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  • What Use are Threads Outside of Parallel Problems on MultiCore Systesm?

    - by Robert S. Barnes
    Threads make the design, implementation and debugging of a program significantly more difficult. Yet many people seem to think that every task in a program that can be threaded should be threaded, even on a single core system. I can understand threading something like an MPEG2 decoder that's going to run on a multicore cpu ( which I've done ), but what can justify the significant development costs threading entails when you're talking about a single core system or even a multicore system if your task doesn't gain significant performance from a parallel implementation? Or more succinctly, what kinds of non-performance related problems justify threading? Edit Well I just ran across one instance that's not CPU limited but threads make a big difference: TCP, HTTP and the Multi-Threading Sweet Spot Multiple threads are pretty useful when trying to max out your bandwidth to another peer over a high latency network connection. Non-blocking I/O would use significantly less local CPU resources, but would be much more difficult to design and implement.

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  • Advice on Mocking System Calls

    - by Robert S. Barnes
    I have a class which calls getaddrinfo for DNS look ups. During testing I want to simulate various error conditions involving this system call. What's the recommended method for mocking system calls like this? I'm using Boost.Test for my unit testing.

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  • Boost.Test: Looking for a working non-Trivial Test Suite Example / Tutorial

    - by Robert S. Barnes
    The Boost.Test documentation and examples don't really seem to contain any non-trivial examples and so far the two tutorials I've found here and here while helpful are both fairly basic. I would like to have a master test suite for the entire project, while maintaining per module suites of unit tests and fixtures that can be run independently. I'll also be using a mock server to test various networking edge cases. I'm on Ubuntu 8.04, but I'll take any example Linux or Windows since I'm writing my own makefiles anyways.

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  • Setting up separate ctags db's for C/C++ standard libs, boost, and third party libs

    - by Robert S. Barnes
    I want to set up separate ctags databases for various libraries in /usr/include/ for use with OmniCppComplete. The idea is to be able to pull in only the libraries needed for a particular project in the target language - C or C++. For example, I'd like to have one database for the standard C libraries, one for system libraries that might be used by either C or C++ programs ( sockets / networking comes to mind ) one for the standard C++ libs / STL / Boost, and then other databases for various third party libraries such as QT or glib. Then I could pull something in simply by typing set tags+= ~/.vim/somelib.tags in vim. I assume that everything related to the C++ stdlib and STL are in the /usr/include/c++ and that Boost is all in /usr/include/boost. Unfortunately it seems that the standard C libs and system libs are just kind of dumped directly into /usr/include/ with a variety of other stuff. How can I get a list of which files and directories belong to which libs? I'm on Ubuntu 8.04.

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  • "Socket operation on non-socket" error due to strange sytax

    - by Robert S. Barnes
    I ran across the error Socket operation on non-socket in some of my networking code when calling connect and spent a lot of time trying to figure out what was causing it. I finally figured out that the following line of code was causing the problem: if ((sockfd = socket( ai->ai_family, ai->ai_socktype, ai->ai_protocol) < 0)) { See the problem? Here's what the line should look like: if ((sockfd = socket( ai->ai_family, ai->ai_socktype, ai->ai_protocol)) < 0) { What I don't understand is why the first, incorrect line doesn't produce a warning. To put it another way, shouldn't the general form: if ( foo = bar() < baz ) do_somthing(); look odd to the compiler, especially running with g++ -Wall -Wextra? If not, shouldn't it at least show up as "bad style" to cppcheck, which I'm also running as part of my compile?

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  • Creating TCP network errors for unit testing

    - by Robert S. Barnes
    I'd like to create various network errors during testing. I'm using the Berkely sockets API directly in C++ on Linux. I'm running a mock server in another thread from within Boost.Test which listens on localhost. For instance, I'd like to create a timeout during connect. So far I've tried not calling accept in my mock server and setting the backlog to 1, then making multiple connections, but all seem to successfully connect. I would think that if there wasn't room in the backlog queue I would at least get a connection refused error if not a timeout. I'd like to do this all programatically if possible, but I'd consider using something external like IPchains to intentionally drop certain packets to certain ports during testing, but I'd need to automate creating and removing rules so I could do it from within my Boost.Test unit tests. I suppose I could mock the various system calls involved, but I'd rather go through a real TCP stack if possible. Ideas?

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  • Issuing multiple requests using HTTP/1.1 Pipelining

    - by Robert S. Barnes
    When using HTTP/1.1 Pipelining what does the standard say about issuing multiple requests without waiting for each request to complete? What do servers do in practice? I ask because I once tried writing a client which would issue a batch of GET requests for multiple files and remember getting errors. I wasn't sure if it was due to me incorrectly issuing the GET's or needing to wait for each individual request to finish before issuing the next GET.

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  • How can I build and parse HTTP URL's / URI's / paths in Perl?

    - by Robert S. Barnes
    I have a wget-like script which downloads a page and then retrieves all the files linked in IMG tags on that page. Given the URL of the original page and the the link extracted from the IMG tag in that page I need to build the URL for the image file I want to retrieve. Currently I use a function I wrote: sub build_url { my ( $base, $path ) = @_; # if the path is absolute just prepend the domain to it if ($path =~ /^\//) { ($base) = $base =~ /^(?:http:\/\/)?(\w+(?:\.\w+)+)/; return "$base$path"; } my @base = split '/', $base; my @path = split '/', $path; # remove a trailing filename pop @base if $base =~ /[[:alnum:]]+\/[\w\d]+\.[\w]+$/; # check for relative paths my $relcount = $path =~ /(\.\.\/)/g; while ( $relcount-- ) { pop @base; shift @path; } return join '/', @base, @path; } The thing is, I'm surely not the first person solving this problem, and in fact it's such a general problem that I assume there must be some better, more standard way of dealing with it, using either a core module or something from CPAN - although via a core module is preferable. I was thinking about File::Spec but wasn't sure if it has all the functionality I would need.

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  • C++ function object terminology functor, deltor, comparitor, etc..

    - by Robert S. Barnes
    Is there a commonly accepted terminology for various types for common functors? For instance I found myself naturally using comparitor for comparison functors like this: struct ciLessLibC : public std::binary_function<std::string, std::string, bool> { bool operator()(const std::string &lhs, const std::string &rhs) const { return strcasecmp(lhs.c_str(), rhs.c_str()) < 0 ? 1 : 0; } }; Or using the term deltor for something like this: struct DeleteAddrInfo { void operator()(const addr_map_t::value_type &pr) const { freeaddrinfo(pr.second); } }; If using these kinds of shorthand terms is common, it there some dictionary of them all someplace?

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  • Testing for a closed socket

    - by Robert S. Barnes
    I'm trying to test for a closed socket that has been gracefully closed by the peer without incurring the latency hit of a double send to induce a SIGPIPE. One of the assumptions here is that the socket if closed was gracefully closed by the peer immediately after it's last write / send. Actual errors like a premature close are dealt with else where in the code. If the socket is still open, there will be 0 or more bytes data which I don't actually want to pull out of the socket buffer yet. I was thinking that I could call int ret = recv(sockfd, buf, 1, MSG_DONTWAIT | MSG_PEEK); to determine if the socket is still connected. If it's connected but there's no data in the buffer I'll get a return of -1 with errno == EAGAIN and return the sockfd for reuse. If it's been gracefully closed by the peer I'll get ret == 0 and open a new connection. I've tested this and it seems to work. However, I suspect there is a small window between when I recv the last bit of my data and when the peer FIN arrives in which I could get a false-positive EAGAIN from my test recv. Is this going to bite me, or is there a better way of doing this?

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  • [Perl] Use a Module / Object which is defined in the same file

    - by Robert S. Barnes
    I need to define some modules and use them all in the same file. No, I can't change the requirement. I would like to do something like the following: { package FooObj; sub new { ... } sub add_data { ... } } { package BarObj; use FooObj; sub new { ... # BarObj "has a" FooObj my $self = ( myFoo => FooObj->new() ); ... } sub some_method { ... } } my $bar = BarObj->new(); However, this results in the message: Can't locate FooObj.pm in @INC ... BEGIN failed... How do I get this to work?

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  • How can I call a Perl package I define in the same file?

    - by Robert S. Barnes
    I need to define some modules and use them all in the same file. No, I can't change the requirement. I would like to do something like the following: { package FooObj; sub new { ... } sub add_data { ... } } { package BarObj; use FooObj; sub new { ... # BarObj "has a" FooObj my $self = ( myFoo => FooObj->new() ); ... } sub some_method { ... } } my $bar = BarObj->new(); However, this results in the message: Can't locate FooObj.pm in @INC ... BEGIN failed... How do I get this to work?

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  • Hitting a Button -> Executing any class function I give it in the parameters (C++)

    - by Barnes Noble
    Can anyone help me with class function parameter callbacks? I'm not so sure how to set it up in my code here: http://codepad.org/fvwHtDjQ Basically I've got a player and an enemy. I have two buttons. One button when clicked should let the player jump. The other should make the enemy hit something. When clicked, each button has to correspond to the class function in the parameters. I'm not sure how to set it up though.

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  • Scrolling an HTML 5 page using JQuery

    - by nikolaosk
    In this post I will show you how to use JQuery to scroll through an HTML 5 page.I had to help a friend of mine to implement this functionality and I thought it would be a good idea to write a post.I will not use any JQuery scrollbar plugin,I will just use the very popular JQuery Library. Please download the library (minified version) from http://jquery.com/download.Please find here all my posts regarding JQuery.Also have a look at my posts regarding HTML 5.In order to be absolutely clear this is not (and could not be) a detailed tutorial on HTML 5. There are other great resources for that.Navigate to the excellent interactive tutorials of W3School.Another excellent resource is HTML 5 Doctor.Two very nice sites that show you what features and specifications are implemented by various browsers and their versions are http://caniuse.com/ and http://html5test.com/. At this times Chrome seems to support most of HTML 5 specifications.Another excellent way to find out if the browser supports HTML 5 and CSS 3 features is to use the Javascript lightweight library Modernizr.In this hands-on example I will be using Expression Web 4.0.This application is not a free application. You can use any HTML editor you like.You can use Visual Studio 2012 Express edition. You can download it here. Let me move on to the actual example.This is the sample HTML 5 page<!DOCTYPE html><html lang="en">  <head>    <title>Liverpool Legends</title>        <meta http-equiv="Content-Type" content="text/html;charset=utf-8" >        <link rel="stylesheet" type="text/css" href="style.css">        <script type="text/javascript" src="jquery-1.8.2.min.js"> </script>     <script type="text/javascript" src="scroll.js">     </script>       </head>  <body>    <header>        <h1>Liverpool Legends</h1>    </header>        <div id="main">        <table>        <caption>Liverpool Players</caption>        <thead>            <tr>                <th>Name</th>                <th>Photo</th>                <th>Position</th>                <th>Age</th>                <th>Scroll</th>            </tr>        </thead>        <tfoot class="footnote">            <tr>                <td colspan="4">We will add more photos soon</td>            </tr>        </tfoot>    <tbody>        <tr class="maintop">        <td>Alan Hansen</td>            <td>            <figure>            <img src="images\Alan-hansen-large.jpg" alt="Alan Hansen">            <figcaption>The best Liverpool Defender <a href="http://en.wikipedia.org/wiki/Alan_Hansen">Alan Hansen</a></figcaption>            </figure>            </td>            <td>Defender</td>            <td>57</td>            <td class="top">Middle</td>        </tr>        <tr>        <td>Graeme Souness</td>            <td>            <figure>            <img src="images\graeme-souness-large.jpg" alt="Graeme Souness">            <figcaption>Souness was the captain of the successful Liverpool team of the early 1980s <a href="http://en.wikipedia.org/wiki/Graeme_Souness">Graeme Souness</a></figcaption>            </figure>            </td>            <td>MidFielder</td>            <td>59</td>        </tr>        <tr>        <td>Ian Rush</td>            <td>            <figure>            <img src="images\ian-rush-large.jpg" alt="Ian Rush">            <figcaption>The deadliest Liverpool Striker <a href="http://it.wikipedia.org/wiki/Ian_Rush">Ian Rush</a></figcaption>            </figure>            </td>            <td>Striker</td>            <td>51</td>        </tr>        <tr class="mainmiddle">        <td>John Barnes</td>            <td>            <figure>            <img src="images\john-barnes-large.jpg" alt="John Barnes">            <figcaption>The best Liverpool Defender <a href="http://en.wikipedia.org/wiki/John_Barnes_(footballer)">John Barnes</a></figcaption>            </figure>            </td>            <td>MidFielder</td>            <td>49</td>            <td class="middle">Bottom</td>        </tr>                <tr>        <td>Kenny Dalglish</td>            <td>            <figure>            <img src="images\kenny-dalglish-large.jpg" alt="Kenny Dalglish">            <figcaption>King Kenny <a href="http://en.wikipedia.org/wiki/Kenny_Dalglish">Kenny Dalglish</a></figcaption>            </figure>            </td>            <td>Midfielder</td>            <td>61</td>        </tr>        <tr>            <td>Michael Owen</td>            <td>            <figure>            <img src="images\michael-owen-large.jpg" alt="Michael Owen">            <figcaption>Michael was Liverpool's top goal scorer from 1997–2004 <a href="http://www.michaelowen.com/">Michael Owen</a></figcaption>            </figure>            </td>            <td>Striker</td>            <td>33</td>        </tr>        <tr>            <td>Robbie Fowler</td>            <td>            <figure>            <img src="images\robbie-fowler-large.jpg" alt="Robbie Fowler">            <figcaption>Fowler scored 183 goals in total for Liverpool <a href="http://en.wikipedia.org/wiki/Robbie_Fowler">Robbie Fowler</a></figcaption>            </figure>            </td>            <td>Striker</td>            <td>38</td>        </tr>        <tr class="mainbottom">            <td>Steven Gerrard</td>            <td>            <figure>            <img src="images\steven-gerrard-large.jpg" alt="Steven Gerrard">            <figcaption>Liverpool's captain <a href="http://en.wikipedia.org/wiki/Steven_Gerrard">Steven Gerrard</a></figcaption>            </figure>            </td>            <td>Midfielder</td>            <td>32</td>            <td class="bottom">Top</td>        </tr>    </tbody></table>          </div>            <footer>        <p>All Rights Reserved</p>      </footer>     </body>  </html>  The markup is very easy to follow and understand. You do not have to type all the code,simply copy and paste it.For those that you are not familiar with HTML 5, please take a closer look at the new tags/elements introduced with HTML 5.When I view the HTML 5 page with Firefox I see the following result. I have also an external stylesheet (style.css). body{background-color:#efefef;}h1{font-size:2.3em;}table { border-collapse: collapse;font-family: Futura, Arial, sans-serif; }caption { font-size: 1.2em; margin: 1em auto; }th, td {padding: .65em; }th, thead { background: #000; color: #fff; border: 1px solid #000; }tr:nth-child(odd) { background: #ccc; }tr:nth-child(even) { background: #404040; }td { border-right: 1px solid #777; }table { border: 1px solid #777;  }.top, .middle, .bottom {    cursor: pointer;    font-size: 22px;    font-weight: bold;    text-align: center;}.footnote{text-align:center;font-family:Tahoma;color:#EB7515;}a{color:#22577a;text-decoration:none;}     a:hover {color:#125949; text-decoration:none;}  footer{background-color:#505050;width:1150px;}These are just simple CSS Rules that style the various HTML 5 tags,classes. The jQuery code that makes it all possible resides inside the scroll.js file.Make sure you type everything correctly.$(document).ready(function() {                 $('.top').click(function(){                     $('html, body').animate({                         scrollTop: $(".mainmiddle").offset().top                     },4000 );                  });                 $('.middle').click(function(){                     $('html, body').animate({                         scrollTop: $(".mainbottom").offset().top                     },4000);                  });                     $('.bottom').click(function(){                     $('html, body').animate({                         scrollTop: $(".maintop").offset().top                     },4000);                  }); });  Let me explain what I am doing here.When I click on the Middle word (  $('.top').click(function(){ ) this relates to the top class that is clicked.Then we declare the elements that we want to participate in the scrolling. In this case is html,body ( $('html, body').animate).These elements will be part of the vertical scrolling.In the next line of code we simply move (navigate) to the element (class mainmiddle that is attached to a tr element.)      scrollTop: $(".mainmiddle").offset().top  Make sure you type all the code correctly and try it for yourself. I have tested this solution will all 4-5 major browsers.Hope it helps!!!

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  • WebLogic Server JMS WLST Script – Who is Connected To My Server

    - by james.bayer
    Ever want to know who was connected to your WebLogic Server instance for troubleshooting?  An email exchange about this topic and JMS came up this week, and I’ve heard it come up once or twice before too.  Sometimes it’s interesting or helpful to know the list of JMS clients (IP Addresses, JMS Destinations, message counts) that are connected to a particular JMS server.  This can be helpful for troubleshooting.  Tom Barnes from the WebLogic Server JMS team provided some helpful advice: The JMS connection runtime mbean has “getHostAddress”, which returns the host address of the connecting client JVM as a string.  A connection runtime can contain session runtimes, which in turn can contain consumer runtimes.  The consumer runtime, in turn has a “getDestinationName” and “getMemberDestinationName”.  I think that this means you could write a WLST script, for example, to dump all consumers, their destinations, plus their parent session’s parent connection’s host addresses.    Note that the client runtime mbeans (connection, session, and consumer) won’t necessarily be hosted on the same JVM as a destination that’s in the same cluster (client messages route from their connection host to their ultimate destination in the same cluster). Writing the Script So armed with this information, I decided to take the challenge and see if I could write a WLST script to do this.  It’s always helpful to have the WebLogic Server MBean Reference handy for activities like this.  This one is focused on JMS Consumers and I only took a subset of the information available, but it could be modified easily to do Producers.  I haven’t tried this on a more complex environment, but it works in my simple sandbox case, so it should give you the general idea. # Better to use Secure Config File approach for login as shown here http://buttso.blogspot.com/2011/02/using-secure-config-files-with-weblogic.html connect('weblogic','welcome1','t3://localhost:7001')   # Navigate to the Server Runtime and get the Server Name serverRuntime() serverName = cmo.getName()   # Multiple JMS Servers could be hosted by a single WLS server cd('JMSRuntime/' + serverName + '.jms' ) jmsServers=cmo.getJMSServers()   # Find the list of all JMSServers for this server namesOfJMSServers = '' for jmsServer in jmsServers: namesOfJMSServers = jmsServer.getName() + ' '   # Count the number of connections jmsConnections=cmo.getConnections() print str(len(jmsConnections)) + ' JMS Connections found for ' + serverName + ' with JMSServers ' + namesOfJMSServers   # Recurse the MBean tree for each connection and pull out some information about consumers for jmsConnection in jmsConnections: try: print 'JMS Connection:' print ' Host Address = ' + jmsConnection.getHostAddress() print ' ClientID = ' + str( jmsConnection.getClientID() ) print ' Sessions Current = ' + str( jmsConnection.getSessionsCurrentCount() ) jmsSessions = jmsConnection.getSessions() for jmsSession in jmsSessions: jmsConsumers = jmsSession.getConsumers() for jmsConsumer in jmsConsumers: print ' Consumer:' print ' Name = ' + jmsConsumer.getName() print ' Messages Received = ' + str(jmsConsumer.getMessagesReceivedCount()) print ' Member Destination Name = ' + jmsConsumer.getMemberDestinationName() except: print 'Error retrieving JMS Consumer Information' dumpStack() # Cleanup disconnect() exit() Example Output I expect the output to look something like this and loop through all the connections, this is just the first one: 1 JMS Connections found for AdminServer with JMSServers myJMSServer JMS Connection:   Host Address = 127.0.0.1   ClientID = None   Sessions Current = 16    Consumer:      Name = consumer40      Messages Received = 1      Member Destination Name = myJMSModule!myQueue Notice that it has the IP Address of the client.  There are 16 Sessions open because I’m using an MDB, which defaults to 16 connections, so this matches what I expect.  Let’s see what the full output actually looks like: D:\Oracle\fmw11gr1ps3\user_projects\domains\offline_domain>java weblogic.WLST d:\temp\jms.py   Initializing WebLogic Scripting Tool (WLST) ...   Welcome to WebLogic Server Administration Scripting Shell   Type help() for help on available commands   Connecting to t3://localhost:7001 with userid weblogic ... Successfully connected to Admin Server 'AdminServer' that belongs to domain 'offline_domain'.   Warning: An insecure protocol was used to connect to the server. To ensure on-the-wire security, the SSL port or Admin port should be used instead.   Location changed to serverRuntime tree. This is a read-only tree with ServerRuntimeMBean as the root. For more help, use help(serverRuntime)   1 JMS Connections found for AdminServer with JMSServers myJMSServer JMS Connection: Host Address = 127.0.0.1 ClientID = None Sessions Current = 16 Consumer: Name = consumer40 Messages Received = 2 Member Destination Name = myJMSModule!myQueue Consumer: Name = consumer34 Messages Received = 2 Member Destination Name = myJMSModule!myQueue Consumer: Name = consumer37 Messages Received = 2 Member Destination Name = myJMSModule!myQueue Consumer: Name = consumer16 Messages Received = 2 Member Destination Name = myJMSModule!myQueue Consumer: Name = consumer46 Messages Received = 2 Member Destination Name = myJMSModule!myQueue Consumer: Name = consumer49 Messages Received = 2 Member Destination Name = myJMSModule!myQueue Consumer: Name = consumer43 Messages Received = 1 Member Destination Name = myJMSModule!myQueue Consumer: Name = consumer55 Messages Received = 1 Member Destination Name = myJMSModule!myQueue Consumer: Name = consumer25 Messages Received = 1 Member Destination Name = myJMSModule!myQueue Consumer: Name = consumer22 Messages Received = 1 Member Destination Name = myJMSModule!myQueue Consumer: Name = consumer19 Messages Received = 1 Member Destination Name = myJMSModule!myQueue Consumer: Name = consumer52 Messages Received = 1 Member Destination Name = myJMSModule!myQueue Consumer: Name = consumer31 Messages Received = 1 Member Destination Name = myJMSModule!myQueue Consumer: Name = consumer58 Messages Received = 1 Member Destination Name = myJMSModule!myQueue Consumer: Name = consumer28 Messages Received = 1 Member Destination Name = myJMSModule!myQueue Consumer: Name = consumer61 Messages Received = 1 Member Destination Name = myJMSModule!myQueue Disconnected from weblogic server: AdminServer     Exiting WebLogic Scripting Tool. Thanks to Tom Barnes for the hints and the inspiration to write this up. Image of telephone switchboard courtesy of http://www.JoeTourist.net/ JoeTourist InfoSystems

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  • 'Getting Started with Oracle Data Integrator 11g: A Hands-On Tutorial' book is now available

    - by Julien Testut
    We are pleased to announce the availability of the first book on Oracle Data Integrator published by Packt Publishing:  Getting Started with Oracle Data Integrator 11g – A Hands-On Tutorial Authors: Peter C. Boyd-Bowman, Christophe Dupupet, Denis Gray, David Hecksel,  Julien Testut, Bernard Wheeler. Congratulations to everyone who contributed to this book! You can get more information about 'Getting Started with Oracle Data Integrator 11g – A Hands-On Tutorial' including the table of contents and a sample chapter at http://www.packtpub.com/oracle-data-integrator-11g-getting-started/book. The book is available on Amazon.com, Amazon.co.uk, Barnes & Noble and Safari Books Online.

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  • What is the advantage to hosting static resources on a separate domain?

    - by Michael Ekstrand
    I notice a lot of sites host their resources on a separate domain from the main site, e.g. StackExchange using sstatic.net, Barnes & Noble using imagesbn.com, etc. I understand that there are benefits to putting your static resources on a separate host, possibly with an efficient static-file web server like nginx, freeing up the main server to focus on serving dynamic content. Similarly, outsourcing to a shared CDN like cloudfront Akamai is logical. What is the benefit to using a separate domain otherwise, though? Why sstatic.net instead of static.stackexchange.com? Update: Several answers miss the core question. I understand that there is benefit to splitting between multiple hosts — parallel downloads, slimmer web server, etc. But what is more elusive is why multiple domains. Why sstatic.net rather than static.stackexchange.com as the host for shared resources? So far, only one answer has addressed that.

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  • Blockbuster Time Machine

    - by David Dorf
    In another example of clinging to the core business much too long, DISH announced its closing the remaining 300 Blockbuster stores.  This reminds us that we must always be looking over our shoulders for the next big thing.  Blockbuster had the opportunity to buy Netflix, but it passed just as Barnes & Noble decided it didn't need to partner with Amazon.  Its so tempting to stick with a profitable business instead of taking a risk on a new idea.  Nevertheless, Blockbuster is history -- and this video from The Onion seals it. Historic ‘Blockbuster’ Store Offers Glimpse Of How Movies Were Rented In The Past

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  • Can my loop be optimized any more? (C++)

    - by Sagekilla
    Below is one of my inner loops that's run several thousand times, with input sizes of 20 - 1000 or more. Is there anything I can do to help squeeze any more performance out of this? I'm not looking to move this code to something like using tree codes (Barnes-Hut), but towards optimizing the actual calculations happening inside, since the same calculations occur in the Barnes-Hut algorithm. Any help is appreciated! typedef double real; struct Particle { Vector pos, vel, acc, jerk; Vector oldPos, oldVel, oldAcc, oldJerk; real mass; }; class Vector { private: real vec[3]; public: // Operators defined here }; real Gravity::interact(Particle *p, size_t numParticles) { PROFILE_FUNC(); real tau_q = 1e300; for (size_t i = 0; i < numParticles; i++) { p[i].jerk = 0; p[i].acc = 0; } for (size_t i = 0; i < numParticles; i++) { for (size_t j = i+1; j < numParticles; j++) { Vector r = p[j].pos - p[i].pos; Vector v = p[j].vel - p[i].vel; real r2 = lengthsq(r); real v2 = lengthsq(v); // Calculate inverse of |r|^3 real r3i = Constants::G * pow(r2, -1.5); // da = r / |r|^3 // dj = (v / |r|^3 - 3 * (r . v) * r / |r|^5 Vector da = r * r3i; Vector dj = (v - r * (3 * dot(r, v) / r2)) * r3i; // Calculate new acceleration and jerk p[i].acc += da * p[j].mass; p[i].jerk += dj * p[j].mass; p[j].acc -= da * p[i].mass; p[j].jerk -= dj * p[i].mass; // Collision estimation // Metric 1) tau = |r|^2 / |a(j) - a(i)| // Metric 2) tau = |r|^4 / |v|^4 real mij = p[i].mass + p[j].mass; real tau_est_q1 = r2 / (lengthsq(da) * mij * mij); real tau_est_q2 = (r2*r2) / (v2*v2); if (tau_est_q1 < tau_q) tau_q = tau_est_q1; if (tau_est_q2 < tau_q) tau_q = tau_est_q2; } } return sqrt(sqrt(tau_q)); }

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  • Creating a multi-column rollover image gallery with HTML 5

    - by nikolaosk
    I know it has been a while since I blogged about HTML 5. I have two posts in this blog about HTML 5. You can find them here and here.I am creating a small content website (only text,images and a contact form) for a friend of mine.He wanted to create a rollover gallery.The whole concept is that we have some small thumbnails on a page, the user hovers over them and they appear enlarged on a designated container/placeholder on a page. I am trying not to use Javascript scripts when I am using effects on a web page and this is what I will be doing in this post.  Well some people will say that HTML 5 is not supported in all browsers. That is true but most of the modern browsers support most of its recommendations. For people who still use IE6 some hacks must be devised.Well to be totally honest I cannot understand why anyone at this day and time is using IE 6.0.That really is beyond me.Well, the point of having a web browser is to be able to ENJOY the great experience that the WE? offers today.  Two very nice sites that show you what features and specifications are implemented by various browsers and their versions are http://caniuse.com/ and http://html5test.com/. At this times Chrome seems to support most of HTML 5 specifications.Another excellent way to find out if the browser supports HTML 5 and CSS 3 features is to use the Javascript lightweight library Modernizr.In this hands-on example I will be using Expression Web 4.0.This application is not a free application. You can use any HTML editor you like.You can use Visual Studio 2012 Express edition. You can download it here. In order to be absolutely clear this is not (and could not be ) a detailed tutorial on HTML 5. There are other great resources for that.Navigate to the excellent interactive tutorials of W3School.Another excellent resource is HTML 5 Doctor.For the people who are not convinced yet that they should invest time and resources on becoming experts on HTML 5 I should point out that HTML 5 websites will be ranked higher than others. Search engines will be able to locate better the content of our site and its relevance/importance since it is using semantic tags. Let's move now to the actual hands-on example. In this case (since I am mad Liverpool supporter) I will create a rollover image gallery of Liverpool F.C legends. I create a folder in my desktop. I name it Liverpool Gallery.Then I create two subfolders in it, large-images (I place the large images in there) and thumbs (I place the small images in there).Then I create an empty .html file called LiverpoolLegends.html and an empty .css file called style.css.Please have a look at the HTML Markup that I typed in my fancy editor package below<!doctype html><html lang="en"><head><title>Liverpool Legends Gallery</title><meta charset="utf-8"><link rel="stylesheet" type="text/css" href="style.css"></head><body><header><h1>A page dedicated to Liverpool Legends</h1><h2>Do hover over the images with the mouse to see the full picture</h2></header><ul id="column1"><li><a href="http://weblogs.asp.net/controlpanel/blogs/posteditor.aspx?SelectedNavItem=Posts§ionid=1153&postid=8927200#"><img src="thumbs/john-barnes.jpg" alt=""><img class="large" src="large-images/john-barnes-large.jpg" alt=""></a></li><li><a href="http://weblogs.asp.net/controlpanel/blogs/posteditor.aspx?SelectedNavItem=Posts§ionid=1153&postid=8927200#"><img src="thumbs/ian-rush.jpg" alt=""><img class="large" src="large-images/ian-rush-large.jpg" alt=""></a></li><li><a href="http://weblogs.asp.net/controlpanel/blogs/posteditor.aspx?SelectedNavItem=Posts§ionid=1153&postid=8927200#"><img src="thumbs/graeme-souness.jpg" alt=""><img class="large" src="large-images/graeme-souness-large.jpg" alt=""></a></li></ul><ul id="column2"><li><a href="http://weblogs.asp.net/controlpanel/blogs/posteditor.aspx?SelectedNavItem=Posts§ionid=1153&postid=8927200#"><img src="thumbs/steven-gerrard.jpg" alt=""><img class="large" src="large-images/steven-gerrard-large.jpg" alt=""></a></li><li><a href="http://weblogs.asp.net/controlpanel/blogs/posteditor.aspx?SelectedNavItem=Posts§ionid=1153&postid=8927200#"><img src="thumbs/kenny-dalglish.jpg" alt=""><img class="large" src="large-images/kenny-dalglish-large.jpg" alt=""></a></li><li><a href="http://weblogs.asp.net/controlpanel/blogs/posteditor.aspx?SelectedNavItem=Posts§ionid=1153&postid=8927200#"><img src="thumbs/robbie-fowler.jpg" alt=""><img class="large" src="large-images/robbie-fowler-large.jpg" alt=""></a></li></ul><ul id="column3"><li><a href="http://weblogs.asp.net/controlpanel/blogs/posteditor.aspx?SelectedNavItem=Posts§ionid=1153&postid=8927200#"><img src="thumbs/alan-hansen.jpg" alt=""><img class="large" src="large-images/alan-hansen-large.jpg" alt=""></a></li><li><a href="http://weblogs.asp.net/controlpanel/blogs/posteditor.aspx?SelectedNavItem=Posts§ionid=1153&postid=8927200#"><img src="thumbs/michael-owen.jpg" alt=""><img class="large" src="large-images/michael-owen-large.jpg" alt=""></a></li></ul></body></html> It is very easy to follow the markup. Please have a look at the new doctype and the new semantic tag <header>. I have 3 columns and I place my images in there.There is a class called "large".I will use this class in my CSS code to hide the large image when the mouse is not on (hover) an image Make sure you validate your HTML 5 page in the validator found hereHave a look at the CSS code below that makes it all happen.img { border:none;}#column1 { position: absolute; top: 30; left: 100; }li { margin: 15px; list-style-type:none;}#column1 a img.large {  position: absolute; top: 0; left:700px; visibility: hidden;}#column1 a:hover { background: white;}#column1 a:hover img.large { visibility:visible;}#column2 { position: absolute; top: 30; left: 195px; }li { margin: 5px; list-style-type:none;}#column2 a img.large { position: absolute; top: 0; left:510px; margin-left:0; visibility: hidden;}#column2 a:hover { background: white;}#column2 a:hover img.large { visibility:visible;}#column3 { position: absolute; top: 30; left: 400px; width:108px;}li { margin: 5px; list-style-type:none;}#column3 a img.large { width: 260px; height:260px; position: absolute; top: 0; left:315px; margin-left:0; visibility: hidden;}#column3 a:hover { background: white;}#column3 a:hover img.large { visibility:visible;}?n the first line of the CSS code I set the images to have no border.Then I place the first column in the page and then remove the bullets from the list elements.Then I use the large CSS class to create a position for the large image and hide it.Finally when the hover event takes place I make the image visible.I repeat the process for the next two columns. I have tested the page with IE 10 and the latest versions of Opera,Chrome and Firefox.Feel free to style your HTML 5 gallery any way you want through the magic of CSS.I did not bother adding background colors and borders because that was beyond the scope of this post. Hope it helps!!!!

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  • A Look Back at 2010 Predictions

    - by David Dorf
    Now is the time of year people make their predictions for next year, but before I start thinking about 2011 it's worth a look back to see how my predictions for 2010 fared. 1. Borders and Blockbuster bite the dust. I would have never predicted a strong brand such as Circuit City could die, but now I know it can happen to anyone. Borders has lost the battle with Barnes & Noble and Blockbuster has lost to Netflix. And just to be sure, Amazon put an extra nail in each coffin. Borders received additional investment from Bennett LeBow to keep it afloat, but the stock is down around $1.25 with no profits in sight. Blockbuster filed for bankruptcy back in September. 2. Every retailer finally has a page on Facebook... but very few figure out how to keep fans engaged. Retailer postings become noise, and fans start to unsubscribe. Twitter goes in the same direction. A few standout retailers will figure out how to use social media, and the rest will remain dumbfounded. Most retailers are on the Facebook bandwagon, and their fan bases seem to be increasing thanks to promotions like The Gap's logo redesign, Lowes' black Friday sneak peak, and Walmart's Crowd Savers. There are several examples of f-commerce advancements, including some interesting integrations from Amazon.3. Smartphones consolidate and grow. More and more people will step-up to smartphones, most of which will choose iPhone, Blackberry, and Android phones. Other smartphones will vanish, and networks will start to strain. But retailers will finally embrace mobile as the next big channel. Retail marketing departments will build mobile apps without the help of their IT department, and eventually they will get into a bind. Android has been on a tear lately stealing market share from Blackberry. Palm and Microsoft are trending down, and Apple is holding steady. Smartphone sales are up 15% and expected to continue. Retailers understand the importance of mobile, and some innovative applications have been produced this year. 4. Google helps the little guys. Google will push its Favorite Places project to help give exposure to small retailers and restaurants. They will enable small retailers to act like big ones by providing storefronts, detailed product information, and coupons for consumers. Google will find a way to bring augmented reality to the masses. I can't say I've seen much new from Google regarding Favorite Places, but they've continued to push local product search. From the PC or smartphone, consumers can search for products and see which nearby stores have it stock. Oracle Retail even productized an integration to Google to support this effort. I suppose if Google ever buys Groupon then it will bring them even closer to local shopping. Google talked about augmented humanity, but that has nothing to do with augmented reality. 5. Steve Jobs Is Bugs Bunny and Steve Ballmer is Elmer Fudd. (OK, I stole that headline from an InformationWeek article. I couldn't resist.) Both Apple and Microsoft will continue to open new stores, but only Apple will show real growth. POSReady 2009 (formerly WEPOS) will continue to share the POS market with Linux. The iPhone and iPod will continue to capture market share, but there won't be an Apple tablet. There won't be an Apple tablet? What was I thinking? While Apple has well over 300 stores, there are less than 10 Microsoft stores. Initial impressions show that even though Microsoft is locating its store near Apple Stores, they are not converting customers, with shoppers citing a lack of assortment and high prices. 6. Consolidation of e-commerce software providers. Software vendors in the areas of search, reviews, online call-centers, payments, and e-commerce will consolidate, partly driven by the success of m-commerce and SaaS. Amazon will find someone else to buy, and eBay will continue to lose momentum. Consolidation of e-commerce providers continued with IBM acquiring Sterling Commerce and CoreMetrics, and Oracle recently announcing the acquisition of ATG. Amazon grabbed Zappos, Woot, and Diapers.com to continue its dominance of online selling. While eBay's Marketplace growth may have slowed, its PayPal division is doing quite well, fueled in part by demand for mobile payments. 7. Book publishers mirror music labels. Just as the iPod brought digital downloads to the masses, the Kindle and Nook will power the e-book revolution. Books will continue to use DRM for a few more years before following the path of music. Publishers will try to preserve the margins of hardbacks by associating e-book releases with paperbacks. Amazon has done a good job providing e-reader clients for smartphones, PCs, and tablets. Competition from Barnes & Noble has forced Amazon to support book loaning, and both companies are making it easier for people to publish ebooks (with or without DRM). Progress is slow but steady. 8. NFC makes inroads, RFID treads water. Near Field Communications start to appear in mobile phones, and retailers beta test its use for payments and loyalty programs. RFID tag costs come down a bit, but not enough to spur accelerated adoption.Nokia announced plans to offer NFC-enabled phones in 2011, and rumors are swirling about NFC in the upcoming iPhone.  I think NFC is heading in the right direction, and I've heard more interest from retailers about specialized uses for RFID.9. Digital Signage goes the way of augmented reality. People use their camera phones to leave geo-tagged notes all over cities, rating stores and restaurants, and "painting" graffiti. But people get tired of holding their phones in front of their faces, so AR glasses are offered in much the same way bluetooth headsets emerged. Retailers experiement with in-store advertising using AR. Several retailers like Pizza Hut, Benetton, and Target have experimented with AR but its still somewhat of a gimmick used by marketing.  I think this prediction is a year or two too early. 10. JDA flip-flops again. After announcing their embracing of the .Net architecture, then switching to J2EE after the Manugistics acquisition, JDA will finally decide to standardize on Apple's Objective C. Everything will be ported to the iPhone and be available on the AppStore. After all, there's not much left to try. This was, of course, a joke but the sentiment is still valid.  JDA seems more supply-chain focused than retail focused, which is a an outcrop if their i2 acquisition.  Of the 10 predictions, I'm going to say I got 6 somewhat correct.  (Don't you just love grading your own paper?)  Soon I'll post my predictions for 2011 so be on the lookout.  Until then here's one more prediction:  Va Tech beats Stanford in the Orange Bowl -- count on it!

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  • Where are those crapware desktop icons located?

    - by an00b
    My new Acer Aspire One netbook came pre-installed with Windows 7 Starter and lots of other promotional software. Some of them (like Norton and McAfee) I uninstalled immediately. Others (like the Barnes & Notble Desktop Reader and the Times Reader) I would like to keep until I see whether they can be useful). Regardless, I would like to remove their desktop icons (making them accessible through the Start menu only), in such a way that when I add another user account, these desktop icons will not appear on that user's desktop. But when I checked my desktop folder C:\Users\an00b\Desktop I noticed that it's empty! So my desktop's folder is empty, but the icons are still visible on the Desktop. How is this possible? Where are they stored in Windows 7? These applications fill my tiny netbook's desktop and when I wanted to delete

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