settingValue isEqualToString:@"Victoria"]) { cell.textLabel.text=nextCurrentItem.title; } else if ([settingValue isEqualToString:@"South Australia"]) { cell.textLabel.text=nextCurrentItem.title; } else if ([settingValue isEqualToString:@"Tasmania"]) { cell.textLabel.text=nextCurrentItem.title; } // Set up the cell... [cell setAccessoryType:UITableViewCellAccessoryDisclosureIndicator]; return cell; }

    Read the article

  • CSS: move a "float:right" element to top (to align with the first element of the list)

    - by Patrick
    hi, I've a sequence of elements and the last one has css "float:left". I would like to display it at the same height of the first element and not on the bottom of the list. (I cannot change the html code, so it is the last in the list). At the same time, I would like to keep it on the right. How can I make it wich CSS ? thanks Code: <div class="field field-type-text field-field-year"> <div class="field-items"> <div class="field-item odd"> <div class="field-label-inline-first"> Year:&nbsp;</div> 2009 </div> </div> </div> <div class="field field-type-text field-field-where"> <div class="field-items"> <div class="field-item odd"> <div class="field-label-inline-first"> Where:&nbsp;</div> Musée Rath, Geneva </div> </div> </div> <div class="field field-type-text field-field-when"> <div class="field-items"> <div class="field-item odd"> <div class="field-label-inline-first"> When:&nbsp;</div> 25.8 – 27.9.2009 </div> </div> </div> <div class="field field-type-text field-field-editor"> <div class="field-items"> <div class="field-item odd"> <div class="field-label-inline-first"> Editor:&nbsp;</div> Blabla Blabla </div> </div> </div> <div class="field field-type-text field-field-material"> <div class="field-items"> <div class="field-item odd"> <div class="field-label-inline-first"> Material/techniques:&nbsp;</div> contemporary art installations </div> </div> </div> <div class="field field-type-text field-field-dimension"> <div class="field-items"> <div class="field-item odd"> <div class="field-label-inline-first"> Dimension:&nbsp;</div> 2 floors in a neoclassical building </div> </div> </div> <div class="field field-type-text field-field-artists"> <div class="field-items"> <div class="field-item odd"> <div class="field-label-inline-first"> Artists:&nbsp;</div> Blablablabla balbalbalbalba </div> </div> </div> .field-field-year, .field-field-where, .field-field-when, .field-field-editor, .field-field-material, .field-field-dimension { width:300px; } .field-field-artists { width:400px; float:right; clear:right; top-margin: -200px; }

    Read the article

  • Using a Button to navigate to another Page in a NavigationWindow

    - by Will
    I'm trying to use the navigation command framework in WPF to navigate between Pages within a WPF application (desktop; not XBAP or Silverlight). I believe I have everything configured correctly, yet its not working. I build and run without errors, I'm not getting any binding errors in the Output window, but my navigation button is disabled. Here's the app.xaml for a sample app: <Application x:Class="Navigation.App" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" StartupUri="First.xaml"> </Application> Note the StartupUri points to First.xaml. First.xaml is a Page. WPF automatically hosts my page in a NavigationWindow. Here's First.xaml: <Page x:Class="Navigation.First" xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation" xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml" Title="First"> <Grid> <Button CommandParameter="/Second.xaml" CommandTarget="{Binding RelativeSource= {RelativeSource FindAncestor, AncestorType={x:Type NavigationWindow}}}" Command="NavigationCommands.GoToPage" Content="Go!"/> </Grid> </Page> The button's CommandTarget is set to the NavigationWindow. The command is GoToPage, and the page is /Second.xaml. I've tried setting the CommandTarget to the containing Page, the CommandParameter to "Second.xaml" (First.xaml and Second.xaml are both in the root of the solution), and I've tried leaving the CommandTarget empty. I've also tried setting the Path to the Binding to various navigational-related public properties on the NavigationWindow. Nothing has worked so far. What am I missing here? I really don't want to do my navigation in code. Clarification. If, instead of using a button, I use a Hyperlink: <Grid> <TextBlock> <Hyperlink NavigateUri="Second.xaml">Go! </Hyperlink> </TextBlock> </Grid> everything works as expected. However, my UI requirements means that using a Hyperlink is right out. I need a big fatty button for people to press. That's why I want to use the button to navigate. I just want to know how I can get the Button to provide the same ability that the Hyperlink does in this case.

    Read the article

  • Performance issues with jms and spring integration. What is wrong with the following configuration?

    - by user358448
    I have a jms producer, which generates many messages per second, which are sent to amq persistent queue and are consumed by single consumer, which needs to process them sequentially. But it seems that the producer is much faster than the consumer and i am having performance and memory problems. Messages are fetched very very slowly and the consuming seems to happen on intervals (the consumer "asks" for messages in polling fashion, which is strange?!) Basically everything happens with spring integration. Here is the configuration at the producer side. First stake messages come in stakesInMemoryChannel, from there, they are filtered throw the filteredStakesChannel and from there they are going into the jms queue (using executor so the sending will happen in separate thread) <bean id="stakesQueue" class="org.apache.activemq.command.ActiveMQQueue"> <constructor-arg name="name" value="${jms.stakes.queue.name}" /> </bean> <int:channel id="stakesInMemoryChannel" /> <int:channel id="filteredStakesChannel" > <int:dispatcher task-executor="taskExecutor"/> </int:channel> <bean id="stakeFilterService" class="cayetano.games.stake.StakeFilterService"/> <int:filter input-channel="stakesInMemoryChannel" output-channel="filteredStakesChannel" throw-exception-on-rejection="false" expression="true"/> <jms:outbound-channel-adapter channel="filteredStakesChannel" destination="stakesQueue" delivery-persistent="true" explicit-qos-enabled="true" /> <task:executor id="taskExecutor" pool-size="100" /> The other application is consuming the messages like this... The messages come in stakesInputChannel from the jms stakesQueue, after that they are routed to 2 separate channels, one persists the message and the other do some other stuff, lets call it "processing". <bean id="stakesQueue" class="org.apache.activemq.command.ActiveMQQueue"> <constructor-arg name="name" value="${jms.stakes.queue.name}" /> </bean> <jms:message-driven-channel-adapter channel="stakesInputChannel" destination="stakesQueue" acknowledge="auto" concurrent-consumers="1" max-concurrent-consumers="1" /> <int:publish-subscribe-channel id="stakesInputChannel" /> <int:channel id="persistStakesChannel" /> <int:channel id="processStakesChannel" /> <int:recipient-list-router id="customRouter" input-channel="stakesInputChannel" timeout="3000" ignore-send-failures="true" apply-sequence="true" > <int:recipient channel="persistStakesChannel"/> <int:recipient channel="processStakesChannel"/> </int:recipient-list-router> <bean id="prefetchPolicy" class="org.apache.activemq.ActiveMQPrefetchPolicy"> <property name="queuePrefetch" value="${jms.broker.prefetch.policy}" /> </bean> <bean id="connectionFactory" class="org.springframework.jms.connection.CachingConnectionFactory"> <property name="targetConnectionFactory"> <bean class="org.apache.activemq.ActiveMQConnectionFactory"> <property name="brokerURL" value="${jms.broker.url}" /> <property name="prefetchPolicy" ref="prefetchPolicy" /> <property name="optimizeAcknowledge" value="true" /> <property name="useAsyncSend" value="true" /> </bean> </property> <property name="sessionCacheSize" value="10"/> <property name="cacheProducers" value="false"/> </bean>

    Read the article

  • Setting up Netbeans/Eclipse for Linux Kernel Development

    - by red.october
    Hi: I'm doing some Linux kernel development, and I'm trying to use Netbeans. Despite declared support for Make-based C projects, I cannot create a fully functional Netbeans project. This is despite compiling having Netbeans analyze a kernel binary that was compiled with full debugging information. Problems include: files are wrongly excluded: Some files are incorrectly greyed out in the project, which means Netbeans does not believe they should be included in the project, when in fact they are compiled into the kernel. The main problem is that Netbeans will miss any definitions that exist in these files, such as data structures and functions, but also miss macro definitions. cannot find definitions: Pretty self-explanatory - often times, Netbeans cannot find the definition of something. This is partly a result of the above problem. can't find header files: self-explanatory I'm wondering if anyone has had success with setting up Netbeans for Linux kernel development, and if so, what settings they used. Ultimately, I'm looking for Netbeans to be able to either parse the Makefile (preferred) or extract the debug information from the binary (less desirable, since this can significantly slow down compilation), and automatically determine which files are actually compiled and which macros are actually defined. Then, based on this, I would like to be able to find the definitions of any data structure, variable, function, etc. and have complete auto-completion. Let me preface this question with some points: I'm not interested in solutions involving Vim/Emacs. I know some people like them, but I'm not one of them. As the title suggest, I would be also happy to know how to set-up Eclipse to do what I need While I would prefer perfect coverage, something that only misses one in a million definitions is obviously fine SO's useful "Related Questions" feature has informed me that the following question is related: http://stackoverflow.com/questions/149321/what-ide-would-be-good-for-linux-kernel-driver-development. Upon reading it, the question is more of a comparison between IDE's, whereas I'm looking for how to set-up a particular IDE. Even so, the user Wade Mealing seems to have some expertise in working with Eclipse on this kind of development, so I would certainly appreciate his (and of course all of your) answers. Cheers

    Read the article

  • How is "clean" testing done on the Macintosh without virtualization?

    - by Schnapple
    One of the things I've run across on Windows is when a web browser plugin or program you're developing makes an assumption that something is installed that, by default, isn't always present on Windows. A perfect example would be .NET - a whole lot of people running Windows XP have never installed any versions of .NET and so the installer needs to detect and remedy this if necessary. The way I've been testing this in Windows is to have a virtual machine with a snapshot of a clean, patched, but otherwise untouched install of XP or Vista or 7 or whatever. When I'm done testing I just discard any changes since the snapshot. Works great. I'm now developing something for the Macintosh, a platform which is very new to me, and I'm seeing that virtualization does not appear to be an option. It's explicitly forbidden in the EULA of Mac OS X, it's only allowed from Mac OS X Server, which seeing as how I'm targeting an end product is of no use to me, and the one program I see which can virtualize it - VirtualBox - only supports the server and actively nukes any discussion of running the consumer/client version of Mac OS X. And the only instructions I find anywhere on the topic seem to involve the use of "hacking" programs which is very much incompatible with the full-time gig I'm trying to do this for. So it looks like virtualization is out, but at various points I'm going to want or need to simulate what it's like to install and run this software on a "clean" Macintosh. How do people usually do this? Just buy multiple Macintoshes and use Time Machine? Am I thinking about this all wrong and everything Just Works? To be clear I'm not trying to run Mac OS X on a Windows machine. I have a Macintosh, I'm fine with virtualizing Mac OS X on Apple hardware, I'm just not seeing a route to making the non-Server version do this. I'm aware that Mac OS X Server can be virtualized but that's not what I'm going for. I'm aware that there are unsanctioned/unsupported methods of making Mac OS X run in virtualization programs like VirtualBox but for legal reasons I am not interested in those. My question is not "how can I do this?" but rather "so this thing I do on Windows seems to not be possible, generally, on the Macintosh, so what do people do to achieve what I'm going for?"

    Read the article

  • iPhone Gps logging inaccurate

    - by Martijn
    I'm logging gps points during a walk. Below it shows the function that the coordinates are saved each 5 seconds. i Did several tests but i cannot get the right accuracy i want. (When testing the sky is clear also tests in google maps shows me that the gps signal is good). here is the code: -(void)viewDidAppear:(BOOL)animated{ if (self.locationManager == nil){ self.locationManager = [[[CLLocationManager alloc] init] autorelease]; locationManager.delegate = self; // only notify under 100 m accuracy locationManager.distanceFilter = 100.0f; locationManager.desiredAccuracy= kCLLocationAccuracyBest; [locationManager startUpdatingLocation]; } } - start logging [NSTimer scheduledTimerWithTimeInterval:5 target:self selector:@selector(getData) userInfo:nil repeats:YES]; </code> <code> -(void)getData{ int distance; // re-use location. if ([ [NSString stringWithFormat:@"%1.2f",previousLat] isEqualToString:@"0.00"]){ // if previous location is not available, do nothing distance = 0; }else{ CLLocation *loc1 = [[CLLocation alloc] initWithLatitude:previousLat longitude:previousLong]; CLLocation *loc2 = [[CLLocation alloc] initWithLatitude:latGlobal longitude:longGlobal]; distance = [loc1 getDistanceFrom: loc2]; } // overwrite latGlobal with new variable previousLat = latGlobal; previousLong = longGlobal; // store location and save data to database // this part goes ok } - (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation { // track the time to get a new gps result (for gps indicator orb) lastPointTimestamp = [newLocation.timestamp copy]; // test that the horizontal accuracy does not indicate an invalid measurement if (newLocation.horizontalAccuracy < 0) return; // test the age of the location measurement to determine if the measurement is cached // don't rely on cached measurements NSTimeInterval locationAge = -[newLocation.timestamp timeIntervalSinceNow]; if (locationAge > 5.0) return; latGlobal = fabs(newLocation.coordinate.latitude); longGlobal= fabs(newLocation.coordinate.longitude); } I have taken a screenshot of the plot results (the walk takes 30 minutes) and an example of what i'am trying to acomplish: http://www.flickr.com/photos/21258341@N07/4623969014/ i really hope someone can put me in the right direction.

    Read the article

  • Programmatically Binding to a Property

    - by M312V
    I know it's a generic title, but my question is specific. I think it will boil down to a question of practice. So, I have the following code: public class Component : UIElement { public Component() { this.InputBindings.Add(new MouseBinding(SomeCommandProperty, new MouseGesture(MouseAction.LeftClick))); } } I could easily aggregate the ViewModel that owns SomeCommandProperty into the Component class, but I'm currently waiving that option assuming there is another way. Component is a child of ComponentCollection which is child of a Grid which DataContext is the ViewModel. ComponentCollection as the name suggests contains a collection of Components. <Grid Name="myGrid"> <someNamespace:ComponentCollection x:Name="componentCollection"/> </Grid> It's the same scenario as the XAML below, but with TextBlock. I guess I'm trying to replicate what's being done in the XAML below programatically. Again, Component's top most ancestor's DataContext is set to ViewModel. <Grid Name="myGrid"> <TextBlock Text="SomeText"> <TextBlock.InputBindings> <MouseBinding Command="{Binding SomeCommandProperty}" MouseAction="LeftClick" /> </TextBlock.InputBindings> </TextBlock> </Grid> Update 1 Sorry, I'm unable to comment because I lack the reputation points. Basically, I have a custom control which inherit from a Panel which children are a collection of Component. It's not a hack, like I've mentioned, I could directly have access to SomeCommandProperty If I aggregate the ViewModel into Component. Doing so, however, feels icky. That is, having direct access to ViewModel from a Model. I guess the question I'm asking is. Given the situation that Component's parent UIElement's DataContext is set to ViewModel, is it possible to access SomeCommandProperty without Component owning a reference to the ViewModel that owns SomeCommandProperty? Programatically, that is. Using ItemsControl doesn't change the fact that I still need to bind SomeCommandProperty to each Items.

    Read the article

  • Migrating from hand-written persistence layer to ORM

    - by Sergey Mikhanov
    Hi community, We are currently evaluating options for migrating from hand-written persistence layer to ORM. We have a bunch of legacy persistent objects (~200), that implement simple interface like this: interface JDBC { public long getId(); public void setId(long id); public void retrieve(); public void setDataSource(DataSource ds); } When retrieve() is called, object populates itself by issuing handwritten SQL queries to the connection provided using the ID it received in the setter (this usually is the only parameter to the query). It manages its statements, result sets, etc itself. Some of the objects have special flavors of retrive() method, like retrieveByName(), in this case a different SQL is issued. Queries could be quite complex, we often join several tables to populate the sets representing relations to other objects, sometimes join queries are issued on-demand in the specific getter (lazy loading). So basically, we have implemented most of the ORM's functionality manually. The reason for that was performance. We have very strong requirements for speed, and back in 2005 (when this code was written) performance tests has shown that none of mainstream ORMs were that fast as hand-written SQL. The problems we are facing now that make us think of ORM are: Most of the paths in this code are well-tested and are stable. However, some rarely-used code is prone to result set and connection leaks that are very hard to detect We are currently squeezing some additional performance by adding caching to our persistence layer and it's a huge pain to maintain the cached objects manually in this setup Support of this code when DB schema changes is a big problem. I am looking for an advice on what could be the best alternative for us. As far as I know, ORMs has advanced in last 5 years, so it might be that now there's one that offers an acceptable performance. As I see this issue, we need to address those points: Find some way to reuse at least some of the written SQL to express mappings Have the possibility to issue native SQL queries without the necessity to manually decompose their results (i.e. avoid manual rs.getInt(42) as they are very sensitive to schema changes) Add a non-intrusive caching layer Keep the performance figures. Is there any ORM framework you could recommend with regards to that?

    Read the article

  • Myself throwing NullReferenceException... needs help

    - by Amit Ranjan
    I know it might be a weird question and its Title too, but i need your help. I am a .net dev , working on platform for the last 1.5 years. I am bit confused on the term usually we say " A Good Programmer ". I dont know ,what are the qualities of a good programmer ? Is the guy who writes a bug free code? or Can develop applications solely? or blah blah blah...lots of points. I dont know... But as far i am concerned , I know I am not a good programmer, still in learning phase an needs a lot to learn in coming days. So you guys are requested to please help me with this two problems of mine My first problem is regarding the proper Error Handling, which is a most debatable aspect of programming. We all know we use ` try { } catch { } finally { } ` in our code to manage exception. But even if I use try { } catch(exception ex) { throw ex } finally { } , different guys have different views. I still dont know the good way to handle errors. I can write code, use try-catch but still i feel I lacks something. When I saw the codes generated by .net fx tools even they uses throw ex or `throw new Exception("this is my exception")`.. I am just wondering what will be the best way to achieve the above. All means the same thing but why we avoid something. If it has some demerits then it must be made obselete.Anyways I still dont have one [how to handle errors efficiently?]. I generally follow the try-catch(execoption ex){throw ex}, and usually got stucked in debates with leads why you follow this why not that... 2.Converting your entire code blocks in modules using Design patterns of some OOPs concepts. How do you guys decide what architeture or pattern will be the best for my upcoming application based on its working, flow etc. I need to know what you guys can see that I can't. Since I know , I dont have that much experience but I can say, with my experience that experience doesnot comes either from degree/certificates or success you made instead it cames from failures you faced or got stucking situations. Pleas help me out.

    Read the article

  • Summarising (permanently) data in a SQL table

    - by Cylindric
    Geetings, Stackers. I have a huge number of data-points in a SQL table, and I want to summarise them in a way reminiscent of RRD. Assuming a table such as ID | ENTITY_ID | SCORE_DATE | SCORE | SOME_OTHER_DATA ----+-----------+------------+-------+----------------- 1 | A00000001 | 01/01/2010 | 100 | some data 2 | A00000002 | 01/01/2010 | 105 | more data 3 | A00000003 | 01/01/2010 | 104 | various text ... | ......... | .......... | ..... | ... ... | A00009999 | 01/01/2010 | 101 | ... | A00000001 | 02/01/2010 | 104 | ... | A00000002 | 02/01/2010 | 119 | ... | A00000003 | 02/01/2010 | 119 | ... | ......... | .......... | ..... | ... | A00009999 | 02/01/2010 | 101 | arbitrary data ... | ......... | .......... | ..... | ... ... | A00000001 | 01/02/2010 | 104 | ... | A00000002 | 01/02/2010 | 119 | ... | A00000003 | 01/01/2010 | 119 | I want to end up with one record per entity, per month: ID | ENTITY_ID | SCORE_DATE | SCORE | ----+-----------+------------+-------+ ... | A00000001 | 01/01/2010 | 100 | ... | A00000002 | 01/01/2010 | 105 | ... | A00000003 | 01/01/2010 | 104 | ... | A00000001 | 01/02/2010 | 100 | ... | A00000002 | 01/02/2010 | 105 | ... | A00000003 | 01/02/2010 | 104 | (I Don't care about the SOME_OTHER_DATA - I'll pick something - either the first or last record probably.) What's an easy way of doing this on a regular basis, so that anything in the last calendar month is summarised in this way? At the moment my plan is kind of: For each EntityID For each month Find average score for all records in given month Update first record with results of previous step Delete all records that aren't the first I can't think of a neat way of doing it though, that doesn't involve lots of updates and iteration. This can either be done in a SQL Stored Procedure, or it can be incorporated into the .Net app that's generating this data, so the solution doesn't really need to be "one big SQL script", but can be :) (SQL-2005)

    Read the article

  • When to call glEnable(GL_FRAMEBUFFER_SRGB)?

    - by Steven Lu
    I have a rendering system where I draw to an FBO with a multisampled renderbuffer, then blit it to another FBO with a texture in order to resolve the samples in order to read off the texture to perform post-processing shading while drawing to the backbuffer (FBO index 0). Now I'd like to get some correct sRGB output... The problem is the behavior of the program is rather inconsistent between when I run it on OS X and Windows and this also changes depending on the machine: On Windows with the Intel HD 3000 it will not apply the sRGB nonlinearity but on my other machine with a Nvidia GTX 670 it does. On the Intel HD 3000 in OS X it will also apply it. So this probably means that I'm not setting my GL_FRAMEBUFFER_SRGB enable state at the right points in the program. However I can't seem to find any tutorials that actually tell me when I ought to enable it, they only ever mention that it's dead easy and comes at no performance cost. I am currently not loading in any textures so I haven't had a need to deal with linearizing their colors yet. To force the program to not simply spit back out the linear color values, what I have tried is simply comment out my glDisable(GL_FRAMEBUFFER_SRGB) line, which effectively means this setting is enabled for the entire pipeline, and I actually redundantly force it back on every frame. I don't know if this is correct or not. It certainly does apply a nonlinearization to the colors but I can't tell if this is getting applied twice (which would be bad). It could apply the gamma as I render to my first FBO. It could do it when I blit the first FBO to the second FBO. Why not? I've gone so far as to take screen shots of my final frame and compare raw pixel color values to the colors I set them to in the program: I set the input color to RGB(1,2,3) and the output is RGB(13,22,28). That seems like quite a lot of color compression at the low end and leads me to question if the gamma is getting applied multiple times. I have just now gone through the sRGB equation and I can verify that the conversion seems to be only applied once as linear 1/255, 2/255, and 3/255 do indeed map to sRGB 13/255, 22/255, and 28/255 using the equation 1.055*C^(1/2.4)+0.055. Given that the expansion is so large for these low color values it really should be obvious if the sRGB color transform is getting applied more than once. So, I still haven't determined what the right thing to do is. does glEnable(GL_FRAMEBUFFER_SRGB) only apply to the final framebuffer values, in which case I can just set this during my GL init routine and forget about it hereafter?

    Read the article

  • Strange Map Reduce Behavior in CouchDB. Rereduce?

    - by Tony
    I have a mapreduce issue with couchdb (both functions shown below): when I run it with grouplevel = 2 (exact) I get accurate output: {"rows":[ {"key":["2011-01-11","staff-1"],"value":{"total":895.72,"count":2,"services":6,"services_ignored":6,"services_liked":0,"services_disliked":0,"services_disliked_avg":0,"Revise":{"total":275.72,"count":1},"Review":{"total":620,"count":1}}}, {"key":["2011-01-11","staff-2"],"value":{"total":8461.689999999999,"count":2,"services":41,"services_ignored":37,"services_liked":4,"services_disliked":0,"services_disliked_avg":0,"Revise":{"total":4432.4,"count":1},"Review":{"total":4029.29,"count":1}}}, {"key":["2011-01-11","staff-3"],"value":{"total":2100.72,"count":1,"services":10,"services_ignored":4,"services_liked":3,"services_disliked":3,"services_disliked_avg":2.3333333333333335,"Revise":{"total":2100.72,"count":1}}}, However, changing to grouplevel=1 so the values for all the different staff keys should be all grouped by date no longer gives accurate output (notice the total is currect but all others are wrong): {"rows":[ {"key":["2011-01-11"],"value":{"total":11458.130000000001,"count":2,"services":0,"services_ignored":0,"services_liked":0,"services_disliked":0,"services_disliked_avg":0,"None":{"total":11458.130000000001,"count":2}}}, My only theory is this has something to do with rereduce, which I have not yet learned. Should I explore that option or am I missing something else here? This is the Map function: function(doc) { if(doc.doc_type == 'Feedback') { emit([doc.date.split('T')[0], doc.staff_id], doc); } } And this is the Reduce: function(keys, vals) { // sum all key points by status: total, count, services (liked, rejected, ignored) var ret = { 'total':0, 'count':0, 'services': 0, 'services_ignored': 0, 'services_liked': 0, 'services_disliked': 0, 'services_disliked_avg': 0, }; var total_disliked_score = 0; // handle status function handle_status(doc) { if(!doc.status || doc.status == '' || doc.status == undefined) { status = 'None'; } else if (doc.status == 'Declined') { status = 'Rejected'; } else { status = doc.status; } if(!ret[status]) ret[status] = {'total':0, 'count':0}; ret[status]['total'] += doc.total; ret[status]['count'] += 1; }; // handle likes / dislikes function handle_services(services) { ret.services += services.length; for(var a in services) { if (services[a].user_likes == 10) { ret.services_liked += 1; } else if (services[a].user_likes >= 1) { ret.services_disliked += 1; total_disliked_score += services[a].user_likes; if (total_disliked_score >= ret.services_disliked) { ret.services_disliked_avg = total_disliked_score / ret.services_disliked; } } else { ret.services_ignored += 1; } } } // loop thru docs for(var i in vals) { // increment the total $ ret.total += vals[i].total; ret.count += 1; // update totals and sums for the status of this route handle_status(vals[i]); // do the likes / dislikes stats if(vals[i].groups) { for(var ii in vals[i].groups) { if(vals[i].groups[ii].services) { handle_services(vals[i].groups[ii].services); } } } // handle deleted services if(vals[i].hidden_services) { if (vals[i].hidden_services) { handle_services(vals[i].hidden_services); } } } return ret; }

    Read the article

  • Throwing cats out of windows

    - by AndrewF
    Imagine you're in a tall building with a cat. The cat can survive a fall out of a low story window, but will die if thrown from a high floor. How can you figure out the longest drop that the cat can survive, using the least number of attempts? Obviously, if you only have one cat, then you can only search linearly. First throw the cat from the first floor. If it survives, throw it from the second. Eventually, after being thrown from floor f, the cat will die. You then know that floor f-1 was the maximal safe floor. But what if you have more than one cat? You can now try some sort of logarithmic search. Let's say that the build has 100 floors and you have two identical cats. If you throw the first cat out of the 50th floor and it dies, then you only have to search 50 floors linearly. You can do even better if you choose a lower floor for your first attempt. Let's say that you choose to tackle the problem 20 floors at a time and that the first fatal floor is #50. In that case, your first cat will survive flights from floors 20 and 40 before dying from floor 60. You just have to check floors 41 through 49 individually. That's a total of 12 attempts, which is much better than the 50 you would need had you attempted to use binary elimination. In general, what's the best strategy and it's worst-case complexity for an n-storied building with 2 cats? What about for n floors and m cats? Assume that all cats are equivalent: they will all survive or die from a fall from a given window. Also, every attempt is independent: if a cat survives a fall, it is completely unharmed. This isn't homework, although I may have solved it for school assignment once. It's just a whimsical problem that popped into my head today and I don't remember the solution. Bonus points if anyone knows the name of this problem or of the solution algorithm.

    Read the article

  • Scalable Database Tagging Schema

    - by Longpoke
    EDIT: To people building tagging systems. Don't read this. It is not what you are looking for. I asked this when I wasn't aware that RDBMS all have their own optimization methods, just use a simple many to many scheme. I have a posting system that has millions of posts. Each post can have an infinite number of tags associated with it. Users can create tags which have notes, date created, owner, etc. A tag is almost like a post itself, because people can post notes about the tag. Each tag association has an owner and date, so we can see who added the tag and when. My question is how can I implement this? It has to be fast searching posts by tag, or tags by post. Also, users can add tags to posts by typing the name into a field, kind of like the google search bar, it has to fill in the rest of the tag name for you. I have 3 solutions at the moment, but not sure which is the best, or if there is a better way. Note that I'm not showing the layout of notes since it will be trivial once I get a proper solution for tags. Method 1. Linked list tagId in post points to a linked list in tag_assoc, the application must traverse the list until flink=0 post: id, content, ownerId, date, tagId, notesId tag_assoc: id, tagId, ownerId, flink tag: id, name, notesId Method 2. Denormalization tags is simply a VARCHAR or TEXT field containing a tab delimited array of tagId:ownerId. It cannot be a fixed size. post: id, content, ownerId, date, tags, notesId tag: id, name, notesId Method 3. Toxi (from: http://www.pui.ch/phred/archives/2005/04/tags-database-schemas.html, also same thing here: http://stackoverflow.com/questions/20856/how-do-you-recommend-implementing-tags-or-tagging) post: id, content, ownerId, date, notesId tag_assoc: ownerId, tagId, postId tag: id, name, notesId Method 3 raises the question, how fast will it be to iterate through every single row in tag_assoc? Methods 1 and 2 should be fast for returning tags by post, but for posts by tag, another lookup table must be made. The last thing I have to worry about is optimizing searching tags by name, I have not worked that out yet. I made an ASCII diagram here: http://pastebin.com/f1c4e0e53

    Read the article

  • Multi-threaded Pooled Allocators

    - by Darren Engwirda
    I'm having some issues using pooled memory allocators for std::list objects in a multi-threaded application. The part of the code I'm concerned with runs each thread function in isolation (i.e. there is no communication or synchronization between threads) and therefore I'd like to setup separate memory pools for each thread, where each pool is not thread-safe (and hence fast). I've tried using a shared thread-safe singleton memory pool and found the performance to be poor, as expected. This is a heavily simplified version of the type of thing I'm trying to do. A lot has been included in a pseudo-code kind of way, sorry if it's confusing. /* The thread functor - one instance of MAKE_QUADTREE created for each thread */ class make_quadtree { private: /* A non-thread-safe memory pool for int linked list items, let's say that it's * something along the lines of BOOST::OBJECT_POOL */ pooled_allocator<int> item_pool; /* The problem! - a local class that would be constructed within each std::list as the * allocator but really just delegates to ITEM_POOL */ class local_alloc { public : //!! I understand that I can't access ITEM_POOL from within a nested class like //!! this, that's really my question - can I get something along these lines to //!! work?? pointer allocate (size_t n) { return ( item_pool.allocate(n) ); } }; public : make_quadtree (): item_pool() // only construct 1 instance of ITEM_POOL per // MAKE_QUADTREE object { /* The kind of data structures - vectors of linked lists * The idea is that all of the linked lists should share a local pooled allocator */ std::vector<std::list<int, local_alloc>> lists; /* The actual operations - too complicated to show, but in general: * * - The vector LISTS is grown as a quadtree is built, it's size is the number of * quadtree "boxes" * * - Each element of LISTS (each linked list) represents the ID's of items * contained within each quadtree box (say they're xy points), as the quadtree * is grown a lot of ID pop/push-ing between lists occurs, hence the memory pool * is important for performance */ } }; So really my problem is that I'd like to have one memory pool instance per thread functor instance, but within each thread functor share the pool between multiple std::list objects.

    Read the article

< Previous Page | 303 304 305 306 307 308 309 310 311 312 313 314  | Next Page >