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  • How do I pass an array to a method?

    - by ambidextorous
    Hey, I have not been able to find a proper answer on any forums about this. But how exactly do I pass an array to a class constructor? public class TestArray { String name; String[] array; public TestArray(String name, String[] anArray){ this.name = name; int len = anArray.length; this.array = new String[len]; for (int i = 0; i < len; i++) { this.array[i] = new String(anArray[i]); } } public static void main(String[] args){ String[] anArray = new String[2]; anArray[0] = new String("Test"); anArray[1] = new String("Test2"); TestArray work = new TestArray("Jordan", anArray); // How to pass the array? } }

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  • I'm new to Java most basic question about arrays!

    - by ambidextorous
    Hey I have not been able to find a proper answer on any forums about this but how exactly do I pass an array to a class? public class TestArray { String name; String[] array; public TestArray(String name, String[] anArray){ this.name = name; int len = anArray.length; this.array = new String[len]; for (int i = 0; i < len; i++){ this.array[i] = new String(anArray[i]); } } } public static void main(String[] args){ String[] anArray = new String[2]; anArray[0] = new String("Test"); anArray[1] = new String("Test2"); TestArray work = new TestArray("Jordan", anArray?); } }

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  • Sort a list numerically in Python

    - by Matthew
    So I have this list, we'll call it listA. I'm trying to get the [3] item in each list e.g. ['5.01','5.88','2.10','9.45','17.58','2.76'] in sorted order. So the end result would start the entire list over again with Santa at the top. Does that make any sense? [['John Doe', u'25.78', u'20.77', '5.01'], ['Jane Doe', u'21.08', u'15.20', '5.88'], ['James Bond', u'20.57', u'18.47', '2.10'], ['Michael Jordan', u'28.50', u'19.05', '9.45'], ['Santa', u'31.13', u'13.55', '17.58'], ['Easter Bunny', u'17.20', u'14.44', '2.76']]

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  • Silverlight Cream for April 07, 2010 -- #833

    - by Dave Campbell
    In this Issue: Alan Mendelevich, Siyamand Ayubi, Rudi Grobler(-2-), Josh Smith, VinitYadav, and Dave Campbell. Shoutouts: Jordan Knight has a demo up of a project he did for DigiGirlz: DigiGirlz, Deep Zoom and Azure, hopefully we'll get source later :) Jeremy Likness has a must-read post on his Ten Reasons to use the Managed Extensibility Framework I put this on another post earlier, but if you want some desktop bling for WP7, Ozymandias has some: I Love Windows Phone Wallpaper If you're not going to be in 'Vegas next week, Tim Heuer reminds us there's an alternative: Watch the Silverlight 4 Launch event and LIVE QA with ScottGu and others From SilverlightCream.com: Ghost Lines in Silverlight Alan Mendelevich reports an issue when drawing lines with odd coordinate values. He originated it in Silverlight 3, but it is there in SL4RC as well... check it out and leave him a comment. A Framework to Animate WPF and Silverlight Pages Similar to the PowerPoint Slides Siyamand Ayubi has an interesting post up on animating WPF or Silverlight pages to make them progress in the manner of a PPT slideshow. And it can also make phone calls… Rudi Grobler has a list of 'tasks' you can do with WP7 such as PhoneCallTask or EmailComposeTask ... looks like this should be plasticized :) Using the GPS, Accelerometer & Vibration Controller Rudi Grobler is also investigating how to use the GPS, Accelerometer, and Vibration in WP7 with a bunch of external links to back it up. Assembly-level initialization at design time Josh Smith has a solution to the problem of initializing design-time data in Blend (did you know that was an issue?) ... the solution is great and so is the running commentary between Josh and Karl Shifflett in the comments! ySurf : A Yahoo Messenger Clone built in Silverlight VinitYadav built a Yahoo Messenger app in Silverlight and has detailed out all the ugly bits for us on the post, plus made everything available. Your First Silverlight Application Dave Campbell's first post at DZone cracking open a beginner's series on Silverlight. If you're expecting something heavy-duty, skip this. If you're wanting to learn Silverlight and haven't jumped in yet, give it a try. Stay in the 'Light! Twitter SilverlightNews | Twitter WynApse | WynApse.com | Tagged Posts | SilverlightCream Join me @ SilverlightCream | Phoenix Silverlight User Group Technorati Tags: Silverlight    Silverlight 3    Silverlight 4    Windows Phone MIX10

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  • Speed up your Silverlight Debugging for large projects

    - by Aligned
    I'm working on a 5+ year old ASP.NET project that has 74+ projects and we've been adding new Silverlight applications to run in the ASP.NET page islands. My machine at work isn't the most powerful, so I find myself waiting a lot for the whole thing to build. I'm using Visual Studio 2010, so that takes up a lot of resources as well. This causes me to get distracted and I start looking at the news... I need to combat that more :-). I can't get a new machine, that's up to someone else, so I've found a few tricks to help. 1. Only build the Silverlight project you're working with. This will build all referenced projects (you can see these by right clicking and clicking Project Dependencies) and package a new XAP (you can see all the actions in your output build window). Then refresh your page with the Silverlight app and it's up-to-date. 2. I was working with a co-worker (thanks Jordan) who was using the the Debug -> attach to processes window. In the Attach to: row there is a "Select..." button. In the dialog, click "Debug these code types:" and select Silverlight. Hit ok. Then all you need to do is find your process (you might need to click the refresh button). I'm usually debugging in IE, so I select the first one and push "i" on the keyboard. That brings me to the IE windows open. Find the one with type of Silverlight, x86. It is usually directly above one with type of x86 that has the page title for "title". Click attach and watch your output window spit out messages about loading debug symbols and your breakpoints enabled (if this doesn't happen you chose the wrong process, hit stop and try again). Now you can debug the client code as normal, server code requires a full F5 or attaching to the correct process. To improve this even further, bind the menu item to a key stroke. I chose ctrl + x, x. (Tools -> Options -> Keyboard, search for Debug.AttachToProcess, set the shortcut keys globaly and assign). Most of the time I build the project, then hit ctrl + x, x then i, then enter and I'm debugging. The process I want is usually the first IE in the list.

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  • Podcast Show Notes: Collaborate 10 Wrap-Up - Part 1

    - by Bob Rhubart
    OK, I know last week I promised you a program featuring Oracle ACE Directors Mike van Alst (IT-Eye) and Jordan Braunstein (TUSC) and The Definitive Guide to SOA: Oracle Service Bus author Jeff Davies. But things happen. In this case, what happened was Collaborate 10 in Las Vegas. Prior to the event I asked Oracle ACE Director and OAUG board member Floyd Teter to see if he could round up a couple of people at the event for an impromtu interview over Skype (I was here in Cleveland) to get their impressions of the event. Listen to Part 1 Floyd, armed with his brand new iPad, went above and beyond the call of duty. At the appointed hour, which turned out to be about hour after the close of Collaborate 10,  Floyd had gathered nine other people to join him in a meeting room somewhere in the Mandalay Bay Convention Center. Here’s the entire roster: Floyd Teter - Project Manager at Jet Propulsion Lab, OAUG Board Blog | Twitter | LinkedIn | Oracle Mix | Oracle ACE Profile Mark Rittman - EMEA Technical Director and Co-Founder, Rittman Mead,  ODTUG Board Blog | Twitter | LinkedIn | Oracle Mix | Oracle ACE Profile Chet Justice - OBI Consultant at BI Wizards Blog | Twitter | LinkedIn | Oracle Mix | Oracle ACE Profile Elke Phelps - Oracle Applications DBA at Humana, OAUG SIG Chair Blog | LinkedIn | Oracle Mix | Book | Oracle ACE Profile Paul Jackson - Oracle Applications DBA at Humana Blog | LinkedIn | Oracle Mix | Book Srini Chavali - Enterprise Database & Tools Leader at Cummins, Inc Blog | LinkedIn | Oracle Mix Dave Ferguson – President, Oracle Applications Users Group LinkedIn | OAUG Profile John King - Owner, King Training Resources Website | LinkedIn | Oracle Mix Gavyn Whyte - Project Portfolio Manager at iFactory Consulting Blog | Twitter | LinkedIn | Oracle Mix John Nicholson - Channels & Alliances at Greenlight Technologies Website | LinkedIn Big thanks to Floyd for assembling the panelists and handling the on-scene MC/hosting duties.  Listen to Part 1 On a technical note, this discussion was conducted over Skype, using Floyd’s iPad, placed in the middle of the table.  During the call the audio was fantastic – the iPad did a remarkable job. Sadly, the Technology Gods were not smiling on me that day. The audio set-up that I tested successfully before the call failed to deliver when we first connected – I could hear the folks in Vegas, but they couldn’t hear me. A frantic, last-minute adjustment appeared to have fixed that problem, and the audio in my headphones from both sides of the conversation was loud and clear.  It wasn’t until I listened to the playback that I realized that something was wrong. So the audio for Vegas side of the discussion has about the same fidelity as a cell phone. It’s listenable, but disappointing when compared to what it sounded like during the discussion. Still, this was a one shot deal, and the roster of panelists and the resulting conversation was too good and too much fun to scrap just because of an unfortunate technical glitch.   Part 2 of this Collaborate 10 Wrap-Up will run next week. After that, it’s back on track with the previously scheduled program. So stay tuned: RSS del.icio.us Tags: oracle,otn,collborate 10,c10,oracle ace program,archbeat,arch2arch,oaug,odtug,las vegas Technorati Tags: oracle,otn,collborate 10,c10,oracle ace program,archbeat,arch2arch,oaug,odtug,las vegas

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  • Evaluating Solutions to Manage Product Compliance? Don’t Wait Much Longer

    - by Evelyn Neumayr
    By Kerrie Foy, Director PLM Product Marketing, Oracle Depending on severity, product compliance issues can cause various problems from run-away budgets to business closures. But effective policies and safeguards can create a strong foundation for innovation, productivity, market penetration and competitive advantage. If you’ve been putting off a systematic approach to product compliance, it is time to reconsider that decision. Why now?  No matter what industry, companies face a litany of worldwide and regional regulations that require proof of product compliance and environmental friendliness for market access.  For example, Restriction of Hazardous Substances (RoHS), a regulation that restricts the use of six dangerous materials used in the manufacture of electronic and electrical equipment, was originally adopted by the European Union in 2003 for implementation in 2006 and has evolved over time through various regional versions for North America, China, Japan, Korea, Norway and Turkey. In addition, the RoHS directive allowed for material exemptions used in Medical Devices, but that exemption ends in 2014. Additional regulations worth watching are the Battery Directive, Waste Electrical and Electronic Equipment (WEEE), and Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) directives. Additional regulations are expected from organizations such as the Food and Drug Administration in the US and similar organizations elsewhere. Meeting compliance requirements and also successfully investing in eco-friendly designs can be a major challenge. It may involve transforming business models, go-to-market strategies, supply networks, quality assurance policies and compliance processes.  Without a single source of truth for product data and without proper processes in place, ensuring product compliance burgeons into a crushing task that is cost-prohibitive and overwhelming.  However, the risk to consumer goodwill and satisfaction, revenue, business continuity, and market potential is too great not to solve the compliance challenge. Companies are beginning to adapt and thrive by implementing systematic approaches to product compliance that are more than functional bandages, they are revenue-generating engines. Consider working with Oracle to help you address your compliance needs. Many of the world’s most innovative leaders and pioneers are leveraging Oracle’s Agile Product Lifecycle Management (PLM) portfolio of enterprise applications to manage the product value chain, centralize product data, automate processes, and launch more eco-friendly products to market faster.   Particularly, the Agile Product Governance & Compliance (PG&C) solution provides out-of-the-box functionality to integrate actionable regulatory information into the enterprise product record from the ideation to the disposal/recycling phase.  Agile PG&C is a comprehensive solution that makes product compliance per corporate initiatives and regulations more reliable and efficient. Throughout product lifecycles, use the solution to support full material disclosures, gain rapid visibility into non-compliance issues, efficiently manage declarations with your suppliers, feed compliance data into a corrective action if a product must be changed, and swiftly satisfy audits by showing all due diligence tracked in one solution. Given the compounding regulation and consumer focus on urgent environmental issues, now is the time to act. Implementing an enterprise-wide systematic approach to product compliance is a competitive investment. From the start, Agile PG&C enables companies to confidently design for compliance and sustainability, reduce the cost of compliance, minimize the risk of business interruption, deliver responsible products, and inspire new innovation.  Don’t wait any longer! To find out more about Agile Product Governance & Compliance download the data sheet, contact your sales representative, or call Oracle at 1-800-633-0738.

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  • XNA Notes 005

    - by George Clingerman
    Another week and another crazy amount of activity going on in the XNA community. I’m fairly certain I missed over half of it. In fact, if I am missing things, make sure to email me and I’ll try and make sure I catch it next week! ([email protected]). Also, if you’ve got any advice, things you like/don’t like about the way these XNA Notes are going let me know. I always appreciate feedback (currently spammers are leaving me the nicest comments so you guys have work to do!) Without further ado, here’s this week’s notes! Time Critical XNA News The XNA Team Blob reminds us that February 7th is the last day to submit XNA 3.1 games to peer review! http://blogs.msdn.com/b/xna/archive/2011/01/31/7-days-left-to-submit-xna-gs-3-1-games-on-app-hub.aspx XNA MVPS Chris Williams kicks off the marketing campaign for our book http://geekswithblogs.net/cwilliams/archive/2011/01/28/143680.aspx Catalin Zima posts the comparison cheat sheet for why Angry Birds is different than Chickens Can’t Fly http://www.amusedsloth.com/2011/02/comparison-cheat-sheet-for-chickens-cant-fly-and-angry-birds/ Jim Perry congratulates the developers selected by Game Developer Magazine for Best Xbox LIVE Indie Games of 2010 http://machxgames.com/blog/?p=24 @NemoKrad posts his XNAKUUG talks for all to enjoy http://twitter.com/NemoKrad/statuses/33142362502864896 http://xna-uk.net/blogs/randomchaos/archive/2011/02/03/xblig-uk-2011-january-amp-february-talk.aspx George  (that’s me!) preps for his XNA talk coming up on the 8th http://twitter.com/clingermangw/statuses/32669550554124288 http://www.portlandsilverlight.net/Meetings/Details/15 XNA Developers FireFly posts the last tutorial in his XNA Tower Defense tutorial series http://forums.create.msdn.com/forums/p/26442/451460.aspx#451460 http://xnatd.blogspot.com/2011/01/tutorial-14-polishing-game.html @fredericmy posts the main difference when porting a game from Windows Phone 7 to Xbox 360 http://fairyengine.blogspot.com/2011/01/main-differences-when-porting-game-from.html @ElementCy creates a pretty rad video of a MineCraft type terrain created using XNA http://www.youtube.com/watch?v=Waw1f7wnl9I Andrew Russel gets the first XNA badge on gamedev.stackexchange http://twitter.com/_AndrewRussell/statuses/32322877004972032 http://gamedev.stackexchange.com/badges?tab=tags And his funding for ExEn has passed $7000 only $3000 to go http://twitter.com/_AndrewRussell/statuses/33042412804771840 Subodh Pushpak blogs about his Windows Phone 7 XNA talk http://geekswithblogs.net/subodhnpushpak/archive/2011/02/01/windows-phone-7-silverlight--xna-development-talk.aspx Slyprid releases the latest version of Transmute and needs more people to test http://twitter.com/slyprid/statuses/32452488418299904 http://forgottenstarstudios.com/ SpynDoctorGames celebrates the 1 year anniversary of Your Doodles Are Bugged! Congrats! http://twitter.com/SpynDoctorGames/statuses/32511689068908544 Noogy (creator of Dust the Elysian Tail) prepares his conversion to XNA 4.0 http://twitter.com/NoogyTweet/statuses/32522008449253376 @philippedasilva posts about the Indiefreaks Game Framework v0.2.0.0 Input management system http://twitter.com/philippedasilva/statuses/32763393957957632 http://indiefreaks.com/2011/02/02/behind-smart-input-system-feature/ Mommy’s Best Games debates what to do about High Scores with their new update http://mommysbest.blogspot.com/2011/02/high-score-shake-up.html @BinaryTweedDeej want to know if there’s anything the community needs to make XNA games for the PC. Give him some feedback! http://twitter.com/BinaryTweedDeej/status/32895453863354368 @mikebmcl promises to write us all a book (I can’t wait to read it!) http://twitter.com/mikebmcl/statuses/33206499102687233 @werezompire is going to live, LIVE, thanks to all the generosity and support from the community! http://twitter.com/werezompire/statuses/32840147644977153 Xbox LIVE Indie Games (XBLIG) Making money in Xbox 360 indie game development. Is it possible? http://www.bitmob.com/articles/making-money-in-xbox-360-indie-game-development-is-it-possible @AlejandroDaJ posts some thoughts abut the bitmob article http://twitter.com/AlejandroDaJ/statuses/31068552165330944 http://www.apathyworks.com/blog/view.php?id=00215 Kobun gets my respect as an XBLIG champion. I’m not sure who Kobun is, but if you’ve every read through the comment sections any time Kotaku writes about XBLIGs you’ll see a lot of confusion, disinformation in there. Kobun has been waging a secret war battling that lack of knowledge and he does it well. Also he’s running a pretty kick ass site for Xbox LIVE Indie Game reviews http://xboxindies.teamkobun.com/ @radiangames releases his last Xbox LIVE Indie Game...for now http://bit.ly/gMK6lE Playing Avaglide with the Kinect controller http://www.youtube.com/watch?v=UqAYbHww53o http://www.joystiq.com/2011/01/30/kinect-hacks-take-to-the-skies-with-avaglide/ Luke Schneider of Radiangames interviewed in Edge magazine http://www.next-gen.biz/features/radiangames-venture Digital Quarters posts thoughts on why XBLIG’s online requirement kills certain genres http://digitalquarters.blogspot.com/2011/02/thoughts-why-xbligs-online-requirement.html Mommy’s Best Games shares the news that several XBLIGs were featured in the March 2011 issue of Famitsu 360 http://forums.create.msdn.com/forums/p/33455/451487.aspx#451487 NaviFairy continues with his Indie-Game-A-Day http://gaygamer.net/2011/02/indie_game_a_day_epic_dungeon.html http://gaygamer.net/2011/02/indie_game_a_day_break_limit_r.html and more every day...that’s kind of the point! Keep your eye on this series! VVGTV continues with it’s awesome reviews/promotions for XBLIGs http://vvgtv.com/ http://vvgtv.com/2011/02/03/iredia-atrams-secret-xblig-review-2/ http://vvgtv.com/2011/02/02/poopocalypse-coming-soon-to-xblig/ ….and even more, you get the point. Magicka is an Indie Game doing really well on Steam AND it’s made using XNA http://www.magickagame.com/ http://twitter.com/Magickagame/statuses/32712762580799488 GameMarx reviews Antipole http://www.gamemarx.com/reviews/73/antipole-is-vvvvvvery-good.aspx Armless Octopus review Alpha Squad http://www.armlessoctopus.com/2011/01/28/xbox-indie-review-alpha-squad/ An interesting article about Kodu that Jim Perry found http://twitter.com/MachXGames/statuses/32848044105924608 http://www.develop-online.net/news/36915/10-year-old-Jordan-makes-games-The-UK-needs-more-like-her XNA Game Development Sgt. Conker posts about the Natur beta, a new book and whether you can make money with XBLIG http://www.sgtconker.com/ http://www.sgtconker.com/2011/01/a-new-book-on-the-block-and-a-new-natur-beta/ http://www.sgtconker.com/2011/01/making-money-in-xbox-360-indie-game-development-is-it-possible/ Tips for setting up SVN http://bit.ly/fKxgFh @bsimser found tons of royalty free music and soundfx for your XNA Games http://twitter.com/bsimser/statuses/31426632933711872 Post on the new features in the next Sunburn Editor http://www.synapsegaming.com/blogs/fivesidedbarrel/archive/2011/01/28/new-editor-features-prefabs-components-and-more.aspx @jasons_novaleaf posts source code for light pre-pass optimizations for #xna http://twitter.com/jasons_novaleaf/statuses/33348855403642880 http://jcoluna.wordpress.com/2011/02/01/xna-4-0-light-pre-pass-optimization-round-one/ I’ve been learning about doing an A.I. for turn based games and this article was a great resource. http://www.gamasutra.com/view/feature/1535/designing_ai_algorithms_for_.php?print=1

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  • How to create a database deadlock using jdbc and JUNIT

    - by Isawpalmetto
    I am trying to create a database deadlock and I am using JUnit. I have two concurrent tests running which are both updating the same row in a table over and over again in a loop. My idea is that you update say row A in Table A and then row B in Table B over and over again in one test. Then at the same time you update row B table B and then row A Table A over and over again. From my understanding this should eventually result in a deadlock. Here is the code For the first test. public static void testEditCC() { try{ int rows = 0; int counter = 0; int large=10000000; Connection c=DataBase.getConnection(); while(counter<large) { int pid = 87855; int cCode = 655; String newCountry="Egypt"; int bpl = 0; stmt = c.createStatement(); rows = stmt.executeUpdate("UPDATE main " + //create lock on main table "SET BPL="+cCode+ "WHERE ID="+pid); rows = stmt.executeUpdate("UPDATE BPL SET DESCRIPTION='SomeWhere' WHERE ID=602"); //create lock on bpl table counter++; } assertTrue(rows == 1); //rows = stmt.executeUpdate("Insert into BPL (ID, DESCRIPTION) VALUES ("+cCode+", '"+newCountry+"')"); } catch(SQLException ex) { ex.printStackTrace(); //ex.getMessage(); } } And here is the code for the second test. public static void testEditCC() { try{ int rows = 0; int counter = 0; int large=10000000; Connection c=DataBase.getConnection(); while(counter<large) { int pid = 87855; int cCode = 655; String newCountry="Jordan"; int bpl = 0; stmt = c.createStatement(); //stmt.close(); rows = stmt.executeUpdate("UPDATE BPL SET DESCRIPTION='SomeWhere' WHERE ID=602"); //create lock on bpl table rows = stmt.executeUpdate("UPDATE main " + //create lock on main table "SET BPL="+cCode+ "WHERE ID="+pid); counter++; } assertTrue(rows == 1); //rows = stmt.executeUpdate("Insert into BPL (ID, DESCRIPTION) VALUES ("+cCode+", '"+newCountry+"')"); } catch(SQLException ex) { ex.printStackTrace(); } } I am running these two separate JUnit tests at the same time and am connecting to an apache Derby database that I am running in network mode within Eclipse. Can anyone help me figure out why a deadlock is not occurring? Perhaps I am using JUnit wrong.

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  • Point in polygon OR point on polygon using LINQ

    - by wageoghe
    As noted in an earlier question, How to Zip enumerable with itself, I am working on some math algorithms based on lists of points. I am currently working on point in polygon. I have the code for how to do that and have found several good references here on SO, such as this link Hit test. So, I can figure out whether or not a point is in a polygon. As part of determining that, I want to determine if the point is actually on the polygon. This I can also do. If I can do all of that, what is my question you might ask? Can I do it efficiently using LINQ? I can already do something like the following (assuming a Pairwise extension method as described in my earlier question as well as in links to which my question/answers links, and assuming a Position type that has X and Y members). I have not tested much, so the lambda might not be 100% correct. Also, it does not take very small differences into account. public static PointInPolygonLocation PointInPolygon(IEnumerable<Position> pts, Position pt) { int numIntersections = pts.Pairwise( (p1, p2) => { if (p1.Y != p2.Y) { if ((p1.Y >= pt.Y && p2.Y < pt.Y) || (p1.Y < pt.Y && p2.Y >= pt.Y)) { if (p1.X < p1.X && p2.X < pt.X) { return 1; } if (p1.X < pt.X || p2.X < pt.X) { if (((pt.Y - p1.Y) * ((p1.X - p2.X) / (p1.Y - p2.Y)) * p1.X) < pt.X) { return 1; } } } } return 0; }).Sum(); if (numIntersections % 2 == 0) { return PointInPolygonLocation.Outside; } else { return PointInPolygonLocation.Inside; } } This function, PointInPolygon, takes the input Position, pt, iterates over the input sequence of position values, and uses the Jordan Curve method to determine how many times a ray extended from pt to the left intersects the polygon. The lambda expression will yield, into the "zipped" list, 1 for every segment that is crossed, and 0 for the rest. The sum of these values determines if pt is inside or outside of the polygon (odd == inside, even == outside). So far, so good. Now, for any consecutive pairs of position values in the sequence (i.e. in any execution of the lambda), we can also determine if pt is ON the segment p1, p2. If that is the case, we can stop the calculation because we have our answer. Ultimately, my question is this: Can I perform this calculation (maybe using Aggregate?) such that we will only iterate over the sequence no more than 1 time AND can we stop the iteration if we encounter a segment that pt is ON? In other words, if pt is ON the very first segment, there is no need to examine the rest of the segments because we have the answer. It might very well be that this operation (particularly the requirement/desire to possibly stop the iteration early) does not really lend itself well to the LINQ approach. It just occurred to me that maybe the lambda expression could yield a tuple, the intersection value (1 or 0 or maybe true or false) and the "on" value (true or false). Maybe then I could use TakeWhile(anontype.PointOnPolygon == false). If I Sum the tuples and if ON == 1, then the point is ON the polygon. Otherwise, the oddness or evenness of the sum of the other part of the tuple tells if the point is inside or outside.

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  • Speeding up a search .net 4.0

    - by user231465
    Wondering if I can speed up the search. I need to build a functionality that has to be used by many UI screens The one I have got works but I need to make sure I am implementing a fast algoritim if you like It's like an incremental search. User types a word to search for eg const string searchFor = "Guinea"; const char nextLetter = ' ' It looks in the list and returns 2 records "Guinea and Guinea Bissau " User types a word to search for eg const string searchFor = "Gu"; const char nextLetter = 'i' returns 3 results. This is the function but I would like to speed it up. Is there a pattern for this kind of search? class Program { static void Main() { //Find all countries that begin with string + a possible letter added to it //const string searchFor = "Guinea"; //const char nextLetter = ' '; //returns 2 results const string searchFor = "Gu"; const char nextLetter = 'i'; List<string> result = FindPossibleMatches(searchFor, nextLetter); result.ForEach(x=>Console.WriteLine(x)); //returns 3 results Console.Read(); } /// <summary> /// Find all possible matches /// </summary> /// <param name="searchFor">string to search for</param> /// <param name="nextLetter">pretend user as just typed a letter</param> /// <returns></returns> public static List<string> FindPossibleMatches (string searchFor, char nextLetter) { var hashedCountryList = new HashSet<string>(CountriesList()); var result=new List<string>(); IEnumerable<string> tempCountryList = hashedCountryList.Where(x => x.StartsWith(searchFor)); foreach (string item in tempCountryList) { string tempSearchItem; if (nextLetter == ' ') { tempSearchItem = searchFor; } else { tempSearchItem = searchFor + nextLetter; } if(item.StartsWith(tempSearchItem)) { result.Add(item); } } return result; } /// <summary> /// Returns list of countries. /// </summary> public static string[] CountriesList() { return new[] { "Afghanistan", "Albania", "Algeria", "American Samoa", "Andorra", "Angola", "Anguilla", "Antarctica", "Antigua And Barbuda", "Argentina", "Armenia", "Aruba", "Australia", "Austria", "Azerbaijan", "Bahamas", "Bahrain", "Bangladesh", "Barbados", "Belarus", "Belgium", "Belize", "Benin", "Bermuda", "Bhutan", "Bolivia", "Bosnia Hercegovina", "Botswana", "Bouvet Island", "Brazil", "Brunei Darussalam", "Bulgaria", "Burkina Faso", "Burundi", "Byelorussian SSR", "Cambodia", "Cameroon", "Canada", "Cape Verde", "Cayman Islands", "Central African Republic", "Chad", "Chile", "China", "Christmas Island", "Cocos (Keeling) Islands", "Colombia", "Comoros", "Congo", "Cook Islands", "Costa Rica", "Cote D'Ivoire", "Croatia", "Cuba", "Cyprus", "Czech Republic", "Czechoslovakia", "Denmark", "Djibouti", "Dominica", "Dominican Republic", "East Timor", "Ecuador", "Egypt", "El Salvador", "England", "Equatorial Guinea", "Eritrea", "Estonia", "Ethiopia", "Falkland Islands", "Faroe Islands", "Fiji", "Finland", "France", "Gabon", "Gambia", "Georgia", "Germany", "Ghana", "Gibraltar", "Great Britain", "Greece", "Greenland", "Grenada", "Guadeloupe", "Guam", "Guatemela", "Guernsey", "Guiana", "Guinea", "Guinea Bissau", "Guyana", "Haiti", "Heard Islands", "Honduras", "Hong Kong", "Hungary", "Iceland", "India", "Indonesia", "Iran", "Iraq", "Ireland", "Isle Of Man", "Israel", "Italy", "Jamaica", "Japan", "Jersey", "Jordan", "Kazakhstan", "Kenya", "Kiribati", "Korea, South", "Korea, North", "Kuwait", "Kyrgyzstan", "Lao People's Dem. Rep.", "Latvia", "Lebanon", "Lesotho", "Liberia", "Libya", "Liechtenstein", "Lithuania", "Luxembourg", "Macau", "Macedonia", "Madagascar", "Malawi", "Malaysia", "Maldives", "Mali", "Malta", "Mariana Islands", "Marshall Islands", "Martinique", "Mauritania", "Mauritius", "Mayotte", "Mexico", "Micronesia", "Moldova", "Monaco", "Mongolia", "Montserrat", "Morocco", "Mozambique", "Myanmar", "Namibia", "Nauru", "Nepal", "Netherlands", "Netherlands Antilles", "Neutral Zone", "New Caledonia", "New Zealand", "Nicaragua", "Niger", "Nigeria", "Niue", "Norfolk Island", "Northern Ireland", "Norway", "Oman", "Pakistan", "Palau", "Panama", "Papua New Guinea", "Paraguay", "Peru", "Philippines", "Pitcairn", "Poland", "Polynesia", "Portugal", "Puerto Rico", "Qatar", "Reunion", "Romania", "Russian Federation", "Rwanda", "Saint Helena", "Saint Kitts", "Saint Lucia", "Saint Pierre", "Saint Vincent", "Samoa", "San Marino", "Sao Tome and Principe", "Saudi Arabia", "Scotland", "Senegal", "Seychelles", "Sierra Leone", "Singapore", "Slovakia", "Slovenia", "Solomon Islands", "Somalia", "South Africa", "South Georgia", "Spain", "Sri Lanka", "Sudan", "Suriname", "Svalbard", "Swaziland", "Sweden", "Switzerland", "Syrian Arab Republic", "Taiwan", "Tajikista", "Tanzania", "Thailand", "Togo", "Tokelau", "Tonga", "Trinidad and Tobago", "Tunisia", "Turkey", "Turkmenistan", "Turks and Caicos Islands", "Tuvalu", "Uganda", "Ukraine", "United Arab Emirates", "United Kingdom", "United States", "Uruguay", "Uzbekistan", "Vanuatu", "Vatican City State", "Venezuela", "Vietnam", "Virgin Islands", "Wales", "Western Sahara", "Yemen", "Yugoslavia", "Zaire", "Zambia", "Zimbabwe" }; } } } Any suggestions? Thanks

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  • A Taxonomy of Numerical Methods v1

    - by JoshReuben
    Numerical Analysis – When, What, (but not how) Once you understand the Math & know C++, Numerical Methods are basically blocks of iterative & conditional math code. I found the real trick was seeing the forest for the trees – knowing which method to use for which situation. Its pretty easy to get lost in the details – so I’ve tried to organize these methods in a way that I can quickly look this up. I’ve included links to detailed explanations and to C++ code examples. I’ve tried to classify Numerical methods in the following broad categories: Solving Systems of Linear Equations Solving Non-Linear Equations Iteratively Interpolation Curve Fitting Optimization Numerical Differentiation & Integration Solving ODEs Boundary Problems Solving EigenValue problems Enjoy – I did ! Solving Systems of Linear Equations Overview Solve sets of algebraic equations with x unknowns The set is commonly in matrix form Gauss-Jordan Elimination http://en.wikipedia.org/wiki/Gauss%E2%80%93Jordan_elimination C++: http://www.codekeep.net/snippets/623f1923-e03c-4636-8c92-c9dc7aa0d3c0.aspx Produces solution of the equations & the coefficient matrix Efficient, stable 2 steps: · Forward Elimination – matrix decomposition: reduce set to triangular form (0s below the diagonal) or row echelon form. If degenerate, then there is no solution · Backward Elimination –write the original matrix as the product of ints inverse matrix & its reduced row-echelon matrix à reduce set to row canonical form & use back-substitution to find the solution to the set Elementary ops for matrix decomposition: · Row multiplication · Row switching · Add multiples of rows to other rows Use pivoting to ensure rows are ordered for achieving triangular form LU Decomposition http://en.wikipedia.org/wiki/LU_decomposition C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-lu-decomposition-for-solving.html Represent the matrix as a product of lower & upper triangular matrices A modified version of GJ Elimination Advantage – can easily apply forward & backward elimination to solve triangular matrices Techniques: · Doolittle Method – sets the L matrix diagonal to unity · Crout Method - sets the U matrix diagonal to unity Note: both the L & U matrices share the same unity diagonal & can be stored compactly in the same matrix Gauss-Seidel Iteration http://en.wikipedia.org/wiki/Gauss%E2%80%93Seidel_method C++: http://www.nr.com/forum/showthread.php?t=722 Transform the linear set of equations into a single equation & then use numerical integration (as integration formulas have Sums, it is implemented iteratively). an optimization of Gauss-Jacobi: 1.5 times faster, requires 0.25 iterations to achieve the same tolerance Solving Non-Linear Equations Iteratively find roots of polynomials – there may be 0, 1 or n solutions for an n order polynomial use iterative techniques Iterative methods · used when there are no known analytical techniques · Requires set functions to be continuous & differentiable · Requires an initial seed value – choice is critical to convergence à conduct multiple runs with different starting points & then select best result · Systematic - iterate until diminishing returns, tolerance or max iteration conditions are met · bracketing techniques will always yield convergent solutions, non-bracketing methods may fail to converge Incremental method if a nonlinear function has opposite signs at 2 ends of a small interval x1 & x2, then there is likely to be a solution in their interval – solutions are detected by evaluating a function over interval steps, for a change in sign, adjusting the step size dynamically. Limitations – can miss closely spaced solutions in large intervals, cannot detect degenerate (coinciding) solutions, limited to functions that cross the x-axis, gives false positives for singularities Fixed point method http://en.wikipedia.org/wiki/Fixed-point_iteration C++: http://books.google.co.il/books?id=weYj75E_t6MC&pg=PA79&lpg=PA79&dq=fixed+point+method++c%2B%2B&source=bl&ots=LQ-5P_taoC&sig=lENUUIYBK53tZtTwNfHLy5PEWDk&hl=en&sa=X&ei=wezDUPW1J5DptQaMsIHQCw&redir_esc=y#v=onepage&q=fixed%20point%20method%20%20c%2B%2B&f=false Algebraically rearrange a solution to isolate a variable then apply incremental method Bisection method http://en.wikipedia.org/wiki/Bisection_method C++: http://numericalcomputing.wordpress.com/category/algorithms/ Bracketed - Select an initial interval, keep bisecting it ad midpoint into sub-intervals and then apply incremental method on smaller & smaller intervals – zoom in Adv: unaffected by function gradient à reliable Disadv: slow convergence False Position Method http://en.wikipedia.org/wiki/False_position_method C++: http://www.dreamincode.net/forums/topic/126100-bisection-and-false-position-methods/ Bracketed - Select an initial interval , & use the relative value of function at interval end points to select next sub-intervals (estimate how far between the end points the solution might be & subdivide based on this) Newton-Raphson method http://en.wikipedia.org/wiki/Newton's_method C++: http://www-users.cselabs.umn.edu/classes/Summer-2012/csci1113/index.php?page=./newt3 Also known as Newton's method Convenient, efficient Not bracketed – only a single initial guess is required to start iteration – requires an analytical expression for the first derivative of the function as input. Evaluates the function & its derivative at each step. Can be extended to the Newton MutiRoot method for solving multiple roots Can be easily applied to an of n-coupled set of non-linear equations – conduct a Taylor Series expansion of a function, dropping terms of order n, rewrite as a Jacobian matrix of PDs & convert to simultaneous linear equations !!! Secant Method http://en.wikipedia.org/wiki/Secant_method C++: http://forum.vcoderz.com/showthread.php?p=205230 Unlike N-R, can estimate first derivative from an initial interval (does not require root to be bracketed) instead of inputting it Since derivative is approximated, may converge slower. Is fast in practice as it does not have to evaluate the derivative at each step. Similar implementation to False Positive method Birge-Vieta Method http://mat.iitm.ac.in/home/sryedida/public_html/caimna/transcendental/polynomial%20methods/bv%20method.html C++: http://books.google.co.il/books?id=cL1boM2uyQwC&pg=SA3-PA51&lpg=SA3-PA51&dq=Birge-Vieta+Method+c%2B%2B&source=bl&ots=QZmnDTK3rC&sig=BPNcHHbpR_DKVoZXrLi4nVXD-gg&hl=en&sa=X&ei=R-_DUK2iNIjzsgbE5ID4Dg&redir_esc=y#v=onepage&q=Birge-Vieta%20Method%20c%2B%2B&f=false combines Horner's method of polynomial evaluation (transforming into lesser degree polynomials that are more computationally efficient to process) with Newton-Raphson to provide a computational speed-up Interpolation Overview Construct new data points for as close as possible fit within range of a discrete set of known points (that were obtained via sampling, experimentation) Use Taylor Series Expansion of a function f(x) around a specific value for x Linear Interpolation http://en.wikipedia.org/wiki/Linear_interpolation C++: http://www.hamaluik.com/?p=289 Straight line between 2 points à concatenate interpolants between each pair of data points Bilinear Interpolation http://en.wikipedia.org/wiki/Bilinear_interpolation C++: http://supercomputingblog.com/graphics/coding-bilinear-interpolation/2/ Extension of the linear function for interpolating functions of 2 variables – perform linear interpolation first in 1 direction, then in another. Used in image processing – e.g. texture mapping filter. Uses 4 vertices to interpolate a value within a unit cell. Lagrange Interpolation http://en.wikipedia.org/wiki/Lagrange_polynomial C++: http://www.codecogs.com/code/maths/approximation/interpolation/lagrange.php For polynomials Requires recomputation for all terms for each distinct x value – can only be applied for small number of nodes Numerically unstable Barycentric Interpolation http://epubs.siam.org/doi/pdf/10.1137/S0036144502417715 C++: http://www.gamedev.net/topic/621445-barycentric-coordinates-c-code-check/ Rearrange the terms in the equation of the Legrange interpolation by defining weight functions that are independent of the interpolated value of x Newton Divided Difference Interpolation http://en.wikipedia.org/wiki/Newton_polynomial C++: http://jee-appy.blogspot.co.il/2011/12/newton-divided-difference-interpolation.html Hermite Divided Differences: Interpolation polynomial approximation for a given set of data points in the NR form - divided differences are used to approximately calculate the various differences. For a given set of 3 data points , fit a quadratic interpolant through the data Bracketed functions allow Newton divided differences to be calculated recursively Difference table Cubic Spline Interpolation http://en.wikipedia.org/wiki/Spline_interpolation C++: https://www.marcusbannerman.co.uk/index.php/home/latestarticles/42-articles/96-cubic-spline-class.html Spline is a piecewise polynomial Provides smoothness – for interpolations with significantly varying data Use weighted coefficients to bend the function to be smooth & its 1st & 2nd derivatives are continuous through the edge points in the interval Curve Fitting A generalization of interpolating whereby given data points may contain noise à the curve does not necessarily pass through all the points Least Squares Fit http://en.wikipedia.org/wiki/Least_squares C++: http://www.ccas.ru/mmes/educat/lab04k/02/least-squares.c Residual – difference between observed value & expected value Model function is often chosen as a linear combination of the specified functions Determines: A) The model instance in which the sum of squared residuals has the least value B) param values for which model best fits data Straight Line Fit Linear correlation between independent variable and dependent variable Linear Regression http://en.wikipedia.org/wiki/Linear_regression C++: http://www.oocities.org/david_swaim/cpp/linregc.htm Special case of statistically exact extrapolation Leverage least squares Given a basis function, the sum of the residuals is determined and the corresponding gradient equation is expressed as a set of normal linear equations in matrix form that can be solved (e.g. using LU Decomposition) Can be weighted - Drop the assumption that all errors have the same significance –-> confidence of accuracy is different for each data point. Fit the function closer to points with higher weights Polynomial Fit - use a polynomial basis function Moving Average http://en.wikipedia.org/wiki/Moving_average C++: http://www.codeproject.com/Articles/17860/A-Simple-Moving-Average-Algorithm Used for smoothing (cancel fluctuations to highlight longer-term trends & cycles), time series data analysis, signal processing filters Replace each data point with average of neighbors. Can be simple (SMA), weighted (WMA), exponential (EMA). Lags behind latest data points – extra weight can be given to more recent data points. Weights can decrease arithmetically or exponentially according to distance from point. Parameters: smoothing factor, period, weight basis Optimization Overview Given function with multiple variables, find Min (or max by minimizing –f(x)) Iterative approach Efficient, but not necessarily reliable Conditions: noisy data, constraints, non-linear models Detection via sign of first derivative - Derivative of saddle points will be 0 Local minima Bisection method Similar method for finding a root for a non-linear equation Start with an interval that contains a minimum Golden Search method http://en.wikipedia.org/wiki/Golden_section_search C++: http://www.codecogs.com/code/maths/optimization/golden.php Bisect intervals according to golden ratio 0.618.. Achieves reduction by evaluating a single function instead of 2 Newton-Raphson Method Brent method http://en.wikipedia.org/wiki/Brent's_method C++: http://people.sc.fsu.edu/~jburkardt/cpp_src/brent/brent.cpp Based on quadratic or parabolic interpolation – if the function is smooth & parabolic near to the minimum, then a parabola fitted through any 3 points should approximate the minima – fails when the 3 points are collinear , in which case the denominator is 0 Simplex Method http://en.wikipedia.org/wiki/Simplex_algorithm C++: http://www.codeguru.com/cpp/article.php/c17505/Simplex-Optimization-Algorithm-and-Implemetation-in-C-Programming.htm Find the global minima of any multi-variable function Direct search – no derivatives required At each step it maintains a non-degenerative simplex – a convex hull of n+1 vertices. Obtains the minimum for a function with n variables by evaluating the function at n-1 points, iteratively replacing the point of worst result with the point of best result, shrinking the multidimensional simplex around the best point. Point replacement involves expanding & contracting the simplex near the worst value point to determine a better replacement point Oscillation can be avoided by choosing the 2nd worst result Restart if it gets stuck Parameters: contraction & expansion factors Simulated Annealing http://en.wikipedia.org/wiki/Simulated_annealing C++: http://code.google.com/p/cppsimulatedannealing/ Analogy to heating & cooling metal to strengthen its structure Stochastic method – apply random permutation search for global minima - Avoid entrapment in local minima via hill climbing Heating schedule - Annealing schedule params: temperature, iterations at each temp, temperature delta Cooling schedule – can be linear, step-wise or exponential Differential Evolution http://en.wikipedia.org/wiki/Differential_evolution C++: http://www.amichel.com/de/doc/html/ More advanced stochastic methods analogous to biological processes: Genetic algorithms, evolution strategies Parallel direct search method against multiple discrete or continuous variables Initial population of variable vectors chosen randomly – if weighted difference vector of 2 vectors yields a lower objective function value then it replaces the comparison vector Many params: #parents, #variables, step size, crossover constant etc Convergence is slow – many more function evaluations than simulated annealing Numerical Differentiation Overview 2 approaches to finite difference methods: · A) approximate function via polynomial interpolation then differentiate · B) Taylor series approximation – additionally provides error estimate Finite Difference methods http://en.wikipedia.org/wiki/Finite_difference_method C++: http://www.wpi.edu/Pubs/ETD/Available/etd-051807-164436/unrestricted/EAMPADU.pdf Find differences between high order derivative values - Approximate differential equations by finite differences at evenly spaced data points Based on forward & backward Taylor series expansion of f(x) about x plus or minus multiples of delta h. Forward / backward difference - the sums of the series contains even derivatives and the difference of the series contains odd derivatives – coupled equations that can be solved. Provide an approximation of the derivative within a O(h^2) accuracy There is also central difference & extended central difference which has a O(h^4) accuracy Richardson Extrapolation http://en.wikipedia.org/wiki/Richardson_extrapolation C++: http://mathscoding.blogspot.co.il/2012/02/introduction-richardson-extrapolation.html A sequence acceleration method applied to finite differences Fast convergence, high accuracy O(h^4) Derivatives via Interpolation Cannot apply Finite Difference method to discrete data points at uneven intervals – so need to approximate the derivative of f(x) using the derivative of the interpolant via 3 point Lagrange Interpolation Note: the higher the order of the derivative, the lower the approximation precision Numerical Integration Estimate finite & infinite integrals of functions More accurate procedure than numerical differentiation Use when it is not possible to obtain an integral of a function analytically or when the function is not given, only the data points are Newton Cotes Methods http://en.wikipedia.org/wiki/Newton%E2%80%93Cotes_formulas C++: http://www.siafoo.net/snippet/324 For equally spaced data points Computationally easy – based on local interpolation of n rectangular strip areas that is piecewise fitted to a polynomial to get the sum total area Evaluate the integrand at n+1 evenly spaced points – approximate definite integral by Sum Weights are derived from Lagrange Basis polynomials Leverage Trapezoidal Rule for default 2nd formulas, Simpson 1/3 Rule for substituting 3 point formulas, Simpson 3/8 Rule for 4 point formulas. For 4 point formulas use Bodes Rule. Higher orders obtain more accurate results Trapezoidal Rule uses simple area, Simpsons Rule replaces the integrand f(x) with a quadratic polynomial p(x) that uses the same values as f(x) for its end points, but adds a midpoint Romberg Integration http://en.wikipedia.org/wiki/Romberg's_method C++: http://code.google.com/p/romberg-integration/downloads/detail?name=romberg.cpp&can=2&q= Combines trapezoidal rule with Richardson Extrapolation Evaluates the integrand at equally spaced points The integrand must have continuous derivatives Each R(n,m) extrapolation uses a higher order integrand polynomial replacement rule (zeroth starts with trapezoidal) à a lower triangular matrix set of equation coefficients where the bottom right term has the most accurate approximation. The process continues until the difference between 2 successive diagonal terms becomes sufficiently small. Gaussian Quadrature http://en.wikipedia.org/wiki/Gaussian_quadrature C++: http://www.alglib.net/integration/gaussianquadratures.php Data points are chosen to yield best possible accuracy – requires fewer evaluations Ability to handle singularities, functions that are difficult to evaluate The integrand can include a weighting function determined by a set of orthogonal polynomials. Points & weights are selected so that the integrand yields the exact integral if f(x) is a polynomial of degree <= 2n+1 Techniques (basically different weighting functions): · Gauss-Legendre Integration w(x)=1 · Gauss-Laguerre Integration w(x)=e^-x · Gauss-Hermite Integration w(x)=e^-x^2 · Gauss-Chebyshev Integration w(x)= 1 / Sqrt(1-x^2) Solving ODEs Use when high order differential equations cannot be solved analytically Evaluated under boundary conditions RK for systems – a high order differential equation can always be transformed into a coupled first order system of equations Euler method http://en.wikipedia.org/wiki/Euler_method C++: http://rosettacode.org/wiki/Euler_method First order Runge–Kutta method. Simple recursive method – given an initial value, calculate derivative deltas. Unstable & not very accurate (O(h) error) – not used in practice A first-order method - the local error (truncation error per step) is proportional to the square of the step size, and the global error (error at a given time) is proportional to the step size In evolving solution between data points xn & xn+1, only evaluates derivatives at beginning of interval xn à asymmetric at boundaries Higher order Runge Kutta http://en.wikipedia.org/wiki/Runge%E2%80%93Kutta_methods C++: http://www.dreamincode.net/code/snippet1441.htm 2nd & 4th order RK - Introduces parameterized midpoints for more symmetric solutions à accuracy at higher computational cost Adaptive RK – RK-Fehlberg – estimate the truncation at each integration step & automatically adjust the step size to keep error within prescribed limits. At each step 2 approximations are compared – if in disagreement to a specific accuracy, the step size is reduced Boundary Value Problems Where solution of differential equations are located at 2 different values of the independent variable x à more difficult, because cannot just start at point of initial value – there may not be enough starting conditions available at the end points to produce a unique solution An n-order equation will require n boundary conditions – need to determine the missing n-1 conditions which cause the given conditions at the other boundary to be satisfied Shooting Method http://en.wikipedia.org/wiki/Shooting_method C++: http://ganeshtiwaridotcomdotnp.blogspot.co.il/2009/12/c-c-code-shooting-method-for-solving.html Iteratively guess the missing values for one end & integrate, then inspect the discrepancy with the boundary values of the other end to adjust the estimate Given the starting boundary values u1 & u2 which contain the root u, solve u given the false position method (solving the differential equation as an initial value problem via 4th order RK), then use u to solve the differential equations. Finite Difference Method For linear & non-linear systems Higher order derivatives require more computational steps – some combinations for boundary conditions may not work though Improve the accuracy by increasing the number of mesh points Solving EigenValue Problems An eigenvalue can substitute a matrix when doing matrix multiplication à convert matrix multiplication into a polynomial EigenValue For a given set of equations in matrix form, determine what are the solution eigenvalue & eigenvectors Similar Matrices - have same eigenvalues. Use orthogonal similarity transforms to reduce a matrix to diagonal form from which eigenvalue(s) & eigenvectors can be computed iteratively Jacobi method http://en.wikipedia.org/wiki/Jacobi_method C++: http://people.sc.fsu.edu/~jburkardt/classes/acs2_2008/openmp/jacobi/jacobi.html Robust but Computationally intense – use for small matrices < 10x10 Power Iteration http://en.wikipedia.org/wiki/Power_iteration For any given real symmetric matrix, generate the largest single eigenvalue & its eigenvectors Simplest method – does not compute matrix decomposition à suitable for large, sparse matrices Inverse Iteration Variation of power iteration method – generates the smallest eigenvalue from the inverse matrix Rayleigh Method http://en.wikipedia.org/wiki/Rayleigh's_method_of_dimensional_analysis Variation of power iteration method Rayleigh Quotient Method Variation of inverse iteration method Matrix Tri-diagonalization Method Use householder algorithm to reduce an NxN symmetric matrix to a tridiagonal real symmetric matrix vua N-2 orthogonal transforms     Whats Next Outside of Numerical Methods there are lots of different types of algorithms that I’ve learned over the decades: Data Mining – (I covered this briefly in a previous post: http://geekswithblogs.net/JoshReuben/archive/2007/12/31/ssas-dm-algorithms.aspx ) Search & Sort Routing Problem Solving Logical Theorem Proving Planning Probabilistic Reasoning Machine Learning Solvers (eg MIP) Bioinformatics (Sequence Alignment, Protein Folding) Quant Finance (I read Wilmott’s books – interesting) Sooner or later, I’ll cover the above topics as well.

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  • Using a mounted NTFS share with nginx

    - by Hoff
    I have set up a local testing VM with Ubuntu Server 12.04 LTS and the LEMP stack. It's kind of an unconventional setup because instead of having all my PHP scripts on the local machine, I've mounted an NTFS share as the document root because I do my development on Windows. I had everything working perfectly up until this morning, now I keep getting a dreaded 'File not found.' error. I am almost certain this must be somehow permission related, because if I copy my site over to /var/www, nginx and php-fpm have no problems serving my PHP scripts. What I can't figure out is why all of a sudden (after a reboot of the server), no PHP files will be served but instead just the 'File not found.' error. Static files work fine, so I think it's PHP that is causing the headache. Both nginx and php-fpm are configured to run as the user www-data: root@ubuntu-server:~# ps aux | grep 'nginx\|php-fpm' root 1095 0.0 0.0 5816 792 ? Ss 11:11 0:00 nginx: master process /opt/nginx/sbin/nginx -c /etc/nginx/nginx.conf www-data 1096 0.0 0.1 6016 1172 ? S 11:11 0:00 nginx: worker process www-data 1098 0.0 0.1 6016 1172 ? S 11:11 0:00 nginx: worker process root 1130 0.0 0.4 175560 4212 ? Ss 11:11 0:00 php-fpm: master process (/etc/php5/php-fpm.conf) www-data 1131 0.0 0.3 175560 3216 ? S 11:11 0:00 php-fpm: pool www www-data 1132 0.0 0.3 175560 3216 ? S 11:11 0:00 php-fpm: pool www www-data 1133 0.0 0.3 175560 3216 ? S 11:11 0:00 php-fpm: pool www root 1686 0.0 0.0 4368 816 pts/1 S+ 11:11 0:00 grep --color=auto nginx\|php-fpm I have mounted the NTFS share at /mnt/webfiles by editing /etc/fstab and adding the following line: //192.168.0.199/c$/Websites/ /mnt/webfiles cifs username=Jordan,password=mypasswordhere,gid=33,uid=33 0 0 Where gid 33 is the www-data group and uid 33 is the user www-data. If I list the contents of one of my sites you can in fact see that they belong to the user www-data: root@ubuntu-server:~# ls -l /mnt/webfiles/nTv5-2.0 total 8 drwxr-xr-x 0 www-data www-data 0 Jun 6 19:12 app drwxr-xr-x 0 www-data www-data 0 Aug 22 19:00 assets -rwxr-xr-x 0 www-data www-data 1150 Jan 4 2012 favicon.ico -rwxr-xr-x 0 www-data www-data 1412 Dec 28 2011 index.php drwxr-xr-x 0 www-data www-data 0 Jun 3 16:44 lib drwxr-xr-x 0 www-data www-data 0 Jan 3 2012 plugins drwxr-xr-x 0 www-data www-data 0 Jun 3 16:45 vendors If I switch to the www-data user, I have no problem creating a new file on the share: root@ubuntu-server:~# su www-data $ > /mnt/webfiles/test.txt $ ls -l /mnt/webfiles | grep test\.txt -rwxr-xr-x 0 www-data www-data 0 Sep 8 11:19 test.txt There should be no problem reading or writing to the share with php-fpm running as the user www-data. When I examine the error log of nginx, it's filled with a bunch of lines that look like the following: 2012/09/08 11:22:36 [error] 1096#0: *1 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client: 192.168.0.199, server: , request: "GET / HTTP/1.1", upstream: "fastcgi://unix:/var/run/php5-fpm.sock:", host: "192.168.0.123" 2012/09/08 11:22:39 [error] 1096#0: *1 FastCGI sent in stderr: "Primary script unknown" while reading response header from upstream, client: 192.168.0.199, server: , request: "GET /apc.php HTTP/1.1", upstream: "fastcgi://unix:/var/run/php5-fpm.sock:", host: "192.168.0.123" It's bizarre that this was working previously and now all of sudden PHP is complaining that it can't "find" the scripts on the share. Does anybody know why this is happening? EDIT I tried editing php-fpm.conf and changing chdir to the following: chdir = /mnt/webfiles When I try and restart the php-fpm service, I get the error: Starting php-fpm [08-Sep-2012 14:20:55] ERROR: [pool www] the chdir path '/mnt/webfiles' does not exist or is not a directory This is a total load of bullshit because this directory DOES exist and is mounted! Any ls commands to list that directory work perfectly. Why the hell can't PHP-FPM see this directory?! Here are my configuration files for reference: nginx.conf user www-data; worker_processes 2; error_log /var/log/nginx/nginx.log info; pid /var/run/nginx.pid; events { worker_connections 1024; multi_accept on; } http { include fastcgi.conf; include mime.types; default_type application/octet-stream; set_real_ip_from 127.0.0.1; real_ip_header X-Forwarded-For; ## Proxy proxy_redirect off; proxy_set_header Host $host; proxy_set_header X-Real-IP $remote_addr; proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for; client_max_body_size 32m; client_body_buffer_size 128k; proxy_connect_timeout 90; proxy_send_timeout 90; proxy_read_timeout 90; proxy_buffers 32 4k; ## Compression gzip on; gzip_types text/plain text/css application/x-javascript text/xml application/xml application/xml+rss text/javascript; gzip_disable "MSIE [1-6]\.(?!.*SV1)"; ### TCP options tcp_nodelay on; tcp_nopush on; keepalive_timeout 65; sendfile on; include /etc/nginx/sites-enabled/*; } my site config server { listen 80; access_log /var/log/nginx/$host.access.log; error_log /var/log/nginx/error.log; root /mnt/webfiles/nTv5-2.0/app/webroot; index index.php; ## Block bad bots if ($http_user_agent ~* (HTTrack|HTMLParser|libcurl|discobot|Exabot|Casper|kmccrew|plaNETWORK|RPT-HTTPClient)) { return 444; } ## Block certain Referers (case insensitive) if ($http_referer ~* (sex|vigra|viagra) ) { return 444; } ## Deny dot files: location ~ /\. { deny all; } ## Favicon Not Found location = /favicon.ico { access_log off; log_not_found off; } ## Robots.txt Not Found location = /robots.txt { access_log off; log_not_found off; } if (-f $document_root/maintenance.html) { rewrite ^(.*)$ /maintenance.html last; } location ~* \.(?:ico|css|js|gif|jpe?g|png)$ { # Some basic cache-control for static files to be sent to the browser expires max; add_header Pragma public; add_header Cache-Control "max-age=2678400, public, must-revalidate"; } location / { try_files $uri $uri/ index.php; if (-f $request_filename) { break; } rewrite ^(.+)$ /index.php?url=$1 last; } location ~ \.php$ { include /etc/nginx/fastcgi.conf; fastcgi_pass unix:/var/run/php5-fpm.sock; } } php-fpm.conf ;;;;;;;;;;;;;;;;;;;;; ; FPM Configuration ; ;;;;;;;;;;;;;;;;;;;;; ; All relative paths in this configuration file are relative to PHP's install ; prefix (/opt/php5). This prefix can be dynamicaly changed by using the ; '-p' argument from the command line. ; Include one or more files. If glob(3) exists, it is used to include a bunch of ; files from a glob(3) pattern. This directive can be used everywhere in the ; file. ; Relative path can also be used. They will be prefixed by: ; - the global prefix if it's been set (-p arguement) ; - /opt/php5 otherwise ;include=etc/fpm.d/*.conf ;;;;;;;;;;;;;;;;;; ; Global Options ; ;;;;;;;;;;;;;;;;;; [global] ; Pid file ; Note: the default prefix is /opt/php5/var ; Default Value: none pid = /var/run/php-fpm.pid ; Error log file ; Note: the default prefix is /opt/php5/var ; Default Value: log/php-fpm.log error_log = /var/log/php5-fpm/php-fpm.log ; Log level ; Possible Values: alert, error, warning, notice, debug ; Default Value: notice ;log_level = notice ; If this number of child processes exit with SIGSEGV or SIGBUS within the time ; interval set by emergency_restart_interval then FPM will restart. A value ; of '0' means 'Off'. ; Default Value: 0 ;emergency_restart_threshold = 0 ; Interval of time used by emergency_restart_interval to determine when ; a graceful restart will be initiated. This can be useful to work around ; accidental corruptions in an accelerator's shared memory. ; Available Units: s(econds), m(inutes), h(ours), or d(ays) ; Default Unit: seconds ; Default Value: 0 ;emergency_restart_interval = 0 ; Time limit for child processes to wait for a reaction on signals from master. ; Available units: s(econds), m(inutes), h(ours), or d(ays) ; Default Unit: seconds ; Default Value: 0 ;process_control_timeout = 0 ; Send FPM to background. Set to 'no' to keep FPM in foreground for debugging. ; Default Value: yes ;daemonize = yes ;;;;;;;;;;;;;;;;;;;; ; Pool Definitions ; ;;;;;;;;;;;;;;;;;;;; ; Multiple pools of child processes may be started with different listening ; ports and different management options. The name of the pool will be ; used in logs and stats. There is no limitation on the number of pools which ; FPM can handle. Your system will tell you anyway :) ; Start a new pool named 'www'. ; the variable $pool can we used in any directive and will be replaced by the ; pool name ('www' here) [www] ; Per pool prefix ; It only applies on the following directives: ; - 'slowlog' ; - 'listen' (unixsocket) ; - 'chroot' ; - 'chdir' ; - 'php_values' ; - 'php_admin_values' ; When not set, the global prefix (or /opt/php5) applies instead. ; Note: This directive can also be relative to the global prefix. ; Default Value: none ;prefix = /path/to/pools/$pool ; The address on which to accept FastCGI requests. ; Valid syntaxes are: ; 'ip.add.re.ss:port' - to listen on a TCP socket to a specific address on ; a specific port; ; 'port' - to listen on a TCP socket to all addresses on a ; specific port; ; '/path/to/unix/socket' - to listen on a unix socket. ; Note: This value is mandatory. ;listen = 127.0.0.1:9000 listen = /var/run/php5-fpm.sock ; Set listen(2) backlog. A value of '-1' means unlimited. ; Default Value: 128 (-1 on FreeBSD and OpenBSD) ;listen.backlog = -1 ; List of ipv4 addresses of FastCGI clients which are allowed to connect. ; Equivalent to the FCGI_WEB_SERVER_ADDRS environment variable in the original ; PHP FCGI (5.2.2+). Makes sense only with a tcp listening socket. Each address ; must be separated by a comma. If this value is left blank, connections will be ; accepted from any ip address. ; Default Value: any ;listen.allowed_clients = 127.0.0.1 ; Set permissions for unix socket, if one is used. In Linux, read/write ; permissions must be set in order to allow connections from a web server. Many ; BSD-derived systems allow connections regardless of permissions. ; Default Values: user and group are set as the running user ; mode is set to 0666 ;listen.owner = www-data ;listen.group = www-data ;listen.mode = 0666 ; Unix user/group of processes ; Note: The user is mandatory. If the group is not set, the default user's group ; will be used. user = www-data group = www-data ; Choose how the process manager will control the number of child processes. ; Possible Values: ; static - a fixed number (pm.max_children) of child processes; ; dynamic - the number of child processes are set dynamically based on the ; following directives: ; pm.max_children - the maximum number of children that can ; be alive at the same time. ; pm.start_servers - the number of children created on startup. ; pm.min_spare_servers - the minimum number of children in 'idle' ; state (waiting to process). If the number ; of 'idle' processes is less than this ; number then some children will be created. ; pm.max_spare_servers - the maximum number of children in 'idle' ; state (waiting to process). If the number ; of 'idle' processes is greater than this ; number then some children will be killed. ; Note: This value is mandatory. pm = dynamic ; The number of child processes to be created when pm is set to 'static' and the ; maximum number of child processes to be created when pm is set to 'dynamic'. ; This value sets the limit on the number of simultaneous requests that will be ; served. Equivalent to the ApacheMaxClients directive with mpm_prefork. ; Equivalent to the PHP_FCGI_CHILDREN environment variable in the original PHP ; CGI. ; Note: Used when pm is set to either 'static' or 'dynamic' ; Note: This value is mandatory. pm.max_children = 50 ; The number of child processes created on startup. ; Note: Used only when pm is set to 'dynamic' ; Default Value: min_spare_servers + (max_spare_servers - min_spare_servers) / 2 pm.start_servers = 20 ; The desired minimum number of idle server processes. ; Note: Used only when pm is set to 'dynamic' ; Note: Mandatory when pm is set to 'dynamic' pm.min_spare_servers = 5 ; The desired maximum number of idle server processes. ; Note: Used only when pm is set to 'dynamic' ; Note: Mandatory when pm is set to 'dynamic' pm.max_spare_servers = 35 ; The number of requests each child process should execute before respawning. ; This can be useful to work around memory leaks in 3rd party libraries. For ; endless request processing specify '0'. Equivalent to PHP_FCGI_MAX_REQUESTS. ; Default Value: 0 pm.max_requests = 500 ; The URI to view the FPM status page. If this value is not set, no URI will be ; recognized as a status page. By default, the status page shows the following ; information: ; accepted conn - the number of request accepted by the pool; ; pool - the name of the pool; ; process manager - static or dynamic; ; idle processes - the number of idle processes; ; active processes - the number of active processes; ; total processes - the number of idle + active processes. ; max children reached - number of times, the process limit has been reached, ; when pm tries to start more children (works only for ; pm 'dynamic') ; The values of 'idle processes', 'active processes' and 'total processes' are ; updated each second. The value of 'accepted conn' is updated in real time. ; Example output: ; accepted conn: 12073 ; pool: www ; process manager: static ; idle processes: 35 ; active processes: 65 ; total processes: 100 ; max children reached: 1 ; By default the status page output is formatted as text/plain. Passing either ; 'html' or 'json' as a query string will return the corresponding output ; syntax. Example: ; http://www.foo.bar/status ; http://www.foo.bar/status?json ; http://www.foo.bar/status?html ; Note: The value must start with a leading slash (/). The value can be ; anything, but it may not be a good idea to use the .php extension or it ; may conflict with a real PHP file. ; Default Value: not set pm.status_path = /status ; The ping URI to call the monitoring page of FPM. If this value is not set, no ; URI will be recognized as a ping page. This could be used to test from outside ; that FPM is alive and responding, or to ; - create a graph of FPM availability (rrd or such); ; - remove a server from a group if it is not responding (load balancing); ; - trigger alerts for the operating team (24/7). ; Note: The value must start with a leading slash (/). The value can be ; anything, but it may not be a good idea to use the .php extension or it ; may conflict with a real PHP file. ; Default Value: not set ping.path = /ping ; This directive may be used to customize the response of a ping request. The ; response is formatted as text/plain with a 200 response code. ; Default Value: pong ping.response = pong ; The timeout for serving a single request after which the worker process will ; be killed. This option should be used when the 'max_execution_time' ini option ; does not stop script execution for some reason. A value of '0' means 'off'. ; Available units: s(econds)(default), m(inutes), h(ours), or d(ays) ; Default Value: 0 ;request_terminate_timeout = 0 ; The timeout for serving a single request after which a PHP backtrace will be ; dumped to the 'slowlog' file. A value of '0s' means 'off'. ; Available units: s(econds)(default), m(inutes), h(ours), or d(ays) ; Default Value: 0 ;request_slowlog_timeout = 0 ; The log file for slow requests ; Default Value: not set ; Note: slowlog is mandatory if request_slowlog_timeout is set ;slowlog = log/$pool.log.slow ; Set open file descriptor rlimit. ; Default Value: system defined value ;rlimit_files = 1024 ; Set max core size rlimit. ; Possible Values: 'unlimited' or an integer greater or equal to 0 ; Default Value: system defined value ;rlimit_core = 0 ; Chroot to this directory at the start. This value must be defined as an ; absolute path. When this value is not set, chroot is not used. ; Note: you can prefix with '$prefix' to chroot to the pool prefix or one ; of its subdirectories. If the pool prefix is not set, the global prefix ; will be used instead. ; Note: chrooting is a great security feature and should be used whenever ; possible. However, all PHP paths will be relative to the chroot ; (error_log, sessions.save_path, ...). ; Default Value: not set ;chroot = ; Chdir to this directory at the start. ; Note: relative path can be used. ; Default Value: current directory or / when chroot ;chdir = /var/www ; Redirect worker stdout and stderr into main error log. If not set, stdout and ; stderr will be redirected to /dev/null according to FastCGI specs. ; Note: on highloaded environement, this can cause some delay in the page ; process time (several ms). ; Default Value: no ;catch_workers_output = yes ; Pass environment variables like LD_LIBRARY_PATH. All $VARIABLEs are taken from ; the current environment. ; Default Value: clean env ;env[HOSTNAME] = $HOSTNAME ;env[PATH] = /usr/local/bin:/usr/bin:/bin ;env[TMP] = /tmp ;env[TMPDIR] = /tmp ;env[TEMP] = /tmp ; Additional php.ini defines, specific to this pool of workers. These settings ; overwrite the values previously defined in the php.ini. The directives are the ; same as the PHP SAPI: ; php_value/php_flag - you can set classic ini defines which can ; be overwritten from PHP call 'ini_set'. ; php_admin_value/php_admin_flag - these directives won't be overwritten by ; PHP call 'ini_set' ; For php_*flag, valid values are on, off, 1, 0, true, false, yes or no. ; Defining 'extension' will load the corresponding shared extension from ; extension_dir. Defining 'disable_functions' or 'disable_classes' will not ; overwrite previously defined php.ini values, but will append the new value ; instead. ; Note: path INI options can be relative and will be expanded with the prefix ; (pool, global or /opt/php5) ; Default Value: nothing is defined by default except the values in php.ini and ; specified at startup with the -d argument ;php_admin_value[sendmail_path] = /usr/sbin/sendmail -t -i -f [email protected] ;php_flag[display_errors] = off ;php_admin_value[error_log] = /var/log/fpm-php.www.log ;php_admin_flag[log_errors] = on ;php_admin_value[memory_limit] = 32M php_admin_value[sendmail_path] = /usr/sbin/sendmail -t -i

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